Happening @ Michigan https://events.umich.edu/list/rss RSS Feed for Happening @ Michigan Events at the University of Michigan. Statistics Department Seminar Series: Sebastien Roch, Professor, Department of Mathematics, University of Wisconsin-Madison (November 22, 2019 10:00am) https://events.umich.edu/event/63890 63890-15977792@events.umich.edu Event Begins: Friday, November 22, 2019 10:00am
Location: West Hall
Organized By: Department of Statistics

Phylogenomics, the estimation of species phylogenies from genome-scale datasets, is a common step in many biological studies. This estimation is complicated by the fact that genes can evolve under processes, including incomplete lineage sorting (ILS), gene duplication and loss (GDL) and horizontal gene transfer (HGT), that make their trees conflict with the species history. I will survey recent progress on some statistical questions that arise in this context. Specifically, the identifiability of standard probabilistic models of phylogenomic data will be discussed, as well as the large-sample properties of computationally efficient methods for species tree estimation.

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Workshop / Seminar Fri, 15 Nov 2019 10:57:30 -0500 2019-11-22T10:00:00-05:00 2019-11-22T11:00:00-05:00 West Hall Department of Statistics Workshop / Seminar Roch
HET Seminars | Illuminating the Early Universe with Dark Matter Minihalos (November 22, 2019 3:00pm) https://events.umich.edu/event/69401 69401-17318564@events.umich.edu Event Begins: Friday, November 22, 2019 3:00pm
Location: West Hall
Organized By: Leinweber Center for Theoretical Physics

As remnants of the earliest stages of structure formation, the smallest dark matter halos provide a unique probe of the density fluctuations generated during inflation and the evolution of the Universe shortly after inflation. The absence of early-forming ultra-compact minihalos (UCMHs) establishes an upper bound on the amplitude of the primordial power spectrum on small scales and has been used to constrain inflationary models. I will show how numerical simulations of UCMH formation reveal that these constraints need to be revised because the dark matter annihilation rate within UCMHs is lower than has been assumed. Nevertheless, we have found that minihalos can still provide unrivaled constraints on the small-scale primordial power spectrum. The abundance of minihalos also encodes information about the evolution of the Universe prior to Big Bang nucleosynthesis (BBN). I will discuss how the pre-BBN thermal history can enhance the minihalo population, thereby boosting the dark matter annihilation rate if dark matter is a thermal relic. Conversely, the nonthermal production of dark matter can suppress the small-scale power spectrum. It is therefore possible to use gamma-ray observations and observations of the Lyman-α forest to learn about the origins of dark matter and the evolution of the Universe during its first second.

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Lecture / Discussion Wed, 13 Nov 2019 13:26:28 -0500 2019-11-22T15:00:00-05:00 2019-11-22T16:00:00-05:00 West Hall Leinweber Center for Theoretical Physics Lecture / Discussion West Hall
HEP-Astro Seminar | The Degree of Fine-Tuning in our Universe -- and Possibly Others (November 25, 2019 4:00pm) https://events.umich.edu/event/67018 67018-16796445@events.umich.edu Event Begins: Monday, November 25, 2019 4:00pm
Location: West Hall
Organized By: Department of Physics

The fundamental constants of nature must fall within a range of values in order for the universe to develop structure and ultimately support life. This talk considers the current constraints on these quantities and assesses the degree of fine-tuning required for the universe to be viable. The first step is to determine what parameters are allowed to vary. In the realm of particle physics, we must specify the strengths of the fundamental forces and the particle masses. The relevant cosmological parameters include the density of the universe, the cosmological constant, the abundance of ordinary matter, the dark matter contribution, and the amplitude of primordial density fluctuations. These quantities are constrained by the requirements that the universe lives for a sufficiently long time, emerges from its early epochs with an acceptable chemical composition, and can successfully produce galaxies. On smaller scales, stars and planets must be able to form and function. The stars must have sufficiently long lifetimes and hot surface temperatures. The planets must be large enough to maintain atmospheres, small enough to remain non-degenerate, and contain enough particles to support a biosphere. We also consider specific fine-tuning issues in stars, including the triple alpha reaction that produces carbon, the case of unstable deuterium, and the possibility of stable diprotons. For all of these issues, the goal of this enterprise is to delineate the range of parameter space for which universes can remain habitable.

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Workshop / Seminar Mon, 25 Nov 2019 18:16:09 -0500 2019-11-25T16:00:00-05:00 2019-11-25T17:00:00-05:00 West Hall Department of Physics Workshop / Seminar West Hall
Prioritize Wellness (November 25, 2019 7:00pm) https://events.umich.edu/event/68979 68979-17205328@events.umich.edu Event Begins: Monday, November 25, 2019 7:00pm
Location: West Hall
Organized By: First Year Experience Programs

Throughout the semester, it is important to recharge and take breaks to be prepared. Join us for a mindful break and a chance to reflect on wellness! Stop by at some of our Drop-In stations and grab a sleep kit!

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Well-being Thu, 07 Nov 2019 13:59:12 -0500 2019-11-25T19:00:00-05:00 2019-11-25T20:00:00-05:00 West Hall First Year Experience Programs Well-being Prioritize Wellness Flyer
HEP-Astro Seminar | Dark Matter Searches in LZ and Beyond (December 2, 2019 1:00pm) https://events.umich.edu/event/69733 69733-17392933@events.umich.edu Event Begins: Monday, December 2, 2019 1:00pm
Location: West Hall
Organized By: HEP - Astro Seminars

LZ will be the world's most sensitive dark matter direct detection experiment, starting to take data in Spring 2020. The experiment is located 1 mi underground in the Sanford Underground Research Facility (SURF) in Lead, SD. LZ consists of a central time projection chamber (TPC) containing 7 tonnes of liquid xenon as dark matter target surrounded by an outer detector (OD) with 17 tonnes of gadolinium doped liquid scintillator to veto neutrons. I will highlight my group's research contributions to TPC assembly as well as to design and manufacturing of the OD. I will demonstrate how the equipment we built, combined with my analysis and phenomenological experience, will lead to most the sensitive searches including novel signatures. The use of active veto detectors has been adopted by all upcoming direct dark matter experiments and are indispensable to the future of the field. I will present status of my program to develop novel scintillating detectors including the first concepts for future veto detectors for the next generation of dark matter experiments.

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Workshop / Seminar Wed, 27 Nov 2019 09:41:07 -0500 2019-12-02T13:00:00-05:00 2019-12-02T14:00:00-05:00 West Hall HEP - Astro Seminars Workshop / Seminar West Hall
HEP-Astro Seminar | SUSY Searches with ATLAS and Potential Improvements from Track Triggers (December 2, 2019 4:00pm) https://events.umich.edu/event/66923 66923-16787709@events.umich.edu Event Begins: Monday, December 2, 2019 4:00pm
Location: West Hall
Organized By: Department of Physics

The lack of evidence for SUSY at the LHC motivates new search strategies such as looking for scenarios with small mass differences between SUSY particles. However, this can bring challenges because of lower momentum visible decay products. SUSY searches with two leptons offer the possibility to use unique shapes in the invariant mass spectrum as an additional discriminant. In this talk, I will go through the details of ATLAS SUSY searches with two leptons, and show some highlights of recent SUSY results. Additionally, I will discuss how track triggers can enhance the discovery reach of these searches, focusing on the ATLAS Fast TracKer as an example along with its Phase-II counterpart.

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Workshop / Seminar Mon, 02 Dec 2019 18:16:24 -0500 2019-12-02T16:00:00-05:00 2019-12-02T17:00:00-05:00 West Hall Department of Physics Workshop / Seminar West Hall
CM-AMO Seminar | Double Feature - Observation of a Ferro-Rotational Order Coupled with Second-Order Nonlinear Optical Fields & Information Scrambling in Quantum Phases (December 3, 2019 4:00pm) https://events.umich.edu/event/66974 66974-16789923@events.umich.edu Event Begins: Tuesday, December 3, 2019 4:00pm
Location: West Hall
Organized By: Department of Physics

Elizabeth Drueke
U-M Physics

Observation of a Ferro-rotational Order Coupled with Second-order Nonlinear Optical Fields

In this talk, I will discuss our recent discovery of ferrorotational order in RbFe(MoO4)2. Classified by an order parameter which is an axial vector invariant under both time-reversal and spatial-inversion operations, this order is closely related to a number of phenomena such as polar vortices, giant magnetoelectric coupling and spin-helicity-driven ferroelectricity, but it has received little attention so far. Here, using high-sensitivity rotational-anisotropy second-harmonic generation, we have exploited the electric quadrupole contribution to the second harmonic generation to directly couple to this centrosymmetric ferro-rotational order in an archetype of type-II multiferroics, RbFe(MoO4)2. We found that two domain states with opposite ferro-rotational vectors emerge with distinct populations at the critical temperature Tc ≈ 195 K and gradually evolve to reach an even ratio at lower temperatures. Moreover, we have identified the ferro-rotational order phase transition as weakly first order and have revealed its coupling field as a unique combination of the induced electric quadrupole second-harmonic generation and the incident fundamental electric fields.


Ceren Dag
U-M Physics

Information Scrambling in Quantum Phases

Out-of-time-order correlators (OTOCs) are well-established tools for studying quantum chaos in quantum many-body systems as well as information properties of black holes. They characterize the information scrambling which is a dynamical phenomenon where both spatial and temporal correlations spread across a many-body system. Recently an unexpected relation between symmetry-breaking quantum phase transitions and information scrambling has been numerically observed. We introduce a new theoretical tool to understand the reasons and the mechanism of this relation, which makes the dynamical detection of long-range ordered quantum phases via OTOCs intuitive. Based on the studies in literature and our numerical results in the XXZ model, our method renders the relation between information scrambling and quantum phase transitions universal.

Speaker Information: Ceren B. Dag is a graduate student in the Physics Department at the University of Michigan Ann Arbor. She works towards her PhD thesis with Kai Sun and Luming Duan.

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Workshop / Seminar Mon, 02 Dec 2019 09:38:15 -0500 2019-12-03T16:00:00-05:00 2019-12-03T17:00:00-05:00 West Hall Department of Physics Workshop / Seminar West Hall
HET SEMINAR | Extending the Double Copy (December 4, 2019 12:00pm) https://events.umich.edu/event/69764 69764-17417427@events.umich.edu Event Begins: Wednesday, December 4, 2019 12:00pm
Location: West Hall
Organized By: Leinweber Center for Theoretical Physics

I will discuss several recent papers on the double copy. In the first part of the talk I will recap work extending the classical double copy correspondence to maximally symmetric curved spacetimes. I will describe how to construct the corresponding single and zeroth copies in asymptotically (A)dS spacetimes in Kerr-Schild form, and will clarify the interpretation of these copies using several examples, pointing out some peculiar features. In the second part of the talk, I will introduce Galileon fields, and will discuss how to generalize and extend the procedure relating gauge and gravity theories through color-kinematics replacements by showing that the classical perturbative double copy of pions corresponds to special Galileons. I will also show how to construct the single copy by mapping the bi-adjoint scalar radiation to the non-linear sigma model radiation through generalized color-kinematics replacements. Finally, if time permits, I will introduce work studying the double copy beyond leading order.

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Lecture / Discussion Mon, 25 Nov 2019 12:25:35 -0500 2019-12-04T12:00:00-05:00 2019-12-04T13:00:00-05:00 West Hall Leinweber Center for Theoretical Physics Lecture / Discussion West Hall
Department Colloquium | Controlling Dissipation in Superconductors: the Oxymoron that Leads to New Superconducting Phases and Transitions (December 4, 2019 4:00pm) https://events.umich.edu/event/65286 65286-16565505@events.umich.edu Event Begins: Wednesday, December 4, 2019 4:00pm
Location: West Hall
Organized By: Department of Physics

Superconductors are exciting materials for basic physics and applications because they conventionally exhibit zero-resistance and zero-dissipation (i.e., no energy loss). However, unconventional superconductors—including high-temperature superconductors and hybrid superconductor-normal (S-N) systems relevant to quantum computation—combine superconductivity with dissipative normal metal-like states. Yet dissipation has been difficult to control and parametrize. In this talk, I will discuss electrical transport experiments on hybrid superconductor-normal metal systems where the dissipation is controlled, leading to new understanding of superconducting states and transitions. In particular, I will show how superconductivity is established in granular S-N systems, how metallic states appear in arrays of S-N systems as the normal metal fraction is increased, and how magnetic fields can be used to control a variety of dissipative phase transitions. The results are relevant to understanding the role of dissipation in superconducting systems, and in correlated materials in general.

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Workshop / Seminar Wed, 04 Dec 2019 18:16:23 -0500 2019-12-04T16:00:00-05:00 2019-12-04T17:00:00-05:00 West Hall Department of Physics Workshop / Seminar West Hall
Department Colloquium | Controlling Dissipation in Superconductors: the Oxymoron that Leads to New Superconducting Phases and Transitions (December 4, 2019 4:00pm) https://events.umich.edu/event/67181 67181-16805264@events.umich.edu Event Begins: Wednesday, December 4, 2019 4:00pm
Location: West Hall
Organized By: Undergrad Physics Events

Superconductors are exciting materials for basic physics and applications because they conventionally exhibit zero-resistance and zero-dissipation (i.e., no energy loss). However, unconventional superconductors—including high-temperature superconductors and hybrid superconductor-normal (S-N) systems relevant to quantum computation—combine superconductivity with dissipative normal metal-like states. Yet dissipation has been difficult to control and parametrize. In this talk, I will discuss electrical transport experiments on hybrid superconductor-normal metal systems where the dissipation is controlled, leading to new understanding of superconducting states and transitions. In particular, I will show how superconductivity is established in granular S-N systems, how metallic states appear in arrays of S-N systems as the normal metal fraction is increased, and how magnetic fields can be used to control a variety of dissipative phase transitions. The results are relevant to understanding the role of dissipation in superconducting systems, and in correlated materials in general.

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Workshop / Seminar Mon, 25 Nov 2019 08:09:38 -0500 2019-12-04T16:00:00-05:00 2019-12-04T17:00:00-05:00 West Hall Undergrad Physics Events Workshop / Seminar West Hall
Statistics Department Seminar Series: Yuqi Gu, Ph.D. Candidate, Department of Statistics, University of Michigan (December 6, 2019 10:00am) https://events.umich.edu/event/69647 69647-17376499@events.umich.edu Event Begins: Friday, December 6, 2019 10:00am
Location: West Hall
Organized By: Department of Statistics

In modern psychological and biomedical research with diagnostic purposes, scientists often formulate the key task as inferring the fine-grained latent information under structural constraints. These structural constraints usually come from the domain experts’ prior knowledge or insight. The emerging family of Structured Latent Attribute Models (SLAMs) accommodate these modeling needs and have received substantial attention in psychology, education, and epidemiology. SLAMs bring exciting opportunities and unique challenges. In particular, with high-dimensional discrete latent attributes and structural constraints encoded by a design matrix, one needs to balance the gain in the model’s explanatory power and interpretability, against the difficulty of understanding and handling the complex model structure.

In the first part of this talk, I present identifiability results that advance the theoretical knowledge of how the design matrix influences the estimability of SLAMs. The new identifiability conditions guide real-world practices of designing cognitive diagnostic tests and also lay the foundation for drawing valid statistical conclusions. In the second part, I introduce a statistically consistent penalized likelihood approach to selecting significant latent patterns in the population. I also propose a scalable computational method. These developments explore an exponentially large model space involving many discrete latent variables, and they address the estimation and computation challenges of high-dimensional SLAMs arising in large-scale scientific measurements. The application of the proposed methodology to the data from an international educational assessment reveals meaningful knowledge structures and latent subgroups of the student populations.

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Workshop / Seminar Wed, 20 Nov 2019 13:22:35 -0500 2019-12-06T10:00:00-05:00 2019-12-06T11:00:00-05:00 West Hall Department of Statistics Workshop / Seminar Yuqi Gu
Life After Graduate School Seminar | From Natural Laws to Writing Laws: A Physicist Turned Policymaker (December 6, 2019 12:00pm) https://events.umich.edu/event/67593 67593-16900781@events.umich.edu Event Begins: Friday, December 6, 2019 12:00pm
Location: West Hall
Organized By: Department of Physics

The US federal government touches all aspects of our lives through its ~$4.5 trillion annual budget (although less than 4% is for research and development), laws, regulations, rules, and policies. Dr. Anna Quider will discuss her experience as a physicist-turned-policymaker working within the federal government at the U.S. House of Representatives and U.S. Department of State, and external to the federal government as a higher education and science advocate. Attendees will learn about career paths into federal policymaking and how input from physicists and the public inform the federal policymaking process. Dr. Quider is presently the Assistant Vice President for Federal Relations for Northern Illinois University and the past-president of The Science Coalition, a national nonprofit dedicated to increasing US federal funding for fundamental scientific research. She was a 2011 APS Congressional Science Fellow and 2012 AAAS Science and Technology Policy Fellow.


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Workshop / Seminar Fri, 06 Dec 2019 18:16:18 -0500 2019-12-06T12:00:00-05:00 2019-12-06T13:00:00-05:00 West Hall Department of Physics Workshop / Seminar West Hall
HET Seminar | UV and IR properties of quantum gravity from amplitudes (December 6, 2019 3:00pm) https://events.umich.edu/event/69833 69833-17433861@events.umich.edu Event Begins: Friday, December 6, 2019 3:00pm
Location: West Hall
Organized By: Leinweber Center for Theoretical Physics

Using the general unitarity cuts method and amplitudes approach, we calculate the 4-point all-plus-helicity graviton amplitudes at 2-loop. This reproduces a well-known result about 2-loop divergence in quantum gravity, and more importantly, we figure out a very simple renormalization scale dependence of gravity theories at 2-loop. And from this scale dependence, we conclude the duality between scalar and 2-form, between 3-form and cosmological constant at quantum level. And after this direct but complicated calculation, we figure out an alternative simple derivation by doing the cuts and integration in 4d, instead of 4-2e dimension. This elucidates the ultraviolet(UV) physics within. Besides, using techniques from amplitudes, we calculate the bending angle of massless projectiles, including graviton, when they pass near a massive object, like the sun, which is represented by a massive scalar. This reveals the long-distance/infrared(IR) properties of quantum gravity, without worrying about the UV details. And we obtain different bending angles for different massless projectile with different spins, which could possibly indicate a violation of classical equivalence principle at quantum level.

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Lecture / Discussion Wed, 27 Nov 2019 13:50:43 -0500 2019-12-06T15:00:00-05:00 2019-12-06T16:00:00-05:00 West Hall Leinweber Center for Theoretical Physics Lecture / Discussion West Hall
Quantitative Biology Seminar | Morphogen Dynamics Control Patterning in a Stem Cell Model of the Human Embryo (December 9, 2019 12:00pm) https://events.umich.edu/event/68969 68969-17205310@events.umich.edu Event Begins: Monday, December 9, 2019 12:00pm
Location: West Hall
Organized By: Department of Physics

During embryonic development, diffusible signaling molecules called morphogens are thought to determine cell fates in a concentration-dependent manner, and protocols for directed stem cell differentiation are based on this picture. However, in the mammalian embryo, morphogen concentrations change rapidly compared to the time for making cell fate decisions. It is unknown how changing ligand levels are interpreted, and whether the precise timecourse of ligand exposure plays a role in cell fate decisions. In this talk I will discuss our work to address this question using human embryonic stem cells (hESCs), focusing on the dynamics of two morphogens that are crucial for vertebrate gastrulation: Nodal and BMP4. We showed that the response of hESCs to BMP4 signaling is indeed is determined by the ligand concentration, but that unexpectedly, the expression of many mesodermal targets of Nodal depends on the rate of concentration increase. In addition, we showed that a stem cell model for the human embryo generates a wave of Nodal signaling with cells experiencing rapidly increasing Nodal specifically in the region of mesendoderm differentiation. The BMP4 and Nodal pathways share the signal transducer Smad4. Using live imaging of hESCs with GFP integrated at the endogenous SMAD4 locus combined with Fluorescence Recovery After Photobleaching (FRAP), we demonstrated that response to rate of Activin change is due to adaptive signaling, which relies on sequestration of SMAD4. We also demonstrated that pulsatile stimulation with Activin induces repeated strong signaling and enhances mesoderm differentiation. Our results break with the paradigm of concentration-dependent differentiation and demonstrate an important role for morphogen dynamics in the cell fate decisions associated with mammalian gastrulation. They suggest a highly dynamic picture of embryonic patterning where some cell fates depend on rapid concentration increase rather than on absolute levels, and point to ligand dynamics as a new dimension to optimize protocols for directed stem cell differentiation.

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Workshop / Seminar Mon, 09 Dec 2019 18:16:12 -0500 2019-12-09T12:00:00-05:00 2019-12-09T13:00:00-05:00 West Hall Department of Physics Workshop / Seminar West Hall
Statistics Department Seminar Series: Zheng Gao, Ph.D. Candidate, Department of Statistics, University of Michigan (December 10, 2019 4:00pm) https://events.umich.edu/event/69697 69697-17382665@events.umich.edu Event Begins: Tuesday, December 10, 2019 4:00pm
Location: West Hall
Organized By: Department of Statistics

We shall revisit some phase transitions in high-dimensional multiple testing problems under sparsity assumptions, and then proceed to characterize some new ones that we recently discovered. In particular, I will describe the signal sizes necessary and sufficient for statistical procedures to simultaneously control false discovery (in terms of family-wise error rate or false discovery rate) and missed detection (in terms of family-wise non-discovery rate or false non-discovery rate) in the simple but ubiquitous signal-plus-noise model

x(i) = \mu(i) + \epsilon(i), \quad i=1,2,\ldots,p

Several well-known procedures are shown to attain said boundaries. Remarkably, these phase transition phenomena continue to hold under a much wider class of models, and under extremely weak dependence assumptions. We provide point-wise, rather than minimax, results, wherever we can. Important practical implications, along with an interesting manifestation of the phase transitions in genome-wide association studies (GWAS), will be discussed.

Behind the statistical results is a probabilistic phenomenon known as relative stability. Much like how the law of large numbers describes the concentration of averages, relative stability --- or the "law of large dimensions" --- describes the concentration of maxima. We provide a complete characterization of the relative stability phenomenon for Gaussian triangular arrays in terms of their correlation structure. Its proof uses classic Sudakov-Fernique and Slepian lemma arguments along with a curious application of Ramsey's coloring theorem.

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Workshop / Seminar Tue, 26 Nov 2019 15:09:11 -0500 2019-12-10T16:00:00-05:00 2019-12-10T17:00:00-05:00 West Hall Department of Statistics Workshop / Seminar Zheng Gao
Poetry & Ethnography: Expanding the Narrative (December 13, 2019 12:00pm) https://events.umich.edu/event/70194 70194-17547062@events.umich.edu Event Begins: Friday, December 13, 2019 12:00pm
Location: West Hall
Organized By: Department of Anthropology

December 13, 2019
Writing Workshop 12 - 2 pm
111 West Hall
Public Lecture 4 - 5:30 pm
Hatcher Graduate Library Gallery

Please join us for the second event of the
Anthropology & Poetry Speaker and Workshop Series. All students, faculty, and staff are welcome.

The generative writing workshop will be held in 111 West Hall from 12 - 2:00 pm. Participants are invited to bring their own materials (field notes, interview transcriptions, photos, etc.) to work with during the writing workshop, although this is not required. No prior experience with poetry is necessary. Lunch will be provided.

The public lecture will be held in the Hatcher Gallery from 4:00 - 5:30 pm.
Refreshments will be provided.

Kenzie Allen is a descendant of the Oneida Nation of Wisconsin. She is currently a lecturer at York University, and an R1-Advanced Opportunity Program Fellow and PhD Candidate in English & Creative Writing at the University of Wisconsin—Milwaukee. Her research centers on documentary and visual poetics, literary cartography, and the enactment of Indigenous sovereignties through creative works. Kenzie’s most recent project is a multimodal book of poetry which incorporates intergenerational histories and diasporic movements, Haudenosaunee traditions, and archival materials of the Carlisle Indian Boarding School. She received her MFA in Poetry from the Helen Zell Writers’ Program at the University of Michigan, and her BA in Anthropology from Washington University in St. Louis. Her poems can be found in Boston Review, Narrative Magazine, Best New Poets, and other venues, and she is the founder and managing editor of the Anthropoid collective.

Thank you to our sponsors: Department of Anthropology, Rackham Graduate School, Department of English Language and Literature, Department of American Culture, Native American Studies, Native American and Indigenous Studies Interest Group, Institute for the Humanities, LSA, Poetry & Poetics Workshop, Latina/o Studies, and the Center for Latin American and Caribbean Studies.

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Workshop / Seminar Wed, 11 Dec 2019 09:45:59 -0500 2019-12-13T12:00:00-05:00 2019-12-13T14:00:00-05:00 West Hall Department of Anthropology Workshop / Seminar Oneida Big Apple Fest
CM Theory Seminar | Imaging Nematic Quantum Hall States and their Interacting Boundary Modes (January 9, 2020 4:00pm) https://events.umich.edu/event/70881 70881-17728770@events.umich.edu Event Begins: Thursday, January 9, 2020 4:00pm
Location: West Hall
Organized By: Department of Physics

Two-dimensional quantum Hall systems offer a versatile platform to explore the interplay between topology and symmetry breaking facilitated by Coulomb interactions. In this talk, I discuss the novel phenomena that arise from spontaneous valley ordering of bismuth surface states in a large magnetic field. Specifically, we observe the emergence of a nematic phase which breaks the rotational symmetry of the underlying crystal and a ferroelectric phase that carries an in-plane electric dipole moment. We use a scanning tunneling microscope to identify and directly image the wavefunctions of these broken-symmetry quantum Hall phases. Furthermore, we explore the boundary between distinct nematic domains, which host counter-propagating 1D modes. By changing the number of modes, we realize strikingly different regimes where the boundary is either metallic or insulating, constrained by Coulomb interactions between these 1D modes.

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Workshop / Seminar Thu, 09 Jan 2020 18:16:31 -0500 2020-01-09T16:00:00-05:00 2020-01-09T17:00:00-05:00 West Hall Department of Physics Workshop / Seminar West Hall
HET Seminar | Searching for Dark Matter Interactions in Cosmology (January 10, 2020 3:00pm) https://events.umich.edu/event/70973 70973-17760246@events.umich.edu Event Begins: Friday, January 10, 2020 3:00pm
Location: West Hall
Organized By: Leinweber Center for Theoretical Physics

There is a substantial effort in the physics community to search for dark matter interactions with the Standard Model of particle physics. Collisions between dark matter particles and baryons exchange heat and momentum in the early Universe, enabling a search for dark matter interactions using cosmological observations in a parameter space that is complementary to that of direct detection. In this talk, I will describe the effects of scattering in cosmology and show constraints using Planck 2015 data and SDSS-identified satellite galaxies of the Milky Way. I will also discuss the implications of late-time scattering during the era of Cosmic Dawn.

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Lecture / Discussion Mon, 06 Jan 2020 16:50:40 -0500 2020-01-10T15:00:00-05:00 2020-01-10T16:00:00-05:00 West Hall Leinweber Center for Theoretical Physics Lecture / Discussion West Hall
Special CM Theory Seminar | Photoinduced Transformation of Nanoscale Domains in Ferroelectric Complex Oxides (January 13, 2020 1:00pm) https://events.umich.edu/event/71126 71126-17779236@events.umich.edu Event Begins: Monday, January 13, 2020 1:00pm
Location: West Hall
Organized By: Department of Physics

Complex oxide materials are an intense and exciting research area of condensed matter physics with their coupling between lattice, charge, and spin. Especially, nanoscale periodic polar configurations in ferroic oxides called ferroelectric domains exhibit novel phenomena leading to an intense flurry of research interests. However, as studies of functional responses to external stimuli have mainly focused on electric and mechanical responses, a new and effective approach to manipulate these polar configurations is on demand. In this presentation, I will discuss our efforts to investigate interaction of light with nanoscale domains and ferroelastic domain walls examined by in-situ and time-resolved x-ray diffraction experiments. By tracking temporal evolution of x-ray domain diffuse scattering, we have found that structural transformation of ferroic domains is optically induced and exhibits nonthermal characteristics. I will also present theoretical considerations to investigate the underlying physics of the photoinduced transformation.

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Workshop / Seminar Mon, 13 Jan 2020 18:16:32 -0500 2020-01-13T13:00:00-05:00 2020-01-13T14:00:00-05:00 West Hall Department of Physics Workshop / Seminar West Hall
MLK Day Department Colloquium | Creating our Future: Attracting and Retaining the Best Students from All Backgrounds (January 15, 2020 4:00pm) https://events.umich.edu/event/71015 71015-17768616@events.umich.edu Event Begins: Wednesday, January 15, 2020 4:00pm
Location: West Hall
Organized By: Department of Physics

Physics now must compete for the best and brightest. How do we collectively locate, nurture, and advance students who will become our colleagues regardless of opportunities they may or may not have had as they began their studies? There is good evidence that strategies used to attract us into the field are missing large numbers of capable and eager students. I will discuss programs and new approaches that are opening the door to students who may not have felt welcome in the past, but who are now bringing their insights and hard work to solving the next generation of physics problems. We will discuss how the Michigan physics department can help with and benefit from these programs.

This is an inaugural MLK Day Department Colloquium.

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Workshop / Seminar Wed, 15 Jan 2020 18:16:44 -0500 2020-01-15T16:00:00-05:00 2020-01-15T17:00:00-05:00 West Hall Department of Physics Workshop / Seminar West Hall
Statistics Department Seminar Series: Yixin Wang, Ph.D. Candidate, Department of Statistics, Columbia University (January 17, 2020 10:00am) https://events.umich.edu/event/69914 69914-17483044@events.umich.edu Event Begins: Friday, January 17, 2020 10:00am
Location: West Hall
Organized By: Department of Statistics

Causal inference from observational data is a vital problem, but it comes with strong assumptions. Most methods assume that we observe all confounders, variables that affect both the causal variables and the outcome variables. But whether we have observed all confounders is a famously untestable assumption. We describe the deconfounder, a way to do causal inference from observational data allowing for unobserved confounding.

How does the deconfounder work? The deconfounder is designed for problems of multiple causal inferences: scientific studies that involve many causes whose effects are simultaneously of interest. The deconfounder uses the correlation among causes as evidence for unobserved confounders, combining unsupervised machine learning and predictive model checking to perform causal inference. We study the theoretical requirements for the deconfounder to provide unbiased causal estimates, along with its limitations and tradeoffs. We demonstrate the deconfounder on real-world data and simulation studies.

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Workshop / Seminar Fri, 10 Jan 2020 11:21:57 -0500 2020-01-17T10:00:00-05:00 2020-01-17T11:00:00-05:00 West Hall Department of Statistics Workshop / Seminar Yixin Wang
CM-AMO Seminar | Probes of Novel Electronic States in Mesoscopic and 2D Quantum Materials (January 21, 2020 4:00pm) https://events.umich.edu/event/71240 71240-17794027@events.umich.edu Event Begins: Tuesday, January 21, 2020 4:00pm
Location: West Hall
Organized By: Department of Physics

Recent advances in the development of exfoliated 2D materials and other mesoscopic systems (e.g. semiconducting nanowires) have led to the discovery of intriguing topological, magnetic, and superconducting states. However, many bulk probes which have been invaluable in understanding complex electronic states such as those found in high-temperature superconductors are no longer applicable. Additionally, many scanned probes which can study physics on the nanoscale are incompatible with the highest quality, state-of-the-art 2D materials-based devices which rely on encapsulation with hexagonal boron nitride. In this talk I will present magnetic imaging studies of more traditional mesoscopic systems, including imaging current distributions in micron-scale devices and studying novel nanowire-based superconducting devices. Secondly, I will describe more recent work realizing low-disorder graphene devices which facilitated the discovery of new topological states of matter. Finally, I will discuss prospects for studying 2D materials both with magnetic imaging and on-chip THz spectroscopy using superconductivity in exfoliated flakes as an example.

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Workshop / Seminar Tue, 21 Jan 2020 18:17:05 -0500 2020-01-21T16:00:00-05:00 2020-01-21T17:00:00-05:00 West Hall Department of Physics Workshop / Seminar West Hall
Department Colloquium | Nuclear Physics from the Standard Model (January 22, 2020 4:00pm) https://events.umich.edu/event/70952 70952-17760228@events.umich.edu Event Begins: Wednesday, January 22, 2020 4:00pm
Location: West Hall
Organized By: Department of Physics

I will discuss the status and future of calculations of nuclei based on the Standard Model of particle physics. With advances in supercomputing, we are beginning to quantitatively understand nuclear structure and interactions directly from the fundamental quark and gluon degrees of freedom. Recent studies provide insight into the neutrino-nucleus interactions relevant to long-baseline neutrino experiments, double beta decay, and theory predictions of dark matter cross-sections at underground detectors. I will also address new work constraining the gluonic structure of nuclei, which will be measurable for the first time at a future electron-ion collider, and explain how machine learning tools are providing new possibilities in this field.

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Workshop / Seminar Wed, 22 Jan 2020 18:16:59 -0500 2020-01-22T16:00:00-05:00 2020-01-22T17:00:00-05:00 West Hall Department of Physics Workshop / Seminar West Hall
Statistics Department Seminar Series: Rina Foygel Barber, Associate Professor, Department of Statistics, University of Chicago (January 24, 2020 10:00am) https://events.umich.edu/event/69910 69910-17483043@events.umich.edu Event Begins: Friday, January 24, 2020 10:00am
Location: West Hall
Organized By: Department of Statistics

Abstract: We introduce the jackknife+, a novel method for constructing predictive confidence intervals that is robust to the distribution of the data. The jackknife+ modifies the well-known jackknife (leave-one-out cross-validation) to account for the variability in the fitted regression function when we subsample the training data. Assuming exchangeable training samples, we prove that the jackknife+ permits rigorous coverage guarantees regardless of the distribution of the data points, for any algorithm that treats the training points symmetrically. Such guarantees are not possible for the original jackknife and we demonstrate examples where the coverage rate may actually vanish. Our theoretical and empirical analysis reveals that the jackknife and jackknife+ intervals achieve nearly exact coverage and have similar lengths whenever the fitting algorithm obeys some form of stability. We also extend to the setting of K-fold cross-validation. Our methods are related to cross-conformal prediction proposed by Vovk [2015] and we discuss connections.

This work is joint with Emmanuel Candes, Aaditya Ramdas, and Ryan Tibshirani.

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Workshop / Seminar Wed, 15 Jan 2020 10:18:08 -0500 2020-01-24T10:00:00-05:00 2020-01-24T11:00:00-05:00 West Hall Department of Statistics Workshop / Seminar Rina Foygel Barber
Supporting Students and Colleagues with Mental Health Challenges, a Practical Workshop (January 24, 2020 11:00am) https://events.umich.edu/event/71744 71744-17877259@events.umich.edu Event Begins: Friday, January 24, 2020 11:00am
Location: West Hall
Organized By: Physics Workshops & Conferences

Based on faculty interest, the Physics DEI committee is sponsoring an interactive workshop focused on practical strategies for supporting students and colleagues who may be experiencing mental health challenges. Refreshments will be served.

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Workshop / Seminar Mon, 20 Jan 2020 10:50:17 -0500 2020-01-24T11:00:00-05:00 2020-01-24T12:00:00-05:00 West Hall Physics Workshops & Conferences Workshop / Seminar West Hall
Andrew Wetzel: Simulating the Milky Way (January 24, 2020 1:00pm) https://events.umich.edu/event/71427 71427-17825687@events.umich.edu Event Begins: Friday, January 24, 2020 1:00pm
Location: West Hall
Organized By: Michigan Institute for Computational Discovery and Engineering

Abstract: The Gaia satellite mission, together with a multitude of ground-based observational surveys, now measure 6-D phase-space coordinates and multi-species elemental abundances for hundreds of millions of stars across the Milky Way. This new era of galactic archeology and near-field cosmology demands a new generation of simulations that achieve high dynamic range to resolve scales of individual stellar populations within a cosmological context. I will describe the new Latte suite of massively parallelized cosmological zoom-in simulations, run on the nation’s most powerful supercomputers, that model the formation of Milky Way-like galaxies at parsec-scale resolution, using the FIRE (Feedback in Realistic Environments) model for star formation and feedback. First I will discuss the formation of the Milky Way disk, including resolving for the first time the dynamics and lifetimes of giant molecular clouds and stars clusters at z = 0. These simulations also self-consistently resolve the formation of satellite dwarf galaxies around each Milky Way-like host. These low-mass galaxies have presented significant challenges to the cold dark matter model, but I will show progress in addressing the “missing satellites” and “too-big-to-fail” problems. Finally, I will discuss synthetic Milky Way surveys that we have created from the Latte simulations, which are publicly available, to provide theoretical modeling insight for the era of Gaia.

Bio: Professor Wetzel is an assistant professor in the physics department and in the astrophysics and cosmology group at the University of California, Davis. He is a theoretical/computational astrophysicist and cosmologist. Using the world’s most powerful supercomputers, he generates cosmological simulations to model the formation of cosmic structures, including galaxies and their stars. He uses these simulations as theoretical laboratories to develop and test models of galaxy formation, stellar dynamics, and the nature of dark matter, with emphasis on our own Milky Way galaxy.

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Workshop / Seminar Tue, 14 Jan 2020 10:59:20 -0500 2020-01-24T13:00:00-05:00 2020-01-24T14:00:00-05:00 West Hall Michigan Institute for Computational Discovery and Engineering Workshop / Seminar A. Wetzel
HET Seminar | Bit threads and holographic monogamy (January 24, 2020 3:00pm) https://events.umich.edu/event/71113 71113-17777078@events.umich.edu Event Begins: Friday, January 24, 2020 3:00pm
Location: West Hall
Organized By: Leinweber Center for Theoretical Physics

Entanglement entropies are well-studied in holographic field theories thanks to the Ryu-Takayanagi formula. Bit threads offer a conceptually and technically powerful new way to think about this formula. In this talk, after introducing bit threads, I will use them to give a new understanding of the so-called monogamy property of holographic entropies. The resulting picture will lead to an intriguing conjecture about the general entanglement structure of holographic states.

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Lecture / Discussion Wed, 08 Jan 2020 14:28:52 -0500 2020-01-24T15:00:00-05:00 2020-01-24T16:00:00-05:00 West Hall Leinweber Center for Theoretical Physics Lecture / Discussion West Hall
HEP-Astro Seminar | New Result on K+→π+vv^- from the NA62 Experiment (January 27, 2020 4:00pm) https://events.umich.edu/event/71101 71101-17777061@events.umich.edu Event Begins: Monday, January 27, 2020 4:00pm
Location: West Hall
Organized By: Department of Physics

The decay K+→π+vv^-, with a very precisely predicted branching ratio of less than 10exp(-10), is one of the best candidates to reveal indirect effects of new physics at the highest mass scales. The NA62 experiment at the CERN SPS is designed to measure the branching ratio of the K+ → π+vv^- with a decay-in-flight technique. NA62 took data so far in 2016-2018. Statistics collected in 2016 allowed NA62 to reach the Standard Model sensitivity for K+→π+vv^- entering the domain of 10exp(-10) single event sensitivity and showing the proof of principle of the experiment. Thanks to the statistics collected in 2017, NA62 surpasses the present best sensitivity. The analysis strategy is reviewed and the preliminary result from the 2017 data set is presented.

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Workshop / Seminar Mon, 27 Jan 2020 18:17:00 -0500 2020-01-27T16:00:00-05:00 2020-01-27T17:00:00-05:00 West Hall Department of Physics Workshop / Seminar West Hall
Special HEP-Astro Seminar | When Stars Go Nonlinear: Large Amplitude Tides and Stellar Oscillations (January 28, 2020 2:00pm) https://events.umich.edu/event/71215 71215-17787739@events.umich.edu Event Begins: Tuesday, January 28, 2020 2:00pm
Location: West Hall
Organized By: Department of Physics

Tides significantly impact the structure, evolution, and fate of many types of close binary systems, including short-period exoplanets, stellar binaries, and coalescing binary neutron stars. In many of these systems, the tide’s amplitude is so large that it cannot be treated as a small, linear perturbation to the background star. In this talk, I will show that nonlinear effects can greatly enhance the rate of tidal dissipation and thus the rate of binary evolution. As examples, I will describe how nonlinear tides influence the orbital decay of hot Jupiters and the gravitational-wave signal of coalescing binary neutron stars and white dwarfs. I will also discuss the nonlinearity of oscillation-modes in solar-like stars, which are excited by turbulent motions within the convective envelope. The rich oscillation spectra observed by space missions such as Kepler and TESS has revolutionized the field of asteroseismology and yielded a wealth of information about the internal and global properties of thousands of stars.

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Workshop / Seminar Tue, 28 Jan 2020 18:16:58 -0500 2020-01-28T14:00:00-05:00 2020-01-28T15:00:00-05:00 West Hall Department of Physics Workshop / Seminar West Hall
Department Colloquium | New Ideas in Dark Matter Detection (January 29, 2020 4:00pm) https://events.umich.edu/event/71102 71102-17777062@events.umich.edu Event Begins: Wednesday, January 29, 2020 4:00pm
Location: West Hall
Organized By: Department of Physics

The nature of the dark matter remains one of the most compelling outstanding questions in physics. Theoretical and experimental focus has been directed in the last several decades on New Physics at the weak scale, including the search for dark matter as a Weakly Interacting Massive Particle (WIMP). We are now looking beyond the WIMP window towards light hidden sectors, and new ideas to search for dark matter must be found. I describe some of these new ideas, including collective excitations in polar materials and superfluid helium, as well as low-gap targets like Dirac semimetals.

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Workshop / Seminar Wed, 29 Jan 2020 18:17:10 -0500 2020-01-29T16:00:00-05:00 2020-01-29T17:00:00-05:00 West Hall Department of Physics Workshop / Seminar West Hall
Statistics Department Seminar Series: Dylan Small, Professor, Department of Statistics, The Wharton School, University of Pennsylvania (January 31, 2020 10:00am) https://events.umich.edu/event/69915 69915-17483046@events.umich.edu Event Begins: Friday, January 31, 2020 10:00am
Location: West Hall
Organized By: Department of Statistics

Gun violence is a problem in America. There are many unresolved questions about what policies would reduce gun violence. I will discuss two attempts at causal inference about gun violence prevention policies that I have worked on, and highlight some ideas about causal inference I have sought to use in this work.

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Workshop / Seminar Fri, 10 Jan 2020 12:13:43 -0500 2020-01-31T10:00:00-05:00 2020-01-31T11:00:00-05:00 West Hall Department of Statistics Workshop / Seminar Dylan Small
Accelerated Master's Degree Program in Statistics Info Session (January 31, 2020 1:00pm) https://events.umich.edu/event/72097 72097-17937824@events.umich.edu Event Begins: Friday, January 31, 2020 1:00pm
Location: West Hall
Organized By: Department of Statistics

Are you an undergraduate student interested in a master’s degree in Applied Statistics? Join us for an info session all about our Accelerated Master’s Degree Program (AMDP) in Applied Statistics!

The AMDP option is for highly-motivated undergraduate students in their senior year who will achieve their MS in Applied Statistics with one more year of graduate study. Students typically apply in the 2nd semester of their junior year.

If this is something you’re considering for the future, join us for the info session to ask questions and learn about the application process, program requirements and timeline!

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Meeting Mon, 27 Jan 2020 11:57:36 -0500 2020-01-31T13:00:00-05:00 2020-01-31T14:00:00-05:00 West Hall Department of Statistics Meeting West Hall
HEP-Astro Seminar | Ultra-Low Energy Calibration of the LUX and LZ Dark Matter Detectors (February 3, 2020 4:00pm) https://events.umich.edu/event/71241 71241-17794028@events.umich.edu Event Begins: Monday, February 3, 2020 4:00pm
Location: West Hall
Organized By: Department of Physics

The Large Underground Xenon (LUX) experiment is a 250 kg active mass dual-phase time-projection chamber (TPC) operating at the 4850 ft level of the Sanford Underground Research Facility in Lead, SD. Various sources, including ^{127}Xe, D-D neutrons, ^{83}mKr, Tritium, and AmBe neutrons are used to perform calibrations of detector responses to electron recoils (ER) and nuclear recoils (NR). I will present an ultra-low energy calibration of ER using an intrinsic ^{127}Xe source and of NR using a short pulsed D-D neutron generator. Radioactive isotope ^{127}Xe is formed in the LUX LXe volume due to cosmogenic activation before the detector was moved one mile underground. A measurement in the early stage of the LUX WS2013 science run unveils ~0.9 million ^{127}Xe atoms in the LUX LXe volume, which provides an ideal source for low energy calibrations. ^{127}Xe decay is a form of electron capture in which a high energy gamma (> 200 keV) is emitted, followed by an associated low energy X-ray cascade over the energy range of 190 eV to 33.2 keV. The relatively long mean free path (mfp) of the gamma-ray (> 0.9 cm) allows the EC decay to produce clearly identified 2-vertex events in the LUX detector. We observe the K (33.2 keV), L (5.2 keV), M (1.1 keV), and N (190 eV) shell cascade events and verify the relative ratio of observed events for each shell. We extract the means and sigmas of the charge signal yields associated with the K, L, M, and N shell events. The N shell cascade analysis includes single extracted electron (SE) events and represents the lowest-energy electronic recoil in situ measurements that have been explored in liquid xenon. A short pulsed D-D neutron NR calibration was performed in situ in the LUX detector in June 2016 after the completion of the LUX WS2013-16 science run. The calibration incorporates a pulsing technique with narrow pulses (20 us / 250 Hz). We have measured, with low systematics, the absolute rates of NR events with ionization signals down to 2 extracted electrons and zero, one or greater detected scintillation photons. A calibration measurement with absolute event rates of charge-only S2 events for the first time in a Xe TPC provides an important probe for ultra-low energy measurements of LXe Qy. This technique provides direct measurements of scintillation and charge yields down to (Ly) 0.45 keVnr and (Qy) 0.27 keVnr, respectively. New calibration results on ultra-low energy nuclear recoil yields are crucial to determine physics search sensitivities for large mass LXe TPCs (LZ experiment) for low mass WIMPs (< 10 GeV) and for coherent neutrino scattering (e.g. ^8B solar neutrino).

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Workshop / Seminar Mon, 03 Feb 2020 18:16:42 -0500 2020-02-03T16:00:00-05:00 2020-02-03T17:00:00-05:00 West Hall Department of Physics Workshop / Seminar West Hall
Department Colloquium | Approaches to Fully-3D Dedicated Molecular Breast Imaging (February 5, 2020 4:00pm) https://events.umich.edu/event/71066 71066-17770769@events.umich.edu Event Begins: Wednesday, February 5, 2020 4:00pm
Location: West Hall
Organized By: Department of Physics

The Multi-Modality Imaging Lab at Duke has developed and characterized several dedicated (human) breast imaging devices which offer no compression (no pain!), fast scans, low dose imaging with ionizing radiation for the patient, and fully-3D, isotropic, high resolution quantitative in vivo image information for physicians. The first is a “one-stop” dedicated breast imaging system for utilizing in vivo molecular imaging with Single Photon Emission Computed Tomography (SPECT) using a 4x5 array of 4x4cm^2 pixelated CZT modules combined with low dose x-ray Computed Tomography (CT) utilizing a 40x30cm^2 CsI(Tl) flat-panel detector coupled to a TFT array. The subsystems were developed individually, then hybridized onto a single platform, allowing fully-3D motions of each subsystem. The 3D acquisitions facilitate overcoming sampling insufficiency issues associated with cone-beam CT imaging in the pendant breast frame. Novel x-ray filtering leading to quasi-monochromatic spectra have enabled low dose CT imaging comparable with standard mammography, providing quantitative accuracy within a few percent of NIST values, while optimizing dose efficiency for image quality. Next is a clinically available cardiac SPECT imaging system utilizing 19 compact (8x8cm^2) CZT cameras with pinhole collimators reconfigured for uncompressed, pendant breast and chest wall imaging. The third system utilizes LGSO scintillation crystals coupled to compact position-sensitive photodetectors in two opposed 15x20cm^2 flat panels enabling fully-3D acquisition for dedicated breast Positron Emission Tomography (PET) imaging; this open system can be combined with dedicated CT. The most current system design is for dual PET-MRI breast imaging using an ultra-high sensitivity configuration of PET detector modules to image both breasts simultaneously, and is evaluated by Monte Carlo techniques. These systems can be used to detect occult disease not otherwise seen in contemporary x-ray mammography or tomosynthesis, improve the specificity of cancer diagnosis, and monitor therapeutic response in patients, without causing additional pain (or fear) for the patient.

SHORT BIO: Martin Tornai is an Associate Professor of Radiology (tenured) and Biomedical Engineering, and a faculty member of the Medical Physics Graduate Program at Duke University. He has an undergraduate degree in physics from Cornell and a PhD in biomedical physics from UCLA. Upon completing his doctoral research on intraoperative nuclear imaging devices in 1997, he was recruited to the Duke faculty where he has engaged in numerous activities locally, nationally and internationally. He is a founding faculty member of Duke’s Medical Physics Graduate Program which will celebrate it’s 15th anniversary, and is active on many administrative committees, teaching, and student research committees, helping guide students in their research efforts. His research interests include dedicated nuclear (SPECT & PET) and x-ray based (CT) breast imaging devices, with which several dozen women have been clinically scanned. Along with his numerous MS, PhD and post-doctoral students and various colleagues, he has published over 150 original papers, proceedings articles, and book chapters. His newer interests include dosimetry for nuclear medicine theranostic applications.

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Workshop / Seminar Wed, 05 Feb 2020 18:17:08 -0500 2020-02-05T16:00:00-05:00 2020-02-05T17:00:00-05:00 West Hall Department of Physics Workshop / Seminar West Hall
Michigan Institute for Research in Astrophysics Presents: "Conversations on Inclusion and Equity" (February 7, 2020 9:30am) https://events.umich.edu/event/71967 71967-17905471@events.umich.edu Event Begins: Friday, February 7, 2020 9:30am
Location: West Hall
Organized By: Michigan Institute for Research in Astrophysics

“Recommendations for a More Inclusive Canadian Astronomy Community”

The Canadian astronomical community is currently undergoing its "Long Range Planning" process, similar to the Decadal Survey in the US. As such, the Equity and Inclusivity Committee (EIC) has recently shared a white paper with a set of recommendations for improving the representation of minoritized peoples and the working conditions in the professional astronomy community: http://myumi.ch/Bo38l. I'll briefly describe these recommendations and then open an informal discussion of their merit (and what we have inevitably missed!).

Please note: Should you require any reasonable accommodations to ensure equal access and opportunity related to this event please contact Stacy Tiburzi at 734-764-3440 or stibu@umich.edu.

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Lecture / Discussion Thu, 30 Jan 2020 15:16:28 -0500 2020-02-07T09:30:00-05:00 2020-02-07T10:20:00-05:00 West Hall Michigan Institute for Research in Astrophysics Lecture / Discussion Dr. Daryl Haggard
Interdisciplinary Seminar in Quantitative Methods (ISQM) (February 7, 2020 10:00am) https://events.umich.edu/event/72393 72393-18000381@events.umich.edu Event Begins: Friday, February 7, 2020 10:00am
Location: West Hall
Organized By: Interdisciplinary Seminar in Quantitative Methods (ISQM)

The Blessings of Multiple Causes (Joint with Yixin Wang)

ABSTRACT: Causal inference from observational data is a vital problem, but it comes with strong assumptions. Most methods require that we observe all confounders, variables that affect both the causal variables and the outcome variables. But whether we have observed all confounders is a famously untestable assumption. We describe the deconfounder, a way to do causal inference with weaker assumptions than the classical methods require.

How does the deconfounder work? While traditional causal methods measure the effect of a single cause on an outcome, many modern scientific studies involve multiple causes, different variables whose effects are simultaneously of interest. The deconfounder uses the correlation among multiple causes as evidence for unobserved confounders, combining unsupervised machine learning and predictive model checking to perform causal inference. We demonstrate the deconfounder on real-world data and simulation studies, and describe the theoretical requirements for the deconfounder to provide unbiased causal estimates.

David works in the fields of machine learning and Bayesian statistics.

The goal of the Interdisciplinary Seminar in Quantitative Methods is to provide an interdisciplinary environment where researchers can present and discuss cutting-edge research in quantitative methodology. The talks are aimed at a broad audience, with emphasis on conceptual rather than technical issues. The research presented is varied, ranging from new methodological developments to applied empirical papers that use methodology in an innovative way. We welcome speakers and audiences from all disciplines and fields, including the social, natural, biomedical, and behavioral sciences.

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Lecture / Discussion Mon, 03 Feb 2020 12:04:40 -0500 2020-02-07T10:00:00-05:00 2020-02-07T11:00:00-05:00 West Hall Interdisciplinary Seminar in Quantitative Methods (ISQM) Lecture / Discussion David Blei
Statistics Department Seminar Series: David Blei, Professor, Department of Statistics and Computer Science, Columbia University (February 7, 2020 10:00am) https://events.umich.edu/event/69917 69917-17483049@events.umich.edu Event Begins: Friday, February 7, 2020 10:00am
Location: West Hall
Organized By: Department of Statistics

Abstract: Causal inference from observational data is a vital problem, but it comes with strong assumptions. Most methods require that we observe all confounders, variables that affect both the causal variables and the outcome variables. But whether we have observed all confounders is a famously untestable assumption. We describe the deconfounder, a way to do causal inference with weaker assumptions than the classical methods require.

How does the deconfounder work? While traditional causal methods measure the effect of a single cause on an outcome, many modern scientific studies involve multiple causes, different variables whose effects are simultaneously of interest. The deconfounder uses the correlation among multiple causes as evidence for unobserved confounders, combining unsupervised machine learning and predictive model checking to perform causal inference. We demonstrate the deconfounder on real-world data and simulation studies, and describe the theoretical requirements for the deconfounder to provide unbiased causal estimates.

This is joint work with Yixin Wang. [*] https://www.tandfonline.com/doi/full/10.1080/01621459.2019.1686987

Biography: David Blei is a Professor of Statistics and Computer Science at Columbia University, and a member of the Columbia Data Science Institute. He studies probabilistic machine learning, including its theory, algorithms, and application. David has received several awards for his research, including a Sloan Fellowship (2010), Office of Naval Research Young Investigator Award (2011), Presidential Early Career Award for Scientists and Engineers (2011), Blavatnik Faculty Award (2013), ACM-Infosys Foundation Award (2013), a Guggenheim fellowship (2017), and a Simons Investigator Award (2019). He is the co-editor-in-chief of the Journal of Machine Learning Research. He is a fellow of the ACM and the IMS.

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Workshop / Seminar Thu, 30 Jan 2020 10:19:09 -0500 2020-02-07T10:00:00-05:00 2020-02-07T11:00:00-05:00 West Hall Department of Statistics Workshop / Seminar David Blei
HET Seminar | Large Signals in the Cosmological Collider (February 7, 2020 3:00pm) https://events.umich.edu/event/71950 71950-17903308@events.umich.edu Event Begins: Friday, February 7, 2020 3:00pm
Location: West Hall
Organized By: Leinweber Center for Theoretical Physics

Cosmological inflation gives a unique opportunity of probing physics at high energies. In particular, non-Gaussianities contain information on new physics particles being produced through the interaction of the inflatons. In this talk, I will discuss the size of such signals and highlight the scenarios in which we expect it to be observable.

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Lecture / Discussion Thu, 23 Jan 2020 11:53:59 -0500 2020-02-07T15:00:00-05:00 2020-02-07T16:00:00-05:00 West Hall Leinweber Center for Theoretical Physics Lecture / Discussion West Hall
The Michigan Anthropology Colloquia Series: “Historical and Environmental Impacts of Pastoralism: Examining the timing, tempo, and character of animal herding among Europe’s first farmers” (February 7, 2020 3:00pm) https://events.umich.edu/event/63286 63286-15612039@events.umich.edu Event Begins: Friday, February 7, 2020 3:00pm
Location: West Hall
Organized By: Department of Anthropology

"The spread of farming (ca. 8000 years ago) ushered in a new chapter in Europe’s cultural and environmental history. The translocation of plants and animals instigated the reorganization of economic activities that reshaped landscapes, communities, and even human biology. Within this broader context, I present new data from the earliest Neolithic villages on the Dalmatian coast of Croatia to explore the timing, tempo, and nature of Neolithic domestic animal management, and its long-term cultural, biological, and ecological effects in the Adriatic and throughout Europe."

The Michigan Anthropology Colloquia Series presents speakers on current topics in the field of anthropology

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Lecture / Discussion Thu, 09 Jan 2020 14:32:36 -0500 2020-02-07T15:00:00-05:00 2020-02-07T17:00:00-05:00 West Hall Department of Anthropology Lecture / Discussion West Hall
HEP-Astro Seminar | Low-energy Nuclear Recoils for Fun and Profit (February 10, 2020 4:00pm) https://events.umich.edu/event/71764 71764-17879416@events.umich.edu Event Begins: Monday, February 10, 2020 4:00pm
Location: West Hall
Organized By: Department of Physics

I will discuss the rapidly-changing panorama of experiments seeking to measure the faint signals produced by keV and sub-keV nuclear recoils in radiation detectors. The initial interest in this area originated from searches for dark matter WIMPs, but has expanded with the demonstration of coherent elastic neutrino-nucleus scattering. I will elaborate on the difficulties involved in understanding the response of detecting materials to this type of interaction, including some recent developments. I will also emphasize the opportunities for nuclear recoil detectors in areas beyond dark matter detection.

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Workshop / Seminar Mon, 10 Feb 2020 18:16:48 -0500 2020-02-10T16:00:00-05:00 2020-02-10T17:00:00-05:00 West Hall Department of Physics Workshop / Seminar West Hall
Distinguished Alumni Speaker Series: Earl Lawrence, Statistical Sciences, Los Alamos National Laboratory (February 14, 2020 10:00am) https://events.umich.edu/event/69918 69918-17483050@events.umich.edu Event Begins: Friday, February 14, 2020 10:00am
Location: West Hall
Organized By: Department of Statistics

Abstract:
Inference with computationally expensive physics models is a big part of statistics at Los Alamos National Laboratory. The first part of that talk will cover some well-known background on the statistical approach computer experiments. This will take place in the context of ongoing work for ChemCam, an instrument on the Mars rover Curiosity whose goal is to determine whether Mars ever had conditions that could have supported microbial life. ChemCam uses laser-induced breakdown spectroscopy to analyze the chemical composition of Martian soil and rocks. Our goal is to use the resulting spectra and a LANL-developed predictive model to estimate the elemental abundances from surface samples. The second part of the talk will cover new work to address computer experiments from exascale supercomputers. The next generation of supercomputers are expected to have I/O limitations relative to their computing ability: they will simulate more than they can save. This requires changes to our usual post-hoc analysis scheme. To address this, we are developing approaches to in situ statistical inference, statistical modeling that gets done inside simulations as they are running. Our early work considers modeling extremes for climate and space weather.

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Workshop / Seminar Wed, 05 Feb 2020 14:37:54 -0500 2020-02-14T10:00:00-05:00 2020-02-14T11:00:00-05:00 West Hall Department of Statistics Workshop / Seminar Earl Lawrence
HET Seminar | Globally consistent three-family Standard Models in F-theory (February 14, 2020 3:00pm) https://events.umich.edu/event/72170 72170-17948640@events.umich.edu Event Begins: Friday, February 14, 2020 3:00pm
Location: West Hall
Organized By: Leinweber Center for Theoretical Physics

We present recent advances in constructions of globally consistent F-theory compactifications with the exact chiral spectrum of the minimal supersymmetric Standard Model. We highlight the first such example and then turn to a subsequent systematic exploration of the landscape of F-theory three-family Standard Models with a gauge coupling unification. Employing algebraic geometry techniques, all global consistency conditions of these models can be reduced to a single geometric criterion on the base of the underlying elliptically fibered Calabi-Yau four-folds. For toric bases, this criterion only depends on an associated polytope and is satisfied for at least quadrillion bases, each of which defines a distinct compactification. We conclude by pointing out important outstanding issues.

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Lecture / Discussion Tue, 28 Jan 2020 14:33:28 -0500 2020-02-14T15:00:00-05:00 2020-02-14T16:00:00-05:00 West Hall Leinweber Center for Theoretical Physics Lecture / Discussion West Hall
The Michigan Anthropology Colloquia Series: "Aging Patterns in Wild Chimpanzees" (February 14, 2020 3:00pm) https://events.umich.edu/event/68799 68799-17153402@events.umich.edu Event Begins: Friday, February 14, 2020 3:00pm
Location: West Hall
Organized By: Department of Anthropology

"Although chimpanzees have been studied in the wild for almost 60 years, until recently, very little is known about how chimpanzees age both physically and socially. This is surprising given that they can live up to 50-60 years in the wild, well past the prime years of their life. In this talk, Dr. Machanda will highlight recent research from her long-term field site, the Kibale Chimpanzee Project, on the physical, physiological and social aging patterns of wild chimpanzees."

The Michigan Anthropology Colloquia Series presents speakers on current topics in the field of anthropology

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Lecture / Discussion Wed, 05 Feb 2020 09:45:56 -0500 2020-02-14T15:00:00-05:00 2020-02-14T17:00:00-05:00 West Hall Department of Anthropology Lecture / Discussion West Hall
HEP-Astro Seminar | Better Neutrinoless Double Beta Decay through Biochemistry (February 17, 2020 4:00pm) https://events.umich.edu/event/72039 72039-17916368@events.umich.edu Event Begins: Monday, February 17, 2020 4:00pm
Location: West Hall
Organized By: Department of Physics

The goal of future neutrinoless double beta decay experiments is to establish whether neutrino is its own antiparticle, by searching for an ultra-rare decay process with a half life that may be more than 10^27 years. Such a discovery would have major implications for cosmology and particle physics, but requires ton-scale detectors with backgrounds below 1 count per ton per year. This is a formidable technological challenge that has prompted consideration of unconventional solutions. I will discuss an approach being developed within the NEXT collaboration: high pressure xenon gas time projection chambers augmented with single molecule fluorescent imaging-based barium tagging. This combines techniques from the fields of biochemistry, super-resolution microscopy, organic synthesis and nuclear physics, possibly enabling the first effectively background-free, ton-scale neutrinoless double beta decay technology.

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Workshop / Seminar Mon, 17 Feb 2020 18:16:52 -0500 2020-02-17T16:00:00-05:00 2020-02-17T17:00:00-05:00 West Hall Department of Physics Workshop / Seminar West Hall
CRLT Physics Workshop | Moving the Needle: Shifting the Conversation Around Sexual Harassment (February 19, 2020 3:00pm) https://events.umich.edu/event/72372 72372-17998152@events.umich.edu Event Begins: Wednesday, February 19, 2020 3:00pm
Location: West Hall
Organized By: Physics Workshops & Conferences

Part research presentation, part embodied case study, and part community conversation, Moving the Needle: Shifting the Conversation around Sexual Harassment challenges participants to expand their understanding of what sexual harassment is, how it impacts individuals and communities, and what makes an environment ripe for its presence. Using the NASEM consensus study report as both grounding and springboard, this session eschews a "tips and tricks" workshop model, instead pointing attendees toward the ongoing reflective practices that individuals and communities will need to commit to in order to address the culturally embedded problem of sexual harassment.

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Workshop / Seminar Wed, 12 Feb 2020 11:35:07 -0500 2020-02-19T15:00:00-05:00 2020-02-19T17:00:00-05:00 West Hall Physics Workshops & Conferences Workshop / Seminar West Hall
Statistics Department Seminar Series: Bhaswar Bhattacharya, Assistant Professor, Department of Statistics, The Wharton School, University of Pennsylvania (February 21, 2020 10:00am) https://events.umich.edu/event/69919 69919-17483051@events.umich.edu Event Begins: Friday, February 21, 2020 10:00am
Location: West Hall
Organized By: Department of Statistics

Abstract: Two of the fundamental problems in non-parametric statistical inference are goodness-of-fit and two-sample testing. These two problems have been extensively studied and several multivariate tests have been proposed over the last thirty years, many of which are based on geometric graphs. These include, among several others, the celebrated Friedman-Rafsky two-sample test based on the minimal spanning tree and the K-nearest neighbor graphs, and the Bickel-Breiman spacings tests for goodness-of-fit. These tests are asymptotically distribution-free, universally consistent, and computationally efficient (both in sample size and in dimension), making them particularly attractive for modern statistical applications.

In this talk, we will derive the detection thresholds and limiting local power of these tests, thus providing a way to compare and justify the performance of these tests in various applications. Several interesting properties emerge, such as a curious phase transition in dimension 8, and a remarkable blessing of dimensionality in detecting scale changes.

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Workshop / Seminar Fri, 31 Jan 2020 16:34:15 -0500 2020-02-21T10:00:00-05:00 2020-02-21T11:00:00-05:00 West Hall Department of Statistics Workshop / Seminar Bhattacharya
Life In Graduate School Seminar | How to Find a Postdoc Position (February 21, 2020 12:00pm) https://events.umich.edu/event/72814 72814-18079325@events.umich.edu Event Begins: Friday, February 21, 2020 12:00pm
Location: West Hall
Organized By: Life in Graduate School Seminars

Three people with postdoc hunting experience in high energy experiment, computational condensed matter and experimental condensed matter will be invited and present their experience and lessons in finding postdoc positions.

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Workshop / Seminar Wed, 12 Feb 2020 13:31:43 -0500 2020-02-21T12:00:00-05:00 2020-02-21T13:00:00-05:00 West Hall Life in Graduate School Seminars Workshop / Seminar West Hall
HET Seminar | Conical singularities of G2-manifolds in mathematics and physics (February 21, 2020 3:00pm) https://events.umich.edu/event/72414 72414-18000399@events.umich.edu Event Begins: Friday, February 21, 2020 3:00pm
Location: West Hall
Organized By: Leinweber Center for Theoretical Physics

I will first give an introduction to and brief history of G2 geometry, to compare and contrast it to Calabi-Yau geometry. G2 manifolds are important in physics because they admit parallel spinors. It is of interest to construct compact examples with singularities. I will then give a survey of some of my work that is related to conical singularities of G2 manifolds, including: desingularization, deformation theory, and a possible strategy to construct such G2 conifolds. This will include some (separate) joint works with Dominic Joyce and Jason Lotay. No previous exposure to G2 geometry will be assumed, but the focus will be more mathematical than physical. I am hoping that some of you can teach me more physics during the day.

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Lecture / Discussion Mon, 03 Feb 2020 14:25:52 -0500 2020-02-21T15:00:00-05:00 2020-02-21T16:00:00-05:00 West Hall Leinweber Center for Theoretical Physics Lecture / Discussion West Hall
HEP-Astro Seminar | SuperTIGER in Antarctica: The Hunt for Ultra-Heavy Cosmic Rays (February 24, 2020 4:00pm) https://events.umich.edu/event/71016 71016-17768617@events.umich.edu Event Begins: Monday, February 24, 2020 4:00pm
Location: West Hall
Organized By: Department of Physics

The Super Trans-Iron Galactic Element Recorder (SuperTIGER) experiment measures the abundances of the merely relativistic and rare ultra-heavy cosmic rays (UHCR) beyond 26Fe produced in neutron-capture processes. Since the galactic cosmic rays do not point back to their sources we must search for other clues of their origins, and some handles on this are their energy spectra and their detailed elemental and isotopic compositions. The predecessor TIGER instrument made preliminary measurements of UHCR abundances resolving individual elements from 30Zn to 40Zr with two Antarctic flights (2001-2002, 2003-2004) totaling ~50 days. These data support a model of galactic cosmic-ray origins with a dominant contribution from OB association massive star clusters where the source material is enhanced by the outflow and super nova ejecta of these stars (~20%), and in which the more refractory elements that condense into dust grains are preferentially accelerated (~4x) over the volatile ones found as gas. SuperTIGER is over four times the size of TIGER, and with its first 55 day Antarctic flight (2012-2013) confirmed the TIGER findings through 40Zr with good statistics, and with the inclusion of data from a second flight (2019-2020) will extend preliminary UHCR abundance measurements through around 56Ba. Our UHCR observations to date show the galactic cosmic-ray source is enhanced by massive star products over solar system (~5 billion year old ISM), which means this comparatively fresh sample of galactic material can shed light on which heavier elements are significant products of massive stars and their associated supernova (SN) nucleosynthesis. This could help provide constraints on models for the synthesis of heavy elements in binary neutron star mergers (BNSM), for which evidence has been observed in ejected material seen in optical observations following LIGO event GW170817. BNSM are rarer than SN by several orders of magnitude or more, and are unlikely to have contributed to the observed fluxes of the UHCR. I will present on the SuperTIGER science, and the unique challenges and charms of scientific ballooning in Antarctica.

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Workshop / Seminar Mon, 24 Feb 2020 18:16:44 -0500 2020-02-24T16:00:00-05:00 2020-02-24T17:00:00-05:00 West Hall Department of Physics Workshop / Seminar West Hall
CM-AMO Seminar | Emergent Ultrafast Structural Dynamics in Complex Oxides and 2D Materials (February 25, 2020 4:00pm) https://events.umich.edu/event/72099 72099-17939962@events.umich.edu Event Begins: Tuesday, February 25, 2020 4:00pm
Location: West Hall
Organized By: Department of Physics

New properties emerge when material systems “scale up” via uniquely connected individual element, or “scale down” by reducing dimensionality and resulting in symmetry breaking. In this talk, I will show recent efforts to use light pulses at terahertz and x-ray frequencies to stimulate and track emergent dynamical properties of materials on ultrafast time scales. In the “scale-up” example, we observed a new set of collective excitations in polar vortices, named vortexons. A unique soft mode is identified as a pair of oscillating vortex cores that can be significantly tuned by thermal strain around room temperature. The discovery of tunable vortexons opens a new avenue for high-frequency dielectrics and optoelectronics applications. In the “scale-down” example, I will show the distinct structural dynamics of monolayer crystals WSe2 from their bulk counterparts. We found the absorbed optical photon energy is preferably coupled to the in-plane lattice vibrations within one picosecond whereas the out-of-plane lattice vibration amplitude remains unchanged during the first ten picoseconds, marking the distinct structural dynamics of monolayer crystals from their bulk counterparts. Looking into the future, the recent progress of developing multimodal, multiscale x-ray imaging platform will be discussed to go beyond the ensemble average for studying nanoscale ultrafast dynamics.

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Workshop / Seminar Tue, 25 Feb 2020 18:16:47 -0500 2020-02-25T16:00:00-05:00 2020-02-25T17:00:00-05:00 West Hall Department of Physics Workshop / Seminar West Hall
Department Colloquium | High Energy Physics Under The Higgs Lamppost (February 26, 2020 4:00pm) https://events.umich.edu/event/72100 72100-17939963@events.umich.edu Event Begins: Wednesday, February 26, 2020 4:00pm
Location: West Hall
Organized By: Department of Physics

For the past half a century, high energy physics has achieved uninterrupted successes. With the milestone discovery of the Higgs boson at the CERN Large Hadron Collider (LHC), high energy physics has entered a new era. The completion of the “Standard Model” (SM) implies, for the first time ever, that we have a relativistic, quantum-mechanical, self-consistent theoretical framework, conceivably valid up to exponentially high energies, even to the Planck scale. Yet, the SM leaves many unanswered questions both from the theoretical and observational perspectives, including the nature of the electroweak superconductivity and its phase transition, the hierarchy between the particle masses and between the observed scales, the nature of dark matter etc. There are thus compelling reasons to believe that new physics beyond the SM exits. We argue that the collective efforts of future high energy physics programs, in particular the future colliders, hold great promise to uncover the laws of nature to a deeper level.

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Workshop / Seminar Wed, 26 Feb 2020 18:17:07 -0500 2020-02-26T16:00:00-05:00 2020-02-26T17:00:00-05:00 West Hall Department of Physics Workshop / Seminar West Hall
Astronomy Colloquium Series Presents (February 27, 2020 3:30pm) https://events.umich.edu/event/70221 70221-17549990@events.umich.edu Event Begins: Thursday, February 27, 2020 3:30pm
Location: West Hall
Organized By: Department of Astronomy

“The Next Step in Deep Extragalactic Surveys”

The original rationale for the James Webb Space Telescope was detecting the first light in the Universe, meaning the first stars and galaxies. This goal has remained as one of the key drivers for the hardware development albeit with the footnote that only the first galaxies, not literally the first individual stars, can be detected. Two of the instruments teams, the NIRCam and NIRSpec Teams, have joined forces to produce a legacy survey with both multi-wavelength imaging and multi-object spectroscopy
using JWST. Expected results as illustrated by a mock catalog and a data challenge will be presented.


Please note: Should you require any accommodations to ensure equal access and opportunity related to this event please contact Stacy Tiburzi at 734-764-3440 or stibu@umich.edu.

Tea will be served beforehand from 3:00-3:30pm in Serpens.

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Lecture / Discussion Thu, 23 Jan 2020 13:05:14 -0500 2020-02-27T15:30:00-05:00 2020-02-27T16:30:00-05:00 West Hall Department of Astronomy Lecture / Discussion Dr. Marcia J. Rieke
CM Theory Seminar | Lattice Models and Monte Carlo Solutions for Quantum Criticality (February 27, 2020 4:00pm) https://events.umich.edu/event/72904 72904-18090326@events.umich.edu Event Begins: Thursday, February 27, 2020 4:00pm
Location: West Hall
Organized By: Department of Physics

In this talk, I will review recent developments in a priori and a posteriori numerical strategies in dealing with quantum many-body systems. Thanks to these philosophical and numerical advancements, novel paradigms in condensed matter and high energy physics such as non-Fermi-liquid, quantum criticality and emergent gauge-field coupled with matter field can be readily accessed with large-scale numerical simulations. These results in turn inspire further analytical and numerical progress towards the complete understanding of few important quantum many body physics problems.

References:
1. TOPICAL REVIEW, J. Phys.: Condens. Matter 31, 463001 (2019)
2. PNAS August 20, 2019 116 (34) 16760-16767
3. Phys. Rev. X 9, 021022 (2019)

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Workshop / Seminar Thu, 27 Feb 2020 18:16:59 -0500 2020-02-27T16:00:00-05:00 2020-02-27T17:00:00-05:00 West Hall Department of Physics Workshop / Seminar West Hall
HEP-Astro Seminar | Shedding 'Nu' Light on the Nature of Matter: The Search for Majorana Neutrinos (March 9, 2020 4:00pm) https://events.umich.edu/event/72101 72101-17939964@events.umich.edu Event Begins: Monday, March 9, 2020 4:00pm
Location: West Hall
Organized By: Department of Physics

Why is the universe dominated by matter, and not antimatter? Neutrinos, with their changing flavors and tiny masses, could provide an answer. If the neutrino is a Majorana particle, meaning that it is its own antiparticle, it would reveal the origin of the neutrino’s mass, demonstrate that lepton number is not a conserved symmetry of nature, and provide a path to leptogenesis in the early universe. To discover whether this is the case, we must search for neutrinoless double-beta decay, a theorized process that would occur in some nuclei. By searching for this extremely rare decay, we can explore new physics at energy scales that only existed in the seconds following the Big Bang.

Detecting this extremely rare process, however, requires us to build very large detectors with very low background rates. Experiments using germanium detectors, like the Majorana Demonstrator, which is currently running, and LEGEND-200, which is moving forward quickly, are a promising strategy to explore lifetimes of up to 10^{28} years. The current generation of experiments have achieved the lowest backgrounds of any technique, and have a clear path forward to move to the ton-scale. I’ll present recent results from the Demonstrator, an update on LEGEND-200’s progress, and prospects for LEGEND-1000.

Reaching lifetimes beyond 10^{28} years, however, will require new techniques and kiloton-scale detectors. NuDot is a proof-of-concept liquid scintillator experiment that will explore new techniques for isotope loading and background rejection in future detectors. I’ll discuss the progress we’ve already made in demonstrating how previously-ignored Cherenkov light signals can help us distinguish signal from background, and the technologies we’re developing with an eye towards the coming generations of experiments.

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Workshop / Seminar Mon, 09 Mar 2020 18:16:42 -0400 2020-03-09T16:00:00-04:00 2020-03-09T17:00:00-04:00 West Hall Department of Physics Workshop / Seminar West Hall
CM-AMO Seminar | Double Feature (March 10, 2020 4:00pm) https://events.umich.edu/event/72102 72102-17939965@events.umich.edu Event Begins: Tuesday, March 10, 2020 4:00pm
Location: West Hall
Organized By: Department of Physics

Pfaffian Formalism for Higher-Order Topological Insulators

Higher-order topological insulators (HOTIs) are characterized by gapless modes that occur at lower-dimensional boundaries than the conventional (first-order) topological insulators (TIs). For example, a 3D second-order TI has gapless 1D hinge modes and gapped 2D surface and gapped 3D bulk, whereas a 3D first-order TI has gapless 2D surface modes. In general, n-th order TI in d-dimensional space has gapless modes at (d-n) dimensional boundary.

In this work, we generalize the Pfaffian formalism, which has been playing an important role in the study of time-reversal invariant first-order topological insulators, to 3D chiral higher-order topological insulators protected by the product of four-fold rotational symmetry C_4 and the time-reversal symmetry T. This Pfaffian description reveals a deep and fundamental link between TIs and HOTIs, and allows important conclusions about TIs to be generalized to HOTIs. In particular, we can generalize Fu-Kane's parity criterion for TIs to HOTIs, and also present a general method to efficiently compute the Z_2 index of 3D chiral HOTIs without a global gauge.

Spatially Coherent Lasing in an Atomically-Thin Heterostructure

Atomically thin two-dimensional (2D) semiconductors are a promising gain media for the next generation of semiconductor lasers and nanophotonics. They have advantages over the traditional III-V semiconductors because they exhibit strong light-matter interaction, are flexible and compact, and allow easy integration with various substrates. Utilizing these advantages, we engineer a lasing device with a rotationally aligned WSe2-MoSe2 van der Waals heterostructure integrated with a one-dimensional (1D) silicon nitride (SiN) grating resonator. Angle-resolved micro-photoluminescence and spatial coherence measurements show signatures of lasing, which include bright emission intensity and formation of extended spatial coherence. This work establishes 2D semiconductor heterostructures as a new type of gain medium.

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Workshop / Seminar Mon, 09 Mar 2020 12:48:01 -0400 2020-03-10T16:00:00-04:00 2020-03-10T17:00:00-04:00 West Hall Department of Physics Workshop / Seminar West Hall
Statistics Department Seminar Series: Jimmy de la Torre, Professor, Human Communication, Development, and Information Sciences, University of Hong Kong (March 10, 2020 4:00pm) https://events.umich.edu/event/73305 73305-18190739@events.umich.edu Event Begins: Tuesday, March 10, 2020 4:00pm
Location: West Hall
Organized By: Department of Statistics

Abstract:
At present, many educational researchers and practitioners are highly interested in using educational assessment to improve student learning. However, it should be noted that assessment and learning can exist as two distinct components, and require a framework that would allow their integration into a single coherent system. The efficiency of such a system will depend on the extent that each component can be implemented adaptively. In this presentation, I will discuss using cognitive diagnosis modeling as a framework for developing a personalize assessment and learning system (PALS). I will discuss what cognitive diagnosis models (CDMs) are, what their unique features are, how they differ from other psychometric models, and how cognitive diagnosis computerized adaptive testing can further capitalize on the advantages of CDMs and make diagnostic testing more efficient. To build the complete PALS, an explicit instructional component that can facilitate learning is needed. I will discuss a number of important issues that need to addressed before a coherent and effective PALS can be built. The presentation will conclude with a discussion of possible future directions, and some of the challenges and recent developments in the area.

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Workshop / Seminar Tue, 25 Feb 2020 17:18:51 -0500 2020-03-10T16:00:00-04:00 2020-03-10T17:00:00-04:00 West Hall Department of Statistics Workshop / Seminar Jimmy de la Torre
Department Colloquium | Spins and Photons for Quantum Information Technologies (March 11, 2020 4:00pm) https://events.umich.edu/event/72134 72134-17942180@events.umich.edu Event Begins: Wednesday, March 11, 2020 4:00pm
Location: West Hall
Organized By: Department of Physics

Large scale quantum networks are envisioned for secure quantum communication between any two points on earth and for the creation of various cryptographic protocols. Quantum networks are also a model for distributed quantum computing. Quantum emitters featuring spin-photon interfaces and quantum memories are crucial elements in the nodes of such networks. Non-classical states of light, such as single and entangled photons, are also critical for novel quantum technologies. Key questions are therefore how to control the nodes of these networks and how to produce the desired photonic states. I will give and overview of the field and present our work focusing on the control of spins and the deterministic generation of highly entangled photonic states from spinful quantum emitters such as color centers and semiconductor quantum dots.

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Workshop / Seminar Wed, 11 Mar 2020 18:16:43 -0400 2020-03-11T16:00:00-04:00 2020-03-11T17:00:00-04:00 West Hall Department of Physics Workshop / Seminar West Hall
Canceled: Statistics Department Seminar Series: Daniel Almirall, Research Associate Professor, Survey Research Center, Institute for Social Research and Research Associate Professor of Statistics (by courtesy), University of Michigan (March 13, 2020 10:00am) https://events.umich.edu/event/69920 69920-17483052@events.umich.edu Event Begins: Friday, March 13, 2020 10:00am
Location: West Hall
Organized By: Department of Statistics

"Assessing Proximal Causal Effects on a Binary Outcome using Data from a Micro-randomized Trial: Case Study Design and Analysis"
Abstract

Emerging mobile health interventions aim to provide support whenever and wherever it is needed. This includes the provision of therapeutic support in (near) real time, as well as the provision of prompts that support the engagement of users in the mobile health application. A micro-randomized trial (MRT) is a new trial design that is useful for addressing scientific questions concerning the construction of mobile health applications of this type.  This talk describes the design and analysis of a micro-randomized trial conducted in collaboration with a local digital behavioral health company based in Ann Arbor. The purpose of the MRT was to (i) test the effectiveness of using a “push” prompt to engage users with a smartphone-based mobile health application, and (ii) to estimate whether the effectiveness of the prompt depends on the time at which the prompt is sent, as well as a prespecified set of user characteristics and other contextual factors. The trial’s primary outcome was binary, namely, whether or not the user engaged with the smartphone app over the next 24 hours. To analyze the data arising from this MRT, we developed a new approach to estimating the proximal causal effects that could accommodate a binary outcome. We describe the design of the MRT, the new data analysis method, and the results.
An explicit goal of this talk is to provide a friendly introduction to some of the ideas underlying the design and analysis of MRTs, as opposed to focusing on technical details of the method.

This is joint work with Susan A. Murphy, Inbal Nahum-Shani and Niranjan Bidargarddi.

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Workshop / Seminar Thu, 12 Mar 2020 09:41:05 -0400 2020-03-13T10:00:00-04:00 2020-03-13T11:00:00-04:00 West Hall Department of Statistics Workshop / Seminar Almirall,Daniel
CANCELED Karma Masters: the Personhood of Tumors and their People in Northern Thailand (March 13, 2020 3:00pm) https://events.umich.edu/event/73475 73475-18243514@events.umich.edu Event Begins: Friday, March 13, 2020 3:00pm
Location: West Hall
Organized By: Department of Anthropology

How can one make sense of ethical action when one is partly the other? In contexts of critical illness in Northern Thailand, many consider broken parts of themselves - from tumors to torn nerves to psychotic voices - to be beings returned to exact revenge for past wrongs. Many thus endeavor to treat their parts well, including their tumors. In this talk, I explore the implications of this hybrid personhood for living an ethical life, opening the possibility of ethical interaction, forgiveness, and love without individuality.

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Lecture / Discussion Thu, 12 Mar 2020 11:40:38 -0400 2020-03-13T15:00:00-04:00 2020-03-13T17:00:00-04:00 West Hall Department of Anthropology Lecture / Discussion karma masters
CANCELED: The Michigan Anthropology Colloquia Series: "The Breakup 2.1: The Ten Year Update" (March 27, 2020 3:00pm) https://events.umich.edu/event/68800 68800-17153403@events.umich.edu Event Begins: Friday, March 27, 2020 3:00pm
Location: West Hall
Organized By: Department of Anthropology

"Since 2007-2008, American undergraduates’ media ecology has changed – Facebook no longer looms as large in undergraduates’ daily media use, instead they tend to turn to Snapchat, Twitter, and Instagram more frequently. Yet this, it turns out, is not a difference that makes a difference when people break up with each other. The similarities in people’s breakup practices between 2008 and 2018 reveal that, regardless of what social media is used, American undergraduates turn to media in moments of breakup as ways to manage three complicated aspects of ending a relationship: untangling all the ways in which people signal intertwined lives, deciphering the quotidian unknowable of another person’s mind, and trying to control who knows what when. At the same time, there has been a degree of conventionalization around phatic connections, visible in a new set of terms – ghosting, sliding into DM, leaving someone on read -- and the accompanying increasingly common array of practices. In short, this talk explores what insights about stabilization and media change can one glean from interviewing US undergraduates about their mediated breakup practices every ten years."

The Michigan Anthropology Colloquia Series presents speakers on current topics in the field of anthropology

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Lecture / Discussion Thu, 12 Mar 2020 11:41:23 -0400 2020-03-27T15:00:00-04:00 2020-03-27T17:00:00-04:00 West Hall Department of Anthropology Lecture / Discussion West Hall
CANCELED: The Michigan Anthropology Colloquia Series (April 3, 2020 3:00pm) https://events.umich.edu/event/63228 63228-15595500@events.umich.edu Event Begins: Friday, April 3, 2020 3:00pm
Location: West Hall
Organized By: Department of Anthropology

The Michigan Anthropology Colloquia Series presents speakers on current topics in the field of anthropology

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Lecture / Discussion Thu, 12 Mar 2020 11:49:49 -0400 2020-04-03T15:00:00-04:00 2020-04-03T17:00:00-04:00 West Hall Department of Anthropology Lecture / Discussion West Hall
CANCELED: The Michigan Anthropology Colloquia Series (April 10, 2020 3:00pm) https://events.umich.edu/event/70094 70094-17530442@events.umich.edu Event Begins: Friday, April 10, 2020 3:00pm
Location: West Hall
Organized By: Department of Anthropology

The Michigan Anthropology Colloquia Series presents speakers on current topics in the field of anthropology

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Lecture / Discussion Thu, 12 Mar 2020 11:43:22 -0400 2020-04-10T15:00:00-04:00 2020-04-10T17:00:00-04:00 West Hall Department of Anthropology Lecture / Discussion West Hall