Happening @ Michigan https://events.umich.edu/list/rss RSS Feed for Happening @ Michigan Events at the University of Michigan. HET BROWN BAG | New Physics and the Black Hole Mass Gap (September 30, 2020 12:00pm) https://events.umich.edu/event/77301 77301-19836071@events.umich.edu Event Begins: Wednesday, September 30, 2020 12:00pm
Location: Off Campus Location
Organized By: Leinweber Center for Theoretical Physics

In this talk I will demonstrate the potential of the black hole mass gap to probe new physics. The mass gap, in which no black holes can be formed, is a standard prediction of stellar structure theory. I will show that new physics that couples to the Standard Model can act as an additional source of energy loss in the cores of population-III stars, dramatically altering their evolution, resulting in large shifts of the gap. The gravitational wave observations by the LIGO/Virgo collaboration will bring the edges of the black hole mass gap in sight in the coming years, making this a promising novel probe of new physics.

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Lecture / Discussion Tue, 06 Oct 2020 14:11:20 -0400 2020-09-30T12:00:00-04:00 2020-09-30T13:00:00-04:00 Off Campus Location Leinweber Center for Theoretical Physics Lecture / Discussion
HET Brown Bag | Detecting terrestrial dark matter traffic jams (November 4, 2020 12:00pm) https://events.umich.edu/event/79063 79063-20184347@events.umich.edu Event Begins: Wednesday, November 4, 2020 12:00pm
Location: Off Campus Location
Organized By: Leinweber Center for Theoretical Physics

Subcomponent dark matter having large interactions with the standard model or with itself can accumulate terrestrially over the age of the earth leading to massive build-ups. This thermalized population is too cold to be visible in traditional direct detection. In this talk I outline a few detection strategies including accelerating this slow dark matter with metastable nuclear isomers or with electrostatic accelerators like LUNA. Intriguingly such a terrestrial component could explain the neutron bottle-beam anomaly and can cause anomalous heating in cryogenic detectors.

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Lecture / Discussion Thu, 05 Nov 2020 14:52:45 -0500 2020-11-04T12:00:00-05:00 2020-11-04T13:00:00-05:00 Off Campus Location Leinweber Center for Theoretical Physics Lecture / Discussion
HET Brown Bag Seminar | UV/IR Mixing and the Hierarchy Problem (November 11, 2020 12:00pm) https://events.umich.edu/event/79274 79274-20262820@events.umich.edu Event Begins: Wednesday, November 11, 2020 12:00pm
Location: Off Campus Location
Organized By: Leinweber Center for Theoretical Physics

The persistence of the hierarchy problem points to a violation of effective field theory expectations. A compelling possibility is that this results from a physical violation of EFT, which may arise from correlations between UV and IR physics—as is broadly demanded by gravity. I will discuss Noncommutative Field Theory as a toy model of UV/IR mixing, where an emergent infrared scale is generated from ultraviolet dynamics. I’ll explore a variety of such theories to develop a picture of how this feature appears, and to glean lessons to guide the realization of UV/IR mixing in more realistic theories.

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Lecture / Discussion Mon, 23 Nov 2020 11:23:52 -0500 2020-11-11T12:00:00-05:00 2020-11-11T13:00:00-05:00 Off Campus Location Leinweber Center for Theoretical Physics Lecture / Discussion
HET Brown Bag Seminar | When High Energy Meets High Intensity (November 25, 2020 12:00pm) https://events.umich.edu/event/79475 79475-20335628@events.umich.edu Event Begins: Wednesday, November 25, 2020 12:00pm
Location: Off Campus Location
Organized By: Leinweber Center for Theoretical Physics

TBD

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Lecture / Discussion Mon, 07 Dec 2020 11:19:35 -0500 2020-11-25T12:00:00-05:00 2020-11-25T13:00:00-05:00 Off Campus Location Leinweber Center for Theoretical Physics Lecture / Discussion
HET Brown Bag | Scattering Amplitudes for Monopoles: Pairwise Little Group and Pairwise Helicity (December 9, 2020 12:00pm) https://events.umich.edu/event/79741 79741-20483901@events.umich.edu Event Begins: Wednesday, December 9, 2020 12:00pm
Location: Off Campus Location
Organized By: Leinweber Center for Theoretical Physics

On-shell methods are particularly suited for exploring the scattering of electrically and magnetically charged objects, for which there is no local and Lorentz invariant Lagrangian description. In this talk we show how to construct a Lorentz-invariant S-matrix for the scattering of electrically and magnetically charged particles, without ever having to refer to a Dirac string. A key ingredient is a revision of our fundamental understanding of multi-particle representations of the Poincar\'e group. Surprisingly, the asymptotic states for electric-magnetic scattering transform with an additional little group phase, associated with pairs of electrically and magnetically charged particles. The corresponding ``pairwise helicity'' is identified with the quantized ``cross product'' of charges, e_1 g_2 - e_2 g_1, for every charge-monopole pair, and represents the extra angular momentum stored in the asymptotic electromagnetic field. We define a new kind of pairwise spinor-helicity variable, which serves as an additional building block for electric-magnetic scattering amplitudes. We then construct the most general 3-point S-matrix elements, as well as the full partial wave decomposition for the 2\to 2 fermion-monopole S-matrix. In particular, we derive the famous helicity flip in the lowest partial wave as a simple consequence of a generalized spin-helicity selection rule, as well as the full angular dependence for the higher partial waves. Our construction provides a significant new achievement for the on-shell program, succeeding where the Lagrangian description has so far failed.

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Lecture / Discussion Mon, 07 Dec 2020 07:53:41 -0500 2020-12-09T12:00:00-05:00 2020-12-09T13:00:00-05:00 Off Campus Location Leinweber Center for Theoretical Physics Lecture / Discussion
HET Brown Bag | Looking forward to new Physics with FASER (December 16, 2020 12:00pm) https://events.umich.edu/event/79760 79760-20486020@events.umich.edu Event Begins: Wednesday, December 16, 2020 12:00pm
Location: Off Campus Location
Organized By: Leinweber Center for Theoretical Physics

Physics searches and measurements at high-energy collider experiments traditionally focus on the high-pT region. However, if particles are light and weakly-coupled, this focus may be completely misguided: light particles are typically highly collimated around the beam line, allowing sensitive searches with small detectors, and even extremely weakly-coupled particles may be produced in large numbers there. The recently approved FASER experiment will use the opportunity and extend the LHC's physic potential by searching for long-lived particles and studying neutrino interactions at TeV energies. In this talk, I will present the physics potential of FASER for new physics searches, neutrino physics, QCD as well as cosmic ray and cosmic neutrino measurement, aiming to stimulate a fruitful discussion with my audience.

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Lecture / Discussion Thu, 10 Dec 2020 11:19:12 -0500 2020-12-16T12:00:00-05:00 2020-12-16T13:00:00-05:00 Off Campus Location Leinweber Center for Theoretical Physics Lecture / Discussion
HET Brown Bag Seminar | Neutrino Oscillations: Where we are, where we’re going (January 20, 2021 12:00pm) https://events.umich.edu/event/80667 80667-20769661@events.umich.edu Event Begins: Wednesday, January 20, 2021 12:00pm
Location: Off Campus Location
Organized By: Leinweber Center for Theoretical Physics

In the last several decades, neutrino oscillations have gone from an experimental anomaly to robust evidence for beyond-the-Standard-Model physics. While much has been learned since the first experiments, several aspects of oscillations remain unknown, including the degree to which CP is violated in the lepton sector. In this talk, I will explore our current knowledge of neutrino oscillations, and discuss how the next generation of experiments can further enlighten us. These upcoming experiments have the ability to test “standard” and BSM neutrino oscillation hypotheses, as well as a multitude of non-neutrino BSM physics scenarios.

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Lecture / Discussion Tue, 12 Jan 2021 16:04:36 -0500 2021-01-20T12:00:00-05:00 2021-01-20T13:00:00-05:00 Off Campus Location Leinweber Center for Theoretical Physics Lecture / Discussion
HET Brown Bag Seminar | Adventures in Non-Supersymmetric String Theory (January 28, 2021 12:00pm) https://events.umich.edu/event/81150 81150-20858312@events.umich.edu Event Begins: Thursday, January 28, 2021 12:00pm
Location: Off Campus Location
Organized By: Leinweber Center for Theoretical Physics

It has long been known that there exist strings with supersymmetry on the world sheet, but not in spacetime. These include the well-known Type 0 strings, as well as a series of seven heterotic strings, all of which are obtained by imposing unconventional GSO projections. Besides these classic examples, relatively little is known about the full space of non-SUSY theories. One of the reasons why non-SUSY strings have remained understudied is the fact that nearly all of them have closed string tachyons, and hence do not admit ten-dimensional flat space as a stable vacuum. The goal of this talk is two-fold. First, using recent advances in condensed matter theory, we will reinterpret GSO projections in terms of topological phases of matter, thereby providing a framework for the classification of non-SUSY strings. Having done so, we will show that for all non-SUSY theories in which a tachyon exists, it can be condensed to give a (meta)stable lower-dimensional vacuum. In many cases, these stable vacua will be two-dimensional string theories already known in the literature.

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Lecture / Discussion Fri, 05 Feb 2021 10:22:43 -0500 2021-01-28T12:00:00-05:00 2021-01-28T13:00:00-05:00 Off Campus Location Leinweber Center for Theoretical Physics Lecture / Discussion
HET Brown Bag | The black hole spectrum in (super)gravity (February 4, 2021 12:00pm) https://events.umich.edu/event/81152 81152-20858314@events.umich.edu Event Begins: Thursday, February 4, 2021 12:00pm
Location: Off Campus Location
Organized By: Leinweber Center for Theoretical Physics

The talk will focus on the spectrum of near-extremal black holes in gravity and near-BPS black holes in supergravity. For concreteness, we will study cases in asymptotically four-dimensional flat space and three-dimensional Anti-de Sitter. This will be done by analyzing quantum effects near the horizon captured by an emergent Jackiw-Teitelboim mode at low temperatures. This will allow us to systematically study questions such as the extremal degeneracy and the size of the gap in the black hole spectrum, which can be compared to some string theory constructions.

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Lecture / Discussion Tue, 09 Feb 2021 14:49:08 -0500 2021-02-04T12:00:00-05:00 2021-02-04T13:00:00-05:00 Off Campus Location Leinweber Center for Theoretical Physics Lecture / Discussion
HET Brown Bag Seminar | Supersymmetry and Computation (February 11, 2021 12:00pm) https://events.umich.edu/event/81151 81151-20949383@events.umich.edu Event Begins: Thursday, February 11, 2021 12:00pm
Location:
Organized By: Leinweber Center for Theoretical Physics

I will discuss various aspects of the interplay between supersymmetry and the theory of classical and quantum computation. I will first introduce basic elements of computational complexity theory and show that the Witten index problem is #P-complete and thus intractable. I will then discuss the role of supersymmetry in defining a special subclass of quantum algorithms and describe the "quantum Witten machine," a quantum algorithm for the generalized Witten index.

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Lecture / Discussion Thu, 04 Feb 2021 09:21:29 -0500 2021-02-11T12:00:00-05:00 2021-02-11T13:00:00-05:00 Leinweber Center for Theoretical Physics Lecture / Discussion
HET Brown Bag | Consistency of the Standard Model Effective Field Theory (February 24, 2021 12:00pm) https://events.umich.edu/event/82009 82009-21004775@events.umich.edu Event Begins: Wednesday, February 24, 2021 12:00pm
Location: Off Campus Location
Organized By: Leinweber Center for Theoretical Physics

In this talk I will describe how the analytic structure of scattering amplitudes impose non-trivial constraints on the standard model effective field theory (SMEFT). For example, in the bosonic sector, I will explain how the bounds imply restrictions on the size of certain CP-odd operators by associated CP-even couplings. This result can be exploited to reveal a connection between constraints derived at colliders and limits on the neutron electric dipole moment. Further, I will demonstrate that in the fermionic sector, IR consistency requires that flavour violating operators are bounded by the flavour conserving variants. While most results will be presented for the SMEFT at dimension 8, I will also describe recent progress allowing a subset of the results to be lifted to dimension 6.

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Lecture / Discussion Wed, 10 Mar 2021 15:19:30 -0500 2021-02-24T12:00:00-05:00 2021-02-24T13:00:00-05:00 Off Campus Location Leinweber Center for Theoretical Physics Lecture / Discussion
HET Brown Bag Seminar | Worldsheet g-function and AdS/CFT (February 25, 2021 12:00pm) https://events.umich.edu/event/81216 81216-20872040@events.umich.edu Event Begins: Thursday, February 25, 2021 12:00pm
Location: Off Campus Location
Organized By: Leinweber Center for Theoretical Physics

Recently there has been new progress in computing a class of observables in N=4 supersymmetric Yang-Mills theory in four dimensions at finite 't Hooft coupling, ranging from correlation functions of "baryonic" operators to leading instanton effects at large N. All those examples share two common features: 1. At weak coupling, they can be computed by an overlap between a matrix product state and an eigenstate of the Hamiltonian of an integrable 1+1d spin chain. 2. Using AdS/CFT, they can be mapped to so-called g-functions on the string worldsheet and can be computed exactly as a function of 't Hooft coupling. After explaining the basic ideas, I will showcase several applications.

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Lecture / Discussion Fri, 26 Feb 2021 12:23:17 -0500 2021-02-25T12:00:00-05:00 2021-02-25T13:00:00-05:00 Off Campus Location Leinweber Center for Theoretical Physics Lecture / Discussion
HET Brown Bag Seminar | Loops and Trees in Generic 4d EFT up to operator dimension 8 (March 10, 2021 12:00pm) https://events.umich.edu/event/82342 82342-21068624@events.umich.edu Event Begins: Wednesday, March 10, 2021 12:00pm
Location: Off Campus Location
Organized By: Leinweber Center for Theoretical Physics

I will talk about the tree and one-loop behavior in a generic 4d EFT of massless scalars, fermions, and vectors, with a particular eye to the high-energy limit of the Standard Model EFT at operator dimensions 6 and 8. First, I will show how to classify the possible Lorentz structures of operators and the subset of these that can arise at tree-level in a weakly coupled UV completion. Then I will show how operators contribute to tree and one-loop helicity amplitudes, exploring the impact of non-renormalization theorems through dimension 8 and helicity selection rules through the full one loop amplitude.

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Lecture / Discussion Thu, 11 Mar 2021 08:22:56 -0500 2021-03-10T12:00:00-05:00 2021-03-10T13:00:00-05:00 Off Campus Location Leinweber Center for Theoretical Physics Lecture / Discussion
HET Brown Bag Seminar | Kaluza-Klein Spectrometry for String Theory Compactifications (March 11, 2021 12:00pm) https://events.umich.edu/event/81153 81153-20858315@events.umich.edu Event Begins: Thursday, March 11, 2021 12:00pm
Location: Off Campus Location
Organized By: Leinweber Center for Theoretical Physics

In this talk, I will present a powerful new method for computing the Kaluza-Klein spectrum of string theory compactifications. This includes geometries with little to no remaining symmetries, hardly accessible to standard methods. I will discuss various applications of this method, including to non-supersymmetric AdS_4 vacua. As I will show, some of these AdS vacua are unstable due to tachyonic Kaluza-Klein modes, while others can be proven to be perturbatively stable. Finally, I will also discuss applications to supersymmetric AdS vacua and the AdS/CFT correspondence

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Lecture / Discussion Wed, 24 Mar 2021 08:10:26 -0400 2021-03-11T12:00:00-05:00 2021-03-11T13:00:00-05:00 Off Campus Location Leinweber Center for Theoretical Physics Lecture / Discussion
HET Brown Bag Seminar | Freeze-in versus Glaciation: freezing into a thermalized hidden sector (March 24, 2021 12:00pm) https://events.umich.edu/event/82238 82238-21060438@events.umich.edu Event Begins: Wednesday, March 24, 2021 12:00pm
Location: Off Campus Location
Organized By: Leinweber Center for Theoretical Physics

The standard freeze-in paradigm has a hidden UV sensitivity in that the initial DM population is assumed to be exactly zero. We explore how a pre-existing population of DM, either alone or as part of a thermalized dark sector, affects the dynamics of freeze-in. The UV sensitivity of this more general scenario, which we dub “glaciation”, is manifested in the dependence of the late-time relic abundance on the size of the initial population. We dispense rather quickly with the case of a stand-alone initial DM abundance, which simply leads to an offset in the relic abundance compared to the standard scenario, but we find rich and interesting dynamics in the case of a pre-existing thermalized dark sector. Our results have important consequences for direct detection experiments searching for freeze-in dark matter.

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Lecture / Discussion Tue, 30 Mar 2021 12:15:28 -0400 2021-03-24T12:00:00-04:00 2021-03-24T13:00:00-04:00 Off Campus Location Leinweber Center for Theoretical Physics Lecture / Discussion