With the direct detection of gravitational waves (GWs) from LIGO in 2016, and recent evidence from the NANOGrav collaboration for a stochastic GW background, GW astronomy is becoming an important tool for understanding the universe. Recently it has been shown that axion dark matter (DM) experiments can extend the search for GWs to much higher frequencies, kHz < f < GHz. In this talk we'll discuss how light DM detectors utilizing single phonon excitations in crystal targets, previously shown to be sensitive to a wide variety of DM candidates, are also sensitive to GWs in the frequency range, THz < f < 100 THz, corresponding to the range of optical phonon energies, meV < \omega < 100 meV. We'll discuss the mechanism by which high frequency GWs can generate single phonons, and consider the detector sensitivity of different target materials. Lastly, we'll discuss how these high frequency GWs may be produced in processes such as black hole inspirals and superradiance.

]]>When do two different looking quantum field theories describe the same physics? This is essentially asking when the quantum field theories are isomorphic. In the case of topological quantum field theories, there are sometimes a way to determine them via topological invariants. For a superconformal field theory, what would be the minimal set of “invariants” to determine when they are isomorphic? I will discuss some approaches to this question in the context of superconformal field theories in four and six dimensions. Utilizing 4d class S theories that also admits 6d (1,0) SCFT origins, I will explain how a certain class of 4d N=2 SCFTs, which a priori look like distinct theories, can be shown to describe the same physics. I will further explain how the 6d (1,0) origin sheds light on the 3d duality.

]]>Locality and unitary forces scattering amplitudes to factorize when taking the momentum of one of the external particles to zero. This factorization has proven very useful for recursion relations for amplitudes at high multplicities. The recursion can break down, however, when the amplitude contains a pole at infinity. In this talk we are going to make modest step towards a prescription of “unitarity at infinity”. We do this by studying on-shell diagrams, which are on-shell gauge invariant objects that appear as cuts of loop integrands in the context of generalized unitarity and serve as building blocks for amplitudes in recursion relations. In the dual formulation, they are associated with cells of the positive Grassmannian. We will describe on-shell diagrams in N<4 supersymmetric Yang-Mills (SYM) theory and show that there exists a diagrammatic operation that corresponds to sending one of the momenta to infinity.

]]>Given that axions are both a promising candidate to solve problems in the Standard Model and are ubiquitous in quantum gravity, it is crucial to accurately determine their signatures. In this talk, we discuss how the axion's compact field space leads to interesting interactions with topological defects, specifically monopoles and strings. In the case of monopoles, we show that, due to the Witten effect, axions interacting with abelian gauge fields generate a potential for the axion from loops of magnetic monopoles, and discuss a simple phenomenological example where this potential is the dominant contribution to the axion mass. In the case of strings, we discuss superconductivity from massless chiral excitations along the string. We show that bulk fermions do not need to become massless in the core of the string for there to be trapped massless excitations, and explore the counterintuitive phase structure of these zero modes, which become less localized to the string as the mass is increased.

]]>Electrons within galaxy groups and clusters Thomson scatter CMB photons out of and into the line of sight, an effect known as patchy screening. In this talk, I will propose a new "temperature inversion" (TI) estimator to detect this effect. I will show that the estimator is unbiased to foregrounds (CIB, tSZ, kSZ). This is a big advantage over the traditional “quadratic estimator” for the patchy screening which is biased by foregrounds and CMB lensing. I will then present the first detection of the patchy screening effect through cross-correlation of the Atacama Cosmology Telescope and Planck satellite CMB data, and unWISE galaxies. This measurement, exceeding 7-sigma in significance, directly probes the distribution of electrons around these galaxies. I will discuss the prospects of this technique to constrain galaxy evolution models. Finally, I will present a vision for some of the exciting science opportunities to come in the coming decade.

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]]>I will describe ongoing work on the thermodynamics of quantum fields in far-from-equilibrium states. The key tool is modular flow, a nonstandard time-evolution map defined relative to a choice of state, which makes that state "look thermal." Famously, the modular flow for the Minkowski vacuum in the Rindler wedge is a geometric boost, which is one way of stating the Unruh effect. In this talk, I will outline a characterization of the settings in which modular flow is geometrically local, i.e., a complete list of "generalized Unruh effects" in arbitrary spacetimes and for arbitrary quantum field theories. The arguments involve analytic manipulations of position-space correlators, which may be of independent interest to those of you working on amplitudes.

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