Christoph Uhlemann (Michigan) : Aspects of five-dimensional superconformal field theories | 9/21//19
Five-dimensional superconformal field theories (5d SCFTs) play an interesting role in the general understanding of quantum field theory. They often provide strongly-coupled UV fixed points with remarkable features for perturbatively non-renormalizable gauge theories, which makes them interesting in their own right. Moreover, prominent lower-dimensional theories can be obtained by compactification from five-dimensional parent theories, and this perspective has led to numerous new insights. A fruitful interplay between string theory and quantum field theory methods has led to a coherent and thorough understanding of 5d SCFTs, and I will review recent developments in this context.
Ian Low (Northwestern) : The Future Frontier of Higgs Physics | 9/20/19
I will summarize what we don't already know about the 125 GeV Higgs boson and discuss directions for future investigation.
Zohar Komogodski (Stonybrook) : Extremal Correlators | 9/20/19
I will review some of the properties of extremal correlators. I will then describe the large charge limit of some N=2 theories in four dimensions. I will derive a dual random matrix description which admits a ’t Hooft expansion, which is dual to the double scaling limit of the gauge theory. I will compute the analytic and non-analytic terms in the ’t Hooft coupling and give some physical interpretation of the results
Bob Wald (UChicago) : Quantum Superposition of Massive Bodies | 10/18/19
We analyse a gedankenexperiment previously considered by Mari et al. that involves quantum superpositions of charged and/or massive bodies ("particles'') under the control of the observers, Alice and Bob. In the electromagnetic case, we show that the quantization of electromagnetic radiation (which causes decoherence of Alice's particle) and vacuum fluctuations of the electromagnetic field (which limits Bob's ability to localize his particle to better than a charge-radius) both are essential for avoiding apparent paradoxes with causality and complementarity. We then analyze the gravitational version of this gedankenexperiment. We show that the analysis
of the gravitational case is in complete parallel with the electromagnetic case provided that gravitational radiation is quantized and that vacuum fluctuations limit the localization of a particle to no better than a Planck length. This provides support for the view that (linearized) gravity should have a quantum field description.
Andreas von Manteuffel (Michigan State) : Two-loop mixed EW-QCD corrections to Drell-Yan lepton pair production | 10/25/19
Drell-Yan lepton pair production is a key process for precision physics at the Large Hadron Collider. In this talk I will consider the two-loop amplitudes required for the full O(\alpha \alpha_s) corrections to this process and discuss the calculation of the required Feynman integrals. While algebraic linear combinations of the integrals fulfill $\;epsilon$ decoupled differential equations, the symbol letters are provably non-rationalizable. I will show that they can nevertheless be integrated in terms of conventional multiple polylogarithms with algebraic arguments, which allow for fast and stable numerical evaluations.
Elena Caceres (U Texas) : Constraining higher-order gravities with subregion duality | 11/1/19
In higher derivative theories, gravity can propagate faster or slower than light. This fact has consequences for holographic constructs in AdS/CFT. In this talk, I will focus on the causal and entanglement wedges. I will argue that, in higher derivative theories, these wedges should be constructed using the fastest mode instead of null rays. I will show that using this proposal, the property of causal wedge inclusion, i.e. the fact that the causal wedge must be contained in the entanglement wedge, leads to more stringent constraints on the couplings than those imposed by hyperbolicity and boundary causality. I will elaborate on the implications of these results.
Maxim Pospelov (Perimeter) : EDMs and CP-odd nucleon forces | 11/8/19
I will describe two recent papers [in the last stages of preparation]:
1. Paramagnetic EDMs (usually interpreted as electron electric dipole moment) have seen a lot of experimental progress in the last decade. I evaluate the sensitivity of electron EDM experiments to hadronic CP-violation, finding an independent limit on e.g. theta-term at the level of 10^(-8).
2. In the second part of my talk I revisit the question of CP-odd axion-nucleon vertices, relevant for the searches of the axionic 5th force.
Tom Faulkner (UIUC) : A Canonical Purification for the Entanglement Wedge Cross-Section | 11/15/19
I will discuss a new entry in the AdS/CFT dictionary relating a geometric quantity called the entanglement wedge cross-section to the entropy of a canonical purification. I will also speculate about a connection to the split property in QFT.
Adrienne Erickcek (U North Carolina) : Illuminating the Early Universe with Dark Matter Minihalos | 11/22/19
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.
Mark Trodden (U Pennsylvania) : Extending the Double Copy | 12/4/19
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.
