Zhen Liu (University of Minnesota) : Physics potential of high energy muon collider | 1/22/21
Momentum has been accumulating to consider high energy muon collider as a future high energy collider possibility, especially on the US soil. Muon collider has unique physics cases, both as a Higgs factory as well as a high energy lepton collider. In this talk, I will review the overall physics pictures for muon colliders and discuss these unique physics cases. In particular, I will show a recent study where we rethink about WIMP DM and their testability at colliders. We show that through the new signature and channels proposed by us, we can draw some conclusive statements about WIMP DM, which can serve as a physics driver case for high energy muon colliders.
Andreas Karch (UTexas) : Information Transfer with a Gravitating Bath | 2/5/21
Recent progress in our understanding of black hole evaporation has mostly occurred in the context of black holes coupled to an external, non-gravitating bath. In order to compare and contrast to what happens to black holes in asymptotically flat space it is imperative to understand whether the non-gravitating bath is just some external spectator or actively changes the physics in this system. Equivalently, one can wonder to what extent the results generalize to the case of a gravitating bath. We use Randall-Sundrum braneworlds, and their holographic interpretation, to answer this important question.
Irina Mocioiu (Penn State ) : Looking for new physics in the neutrino sector | 2/12/21
I will briefly review the motivation for the existence of new physics in the neutrino sector and I will describe a few different ways of looking for such new physics.
Oren Bergman (Israel Institute of Technology) : Generalized symmetries and holography in supersymmetric Chern-Simons theories | 2/19/21
In this talk I will revisit holographic duality for maximally supersymmetric 3d Chern-Simons gauge theories. By revealing the generalized global symmetries of the field theories I will provide a unified picture of holography that incorporates all known theories.
Vijay Balasubramanian (UPenn) : Quantum Complexity, Integrability, and Chaos | 3/4/21
The states of quantum systems grow in complexity over time as entanglement spreads between degrees of freedom. Following ideas in computer science, we formulate the complexity of time evolution as the length of the shortest geodesic on the unitary group manifold between the identity and the time evolution operator, and use the SYK family of models with N fermions to study this quantity in free, integrable, and chaotic systems. In all cases, the complexity initially grows linearly in time, and the shortest path lies along the physical time evolution. This linear growth is eventually truncated by "shortcuts" on the unitary manifold that are shorter than the physical time evolution. We explicitly locate such shortcuts and hence show that in the free theory, shortcuts occur at a time of O(N^1/2), truncating complexity growth at this scale. We also find an explicit operator which "fast-forwards" time evolution with this complexity. In a class of integrable theories, we show that shortcuts appear in a time upper bounded by O(poly(N)), again truncating complexity growth. Finally, in chaotic theories we argue that shortcuts do not occur until exponential times, after which it becomes possible to find infinitesimally nearby fixed-complexity approximations to the time evolution operator. We relate these results to the Eigenstate Complexity Hypothesis, a new criterion on the spectrum of energy eigenstates that guarantees an exponential increase of complexity over time that is consistent with maximal chaos.
Mark Goodsell (LPTHE, Jussieu, Paris) : How to constrain your favo(u)rite theory | 3/12/21
LHC searches typically publish limits on not only specific models, but specific scenarios within a model. For a theorist to confront a different model or scenario to the latest limits therefore requires a whole chain of tools and calculations to map from Lagrangian parameters to data. With the immense range of possible models now under consideration this begs for automation and genericity. Along with an overview of the state of the art of this toolchain, I will review my recent work, in particular on generic unitarity calculations in the context of the SARAH package; and on recasting both prompt and long-lived LHC searches for electroweakinos so that they can be applied to any model.
Aleksey Cherman (University of Minnesota) : Lifetimes of (near-)eternal false vacua | 3/19/21
We're used to the idea that false vacua in quantum field theory can always decay with some finite rate. I'll explain why the title of the talk makes sense anyway by discussing some simple QFTs which have false vacua which can live an arbitrarily long time. Their lifetime is set by the short-distance details of the theory, rather than the familiar long-distance ingridients discussed in textbook presentations of false-vacuum decay. The talk will focus on examples in 2d and 4d, with the 4d example having the same propagating degrees of freedom as conventional QCD, and the (near) eternal false vacua will turn out to be consequences of (nearly exact) (d-3)-form global symmetries.
Jonathan Heckman (UPenn) : A Model of Couplings | 4/9/21
String theory predicts that the couplings of Nature descend from dynamical fields. All known string-motivated particle physics models also come with a wide range of possible extra sectors. It is common to posit that such moduli are frozen to a background value, and that extra sectors can be nearly completely decoupled. In this talk we show that performing a partial trace over all sectors other than the visible sector generically puts the visible sector in a mixed state, with coupling constants drawn from a quantum statistical ensemble. An observable consequence of this entanglement between visible and extra sectors is that the reported values of couplings will appear to have an irreducible variance. There is a consequent interplay between energy range and precision of an experiment that allows an extended reach for new physics.
