During the semester we have a high energy seminar and a lunch seminar. In addition to these two seminars we participate in a joint theoretical high energy theory seminar in Newe Shalom. The joint seminar takes place on Tuesdays from 10:30 until 13:30 and includes two talks and lunch. This seminar is attended by the high energy groups of all the Israeli institutions and usually attracts a crowd of roughly twenty participants.
Title: Deviations from factorization in SYK
Abstract: Recently, there has been a revived interest in multi-boundary holographic systems and the contribution of Euclidean wormholes, in particular in Jackiw-Teitelboim (JT) gravity. We consider Sachdev-Ye-Kitaev (SYK) as a microscopic model for such holographic systems. While in JT gravity the non-factorizing contributions come from geometric wormholes, we get that in SYK there are much larger contributions. We give a diagrammatic description of all those leading contributions, analogous to Feynman diagrams. The holographic behavior is particularly interesting for fixed SYK couplings due to factorization, and we comment on that as well.
Title: 6d/5d dualities from Higgsing
Abstract: (Based on https://arxiv.org/abs/2103.02799 with a slightly different title.)
5d supersymmetric gauge theories are sometimes UV completed by 6d SCFTs. One such example is the duality between the affine quiver gauge theory in 5d and 6d so-called “conformal matter” theory labeled by a D or E type lie algebra. In this talk we will see that starting from this duality and performing nilpotent Higgsing on both sides, one can generate a huge set of 6d/5d dualities. The 6d side often involves a twist along a compactification by a discrete symmetry. The 5d side does not always admit a gauge theory description, but sometimes does and involves an exceptional gauge group including G or F type or an exceptional (non-fundamental) matter content. As a byproduct, we get a web-based formalism to compute the Nekrasov partition function for some of the exceptional 5d gauge theories.
Title: The Onset of Quantum Chaos
Abstract: We study the quantum version of the Lyapunov exponent in disordered theories. Generically the quantum Lyapunov exponent can only be computed in isolated CFTs, and so not much is known about the way in which chaos grows as we deform the theory away from weak coupling. In this talk we describe families of theories in which the disorder coupling is an exactly marginal deformation, allowing us to follow the Lyapunov exponent from weak to strong coupling. We find surprising behaviors in some cases, including a discontinuous transition into chaos, which we compare to the expectation from classical chaos. We also describe a new method allowing for computations in nontrivial CFTs deformed by disorder.
Title: Large Charge Phases of CFTs
Abstract: CFTs with additional global symmetries often possess significant simplification in the regime in which the charges associated with the global symmetries become large. In this talk, we review some recent developments in the subject of CFTs atlarge global charges. We present results that are based on two papers: The first, (based on https://arxiv.org/abs/2102.12583)involves the study of constraints due to spontaneously broken boosts and dilatation symmetries around heavy states, and the implications of the symmetry breaking for the spectrum of CFTs. In the second, we study boundary conformal field theories (BCFTs) witha global U(1) symmetry at the large charge regime.
Title: Complexity for CFTs in General Dimensions
Abstract: In this talk, I will discuss circuit complexity for conformal field theory states in arbitrary dimensions. The circuits start from a primary state and move along a unitary representation of the Lorentzian conformal group. I will consider different choices of distance functions and explain how they can be understood in terms of the geometry of coadjoint orbits of the conformal group. This analysis will highlight a connection between the coadjoint orbits of the conformal group and timelike geodesics in anti-de Sitter spacetimes, with interesting implications regarding the holographic complexity proposals. This is based on a work with Nicolas Chagnet, Jan de Boer and Claire Zukowski.
Title: Emergent symmetries in 3d and compactification from 5d
Abstract: We study the phenomenon of symmetry enhancement in quantum field theories in three dimensions, where the global symmetry of a model is larger in the IR than in the UV. We focus on supersymmetric theories where the situation is more tractable,and find an organizing principle for such enhancements in the form of compactifications of 5d theories on Riemann surfaces with flux in their global symmetries. We illustrate this by considering the compactification of the so-called 5d Seiberg SCFTs on tori,and obtain 3d theories with enhanced IR symmetries given by the 5d symmetry preserved by the chosen flux.
Title: The structure of the initial conditions of the universe
Abstract: I will review what we know about the initial conditions of the universe from observations. Then, I will explain how they arise within the framework of inflation, and describe recent progress in classifying (or “bootstrapping”) the possible correlation functions between primordial fluctuations. Finally, time permitting, I will touch upon work in progress trying to apply the bootstrap philosophy to more general cosmologies.