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.

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` ` Sun Mon Tue Wed Thu Fri Sat Luca Delacretaz (Chicago) 10:30 am Luca Delacretaz (Chicago) Dec 6 @ 10:30 am – 11:30 am Title: Thermalization and Chaos in 1+1d QFTs Abstract: Nonintegrable QFTs are expected to thermalize and exhibit emergence of hydrodynamics and chaos. In weakly coupled QFTs, kinetic theory captures local thermalization; such a versatile tool is absent … Alba Grassi (Geneva) 12:00 pm Alba Grassi (Geneva) Dec 6 @ 12:00 pm – 1:00 pm Title: Holographic thermal correlators from supersymmetric instantons.Abstract: I will present an exact formula for the thermal scalar two-point function in four-dimensional holographic conformal field theories. The problem of finding it reduces to the analysis of … Sergei Dubovsky (NYU) 10:30 am Sergei Dubovsky (NYU) Dec 13 @ 10:30 am – 11:30 am Title: Quantization of the Zigzag ModelAbstract: The zigzag model is a relativistic integrable N-body system describing the leading high-energy semiclassical dynamics on the worldsheet of long confining strings in massive adjoint two-dimensional QCD. I will discuss quantization … Uri Kol (Harvard) 12:00 pm Uri Kol (Harvard) Dec 13 @ 12:00 pm – 1:00 pm Title: Classical Physics from Scattering AmplitudesAbstract:Recent years have seen great progress in our understanding of the emergence of classical physics from quantum scattering amplitudes, in both gauge and gravitational theories. This program is motivated by several reasons. …

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**Title**: Thermalization and Chaos in 1+1d QFTs

**Abstract**: Nonintegrable QFTs are expected to thermalize and exhibit emergence of hydrodynamics and chaos. In weakly coupled QFTs, kinetic theory captures local thermalization; such a versatile tool is absent away from the perturbative regime. I will present analytical and numerical results using nonperturbative methods to study thermalization at strong coupling. I will show how requiring causality in the thermal state leads to strong analytic constraints on the thermodynamics and out-of-equilibrium properties of any relativistic 1+1d QFT. I will then discuss Lightcone Conformal Truncation (LCT) as a powerful numerical tool to study thermalization of QFTs. Applied to phi^{}^4 theory in 1+1d, LCT reveals eigenstate thermalization and onset of random matrix universality at any nonzero coupling. Finally, I will discuss prospects for observing the emergence of hydrodynamics in QFTs using Hamiltonian truncation.

**Title**: Holographic thermal correlators from supersymmetric instantons.

**Abstract**: I will present an exact formula for the thermal scalar two-point function in four-dimensional holographic conformal field theories. The problem of finding it reduces to the analysis of the wave equation on the AdS-Schwarzschild background. The two-point function is computed from the connection coefficients of the Heun equation, which can be expressed in terms of the Nekrasov-Shatashvili partition function of an SU(2) supersymmetric gauge theory with four fundamental hypermultiplets. At large spin the instanton expansion of the thermal two-point function directly maps to the light-cone bootstrap analysis of the heavy-light four-point function. Using this connection, we obtain the OPE data of heavy-light double-twist operators directly from the Nekrasov-Shatashvili function.

**Title**: Quantization of the Zigzag Model

**Abstract**: The zigzag model is a relativistic integrable N-body system describing the leading high-energy semiclassical dynamics on the worldsheet of long confining strings in massive adjoint two-dimensional QCD. I will discuss quantization of this model. I will demonstrate that to achieve a consistent quantization of the model it is necessary to account for the non-trivial geometry of phase space. The resulting Poincaré invariant integrable quantum theory is a close cousin of TT¯ deformed models.

__Title__: Classical Physics from Scattering Amplitudes

__Abstract__:

Recent years have seen great progress in our understanding of the emergence of classical physics from quantum scattering amplitudes, in both gauge and gravitational theories. This program is motivated by several reasons. One of them is the idea that amplitudes manifest certain physical properties that are not apparent otherwise. As an example of this idea, I will show how the double copy property of scattering amplitudes constrains the structure of the worldline EFT.

**Title**: Field theory defects through double scaling limits

**Abstract**: Defect operators in field theory are very interesting for a number of reasons. Drawing inspiration from techniques which have been very recently applied to uncover interesting properties of sectors of operators with large charge under a global symmetry, we will study defects in the Wilson-Fisher fixed point near d=4,6 dimensions. Combining with localization, we will also use a double-scaling limit for certain Wilson loops in N=2 supersymmetric theories in 4d which allows to make exact statements at finite N.

**Title**: Bounds on Regge growth of flat space scattering from bounds on chaos

**Abstract**: We will explain a study of four-point functions of scalars, conserved currents, and stress tensors in a conformal field theory, generated by a local contact term in the dual bulk description, in two different causal configurations. The first is the standard Regge configuration in which the chaos bound applies. The second is the ‘causally scattering configuration’ in which the correlator develops a bulk point singularity. We find an expression for the coefficient of the bulk point singularity in terms of the bulk S matrix of the dual bulk metric, gauge fields, and scalars, and use it to determine the Regge scaling of the correlator on the causally scattering sheet in terms of the Regge growth of this S matrix. We then demonstrate that the Regge scaling on this sheet is governed by the same power as in the standard Regge configuration, and so is constrained by the chaos bound, which turns out to be violated unless the bulk flat space S matrix grows no faster than $s^2$ in the Regge limit. It follows that in the context of the AdS/CFT correspondence, the chaos bound applied to the boundary field theory implies that the S matrices of the dual bulk scalars, gauge fields, and gravitons obey the Classical Regge Growth (CRG) conjecture. We will also comment on recent progress in the same direction.

**Title**: Line defects in CFTs: from magnets to Wilson lines

**Abstract**: Line defects describe one-dimensional probes of a quantum field theory. Physically interesting examples can be found in different systems, ranging from condensed matter physics to gauge theories. In this talk, I will briefly review some recent results on the renormalization group approach to line defects in CFTs. I will then discuss some applications. In particular, I will discuss some interesting RG flows for Wilson lines in massless gauge theories, and their relation with an instability to screening by charged fields.

**Title**: Global symmetry breaking and defect conformal manifolds

**Abstract**:In the presence of exactly marginal operators, one can deform a conformal field theory to other such theories, forming a space of theories living on what’s known as the conformal manifold. In a theory with conformal defects, one may be able to retain the bulk theory but transform the defect along what I’ll call the “defect conformal manifold”. This requires the existence of exactly marginal defect operators. A simple setting where this happens is in the presence of a global symmetry broken by the defect. The broken symmetry current gives rise to an exactly marginal defect operator and a defect conformal manifold which is the symmetry breaking coset. This simple observation lets us derive an exact identity for integrated 4-point functions of the marginal defect operator which is highly nontrivial. We implement this in several models where the 4-point functions have been previously calculated.

**Title**: Effective theory of sub-maximal chaos

**Abstract**: I will present progress on formulating an effective description of the quantum butterfly effect at late times. After discussing maximally chaotic examples, I will turn to a particular limit of the SYK model that displays sub-maximal chaos and discuss its effective description. The final results can be matched in detail to stringy corrections to the gravitational eikonal S-matrix in holographic CFTs, including a stringy Regge trajectory, bulk to boundary propagators, and multi-string effects that are unexplored holographically.