Theory Seminar

Large N Expansion and Strings Out of Equilibrium.

We use the methods of large N expansion in non-equilibrium many-body systems with matrix degrees of freedom, to identify some universal features of the anticipated dual description in terms of non-equilibrium string perturbation theory.  We find that string worldsheets exhibit a triple decomposition, associated with the forward and backward branches of the Schinger-Keldysh time contour, and with the point at the "end of time" where the two branches meet.

Zoom link :https://uky.zoom.us/j/85746922492?pwd=d0hyUndXVEF6NUw0ejA4clVwVHFPQT09

Password: 693452

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Inside the Hologram: The bulk observer's experience

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I will present a holographic framework for reconstructing the experience of bulk observers in AdS/CFT. In particular, I will show how to recover the proper time and energy distribution measured along bulk worldlines, directly in the CFT via a universal, background-independent prescription. For an observer falling into an eternal AdS black hole, the proposal resolves a conceptual puzzle raised by Marolf and Wall. Notably, the prescription does not rely on an external dynamical Hamiltonian or the AdS boundary conditions and is, therefore, outlining a general framework for the emergence of time.

 

Recording: https://uky.zoom.us/rec/share/MNYWXm-2WNwA-aWN4jxOzjfQp5Kf3UkpZXL-awLVccEdkni4Rg3wA5UJR0gPoAJl.sihdRZAuILIOn9rO

 

 

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Quantum Codes and Conformal Field Theories

There is a rich web of connections between classical error-correcting codes, Euclidean lattices, and chiral conformal field theories.  I will explain an analogous relationship between quantum error-correcting codes, Lorentzian lattices, and nonchiral CFTs arising from toroidal compactifications of strings.  Specifically, I will show how quantum stabilizer codes are embedded in the operator algebras of associated Narain CFTs.   With respect to “code” CFTs, the constraints of modular invariance reduce to simple algebraic equations.  
Solving these equations provides many examples of physically distinct CFTs with the same spectrum; we also find many solutions that do not correspond to any code CFT, and likely do not correspond to any CFT at all.  This exposes a crucial limitation of the conformal bootstrap program – that in general, a solution of the bootstrap equations implies neither the existence nor the uniqueness of a corresponding CFT.  
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Machine learning as a discovery tool in hep-th

Machine learning provides a new tool for analyzing Big Data and Small Data in mathematics and theoretical physics. In this talk, I discuss two case studies. The first predicts the volume of the knot complement of hyperbolic knots from the Jones polynomial. The second predicts the masses of baryons such as the proton and neutron from knowledge only of the meson spectrum and distinguishes between different composition hypotheses for exotic QCD resonances. Both investigations point to the existence of new analytic formulae.
 
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Gravity from Averaging CFTs

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I will explore the idea that certain theories of gravity in Anti-de

Sitter space are dual to an average over an ensemble of quantum

theories, rather than to a specific quantum theory.  I will describe

an average over Narain’s family of two-dimensional conformal field

theories which describe free bosons on a torus, and compute the

partition function using the Siegel-Weil formula.  The result takes

the form of a sum over geometries as one would expect in a theory of

gravity.  But the gravitational theory looks more like a Chern-Simons

theory than like Einstein gravity.

 

Zoom: https://uky.zoom.us/j/94475622713

 

Recording: https://uky.zoom.us/rec/share/QQujHqM5YhGd-8VMLiGw6DUPPftssuHC4vi3h_n-x27Jwbc-wBTtv5TIxvEdpxzg.EVGdktXNhdQIWDgV


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A Covariant Lattice and its Application to String Bits

We explore a possibility of constructing lattice theories from a basic principle where lattice is viewed as a restriction of the continuum. This allows us to derive a discrete derivative, nonlocal on the lattice, that satisfies Liebniz rule. As a result a theorem related to locality follows which states that any local equation in the classical continuum theory holds true also locally on the lattice. Using this one is able to preserve a remnant of all the global and gauge symmetries, which, in two dimensions, can be lifted to include local diffeomorphism and Weyl symmetries as well. Consequently, one is able, for example, to carry out classical BRST construction of covariant sting bits (for the first time).



This lattice derivative is, in some sense, similar to SLAC derivative discussed earlier in the literature. However, we point out that its action suffers from branch cut ambiguities while acting on Fourier basis. This may indicate that quantization is not straightforward and may have to be done entirely in position space.

https://uky.zoom.us/j/98298147329

 

Recording: https://uky.zoom.us/rec/share/DcpK6kBPxVZpLYYGq4IjzCN34vxUxAh5F1huXQEzfdMD9kDf3J6xvZJLVs_AaKLg.zG6RFkPs8EmzYdpQ

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Complexity and Conformal Field Theory

Viewing fundamental physics processes through the lenses of quantum information storage and processing is a new frontier in gravity and quantum field theory. Much of what we have learnt in the past decade builds on the notion of entanglement and its entropy. The latter quantifies how hard it is to store a quantum-many body state of interest on a classical computer. Complexity is a new player in the high-energy physics context and quantifies how hard it is to prepare a quantum-many body state using limited resources. Learning from the success story of entanglement entropy, establishing universal results on complexity in two-dimensional conformal field theories should open many new research directions, including finding a precise gravity dual. I will discuss recent progress on this problem reported in 2005.02415 and 2007.11555 with Flory.

 

Recording: https://uky.zoom.us/rec/share/UsIbWHaXi4DJ04EDDouJbMB0CPmJUvY0bCQSf5jIhZNJBPJE5-TTbj-Oq4NWVtYr.xSXcjGefvoy1F8o2

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Email allicsiva@uky.edu for zoom info
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Asymptotic Symmetries & Celestial CFT

 

Abstract:

A universal relationship between asymptotic symmetries, QFT soft theorems, and low energy observables has reinvigorated attempts at flat space holography.  In this talk we introduce a map from 4d S-matrix elements to 2d correlators in the putative dual Celestial CFT.  In particular, we will focus on recent progress towards understanding elements of the IR triangle from the perspective of our Celestial CFT.

 

Note the unusual start time!

 

Recording: https://uky.zoom.us/rec/play/-Jlt4l4Zj7OW4tELdw9Yj4zi5p4rvUrm3OLcosykvV…

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Towards an infrared realization of dS_2 in AdS_2

We explore the possibility of embedding a dS_2 universe in the interior of an asymptotically AdS_2 spacetime. We consider the problem macroscopically, discussing various constraints from gravitational models. We also discuss potential microscopic paths guided by the perspective of AdS_2 holography. 

Zoom Link : https://uky.zoom.us/j/95988631148

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