Theory Seminar

QCD trace anomaly and the proton mass problem

The trace anomaly of QCD is fundamentally important as it imparts mass to hadrons and nuclei, hence to the visible universe.
In this talk, I will introduce two recent developments regarding the anomaly. In the first part, I discuss the decomposition of the trace anomaly into the quark and gluon parts. This is a well-defined field theoretical problem that can be addressed in perturbation theory. In the second part, I will explain how to measure the gluon condensate $\lange P|F^{\mu\nu}F_{\mu\nu}|P\rangle$, which constitutes the major part of the trace anomaly, in near-threshold $J/\psi$ production in electron-proton scattering. After giving a review of the existing theoretical approaches and the experimental situation, I will explain our new approaches to both photo-production and lepto-production.
 
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Virasoro blocks and quasimodular forms

Abstract : We analyse Virasoro blocks as an expansion in heavy exchange dimension. For the one point torus block and the four point sphere block each order in the expansion can be written as polynomials in the Eisenstein series. These polynomials are further constrained to satisfy a recursion relation, which can be re-expressed as a noiseless KPZ equation for the blocks. This structure can be utilized along with the Zamolodchikov recursions to develop an algorithm to construct blocks in the heavy regime. We apply our results to find the corrections to averaged heavy-heavy-light OPE coefficients.

https://uky.zoom.us/j/99297500671

 

Recording: https://uky.zoom.us/rec/share/AsE8BaVwSqD1qJKmwnYn39GqIfhuLzqQjpTYGxwQB9C00GKOFaZtuuRURVNvSzTn.YsBz5vtRuhDXhbwZ


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Location:
zoom
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Towards Microscopic Models of Big Bang Cosmology

 In this talk, we review an approach to describing cosmological

physics using ordinary AdS/CFT, where the cosmological physics is the

effective description of an end-of-the-world brane which cuts off the

second asymptotic region of a two-sided black hole. The worldvolume

geometry of the brane is an FRW big-bang/big-crunch spacetime. In

favorable circumstances, the brane acts as a Randall-Sundrum Planck

brane so that gravity localizes. We describe a microscopic construction

for such an end-of-the-world brane with localized gravity in AdS/CFT,

starting from N=4 SYM theory. We suggest specific microscopic states of

N=4 SYM theory that may encode the physics in a four-dimensional

cosmological spacetime.

 
 
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Calculating Nature Naturally

Studying nature directly from fundamental degrees of freedom is often computationally limited by 
physical characteristics of exponentially growing configuration (Hilbert) spaces with particle number 
and signal-to-noise problems. This leaves many systems of interest to nuclear and particle physics 
intractable for known algorithms with current and foreseeable classical computational resources. By 
leveraging their natural capacity to describe entangled many-body states, the use of quantum systems 
themselves to form a computational framework is envisioned to be advantageous.  In this talk, I will 
share a developing perspective on the entanglement structure of quantum fields and discuss implications 
for their efficient simulation on quantum computational architectures. 
 
 
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Location:
zoom
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Breaking of Discrete and Continuous Symmetries in Coupled SYK or Tensor Models

A large number of Majorana fermions with interactions coupling four of them at a time can exhibit interesting quantum dynamics. Models of this kind include the Sachdev-Ye-Kitaev (SYK) model, where the coefficients of quartic interactions are randomly distributed, and the Tensor models, where they respect continuous symmetries. These models exhibit approximate invariance under scaling of the time and have power law fall-off of the correlation functions.

In this talk we will discuss a pair of SYK or Tensor models coupled by the quartic interactions, and show that they produce a richer set of phenomena. These include a line of fixed points, where critical exponents vary along the line and formally acquire imaginary parts outside it. For one sign of the coupling constant, the approximate scale invariance continues to hold. For the other, a gap opens in the energy spectrum, resulting in exponential fall-off of correlation functions. This is indicative of breaking of a discrete symmetry. Thus, our quantum mechanical model exhibits dynamical phenomena characteristic of higher dimensional quantum field theories. Furthermore, the gapped phase of our model may be dual to a certain traversable wormhole in two-dimensional space-time.

The talk will end with a similar discussion of a pair of complex SYK models coupled by a quartic interaction which preserves the U(1) x U(1) symmetry. For a range of parameters, this model gives rise to breaking of one of the U(1) symmetries. This is demonstrated via an analysis of the large N Dyson-Schwinger equations, as well as by Exact Diagonalizations of the finite N Hamiltonians.

Zoom link : https://uky.zoom.us/j/97553578130

 

Recording: https://uky.zoom.us/rec/play/rTWoRCvq8JEfgyyhHKGAlcV2a6XRi8DwaILPRPBY_Y…-?continueMode=true

Date:
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Event Series:

Inflation and Alternative Early Universe Scenarios in Light of the Swampland Constraints

Abstract :  The inflationary scenario has become the standard
paradigm of early universe cosmology, but it is not

the only scenario which can explain the currently

available data on the large-scale structure of the

universe. I will compare inflation with two alternative

scenarios, the "Ekpyrotic bounce" scenario, and

"String Gas Cosmology". I will then argue that

there are severe obstacles to embed inflationary

cosmology into quantum gravity, and that the

alternative scenarios may be more promising"  
 
 
Date:
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Location:
Zoom
Event Series:

New parameterizations and applications of nucleon electromagnetic form factors

In the past decade, renewed interest in the nucleon electromagnetic form factors was sparked by new measurements of electron-proton scattering at low Q^2 by the A1 Collaboration and of the proton charge radius in muonic hydrogen by the CREMA Collaboration. Subsequent theoretical developments re-examined longstanding assumptions on the parameterizations of these form factors. In this talk, I will review some of these developments, then present new parameterizations of the form factors that are the result of work in the past few years. Finally, I will outline applications of these form factors in both atomic physics and for the US program of precision neutrino measurements.

 

Recorded talk and slides: https://www.dropbox.com/sh/sek9spcry22xorw/AABHxLmJwsrae-E0zEftz7HWa?dl=0

Date:
-
Location:
online

New parameterizations and applications of nucleon electromagnetic form factors

In the past decade, renewed interest in the nucleon electromagnetic form factors was sparked by new measurements of electron-proton scattering at low Q^2 by the A1 Collaboration and of the proton charge radius in muonic hydrogen by the CREMA Collaboration. Subsequent theoretical developments re-examined longstanding assumptions on the parameterizations of these form factors. In this talk, I will review some of these developments, then present new parameterizations of the form factors that are the result of work in the past few years. Finally, I will outline applications of these form factors in both atomic physics and for the US program of precision neutrino measurements.

 

Recorded talk and slides: https://www.dropbox.com/sh/sek9spcry22xorw/AABHxLmJwsrae-E0zEftz7HWa?dl=0

Date:
-
Location:
online