Public Abstract

DE-SC0011637: Theory of Particles, Fields and Strings

Award Status: Active

Institution: University of Washington, Seattle, WA
UEI: HD1WMN6945W6
DUNS: 605799469

Most Recent Award Date: 02/15/2023
Number of Support Periods: 9
PM: Kilgore, William

Current Budget Period: 05/01/2023 - 04/30/2024
Current Project Period: 11/01/2020 - 04/30/2024
PI: Sharpe, Stephen

Supplement Budget Period: N/A

Public Abstract

Title: Theory of Particles, Fields and Strings PI: Stephen Sharpe This is a proposal to fund the research of two faculty members in the Particles, Fields and Strings theory group in the Physics department at the University of Washington. Major efforts include studies of applications of gauge/string duality to QCD-related phenomena, properties of dense quark matter and related systems, developing new applications of lattice gauge theory, and studying astrophysical and cosmological implications of new physics, This research will facilitate the extraction of signatures of new physics from experiments, as well as the prediction of new phenomena within established quantum field theories. Prof. Stephen Sharpe will use the methods of effective field theory to address the several open problems. The first is to complete the development of a theoretical formalism needed to determine three-particle scattering amplitudes from the finite-volume spectrum of general field theories, and in particular QCD. This is needed to use the results from numerical simulations of lattice QCD in order to determine physically measurable quantities such as resonance parameters. The second is to develop a method to allow the first-principles calculation of weak amplitudes such as that for the K → 3π decay. The third is to generalize the formalism to four particles, which will open up the possibility of using lattice QCD to predict CP violation in some decays of charmed mesons, which has been experimentally measured. A additional project will study the use of twisted-mass fermions to calculate scattering and decay amplitudes. Such calculations are underway by the ETM collaboration, but so far a non-unitary set-up leads to poorly understood systematic errors. These errors will be studied using chiral perturbation theory. Sharpe will also continue his contributions to the Flavor Lattice Averaging Group and the Particle Data Group. A student working with Sharpe (previously working with Prof. Ann Nelson, now deceased) will continue his studies of astrophysical and cosmological signatures of physics beyond the standard model, such as axions. Prof. Laurence Yaffe will study non-perturbative issues in non-abelian gauge theories, using analytic and numerical methods. A major project will aim to understand whether there is a phase transition between low and high density QCD at zero (or low) temperature. This addresses the fundamental issue of what happens to strongly-interacting matter as one increases the density. The proposed work aims to shed light on this issue by studying the phase diagrams of scalar-gauge models in 2+1 and 3+1 dimensions which exhibit similar topological features including vortices and superfluid phases. In a second project, Yaffe aims to study the physics of heavy ion collisions using the gauge-gravity (holographic) correspondence to solve problems in a theory closely related to QCD. The problem then becomes one in five-dimensional general relativity, which, in previous work, Yaffe has solved numerically in the limit that transverse gradients across the Lorentz-contracted projectiles are ignored. The proposed work aims first to formulate of a consistent expansion of gravitational dynamics for holographic collisions when transverse gradients are small compared to longitudinal gradients, but not vanishing. This is the case in practical heavy-ion collisions. As a second step, this new formulation will be implemented numerically and used to interpret experimental results.

Title: Theory of Particles, Fields and Strings

PI: Stephen Sharpe

This is a proposal to fund the research of two faculty members in the Particles, Fields and Strings theory group in the Physics department at the University of Washington. Major efforts include studies of applications of gauge/string duality to QCD-related phenomena, properties of dense quark matter and related systems, developing new applications of lattice gauge theory, and studying astrophysical and cosmological implications of new physics, This research will facilitate the extraction of signatures of new physics from experiments, as well as the prediction of new phenomena within established quantum field theories.

Prof. Stephen Sharpe will use the methods of effective field theory to address the several open problems. The first is to complete the development of a theoretical formalism needed to determine three-particle scattering amplitudes from the finite-volume spectrum of general field theories, and in particular QCD. This is needed to use the results from numerical simulations of lattice QCD in order to determine physically measurable quantities such as resonance parameters. The second is to develop a method to allow the first-principles calculation of weak amplitudes such as that for the K → 3π decay. The third is to generalize the formalism to four particles, which will open up the possibility of using lattice QCD to predict CP violation in some decays of charmed mesons, which has been experimentally measured.

A additional project will study the use of twisted-mass fermions to calculate scattering and decay amplitudes. Such calculations are underway by the ETM collaboration, but so far a non-unitary set-up leads to poorly understood systematic errors. These errors will be studied using chiral perturbation theory.

Sharpe will also continue his contributions to the Flavor Lattice Averaging Group and the Particle Data Group.

A student working with Sharpe (previously working with Prof. Ann Nelson, now deceased) will continue his studies of astrophysical and cosmological signatures of physics beyond the standard model, such as axions.

Prof. Laurence Yaffe will study non-perturbative issues in non-abelian gauge theories, using analytic and numerical methods. A major project will aim to understand whether there is a phase transition between low and high density QCD at zero (or low) temperature. This addresses the fundamental issue of what happens to strongly-interacting matter as one increases the density. The proposed work aims to shed light on this issue by studying the phase diagrams of scalar-gauge models in 2+1 and 3+1 dimensions which exhibit similar topological features including vortices and superfluid phases.

In a second project, Yaffe aims to study the physics of heavy ion collisions using the gauge-gravity (holographic) correspondence to solve problems in a theory closely related to QCD. The problem then becomes one in five-dimensional general relativity, which, in previous work, Yaffe has solved numerically in the limit that transverse gradients across the Lorentz-contracted projectiles are ignored. The proposed work aims first to formulate of a consistent expansion of gravitational dynamics for holographic collisions when transverse gradients are small compared to longitudinal gradients, but not vanishing. This is the case in practical heavy-ion collisions. As a second step, this new formulation will be implemented numerically and used to interpret experimental results.