WITP Summer Student Symposium 2020
21 Aug 2020, Online
Abstracts
Naman Agarwal
Holographic Complexity in 10-Dimensions
In the regime of puzzles surrounding black holes and their perplexing properties, a promising solution is introduced by the concept of Quantum Holographic Complexity. Even though the theory and the conjectures it draws are relatively new, it has attracted a huge amount of attention since it has been introduced. In the talk, we will have a brief look into what is Holographic complexity and how do we go about defining it. We are especially interested in looking at its behaviour in the full ten-dimensional picture of String Theory and spacetimes it deals with. We will also look at AdS/CFT correspondence, motivating it and understanding how it lets us calculate and study complexity.
Wade Cowie
Fast Fourier Transforms and Phase Transitions
We are interested in studying phase transitions in graphene. I will
discuss the basic structure of the problem and point out some of the
calculation difficulties. Fast Fourier Transforms are known to be
computationally efficient, but they are not normally used to study
phase transitions. I will explain why not, and describe a method we
have developed to use FFT’s to solve an integral equation that models
the behaviour of graphene, and exhibits a phase transition. I will
compare the speed and accuracy of our method with a calculation that
uses conventional integration methods.
Brad Cownden
Pumped Scalars in Global AdS
Pumped scalar fields on asymptotically AdSd+1 backgrounds
are related
to strongly coupled field theories in d-dimensions with
time-dependent Hamiltonians through the AdS/CFT correspondence. While
these systems have been examined numerically, a perturbative description
that captures the weakly turbulent transfer of energy to
short length scales has yet to be developed. In this talk, we describe
the work done in [1912.07143] towards achieving this perturbative
description. Unlike previous examinations in the literature, which
focused on time-independent boundary conditions, the existence of a
time-dependent term in the boundary condition for the scalar field
means the scalar field solution contains two distinct parts:
normalizable and non-normalizable modes. We study the effects of
different choices for the boundary term on the time evolution of the
first-order part of the scalar field. In each case, we calculate
possible resonances from the produced from interactions between
normalizable and non-normalizable modes, and — for certain choices of
mass and dimension — evaluate the terms numerically. We show that the
activation of a time-dependent boundary term results in multiple
possible resonances, none of which are naturally vanishing.
Bailey Forster
Collective Modes in Anisotropic Plasmas: Part 2
The behaviour of quarks can be studied through high velocity nuclei
collisions which produce a plasma. Experimental results suggest that
these plasmas reach equilibrium much faster than expected. This
phenomenon can be explained by the presence of unstable or imaginary
modes in the dispersion equations. Our goal is to search for
collective modes in anisotropic plasmas. This talk will discuss the
formulation of dispersion equations by inverting tensor propagators
using tensor decomposition and will describe how an appropriate tensor
basis is constructed. The dispersion equations of anisotropic systems
must be solved numerically. This presents a technical problem which
can be addressed with a Nyquist analysis.
Michael Grehan
Calculating Holographic Complexity of Numerical Black Hole Collapse
in AdS
Hawking radiation gave rise to the information paradox which has led
physicists to believe a better understanding of gravity is needed to
create a theory of quantum gravity. Calculating information
quantities, such as complexity, that correspond to a black hole may
help provide this understanding. Previous work to calculate
holographic complexity in AdS has been done in a simplified manner
that allowed analytical solutions. Our work calculates the complexity
using numerical methods, in a non-simplified manner, which will allow
us to better understand the quantum state of a forming black hole. We
performed holographic complexity calculations for both the action and
the volume conjecture, in both 4 and 5 dimensional AdS.
Sofiya Makar
Collective Modes in Anisotropic Plasmas: Part 1
Our goal is to study collective effects in quark-gluon plasmas. The
general idea is to understand how single-particle properties are
modified when particles live together in a plasma. Specifically, we
want to determine the resonance condition which corresponds to optimal
frequencies at which an individual particle becomes most aware of its
neighbours. After a brief introduction, this talk will focus on
numerical techniques that are used to obtain the resonance condition.
Brett Meggison
Anisotropic Graphene
We study the effects of anisotropic strain of the graphene lattice on
the critical coupling constant. If the critical coupling constant can
be decreased with anisotropy, it will make certain electronic
applications of graphene physically realizable. We use a low energy
effective field theory, relaxing many of the strict approximations
made by previous studies in an attempt to help resolve conflicting
results. We find that increasing anisotropy results in an increase in
the value of the critical coupling.
Christopher Phillips
Equilibration of Quark-Gluon Plasmas
Heavy ion collisions are a useful tool in the study of the fundamental
interactions between subatomic particles. The nuclei in these ions are
composed of quarks and gluons, whose interactions are governed by
quantum chromodynamics (QCD). A high energy heavy ion collision
produces a plasma of excited gluons. The energy and pressure of this
plasma can be extracted from the solution to the classical equation of
motion. However, this calculation gives unphysical behaviour —
it predicts that the system does not equilibrate, but in fact moves
farther away from equilibrium with time. This happens because
time-dependent quantum fluctuations rapidly overpower the classical
solutions. A resummation technique has been developed to include all
contributions at next-to-leading order. The technique has not yet been
ap- plied to QCD, because of the technical difficulty of the
calculation. I will show results for a scalar φ4 theory
in Minkowski space, which show the expected physical behaviour of
equilibration. We are currently working on the corresponding
calculation in an expanding coordinate system, which is more
physically relevant to the study of a quark-gluon plasma. Some
preliminary results will be shown.
Shawna Skelton
Range of Entanglements in Spin Chains
Models with long range interactions, such as a modified transverse
Ising model, are a promising way to examine how local and total
entanglement relate. Quantitatively, entanglement of formation is a
suited measure to describe the quantum correlations between individual
sites in a spin chain. Utilizing infinite matrix product states, we
identify the relationship between the range of pairwise entanglement
and the range of interactions in the ground state of the Ising
model. We then examine how the entanglement of formation varies with
model parameters near a critical point, in an approach extendable to
other quantum correlation measures such as the quantum discord.