569 Emergent States of Matter
Term essays Spring 2021
These essays were written by students taking Physics 569 Emergent States of Matter, Spring 2021, at the University of Illinois at Urbana-Champaign. The copyright of each essay is due to the author.
Please acknowledge the essay title, author, and this course in any citation to these articles.
The information, opinions and interpretations expressed are those of the authors, not necessarily those of the instructor.
Author: Nan Zhang
Title: Cosmic Strings
Abstract:
This essay discusses the generating, gravitational description and observable effects of cosmic strings. In this essay, cosmic strings, as linear topological defects, are shown to be generated by the spontaneously symmetry breaking of gauge fields during the inflationary era. By studying the metric around a single infinite-length straight cosmic string, we explain carefully how the cosmic string changes a flat space into a conical space and results in the deflection of light passing by. We explore the double images, accretion effects and CMB anisotropy caused by the cosmic strings and introduce the efforts to detect cosmic strings based on the observable effects.
Author:
Mark Hirsbrunner
Title: Odd Viscosity in Chiral Active
Matter: Theory and Experiment
Abstract: Chiral active matter is a hydrodynamic phase composed of
self-spinning microscopic constituent particles. The non-equilibrium
steady states of chiral active matter realize a novel dissipationless
transport coefficient called the odd viscosity. In this paper I provide
an overview of theories regarding the formation of odd viscosity in
chiral active matter, both from a top-down hydrodynamic perspective and
from a bottom-up microscopic perspective. Fluids with an odd viscosity
support exotic topological waves and surface flows not found in
conventional fluids. I briefly discuss the theory underlying these novel
features and present experiments that observe these effects in two very
different chiral active fluids.
Author: Adam Bauer
Title: On the emergence of flocking in birds
Abstract: This essay will provide a brief overview of the many approaches
scientists have taken to study bird flocking, including numerical,
observational, and analytic methods. We discuss the pioneering work first
done in numerical modeling and theoretical physics, and how these
approaches are challenged by observational data. Lastly, we discuss an
observationally motivated theoretical framework for studying flocking.
Author: Chenghao Zhang
Title: Experiment and Theory of Glass
transition
Abstract:
Though belong to well-known state of matter, microscopic understanding of
glassy state is still challenging for scientists. This article will
summarize theoreticaland experimental effort have been made to unveil
mystery of glass, begin with experimental phenomena like dramatic change
of viscosity below glass transition temperature Tg , fragility, aging and
dynamical correlation function of glass etc. For theoretical side, we
emphasize random first-order transition theory of glass
transition studied by Peter Wolynes.
Author:
Zihan Wang
Title: Emergent Ecology: Neutral Theory of
Ecosystems
Abstract: This essay discusses the neutral theory (NT) of ecosystems,
from the aspects of analytical model, simulation results and comparison
to empirical data. Certain macroecological properties are shown to be
emergent from NT. It also discusses how the neutrality itself could be
viewed as an emergent property from evolutionary dynamics, and how can
the NT be possibly be reconciled with the classical niche theory.
Author:
Marc Klinger
Title: Evolutionary Game Theory – From
Cooperation to Topological Phases
Abstract:
In this essay, we provide an introduction to the machinery of Rational
and Evolutionary Game Theory, and observe how complex and even
potentially counter-intuitive phenomena can emerge therein from a
relatively simple set of strategic interactions.
Author:
Riley Vesto
Title: Turing Pattern Formation from
Reaction-Diffusion Equations and Applications
Abstract:
Turing patterns are finite-wavelength, stationary formations which can
develop from homogeneous initial conditions following local
reaction-diffusion equations. This essay provides a phenomenological
description of how Turing patterns form, describes methods of preparing
Turing patterns, and provides some examples of Turing patterns which
appear in nature.
Author:
Rajas Chari
Title: Network theory applications in
complex systems
Abstract: Network theory provides a great framework to study a
myriad of phenomena occurring in nature. In this report we describe the
different ways in which networks are characterized by studying empirical
networks. We then study the popular descriptive models used to build and
study networks with properties similar to empirical networks. We also
explore methods from physics which can be used to analyze networks,
including statistical mechanics and dynamical systems. Finally, we
discuss the potential of renormalization group theory to study networks.
Author:
Shengzhu Yin
Title: Hidden Geometry and Coarse-graining
Metabolism Network
Abstract:
Network Cartography is a key visualization of an organism’s mechanism of
processing. In a sense, life is an ultimate emergent phenomenon that can
be found in nature. However, most cartography only contains topological
information, i.e., a mathematical graph. In this essay, we will take a
look into series of recent development that further incorporates
geometrical information into these metabolic cartography. As a final
result, we will see an emergent pattern by utilizing this additional
information.
Author: Jinchao Zhao
Title: The electron pairing of Iron-based Superconductors
Abstract: Iron-based superconductors are the second family of High-Tc super-conductors people have found until now besides cuperates. This essay presents a review of experimental measurements on iron based superconductors, and aims at the difference and potential links between the pairing mechanism of these two families of high-Tc superconductors.
Author:
Dmitry Manning-Coe
Title: Towards an emergent
macroeconomics
Abstract:
Despite substantial interest after the financial crisis, interest in
deriving macroeconomic phenomena as emergent quantities has waned. I
will argue that the existence of robust scaling laws and fluctuations on
the order of economic quantities themselves are the kinds of things that
should be explained by an emergent framework. To make this plausible I
will show how emergent frameworks in biology and population modelling
are able to explain similar phenomena.
Author:
Michael O’Boyle
Title: The Impact of Superfluids and
Superconductors on Neutron Star Cooling
Abstract:
Neutron stars, remnants of stellar collapse whose densities exceed those
of atomic nuclei, consist of a strongly interacting liquid of unbounded
protons and neutrons (to first approximation) whose temperature is
greatly below the Fermi temperature. They are subject to attractive
nuclear interactions, so it is commonly believed that Cooper pairs will
form in the degenerate matter. This would give rise to superfluid
neutrons and superconducting protons. However, modelling degenerate
nuclear matter remains an elusive problem, so little is known about the
physics of the condensates. This essay will explore perhaps the most
significant observational consequence of super-phases in neutron stars:
their impact on the star’s rate of cooling from a thermal initial
configuration into a degenerate ground state. Specifically, we will
discuss Cassiopeia A, the youngest and most rapidly cooling known
neutron star, observations of which have allowed constraints to be
placed on the super-phase phenomena.
Author: Shubhang Goswami
Our current understanding of physics lies in a reductionist approach. An attempt to put physics under a non-hierarchical footing more in line with Emergence was proposed by Chew in 1968. In this essay, I will explore this approach based on self-consistency, talk about its success, its decline, and its renewed life in critical phenomenon. I will describe how time could possibly emerge from the bootstrap approach. I will elaborate on possible future connections with different fields of physics that could benefit from the Bootstrap approach and vice versa. Finally, I will end with a brief remark on whether we can shed the idea of a particle.
Author: Vincent Hickl
Title: Dynamics of topological defects in
passive and active liquid crystals
Abstract: Topological defects arise in a variety of physical systems
that undergo symmetry-breaking phase transitions into a state of higher
order. Liquid crystals (LCs) are a useful set of systems for studying
the interactions of multiple defects, particularly their creation and
mutual annihilation. In this essay, the basic interactions of defects in
LCs are described through the lens of recent experimental and
theoretical advances in (quasi-)2-dimensional systems. Then, recent
findings in active nematics are described, demonstrating how
non-equilibrium interactions can give rise to very different defect
behaviors. Unlike equilibrium systems, active nematic liquid crystals
can exhibit spontaneous defect creation, leading to turbulent-like
dynamics. These systems exemplify how relatively simple interactions
between many microscopic objects can lead to complex emergent phenomena
at larger scales.
Author: Mayisha Zeb
Nakib
Title: Active Flocks that Squawk: Geese on
2D Sheets
Abstract: This essay explores agent based modeling and the Vicsek model
to help explain emergent behaviors of migrating snow geese on a 2D lake
surface. We will also review other 2D biological flocks such as surf
scooters on the ocean. In addition, we will cover 3D swarms of krill in
a more recent paper that takes into account transfer entropy and mutual
information to explain swarm behavior due to more complicated social
interactions.
Title: Using
entanglement to characterize topological phases of matter
Author: Faisal Alam
Abstract: Off diagonal long range order is often used to
characterize emergent phenomena like ferromagnetism and superfluidity.
Similarly entanglement entropy and entanglement spectrum can be used to
characterize topological phases of matter. In such phases the
interplay between interactions, symmetry and topology lead to emergent
fractional charge, fractional statistics and non-trivial edge states.
In this essay we review how entanglement signatures can be used to
deduce these properties from the ground state of the system alone.
Author: Jairo M. Rojas
Title: Criticality in Living Systems
Abstract:
Various phenomena present in living systems, such as tissues, bacterial
colonies, and neural networks, are the result of the interaction of a
large number of components and, therefore, can be studied using
statistical physics techniques. Thanks to new experimental technologies,
it is now possible to study biological systems in detail and build
statistical mechanics models directly from the data. Interestingly, the
parameters for the models found are very close to a critical point. This
essay describes experimental observations, simulations, and mathematical
analyzes of biological systems where criticality has been found and
discusses the presence of self-organizing criticality phenomena as a
result of evolution.
Author: Matthew Thibodeau
Title: Measurement-Induced Phase Transitions
Abstract:
When some unitary
quantum circuits are punctuated by periodic measurements, distinct
phases
can emerge, where the order parameter is related to the entanglement
properties of the circuits.
This term paper describes recent progress in the identification and
characterization of these phases.
We provide a selection of circuit models that exhibit this phenomenon,
detail the analytic and
numerical arguments that show the emergence of high- and
low-entanglement phases, and then
describe some important properties of the circuits and states that can
emerge, including topological
protection and quantum error correction capabilities.
Author: Ryan Bogucki
Title: Criticality
in living matter: a universal mechanism of charge transport in
biomolecules
Abstract
In recent experimental works using metallic contacts attached to
proteins, an
anomalously large, temperature-independent long-range conductance has
been mea-
sured across numerous proteins with no known role in electron transfer
processes.
The exact mechanism by which this phenomenon occurs is unknown, although
several recent theoretical works suggest that proteins belong to a
larger class of
biomolecules tuned precisely to a metal-insulator critical point, where
decoherence
plays a pivotal role for the robust conductance measured in proteins.
Along with
having strong dependence on molecular conformation, the ubiquitous
nature of the
phenomenon suggests that it was evolutionarily selected for, as the
probability to
find even a single critical molecule by chance is astronomically low. In
this paper, we
discuss the current modeling efforts which realize the physics for this
phenomenon,
their relation to experiment, as well as potential evolutionary roles.
Author: Daniel Belkin
Title: Anderson
Localization
Abstract
This work covers the theory of Anderson localization. The behavior of
Anderson’s original model is discussed, as is the derivation of Wegner’s
nonlinear σ model. A relationship to Goldstone’s theorem in this context
is covered. We then discuss an experimental demonstration of Anderson
localization in a three-dimensional ultracold atom system. Finally,
extensions to weak interactions via theory and numerics are discussed.
Author: Chunyu Lu
Title: The development of the inflation
models
Abstract: This article is about different inflation models and phase
transitions related to the models. We would focus on what kind of
observational effects they can predict and explore different cosmological
surveys to see the constrains they could give to the inflation model.