569 Emergent States of Matter
Term essays Fall 2010
These essays were written by students taking Physics 569 Emergent States of Matter, Fall 2010, 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: Chia Cheng Chang
Title: Phase Transition of Finance
This essay discusses the observation of a phase transition in financial markets. Theoretical models including the Herding model and Minority Games are explored as options to understand the phenomena.
Author: Po-Yao Chang
Title: High Density Quark Matter and Color Superconductivity
Due to the nature of attractive interaction in quantum chromodynamics (QCD), quark matter is expected to be formed a cooper-pair at high density and low temperature. Here I'll describe some possible quark pairing phases in high density quark matter and showing the correspondence superconductivity in BSC theory. Based on the current understanding of the color superconductivity (CSC) phase, we might have a clear view to understand the color superconductivity inside the neutron stars.
Author: Jing Yan
Title: Collective Motion of Animals
Recent Findings From Field Study and Model Experiments Abstract: This paper summarizes recent results from field studies on collective motion of animals, as well as model experiments that are designed to mimic the natural collective motion. Simulations that incorporate new ingredients from these experiments will also be discussed.
Author: Alicia Kollar
Title: The Anomalous Nernst Effect, Diamagnetism, and Cooper Pairing above Tc in Cuprates
Cuprate high temperature superconductors have been known for more than 20 years, but the so-called pseudogap regime that lies above the superconducting dome on the hole-doped side of the phase diagram is still largely unknown. Recently, Li et al. (2010)  published an extensive examination of fluctuating diamagnetism above T c in several families of cuprates which indicates the presence of a vortex-liquid state as much as 50-100 K above T c . They find compelling evidence that the Cooper paired condensate survives above T c but with an extremely short coherence length that precludes the macroscopic coherence required for phenomena such as the Meissner effect. In this paper I present a basic review of the results obtained by Li et al. (2010) as well as results of earlier investigations into both diamagnetism and the Nernst effect.
Author: Bradley Christensen
Title: Stability of Optical Vortices in Turbulent Media
Optical communications rely on light as a carrier of information. One possibility of transmitting information with light is to use topological defects in the phase, an optical vortex, with the associated topological charge as a multi-bit. Due to the defect nature of optical vortices, they cannot be unwound through continuous deformations – potentially a robust way of sending information. However, one must verify the stability of these vortices for the medium that will transmit the information. In this paper I will discuss the stability of optical vortices against atmospheric turbulence by reviewing relevant simulations.
Author: Kevin Roberts
Title: Cosmic Strings
Abstract: This paper is a short introduction to cosmic strings: what they are, how they form, and observational consequences.
Author: Nathaniel Burdick
Title: Quantum liquid crystals in strongly correlated materials and ultracold gases
Classical liquid crystal phases are characterized by broken symmetries. Phases within strongly correlated materials that break similar symmetries have been predicted and observed, and systems exhibiting such phases have been deemed quantum liquid crystals (QLC). This paper presents the existence of QLC behavior in the quantum Hall system GaAs/GaAlAs, the strontium ruthenate Sr_3Ru_2O_7, and arguably the cuprate superconductor YBa_2Cu_3O_(6+x), as well as the possibility of producing QLC phases in ultracold dipolar gases.
Author: Mark Schubel
Title: Being in Two Places at Once: Spin-Charge Separation
High-energy experiments have shown that the electron is a point-like particle with spin-1/2 and electric charge -e. In highly correlated condensed matter systems these two properties can decouple in the lowest level excitations with the creation of two new quasiparticles: spinons (which carry spin) and chargons (which carry electric charge). I investigate the conditions under which this phenomena occurs, how common it is in nature and the experimental evidence for it, as well as look at the frontier in both theory and experiment in two-dimensional systems such as high-temperature superconductors and cold atom experiments.
Author: Jian Yang
Title: Self assembly and self-organization of supermolecular liquid crystals in the context of anisotropic building blocks
We have reviewed some recent work on self-assembly and self-organization of supermolecular liquid crystals in the context of anisotropic building blocks. These novel anisotropic units, either on the level of mesogenic group or particles, are expected to become the building blocks of novel materials based on successful self-assembled structures desired. A variety of liquid crystal phases are observed accompanied by novel pattern formation in such systems. In general, it is shown that anisotropic building blocks have the potential to serve as a new route to general materials design strategy.
Author: Chih-Chieh Chen
Title: Emergent Gravity
The idea of the emergent gravity came from the study of black hole thermo- dynamics. Basically by inversion the logic in the derivation of the black hole entropy, we may take the entropy as the fundamental object and the gravity as something emerges from the microscopic interactions of fundamental par- ticles. We discuss the entropic force description of gravity, its relation to the AdS/CFT correspondence, some possible consequences in cosmology, and a criticism based on the gravitational quantum well experiment of neutrons.
Author: Cory Stephenson
Title: Hebbian neural networks and the emergence of minds
The construction of neural networks is introduced, and their emergent properties are discussed. A simulation is run to demonstrate a simple novelty filter using a hebbian learning rule. Emergent properties such as pattern recognition and distributed memory storage and retrieval are discussed in the context of time reversal symmetry breaking. Parallels are drawn throughout between these emergent properties and the human mind.
Author: Lo, Ka Wai
Title: Neutron Star and Superfluidity
It is expected that under high density, nucleons in neutron star can form copper pairs and give rise to superfluidity. In this paper, the underlying principle will be briefly reviewed. Astrophysical implications such as explanation of pulsar glitches by the two components model and effect on cooling of neutron stars will be discussed.
Author: Ayah T. Massoud
Title: Dynamics and Self-organization in Aeolian Ripples
Aeolian ripples arise instantaneously from sandy beds subjected to winds sufficient to cause saltation to surface grains. It is now widely believed that the process of ripple formation is a self-organizing phenomenon involving non-linear dynamics in the variation of flux of secondary grains that are ejected through saltation. In addition, the metric entropy and interaction matrix of the system alter governs the dynamics and emergent behavior in the patterns. In this paper we will review the dynamics, self-organization and entropy pertaining to Aeolian ripples. Finally, we will briefly discuss difficulties in studying dune fields.
Author: Wladimir A. Benalcazar
Title: The emergence of leadership and its relationship with the decision-making process
As societies or animal groups form, many collective behaviors emerge from their individual interactions. This literature review will look into the emergence of leadership and its relationship with the decisionmaking process in di_erent scenarios, for example, in information exchange networks, where information ows according to trust networks built upon knowledge of other agents' rate of success, or in large animal groups, where information ows despite the individuals' lack of knowledge on whether others have information, or even seek to satiate the same needs at all.
Author: Leslie Ross
Title: Magnetic Phases of the Cuprates
The cuprate superconductors have a far more complicated magnetic phase diagram than the traditional BCS superconductors. This essay will describe the experimental evidence of and theoretical basis for the novel phases associated with these high-$T_c$ superconductors, including vortex lattices and the pseudogap, and discuss the extent to which these phases (and their associated phase transitions) are universal, and to what extent they are determined by both intrinsic material properties and material doping.
Author: Hong-Yan Shih
Title: Emergent Cooperation in Evolutionary Game Theory Coupled with Environment.
How cooperation happens in evolutionary is a long-standing puzzle and has been investigated by various models based on game theory. In nature, since interacting species evolve in a changing environment, the population size should also depend on the environmental influence. Here we introduce a stochastic model whose population-growing dynamics are coupled with the internal prisoner's dilemma game. As a result, a transient but robust increase of cooperation emerges, which indicates that cooperators may overcome the desperate dilemma in a genuinely stochastic evolution.
Author: Xueda Wen
Title: Half-Quantum vortices in a two-dimensional chiral p-wave superconductor
Abstract: In this term paper we give a brief introduction to the half-quantum vortices (HQVs) in a two-dimensional chiral p-wave superconductor such as $Sr_2RuO_4$, which contains zero-energy Majorana fermions staying in the cores of vortices. Then we introduce the non-abelian statistics of half-quantum vortices in this system, which can be used to make topological quantum computation. To observe HQVs in experiments, the stability of HQVs in $Sr_2RuO_4$ is discussed. In addition, we give a discussion on the proposals for observing HQVs in experiments proposed by several groups and introduce the developments in experiments.
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