569 Emergent States of Matter

Term essays Fall 2006

These essays were written by students taking Physics 569 Emergent States of Matter, Fall 2006, 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: Steve Barr

Title: Kinetics of Phase Transitions in Liquid Crystals

When a liquid crystal system is quenched across a phase boundary, it is observed that nuclei of the ordered phase form and then grow. This growth can be described by a universal growth law.  There are many other systems which are also described by a universal growth law and much work has been done in understanding those systems.  Only recently, however, has this been investigated in systems that form liquid crystals. In this paper I will discuss the experiments performed to determine the growth laws and the size distribution of the nuclei in liquid crystal systems and how the results compare with the general theoretical predictions for these quantities.

Author: Zhongzhou Chen

Title: Modeling Collective Animal Behavior --- From Ants to Human.

Understanding the collective behavior of large groups of animals is an interesting and challenging topic. Despite the diversity of animal species as well as the intrinsic complexity of individual animal, it has been shown that a wide range of collective behavior of the group can arise from much simpler behavior of the individuals. In this paper we will look into several typical examples of common types of collective behavior, arranging from ant trails to Fish schools and even humans, and introduce theoretical and computational model developed for these and other similar cases, in order to give a brief overview of the field's latest developments

Author: Ibrahim Cisse

Title: Phase transitions in lipid membranes

Abstract:  Lipids are biological polymers with both a hydrophilic and a hydrophobic part. When in solution, lipids can regroup to form vesicles. These vesicles have membranes which undergo phase transitions. Here we explore the properties emerging from the lipid stacking and particularly underline their usage in recent literature.

Author: Anne C. Hanna

Title: A Review of Liquid-Glass Transitions

Supercooling of almost any liquid can induce a transition to an amorphous solid phase.  This does not appear to be a phase transition in the usual sense --- it does not involved sharp discontinuities in any system parameters and does not occur at a well-defined temperature --- instead, it is due to a rapid increase in the relaxation time of the material, which prevents it from reaching equilibrium on timescales accessible to experimentation.  I will examine various models of this transition, including elastic, mode-coupling, and frustration-based explanations, and discuss some of the problems and apparent paradoxes found in these models.

Author: Hovhannes Khandanyan

Title:  Electroweak Symmetry Breaking. Higgs Particle   Discovery Potential within the ATLAS Experiment

One of the most important questions in particle physics is the nature of electroweak symmetry breaking. This issue is one of the essential  considerations in Standard Model (SM), which is yet, the most successfully developed theory to explain the physics of the fundamental particles and their interaction. The issue of the origin of the masses of the gauge bosons mediating weak interaction is one of the most important unanswered questions of the Standard Model. Currently, it is widely believed that this question can be answered by invoking the Higgs mechanism, which requires the onset of  spontaneous symmetry breaking of the local gauge symmetry and provides a mass generation mechanism for both of the SU(2) weak gauge bosons and the observed massive quarks and leptons. It also predicts the existence of a massive scalar particle known as Higgs boson. The best experimental verification of the existence of  the Higgs Mechanism would be the discovery of its physically detectable manifestation, the Higgs boson. One of the main physical goals of the experiment at the LHC is the search for the Higgs Particles. Over a large fraction of the mass range the discovery of the Standard Model Higgs boson will be possible in two or more independent channels. It has been also shown that, if discovered important Higgs boson parameters like the mass and the width can be measured. Together with measurements of the production rates and some couplings and branching ratios they will provide useful constraints on the Higgs couplings to fermions and bosons which in turn can be used to test the Standard Model predictions.

Author: Ki Lie

Title: Unconventional Superconductivity in Layered Organic Superconductors


Like the high-Tc copper oxides, organic superconductors are another class of superconductors that cannot be fully explained by the conventional BCS theory, due to the repulsive effective interactions between the charge carriers. Experiments display similarities between these systems and the high-Tc copper oxides in their pairing symmetry and their phase diagram. In this paper, some results from experiments in organics are summarized and a suggested model of this superconductivity induced by strong electron correlation is discussed.

Author: Will Link

Title: RHIC and the Quark Gluon Plasma


One of the American Institute of Physics's top stories of the year 2005 was the discovery of the quark gluon plasma at RHIC.  In this paper, the basic theory of the quark gluon plasma is reviewed, and the experimental evidence from RHIC discussed.

Author:  Andrew Maginniss

Title:  Self-Ordered Motion within Biological Systems


This essay explores the emergence of collective motion within biological systems by modeling them as swarms of identical self-propelled particles with biological motivation.  The results show that it is indeed possible to simulate cohesive, collective motion similar to that of existing life forms.

Author: David McKay

Title: Quasiparticle BEC

Bose-Einstein condensation (BEC) is a broken symmetry state in which there is macroscopic occupation of the ground state of the system. In this paper, I will detail several recent observations of quasiparticle BEC in solids. The advantage of quasiparticle BEC is the low mass of these quasiparticles, resulting in BEC at temperatures on the order of 10 Kelvin. Examples of possible systems for quasiparticle BEC include magnons (quantized spin-waves) in magnetic materials, excitons (electron-hole pairs) in semiconductors and polaritons (photon-exciton entangled states) in microcavities.

Author: Luke Myers

Title: Phase Transitions in Insect Populations

Abstract: This paper will examine recent work on the phase transitions that appear in collective behavior of insect populations. Basic models will be defined and then compared with experimental results. These results indicate that the collective behvior can be predicted without having to model the complexity of the individual biological entity.

Name: Zhenhua Ning

Title: Vortex Glass Transition in High Tc Superconductor

Abstract: This paper tries to give a clear description of the motion of vortex and the vortex glass transitions in high $T_{c}$ superconductors from both theoretical analysis and experimental observation. Then a controversy of the location of the vortex glass transition in high $T_{c}$ superconductors is brought forward by comparing different datum from different groups. A possible resolution is discussed thereafter.

Author: Philip Powell

Title: Current Studies of the BCS-BEC Crossover via Feshbach Resonance

Abstract: In this paper we review the properties of these Bose-Einstein condensates and degenerate Fermi gases and the experimental techniques which have made them realizable.  We then discuss the recent use of a Feshbach resonance which allows one to move continuously from a loosely bound Bardeen-Cooper-Schrieffer (BCS) limit to a molecular Bose-Einstein condensate (BEC) limit.  Finally, we review studies that have demonstrated the emergence of a condensate in both limits, consider the properties of these two limits, and discuss future work which may elucidate the nature of the BCS-BEC crossover.

Author: Rob Putman

Title: The Emergence of Language

Abstract:  Language is clearly an emergent phenomenon that is critical to societal development.  In this paper I discuss how a consistent language can be developed by a population that experiences pair-wise communication interactions.  Both vocabulary and grammar are shown to emergent in this model.  The stability of the emergent grammar is also discussed.

Author: Aruna Rajan

Title: How did protein amino acids get left-handed while sugars got right-handed?

Although chiral (mirror-symmetric) pairs of molecules are synthesized in equal proportion in laboratory experiments, life is partial to only one molecule of the pair. There have been many experimental and theoretical efforts to explain why living organisms have only L-amino acids in proteins and D-sugars in RNA and DNA, but it still remains an open question. I shall review some of the major efforts in explaining homochirality in living systems, and present my perspective on each of them. Finally, further directions in answering this question will be explored.

Author : Dinesh Raut

Title: Q-Balls


Q-balls are soliton-like solutions that exist in certain types of scalar field theories and they appear naturally in Sypersymmetric extensions of Standard Model (SSM). In the first section of the paper the basic formalism demonstrating the existence of Q-balls is outlined. Second section talks about emergence of Q-Balls in SSM. Third section talks how such objects can be formed in the early univesre. In the final section some observational aspects of Q-Ball detection are discussed. Appendix proves a useful general theorem which is required for establishing existence of Q-balls.

Author : Wonki Roh

Title : Soft elasticity and spontaneous shears in smectic elastomers

In this termpaper, properties of smectic phases in elastomers and transition from smectic A to smectic C with spontaneous shearing are presented. Experimental results are introduced to be compared with numerical results.

Author: Arnab Samanta

Title: Emergence in liquid crystals: the blue phases

The blue phases refer to a group of very unique thermodynamically stable phases observed in chiral nematic liquid crystals that exhibit orientational order. These phases are found to appear over a very narrow temperature band in between the isotropic and helical phases of such crystals. In fact, the phase diagram will reveal that there are three such phases. In this essay we will be exploring the origin of such phases using both experimental and theoretical studies. We will be discussing the various aspects of such phases that have already been explained and in addition will also highlight the many unexplained anomalies.

Author: Ming Yang Jeremy Tan

Title: The spread of misinformation

How does information behave? A recent controversial approach is to use ideas in evolutionary biology to study the spread of information. However, in order for the information to `evolve', there has to be some mechanism for variation. This paper would explore the ideas of memes which use the evolutionary biology approach as well as the pitfalls in using this picture. Finally, we will focus our attention on the fidelity of information which affects the variation of memes. A multi-agent model was used to study the effects of misperception and miscommunication in a simple resource gathering simulation.

Author: Teck Leong Tan

Title: Phase Transition of Polymers on Surfaces

Self-avoiding walk provides a good working model for polymers in a good solvent, where the monomer-surface interaction is stronger than the monomer-monomer interaction. The model is the best known example of a surface geometrical phase transition and is discussed extensively by De'Bell et.al [1]. However, in a poor solvent (where the monomer-monomer interaction is stronger) a self-attracting self-avoiding walk (SASAW) model is more applicable [2]. In this paper, I shall compare the outcome (e.g phase diagrams) of the 2 models.

Author: David Wells

Title: The Emergence of Darwinian Evolution

Horizontal gene transfer (HGT) is seen to have been a pervasive phenomenon in the early history of life, necessitating a new evolutionary model for the deep past. We find that in this early time, HGT is the dominant evolutionary mechanism, in fact completely obscuring vertical descent at the time of the universal ancestor---a time of communal evolution out of which Darwinian evolution was to emerge.

Author: Jonathan K. Whitmer

Title: The Emergence of Social Hierarchies, or, How to Win Fights and Influence People


The Bonabeau model attempts to explain the origin of hierarchical structure in society on the basis of random aggressive interactions between agents in the society. Agents which win most of their fights rise higher in the hierarchy, while those who lose most fights occupy the lower tiers. This model grew out of ethological studies on eusocial wasps, but has been subsequently modified to represent broader social structures. The model exhibits a transition from an egalitarian to a hierarchical structure as a function of the population density, the importance value of the interactions, and the rate at which past results are forgotten. This paper presents the background for and assumptions in the model, discusses its phase behavior, and the extensions that have been made to the model. 

Author: Joseph A. Yasi

Title: Quantum Information Storage with Slow and Stopped Light

Abstract: This essay describes the phenomena where the group velocity of light is reduced to  ultraslow speeds, and even stopped in atomic gases.  The coherent coupling of photons to atomic spin excitations in the gases through Electromagnetically Induced Transparency (EIT) is discussed, and experimental observation is presented as evidence of the phenomena with specific focus on the emergence of excited states in the material for quantum infomation storage and processing.

Author: Youcai Wang

Title: Emergent Properties of human cooperation under Evolutionary game

This essay will introduce the emergent properties of human cooperation under evolutionary selection. The propensity for altruism, punishment, and reward is one of the emergent properties that have co-evolved with cooperation by providing an efficient feedback mechanism. The numerical simulation of an evolutionary agent-based model of repeated agent interactions with feedback-by-punishments is a robust emergent property selected by the evolutionary rules of the model. At the same time, it illustrates emergent cooperation under the other situations such as randomness, and circumstance fluctuations. It also presents the phenomenology of the different phase diagram under different circumstance. There are many phenomenological similarities between the course of emergent states of matter and recent history in China. I will briefly introduce how to use these phases to explain the last few decades of China's history.  This essay simplifies the complicated situation for possible future research.

Author: Min Yu

Title: Self-organization of nanoparticles

Abstract: Spontaneous self-organization of nanoparticles has been a topic of intense experimental and theoretical investigations. In this paper, one novel, and simple experiment will be reviewed, where zero-dimensional $CdTe$ nanoparticles self-organize into intermediate pearl necklace-like aggregates, then recrystallize into one-dimensional nanowires. Computational simulation demonstrates that the dipole-dipole interaction is the main driving force for this self-organization process. Similarly, the $CA$ stabilized $Au$ nanoparticles can self-assemble into pearl necklace-like nanostructures by tuning the PH value of the $Au$ solution. The driving force for metal nanoparticle self-assemly will also be revealed.

Author: Shi Yuan

Title: Bose-Einstein condensation in optical lattices

The advent of coherent matter waves in the form of Bose-Einstein condensation, coupled with periodic potentials in the form of optical lattices, has established a new area of research on the boundary between atomic and condensed matter physics. This essay is a brief review of the recent theoretical and experimental progress in the area of degenerate Bose gases loaded into optical lattices.

Author: Longxiang Zhang

Title: Fractional Quantum Hall Effect: the Extended Hamiltonian Theory(EHT) approach


Phenomenology of Fractional Quantum Hall Effect(FQHE), especially charge fractization and quantization of Hall conductance, is presented here in a brief manner. Focus is concentrated on Extended Hamiltonian Theory(EHT) approach to FQHE. Natural appearance of fractional charge of composite particles, quantized Hall conductance in the expanded Hilbert space introduced in EHT is explored at mean field level. The effect of charge localization is also briefly discussed which accounts for the existence of Hall conductance plateau.

Author: ShengQuan Zhou.

Title: BCS Pairing Dynamics

This term essay describes the time evolution of the order parameter in ultracold atomic fermions with time-dependent pairing interaction. Following an abrupt change of the pairing strength, the order parameter undergoes undamped oscillation, damping oscillation and exponential decay in different dynamical regimes respectively.

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