Article Index

This page lists all of the abstracts for the Spring 2013 colloquium series. For dates and speakers, see Colloquium.


"Systems of interacting particles described as ideal gases with fractional exclusion statistics," March 29, 2013, 12n, MH 606

Dragos-Victor Anghel, Department of Theoretical Physics, IFIN-HH, Bucharest, Romania


The concept of fractional exclusion statistics (FES) was introduced by Haldane and the statistical properties of FES systems were calculated independently by several authors, by different methods. The FES was observed in several types of systems, like quasiparticle excitations at lowest Landau level in the fractional quantum Hall effect, spin on excitations quantum antiferomagnets, Bose and Fermi systems described in the thermodynamic Bethe anzats, excitations or motifs of spins in spin chains, elementary volumes obtained by coarse-graining in the phase-space of a system,etc. More recently, a stochastic method for the simulation of the time evolution of FES systems was introduced [3] and the general FES formalism was amended to include the change of the FES parameters at the change of the particle species. This amendment allows us to describe general interacting particle systems as ideal systems which obey FES.
 In this presentation I will introduce the concept of FES, its basic properties and I will show some applications. I focus on the general procedure by which interacting particle systems can be described as ideal FES gases.


"Magnetic Relaxation in Single Chain Magnets," April 26, 2013, 12n, MH 606

Thomas Gredig, California State University Long Beach

Magnetic interactions play a significant role in many modern applications.  The magnetic properties of many alloys have been characterized and studied in depth showing a broad array of interesting phenomena, which include the hardness, coercivity, saturation magnetization, and critical behavior near the transition point. Rather than finding new properties through exploring new materials, we show that properties of the material can be designed. For that purpose, we use a single chain magnet, called iron phthalocyanine, to form iron chains of different length, oriented in different directions. The iron chains are embedded in a carbon matrix and self-assemble on the substrate, when deposited via thermal evaporation.  We show that through design - tuning the length of the chain - properties, such as the coercivity, and magnetic relaxation can be selected. This system can have long magnetic relaxation times, where the remanent moment slowly decays. These results are compared to findings from spin-glasses.

This project is supported by National Science Foundation grant DMR-0847552.

"Neutron stars as billion degree superconductors," May 3, 2013, 12n, MH 606

Prashanth Jaikumar, California State University Long Beach

Neutron stars are highly compact remnants of a supernova explosion and display several amazing and extreme properties. Their core density can be much higher than the density of an atomic nucleus and under such enormous pressure, new phases of matter become thermodynamically favorable. One such phase is superconducting quark matter, which unlike terrestrial materials, is superconducting at even a billion degrees. Though made up of quarks, it can potentially display familiar features of electronic systems such as long-range order, ferromagnetism and gapless superconductivity. We will discuss the emergence and implications of these novel phases for neutron star phenomena from physical parameters like mass-radius properties and rotation rates to more subtle signals like neutrino bursts and gravitational waves.