Talk 1: A NOVEL APPROACH TO MONTE CARLO SINTERING SIMULATION WITH ANISOTROPIC GRAIN GROWTH Talk 2: COMPOSITION, STRUCTURE AND THERMAL EVOLUTION OF STRANGE QUARK STARS
TITLE:
Talk 1: A NOVEL APPROACH TO MONTE CARLO SINTERING SIMULATION WITH ANISOTROPIC GRAIN GROWTH
Talk 2: COMPOSITION, STRUCTURE AND THERMAL EVOLUTION OF STRANGE QUARK STARS
DATE:
Friday, September 25th, 2009
TIME:
3:30 PM
LOCATION:
GMCS 214
SPEAKER:
Speaker 1 : Gordon Brown, PhD Student, CSRC
Speaker 2 : Rodrigo Negreieros, PhD Student, CSRC
ABSTRACT:
Abstract 1: Despite the wide use of Monte Carlo (MC) simulations for understanding the microstructural evolution of sintering bodies, few of these models accommodate anisotropic material grain growth. Some interesting phenomena are associated with anisotropic grain growth, which makes this area of research important.
This paper focuses on the use of a two-dimensional Potts MC algorithm to simulate the evolution of the granular structure of anisotropic materials. This algorithm incorporates the sintering mechanisms of grain growth, pore migration and vacancy annihilation. The anisotropy is introduced using Wolff plots to map the anisotropy in the surface energy of the grains. Limitations of this algorithm imposed by the underlying lattice structure are identified and analyzed. A novel solution to mitigate these artifacts is proposed and evaluated.
This type of Potts MC model is widely used in many fields including problems in statistical physics, weather simulation, radiation damage, etc. In almost all of these applications, the artifacts resulting from the underlying lattice structure are a concern. The ability to incorporate anisotropic grain growth in our meso-scale modeling allows the investigation of anisotropic granular development under several different situations to better understand some of the observed anisotropic phenomena like patterning in sintered materials.
Abstract 2: Compact stars made of quark matter rather than confined ordinary matter, are expected to form a color superconductor. This superconductor ought to be threaded with rotational vortex lines within which the star’s interior magnetic field is confined. The vortices (and thus magnetic flux) would be expelled from the star during stellar spin-down, leading to magnetic reconnection at the surface of the star and the prolific production of thermal energy. In this talk, I will show that this energy release can re-heat quark stars to exceptionally high temperatures, such as observed for Soft Gamma Repeaters (SGRs), Anomalous X-Ray pulsars (AXPs), and X-ray dim isolated neutron stars (XDINs).
I will also outline the properties of compact stars made up of quark matter, giving special attention to the thermal evolution of these objects. I will show that by modelling SGRs, AXPs and XDINs as superconducting quark matter we obtain an unprecedented agreement with observed data.
HOST:
Jose Castillo
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