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Full-Text Articles in Physics

Microscale Simulation Of Martensitic Microstructure Evolution, Valery I. Levitas, Alexander V. Idesman, Dean L. Preston Sep 2004

Microscale Simulation Of Martensitic Microstructure Evolution, Valery I. Levitas, Alexander V. Idesman, Dean L. Preston

Valery I. Levitas

A new model for the evolution of multivariant martensitic microstructure in single crystals and polycrystals is developed. In contrast with Landau-Ginzburg models, which are limited in practice to nanoscale specimens, this new scale-free model is valid for length scales greater than 100 nm and without an upper bound. It is based on a thermodynamic potential in the volume fractions of the martensitic variants that exhibits an instability resulting in microstructure formation. Simulated microstructures in elastic single crystals and polycrystals under uniaxial loading are in qualitative agreement with those observed experimentally.


Reliable First-Principles Alloy Thermodynamics Via Truncated Cluster Expansions, Nikolai A. Zarkevich, Duane D. Johnson Jun 2004

Reliable First-Principles Alloy Thermodynamics Via Truncated Cluster Expansions, Nikolai A. Zarkevich, Duane D. Johnson

Nikolai A. Zarkevich

In alloys cluster expansions (CE) are increasingly used to combine first-principles electronicstructure calculations and Monte Carlo methods to predict thermodynamic properties. As a basis-set expansion in terms of lattice geometrical clusters and effective cluster interactions, the CE is exact if infinite, but is tractable only if truncated. Yet until now a truncation procedure was not well defined and did not guarantee a reliable truncated CE. We present an optimal truncation procedure for CE basis sets that provides reliable thermodynamics. We then exemplify its importance in Ni3V, where the CE has failed unpredictably, and now show agreement to a range of …


Driven Diffusive Systems: How Steady States Depend On Dynamics, D. P. Landau, Wooseop Kwak, Beate Schmittmann Jun 2004

Driven Diffusive Systems: How Steady States Depend On Dynamics, D. P. Landau, Wooseop Kwak, Beate Schmittmann

Beate Schmittmann

In contrast to equilibrium systems, nonequilibrium steady states depend explicitly on the underlying dynamics. Using Monte Carlo simulations with Metropolis, Glauber, and heat bath rates, we illustrate this expectation for an Ising lattice gas, driven far from equilibrium by an “electric” field. While heat bath and Glauber rates generate essentially identical data for structure factors and two-point correlations, Metropolis rates give noticeably weaker correlations, as if the “effective” temperature were higher in the latter case. We also measure energy histograms and define a simple ratio which is exactly known and closely related to the Boltzmann factor for the equilibrium case. …


Heavy Quark Production By A Quasi-Classical Color Field In Proton-Nucleus Collisions, Kirill Tuchin Jan 2004

Heavy Quark Production By A Quasi-Classical Color Field In Proton-Nucleus Collisions, Kirill Tuchin

Kirill Tuchin

We calculate the inclusive heavy quark production cross section for proton-nucleus collisions at high energies. We perform calculation in a quasi-classical approximation (McLerran-Venugopalan model) neglecting all low-x evolution effects. The derived expression for the differential cross section can be applied for studying the heavy quark production in the central rapidity region at RHIC.


Nuclear Modification Factor In D + Au Collisions: Onset Of Suppression In The Color Glass Condensate, Dmitri Kharzeev, Yuri V. Kovchegov, Kirill Tuchin Jan 2004

Nuclear Modification Factor In D + Au Collisions: Onset Of Suppression In The Color Glass Condensate, Dmitri Kharzeev, Yuri V. Kovchegov, Kirill Tuchin

Kirill Tuchin

We perform a quantitative analysis of the nuclear modification factor in deuteron-gold collisions R dAu within the Color Glass Condensate approach, and compare our results with the recent data from RHIC experiments. Our model leads to Cronin enhancement at mid-rapidity, while at forward rapidities it predicts strong suppression of R dAu at all PT due to low-x evolution. We demonstrate that our results are consistent with the data for dAu charged hadron spectra, R dAu and R CP recently reported for rapidities in the interval η=0-3.2 by the BRAHMS experiment at RHIC. We also make a prediction for R pA …


Particle Correlations At High Partonic Density, Kirill Tuchin Jan 2004

Particle Correlations At High Partonic Density, Kirill Tuchin

Kirill Tuchin

We discuss manifestations of the particle correlations at high partonic density in the heavy-ion collisions at RHIC. In particular, we argue that the elliptic flow variable v% is dominated by particle correlations at high PT


Qcd In Curved Space-Time: A Conformal Bag Model, Dmitri Kharzeev, Eugene Levin, Kirill Tuchin Jan 2004

Qcd In Curved Space-Time: A Conformal Bag Model, Dmitri Kharzeev, Eugene Levin, Kirill Tuchin

Kirill Tuchin

We construct an effective low energy Lagrangian using constraints imposed by the renormalization group. Degrees of freedom are gluons and a scalar glueball. This effective theory has a dual description as classical gluodynamics on a curved conformal background. Color fields are dynamically confined, and the strong coupling freezes at distances larger than the glueball size. We make specific predictions (in particular, on the Nc dependence of glueball properties) which can be tested in lattice simulations of gluodynamics.