Statistical Modeling of a Dislocation Phase-Field in Ductile Single Crystals

2001 ◽  
Vol 701 ◽  
Author(s):  
M. Koslowski ◽  
M. Ortiz ◽  
A.M. Cuitino
Keyword(s):  
Single Crystals ◽  
Finite Temperature ◽  
Mean Field ◽  
Hysteresis Loops ◽  
Field Approximation ◽  
Dissipative Systems ◽  
Mean Field Approximation ◽  
Metropolis Monte Carlo ◽  
Different Temperatures ◽  
Shear Stress Field

ABSTRACTA model for the description of strain hardening and hysteresis at different temperatures and strain rates in ductile single crystals is introduced. The theory accounts for: and arbitrary number and arrangement of dislocation lines over a slip plane; the long-range elastic interactions between dislocation lines; the core structure of the dislocations; the interaction between the dislocations and applied resolved shear stress field; and the dissipative in teractions with short-range obstacles and lattice friction, resulting in hardening, path dependency and hysteresis. We introduce a variational formulation for the statistical mechanics of dissipative systems. The influence of finite temperature as well as the mechanics are modeled with Metropolis Monte Carlo simulations and a mean field approximation. The theory predicts a range of behaviors which are in qualitative agreement with observation, including: hardening and dislocation multiplication under monotonic loading and hysteresis loops under under cyclic loading. The flow stress was found to be dependent on the temperature and on the strain rate only at finite temperature.

Magneto—Optical Properties of Amorphous TbFe Alloys

1985 ◽  
Vol 58 ◽  
Author(s):  
M. Mansuripur ◽  
M. Ruane ◽  
P. Wolniansky ◽  
S. Chase ◽  
R. Rosenvold
Keyword(s):  
Mean Field ◽  
Hysteresis Loops ◽  
Perpendicular Magnetic Anisotropy ◽  
Field Approximation ◽  
Anisotropy Energy ◽  
Optical Methods ◽  
Mean Field Approximation ◽  
Kerr Rotation ◽  
The Mean ◽  
Good Agreement

ABSTRACTHysteresis loops and anisotropy energy constants are measured in a magneto—optical system that combines Kerr rotation and ellipticity to enhance signal strength. Temperature dependence of the polar Kerr effect is compared with the magnetization of the iron subnetwork in the mean—field approximation and good agreement is obtained. Perpendicular magnetic anisotropy is studied by magneto—optical methods, yielding the first two coefficients of the series expansion of anisotropy energy in terms of the angleof deviation from the easy axis.

QUADRUPOLE DEFORMATION IN NUCLEI AT FINITE TEMPERATURE

1998 ◽  
Vol 13 (33) ◽  
pp. 2705-2713 ◽  
Author(s):  
B. J. COLE ◽  
H. G. MILLER ◽  
R. M. QUICK
Keyword(s):  
Phase Transition ◽  
Finite Temperature ◽  
Mean Field ◽  
Field Approximation ◽  
Quadrupole Deformation ◽  
Mean Field Approximation ◽  
Zero Temperature ◽  
Average Deformation ◽  
The Mean ◽  
Shape Changes

The intrinsic quadrupole deformation has been calculated at finite temperature in 20 Ne both in the mean-field approximation and using an exact shell model diagonalization. The results support the view that the phase transition seen at finite temperature in mean-field calculations is not due to the change in nuclear shape from deformed to spherical, but rather is a collective-to-non-collective transition. Both calculations indicate that the average deformation of 20 Ne changes from β rms ≈0.31 at zero temperature to just over β rms =0.2 at T=3.0 MeV. The calculations also suggest that, in the mean-field approximation, the square of the quadrupole operator, Q[2]·Q[2], is a better indicator of shape changes than Q[2] itself.

Self-consistent approximations for field theories at finite temperature

1993 ◽  
Vol 71 (5-6) ◽  
pp. 285-294
Author(s):  
M. H. Thoma
Keyword(s):  
Finite Temperature ◽  
Mean Field ◽  
Field Approximation ◽  
Two Dimensions ◽  
Mean Field Approximation ◽  
Coupling Constant ◽  
Starting Point ◽  
Consistent Approximations ◽  
The Mean ◽  
Mean Field Approximations

Various mean field approximations at finite temperature are used for calculating ground state energies and propagators of the [Formula: see text] theory in two dimensions and quantum chromodynamics (QCD). In the case of the [Formula: see text] theory a symmetry restoration is observed above a critical coupling constant if a temperature independent renormalization is used. In the case of QCD the mean field approximation is insufficient but can be regarded as a starting point for more complicated approximations, which are discussed qualitatively.

FINITE TEMPERATURE MATTER SUBJECT TO STRONG MAGNETIC FIELDS

2011 ◽  
Vol 20 (supp02) ◽  
pp. 93-99
Author(s):  
DÉBORA PERES MENEZES ◽  
SIDNEY SANTOS AVANCINI ◽  
CONSTANÇA PROVIDÊNCIA
Keyword(s):  
Magnetic Fields ◽  
Quark Matter ◽  
Finite Temperature ◽  
Mean Field ◽  
Heavy Ion ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Strong Magnetic Fields ◽  
Quark Masses ◽  
Ion Collisions

Quark matter at finite temperature and subject to strong magnetic fields is possibly present in the early stages of heavy ion collisions and in the interior of protoneutron stars. We use the mean field approximation to investigate this type of quark matter described by the Nambu–Jona-Lasinio model. The effect of the magnetic field on the effective quark masses and chemical potentials is only felt for quite strong magnetic fields, above 5 × 1018 G , with larger effects for the lower densities. Spin polarizations are more sensitive to weaker magnetic fields and are larger for lower temperatures and lower densities.

GREEN FUNCTIONS IN t-J MODEL OF HIGH-Tc SUPERCONDUCTIVITY

1994 ◽  
Vol 08 (22) ◽  
pp. 3137-3155 ◽  
Author(s):  
VAN HIEU NGUYEN
Keyword(s):  
Real Time ◽  
Finite Temperature ◽  
Mean Field ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Green Functions ◽  
Imaginary Time ◽  
High Tc ◽  
High Tc Superconductivity ◽  
The Mean

The explicit expressions of the imaginary time normal and anomalous two–point Green functions in the t-J model of high-T c superconductivity without the single occupation constraint as well as those of the real time ones at a finite temperature are derived in the mean field approximation. The possible applications of these results are outlined.

FISSION BARRIERS AT FINITE TEMPERATURE: A THEORETICAL DESCRIPTION WITH THE GOGNY FORCE

2009 ◽  
Vol 18 (04) ◽  
pp. 861-868 ◽  
Author(s):  
V. MARTIN ◽  
L. M. ROBLEDO
Keyword(s):  
Finite Temperature ◽  
Level Density ◽  
Mean Field ◽  
Field Approximation ◽  
Theoretical Description ◽  
Mean Field Approximation ◽  
Density Parameter ◽  
Fission Barriers ◽  
Pairing Correlations ◽  
The Impact

The evolution with temperature of nuclear properties relevant to fission are analyzed in the case of the 240 Pu nucleus by using the standard finite temperature mean field approximation (including pairing correlations) and the Gogny D1S force. To be more specific, potential energy curves, pairing correlation energies, level density parameter a, collective quadrupole mass, etc are considered. The impact of their evolution with temperature in the quantum decay rate, meaningful only in the low temperature regime, is also considered.

THE EFFECT OF FINITE TEMPERATURE ON THE NUCLEON PROPERTIES IN THE EXTENDED LINEAR SIGMA MODEL

2012 ◽  
Vol 21 (06) ◽  
pp. 1250061 ◽  
Author(s):  
M. ABU-SHADY
Keyword(s):  
Finite Temperature ◽  
Sigma Model ◽  
Magnetic Moments ◽  
Mean Field ◽  
Field Approximation ◽  
Linear Sigma Model ◽  
Mean Field Approximation ◽  
Coupling Constant ◽  
Field Equations ◽  
Pion Nucleon

The extended quark sigma model, which includes higher-order mesonic interactions is applied at finite temperature. The field equations are solved using the mean-field approximation. Nucleon properties such as the nucleon mass, the magnetic moments of the proton and neutron, and the pion-nucleon coupling constant are examined as functions of temperature. The obtained results indicate that the deconfinement phase transition conditions are satisfied in the present work at higher values of temperature. A comparison with other models is presented.

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