scholarly journals Particle-number projection in the finite-temperature mean-field approximation

2017 ◽  
Vol 96 (1) ◽  
Author(s):  
P. Fanto ◽  
Y. Alhassid ◽  
G. F. Bertsch
Keyword(s):  
Finite Temperature ◽  
Particle Number ◽  
Mean Field ◽  
Field Approximation ◽  
Mean Field Approximation

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.

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.

scholarly journals Pairing correlations and symmetries in odd-A nuclei.

2018 ◽  
Vol 178 ◽  
pp. 02002 ◽  
Author(s):  
J. Luis Egido ◽  
Marta Borrajo
Keyword(s):  
Angular Momentum ◽  
Particle Number ◽  
Mean Field ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Angular Momentum Projection ◽  
Hartree Fock ◽  
Pairing Correlations ◽  
Highly Correlated

The pairing correlations in odd-A nuclei are analyzed in the mean field approximation and beyond. In particular the role of symmetry conservation is investigated. We find that particle number projection after the variation (PN-PAV) has little effect on the pairing correlations specially in the weak pairing regime. This is in contrast to the variation after particle number projection (PN-VAP) approach where a strong effect is found. The situation is specially critical in odd nuclei because the pairing correlations vanish due to the blocking effect and the Hartree-Fock-Bogoliubov wave function collapses to the Hartree-Fock one. The PN-VAP, however, handles perfectly the exact blocking providing highly correlated wave functions. The role of the angular momentum projection is studied only in the PAV approach. We find small changes of the pairing correlation, at least at small angular momentum. In the calculations we use the Gogny interaction well suited to this kind of studies.

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.

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