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 Determination of the Magnetoelectric Coupling Coefficient in Ferroelectric–Ferromagnetic Composite Based on PZT–Ferrite

2013 ◽  
Vol 58 (4) ◽  
pp. 1401-1403 ◽  
Author(s):  
J.A. Bartkowska ◽  
R. Zachariasz ◽  
D. Bochenek ◽  
J. Ilczuk
Keyword(s):  
Dielectric Permittivity ◽  
Coupling Coefficient ◽  
Mean Field ◽  
Field Approximation ◽  
Theoretical Description ◽  
Magnetoelectric Coupling ◽  
Mean Field Approximation ◽  
Dielectric Measurements ◽  
Temperature Dependences ◽  
Multiferroic Composite

Abstract In the present work, the magnetoelectric coupling coefficient, from the temperature dependences of the dielectric permittivity for the multiferroic composite was determined. The research material was ferroelectric-ferromagnetic composite on the based PZT and ferrite. We investigated the temperature dependences of the dielectric permittivity (") for the different frequency of measurement’s field. From the dielectric measurements we determined the temperature of phase transition from ferroelectric to paraelectric phase. For the theoretical description of the temperature dependence of the dielectric constant, the Hamiltonian of Alcantara, Gehring and Janssen was used. To investigate the dielectric properties of the multiferroic composite this Hamiltonian was expressed under the mean-field approximation. Based on dielectric measurements and theoretical considerations, the values of the magnetoelectric coupling coefficient were specified.

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.

How the heterogeneous infection rate effect on the epidemic spreading in activity-driven network

2016 ◽  
Vol 27 (06) ◽  
pp. 1650057 ◽  
Author(s):  
Dun Han ◽  
Dandan Li ◽  
Chao Chen ◽  
Mei Sun
Keyword(s):  
Infection Rate ◽  
Mean Field ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Epidemic Spread ◽  
Epidemic Threshold ◽  
Individual Activity ◽  
Immunization Strategies ◽  
The Individual ◽  
The Impact

In this paper, we research the impact of the heterogeneous infection rate on the epidemic spread in the activity-driven networks. By using the mean field approximation, the epidemic threshold is theoretically obtained. Several immunization strategies that could curb the epidemic spread are presented. Based on the theoretical analysis and simulation results, we obtain that the epidemic would be prevented effectively if the infection rate strongly correlates with the individual activity. However, if infection rate has a little correlation with the individual activity, most of the individuals may be infected. In addition, the epidemic can be suppressed soon if the individuals with high activity are immunized preferentially.

Magnetism and magnetic anisotropy in UGa2

MRS Advances ◽  
2020 ◽  
Vol 5 (51) ◽  
pp. 2639-2645
Author(s):  
Banhi Chatterjee ◽  
Jindřich Kolorenč
Keyword(s):  
Density Functional ◽  
Magnetocrystalline Anisotropy ◽  
Magnetic Moments ◽  
Mean Field ◽  
Field Approximation ◽  
Theoretical Description ◽  
Mean Field Approximation ◽  
Functional Theory ◽  
Hubbard Interaction ◽  
The Density Functional Theory

AbstractWe investigate whether first-principles calculations with an improved description of electronic correlations can explain the large magnetic moments and the strong magnetocrystalline anisotropy in the ferromagnetic compound UGa2. The correlations are treated within a static mean-field approximation DFT+U combining the density functional theory (DFT) with an onsite Hubbard interaction U. We find that DFT+U improves the agreement of the magnetic moments with the experiment compared to DFT but worsens the theoretical description of the magnetocrystalline anisotropy.

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.

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