MEAN FIELD THEORY OF RVB

1988 ◽  
Vol 02 (05) ◽  
pp. 577-583 ◽  
Author(s):  
Hidetoshi FUKUYAMA
Keyword(s):  
Field Theory ◽  
Mean Field Theory ◽  
Mean Field ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Temperature Dependences ◽  
Physical Quantities

Implication of mean field approximation to RVB are explored and the temperature dependences of various physical quantities are evaluated. The results are discussed in the light of recent experiments.

scholarly journals Calculation of the Static Properties of Local Moment Systems by the Mean Field Method

1975 ◽  
Vol 28 (6) ◽  
pp. 685 ◽  
Author(s):  
AM Stewart
Keyword(s):  
Field Theory ◽  
Mean Field Theory ◽  
Mean Field ◽  
Field Approximation ◽  
Field Method ◽  
Local Moment ◽  
Mean Field Approximation ◽  
Static Properties ◽  
The Past ◽  
The Mean

It is demonstrated that two different methods which have been used in the past to calculate the static properties oflocal moment systems in the mean field approximation are incomplete. A proof is given of the correctness of another method that the author has used in several previous calculations. It is found that some exact and very general relationships exist between the conduction electron magnetization and the local moment magnetization even when it is not valid to treat the interactions between the magnetic atoms by mean field theory.

scholarly journals THE CJT CALCULATION IN STUDYING NUCLEAR MATTER BEYOND MEAN FIELD APPROXIMATION

2008 ◽  
Vol 23 (21) ◽  
pp. 1769-1780 ◽  
Author(s):  
SONG SHU ◽  
JIA-RONG LI
Keyword(s):  
Field Theory ◽  
Nuclear Matter ◽  
Chemical Potential ◽  
Mean Field Theory ◽  
Mean Field ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Medium Effects ◽  
Effective Masses ◽  
Walecka Model

We have introduced the Cornwall–Jackiw–Tomboulis (CJT) resummation scheme in studying nuclear matter. Based on the CJT formalism and using Walecka model, we have derived a set of coupled Dyson equations of nucleons and mesons. Neglecting the medium effects of the mesons, the usual mean field theory (MFT) results can be obtained. The beyond MFT calculations have been performed by thermodynamic consistently determining the meson effective masses and solving the coupled gap equations for nucleons and mesons together. The numerical results for the nucleon and meson effective masses at finite temperature and chemical potential in nuclear matter are discussed.

CAR-ORIENTED MEAN-FIELD THEORY REVISITED

2004 ◽  
Vol 18 (17) ◽  
pp. 887-894 ◽  
Author(s):  
YU-FUNG CHIEN ◽  
DING-WEI HUANG
Keyword(s):  
Field Theory ◽  
Mean Field Theory ◽  
Mean Field ◽  
Critical Density ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Stochastic Noise ◽  
Collective Effect ◽  
Self Consistent ◽  
The Mean

We study the Car-Oriented Mean-Field approximation (COMF) to the Nagel–Schreckenberg model in the case of v max =3. The self-consistent equations are obtained. The solution is reached by the method of iteration. When the stochastic noise is small, the numerical simulations can be well described by the mean-field theory. When the stochastic noise is large, the flux around critical density is overestimated. The overshooting of the free flow can be attributed to the collective effect of the stochastic noise.

MEAN-FIELD THEORY OF ANYONS NEAR BOSE STATISTICS

1994 ◽  
Vol 08 (01) ◽  
pp. 41-48
Author(s):  
JOHN MCCABE ◽  
RICHARD MACKENZIE
Keyword(s):  
Field Theory ◽  
Mean Field Theory ◽  
Mean Field ◽  
Hard Core ◽  
Meissner Effect ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Bose Statistics ◽  
Domain Of Validity

We argue the validity of a mean-field approximation for a free anyon gas near Bose statistics, and show that the anyon gas can exhibit a Meissner effect in the domain of validity of the approximation only due to a hard-core repulsion.

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.

scholarly journals Kinetic field theory: Non-linear cosmic power spectra in the mean-field approximation

2021 ◽  
Vol 10 (6) ◽  
Author(s):  
Matthias Bartelmann ◽  
Johannes Dombrowski ◽  
Sara Konrad ◽  
Elena Kozlikin ◽  
Robert Lilow ◽  
...  
Keyword(s):  
Field Theory ◽  
Power Spectrum ◽  
Mean Field ◽  
Power Spectra ◽  
Field Approximation ◽  
Density Fluctuations ◽  
Mean Field Approximation ◽  
Non Linear ◽  
Two Parameters ◽  
Kinetic Field

We use the recently developed Kinetic Field Theory (KFT) for cosmic structure formation to show how non-linear power spectra for cosmic density fluctuations can be calculated in a mean-field approximation to the particle interactions. Our main result is a simple, closed and analytic, approximate expression for this power spectrum. This expression has two parameters characterising non-linear structure growth which can be calibrated within KFT itself. Using this self-calibration, the non-linear power spectrum agrees with results obtained from numerical simulations to within typically \lesssim10\,\%≲10% up to wave numbers k\lesssim10\,h\,\mathrm{Mpc}^{-1}k≲10hMpc−1 at redshift z = 0z=0. Adjusting the two parameters to optimise agreement with numerical simulations, the relative difference to numerical results shrinks to typically \lesssim 5\,\%≲5%. As part of the derivation of our mean-field approximation, we show that the effective interaction potential between dark-matter particles relative to Zel’dovich trajectories is sourced by non-linear cosmic density fluctuations only, and is approximately of Yukawa rather than Newtonian shape.

Spontaneous magnetization of ferromagnet in mean-field Heisenberg model

2019 ◽  
Vol 33 (04) ◽  
pp. 1950036 ◽  
Author(s):  
Artur P. Durajski ◽  
Anna B. Olesik ◽  
Anita E. Auguscik
Keyword(s):  
Field Theory ◽  
Magnetic Susceptibility ◽  
Curie Temperature ◽  
Heisenberg Model ◽  
Spontaneous Magnetization ◽  
Mean Field Theory ◽  
Mean Field ◽  
Function Technique ◽  
Heisenberg Ferromagnet ◽  
Temperature Dependences

The Heisenberg ferromagnet model has been studied theoretically using the Weiss mean-field theory and Green’s function technique. The equations for the Curie temperature, magnetization, and magnetic susceptibility were analytically derived. Moreover, we proved, that our results are useful in description of real materials. The calculated value of Curie temperature for [Formula: see text] alloy correspond well with the experimental results obtained recently on the base of the temperature dependences of magnetization.

MEAN-FIELD THEORY FOR LAYERED HIGH-TEMPERATURE SUPERCONDUCTORS

1988 ◽  
Vol 02 (05) ◽  
pp. 1059-1065 ◽  
Author(s):  
D. Baeriswyl ◽  
T. Schneider
Keyword(s):  
High Temperature Superconductors ◽  
Mean Field Theory ◽  
Mean Field ◽  
Three Dimensional ◽  
Interlayer Coupling ◽  
Interlayer Spacing ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Pairing Mechanism ◽  
The Mean

Using the mean-field approximation we study a model for quasi-two-dimensional layered superconductors. The interlayer coupling, assumed to be mediated by a small electron hopping term, is found to leave Tc practically unaffected. Consequently, a three-dimensional pairing mechanism is required to explain the observed dependence of Tc on the average interlayer spacing in the Bi and Tl compounds.

A Quantum Field Theory Approach to Simple Liquids: The Elementary Excitations of Helium 4

1997 ◽  
Vol 11 (03) ◽  
pp. 337-354
Author(s):  
R. Mele ◽  
G. Preparata ◽  
S. Villa
Keyword(s):  
Field Theory ◽  
Quantum Field Theory ◽  
Mean Field ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Theory Approach ◽  
Quantum Field ◽  
Static Structure ◽  
Loop Correction ◽  
Simple Liquids

In the framework of Quantum Field Theory we propose a novel approach to the theory of bosonic simple liquids, formulated in terms of a scalar, complex quantum field, the wave-field Ψ(x,t). The problem is treated in a mean-field approximation, diagonalizing the quadratic part of the Hamiltonian à la Bogoliubov and calculating in a perturbative scheme the one-loop correction to the self-energy function. We derive the dispersion relation and the dynamic and static structure factors of the liquid 4 He , obtaining results that are successfully compared with experimental data.

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