A NEW FERMION-SPIN TRANSFORMATION TO IMPLEMENT THE CHARGE-SPIN SEPARATION

1993 ◽  
Vol 07 (15) ◽  
pp. 1013-1019 ◽  
Author(s):  
SHIPING FENG ◽  
Z.B. SU ◽  
L. YU
Keyword(s):  
Mean Field ◽  
Hard Core ◽  
Field Approximation ◽  
Degree Of Freedom ◽  
Mean Field Approximation ◽  
Dimensional Case ◽  
Spinless Fermion ◽  
The Mean ◽  
Charge Degree ◽  
Good Agreement

We propose a new fermion-spin transformation to implement the charge-spin separation in the large U Hubbard, or the equivalent t-J model. The charge degree of freedom is represented by a spinless fermion while the spin degree of freedom is represented by a hard-core boson. The local constraint for single occupancy is exactly satisfied. Very good agreement with exact solution is obtained for one-dimensional case in the mean field approximation, regarding the total energy, gapless spinon and holon spectra, and the momentum distribution of physical electrons. The same approximation yields good doping dependence of the staggered magnetization in the two-dimensional case.

scholarly journals Особенности фазовой диаграммы полужестких бозонов на квадратной решетке

2021 ◽  
Vol 63 (9) ◽  
pp. 1361
Author(s):  
В.В. Конев ◽  
Ю.Д. Панов
Keyword(s):  
Mean Field ◽  
Hard Core ◽  
Field Approximation ◽  
Charge Ordering ◽  
Mean Field Approximation ◽  
New Order ◽  
Model Parameters ◽  
Local Correlation ◽  
The Mean ◽  
Limit Form

We investigated the phase diagrams of a system of charged semi-hardcore bosons in the mean-field approximation. It is shown that an increase in the local correlation parameter leads to the transformation of the phase diagram of the system from the form characteristic of hard-core bosons to the limit form with a parabolic dependence of the critical temperature of the charge ordering on the boson concentration. The evolution between these limiting cases depends on the ratio of the model parameters and is accompanied by various effects, including a change in the type of phase transition, the appearance of new order-order transitions, and the appearance of new critical points.

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.

NUCLEON PROPERTIES FROM MODIFIED SIGMA MODEL

2007 ◽  
Vol 22 (14n15) ◽  
pp. 2673-2681 ◽  
Author(s):  
M. RASHDAN ◽  
M. ABU-SHADY ◽  
T. S. T. ALI
Keyword(s):  
Sigma Model ◽  
Mean Field ◽  
Field Approximation ◽  
Higher Order ◽  
Original Model ◽  
Mean Field Approximation ◽  
Field Equations ◽  
The Mean ◽  
Better Than ◽  
Good Agreement

Birse and Banerjee model is extended to include higher-order mesonic interactions. The field equations have been solved in the mean-field approximation and a good agreement with the data for the nucleon properties has been obtained. The agreement is better than that obtained by the original model of Birse and Banerjee which indicates the important of the inclusion of higher-order meson correlations.

ON THE VALIDITY OF MEAN-FIELD THEORY FOR ANYONS ON A LATTICE

1992 ◽  
Vol 06 (30) ◽  
pp. 1951-1960 ◽  
Author(s):  
A.A. OVCHINNIKOV ◽  
An. A. OVCHINNIKOV
Keyword(s):  
Large Deviation ◽  
Mean Field Theory ◽  
Mean Field ◽  
Hard Core ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Phase Fluctuations ◽  
Fermi Statistics ◽  
The Mean ◽  
Field Approaches

We examine the validity of the mean-field approximation for anyons on a lattice at high density. The phase fluctuations for a large deviation from the Fermi statistics, in particular for the hard core bosons, are shown to be large. The importance of the phase fluctuations in different fermionic mean-field approaches for the antiferromagnetic Heisenberg model is stressed.

EXTENDED LINEAR SIGMA MODEL IN HIGHER ORDER MESONIC INTERACTIONS

2006 ◽  
Vol 15 (01) ◽  
pp. 143-152 ◽  
Author(s):  
M. RASHDAN ◽  
M. ABU-SHADY ◽  
T. S. T. ALI
Keyword(s):  
Sigma Model ◽  
Mean Field ◽  
Field Approximation ◽  
Higher Order ◽  
Linear Sigma Model ◽  
Mean Field Approximation ◽  
Field Equations ◽  
The Mean ◽  
Better Than ◽  
Good Agreement

The Gell-Mann and Levy model, as well as the Birse and Banerjee model, describe quark interactions via the exchange of σ- and π-mesons. We extend these models to include higher order mesonic interactions. The field equations were solved in the mean-field approximation and good agreement with the data for nucleon properties was obtained. Our agreement is better than that obtained by the original model of Birse and Banerjee and by other models. This indicates the importance of including higher order meson correlations.

POLARONIC MECHANISM OF SUPERCONDUCTIVITY IN DOPED FULLERIDE SYSTEMS

2009 ◽  
Vol 23 (04) ◽  
pp. 615-638 ◽  
Author(s):  
SURESH CHANDER TIWARI ◽  
ARVIND KASHYAP ◽  
ANIL K. SURANA ◽  
RADHA K. PALIWAL ◽  
SHYAM L. KAKANI
Keyword(s):  
Mean Field ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Phonon Coupling ◽  
Strong Electron ◽  
Electron Phonon Coupling ◽  
Self Consistent ◽  
The Mean ◽  
Consistent Equation ◽  
Good Agreement

A polaronic model of superconductivity in doped fulleride systems is presented. The normal and anomalous one-particle Green's functions are derived for a system with strong electron phonon coupling. The study of collapse of the electron band and the phonon vacuum is presented within the mean-field approximation. Self-consistent equation for the superconductivity order parameter (Δ) is derived using Green's fucntion technique and following Lang and Firsov transformations. Expressions for specific heat, density of states, free energy and critical field based on this model have been derived. The theory is applied to explain the experimental results in the systems K 3 C 60 and Rb 3 C 60. These results are in good agreement with the available experimental data.

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