scholarly journals A model to study finite-size and magnetic effects on the phase transition of a fermion interacting system

2018 ◽  
Vol 32 (08) ◽  
pp. 1850091
Author(s):  
Emerson B. S. Corrêa ◽  
César A. Linhares ◽  
Adolfo P. C. Malbouisson
Keyword(s):  
Phase Transition ◽  
Symmetry Breaking ◽  
Order Phase Transition ◽  
Chemical Potential ◽  
Strong Dependence ◽  
Finite Size ◽  
Coupling Constants ◽  
Magnetic Catalysis ◽  
First Order Phase Transition ◽  
Interacting Systems

We present a model to study the effects from external magnetic field, chemical potential and finite size on the phase structures of a massive four- and six-fermion interacting systems. These effects are introduced by a method of compactification of coordinates, a generalization of the standard Matsubara prescription. Through the compactification of the z-coordinate and of imaginary time, we describe a heated system with the shape of a film of thickness L, at temperature [Formula: see text] undergoing first- or second-order phase transition. We have found a strong dependence of the temperature transition on the coupling constants [Formula: see text] and [Formula: see text]. Besides inverse magnetic catalysis and symmetry breaking for both kinds of transition, we have found an inverse symmetry breaking phenomenon with respect to first-order phase transition.

scholarly journals Critical end point in a thermomagnetic nonlocal NJL model

2017 ◽  
Vol 32 (26) ◽  
pp. 1750162 ◽  
Author(s):  
F. Márquez ◽  
R. Zamora
Keyword(s):  
Magnetic Field ◽  
Phase Transition ◽  
Phase Diagram ◽  
Order Phase Transition ◽  
Chemical Potential ◽  
First Order ◽  
End Point ◽  
First Order Phase Transition ◽  
First Order Phase ◽  
The Magnetic Field

In this paper, we explore the critical end point in the [Formula: see text] phase diagram of a thermomagnetic nonlocal Nambu–Jona-Lasinio model in the weak field limit. We work with the Gaussian regulator, and find that a crossover takes place at [Formula: see text], [Formula: see text]. The crossover turns to a first-order phase transition as the chemical potential or the magnetic field increases. The critical end point of the phase diagram occurs at a higher temperature and lower chemical potential as the magnetic field increases. This result is in accordance to similar findings in other effective models. We also find that there is a critical magnetic field, for which a first-order phase transition takes place even at [Formula: see text].

Phase Transitions in 3D Site-Diluted Potts Model with Spin States q=4

2010 ◽  
Vol 168-169 ◽  
pp. 357-360 ◽  
Author(s):  
Akai K. Murtazaev ◽  
A.B. Babaev ◽  
G.Ya. Aznaurova
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Order Phase Transition ◽  
Potts Model ◽  
Finite Size ◽  
Critical Parameters ◽  
Spin States ◽  
Spin Concentration ◽  
First Order Phase Transition ◽  
First Order Phase

We study the phase transitions and critical phenomena in 3D site-diluted (with nonmagnetic impurities) Potts model with spin states q=4 by Monte-Carlo method. The systems with linear sizes L=20-32 and spin concentrations p=1.00, 0.90, 0.65 are examined. Using the Binder cumulants method the forth order it is shown that the second-order phase transition is observed in strongly diluted model at spin concentration p=0.65; the pure model (p=1.00) and weakly diluted one (p=0.90) reveals the first-order phase transition. On the basis of finite-size scaling theory the static critical parameters of heat capacity, susceptibility, magnetization, and correlation length exponent are calculated.

Finite-size scaling of O(n) models with singular behaviour: Magnetization and susceptibility in the presence of an external field

1991 ◽  
Vol 69 (6) ◽  
pp. 753-760 ◽  
Author(s):  
Scott Allen ◽  
R. K. Pathria
Keyword(s):  
Phase Transition ◽  
External Field ◽  
Order Phase Transition ◽  
Finite Size ◽  
Spherical Model ◽  
Complete Agreement ◽  
Continuous Variables ◽  
First Order Phase Transition ◽  
Transition Formula ◽  
First Order Phase

The analysis of a previous study (Allen and Pathria. Can. J. Phys. 67, 952 (1989)) on finite-size effects in systems with O(n) symmetry [Formula: see text], confined to geometry Ld−d′ × ∞d′ (where d and d′ are continuous variables such that 2 < d′ < d < 4) and subjected to periodic boundary conditions, is extended (i) to include the region of first-order phase transition (T < Tc) as well as the region of second-order phase transition [Formula: see text] and (ii) to allow the presence of an external field H > 0. Predictions, involving both amplitudes and exponents, are made on the magnetization m and susceptibility χ in different regimes of the variables T, H, and L. Analytical verification of the predicted results is carried out in the case of the spherical model of ferromagnetism (n = ∞), and complete agreement is found.

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