A FIRST ORDER PHASE TRANSITION IN ISING FERRIMAGNETS

1995 ◽  
Vol 09 (21) ◽  
pp. 1347-1351 ◽  
Author(s):  
HASAN M. AL MUKADAM ◽  
DIMO I. UZUNOV
Keyword(s):  
Phase Transition ◽  
Order Parameter ◽  
Mean Field Theory ◽  
Mean Field ◽  
First Order ◽  
First Order Phase Transition ◽  
Exchange Constants ◽  
The Mean ◽  
First Order Phase ◽  
Ising Spins

The mean field theory is used for the analysis of a two-sublattice system of Ising spins, which describes ferro-, antiferro-, and ferrimagnetic orderings. It is proven that the phase transition in these systems is of a first order when the exchange constants of the sublattices are different. The free energy, the order parameter profiles and the latent heat of the phase transition are calculated for almost equivalent sublattices.

Notizen: Monte-Carlo Simulation of a Two-dimensional Dipolar Lattice

1977 ◽  
Vol 32 (11) ◽  
pp. 1320-1322 ◽  
Author(s):  
S. Romano
Keyword(s):  
Monte Carlo ◽  
Mean Field Theory ◽  
Mean Field ◽  
Square Lattice ◽  
Electrostatic Energy ◽  
Two Dimensional ◽  
First Order ◽  
First Order Phase Transition ◽  
The Mean ◽  
First Order Phase

Abstract Monte-Carlo calculations were carried out on a system consisting of 256 point-dipoles, whose centres are fixed in a two-dimensional square lattice with the usual boundary con­dition; the Epstein-Ewald-Kornfeld algorithm was used in evaluating the electrostatic energy. No evidence of a first-order phase transition was found, and the results suggest there might be a second-order one. Additional calculations were carrierd out using the mean-field theory, which was found to overestimate the transition temperature by about a factor two.

scholarly journals Continuous phase transitions on Galton–Watson trees

2021 ◽  
pp. 1-31
Author(s):  
Tobias Johnson
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Discrete Systems ◽  
Continuous Phase ◽  
Recursive Structure ◽  
Continuous Phase Transition ◽  
First Order ◽  
First Order Phase Transition ◽  
The Mean ◽  
First Order Phase

Abstract Distinguishing between continuous and first-order phase transitions is a major challenge in random discrete systems. We study the topic for events with recursive structure on Galton–Watson trees. For example, let $\mathcal{T}_1$ be the event that a Galton–Watson tree is infinite and let $\mathcal{T}_2$ be the event that it contains an infinite binary tree starting from its root. These events satisfy similar recursive properties: $\mathcal{T}_1$ holds if and only if $\mathcal{T}_1$ holds for at least one of the trees initiated by children of the root, and $\mathcal{T}_2$ holds if and only if $\mathcal{T}_2$ holds for at least two of these trees. The probability of $\mathcal{T}_1$ has a continuous phase transition, increasing from 0 when the mean of the child distribution increases above 1. On the other hand, the probability of $\mathcal{T}_2$ has a first-order phase transition, jumping discontinuously to a non-zero value at criticality. Given the recursive property satisfied by the event, we describe the critical child distributions where a continuous phase transition takes place. In many cases, we also characterise the event undergoing the phase transition.

FINITE-SIZE SCALING ANALYSIS OF THE DECAY OF AN UNSTABLE STATE DURING A FIRST ORDER PHASE TRANSITION

1988 ◽  
Vol 02 (02) ◽  
pp. 527-536 ◽  
Author(s):  
JORGE VIÑALS ◽  
DAVID JASNOW
Keyword(s):  
Phase Transition ◽  
Order Phase Transition ◽  
Structure Factor ◽  
Order Parameter ◽  
Finite Size ◽  
Unstable State ◽  
Finite Size Scaling ◽  
First Order ◽  
First Order Phase Transition ◽  
First Order Phase

We extend standard finite-size scaling methods to study the dynamical evolution of an unstable state far from equilibrium as the system undergoes a first order phase transition. We suggest that the nonequilibrium structure factor S(q, t, L), at late times and for large enough lattice sizes, scales as S(q, t, L)=LdF(qL, t1/x/L). L is the linear dimension of the system and 1/x is the domain growth exponent. We obtain x=2 in the case of the kinetic Ising model with a nonconserved order parameter. For a critical quench in a system with conserved order parameter, scaling of the peak of the structure factor gives 1/x≈0.27. Higher wavenumbers, however, are more consistent with x=3.

scholarly journals Mean-Field Analysis of Sourlas Codes with Adiabatic Reverse Annealing

2021 ◽  
pp. 319-334
Author(s):  
Shunta Arai
Keyword(s):  
Phase Transition ◽  
Order Phase Transition ◽  
Ground State ◽  
Mean Field ◽  
Error Correcting Codes ◽  
Field Analysis ◽  
First Order ◽  
Candidate Solution ◽  
First Order Phase Transition ◽  
First Order Phase

AbstractIn this chapter, we analyze the typical performance of adiabatic reverse annealing (ARA) for Sourlas codes. Sourlas codes are representative error-correcting codes related to p-body spin-glass models and have a first-order phase transition for $$p>2$$ p > 2 , which degrades the estimation performance. In the ARA formulation, we introduce the initial Hamiltonian which incorporates the prior information of the solution into a vanilla quantum annealing (QA) formulation. The ground state of the initial Hamiltonian represents the initial candidate solution. To avoid the first-order phase transition, we apply ARA to Sourlas codes. We evaluate the typical ARA performance for Sourlas codes using the replica method. We show that ARA can avoid the first-order phase transition if we prepare for the proper initial candidate solution.

35Cl NQR Spectra of Substituted N-(Phenyl)-2,2,2-Trichloroacetamides

1999 ◽  
Vol 54 (3-4) ◽  
pp. 261-269 ◽  
Author(s):  
B. Thimme Gowda ◽  
D. Krishna Bhat ◽  
Hartmut Fuess ◽  
Alarich Weiss
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
Order Phase Transition ◽  
Phenyl Ring ◽  
First Order ◽  
First Order Phase Transition ◽  
35Cl Nqr ◽  
The Mean ◽  
First Order Phase ◽  
35Cl Nqr Spectra

Several substituted acetamides, XyC6H5_ y NHCOCCl3 (X=CH3 , NO2 , or Br and y= 1 or 2) have been synthesized and studied by NQR. The effect of ring substitution on the average υ(35Cl) NQR of the trichloroacetyl group is not substantial, but it affects the crystal structure of the substituted com-pounds. The NQR spectra of XyC6H5-y NHCOCCl 3 (where Xy =4-CH3 , 4-NO2 , and 2,3-(CH3)2) show six 35Cl NQR frequencies, each indicating the presence of two molecules in their respective asym-metric units. The temperature dependence of υ(35Cl) NQR of N-(4-methylphenyl)-2,2,2-trichloroacet-amide reveals that it undergoes a first order phase transition around 205 K. Its spectrum shows six lines up to 205 K and three lines thereafter. The latter triplet part of the spectrum fades out around 250 K due to librational motions in the crystal lattice, as the torsional motions of the CCl3 group are easily excit-ed. The 35Cl NQR spectra of all the methylsubstituted amides have been compared with those of the corresponding chlorosubstituted compounds. Generally there is no systematic variation of the mean val-ues of υ(35Cl) NQR or the trichloroacetyl group with the substituents in the phenyl ring. The ω C-Cl frequencies of the trichloroacetyl group of all the v-substituted N-(phenyl)-2,2,2-trichloroacetamides have been estimated using NQR substituent parameters (k) and the frequencies of N-(phenyl)-2,2,2-tri-chloroacetamide. Agreement between these values and the experimental frequencies is quite good. The υ(35Cl) NQR of these amides has also been correlated with Σki of the substituents. Further υ(35Cl) NQR spectra of mono-and trichloroacetamides have been correlated.

scholarly journals Спектры комбинационного рассеяния поликристаллических сульфатов лития, натрия и калия в предпереходной температурной области ниже структурного фазового перехода

2019 ◽  
Vol 61 (8) ◽  
pp. 1513
Author(s):  
А.Р. Алиев ◽  
И.Р. Ахмедов ◽  
М.Г. Какагасанов ◽  
З.А. Алиев
Keyword(s):  
Phase Transition ◽  
Order Parameter ◽  
Potassium Sulfate ◽  
Temperature Phase ◽  
Relaxation Processes ◽  
Lithium Sulfate ◽  
First Order ◽  
First Order Phase Transition ◽  
First Order Phase ◽  
Low Temperature Phase

Molecular relaxation processes in lithium sulfate (Li2SO4), sodium sulfate (Na2SO4) and potassium sulfate (K2SO4) were studied by Raman spectroscopy. A decrease in the order parameter in the low-temperature phase is observed when approaching a phase transition, which, for example, is typical of a first-order phase transition close to the second. The existence of the pretransition region in the studied sulfates Li2SO4, Na2SO4 and K2SO4 was found.

scholarly journals Gravitational wave signals of dark matter freeze-out

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
Danny Marfatia ◽  
Po-Yan Tseng
Keyword(s):  
Phase Transition ◽  
Dark Matter ◽  
Gravitational Waves ◽  
Order Phase Transition ◽  
First Order ◽  
Stochastic Background ◽  
First Order Phase Transition ◽  
Relic Abundance ◽  
First Order Phase ◽  
Freeze Out

Abstract We study the stochastic background of gravitational waves which accompany the sudden freeze-out of dark matter triggered by a cosmological first order phase transition that endows dark matter with mass. We consider models that produce the measured dark matter relic abundance via (1) bubble filtering, and (2) inflation and reheating, and show that gravitational waves from these mechanisms are detectable at future interferometers.

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