scholarly journals Phase transitions in the logarithmic Maxwell O(3)-sigma model

2021 ◽  
Vol 81 (11) ◽  
Author(s):  
F. C. E. Lima ◽  
C. A. S. Almeida
Keyword(s):  
Magnetic Field ◽  
Phase Transitions ◽  
Sigma Model ◽  
Vacuum Expectation ◽  
Vacuum Expectation Value ◽  
3 Dimensional ◽  
Multiple Phase ◽  
Dimensional Spacetime ◽  
Infinite Set ◽  
The Magnetic Field

AbstractWe investigate the presence of topological structures and multiple phase transitions in the O(3)-sigma model with the gauge field governed by Maxwell’s term and subject to a so-called Gausson’s self-dual potential. To carry out this study, it is numerically shown that this model supports topological solutions in 3-dimensional spacetime. In fact, to obtain the topological solutions, we assume a spherically symmetrical ansatz to find the solutions, as well as some physical behaviors of the vortex, as energy and magnetic field. It is presented a planar view of the magnetic field as an interesting configuration of a ring-like profile. To calculate the differential configurational complexity (DCC) of structures, the spatial energy density of the vortex is used. In fact, the DCC is important because it provides us with information about the possible phase transitions associated with the structures located in the Maxwell–Gausson model in 3D. Finally, we note from the DCC profile an infinite set of kink-like solutions associated with the parameter that controls the vacuum expectation value.

SPECTRAL PROPERTIES AND SYMMETRIES OF DOUBLE COVERINGS OF GRAPHS WITH APPLICATIONS TO SUPERCONDUCTIVITY

2005 ◽  
Vol 15 (02) ◽  
pp. 301-324
Author(s):  
JACOB RUBINSTEIN ◽  
MICHELLE SCHATZMAN
Keyword(s):  
Magnetic Field ◽  
Phase Transition ◽  
Phase Transitions ◽  
Ground State ◽  
Spectral Properties ◽  
Embedded Graph ◽  
Symmetry Constraints ◽  
The Laplace Operator ◽  
The Magnetic Field ◽  
Double Coverings

Let M be a planar embedded graph, and let [Formula: see text] be its double covering. We count the multiplicity of the ground states of the Laplace operator on [Formula: see text] under certain symmetry constraints. The examples of interest for us are ladder-like graphs made out of n, identical rectangles. We find that in the case of an odd n, the multiplicity of the ground state is 2, and if n, is even, the ground state is simple. This result gives an answer to a conjecture by Parks on the type of phase transitions that can occur in a superconducting ladder: Parks conjectured that in the case when the magnetic field is one half fluxoid per rectangle, the phase transition would be continuous in the case of a ladder made out of two rectangles. Our result indeed implies Parks conjecture and generalizes it to any even ladder. The mathematics of this paper is a mixture of topology, symmetry arguments and comparison theorem between the eigenvalues of Laplace operators on graphs with well chosen boundary conditions.

Vacuum polarization in the background of conical singularity

2020 ◽  
Vol 35 (02n03) ◽  
pp. 2040030
Author(s):  
Yuri V. Grats ◽  
Pavel Spirin
Keyword(s):  
Green’S Function ◽  
Green's Function ◽  
Energy Momentum Tensor ◽  
Vacuum Expectation ◽  
Vacuum Expectation Value ◽  
Momentum Tensor ◽  
Massless Scalar ◽  
Massless Scalar Field ◽  
Dimensional Spacetime ◽  
Higher Dimensional

We consider the gravity-induced effects associated with a massless scalar field living in a higher-dimensional spacetime being the tensor product of Minkowski space and spherically-symmetric space with angle deficit. These spacetimes are considered as simple models for a multidimensional global monopole or cosmic string with flat extra dimensions, where the deficit of solid angle is proportional to Newton constant and tension. Thus, we refer to them as conical backgrounds. In terms of the angular deficit value, we derive the perturbative expression for the scalar Green’s function and compute it to the leading order. With the use of this Green’s function we compute the renormalized vacuum expectation value of the scalar-field’s energy-momentum tensor. We make some general note on the linear-on-curvature part of the trace of even coefficients of Schwinger-deWitt expansion.

Influence of the magnetic field on phase transitions in PrAlO3

2010 ◽  
Vol 108 (11) ◽  
pp. 116102 ◽  
Author(s):  
C. Filipič ◽  
V. Bobnar ◽  
S. Turczynski ◽  
D. A. Pawlak ◽  
M. Wencka ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Phase Transitions ◽  
The Magnetic Field

scholarly journals Аномалии магнитной восприимчивости при фазовых переходах второго рода вне точки Кюри

2018 ◽  
Vol 60 (9) ◽  
pp. 1669
Author(s):  
Г.К. Чепурных ◽  
В.А. Чёрная ◽  
О.Г. Медведовская
Keyword(s):  
Magnetic Field ◽  
Magnetic Susceptibility ◽  
Phase Transitions ◽  
Critical Field ◽  
Landau Theory ◽  
Experimental Investigations ◽  
Magnetic Field Direction ◽  
Similarity And Difference ◽  
The Magnetic Field ◽  
Cobalt Fluoride

AbstractTaking into account the inexhaustible interest in studying the peculiarities of physical properties in the neighborhood of phase transitions and the growth of experimental investigations of cobalt fluoride, we have studied the peculiarities of magnetic susceptibility in the vicinity of the critical field H _C at which cobalt fluoride performs the second-order phase transition from the antiferromagnetic phase to the angular phase. It is discovered that in the magnetic field H ‖ C _4, the magnetic susceptibility becomes infinite at H → H _C. It is shown that as the magnetic field direction deviates from the C _4 axis, the magnetic susceptibility in the critical field H _C proves to be finite. It is also shown that the change in the magnetic susceptibility with the change in the magnetic field considerably decreases at extremely insignificant deviations of the field H from the C _4 axis. Since the calculations are performed in terms of the Landau theory of phase transitions, we pay attention to the similarity and difference between the obtained results and those in the vicinity of the Curie point obtained by using the Landau theory of phase transitions.

Magnetostriction near the magnetic-field-induced phase transitions of Cr2O3

Physica B+C ◽  
1977 ◽  
Vol 86-88 ◽  
pp. 1126-1127 ◽  
Author(s):  
R.D. Yacovitch ◽  
Y. Shapira
Keyword(s):  
Magnetic Field ◽  
Phase Transitions ◽  
The Magnetic Field

scholarly journals Скачкообразные процессы магнитного разупорядочения, стимулированные магнитным полем в системах со структурной неустойчивостью

2020 ◽  
Vol 62 (5) ◽  
pp. 710
Author(s):  
В.И. Вальков ◽  
А.В. Головчан ◽  
В.В. Коледов ◽  
Б.М. Тодрис ◽  
В.И. Митюк
Keyword(s):  
Magnetic Field ◽  
Phase Transitions ◽  
Static Magnetic Fields ◽  
First Order ◽  
Temperature Dependences ◽  
Second Order Transition ◽  
First Order Phase ◽  
Experimental Pressure ◽  
The Magnetic Field ◽  
Theoretical Results

A theoretical analysis of the features of structural and magnetostructural first-order phase transitions in magnetocaloric helimagnetic alloys of the Mn_{1-x}Cr_{x}NiGe system has been carried out. To describe the observed displacive structural transitions hex(P6_{3}/mmc)<->orth(P_{nma}), we used the local soft mode model in the approximation of a biased harmonic oscillator. In the absence of a magnetic field, the emergence of a helimagnetic order as a structurally induced second-order transition was described in the framework of the Heisenberg model, taking into account the dependence of the exchange integrals on the structural order parameters and elastic strains. In the presence of a magnetic field, it was found that the approximation of the characteristic temperatures for the helimagnetic HM(P_{nma}) and lability temperatures of the hexagonal paramagnetic PM(P6_{3}/mmc) states, due to the influence of the magnetic field, leads to the appearance of previously unexplored peripheral magnetostructural first-order phase transitions with insignificant magnetization jumps that increase with increasing magnetic induction.In this case, as the pressure increases to 4 kbar with constant induction of the magnetic field, the peripheral transitions transform into reversible first-order magnetostructural transitions, and at even higher pressures (10-14 kbar) into full-fledged first-order magnetostructural transitions with magnetization jumps comparable with maximum value of magnetization. Experimental pressure studies of the temperature dependences of magnetization in static magnetic fields with an induction of up to 1 T and a pressure of up to 14 kbar confirm the theoretical results.

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