scholarly journals Effective electromagnetic lagrangian at finite temperature and density in the electroweak model

Open Physics ◽  
2011 ◽  
Vol 9 (4) ◽  
Author(s):  
Andrea Erdas
Keyword(s):  
Magnetic Field ◽  
Free Energy ◽  
Partition Function ◽  
Field Strength ◽  
Constant Magnetic Field ◽  
Finite Temperature ◽  
Weak Coupling ◽  
Weak Coupling Limit ◽  
Effective Coupling ◽  
Electroweak Model

AbstractUsing the exact propagators in a constant magnetic field, the effective electromagnetic lagrangian at finite temperature and density is calculated to all orders in the field strength B within the framework of the complete electroweak model, in the weak coupling limit. The partition function and free energy are obtained explicitly and the finite temperature effective coupling is derived in closed form. Some implications of this result, potentially interesting to astrophysics and cosmology, are discussed.

OPERATOR ANALYSIS OF AN RPA-REDUCED POLARON MODEL WITHIN THE BOGOLUBOV REPRESENTATION IN MAGNETIC FIELD AT FINITE TEMPERATURE. PART 1

2009 ◽  
Vol 23 (24) ◽  
pp. 4843-4853
Author(s):  
NIKOLAI BOGOLUBOV ◽  
ANNA GHAZARYAN ◽  
YAREMA PRYKARPATSKY
Keyword(s):  
Magnetic Field ◽  
Free Energy ◽  
Constant Magnetic Field ◽  
Finite Temperature ◽  
Ionic Crystal ◽  
Polaron Model ◽  
Exactly Solvable

The polaron model in ionic crystal is studied in the N. Bogolubov representation using a special RPA-approximation. A new exactly solvable approximated polaron model is derived and described in detail. Its free energy at finite temperature is calculated analytically. The polaron free energy in the constant magnetic field at finite temperature is also discussed.

ENERGY BAND OVERLAPPING IN HIGH-Tc SUPERCONDUCTORS

1996 ◽  
Vol 10 (30) ◽  
pp. 1483-1490 ◽  
Author(s):  
M. MORENO ◽  
R. M. MÉNDEZ-MORENO ◽  
M. A. ORTIZ ◽  
S. OROZCO
Keyword(s):  
Weak Coupling ◽  
Cuprate Superconductors ◽  
Weak Coupling Limit ◽  
Band Model ◽  
Coupling Constant ◽  
High Tc Superconductors ◽  
Energy Bands ◽  
Effective Coupling ◽  
High Tc ◽  
Two Band Model

Multi-band superconductors are analyzed and the relevance of overlapping energy bands to the high-T c of these materials is studied. Within the BCS framework, a two band model with generalized Fermi surface topologies is developed. Values of the overlapped occupancy parameters for typical cuprate superconductors are obtained as a function of the ratio R and the effective coupling constant, λ, in the weak-coupling limit. The overlap scale is of the order or lower than the cutoff (Debye) energy. The typical behavior of the isotope effect is obtained. As these superconductors have transition temperatures above the phonon barrier, the results of this approach are important to the generic understanding of the high-T c superconducting mechanism.

Formation of non-thermal electron velocity distribution functions in kinetic magnetic reconnection

2021 ◽  
Author(s):  
Xin Yao ◽  
Patricio A. Muñoz ◽  
Jörg Büchner
Keyword(s):  
Magnetic Field ◽  
Free Energy ◽  
Field Strength ◽  
Magnetic Reconnection ◽  
Electron Beams ◽  
Distribution Functions ◽  
Electron Velocity ◽  
Diffusion Region ◽  
Electron Velocity Distribution ◽  
Velocity Distribution Functions

<div> <div>Magnetic reconnection can convert magnetic energy into non-thermal particle energy in the form of electron beams. Those accelerated electrons can, in turn, cause radio emission in environments such as solar flares. The actual properties of those electron velocity distribution functions (EVDFs) generated by reconnection are still not well understood. In particular the properties that are relevant for the micro-instabilities responsible for radio emission. We aim thus at characterizing the electron distributions functions generated by 3D magnetic reconnection by means of fully kinetic particle-in-cell (PIC) code simulations. Our goal is to characterize the possible sources of free energy of the generated EVDFs in dependence on an external (guide) magnetic field strength. We find that: (1) electron beams with positive gradients in their parallel (to the local magnetic field direction) distribution functions are observed in both diffusion region (parallel crescent-shaped EVDFs) and separatrices (bump-on-tail EVDFs). These non-thermal EVDFs cause counterstreaming and bump-on-tail instabilities. These electrons are adiabatic and preferentially accelerated by a parallel electric field in regions where the magnetic moment is conserved. (2) electron beams with positive gradients in their perpendicular distribution functions are observed in regions with weak magnetic field strength near the current sheet midplane. The characteristic crescent-shaped EVDFs (in perpendicular velocity space) are observed in the diffusion region. These non-thermal EVDFs can cause electron cyclotron maser instabilities. These non-thermal electrons in perpendicular velocity space are mainly non-adiabatic. Their EVDFs are attributed to electrons experiencing an E×B drift and meandering motion. (3) As the guide field strength increases, the number of locations in the current sheet with distributions functions featuring a perpendicular source of free energy significantly decreases.</div> </div>

Reorganizing Finite Temperature Field Theory: Part I.: Scalar Field Theory

2001 ◽  
Vol 16 (supp01c) ◽  
pp. 1277-1280 ◽  
Author(s):  
Michael Strickland
Keyword(s):  
Field Theory ◽  
Perturbation Theory ◽  
Temperature Field ◽  
Finite Temperature ◽  
Weak Coupling ◽  
Weak Coupling Limit ◽  
Finite Temperature Field Theory ◽  
Expansion Point ◽  
Perturbative Limit ◽  
Standard Perturbation Theory

I present a method for self-consistently including the effects of screening in finite-temperature field theory calculations. The method reproduces the perturbative limit in the weak-coupling limit and for intermediate couplings this method has much better convergence than standard perturbation theory. The method relies on a reorganization of perturbation theory accomplished by shifting the expansion point used to calculate quantum loop corrections. I will present results from a three-loop calculation within this formalism for scalar λϕ4.

scholarly journals Directed Polymers and Interfaces in Disordered Media

Polymers ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 1066
Author(s):  
Róbinson J. Acosta Diaz ◽  
Christian D. Rodríguez-Camargo ◽  
Nami F. Svaiter
Keyword(s):  
Field Theory ◽  
Free Energy ◽  
Partition Function ◽  
Saddle Point ◽  
Finite Temperature ◽  
Series Representation ◽  
Replica Method ◽  
Quenched Disorder ◽  
Directed Polymers ◽  
Disordered Media

We consider field theory formulation for directed polymers and interfaces in the presence of quenched disorder. We write a series representation for the averaged free energy, where all the integer moments of the partition function of the model contribute. The structure of field space is analysed for polymers and interfaces at finite temperature using the saddle-point equations derived from each integer moments of the partition function. For the case of an interface we obtain the wandering exponent ξ = ( 4 − d ) / 2 , also obtained by the conventional replica method for the replica symmetric scenario.

scholarly journals Magnetic field corrections to the repulsive Casimir effect at finite temperature

2016 ◽  
Vol 31 (07) ◽  
pp. 1650018 ◽  
Author(s):  
Andrea Erdas
Keyword(s):  
Magnetic Field ◽  
Free Energy ◽  
High Temperature ◽  
Finite Temperature ◽  
Casimir Effect ◽  
Massless Scalar ◽  
Massless Scalar Field ◽  
Parallel Plates ◽  
The Magnetic Field ◽  
Plate Distance

I investigate the finite temperature Casimir effect for a charged and massless scalar field satisfying mixed (Dirichlet–Neumann) boundary conditions on a pair of plane parallel plates of infinite size. The effect of a uniform magnetic field, perpendicular to the plates, on the Helmholtz free energy and Casimir pressure is studied. The [Formula: see text]-function regularization technique is used to obtain finite results. Simple analytic expressions are obtained for the zeta function and the free energy, in the limits of small plate distance, high temperature and strong magnetic field. The Casimir pressure is obtained in each of the three limits and the situation of a magnetic field present between and outside the plates, as well as that of a magnetic field present only between the plates is examined. It is discovered that, in the small plate distance and high temperature limits, the repulsive pressure is less when the magnetic field is present between the plates but not outside, than it is when the magnetic field is present between and outside the plates.

QUANTUM PHASE ANALYSIS OF AN ANISOTROPIC (XYZ) HEISENBERG SPIN-1/2 CHAIN UNDER A UNIFORM AND STAGGERED MAGNETIC FIELD

2009 ◽  
Vol 23 (16) ◽  
pp. 3363-3368
Author(s):  
SUJIT SARKAR
Keyword(s):  
Magnetic Field ◽  
Phase Analysis ◽  
Spin Chain ◽  
Weak Coupling ◽  
Weak Coupling Limit ◽  
Quantum Phase ◽  
Quantum Phases ◽  
Heisenberg Spin ◽  
Spin Particle ◽  
Integer Spin

We study quantum phases of an anisotropic (XYZ) Heisenberg spin-1/2 chain under a mixed magnetic field (uniform and staggered), along with its variant. Our model consists of two competing relevant operators, anisotropy a, and staggered magnetic field hs. Depending on the sign of a this model describes either the physics of solitonic confinement, or the Ising transition between gapped phases. In our case excitations are the integer spin particle in contrast to the half-integer spin particle of frustrated dimerized spin chain. We do all analysis in weak coupling limit.

Quantized density wave ordering induced by a magnetic field in quasi one-dimensional conductors in the weak coupling limit

Physica B+C ◽  
1986 ◽  
Vol 143 (1-3) ◽  
pp. 436-438
Author(s):  
D. Poilblanc ◽  
M. Héritier ◽  
G. Montambaux ◽  
P. Lederer
Keyword(s):  
Magnetic Field ◽  
Weak Coupling ◽  
Density Wave ◽  
Weak Coupling Limit ◽  
One Dimensional
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