scholarly journals WIGNER FUNCTIONS OF THERMO NUMBER STATE, PHOTON SUBTRACTED AND ADDED THERMO VACUUM STATE AT FINITE TEMPERATURE

2009 ◽  
Vol 24 (28) ◽  
pp. 2263-2274 ◽  
Author(s):  
LI-YUN HU ◽  
HONG-YI FAN
Keyword(s):  
Finite Temperature ◽  
Vacuum State ◽  
Statistical Properties ◽  
Wigner Functions ◽  
New Approach ◽  
Number State ◽  
Thermo Field Dynamics ◽  
Thermo Vacuum State

Based on Takahashi–Umezawa thermo field dynamics and the order-invariance of Weyl ordered operators under similar transformations, we present a new approach to derive the exact Wigner functions of thermo number state, photon subtracted and added thermo vacuum state. We find that these Wigner functions are related to the Gaussian–Laguerre type functions of temperature, whose statistical properties are then analyzed.

scholarly journals Proposal of a Computational Approach for Simulating Thermal Bosonic Fields in Phase Space

Physics ◽  
2019 ◽  
Vol 1 (3) ◽  
pp. 402-411 ◽  
Author(s):  
Alessandro Sergi ◽  
Roberto Grimaudo ◽  
Gabriel Hanna ◽  
Antonino Messina
Keyword(s):  
Phase Space ◽  
Thermal Noise ◽  
Fock Space ◽  
Vacuum State ◽  
Thermal Bath ◽  
Wigner Transform ◽  
Thermal Vacuum ◽  
Thermo Field Dynamics ◽  
Augmented Space ◽  
Thermal Vacuum State

When a quantum field is in contact with a thermal bath, the vacuum state of the field may be generalized to a thermal vacuum state, which takes into account the thermal noise. In thermo field dynamics, this is realized by doubling the dimensionality of the Fock space of the system. Interestingly, the representation of thermal noise by means of an augmented space is also found in a distinctly different approach based on the Wigner transform of both the field operators and density matrix, which we pursue here. Specifically, the thermal noise is introduced by augmenting the classical-like Wigner phase space by means of Nosé–Hoover chain thermostats, which can be readily simulated on a computer. In this paper, we illustrate how this may be achieved and discuss how non-equilibrium quantum thermal distributions of the field modes can be numerically simulated.

scholarly journals Casimir effect and Stefan–Boltzmann law at finite temperature in a Friedmann–Robertson–Walker universe

2020 ◽  
Vol 29 (07) ◽  
pp. 2050045
Author(s):  
A. F. Santos ◽  
S. C. Ulhoa ◽  
Faqir C. Khanna
Keyword(s):  
Finite Temperature ◽  
Casimir Effect ◽  
Coupling Parameter ◽  
Momentum Tensor ◽  
Thermo Field Dynamics ◽  
Expansion Of The Universe ◽  
The Universe ◽  
Boltzmann Law ◽  
Friedmann Robertson Walker ◽  
General Scale

A spatially flat Friedmann–Robertson–Walker background with a general scale factor is considered. In this spacetime, the energy–momentum tensor of the scalar field with a general curvature coupling parameter is obtained. Using the Thermo Field Dynamics (TFD) formalism, the Stefan–Boltzmann law and the Casimir effect at finite temperature are calculated. The Casimir effect at zero temperature is also considered. The expansion of the universe changes these effects. A discussion of these modifications is presented.

scholarly journals Galilean covariance, Casimir effect and Stefan–Boltzmann law at finite temperature

2017 ◽  
Vol 32 (16) ◽  
pp. 1750094 ◽  
Author(s):  
S. C. Ulhoa ◽  
A. F. Santos ◽  
Faqir C. Khanna
Keyword(s):  
Field Theory ◽  
Quantum Field Theory ◽  
Finite Temperature ◽  
Temperature Effects ◽  
Casimir Effect ◽  
Quantum Field ◽  
Covariant Quantum ◽  
Thermo Field Dynamics ◽  
Boltzmann Law ◽  
Galilean Covariance

The Galilean covariance, formulated in 5-dimensions space, describes the nonrelativistic physics in a way similar to a Lorentz covariant quantum field theory being considered for relativistic physics. Using a nonrelativistic approach the Stefan–Boltzmann law and the Casimir effect at finite temperature for a particle with spin zero and 1/2 are calculated. The thermo field dynamics is used to include the finite temperature effects.

scholarly journals The Solution to the Cosmological Constant Problem

2019 ◽  
Author(s):  
Brian Craig
Keyword(s):  
Cosmological Constant ◽  
Gamma Rays ◽  
Mass Density ◽  
Empty Space ◽  
Vacuum State ◽  
Cosmological Constant Problem ◽  
New Approach ◽  
Solid Crystal ◽  
Low Mass ◽  
The Universe

To account for the very low mass density associated with Dark Energy and the Cosmological Constant, a new approach to the ground state of empty space is presented. The resulting model for the vacuum state associated with empty space proposes a crystalline-like texture for the chromatic structure of empty space. This vacuum state has the appropriate mass density and predicts acceleration for the Universe expansion. Furthermore, the model predicts that this texture is anisotropic and may lead to measurable changes in the production of electron and positron pairs by gamma rays incident on a solid crystal of low mass density such as graphite.

scholarly journals Lorentz violation, gravitoelectromagnetism and Bhabha scattering at finite temperature

2018 ◽  
Vol 33 (10n11) ◽  
pp. 1850061 ◽  
Author(s):  
A. F. Santos ◽  
Faqir C. Khanna
Keyword(s):  
Differential Cross Section ◽  
Cross Section ◽  
Differential Cross ◽  
Finite Temperature ◽  
Lorentz Violation ◽  
High Energy ◽  
Gravitation Field ◽  
Bhabha Scattering ◽  
Thermo Field Dynamics ◽  
Very High Energy

Gravitoelectromagnetism (GEM) is an approach for the gravitation field that is described using the formulation and terminology similar to that of electromagnetism. The Lorentz violation is considered in the formulation of GEM that is covariant in its form. In practice, such a small violation of the Lorentz symmetry may be expected in a unified theory at very high energy. In this paper, a non-minimal coupling term, which exhibits Lorentz violation, is added as a new term in the covariant form. The differential cross-section for Bhabha scattering in the GEM framework at finite temperature is calculated that includes Lorentz violation. The Thermo Field Dynamics (TFD) formalism is used to calculate the total differential cross-section at finite temperature. The contribution due to Lorentz violation is isolated from the total cross-section. It is found to be small in magnitude.

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