scholarly journals Spinor field in Bianchi type-IX space–time

2018 ◽  
Vol 96 (10) ◽  
pp. 1074-1084
Author(s):  
Bijan Saha
Keyword(s):  
Spinor Field ◽  
Bianchi Type ◽  
Energy Momentum Tensor ◽  
Early Stage ◽  
Momentum Tensor ◽  
Space Time ◽  
Rapid Expansion ◽  
Coupling Constant ◽  
The One

Within the scope of Bianchi type-IX cosmological model we have studied the role of spinor field in the evolution of the Universe. It is found that unlike the diagonal Bianchi models in this case the components of energy–momentum tensor of spinor field along the principal axis are not the same (i.e., [Formula: see text]), even in the absence of spinor field nonlinearity. The presence of nontrivial non-diagonal components of energy–momentum tensor of the spinor field imposes severe restrictions both on geometry of space–time and on the spinor field itself. As a result the space–time turns out to be either locally rotationally symmetric or isotropic. In this paper we considered the Bianchi type-IX space–time both for a trivial b, that corresponds to standard Bianchi type-IX and the one with a non-trivial b. It was found that a positive self-coupling constant λ1 gives rise to an oscillatory mode of expansion, while a trivial λ1 leads to rapid expansion at the early stage of evolution.

scholarly journals Nonlinear Spinor Field in Non-Diagonal Bianchi Type Space-Time

2018 ◽  
Vol 173 ◽  
pp. 02018
Author(s):  
Bijan Saha
Keyword(s):  
Spinor Field ◽  
Bianchi Type ◽  
Space Time ◽  
Coupling Constant ◽  
Nonlinear Spinor ◽  
Bianchi Models ◽  
Rotationally Symmetric ◽  
Big Crunch ◽  
The Universe

Within the scope of the non-diagonal Bianchi cosmological models we have studied the role of the spinor field in the evolution of the Universe. In the non-diagonal Bianchi models the spinor field distribution along the main axis is anisotropic and does not vanish in the absence of the spinor field nonlinearity. Hence within these models perfect fluid, dark energy etc. cannot be simulated by the spinor field nonlinearity. The equation for volume scale V in the case of non-diagonal Bianchi models contains a term with first derivative of V explicitly and does not allow exact solution by quadratures. Like the diagonal models the non-diagonal Bianchi space-time becomes locally rotationally symmetric even in the presence of a spinor field. It was found that depending on the sign of the coupling constant the model allows either an open Universe that rapidly grows up or a close Universe that ends in a Big Crunch singularity.

scholarly journals Spinors in Cylindrically Symmetric Space–Time

Universe ◽  
2020 ◽  
Vol 6 (9) ◽  
pp. 152
Author(s):  
Bijan Saha
Keyword(s):  
Gravitational Field ◽  
Symmetric Space ◽  
Spinor Field ◽  
Bianchi Type ◽  
Energy Momentum Tensor ◽  
Momentum Tensor ◽  
Space Time ◽  
Type I ◽  
Nonlinear Spinor ◽  
Cylindrically Symmetric

We studied the behavior of nonlinear spinor field within the scope of a static cylindrically symmetric space–time. It is found that the energy-momentum tensor (EMT) of the spinor field in this case possesses nontrivial non-diagonal components. The presence of non-diagonal components of the EMT imposes three-way restrictions either on the space–time geometry or on the components of the spinor field or on both. It should be noted that the analogical situation occurs in cosmology when the nonlinear spinor field is exploited as a source of gravitational field given by the Bianchi type-I cosmological model.

scholarly journals Spinor field with polynomial nonlinearity in LRS Bianchi type-I space–time

2016 ◽  
Vol 94 (1) ◽  
pp. 116-121 ◽  
Author(s):  
Bijan Saha
Keyword(s):  
Spinor Field ◽  
Nonlinear Term ◽  
Bianchi Type ◽  
Mass Term ◽  
Momentum Tensor ◽  
Type I ◽  
Coupling Constant ◽  
Bianchi Type I ◽  
Polynomial Type

Within the scope of the locally rotationally symmetric (LRS) Bianchi type-I cosmological model the role of spinor field on the evolution of the Universe is investigated. In doing so, we have considered a polynomial type of nonlinearity. It is found that, depending on the sign of the self-coupling constant, the model allows either an accelerated mode of expansion or an oscillatory mode of evolution. While the non-diagonal components of the energy–momentum tensor of the spinor field in the case of a full Bianchi type-I model lead to the vanishing mass and nonlinear term in the spinor field Lagrangian, in the case of an LRS Bianchi type-I model neither the mass term nor the nonlinear term of the spinor field vanish.

scholarly journals QUANTUM EVOLUTION OF SCALAR FIELDS IN ROBERTSON-WALKER SPACE-TIME

1996 ◽  
Vol 11 (21) ◽  
pp. 3957-3971 ◽  
Author(s):  
H.C. REIS ◽  
O.J.P. ÉBOLI
Keyword(s):  
Field Theory ◽  
Energy Momentum Tensor ◽  
Gaussian Approximation ◽  
Scalar Fields ◽  
Momentum Tensor ◽  
Space Time ◽  
Quantum Evolution ◽  
Coupling Constant ◽  
Pure States ◽  
Schrödinger Picture

We study the λɸ4 field theory in a flat Robertson-Walker space-time using the functional Schrödinger picture. We introduce a simple Gaussian approximation to analyze the time evolution of pure states and we establish the renormalizability of the approximation. We also show that the energy–momentum tensor in this approximation is finite once we consider the usual mass and coupling constant renormalizations.

MASS AND ENERGY-MOMENTUM TENSOR OF QUANTUM STRINGS IN GRAVITATIONAL SHOCK-WAVES

1992 ◽  
Vol 07 (13) ◽  
pp. 3043-3064 ◽  
Author(s):  
H. J. DE VEGA ◽  
N. SANCHEZ
Keyword(s):  
Shock Waves ◽  
Energy Momentum Tensor ◽  
Fock Space ◽  
Momentum Tensor ◽  
Space Time ◽  
Integral Representations ◽  
Tree Level ◽  
Expectation Values ◽  
Localized Source

We investigate at the quantum level the nonlinear transformation relating the string operators (zero modes and oscillators) and Fock space states before and after the collision with gravitational shock waves. This throws light on the rôle of the space–time geometry in this problem. We do all the treatment for a general shock wave space–time of any localized source. We compute the exact expectation values of the total number (N) and mass ( M 2) operators and show that they are finite, which generalize our previous results in the Aichelburg–Sexl geometry. We study the energy-momentum tensor of the string and compute the exact expectation values of all its components. We analyze vacuum polarization and quadratic fluctuations. All these physical magnitudes are finite. We express all of them in terms of exact integral representations in which the role of the real pole singularities characteristic of the tree level string spectrum (real mass resonances) are clearly exhibited. The presence of such poles is not at all related to the structure of the space–time geometry (which may or may not be singular).

The Application of UX Research in New Energy Vehicle Innovation

2019 ◽  
Vol 1 (1) ◽  
Author(s):  
Menghan TAO ◽  
Ning XIAO ◽  
Xingfu ZHAO ◽  
Wenbin LIU
Keyword(s):  
Early Stage ◽  
Rapid Expansion ◽  
The Other ◽  
Innovative Product ◽  
Stage Of Development ◽  
New Energy ◽  
New Energy Vehicle ◽  
The One ◽  
New Energy Vehicles ◽  
Degree Of Innovation

New energy vehicles(NEV) as a new thing for sustainable development, in China, on the one hand has faced the rapid expansion of the market; the other hand, for the new NEV users, the current NEVs cannot keep up with the degree of innovation. This paper demonstrates the reasons for the existence of this systematic challenge, and puts forward the method of UX research which is different from the traditional petrol vehicles research in the early stage of development, which studies from the user's essence level, to form the innovative product programs which meet the needs of users and being real attractive.

CASIMIR EFFECT FOR THE ROBIN SURFACES IN STATIC ROBERTSON–WALKER SPACE–TIME

2011 ◽  
Vol 20 (02) ◽  
pp. 161-168 ◽  
Author(s):  
MOHAMMAD R. SETARE ◽  
M. DEHGHANI
Keyword(s):  
Scalar Field ◽  
Energy Momentum Tensor ◽  
Casimir Effect ◽  
Vacuum Expectation ◽  
Robin Boundary Condition ◽  
Momentum Tensor ◽  
Space Time ◽  
Conformally Invariant ◽  
Time Space ◽  
Robin Boundary

We investigate the energy–momentum tensor for a massless conformally coupled scalar field in the region between two curved surfaces in k = -1 static Robertson–Walker space–time. We assume that the scalar field satisfies the Robin boundary condition on the surfaces. Robertson–Walker space–time space is conformally related to Rindler space; as a result we can obtain vacuum expectation values of the energy–momentum tensor for a conformally invariant field in Robertson–Walker space–time space from the corresponding Rindler counterpart by the conformal transformation.

N=2 SUPERCONFORMAL INTERACTING BOSONIC MODELS

1992 ◽  
Vol 07 (04) ◽  
pp. 345-356 ◽  
Author(s):  
RON COHEN
Keyword(s):  
Free Energy ◽  
Energy Momentum Tensor ◽  
Central Charge ◽  
Oriented Graph ◽  
Momentum Tensor ◽  
Superconformal Algebra ◽  
Chiral Algebra ◽  
Bosonic Model ◽  
Coset Models

Bosonic representations of N=2 superconformal algebra are studied. We show that the free energy momentum tensor decomposes into an orthogonal sum of the interacting bosonic model (IBM) and a coset-like tensors. We define the notion of flags of models and show that the central charge does not decrease along the flags. We examine the conditions for an arbitrary un-oriented graph to form an IBM. We discuss several properties of the chiral algebra of these models and examine the role of the continuous parameters by studying an example. Finally we discuss the relations between these models and the N=2 superconformal coset models.

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