Fermions and expanding universe

2015

Astrophys Space Sci

Recently many authors studied the Dirac spinors within the scope of different cosmological models with torsion [24-27, 37, 39]. Dirac spinors in Bianchi type-I f (R) cosmology with torsion was studied in [39], where it was shown that the dynamic behavior of the universe depends on the particular choice of the function f (R). In this paper tt was highlighted that, despite the anisotropic background the Einstein tensor is diagonal, whereas, because of intrinsic feature of spinor field, the energy tensor is non-diagonal. Dirac field equations coupled to electrodynamics and torsion fields were investigated in [27]. It was shown that minimal coupling between the torsion tensor and Dirac spinors generates a spin-spin interaction [25]. In [26] it was shown that the spacetime torsion, generated by Dirac spinors, induces gravitational repulsion. Nonsingular Dirac particles in spacetime with torsion were studied in [24].

Section: Introductionmentioning

confidence: 99%

Nonlinear spinor fields in Bianchi type-I spacetime: problems and possibilities

2015

Astrophys Space Sci

“…are among the most studied ones, though some other models of dark energy are also proposed. After some remarkable works by different authors [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34], showing the important role of spinor field in the evolution of the Universe, it has been extensively used to model the dark energy. This success is directly related to its ability to answer some fundamental questions of modern cosmology: (i) Problem of initial singularity and its possible elimination [22][23][24][25][26][35][36][37][38]; (ii) problem of isotropization [24,25,27,36,39] and (iii) late time acceleration of the Universe [28-30, 32, 35-38, 40, 41].…”

Section: Introductionmentioning

confidence: 99%

Nonlinear spinor fields in Bianchi type-VI0 spacetime

2015

Eur. Phys. J. Plus

Within the scope of Bianchi type-VI cosmological model we study the role of spinor field in the evolution of the Universe. It is found that due to the spinor affine connections the energy-momentum tensor of the spinor field possesses non-diagonal components. The non-triviality of non-diagonal components of the energy-momentum tensor imposes some severe restrictions either on the spinor field or on the metric functions or on both of them. But unlike in cases of Bianchi type-I or V I 0 , in case of Bianchi type-VI model it does not lead to the elimination of spinor field nonlinearity or mass term in the spinor field Lagrangian. It is also found that depending on the sign of self-coupling constant the model can give rise to late time acceleration or generate oscillatory mode of evolution.

“…However, in cosmology, the role of spinor field was generally considered to be restricted. Only recently, after some remarkable works by different authors [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20], showing the important role that spinor fields play on the evolution of the Universe, the situation began to change. This change of attitude is directly related to some fundamental questions of modern cosmology: (i) problem of initial singularity; (ii) problem of isotropization and (iii) late time acceleration of the Universe.…”

Section: Introductionmentioning

confidence: 99%

Nonlinear Spinor Fields in Bianchi Type-I Spacetime Reexamined

2013

Int J Theor Phys

The specific behavior of spinor field in curve space-time with the exception of FRW model almost always gives rise to non-trivial non-diagonal components of the energy-momentum tensor. This non-triviality of non-diagonal components of the energy-momentum tensor imposes some severe restrictions either on the spinor field or on the metric functions. In this paper within the scope of an anisotropic Bianchi type-I Universe we study the role of spinor field in the evolution of the Universe. It is found that there exist two possibilities. In one scenario the initially anisotropic Universe evolves into an isotropic one asymptotically, but in this case the spinor field itself undergoes some severe restrictions. In the second scenario the isotropization takes places almost at the beginning of the process.