Exact Solution and Exotic Fluid in Cosmology

Abstract

Abstract:We investigate cosmological consequences of nonlinear sigma model coupled with a cosmological fluid which satisfies the continuity equation. The target space action is of the de Sitter type and is composed of four scalar fields. The potential which is a function of only one of the scalar fields is also introduced. We perform a general analysis of the ensuing cosmological equations and give various critical points and their properties. Then, we show that the model exhibits an exact cosmological solution which yields a transition from matter domination into dark energy epoch and compare it with the Λ-CDM behavior. Especially, we calculate the age of the Universe and show that it is consistent with the observational value if the equation of the state ω f of the cosmological fluid is within the range of 0.13 < ω f < 0.22. Some implication of this result is also discussed.

Cosmological phase space analysis of the F (X) - V (phi) scalar field and bouncing solutions

“…The last case is when both x and y are different from zero. From (17,18) we can see that the critical points satisfy…”

“…This method is equivalent to the one used for canonical scalar fields in [17] and allows us to identify the general behavior of the cosmological solutions associated with the present Lagrangian. This method has been applied to a wide range of cosmological models, for example [18][19][20][21][22][23][24][25][26]. It can be used to determine the presence and stability of solutions of cosmological interest, such as those with de Sitter phases or with scaling behaviors.…”

A class of exact solutions with spatial acceleration for the description of viscous incompressible fluid flows in the field of mass forces

“…Примером такого поля является поле тяготения. Помимо силы тяжести большое влияние на характеристики течения оказывают также магнитное и электрическое поля, особенно когда речь идет о течении ферромагнитных жидкостей [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. Жидкости такого типа не существуют в природе, они были созданы искусственным путем посредством добавления измельченного магнитного материала в жидкостьноситель при поиске способов перемещения ракетного топлива в условиях низкой гравитации [5].…”

Charged wormhole solutions in Einstein-Cartan gravity

“…However, all classical matter fields respect the standard energy conditions. By increasing the accuracy of measurements in observational cosmology and discovery of cosmic acceleration of the Universe, different cosmological models of dark energy with exotic equations of state have been put forward [7]. Among these models, possible traversable wormhole geometries can be built by matter fields with exotic EMT [8], phantom or quintom-type energy [9] and interacting dark sectors [10].…”

“…As has been pointed out by[33,34], the electromagnetic field does not couple with the spacetime torsion thus, the Maxwell field equations(7) are written in their usual way. If the electromagnetic field couples to torsion the gauge invariance is broken.…”