On some physical aspects of isotropic cosmology in Riemann-Cartan spacetime

Abstract

Abstract. Isotropic cosmology built in the framework of the Poincaré gauge theory of gravity based on sufficiently general expression of gravitational Lagrangian is considered. The derivation of cosmological equations and equations for torsion functions in the case of the most general homogeneous isotropic models is given. Physical aspects of isotropic cosmology connected with possible solution of dark energy problem and problem of cosmological singularity are discussed.

Poincaré gauge theory of gravity, gravitational interaction and regular accelerating universe

“…(14)- (17) allows to build regular Big Bang model of the Universe with accelerating stage of cosmological expansion at present epoch without using the notion of dark energy by virtue of the change of gravitational interaction by certain conditions in comparison with GR (see Refs. [21][22][23][24][25][26][27]. Let us to consider the most important physical consequences obtained by investigation of HIM by using eqs.…”

Cosmology in Poincaré gauge gravity with a pseudoscalar torsion

“…A famous example is the Poincaré gauge theory of Gravity [30][31][32][33][34][35][36][37]. Some works have been done to develop a model of geometric dark energy in the Poincaré gauge theory framework [38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56]. In [38][39][40][41][42][43] the effect of torsion is to introduce an extra-term into matter density and pressure which gives rise to an accelerated behavior of the universe.…”

“…The torsion model in [44][45][46][47][48] contributes an oscillating aspect to the expansion rate of the universe and displays features similar to those of only the presently observed accelerating universe. In [49][50][51][52][53][54][55][56] the Lagrangian involves too many terms and indefinite parameters, which make the field equations complicated and difficult to solve and the role of each term obscure. In order to simplify the field equations, some restrictions on indefinite parameters have to be imposed.…”

“…It has a well posed initial value problem without any ghost or tachyonic propagation. Also, the field equations are allowed to contain higher derivatives in [65], which is different from [49][50][51][52][53][54][55][56], where some restrictions on indefinite parameters are imposed in order to exclude higher order derivatives. In addition, for the first family we solve the cosmological equations corresponding to the scalar torsion function by using the dynamical system approach in ref.…”

Limiting energy density and a regular accelerating universe in Riemann-Cartan spacetime

“…It should be noted that isotropic cosmology with a ≠ 0 possesses some principal problems: in particular, cosmological equations at physically available initial conditions lead in this case to not physical solutions [16] and do not exclude singular solutions; moreover, the presence of the second derivative of the Hubble parameter in cos mological equations leads to its oscillating behavior at asymptotics [17]. The second restriction concerns the parameter q 2 : if q 2 ≠ 0, the equation for the torsion function S 2 is differential equation of the second order that leads to oscillating behavior of the Hubble param eter [14]; by putting q 2 = 0 we will obtain physically necessary consequences.…”