Focusing conditions for extended teleparallel gravity theories

被引：2

作者：

Vinckers, U. K. Beckering ^{[1
]}

De La Cruz-Dombriz, A. ^{[1
]}

Torralba, F. J. Maldonado ^{[1
,2
]}

机构：

[1] Univ Cape Town, Cosmol & Grav Grp, Dept Math & Appl Math, ZA-7701 Cape Town, South Africa

[2] Univ Groningen, Van Swinderen Inst, NL-9747 AG Groningen, Netherlands

来源：

JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS | 2020年 / 12期

基金：

新加坡国家研究基金会; 欧盟地平线“2020”;

关键词：

modified gravity; cosmology of theories beyond the SM; dark energy theory; gravity; ENERGY CONDITIONS; TORSION; SPIN;

D O I：

10.1088/1475-7516/2020/12/020

中图分类号：

P1 [天文学];

学科分类号：

0704 ;

摘要：

In the context of extended theories of teleparallel gravity f (T) we derive the focusing conditions for a one-parameter dependent congruence of timelike auto-parallels of the Levi-Civita connection. We also consider the f (T) field equations for a general metric tensor before moving on to consider a spatially flat Robertson-Walker space-time. Following this, we study the expansion rate for a one-parameter dependent congruence of timelike auto-parallel curves of the Levi-Civita connection. Given the fact that test particles follow auto-parallels of the Levi-Civita connection, the torsion-free Raychaudhuri equation is used in order to determine the desired focusing conditions. Finally we study the obtained focusing conditions for three f(T) paradigmatic cosmological models and discuss the satisfaction or violation of these conditions. Through this, we find f(T) models that allow for the weak and strong focusing conditions to be satisfied or violated. It is mentioned that this behaviour can also be found in the so-called f(R) and f (Q) theories.

引用

页数：30

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