The future of the universe in modified gravitational theories: approaching a finite-time future singularity

By Kazuharu Bamba, Shin'ichi Nojiri, Sergei D. Odintsov. 2008

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We investigate the future evolution of the dark energy universe in modified gravities, including F(R) gravity, and string-inspired scalar Gauss–Bonnet and modified Gauss–Bonnet ones, and ideal fluid with an inhomogeneous equation of state (EoS). The modified Friedmann–Robertson–Walker dynamics for all of these theories may be presented in a universal form by using the effective ideal fluid with an inhomogeneous EoS without specifying its explicit form. We construct several examples of a modified gravity which produces accelerating cosmologies ending at the finite-time future singularities of all four known types by applying a reconstruction program. Some scenarios for resolving a finite-time future singularity are presented. Among these scenarios, the most natural one is related to additional modification of the gravitational action in the early universe. In addition, late-time cosmology in the non-minimal Maxwell–Einstein theory is considered. We investigate the forms of non-minimal gravitational coupling which generate finite-time future singularities and the general conditions for this coupling such that the finite-time future singularities cannot emerge. Furthermore, it is shown that the non-minimal gravitational coupling can remove the finite-time future singularities or make the singularity stronger (or weaker) in modified gravity.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/7abfc862ed9c0cb04d9ec492e288a12040959e7d

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Citations in the corpus

Modified Gravity and Cosmology (2011, background): “Further, one can show that the addition of higher powers of R to the gravitational Lagrangian again helps defend it from instability [968, 421, 970].”
f(R) Theories (2010, background): “curvature singularity appears in the past, which is not related to the future singularities studied in [461, 54].”
Inflationary Cosmology in Modified Gravity Theories (2015, background): “(For LQC in teleparallelism, finite-time future singularities [82,83] have been examined in Reference [84], and bouncing behaviors have also been studied in References [85,86].”