Abstract Gibbons and Hawking ( Phys. Rev. D , 15 (1977) 2738) have shown that the horizon of de Sitter space emits radiation in same way as event black hole. But actual cosmological horizons are not horizons, except space. Nevertheless, this paper proves Gibbons' Hawking's formula an exact result for any flat expanding with strictly positive Hubble parameter. The gives visual intuitive insight ...

The low energy effective actions which arise from string theory or M-theory are considered in the cosmological context, where the graviton, dilaton and antisymmetric tensor field strengths depend only on time. We show that previous results can be extended to include cosmological solutions that are related to the EN Toda equations. The solutions of the Wheeler-DeWitt equation in minisuperspace a...

In this letter we will revise the steps followed by A. Einstein when he first wrote on cosmology from the point of view of the general theory of relativity. We will argue that his insightful line of thought leading to the introduction of the cosmological constant in the equations of motion has only one weakness: The constancy of the cosmological term, or what is the same, its independence of th...

It has been suggested that recent cosmological and flavor-oscillation data favor the existence of additional neutrino species beyond the three predicted by the Standard Model of particle physics. We apply Bayesian model selection to determine whether there is indeed any evidence from current cosmological datasets for the standard cosmological model to be extended to include additional neutrino ...

Although the standard lambda cold dark matter cosmological model is quite successful in describing universe, there are still several issues that not resolved. Some of these constant problem, certain anomalies cosmic microwave background radiation and whether general relativity valid on large scales. Therefore, it interesting to examine modified theories an attempt solve problems, entire range p...

As a compelling pattern for the holographic principle, our covariant entropy bound conjecture is proposed for more general dynamical horizons. Then we apply our conjecture to ΛCDM cosmological models, where we find it imposes a novel upper bound 10 on the cosmological constant for our own universe by taking into account the dominant entropy contribution from super-massive black holes, which thu...