On the "Causality argument" in bouncing cosmologies.
نویسندگان
چکیده
We exhibit a situation in which cosmological perturbations of astrophysical relevance propagating through a bounce are affected in a scale-dependent way. Involving only the evolution of a scalar field in a closed universe described by general relativity, the model is consistent with causality. Such a specific counterexample leads to the conclusion that imposing causality is not sufficient to determine the spectrum of perturbations after a bounce provided it is known before. We discuss consequences of this result for string motivated scenarios.
منابع مشابه
Cosmological argument in proving the existence of God from Imam Khomeini's (RA) point of view
This article reviews Cosmological argument in proving the existence of God from the viewpoint of Imam Khomeini (RA). At first, various views to the existence of God are reviewed and then its etymology will be reviewed. Cosmological argument proves God through universal premises about truth and world and and the Movement Argument, Casual Argument and Necessity and Possibility Argument are dif...
متن کاملUnstable growth of curvature perturbations in nonsingular bouncing cosmologies.
Bouncing cosmologies require an ekpyrotic contracting phase (w≫1) in order to achieve flatness, homogeneity, and isotropy. Models with a nonsingular bounce further require a bouncing phase that violates the null energy condition (w<-1). We show that the transition from the ekpyrotic phase to the bouncing phase creates problems for cosmological perturbations. A component of the adiabatic curvatu...
متن کاملGeneral solution for scalar perturbations in bouncing cosmologies
Bouncing cosmologies, suggested by String/M-theory, may provide an alternative to standard inflation to account for the origin of inhomogeneities in our universe. The fundamental question regards the correct way to evolve the scalar perturbations through the bounce. In this work, we determine the evolution of perturbations and the final spectrum for an arbitrary (spatially flat) bouncing cosmol...
متن کاملIsotropic and Anisotropic Bouncing Cosmologies in Palatini Gravity
We study isotropic and anisotropic (Bianchi I) cosmologies in Palatini f(R) and f(R,RμνR μν) theories of gravity and consider the existence of non-singular bouncing solutions in the early universe. We find that all f(R) models with isotropic bouncing solutions develop shear singularities in the anisotropic case. On the contrary, the simple quadratic model R+ aR/RP +RμνR /RP exhibits regular bou...
متن کاملug 2 00 2 THE dS / CFT CORRESPONDENCE AND THE BIG SMASH by Brett McInnes
Recent observations suggest that the cosmological equation-of-state parameter w is close to−1. To say this is to imply thatw could be slightly less than−1, which leads to R.Caldwell’s “Phantom cosmologies”. These often have the property that they end in a “Big Smash”, a final singularity in which the Universe is destroyed in a finite proper time by excessive expansion. We show that, classically...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
عنوان ژورنال:
- Physical review letters
دوره 92 6 شماره
صفحات -
تاریخ انتشار 2004