Anisotropy dissipation in brane-world inflation

Abstract

We examine the behavior of an anisotropic brane-world in the presence of inflationary scalar fields. We show that, contrary to naive expectations, a large anisotropy does not adversely affect inflation. On the contrary, a large initial anisotropy introduces more damping into the scalar field equation of motion, resulting in greater inflation. The rapid decay of anisotropy in the brane-world significantly increases the class of initial conditions from which the observed universe could have originated. This generalizes a similar result in general relativity. A unique feature of Bianchi I brane-world cosmology appears to be that for scalar fields with a large kinetic term the initial expansion of the universe is quasi-isotropic. The universe grows more anisotropic during an intermediate transient regime until anisotropy finally disappears during inflationary expansion.98.90.Cq 04.50.+h

Singularities on the brane are not isotropic

“…This models are represented by a stationary (equilibrum) point, denoted F b , in the phase space of homogeneous Bianchi models consider in [8,9], as well as in the phase space of a special class of inhomogeneous G 2 cosmological models. In both cases F b is found to be the source, or past attractor, for the generic dynamics for w > 0 (w = 0 is also included in the homogeneous case), consistently with [4][5][6][7]. Finally, we note that the condition for inflation in general is [26] w < − 1 3…”

“…Here we consider the particular implementation developed in [2] in order to generalise a previous model by Randall and Sundrum [3], where the bulk is 5-dimensional (5-d) and contains only a cosmological constant, assumed to be negative. In this context various authors [4][5][6][7][8][9] have considered an homogeneous and anisotropic brane, finding an intriguing result: unlike general relativity, where in general the cosmological singularity is anisotropic, the past attractor for homogeneous anisotropic models in the brane is a simple Robertson-Walker model. In particular, it is found in [8,9] that this is also true for Bianchi IX models, as well as for some inhomogeneous models.…”

Kasner–AdS spacetime and anisotropic brane-world cosmology

“…Inflation on the brane has been considered in the literature (see for example [10][11][12][13]), and even the tendency of the brane embedded into AdS bulk to dissipate anisotropy was reported [14,15], but it is not perfectly clear what would happen if the bulk itself was anisotropic (or non-homogeneous, for that matter). Would inflation on the brane be enough to isotropize both the brane and the bulk (which has much larger volume), or would some sort of "bulk inflation" be needed?…”

“…A number of cosmological scenarios based on the brane-world concept was explored [5][6][7][8][9], including some models with inflation on the brane [10][11][12][13] and different embedding geometries [14,15].…”

Localization of gauge bosons in the 5D standing wave braneworld

“…When the amplitude of anisotropy is small with respect to the tension of the brane (quasi-isotropic limit) effects of anisotropy will be observable only for cosmological distances. One can study brane cosmological model where anisotropy dissipates via inflation [11], or by leakage of thermal graviton radiation into the bulk [12].…”