Eternally Accelerating Spacelike Braneworld Cosmologies

Abstract

We construct an eternally inflating spacelike brane world model. If the space dimension of the brane is three (SM2) or six (SM5) for M theory or four (SD3) for superstring theory, a time-dependent n-form field would supply a constant energy density and cause exponentially expansion of the spacelike brane. In these cases, the hyperbolic space perpendicular to the brane would keep its scale factor constant. In the other cases, however, the extra space would vary in size.

Stability of S-Brane Singular Solutions and Expansion of the Universe

“…Firstly, we present a single singular S p -brane solution with zero dilaton coupling (SM p and SD p=3 -brane solutions) according to our previous papers [11] [12]. We consider D dimensional Einstein gravity coupled to a dilaton field φ and an n-form field strength, F n , as a low-energy effective theory of M-theory/superstring theory, whose action I is…”

“…Here we assume e −αt < 1. Substituting (11) to the equations ( 7) and expanding the equations up to the first order of e −αt , we get…”

“…In our previous papers, we obtained S-brane solutions with a static internal space and an exponentially expanding external space where the brane exists [11] [12]. These solutions are singular solutions, because they can not be obtained by any choice of integral constants in S-brane general solutions [13].…”

Eternally Inflating Cosmologies From Intersecting Spacelike Branes

“…We use x i , i = 1, • • • , and p + 1 as the coordinates of the space where the branes exist. A recent study has posited singular single-brane solutions for the case where only one minus sign is to be included in the metric [20]. General orthogonally intersecting solutions where the metric functions u and v and fields φ and F depend only on one timelike coordinate have also been proposed [23].…”

“…Higherorder quantum corrections have been added to the action, and solutions which include exponentially expanding braneworld and static extra space have been found numerically [18,19]. In a recent paper [20], we pointed out the existence of singular single-brane solutions to Einstein gravity coupled to a dilaton and an n-field. One of these analytic solutions includes a 4-dimensional exponentially expanding Robertson-Walker spacetime consisting of an SM2-brane and a time axis, and an extra hyperbolic space H D−p−2 with a constant scale factor.…”