On the classical stability of orientifold cosmologies

Abstract

We analyze the classical stability of string cosmologies driven by the dynamics of orientifold planes. These models are related to timedependent orbifolds, and resolve the orbifold singularities which are otherwise problematic by introducing orientifold planes. In particular, we show that the instability discussed by Horowitz and Polchinski for pure orbifold models is resolved by the presence of the orientifolds. Moreover, we discuss the issue of stability of the cosmological Cauchy horizon, and we show that it is stable to small perturbations due to in-falling matter.

Diode-Pumped Passively Q-Switched and Mode-Locked Nd:LuVO4Laser with a GaAs Wafer

“…Alternatively, their expanding regions may describe accelerating cosmologies, a subject that recently has received much attention from the string community [6,7] 1 . These solutions appear to evade the usual singularity or no-go theorems because of the negative tension of the time-like singularities which appear [9]- [14].…”

“…See, however, ref [14]. who argue that these geometries may be stable if the boundary conditions are chosen appropriately.…”

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“…Adding a particle in such a spacetime amounts to also adding in the covering space an infinite number of boosted images, causing strong backreaction, and possibly gravitational collapse [44]. See also [45] for a counterexample.…”

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“…It is important to note that the corresponding closed null curve intersects the y = 0 surface, so it is possible that cutting off the y < 0 region cures any pathology arising from the polarization surfaces, as proposed in [13,18]. For a scalar field φ of mass M the two-point function can be written in Euclidean Schwinger parameterization as…”