Initial conditions for bubble universes

Abstract

The "bubble universes" of Coleman and De Luccia play a crucial role in string cosmology. Since our own Universe is supposed to be of this kind, bubble cosmology should supply definite answers to the long-standing questions regarding cosmological initial conditions. In particular, it must explain how an initial singularity is avoided, and also how the initial conditions for Inflation were established. We argue that the simplest non-anthropic approach to these problems involves a requirement that the spatial sections defined by distinguished bubble observers should not be allowed to have arbitrarily small volumes. Casimir energy is a popular candidate for a quantum effect which can ensure this, but [because it violates energy conditions] there is a danger that it could lead to non-perturbative instabilities in string theory. We make a simple proposal for the initial conditions of a bubble universe, and show that our proposal ensures that the system is non-perturbatively stable. Thus, low-entropy conditions can be established at the beginning of a bubble universe without violating the Second Law of thermodynamics and without leading to instability in string theory. These conditions are inherited from the ambient spacetime.

Entanglement Entropy of the Early Universe in Generalized Chaplygin Gas Model

“…For example one approach is the spontaneous eternal inflation where inflation can occur both forward and backward in time [3]. This has also been treated in string theory in the form of bubble cosmology [4] where universes that realize the complete set of string vacuum solutions were constructed [5] [6]. More recently the tripartite partition of a physical system [7] was introduced where the entropy was found to decrease dramatically after inflation as a means to solve the problem.…”

Scientific Approaches to the Philosophy of Religion

“…30. Also see McInnis (2007aMcInnis ( , 2007bMcInnis ( , 2008 for a string-based model of this type. 31.…”

Black hole final state conspiracies

“…In the latter, the action increases rapidly and diverges towards +∞, so while the introduction of matter [including the effects of Hawking radiation] into the spacetime will change the details, it is unlikely to change the qualitative behaviour, particularly for large values of r. In the case of flat event horizons, however, the action is always finite, and it is always small if the entropy of the black hole is small. Experience in the cosmological case [40] [17] shows that, in such cases, there can be a danger that the action will become negative at large r. On the other hand, in all cases -including black holes with positively curved event horizons -the action is close to zero near to r = r eh . One might be concerned that, if the spacetime around the black hole is not exactly empty, then the action might become negative either at very large values of r or near to the event horizon.…”

“…The number of possible distinct sets of this kind is a measure of the initial entropy of the Universe. Crucially, however, the number of initial data sets we need to consider is cut down by the constraints [[48], Chapter 10], which require the sets to satisfy R(h) = K ab K ab + 16πρ (17) and…”

“…Now let us try to apply this theory to the spacetime edge that [presumably] replaces the singularity inside an AdS black hole. We simply repeat the above reasoning in this case, that is, we just consider all possible "initial" data sets and impose (17) (18), and (19) [and require K ab to be traceless] on the edge and nothing more. [To do otherwise would expose us to the criticism [46] that we are building in a past/future distinction from the outset.]…”