26 research outputs found
Inflation and Holography in String Theory
The encoding of an inflating patch of space-time in terms of a dual theory is
discussed. Following Bousso's interpretation of the holographic principle, we
find that those are generically described not by states in the dual theory but
by density matrices. We try to implement this idea on simple deformations of
the AdS/CFT examples, and an argument is given as to why inflation is so
elusive to string theory.Comment: 15 pages, LaTeX, 2 figures. Uses psbox.te
Generalized Quantum Theory of Recollapsing Homogeneous Cosmologies
A sum-over-histories generalized quantum theory is developed for homogeneous
minisuperspace type A Bianchi cosmological models, focussing on the particular
example of the classically recollapsing Bianchi IX universe. The decoherence
functional for such universes is exhibited. We show how the probabilities of
decoherent sets of alternative, coarse-grained histories of these model
universes can be calculated. We consider in particular the probabilities for
classical evolution defined by a suitable coarse-graining. For a restricted
class of initial conditions and coarse grainings we exhibit the approximate
decoherence of alternative histories in which the universe behaves classically
and those in which it does not. For these situations we show that the
probability is near unity for the universe to recontract classically if it
expands classically. We also determine the relative probabilities of
quasi-classical trajectories for initial states of WKB form, recovering for
such states a precise form of the familiar heuristic "J d\Sigma" rule of
quantum cosmology, as well as a generalization of this rule to generic initial
states.Comment: 41 pages, 4 eps figures, revtex 4. Modest revisions throughout.
Physics unchanged. To appear in Phys. Rev.
Spontaneous Creation of Inflationary Universes and the Cosmic Landscape
We study some gravitational instanton solutions that offer a natural
realization of the spontaneous creation of inflationary universes in the brane
world context in string theory. Decoherence due to couplings of higher
(perturbative) modes of the metric as well as matter fields modifies the
Hartle-Hawking wavefunction for de Sitter space. Generalizing this new
wavefunction to be used in string theory, we propose a principle in string
theory that hopefully will lead us to the particular vacuum we live in, thus
avoiding the anthropic principle. As an illustration of this idea, we give a
phenomenological analysis of the probability of quantum tunneling to various
stringy vacua. We find that the preferred tunneling is to an inflationary
universe (like our early universe), not to a universe with a very small
cosmological constant (i.e., like today's universe) and not to a 10-dimensional
uncompactified de Sitter universe. Such preferred solutions are interesting as
they offer a cosmological mechanism for the stabilization of extra dimensions
during the inflationary epoch.Comment: 52 pages, 7 figures, 1 table. Added discussion on supercritical
string vacua, added reference
Prevalência das dermatopatias não-tumorais em cães do município de Santa Maria, Rio Grande do Sul (2005-2008)
Consumption of flavonoids in onions and black tea: lack of effect on F-2-isoprostanes and autoantibodies to oxidized LDL in healthy humans
Effect of dietary quercetin on oxidative DNA damage in healthy human subjects.
British Journal of Nutrition846919-925BJNU