58,295 research outputs found
Asymptotic cosmological solutions for string/brane gases with solitonic fluxes
We present new cosmological solutions for brane gases with solitonic fluxes
that can dynamically explain the existence of three large spatial dimensions.
This reasserts the importance of fluxes for understanding the full space of
solutions in a potential implementation of the Brandenberger-Vafa mechanism
with M2-branes. Additionally, we study a particular example in which the
cosmological dynamics supported by a string gas with a NS flux in the
ten-dimensional dilaton gravity framework is asymptotically equivalent to that
of a M2-brane gas with a certain wrapping configuration in eleven-dimensional
supergravity. We speculate that this connection between the ten- and
eleven-dimensional implementations of the Brandenberger-Vafa mechanism could be
a general feature.Comment: 9 pages, 2 figures, revtex
Can the string scale be related to the cosmic baryon asymmetry?
In a previous work, a mechanism was presented by which baryon asymmetry can
be generated during inflation from elliptically polarized gravitons.
Nonetheless, the mechanism only generated a realistic baryon asymmetry under
special circumstances which requires an enhancement of the lepton number from
an unspecified GUT. In this note we provide a stringy embedding of this
mechanism through the Green-Schwarz mechanism, demonstrating that if the
model-independent axion is the source of the gravitational waves responsible
for the lepton asymmetry, one can observationally constrain the string scale
and coupling.Comment: 12 Pages, typo corrected in the tex
Geometry of fully coordinated, two-dimensional percolation
We study the geometry of the critical clusters in fully coordinated
percolation on the square lattice. By Monte Carlo simulations (static
exponents) and normal mode analysis (dynamic exponents), we find that this
problem is in the same universality class with ordinary percolation statically
but not so dynamically. We show that there are large differences in the number
and distribution of the interior sites between the two problems which may
account for the different dynamic nature.Comment: ReVTeX, 5 pages, 6 figure
Late time evolution of brane gas cosmology and compact internal dimensions
We study the late-time behavior of a universe in the framework of brane gas
cosmology. We investigate the evolution of a universe with a gas of
supergravity particles and a gas of branes. Considering the case when different
dimensions are anisotropically wrapped by various branes, we have derived
Friedman-like equations governing the dynamics of wrapped and unwrapped
subvolumes. We point out that the compact internal dimensions are wrapped by
three or higher dimensional branes.Comment: 16 pages, typos, references, comment on the possibility of
stabilizing the internal dimensions with fluxe
- …