5,641 research outputs found
Landscape Predictions from Cosmological Vacuum Selection
In BP models with hundreds of fluxes, we compute the effects of cosmological
dynamics on the probability distribution of landscape vacua. Starting from
generic initial conditions, we find that most fluxes are dynamically driven
into a different and much narrower range of values than expected from landscape
statistics alone. Hence, cosmological evolution will access only a tiny
fraction of the vacua with small cosmological constant. This leads to a host of
sharp predictions. Unlike other approaches to eternal inflation, the
holographic measure employed here does not lead to "staggering", an excessive
spread of probabilities that would doom the string landscape as a solution to
the cosmological constant problem.Comment: 15 pages, 6 figures, v4 prd format, minor editin
Inflation and Large Internal Dimensions
We consider some aspects of inflation in models with large internal
dimensions. If inflation occurs on a 3D wall after the stabilization of
internal dimensions in the models with low unification scale (M ~ 1 TeV), the
inflaton field must be extremely light. This problem may disappear In models
with intermediate (M ~10^{11} GeV) to high (M ~ 10^{16} GeV) unification scale.
However, in all of these cases the wall inflation does not provide a complete
solution to the horizon and flatness problems. To solve them, there must be a
stage of inflation in the bulk before the compactification of internal
dimensions.Comment: 4 pages, revtex, minor modification
Dynamical renormalization group methods in theory of eternal inflation
Dynamics of eternal inflation on the landscape admits description in terms of
the Martin-Siggia-Rose (MSR) effective field theory that is in one-to-one
correspondence with vacuum dynamics equations. On those sectors of the
landscape, where transport properties of the probability measure for eternal
inflation are important, renormalization group fixed points of the MSR
effective action determine late time behavior of the probability measure. I
argue that these RG fixed points may be relevant for the solution of the gauge
invariance problem for eternal inflation.Comment: 11 pages; invited mini-review for Grav.Cos
Living with ghosts in Lorentz invariant theories
We argue that theories with ghosts may have a long lived vacuum state even if
all interactions are Lorentz preserving. In space-time dimension D = 2, we
consider the tree level decay rate of the vacuum into ghosts and ordinary
particles mediated by non-derivative interactions, showing that this is finite
and logarithmically growing in time. For D > 2, the decay rate is divergent
unless we assume that the interaction between ordinary matter and the ghost
sector is soft in the UV, so that it can be described in terms of non-local
form factors rather than point-like vertices. We provide an example of a
nonlocal gravitational-strength interaction between the two sectors, which
appears to satisfy all observational constraints.Comment: 17 pages, comments and references adde
Vacuum Decay on a Brane World
The bubble nucleation rate for a first order phase transition occurring on a
brane world is calculated. Both the Coleman-de Luccia thin wall instanton and
the Hawking-Moss instanton are considered. The results are compared with the
corresponding nucleation rates for standard four-dimensional gravity.Comment: 5 page
Towards a gauge invariant volume-weighted probability measure for eternal inflation
An improved volume-weighted probability measure for eternal inflation is
proposed. For the models studied in this paper it leads to simple and
intuitively expected gauge-invariant results.Comment: 16 pages, 3 figs, few misprints corrected, comments adde
Nuclear Physics in a Susy Universe
We refine a previous zeroth order analysis of the nuclear properties of a
supersymmetric (susy) universe with standard model particle content plus
degenerate susy partners. No assumptions are made concerning the Higgs
structure except we assume that the degenerate fermion/sfermion masses are
non-zero. This alternate universe has been dubbed Susyria and it has been
proposed that such a world may exist with zero vacuum energy in the string
landscape.Comment: 8 pages, 1 figur
Phase transition in scalar -theory beyond the super daisy resummations
The temperature phase transition in scalar field theory with
spontaneous symmetry breaking is investigated in a partly resummed perturbative
approach. The second Legendre transform is used and the resulting gap equation
is considered in the extrema of the free energy functional. It is found that
the phase transition is of first order in the super daisy as well as in a
certain beyond super daisy resummations. No unwanted imaginary parts in the
free energy are found but a loss of the smallness of the effective expansion
parameter near the phase transition temperature is found in both cases. This
means an insufficiency of the resummations or a deficit of the perturbative
approach.Comment: 14 page
Functional Approach to Stochastic Inflation
We propose functional approach to the stochastic inflationary universe
dynamics. It is based on path integral representation of the solution to the
differential equation for the scalar field probability distribution. In the
saddle-point approximation scalar field probability distributions of various
type are derived and the statistics of the inflationary-history-dependent
functionals is developed.Comment: 20 pages, Preprint BROWN-HET-960, uses phyzz
Integral functions of electron lateral distribution and their fluctuations in electron-photon cascades
Monte Carlo simulated lateral distribution functions for electrons of EPC developing in lead, at superhigh energies (.1-1 PeV) for depths t or = 60 c.u. delta t=1t. c.u. are presented. The higher moment characteristics, i.e., variation, asymmetry, excess, are presented along with analytical solutions for the same characteristics at fixed observation level calculated to theory approximations A and B by using numerical inversion of the Laplace transformation. The conclusion is made of a complex, usually non-Gaussian shape of the function of the particle number distribution within a circle of given radius at fixed depth
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