2,070 research outputs found
Cosmology in the Randall-Sundrum Brane World Scenario
The cosmology of the Randall-Sundrum scenario for a positive tension brane in
a 5-D Universe with localized gravity has been studied extensively recently.
Here we extend it to more general situations. We consider the time-dependent
situation where the two sides of the brane are different AdS/Schwarzschild
spaces. We show that the expansion rate in these models during inflation could
be larger than in brane worlds with compactified extra dimensions of fixed
size. The enhanced expansion rate could lead to the production of density
perturbations of substantially larger amplitude.Comment: 11 pages, revte
Understanding the Nature of ICT-based Innovation Processes in Education - A Theoretical Framework for Informing Policy, Research and Action
Exciting gauge field and gravitons in a brane-anti-brane annihilation
In this paper we point out the inevitability of an explosive production of
gauge field and gravity wave during an open string tachyon condensation in a
cosmological setting. We will be particularly studying an example of
brane-anti-brane inflation in a warped throat where inflation ends via tachyon
condensation. We point out that a tachyonic instability helps fragmenting the
homogeneous tachyon and excites gauge field and contributes to the stress
energy tensor which also feeds into the gravity waves.Comment: 4 pages 8 fig
Shell-model calculations of two-neutrino double-beta decay rates of Ca with GXPF1A interaction
The two-neutrino double beta decay matrix elements and half-lives of
Ca, are calculated within a shell-model approach for transitions to the
ground state and to the first excited state of Ti. We use the full
model space and the GXPF1A interaction, which was recently proposed to
describe the spectroscopic properties of the nuclei in the nuclear mass region
A=47-66. Our results are =
and = . The result for the
decay to the Ti 0 ground state is in good agreement with experiment.
The half-life for the decay to the 2 state is two orders of magnitude
larger than obtained previously.Comment: 6 pages, 4 figure
A Probabilistic Analysis of Kademlia Networks
Kademlia is currently the most widely used searching algorithm in P2P
(peer-to-peer) networks. This work studies an essential question about Kademlia
from a mathematical perspective: how long does it take to locate a node in the
network? To answer it, we introduce a random graph K and study how many steps
are needed to locate a given vertex in K using Kademlia's algorithm, which we
call the routing time. Two slightly different versions of K are studied. In the
first one, vertices of K are labelled with fixed IDs. In the second one,
vertices are assumed to have randomly selected IDs. In both cases, we show that
the routing time is about c*log(n), where n is the number of nodes in the
network and c is an explicitly described constant.Comment: ISAAC 201
Nonlinear Sigma Models with Compact Hyperbolic Target Spaces
We explore the phase structure of nonlinear sigma models with target spaces corresponding to compact quotients of hyperbolic space, focusing on the case of a hyperbolic genus-2 Riemann surface. The continuum theory of these models can be approximated by a lattice spin system which we simulate using Monte Carlo methods. The target space possesses interesting geometric and topological properties which are reflected in novel features of the sigma model. In particular, we observe a topological phase transition at a critical temperature, above which vortices proliferate, reminiscent of the Kosterlitz-Thouless phase transition in the O(2) model [1, 2]. Unlike in the O(2) case, there are many different types of vortices, suggesting a possible analogy to the Hagedorn treatment of statistical mechanics of a proliferating number of hadron species. Below the critical temperature the spins cluster around six special points in the target space known as Weierstrass points. The diversity of compact hyperbolic manifolds suggests that our model is only the simplest example of a broad class of statistical mechanical models whose main features can be understood essentially in geometric terms
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