7,399 research outputs found
The initial conditions of the Universe and holography
We address the initial conditions for an expanding cosmology using the
holographic principle. For the case of a closed model, the old prescription of
Fishler and Susskind, that uses the particle horizon to encode the bulk degrees
of freedom, can be implemented for accelerated models with enough acceleration.
As a bonus we have singularity free bouncing models. The bound is saturated for
co-dimension one branes dominated universes.Comment: Talk presented at the XXVIII Spanish Relativity Meeting E.R.E. 2005,
Oviedo, September 6-10, 2005, to be published by AIP Conference Proceedings,
4 page
Magnetization switching in nanoscale ferromagnetic grains: simulations with heterogeneous nucleation
We present results obtained with various types of heterogeneous nucleation in
a kinetic Ising model of magnetization switching in single-domain ferromagnetic
nanoparticles. We investigate the effect of the presence of the system boundary
and make comparison with simulations on periodic lattices. We also study
systems with bulk disorder and compare how two different types of disorder
influence the switching behavior.Comment: 3 pages, 4 Postscript figure
Graphical and Kinematical Approach to Cosmological Horizons
We study the apparition of event horizons in accelerated expanding
cosmologies. We give a graphical and analytical representation of the horizons
using proper distances to coordinate the events. Our analysis is mainly
kinematical. We show that, independently of the dynamical equations, all the
event horizons tend in the future infinity to a given expression depending on
the scale factor that we call asymptotic horizon. We also encounter a subclass
of accelerating models without horizon. When the ingoing null geodesics do not
change concavity in its cosmic evolution we recover the de Sitter and
quintessence-Friedmann-Robertson-Walker models.Comment: Latex2e, 27 pages, 4 figures, submitted to Class. Quantum Gra
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