24,385 research outputs found
Extracting New Physics from the CMB
We review how initial state effects generically yield an oscillatory
component in the primordial power spectrum of inflationary density
perturbations. These oscillatory corrections parametrize unknown new physics at
a scale and are potentially observable if the ratio is
sufficiently large. We clarify to what extent present and future CMB data
analysis can distinguish between the different proposals for initial state
corrections.Comment: Invited talk by B. Greene at the XXII Texas Symposium on Relativistic
Astrophysics, Stanford University, 13-17 December 2004, (TSRA04-0001), 8
pages, LaTeX, some references added, added paragraph at the end of section 2
and an extra note added after the conclusions regarding modifications to the
large k power spectra deduced from galaxy survey
Raising the unification scale in supersymmetry
In the minimal supersymmetric standard model, the three gauge couplings
appear to unify at a mass scale near GeV. We investigate the
possibility that intermediate scale particle thresholds modify the running
couplings so as to increase the unification scale. By requiring consistency of
this scenario, we derive some constraints on the particle content and locations
of the intermediate thresholds. There are remarkably few acceptable solutions
with a single cleanly defined intermediate scale far below the unification
scale.Comment: 22 pages, macros included. One figure, available at
ftp://ftp.phys.ufl.edu/incoming/rais.ep
Comparing key compositional indicators in Jupiter with those in extra-solar giant planets
Spectroscopic transiting observations of the atmospheres of hot Jupiters
around other stars, first with Hubble Space Telescope and then Spitzer, opened
the door to compositional studies of exoplanets. The James Webb Space Telescope
will provide such a profound improvement in signal-to-noise ratio that it will
enable detailed analysis of molecular abundances, including but not limited to
determining abundances of all the major carbon- and oxygen-bearing species in
hot Jupiter atmospheres. This will allow determination of the carbon-to-oxygen
ratio, an essential number for planet formation models and a motivating goal of
the Juno mission currently around JupiterComment: Submitted to the Astro2020 Decadal Survey as a white paper; thematic
areas "Planetary Systems" and "Star and Planet Formation
Bose-Einstein condensate of kicked rotators with time-dependent interaction
A modification of the quantum kicked rotator is suggested with a
time-dependent delta-kicked interaction parameter which can be realized by a
pulsed turn-on of a Feshbach resonance. The mean kinetic energy increases
exponentially with time in contrast to a merely diffusive or linear growth for
the first few kicks for the quantum kicked rotator with a constant interaction
parameter. A recursive relation is derived in a self-consistent random phase
approximation which describes this superdiffusive growth of the kinetic energy
and is compared with numerical simulations. Unlike in the case of the quantum
rotator with constant interaction, a Lax pair is not found. In general the
delta-kicked interaction is found to lead to strong chaotic behaviour.Comment: 4 pages, 3 figure
On the Theory of Fermionic Preheating
In inflationary cosmology, the particles constituting the Universe are
created after inflation due to their interaction with moving inflaton field(s)
in the process of preheating. In the fermionic sector, the leading channel is
out-of equilibrium particle production in the non-perturbative regime of
parametric excitation, which respects Pauli blocking but differs significantly
from the perturbative expectation. We develop theory of fermionic preheating
coupling to the inflaton, without and with expansion of the universe, for light
and massive fermions, to calculate analytically the occupation number of
created fermions, focusing on their spectra and time evolution. In the case of
large resonant parameter we extend for rermions the method of successive
parabolic scattering, earlier developed for bosonic preheating. In an expanding
universe parametric excitation of fermions is stochastic. Created fermions very
quickly, within tens of inflaton oscillations, fill up a sphere of radius
in monetum space. We extend our formalism to the production of
superheavy fermions and to `instant' fermion creation.Comment: 14 pages, latex, 12 figures, submitted for publicatio
Ultracold atom-molecule collisions with fermionic atoms
Elastic and inelastic properties of weakly bound s- and p-wave molecules of
fermionic atoms that collide with a third atom are investigated. Analysis of
calculated collisional properties of s-wave dimers of fermions in different
spin states permit us to compare and highlight the physical mechanisms that
determine the stability of s-wave and p-wave molecules. In contrast to s-wave
molecules, the collisional properties of p-wave molecules are found to be
largely insensitive to variations of the p-wave scattering length and that
these collisions will usually result in short molecular lifetimes. We also
discuss the importance of this result for both theories and experiments
involving degenerate Fermi gases.Comment: 6 pages, 2 figure
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