82,689 research outputs found
Conformal Inflation Coupled to Matter
We formulate new conformal models of inflation and dark energy which
generalise the Higgs-Dilaton scenario. We embed these models in unimodular
gravity whose effect is to break scale invariance in the late time Universe. In
the early Universe, inflation occurs close to a maximum of both the scalar
potential and the scalar coupling to the Ricci scalar in the Jordan frame. At
late times, the dilaton, which decouples from the dynamics during inflation,
receives a potential term from unimodular gravity and leads to the acceleration
of the Universe. We address two central issues in this scenario. First we show
that the Damour-Polyalov mechanism, when non-relativistic matter is present
prior to the start of inflation, sets the initial conditions for inflation at
the maximum of the scalar potential. We then show that conformal invariance
implies that matter particles are not coupled to the dilaton in the late
Universe at the classical level. When fermions acquire masses at low energy,
scale invariance is broken and quantum corrections induce a coupling between
the dilaton and matter which is still small enough to evade the gravitational
constraints in the solar system.Comment: 24 page
Enhanced backscatter of optical beams reflected in turbulent air
Optical beams propagating through air acquire phase distortions from
turbulent fluctuations in the refractive index. While these distortions are
usually deleterious to propagation, beams reflected in a turbulent medium can
undergo a local recovery of spatial coherence and intensity enhancement
referred to as enhanced backscatter (EBS). Using a combination of lab-scale
experiments and simulations, we investigate the EBS of optical beams reflected
from corner cubes and rough surfaces, and identify the regimes in which EBS is
most distinctly observed.Comment: 10 pages, 8 figure
Brane-World Cosmology, Bulk Scalars and Perturbations
We investigate aspects of cosmology in brane world theories with a bulk
scalar field. We concentrate on a recent model motivated from supergravity in
singular spaces. After discussing the background evolution of such a
brane-world, we present the evolution of the density contrast. We compare our
results to those obtained in the (second) Randall-Sundrum scenario and usual 4D
scalar-tensor theories.Comment: 29 pages, one figure, JHEP3-styl
Cosmic Strings, Zero Modes and SUSY breaking in Nonabelian N=1 Gauge Theories
We investigate the microphysics of cosmic strings in Nonabelian gauge
theories with N=1 supersymmetry. We give the vortex solutions in a specific
example and demonstrate that fermionic superconductivity arises because of the
couplings and interactions dictated by supersymmetry. We then use supersymmetry
transformations to obtain the relevant fermionic zero modes and investigate the
role of soft supersymmetry breaking on the existence and properties of the
superconducting strings.Comment: 12 pages, RevTex, submitted to Phys. Rev.
Substantiation data for hypersonic cruise vehicle wing structure evaluation - Volume 1, sections 1-10
Trajectory, load, aerodynamic heating, materials, structural, and thermal analyses for hypersonic cruise vehicle wing
High-precision elements of double-lined spectroscopic binaries from combined interferometry and spectroscopy. Application to the beta Cephei star beta Centauri
We present methodology to derive high-precision estimates of the fundamental
parameters of double-lined spectroscopic binaries. We apply the methods to the
case study of the double-lined beta Cephei star beta Centauri. We also present
a detailed analysis of beta Centauri's line-profile variations caused by its
oscillations. We point out that a systematic error in the orbital amplitudes,
and any quantities derived from them, occurs if the radial velocities of
blended component lines are computed without spectral disentangling. This
technique is an essential ingredient in the derivation of the physical
parameters if the goal is to obtain a precision of only a few percent. We have
devised iteration schemes to obtain the orbital elements for systems whose
lines are blended throughout the orbital cycle. We find the following
parameters for beta Cen: and , an age of years. We deduce two oscillation
frequencies for the broad-lined primary of beta Centauri with degrees higher
than 2. We propose that our iteration schemes be used in any future derivations
of the spectroscopic orbital parameters of double-lined binaries with blended
component lines to which disentangling can be successfully applied.Comment: 12 pages, 13 figures, accepted for publication in A&
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