62,724 research outputs found
Vector field mediated models of dynamical light velocity
A vector-tensor theory of gravity that was introduced in an earlier
publication is analyzed in detail and its consequences for early universe
cosmology are examined. The multiple light cone structure of the theory
generates different speeds of gravitational and matter wave fronts, and the
contraction of these light cones produces acausal, superluminary inflation that
can resolve the initial value problems of cosmology.Comment: 16 pages, uses amsar
Entangling photons using a charged quantum dot in a microcavity
We present two novel schemes to generate photon polarization entanglement via
single electron spins confined in charged quantum dots inside microcavities.
One scheme is via entangled remote electron spins followed by
negatively-charged exciton emissions, and another scheme is via a single
electron spin followed by the spin state measurement. Both schemes are based on
giant circular birefringence and giant Faraday rotation induced by a single
electron spin in a microcavity. Our schemes are deterministic and can generate
an arbitrary amount of multi-photon entanglement. Following similar procedures,
a scheme for a photon-spin quantum interface is proposed.Comment: 4 pages, 4 figure
A Lensing Reconstruction of Primordial Cosmic Microwave Background Polarization
We discuss a possibility to directly reconstruct the CMB polarization field
at the last scattering surface by accounting for modifications imposed by the
gravitational lensing effect. The suggested method requires a tracer field of
the large scale structure lensing potentials that deflected propagating CMB
photons from the last scattering surface. This required information can come
from a variety of observations on the large scale structure matter
distribution, including convergence reconstructed from lensing shear studies
involving galaxy shapes. In the case of so-called curl, or B,-modes of CMB
polarization, the reconstruction allows one to identify the distinct signature
of inflationary gravitational waves.Comment: 6 pages, 2 figures; PRD submitte
Extended quark mean-field model for neutron stars
We extend the quark mean-field (QMF) model to strangeness freedom to study
the properties of hyperons () in infinite baryon matter and
neutron star properties. The baryon-scalar meson couplings in the QMF model are
determined self-consistently from the quark level, where the quark confinement
is taken into account in terms of a scalar-vector harmonic oscillator
potential. The strength of such confinement potential for quarks is
constrained by the properties of finite nuclei, while the one for quark is
limited by the properties of nuclei with a hyperon. These two
strengths are not same, which represents the SU(3) symmetry breaking
effectively in the QMF model. Also, we use an enhanced coupling with
the vector meson, and both and hyperon potentials can be
properly described in the model. The effects of the SU(3) symmetry breaking on
the neutron star structures are then studied. We find that the SU(3) breaking
shifts earlier the hyperon onset density and makes hyperons more abundant in
the star, in comparisons with the results of the SU(3) symmetry case. However,
it does not affect much the star's maximum mass. The maximum masses are found
to be with hyperons and without hyperons. The
present neutron star model is shown to have limitations on explaining the
recently measured heavy pulsar.Comment: 7 pages, 7 figures, Phys. Rev. C (2014) accepte
Reionization Revisited: Secondary CMB Anisotropies and Polarization
Secondary CMB anisotropies and polarization provide a laboratory to study
structure formation in the reionized epoch. We consider the kinetic
Sunyaev-Zel'dovich effect from mildly nonlinear large-scale structure and show
that it is a natural extension of the perturbative Vishniac effect. If the gas
traces the dark matter to overdensities of order 10, as expected from
simulations, this effect is at least comparable to the Vishniac effect at
arcminute scales. On smaller scales, it may be used to study the thermal
history-dependent clustering of the gas. Polarization is generated through
Thomson scattering of primordial quadrupole anisotropies, kinetic (second order
Doppler) quadrupole anisotropies and intrinsic scattering quadrupole
anisotropies. Small scale polarization results from the density and ionization
modulation of these sources. These effects generically produce comparable E and
B-parity polarization, but of negligible amplitude (0.001-0.01 uK) in adiabatic
CDM models. However, the primordial and kinetic quadrupoles are observationally
comparable today so that a null detection of B-polarization would set
constraints on the evolution and coherence of the velocity field. Conversely, a
detection of a cosmological B-polarization even at large angles does not
necessarily imply the presence of gravity waves or vorticity. For these
calculations, we develop an all-sky generalization of the Limber equation that
allows for an arbitrary local angular dependence of the source for both scalar
and symmetric trace-free tensor fields on the sky.Comment: 14 pages, 12 figures, minor changes and typo fixes reflect published
versio
Giant optical Faraday rotation induced by a single electron spin in a quantum dot: Applications to entangling remote spins via a single photon
We propose a quantum non-demolition method - giant Faraday rotation - to
detect a single electron spin in a quantum dot inside a microcavity where
negatively-charged exciton strongly couples to the cavity mode. Left- and
right-circularly polarized light reflected from the cavity feels different
phase shifts due to cavity quantum electrodynamics and the optical spin
selection rule. This yields giant and tunable Faraday rotation which can be
easily detected experimentally. Based on this spin-detection technique, a
scalable scheme to create an arbitrary amount of entanglement between two or
more remote spins via a single photon is proposed.Comment: 5 pages, 3 figure
Addendum to "Superimposed Oscillations in the WMAP Data?"
We elaborate further on the possibility that the inflationary primordial
power spectrum contains superimposed oscillations. We study various effects
which could influence the calculation of the multipole moments in this case. We
also present the theoretical predictions for two other cosmological
observables, the matter power spectrum and the EE polarization channel.Comment: 4 pages, 3 figures, uses RevTex4, matches published versio
CMB Lensing Reconstruction on the Full Sky
Gravitational lensing of the microwave background by the intervening dark
matter mainly arises from large-angle fluctuations in the projected
gravitational potential and hence offers a unique opportunity to study the
physics of the dark sector at large scales. Studies with surveys that cover
greater than a percent of the sky will require techniques that incorporate the
curvature of the sky. We lay the groundwork for these studies by deriving the
full sky minimum variance quadratic estimators of the lensing potential from
the CMB temperature and polarization fields. We also present a general
technique for constructing these estimators, with harmonic space convolutions
replaced by real space products, that is appropriate for both the full sky
limit and the flat sky approximation. This also extends previous treatments to
include estimators involving the temperature-polarization cross-correlation and
should be useful for next generation experiments in which most of the
additional information from polarization comes from this channel due to
sensitivity limitations.Comment: Accepted for publication in Phys. Rev. D; typos correcte
Random-cluster multi-histogram sampling for the q-state Potts model
Using the random-cluster representation of the -state Potts models we
consider the pooling of data from cluster-update Monte Carlo simulations for
different thermal couplings and number of states per spin . Proper
combination of histograms allows for the evaluation of thermal averages in a
broad range of and values, including non-integer values of . Due to
restrictions in the sampling process proper normalization of the combined
histogram data is non-trivial. We discuss the different possibilities and
analyze their respective ranges of applicability.Comment: 12 pages, 9 figures, RevTeX
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