1,214 research outputs found
Sum Rule Description of Color Transparency
The assumption that a small point-like configuration does not interact with
nucleons leads to a new set of sum rules that are interpreted as models of the
baryon-nucleon interaction. These models are rendered semi-realistic by
requiring consistency with data for cross section fluctuations in proton-proton
diffractive collisions.Comment: 22 pages + 3 postscript figures attache
Nonlocal properties of entangled two-photon generalized binomial states in two separate cavities
We consider entangled two-photon generalized binomial states of the
electromagnetic field in two separate cavities. The nonlocal properties of this
entangled field state are analyzed by studying the electric field correlations
between the two cavities. A Bell's inequality violation is obtained using an
appropriate dichotomic cavity operator, that is in principle measurable.Comment: 5 pages, 1 figur
Linear amplification and quantum cloning for non-Gaussian continuous variables
We investigate phase-insensitive linear amplification at the quantum limit
for single- and two-mode states and show that there exists a broad class of
non-Gaussian states whose nonclassicality survives even at an arbitrarily large
gain. We identify the corresponding observable nonclassical effects and find
that they include, remarkably, two-mode entanglement. The implications of our
results for quantum cloning outside the Gaussian regime are also addressed.Comment: published version with reference updat
Phase properties of hypergeometric states and negative hypergeometric states
We show that the three quantum states (Plya states, the
generalized non-classical states related to Hahn polynomials and negative
hypergeometric states) introduced recently as intermediates states which
interpolate between the binomial states and negative binomial states are
essentially identical. By using the Hermitial-phase-operator formalism, the
phase properties of the hypergeometric states and negative hypergeometric
states are studied in detail. We find that the number of peaks of phase
probability distribution is one for the hypergeometric states and for the
negative hypergeometric states.Comment: 7 pages, 4 figure
Statistics of Raman-Active Excitations via Masurement of Stokes-Anti-Stokes Correlations
A general fundamental relation connecting the correlation of Stokes and
anti-Stokes modes to the quantum statistical behavior of vibration and pump
modes in Raman-active materials is derived. We show that under certain
conditions this relation can be used to determine the equilibrium number
variance of phonons.Time and temperature ranges for which such conditions can
be satisfied are studied and found to be available in todays' experimental
standards. Furthermore, we examine the results in the presence of multi-mode
pump as well as for the coupling of pump to the many vibration modes and
discuss their validity in these cases.Comment: 12 pages, 1 figure, accepted for publication in Phys.Rev.
Roper excitation in reactions
We calculate differential cross sections and the spin transfer coefficient
in the reaction for proton
bombarding energies from 1 to 10 GeV and invariant masses spanning
the region of the N(1440) Roper resonance. Two processes --
excitation in the -particle and Roper excitation in the proton -- are
included in an effective reaction model which was shown previously to reproduce
existing inclusive spectra. The present calculations demonstrate that these two
contributions can be clearly distinguished via , even under kinematic
conditions where cross sections alone exhibit no clear peak structure due to
the excitation of the Roper.Comment: 12 pages, 11 ps figures, Late
Novel approach to the study of quantum effects in the early universe
We develop a theoretical frame for the study of classical and quantum
gravitational waves based on the properties of a nonlinear ordinary
differential equation for a function of the conformal time
, called the auxiliary field equation. At the classical level,
can be expressed by means of two independent solutions of the
''master equation'' to which the perturbed Einstein equations for the
gravitational waves can be reduced. At the quantum level, all the significant
physical quantities can be formulated using Bogolubov transformations and the
operator quadratic Hamiltonian corresponding to the classical version of a
damped parametrically excited oscillator where the varying mass is replaced by
the square cosmological scale factor . A quantum approach to the
generation of gravitational waves is proposed on the grounds of the previous
dependent Hamiltonian. An estimate in terms of and
of the destruction of quantum coherence due to the gravitational
evolution and an exact expression for the phase of a gravitational wave
corresponding to any value of are also obtained. We conclude by
discussing a few applications to quasi-de Sitter and standard de Sitter
scenarios.Comment: 20 pages, to appear on PRD. Already published background material has
been either settled up in a more compact form or eliminate
Approach to Perturbative Results in the N-Delta Transition
We show that constraints from perturbative QCD calculations play a role in
the nucleon to Delta(1232) electromagnetic transition even at moderate momentum
transfer scales. The pQCD constraints, tied to real photoproduction data and
unseparated resonance response functions, lead to explicit forms for the
helicity amplitudes wherein the E2/M1 ratio remains small at moderately large
momentum transfer.Comment: 4 pages, 2 figures, ReVTe
Frequency of and Prognostic Significance of Atrial Fibrillation in Patients Undergoing Transcatheter Aortic Valve Implantation
The prognostic implications of preexisting atrial fibrillation (AF) and new-onset AF (NOAF) in transcatheter aortic valve implantation (TAVI) remain uncertain. This study assesses the epidemiology of AF in patients treated with TAVI and evaluates their outcomes according to the presence of preexisting AF or NOAF. A retrospective analysis of 708 patients undergoing TAVI from 2 heart hospitals was performed. Patients were divided into 3 study groups: sinus rhythm (n = 423), preexisting AF (n = 219), and NOAF (n = 66). Primary outcomes of interest were all-cause death and stroke both at 30-day and at 1-year follow-up. Preexisting AF was present in 30.9% of our study population, whereas NOAF was observed in 9.3% of patients after TAVI. AF and NOAF patients showed a higher rate of 1-year all-cause mortality compared with patients in sinus rhythm (14.6% vs 6.5% for preexisting AF and 16.3% vs 6.5% for NOAF, p = 0.007). No differences in 30-day mortality were observed between groups. In patients with AF (either preexisting and new-onset), those discharged with single antiplatelet therapy displayed higher mortality rates at 1 year (42.9% vs 11.7%, p = 0.006). Preexisting AF remained an independent predictor of mortality at 1-year follow-up (hazard ratio [HR] 2.34, 95% CI 1.22 to 4.48, p = 0.010). Independent predictors of NOAF were transapical and transaortic approach as well as balloon postdilatation (HR 3.48, 95% CI 1.66 to 7.29, p = 0.001; HR 5.08, 95% CI 2.08 to 12.39, p <0.001; HR 2.76, 95% CI 1.25 to 6.08, p = 0.012, respectively). In conclusion, preexisting AF is common in patients undergoing TAVI and is associated with a twofold increased risk of 1-year mortality. This negative effect is most pronounced in patients discharged with single antiplatelet therapy compared with other antithrombotic regimens
Position-momentum local realism violation of the Hardy type
We show that it is, in principle, possible to perform local realism violating
experiments of the Hardy type in which only position and momentum measurements
are made on two particles emanating from a common source. In the optical
domain, homodyne detection of the in-phase and out-of-phase amplitude
components of an electromagnetic field is analogous to position and momentum
measurement. Hence, local realism violations of the Hardy type are possible in
optical systems employing only homodyne detection.Comment: 10 pages, no figures, to be published in Physical Review
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