5,502 research outputs found
Self-consistent Green's function calculation of 16O at small missing energies
Calculations of the one-hole spectral function of 16O for small missing
energies are reviewed.
The self-consistent Green's function approach is employed together with the
Faddeev equations technique in order to study the coupling of both
particle-particle and particle-hole phonons to the single-particle motion. The
results indicate that the characteristics of hole fragmentation are related to
the low-lying states of 16O and an improvement of the description of this
spectrum, beyond the random phase approximation, is required to understand the
experimental strength distribution.
A first calculation in this direction that accounts for two-phonon states is
discussed.Comment: Proceedings of ``Nuclear Forces and the Quantum Many-Body Problem'',
INT, Oct. 4-8, 200
Effects of nuclear correlations on the O reactions to discrete final states
Calculations of the O cross sections to the ground state and
first excited levels of the C and N nuclei are presented.
The effects of nuclear fragmentation have been obtained in a self-consistent
approach and are accounted for in the determination of the two-nucleon removal
amplitudes.
The Hilbert space is partitioned in order to compute the contribution of both
long- and short-range effects in a separate way.
Both the two-proton and the proton-neutron emission cross sections have been
computed within the same models for the reaction mechanism and the contribution
from nuclear structure, with the aim of better comparing the differences
between the two physical processes.
The O reaction is found to be sensitive to short-range
correlations, in agreement with previous results. The O cross
section to final states is dominated by the current and tensor
correlations. For both reactions, the interplay between collective (long-range)
effects and short-range and tensor correlations plays an important role. This
suggests that the selectivity of reactions to the final state can be
used to probe correlations also beyond short-range effects.Comment: 13 pages, 9 figure
Role of Long-Range Correlations on the Quenching of Spectroscopic Factors
We consider the proton and neutron quasiparticle orbits around the
closed-shell 56Ni and 48Ca isotopes. It is found that large model spaces
(beyond the capability of shell-model applications) are necessary for
predicting the quenchings of spectroscopic factors.
The particle-vibration coupling is identified as the principal mechanism.
Additional correlations--due to configuration with several particle-hole
excitations--are estimated using shell-model calculations and generate an extra
reduction which is < ~4% for most quasiparticle states. The theoretical
calculations nicely agree with (e,e'p) and heavy ion knock-out experiments.
These results open a new path for a microscopic understanding of the
shell-model.Comment: Minor comments added and typos corrected. Accepted for publication on
Phys. Rev. Let
Faddeev description of two-hole one-particle motion and the single-particle spectral function
The Faddeev technique is employed to address the problem of describing the influence of both particle-particle and particle-hole phonons on the single-particle self-energy. The scope of the few-body Faddeev equations is extended to describe the motion of two-hole one-particle (two-particle one-hole) excitations. This formalism allows to sum both particle-particle and particle-hole phonons, obtained separately in the Random Phase Approximation. The appearance of spurious solutions for the present application of the Faddeev method is related to the inclusion of a consistent set of diagrams. The formalism presented here appears practical for finite nuclei and achieves a simultaneous inclusion of particle-particle and particle-hole phonons to all orders while the spurious solutions are properly eliminated
Spectroscopic Factors in 16O and Nucleon Asymmetry
The self-consistent Green's functions method is employed to study the
spectroscopic factors of quasiparticle states around 16O, 28O, 40Ca and 60Ca.
The Faddeev random phase approximation (FRPA) is used to account for the
coupling of particles with collective excitation modes. Results for 16O are
reviewed first. The same approach is applied to isotopes with large
proton-neutron asymmetry to estimate its effect on spectroscopic factors. The
results, based on the chiral N3LO force, exhibit an asymmetry dependence
similar to that observed in heavy-ion knockout experiments but weaker in
magnitude.Comment: Proceedings of the "KGU Yokohama Autumn School of Nuclear Physics",
October 9-10, 200
Continuous-Variable Quantum Computing in Optical Time-Frequency Modes using Quantum Memories
We develop a scheme for time-frequency encoded continuous-variable
cluster-state quantum computing using quantum memories. In particular, we
propose a method to produce, manipulate and measure 2D cluster states in a
single spatial mode by exploiting the intrinsic time-frequency selectivity of
Raman quantum memories. Time-frequency encoding enables the scheme to be
extremely compact, requiring a number of memories that is a linear function of
only the number of different frequencies in which the computational state is
encoded, independent of its temporal duration. We therefore show that quantum
memories can be a powerful component for scalable photonic quantum information
processing architectures.Comment: 5 pages, 6 figures, and supplementary information. Updated to be
consistent with published versio
Microscopic self-energy calculations and dispersive optical-model potentials
Nucleon self-energies for 40Ca, 48Ca, 60Ca isotopes are generated with the
microscopic Faddeev-random-phase approximation (FRPA). These self-energies are
compared with potentials from the dispersive optical model (DOM) that were
obtained from fitting elastic-scattering and bound-state data for 40Ca and
48Ca. The \textit{ab initio} FRPA is capable of explaining many features of the
empirical DOM potentials including their nucleon asymmetry dependence. The
comparison furthermore provides several suggestions to improve the functional
form of the DOM potentials, including among others the exploration of parity
and angular momentum dependence. The non-locality of the FRPA imaginary
self-energy, illustrated by a substantial orbital angular momentum dependence,
suggests that future DOM fits should consider this feature explicitly. The
roles of the nucleon-nucleon tensor force and charge-exchange component in
generating the asymmetry dependence of the FPRA self-energies are explored. The
global features of the FRPA self-energies are not strongly dependent on the
choice of realistic nucleon-nucleon interaction.Comment: Submitted to Phys. Rev.
A tradeoff in simultaneous quantum-limited phase and loss estimation in interferometry
Interferometry with quantum light is known to provide enhanced precision for
estimating a single phase. However, depending on the parameters involved, the
quantum limit for the simultaneous estimation of multiple parameters may not
attainable, leading to trade-offs in the attainable precisions. Here we study
the simultaneous estimation of two parameters related to optical
interferometry: phase and loss, using a fixed number of photons. We derive a
trade-off in the estimation of these two parameters which shows that, in
contrast to single-parameter estimation, it is impossible to design a strategy
saturating the quantum Cramer-Rao bound for loss and phase estimation in a
single setup simultaneously. We design optimal quantum states with a fixed
number of photons achieving the best possible simultaneous precisions. Our
results reveal general features about concurrently estimating Hamiltonian and
dissipative parameters, and has implications for sophisticated sensing
scenarios such as quantum imaging.Comment: 9 pages, 6 figure
Gluonic and leptonic decays of heavy quarkonia and the determination of and
QCD running coupling constant and are
determined from heavy quarkonia and decays. The
decay rates of and for and
are estimated by taking into account both relativistic and QCD
radiative corrections. The decay amplitudes are derived in the Bethe-Salpeter
formalism, and the decay rates are estimated by using the meson wavefunctions
which are obtained with a QCD-inspired inter-quark potential. For the
decay we find the relativistic correction to be very large
and to severely suppress the decay rate. Using the experimental values of ratio
R_g\equiv \frac {\Gamma (V\longrightarrow 3g)}% {\Gamma (V\longrightarrow
e^{+}e^{-})}\approx 10,~32 for respectively, and the
calculated widths , we find and
. These values for the QCD running coupling
constant are substantially enhanced, as compared with the ones obtained without
relativistic corrections, and are consistent with the QCD scale parameter
. We also find that these
results are mainly due to kinematic corrections and not sensitive to the
dynamical models.Comment: 15 pages in Late
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