15,004 research outputs found
A new Fermi smearing approach for scattering of multi-GeV electrons by nuclei
The cross section for electron scattering by nuclei at high momentum
transfers is calculated within the Fermi smearing approximation (FSA), where
binding effects on the struck nucleon are introduced via the relativistic
Hartree approximation (RHA). The model naturally preserves current
conservation, since the response tensor for an off-shell nucleon conserves the
same form that for a free one but with an effective mass. Different
parameterizations for the inelastic nucleon structure function, are analyzed.
The smearing at the Fermi surface is introduced through a momentum distribution
obtained from a perturbative nuclear matter calculation. Recent CEBAF data on
inclusive scattering of 4.05 GeV electrons on Fe are well reproduced for
all measured geometries for the first time, as is evident from the comparison
with previous calculations.Comment: 8 pages in Revtex4 style, 6 eps figures, to appear in Physical Review
Quantum dynamics in photonic crystals
Employing a recently developed method that is numerically accurate within a
model space simulating the real-time dynamics of few-body systems interacting
with macroscopic environmental quantum fields, we analyze the full dynamics of
an atomic system coupled to a continuum light-field with a gapped spectral
density. This is a situation encountered, for example, in the radiation field
in a photonic crystal, whose analysis has been so far been confined to limiting
cases due to the lack of suitable numerical techniques. We show that both
atomic population and coherence dynamics can drastically deviate from the
results predicted when using the rotating wave approximation, particularly in
the strong coupling regime. Experimental conditions required to observe these
corrections are also discussed.Comment: 5 pages, 2 figures Updated with published versio
Isospin mode splitting and mixing in asymmetric nuclear matter
We estimate exclusive density and asymmetry parameter dependent dispersion
relations of various charged states of pions in asymmetric nuclear matter. The
possibility of matter induced mixing of with is clearly exposed
with the further mass modification of meson due to mixing. Asymmetry
driven mass splitting and mixing amplitude are of the same order as the
corresponding values in vacuum. Closed form analytic results for the mass
shifts and dispersion relations with and without mixing are presented.
Furthermore, we discuss the sensitivity of our results on the scalar mean field
within the framework of Quantum Hadrodynamics.Comment: 8 pages, 4 Figure
Gradient Symplectic Algorithms for Solving the Radial Schrodinger Equation
The radial Schrodinger equation for a spherically symmetric potential can be
regarded as a one dimensional classical harmonic oscillator with a
time-dependent spring constant. For solving classical dynamics problems,
symplectic integrators are well known for their excellent conservation
properties. The class of {\it gradient} symplectic algorithms is particularly
suited for solving harmonic oscillator dynamics. By use of Suzuki's rule for
decomposing time-ordered operators, these algorithms can be easily applied to
the Schrodinger equation. We demonstrate the power of this class of gradient
algorithms by solving the spectrum of highly singular radial potentials using
Killingbeck's method of backward Newton-Ralphson iterations.Comment: 19 pages, 10 figure
Critical velocity for superfluid flow across the BEC-BCS crossover
Critical velocities have been observed in an ultracold superfluid Fermi gas
throughout the BEC-BCS crossover. A pronounced peak of the critical velocity at
unitarity demonstrates that superfluidity is most robust for resonant atomic
interactions. Critical velocities were determined from the abrupt onset of
dissipation when the velocity of a moving one dimensional optical lattice was
varied. The dependence of the critical velocity on lattice depth and on the
inhomogeneous density profile was studied
Phase diagram and universality of the Lennard-Jones gas-liquid system
The gas-liquid phase transition of the three-dimensional Lennard-Jones
particles system is studied by molecular dynamics simulations. The gas and
liquid densities in the coexisting state are determined with high accuracy. The
critical point is determined by the block density analysis of the Binder
parameter with the aid of the law of rectilinear diameter. From the critical
behavior of the gas-liquid coexsisting density, the critical exponent of the
order parameter is estimated to be . Surface tension is
estimated from interface broadening behavior due to capillary waves. From the
critical behavior of the surface tension, the critical exponent of the
correlation length is estimated to be . The obtained values of
and are consistent with those of the Ising universality class.Comment: 8 pages, 8 figures, new results are adde
The Gamow-Teller States in Relativistic Nuclear Models
The Gamow-Teller(GT) states are investigated in relativistic models. The
Landau-Migdal(LM) parameter is introduced in the Lagrangian as a contact term
with the pseudo-vector coupling. In the relativistic model the total GT
strength in the nucleon space is quenched by about 12% in nuclear matter and by
about 6% in finite nuclei, compared with the one of the Ikeda-Fujii-Fujita sum
rule. The quenched amount is taken by nucleon-antinucleon excitations in the
time-like region. Because of the quenching, the relativistic model requires a
larger value of the LM parameter than non-relativistic models in describing the
excitation energy of the GT state. The Pauli blocking terms are not important
for the description of the GT states.Comment: REVTeX4, no figure
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