83,902 research outputs found
Green's function for the Relativistic Coulomb System via Sum Over Perturbation Series
We evaluate the Green's function of the D-dimensional relativistic Coulomb
system via sum over perturbation series which is obtained by expanding the
exponential containing the potential term in the path integral
into a power series. The energy spectra and wave functions are extracted from
the resulting amplitude.Comment: 13 pages, ReVTeX, no figure
Analysis of effects of macroscopic propagation and multiple molecular orbitals on the minimum in high-order harmonic generation of aligned CO
We report theoretical calculations on the effect of the multiple orbital
contribution in high-order harmonic generation (HHG) from aligned CO with
inclusion of macroscopic propagation of harmonic fields in the medium. Our
results show very good agreements with recent experiments for the dynamics of
the minimum in HHG spectra as laser intensity or alignment angle changes.
Calculations are carried out to check how the position of the minimum in HHG
spectra depends on the degrees of molecular alignment, laser focusing
conditions, and the effects of alignment-dependent ionization rates of the
different molecular orbitals. These analyses help to explain why the minima
observed in different experiments may vary.Comment: 7 figure
Path integral for a relativistic Aharonov-Bohm-Coulomb system
The path integral for the relativistic spinless Aharonov-Bohm-Coulomb system
is solved, and the energy spectra are extracted from the resulting amplitude.Comment: 6 pages, Revte
Production of Milky Way structure by the Magellanic Clouds
Previous attempts at disturbing the galactic disk by the Magellanic Clouds
relied on direct tidal forcing. However, by allowing the halo to actively
respond rather than remain a rigid contributor to the rotation curve, the
Clouds may produce a wake in the halo which then distorts the disk. Recent work
reported here suggests that the Magellanic Clouds use this mechanism to produce
disk distortions sufficient to account for both the radial location, position
angle and sign of the HI warp and observed anomalies in stellar kinematics
towards the galactic anticenter and LSR motion.Comment: 8 pages, uuencoded compressed PostScript, no figures, html version
with figures and mpeg simulations available at
http://www-astro.phast.umass.edu/Preprints/martin/martin1/lmc_online.htm
Signal of Bose condensation in an optical lattice at finite temperature
We discuss the experimental signal for the Bose condensation of cold atoms in
an optical lattice at finite temperature. Instead of using the visibility of
the interference pattern via the time-of-flight imaging, we show that the
momentum space density profile in the first Brillouin zone, in particular its
bimodal distribution, provides an unambiguous signal for the Bose condensation.
We confirm this point with detailed calculation of the change in the atomic
momentum distribution across the condensation phase transition, taking into
account both the global trapping potential and the atomic interaction effects.Comment: 4 pages, 2 figures, replaced with the published versio
The Dynamical Additivity And The Strong Dynamical Additivity Of Quantum Operations
In the paper, the dynamical additivity of bi-stochastic quantum operations is
characterized and the strong dynamical additivity is obtained under some
restrictions.Comment: 9 pages, LaTeX, change the order of name
Synchronization of One Dimensional Array of Point Josephson Junctions Coupled to a Common Load
We study the synchronization in a one dimensional array of point Josephson
junctions coupled to a common capacitor, which establishes a long-range
interaction between junctions and synchronizes them. The stability diagram of
synchronization in a noise-free system is obtained. The current when junctions
transform from resistive state into superconducting state, is then calculated
and its dependence on the shunt parameters and the dissipation of junctions is
revealed. In the presence of thermal noise, the synchronized oscillations are
destroyed at a critical temperature and the system undergoes a continuous phase
transition of desynchronization. A possible stability diagram of the
synchronized oscillations with respect to thermal noise, current, dissipations
and shunt capacitance is then constructed. Finally we investigate the dynamic
relaxation from random oscillations into synchronized state. The relaxation
time increases with the system size and temperature, but is reduced by the
shunt capacitor.Comment: 11.2 pages, 14 figure
Directed percolation near a wall
Series expansion methods are used to study directed bond percolation clusters
on the square lattice whose lateral growth is restricted by a wall parallel to
the growth direction. The percolation threshold is found to be the same
as that for the bulk. However the values of the critical exponents for the
percolation probability and mean cluster size are quite different from those
for the bulk and are estimated by and respectively. On the other hand the exponent
characterising the scale of the cluster size
distribution is found to be unchanged by the presence of the wall.
The parallel connectedness length, which is the scale for the cluster length
distribution, has an exponent which we estimate to be and is also unchanged. The exponent of the mean
cluster length is related to and by the scaling
relation and using the above estimates
yields to within the accuracy of our results. We conjecture that
this value of is exact and further support for the conjecture is
provided by the direct series expansion estimate .Comment: 12pages LaTeX, ioplppt.sty, to appear in J. Phys.
Ground states of hard-core bosons in one dimensional periodic potentials
With Girardeau's Fermi-Bose mapping, we find the exact ground states of
hard-core bosons residing in a one dimensional periodic potential. The analysis
of these ground states shows that when the number of bosons is commensurate
with the number of wells in the periodic potential, the boson system is a
Mott insulator whose energy gap, however, is given by the single-particle band
gap of the periodic potential; when is not commensurate with , the
system is a metal (not a superfluid). In fact, we argue that there may be no
superfluid phase for any one-dimensional boson system in terms of Landau's
criterion of superfluidity. The Kronig-Penney potential is used to illustrate
our results.Comment: 6 pages, 6 figure
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