192 research outputs found
Verifying a quasi-classical spin model of perturbed quantum rewinding in a Fermi gas
We systematically test a quasi-classical spin model of a large spin-lattice
in energy space, with a tunable, reversible Hamiltonian and effective
long-range interactions. The system is simulated by a weakly interacting Fermi
gas undergoing perturbed quantum rewinding using radio-frequency(RF) pulses.
The model reported here is found to be in a quantitative agreement with
measurements of the ensemble-averaged energy-resolved spin density. This work
elucidates the effects of RF detunings on the system and measurements, pointing
the way to new correlation measurement methods.Comment: 13 pages 8 figure
The Updated Zwicky Catalog (UZC)
The Zwicky Catalog of galaxies (ZC), with m_Zw<=15.5mag, has been the basis
for the Center for Astrophysics (CfA) redshift surveys. To date, analyses of
the ZC and redshift surveys based on it have relied on heterogeneous sets of
galaxy coordinates and redshifts. Here we correct some of the inadequacies of
previous catalogs by providing: (1) coordinates with <~2 arcsec errors for all
of the Nuzc catalog galaxies, (2) homogeneously estimated redshifts for the
majority (98%) of the data taken at the CfA (14,632 spectra), and (3) an
estimate of the remaining "blunder" rate for both the CfA redshifts and for
those compiled from the literature. For the reanalyzed CfA data we include a
calibrated, uniformly determined error and an indication of the presence of
emission lines in each spectrum. We provide redshifts for 7,257 galaxies in the
CfA2 redshift survey not previously published; for another 5,625 CfA redshifts
we list the remeasured or uniformly re-reduced value. Among our new
measurements, Nmul are members of UZC "multiplets" associated with the original
Zwicky catalog position in the coordinate range where the catalog is 98%
complete. These multiplets provide new candidates for examination of tidal
interactions among galaxies. All of the new redshifts correspond to UZC
galaxies with properties recorded in the CfA redshift compilation known as
ZCAT. About 1,000 of our new measurements were motivated either by inadequate
signal-to-noise in the original spectrum or by an ambiguous identification of
the galaxy associated with a ZCAT redshift. The redshift catalog we include
here is ~96% complete to m_Zw<=15.5, and ~98% complete (12,925 galaxies out of
a total of 13,150) for the RA(1950) ranges [20h--4h] and [8h--17h] and
DEC(1950) range [-2.5d--50d]. (abridged)Comment: 34 pp, 7 figs, PASP 1999, 111, 43
Polarons in the radio-frequency spectrum of a quasi-two-dimensional Fermi gas
We measure radio-frequency spectra for a two-component mixture of a Li
atomic Fermi gas in the quasi-two-dimensional regime. Near the Feshbach
resonance, where the transverse Fermi energy is large compared to the
confinement-induced dimer binding energies for the initial and final states, we
find that the observed resonances do not correspond to transitions between
confinement-induced dimers. The spectrum appears to be well-described by
transitions between noninteracting polaron states in two dimensions.Comment: 5 pages, 4 figures and supplementary material 4 pages, 3 figure
J/psi c\bar{c} production in e+e- and hadronic interactions
Predictions of the nonperturbative Quark Gluon Strings model based on the
1/N-expansion in QCD and string picture of interactions for production of
states containing heavy quarks are considered. Relations between fragmentation
functions for different states are used to predict the fragmentation function
of c-quark to J/psi-mesons. The resulting cross section for J/psi-production in
e+e- annihilation is in a good agreement with recent Belle result. It is argued
that associated production of c\bar{c} states with open charm should give a
substantial contribution to production of these states in hadronic interactions
at very high energies.Comment: 7 pages, 2 figure
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