28,090 research outputs found
3P_2-3F_2 pairing in neutron matter with modern nucleon-nucleon potentials
We present results for the pairing gap in neutron matter with
several realistic nucleon-nucleon potentials, in particular with recent,
phase-shift equivalent potentials. We find that their predictions for the gap
cannot be trusted at densities above , where is
the saturation density for symmetric nuclear matter. In order to make
predictions above that density, potential models which fit the nucleon-nucleon
phase shifts up to about 1 GeV are required.Comment: Revtex style, 19 pages, 6 figures inlude
Star formation rates and chemical abundances of emission line galaxies in intermediate-redshift clusters
We examine the evolutionary status of luminous, star-forming galaxies in
intermediate-redshift clusters by considering their star formation rates and
the chemical and ionsiation properties of their interstellar emitting gas. Our
sample consists of 17 massive, star-forming, mostly disk galaxies with
M_{B}<-20, in clusters with redshifts in the range 0.31< z <0.59, with a median
of =0.42. We compare these galaxies with the identically selected and
analysed intermediate-redshift field sample of Mouhcine et al. (2006), and with
local galaxies from the Nearby Field Galaxy Survey of Jansen et al. (2000).
From our optical spectra we measure the equivalent widths of OII, Hbeta and
OIII emission lines to determine diagnostic line ratios, oxygen abundances, and
extinction-corrected star formation rates. The star-forming galaxies in
intermediate-redshift clusters display emission line equivalent widths which
are, on average, significantly smaller than measured for field galaxies at
comparable redshifts. However, a contrasting fraction of our cluster galaxies
have equivalent widths similar to the highest observed in the field. This
tentatively suggests a bimodality in the star-formation rates per unit
luminosity for galaxies in distant clusters. We find no evidence for further
bimodalities, or differences between our cluster and field samples, when
examining additional diagnostics and the oxygen abundances of our galaxies.
This maybe because no such differences exist, perhaps because the cluster
galaxies which still display signs of star-formation have recently arrived from
the field. In order to examine this topic with more certainty, and to further
investigate the way in which any disparity varies as a function of cluster
properties, larger spectroscopic samples are needed.Comment: 10 pages, 6 figures, MNRAS in pres
Scattering into Cones and Flux across Surfaces in Quantum Mechanics: a Pathwise Probabilistic Approach
We show how the scattering-into-cones and flux-across-surfaces theorems in
Quantum Mechanics have very intuitive pathwise probabilistic versions based on
some results by Carlen about large time behaviour of paths of Nelson
diffusions. The quantum mechanical results can be then recovered by taking
expectations in our pathwise statements.Comment: To appear in Journal of Mathematical Physic
Charge transfer and positron states at alkali-metal-covered nickel surfaces
We report calculations of the positron surface state on clean and alkali-metal- (Na,Cs) covered Ni surfaces. It is shown that the alkali adsorption increases the surface-state binding energy. With the lowering of the electron work function, this leads to positronium desorption energies which are weakly dependent on the alkali coverage, in agreement with the recent experiments of Gidley, Köymen, and Capehart. It is shown that the positron becomes mainly localized between the substrate and the overlayer, and that the lifetime is shorter for positrons on the alkali-metal-covered surface.Peer reviewe
Embedding massive flavor in ABJM
We add massive fundamental matter to the ABJM model by adding D6-branes
wrapped asymptotically over RP3. We find two types of solutions at finite
temperature, one that enters the black hole and one that ends before the black
hole. We analyze the behavior of the free energy as a function of temperature,
and find that the system exhibits a phase transition between the two types of
solutions, similar to what happens in the D3-D7 system. We also analyze the
meson spectrum in the model and find several massive scalar modes, again, quite
like the D3-D7 system. We end with a calculation of the conductivities in the
two phases.Comment: 26 pages, 6 figures; version published in JHE
Decay rate measurement of the first vibrationally excited state of MgH in a cryogenic Paul trap
We present a method to measure the decay rate of the first excited
vibrational state of simple polar molecular ions being part of a Coulomb
crystal in a cryogenic linear Paul trap. Specifically, we have monitored the
decay of the == towards the ==
level in MgH by saturated laser excitation of the ==-== transition followed by state selective
resonance enhanced two-photon dissociation out of the == level. The technique enables the determination of decay rates, and
thus absorption strengths, with an accuracy at the few percent level.Comment: 5 pages, 4 figure
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