16,173 research outputs found
Towards a fully self-consistent spectral function of the nucleon in nuclear matter
We present a calculation of nuclear matter which goes beyond the usual
quasi-particle approximation in that it includes part of the off-shell
dependence of the self-energy in the self-consistent solution of the
single-particle spectrum. The spectral function is separated in contributions
for energies above and below the chemical potential. For holes we approximate
the spectral function for energies below the chemical potential by a
-function at the quasi-particle peak and retain the standard form for
energies above the chemical potential. For particles a similar procedure is
followed. The approximated spectral function is consistently used at all levels
of the calculation. Results for a model calculation are presented, the main
conclusion is that although several observables are affected by the inclusion
of the continuum contributions the physical consistency of the model does not
improve with the improved self-consistency of the solution method. This in
contrast to expectations based on the crucial role of self-consistency in the
proofs of conservation laws.Comment: 26 pages Revtex with 4 figures, submitted to Phys. Rev.
A comprehensive Maximum Likelihood analysis of the structural properties of faint Milky Way satellites
We derive the structural parameters of the recently discovered very low
luminosity Milky Way satellites through a Maximum Likelihood algorithm applied
to SDSS data. For each satellite, even when only a few tens of stars are
available down to the SDSS flux limit, the algorithm yields robust estimates
and errors for the centroid, position angle, ellipticity, exponential
half-light radius and number of member stars. This latter parameter is then
used in conjunction with stellar population models of the satellites to derive
their absolute magnitudes and stellar masses, accounting for `CMD shot-noise'.
We find that faint systems are somewhat more elliptical than initially found
and ascribe that to the previous use of smoothed maps which can be dominated by
the smoothing kernel. As a result, the faintest half of the Milky Way dwarf
galaxies (M_V>-7.5) is significantly (4-sigma) flatter (e=0.47+/-0.03) than its
brightest half (M_V<-7.5, e=0.32+/-0.02). From our best models, we also
investigate whether the seemingly distorted shape of the satellites, often
taken to be a sign of tidal distortion, can be quantified. We find that, except
for tentative evidence of distortion in CVnI and UMaII, these can be completely
accounted for by Poisson scatter in the sparsely sampled systems. We consider
three scenarios that could explain the rather elongated shape of faint
satellites: rotation supported systems, stars following the shape of more
triaxial dark matter subhalos, or elongation due to tidal interaction with the
Milky Way. Although none of these is entirely satisfactory, the last one
appears the least problematic, but warrants much deeper observations to track
evidence of such tidal interaction.Comment: 20 pages, 11 figures, ApJ in press; some typos corrected, magnitude
of BooII corrected (thanks go to Shane Walsh for spotting the erroneous
original value
A Look At Three Different Scenarios for Bulge Formation
In this paper, we present three qualitatively different scenarios for bulge
formation: a secular evolution model in which bulges form after disks and
undergo several central starbursts, a primordial collapse model in which bulges
and disks form simultaneously, and an early bulge formation model in which
bulges form prior to disks. We normalize our models to the local z=0
observations of de Jong & van der Kruit (1994) and Peletier & Balcells (1996)
and make comparisons with high redshift observations. We consider model
predictions relating directly to bulge-to-disk properties. As expected, smaller
bulge-to-disk ratios and bluer bulge colors are predicted by the secular
evolution model at all redshifts, although uncertainties in the data are
currently too large to differentiate strongly between the models.Comment: 19 pages, 6 figures, accepted for publication in the Astrophysical
Journa
Neutrino interaction classification with a convolutional neural network in the DUNE far detector
Prospects for beyond the Standard Model physics searches at the Deep Underground Neutrino Experiment
Relativistic Brueckner-Hartree-Fock calculations with explicit intermediate negative energy states
In a relativistic Brueckner-Hartree-Fock calculation we include explicit
negative-energy states in the two-body propagator. This is achieved by using
the Gross spectator-equation, modified by medium effects. Qualitatively our
results compare well with other RBHF calculations. In some details significant
differences occur, e.g, our equation of state is stiffer and the momentum
dependence of the self-energy components is stronger than found in a reference
calculation without intermediate negative energy states.Comment: 13 pages Revtex, 5 figures included seperatel
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