1,678 research outputs found
Influence of the interface corrugation on the subband dispersions and the optical properties of (113)-oriented GaAs/AlAs superlattices
Strangeness Production in the HSD Transport Approach from SIS to SPS energies
We study systematically the production of strangeness in nuclear reactions
from SIS to SPS energies within the covariant hadronic transport approach HSD.
Whereas the proton and pion rapidity distributions as well as pion transverse
momentum spectra are well described in the hadronic transport model from 2-200
AGeV, the and spectra are noticeably underestimated at AGS energies
while the spectra match well at SIS and SPS energies with the
experimental data. We conclude that the failure of the hadronic model at AGS
energies points towards a nonhadronic phase during the collision of heavy
systems around 10 AGeV.Comment: 25 pages, 19 figure
Probing hadronic formation times with antiprotons in p+A reactions at AGS energies
The production of antiprotons in reactions is calculated in a
microscopic transport approach employing hadronic and string degrees of freedom
(HSD). It is found that the abundancies of antiprotons as observed by the E910
Collaboration in reactions at 12.3 GeV/c as well as 17.5 GeV/c can
approximately be described on the basis of primary proton-nucleon and secondary
meson-baryon production channels for all targets. The transport calculations
demonstrate that the antiproton rapidity distributions for heavy targets are
sensitive to the (or hadron) formation time in the nuclear medium.
Within our analysis the data from the E910 Collaboration are reasonably
described with a formation time of fm/c in the hadron rest frame.Comment: 18 pages, LaTeX, 8 postscript figures; submitted to Nucl. Phys.
Parton-Hadron-String Dynamics: an off-shell transport approach for relativistic energies
The dynamics of partons, hadrons and strings in relativistic nucleus-nucleus
collisions is analyzed within the novel Parton-Hadron-String Dynamics (PHSD)
transport approach, which is applied to Pb+Pb collisions from 20 to 160 A GeV
in order to explore the space-time regions of 'partonic matter'. We find that
even central collisions at the top-SPS energy of 158 A GeV show a large
fraction of non-partonic, i.e. hadronic or string-like matter, which can be
viewed as a hadronic corona. Furthermore, we observe that the partonic phase
has a very low impact on rapidity distributions of hadrons but a sizeable
influence on the transverse mass distribution of final kaons due to the
repulsive partonic mean fields. We also find a significant effect on the
production of multi-strange antibaryons due to a slightly enhanced
pair production in the partonic phase from massive time-like gluon decay and a
larger formation of antibaryons in the hadronization process. All differential
hadron spectra are analyzed in comparison to the data of experimental
collaborations.Comment: 33 pages, 23 figures, submitted to Nulc. Phys.
Rigorous mean-field dynamics of lattice bosons: Quenches from the Mott insulator
We provide a rigorous derivation of Gutzwiller mean-field dynamics for
lattice bosons, showing that it is exact on fully connected lattices. We apply
this formalism to quenches in the interaction parameter from the Mott insulator
to the superfluid state. Although within mean-field the Mott insulator is a
steady state, we show that a dynamical critical interaction exists, such
that for final interaction parameter the Mott insulator is
exponentially unstable towards emerging long-range superfluid order, whereas
for the Mott insulating state is stable. We discuss the implications
of this prediction for finite-dimensional systems.Comment: 6 pages, 3 figures, published versio
Dilepton Production at SPS-energy Heavy Ion Collisions
The production of dileptons is studied within a hadronic transport model. We
investigate the sensitivity of the dilepton spectra to the initial
configuration of the hadronic phase in a ultrarelativistic heavy ion collision.
Possible in medium correction due to the modifications of pions and the pion
form factor in a hadronic gas are discussed.Comment: Dedicated to Gerry Brown in honor of the 32nd celebration of his 39th
birthday. 31 pages Latex including 13 eps-figures, uses psfig.sty and
epsf.st
Correlations and Fluctuations in High-Energy Nuclear Collisions
Nucleon correlations in the target and projectile nuclei are shown to reduce
significantly the fluctuations in multiple nucleon-nucleon collisions, total
multiplicity and transverse energy in relativistic heavy-ion collisions, in
particular for heavy projectile and target. The interplay between cross-section
fluctuations, from color transparency and opacity, and nuclear correlations is
calculated and found to be able to account for large fluctuations in transverse
energy spectra. Numerical implementation of correlations and cross-section
fluctuations in Monte-Carlo codes is discussed.Comment: 30 pages, in Revtex, plus 4 figures. Figures and preprint can be
obtained by mailing address to: [email protected]
SQM 2006: Theory Summary and Perspectives
In this write-up of my SQM 2006 Theory Summary talk I focus on a selection of
key contributions which I consider to have a large impact on the current status
of the field of strangeness physics or which may have the potential to
significantly advance strangeness -- or in general flavor physics -- in the
near future.Comment: 16 pages, 4 figures, SQM 2006 proceedings. Revised version containing
two modifications to the transport theory sectio
The Palomar Transient Factory Orion Project: Eclipsing Binaries and Young Stellar Objects
The Palomar Transient Factory (PTF) Orion project is an experiment within the
broader PTF survey, a systematic automated exploration of the sky for optical
transients. Taking advantage of the wide field of view available using the PTF
camera at the Palomar 48" telescope, 40 nights were dedicated in December
2009-January 2010 to perform continuous high-cadence differential photometry on
a single field containing the young (7-10Myr) 25 Ori association. The primary
motivation for the project is to search for planets around young stars in this
region. The unique data set also provides for much ancillary science. In this
first paper we describe the survey and data reduction pipeline, and present
initial results from an inspection of the most clearly varying stars relating
to two of the ancillary science objectives: detection of eclipsing binaries and
young stellar objects. We find 82 new eclipsing binary systems, 9 of which we
are candidate 25 Ori- or Orion OB1a-association members. Of these, 2 are
potential young W UMa type systems. We report on the possible low-mass (M-dwarf
primary) eclipsing systems in the sample, which include 6 of the candidate
young systems. 45 of the binary systems are close (mainly contact) systems; one
shows an orbital period among the shortest known for W UMa binaries, at
0.2156509 \pm 0.0000071d, with flat-bottomed primary eclipses, and a derived
distance consistent with membership in the general Orion association. One of
the candidate young systems presents an unusual light curve, perhaps
representing a semi-detached binary system with an inflated low-mass primary or
a star with a warped disk, and may represent an additional young Orion member.
Finally, we identify 14 probable new classical T-Tauri stars in our data, along
with one previously known (CVSO 35) and one previously reported as a candidate
weak-line T-Tauri star (SDSS J052700.12+010136.8).Comment: 66 pages, 27 figures, accepted to Astronomical Journal. Minor
typographical corrections and update to author affiliation
Mutual Potential of Homogeneous Polyhedra
The mutual gravitational potential between a pair of homogeneous polyhedra is expressed using an infinite series. The nested volume integrals are evaluated analytically and result in simple tensor expressions containing no special functions. However, complexity increases as O (6 n ), where n is the term degree. An alternate formulation due to Liebenthal is also presented.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42570/1/10569_2004_Article_4621.pd
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