20,662 research outputs found
The role of shear in dissipative gravitational collapse
In this paper we investigate the physics of a radiating star undergoing
dissipative collapse in the form of a radial heat flux. Our treatment clearly
demonstrates how the presence of shear affects the collapse process; we are in
a position to contrast the physical features of the collapsing sphere in the
presence of shear with the shear-free case. By employing a causal heat
transport equation of the Maxwell-Cattaneo form we show that the shear leads to
an enhancement of the core temperature thus emphasizing that relaxational
effects cannot be ignored when the star leaves hydrostatic equilibrium.Comment: 15 pages, To appear in Int. J. Mod. Phys.
Simulation of electron transport in quantum well devices
Double barrier resonant tunneling diodes (DBRTD) have received much attention as possible terahertz devices. Despite impressive experimental results, the specifics of the device physics (i.e., how the electrons propagate through the structure) are only qualitatively understood. Therefore, better transport models are warranted if this technology is to mature. In this paper, the Lattice Wigner function is used to explain the important transport issues associated with DBRTD device behavior
The Stability of Strange Star Crusts and Strangelets
We construct strangelets, taking into account electrostatic effects,
including Debye screening, and arbitrary surface tension sigma of the interface
between vacuum and quark matter. We find that there is a critical surface
tension sigma_crit below which large strangelets are unstable to fragmentation
and below which quark star surfaces will fragment into a crystalline crust made
of charged strangelets immersed in an electron gas. We derive a
model-independent relationship between sigma_crit and two parameters that
characterize any quark matter equation of state. For reasonable model equations
of state, we find sigma_crit typically of order a few MeV/fm^2. If sigma <=
sigma_crit, the size-distribution of strangelets in cosmic rays could feature a
peak corresponding to the stable strangelets that we construct.Comment: 11 pages, LaTe
Meissner screening mass in two-flavor quark matter at nonzero temperature
We calculate the Meissner screening mass of gluons 4--7 in two-flavor quark
matter at nonzero temperature. To this end, we study the effective potential of
the 2SC/g2SC phases including a vector condensate . We find
that the Meissner mass becomes real at the critical temperature which is about
the half of the chemical potential mismatch. The phase diagram of the neutral
two-flavor color superconductor is presented in the plane of temperature and
coupling strength. We indicate the unstable region for gluons 4--7 on the phase
diagram.Comment: 4 pages, 3 figures, minor revisions to text, version to appear in PR
Star-forming Galaxies in the 'Redshift Desert'
We describe results of optical and near-IR observations of a large
spectroscopic sample of star-forming galaxies photometrically-selected to lie
in the redshift range 1.4 < z < 2.5, often called the ``redshift desert''
because of historical difficulty in obtaining spectroscopic redshifts in this
range. We show that the former ``redshift desert'' is now very much open to
observation.Comment: 10 pages, 6 figures, to appear in the Proceedings of the ESO/USM/MPE
Workshop on "Multiwavelength Mapping of Galaxy Formation and Evolution", eds.
R. Bender and A. Renzin
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