5,116 research outputs found
Hodge numbers for the cohomology of Calabi-Yau type local systems
We use Higgs cohomology to determine the Hodge numbers of the first
intersection cohomology group of a local system V arising from the third direct
image of a family of Calabi-Yau 3-folds over a smooth, quasi-projective curve.
We give applications to Rhode's families of Calabi-Yau 3-folds without MUM.Comment: Some signs corrected. This article draws heavily from arXiv:0911.027
Supersymmetric Brane World Scenarios from Off-Shell Supergravity
Using N=2 off-shell supergravity in five dimensions, we supersymmetrize the
brane world scenario of Randall and Sundrum. We extend their construction to
include supersymmetric matter at the fixpoints.Comment: 15 pages, no figures, late
Exact results for some Madelung type constants in the finite-size scaling theory
A general formula is obtained from which the madelung type constant: extensively used in the finite-size
scaling theory is computed analytically for some particular cases of the
parameters and . By adjusting these parameters one can obtain
different physical situations corresponding to different geometries and
magnitudes of the interparticle interaction.Comment: IOP- macros, 5 pages, replaced with amended version (1 ref. added
The discovery of two extremely low luminosity Milky Way globular clusters
We report the discovery of two extremely low luminosity globular clusters in
the Milky Way Halo. These objects were detected in the Sloan Digital Sky Survey
Data Release 5 and confirmed with deeper imaging at the Calar Alto Observatory.
The clusters, Koposov 1 and Koposov 2, are located at kpc and
appear to have old stellar populations and luminosities of only
mag. Their observed sizes of pc are well within the expected tidal
limit of 10 pc at that distance. Together with Palomar 1, AM 4 and
Whiting 1, these new clusters are the lowest luminosity globulars orbiting the
Milky Way, with Koposov 2 the most extreme. Koposov 1 appears to lie close to
distant branch of the Sagittarius stream. The half-mass relaxation times of
Koposov 1 and 2 are only and Myr respectively (2 orders of
magnitude shorter than the age of the stellar populations), so it would seem
that they have undergone drastic mass segregation. Since they do not appear to
be very concentrated, their evaporation timescales may be as low as . These discoveries show that the structural parameter space of
globular clusters in the Milky Way halo is not yet fully explored. They also
add, through their short remaining survival times, significant direct evidence
for a once much larger population of globular clusters.Comment: accepted for publication in ApJ, minor revision
GHOSTS I: A New Faint very Isolated Dwarf Galaxy at D = 12 +/- 2 Mpc
We report the discovery of a new faint dwarf galaxy, GHOSTS I, using HST/ACS
data from one of our GHOSTS (Galaxy Halos, Outer disks, Substructure, Thick
disk, and Star clusters) fields. Its detected individual stars populate an
approximately one magnitude range of its luminosity function (LF). Using
synthetic color-magnitude diagrams (CMDs) to compare with the galaxy's CMD, we
find that the colors and magnitudes of GHOSTS I's individual stars are most
consistent with being young helium-burning and asymptotic giant branch stars at
a distance of 12 +/- 2 Mpc. Morphologically, GHOSTS I appears to be actively
forming stars, so we tentatively classify it as a dwarf irregular (dIrr)
galaxy, although future HST observations deep enough to resolve a larger
magnitude range in its LF are required to make a more secure classification.
GHOSTS I's absolute magnitude is , making it one
of the least luminous dIrr galaxies known, and its metallicity is lower than
[Fe/H] =-1.5 dex. The half-light radius of GHOSTS I is 226 +/- 38 pc and its
ellipticity is 0.47 +/- 0.07, similar to Milky Way and M31 dwarf satellites at
comparable luminosity. There are no luminous massive galaxies or galaxy
clusters within ~ 4 Mpc from GHOSTS I that could be considered as its host,
making it a very isolated dwarf galaxy in the Local Universe.Comment: 8 pages, 7 figures. Accepted for publication in Ap
Ultracompact, low-loss directional couplers on InP based on self-imaging by multimode interference
We report extremely compact (494-”m-long 3 dB splitters, including input/output bends), polarization-insensitive, zero-gap directional couplers on InP with a highly multimode interference region that are based on the self-imaging effect. We measured cross-state extinctions better than 28 dB and on-chip insertion losses of 0.5 dB/coupler plus 1 dB/cm guide propagation loss at 1523 nm wavelength
Modelling the dynamical evolution of the Bootes dwarf spheroidal galaxy
We investigate a wide range of possible evolutionary histories for the
recently discovered Bootes dwarf spheroidal galaxy, a Milky Way satellite. By
means of N-body simulations we follow the evolution of possible progenitor
galaxies of Bootes for a variety of orbits in the gravitational potential of
the Milky Way. The progenitors considered cover the range from dark-matter-free
star clusters to massive, dark-matter dominated outcomes of cosmological
simulations. For each type of progenitor and orbit we compare the observable
properties of the remnant after 10 Gyr with those of Bootes observed today. Our
study suggests that the progenitor of Bootes must have been, and remains now,
dark matter dominated. In general our models are unable to reproduce the
observed high velocity dispersion in Bootes without dark matter. Our models do
not support time-dependent tidal effects as a mechanism able to inflate
significantly the internal velocity dispersion. As none of our initially
spherical models is able to reproduce the elongation of Bootes, our results
suggest that the progenitor of Bootes may have had some intrinsic flattening.
Although the focus of the present paper is the Bootes dwarf spheroidal, these
models may be of general relevance to understanding the structure, stability
and dark matter content of all dwarf spheroidal galaxies.Comment: 10 pages, 7 figures, accepted by MNRA
Universal contributions to scalar masses from five dimensional supergravity
We compute the effective Kahler potential for matter fields in warped
compactifications, starting from five dimensional gauged supergravity, as a
function of the matter fields localization. We show that truncation to zero
modes is inconsistent and the tree-level exchange of the massive gravitational
multiplet is needed for consistency of the four-dimensional theory. In addition
to the standard Kahler coming from dimensional reduction, we find the quartic
correction coming from integrating out the gravity multiplet. We apply our
result to the computation of scalar masses, by assuming that the SUSY breaking
field is a bulk hypermultiplet. In the limit of extreme opposite localization
of the matter and the spurion fields, we find zero scalar masses, consistent
with sequestering arguments. Surprisingly enough, for all the other cases the
scalar masses are tachyonic. This suggests the holographic interpretation that
a CFT sector always generates operators contributing in a tachyonic way to
scalar masses. Viability of warped su- persymmetric compactifications
necessarily asks then for additional contributions. We discuss the case of
additional bulk vector multiplets with mixed boundary conditions, which is a
partic- ularly simple and attractive way to generate large positive scalar
masses. We show that in this case successful fermion mass matrices implies
highly degenerate scalar masses for the first two generations of squarks and
sleptons.Comment: 23 pages. v2: References added, new section on effect of additional
bulk vector multiplets and phenomenolog
Heart and Lung Transplantation in the United States, 1996â2005
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74833/1/j.1600-6143.2007.01783.x.pd
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