5,118 research outputs found
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
Lp-cohomology of negatively curved manifolds
We compute the -cohomology spaces of some negatively curved manifolds.
We deal with two cases: manifolds with finite volume and sufficiently pinched
negative curvature, and conformally compact manifolds
Vacuum energy for the supersymmetric twisted D-brane in constant electromagnetic field
We calculate vacuum energy for twisted SUSY D-brane on toroidal background
with constant magnetic or constant electric field. Its behaviour for toroidal
D-brane (p=2) in constant electric field shows the presence of stable minimum
for twisted versions of the theory. That indicates such a background maybe
reasonable groundstate.Comment: LaTeX, 10 page
Leo V: A Companion of a Companion of the Milky Way Galaxy
We report the discovery of a new Milky Way dwarf spheroidal galaxy in the
constellation of Leo identified in data from the Sloan Digital Sky Survey. Leo
V lies at a distance of about 180 kpc, and is separated by about 3 degrees from
another recent discovery, Leo IV. We present follow-up imaging from the Isaac
Newton Telescope and spectroscopy from the Hectochelle fiber spectrograph at
the Multiple Mirror Telescope. Leo V's heliocentric velocity is 173.4 km/s,
which is offset by about 40 km/s from that of Leo IV. A simple interpretation
of the kinematic data is that both objects may lie on the same stream, though
the implied orbit is only modestly eccentric (e = 0.2)Comment: Submitted to ApJ (Letters
Improved photometry of SDSS crowded field images: Structure and dark matter content in the dwarf spheroidal galaxy Leo I
We explore how well crowded field point-source photometry can be accomplished
with SDSS data: We present a photometric pipeline based on DoPhot, and tuned
for analyzing crowded-field images from the SDSS. Using Monte Carlo simulations
we show that the completeness of source extraction is above 80% to i < 21 (AB)
and a stellar surface density of about 200 sq.amin. Hence, a specialized data
pipeline can efficiently be used for e.g. nearby resolved galaxies in SDSS
images, where the standard SDSS photometric package Photo, when applied in
normal survey mode, gives poor results. We apply our pipeline to an area of
about 3.55sq.deg. around the dwarf spheroidal galaxy (dSph) Leo I, and
construct a high S/N star-count map of Leo I via an optimized filter in
color-magnitude space (g,r,i). Although the radial surface-density profile of
the dwarf deviates from the best fit empirical King model towards outer radii,
we find no evidence for tidal debris out to a stellar surface-density of
4*10^(-3) of the central value. We determine the total luminosity of Leo I, and
model its mass using the spherical and isotropic Jeans equation. Assuming that
'mass follows light' we constrain a lower limit of the total mass of the dSph
to be (1.7+/-0.2)*10^7 Msol. Contrary, if the mass in Leo I is dominated by a
constant density dark-matter (DM) halo, then the mass within the central 12' is
(2+/-0.6)*10^8 Msol. This leads to a mass-to-light ratio of >>6 (Ic_sol), and
possibly >75 if the DM halo dominates the mass and extends further out than
12'. In summary, our results show that Leo I is a symmetric, relaxed and bound
system; this supports the idea that Leo I is a dark-matter dominated system.Comment: 13 pages, 11 figures; accepted for publication in A
A Wide Field Survey of Satellite Galaxies around the Spiral Galaxy M106
We present a wide field survey of satellite galaxies in M106 (NGC 4258)
covering a 1.7\degr \times 2\degr field around M106 using
Canada-France-Hawaii Telescope/MegaCam. We find 16 satellite galaxy candidates
of M106.
Eight of these galaxies are found to be dwarf galaxies that are much smaller
and fainter than the remaining galaxies. Four of these galaxies are new
findings. Surface brightness profiles of 15 out of 16 satellite galaxies can be
represented well by an exponential disk profile with varying scale length. We
derive the surface number density distribution of these satellite galaxies. The
central number density profile (d kpc) is well fitted by a power-law
with a power index of , similar to the expected power index of
isothermal distribution. The luminosity function of these satellites is
represented well by the Schechter function with a faint end slope of
. Integrated photometric properties (total luminosity,
total colour, and disk scale length) and the spatial distribution of these
satellite galaxies are found to be roughly similar to those of the Milky Way
and M31.Comment: Accepted by MNRA
The Via Lactea INCITE Simulation: Galactic Dark Matter Substructure at High Resolution
It is a clear unique prediction of the cold dark matter paradigm of
cosmological structure formation that galaxies form hierarchically and are
embedded in massive, extended dark halos teeming with self-bound substructure
or "subhalos". The amount and spatial distribution of subhalos around their
host provide unique information and clues on the galaxy assembly process and
the nature of the dark matter. Here we present results from the Via Lactea
INCITE simulation, a one billion particle, one million cpu-hour simulation of
the formation and evolution of a Galactic dark matter halo and its substructure
population.Comment: 10 pages, Proceedings of the SciDAC 2008 conference, (Seattle, July
13-17, 2008
The Smallest Mass Ratio Young Star Spectroscopic Binaries
Using high resolution near-infrared spectroscopy with the Keck telescope, we
have detected the radial velocity signatures of the cool secondary components
in four optically identified pre-main-sequence, single-lined spectroscopic
binaries. All are weak-lined T Tauri stars with well-defined center of mass
velocities. The mass ratio for one young binary, NTTS 160905-1859, is M2/M1 =
0.18+/-0.01, the smallest yet measured dynamically for a pre-main-sequence
spectroscopic binary. These new results demonstrate the power of infrared
spectroscopy for the dynamical identification of cool secondaries. Visible
light spectroscopy, to date, has not revealed any pre-main-sequence secondary
stars with masses <0.5 M_sun, while two of the young systems reported here are
in that range. We compare our targets with a compilation of the published young
double-lined spectroscopic binaries and discuss our unique contribution to this
sample.Comment: Accepted for publication in the April, 2002, ApJ; 6 figure
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
On orbifold theory and N=2, D=5 gauged supergravity
We have studied the most general N=2 supergravity in five dimensions in
context with the orbifold theory based on . Various ways to
treat the supersymmetry with singular sources placed in orbifold fixed points
were proposed in past. Supersymmetric branes were consistently introduced in a
bulk where a gauged supergravity was present. In this paper we find that in the
supergravity with general gauging, the possibility to obtain a
supersymmetric brane world is constrained. Imposing the compatibility of
supersymmetry transformation rules with the orbifold condition, we find the
necessary and sufficient condition to obtain supersymmetric branes and bulk
independently. We comment that the same condition guarantees naturally the
presence of singular BPS solutions.Comment: 16 page
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