6,029 research outputs found
Readout and Control of a Power-recycled Interferometric Gravitational-wave Antenna
Interferometric gravitational wave antennas are based on Michelson
interferometers whose sensitivity to small differential length changes has been
enhanced by adding multiple coupled optical resonators. The use of optical
cavities is essential for reaching the required sensitivity, but sets
challenges for the control system which must maintain the cavities near
resonance. The goal for the strain sensitivity of the Laser Interferometer
Gravitational-wave Observatory (LIGO) is 10^-21 rms, integrated over a 100 Hz
bandwidth centered at 150 Hz. We present the major design features of the LIGO
length and frequency sensing and control system which will hold the
differential length to within 5 10^-14 m of the operating point. We also
highlight the restrictions imposed by couplings of noise into the gravitational
wave readout signal and the required immunity against them.Comment: Presentation at ICALEPCS 2001, San Jose, November 2001, (WECT003), 3
page
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
A Search for Planetary Nebulae With the SDSS: the outer regions of M31
We have developed a method to identify planetary nebula (PN) candidates in
imaging data of the Sloan Digital Sky Survey (SDSS). This method exploits the
SDSS' five-band sampling of emission lines in PN spectra, which results in a
color signature distinct from that of other sources. Selection criteria based
on this signature can be applied to nearby galaxies in which PNe appear as
point sources. We applied these criteria to the whole area of M31 as scanned by
the SDSS, selecting 167 PN candidates that are located in the outer regions of
M31. The spectra of 80 selected candidates were then observed with the 2.2m
telescope at Calar Alto Observatory. These observations and cross-checks with
literature data show that our method has a selection rate efficiency of about
90%, but the efficiency is different for the different groups of PNe
candidates.
In the outer regions of M31, PNe trace different well-known morphological
features like the Northern Spur, the NGC205 Loop, the G1 Clump, etc. In
general, the distribution of PNe in the outer region 8<R<20 kpc along the minor
axis shows the "extended disk" - a rotationally supported low surface
brightness structure with an exponential scale length of 3.21+/-0.14 kpc and a
total mass of ~10^10 M_{\sun}, which is equivalent to the mass of M33. We
report the discovery of three PN candidates with projected locations in the
center of Andromeda NE, a very low surface brightness giant stellar structure
in the outer halo of M31. Two of the PNe were spectroscopically confirmed as
genuine PNe. These two PNe are located at projected distances along the major
axis of ~48 Kpc and ~41 Kpc from the center of M31 and are the most distant PNe
in M31 found up to now.Comment: 58 pages, 17 figures, 2 tables, Accepted to Astronomical Journa
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
Stability of the Higgs mass in theories with extra dimensions
We analyze the ultraviolet stability of the Higgs mass in recently proposed
Kaluza-Klein models compactified on S_1/Z_2 or S_1/(Z_2\times Z_2'), both at
the field theory and string theory level. Fayet-Iliopoulos terms of U(1)
hypercharge are shown to be of vital importance for this discussion. Models
with a single Higgs doublet seem to be generically affected by quadratic
divergences.Comment: Contribution to the Proceedings of Durham IPPP meeting May 2001.(12
pages, LaTeX
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
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
Improving Disciplinary Practices in an Urban School: Solving the Problem of Practice
In this article, the authors share a case study of a special educator who worked closely with a leadership team in an urban elementary school to establish universal behavior expectations for all students. The special educator was a behavior coach in the urban elementary school located in a southwestern school of the United States of America. Following an action research framework, the special educator also the lead author worked closely with the leadership team to solve the issue of high office disciplinary referrals (ODRs) for aggressive behaviors. The aggressive behaviors included actions that harm others, such as assault, bullying, hitting, etc. The methodology included the team establishing universal expectations within the school-wide positive behavior supports framework taking into consideration parental feedback and university colleagues’ input. To evaluate the effectiveness of universal expectations, the team tracked the number of ODRs for two years. Findings indicate that the adoption of schoolwide behavior expectations resulted in the overall reduction of ODRs by 47% and ODRs for aggressive behaviors reduced by 50% from Year 1 to 2. These findings have implications for educators serving students in urban schools settings
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
Foregrounding the Margins: A Dialogue about Literacy, Learning, and Social Annotation
Annotation, or the addition of a note to a text, enables readers-as-writers to make their thinking visible. This article, which is structured as a dialogue among four literacy educators, discusses the potential for social annotation to transform literacy learning, assessment, and teacher education. Collectively, the authors argue for social annotation as a vital and transformative practice in hybrid and post-pandemic education. The authors reflect on their personal and pedagogical uses of annotation, sharing related resources for educators across K-12 and higher education contexts
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