1,404 research outputs found
The Decay of the Inflaton in No-scale Supergravity
We study the decay of the inflaton in no-scale supergravity and show that
decay due to the gravitational interactions through supergravity effects is
highly suppressed relative to the case in minimal supergravity or models with a
generic Kahler potential. We also show that decay to gravitinos is suppressed.
We demonstrate that decay and sufficient reheating are possible with the
introduction of a non-trivial gauge kinetic term. This channel may be dominant
in no-scale supergravity, yet yields a re-heating temperature which is low
enough to avoid the gravitino problem while high enough for Big Bang
Nucleosynthesis and baryogenesis.Comment: Added the footnote in the conclusion section which discusses the
constrains on the explicit inflaton couplings to the matter fields via
non-renormalizable operators. To appear in JCA
Cross-correlating the Thermal Sunyaev-Zel'dovich Effect and the Distribution of Galaxy Clusters
We present the analytical formulas, derived based on the halo model, to
compute the cross-correlation between the thermal Sunyaev-Zel'dovich (SZ)
effect and the distribution of galaxy clusters. By binning the clusters
according to their redshifts and masses, this cross-correlation, the so-called
stacked SZ signal, reveals the average SZ profile around the clusters. The
stacked SZ signal is obtainable from a joint analysis of an
arcminute-resolution cosmic microwave background (CMB) experiment and an
overlapping optical survey, which allows for detection of the SZ signals for
clusters whose masses are below the individual cluster detection threshold. We
derive the error covariance matrix for measuring the stacked SZ signal, and
then forecast for its detection from ongoing and forthcoming combined
CMB-optical surveys. We find that, over a wide range of mass and redshift, the
stacked SZ signal can be detected with a significant signal to noise ratio
(total S/N \gsim 10), whose value peaks for the clusters with intermediate
masses and redshifts. Our calculation also shows that the stacking method
allows for probing the clusters' SZ profiles over a wide range of scales, even
out to projected radii as large as the virial radius, thereby providing a
promising way to study gas physics at the outskirts of galaxy clusters.Comment: 11 pages, 6 figures, 3 tables, minor revisions reflect PRD published
versio
Positrons in Cosmic Rays from Dark Matter Annihilations for Uplifted Higgs Regions in MSSM
We point out that there are regions in the MSSM parameter space which
successfully provide a dark matter (DM) annihilation explanation for observed
positron excess (e.g. PAMELA), while still remaining in agreement with all
other data sets. Such regions (e.g. the uplifted Higgs region) can realize an
enhanced neutralino DM annihilation dominantly into leptons via a Breit-Wigner
resonance through the CP-odd Higgs channel. Such regions can give the proper
thermal relic DM abundance, and the DM annihilation products are compatible
with current antiproton and gamma ray observations. This scenario can succeed
without introducing any additional degrees of freedom beyond those already in
the MSSM.Comment: 11 pages, 9 figure
A normalization strategy applied to HiCEP (an AFLP-based expression profiling) analysis: Toward the strict alignment of valid fragments across electrophoretic patterns
BACKGROUND: Gene expression analysis based on comparison of electrophoretic patterns is strongly dependent on the accuracy of DNA fragment sizing. The current normalization strategy based on molecular weight markers has limited accuracy because marker peaks are often masked by intense peaks nearby. Cumulative errors in fragment lengths cause problems in the alignment of same-length fragments across different electropherograms, especially for small fragments (< 100 bp). For accurate comparison of electrophoretic patterns, further inspection and normalization of electrophoretic data after fragment sizing by conventional strategies is needed. RESULTS: Here we describe a method for the normalization of a set of time-course electrophoretic data to be compared. The method uses Gaussian curves fitted to the complex peak mixtures in each electropherogram. It searches for target ranges for which patterns are dissimilar to the other patterns (called "dissimilar ranges") and for references (a kind of mean or typical pattern) in the set of resultant approximate patterns. It then constructs the optimal normalized pattern whose correlation coefficient against the reference in the range achieves the highest value among various combinations of candidates. We applied the procedure to time-course electrophoretic data produced by HiCEP, an AFLP-based expression profiling method which can detect a slight expression change in DNA fragments. We obtained dissimilar ranges whose electrophoretic patterns were obviously different from the reference and as expected, most of the fragments in the detected ranges were short (< 100 bp). The normalized electrophoretic patterns also agreed well with reference patterns. CONCLUSION: The normalization strategy presented here demonstrates the importance of pre-processing before electrophoretic signal comparison, and we anticipate its usefulness especially for temporal expression analysis by the electrophoretic method
Parameterizing the Power Spectrum: Beyond the Truncated Taylor Expansion
The power spectrum is traditionally parameterized by a truncated Taylor
series: . It is
reasonable to truncate the Taylor series if , but
it is not if . We argue that there is no good
theoretical reason to prefer , and show that current
observations are consistent with even for
. Thus, there are regions of parameter space, which are both
theoretically and observationally relevant, for which the traditional truncated
Taylor series parameterization is inconsistent, and hence it can lead to
incorrect parameter estimations. Motivated by this, we propose a simple
extension of the traditional parameterization, which uses no extra parameters,
but that, unlike the traditional approach, covers well motivated inflationary
spectra with . Our parameterization therefore covers not only
standard-slow-roll inflation models but also a much wider class of inflation
models. We use this parameterization to perform a likelihood analysis for the
cosmological parameters.Comment: References added. Typo correcte
The Earliest Optical Observations of GRB 030329
We present the earliest optical imaging observations of GRB 030329 related to
SN 2003dh. The burst was detected by the HETE-2 satellite at 2003 March 29,
11:37:14.67 UT. Our wide-field monitoring started 97 minutes before the trigger
and the burst position was continuously observed. We found no precursor or
contemporaneous flare brighter than () in 32 s (64 s) timescale
between 10:00 and 13:00 UT. Follow-up time series photometries started at
12:51:39 UT (75 s after position notice through the GCN) and continued for more
than 5 hours. The afterglow was at min after burst.
Its fading between 1.2 and 6.3 hours is well characterized by a single
power-law of the form in -band. No significant flux variation was
detected and upper limits are derived as % in
minutes to hours timescales and % in seconds to
minutes timescales. Such a featureless lightcurve is explained by the smooth
distribution of circumburst medium. Another explanation is that the optical
band was above the synchrotron cooling frequency where emergent flux is
insensitive to the ambient density contrasts. Extrapolation of the afterglow
lightcurve to the burst epoch excludes the presence of an additional flare
component at minutes as seen in GRB 990123 and GRB 021211.Comment: ApJL, in pres
Optical evidence for symmetry changes above the Neel temperature in KCuF3
We report on optical measurements of the 1D Heisenberg antiferromagnet KCuF3.
The crystal-field excitations of the Cu2+ ions have been observed and their
temperature dependence can be understood in terms of magnetic and
exchange-induced dipole mechanisms and vibronic interactions. Above T_N we
observe a new temperature scale T_S characterized by the emergence of narrow
absorption features that correlate with changes of the orbital ordering as
observed by Paolasini et al. [Phys. Rev. Lett. 88, 106403 (2002)]. The
appearance of these optical transitions provides evidence for a symmetry change
above the Neel temperature that affects the orbital ordering and paves the way
for the antiferromagnetic ordering.Comment: 4 pages, 2 figure
From the Spectrum to Inflation : An Inverse Formula for the General Slow-Roll Spectrum
We propose a general inverse formula for extracting inflationary parameters
from the observed power spectrum of cosmological perturbations. Under the
general slow-roll scheme, which helps to probe the properties of inflation in a
model independent way, we invert the leading order, single field, power
spectrum formula. We also give some physically interesting examples to
demonstrate its wide applicability and illuminate its properties.Comment: 8 pages, no figure ; References expande
Fingerprints of spin-orbital physics in cubic Mott insulators: Magnetic exchange interactions and optical spectral weights
The temperature dependence and anisotropy of optical spectral weights
associated with different multiplet transitions is determined by the spin and
orbital correlations. To provide a systematic basis to exploit this close
relationship between magnetism and optical spectra, we present and analyze the
spin-orbital superexchange models for a series of representative
orbital-degenerate transition metal oxides with different multiplet structure.
For each case we derive the magnetic exchange constants, which determine the
spin wave dispersions, as well as the partial optical sum rules. The magnetic
and optical properties of early transition metal oxides with degenerate
orbitals (titanates and vanadates with perovskite structure) are shown
to depend only on two parameters, viz. the superexchange energy and the
ratio of Hund's exchange to the intraorbital Coulomb interaction, and on
the actual orbital state. In systems important corrections follow from
charge transfer excitations, and we show that KCuF can be classified as a
charge transfer insulator, while LaMnO is a Mott insulator with moderate
charge transfer contributions. In some cases orbital fluctuations are quenched
and decoupling of spin and orbital degrees of freedom with static orbital order
gives satisfactory results for the optical weights. On the example of cubic
vanadates we describe a case where the full quantum spin-orbital physics must
be considered. Thus information on optical excitations, their energies,
temperature dependence and anisotropy, combined with the results of magnetic
neutron scattering experiments, provides an important consistency test of the
spin-orbital models, and indicates whether orbital and/or spin fluctuations are
important in a given compound.Comment: 34 pages, 16 figure
Flavour constraints on scenarios with two or three heavy squark generations
We re-assess constraints from flavour-changing neutral currents in the kaon
system on supersymmetric scenarios with a light gluino, two heavy generations
of squarks and a lighter third generation. We compute for the first time limits
in scenarios with three heavy squark families, taking into account QCD
corrections at the next-to-leading order. We compare our limits with those in
the case of two heavy families. We use the mass insertion approximation and
consider contributions from gluino exchange to constrain the mixing between the
first and second squark generation. While it is not possible to perform a
general analysis, we assess the relevance of each kind of flavour- and
CP-violating parameters. We also provide ready to use magic numbers for the
computation of the Wilson coefficients at 2 GeV for these scenarios.Comment: 23 pages, 14 figures; v3: matches published version (contains
improvements in the presentation and clarifications
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