282 research outputs found
Double Threefold Degeneracies for Active and Sterile Neutrinos
We explore the possibility that the 3 active (doublet) neutrinos have nearly
degenerate masses which are split only by the usual seesaw mechanism from 3
sterile (singlet) neutrinos in the presence of a softly broken symmetry.
We take the unconventional view that the sterile neutrinos may be light, i.e.
less than 1 keV, and discuss some very interesting and novel phenomenology,
including a connection between the LSND neutrino data and solar neutrino
oscillations.Comment: 8 pages, no figur
Polynomial Interpretation of Multipole Vectors
Copi, Huterer, Starkman and Schwarz introduced multipole vectors in a tensor
context and used them to demonstrate that the first-year WMAP quadrupole and
octopole planes align at roughly the 99.9% confidence level. In the present
article the language of polynomials provides a new and independent derivation
of the multipole vector concept. Bezout's Theorem supports an elementary proof
that the multipole vectors exist and are unique (up to rescaling). The
constructive nature of the proof leads to a fast, practical algorithm for
computing multipole vectors. We illustrate the algorithm by finding exact
solutions for some simple toy examples, and numerical solutions for the
first-year WMAP quadrupole and octopole. We then apply our algorithm to Monte
Carlo skies to independently re-confirm the estimate that the WMAP quadrupole
and octopole planes align at the 99.9% level.Comment: Version 1: 6 pages. Version 2: added uniqueness proof to Corollary 2;
added proper citation (to Starkman et al.) for Open Question; other minor
improvement
Assessing Alternatives for Directional Detection of a WIMP Halo
The future of direct terrestrial WIMP detection lies on two fronts: new, much
larger low background detectors sensitive to energy deposition, and detectors
with directional sensitivity. The former can large range of WIMP parameter
space using well tested technology while the latter may be necessary if one is
to disentangle particle physics parameters from astrophysical halo parameters.
Because directional detectors will be quite difficult to construct it is
worthwhile exploring in advance generally which experimental features will
yield the greatest benefits at the lowest costs. We examine the sensitivity of
directional detectors with varying angular tracking resolution with and without
the ability to distinguish forward versus backward recoils, and compare these
to the sensitivity of a detector where the track is projected onto a
two-dimensional plane. The latter detector regardless of where it is placed on
the Earth, can be oriented to produce a significantly better discrimination
signal than a 3D detector without this capability, and with sensitivity within
a factor of 2 of a full 3D tracking detector. Required event rates to
distinguish signals from backgrounds for a simple isothermal halo range from
the low teens in the best case to many thousands in the worst.Comment: 4 pages, including 2 figues and 2 tables, submitted to PR
Excess Clustering on Large Scales in the MegaZ DR7 Photometric Redshift Survey
We observe a large excess of power in the statistical clustering of luminous red galaxies in the photometric SDSS galaxy sample called MegaZ DR7. This is seen over the lowest multipoles in the angular power spectra C-l in four equally spaced redshift bins between 0: 45 <= z <= 0: 65. However, it is most prominent in the highest redshift band at similar to 4 sigma and it emerges at an effective scale k less than or similar to 0: 01 h Mpc(-1). Given that MegaZ DR7 is the largest cosmic volume galaxy survey to date (3.3(Gpch(-1))(3)) this implies an anomaly on the largest physical scales probed by galaxies. Alternatively, this signature could be a consequence of it appearing at the most systematically susceptible redshift. There are several explanations for this excess power that range from systematics to new physics. We test the survey, data, and excess power, as well as possible origins
The Big Occulting Steerable Satellite (BOSS)
Natural (such as lunar) occultations have long been used to study sources on
small angular scales, while coronographs have been used to study high contrast
sources. We propose launching the Big Occulting Steerable Satellite (BOSS), a
large steerable occulting satellite to combine both of these techniques. BOSS
will have several advantages over standard occulting bodies. BOSS would block
all but about 4e-5 of the light at 1 micron in the region of interest around
the star for planet detections. Because the occultation occurs outside the
telescope, scattering inside the telescope does not degrade this performance.
BOSS could be combined with a space telescope at the Earth-Sun L2 point to
yield very long integration times, in excess of 3000 seconds. If placed in
Earth orbit, integration times of 160--1600 seconds can be achieved from most
major telescope sites for objects in over 90% of the sky. Applications for BOSS
include direct imaging of planets around nearby stars. Planets separated by as
little as 0.1--0.25 arcseconds from the star they orbit could be seen down to a
relative intensity as little as 1e-9 around a magnitude 8 (or brighter) star.
Other applications include ultra-high resolution imaging of compound sources,
such as microlensed stars and quasars, down to a resolution as little as 0.1
milliarcseconds.Comment: 25pages, 4 figures, uses aaspp4, rotate, and epsfig. Submitted to the
Astrophysical Journal. For more details see
http://erebus.phys.cwru.edu/~boss
Cosmic Topology of Polyhedral Double-Action Manifolds
A special class of non-trivial topologies of the spherical space S^3 is
investigated with respect to their cosmic microwave background (CMB)
anisotropies. The observed correlations of the anisotropies on the CMB sky
possess on large separation angles surprising low amplitudes which might be
naturally be explained by models of the Universe having a multiconnected
spatial space. We analysed in CQG 29(2012)215005 the CMB properties of prism
double-action manifolds that are generated by a binary dihedral group D^*_p and
a cyclic group Z_n up to a group order of 180. Here we extend the CMB analysis
to polyhedral double-action manifolds which are generated by the three binary
polyhedral groups (T^*, O^*, I^*) and a cyclic group Z_n up to a group order of
1000. There are 20 such polyhedral double-action manifolds. Some of them turn
out to have even lower CMB correlations on large angles than the Poincare
dodecahedron
Effect of Finite Mass on Primordial Nucleosynthesis
We have calculated the small effect of finite nucleon mass on the
weak-interaction rates that interconvert protons and neutrons in the early
Universe. We have modified the standard code for primordial nucleosynthesis to
include these corrections and find a small, systematic increase in the 4He
yield, , depending slightly on the
baryon-to-photon ratio. The fractional changes in the abundances of the other
light elements are a few percent or less for interesting values of the
baryon-to-photon ratio.Comment: 15 pages, 8 figures, uses psfig.st
Large Scale Traces of Solar System Cold Dust on CMB Anisotropies
We explore the microwave anisotropies at large angular scales produced by the
emission from cold and large dust grains, expected to exist in the outer parts
of the Solar System, using a simple toy model for this diuse emission. Its
amplitude is constrained in the Far-IR by the COBE data and is compatible with
simulations found in the literature. We analyze the templates derived after
subtracting our model from the WMAP ILC 7 yr maps and investigate on the
cosmological implications of such a possible foreground. The anomalies related
to the low quadrupole of the angular power spectrum, the two-point correlation
function, the parity and the excess of signal found in the ecliptic plane are
significantly alleviated. An impact of this foreground for some cosmological
parameters characterizing the spectrum of primordial density perturbations,
relevant for on-going and future CMB anisotropy experiments, is found.Comment: Issue 2.0, Accepted for pub. in MNRAS, Apr 8th, 2011, (sub. Oct 4th,
2010); 10 pages, 6 Figures, 1 table; pdflatex with mn2e, AMS, natbib,
txfonts, graphic
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