600,806 research outputs found
Scars on the CBR?
We ask whether the universe can be a patchwork consisting of distinct regions
of matter and antimatter. In previous work we demonstrated that
post-recombination matter-antimatter contact near regional boundaries leads to
an observable (but unobserved) gamma-ray flux for domain sizes of less than a
few thousand Mpc, thereby excluding such domains. In this paper we consider the
pre-recombination signal from domains of larger size.Comment: 6 pages, late
The Scale-Invariant Scotogenic Model
We investigate a minimal scale-invariant implementation of the scotogenic
model and show that viable electroweak symmetry breaking can occur while
simultaneously generating one-loop neutrino masses and the dark matter relic
abundance. The model predicts the existence of a singlet scalar (dilaton) that
plays the dual roles of triggering electroweak symmetry breaking and sourcing
lepton number violation. Important constraints are studied, including those
from lepton flavor violating effects and dark matter direct-detection
experiments. The latter turn out to be somewhat severe, already excluding large
regions of parameter space. None the less, viable regions of parameter space
are found, corresponding to dark matter masses below (roughly) 10 GeV and above
200 GeV.Comment: 21 pages, 8 figures; v2 JHEP versio
On Cosmological Implication of the Trace Anomaly
We establish a connection between the trace anomaly and a thermal radiation
in the context of the standard cosmology. This is done by solving the covariant
conservation equation of the stress tensor associated with a conformally
invariant quantum scalar field. The solution corresponds to a thermal radiation
with a temperature which is given in terms of a cut-off time excluding the
spacetime regions very close to the initial singularity. We discuss the
interrelation between this result and the result obtained in a two-dimensional
schwarzschild spacetime.Comment: 8 pages, no figure
Measurement of the CP asymmetry in Bº → K*º μ+μ- decays
A measurement of the CP asymmetry in Bº → K*º μ+μ- decays is presented, based on 1.0 fb(-1) of pp collision data recorded by the LHCb experiment during 2011. The measurement is performed in six bins of invariant mass squared of the μ+μ- pair, excluding the J/ψ and ψ(2S) resonance regions. Production and detection asymmetries are removed using the Bº → J/ψ K*+º decay as a control mode. The integrated CP asymmetry is found to be -0.072 ± 0.040(stat) ± 0.005(syst), consistent with the standard model
Axion hot dark matter bounds
We derive cosmological limits on two-component hot dark matter consisting of
neutrinos and axions. We restrict the large-scale structure data to the safely
linear regime, excluding the Lyman-alpha forest. We derive Bayesian credible
regions in the two-parameter space consisting of m_a and sum(m_nu).
Marginalizing over sum(m_nu) provides m_a<1.02 eV (95% CL). In the absence of
axions the same data and methods give sum(m_nu)< 0.63 eV (95% CL).Comment: Contribution to Proc. 4th Patras Workshop on Axions, WIMPs and WISPs
(18-21 June 2008, DESY
A Photometric Method for Quantifying Asymmetries in Disk Galaxies
A photometric method for quantifying deviations from axisymmetry in optical
images of disk galaxies is applied to a sample of 32 face-on and nearly face-on
spirals. The method involves comparing the relative fluxes contained within
trapezoidal sectors arranged symmetrically about the galaxy center of light,
excluding the bulge and/or barred regions. Such a method has several advantages
over others, especially when quantifying asymmetry in flocculent galaxies.
Specifically, the averaging of large regions improves the signal-to-noise in
the measurements; the method is not strongly affected by the presence of spiral
arms; and it identifies the kinds of asymmetry that are likely to be
dynamically important. Application of this "method of sectors" to R-band images
of 32 disk galaxies indicates that about 30% of spirals show deviations from
axisymmetry at the 5-sigma level.Comment: 17 pages, 2 tables and 6 figures, uses psfig and AAS LaTex; to appear
in A
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