12,219 research outputs found
Polarizing primordial gravitational waves by parity violation
We study primordial gravitational waves (PGWs) in the Horava-Lifshitz (HL)
theory of quantum gravity, in which high-order spatial derivative operators,
including the ones violating parity, generically appear in order for the theory
to be power-counting renormalizable and ultraviolet (UV) complete. Because of
both parity violation and non-adiabatic evolution of the modes due to a
modified dispersion relationship, a large polarization of PGWs becomes
possible, and it could be well within the range of detection of the BB, TB and
EB power spectra of the forthcoming cosmic microwave background (CMB)
observations.Comment: revtex4, 3 figures. Phys. Rev. D87, 103512 (2013
Short-Baseline Electron Neutrino Oscillation Length After Troitsk
We discuss the implications for short-baseline electron neutrino
disappearance in the 3+1 mixing scheme of the recent Troitsk bounds on the
mixing of a neutrino with mass between 2 and 100 eV. Considering the Troitsk
data in combination with the results of short-baseline nu_e and antinu_e
disappearance experiments, which include the reactor and Gallium anomalies, we
derive a 2 sigma allowed range for the effective neutrino squared-mass
difference between 0.85 and 43 eV^2. The upper bound implies that it is likely
that oscillations in distance and/or energy can be observed in radioactive
source experiments. It is also favorable for the ICARUS@CERN experiment, in
which it is likely that oscillations are not washed-out in the near detector.
We discuss also the implications for neutrinoless double-beta decay.Comment: 5 pages. Final version published in Phys.Rev. D87 (2013) 01300
Nuclear Reactions from Lattice QCD
One of the overarching goals of nuclear physics is to rigorously compute
properties of hadronic systems directly from the fundamental theory of strong
interactions, Quantum Chromodynamics (QCD). In particular, the hope is to
perform reliable calculations of nuclear reactions which will impact our
understanding of environments that occur during big bang nucleosynthesis, the
evolution of stars and supernovae, and within nuclear reactors and high
energy/density facilities. Such calculations, being truly ab initio, would
include all two-nucleon and three- nucleon (and higher) interactions in a
consistent manner. Currently, lattice QCD provides the only reliable option for
performing calculations of some of the low- energy hadronic observables. With
the aim of bridging the gap between lattice QCD and nuclear many-body physics,
the Institute for Nuclear Theory held a workshop on Nuclear Reactions from
Lattice QCD on March 2013. In this review article, we report on the topics
discussed in this workshop and the path planned to move forward in the upcoming
years.Comment: 35 pages, 13 figures, 1 table, review article for the "Nuclear
Reactions from Lattice QCD" workshop hosted by the Institute for Nuclear
Theory on March 2013; version 2 includes updated references and extended
discussion of previous wor
NLO merging in tt+jets
In this talk the application of the recently introduced methods to merge NLO
calculations of successive jet multiplicities to the production of top pairs in
association with jets will be discussed, in particular a fresh look is taken at
the top quark forward-backward asymmetries. Emphasis will be put on the
achieved theoretical accuracy and the associated perturbative and
non-perturbative error estimates.Comment: 6 pages, 3 figures, proceedings contribution for EPS 2013, Stockholm,
17-24 Jul
The Infrared Diameter -- Velocity Dispersion Relation for Elliptical Galaxies
Using single channel infrared photometry from the literature, a provisional
K-band diameter--velocity dispersion relation for elliptical galaxies in the
Coma and Virgo clusters is derived. The Coma cluster relation has \~1.5 times
lower scatter at K than in B or V. Excluding 4 outliers, the RMS scatter at K
for 24 galaxies in Coma is only 4.8% in distance, close to the limit implied by
the observational errors. Distance estimates based on the IR \Dsig relation
will be more accurate than those derived from optical data. The improvement in
the infrared is attributed to a decrease in sensitivity to stellar population
parameters (age, metallicity, and slope of the IMF) as well as lower internal
extinction from dust compared to the optical. That the \Dsig relation has a
larger scatter in the optical indicates that there are detectable, but small,
stellar population or dust content differences among the Coma ellipticals.
Since the \Dsig relations are based on the fundamental plane, this result
promises that the fundamental plane is thinner in the infrared than it is in
the optical.
Infrared photometric data available for Virgo are limited to just 13 objects;
the spread in distance due to the depth of the cluster precludes any
significant improvement over B and V. A relative Coma-Virgo distance of 5.56 is
derived from the K band data, in agreement with estimates in other colors and
using other techniques, indicating that there is no significant age difference
between Virgo and Coma ellipticals.Comment: 10 pages, 3 Postscript figures, uuencoded and Z-compressed with csh
script uufiles; to appear in the September Astronomical Journa
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