3,017 research outputs found
Quantum Symmetries and Strong Haagerup Inequalities
In this paper, we consider families of operators in
a tracial C-probability space , whose joint
-distribution is invariant under free complexification and the action of
the hyperoctahedral quantum groups . We prove a strong
form of Haagerup's inequality for the non-self-adjoint operator algebra
generated by , which generalizes the
strong Haagerup inequalities for -free R-diagonal families obtained by
Kemp-Speicher \cite{KeSp}. As an application of our result, we show that
always has the metric approximation property (MAP). We also apply
our techniques to study the reduced C-algebra of the free unitary
quantum group . We show that the non-self-adjoint subalgebra generated by the matrix elements of the fundamental corepresentation of
has the MAP. Additionally, we prove a strong Haagerup inequality for
, which improves on the estimates given by Vergnioux's property
RD \cite{Ve}
The system parameters of DW Ursae Majoris
We present new constraints on the system parameters of the SW Sextantis star
DW Ursae Majoris, based on ultraviolet (UV) eclipse observations with the
Hubble Space Telescope. Our data were obtained during a low state of the
system, in which the UV light was dominated by the hot white dwarf (WD)
primary. Eclipse analysis, using the full Roche lobe geometry, allows us to set
firm limits on the masses and radii of the system components and the distance
between them: 0.67 \leq M_1/M_sun \leq 1.06, 0.008 \leq R_1/R_sun \leq 0.014,
M_2/M_sun > 0.16, R_2/R_sun > 0.28 and a/R_sun > 1.05. For q = M_2/M_1 < 1.5
the inclination must satisfy i > 71 degrees. Using Smith & Dhillon's
mass-period relation for CV secondaries, our estimates for the system
parameters become M_1/M_sun = 0.77 \pm 0.07, R_1/R_sun = 0.012 \pm 0.001,
M_2/M_sun = 0.30 \pm 0.10, R_2/R_sun = 0.34 \pm 0.04, q =0.39 \pm 0.12, i = 82
\pm 4 degrees and a/R_sun = 1.14 \pm 0.06. We have also estimated the spectral
type of the secondary, M3.5 \pm 1.0, and distance to the system, d =930 \pm 160
pc, from time-resolved I- and K-band photometry. Finally, we have repeated
Knigge et al.'s WD model atmosphere fit to the low-state UV spectrum of DW UMa
in order to account for the higher surface gravity indicated by our eclipse
analysis. In this way we obtained a second estimate for the distance, d = 590
\pm 100 pc, which allows us to obtain a second estimate for the spectral type
of the secondary, M7 \pm 2.0. We conclude that the true value for the distance
and spectral type will probably be in between the values obtained by the two
methods.Comment: 23 pages including 5 figures and 3 tables. Accepted for publication
in Ap
Internet-based medical education: a realist review of what works, for whom and in what circumstances
http://creativecommons.org/licenses/by/2.0
A combined maximum-likelihood analysis of the high-energy astrophysical neutrino flux measured with IceCube
Evidence for an extraterrestrial flux of high-energy neutrinos has now been
found in multiple searches with the IceCube detector. The first solid evidence
was provided by a search for neutrino events with deposited energies
TeV and interaction vertices inside the instrumented volume. Recent
analyses suggest that the extraterrestrial flux extends to lower energies and
is also visible with throughgoing, -induced tracks from the Northern
hemisphere. Here, we combine the results from six different IceCube searches
for astrophysical neutrinos in a maximum-likelihood analysis. The combined
event sample features high-statistics samples of shower-like and track-like
events. The data are fit in up to three observables: energy, zenith angle and
event topology. Assuming the astrophysical neutrino flux to be isotropic and to
consist of equal flavors at Earth, the all-flavor spectrum with neutrino
energies between 25 TeV and 2.8 PeV is well described by an unbroken power law
with best-fit spectral index and a flux at 100 TeV of
.
Under the same assumptions, an unbroken power law with index is disfavored
with a significance of 3.8 () with respect to the best
fit. This significance is reduced to 2.1 () if instead we
compare the best fit to a spectrum with index that has an exponential
cut-off at high energies. Allowing the electron neutrino flux to deviate from
the other two flavors, we find a fraction of at Earth.
The sole production of electron neutrinos, which would be characteristic of
neutron-decay dominated sources, is rejected with a significance of 3.6
().Comment: 16 pages, 10 figures; accepted for publication in The Astrophysical
Journal; updated one referenc
The IceCube Neutrino Observatory - Contributions to ICRC 2015 Part II: Atmospheric and Astrophysical Diffuse Neutrino Searches of All Flavors
Papers on atmospheric and astrophysical diffuse neutrino searches of all
flavors submitted to the 34th International Cosmic Ray Conference (ICRC 2015,
The Hague) by the IceCube Collaboration.Comment: 66 pages, 36 figures, Papers submitted to the 34th International
Cosmic Ray Conference, The Hague 2015, v2 has a corrected author lis
Characterization of the Atmospheric Muon Flux in IceCube
Muons produced in atmospheric cosmic ray showers account for the by far
dominant part of the event yield in large-volume underground particle
detectors. The IceCube detector, with an instrumented volume of about a cubic
kilometer, has the potential to conduct unique investigations on atmospheric
muons by exploiting the large collection area and the possibility to track
particles over a long distance. Through detailed reconstruction of energy
deposition along the tracks, the characteristics of muon bundles can be
quantified, and individual particles of exceptionally high energy identified.
The data can then be used to constrain the cosmic ray primary flux and the
contribution to atmospheric lepton fluxes from prompt decays of short-lived
hadrons.
In this paper, techniques for the extraction of physical measurements from
atmospheric muon events are described and first results are presented. The
multiplicity spectrum of TeV muons in cosmic ray air showers for primaries in
the energy range from the knee to the ankle is derived and found to be
consistent with recent results from surface detectors. The single muon energy
spectrum is determined up to PeV energies and shows a clear indication for the
emergence of a distinct spectral component from prompt decays of short-lived
hadrons. The magnitude of the prompt flux, which should include a substantial
contribution from light vector meson di-muon decays, is consistent with current
theoretical predictions.Comment: 36 pages, 39 figure
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