295 research outputs found
Observation of Entanglement-Dependent Two-Particle Holonomic Phase
Holonomic phases---geometric and topological---have long been an intriguing
aspect of physics. They are ubiquitous, ranging from observations in particle
physics to applications in fault tolerant quantum computing. However, their
exploration in particles sharing genuine quantum correlations lack in
observations. Here we experimentally demonstrate the holonomic phase of two
entangled-photons evolving locally, which nevertheless gives rise to an
entanglement-dependent phase. We observe its transition from geometric to
topological as the entanglement between the particles is tuned from zero to
maximal, and find this phase to behave more resilient to evolution changes with
increasing entanglement. Furthermore, we theoretically show that holonomic
phases can directly quantify the amount of quantum correlations between the two
particles. Our results open up a new avenue for observations of holonomic
phenomena in multi-particle entangled quantum systems.Comment: 8 pages, 6 figure
Bayesian astrostatistics: a backward look to the future
This perspective chapter briefly surveys: (1) past growth in the use of
Bayesian methods in astrophysics; (2) current misconceptions about both
frequentist and Bayesian statistical inference that hinder wider adoption of
Bayesian methods by astronomers; and (3) multilevel (hierarchical) Bayesian
modeling as a major future direction for research in Bayesian astrostatistics,
exemplified in part by presentations at the first ISI invited session on
astrostatistics, commemorated in this volume. It closes with an intentionally
provocative recommendation for astronomical survey data reporting, motivated by
the multilevel Bayesian perspective on modeling cosmic populations: that
astronomers cease producing catalogs of estimated fluxes and other source
properties from surveys. Instead, summaries of likelihood functions (or
marginal likelihood functions) for source properties should be reported (not
posterior probability density functions), including nontrivial summaries (not
simply upper limits) for candidate objects that do not pass traditional
detection thresholds.Comment: 27 pp, 4 figures. A lightly revised version of a chapter in
"Astrostatistical Challenges for the New Astronomy" (Joseph M. Hilbe, ed.,
Springer, New York, forthcoming in 2012), the inaugural volume for the
Springer Series in Astrostatistics. Version 2 has minor clarifications and an
additional referenc
Avoiding selection bias in gravitational wave astronomy
When searching for gravitational waves in the data from ground-based
gravitational wave detectors it is common to use a detection threshold to
reduce the number of background events which are unlikely to be the signals of
interest. However, imposing such a threshold will also discard some real
signals with low amplitude, which can potentially bias any inferences drawn
from the population of detected signals. We show how this selection bias is
naturally avoided by using the full information from the search, considering
both the selected data and our ignorance of the data that are thrown away, and
considering all relevant signal and noise models. This approach produces
unbiased estimates of parameters even in the presence of false alarms and
incomplete data. This can be seen as an extension of previous methods into the
high false rate regime where we are able to show that the quality of parameter
inference can be optimised by lowering thresholds and increasing the false
alarm rate.Comment: 13 pages, 2 figure
Electron Neutrino Mass Measurement by Supernova Neutrino Bursts and Implications on Hot Dark Matter
We present a new strategy for measuring the electron neutrino mass (\mnue)
by future detection of a Galactic supernova in large underground detectors such
as the Super-Kamiokande (SK). This method is nearly model-independent and one
can get a mass constraint in a straightforward way from experimental data
without specifying any model parameters for profiles of supernova neutrinos. We
have tested this method using virtual data generated from a numerical model of
supernova neutrino emission by realistic Monte-Carlo simulations of the SK
detection. It is shown that this method is sensitive to \mnue of 3 eV
for a Galactic supernova, and this range is as low as the prediction of the
cold+hot dark matter scenario with a nearly degenerate mass hierarchy of
neutrinos, which is consistent with the current observations of solar and
atmospheric neutrino anomalies and density fluctuations in the universe.Comment: 4 pages including 1 figure, accepted by Phys. Rev. Let
Superluminal neutrinos in long baseline experiments and SN1987a
Precise tests of Lorentz invariance in neutrinos can be performed using long
baseline experiments such as MINOS and OPERA or neutrinos from astrophysical
sources. The MINOS collaboration reported a measurement of the muonic neutrino
velocities that hints to super-luminal propagation, very recently confirmed at
6 sigma by OPERA. We consider a general parametrisation which goes beyond the
usual linear or quadratic violation considered in quantum-gravitational models.
We also propose a toy model showing why Lorentz violation can be specific to
the neutrino sector and give rise to a generic energy behaviour E^alpha, where
alpha is not necessarily an integer number. Supernova bounds and the preferred
MINOS and OPERA regions show a tension, due to the absence of shape distortion
in the neutrino bunch in the far detector of MINOS. The energy independence of
the effect has also been pointed out by the OPERA results.Comment: 22 pages, 7 figures; comment on Cherenkov emission added, version
matching JHEP published pape
Search for low energy neutrinos in correlation with the 8 events observed by the EXPLORER and NAUTILUS detectors in 2001
We report on a search for low-energy neutrino (antineutrino) bursts in
correlation with the 8 time coincident events observed by the gravitational
waves detectors EXPLORER and NAUTILUS (GWD) during the year 2001. The search,
conducted with the LVD detector (INFN Gran Sasso National Laboratory, Italy),
has considered several neutrino reactions, corresponding to different neutrino
species, and a wide range of time intervals around the (GWD) observed events.
No evidence for statistically significant correlated signals in LVD has been
found. Assuming two different origins for neutrino emission, the cooling of a
neutron star from a core-collapse supernova or from coalescing neutron stars
and the accretion of shocked matter, and taking into account neutrino
oscillations, we derive limits to the total energy emitted in neutrinos and to
the amount of accreting mass, respectively.Comment: Accepted for publication in Astronomy and Astrophysic
Spin-Flavour Oscillations and Neutrinos from SN1987A
The neutrino signal from SN1987A is analysed with respect to spin-flavour
oscillations between electron antineutrinos, , and muon
neutrinos, , by means of a maximum likelihood analysis.
Following Jegerlehner et al. best fit values for the total energy released in
neutrinos, , and the temperature of the electron antineutrino,
, for a range of mixing parameters and progenitor models are
calculated. In particular the dependence of the inferred quantities on the
metallicity of the supernova is investigated and the uncertainties involved in
using the neutrino signal to determine the neutrino magnetic moment are pointed
out.Comment: 14 pages, RevTeX, 4 figures, to appear in Physical Review
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