24,702 research outputs found
Adaptively Smoothed Seismicity Earthquake Forecasts for Italy
We present a model for estimating the probabilities of future earthquakes of
magnitudes m > 4.95 in Italy. The model, a slightly modified version of the one
proposed for California by Helmstetter et al. (2007) and Werner et al. (2010),
approximates seismicity by a spatially heterogeneous, temporally homogeneous
Poisson point process. The temporal, spatial and magnitude dimensions are
entirely decoupled. Magnitudes are independently and identically distributed
according to a tapered Gutenberg-Richter magnitude distribution. We estimated
the spatial distribution of future seismicity by smoothing the locations of
past earthquakes listed in two Italian catalogs: a short instrumental catalog
and a longer instrumental and historical catalog. The bandwidth of the adaptive
spatial kernel is estimated by optimizing the predictive power of the kernel
estimate of the spatial earthquake density in retrospective forecasts. When
available and trustworthy, we used small earthquakes m>2.95 to illuminate
active fault structures and likely future epicenters. By calibrating the model
on two catalogs of different duration to create two forecasts, we intend to
quantify the loss (or gain) of predictability incurred when only a short but
recent data record is available. Both forecasts, scaled to five and ten years,
were submitted to the Italian prospective forecasting experiment of the global
Collaboratory for the Study of Earthquake Predictability (CSEP). An earlier
forecast from the model was submitted by Helmstetter et al. (2007) to the
Regional Earthquake Likelihood Model (RELM) experiment in California, and, with
over half of the five-year experiment over, the forecast performs better than
its competitors.Comment: revised manuscript. 22 pages, 3 figures, 2 table
Universal three-body recombination and Efimov resonances in an ultracold Li-Cs mixture
We study Efimov resonances via three-body loss in an ultracold two-component
gas of fermionic Li and bosonic Cs atoms close to a Feshbach
resonance at 843~G, extending results reported previously [Pires \textit{et
al.}, Phys. Rev. Lett. 112, 250404 (2014)] to temperatures around 120~nK. The
experimental scheme for reaching lower temperatures is based upon compensating
the gravity-induced spatial separation of the mass-imbalanced gases with
bichromatic optical dipole traps. We observe the first and second excited
Li-Cs-Cs Efimov resonance in the magnetic field dependence of the three-body
event rate constant, in good agreement with the universal zero-range theory at
finite temperature [Petrov and Werner, Phys. Rev. A 92, 022704 (2015)].
Deviations are found for the Efimov ground state, and the inelasticity
parameter is found to be significantly larger than those for
single-species systems
Universal joint-measurement uncertainty relation for error bars
We formulate and prove a new, universally valid uncertainty relation for the necessary error bar widths in any approximate joint measurement of position and momentum
Neutrino Masses and Absence of Flavor Changing Interactions in the 2HDM from Gauge Principles
We propose several Two Higgs Doublet Models with the addition of an Abelian
gauge group which free the usual framework from flavor changing neutral
interactions and explain neutrino masses through the seesaw mechanism. We
discuss the kinetic and mass-mixing gripping phenomenology which encompass
several constraints coming from atomic parity violation, the muon anomalous
magnetic moment, rare meson decays, Higgs physics, LEP precision data,
neutrino-electron scattering, low energy accelerators and LHC probes.Comment: 54 pages, 10 figure
A non-pulsating neutron star in the supernova remnant HESS J1731-347 / G353.6-0.7 with a carbon atmosphere
Context: The CCO candidate in the center of the supernova remnant shell HESS
J1731-347 / G353.6-0.7 shows no pulsations and exhibits a blackbody-like X-ray
spectrum. If the absence of pulsations is interpreted as evidence for the
emitting surface area being the entire neutron star surface, the assumption of
the measured flux being due to a blackbody emission translates into a source
distance that is inconsistent with current estimates of the remnant's distance.
Aims: With the best available observational data, we extended the pulse period
search down to a sub-millisecond time scale and used a carbon atmosphere model
to describe the X-ray spectrum of the CCO and to estimate geometrical
parameters of the neutron star. Methods: To search for pulsations we used data
of an observation of the source with XMM-Newton performed in timing mode. For
the spectral analysis, we used earlier XMM-Newton observations performed in
imaging mode, which permits a more accurate treatment of the background. The
carbon atmosphere models used to fit the CCO spectrum are computed assuming
hydrostatic and radiative equilibria and take into account pressure ionization
and the presence of spectral lines. Results: Our timing analysis did not reveal
any pulsations with a pulsed fraction above ~8% down to 0.2 ms. This finding
further supports the hypothesis that the emitting surface area is the entire
neutron star surface. The carbon atmosphere model provides a good fit to the
CCO spectrum and leads to a normalization consistent with the available
distance estimates of the remnant. The derived constraints on the mass and
radius of the source are consistent with reasonable values of the neutron star
mass and radius. After the CCO in Cas A, the CCO in HESS J1731-347 / G353.6-0.7
is the second object of this class for which a carbon atmosphere model provides
a consistent description of X-ray emission.Comment: 6 pages, 5 figures, accepted for publication in
Astronomy&Astrophysic
Phase transitions and the internal noise structure of nonlinear Schr\"odi nger equation solitons
We predict phase-transitions in the quantum noise characteristics of systems
described by the quantum nonlinear Schr\"odinger equation, showing them to be
related to the solitonic field transition at half the fundamental soliton
amplitude. These phase-transitions are robust with respect to Raman noise and
scattering losses. We also describe the rich internal quantum noise structure
of the solitonic fields in the vicinity of the phase-transition. For optical
coherent quantum solitons, this leads to the prediction that eliminating the
peak side-band noise due to the electronic nonlinearity of silica fiber by
spectral filtering leads to the optimal photon-number noise reduction of a
fundamental soliton.Comment: 10 pages, 5 figure
A tight Tsirelson inequality for infinitely many outcomes
We present a novel tight bound on the quantum violations of the CGLMP
inequality in the case of infinitely many outcomes. Like in the case of
Tsirelson's inequality the proof of our new inequality does not require any
assumptions on the dimension of the Hilbert space or kinds of operators
involved. However, it is seen that the maximal violation is obtained by the
conjectured best measurements and a pure, but not maximally entangled, state.
We give an approximate state which, in the limit where the number of outcomes
tends to infinity, goes to the optimal state for this setting. This state might
be potentially relevant for experimental verifications of Bell inequalities
through multi-dimenisonal entangled photon pairs.Comment: 5 pages, 2 figures; improved presentation, change in title, as
published
The virtual observatory service TheoSSA: Establishing a database of synthetic stellar flux standards. II. NLTE spectral analysis of the OB-type subdwarf Feige 110
In the framework of the Virtual Observatory (VO), the German Astrophysical
Virtual Observatory (GAVO) developed the registered service TheoSSA
(Theoretical Stellar Spectra Access). It provides easy access to stellar
spectral energy distributions (SEDs) and is intended to ingest SEDs calculated
by any model-atmosphere code, generally for all effective temperature, surface
gravities, and elemental compositions. We will establish a database of SEDs of
flux standards that are easily accessible via TheoSSA's web interface.
The OB-type subdwarf Feige 110 is a standard star for flux calibration.
State-of-the-art non-local thermodynamic equilibrium (NLTE) stellar-atmosphere
models that consider opacities of species up to trans-iron elements will be
used to provide a reliable synthetic spectrum to compare with observations.
In case of Feige 110, we demonstrate that the model reproduces not only its
overall continuum shape from the far-ultraviolet (FUV) to the optical
wavelength range but also the numerous metal lines exhibited in its FUV
spectrum.
We present a state-of-the-art spectral analysis of Feige 110. We determined
, and
the abundances of He, N, P, S, Ti, V, Cr, Mn, Fe, Co, Ni, Zn, and Ge. Ti, V,
Mn, Co, Zn, and Ge were identified for the first time in this star. Upper
abundance limits were derived for C, O, Si, Ca, and Sc.
The TheoSSA database of theoretical SEDs of stellar flux standards guarantees
that the flux calibration of astronomical data and cross-calibration between
different instruments can be based on models and SEDs calculated with
state-of-the-art model-atmosphere codes.Comment: 19 pages, 7 figure
A Fast Algorithm for Simulating the Chordal Schramm-Loewner Evolution
The Schramm-Loewner evolution (SLE) can be simulated by dividing the time
interval into N subintervals and approximating the random conformal map of the
SLE by the composition of N random, but relatively simple, conformal maps. In
the usual implementation the time required to compute a single point on the SLE
curve is O(N). We give an algorithm for which the time to compute a single
point is O(N^p) with p<1. Simulations with kappa=8/3 and kappa=6 both give a
value of p of approximately 0.4.Comment: 17 pages, 10 figures. Version 2 revisions: added a paragraph to
introduction, added 5 references and corrected a few typo
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