9,283 research outputs found
Classical novae and type I X-ray bursts: challenges for the 21st century
Classical nova explosions and type I X-ray bursts are the most frequent types
of thermonuclear stellar explosions in the Galaxy. Both phenomena arise from
thermonuclear ignition in the envelopes of accreting compact objects in close
binary star systems. Detailed observations of these events have stimulated
numerous studies in theoretical astrophysics and experimental nuclear physics.
We discuss observational features of these phenomena and theoretical efforts to
better understand the energy production and nucleosynthesis in these
explosions. We also examine and summarize studies directed at identifying
nuclear physics quantities with uncertainties that significantly affect model
predictions.Comment: 40 pages, accepted for AIP Advances: Stardust - Progress and Problems
in Nuclear Astrophysic
Decidability of the interval temporal logic ABBar over the natural numbers
In this paper, we focus our attention on the interval temporal logic of the
Allen's relations "meets", "begins", and "begun by" (ABBar for short),
interpreted over natural numbers. We first introduce the logic and we show that
it is expressive enough to model distinctive interval properties,such as
accomplishment conditions, to capture basic modalities of point-based temporal
logic, such as the until operator, and to encode relevant metric constraints.
Then, we prove that the satisfiability problem for ABBar over natural numbers
is decidable by providing a small model theorem based on an original
contraction method. Finally, we prove the EXPSPACE-completeness of the proble
Nucleosynthesis in Type I X-ray Bursts
Type I X-ray bursts are thermonuclear explosions that occur in the envelopes
of accreting neutron stars. Detailed observations of these phenomena have
prompted numerous studies in theoretical astrophysics and experimental nuclear
physics since their discovery over 35 years ago. In this review, we begin by
discussing key observational features of these phenomena that may be sensitive
to the particular patterns of nucleosynthesis from the associated thermonuclear
burning. We then summarize efforts to model type I X-ray bursts, with emphasis
on determining the nuclear physics processes involved throughout these bursts.
We discuss and evaluate limitations in the models, particularly with regard to
key uncertainties in the nuclear physics input. Finally, we examine recent,
relevant experimental measurements and outline future prospects to improve our
understanding of these unique environments from observational, theoretical and
experimental perspectives.Comment: Accepted by Prog. Part. Nucl. Phys., 45 pages, 14 figure
High energy extension of the FLUKA atmospheric neutrino flux
The atmospheric neutrino flux calculated with FLUKA was originally limited to
100-200 GeV for statistical reasons. In order to make it available for the
analysis of high energy events, like upward through-going muons detected by
neutrino telescopes, we have extended the calculation so to provide a reliable
neutrino yield per primary nucleon up to about 10**6 GeV/nucleon, as far as the
interaction model is concerned. We point out that the primary flux model above
100 GeV/nucleon still contributes with an important systematic error to the
neutrino flux.Comment: Extended version (10 pages) of the contribution to ICRC 2003, with
the addition of flux table
The FLUKA Monte Carlo, non-perturbative QCD and Cosmic Ray cascades
The FLUKA Monte Carlo code, presently used in cosmic ray physics, contains
packages to sample soft hadronic processes which are built according to the
Dual Parton Model. This is a phenomenological model capable of reproducing many
of the features of hadronic collisions in the non perturbative QCD regime. The
basic principles of the model are summarized and, as an example, the associated
Lambda-K production is discussed. This is a process which has some relevance
for the calculation of atmospheric neutrino fluxes.Comment: Extended version of the work for the proceedings of the workshop on
QCD at Cosmic Ray Energies, Erice, Aug. 30 - Sep. 4 2004, Ital
Atmospheric neutrinos in a Large Liquid Argon detector
In view of the evaluation of the physics goals of a large Liquid Argon TPC,
evolving from the ICARUS technology, we have studied the possibility of
performing precision measurements on atmospheric neutrinos. For this purpose we
have improved existing Monte Carlo neutrino event generators based on FLUKA and
NUX by including the 3-flavor oscillation formalism and the numerical treatment
of Earth matter effects. By means of these tools we have studied the
sensitivity in the measurement of Theta(23) through the accurate measurement of
electron neutrinos. The updated values for Delta m^2(23) from Super-Kamiokande
and the mixing parameters as obtained by solar and KamLand experiments have
been used as reference input, while different values of Theta(13) have been
considered. An exposure larger than 500 kton yr seems necessary in order to
achieve a significant result, provided that the present knowledge of systematic
uncertainties is largely improved.Comment: Talk given at the worksgop "Cryogenic Liquid Detectors for Future
Particle Physics", LNGS (Italy) March 13th-14th, 200
Bimagnon studies in cuprates with Resonant Inelastic X-ray Scattering at the O K edge. II - The doping effect in La2-xSrxCuO4
We present RIXS data at O K edge from La2-xSrxCuO4 vs. doping between x=0.10
and x=0.22 with attention to the magnetic excitations in the Mid-Infrared
region. The sampling done by RIXS is the same as in the undoped cuprates
provided the excitation is at the first pre-peak induced by doping. Note that
this excitation energy is about 1.5 eV lower than that needed to see bimagnons
in the parent compound. This approach allows the study of the upper region of
the bimagnon continuum around 450 meV within about one third of the Brilluoin
Zone around \Gamma. The results show the presence of damped bimagnons and of
higher even order spin excitations with almost constant spectral weight at all
the dopings explored here. The implications on high Tc studies are briefly
addressed
Coherent molecule formation in anharmonic potentials near confinement-induced resonances
We perform a theoretical and experimental study of a system of two ultracold
atoms with tunable interaction in an elongated trapping potential. We show that
the coupling of center-of-mass and relative motion due to an anharmonicity of
the trapping potential leads to a coherent coupling of a state of an unbound
atom pair and a molecule with a center of mass excitation. By performing the
experiment with exactly two particles we exclude three-body losses and can
therefore directly observe coherent molecule formation. We find quantitative
agreement between our theory of inelastic confinement-induced resonances and
the experimental results. This shows that the effects of center-of-mass to
relative motion coupling can have a significant impact on the physics of
quasi-1D quantum systems.Comment: 7 pages, 4 figure
Analogue Gravity and ultrashort laser pulse filamentation
Ultrashort laser pulse filaments in dispersive nonlinear Kerr media induce a
moving refractive index perturbation which modifies the space-time geometry as
seen by co-propagating light rays. We study the analogue geometry induced by
the filament and show that one of the most evident features of filamentation,
namely conical emission, may be precisely reconstructed from the geodesics. We
highlight the existence of favorable conditions for the study of analogue black
hole kinematics and Hawking type radiation.Comment: 4 pages, revised versio
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