3,904 research outputs found
On the Benjamin and related equations
We consider in this paper various theoretical and numerical issues on
classical one dimensional models of internal waves with surface tension.They
concern the Cauchy problem, including the long time dynamic, localized solitons
or multisolitons, the soliton resolution property. We survey known results,
present a few new ones together with open questions and conjectures motivated
by numerical simulations.
A major issue is to emphasize the differences of the qualitative behavior of
solutions with those of the same equations without the capillary term
Constraining the properties of neutron star crusts with the transient low-mass X-ray binary Aql X-1
Aql X-1 is a prolific transient neutron star low-mass X-ray binary that
exhibits an accretion outburst approximately once every year. Whether the
thermal X-rays detected in intervening quiescent episodes are the result of
cooling of the neutron star or due to continued low-level accretion remains
unclear. In this work we use Swift data obtained after the long and bright 2011
and 2013 outbursts, as well as the short and faint 2015 outburst, to
investigate the hypothesis that cooling of the accretion-heated neutron star
crust dominates the quiescent thermal emission in Aql X-1. We demonstrate that
the X-ray light curves and measured neutron star surface temperatures are
consistent with the expectations of the crust cooling paradigm. By using a
thermal evolution code, we find that ~1.2-3.2 MeV/nucleon of shallow heat
release describes the observational data well, depending on the assumed
mass-accretion rate and temperature of the stellar core. We find no evidence
for varying strengths of this shallow heating after different outbursts, but
this could be due to limitations of the data. We argue that monitoring Aql X-1
for up to ~1 year after future outbursts can be a powerful tool to break model
degeneracies and solve open questions about the magnitude, depth and origin of
shallow heating in neutron star crusts.Comment: 14 pages, 5 figures, 3 tables, accepted to MNRA
Well-posedness and stability results for the Gardner equation
In this article we present local well-posedness results in the classical
Sobolev space H^s(R) with s > 1/4 for the Cauchy problem of the Gardner
equation, overcoming the problem of the loss of the scaling property of this
equation. We also cover the energy space H^1(R) where global well-posedness
follows from the conservation laws of the system. Moreover, we construct
solitons of the Gardner equation explicitly and prove that, under certain
conditions, this family is orbitally stable in the energy space.Comment: 1 figure. Accepted for publication in Nonlin.Diff Eq.and App
Espectro polínico de la franja litoral en la provincia de Granada: periodo estudiado 2003-2005
XV lnternational A.P.L.E. Symposium of Palynolog
Estudio de la actividad alergénica de Olea europaea L. y su relación con ingresos de pacientes en los Servicios de Urgencias (Hospital San Cecilio de Granada)
XV lnternational A.P.L.E. Symposium of Palynolog
Microscopic cluster model for the description of (18O,16O) two-neutron transfer reactions
Excitation energy spectra and absolute cross-section angular distributions were measured for the 13C(18O,16O)15C two-neutron transfer reaction at 84 MeV incident energy. Exact finite-range coupled reaction channel calculations are used to analyse the data considering both the direct two-neutron transfer and the two-step sequential mechanism. For the direct calculations, two approaches are discussed: The extreme cluster and the newly introduced microscopic cluster. The latter makes use of spectroscopic amplitudes in the centre-of-mass reference frame, derived from shell-model calculations. The results describe well the experimental cross sections
Microscopic cluster model for the description of new experimental results on the C 13 (O 18, O 16) C 15 two-neutron transfer at 84 MeV incident energy
The C13(O18,O16)C15 reaction is studied at 84 MeV incident energy. Excitation energy spectra and absolute cross-section angular distributions for the strongest transitions are measured with good energy and angular resolutions. Strong selectivity for two-neutron configurations in the states of the residual nucleus is found. The measured cross-section angular distributions are analyzed by exact finite-range coupled reaction channel calculations. The two-particle wave functions are extracted using the extreme cluster and the independent coordinate scheme with shell-model derived coupling strengths. A new approach also is introduced, the microscopic cluster, in which the spectroscopic amplitudes in the center-of-mass reference frame are derived from shell-model calculations using the Moshinsky transformation brackets. This new model is able to describe well the experimental cross section and to highlight cluster configurations in the involved wave functions
Decoherence-Free Emergence of Macroscopic Local Realism for entangled photons in a cavity
We investigate the influence of environmental noise on polarization entangled
light generated by parametric emission in a cavity. By adopting a recently
developed separability criterion, we show that: i) self-stimulation may
suppress the detrimental influence of noise on entanglement; ii) when
self-stimulation becomes effective, a classical model of parametric emission
incorporating noise provides the same results of quantum theory for the
expectation values involved in the separability criterion. Moreover we show
that, in the macroscopic limit, it is impossible to observe violations of local
realism with measurements of -particle correlations, whatever n but finite.
These results provide an interesting example of the emergence of macroscopic
local realism in the presence of strong entanglement even in the absence of
decoherence.Comment: 1 figur
Hierarchical Self-Assembly of Supramolecular Helical Fibres from Amphiphilic C3-Symmetrical Functional Tris(tetrathiafulvalenes)
The preparation and self-assembly of the enantiomers of a series of C3-symmetric compounds incorporating three tetrathiafulvalene (TTF) residues is reported. The chiral citronellyl and dihydrocitronellyl alkyl chains lead to helical one dimensional stacks in solution. Molecular mechanics and dynamics simulations combined with experimental and theoretical circular dichroism support the observed helicity in solution. These stacks self-assemble to give fibres that have morphologies that depend on the nature of the chiral alkyl group and the medium in which the compounds aggregate. An inversion of macroscopic helical morphology of the citronellyl compound is observed when compared to analogous 2-methylbutyl chains, which is presumably a result of the stereogenic centre being further away from the core of the molecule. This composition still allows both morphologies to be observed, whereas an achiral compound shows no helicity. The morphology of the fibres also depends on the flexibility at the chain ends of the amphiphilic components, as there is not such an apparently persistent helical morphology for the dihydrocitronellyl derivative as for that prepared from citronellyl chains
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