17,747 research outputs found
Generalised Fractional Evolution Equations of Caputo Type
This paper is devoted to the study of generalised time-fractional evolution
equations involving Caputo type derivatives. Using analytical methods and
probabilistic arguments we obtain well-posedness results and stochastic
representations for the solutions. These results encompass known linear and
non-linear equations from classical fractional partial differential equations
such as the time-space-fractional diffusion equation, as well as their far
reaching extensions. \\ Meaning is given to a probabilistic generalisation of
Mittag-Leffler functions.Comment: To be published in 'Chaos, Solitons & Fractals
Measuring multipole moments of Weyl metrics by means of gyroscopes
Using the technique of Rindler and Perlick we calculate the total precession
per revolution of a gyroscope circumventing the source of Weyl metrics. We
establish thereby a link between the multipole moments of the source and an
``observable'' quantity. Special attention deserves the case of the
gamma-metric. As an extension of this result we also present the corresponding
expressions for some stationary space-times.Comment: 18 pages Latex, To appear in J.Math.Phy
Watson's theorem and the axial transition
We present a new determination of the axial form factors from
neutrino induced pion production data. For this purpose, the model of Hernandez
{\it et al.} [Phys. Rev. D76, 033005 (2007)] is improved by partially restoring
unitarity. This is accomplished by imposing Watson's theorem on the dominant
vector and axial multipoles. As a consequence, a larger , in good
agreement with the prediction from the off-diagonal Goldberger-Treiman
relation, is now obtained.Comment: 17 latex pages, 7 figures, 2 tables. Some typos correcte
Notes on proper homotopy theories associated with compact PL-manifolds
The purpose of this note is to present a bigraded sequence of functors associated with compact PL-manifolds . These functors are invariant of proper homotopy type, and distinguish topological spaces which have the same homotopy type. On the category of compact topological spaces these functors agree with the Hurewicz homotopy groups, hence the principal interest of these functors is for noncompact spaces
Probing the chiral weak Hamiltonian at finite volumes
Non-leptonic kaon decays are often described through an effective chiral weak
Hamiltonian, whose couplings ("low-energy constants") encode all
non-perturbative QCD physics. It has recently been suggested that these
low-energy constants could be determined at finite volumes by matching the
non-perturbatively measured three-point correlation functions between the weak
Hamiltonian and two left-handed flavour currents, to analytic predictions
following from chiral perturbation theory. Here we complete the analytic side
in two respects: by inspecting how small ("epsilon-regime") and intermediate or
large ("p-regime") quark masses connect to each other, and by including in the
discussion the two leading Delta I = 1/2 operators. We show that the
epsilon-regime offers a straightforward strategy for disentangling the
coefficients of the Delta I = 1/2 operators, and that in the p-regime
finite-volume effects are significant in these observables once the
pseudoscalar mass M and the box length L are in the regime ML \lsim 5.0.Comment: 37 pages. v2: some additions and clarifications; published versio
Three carbon-enhanced metal-poor dwarf stars from the SDSS - Chemical abundances from CO^5BOLD 3D hydrodynamical model atmospheres
The origin of carbon-enhanced metal-poor stars enriched with both s and r
elements is highly debated. Detailed abundances of these types of stars are
crucial to understand the nature of their progenitors. The aim of this
investigation is to study in detail the abundances of SDSS J1349-0229, SDSS
J0912+0216 and SDSS J1036+1212, three dwarf CEMP stars, selected from the Sloan
Digital Sky Survey. Using high resolution VLT/UVES spectra (R ~ 30 000) we
determine abundances for Li, C, N, O, Na, Mg, Al, Ca, Sc, Ti, Cr, Mn, Fe, Co,
Ni and 21 neutron-capture elements. We made use of CO^5BOLD 3D hydrodynamical
model atmospheres in the analysis of the carbon, nitrogen and oxygen
abundances. NLTE corrections for C I and O I lines were computed using the Kiel
code. We classify SDSS J1349-0229 and SDSS J0912+0216 as CEMP-r+s stars. SDSS
J1036+1212 belongs to the class CEMP-no/s, with enhanced Ba, but deficient Sr,
of which it is the third member discovered to date. Radial-velocity variations
have been observed in SDSS J1349-0229, providing evidence that it is a member
of a binary system. The chemical composition of the three stars is generally
compatible with mass transfer from an AGB companion. However, many details
remain difficult to explain. Most notably of those are the abundance of Li at
the level of the Spite plateau in SDSS J1036+1212 and the large over-abundance
of the pure r-process element Eu in all three stars.Comment: 12 pages, 15 figures. Accepted for publication in A&
High-order harmonic generation driven by chirped laser pulses induced by linear and non linear phenomena
We present a theoretical study of high-order harmonic generation (HHG) driven
by ultrashort optical pulses with different kind of chirps. The goal of the
present work is perform a detailed study to clarify the relevant parameters in
the chirped pulses to achieve a noticeable cut-off extensions in HHG. These
chirped pulses are generated using both linear and nonlinear dispersive
media.The description of the origin of the physical mechanisms responsible of
this extension is, however, not usually reported with enough detail in the
literature. The study of the behaviour of the harmonic cut-off with these kind
of pulses is carried out in the classical context, by the integration of the
Newton-Lorentz equation complemented with the quantum approach, based on the
integration of the time dependent Schr\"odinger equation in full dimensions
(TDSE-3D), we are able to understand the underlying physics.Comment: 13 pages, 8 figure
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