225 research outputs found
On isovector meson exchange currents in the Bethe-Salpeter approach
We investigate the nonrelativistic reduction of the Bethe-Salpeter amplitude
for the deuteron electrodisintegration near threshold energies. To this end,
two assumptions have been used in the calculations: 1) the static approximation
and 2) the one iteration approximation. Within these assumptions it is possible
to recover the nonrelativistic result including a systematic extension to
relativistic corrections. We find that the so-called pair current term can be
constructed from the -wave contribution of the deuteron Bethe-Salpeter
amplitude. The form factor that enters into the calculation of the pair current
is constrained by the manifestly gauge independent matrix elements.Comment: 15 pages, incl. 3 figures, to be published Phys. Rev.
The relativistic impulse approximation for the exclusive electrodisintegration of the deuteron
The electrodisintegration of the deuteron in the frame of the Bethe-Salpeter
approach with a separable kernel of the nucleon-nucleon interaction is
considered. This conception keeps the covariance of a description of the
process. A comparison of relativistic and nonrelativistic calculations is
presented. The factorization of the cross section of the reaction in the
impulse approximation is obtained by analytical calculations. It is shown that
the photon-neutron interaction plays an important role.Comment: 31 pages, 14 figures, 1 tabl
Superscaling and Neutral Current Quasielastic Neutrino-Nucleus Scattering beyond the Relativistic Fermi Gas Model
The superscaling analysis is extended to include quasielastic (QE) scattering
via the weak neutral current of neutrinos and antineutrinos from nuclei. The
scaling function obtained within the coherent density fluctuation model (used
previously in calculations of QE inclusive electron and charge-changing (CC)
neutrino scattering) is applied to neutral current neutrino and antineutrino
scattering with energies of 1 GeV from C with a proton and neutron
knockout (u-channel inclusive processes). The results are compared with those
obtained using the scaling function from the relativistic Fermi gas model and
the scaling function as determined from the superscaling analysis (SuSA) of QE
electron scattering.Comment: 10 pages, 6 figures, published in Phys. Rev.
Formulas and equations for finding scattering data from the Dirichlet-to-Neumann map with nonzero background potential
For the Schrodinger equation at fixed energy with a potential supported in a
bounded domain we give formulas and equations for finding scattering data from
the Dirichlet-to-Neumann map with nonzero background potential. For the case of
zero background potential these results were obtained in [R.G.Novikov,
Multidimensional inverse spectral problem for the equation
-\Delta\psi+(v(x)-Eu(x))\psi=0, Funkt. Anal. i Ego Prilozhen 22(4), pp.11-22,
(1988)]
Determination of Matter Surface Distribution of Neutron-rich Nuclei
We demonstrate that the matter density distribution in the surface region is
determined well by the use of the relatively low-intensity beams that become
available at the upcoming radioactive beam facilities. Following the method
used in the analyses of electron scattering, we examine how well the density
distribution is determined in a model-independent way by generating pseudo data
and by carefully applying statistical and systematic error analyses. We also
study how the determination becomes deteriorated in the central region of the
density, as the quality of data decreases. Determination of the density
distributions of neutron-rich nuclei is performed by fixing parameters in the
basis functions to the neighboring stable nuclei. The procedure allows that the
knowledge of the density distributions of stable nuclei assists to strengthen
the determination of their unstable isotopes.Comment: 41 pages, latex, 27 figure
Distribution of Temperature and Strength in the Central Andean Lithosphere and Its Relationship to Seismicity and Active Deformation
We present three-dimensional (3D) models of the present-day steady-state conductive thermal field and strength distribution in the lithosphere beneath the Central Andes. Our primary objective was to investigate the influence that the structure of the Central Andean lithosphere has on its thermal and rheological state, and the relationship between the latter and the active deformation in the region. We used our previous data-driven and gravity-constrained 3D density model as starting point for the calculations. We first assigned lithology-derived thermal and rheological properties to the different divisions of the density model and defined temperature boundary conditions. We then calculated the 3D steady-state conductive thermal field and the maximum differential stresses for both brittle and ductile behaviors. We find that the thickness and composition of the crust are the main factors affecting the modeled thermal field, and consequently also the strength distribution. The orogen is characterized by a thick felsic crust with elevated temperatures and a low integrated strength, whereas the foreland and forearc are underlain by a more mafic and thinner crust with lower temperatures and a higher integrated strength. We find that most of the intraplate deformation coincides spatially with the steepest strength gradients and suggest that the high potential energy of the orogen together with the presence of rheological lateral heterogeneities produce high compressional stresses and strong strain localization along the margins of the orogen. We interpret earthquakes within the modeled ductile field to be related to the weakening effect of long-lived faults and/or the presence of seismic asperities.Fil: Ibarra, Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; ArgentinaFil: Prezzi, Claudia Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; ArgentinaFil: Bott, Judith. German Research Centre for Geosciences; AlemaniaFil: Scheck Wenderoth, Magdalena. German Research Centre for Geosciences; AlemaniaFil: Strecker, Manfred. Universitat Potsdam; Alemani
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