2,095 research outputs found
The host-galaxy response to the afterglow of GRB 100901A
For Gamma-Ray Burst 100901A, we have obtained Gemini-North and Very Large
Telescope optical afterglow spectra at four epochs: one hour, one day, three
days and one week after the burst, thanks to the afterglow remaining unusually
bright at late times. Apart from a wealth of metal resonance lines, we also
detect lines arising from fine-structure levels of the ground state of Fe II,
and from metastable levels of Fe II and Ni II at the host redshift (z =
1.4084). These lines are found to vary significantly in time. The combination
of the data and modelling results shows that we detect the fall of the Ni II 4
F9/2 metastable level population, which to date has not been observed. Assuming
that the population of the excited states is due to the UV-radiation of the
afterglow, we estimate an absorber distance of a few hundred pc. This appears
to be a typical value when compared to similar studies. We detect two
intervening absorbers (z = 1.3147, 1.3179). Despite the wide temporal range of
the data, we do not see significant variation in the absorption lines of these
two intervening systems.Comment: 17 pages, 9 figures. Accepted by Monthly Notices of the Royal
Astronomical Society on Jan 11th 201
From Majorana theory of atomic autoionization to Feshbach resonances in high temperature superconductors
The Ettore Majorana paper - Theory of incomplete P triplets- published in
1931, focuses on the role of selection rules for the non-radiative decay of two
electron excitations in atomic spectra, involving the configuration interaction
between discrete and continuum channels. This work is a key step for
understanding the 1935 work of Ugo Fano on the asymmetric lineshape of two
electron excitations and the 1958 Herman Feshbach paper on the shape resonances
in nuclear scattering arising from configuration interaction between many
different scattering channels. The Feshbach resonances are today of high
scientific interest in many different fields and in particular for ultracold
gases and high Tc superconductivity.Comment: 13 pages, 7 figures. Journal of Superconductivity and Novel Magnetism
to be publishe
Evidence of the effect of strong stripping channels on the dynamics of the 8 Li + 58Ni reaction
The 8
Li + 58Ni collision is investigated at 23.9, 26.1, 28.7, and 30 MeV bombarding energies. Quasielastic
angular distributions and the singles 7
Li angular and energy distributions are presented. Coupled-reaction
channels (CRC) calculations, which include the coupling of the elastic channel to 59Ni = 58Ni + n states above
and below the neutron threshold, provide a simultaneous description of the quasielastic and transfer distributions
and evidence the strong effect of the one-neutron transfer/breakup channels on the quasielastic scattering. The 7
Li angular and energy distributions have been also successfully analyzed combining the continuum discretized
coupled channels (CDCC) method, for the elastic breakup, and the IAV model of Ichimura, Austern, and Vincent
[Phys. Rev. C 32, 431 (1985)], for the nonelastic breakup. These calculations indicate that most of the 7
Li yields
are due to nonelastic breakup contributions (transfer), whereas elastic breakup plays a minor role.Fundação de Amparo à Pesquisa do Estado de São Paulo, FAPESP (Brazil), Contratos No. 2019/02759-0, No. 2019/07767-1, No. 2016/17612-7 y No. 2013/22100-7Coordenação de Aperfeiçoamento de Pessoal de Nével Superior, Brasil (CAPES), código de financiación: 88887.355019/2019Ministerio de Ciencia, Innovación y Universidades de España. proyecto No. FIS2017-88410-PFondo Europeo de Desarrollo Regional (FEDER)Programa Horizon 2020 de la Unión Europea No. 65400
Shape resonance for the anisotropic superconducting gaps near a Lifshitz transition: the effect of electron hopping between layers
The multigap superconductivity modulated by quantum confinement effects in a
superlattice of quantum wells is presented. Our theoretical BCS approach
captures the low-energy physics of a shape resonance in the superconducting
gaps when the chemical potential is tuned near a Lifshitz transition. We focus
on the case of weak Cooper-pairing coupling channels and strong pair exchange
interaction driven by repulsive Coulomb interaction that allows to use the BCS
theory in the weak-coupling regime neglecting retardation effects like in
quantum condensates of ultracold gases. The calculated matrix element effects
in the pairing interaction are shown to yield a complex physics near the
particular quantum critical points due to Lifshitz transitions in multigap
superconductivity. Strong deviations of the ratio from the
standard BCS value as a function of the position of the chemical potential
relative to the Lifshitz transition point measured by the Lifshitz parameter
are found. The response of the condensate phase to the tuning of the Lifshitz
parameter is compared with the response of ultracold gases in the BCS-BEC
crossover tuned by an external magnetic field. The results provide the
description of the condensates in this regime where matrix element effects play
a key role.Comment: 12 pages, 6 figure
Scaling properties in off equilibrium dynamical processes
In the present paper, we analyze the consequences of scaling hypotheses on
dynamic functions, as two times correlations . We show, under general
conditions, that must obey the following scaling behavior , where the scaling variable is
and , two
undetermined functions. The presence of a non constant exponent
signals the appearance of multiscaling properties in the dynamics.Comment: 6 pages, no figure
Comparative chromosome painting discloses homologous Segments in distantly related mammals
Comparative chromosome painting, termed ZOO-FISH, using DNA libraries from flow
sorted human chromosomes 1,16,17 and X, and mouse chromosome 11 discloses the
presence of syntenic groups in distantly related mammalian Orders ranging from
primates (Homo sapiens), rodents (Mus musculus), even-toed ungulates (Muntiacus
muntjak vaginalis and Muntiacus reevesi) and whales (Balaenoptera physalus). These
mammalian Orders have evolved separately for 55-80 million years (Myr). We conclude
that ZOO-FISH can be used to generate comparative chromosome maps of a large
number of mammalian species
The Shapes of Dirichlet Defects
If the vacuum manifold of a field theory has the appropriate topological
structure, the theory admits topological structures analogous to the D-branes
of string theory, in which defects of one dimension terminate on other defects
of higher dimension. The shapes of such defects are analyzed numerically, with
special attention paid to the intersection regions. Walls (co-dimension 1
branes) terminating on other walls, global strings (co-dimension 2 branes) and
local strings (including gauge fields) terminating on walls are all considered.
Connections to supersymmetric field theories, string theory and condensed
matter systems are pointed out.Comment: 24 pages, RevTeX, 21 eps figure
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