6,668 research outputs found
Path integrals and degrees of freedom in many-body systems and relativistic field theories
The identification of physical degrees of freedom is sometimes obscured in
the path integral formalism, and this makes it difficult to impose some
constraints or to do some approximations. I review a number of cases where the
difficulty is overcame by deriving the path integral from the operator form of
the partition function after such identification has been made.Comment: 15 pages, volume in honor of prof.Yu.A.Simono
ASCA view on High-Redshift Radio-Quiet Quasars
We briefly discuss the latest ASCA results on the X-ray spectral properties
of high-redshift radio-quiet quasars.Comment: 4 pages, 1 figure, to appear in the Proceedings of the Conference
"X-ray Astronomy '999: Stellar Endpoints, AGNs, and the Diffuse X-ray
Background (September 6-10 - 1999
Boson Dominance in nuclei
We present a new method of bosonization of fermion systems applicable when
the partition function is dominated by composite bosons. Restricting the
partition function to such states we get an euclidean bosonic action from which
we derive the Hamiltonian. Such a procedure respects all the fermion
symmetries, in particular fermion number conservation, and provides a boson
mapping of all fermion operators.Comment: 12 page
Towards an optical potential for rare-earths through coupled channels
The coupled-channel theory is a natural way of treating nonelastic channels,
in particular those arising from collective excitations, defined by nuclear
deformations. Proper treatment of such excitations is often essential to the
accurate description of reaction experimental data. Previous works have applied
different models to specific nuclei with the purpose of determining
angular-integrated cross sections. In this work, we present an extensive study
of the effects of collective couplings and nuclear deformations on integrated
cross sections as well as on angular distributions in a consistent manner for
neutron-induced reactions on nuclei in the rare-earth region. This specific
subset of the nuclide chart was chosen precisely because of a clear static
deformation pattern. We analyze the convergence of the coupled-channel
calculations regarding the number of states being explicitly coupled. Inspired
by the work done by Dietrich \emph{et al.}, a model for deforming the spherical
Koning-Delaroche optical potential as function of quadrupole and hexadecupole
deformations is also proposed. We demonstrate that the obtained results of
calculations for total, elastic and inelastic cross sections, as well as
elastic and inelastic angular distributions correspond to a remarkably good
agreement with experimental data for scattering energies above around a few
MeV.Comment: 7 pages, 6 figures. Submitted to the proceedings of the XXXVI
Reuni\~ao de Trabalho de F\'{\i}sica Nuclear no Brasil (XXXVI Brazilian
Workshop on Nuclear Physics), held in Maresias, S\~ao Paulo, Brazil in
September 2013, which should be published on AIP Conference Proceeding
Series. arXiv admin note: substantial text overlap with arXiv:1311.1115,
arXiv:1311.042
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