8,882 research outputs found
Self-dual formulations of d=3 gravity theories in the path-integral framework
We study the connection, at the quantum level, between d=2+1 dimensional
self-dual models with actions of growing (from first to fourth) order,
governing the dynamics of helicity +2 (or -2) massive excitations. We obtain
identities between generating functionals of the different models using the
path-integral framework, this allowing to establish dual maps among relevant
vacuum expectation values. We check consistency of these v.e.v.'s with the
gauge invariance gained in each mapping.Comment: 26 pages. LaTeX. Minor changes. Published in Int. J Modern Phys. A;
http://www.worldscinet.com/ijmp
Ground state of medium-heavy doubly-closed shell nuclei in correlated basis function theory
The correlated basis function theory is applied to the study of medium-heavy
doubly closed shell nuclei with different wave functions for protons and
neutrons and in the jj coupling scheme. State dependent correlations including
tensor correlations are used. Realistic two-body interactions of Argonne and
Urbana type, together with three-body interactions have been used to calculate
ground state energies and density distributions of the 12C, 16O, 40Ca, 48Ca and
208Pb nuclei.Comment: Latex 10 pages, 3 Tables, 10 Figure
Baroclinic instability with variable gravity: A perturbation analysis
Solutions for a quasigeostrophic baroclinic stability problem in which gravity is a function of height were obtained. Curvature and horizontal shear of the basic state flow were omitted and the vertical and horizontal temperature gradients of the basic state were taken as constant. The effect of a variable dielectric body force, analogous to gravity, on baroclinic instability for the design of a spherical, baroclinic model for Spacelab was determined. Such modeling could not be performed in a laboratory on the Earth's surface because the body force could not be made strong enough to dominate terrestrial gravity. A consequence of the body force variation and the preceding assumptions was that the potential vorticity gradient of the basic state vanished. The problem was solved using a perturbation method. The solution gives results which are qualitatively similar to Eady's results for constant gravity; a short wavelength cutoff and a wavelength of maximum growth rate were observed. The averaged values of the basic state indicate that both the wavelength range of the instability and the growth rate at maximum instability are increased. Results indicate that the presence of the variable body force will not significantly alter the dynamics of the Spacelab experiment. The solutions are also relevant to other geophysical fluid flows where gravity is constant but the static stability or Brunt-Vaisala frequency is a function of height
Renormalized Fermi hypernetted chain approach in medium-heavy nuclei
The application of the Correlated basis function theory and of the Fermi
hypernetted chain technique, to the description of the ground state of
medium-heavy nuclei is reviewed. We discuss how the formalism, originally
developed for symmetric nuclear matter, should be changed in order to describe
finite nuclear systems, with different number of protons and neutrons. This
approach allows us to describe doubly closed shell nuclei by using microscopic
nucleon-nucleon interactions. We presents results of numerical calculations
done with two-nucleon interactions of Argonne type,implemented with three-body
forces of Urbana type. Our results regard ground-state energies, matter, charge
and momentum distributions, natural orbits, occupation numbers, quasi-hole wave
functions and spectroscopic factors of 12C, 16O, 40Ca, 48Ca and 208Pb nuclei.Comment: 127 Pages, 37 figures, Accepted for publication in Physics Report
Critical point symmetries in boson-fermion systems. The case of shape transition in odd nuclei in a multi-orbit model
We investigate phase transitions in boson-fermion systems. We propose an
analytically solvable model (E(5/12)) to describe odd nuclei at the critical
point in the transition from the spherical to -unstable behaviour. In
the model, a boson core described within the Bohr Hamiltonian interacts with an
unpaired particle assumed to be moving in the three single particle orbitals
j=1/2,3/2,5/2. Energy spectra and electromagnetic transitions at the critical
point compare well with the results obtained within the Interacting Boson
Fermion Model, with a boson-fermion Hamiltonian that describes the same
physical situation.Comment: Phys. Rev. Lett. (in press
Momentum distributions and spectroscopic factors of doubly-closed shell nuclei in correlated basis function theory
The momentum distributions, natural orbits, spectroscopic factors and
quasi-hole
wave functions of the C12, O16, Ca40, Ca48, and Pb208 doubly closed shell
nuclei, have been calculated in the framework of the Correlated Basis Function
theory, by using the Fermi hypernetted chain resummation techniques. The
calculations have been done by using the realistic Argonne v8' nucleon-nucleon
potential, together with the Urbana IX three-body interaction. Operator
dependent correlations, which consider channels up to the tensor ones, have
been
used. We found noticeable effects produced by the correlations. For high
momentum values, the momentum distributions show large enhancements with
respect to the independent particle model results. Natural orbits occupation
numbers are depleted by about the 10\% with respect to the independent particle
model values. The effects of the correlations on the spectroscopic factors are
larger on the more deeply bound states.Comment: Modified version of the previous paper (there are new figures). The
paper has been accepted for publication in Physical Review
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