8,959 research outputs found
Correlations and realistic interactions in doubly closed shell nuclei
We review the latest variational calculations of the ground state properties
of doubly closed shell nuclei, from C to Pb, with semirealistic
and realistic two- and three-nucleon interactions. The studies are carried on
within the framework of the correlated basis function theory and integral
equations technique, with state dependent correlations having central and
tensor components. We report results for the ground state energy, one- and
two-body densities and static structure functions. For O and Ca
we use modern interactions and find that the accuracy of the method is
comparable to that attained in nuclear matter with similar hamiltonians, giving
nuclei underbound by 2 MeV/A. The computed Coulomb sums are in complete
agreement with the latest analysis of the experimental data.Comment: 11 Latex pages, 2 ps figures. Talk delivered at the 10th
International Conference on Recent Progress In Many-Body Theories, Seattle
1999. To appear in "Advances in Quantum Many-Body Theory", vol.3, World
Scientifi
FARC Terrorism in Colombia: A Clustering Analysis
This paper applies clustering analysis to the Colombian armed conflict. Indeed, when applied to a FARC terrorist act database, this statistical procedure finds a natural clustering of the diferent FARC units according to the diferent types of terrorist acts they commit and identities the military hard core of the FARC. The facts revealed in this paper should be useful not only for future military strategies, but also to determine a better priorization and geographical allocation of the scarce military resources.Clustering Analysis,
Military Expenditure and Economic Activity: The Colombian Case
We enhance a standard RBC model to account for military expenditure and the costs of an internal conflict or war. The model captures the natural trade-off in military expenditure: crowding out of private consumption and investment but less destruction (and, therefore, higher marginal productivity) of private capital (and labor). Hence, military expenditure below (above) a certain threshold generates a positive (negative) net benefit in terms of output. The model is calibrated to an annual frequency using Colombian data. We find that an increase in military expenditure of 1% GDP (the current policy of Colombian authorities) increases investment and output above the steady state during several periods, before the shock fades away. Even though consumption falls on impact (to open up space for the additional military expenditure and private investment), it increases above its stationary trend after three periods, remains on positive grounds thereafter, and the cumulated net gain is positive.Real business cycle, stationary state, military expenditure, crowding-out, productivity shock
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
New Results in the CBF theory for medium-heavy nuclei
Momentum distributions, spectroscopic factors and quasi-hole wave functions
of medium-heavy 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 microscopic two-body nucleon-nucleon potentials of Argonne type, together
with three-body interactions. Operator dependent correlations, up to the tensor
channels, have been used.Comment: 6 pages, 3 figures, proceeding of the "XI Convegno su problemi di
Fisica Nucleare Teorica" 11-14 Ottobre 2006, Cortona, Ital
Thermal Radiation from a Fluctuating Event Horizon
We consider a pointlike two-level system undergoing uniformly accelerated
motion. We evaluate the transition probability for a finite time interval of
this system coupled to a massless scalar field near a fluctuating event
horizon. Horizon fluctuations are modeled using a random noise which generates
light-cone fluctuations. We study the case of centered, stationary and Gaussian
random processes. The transition probability of the system is obtained from the
positive-frequency Wightman function calculated to one loop order in the noise
averaging process. Our results show that the fluctuating horizon modifies the
thermal radiation but leaves unchanged the temperature associated with the
acceleration.Comment: 8 pages, 3 figure
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
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