Spin projection in the shell model Monte Carlo method and the spin distribution of nuclear level densities

We introduce spin projection methods in the shell model Monte Carlo approach and apply them to calculate the spin distribution of level densities for iron-region nuclei using the complete $(pf+g_{9/2})$-shell. We compare the calculated distributions with the spin-cutoff model and extract an energy-dependent moment of inertia. For even-even nuclei and at low excitation energies, we observe a significant suppression of the moment of inertia and odd-even staggering in the spin dependence of level densities.Comment: 4 pages, 4 figure

Ground state energy fluctuations in nuclear matter II

Improvements are performed on a recently proposed statistical theory of the mean field of a many-fermion system. The dependence of the predictions of the theory upon its two basic ingredients, namely the Hartree-Fock energy and the average energy of the two particle-two hole excitations, is explored.Comment: 16 pages, 1 figure, revte

Quantum Mechanics of Extended Objects

We propose a quantum mechanics of extended objects that accounts for the finite extent of a particle defined via its Compton wavelength. The Hilbert space representation theory of such a quantum mechanics is presented and this representation is used to demonstrate the quantization of spacetime. The quantum mechanics of extended objects is then applied to two paradigm examples, namely, the fuzzy (extended object) harmonic oscillator and the Yukawa potential. In the second example, we theoretically predict the phenomenological coupling constant of the $\omega$ meson, which mediates the short range and repulsive nucleon force, as well as the repulsive core radius.Comment: RevTex, 24 pages, 1 eps and 5 ps figures, format change

Spherical codes, maximal local packing density, and the golden ratio

The densest local packing (DLP) problem in d-dimensional Euclidean space Rd involves the placement of N nonoverlapping spheres of unit diameter near an additional fixed unit-diameter sphere such that the greatest distance from the center of the fixed sphere to the centers of any of the N surrounding spheres is minimized. Solutions to the DLP problem are relevant to the realizability of pair correlation functions for packings of nonoverlapping spheres and might prove useful in improving upon the best known upper bounds on the maximum packing fraction of sphere packings in dimensions greater than three. The optimal spherical code problem in Rd involves the placement of the centers of N nonoverlapping spheres of unit diameter onto the surface of a sphere of radius R such that R is minimized. It is proved that in any dimension, all solutions between unity and the golden ratio to the optimal spherical code problem for N spheres are also solutions to the corresponding DLP problem. It follows that for any packing of nonoverlapping spheres of unit diameter, a spherical region of radius less than or equal to the golden ratio centered on an arbitrary sphere center cannot enclose a number of sphere centers greater than one more than the number that can be placed on the region's surface.Comment: 12 pages, 1 figure. Accepted for publication in the Journal of Mathematical Physic

Level density of a Fermi gas: average growth and fluctuations

We compute the level density of a two--component Fermi gas as a function of the number of particles, angular momentum and excitation energy. The result includes smooth low--energy corrections to the leading Bethe term (connected to a generalization of the partition problem and Hardy--Ramanujan formula) plus oscillatory corrections that describe shell effects. When applied to nuclear level densities, the theory provides a unified formulation valid from low--lying states up to levels entering the continuum. The comparison with experimental data from neutron resonances gives excellent results.Comment: 4 pages, 1 figur

Exclusive K+K^+ production in proton-nucleus collisions

The exclusive $K^+$ meson production in a proton-nucleus collision, leading to two body final states, is investigated in a fully covariant two-nucleon model based on the effective Lagrangian picture. The explicit kaon production vertex is described via creation, propagation and decay into relevant channel of $N^*$(1650), $N^*$(1710) and $N^*$(1720) intermediate baryonic states in the initial collision of the projectile nucleon with one of its target counterparts which is modeled by the one-pion exchange process. The calculated cross sections show strong sensitivity to the medium effects on pion propagator and to the final hypernuclear state excited in the reaction.Comment: Two new figures, version accepted for publication by Phys. Rev.

Effect of Dose on Serum Pharmacokinetics of Intravenous Ciprofloxacin with Identification and Characterization of Extravascular Compartments Using Noncompartmental and Compartmental Pharmacokinetic Models

The effect of dose on the pharmacokinetics of ciprofloxacin in serum and urine following single intravenous doses of 100, 150, and 200 mg was studied in nine healthy volunteers. Mean peak levels in serum were 1.4, 2.0, and 3.2 mg/liter for the 100-, 150-, and 200-mg doses, respectively. The data on concentrations in serum were best described by a three-compartment pharmacokinetic model. The terminal half-life (from noncompartmental analysis) averaged between 4.2 and 4.6 h. Average urinary recovery ranged between 45.8 and 48.1%. The average renal clearance of ciprofloxacin was 2.9- to 3.4-fold greater than the measured creatinine clearance. Total serum and renal clearances decreased with increasing dose; however, this was not statistically significant (P \u3e 0.05; repeated-measures analysis of variance). Ciprofloxacin was well tolerated by all subjects. In this dose range, ciprofloxacin pharmacokinetics are independent of dose

Unitarity constraint for threshold coherent pion photoproduction on the deuteron and chiral perturbation theory

The contribution of the two-step process gamma + d -> p + n -> pi0 + d to the imaginary part of the amplitude for coherent pion production on the deuteron is calculated exploiting unitarity constraints. The result shows that this absorptive process is not negligible and has to be considered in an extraction of the elementary neutron production amplitude from the gamma + d -> pi0 + d cross section at threshold. In addition, it is argued that a consistent calculation of gamma + d -> pi0 + d in baryon chiral perturbation theory beyond next-to-leading order requires the inclusion of this absorptive process.Comment: 11 pages revtex including 2 postscript figure

Scaling Analysis of Fluctuating Strength Function

We propose a new method to analyze fluctuations in the strength function phenomena in highly excited nuclei. Extending the method of multifractal analysis to the cases where the strength fluctuations do not obey power scaling laws, we introduce a new measure of fluctuation, called the local scaling dimension, which characterizes scaling behavior of the strength fluctuation as a function of energy bin width subdividing the strength function. We discuss properties of the new measure by applying it to a model system which simulates the doorway damping mechanism of giant resonances. It is found that the local scaling dimension characterizes well fluctuations and their energy scales of fine structures in the strength function associated with the damped collective motions.Comment: 22 pages with 9 figures; submitted to Phys. Rev.