Correlations in Nuclear Masses

It was recently suggested that the error with respect to experimental data in nuclear mass calculations is due to the presence of chaotic motion. The theory was tested by analyzing the typical error size. A more sensitive quantity, the correlations of the mass error between neighboring nuclei, is studied here. The results provide further support to this physical interpretation.Comment: 4 pages, 2 figure

Further experiments with the Iowa air blast seed separator for the analysis of small-seeded grasses

In recent years attempts, have been made in Europe and North America to improve seed laboratory machines used for the separation of chaff from heavy seeds in grasses. The most important European contribution is probably the Gilchrist seed separator used at the seed testing station in Edinburgh, Scotland. The Holland (Leendertz) separator has some merit, but its chief weakness as shown by Porter (7) was the inconstant speed of the motor which made it. impossible to deliver the same volume of air through the separator tube each time the valve was opened to a given point. Replacement of the motor by one that operated at constant speed was found by Brown and Porter (1) to correct the defect reasonably well. The use of bolting cloth in place of a metal screen is also a disadvantage. Following the initial work Porter (8) described a new seed separator equipped with a combined motor\u27 and fan unit of standard specifications which made uniform separations of bluegrass, redtop and orchard grass samples either by repeated blowings of the same sub-sample or by a single blowing for each of many replicate sub-samples. He also employed synthetic samples to check the accuracy and uniformity of separation. These results were obtained with samples from the same lot and indicated that for any given lot of seed it was possible to obtain uniform results if care was used in reading the dial opening on the valve or the manometer which indicated pressure in the compression chamber. It is noteworthy that in his experiments Porter (8) showed that if the weight of sample varied from 112 to 2 grams of blue-\u27 grass seed, the dial reading was more dependable than pressure as measured in the compression chamber, and further that pressure as measured in the blowing tube was about as reliable as the dial reading. He showed, however, that with samples having a low weight per bushel the amount of germinable seed removed at a given opening was greater than with samples having a high weight per bushel

Semiclassical Theory of Bardeen-Cooper-Schrieffer Pairing-Gap Fluctuations

Superfluidity and superconductivity are genuine many-body manifestations of quantum coherence. For finite-size systems the associated pairing gap fluctuates as a function of size or shape. We provide a parameter free theoretical description of pairing fluctuations in mesoscopic systems characterized by order/chaos dynamics. The theory accurately describes experimental observations of nuclear superfluidity (regular system), predicts universal fluctuations of superconductivity in small chaotic metallic grains, and provides a global analysis in ultracold Fermi gases.Comment: 4 pages, 2 figure

Survival Probability of a Doorway State in regular and chaotic environments

We calculate survival probability of a special state which couples randomly to a regular or chaotic environment. The environment is modelled by a suitably chosen random matrix ensemble. The exact results exhibit non--perturbative features as revival of probability and non--ergodicity. The role of background complexity and of coupling complexity is discussed as well.Comment: 19 pages 5 Figure

Adiabatic Approximation for weakly open systems

We generalize the adiabatic approximation to the case of open quantum systems, in the joint limit of slow change and weak open system disturbances. We show that the approximation is ``physically reasonable'' as under wide conditions it leads to a completely positive evolution, if the original master equation can be written on a time-dependent Lindblad form. We demonstrate the approximation for a non-Abelian holonomic implementation of the Hadamard gate, disturbed by a decoherence process. We compare the resulting approximate evolution with numerical simulations of the exact equation.Comment: New material added, references added and updated, journal reference adde

Super-shell structure in harmonically trapped fermionic gases and its semi-classical interpretation

It was recently shown in self-consistent Hartree-Fock calculations that a harmonically trapped dilute gas of fermionic atoms with a repulsive two-body interaction exhibits a pronounced {\it super-shell} structure: the shell fillings due to the spherical harmonic trapping potential are modulated by a beat mode. This changes the ``magic numbers'' occurring between the beat nodes by half a period. The length and amplitude of the beating mode depends on the strength of the interaction. We give a qualitative interpretation of the beat structure in terms of a semiclassical trace formula that uniformly describes the symmetry breaking U(3) $\to$ SO(3) in a 3D harmonic oscillator potential perturbed by an anharmonic term $\propto r^4$ with arbitrary strength. We show that at low Fermi energies (or particle numbers), the beating gross-shell structure of this system is dominated solely by the two-fold degenerate circular and (diametrically) pendulating orbits.Comment: Final version of procedings for the 'Nilsson conference

Phase transitions towards frequency entrainment in large oscillator lattices

We investigate phase transitions towards frequency entrainment in large, locally coupled networks of limit cycle oscillators. Specifically, we simulate two-dimensional lattices of pulse-coupled oscillators with random natural frequencies, resembling pacemaker cells in the heart. As coupling increases, the system seems to undergo two phasetransitions in the thermodynamic limit. At the first, the largest cluster of frequency entrained oscillators becomes macroscopic. At the second, global entrainment settles. Between the two transitions, the system has features indicating self-organized criticality.Comment: 4 pages, 5 figures, submitted to PR

On the role of shake-off in single-photon double ionization

The role of shake-off for double ionization of atoms by a single photon with finite energy has become the subject of debate. In this letter, we attempt to clarify the meaning of shake-off at low photon energies by comparing different formulations appearing in the literature and by suggesting a working definition. Moreover, we elaborate on the foundation and justification of a mixed quantum-classical ansatz for the calculation of single-photon double ionization

Cohomological finiteness conditions for a class of metabelian groups

We consider a class of metabelian groups first studied by Baumslag and Stammbach and we show that these groups are consistent with the Bieri-Groves conjecture which relates cohomological finiteness conditions to the Bieri-Neumann-Strebel sigma invariant.Comment: 10 pages Accepted for publication in the Bulletin of the London Mathematical Societ