Microscopic Enhancement of Heavy-Element Production

Realistic fusion barriers are calculated in a macroscopic-microscopic model for several soft-fusion heavy-ion reactions leading to heavy and superheavy elements. The results obtained in such a realistic picture are very different from those obtained in a purely macroscopic model. For reactions on 208:Pb targets, shell effects in the entrance channel result in fusion-barrier energies at the touching point that are only a few MeV higher than the ground state for compound systems near Z = 110. The entrance-channel fragment-shell effects remain far inside the touching point, almost to configurations only slightly more elongated than the ground-state configuration, where the fusion barrier has risen to about 10 MeV above the ground-state energy. Calculated single-particle level diagrams show that few level crossings occur until the peak in the fusion barrier very close to the ground-state shape is reached, which indicates that dissipation is negligible until very late in the fusion process. Whereas the fission valley in a macroscopic picture is several tens of MeV lower in energy than is the fusion valley, we find in the macroscopic-microscopic picture that the fission valley is only about 5 MeV lower than the fusion valley for soft-fusion reactions leading to compound systems near Z = 110. These results show that no significant ``extra-extra-push'' energy is needed to bring the system inside the fission saddle point and that the typical reaction energies for maximum cross section in heavy-element synthesis correspond to only a few MeV above the maximum in the fusion barrier.Comment: 7 pages. LaTeX. Submitted to Zeitschrift fur Physik A. 5 figures not included here. Complete preprint, including device-independent (dvi), PostScript, and LaTeX versions of the text, plus PostScript files of the figures, available at http://t2.lanl.gov/publications/publications.html or at ftp://t2.lanl.gov/pub/publications/mehe

Vocalization Influences Auditory Processing in Collicular Neurons of the CF-FM-Bat, Rhinolophus ferrumequinum

1. In awake Greater Horseshoe bats (Rhinolophus ferrumequinum) the responses of 64 inferior colliculus neurons to electrically elicited vocalizations (VOC) and combinations of these with simulated echoes (AS: pure tones and AS(FM): sinusoidally frequency-modulated tones mimicking echoes from wing beating insects) were recorded. 2. The neurons responding to the species-specific echolocation sound elicited by electrical stimulation of the central grey matter had best frequencies between 76 and 86 kHz. The response patterns to the invariable echolocation sound varied from unit to unit (Fig. 1). 3. In 26 neurons the responses to vocalized echolocation sounds markedly differed from those to identical artificial ones copying the CF-portion of the vocalized sound (AS). These neurons reacted with a different response to the same pure tone whether it was presented artificially or vocalized by the bat (Fig. 2). In these neurons vocalization activities qualitatively alter the responsiveness to the stimulus parameters of the echoes. 4. A few neurons neither responded to vocalization nor to an identical pure tone but discharged when vocalization and pure tone were presented simultaneously. 5. In 2 neurons synchronized encoding of small frequency-modulations of the pure tone (mimicking an echo returning from a wing beating prey) occurred only during vocalization. Without vocalization the neurons did not respond to the identical stimulus set (Fig. 3). In these neurons vocalization activities enhanced FM-encoding capabilities otherwise not present in these neurons. 6. FM-encoding depended on the timing between vocalization and frequency-modulated signal (echo). As soon as vocalization and FM-signal no more overlapped or at least 60–80 ms after onset of vocalization synchronized firing to the FM was lost (4 neurons) (Fig. 4). 7. 4 neurons weakly responded to playbacks of the bat's own vocalization 1 ms after onset of vocalization. But when the playback frequency was shifted to higher frequencies by more than 400 Hz the neurons changed firing patterns and the latency of the first response peak (Fig. 5). These neurons sensitive to frequency shifts in the echoes returning during vocalization may be relevant to the Doppler-shift compensation mechanism in Greater Horseshoe bats

Kleene algebra with domain

We propose Kleene algebra with domain (KAD), an extension of Kleene algebra with two equational axioms for a domain and a codomain operation, respectively. KAD considerably augments the expressiveness of Kleene algebra, in particular for the specification and analysis of state transition systems. We develop the basic calculus, discuss some related theories and present the most important models of KAD. We demonstrate applicability by two examples: First, an algebraic reconstruction of Noethericity and well-foundedness; second, an algebraic reconstruction of propositional Hoare logic.Comment: 40 page

Magnetic multipole analysis of kagome and artificial ice dipolar arrays

We analyse an array of linearly extended monodomain dipoles forming square and kagome lattices. We find that its phase diagram contains two (distinct) finite-entropy kagome ice regimes - one disordered, one algebraic - as well as a low-temperature ordered phase. In the limit of the islands almost touching, we find a staircase of corresponding entropy plateaux, which is analytically captured by a theory based on magnetic charges. For the case of a modified square ice array, we show that the charges ('monopoles') are excitations experiencing two distinct Coulomb interactions: a magnetic 'three-dimensional' one as well as a logarithmic `two dimensional' one of entropic origin.Comment: 4 pages, 2 figures; v2: minor changes as in final published versio

On tree-decompositions of one-ended graphs

A graph is one-ended if it contains a ray (a one way infinite path) and whenever we remove a finite number of vertices from the graph then what remains has only one component which contains rays. A vertex $v$ {\em dominates} a ray in the end if there are infinitely many paths connecting $v$ to the ray such that any two of these paths have only the vertex $v$ in common. We prove that if a one-ended graph contains no ray which is dominated by a vertex and no infinite family of pairwise disjoint rays, then it has a tree-decomposition such that the decomposition tree is one-ended and the tree-decomposition is invariant under the group of automorphisms. This can be applied to prove a conjecture of Halin from 2000 that the automorphism group of such a graph cannot be countably infinite and solves a recent problem of Boutin and Imrich. Furthermore, it implies that every transitive one-ended graph contains an infinite family of pairwise disjoint rays

Paired composite fermion wavefunctions

We construct a family of BCS paired composite fermion wavefunctions that generalize, but remain in the same topological phase as, the Moore-Read Pfaffian state for the half-filled Landau level. It is shown that for a wide range of experimentally relevant inter-electron interactions the groundstate can be very accurately represented in this form.Comment: 4 pages, 2 figure