Nucleon propagation through nuclear matter in chiral effective field theory

We treat the propagation of nucleon in nuclear matter by evaluating the ensemble average of the two-point function of nucleon currents in the framework of the chiral effective field theory. We first derive the effective parameters of nucleon to one loop. The resulting formula for the effective mass was known previously and gives an absurd value at normal nuclear density. We then modify it following Weinberg's method for the two-nucleon system in the effective theory. Our results for the effective mass and the width of nucleon are compared with those in the literature.Comment: 11 pages including 4 figures. To appear in Eur. J. Phys.

Perturbative nonequilibrium dynamics of phase transitions in an expanding universe

A complete set of Feynman rules is derived, which permits a perturbative description of the nonequilibrium dynamics of a symmetry-breaking phase transition in $\lambda\phi^4$ theory in an expanding universe. In contrast to a naive expansion in powers of the coupling constant, this approximation scheme provides for (a) a description of the nonequilibrium state in terms of its own finite-width quasiparticle excitations, thus correctly incorporating dissipative effects in low-order calculations, and (b) the emergence from a symmetric initial state of a final state exhibiting the properties of spontaneous symmetry breaking, while maintaining the constraint $\equiv 0$. Earlier work on dissipative perturbation theory and spontaneous symmetry breaking in Minkowski spacetime is reviewed. The central problem addressed is the construction of a perturbative approximation scheme which treats the initial symmetric state in terms of the field $\phi$, while the state that emerges at later times is treated in terms of a field $\zeta$, linearly related to $\phi^2$. The connection between early and late times involves an infinite sequence of composite propagators. Explicit one-loop calculations are given of the gap equations that determine quasiparticle masses and of the equation of motion for $$ and the renormalization of these equations is described. The perturbation series needed to describe the symmetric and broken-symmetry states are not equivalent, and this leads to ambiguities intrinsic to any perturbative approach. These ambiguities are discussed in detail and a systematic procedure for matching the two approximations is described.Comment: 22 pages, using RevTeX. 6 figures. Submitted to Physical Review

Damping Rates and Mean Free Paths of Soft Fermion Collective Excitations in a Hot Fermion-Gauge-Scalar Theory

We study the transport coefficients, damping rates and mean free paths of soft fermion collective excitations in a hot fermion-gauge-scalar plasma with the goal of understanding the main physical mechanisms that determine transport of chirality in scenarios of non-local electroweak baryogenesis. The focus is on identifying the different transport coefficients for the different branches of soft collective excitations of the fermion spectrum. These branches correspond to collective excitations with opposite ratios of chirality to helicity and different dispersion relations. By combining results from the hard thermal loop (HTL) resummation program with a novel mechanism of fermion damping through heavy scalar decay, we obtain a robust description of the different damping rates and mean free paths for the soft collective excitations to leading order in HTL and lowest order in the Yukawa coupling. The space-time evolution of wave packets of collective excitations unambiguously reveals the respective mean free paths. We find that whereas both the gauge and scalar contribution to the damping rates are different for the different branches, the difference of mean free paths for both branches is mainly determined by the decay of the heavy scalar into a hard fermion and a soft collective excitation. We argue that these mechanisms are robust and are therefore relevant for non-local scenarios of baryogenesis either in the Standard Model or extensions thereof.Comment: REVTeX, 19 pages, 4 eps figures, published versio

Real-time Relaxation and Kinetics in Hot Scalar QED: Landau Damping

The real time evolution of field condensates with soft length scales k^{-1}>(eT)^{-1} is solved in hot scalar electrodynamics, with a view towards understanding relaxational phenomena in the QGP and the electroweak plasma. We find that transverse gauge invariant non-equilibrium expectation values of fields relax via {\em power laws} to asymptotic amplitudes that are determined by the quasiparticle poles. The long time relaxational dynamics and relevant time scales are determined by the behaviour of the retarded self-energy not at the small frequencies, but at the Landau damping thresholds. This explains the presence of power laws and not of exponential decay. Furthermore, we derive the influence functional, the Langevin equation and the fluctuation-dissipation theorem for the soft modes, identifying the correlation functions that emerge in the classical limit. We show that a Markovian approximation fails to describe the dynamics {\em both} at short and long times. We also introduce a novel kinetic approach that goes beyond the standard Boltzmann equation and incorporates off-shell processes and find that the distribution function for soft quasiparticles relaxes with a power law through Landau damping. We also find an unusual dressing dynamics of bare particles and anomalous (logarithmic) relaxation of hard quasiparticles.Comment: 41 pages, 5 figures, uses revtex, replaced with version to appear in Phys. Rev.

Nocturnal activity in wild chimpanzees (Pan troglodytes): evidence for flexible sleeping patterns and insights into human evolution

Objectives – We investigated occurrences and patterns of terrestrial nocturnal activity in wild chimpanzees (Pan troglodytes) and modelled the influence of various ecological predictors on nocturnal activity. Methods – Data were extracted from terrestrial camera-trap footage and ecological surveys from 22 chimpanzee study sites participating in the Pan African Programme: The Cultured Chimpanzee. We described videos demonstrating nocturnal activity, and we tested the effects of the percentage of forest, abundance of predators (lions, leopards and hyenas), abundance of large mammals (buffalos and elephants), average daily temperature, rainfall, human activity, and percent illumination on the probability of nocturnal activity. Results – We found terrestrial nocturnal activity to occur at 18 of the 22 study sites, at an overall average proportion of 1.80% of total chimpanzee activity, and to occur during all hours of the night, but more frequently during twilight hours. We found a higher probability of nocturnal activity with lower levels of human activity, higher average daily temperature, and at sites with a larger percentage of forest. We found no effect of the abundance of predators and large mammals, rainfall, or moon illumination. Discussion – Chimpanzee terrestrial nocturnal activity appears widespread yet infrequent, which suggests a consolidated sleeping pattern. Nocturnal activity may be driven by the stress of high daily temperatures and may be enabled at low levels of human activity. Human activity may exert a relatively greater influence on chimpanzee nocturnal behavior than predator presence. We suggest that chimpanzee nocturnal activity is flexible, enabling them to respond to changing environmental factors

Nocturnal activity in wild chimpanzees (Pan troglodytes): evidence for flexible sleeping patterns and insights into human evolution

Objectives – We investigated occurrences and patterns of terrestrial nocturnal activity in wild chimpanzees (Pan troglodytes) and modelled the influence of various ecological predictors on nocturnal activity. Methods – Data were extracted from terrestrial camera-trap footage and ecological surveys from 22 chimpanzee study sites participating in the Pan African Programme: The Cultured Chimpanzee. We described videos demonstrating nocturnal activity, and we tested the effects of the percentage of forest, abundance of predators (lions, leopards and hyenas), abundance of large mammals (buffalos and elephants), average daily temperature, rainfall, human activity, and percent illumination on the probability of nocturnal activity. Results – We found terrestrial nocturnal activity to occur at 18 of the 22 study sites, at an overall average proportion of 1.80% of total chimpanzee activity, and to occur during all hours of the night, but more frequently during twilight hours. We found a higher probability of nocturnal activity with lower levels of human activity, higher average daily temperature, and at sites with a larger percentage of forest. We found no effect of the abundance of predators and large mammals, rainfall, or moon illumination. Discussion – Chimpanzee terrestrial nocturnal activity appears widespread yet infrequent, which suggests a consolidated sleeping pattern. Nocturnal activity may be driven by the stress of high daily temperatures and may be enabled at low levels of human activity. Human activity may exert a relatively greater influence on chimpanzee nocturnal behavior than predator presence. We suggest that chimpanzee nocturnal activity is flexible, enabling them to respond to changing environmental factors

Erprobung von hoechstaufloesenden Satelliten- und Flugzeugdaten zur Untersuchung Subrosionserscheinungen und Destabilisierungsvorgaengen im Altbergbau. Teilprojekt: FE-Monitoring Schlussbericht

SIGLEAvailable from TIB Hannover: FO2B1506 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung und Forschung, Berlin (Germany); DLR Deutsches Zentrum fuer Luft- und Raumfahrt e.V., Bonn (Germany)DEGerman