Level Crossing Along Sphaleron Barriers

In the electroweak sector of the standard model topologically inequivalent vacua are separated by finite energy barriers, whose height is given by the sphale\-ron. For large values of the Higgs mass there exist several sphaleron solutions and the barriers are no longer symmetric. We construct paths of classical configurations from one vacuum to a neighbouring one and solve the fermion equations in the background field configurations along such paths, choosing the fermions of a doublet degenerate in mass. As in the case of light Higgs masses we observe the level crossing phenomenon also for large Higgs masses.Comment: 17 pages, latex, 10 figures in uuencoded postscript files. THU-94/0

PI4,5P2 regulates the polarized trafficking of integrins through EXO70 for directional cell migration

The polarized delivery of integrin adhesion molecules to the leading edge is required for cell migration and has been linked to cancer cell invasion, cancer aggressiveness, and poor patient outcome (1,2). Thus, regulators of integrin traffic may represent new molecular targets to inhibit tumor progression. However, identifying the regulatory networks that control integrin traffic has posed a big challenge, because, in contrast to the internalization of other cargoes, integrins take diverse routes, depending on their specific ligand, activation state, type of adhesion structure and cell type assayed

Analytical solution of the geodesic equation in Kerr-(anti) de Sitter space-times

The complete analytical solutions of the geodesic equations in Kerr-de Sitter and Kerr-anti-de Sitter space-times are presented. They are expressed in terms of Weierstrass elliptic p, zeta, and sigma functions as well as hyperelliptic Kleinian sigma functions restricted to the one-dimensional theta-divisor. We analyze the dependency of timelike geodesics on the parameters of the space-time metric and the test-particle and compare the results with the situation in Kerr space-time with vanishing cosmological constant. Furthermore, we systematically can find all last stable spherical and circular orbits and derive the expressions of the deflection angle of flyby orbits, the orbital frequencies of bound orbits, the periastron shift, and the Lense-Thirring effect.Comment: 18 pages, 11 figure

Multisphalerons in the Weinberg-Salam Theory

We construct multisphaleron solutions in the Weinberg-Salam theory. The multisphaleron solutions carry Chern-Simons charge $n/2$, where $n$ is an integer, counting the winding of the fields in the azimuthal angle. The well-known sphaleron has $n=1$. The multisphalerons possess axial symmetry and parity reflection symmetry. We vary the Higgs mass and the mixing angle. For small $n$ the energies of the multisphalerons are on the order of $n$ times the energy of the sphaleron and their magnetic dipole moments are on the order of $n$ times the magnetic dipole moment of the sphaleron.Comment: 18 pages, latex, 17 figures in uuencoded postscript files. THU-94/1

Structure factor and dynamics of the helix-coil transition

Thermodynamical properties of the helix-coil transition were successfully described in the past by the model of Lifson, Poland and Sheraga. Here we compute the corresponding structure factor and show that it possesses a universal scaling behavior near the transition point, even when the transition is of first order. Moreover, we introduce a dynamical version of this model, that we solve numerically. A Langevin equation is also proposed to describe the dynamics of the density of hydrogen bonds. Analytical solution of this equation shows dynamical scaling near the critical temperature and predicts a gelation phenomenon above the critical temperature. In the case when comparison of the two dynamical approaches is possible, the predictions of our phenomenological theory agree with the results of the Monte Carlo simulations.Comment: 11 pages, 7 figure

Rotating black holes with equal-magnitude angular momenta in d=5 Einstein-Gauss-Bonnet theory

We construct rotating black hole solutions in Einstein-Gauss-Bonnet theory in five spacetime dimensions. These black holes are asymptotically flat, and possess a regular horizon of spherical topology and two equal-magnitude angular momenta associated with two distinct planes of rotation. The action and global charges of the solutions are obtained by using the quasilocal formalism with boundary counterterms generalized for the case of Einstein-Gauss-Bonnet theory. We discuss the general properties of these black holes and study their dependence on the Gauss-Bonnet coupling constant $\alpha$. We argue that most of the properties of the configurations are not affected by the higher derivative terms. For fixed $\alpha$ the set of black hole solutions terminates at an extremal black hole with a regular horizon, where the Hawking temperature vanishes and the angular momenta attain their extremal values. The domain of existence of regular black hole solutions is studied. The near horizon geometry of the extremal solutions is determined by employing the entropy function formalism.Comment: 25 pages, 7 figure

The Sphaleron Barrier in the Presence of Fermions

We calculate the minimal energy path over the sphaleron barrier in the pre\-sen\-ce of fermions, assuming that the fermions of a doublet are degenerate in mass. This allows for spherically symmetric ans\"atze for the fields, when the mixing angle dependence is neglected. While light fermions have little influence on the barrier, the presence of heavy fermions ($M_F \sim$ TeV) strongly deforms the barrier, giving rise to additional sphalerons for very heavy fermions ($M_F \sim$ 10 TeV). Heavy fermions form non-topological solitons in the vacuum sector.Comment: 19 pages, latex, 18 figures in 3 seperate uuencoded postscript files THU-93/1

Generalized conductance sum rule in atomic break junctions

When an atomic-size break junction is mechanically stretched, the total conductance of the contact remains approximately constant over a wide range of elongations, although at the same time the transmissions of the individual channels (valence orbitals of the junction atom) undergo strong variations. We propose a microscopic explanation of this phenomenon, based on Coulomb correlation effects between electrons in valence orbitals of the junction atom. The resulting approximate conductance quantization is closely related to the Friedel sum rule.Comment: 4 pages, 1 figure, appears in Proceedings of the NATO Advanced Research Workshop ``Size dependent magnetic scattering'', Pecs, Hungary, May 28 - June 1, 200

A scalar field instability of rotating and charged black holes in (4+1)-dimensional Anti-de Sitter space-time

We study the stability of static as well as of rotating and charged black holes in (4+1)-dimensional Anti-de Sitter space-time which possess spherical horizon topology. We observe a non-linear instability related to the condensation of a charged, tachyonic scalar field and construct "hairy" black hole solutions of the full system of coupled Einstein, Maxwell and scalar field equations. We observe that the limiting solution for small horizon radius is either a hairy soliton solution or a singular solution that is not a regular extremal solution. Within the context of the gauge/gravity duality the condensation of the scalar field describes a holographic conductor/superconductor phase transition on the surface of a sphere.Comment: 16 pages including 8 figures, v2: discussion on soliton solutions extended; v3: matches version accepted for publication in JHE

Study of internal structures of 9,10Be and 10B in scattering of 4He from 9Be

A study of inelastic scattering and single-particle transfer reactions was performed by an alpha beam at 63 MeV on a 9$Be target. Angular distributions of the differential cross sections for the 9Be(4He,4He')9Be*, 9Be(4He,3He)10Be and 9Be(4He,t)10B reactions were measured. Experimental angular distributions of the differential cross sections for the ground state and a few low-lying states were analyzed in the framework of the optical model, coupled channels and distorted-wave Born approximation. An analysis of the obtained spectroscopic factors was performed.Comment: 16 pages, 7 figures, 3 tables, regular paper, mispritns are corrected in new versio