Role of the Coulomb interaction in the flow and the azimuthal distribution of kaons from heavy ion reactions

Coulomb final-state interaction of positive charged kaons in heavy ion reactions and its impact on the kaon transverse flow and the kaon azimuthal distribution are investigated within the framework of QMD (Quantum Molecular Dynamics) model. The Coulomb interaction is found to tend to draw the flow of kaons away from that of nucleons and lead to a more isotropic azimuthal distribution of kaons in the target rapidity region. The recent FOPI data have been analyzed by taking into accout both the Coulomb interaction and a kaon in-medium potential of the strong interaction. It is found that both the calculated kaon flows with only the Coulomb interaction and with both the Coulomb interaction and the strong potential agree within the error bars with the data. The kaon azimuthal distribution exhibits asymmetries of similar magnitude in both theoretical approaches. This means, the inclusion of the Coulomb potential makes it more difficult to extract information of the kaon mean field potential in nuclear matter from the kaon flow and azimuthal distribution data.Comment: 14 pages Latex, 4 PS-file

Liouville integrability of a class of integrable spin Calogero-Moser systems and exponents of simple Lie algebras

In previous work, we introduced a class of integrable spin Calogero-Moser systems associated with the classical dynamical r-matrices with spectral parameter, as classified by Etingof and Varchenko for simple Lie algebras. Here the main purpose is to establish the Liouville integrability of these systems by a uniform method

QCD Loop Corrections to Top Production and Decay at e^+ e^- Colliders

We present a computation of QCD next-to-leading order virtual corrections to the top production and decay process at linear colliders. The top quarks are allowed to be off-shell and the production and decay subprocesses are treated together, thus allowing for interference effects. The framework employed for our computation is the double pole approximation (DPA). We describe the implementation of this approximation for the top production and decay process and compare it with the implementation of DPA for the evaluation of QED corrections to the W pair production at LEP II. Similarities and differences between the two cases are pointed out. One result of interest is the incomplete cancelation of interference corrections. Other results include values for the total NLO top production cross section, and the impact the nonfactorizable (interference) corrections have on the top invariant mass distribution.Comment: 27 pages, 8 ps figures; reference added to introductio

Scaling of Aharonov-Bohm couplings and the dynamical vacuum in gauge theories

Recent results on the vacuum polarization induced by a thin string of magnetic flux lead us to suggest an analogue of the Copenhagen `flux spaghetti' QCD vacuum as a possible mechanism for avoiding the divergence of perturbative QED, thus permitting consistent completion of the full, nonperturbative theory. The mechanism appears to operate for spinor, but not scalar, QED.Comment: 11 pages, ITP-SB-92-40, (major conceptual evolution from original

Non-existence of stationary two-black-hole configurations: The degenerate case

In a preceding paper we examined the question whether the spin-spin repulsion and the gravitational attraction of two aligned sub-extremal black holes can balance each other. Based on the solution of a boundary value problem for two separate (Killing-) horizons and a novel black hole criterion we were able to prove the non-existence of the equilibrium configuration in question. In this paper we extend the non-existence proof to extremal black holes.Comment: 18 pages, 2 figure

Charge-conjugation violating neutrino interactions in supernovae

The well known charge conjugation violating interactions in the Standard Model increase neutrino- and decrease anti-neutrino- nucleon cross sections. This impacts neutrino transport in core collapse supernovae through "recoil" corrections of order the neutrino energy $k$ over the nucleon mass $M$. All $k/M$ corrections to neutrino transport deep inside a protoneutron star are calculated from angular integrals of the Boltzmann equation. We find these corrections significantly modify neutrino currents at high temperatures. This produces a large mu and tau number for the protoneutron star and can change the ratio of neutrons to protons. In addition, the relative size of neutrino mean free paths changes. At high temperatures, the electron anti-neutrino mean free path becomes {\it longer} than that for mu or tau neutrinos.Comment: 14 pages, 2 included ps figures, subm. to Phys. Rev.

Localized Random Lasing Modes and a New Path for Observing Localization

We demonstrate that a knowledge of the density-of-states and the eigenstates of a random system without gain, in conjunction with the frequency profile of the gain, can accurately predict the mode that will lase first. Its critical pumping rate can be also obtained. It is found that the shape of the wavefunction of the random system remains unchanged as gain is introduced. These results were obtained by the time-independent transfer matrix method and finite-difference-time-domain (FDTD) methods. They can be also analytically understood by generalizing the semi-classical Lamb theory of lasing in random systems. These findings provide a new path for observing the localization of light, such as looking for mobility edge and studying the localized states. %inside the random systems..Comment: Sent to PRL. 3 figure

ac Josephson effect in the resonant tunneling through mesoscopic superconducting junctions

We investigate ac Josephson effect in the resonant tunneling through mesoscopic superconducting junctions. In the presence of microwave irradiation, we show that the trajectory of multiple Andreev reflections can be closed by emitting or absorbing photons. Consequently, photon-assisted Andreev states are formed and play the role of carrying supercurrent. On the Shapiro steps, dc component appears when the resonant level is near a series of positions with spacing of half of the microwave frequency. Analytical result is derived in the limit of infinite superconducting gap, based on which new features of ac Josephson effect are revealed.Comment: 11 pages, 3 figure

Solution of the Fan Diagram Equation in 2+1 Dimensional QCD

We investigate the Balitsky-Kovchegov (BK) equation for D=3 space-time dimensions, corresponding to one transverse coordinate, and we show that it can be solved analytically. The explicit solutions are found in the linear approximation and for the paricular cases when they do not depend on the impact parameter of the dipole or on its rapidity. It is shown, that in a general case different solutions are related by an infinite parameter group of transformations. The key observation is that the equation has the Kowalewskaya-Painlev\'{e} property, which gives the possibility of reducing the non-linear problem to the solution of a linear integral equation.Comment: 23 page

Exotic smooth structures on 4-manifolds with zero signature

For every integer $k\geq 2$, we construct infinite families of mutually nondiffeomorphic irreducible smooth structures on the topological $4$-manifolds $(2k-1)(S^2\times S^2)$ and (2k-1)(\CP#\CPb), the connected sums of $2k-1$ copies of $S^2\times S^2$ and \CP#\CPb.Comment: 6 page