Modern Physics Letters A

The Antarctic Muon And Neutrino Detector Array (AMANDA) has been taking data since 2000 and its data acquisition system was upgraded in January 2003 to read out the complete digitized waveforms from the buried Photomultipliers (PMTs) using Transient Waveform Recorders (TWR). This system currently runs in parallel with the standard AMANDA data acquisition system. Once AMANDA is incorporated into the 1 km³ detector IceCube, only the TWR system will be kept. We report results from a first atmospheric neutrino analysis on data collected in 2003 with TWR. Good agreement in event rate and angular distribution verify the performance of the TWR system. A search of the northern hemisphere for localized event clusters shows no statistically significant excess, thus a flux limit is calculated, which is in full agreement with previous results based on the standard AMANDA data acquisition system. We also update the status of a search for diffusely distributed neutrinos with ultra high energy (UHE) using data collected by the TWR system.

Over these past few years several quantum-gravity research groups have been exploring the possibility that in some Planck-scale nonclassical descriptions of spacetime one or another form of nonclassical spacetime symmetries might arise. One of the most studied scenarios is based on the use of Hopf algebras, but previous attempts were not successful in deriving constructively the properties of the conserved charges one would like to obtain from the Hopf structure, and this in turn did not allow a crisp physical characterization of the new concept of spacetime symmetry. Working within the example of κ-Minkowski noncommutative spacetime, known to be particularly troublesome from this perspective, we observe that these past failures in the search of the charges originated from not recognizing the crucial role that the noncommutative transformation parameters play in the symmetry analysis. We show that, if indeed one introduces appropriate noncommutative transformation parameters, all the steps of the Noether analysis can be easily performed, obtaining an explicit formula for the charges carried by fields that are solutions of the equation of motion.

Approximate relations among transverse momentum dependent quark distribution functions are established in the framework of the QCD parton model. The validity of such results survives QCD evolution effects, owing to the Politzer theorem on equations of motion. Furthermore the model fixes an energy scale, involved in the parametrization of the correlator, which determines the Q² dependence of the azimuthal asymmetries in inclusive reactions. Some of the present data — in particular the sin 2ϕ single spin asymmetry in semi-inclusive deep inelastic scattering (SIDIS) and the cos ϕ asymmetry in unpolarized SIDIS — support model predictions. Further measurements of SIDIS and Drell–Yan asymmetries are suggested, in particular the SIDIS double spin asymmetry, which allows to determine approximately the proton transversity.

We investigate an operator ordering problem in two-dimensional N = 1 supersymmetric model which consists of n real superfields. There arises an operator ordering problem when the target space is curved. We have to fix the ordering in quantum operator properly to obtain the correct supersymmetry algebra. We demonstrate that the super-Poincaré algebra fixes the correct operator ordering. We obtain a supercurrent with correct operator ordering and a central extension of supersymmetry algebra.

In this letter, we consider a model of the universe filled with modified Chaplygin gas and another fluid (with barotropic equation of state) and its role in accelerating phase of the universe. We have assumed that the mixture of these two fluid models is valid from (i) the radiation era to ΛCDM for -1 ≤ γ ≤ 1 and (ii) the radiation era to quintessence model for γ < -1. For these two fluid models, the statefinder parameters describe different phase of the evolution of the universe.

We investigate matter collineations of plane symmetric spacetimes when the energy–momentum tensor is degenerate. There exists three interesting cases where the group of matter collineations is finite-dimensional. The matter collineations in these cases are either four, six or ten in which four are isometries and the rest are proper.

In this paper, we first rewrite the Lagrangian density of the electromagnetic field corresponding to the source with electric and magnetic charges. Then, in the background of Reissner–Nordström black hole spacetime, we extend the Parikh–Wilczek tunneling framework and calculate the emission spectrum of the outgoing particles with electric and magnetic charges. For the sake of simplicity, we only consider the case that the rate of electric and magnetic charge of the emission particle is constant and equals that of the black hole. In this case, the emission spectrum deviates from the pure thermal spectrum, but it is consistent with an underlying unitary theory and takes the same functional form as that of the uncharged massless particles. Finally, a discussion about the result is presented.

After explicitly constructing the symmetric space sigma model Lagrangian in terms of the coset scalars of the solvable Lie algebra gauge in the current formalism, we derive the field equations of the theory.