April 2004 arXiv papers — page 3

Juan Marcos Cerviño

We present a deterministic and explicit algorithm to compute the endomorphism rings of supersingular elliptic curves. As an example we compute the endomorphism rings of all supersingular elliptic curves defined over characteristic p=29,...,97.

Barry Simon, Vilmos Totik

We prove that there is a universal measure on the unit circle such that any probability measure on the unit disk is the limit distribution of some subsequence of the corresponding orthogonal polynomials. This follows from an extension of a result of Alfaro and Vigil (which answered a question of Turán): namely, for $n<N$, one can freely prescribe the $n$-th

Evgeny Shchepin

It is proved that for every fractal continuous mapping F: I\to I^2 of the unit interval onto the unit square there is a pair of points x,y\in I, such that |F(x)-F(y)|^2\ge 5|x-y|.

Jaume Llibre, Nicolae Vulpe

We classify all cubic systems possessing the maximum number of invariant straight lines (real or complex) taking into account their multiplicities. We prove that there are exactly 23 topological different classes of such systems. For every class we provide the configuration of its invariant straight lines in the Poincare disc. Moreover, every class is charac

Vladimir Lin

E. Artin described all irreducible representations of the braid group B_k to the symmetric group S(k). We strengthen some of his results and, moreover, exhibit a complete picture of homomorphisms of B_k to S(n) for n<2k+1. We show that the image of such ahomomorphism f is cyclic whenever either (*) n<k\ne 4 or (**) f is irreducible and 6<k<n<2k. For k>6 ther

R. Gonzalo, J. A. Jaramillo

We introduce UDSp-property (resp. UDTq-property) in Banach lattices as the property that every normalized disjoint sequence has a subsequence with an upper p-estimate (resp. lower q-estimate). In the case of rearrangement invariant spaces, the relationships with Boyd indices of the space are studied. Some applications of these properties are given to the hig

S. Buyalo, V. Schroeder

We introduce a new quasi-isometry invariant of metric spaces called the hyperbolic dimension, hypdim, which is a version of the Gromov&#39;s asymptotic dimension, asdim. The hyperbolic dimension is at most the asymptotic dimension, however, unlike the asymptotic dimension, the hyperbolic dimension of any Euclidean space R^n is zero (while asdim R^n=n.) This

Aleksandar Ivić

Mean square estimates for $Z_2(s) = \int_1^\infty |ζ(1/2+ix)|^4x^{-s}dx (\Re s > 1)$ are discussed, and some related Mellin transforms of quantities connected with the fourth power moment of $|ζ(1/2+ix)|^4$.

T. Kopf, R. Otahalova

A general simplicity problem in category theory is proposed. A particular example, the simplest choice of generators of an algebra is specified and illustrated by an example.

Vladimir Lin

We study holomorphic self-maps of non-ordered n-point configuration spaces C^n(X), where X is either affine or projective complex line. The complex Lie group Aut(X) acts diagonally on C^n(X). We prove that for n>4 every endomorphism F of C^n(X) either is tame meaning that it is of the form F(Q)=T(Q)Q for a certain morphism T of C^n(X) to Aut(X) or carries th

Jiang Dong Hua

In 1983, C. McGibbon and J. Neisendorfer have given a proof for one conjecture in J.-P. Serre&#39;s famous paper (1953). In 1985, another proof was given by J. Lannes and L. Schwartz. Since then, one considers a more general conjecture: if the reduced mod 2 cohomology of any 1-connected polyGEM is of finite type and is not trivial, then it contains at least

Fabrizio Catanese

We give infinite series of groups Gamma and of compact complex surfaces of general type S with fundamental group Gamma such that 1) Any surface S&#39; with the same Euler number as S, and fundamental group Gamma, is diffeomorphic to S. 2) The moduli space of S consists of exactly two connected components, exchanged by complex conjugation. Whence, i) On the o

Natalia Saulina, Cumrun Vafa

We define the notion of A-model Lagrangian D-branes as introducing defects in the Calabi-Yau crystal. The crystal melting in the presence of these defects reproduces all genus string amplitudes as well as leads to additional non-perturbative terms.

Keith Copsey

I solve for the behavior of scalars in Lorentzian AdS with time dependent boundary conditions, focusing in particular on the dilaton. This corresponds, via the AdS-CFT correspondence, to considering a gauge theory with a time dependent coupling. Changes which keep the gauge coupling nonzero result in finite but physically interesting states in the bulk, incl

Anton Kapustin, Arvind Murugan

We study the fatgraph expansion for the Complex Matrix Quantum Mechanics (CMQM) with a Chern-Simons coupling. In the double-scaling limit this model is believed to describe Type 0A superstrings in 1+1 dimensions in a Ramond-Ramond electric field. With Euclidean time compactified, we show that the RR electric field acts as a chemical potential for vortices li

Tarek Ibrahim, Pran Nath, Anastasios Psinas

We extend previous analyses of the supersymmetric loop correction to the charged Higgs couplings to include the coupling $H^{\pm}χ^{\mp}χ^0$. The analysis completes the previous analyses where similar corrections were computed for $H^+\bar t b$ ($H^-t\bar b$), and for $H^+τ^- \barν_τ$ ($H^- τ^+ ν_τ$) couplings within the minimal supersymmetric standard model

R. N. Mohapatra, Siew-Phang Ng, Haibo Yu

We present calculations of the magnetic moment contribution to neutrino electron scattering in large extra dimension brane-bulk models (LED) with three bulk neutrinos. We discuss the cases with two and three large extra dimensions of sizes $R$. The calculations are done using reactor flux from Uranium, $^{235}U$ as the neutrino source. We find that if the el

Richard F. Lebed, Daniel R. Martin

Using a recent calculation of transition magnetic moments in the 1/N_c expansion and a calculation showing the suppression of E2/M1 by powers of N_c, we compute the widths for the radiative decays Sigma^* --> Sigma gamma, Sigma^* --> Lambda gamma, and Xi^* --> Xi gamma.

Graciela Gelmini, Gabriele Varieschi, Thomas Weiler

Neutrinos from far-away sources annihilating at the Z resonance on relic neutrinos may give origin to the extreme-energy cosmic rays (EECR). If ``Z-bursts&#39;&#39; are responsible for the EECR events, then we show that the non-observation of cosmic ray events at energies above 2 x 10^20 eV by the AGASA Collaboration implies a lower bound around 0.3 eV on th

Eberhard Klempt

Hadron spectroscopy has received revitalised interest due to the discovery of states with unexpected properties. Discussed are the recent findings at BABAR, CLEO, BELLE and BES. A detailed report is given on the many experiments reporting evidence (or counter--evidence) for the $Θ^+(1540)$ and other pentaquarks. In conventional meson and in baryon spectrosco

Kari Enqvist, Asko Jokinen, Anupam Mazumdar

We demonstrate that the MSSM flat directions can naturally account for the seed magnetic fields in the early Universe. The non-zero vacuum expectation value of an MSSM flat direction condensate provides masses to the gauge fields and thereby breaks conformal invariance. During inflation the condensate receives spatial perturbations and $SU(2) x U(1)_Y$ gauge

Stefan Antusch, Patrick Huber, Joern Kersten, Thomas Schwetz

We discuss the potential of long-baseline neutrino oscillation experiments to determine deviations from maximal ν_μ-ν_τmixing. We compare the obtainable sensitivities to predictions from neutrino mass models and to the size of quantum corrections. We find that the theoretical expectations for deviations are typically well within experimental reach.

B. I. Ermolaev, M. Greco, S. I. Troyan

Accounting for double-logarithms of x and running QCD coupling leads to expressions for both the non-singlet and singlet components of $g_1$. These expressions manifest the Regge asymptotics when x ->0 and differ considerably from the DGLAP expressions at small values of x.

G. Lazarides, C. Pallis

We review the construction of a concrete supersymmetric grand unified model, which naturally leads to a moderate violation of &#34;asymptotic&#34; Yukawa unification and, thus, can allow an acceptable b-quark mass within the constrained minimal supersymmetric standard model with mu>0. The model possesses a wide and natural range of parameters which is consis

G. C. Rossi, G. Veneziano

Interpreting the recently discovered narrow exotic baryons as pentaquark states, we discuss, along an old argument of ours, the isospin mixing occurring within the two doublets of $Q = -1$ and Q=0 states lying inside the $S=-2$ ($Ξ$-cascade) sector. We argue that, at least within the Jaffe-Wilczek assignment, presently available data already indicate that mi

P. Zenczykowski

Paper withdrawn by the author after learning that its main conclusion was given earlier in a slightly different language in Appendix D of A. J. Buras, R. Fleischer, S. Recksiegel, and F.Schwab, hep-ph/0402112.

George Tamminga Fleming

Domain wall fermions are a new lattice fermion formulation which preserves the full chiral symmetry of the continuum at finite lattice spacing, up to terms exponentially small in an extra parameter. We discuss the main features of the formulation and its application to study of QCD with two light fermions of equal mass. We also present numerical studies of t

John P. Costella

The intrinsically nonlinear nature of quantum field theory provides a fundamental complication for lattice calculations, when the physical implications of the subtleties of Fourier theory are taken into account. Even though the fundamental fields are constrained to the first Brillouin zone, Fourier theory tells us that the high-momentum components of product

Marta Felcini

The aim of this CP symmetry test in positronium is to measure the CP violation amplitude parameter \ccp. This is derived from the measurement of the asymmetry in an angular distribution of the photons from the decay of the ortho-positronium in a magnetic field. The Standard Model prediction for \ccp\ is a value of the order of $10^{-9}$. Thus the observation

D0 Collaboration

We examine properties of ttbar candidates events in lepton+jets final states to establish the helicities of the W bosons in t->W+b decays. Our analysis is based on a direct calculation of a probability that each event corresponds to a ttbar final state, as a function of the helicity of the W boson. We use the 125 events/pb sample of data collected by the DO

I. Abt, M. Altmann, A. Bakalyarov, I. Barabanov

This Letter of Intent has been submitted to the Scientific Committee of the INFN Laboratori Nazionali del Gran Sasso (LNGS) in March 2004. It describes a novel facility at the LNGS to study the double beta decay of 76Ge using an (optionally active) cryogenic fluid shield. The setup will allow to scrutinize with high significance on a short time scale the cur

J W C McNabb, M Ashley, L S Finn, E Rotthoff

In the search for unmodeled gravitational wave bursts, there are a variety of methods that have been proposed to generate candidate events from time series data. Block Normal is a method of identifying candidate events by searching for places in the data stream where the characteristic statistics of the data change. These change-points divide the data into b

Luca Lusanna

Since the main open problem of contemporary physics is to find a unified description of the four interactions, we present a possible scenario which, till now only at the classical level, is able to englobe experiments ranging from experimental space gravitation to atomic and particle physics. After a reformulation of special relativistic physics in a form ta

D. Alba, L. Lusanna

After a review of the 1+3 point of view on non-inertial observers and of the problems of rotating reference frames, we underline that was is lacking in their treatment is a good global notion of simultaneity due to the restricted validity of the existing 4-coordinates associated to an accelerated observer (like the Fermi normal ones). We show that the relati

Emmanuel I. Rashba

In Maxwellian electrodynamics, specific properties of the responses to external fields are included in constitutive equations. For noncentrosymmetric semiconductors, spin conductivity can be expressed in terms of the contribution of electric-dipole transitions between spin-split spectrum branches to the dielectric function. In a dissipationless regime, a spi

Niels Gronbech-Jensen, Matteo Cirillo

We investigate theoretically the thermal escape behavior of trapped magnetic fluxons in long annular Josephson junctions in dc magnetic fields, and perturbed by a probing ac current. The study is motivated by recently published experimental data that show multi-peaked escape distributions for increasing bias current in the extreme low temperature regime when

A. Ghatak, L. Mahadevan, J. Y. Chung, M. K. Chaudhury

Inspired by the observation that many naturally occurring adhesives arise as textured thin films, we consider the displacement controlled peeling of a flexible plate from an incision-patterned thin adhesive elastic layer. We find that crack initiation from an incision on the film occurs at a load much higher than that required to propagate it on a smooth adh

Alexey Nikulov

It is shown that one of consequences of basic principle of quantum mechanics at the mesoscopic level is violation of the second law of thermodynamics and that an experimental evidence of this violation was obtained long ago.

V. N. Glazkov, A. I. Smirnov, H. -A. Krug von Nidda, A. Loidl

The fraction of the paramagnetic phase surviving at the impurity-induced antiferromagnetic order transition of the doped spin-Peierls magnet Cu(1-x)Mg(x)GeO3 (x < 5%) is found to increase with an external magnetic field. This effect is qualitatively explained by the competition of Zeeman energy and exchange interaction between local antiferromagnetic cluster

R. J. Radwanski, Z. Ropka

We have developed the crystal-field approach with strong electron correlations, extended to the Quantum Atomistic Solid-State theory (QUASST), as a physically relevant theoretical model for the description of electronic and magnetic properties of 3d-atom compounds. Its applicability has been illustrated for LaCoO3, FeBr2 and Na2V3O7. According to the QUASST

Sylvain Capponi, Andreas Laeuchli, Matthieu Mambrini

We demonstrate the utility of the numerical Contractor Renormalization (CORE) method for quantum spin systems by studying one and two dimensional model cases. Our approach consists of two steps: (i) building an effective Hamiltonian with longer ranged interactions using the CORE algorithm and (ii) solving this new model numerically on finite clusters by exac

R. Hedden, V. Meden, Th. Pruschke, K. Schoenhammer

We apply the functional renormalization group method to the calculation of dynamical properties of zero-dimensional interacting quantum systems. As case studies we discuss the anharmonic oscillator and the single impurity Anderson model. We truncate the hierarchy of flow equations such that the results are at least correct up to second order perturbation the

Wolfgang Knospe, Ludger Santen, Andreas Schadschneider, Michael Schreckenberg

Based on a detailed microscopic test scenario motivated by recent empirical studies of single-vehicle data, several cellular automaton models for traffic flow are compared. We find three levels of agreement with the empirical data: 1) models that do not reproduce even qualitatively the most important empirical observations, 2) models that are on a macroscopi

Marcel Ausloos, Rudi Cloots, Nicolas Vandewalle

Peritectic growth of bulk superconducting cuprate perovskite, like YBa2Cu3O7-x has been studied. The microstructure features are recalled. The simplest model giving the best description of the microstructure complexity at the mesoscopic scale is an Eden model adapted to chemical reactions. A repulsive dynamical interaction between the front and the solid 211

R. P. S. M. Lobo, J. J. Tu, Eun-Mi Choi, Hyeong-Jin Kim

We studied the far-infrared reflectance of superconducting MgB2 in and out of equilibrium using pulsed synchrotron radiation. The equilibrium data can be described by a single energy gap at 2 Delta / hc = 43 cm-1. The fit improves slightly at lower frequencies when two gaps (at 30 cm-1 and 56 cm-1$) are assumed to exist. The non equilibrium data is obtained

G. Palagyi, S. Dietrich

Geometrical structures of confining surfaces profoundly influence the adsorption of fluids upon approaching a critical point T_c in their bulk phase diagram, i.e., for t=(T-T_c)/T_c -> +/-0. Guided by general scaling considerations, we calculate, within mean-field theory, the temperature dependence of the order parameter profile in a wedge with opening angle

F. Verstraete, D. Porras, J. I. Cirac

We introduce a picture to analyze the density matrix renormalization group (DMRG) numerical method from a quantum information perspective. This leads us to introduce some modifications for problems with periodic boundary conditions in which the results are dramatically improved. The picture also explains some features of the method in terms of entanglement a

Ch. Simon, A. Pautrat, G. Poulain, C. Goupil

The influence of Twin Boundaries (TB) on the Flux Line Lattice(FLL) structure was investigated by Small Angle Neutron Scattering (SANS). YBaCuO single crystals possessing different TB densities were studied. The SANS experiments show that the TB strongly modify the structure of the FLL. The flux lines meander as soon as the magnetic field makes an angle with

H. Saarikoski, A. Harju, M. J. Puska, R. M. Nieminen

We study electronic structures of two-dimensional quantum dots in high magnetic fields using the density-functional theory (DFT) and the exact diagonalization (ED). With increasing magnetic field, beyond the formation of the totally spin-polarized maximum density droplet (MDD) state, the DFT gives the ground-state total angular momentum as a continuous funct

N. B. Ivanov, J. Richter

Using exact numerical diagonalization and the conformal field theory approach, we study the effect of magnetic frustrations due to diagonal exchange bonds in a system of two coupled mixed-spin $(1,{1/2})$ Heisenberg chains. It is established that relatively moderate frustrations are able to destroy the ferrimagnetic state and to stabilize the critical spin-l

T. Schneider, H. Keller

Anisotropy, thermal and quantum fluctuations and their dependence on dopant concentration appear to be present in all cuprate superconductors, interwoven with the microscopic mechanisms responsible for superconductivity. Here we review anisotropy, in-plane and c-axis penetration depths, isotope effect and conductivity measurements to reassess the universal b

A. Giuliani, V. Mastropietro

The Ashkin-Teller (AT) model is a generalization of Ising 2-d to a four states spin model; it can be written in the form of two Ising layers (in general with different couplings) interacting via a four-spin interaction. It was conjectured long ago (by Kadanoff and Wegner, Wu and Lin, Baxter and others) that AT has in general two critical points, and that uni

S. Schwieger, W. Nolting

We study the influence of collective magnetic excitations on the interlayer exchange coupling (IEC) in metallic multilayers. The results are compared to other models that explain the temperature dependence of the IEC by mechanisms within the spacer or at the interfaces of the multilayers. As a main result we find that the reduction of the IEC with temperatur

Giovanni Gallavotti

Recently the ``Fluctuation theorem&#39;&#39; has been criticized and incorrect incorrect contents have been atributed to it. Here I reestablish and comment the original statements.

V. V. Khovailo, R. Kainuma, T. Abe, K. Oikawa

Ni57.5Mn17.5Ga25 shape memory alloy exhibits a complex transformation behavior, appearing after aging. Aging in the austenitic state resulted in an ordinary decrease of the martensitic transformation temperature. Contrary to this, aging in the martensitic state brought about unusual features of the martensitic transformation observed so far only in Ni-Ti all

M. N. Huda, A. K. Ray

We have studied the chemisorption processes of O2 on the (100) surface of uranium using generalized gradient approximation to density functional theory. Dissociative adsorptions of O2 are significantly favored compared to molecular adsorptions. We found interstitial adsorption of molecular oxygen to be less probable, as no bound states were found in this cas

Alexander N. Korotkov

We propose an experiment on quantum feedback control of a solid-state qubit, which is almost within the reach of the present-day technology. Similar to the earlier proposal, the feedback loop is used to maintain the coherent (Rabi) oscillations in a qubit for an arbitrary long time; however, this is done in a significantly simpler way, which requires much sm

Y. Luo, C. Verdozzi, N. Kioussis

Exact diagonalization calculations reveal that the energy spacing $Δ$ in the conduction band tunes the interplay between the {\it local} Kondo and {\it non local} RKKY interactions, giving rise to a &#34;Doniach phase diagram&#34; for a nanocluster with regions of prevailing Kondo or RKKY correlations. The parity of the total number of electrons alters the c

V. B. Shenoy, A. Ramasubramaniam, H. Ramanarayan, D. T. Tambe

We show that the decay of sinusoidal ripples on crystal surfaces, where mass transport is limited by the attachment and detachment of atoms at the step-edges, is remarkably different from the decay behavior that has been reported until now. Unlike the decreasing or at most constant rate of amplitude decay of sinusoidal profiles observed in earlier work, we f

Eduardo Fradkin, David A. Huse, R. Moessner, V. Oganesyan

Quantum dimer models on bipartite lattices exhibit Rokhsar-Kivelson (RK) points with exactly known critical ground states and deconfined spinons. We examine generic, weak, perturbations around these points. In d=2+1 we find a first order transition between a ``plaquette&#39;&#39; valence bond crystal and a region with a devil&#39;s staircase of commensurate

Maciej M. Duras

The random matrix ensembles (RME) of quantum statistical Hamiltonian operators, e.g. Gaussian random matrix ensembles (GRME) and Ginibre random matrix ensembles (Ginibre RME), are applied to following quantum statistical systems: nuclear systems, molecular systems, and two-dimensional electron systems (Wigner-Dyson electrostatic analogy). Measures of quantum

R G Mani, J H Smet, K von Klitzing, V Narayanamurti

Oscillations of the resistance observed under electromagnetic wave excitation in the high mobility GaAs/AlGaAs 2DES are examined as a function of the radiation frequency and the power, utilizing an empirical lineshape based on exponentially damped sinusoids. The fit-analysis indicates the resistance oscillation frequency, F, increases with the radiation freq

Zohar Nussinov

We examine n component spin systems with arbitrary two spin interactions (of unspecified range) within a general framework to highlight some new subtleties present in incommensurate systems. We determine the ground states of all translationally invariant O(n>1) systems and prove that barring commensurability effects they are always spiral- no other ground st

E. Verner, F. Bruhweiler, D. Verner, S. Johansson

The enrichment of Fe, relative to alpha-elements such as O and Mg, represents a potential means to determine the age of quasars and probe the galaxy formation epoch. To explore how \ion{Fe}{2} emission in quasars is linked to physical conditions and abundance, we have constructed a 830-level \ion{Fe}{2} model atom and investigated through photoionization cal

Ricardo P. Schiavon, James A. Rose, Stephane Courteau, Lauren MacArthur

A major uncertainty in the spectroscopic dating of extragalactic globular clusters concerns the degenerate effect that age and horizontal branch morphology have on the strength of Balmer lines. In this Letter we show that the ratio between the equivalent widths of Hdelta and Hbeta is far more sensitive to horizontal branch morphology than to age, thus making

C. A. Terrero-Escalante

Conditions for accelerated expansion of Friedmann-Robertson-Walker space-time are analyzed. Connection of this scenario with present-day observations are reviewed. It is explained how a scalar field could be responsible for cosmic acceleration observed in present times and predicted for the very early Universe. Ideas aimed at answering whether is that the ac

Hannah Jang-Condell, Dimitar D. Sasselov

We revisit the computation of a &#34;snow line&#34; in a passive protoplanetary disk during the stage of planetesimal formation. We examine how shadowing and illumination in the vicinity of a planet affects where in the disk ice can form, making use of our method for calculating radiative transfer on disk perturbations with some improvements on the model. We

C. M. Gutierrez, M. Azzaro

In this second paper dedicated to the study of satellite galaxies we present broad-band photometry in the B, V, R and I filters of 49 satellite galaxies orbiting giant isolated spiral galaxies. First analysis of the properties of these objects are presented by means of color--color and color--magnitude diagrams for early- and late-type satellites. Although w

Sergey Trudolyubov, William Priedhorsky

We present the results of the ongoing XMM-Newton survey of M31. 17 X-ray sources detected in the survey have bright radio counterparts, and 15 X-ray sources coincide with SNR candidates from optical and radio surveys. 15 out of 17 sources with radio counterparts, not SNR candidates, have spectral properties similar to that observed for background radio galax

Michael Endl, Artie P. Hatzes, William D. Cochran, Barbara McArthur

Since the beginning of precise Doppler surveys, which have had stunning success in detecting extrasolar planetary companions, one surprising enigma has emerged: the relative paucity of spectroscopic binaries where the secondary mass lies in between the stellar and planetary mass regime. This gap in the mass function for close-in (a < 3 - 4 AU) companions to

E. Middelberg

We have a project to measure magnetic fields in the obscuring tori of AGNs. We observed five free-free absorbed jets in radio galaxies with polarimetric VLBI at 15 GHz to determine Faraday rotation measures. Surprisingly, all sources are unpolarized, putting severe constraints on the degree of magnetic field turbulence and the gas distribution in these objec

L. Kuiper, W. Hermsen, M. Mendez

We report the discovery of non-thermal pulsed X-ray/soft gamma-ray emission up to about 150 keV from the anomalous X-ray pulsar AXP 1E 1841-045 located near the centre of supernova remnant Kes 73 using RXTE PCA and HEXTE data. The morphology of the double-peaked pulse profile changes rapidly with energy from 2 keV up to about 8 keV, above which the pulse sha

G. T. Birk, H. Lesch, C. Konz

The Earth is a planet with a dipolar magnetic field which is agitated by a magnetized plasma wind streaming from the Sun. The magnetic field shields the Earth&#39;s surface from penetrating high energy solar wind particles, as well as interstellar cosmic rays. The magnetic dipole has reversed sign some hundreds of times over the last 400 million years. These

Susan E. Thompson, J. C. Clemens, M. H. van Kerkwijk, M. Sean O&#39;Brien

The pulsating white dwarf star PY Vul (G~185-32) exhibits pulsation modes with peculiar properties that set it apart from other variable stars in the ZZ Ceti (DAV) class. These peculiarities include a low total pulsation amplitude, a mode with bizarre amplitudes in the ultraviolet, and a mode harmonic that exceeds the amplitude of its fundamental. Here, we p

H. Bouy, W. Brandner, E. L. Martin, X. Delfosse

We present imaging and spectroscopic observations with HST (WFPC2, ACS/HRC and STIS), VLT (FORS2) and Keck (HIRES) of the dM8 ultra-cool dwarf DENIS-P J185950.9-370632, located in the R-CrA region. The presence of lithium absorption at 670.8 nm and the strong Halpha emission indicate a young age and a sub-stellar mass. Our diffraction-limited images resolve

L. Coccato, E. Dalla Bonta&#39;, M. Sarzi, A. Pizzella

We present long-slit HST/STIS measurements of the ionized-gas kinematics in the nucleus of three disk galaxies, namely NGC 2179, NGC 4343, NGC 4435. The sample galaxies have been selected on the basis of their ground-based spectroscopy, for displaying a strong central velocity gradient for the ionized gas, which is consistent with the presence of a circum nu

D. Londish, J. Heidt, B. J. Boyle, S. M. Croom

High signal-to-noise spectroscopy has established a redshift of z=0.494 for the source 2QZJ215454.3-305654, originally selected from the 2dF/6dF QSO Redshift Surveys as one of 45 candidate BL Lac objects displaying a featureless continuum at optical wavelengths. Radio observations using the Australia Telescope Compact Array at 1.4 GHz place a 3σupper limit o

B. Cedres, M. A. Urbaneja, J. Cepa

We present the oxygen abundance determination for 90 HII regions in the inner parts of the grand design galaxy M101. The abundances were derived employing the P method (Pilyugin 2001a). A comparison is made with previous determinations using another calibration and direct measurements of electron temperature to derive the oxygen abundance. The results show a

T. Venturi, D. Dallacasa, F. Stefanachi

We present the results of VLBA observations of the radio galaxy 3C317, associated with the cD galaxy UGC 09799 at the centre of the cooling core cluster of galaxies A2052. These observations were carried out at 1.7 GHz, 4.9 GHz and 8.3 GHz, in polarimetric mode, and allowed us to image the parsec scale region of the source. Our analysis suggests that the nuc

Fredrick A. Jenet, Scott M. Ransom

The recent discovery of J0737-3039A & B-two pulsars in a highly relativistic orbit around one another - offers an unprecedented opportunity to study the elusive physics of pulsar radio emission. The system contains a rapidly rotating pulsar with a spin period of 22.7 ms and a slow companion with a spin period of 2.77 s, hereafter referred to as &#39;A&#39; a

H. C. Spruit, H. Steinle, G. Kanbach

Coordinated observations X-ray+optical observations of two southern X-ray binaries, the black hole candidate XTE J1746-321 and the neutron star accreter Cir X-1 (a `microquasar&#39;) are reported. With a photon counting optical photometer on the 1.9m telescope at Sutherland, South Africa and the PCA detector on RXTE, 4h each of simultaneous data were obtaine

Peter Rastall

In gravitostatics, the minimally generalized Newtonian theory, the simplest cosmological model implies a cosmological redshift with acceleration parameter -1. If the gravitational potential satisfies a wave equation, the total mass density (visible plus dark) is one third of the critical density, in good agreement with observation. There is no horizon proble

S. Hossenfelder

Large extra dimensions lower the Planck scale to values soon accessible. Motivated by string theory, the models of large extra dimensions predict a vast number of new effects in the energy range of the lowered Planck scale, among them the production of TeV-mass black holes. But not only is the Planck scale the energy scale at which effects of modified gravit

Gaston Giribet, Daniel Lopez-Fogliani

Free field representations of vertex algebra in SL(2,R)/U(1) x U(1) WZNW model are constructed by considering a twisted version of the Bershadsky-Kutasov free field description of discrete states in the two-dimensional black hole CFT. These correspond to conjugate representations describing primary states in the model on SL(2,R)/U(1) x U(1). A particular eva

S. Deser, J. Franklin, B. Tekin

Spherically symmetric solutions of generic gravitational models are optimally, and legitimately, obtained by expressing the action in terms of the two surviving metric components. This shortcut is not to be overdone, however: a one-function ansatz invalidates it, as illustrated by the incorrect solutions of [1].

Dirk Puetzfeld

We provide a brief chronological guide to the literature on non-Riemannian cosmological models. Developments in this field are traced back to the early seventies and are given in table form.

Bernd Reimann

Slice stretching effects such as slice sucking and slice wrapping arise when foliating the extended Schwarzschild spacetime with maximal slices. For arbitrary spatial coordinates these effects can be quantified in the context of boundary conditions where the lapse arises as a linear combination of odd and even lapse. Favorable boundary conditions are then de

Roni Harnik, Daniel T. Larson, Hitoshi Murayama, Marc Thormeier

We advocate the idea that proton decay may probe physics at the Planck scale instead of the GUT scale. This is possible because supersymmetric theories have dimension-5 operators that can induce proton decay at dangerous rates, even with R-parity conservation. These operators are expected to be suppressed by the same physics that explains the fermion masses

Anze Slosar, Uros Seljak

Many recent analyses have indicated that large scale WMAP data display anomalies that appear inconsistent with the standard cosmological paradigm. However, the effects of foreground contamination, which require elimination of some fraction of the data, have not been carefully investigated due to the complexity in the analysis. Here we develop a general forma

David Iglesias-Ponte, Aïssa Wade

We give simple characterizations of contact 1-forms in terms of Dirac structures. We also relate normal almost contact structures to the theory of Dirac structures.

C. Anastasiou, A. Lazopoulos

We present a program for the reduction of large systems of integrals to master integrals. The algorithm was first proposed by Laporta; in this paper, we implement it in MAPLE. We also develop two new features which keep the size of intermediate expressions relatively small throughout the calculation. The program requires modest input information from the use

T. Masuda, A. Zheludev, K. Uchinokura, J. -H. Chung

Follow-up neutron measurements, performed on a sample much larger than the one used in the original study, show that in the energy range 0.5-45 meV the magnetic excitations in BaCu2SiGeO7 are indistinguishable from those in conventional (disorder-free) quantum S=1/2 chains. Scrutinizing the previous data, we found that the analysis was affected by a poorly i

Aurel Bulgac, George F. Bertsch

We calculate the oscillation frequencies of trapped Fermi condensate with particular emphasis on the equation of state of the interacting Fermi system. We confirm Stringari&#39;s finding that the frequencies are independent of the interaction in the unitary limit, and we extend the theory away from that limit, where the interaction does affect the frequencie

Benjamin Grinstein, Dan Pirjol

We present a model-independent description of the exclusive rare decays B-> K* e+e- in the low recoil region (large lepton invariant mass q^2 ~ m_b^2). In this region the long-distance effects from quark loops can be computed with the help of an operator product expansion in 1/Q, with Q={m_b, \sqrt{q^2}}. Nonperturbative effects up to and including terms sup

Xiao Yang, Paul Fendley

We show that several well-known one-dimensional quantum systems possess a hidden nonlocal supersymmetry. The simplest example is the open XXZ spin chain with Δ=-1/2. We use the supersymmetry to place lower bounds on the ground state energy with various boundary conditions. For an odd number of sites in the periodic chain, and with a particular boundary magne

V. M. Apel, Maria A. Davidovich, G. Chiappe, E. V. Anda

Phase effects on the conductance of a double-dot system in a ring structure threaded by a magnetic flux are studied. The Aharonov-Bohm effect combined with the dot many-body charging effects determine the phases of the currents going through each arm of the ring. The cases for zero magnetic flux or half a quantum of flux are discussed in detail. It is shown

Gerold Betschart, Chris A. Clarkson

We study scalar field and electromagnetic perturbations on Locally Rotationally Symmetric (LRS) class II spacetimes, exploiting a recently developed covariant and gauge-invariant perturbation formalism. From the Klein-Gordon equation and Maxwell&#39;s equations, respectively, we derive covariant and gauge-invariant wave equations for the perturbation variabl

Marcella Bona

I present the results of searches for B meson decays into two charmless mesons. I take into account final states made up of two pseudo-scalar (PP) or one pseudo-scalar and one vector (PV). The measurements use the data samples collected and analysed by the B-factory experiments at the $Υ(4S)$ resonance energy: BABAR, Belle and CLEO.

Shahid Hussain, Douglas W. McKay

PeV neutrinos produce particle showers when they interact with the atomic nuclei in ice. We briefly describe characteristics of these showers and the radio Cherenkov signal produced by the showers. We study pulses from electromagnetic (em), hadronic, and combined em-hadronic showers and propose extrapolations to EeV energies.

Robert H. Brandenberger, S. Randjbar-Daemi

In this note we demonstrate that chaotic inflation can naturally be realized in the context of an anomaly free minimal gauged supergravity in D=6 which has recently been the focus of some attention. This particular model has a unique maximally symmetric ground state solution, $R^{3,1} \times S^2$ which leaves half of the six-dimensional supersymmetries unbro