March 2000 arXiv papers — page 6

Krzysztof A. Meissner, Marek Olechowski

We present calculation of the anomaly cancellation in M-theory on orbifolds $S^1/Z_2$ and $T^5/Z_2$ in the upstairs approach. The main requirement that allows one to uniquely define solutions to the modified Bianchi identities in this case is that the field strength $G$ be globally defined on $S^1$ or $T^5$ and properly transforming under $Z_2$. We solve for

Gert Aarts, Gian Franco Bonini, Christof Wetterich

Thermalization of classical fields is investigated in a ϕ^4 scalar field theory in 1+1 dimensions, discretized on a lattice. We numerically integrate the classical equations of motion using initial conditions sampled from various nonequilibrium probability distributions. Time-dependent expectation values of observables constructed from the canonical momentum

C. Anastasiou, T. Gehrmann, C. Oleari, E. Remiddi

The class of the two-loop massless crossed boxes, with light-like external legs, is the final unresolved issue in the program of computing the scattering amplitudes of 2 --> 2 massless particles at next-to-next-to-leading order. In this paper, we describe an algorithm for the tensor reduction of such diagrams. After connecting tensor integrals to scalar ones

A. Belyaev, E. Boos

We have reexamined the tW+X single top-quark production process which is important at the LHC contrary to the Tevatron. The special attention was paid to the treatment of the 2->2[Wt] process and the part of it's next-to-leading correction: 2->3[Wtb] process. We show that 2->3[Wtb] process has to be correctly taken into account with a proper subtraction

C. P. Bachas

This is a brief review of the present status, of some recent developments and of the open challenges in string/M theory.

G. Amoros, J. Bijnens, P. Talavera

The $F$ and $G$ form-factors of $K_{\ell4}$ and the quark condensates are calculated to ${\cal O}(p^6)$ in Chiral Perturbation Theory (CHPT). Full formulas are presented as much as possible. A full refit of most of the ${\cal O}(p^4)$ CHPT parameters is done with a discussion of all inputs and underlying assumptions. We discuss the consequences for the vacuu

Sandhya Choubey, Kamales Kar

The neutrinos and antineutrinos of all the three flavors released from a galactic supernova will be detected in the water Cerenkov detectors. We show that even though the neutral current interaction is flavor blind, and hence neutrino flavor mixing cannot alter the total neutral current signal in the detector, it can have a non-trivial impact on the delay of

R. Lafaye, D. J. Miller, M. Muhlleitner, S. Moretti

The reconstruction of the Higgs potential in the Minimal Supersymmetric Standard Model (MSSM) requires the measurement of the trilinear Higgs self-couplings. The `double Higgs production' subgroup has been investigating the possibility of detecting signatures of processes carrying a dependence on these vertices at the Large Hadron Collider (LHC) and futu

J. Cox, K. Holland

The recently developed Meron-Cluster algorithm completely solves the exponentially difficult sign problem for a number of models previously inaccessible to numerical simulation. We use this algorithm in a high-precision study of a model of N=1 flavor of staggered fermions in (2+1)-dimensions with a four-fermion interaction. This model cannot be explored usin

M. N. Achasov, S. E. Baru, K. I. Beloborodov, A. V. Berdyugin

Rare radiative decay $ϕ\toηπ^0γ$ was studied with SND detector at {VEPP-2M} electron-positron collider and its branching ratio was measured: $B(ϕ\toηπ^0γ)=(0.88\pm0.14\pm0.09)\cdot 10^{-4}$. Significant contribution of the $a_0(980)γ$ intermediate state was observed in the decay. The result is based on total integrated luminosity corresponding to $2\cdot10^7

P. R. B. Saull

Two recent results in ep physics using the ZEUS detector at HERA are discussed: a measurement of the prompt photon production cross section in photoproduction, and the first observation of Deeply Virtual Compton Scattering in DIS.

B. Buschbeck, H. C. Eggers, P. Lipa

Discussions about Bose-Einstein correlations between decay products of coproduced W-bosons again raise the question about the behaviour of correlations if several strings are produced. This is studied by the multiplicity dependence of correlation functions of particle pairs with like-sign and opposite-sign charge in \bar{p}p reactions at sqrt{s} = 630 GeV.

V. C. de Andrade, L. C. T. Guillen, J. G. Pereira

In the context of a gauge theory for the translation group, a conserved energy-momentum gauge current for the gravitational field is obtained. It is a true spacetime and gauge tensor, and transforms covariantly under global Lorentz transformations. By rewriting the gauge gravitational field equation in a purely spacetime form, it becomes the teleparallel equ

E. Chassande-Mottin, S. V. Dhurandhar

It is known by the experience gained from the gravitational wave detector proto-types that the interferometric output signal will be corrupted by a significant amount of non-Gaussian noise, large part of it being essentially composed of long-term sinusoids with slowly varying envelope (such as violin resonances in the suspensions, or main power harmonics) an

Daniel M. Mueth, Georges F. Debregeas, Greg S. Karczmar, Peter J. Eng

Granular materials react to shear stresses differently than do ordinary fluids. Rather than deforming uniformly, materials such as dry sand or cohesionless powders develop shear bands: narrow zones containing large relative particle motion leaving adjacent regions essentially rigid[1,2,3,4,5]. Since shear bands mark areas of flow, material failure and energy

Robert Haslinger, Nic Shannon

Core hole photoemission (XPS) provides a powerful indirect probe of the low energy excitations of a many electron system. We argue that XPS can be used to study the way in which a gap opens at a metal-superconductor or metal- insulator transition. We consider the "universal" physics of how the loss of low energy excitations modifies XPS spectra in th

Z. Dogic, A. P. Philipse, S. Fraden, J. K. G. Dhont

In the first part of this paper, an approximate theory is developed for the leading order concentration dependence of the sedimentation coefficient for rod-like colloids/polymers/macromolecules. To first order in volume fraction $ϕ$ of rods, the sedimentation coefficient is written as $1+αϕ$. For large aspect ratio L/D (L is the rod length, D it's thickn

T. Jungwirth, A. H. MacDonald

Broken symmetry ground states with uniform electron density are common in quantum Hall systems when two Landau levels simultaneously approach the chemical potential at integer filling factor $ν$. The close analogy between these two-dimensional electron system states and conventional itinerant electron ferromagnets can be emphasized by using a pseudospin labe

S. Das Sarma, E. H. Hwang, Igor Zutic

We present the results on the anomalous 2D transport behavior by employing Drude-Boltzmann transport theory and taking into account the realistic charge impurity scattering effects. Our results show quantitative agreement with the existing experimental data in several different systems and address the origin of the strong and non-monotonic temperature depend

Alexei K. Kolezhuk

The phase diagram of antiferromagnetic spin-S chain with XY-type anisotropy and frustrating next-nearest-neighbor interaction is studied in the limit of large integer S with the help of a field-theoretical approach. It is shown that the existence of gapless and gapped chiral phases found in recent numerical studies [M.Kaburagi et al., J. Phys. Soc. Jpn. vol.

H. Stahl, J. Appenzeller, R. Martel, Ph. Avouris

We investigate the coupling between individual tubes in a rope of single-wall carbon nanotubes using four probe resistance measurements. By introducing defects through the controlled sputtering of the rope we generate a strong non-monotonic temperature dependence of the four terminal resistance. This behavior reflects the interplay between localization in th

K. N. Yugay, N. V. Blinov, I. V. Shirokov

A long Josephson junction in a constant external magnetic field and in the presence of a dc bias current is investigated. It is shown that the system, simulated by the sine-Gorgon equation, "remembers" a rapidly damping initial perturbation and final asymptotic states are determined exactly with this perturbation. Numerical solving of the boundary si

Alexei Vazquez

Directed sandpile models with different toppling rules are studied by means of numerical simulations in two dimensions, with the purpose of determining the different universality classes. It is concluded that the random-threshold directed model is in the same universality of the Manna directed model where multiple toppling events plays a determinant role. Th

Masaaki Nakamura, Kazuhito Itoh, Norihiro Muramoto

Phase diagrams of the one-dimensional extended Hubbard model with a nearest neighbor interaction $V$ and site-off-diagonal (bond-charge $X$ and bond-bond $W$) interactions at half-filling are obtained numerically, using the level-crossing approach for finite-size clusters. This analysis is straightforward extension of the preceding work [cond-mat/9909277], w

Bogdan R. Bulka

Current and its noise in a ferromagnetic double tunnel barrier device with a small spacer particle were studied in the framework of the sequential tunneling approach. Analytical formulae were derived for electron tunneling through the spacer particle containing only a single energy level. It was shown that Coulomb interactions of electrons with a different s

A. Djannati-Atai, F. Piron, A. Barrau, L. Iacoucci

The BL Lac object Mrk 501 went into a very high state of activity during 1997, both in VHE gamma-rays and X-rays. We present here results from observations at energies above 250 GeV carried out between March and October 1997 with the CAT Cerenkov imaging Telescope. The average differential spectrum between 30 GeV and 13 TeV shows significant curvature and is

Guo Xin Chen, Anil K. Pradhan

Relativistic atomic structure calculations for electric dipole E1, electric quadrupole E2 and magnetic dipole M1 transition probabilities among the first 80 fine-structure levels of Fe VI, dominated by configurations 3d^3, 3d^24s, and 3d^24p, are carried out using the Breit-Pauli version of the code Superstructure. Experimental energies are used to improve t

Sultana N. Nahar

Theoretically self-consistent calculations for photoionization and (e + ion) recombination are described. An identical eigenfunction expansion for the ion is employed in coupled channel calculations for both processes, thus ensuring consistently accurate cross sections and rates in an ab initio manner. The theoretical treatment of (e + ion) recombination sub

Roman V. Buniy, John P. Ralston

Radio Cherenkov emission underlines detection of high energy particles via a signal growing like the particle-energy-squared. Cosmic ray-induced electromagnetic showers are a primary application. While many studies have treated the phenomenon approximately, none have attempted to incorporate all the physical scales involved in problems with time- or spatiall

S. W. Digel, I. V. Moskalenko, J. F. Ormes, P. Sreekumar

Gamma rays in the band from 20 MeV to 300 GeV, used in combination with data from radio and X-ray bands, provide a powerful tool for studying the origin of cosmic rays in our sister galaxies Andromeda and the Magellanic Clouds. Gamma-ray Large Area Space Telescope (GLAST) will spatially resolve these galaxies and measure the spectrum and intensity of diffuse

Re'em Sari, Peter Meszaros

The standard model of Gamma-Ray Bursts afterglows is based on synchrotron radiation from a blast wave produced when the relativistic ejecta encounters the surrounding medium. We reanalyze the refreshed shock scenario, in which slower material catches up with the decelerating ejecta and reenergizes it. This energization can be done either continuously or in d

L. I. Onuora, P. A. Thomas

The alignment of clusters of galaxies with their nearest neighbours and between clusters within a supercluster is investigated using simulations of 512^{3} dark matter particles for \LambdaCDM and \tauCDM cosmological models. Strongly significant alignments are found for separations of up to 15h^{-1}Mpc in both cosmologies, but for the \LambdaCDM model the a

M. Limongi, O. Straniero, A. Chieffi

We present the evolutionary properties of a set of massive stellar models (namely 13, 15, 20 and 25 $\rm M_\odot$) from the main sequence phase up to the onset of the iron core collapse. All these models have initial solar chemical composition, i.e. Y=0.285 and Z=0.02. A 179 isotope network, extending from neutron up to $\rm ^{68}Zn$ and fully coupled to the

E. Battaner, H. Lesch

There are at present more then 30 theories about the origin of cosmic magnetic fields at galactic and intergalactic scales. Most of them rely on concepts of elementary particle physics, like phase transitions in the early Universe, string theory and processes during the inflationary epoch. Here we present some more astrophysical arguments to provide some gui

Chang S. Chan, Percy L. Paul, Herman Verlinde

We give a short review of a large class of warped string geometries, obtained via F-theory compactified on Calabi-Yau fourfolds, that upon reduction to 5 dimensions give consistent supersymmetric realizations of the RS compactification scenario.

P. Gopakumar, G. V. Vijayagovindan

The flatness and cosmological constant problems are solved with varying speed of light c, gravitational coupling strength G and cosmological parameter Lambda, by explicitly assuming energy conservation of observed matter. The present solution to the flatness problem is the same as the previous solution in which energy conservation was absent.

Abhas Mitra

GRB 990123 is the most luminous event detected so far, and in an important paper, Hjorth et al. (1999) reported an upper limit on the degree of linear polarization of the optical afterglow for this burst (P <2.3%). One of the interprtations for this small value of P was that the emission was probably due a relativistic jet with ordered magnetic field, and th

T. Matos, F. S. Guzman, D. Nunez

We study a spherically symmetric fluctuation of scalar dark matter in the cosmos and show that it could be the dark matter in galaxies, provided that the scalar field has an exponential potential whose overall sign is negative and whose exponent is constrained observationally by the rotation velocities of galaxies. The local space-time of the fluctuation con

Ehud Fuchs

We study theories generated by orbifolding the {\cal N}=4 super conformal U(N) Yang Mills theory with finite N, focusing on the rôle of the remnant U(1) gauge symmetries of the orbifold process. It is well known that the one loop beta functions of the non abelian SU(N) gauge couplings vanish in these theories. It is also known that in the large N limit the b

Stefan Kettemann

The crossover in energy level statistics of a quasi-1-dimensional disordered wire as a function of its length L is used, in order to derive its averaged localization length, without magnetic field, in a magnetic field and for moderate spin orbit scattering strength. An analytical function of the magnetic field for the local level spacing is obtained, and fou

Martin Maul

A semi-classical picture is given for the production of exclusive meson pairs in γγ^* scattering using elements of the Lund string fragmentation model, spin and C-parity conservation. The model can be generalized to the production of any few meson states in scattering reactions at intermediate momentum transfers. As an example we show that we get a consisten

T. Rauscher, F. -K. Thielemann, J. Goerres, M. Wiescher

The reaction rates for alpha capture processes on self-conjugate nuclei in the mass range A=20-40 have been investigated. The rates were calculated using the statistical model code NON-SMOKER taking into account isospin suppression rules. These theoretical predictions are compared with rates derived from the available experimental data about the alpha captur

A. Ludu, G. Stoitcheva, J. P. Draayer

We introduce a generalized similarity analysis which grants a qualitative description of the localised solutions of any nonlinear differential equation. This procedure provides relations between amplitude, width, and velocity of the solutions, and it is shown to be useful in analysing nonlinear structures like solitons, dublets, triplets, compact supported s

Andrei Ludu, Jerry P. Draayer

Localized patterns and nonlinear oscillation formation on the bounded free surface of an ideal incompressible liquid are analytically investigated . Cnoidal modes, solitons and compactons, as traveling non-axially symmetric shapes are discused. A finite-difference differential generalized Korteweg-de Vries equation is shown to describe the three-dimensional

Andrei Ludu, Jerry P. Draayer

The nolinear hydrodynamic equations of the surface of a liquid drop are shown to be directly connected to Korteweg de Vries (KdV, MKdV) systems, giving traveling solutions that are cnoidal waves. They generate multiscale patterns ranging from small harmonic oscillations (linearized model), to nonlinear oscillations, up through solitary waves. These non-axis-

H. Engler, T. Weber, M. Mudrich, R. Grimm

We have trapped cesium atoms over many minutes in the focus of a CO$_2$-laser beam employing an extremely simple laser system. Collisional properties of the unpolarized atoms in their electronic ground state are investigated. Inelastic binary collisions changing the hyperfine state lead to trap loss which is quantitatively analyzed. Elastic collisions result

R. A. Gherghescu, A. Ludu, J. P. Draayer

This work reports on calculations of the deformation energy of a nucleus plus an emitted cluster as a soliton moving on its surface. The potential barrier against the emission of a soliton is calculated within the macroscopic-microscopic method. The outer turning point of the barrier determines limitations on the geometrical and kinematical parameters for th

Andrei Ludu, Martin Greiner, Jerry P. Draayer

Wavelets, known to be useful in non-linear multi-scale processes and in multi-resolution analysis, are shown to have a q-deformed algebraic structure. The translation and dilation operators of the theory associate with any scaling equation a non-linear, two parameter algebra. This structure can be mapped onto the quantum group $su_{q}(2)$ in one limit, and a

Yongge Tian

A variety of universal similarity factorization equalities over real Clifford algebras ${\cal R}_{p,q}$ are established. On the basis of these equalities, real, complex and quaternion matrix representations of elements in ${\cal R}_{p,q}$ can be explicitly determined.

Yongge Tian

A set of valuable universal similarity factorization equalities is established over complex Clifford algebras $\Cn.$ Through them matrix representations of complex Clifford algebras $\Cn$ can directly be derived, and their properties can easily be determined.

Richard Hain

This paper addresses the following question of Oort: &#34;Are there any postive dimensional locally symmetric subvarieties of the moduli space of abelian varieties that are contained in the jacobian locus and contain the jacobian of at least one smooth curve? Some partial results are given.

Yongge Tian

A set of valuable universal similarity factorization equalities are established over complex Clifford algebras $\Cn.$ Through them matrix representations of complex Clifford algebras $\Cn$ can directly be derived, and their properties can easily be determined.

S. V. Chekanov

A Monte Carlo simulation based on O(alpha_s) QCD matrix elements matched to parton showers shows that final-state hadrons in deep inelastic scattering (DIS) can be used to tag events with a single (anti)quark recoiled against the proton. The method is particularly suited to study the mean charge of leading particles, which is sensitive to fragmentation and s

A. A. Babich, P. Osland, A. A. Pankov, N. Paver

For contact-interaction searches at the Linear Collider, we discuss the advantages of polarizing both the electron and the positron beams as compared with polarizing only the electron beam. In particular, for the processes e^+e^-\to μ^+μ^-, τ^+τ^-, b\bar{b} and c\bar{c} at a future e^+e^- collider with \sqrt{s}=0.5 TeV we derive model-independent bounds on t

S. Tsujikawa

We investigate the particle production of a scalar field $χ$ coupled to an inflaton field $ϕ$ ($g^2ϕ^2χ^2/2$) in the {\it oscillating inflation} model, which was recently proposed by Damour and Mukhanov. Although the fluctuation of the $ϕ$ field can be effectively enhanced during a stage of the oscillating inflation, the maximum fluctuation is suppressed as

Andreas Siebert

This paper presents invariants under gamma correction and similarity transformations. The invariants are local features based on differentials which are implemented using derivatives of the Gaussian. The use of the proposed invariant representation is shown to yield improved correlation results in a template matching scenario.

Ernst Helmut Brandt

The magnetic response of type-II superconductors can be irreversible due to two different reasons: vortex pinning and barriers for flux penetration. Even without bulk pinning and in absence of a microscopic Bean-Lingston surface barrier for vortex penetration, superconductors of nonellipsoidal shape can exhibit a large geometric barrier for flux penetration.

Igor V. Igumenshchev, Marek A. Abramowicz

We present a systematic numerical study of two-dimensional axisymmetric accretion flows around black holes. The flows have no radiative cooling and are treated in the framework of the hydrodynamical approximation. The models calculated in this study cover the large range of the relevant parameter space. There are four types of flows, determined by the values

Badis Ydri

We give a perturbative quantization of space-time $R^4$ in the case where the commutators $C^{μν}=[X^μ,X^ν]$ of the underlying algebra generators are not central . We argue that this kind of quantum space-times can be used as regulators for quantum field theories . In particular we show in the case of the $ϕ^4$ theory that by choosing appropriately the commu

Goro Hatayama, Atsuo Kuniba, Taichiro Takagi

Solvable vertex models in statistical mechanics give rise to soliton cellular automata at q=0 in a ferromagnetic regime. By means of the crystal base theory we study a class of such automata associated with non-exceptional quantum affine algebras U&#39;_q(\hat{\geh}_n). Let B_l be the crystal of the U&#39;_q(\hat{\geh}_n)-module corresponding to the l-fold s

Alex Kaivarainen

1. The state equation for real gas 2. New state equation for condensed matter 3.Vapor pressure 4. Surface tension 5. Mesoscopic theory of thermal conductivity 6. Mesoscopic theory of viscosity for liquids and solids 7. Brownian diffusion 8. Self-diffusion in liquids and solids 9. Mesoscopic approach to proton conductivity in water, ice and other systems, con

Ruediger Goebel, Saharon Shelah

We continue [GbSh:568] (math.LO/0003164), proving a stronger result under the special continuum hypothesis (CH). The original question of Eklof and Mekler related to dual abelian groups. We want to find a particular example of a dual group, which will provide a negative answer to the question. In order to derive a stronger and also more general result we wil

Ruediger Goebel, Saharon Shelah

In &#34;Almost Free Modules, Set-theoretic Methods&#34;, Eklof and Mekler raised the question about the existence of dual abelian groups G which are not isomorphic to Z+G. Recall that G is a dual group if G ~ D^* for some group D with D^*=Hom(D,Z). The existence of such groups is not obvious because dual groups are subgroups of cartesian products Z^D and the

Saharon Shelah

We prove the following: there is a primitive recursive function f_-^*(-,-), in the three variables, such that: for every natural numbers t,n>0, and c, for any natural number k>=f^*_t(n,c) the following holds. Assume L is an alphabet with n>0 letters, M is the family of non empty subsets of {1,...,k} with =<t members and V is the set of functions from M to L,

Kenichiro Kimura

We construct certain systems of elements in K_2 of CM elliptic curves. When the classnumber of the field of CM is 1, the image of this system under the regulator map forms an Euler system in the sense of Rubin.

Andrea Maffei

In this paper we define an action of the Weyl group on the quiver varieties $M_{m,\grl}(d,v)$ with generic $(m,\grl)$. To do it we describe a set of generators of the projective ring of a quiver variety. We also prove connectness for the smooth quiver variety $M(d,v)$ and normality for $M_0(d,v)$ in the case of a quiver of finite type and $d-v$ a regular wei

Alexander B. Givental

A K-theoretic counterpart of quantum cohomology theory is discussed.

Fiorenzo Bastianelli, Roberto Zucchini

We compute all 3-point functions of the ``universal&#39;&#39; scalar operators contained in the interacting, maximally supersymmetric CFTs at large N by using the AdS/CFT correspondence. These SCFTs are related to the low energy description of M5, M2 and D3 branes, and the common set of universal scalars corresponds through the AdS/CFT relation to the fluctu

S. L. Lebedev

The vacuum energy-momentum tensor (EMT) and the vacuum energy corresponding to massive scalar field on $\Re_{t}\times [0,l] \times \Re^{D-2}$ space-time with boundary condition involving a dimensional parameter ($δ$) are found. The dependent on the cavity size $l$ Casimir energy $\wt E_{C}$ is a uniquely determinable function of mass $m$, size $l$ and &#34;s

Soon-Tae Hong, Yong-Wan Kim, Young-Jai Park

We obtain the higher dimensional global flat embeddings of static, rotating, and charged BTZ black holes. On the other hand, we also study the similar higher dimensional flat embeddings of the (2+1) de Sitter black holes which are the counterparts of the anti-de Sitter BTZ black holes. As a result, the charged dS black hole is shown to be embedded in (3+2) G

Salvatore Torquato, Thomas M. Truskett, Pablo G. Debenedetti

Despite its long history, there are many fundamental issues concerning random packings of spheres that remain elusive, including a precise definition of random close packing (RCP). We argue that the current picture of RCP cannot be made mathematically precise and support this conclusion via a molecular dynamics study of hard spheres using the Lubachevsky-Sti

S. B. Field, S. S. James, J. Barentine, V. Metlushko

High-resolution scanning Hall probe microscopy has been used to image vortex configurations in very large periodic arrays of artificial pinning sites. Strong matching effects are seen at fields where either one or two vortices can sit at a site; with three vortices per site, however, no clear matching is observed. Matching effects have been also been observe

Y. Petrov, T. Egami, R. J. McQueeney, M. Yethiraj

Temperature and composition dependences of high-energy longitudinal optical (LO) phonons in YBa2Cu3O{6+x}, studied by inelastic neutron scattering measurements, provide clear evidence for temperature dependent spatial inhomogeneity of doped charges. The measurements indicate that charge doping increases the volume fraction of the charged regions, while the l

Kazumi Maki, Stephan Haas

A scenario for the unusual paramagnetic reentrance behavior at ultra-low temperatures in Nb-Ag, Nb-Au, and Nb-Cu cylinders is presented. For the diamagnetic response down to temperatures of the order 15 mK, the standard theory (quasi-classical approximation) for superconductors appears to work very well, assuming that Ag, Au, and Cu remain in the normal stat

Fernando M. Ramos, Reinaldo R. Rosa, Camilo Rodrigues Neto, Ademilson Zanandrea

In this paper we describe two new computational operators, called complex entropic form (CEF) and generalized complex entropic form (GEF), for pattern characterization of spatially extended systems. Besides of being a measure of regularity, both operators permit to quantify the degree of phase disorder associated with a given gradient field. An application o

Mahn-Soo Choi, C. Bruder

We investigate a modified Anderson model to study the local density of states (LDOS) of a molecular wire adsorbed on a metal. Using a self-consistent mean-field type approach we find an exponential decay of the LDOS along the molecule. A repulsive on-site interaction on the molecule suppresses the tunneling and decreases the characteristic decay length.

J. -E. Wegrowe

In order to describe the recently observed effect of current induced magnetization reversal in magnetic nanostructures, the thermokinetic theory is applied to a metallic ferromagnet in contact with a reservoir of spin polarized conduction electrons. The spin flip relaxation of the conduction electrons is described thermodynamically as a chemical reaction. Th

Rajendra Bhandari

The response of a pair of differently polarized antennas is determined by their polarization states AND a phase between them which has a geometric part which becomes discontinuous at singular points in the parameter space. Such phase singularities have been observed in optical polarization experiments [R.Bhandari, Physics Reports 281 (1997) 1]. It is pointed

Eliot Quataert, Andrei Gruzinov

Two-temperature spherical accretion flows produce $\approx 100$ Mev gamma-rays from the decay of neutral pions created in proton-proton collisions close to the black hole; they also produce $\sim 10$ keV X-rays by bremsstrahlung emission at large radii. The gamma-ray to X-ray luminosity ratio is nearly independent of black hole mass and accretion rate. It do

Arvind Rajaraman, Moshe Rozali

We study the renormalization of non-commutative gauge theories with matter. As in the scalar field theory cases, there are logarithmic infrared divergences resulting from integrating out high momentum modes. In order to reproduce the correct infrared behaviour, the Wilsonian effective action has to include certain &#39;&#39;closed string`` modes with prescri

Paolo Aschieri, Daniel Brace, Bogdan Morariu, Bruno Zumino

In this paper we prove a conjecture regarding the form of the Born-Infeld Lagrangian with a U(1)^2n gauge group after the elimination of the auxiliary fields. We show that the Lagrangian can be written as a symmetrized trace of Lorentz invariant bilinears in the field strength. More generally we prove a theorem regarding certain solutions of unilateral matri

Carl H. Albright, S. M. Barr

A full account is given of the procedure used by the authors to construct an SO(10) supersymmetric grand unified model of the fermion mass matrices. Various features of the model which gives remarkably accurate results for the quark and lepton masses and mixings were presented earlier in separate publications. The construction of the matrices is first discus

Eliot Quataert, Eugene I. Chiang

We examine the angular momentum transport properties of disks composed of macroscopic particles whose velocity dispersions are externally enhanced (``stirred&#39;&#39;). Our simple Boltzmann equation model serves as an analogy for unmagnetized fluid disks in which turbulence may be driven by thermal convection. We show that interparticle collisions in partic

Yolanda Lozano

Starting with the non-BPS D0-brane solution of IIB/$(-1)^{F_L}I_4$ constructed recently by Eyras and Panda we construct via T-duality the non-BPS D2-brane and D1-brane solutions of IIB/$(-1)^{F_L}I_4$ and IIA/$(-1)^{F_L}I_4$ predicted by Sen. The D2-brane couples magnetically to the vector field of the NS5B-brane living in the twisted sector of the Type IIB

Jose Ramon Espinosa, Ren-Jie Zhang

Using an effective potential approach, we compute two-loop radiative corrections to the MSSM lightest ${\cal CP}$-even Higgs boson mass $M_{h^0}$ to ${\cal O}(α_t^2)$ for arbitrary left-right top-squark mixing and $\tanβ$. We find that these corrections can increase $M_{h^0}$ by as much as 5 GeV; assuming a SUSY scale of 1 TeV, the upper bound on the Higgs b

Antonio Riotto, Igor Tkachev

Recently the problem of singular galactic cores and over-abundant formation of dwarf galaxies, inherent to the standard cold dark matter model, had attracted a great deal of attention. One scenario which may be free of these problems invokes a self-interacting Bose-field. We find the limiting core density in this model due to the self-annihilation of the sca

P. Maddaloni, M. Modugno, C. Fort, F. Minardi

Two 87Rb condensates (F=2, m_f=2 and m_f=1) are produced in highly displaced harmonic traps and the collective dynamical behaviour is investigated. The mutual interaction between the two condensates is evidenced in the center-of-mass oscillations as a frequency shift of 6.4(3)%. Calculations based on a mean-field theory well describe the observed effects of

Saulo Carneiro

We study a rotating and expanding, Godel type metric, originally considered by Korotkii and Obukhov, showing that, in the limit of large times and nearby distances, it reduces to the open metric of Friedmann. In the epochs when radiation or dust matter dominate the energy density, our solutions are similar to the isotropic ones and, in what concerns processe

J. Nishimura, G. Vernizzi

We study the IIB matrix model, which is conjectured to be a nonperturbative definition of superstring theory, by introducing an integer deformation parameter `nu&#39; which couples to the imaginary part of the effective action induced by fermions. The deformed IIB matrix model continues to be well-defined for arbitrary `nu&#39;, and it preserves gauge invari

P. H. Damgaard, U. M. Heller, R. Niclasen, K. Rummukainen

We compute the low-lying spectrum of the staggered Dirac operator above and below the finite temperature phase transition in both quenched QCD and in dynamical four flavor QCD. In both cases we find, in the high temperature phase, a density with close to square root behavior, $ρ(λ) \sim (λ-λ_0)^{1/2}$. In the quenched simulations we find, in addition, a volu

I. Hapke-Wurst, U. Zeitler, H. Frahm, A. G. M. Jansen

Current steps attributed to resonant tunneling through individual InAs quantum dots embedded in a GaAs-AlAs-GaAs tunneling device are investigated experimentally in magnetic fields up to 28 T. The steps evolve into strongly enhanced current peaks in high fields. This can be understood as a field-induced Fermi-edge singularity due to the Coulomb interaction b

Lu-Ming Duan, G. Giedke, J. I. Cirac, P. Zoller

We give a detailed description of the entanglement purification protocol which generates maximally entangled states with high efficiencies from realistic Gaussian continuous variable entangled states. The physical implementation of this protocol is extensively analyzed using high finesse cavities and cavity enhanced cross Kerr nonlinearities. In particular,

Franc Forstneric, Erik Low, Nils Øvrelid

We construct a family of integral kernels for solving the \bar\partial equation with C^k and Holder estimates in thin tubes around totally real submanifolds in complex Eulidean spaces (theorems 1.1 and 3.1). Combining this with the proof of a theorem of Serre we solve the d-equation with estimates for holomorphic forms in such tubes (theorem 5.1). We apply t

J. Nemchik

In the color dipole gBFKL dynamics we predict a strikingly different Q^2 and energy dependence of the diffraction slope for the elastic production of ground state V(1S) and radially excited V&#39;(2S) light vector mesons. The color dipole model predictions for the diffraction slope for ρ^0 and ϕ^0 production are in a good agreement with the data from the fix

K. Kajantie, M. Laine, T. Neuhaus, A. Rajantie

We study with lattice Monte Carlo simulations the relation of global O(2) symmetry breaking in three dimensions to the properties of a geometrically defined vortex loop network. We find that different definitions of constructing a network lead to different results even in the thermodynamic limit, and that with typical definitions the percolation transition d

Yu. P. Goncharov, N. E. Firsova

An algorithm for numerical computation of the barrier transparency for the potentials surrounding Schwarzschild black holes is described for massive scalar particles. It is then applied to calculate the total (including all particle species and the contributions of twisted field configurations connected with Dirac monopoles) luminosity for the pion-kaon Hawk

E. A. Bergshoeff, M. de Roo, T. C. de Wit, E. Eyras

We employ T-duality to restrict the tachyon dependence of effective actions for non-BPS D-branes. For the Born-Infeld part the criteria of T-duality and supersymmetry are satisfied by a simple extension of the D-brane Born-Infeld action.

Pieter-Jan De Smet, Joris Raeymaekers

We compute the tachyon potential to level 4 in NS superstring field theory. We obtain 89% of the conjectured vacuum energy.

G. Cvetic, Ji-Young Yu

Recently, Weniger (delta sequence) method has been proposed by the authors of Ref. [1] (Jentschura et al.) for resummation of truncated perturbation series in quantum field theories. Those authors presented numerical evidence suggesting that this method works better than Pade approximants when we resum a function with singularities in the Borel plane but not

M. Matsuda, T. Matsuoka

The quark mixing matrix $V_{CKM}$ is studied in depth on the basis of superstring inspired $SU(6)\times SU(2)_R$ model with global flavor symmetries. The sizable mixings between right-handed down-type quark $D^c$ and colored Higgs field $g^c$ potentially occur but no such mixings in up-type quark sector. In the model the hierarchical pattern of $V_{CKM}$ is