January 2003 arXiv papers — page 25

E. Verlinde, M. Vonk

As was shown by Aharony, Hanany and Kol and independently by Sen, type IIB string theory admits configurations where strings of different charges (p_i, q_i) form so-called string networks. We argue that these networks blow up into "supersheets": supersymmetric spinning cylindrical D3-branes carrying electric and magnetic fluxes. These supersheets are

T. Banks

This paper reexamines the question of vacuum decay in theories of quantum gravity. In particular it suggests that decay into stable flat or AdS vacua, never occurs. Instead, vacuum decay occurs, if at all, into a cosmological spacetime. If the latter has negative cosmological constant, it undergoes a Big Crunch, which suggests that the whole picture is incon

Giovanni Modanese

Motivated by recent works on the origin of inertial mass, we revisit the relationship between the mass of charged particles and zero-point electromagnetic fields. To this end we first introduce a simple model comprising a scalar field coupled to stochastic or thermal electromagnetic fields. Then we check if it is possible to start from a zero bare mass in th

J. R. Pelaez, A. Gomez Nicola

We report on our recent progress in the generation of resonant behavior in unitarized meson-meson scattering amplitudes obtained from Chiral Perturbation Theory. These amplitudes provide simultaneously a remarkable description of the resonance region up to 1.2 GeV as well as the low energy region, since they respect the chiral symmetry expansion. By studying

Matteo Cacciari, Einan Gardi

We study perturbative and non-perturbative aspects of heavy-quark fragmentation into hadrons, emphasizing the large-x region, where x is the energy fraction of the detected hadron. We first prove that when the moment index N and the quark mass m get large simultaneously with the ratio (N Lambda/m) fixed, the fragmentation function depends on this ratio alone

E. G. Drukarev

It is shown how the QCD sum rules can be applied for the investigation of the density dependence of the nucleon parameters. These characteristics can be expressed through the expectation values of QCD operators in nuclear matter. In certain approximations the expectation values are related to the observables. First applications of the approach reproduced som

S. A. Kulagin

We discuss nuclear effects in the Paschos-Wolfenstein relationship in the context of extraction of the weak mixing angle. We point out that the neutron excess correction to the Paschos-Wolfenstein relationship for a neutron-rich target is negative and large on the scale of experimental errors of a recent NuTeV measurement. We found a larger neutron excess co

Gerhart Seidl

We present a model for lepton masses and mixing angles using the deconstruction setup, based on a non-Abelian flavor symmetry which is a split extension of the Klein group. The symmetries enforce an approximately maximal atmospheric mixing angle theta_{23}, a nearly vanishing reactor mixing angle theta_{13}, and the hierarchy of charged lepton masses. The ch

N. G. Marchuk

In the model every quark or lepton is identified with a quartet of four "more elementary" particles. One particle in a quartet is a massive spin-0 boson and other three particles are massless spin-1/2 fermions.

A. K. Chaudhuri

In the extra dimensional theories, with TeV scale Plank constant, black holes may be produced in the Large Hadron Collider experiments. We have argued that in the d-dimensional black hole, the intrinsically 4-dimensional brane fields do not see the same geometry at the horizon, as in a 4-dimensional space-time. Kaluza-Klein modes invades the brane and surrou

E. O. Iltan, H. Sundu

We calculate the new physics effects on the anomalous magnetic moment of the muon in the framework of the two Higgs doublet model. We predict an upper bound for the lepton flavor violating coupling, which is responsible for the point like interaction between muon and tau, by using the uncertainty in the experimental result of the muon anomalous magnetic mome

Thomas R. Hemmert, Massimiliano Procura, Wolfram Weise

We summarize developments concerning the quark mass dependence of nucleon magnetic moments and the axial-vector coupling constant g_A. The aim is to explore the feasibility of chiral effective field theory methods for the extrapolation of lattice QCD results, from the relatively large quark masses that can be handled in such computations down to the physical

J. M. Carmona, A. Cruz, L. A. Fernandez, S. Jimenez

It is shown that a bosonic formulation of the double-exchange model, one of the classical models for magnetism, generates dynamically a gauge-invariant phase in a finite region of the phase diagram. We use analytical methods, Monte Carlo simulations and Finite-Size Scaling analysis. We study the transition line between that region and the paramagnetic phase.

Markus Hamann

Ongoing studies for the TESLA TPC with GEM readout at DESY/Hamburg University are presented. They include basic GEM performances, tracking and the determination of the resolution using different pad sizes and geometries as well as ion feedback measurements.

Ignazio Ciufolini, Franco Ricci

We derive the delay in travel time of photons due to the spin of a body both inside a rotating shell and outside a rotating body. We then show that this time delay by the spin of an astrophysical object might be detected in different images of the same source by gravitational lensing; it might be relevant in the determination of the Hubble constant using acc

Brien C. Nolan

We derive global weak solutions of Einstein's equations for spherically symmetric dust-filled space-times which admit shell-crossing singularities. In the marginally bound case, the solutions are weak solutions of a conservation law. In the non-marginally bound case, the equations are solved in a generalized sense involving metric functions of bounded va

Iver Brevik

The holographic principle in a radiation dominated universe is extended to incorporate the case of a bulk-viscous cosmic fluid. This corresponds to a nonconformally invariant theory. Generalization of the Cardy-Verlinde entropy formula to the viscous case appears to be possible from a formal point of view, although we question on physical grounds the manner

Anand S. Sengupta, Sanjeev Dhurandhar, Albert Lazzarini

The first scientific runs of kilometer scale laser interferometric detectors like LIGO are underway. Data from these detectors will be used to look for signatures of gravitational waves (GW) from astrophysical objects like inspiraling neutron star/blackhole binaries using matched filtering. The computational resources required for online flat-search implemen

S. Choi, V. Chernyak, S. Mukamel

Using the Liouville space framework developed in nonlinear optics we calculate the linear response functions and susceptibilities of Bose-Einstein condensates (BEC) subject to an arbitrary mechanical force. Distinct signatures of the dynamics of finite temperature BEC are obtained by solving the Hartree-Fock-Bogoliubov theory. Numerical simulations of the po

Mike Sutherland, D. G. Hawthorn, R. W. Hill, F. Ronning

Heat transport in the cuprate superconductors YBa$_2$Cu$_3$O$_{y}$ and La$_{2-x}$Sr$_x$CuO$_4$ was measured at low temperatures as a function of doping. A residual linear term kappa_{0}/T is observed throughout the superconducting region and it decreases steadily as the Mott insulator is approached from the overdoped regime. The low-energy quasiparticle gap

D. L. Stein

Spin glasses are magnetic systems exhibiting both quenched disorder and frustration, and have often been cited as examples of `complex systems.' In this talk I review some of the basic notions of spin glass physics, and discuss how some of our recent progress in understanding their properties might lead to new viewpoints of how they manifest `complexity&

T. S. Grigera, V. Martin-Mayor, G. Parisi, P. Verrocchio

Glasses are amorphous solids, in the sense that they display elastic behaviour. In crystals, elasticity is associated with phonons, quantized sound-wave excitations. Phonon-like excitations exist also in glasses at very high frequencies (THz), and they remarkably persist into the supercooled liquid. A universal feature of these amorphous systems is the Boson

J. K. Wahlstrand, R. Merlin

We report on the generation of coherent phonon polaritons in ZnTe, GaP and LiTaO$_{3}$ using ultrafast optical pulses. These polaritons are coupled modes consisting of mostly far-infrared radiation and a small phonon component, which are excited through nonlinear optical processes involving the Raman and the second-order susceptibilities (difference frequenc

M. Cavallini, F. Biscarini, V. Dediu, P. Nozar

The ferromagnetic phase in La0.7Sr0.3MnO3 manganite is completely spin polarized (100%) at room temperature. This is demonstrated on high quality epitaxial films by Spin-Polarized Scanning Tunneling Microscopy. The films consist of a highly homogeneous ferromagnetic (FM) phase in which minority paramagnetic (PM) defects are embedded (less than 1% for best fi

D. Long, P. Sotta

Recent experiments have demonstrated that the glass transition temperature of thin polymer films can be shifted as compared to the same polymer in the bulk, the amplitude and the sign of this effect depending on the interaction between the polymer and the substrate. A model has been proposed recently for explaining these effects in two limiting cases: suspen

Z. Burda, J. Jurkiewicz, M. A. Nowak

Econophysics is an approach to quantitative economy using ideas, models, conceptual and computational methods of statistical physics. In recent years many of physical theories like theory of turbulence, scaling, random matrix theory or renormalization group were successfully applied to economy giving a boost to modern computational techniques of data analysi

D. Schmalfuss, R. Herms, J. Richter, J. Schulenburg

We study a two-dimensional (2D) spin-half Heisenberg model related to the quasi 2D antiferromagnets (Ba,Sr)2Cu3O4Cl2 by means of exact diagonalization and spin-wave theory. The model consists of two inequivalent interpenetrating square-lattice Heisenberg antiferromagnets A and B. While the antiferromagnetic interaction JAA within the A subsystem is strong th

Herve Henry, Herbert Levine

Motivated by recent experiments on intracellular calcium dynamics, we study the general issue of fluctuation-induced nucleation of waves in excitable media. We utilize a stochastic Fitzhugh-Nagumo model for this study, a spatially-extended non-potential pair of equations driven by thermal (i.e. white) noise. The nucleation rate is determined by finding the m

M. Hofmann, T. Lorenz, K. Berggold, M. Gr"uninger

The in-plane thermal conductivity $k$ of the two-dimensional antiferromagnetic monolayer cuprate Sr$_2$CuO$_2$Cl$_2$ is studied. Analysis of the unusual temperature dependence of $k$ reveals that at low temperatures the heat is carried by phonons, whereas at high temperatures magnetic excitations contribute significantly. Comparison with other insulating lay

A. Maeda, R. Inoue, H. Kitano, N. Motoyama

Nonlinear conduction (NLC) of the two-leg spin ladder, Sr$_{14-x}$Ca$_x$Cu$_{24}$O$_{41}$, was investigated for the $x$=0, 1 and 12 materials . Although insulating materials ($x$=0 and 1) exibited the NLC both in the ladder- and rung directions, the NLC in the ladder direction of the $x$=0-material was found to be very special. We considered this to be due t

Tsuyoshi Sekitani, Michio Naito, Noboru Miura

We present high-field magnetotransport properties of high-quality single-crystalline thin films of heavily underdoped nonsuperconducting (La,Ce)2CuO4, (Pr,Ce)2CuO4, and (Nd,Ce)2CuO4. All three materials show identical behavior. They are metallic at high temperatures and show an insulating upturn at low temperatures. The insulating upturn has a log T dependen

Yuh-Kae Lin, Yueh-Nan Chen, Der-San Chuu

The bound state energies of L-shaped or T-shaped quantum wires in inhomogeous magnetic fields are found to depend strongly on the asymmetric parameter $α=W_{2}/W_{1}$, i.e. the ratio of the arm widths. Two effects of magnetic field on bound state energies of the electron are obtained. One is the depletion effect which purges the electron out of the OQD syste

Akinori Awazu

The segregation and the phase inversion are investigated through a simple granular system which consists of only two inelastic hard spheres in a square box with an energy source. With the variation of the coefficient of restitution, the mass ratio between two spheres or the box size, we show that two types of segregated states and crossover between them are

Adilson E. Motter, Ying-Cheng Lai

We live in a modern world supported by large, complex networks. Examples range from financial markets to communication and transportation systems. In many realistic situations the flow of physical quantities in the network, as characterized by the loads on nodes, is important. We show that for such networks where loads can redistribute among the nodes, inten

Jinfeng Zhang, Rong Chen, Chao Tang, Jie Liang

Single domain proteins are thought to be tightly packed. The introduction of voids by mutations is often regarded as destabilizing. In this study we show that packing density for single domain proteins decreases with chain length. We find that the radius of gyration provides poor description of protein packing but the alpha contact number we introduce here c

K. C. Hall, K. Gundogdu, E. Altunkaya, W. H. Lau

We report an enhancement of the electron spin relaxation time (T1) in a (110) InAs/GaSb superlattice by more than an order of magnitude (25 times) relative to the corresponding (001) structure. The spin dynamics were measured using polarization sensitive pump probe techniques and a mid-infrared, subpicosecond PPLN OPO. Longer T1 times in (110) superlattices

Lawrence M. Widrow, Kathryn M. Perrett, Sherry H. Suyu

We present a suite of semi-analytic disk-bulge-halo models for the Andromeda galaxy (M31) which satisfy three fundamental conditions: (1) internal self-consistency; (2) consistency with observational data; and (3) stability of the disk against the formation of a central bar. The models are chosen from a set first constructed by Kuijken and Dubinski. We devel

F. Halzen

We introduce neutrino astronomy starting from the observational fact that Nature accelerates protons and photons to energies in excess of 10^{20} and 10^{13} eV, respectively. Although the discovery of cosmic rays dates back a century, we do not know how and where they are accelerated. We review the observations as well as speculations about the sources. Amo

B. F. Liu, S. Mineshige, K. Ohsuga

We investigate a corona coupled with underlying disk through magnetic field and radiation field, and present emergent spectra calculated from Monte Carlo simulations. The spectra are determined for given black-hole mass and accretion rate. We find two types of solutions corresponding for hard spectrum and soft spectrum. In the hard-spectrum solution, the acc

F. Bocchino, A. M. Bykov

We present \xmm observations of hard X-ray emission from the field of IC443, a supernova remnant interacting with a molecular cloud. The hard emission from the field is dominated by 12 isolated sources having 2--10 keV flux $\ga 10^{-14}$ $\enf$. Only a fraction of the sources are expected to be extragalactic or stars on statistical grounds, while the others

G. Perrin

I present in this paper a method to calibrate data obtained from optical and infrared interferometers. I show that correlated noises and errors need to be taken into account for a very good estimate of individual error bars but also when model fitting the data to derive meaningful model parameters whose accuracies are not overestimated. It is also shown that

Kumud Pandey, Udit Narain, N. K. Lohani

Using recent data for the photosphere-chromosphere region of the solar atmosphere the magnetic reconnection in tripolar geometry has been investigated through the procedure of Sturrock (1999). Particular attention has been given to the width of the reconnecting region, wave number of the rapidly growing tearing mode, island length scales, frequency of MHD fl

A. Blanchard

We are at a specific period of modern cosmology, during which the large increase of the amount of data leads to the idea that the determination of cosmological parameters has been achieved with a rather good precision. There is a large consensus around the so-called concordance model. Indeed this model does fit an impressive set of independent data: CMB $C_l

David Gittins, Cathie Clarke, Matthew Bate

We present a full hydrodynamical investigation of a system of self-contained, interacting gas `cloudlets'. Calculations are performed using SPH, and cloudlets are allowed to collide, dissipate kinetic energy, merge and undergo local gravitational collapse. The numerical feasibility of such a technique is explored, and the resolution requirements examined

Xiaohui Fan, Michael A. Strauss, Donald P. Schneider, Robert H. Becker

We present the discovery of three new quasars at z>6 in 1300 deg^2 of SDSS imaging data, J114816.64+525150.3 (z=6.43), J104845.05+463718.3 (z=6.23) and J163033.90+401209.6 (z=6.05). The first two objects have weak Ly alpha emission lines; their redshifts are determined from the positions of the Lyman break. They are only accurate to 0.05 and could be affecte

A. Boselli, G. Gavazzi, G. Sanvito

We present a multifrequency dataset for an optically-selected, volume-limited, complete sample of 118 late-type galaxies (>= S0a) in the Virgo cluster. The database includes UV, visible, near-IR, mid-IR, far-IR, radio continuum photometric data as well as spectroscopic data of Halpha, CO and HI lines, homogeneously reduced, obtained from our own observations

C. Burigana, R. Salvaterra

We analyse the implications of future observations of the CMB absolute temperature at centimeter and decimeter wavelengths, necessary to complement the accurate COBE/FIRAS data. Our analysis shows that forthcoming ground and balloon measures will allow a better understanding of free-free distortions but will not be able to significantly improve the constrain

Bjoern Malte Schaefer, Nobuyuki Kawai

The High-Energy Transient Explorer (HETE-2), launched in October 2000, is a satellite experiment dedicated to the study of gamma-ray bursts in a very wide energy range from soft X-ray to gamma-ray wavelengths. The intermediate X-ray range (2-30keV) is covered by the Wide-field X-ray Monitor WXM, a coded aperture imager. In this article, an algorithm for reco

Arthur Kosowsky

The cosmic microwave background is now fulfilling its promise of determining the basic cosmological parameters describing our Universe. Future study of the microwave background will mostly be directed towards two basic questions: a complete characterization of the initial perturbations, and probes of the nonlinear evolution of structure in the Universe. The

Didier Barret, Jean-Francois Olive, Tim Oosterbroek

4U1812-12 is a faint persistent and weakly variable neutron star X-ray binary. It was observed by BeppoSAX between April 20th and 21st, 2000 in a hard spectral state with a bolometric luminosity of ~2x10^36 ergs/s. Its broad band energy spectrum is characterized by the presence of a hard X-ray tail extending above ~100 keV. It can be represented as the sum o

L. Magrini, M. Perinotto, R. L. M. Corradi, A. Mampaso

Spectroscopic observations of 48 emission-line objects of M33 have been obtained with the multi-object, wide field, fibre spectrograph AF2/WYFFOS at the 4.2m WHT telescope (La Palma, Spain). Line intensities and logarithmic extinction, cbeta, are presented for 42 objects. Their location in the Sabbadin & D'Odorico diagnostic diagram (Halpha/[SII] vs Hlap

I. A. Maslov, S. A. Aust, V. V. Eremin, G. I. Zubenko

We suggest the all-sky survey at the International Space Station by four little wide-angle telescopes with polarization filters and CCD-arrays spread by several meters one from another. The video information processing will be carried out by real-time multiprocessor system on the board of the station. This experiment would allow to observe the sunlit space d

R. I. Hynes, D. Steeghs, J. Casares, P. A. Charles

We present outburst spectroscopy of GX339-4 which may reveal the motion of its elusive companion star. NIII lines exhibit sharp emission components moving over ~300 km/s in a single night. The most plausible interpretation of these components is that they are formed by irradiation of the companion star and the velocities indicate its orbital motion. We also

Andres Jordan, Michael J. West, Patrick Cote, Ronald O. Marzke

Deep imaging with WFPC2 and the Hubble Space Telescope has been used to search for a population of intergalactic globular clusters (GCs) belonging to Abell 1185, a richness I cluster at cz = 9800 km/s. The field is noteworthy in that it contains no bright galaxies and yet is centered on the peak of the cluster's X-ray surface brightess distribution. We d

Ilian T. Iliev, Evan Scannapieco, Hugo Martel, Paul R. Shapiro

Hydrogen atoms inside virialized minihalos generate a radiation background from redshifted 21-cm line emission whose angular fluctuations reflect clustering during before and during reionization. We have shown elsewhere that this emission may be detectable with the planned Low Frequency Array (LOFAR) and Square Kilometer Array (SKA) in a flat LambdaCDM. This

M. Gutperle, A. Strominger

The timelike boundary Liouville (TBL) conformal field theory consisting of a negative norm boson with an exponential boundary interaction is considered. TBL and its close cousin, a positive norm boson with a non-hermitian boundary interaction, arise in the description of the $c=1$ accumulation point of $c<1$ minimal models, as the worldsheet description of o

Glenn Barnich

Boundary charges in gauge theories (like the ADM mass in general relativity) can be understood as integrals of linear conserved n-2 forms of the free theory obtained by linearization around the background. These forms are associated one-to-one to reducibility parameters of this background (like the time-like Killing vector of Minkowski space-time). In this p

Ming Zhu, E. R. Seaquist, Nario Kuno

For the Antennae interacting galaxy pair, we have obtained high quality, fully sampled $^{12}$CO J=1-0, 2-1 and 3-2 maps of the regions surrounding the nuclei and the area of overlap between the two galaxies, with an angular resolution of 15" or 1.5 kpc. The $^{12}$CO J=1-0, 2-1, 3-2 emission all peak in the overlap region, which contains ~ 4 x 10^9 solar ma

A. L. Hungerford, C. L. Fryer, M. S. Warren

We present 3-dimensional SPH simulations of supernova explosions from 100 seconds to 1 year after core-bounce. By extending our modelling efforts to a 3-dimensional hydrodynamics treatment, we are able to investigate the effects of explosion asymmetries on mixing and gamma-ray line emergence in supernovae. A series of initial explosion conditions are impleme

T. Han, D. Rainwater, G. Valencia

We consider the possibility of studying novel particles at the TeV scale with enhanced couplings to the top quark via top quark pair production at the LHC and VLHC. In particular we discuss the case of neutral scalar and vector resonances associated with a strongly interacting electroweak symmetry breaking sector. We constrain the couplings of these resonanc

F. Maltoni, Z. Sullivan, S. Willenbrock

Higgs bosons with enhanced coupling to bottom quarks are copiously produced at hadron colliders via b\bar{b} -> h, where the initial b quarks reside in the proton sea. We revisit the calculation of the next-to-leading-order cross section for this process and argue that the appropriate factorization scale for the b distribution functions is approximately m_h/

Harald Fritzsch, Yu-Feng Zhou

The inclusive and exclusive B decays into the eta&#39; meson plus others are investigated in a model based on the QCD anomaly. The invariant mass distribution is discussed. The constraint of the effective coupling is obtained from the data of the exclusive decay modes. The branching ratio of J/psi -> eta&#39;eta gamma is predicted to be as large as 5.4*10^{-

Hal Tasaki

It is believed that strong ferromagnetic orders in some solids are generated by subtle interplay between quantum many-body effects and spin-independent Coulomb interactions between electrons. Here we describe our rigorous and constructive approach to ferromagnetism in the Hubbard model, which is a standard idealized model for strongly interacting electrons i

Frank C. van den Bosch, H. J. Mo, Xiaohu Yang

We use the observed abundance and clustering of galaxies from the 2dFGRS to determine the matter density Omega_m and the linear amplitude of mass fluctuations sigma_8. We use a method based on the conditional luminosity function, which allows straightforward computation of the luminosity dependent bias of galaxies. In addition, it allows the inclusion of con

Roberto P. Mignani, Werner Becker

About 100 millisecond (ms) pulsars have been identified in the Galaxy, and only ~10% of them are solitary, i.e. without a binary companion. Nothing is known on the optical emission properties of millisecond pulsars. Observations of solitary millisecond pulsars are the only way to detect their faint optical radiation, otherwise buried by the brighter white dw

J. Gracia, J. Peitz, Ch. Keller, M. Camenzind

We consider time-dependent models for rotating accretion flows onto black holes, where a transition takes place from an outer cooling-dominated disc to a radiatively inefficient flow in the inner region. In order to allow for a transition of this type we solve the energy equation, both, for the gas and for the radiation field, including a radiative cooling f

Enrico Carlon, Péter Lajkó, Heiko Rieger, Ferenc Iglói

Extensive DMRG calculations for spin S=1/2 and S=3/2 disordered antiferromagnetic Heisenberg chains show a rather distinct behavior in the two cases. While at sufficiently strong disorder both systems are in a random singlet phase, we show that weak disorder is an irrelevant perturbation for the S=3/2 chain, contrary to what expected from a naive application

Chong-Sun Chu, Valentin V. Khoze

The PP-wave/SYM proposal in its original form emphasizes a duality relation between the masses of the string states and the anomalous dimensions of the corresponding BMN operators in gauge theory, the mass--dimension type duality. In this paper, we give evidence in favour of another duality relation of the vertex--correlator type, which relates the coefficie

Yuji Sugawara

We study the thermal partition function of superstring on the pp-wave background with the circle compactification along a transverse direction. We calculate it in the two ways: the operator formalism and the path-integral calculation. The former gives the finite result with no subtlety of the Wick rotation, which only contains the contributions of physical s

Jean Alexandre

Starting from N=1 scalar and vector supermultiplets in 2+1 dimensions, we construct superfields which constitute Lagrangians invariant under N=2 supersymmetries. We first recover the N=2 supersymmetric Abelian-Higgs model and then the N=2 pure super Yang-Mills model. The conditions for this elevation are consistent with previous results found by other author

A. Borowiec, J. Lukierski, V. N. Tolstoy

The twisting function describing a nonstandard (super-Jordanian) quantum deformation of $osp(1|2)$ is given in explicite closed form. The quantum coproducts and universal R-matrix are presented. The non-uniqueness of the twisting function as well as two real forms of the deformed $osp(1|2)$ superalgebras are considered. One real quantum $osp(1|2)$ superalgeb

A. I. Farinas Sanchez, R. Paredes V., B. Berche

The nematic-to-isotropic orientational phase transition, or equivalently the $RP^2$ model, is considered in two dimensions and the question of the nature of the phase transition is addressed. Using powerful conformal techniques adapted to the investigation of critical properties of two-dimensional scale-invariant systems, we report strong evidences for a tra

Gerald B. Cleaver, Alon E. Faraggi, Sander Nooij

The orbifold GUT doublet-triplet splitting mechanism was discussed in 1994 in the framework of the NAHE-based free fermionic models in which the SO(10) GUT symmetry is broken to SO(6) X SO(4), SU(3) X SU(2) X U(1)^2, or SU(3) X U(1) X SU(2)^2. In this paper we study NAHE-based free fermionic models in which the SO(10) symmetry is broken at the string level t

C. Duval, A. M. El Gradechi, V. Ovsienko

We consider the Poisson algebra S(M) of smooth functions on T^*M which are fiberwise polynomial. In the case where M is locally projectively (resp. conformally) flat, we seek the star-products on S(M) which are SL(n+1,R) (resp. SO(p+1,q+1))-invariant. We prove the existence of such star-products using the projectively (resp. conformally) equivariant quantiza

M. P. A. Jones, C. J. Vale, D. Sahagun, B. V. Hall

We describe an experiment in which Bose-Einstein condensates and cold atom clouds are held by a microscopic magnetic trap near a room temperature metal wire 500 $μ$m in diameter. The ensemble of atoms breaks into fragments when it is brought close to the ceramic-coated aluminum surface of the wire, showing that fragmentation is not peculiar to copper surface

B. Chandrasekhar, Prasanta K. Panigrahi

The one-loop contribution to vacuum polarization is calculated for the adjoint fermions in three dimensional noncommutative spaces, both at zero and finite temperature. At zero temperature, we confirm a previously found result for the parity odd part and subsequently analyze the even parity part, which exhibits UV/IR mixing. We discuss in detail, two regimes

Ali Kaya, Tonguc Rador

We present a cosmological model in 1+m+p dimensions, where in m-dimensional space there are uniformly distributed p-branes wrapping over the extra p-dimensions. We find that during cosmological evolution m-dimensional space expands with the exact power-law corresponding to pressureless matter while the extra p-dimensions contract. Adding matter, we also obta

G. Bimonte, R. Musto

We critically analyze the problem of formulating duality between fringe visibility and which-way information, in multibeam interference experiments. We show that the traditional notion of visibility is incompatible with any intuitive idea of complementarity, but for the two-beam case. We derive a number of new inequalities, not present in the two-beam case,

Miguel A. Munoz, Romualdo Pastor-Satorras

We propose a general Langevin equation describing the universal properties of synchronization transitions in extended systems. By means of theoretical arguments and numerical simulations we show that the proposed equation exhibits, depending on parameter values, either: i) a continuous transition in the bounded Kardar-Parisi-Zhang universality class, with a

Jozsef Zsigrai

A generalization of the notion of ellipsoids to curved Riemannian spaces is given and the possibility to use it in describing the shapes of rotating bodies in general relativity is examined. As an illustrative example, stationary, axisymmetric perfect-fluid spacetimes with a so-called confocal inside ellipsoidal symmetry are investigated in detail under the

K. Kodaira, Y. Taniguchi, N. Kashikawa, N. Kaifu

We have performed a deep optical imaging survey using a narrowband filter ($NB921$) centered at $λ=$ 9196 Å~ together with $i^\prime$ and $z^\prime$ broadband filters covering an 814 arcmin$^2$ area of the Subaru Deep Field. We obtained a sample of 73 strong $NB921$-excess objects based on the following two color criteria; $z^\prime - NB921 > 1$ and $i^\prim

Dorit Aharonov, Amnon Ta-Shma

The design of new quantum algorithms has proven to be an extremely difficult task. This paper considers a different approach to the problem, by studying the problem of &#39;quantum state generation&#39;. This approach provides intriguing links between many different areas: quantum computation, adiabatic evolution, analysis of spectral gaps and groundstates o

F. Bezrukov, D. Levkov

A semiclassical method for the calculation of tunneling exponent in systems with many degrees of freedom is developed. We find that corresponding classical solution as function of energy form several branches joint by bifurcation points. A regularization technique is proposed, which enables one to choose physically relevant branches of solutions everywhere i

C. Farina, F. C. Santos, A. C. Tort

We show that in order to account for the repulsive Casimir effect in the parallel plate geometry in terms of the quantum version of the Lorentz force, virtual surface densities of magnetic charges and currents must be introduced. The quantum version of the Lorentz force expressed in terms of the correlators of the electric and magnetic fields for planar geom

S. R. D. French, D. P. Rickles

\noindent In our contribution to this volume we deal with \emph{discrete} symmetries: these are symmetries based upon groups with a discrete set of elements (generally a set of elements that can be enumerated by the positive integers). In physics we find that discrete symmetries frequently arise as `internal&#39;, non-spacetime symmetries. Permutation symmet

Jonathan A. Jones

While Nuclear Magnetic Resonance (NMR) techniques are unlikely to lead to a large scale quantum computer they are well suited to investigating basic phenomena and developing new techniques. Indeed it is likely that many existing NMR techniques will find uses in quantum information processing. Here I describe how the composite rotation (composite pulse) metho

John Ashmead

The space quantization induced by a Stern-Gerlach experiment is normally explained by invoking the ``collapse of the wave function.&#39;&#39; This is a rather mysterious idea; it would be better to explain the Stern-Gerlach results without using it. We re-analyze the Stern-Gerlach experiment using path integrals. We find if we model explicitly the finite wid

A. Sibirtsev, K. Tsushima, S. Krewald

Systematic analysis of available data for $ω$-meson photoproduction is given in frame of Regge theory. At photon energies above 20 GeV the $γ{+}p{\to}ω{+}p$ reaction is entirely dominated by Pomeron exchange. However, it was found that Pomeron exchange model can not reproduce the $γ{+}p{\to}ρ{+}p$ and $γ{+}p{\to}ω{+}p$ data at high energies simultaneously wi

M. M. Giannini

The formulation of the Gerasimov-Drell-Hearn sum rule is revisited, showing its connection with other sum rules occurring in electron scattering and discussing the problem of its saturation, both from the theoretical and experimental point of v iew. The generalisation to other nuclear targets is also reported.

M. M. Giannini, E. Santopinto, A. Vassallo

We report on the recent results of the hypercentral constituent quark model. The model contains a spin independent three-quark interaction which is inspired by QCD lattice calculations and reproduces the average energy values of the SU(6) multiplets. The splittings are obtained with a residual generalized SU(6)-breaking interaction, including an isospin depe

Jörn Davidsen, Raymond Kapral

We show that defect-mediated turbulence can exist in media where the underlying local dynamics is deterministically chaotic. While many of the characteristics of defect-mediated turbulence, such as the exponential decay of correlations and a squared Poissonian distribution for the number of defects, are identical to those seen in oscillatory media, the fluct

Vered Rom-Kedar

A family of maps or flows depending on a parameter $ν$ which varies in an interval, spans a certain property if along the interval this property depends continuously on the parameter and achieves some asymptotic values along it. We consider families of periodically forced Hamiltonian systems for which the appropriately scaled frequency $\barω(ν)$ is spanned,

T. A. Larsson

For sp(n+2) and each exceptional Lie algebra a realization of depth 2 preserving the spaces spanned by a contact one-form and a bilinear form is given. For e_7 and e_6 a realization of depth 1 preserving a lightcone and the space spanned by a bilinear form is also presented. This makes the origin of the exceptions clear.

Michael Aizenman, Alexander Elgart, Jeffrey H. Schenker

This paper has been withdrawn by the authors, due to an error in the proof of Lemma 3.1.

Leonid G. Fel, Konstantin M. Khanin

We study the effective conductivity $σ_e$ for a random wire problem on the $d$-dimensional cubic lattice ${\mathbb Z}^d, d \geq 2$ in the case when random conductivities on bonds are independent identically distributed random variables. We give exact expressions for the expansion of the effective conductivity in terms of the moments of the disorder parameter

A. Eremenko, D. Novikov

Suppose that Fourier transform of a function f is zero on the interval [-a,a]. We prove that the lower density of sign changes of f is at least a/pi, provided that f is a locally integrable temperate distribution in the sense of Beurling, with non-quasianalytic weight. We construct an example showing that the last condition cannot be omitted.

Murray Elder, Jon McCammond, John Meier

Thurston conjectured that a closed triangulated 3-manifold in which every edge has degree 5 or 6, and no two edges of degree 5 lie in a common 2-cell, has word-hyperbolic fundamental group. We establish Thurston&#39;s conjecture by proving that such a manifold admits a piecewise Euclidean metric of non-positive curvature and the universal cover contains no i

Murray Elder, Jon McCammond

In this article we give an explicit algorithm which will determine, in a discrete and computable way, whether a finite piecewise Euclidean complex is non-positively curved. In particular, given such a complex we show how to define a boolean combination of polynomial equations and inequalities in real variables, i.e. a real semi-algebraic set, which is empty

Sostenes Lins, Valdenberg Silva

If a graph $G_M$ is embedded into a closed surface $S$ such that $S \backslash G_M$ is a collection of disjoint open discs, then $M=(G_M,S)$ is called a {\em map}. A {\em zigzag} in a map $M$ is a closed path which alternates choosing, at each star of a vertex, the leftmost and the rightmost possibilities for its next edge. If a map has a single zigzag we sh

C. R. E. Raja

We prove that a hypergroup admitting a countable basis and an invariant Haar measure has normed convergence property if and only if it is compact.