March 2000 arXiv papers — page 25

Wladyslaw A. Majewski

Several problems concerning separable states are clarified on the basis of Choi's scheme and old Kadison and Tomiyama results. Moreover, we generalize Terhal's construction of positive maps.

Alberto Alvarez, Emilio Hernandez-Garcia, Joaquin Tintore

Small-scale oceanic motions, in combination with bottom topography, induce mean large-scale along-isobaths flows. The direction of these mean flows is usually found to be anticyclonic (cyclonic) over bumps (depressions). Here we employ a quasigeostrophic model to show that the current direction of these topographically induced large-scale flows can be revers

Calin Galeriu

This paper presents an intuitive, geometrical derivation of the relativistic addition of velocities, and of the electromagnetic interaction between two uniformly moving charged particles, based on 2 spatial + 1 temporal dimensional Minkowski diagrams. We calculate the relativistic addition of velocities by projecting the world-line of the particle on the spa

Tova Feldmann, Ronnie Kosloff

The performance in finite time of a discrete heat engine with internal friction is analyzed. The working fluid of the engine is composed of an ensemble of noninteracting two level systems. External work is applied by changing the external field and thus the internal energy levels. The friction induces a minimal cycle time. The power output of the engine is o

Nancy L. Garcia, Jose L. Palacios

Using the electric and coupling approaches, we derive a series of results concerning the mixing times for the stratified random walk on the d-cube, inspired in the results of Chung and Graham (1997) Stratified random walks on the n-cube.

A. Bianconi, G. Bonomi, M. P. Bussa, E. Lodi Rizzini

We show that the quantum uncertainty principle puts some limits on the effectiveness of the antinucleon-nucleus annihilation at very low energies. This is caused by the fact that the realization a very effective short-distance reaction process implies information on the relative distance of the reacting particles. Some quantitative predictions are possible o

Vyacheslav V. Stepanov, Gerhard Muller

For a two-spin model which is (classically) integrable on a five-dimensional hypersurface in six-dimensional parameter space and for which level degeneracies occur exclusively (with one known exception) on four-dimensional manifolds embedded in the integrability hypersurface, we investigate the relations between symmetry, integrability, and the assignment of

Joshua A. Tempkin

Lyapunov exponents can be difficult to determine from experimental data. In particular, when using embedding theory to build chaotic attractors in a reconstruction space, extra "spurious" Lyapunov exponents arise that are not Lyapunov exponents of the original system. By studying the local linearization matrices that are key to the Eckmann-Ruelle met

P. G. Kevrekidis, M. I. Weinstein

In this paper we consider two models of soliton dynamics (the sine Gordon and the ϕ^4 equations) on a 1-dimensional lattice. We are interested in particular in the behavior of their kink-like solutions inside the Peierls- Nabarro barrier and its variation as a function of the discreteness parameter. We find explicitly the asymptotic states of the system for

Matthias W. Reinsch

Two-, three- and four-dimensional representations of Penrose tilings of the plane are described. The vertices that occur in these representations lie on lattices. Symmetries and methods of visualizing these representations are discussed. The question of efficiently storing the information necessary to reconstruct a tiling is addressed.

Elliott H. Lieb, Heinz Siedentop

We consider the relativistic electron-positron field interacting with itself via the Coulomb potential defined with the physically motivated, positive, density-density quartic interaction. The more usual normal-ordered Hamiltonian differs from the bare Hamiltonian by a quadratic term and, by choosing the normal ordering in a suitable, self-consistent manner,

Paolo Cascini

We define a new class of holomorphic (n-1)-bundles on the n-dimensional complex projective space, that contains the Tango bundles and their stable Horrock's pull-backs; we show that these bundles are invariant under small deformations and that their isomorphism classes correspond to smooth points of moduli spaces.

Ivan Cherednik

We use one-dimensional double affine Hecke algebras to introduce q-counterparts of the Gauss integrals and new types of Gauss-Selberg sums at roots of unity.

Joseph Le Potier, Alexander Tikhomirov

Let ${\rm F}$ be a rank-2 semi-stable sheaf on the projective plane, with Chern classes $c_{1}=0,c_{2}=n$. The curve $β_{\rm F}$ of jumping lines of ${\rm F}$, in the dual projective plane, has degree $n$. Let ${\rm M}_{n}$ be the moduli space of equivalence classes of semi-stables sheaves of rank 2 and Chern classes $(0,n)$ on the projective plane and ${\ca

Sergey Arkhipov

In this note we give a definition of semiinfinite cohomology for Tate Lie algebras using the language of Differential Graded Lie algebroids with Curvature (CDG Lie algebroids).

Y Safarov

The main aim of the paper is to present a general version of the Fourier Tauberian theorem for monotone functions. This result, together with Berezin's inequality, allows us to obtain a refined version the Li-Yau estimate for the counting function of the Dirichlet Laplacian which implies the Li-Yau estimate itself and, at the same time, the asymptotic re

Antoine Chambert-Loir, Yuri Tschinkel

This paper is devoted to the estimation of the number of points of bounded height on fibrations in toric varieties over algebraic varieties, generalizing previous work by Strauch and the second author. Under reasonable hypotheses on ``Arakelov L-functions'' of the base, we show how to deduce a good estimate for the open subset of the total space of t

David Kazhdan, Alexander Polishchuk

This is a sequel to math.AG/0003009. Here we study identities for the Fourier transform of "elementary functions" over finite field containing "exponents" of monomial rational functions. It turns out that these identities are governed by monomial identities between Gauss sums. We show that similar to the case of complex numbers such identitie

P. Marios Petropoulos

String theory on curved backgrounds has received much attention on account of both its own interest, and of its relation with gauge theories. Despite the progress made in various directions, several quite elementary questions remain unanswered, in particular in the very simple case of three-dimensional anti-de Sitter space. I will very briefly review these p

Hugo Garcia-Compean, Oscar Loaiza-Brito

In these lectures we review the basic ideas of perturbative and non-perturbative string theory. On the non-perturbative side we give an introduction to D-branes and string duality. The elementary concepts of non-BPS branes and noncommutative gauge theories are also discussed.

S. W. Hawking, Thomas Hertog, Neil Turok

We compute the spectrum of primordial gravitational wave perturbations in open de Sitter spacetime. The background spacetime is taken to be the continuation of an O(5) symmetric instanton saddle point of the Euclidean no boundary path integral. The two-point tensor fluctuations are computed directly from the Euclidean path integral. The Euclidean correlator

J. M. Speight

Kink dynamics in spatially discrete nonlinear Klein-Gordon systems is considered. For special choices of the substrate potential, such systems support continuous translation orbits of static kinks with no (classical) Peierls-Nabarro barrier. It is shown that these kinks experience, nevertheless, a lattice-periodic confining potential, due to purely quantum e

Markus H. Thoma

Following an argument by Kirzhnits we rederive an exact expression for the energy loss of a fast charged particle in a relativistic plasma using the quantum field theoretical language. We compare this result to perturbative calculations of the collisional energy loss of an energetic electron or muon in an electron-positron plasma and of an energetic parton i

Wolfgang Jaus

If the CKM matrix element $V_{ud}$, that can be derived from superallowed nuclear decays, neutron decay and pion beta decay, is used for a precision test of the unitarity of the CKM matrix, the combination of the present world data seems to indicate a small violation of the unitarity condition for the first row. While an accurate calculation of the radiative

Paolo Lipari

The atmospheric neutrino fluxes observed by underground detectors are not symmetric for rotations around the vertical axis. The flux is largest (smallest) for the nu's traveling toward east (west). This asymmetry is the result of the effects of the geomagnetic field on the primary cosmic rays and on their showers. The size of the asymmetry is to a good a

T. Reisz, H. J. Rothe

Lattice gauge theories with Wilson fermions break chiral symmetry. In the U(1) axial vector current this manifests itself in the anomaly. On the other hand it is generally expected that the axial vector flavour mixing current is non-anomalous. We give a short, but strict proof of this to all orders of perturbation theory, and show that chiral symmetry restau

D. Bakari, H. Dekhissi, J. Derkaoui, G. Giacomelli

After a short review of Q-balls properties, in this paper we discuss their interaction with matter, and their energy losses in the earth, for a large range of velocities. These calculations are used to compute the fractional angular acceptance of a detector located at Gran Sasso Laboratory. Furthermore we computed the light yield in liquid scintillators, the

B. J. Carr

We discuss spherically symmetric perfect fluid solutions of Einstein's equations which have equation of state ($p=αμ$) and which are self-similar in the sense that all dimensionless variables depend only upon $z\equiv r/t$. For each value of $α$, such solutions are described by two parameters and have now been completely classified. There is a 1-paramete

Fang-Pei Chen

The debate on conservation laws in general relativity eighty years ago is reviewed and restudied. The physical meaning of the identities in the conservation laws for matter plus gravitational field is reexamined and new interpretations for gravitational wave are given. The conclusions of these studies are distinct from the prevalent views, it can be demonstr

B. J. Carr

We classify all spherically symmetric dust solutions of Einstein's equations which are self-similar in the sense that all dimensionless variables depend only upon $z\equiv r/t$. We show that the equations can be reduced to a special case of the general perfect fluid models with equation of state $p=αμ$. The most general dust solution can be written down

Janusz Garecki

In this paper we present our point of view on correct physical interpretation of the Bel-Robinson tensor within the framework of the standard General Relativity ({\bf GR}), i.e., within the framework of the {\bf GR} without supplementary elements like arbitrary vector field, distinguished tetrads field or second metric. We show that this tensor arises as a c

S. Manoff

Different (not only by sign) affine connections are introduced for contravariant and covariant tensor fields over a differentiable manifold by means of a non-canonical contraction operator, defining the notion dual bases and commuting with the covariant and with the Lie-differential operator. Classification of the linear transports on the basis of the connec

L. Richterek, J. Novotny, J. Horsky

The method based on the Horsky-Mitskievitch conjecture is applied to the Levi-Civita vacuum metric. It is shown, that every Killing vector is connected with a particular class of Einstein-Maxwell fields and each of those classes is found explicitly. Some of obtained classes are quite new. Radial geodesic motion in constructed space-times is discussed and gra

Reinaldo Gleiser, Gaurav Khanna, Richard Price, Jorge Pullin

Using approximate techniques we study the final moments of the collision of two (individually non-spinnning) black holes which inspiral into each other. The approximation is based on treating the whole space-time as a single distorted black hole. We obtain estimates for the radiated energy, angular momentum and waveforms for the gravitational waves produced

Hoshi Mistry, Prasan Roy, Krithi Ramamritham, S. Sudarshan

Because the presence of views enhances query performance, materialized views are increasingly being supported by commercial database/data warehouse systems. Whenever the data warehouse is updated, the materialized views must also be updated. However, whereas the amount of data entering a warehouse, the query loads, and the need to obtain up-to-date responses

Prasan Roy, Krithi Ramamritham, S. Seshadri, Pradeep Shenoy

In data warehouse and data mart systems, queries often take a long time to execute due to their complex nature. Query response times can be greatly improved by caching final/intermediate results of previous queries, and using them to answer later queries. In this paper we describe a caching system called Exchequer which incorporates several novel features in

Martin Staedele, Richard M. Martin

We study metallization of molecular hydrogen under pressure using exact exchange (EXX) Kohn-Sham density-functional theory in order to avoid well-known underestimates of band gaps associated with standard local-density or generalized-gradient approximations. Compared with the standard methods, the EXX approach leads to considerably (1 - 2 eV) higher gaps and

Thorsten Emig, Mehran Kardar

We examine probability distributions for thermodynamic quantities in finite-sized random systems close to criticality. Guided by available exact results, a general ansatz is proposed for replicated free energies, which leads to scaling forms for cumulants of various macroscopic observables. For the specific example of a planar flux line lattice in a two dime

Eduardo C. Marino, Marcello B. Silva Neto

We present an analytic expression for the finite temperature sublattice magnetization, at the Josephson scale, in two dimensional quantum antiferromagnets with short range Néel order. Our expression is able to reproduce both the qualitative behaviour of the phase diagram $M(T)/M_{0}$ and the experimental values of the Néel temperature $T_{N}$ for either dope

Jongsoon Park, Vladimir Privman

Formation of monodispersed colloidal particles is a complex process: nuclei, produced rapidly in a supersaturated solution, grow to nanosize primary particles, which then aggregate (coagulate) to form much larger final colloids. This paper reviews a kinetic model that explains the formation of dispersions of narrow size distribution in such processes. Numeri

Paola Gallo

Molecular dynamics simulations of SPC/E water confined in a Silica pore are presented. The simulations have been performed at different hydration levels and temperatures to study the single-particle dynamics. Due to the confinement and to the presence of a hydrophilic surface, the dynamic behaviour of the liquid appears to be strongly dependent on the hydrat

Nicholas Angelo Gross, M. Ignatiev, Bulbul Chakraborty

Many systems where interactions compete with each other or with constraints are well described by a model first introduced by Brazovskii. Such systems include block copolymers, alloys with modulated phases, Rayleigh-Benard Cells and type-I superconductors. The hallmark of this model is that the fluctuation spectrum is isotropic and has a minimum at a nonzero

M. Bernaschi, L. Grilli, L. Marangio, S. Succi

We present cross and time series analysis of price fluctuations in the U.S. Treasury fixed income market. By means of techniques borrowed from statistical physics we show that the correlation among bonds depends strongly on the maturity and bonds' price increments do not fulfill the random walk hyphoteses.

David Guery-Odelin

Using the average method, we derive a close set of linear equations that describes the spinning up of an harmonically trapped gas by a rotating anisotropy. We find explicit expressions for the needed to transfer angular momentum as well as the decay time induced by a static residual anisotropy. These different time scales are compared with the measured nucle

D. Reguera, J. M. Rubí, A. Pérez-Madrid

We report a new phenomenon occurring in field-responsive suspensions: shear-induced anomalous stresses. Competition between a rotating field and a shear flow originates a multiplicity of anomalous stress behaviors in suspensions of bounded dimers constituted by induced dipoles. The great variety of stress regimes includes non-monotonous behaviors, multi-reso

O. A. Tkachenko, V. A. Tkachenko, D. G. Baksheyev, C. -T. Liang

Low-temperature transport properties of a lateral quantum dot formed by overlaying finger gates in a clean one-dimensional channel are investigated. Continuous and periodic oscillations superimposed upon ballistic conductance steps are observed, when the conductance G of the dot changes within a wide range 0<G<6e^2/h. Calculations of the electrostatics confi

M. Crescimanno, A. S. Landsberg

Recently, Schmidt and Schnack (cond-mat/9803151, cond-mat/9810036), following earlier references, reiterate that the specific heat of N non-interacting bosons in a one-dimensional harmonic well equals that of N fermions in the same potential. We show that this peculiar relationship between specific heats results from a more dramatic equivalence between bose

Dima Mozyrsky, Vladimir Privman

We present an exact derivation of a process in which a microscopic measured system interacts with heat-bath and pointer modes of a measuring device, via a coupling involving a general Hermitian operator $Λ$ of the system. In the limit of strong interaction with these modes, over a small time interval, we derive the exact effective many-body density matrix of

A. D. Gromko, Y. -D. Chuang, D. S. Dessau, K. Nakamura

We present new results from Angle-Resolved Photoemission experiments (ARPES) on overdoped Bi_{2}Sr_{2}CaCu_{2}O_{8+d} (BSCCO) crystals. With greatly improved energy and momentum resolution, we clearly identify the existence of electron-like portions of the Fermi Surface (FS) near \bar{M} at hν=33eV. This is consistent with previously reported data and is rob

Gibor Basri, Subhanjoy Mohanty, France Allard, Peter H. Hauschildt

We present Keck HIRES spectra of 6 late-M dwarfs and 11 L dwarfs. Our goal is to assign effective temperatures to the objects using detailed atmospheric models and fine analysis of the alkali resonance absorption lines of CsI and RbI. These yield mutually consistent results (+-150 K) when we use ``cleared-dust&#39;&#39; models, which account for the removal

S. Molinari, A. Noriega-Crespo, C. Ceccarelli, B. Nisini

We have used the two spectrometers on the Infrared Space Observatory to observe the HH 7-11 flow, its red-shifted counterpart, and the candidate exciting source SVS 13, in the star formation region NGC 1333. We detect atomic ([OI]63um and 145um, [SiII]34.8um, [CII]158um) and molecular (H_2, CO, H_2O) lines at various positions along the bipolar flow. Most of

Yasushi Ikebe, Karen Leighly, Yasuo Tanaka, Takao Nakagawa

The wide-band energy spectrum of NGC6240 over the range 0.5-200keV is investigated using the RXTE and ASCA data. The RXTE data provide the spectrum beyond the ASCA range (0.5-10 keV) with significant detection of signals up to 20keV and the upper limits above 20keV. The spectrum above 10keV is found to be very flat. A strong iron-K emission line discovered i

S. H. Lubow, G. I. Ogilvie

We consider the dynamics of a protostellar disk surrounding a star in a circular-orbit binary system. Our aim is to determine whether, if the disk is initially tilted with respect to the plane of the binary orbit, the inclination of the system will increase or decrease with time. The problem is formulated in the binary frame in which the tidal potential of t

B. J. Carr, C. A. Goymer

We discuss the various ways in which primordial black holes may have formed in the early Universe and how the effects of such black holes can be used to place constraints on cosmological models. We show that such constraints may be severely modified if the value of the gravitational &#34;constant&#34; G varies with cosmological epoch, a possibility which ari

E. Parizot, L. Drury

Recently models based on the acceleration of metal-rich material inside superbubbles have been proposed to account for the observed abundances of Be and B in metal-poor halo stars. We analyse some of the implications of these models for the distribution of the Be/O and B/O abundance ratios. In particular, we discuss the possible scatter in the data and argue

Christian Hettlage, Karl Mannheim

Key diagnostics of non-thermal plasmas, such as the position of the synchrotron self-absorption turnover or the Faraday rotation optical depth, depend crucially on the unobserved low-energy electron spectrum. We investigate the effect of physically viable assumptions about the low-energy electron spectrum on the magnetic field strength as inferred from the p

M. Gliozzi, Th. Boller, W. Brinkmann, W. N. Brandt

We present the results of ROSAT High Resolution Imager (HRI) observations and the survey data of the radio-loud Narrow-Line Seyfert 1 galaxy (NLS1) PKS 0558--504. We find strong and persistent X-ray variability on both short and medium time-scales. The most extreme amplitude variations require a radiative efficiency exceeding the theoretical maximum for a Sc

S. Randich, L. Pasquini, R. Pallavicini

We present Li abundances for 14 solar-type stars in the intermediate age (~ 2 Gyr) clusters IC 4651 and NGC 3680. The log n(Li) vs. effective temperature distributions are compared with those of the similar age cluster NGC 752, of the younger Hyades (600 Myr) and of the older M 67 (4.5 Gyr) and NGC 188 (6-7 Gyr) clusters. Neither IC 4651 nor NGC 3680 show th

P. Giommi, G. Ghisellini, P. Padovani, G. Tagliaferri

BL Lacertae objects are extreme extragalactic sources characterized by the emission of strong and rapidly variable nonthermal radiation over the entire electromagnetic spectrum. Synchrotron emission followed by inverse Compton scattering in a relativistic beaming scenario is generally thought to be the mechanism powering these objects. ...

M. Dahlem, A. N. Parmar, T. Oosterbroek, A. Orr

Spectral fits to X-ray data from both NGC 253 and M 82 provide ambiguous results. The so-called ``best fit&#39;&#39; results depend on the instrument with which the data were obtained and obviously on the choice of spectral model composition. We show that different spectral models can be fit equally well to BeppoSAX data of both galaxies. Metallicities are u

F. Tavecchio, L. Maraschi, G. Ghisellini, A. Celotti

We present $Beppo$SAX observations of the $γ$-ray emitting quasars 0836+710, 1510-089 and 2230+114. All the objects have been detected in the PDS up to 100 keV and have extremely flat power-law spectra above 2 keV ($α_x$=0.3--0.5). 0836+710 shows absorption higher than the galactic value and marginal evidence for the presence of the redshifted 6.4 keV Iron l

Jeremy Goodman

It seems necessary to suppress, at least partially, the formation of structure on subgalactic scales. As an alternative to warm or collisional dark matter, I postulate a condensate of massive bosons interacting via a repulsive interparticle potential, plus gravity. This leads to a minimum lengthscale for bound objects, and to superfluidity. Galactic dynamics

Shin Mineshige, Toshihiro Kawaguchi, Mitsuru Takeuchi, Kiyoshi Hayashida

Narrow-line Seyfert 1 galaxies (NLS1s) exhibit extreme soft X-ray excess and large variability. We argue that both features can be basically accounted for by the slim disk model. We assume that a central black-hole mass in NLS1 is relatively small, $M \sim 10^{5-7}M_\odot$, and that a disk shines nearly at the Eddington luminosity, $L_{\rm E}$. Then, the dis

J. M. Wrobel, J. R. Herrnstein

Four quiescent elliptical galaxies were imaged with the NRAO VLA at 8.5 GHz. Within the context of canonical advection-dominated accretion flows (ADAFs), these VLA images plus published black hole masses constrain the accretion rates to be $ <1.6\times10^{-4}$, $ <3.6\times10^{-4}$, $\le7.8\times10^{-4}$, and $\le7.4\times10^{-4}$ of the Eddington rates. The

A. Udalski, K. Zebrun, M. Szymanski, M. Kubiak

We present the Catalog of microlensing events detected toward the Galactic bulge in three observing seasons, 1997--1999, during the OGLE-II microlensing survey. The search for microlensing events was performed using a database of about 4*10^9 photometric measurements of about 20.5 million stars from the Galactic bulge. The Catalog comprises 214 cases of micr

T. Lasserre, EROS Collaboration

We combine new results from the search for microlensing towards the Large Magellanic Cloud (LMC) by EROS2 (Experience de Recherche d&#39;Objets Sombres) with limits previously reported by EROS1 and EROS2 towards both Magellanic Clouds. The derived upper limit on the abundance of stellar mass MACHOs rules out such objects as an important component of the Gala

David M. Wittman, J. Anthony Tyson, David Kirkman, Ian Dell&#39;Antonio

Most of the matter in the universe is not luminous and can be observed directly only through its gravitational effect. An emerging technique called weak gravitational lensing uses background galaxies to reveal the foreground dark matter distribution on large scales. Light from very distant galaxies travels to us through many intervening overdensities which g

T. Nagao, S. M. Nishigaki

The zero momentum sectors in effective theories of QCD coupled to pseudoreal (two colors) and real (adjoint) quarks have alternative descriptions in terms of chiral orthogonal and symplectic ensembles of random matrices. Using this correspondence, we compute correlation functions of Dirac operator eigenvalues within a sector with an arbitrary topological cha

Cesar Gomez, Bert Janssen, Pedro J. Silva

A brane world in the presence of a bulk black hole is constructed. The brane tension is fine tuned in terms of the black hole mass and cosmological constant. Gravitational perturbations localized on the brane world are discussed.

A. A. Sousa, J. W. Maluf

We consider the most general class of teleparallel gravitational {}{}theories quadratic in the torsion tensor, in three space-time dimensions, and carry out a detailed investigation of its Hamiltonian formulation in Schwinger&#39;s time gauge. This general class is given by a family of three-parameter theories. A consistent implementation of the Legendre tra

Maxim Pospelov, Tonnis ter Veldhuis

We use the results of direct and indirect searches for weakly interacting massive particles (WIMPs) to obtain bounds on various electro-magnetic form factors of WIMPs. The limits on the recoil signal in underground dark matter detection experiments, with standard assumptions about the density and r.m.s. velocity of WIMPs in the halo, can be translated into t

Peter W. Shor, John Preskill

We prove the security of the 1984 protocol of Bennett and Brassard (BB84) for quantum key distribution. We first give a key distribution protocol based on entanglement purification, which can be proven secure using methods from Lo and Chau&#39;s proof of security for a similar protocol. We then show that the security of this protocol implies the security of

F Loran, A Shirzad

We introduce &#34;chain by chain&#34; method for constructing the constraint structure of a system possessing both first and second class constraints. We show that the whole constraints can be classified into completely irreducible first or second class chains. We found appropriate redefinition of second class constraints to obtain a symplectic algebra among

J. L. Chkareuli, C. D. Froggatt, I. G. Gogoladze, A. B. Kobakhidze

We construct a realistic SU(7) model which provides answers to many questions presently facing the prototype SU(5) SUSY GUT. Among them are a solution to the doublet-triplet splitting problem, string scale unification, proton decay, the hierarchy of baryon vs lepton number violation and neutrino masses.

Chong-Sun Chu

We consider noncommutative gauge theory with Dirac or Majorana fermions in odd dimensional spacetime and compute the induced noncommutative Chern-Simons action generated at 1-loop. We observe that the Chern-Simons term induced by a Dirac fermion has a smooth limit when $þ---> 0$, but there is a finite jump for the Chern-Simons term induced by a Majorana spin

David Bacon, Alexandre Refregier, Richard Ellis

We report a detection of the coherent distortion of faint galaxies arising from gravitational lensing by foreground structures. This ``cosmic shear&#39;&#39; is potentially the most direct measure of the mass power spectrum, as it is unaffected by poorly-justified assumptions made concerning the biasing of the distribution. Our detection is based on an initi

M. A. Smondyrev, B. Gerlach, M. O. Dzero

The polaron energy and the effective mass are calculated for an electron confined in a finite quantum well constructed of $GaAs/Al_x Ga_{1-x} As$ layers. To simplify the study we suggest a model in which parameters of a medium are averaged over the ground-state wave function. The rectangular and the Rosen-Morse potential are used as examples. To describe the

Gerard &#39;t Hooft

After a pedagogical overview of the present status of High-Energy Physics, some problems concerning physics at the Planck scale are formulated, and an introduction is given to a notion that became known as ``the holographic principle&#34; in Planck scale physics, which is arrived at by studying quantum mechanical features of black holes.

Antony A. Stark

The emerging technology of large (~ 10,000 pixel) submillimeter-wave bolometer arrays presents a novel optical design problem---how can such arrays be fed by diffraction-limited telescope optics where the primary mirror is less than 100,000 wavelengths in diameter? Standard Cassegrain designs for radiotelescope optics exhibit focal surface curvature so large

F. A. Danevich, A. Sh. Georgadze, V. V. Kobychev, B. N. Kropivyansky

A new phase of 116Cd double beta decay experiment is in progress in the Solotvina Underground Laboratory. Four enriched 116CdWO4 scintillators with total mass 339 g are used in a set up, whose active shield is made of 15 natural CdWO4 crystals (20.6 kg). The background rate in the energy interval 2.5-3.2 MeV is 0.03 counts/y*kg*keV. The half-life for 2-neutr

L. Polley

In 1989, Deutsch gave a basic physical explanation of why quantum-mechanical probabilities are squares of amplitudes. Essentially, a general state vector is transformed into a highly symmetric equal-amplitude superposition. The argument was recently elaborated and publicised by DeWitt. It has remained incomplete, however, inasmuch as both authors anticipate

Nuno Costa Dias, Joao Nuno Prata

We investigate the possibility that the semiclassical limit of quantum mechanics might be correctly described by a classical dynamical theory, other than standard classical mechanics. Using a set of classicality criteria proposed in a related paper, we show that the time evolution of a set of quantum initial data satisfying these criteria is fully consistent

Giuseppe Castagnoli

The complementary roles played by parallel quantum computation and quantum measurement in originating the quantum speed-up are illustrated through an analogy with a famous metaphor by J.L. Borges.

Guifré Vidal

In this note we consider the problem of preparing a {\em single} copy of an arbitrary two-qubit mixed state $ρ$ starting from an entangled pure state $ψ$ and using only local operations assisted with classical communication. We present an analytical expression for the minimal amount of pure state entanglement required, and describe the corresponding local st

G. J. Milburn, Paul Alsing

We show that the quantum phase transition of the Tavis-Cummings model can be realised in a linear ion trap of the kind proposed for quantum computation. The Tavis-Cummings model describes the interaction between a bosonic degree of freedom and a collective spin. In an ion trap, the collective spin system is a symmetrised state of the internal electronic stat

C. Search, P. R. Berman

It is shown that the magnetic state decoherence produced by collisions in a thermal vapor can be suppressed by the application of a train of ultrafast optical pulses.

Stephen L. Adler, Indrajit Mitra

We evaluate the exact equilibrium distribution of gas molecules adsorbed on an active surface with an infinite number of attachment sites. Our result is a Poisson distribution having mean $X = {μP P_s \over P_e}$, with $μ$ the mean gas density, $ P_s$ the sticking probability, $P_e$ the evaporation probability in a time interval $τ$, and $P$ Smoluchowski&#39

J. Dobaczewski, J. Dudek

We describe the new version (v1.75r) of the code HFODD which solves the nuclear Skyrme-Hartree-Fock problem by using the Cartesian deformed harmonic-oscillator basis. Three minor errors that went undetected in the previous version have been corrected. The new version contains an interface to the LAPACK subroutine ZHPEV. Several methods of terminating the Har

W. Cassing, S. Juchem

Equilibration times for nuclear matter configurations -- modelling intermediate and high energy nucleus-nucleus collisions -- are evaluated within the semiclassical off-shell transport approach developed recently. The transport equations are solved for a finite box in coordinate space employing periodic boundary conditions. The off-shell transport model is s

S. Fujii, R. Okamoto, K. Suzuki

A method for a microscopic description of Lambda hypernuclei is formulated in the framework of the unitary-model-operator approach. A unitarily transformed hamiltonian is introduced and given in a cluster expansion form. The structure of three-body-cluster terms are discussed especially on the Lambda single-particle energy. The Lambda single-particle energie

D. Gomez-Ullate, A. Gonzalez-Lopez, M. A. Rodriguez

We develop a systematic procedure for constructing quantum many-body problems whose spectrum can be partially or totally computed by purely algebraic means. The exactly-solvable models include rational and hyperbolic potentials related to root systems, in some cases with an additional external field. The quasi-exactly solvable models can be considered as def

V. B. Taranenko, C. O. Weiss

We demonstrate experimentally the bistable nature of the bright spatial solitons in a semiconductor microresonator and show that they can be created and destroyed by incoherent local optical injection.

Haruhiko Nishimura, Naofumi Katada, Kazuyuki Aihara

We set up a signal-driven scheme of the chaotic neural network with the coupling constants corresponding to certain information, and investigate the stochastic resonance-like effects under its deterministic dynamics, comparing with the conventional case of Hopfield network with stochastic noise. It is shown that the chaotic neural network can enhance weak su

G. P. Pronko

We suggest the procedure of the construction of Baxter Q-operators for Toda chain . Apart from the one-paramitric family of Q-operators, considered in our recent paper (hep-th/9908179) we also give the construction of two basic Q-operators and the derivation of the functional relations for these operators. Also we have found the relation of the basic Q-opera

I. G. Korepanov

Given five points in a three-dimensional euclidean space, one can consider five tetrahedra, using those points as vertices. We present a pentagon-like formula containing the product of three volumes of those tetrahedra in its l.h.s. and the product of the two remaining tetrahedron volumes in its r.h.s., as well as the derivative of the &#34;discrete curvatur

A. A. Glutsuk

Consider a parallel plane foliation on real finite-dimensional linear vector space. It induces a foliation on the torus obtained by factorization of the space by the integer lattice (let us denote the latter foliation by F). Let g be arbitrary metric on the torus. It induces a complex structure on each leaf of F such that all the leaves are parabolic: each i

Mladen Bestvina, Mark Feighn, Michael Handel

The Tits alternative for Out(F_n) is reduced to the case where all elements in the subgroup under consideration grow polynomially.

Thomas C. Sideris

The nonlinear hyperbolic system of pde&#39;s governing the evolution of the deformation of isotropic hyperelastic materials is considered. In the absence of boundaries and with an additional nonresonance or null condition, the system has global smooth solutions starting close to a one-parameter family of homogeneous dilations. The proof combines energy estim

Colette Mœglin

On montre comment les conjectures d&#39;Arthur permettent de calculer les points de réductibilité pour les induites de cuspidales des groupes classiques. Les conjectures d&#39;Arthur utilisées portent sur l&#39;existence d&#39;un relèvement faible des représentations automorphes cuspidales d&#39;un groupe classique vers un groupe linéaire convenable. Et les

Ravi Ramakrishna

In this paper we show how to construct, for most p >= 5, two types of surjective representations ρ:G_Q=Gal(\bar{Q}/Q) -> GL_2(Z_p) that are ramified at an infinite number of primes. The image of inertia at almost all of these primes will be torsion-free. The first construction is unconditional. The catch is that we cannot say whether ρ|_{G_p=Gal(\bar{Q_p}/Q_