March 1998 arXiv papers — page 6

T. S. Evans

Elizalde, Vanzo, and Zerbini have shown that the effective action of two free Euclidean scalar fields in flat space contains a `multiplicative anomaly' when zeta-function regularization is used. This is related to the Wodzicki residue. I show that there is no anomaly when using a wide range of other regularization schemes and further that this anomaly ca

A. D. Popov

Geometry of the solution space of the self-dual Yang-Mills (SDYM) equations in Euclidean four-dimensional space is studied. Combining the twistor and group-theoretic approaches, we describe the full infinite-dimensional symmetry group of the SDYM equations and its action on the space of local solutions to the field equations. It is argued that owing to the r

Fabio Gavarini, Gilles Halbout

Let $ \mathfrak{g} $ be a quasitriangular Lie bialgebra over a field $ K $ of characteristic zero, and let $ \mathfrak{g}^* $ be its dual Lie bialgebra. We prove that the formal Poisson group $ K\big[\big[\mathfrak{g}^*\big]\big] $ is a braided Hopf algebra, thus generalizing a result due to Reshetikhin (in the case $ \, \mathfrak{g} = \mathfrak{sl}(2,K) \,

Prakash Mathews, P. Poulose, K. Sridhar

We use NRQCD to predict the cross section for $η_c$ production at the Tevatron. The non-perturbative matrix elements required are obtained, using heavy-quark symmetry, from the matrix elements determined from the CDF $J/ψ$ data. Our numbers are, therefore, predictions of NRQCD and provide a very good test of it. Even after taking into account the small branc

Guangjun Mao, L. Neise, H. Stöcker, W. Greiner

We derive the relativistic quantum transport equation for the pion distribution function based on an effective Lagrangian of the QHD-II model. The closed time-path Green's function technique, the semi-classical, quasi-particle and Born approximation are employed in the derivation. Both the mean field and collision term are derived from the same Lagrangia

G. J. Gounaris, J. Layssac, F. M. Renard

We study Higgs + jet production at hadron colliders in order to look for new physics residual effects possibly described by the $dim=6$ operators $Ø_{GG}$ and ${\widetildeØ}_{GG}$ which induce anomalous $Hgg$ and $Hggg$ couplings. Two ways for constraining these operators at LHC may be ~useful. The first is based on the total Higgs boson production rate indu

O. Jahn, F. Lenz

An investigation of singular fields emerging in the process of transforming QCD to the axial gauge is presented. The structure of the singularities is analyzed. It is shown that apart from well known neutral magnetic monopole singularities, the field configurations also exhibit singularities in their charged and transverse components. This complex singularit

Yong-Wan Kim, Young-Jai Park, Sean J. Yoon

We systematically embed the SU(2)$\times$U(1) Higgs model in the unitary gauge into a fully gauge-invariant theory by following the generalized BFT formalism. We also suggest a novel path to get a first-class Lagrangian directly from the original second-class one using the BFT fields.

D. P. Roy

I start with a brief introduction to Higgs mechanism and supersymmetry. Then I discuss the theoretical expectations, current limits and search strategies for Higgs boson(s) at LHC --- first in the SM and then in the MSSM. Finally I discuss the signatures and search strategies for the superparticles.

K. Urbanowski, J. Piskorski

The Lee, Oehme and Yang (LOY) theory of time evolution in two state subspace of states of the complete system is discussed. Some inconsistencies in assumptions and approximations used in the standard derivation of the LOY effective Hamiltonian, H(LOY), governig this time evolution are found. Eliminating these inconsistecies and using the LOY method, approxim

Antonio Dobado, Antonio L. Maroto

In this paper we show how the nonlocal effective action for gravity, obtained after integrating out the matter fields, can be used to compute particle production and spectra for different space-time metrics. Applying this technique to several examples, we find that the perturbative calculation of the effective action up to second order in curvatures yields e

Karl Jansen, Rainer Sommer

We consider O(a) improvement for two flavor lattice QCD. The improvement term in the action is computed non-perturbatively for a large range of the bare coupling. The position of the critical line and higher order lattice artifacts remaining after improvement are estimated. We also discuss the behavior of the HMC algorithm in our simulations.

Masayuki Matsuzaki, Tomonori Tanigawa

We calculate the $^1S_0$ pairing gap in nuclear matter by adopting the "in-medium Bonn potential" proposed by Rapp et al. [e-print nucl-th/9706006], which takes into account the in-medium meson mass decrease, as the particle-particle interaction in the gap equation. The resulting gap is significantly reduced in comparison with the one obtained by ado

Andrew G. White, Jay R. Mitchell, Olaf Nairz, Paul G. Kwiat

Using the complementary wave- and particle-like natures of photons, it is possible to make ``interaction-free'' measurements where the presence of an object can be determined with no photons being absorbed. We investigated several ``interaction-free'' imaging systems, i.e. systems that allow optical imaging of photosensitive objects with less

Scott Thomas

The effects of CP-odd supersymmetric phases on slepton pair production are considered. It is shown that CP-even observables in $e^+ e^-$ and $e^- e^-$ collisions, such as the total selectron cross section, can depend on CP-odd supersymmetric phases through interference between different tree level amplitudes. Left handed selectron pair production in $e^- e^-

J. C. Osborn, J. J. M. Verbaarschot

Eigenvalues and eigenfunctions of the QCD Dirac operator are studied for gauge field configurations given by a liquid of instantons. We find that for energy differences $δE$ below an energy scale $E_c$ the eigenvalue correlations are given by Random Matrix Theories with the chiral symmetries of the QCD partition function. For eigenvalues near zero this energ

A. I. Bobenko, B. Lorbeer, Yu. B. Suris

Discretizations of the Euler top sharing the integrals of motion with the continuous time system are studied. Those of them which are also Poisson with respect to the invariant Poisson bracket of the Euler top are characterized. For all these Poisson discretizations a solution in terms of elliptic functions is found, allowing a direct comparison with the con

P. Maraner

Geometric quantization procedures go usually through an extension of the original theory (pre-quantization) and a subsequent reduction (selection of the physical states). In this context we describe a full geometrical mechanism which provides dynamically the desired reduction.

L. Diosi, N. Gisin, W. T. Strunz

We present a nonlinear stochastic Schroedinger equation for pure states describing non-Markovian diffusion of quantum trajectories. It provides an unravelling of the evolution of a quantum system coupled to a finite or infinite number of harmonic oscillators, without any approximation. Its power is illustrated by several examples, including measurement-like

C. Wiele, F. Haake, C. Rocke, A. Wixforth

We propose to pump semiconductor quantum dots with surface acoustic waves which deliver an alternating periodic sequence of electrons and holes. In combination with a good optical cavity such regular pumping could entail anti-bunching and sub-Poissonian photon statistics. In the bad-cavity limit a train of equally spaced photons would arise.

Vicki Schroeder, M. B. Baker, John Latham

The maximum measured electric fields in thunderclouds are an order of magnitude less than the fields required for electric breakdown of the air. One explanation for lightning initiation in these low fields is that electric breakdown first occurs at the surfaces of raindrops where the ambient field is enhanced very locally due to the drop geometry. Laboratory

Xinwei Kong, Finn Ravndal

Using effective field theory for a proton and antiproton bound in a Coulomb potential, the shift of the ground state energy level is calculated to arbitrary order in the scattering length. Including the next order contact interaction, the correction due to the effective range parameter can also be obtained.

Marcin Mazur

We discuss the following conjecture of Kitaoka: if a finite subgroup $G$ of $GL_{n}(O_{K})$ is invariant under the action of $Gal(K/\Bbb Q)$ then it is contained in $GL_{n}(K^{ab})$. Here $O_{K}$ is the ring of integers in a finite, Galois extension $K$ of $\Bbb Q$ and $K^{ab}$ is the maximal, abelian subextension of $K$. Our main result reduces this conject

Boris Dubrovin

This paper is based on the author's talk at 1997 Taniguchi Symposium ``Integrable Systems and Algebraic Geometry''. We consider an approach to the theory of Frobenius manifolds based on the geometry of flat pencils of contravariant metrics. It is shown that, under certain homogeneity assumptions, these two objects are identical. The flat pencils

Sarah L. Day, Brian R. Grivna, Earle P. McCartney, Cesar E. Silva

We construct a rank one infinite measure preserving transformation $T$ such that for all sequences of nonzero integers $\{k_{1},..., k_{r}\}$, $T^{k_{1}}\times...\times T^{k_{r}}$ is ergodic.

Anne Cortella, Boris Kunyavskii

Given a generic field extension F/k of degree n>3 (i.e. the Galois group of the normal closure of F is isomorphic to the symmetric group $S_n$), we prove that the norm torus, defined as the kernel of the norm map $N:R_{F/k}(G_m)\to\G_m$, is not rational over k.

Aleksandrs Mihailovs

The spaces of invariants of tensor powers of the defining representation of Sp(2n) are provided with the bases parametrized by symplectic wave graphs introduced here especially for this purpose. The proof utilizes a game similar to Tetris, named here S-tris. This work continues my previous work on the tensor invariants of SL(n), wave graphs and L-tris.

Robion C. Kirby, Laurence R. Taylor

The title says it all.

Russell Lyons

We give a simple non-analytic proof of Biggins' theorem on martingale convergence for branching random walks.

Gilad Lifschytz

We discuss the connection between Matrix string theory and the DLCQ of string theory. Using this connection we describe the sense in which perturbative string amplitudes are reproduced in the Matrix string theory. Using recent realization of the connection between SYM and Supergravity, we suggest how to describe Matrix theory with non-flat backgrounds.

O. W. Greenberg

This paper proposes a variational principle for the solutions of quantum field theories in which the ``trial functions'' are chosen from the algebra of asymptotic fields, and illustrates this variational principle in simple cases.

P. Maraner

The coupling to a 2+1 background geometry of a quantized charged test particle in a strong magnetic field is analyzed. Canonical operators adapting to the fast and slow freedoms produce a natural expansion in the inverse square root of the magnetic field strength. The fast freedom is solved to the second order. At any given time, space is parameterized by a

Jorgen Rasmussen

The two-point functions in affine current algebras based on simple Lie algebras are constructed for all representations, integrable or non-integrable. The weight of the conjugate field to a primary field of arbitrary weight is immediately read off.

Nima Arkani-Hamed, Michael Dine, Stephen P. Martin

We consider supersymmetry breaking in theories with gaugino condensation in the presence of an anomalous U(1) symmetry with anomaly cancellation by the Green-Schwarz mechanism. In these models, a Fayet-Iliopoulos D-term can give important contributions to the soft supersymmetry-breaking scalar masses. Most discussions of this possibility have ignored the dil

Bing An Li, Dao-neng Gao, Mu-lin Yan

In the framework of an effective chiral theory of mesons, pi K scattering is stydied. The scattering lengths, phase shifts, and cross sections are calculated. Theoretical results agree well with data. There is no new parameter in this study.

Gino Segre

Primordial magnetic fields present between the eras of neutrino decoupling and of positron-electron annihilation can lead to the emission of neutrino-anti neutrino pairs or axions by electrons in excited Landau levels, thereby changing the electron energy spectrum. The rate is calculated and shown to not affect significantly the standard Big Bang picture.

V. Gupta, P. Ritto, G. Sanchez-Colon

The spin 1/2 baryons are pictured as a composite system made out of a "core" of three valence quarks (as in the simple quark model) surrounded by a "sea" (of gluon and $q\bar{q}$ pairs) which is specified by its total quantum numbers. We assume the sea is a SU(3) flavor octet with spin 0 or 1 but no color. This model, considered earlier, is u

Joseph D. Lykken

Three case studies are presented of slepton pair production followed by two-body or quasi-two-body decays at a muon collider. Precision mass measurements are possible using a variety of kinematic fitting methods. Standard Model and supersymmetric backgrounds are easily controlled by kinematic cuts. In all three cases it appears that detector resolutions, not

M. Bertini, M. Genovese, N. N. Nikolaev, B. G. Zakharov

We present our study of the diffraction in charged current DIS. We analyse the perturbatively tractable excitation of heavy quarks, emphasizing the peculiarities of the Regge factorization breaking in excitation of open charm.

D0 Collaboration, B. Abbott et al

We have searched for central production of a pair of photons with high transverse energies in $p\bar p$ collisions at $\sqrt{s} = 1.8$ TeV using $70 pb^{-1}$ of data collected with the DØdetector at the Fermilab Tevatron in 1994--1996. If they exist, virtual heavy pointlike Dirac monopoles could rescatter pairs of nearly real photons into this final state vi

D. Asner

Using data recorded by the CLEO-II detector at CESR we have searched for four radiative decay modes of the $D^0$ meson: $D^0\toϕγ$, $D^0\toωγ$, $D^0\to\bar{K}^{*}γ$, and $D^0\toρ^0γ$. We obtain 90% CL upper limits on the branching ratios of these modes of $1.9\times 10^{-4}$, $2.4\times 10^{-4}$, $7.6\times 10^{-4}$ and $2.4\times 10^{-4}$ respectively.

The WA89 Collaboration, M. I. Adamovich et al

CERN experiment WA89 has studied charmed particles produced by a Sigma^- beam at 340 GeV/c on nuclear targets. Production of particles which have light quarks in common with the beam is compared to production of those which do not. Considerable production asymmetries between D^- and D^p, D_s^ and D_s^+ and Lambda_c and Antilambda_c are observed. The results

M. W. Choptuik

In recent years it has become apparent that intriguing phenomenology exists at the threshold of black hole formation in a large class of general relativistic collapse models. This phenomenology, which includes scaling, self-similarity and universality, is largely analogous to statistical mechanical critical behaviour, a fact which was first noted empirically

Redouane Fakir

Stochastic resonance holds much promise for the detection of weak signals in the presence of relatively loud noise. Following the discovery of nondynamical and of aperiodic stochastic resonance, it was recently shown that the phenomenon can manifest itself even in the presence of nonstationary signals. This was found in a composite system of differentiated t

Daniel ben-Avraham

Some models of diffusion-limited reaction processes in one dimension lend themselves to exact analysis. The known approaches yield exact expressions for a limited number of quantities of interest, such as the particle concentration, or the distribution of distances between nearest particles. However, a full characterization of a particle system is only provi

Kay Joerg Wiese, Mehran Kardar

We introduce a generalization of the O(N) field theory to N-colored membranes of arbitrary inner dimension D. The O(N) model is obtained for D->1, while N->0 leads to self-avoiding tethered membranes (as the O(N) model reduces to self-avoiding polymers). The model is studied perturbatively by a 1-loop renormalization group analysis, and exactly as N->infinit

E. Z. Kurmaev, V. M. Cherkashenko, Yu. M. Yarmoshenko, St. Bartkowski

A VO2 single-crystal has been subject of a combined investigation by high resolution XPS, x-ray emission spectroscopy with electron and energy-selective x-ray excitation (V L-alpha, V K-beta-5- and O K-alpha emission) and x-ray absorption spectroscopy (O1s). We performed first principles tight-binding LMTO band structure calculations of VO2 in both monoclini

G. Kamieniarz, P. Kozlowski, R. Dekeyser

The universal critical point ratio $Q$ is exploited to determine positions of the critical Ising transition lines on the phase diagram of the Ashkin-Teller (AT) model on the square lattice. A leading-order expansion of the ratio $Q$ in the presence of a non-vanishing thermal field is found from finite-size scaling and the corresponding expression is fitted t

F. Mancini

A formulation of the Green's function method is presented in the n-pole approximation. Without referring to a specific model we give a general scheme of calculations that easily permits the computation of the "single-particle" Green's function in terms of the energy matrix. A theorem is proved which states that the moments of the spectral den

E. Dekel, D. Gershoni, E. Ehrenfreund, D. Spektor J. M. Garcia

We apply low temperature confocal optical microscopy to spatially resolve, and spectroscopically study a single self assembled quantum dot. By comparing the emission spectra obtained at various excitation levels to a theoretical many body model, we show that: Single exciton radiative recombination is very weak. Sharp spectral lines are due to optical transit

S. S. Banerjee et al

The reentrant nature of Peak Effect is established in a single crystal of 2H-NbSe_2 via electrical transport and dc magnetisation studies. The role of disorder on the reentrant branch of PE has been examined in three single crystals with varying levels of quenched random disorder. Increasing disorder presumably shrinks the (H,T) parameter space over which vo

A. Hosseini, S. Kamal, D. A. Bonn, R. Liang

New measurements of surface impedance in ybco show that the c-axis penetration depth and conductivity below Tc exhibit behaviour different from that observed in the planes. The c-axis penetration depth never has the linear temperature dependence seen in the ab-plane. Instead of the conductivity peak seen in the planes, the c-axis microwave conductivity falls

Diptiman Sen

We study perturbation theory in certain quantum mechanics problems in which the perturbing potential diverges at some points, even though the energy eigenvalues are smooth functions of the coefficient of the potential. We discuss some of the unusual techniques which are required to obtain perturbative expansions of the energies in such cases. These include a

T. Ikegami, S. Miyashita, H. Rieger

The site-diluted transverse field Ising model in two dimensions is studied with Quantum-Monte-Carlo simulations. Its phase diagram is determined in the transverse field (Gamma) and temperature (T) plane for various (fixed) concentrations (p). The nature of the quantum Griffiths phase at zero temperature is investigated by calculating the distribution of the

T. J. Davidge

Deep J, H, and K images are used to probe the evolved stellar contents in the central regions of the Sculptor group galaxies NGC55, NGC300, and NGC7793. The brightest stars are massive red supergiants (RSGs) with K ~ 15 - 15.5. The peak RSG brightness is constant to within ~0.5 mag in K, suggesting that NGC55, NGC300, and NGC7793 are at comparable distances.

L. Knox, J. R. Bond, A. H. Jaffe, M. Segal

To extract reliable cosmic parameters from cosmic microwave background datasets, it is essential to show that the data are not contaminated by residual non-cosmological signals. We describe general statistical approaches to this problem, with an emphasis on the case in which there are two datasets that can be checked for consistency. A first visual step is t

Kimberly C. B. New, Joel E. Tohline, Juhan Frank, Horst M. Vaeth

Warped H I gas layers in the outer regions of spiral galaxies usually display a noticeably twisted structure. This structure almost certainly arises primarily as a result of differential precession in the H I disk as it settles toward a preferred orientation in an underlying dark halo potential well that is not spherically symmetric. In an attempt to better

D. Fargion

Splitting by atomic bombs an asteroid in flight is the best way to deflect its trajectory. How and when it should be done is described.

Jeroen Homan, Michiel van der Klis, Rudy Wijnands, Brian Vaughan

We report the discovery of a quasi-periodic oscillation (QPO) at 61.0+/-1.7 Hz with the Rossi X-Ray Timing Explorer in the low-mass X-ray binary and persistently bright atoll source GX 13+1 (4U 1811-17). The QPO had an rms amplitude of 1.7+/-0.2 % (2-13.0 keV) and a FWHM of 15.9+/-4.2 Hz. Its frequency increased with count rate and its amplitude increased wi

Ruth Dgani, Noam Soker

In a recent analysis of the radio emission from the planetary nebula A30, Dgani, Evans & White (1998) claim that the emission, located in the inner region, is probably dominated by nonthermal emission. We propose a model to explain this. We assume that the fast wind, blown by the central star of A30 carries a very weak magnetic field. The interaction of this

Ruth A. Daly, E. J. Guerra, Lin Wan

Fourteen classical double radio galaxies with redshifts between zero and two were used to determine the cosmological parameters $Ω_m$, $Ω_Λ$, and $Ω_k$, where these are the normalized values of the mean mass density, cosmological constant, and space curvature at the present epoch. A low value of $Ω_m$ is obtained, and $Ω_m = 1$ is ruled out with 97.5% confid

Alok R. Patnaik, Richard W. Porcas

We present multi-frequency radio continuum VLBI observations of the gravitational lens system B0218+357 carried out using a global VLBI network and the VLBA. The source has been observed with resolutions from 0.2 milliarcsec to 5 milliarcsec and displays interesting structure. The spectral properties of various components show that the lensed object is a sta

Frederick K. Lamb, M. Coleman Miller, Dimitrios Psaltis

One of the most dramatic discoveries made with the Rossi X-Ray Timing Explorer is that many accreting neutron stars in low-mass binary systems produce strong, remarkably coherent, high-frequency X-ray brightness oscillations. The 325-1200 Hz quasi-periodic oscillations (QPOs) observed in the accretion-powered emission are thought to be produced by gas orbiti

Carlos Allende Prieto, Ramon J. Garcia Lopez

We present accurate measurements of the central wavelengths of 4947 atomic absorption lines in the solar optical spectrum. The wavelengths, precise to a level ~ 50-150 m/s, are given for both flux and disc-centre spectra, as measured in relatively recent FTS solar atlases. This catalogue modernizes existing sources based on photographic measurements and prov

Kandaswamy Subramanian, John D. Barrow

An inhomogeneous cosmological magnetic field will create Alfven-wave modes that induce a small rotational velocity perturbation on the last scattering surface of the microwave background radiation. The Alfven-wave mode survives Silk damping on much smaller scales than the compressional modes. This, in combination with its rotational nature, ensures that ther

SAGE Collaboration, J. N. Abdurashitov

The neutrino capture rate measured by the Russian-American Gallium Experiment is well below that predicted by solar models. To check the response of this experiment to low-energy neutrinos, a 517 kCi source of 51Cr was produced by irradiating 512.7 g of 92.4%-enriched 50Cr in a high-flux fast neutron reactor. This source, which mainly emits monoenergetic 747

H. A. Kastrup

The grand canonical partition functions for primitive droplet nucleation models with an excess energy epsilon_n = - mu n + sigma n^{1-eta}, eta = 1/d, for droplets of n constituents in d dimensions are calculated exacly in closed form in the cases d=2 and 3 for all (complex) mu by exploiting the fact that the partition functions obey simple PDE.

John H. Schwarz, Nathan Seiberg

String theory and supersymmetry are theoretical ideas that go beyond the standard model of particle physics and show promise for unifying all forces. After a brief introduction to supersymmetry, we discuss the prospects for its experimental discovery in the near future. We then show how the magic of supersymmetry allows us to solve certain quantum field theo

Kirill Krasnov

We show that, apart from the usual area operator of non-perturbative quantum gravity, there exists another, closely related, operator that measures areas of surfaces. Both corresponding classical expressions yield the area. Quantum mechanically, however, the spectra of the two operators are different, coinciding only in the limit when the spins labelling the

Hagen Kleinert

The graphical extrapolation procedure to infinite order of variational perturbation theory in a recent calculation of critical exponents of three-dimensional $ϕ^4$-theories at infinite couplings is improved by another way of plotting the results.

Nicolas J. Cerf

A family of quantum cloning machines is introduced that produce two approximate copies from a single quantum bit, while the overall input-to-output operation for each copy is a Pauli channel. A no-cloning inequality is derived, describing the balance between the quality of the two copies. This also provides an upper bound on the quantum capacity of the Pauli

Mark S. Byrd, E. C. G. Sudarshan

The ``$D$'' matrices for all states of the two fundamental representations and octet are shown in the generalized Euler angle parameterization. The raising and lowering operators are given in terms of linear combinations of the left invariant vector fields of the group manifold in this parameterization. Using these differential operators the highest

V. V. Borzov, E. V. Damaskinsky, P. P. Kulish

The spectral measure of the position (momentum) operator $X$ for $q$-deformed oscillator is calculated in the case of the indetermine Hamburger moment problem. The exposition is given for concrete choice of generators for $q$-oscillator algebra, although developed technique apply for every other cases with indetermine moment problem. The Stieltjes transforma

Alexandre Kabanov, Takashi Kimura

Let $V$ be a smooth, projective, convex variety. We define tautological $ψ$ and $κ$ classes on the moduli space of stable maps $\M_{0,n}(V)$, give a (graphical) presentation for these classes in terms of boundary strata, derive differential equations for the generating functions of the Gromov-Witten invariants of $V$ twisted by these tautological classes, an

Tae-Sun Park

The properties of low-energy neutron-proton systems are studied in an effective field theory where only nucleons figure as relevant degrees of freedom. With a finite momentum cut-off regularization scheme, we show that the large scattering lengths of the np systems do not spoil the convergence of the effective field theory, which turns out to be extremely su

The OPAL Collaboration, K. Ackerstaff et al

Using radiative Z^0 -> τ^+ τ^- γevents collected with the OPAL detector at LEP at \sqrt{s}= M_Z during 1990-95, a direct study of the electromagnetic current at the τγvertex has been performed in terms of the anomalous magnetic form factor F_2 of the τlepton. The analysis is based on a data sample of 1429 e^+ e^- -> τ^+ τ^- γevents which are examined for a d

A Priel, I Kanter, D A Kessler

We study the properties of a noisy time series generated by a continuous-valued feed-forward network in which the next input vector is determined from past output values. Numerical simulations of a perceptron-type network exhibit the expected broadening of the noise-free attractor, without changing the attractor dimension. We show that the broadening of the

Juhao Wu, A. Widom

For spin one atoms localized in a quadrapole magnetic field gradient, the atoms may be impeded from spin flipping their way out from the center of the trap by the application of a rotating uniform magnetic field. From a quantum mechanical viewpoint, such a trap for a Bose condensate is equivalent to having a superfluid in a rotating bucket. Vorticity is then

I. Androutsopoulos, G. D. Ritchie, P. Thanisch

Most existing natural language database interfaces (NLDBs) were designed to be used with database systems that provide very limited facilities for manipulating time-dependent data, and they do not support adequately temporal linguistic mechanisms (verb tenses, temporal adverbials, temporal subordinate clauses, etc.). The database community is becoming increa

S. E. Thorsett, Deepto Chakrabarty

There are now about fifty known radio pulsars in binary systems, including at least five in double neutron star binaries. In some cases, the stellar masses can be directly determined from measurements of relativistic orbital effects. In others, only an indirect or statistical estimate of the masses is possible. We review the general problem of mass measureme

Inga M. Schmoldt, Prasenjit Saha

Peebles (1989) showed that in the gravitational instability picture galaxy orbits can be traced back in time from a knowledge of their current positions, via a variational principle. We modify this variational principle so that galaxy redshifts can be input instead of distances, thereby recovering the distances. As a test problem, we apply the new method to

Ehud Cohen, Tsvi Piran, Re'em Sari

We derive a self similar solution for the propagation of an extreme relativistic (or Newtonian) radiative spherical blast wave into a surrounding cold medium. The solution is obtained under the assumption that the radiation process is fast, it takes place only in the vicinity of the shock and that it radiates away a fixed fraction of the energy generated by

Romeel Davé, Uffe Hellsten, Lars Hernquist, Neal Katz

We search for OVI absorption in a Keck HIRES spectrum of the z=3.62 quasar Q1422+231. Comparison of CIV measurements to cosmological simulations shows that \lya forest absorbers with N_HI > 10^{14.5} have [C/H]~=-2.5, for the UV background spectrum of Haardt & Madau (HM). Lower column density absorption arises in lower density gas, where OVI is the most sens

Pedro G. Ferreira, Joao Magueijo, Krzysztof M. Górski

We introduce and study the distribution of an estimator for the normalized bispectrum of the Cosmic Microwave Background (CMB) anisotropy. We use it to construct a goodness of fit statistic to test the coadded 53 and 90 GHz COBE-DMR 4 year maps for non-Gaussianity. Our results indicate that Gaussianity is ruled out at the confidence level in excess of 98%. T

J. D. Cohn, D. I. Kaiser

In the hyperbolic slicing of de Sitter space appropriate for open universe models, a curvature scale is present and supercurvature fluctuations are possible. In some cases, the expansion of a scalar field in the Bunch-Davies vacuum includes supercurvature modes, as shown by Sasaki, Tanaka and Yamamoto. We express the normalizable vacuum supercurvature modes

E. J. Copeland, T. W. B. Kibble, D. A. Steer

We set up and analyse a model for the non-equilibrium evolution of a network of cosmic strings initially containing only loops and no infinite strings. Due to this particular initial condition, our analytical approach differs significantly from existing ones. We describe the average properties of the network in terms of the distribution function n(l,t) dl, t

E. I. Buchbinder, I. L. Buchbinder, E. A. Ivanov, S. M. Kuzenko

We explicitly demonstrate that the perturbative holomorphic contribution to the off-shell effective action of N=2 U(1) gauge supermultiplet is an entire effect of the minimal coupling to a hypermultiplet with the mass generated by a central charge in N=2 superalgebra. The central charge is induced by a constant vacuum N=2 gauge superfield strength spontaneou

D. T. Son

We show that the decaying magnetohydrodynamic turbulence leads to a more rapid growth of the correlation length of a primordial magnetic field than that caused by the expansion of the Universe. As an example, we consider the magnetic fields created during the electroweak phase transition. The expansion of the universe alone would yield a correlation length a

S. B. Dubovichenko, A. V. Dzhazairov-Kakhramanov

Photodisintegration and radiative capture in the N2H, N3H, N3He, 2H2H, 2H3He, 2H4He, 3He3H, 4He3H, and 4He3He channels are studied on the basis of the corresponding two-cluster potential models. The astrophysical S factors at low energies are calculated. It is shown that various electromagnetic characteristics of light nuclei, including the Coulomb form fact

Michael T. Greene, Bert Wiest

Given a knot K in the 3-sphere, consider a singular disk bounded by K and the intersections of K with the interior of the disk. The absolute number of intersections, minimised over all choices of singular disk with a given algebraic number of intersections, defines the framing function of the knot. We show that the framing function is symmetric except at a f

Judith J. McDonald, Hans Schneider

It is well known that any nonsingular M-matrix admits an LU factorization into M-matrices (with L and U lower and upper triangular respectively) and any singular M-matrix is permutation similar to an M-matrix which admits an LU factorization into M-matrices. Varga and Cai establish necessary and sufficient conditions for a singular M-matrix (without permutat

Pedro F. Gonzalez-Diaz

We discuss the coordinate complexification necessary to obtain a spatially homogeneous open universe in the singular instantonic solution recently suggested by Hawking and Turok (hep-th/9802030), concluding that only the time coordinate $σ$ of the spatially inhomogeneous De Sitter-like Lorentzian solution and its scale factor should be rotated in order to co

I. V. Volovich

Using a proposal of Maldacena one describes the large N limit of gauge theories in terms of supergravity solutions on anti-de Sitter space. From this point of view we discuss a possible scenario for quark confinement in gauge theory by describing hadrons as strongly curved universes. In particular an interpretation of black hole as a bag model in SQCD is dis

Paul H. Frampton, Masayasu Harada

The CP parameters $ε$ and $ε'/ε$ are calculated in the aspon model of spontaneous CP violation, a model which solves the strong CP problem. A new range for the scale of spontaneous breaking of CP is found. It is shown that $ε'/ε$ is suppressed by $\sim x^2 v^2/(κ^2 \sin^5 θ_C) \sim 5 \times 10^{-3}$ relative to the Standard Model. If experiment finds

Q. Y. Liu, S. P. Mikheyev, A. Yu. Smirnov

We consider a solution of the atmospheric neutrino problem based on oscillations of muon neutrinos to sterile neutrinos: $ν_μ$ $\leftrightarrow$ $ν_s$. The zenith angle ($Θ$) dependences of the neutrino and upward-going muon fluxes in presence of these oscillations are studied. The dependences have characteristic form with two dips: at $\cos Θ= -0.6 ÷-0.2$ a

W-Y. P. Hwang, Kwei-Chou Yang

Isospin symmetry breaking in the quark condensates, $< \bar dd> \not= < \bar uu>$, is a fundamental parameter in both the QCD sum rule studies and the chiral perturbation theory. In this article, we apply the QCD sum rule method to treat the hyperon mass difference ${1\over 2}(m_{Σ^-}+m_{Σ^0})-m_{Σ^+}$ in order to obtain a reasonable estimate on such isospin

The OPAL Collaboration, K. Ackerstaff et al

A search is described for the neutral Higgs bosons h^0 and A^0 predicted by models with two scalar field doublets and, in particular, the Minimal Supersymmetric Standard Model (MSSM). The search in the Z^0 h^0 and h^0 A^0 production channels is based on data corresponding to an integrated luminosity of 25 pb^{-1} from e^+e^- collisions at centre-of-mass ener

M. E. Cates, J. Wittmer, J. P. Bouchaud, P. Claudin

The pressure distribution beneath a conical sandpile, created by pouring sand from a point source onto a rough rigid support, shows a pronounced minimum below the apex (`the dip&#39;). Recent work of the authors has attempted to explain this phenomenon by invoking local rules for stress propagation that depend on the local geometry, and hence on the construc

R. O. Vallejos, R. S. Mendes, L. R. da Silva, C. Tsallis

As a first step towards the understanding of the thermodynamical properties of quasiperiodic structures, we have performed both analytical and numerical calculations associated with succesive hierarchical approximations to multiscale fractal energy spectra. We show that, in a certain range of temperatures, the specific heat displays log-periodic oscillations

M. M. Kozlov, D. Andelman

We give a short overview of existing approaches describing shapes and energetics of amphiphilic aggregates. In particular, we consider recent experimental data and theory in relation to mixed aggregates. We point out the outstanding questions deserving further investigations such as stability of single-component vesicles and size growth of mixed vesicles ind