November 1998 arXiv papers — page 9

Z. Gedik, M. Bayindir

We study the localization property of a two-dimensional noninteracting electron gas in the presence of randomly distributed short-range scatterers. We evaluate the participation number of the eigenstates obtained by exact diagonalization technique. At low impurity concentrations we obtain self-averaged values showing that all states, except those exactly at

Eric Braaten, Agustin Nieto

Quantum corrections to the properties of a homogeneous interacting Bose gas at zero temperature can be calculated as a low-density expansion in powers of $\sqrt{ρa^3}$, where $ρ$ is the number density and $a$ is the S-wave scattering length. We calculate the ground state energy density to second order in $\sqrt{ρa^3}$. The coefficient of the $ρa^3$ correctio

R. M. Cavallo

We present new data and discuss the relationship between the Al abundances on the red giant branches (RGBs) and the horizontal-branch (HB) morphologies of the second-parameter pair of globular clusters M3 and M13. Since Al is produced during RGB evolution inside the H-burning shell where He is synthesized, its overabundance in stellar atmospheres can indicat

Laura Ferrarese, Holland Ford

We discuss Hubble Space Telescope optical images and spectra of NGC 6251, a giant E2 galaxy and powerful radio source at a distance of 106 Mpc (for H_0 = 70 km/s/Mpc). The galaxy is known to host a very well defined dust disk (O'Neil et al. 1994); the exceptional resolution of our V and I images allows a detailed study of the disk structure. Furthermore,

L. J. Greenhill, C. R. Gwinn, C. Schwartz, J. M. Moran

The BN/KL region in the Orion molecular cloud is an archetype in the study of the formation of stars much more massive than the Sun. This region contains luminous young stars and protostars, but it is difficult to study because of overlying dust and gas. Our basic expectations are shaped to some extent by the present theoretical picture of star formation, th

T. Joseph W. Lazio, K. R. Anantharamaiah, W. M. Goss, Namir E. Kassim

G359.87+0.18 is an enigmatic object located 15' from Sgr A*. It has been variously classified as an extragalactic source, Galactic jet source, and young supernova remnant. We present new observations of G359.87+0.18 between 0.33 and 15 GHz and use these to argue that this source is an Faranoff-Riley II radio galaxy. We are able to place a crude limit on

R. J. Reynolds, L. M. Haffner, S. L. Tufte

The Wisconsin H-Alpha Mapper (WHAM) is a new facility dedicated to the study of faint optical emission lines from diffuse interstellar gas. During its first 18 months of operation, WHAM carried out a survey of the interstellar H-alpha emission associated with the warm, ionized component of the interstellar medium. The observations consisted of 37,000 spectra

Kenneth R. Sembach

The Far Ultraviolet Spectroscopic Explorer (FUSE) is a NASA astronomy mission that will explore the 905-1187 A wavelength region at high spectral resolution. Funded by NASA's Explorer Program, this Origins mission is scheduled for a 1999 launch and at least three years of operations. The development of FUSE is being led by the Johns Hopkins University, w

S. L. Tufte, R. J. Reynolds, L. M. Haffner

The nature of turbulence in the warm ionized component of the interstellar medium (WIM) can be investigated using Fabry-Perot spectroscopy of optical emission lines. The H-alpha intensity provides the emission measure (EM) along a line of sight, which is used in conjunction with the scattering measure, rotation measure, and dispersion measure to study inters

Aaron Sokasian, Eric Gawiser, George F. Smoot

We estimate the contribution of extragalactic radio sources to fluctuations in sky temperature over the range of frequencies (10-300 GHz) used for Cosmic Microwave Background (CMB) anisotropy measurements. CMB anisotropy observations at high resolution and low frequencies are especially sensitive to this foreground. We have compiled a catalog of 2207 bright

A. J. Norton, A. P. Beardmore, Alasdair Allan, Coel Hellier

We present data from long ROSAT HRI observations of the intermediate polars YY Dra and V709 Cas which show that V709 Cas, like YY Dra, exhibits a double-peaked X-ray pulse profile. Neither system shows evidence for X-ray beat period or orbital modulation, so both must be disc-fed accretors seen at low inclination angles. We argue that the short spin periods

Carlotta Gruppioni, Marco Mignoli, Gianni Zamorani

Deep imaging and spectroscopy have been carried out for optical counterparts of a sample of 68 faint radio sources (S > 0.2 mJy) in the ``Marano Field''. About 60% of the sources have been optically identified on deep CCD exposures (limit R ~ 24.0) or ESO 3.6-m plates (limit bJ ~ 22.5). Thirty-four spectra (50% of the total radio sample) were obtaine

Kazuyuki Omukai, Ryoichi Nishi

The evolution of collapsing metal free protostellar clouds is investigated for various masses and initial conditions. We perform hydrodynamical calculations for spherically symmetric clouds taking account of radiative transfer of the molecular hydrogen lines and the continuum, as well as of chemistry of the molecular hydrogen. The collapse is found to procee

Pasi Hakala, Panu Muhli, Guillaume Dubus

We present results of the first multicolour photometric study of 4U1957+115, one of the optically less studied low mass X-ray binaries (LMXB). Our quasi-simultaneous UBVRI observations reveal that the light curve pulse shape over the 9.33 hr period discovered by Thorstensen (1987) has changed substantially since his earlier V band studies. The light curve no

S. Sridhar, J. Touma

We classify orbits of stars that are bound to central black holes in galactic nuclei. The stars move under the combined gravitational influences of the black hole and the central star cluster. Within the sphere of influence of the black hole, the orbital periods of the stars are much shorter than the periods of precession. We average over the orbital motion

T. Kawaguchi, S. Mineshige

Number of monitoring observations of continuum emission from Active Galactic Nuclei (AGNs) have been made in optical--X-ray bands. The results obtained so far show (i) random up and down on timescales longer than decades, (ii) no typical timescales of variability on shorter timescales and (iii) decreasing amplitudes as timescales become shorter. The second f

G. Matt, M. Guainazzi, R. Maiolino, S. Molendi

The Circinus Galaxy has been observed, for the first time above 10 keV, by BeppoSAX. An excess emission above the extrapolation of the best fit 0.1--10 keV spectrum is apparent in the PDS data. The most likely explanation is that we are observing the nucleus through a column density of about 4x10**24 cm-2, i.e. large enough to completely block the radiation

Martin Kerscher

Second-order measures, such as the two-point correlation function, are geometrical quantities describing the clustering properties of a point distribution. In this article well-known estimators for the correlation integral are reviewed and their relation to geometrical estimators for the two-point correlation function is put forward. Simulations illustrate t

H. Kjeldsen, T. R. Bedding, S. Frandsen, T. H. Dall

We report the most sensitive search yet made for solar-like oscillations. We observed the star alpha Cen A in Balmer-line equivalent widths over six nights with both the 3.9m Anglo-Australian Telescope and the ESO 3.6m telescope. We set an upper limit on oscillations of 1.4 times solar and found tentative evidence for p-mode oscillations. We also found a pow

Hee-Won Lee

A line photon incident in an electron-scattering medium is transferred in a diffusive way both in real space and in frequency space, and the mean number of scatterings changes as the wavelength shifts from the line center. This leads to the profile broadening and polarization dependence on the wavelength shift as a function of the Thomson optical depth $τ_T$

P. Cinzano, F. J. Diaz Castro

The direction of the upward light emission has different polluting effects on the sky depending on the distance of the observation site. We studied with detailed models for light pollution propagation the ratio $(b_{H})/(b_{L})$, at given distances from a city, between the artificial sky luminance $b_{H}$ produced by its upward light emission between a given

Vicki L. Sarajedini, Richard F. Green, Richard E. Griffiths, Kavan Ratnatunga

This study explores the space density and properties of active galaxies to z=0.8. We have investigated the frequency and nature of unresolved nuclei in galaxies at moderate redshift as indicators of nuclear activity such as Active Galactic Nuclei (AGN) or starbursts. Candidates are selected by fitting imaged galaxies with multi-component models using maximum

Sanjay Reddy, Madappa Prakash, James M. Lattimer, Jose A. Pons

An extensive study of the effects of correlations on both charged and neutral current weak interaction rates in dense matter is performed. Both strong and electromagnetic correlations are considered.The propagation of particle-hole interactions in the medium plays an important role in determining the neutrino mean free paths. The effects due to Pauli-Blockin

P. Cinzano

The knowledge of the contribution $b_d(d)$ to the artificial sky luminance in a given point of the sky of a site produced by the sources beyond a given distance $d$ from it is important to understand the behaviour of light pollution in diffusely urbanized areas and to estimate which fraction of the artificial luminance would be regulated by norms or laws lim

Vicki L. Sarajedini, Richard F. Green, Richard E. Griffiths, Kavan Ratnatunga

This study explores the space density and properties of active galaxies to z=0.8. We have investigated the frequency and nature of unresolved nuclei in galaxies at moderate redshift as indicators of nuclear activity such as Active Galactic Nuclei (AGN) or starbursts. Candidates are selected by fitting imaged galaxies with multi-component models using maximum

B. Eden, P. S. Howe, C. Schubert, E. Sokatchev

Four-point functions of gauge-invariant operators in D=4, N=4 supersymmetric Yang-Mills theory are studied using N=2 harmonic superspace perturbation theory. The results are expressed in terms of differential operators acting on a scalar two loop integral. The leading singular behaviour is obtained in the limit that two of the points approach one another. We

Craig J. Hogan

Intrinsically cold particle dark matter inevitably creates halos with sharp discontinuities in projected surface density caused by the projection of fold catastrophes onto the sky. In principle, these imperfections can be detected and measured with gravitational lensing through discontinuities in image magnification and image structure. Lens solutions are di

Cenalo Vaz, Louis Witten

We examine the Wheeler-DeWitt equaton for a static, eternal Schwarzschild black hole in Kucha\v r-Brown variables and obtain its energy eigenstates. Consistent solutions vanish in the exterior of the Kruskal manifold and are non-vanishing only in the interior. The system is reminiscent of a particle in a box. States of definite parity avoid the singular geom

R. B. Mann, D. Robbins, T. Ohta

We consider the N-body problem in (1+1) dimensional lineal gravity. For 2 point masses (N=2) we obtain an exact solution for the relativistic motion. In the equal mass case we obtain an explicit expression for their proper separation as a function of their mutual proper time. Our solution gives the exact Hamiltonian to infinite order in the gravitational cou

I. V. Moskalenko, A. W. Strong

The inverse Compton scattering of interstellar photons off cosmic-ray electrons seems to play a more important role in the generation of diffuse emission from the Galaxy than thought before. The background radiation field of the Galaxy is highly anisotropic since it is dominated by the radiation from the Galactic plane. An observer in the Galactic plane thus

A. De Rujula, M. B. Gavela, P. Hernandez

Data from atmospheric and solar neutrinos indicate that there are at least three neutrino types involved in oscillation phenomena. Even if the corresponding neutrino mass scales are very different, the inevitable reference to mixing between more than two neutrino types has profound consequences on the planning of the accelerator experiments suggested by thes

Patricia Dolez, Benoit des Ligneris, Marcel Aubin, When Zhu

Creating complex flux configurations by superposing a dc current or magnetic field onto the ac current in a type II superconducting tape should lead to a variety of peculiar behaviors. An example is the appearance of the Clem valley, a minimum in the ac losses as a function of the dc bias amplitude, which has been theoretically studied by LeBlanc et al., in

Liu Yang, M. P. Anantram, Jie Han, J. P. Lu

We use a simple picture based on the $π$ electron approximation to study the bandgap variation of carbon nanotubes with uniaxial and torsional strain. We find (i) that the magnitude of slope of bandgap versus strain has an almost universal behaviour that depends on the chiral angle, (ii) that the sign of slope depends on the value of $(n-m) \bmod 3$ and (iii

J. Berges, D. -U. Jungnickel, C. Wetterich

We present an analytical description of the phase transitions from a nucleon gas to nuclear matter and from nuclear matter to quark matter within the same model. The equation of state for quark and nuclear matter is encoded in the effective potential of a linear sigma model. We exploit an exact differential equation for its dependence upon the chemical poten

Bernhard Bodmann, Hajo Leschke, Simone Warzel

Adapting ideas of Daubechies and Klauder [J. Math. Phys. {\bf 26} (1985) 2239] we derive a rigorous continuum path-integral formula for the semigroup generated by a spin Hamiltonian. More precisely, we use spin-coherent vectors parametrized by complex numbers to relate the coherent representation of this semigroup to a suitable Schrödinger semigroup on the H

L. Giusti, A. Romanino, A. Strumia

The LEP2 experiments pose a serious naturalness problem for supersymmetric models. The problem is stronger in gauge mediation than in supergravity models. Particular scenarios, like electroweak baryogenesis or gauge mediation with light messengers, are strongly disfavoured. Searching a theoretical reason that naturally explains why supersymmetry has not been

S. Baez, A. P. Balachandran, S. Vaidya, B. Ydri

Monopoles and solitons have important topological aspects like quantized fluxes, winding numbers and curved target spaces. Naive discretizations which substitute a lattice of points for the underlying manifolds are incapable of retaining these features in a precise way. We study these problems of discrete physics and matrix models and discuss mathematically

Marco Laucelli Meana, Jesús Puente Peñalba

In this work we use the Matrix Model of Strings in order to extract some non-perturbative information on how the Hagedorn critical temperature arises from eleven-dimensional physics. We study the thermal behavior of M and Matrix theories on the compactification backgrounds that correspond to string models. We obtain some information that allows us to state t

Sin Kyu Kang, C. S. Kim

Recently, many authors showed that if the solar and atmospheric neutrino data are both described by maximal mixing vacuum oscillations at the relevant mass scale, then there exists a unique bi-maximal lepton mixing matrix for three neutrino flavors. We construct the lepton mass matrices from the symmetry principle so that maximal mixings for the atmospheric

R. J. Baxter

We discuss the hard-hexagon and hard-square problems, as well as the corresponding problem on the honeycomb lattice. The case when the activity is unity is of interest to combinatorialists, being the problem of counting binary matrices with no two adjacent 1's. For this case we use the powerful corner transfer matrix method to numerically evaluate the pa

A. F. Morpurgo, D. B. Robinson, C. M. Marcus

We report a new technique for fabricating metallic electrodes on insulating substrates with separations on the 1 nm scale. The fabrication technique, which combines lithographic and electrochemical methods, provides atomic resolution without requiring sophisticated instrumentation. The process is simple, controllable, reversible, and robust, allowing rapid f

Ron Donagi, Andre Lukas, Burt A. Ovrut, Daniel Waldram

In this letter, we introduce a general theory for the construction of particle physics theories, with three families and realistic gauge groups, within the context of heterotic M-theory. This is achieved using semi-stable holomorphic gauge bundles over elliptically fibered Calabi-Yau three-folds. Construction of realistic theories is facilitated by the appea

J. -C. Geminard, W. Losert, J. P. Gollub

The mechanical response of a wet granular layer to imposed shear is studied experimentally at low applied normal stress. The granular material is immersed in water and the shear is applied by sliding a plate resting on the upper surface of the layer. We monitor simultaneously the horizontal and the vertical displacements of the plate to submicron accuracy wi

S. M. Roy

We present a new causal quantum mechanics in one and two dimensions developed recently at TIFR by this author and V. Singh. In this theory both position and momentum for a system point have Hamiltonian evolution in such a way that the ensemble of system points leads to position and momentum probability densities agreeing exactly with ordinary quantum mechani

Harry Buhrman, Ronald de Wolf

We prove lower bounds on the error probability of a quantum algorithm for searching through an unordered list of N items, as a function of the number T of queries it makes. In particular, if T=O(sqrt{N}) then the error is lower bounded by a constant. If we want error <1/2^N then we need T=Omega(N) queries. We apply this to show that a quantum computer cannot

B. G. Sidharth

In this paper we suggest a formulation that would bear out the spirit of Prigogine&#39;s &#34;Order Out of Chaos&#34; and Wheeler&#39;s &#34;Law Without Law&#34;. In it a typical elementary particle length, namely the pion Compton wavelength arises from the random motion of the N particles in the universe of dimension R. It is then argued in the light of rec

Peter Schuster, Walter Fontana

The relationship between sequences and secondary structures or shapes in RNA exhibits robust statistical properties summarized by three notions: (1) the notion of a typical shape (that among all sequences of fixed length certain shapes are realized much more frequently than others), (2) the notion of shape space covering (that all typical shapes are realized

M. Kibler, M. Daoud

Models describing one- and two-photon transitions for ions in crystalline environments are unified and extended to the case of parity-allowed and parity- forbidden p-photon transitions. The number of independent parameters for characterizing the polarization dependence is shown to depend on an ensemble of properties and rules which combine symmetry considera

M. Kibler, M. Daoud

Finite symmetry adaptation techniques are applied to the determination of the intensity strength of two-photon transitions for ions with one partly-filled shell nl in crystalline environments of symmetry G. We treat the case of intra- configurational transitions as well as the case of inter-configurational transitions. In both cases, the Wigner-Racah algebra

C. J. Lewa

A method was presented of profiling the magnetic field, with a zero vector of magnetic flux density $B_{r}$ and strong gradient G, enabling conditions for the Stern-Gerlach spectroscopy to be accomplished in condensed matter (the method has been called magnetic field gradient spectroscopy - MGRS), as well the previously proposed magnetic resonance spectrosco

M. Daoud, M. Kibler

Symmetry adaptation techniques are applied to the determination of the intensity of two-photon absorption transitions, between Stark levels of configurations with opposite parities, for transition ions in finite symmetry environments. The equivalence between third-order mechanisms and second- plus first-order mechanisms is clearly established. A compact form

M. Kibler

Symmetry adaptation techniques are applied to the determination of the intensity of two-photon transitions for transition ions in finite symmetry environments. We treat the case of intra-configurational transitions with some details and briefly report some results on inter-configurational transitions. In particular, for intra-configurational transitions, we

Oscar Bolina, L. H. A. Monteiro

In a simplified fashion, the motion of the eyeball in its orbit consists of rotations around a fixed point. Therefore, this motion can be described in terms of the Euler&#39;s angles of rigid body dynamics. However, there is a physiological constraint in the motion of the eye which reduces to two its degrees of freedom. This paper reviews the basic features

Victor M. Burlakov

Dynamical coherent structure (pattern) formation in the Klein-Gordon lattice excited by periodic external field near the optical resonance is studied. It is shown that besides spatial patterns discovered recently (V.M.Burlakov, Phys.Rev.Lett. 80, 3988 (1998)) the spatio-temporal patterns can be generated in the lattice in rather broad region of excitation pa

A. Covello, L. Coraggio, A. Gargano, N. Itako

We address the two main questions relevant to microscopic nuclear structure calculations starting from a free NN potential. These concern the accuracy of these kinds of calculations and the extent to which they depend on the potential used as input. Regarding the first question, we present some results obtained for nuclei around doubly magic 132Sn and 208Pb

Vivek Kumar Tiwari, Anirban Kundu

We show how the nuclear medium affects the masses of the $η$ and $η&#39;$ mesons. The change should be easily detectable for dense matter and/or strong $η(η&#39;)N\bar N$ coupling. We also find that the $η-η&#39;$ mixing angle is less in magnitude in the nuclear matter than in vacuum.

K. Tsushima

Using the quark-meson coupling (QMC) model, we investigate theoretically whether $η$ and $ω$ mesons form meson-nucleus bound states. We study several nuclei from $^{6}$He to $^{208}$Pb, including those which are the final nuclei in the proposed experiment at GSI. Results for the $ω$ are compared with those of the Walecka model. Our results suggest that one s

Chi-Keung Chow, Thomas D. Cohen

We thank Tom Schafer for pointing out difficulties in this paper.

Thomas D. Cohen, Chi-Keung Chow

We thank Tom Schafer for pointing out difficulties in this paper.

Joakim Nystrand, Spencer Klein, the STAR Collaboration

Ultra-relativistic heavy-ions carry strong electromagnetic and nuclear fields. Interactions between these fields in peripheral nucleus-nucleus collisions can probe many interesting physics topics. This presentation will focus on coherent two-photon and photonuclear processes at RHIC. The rates for these interactions will be high. The coherent coupling of all

V. Aldaya, J. Guerrero, G. Marmo

In this paper we are mainly concerned with the study of polarizations (in general of higher-order type) on a connected Lie group with a U(1)-principal bundle structure. The representation technique used here is formulated on the basis of a group quantization formalism previously introduced which generalizes the Kostant-Kirillov co-adjoint orbits method for c

Michael Farber

S.P.Novikov developed an analog of the Morse theory for closed 1-forms. In this paper I suggest an analog of the Lusternik - Schnirelman theory for closed 1-forms.

Greg Martin

An Egyptian fraction is a sum of distinct unit fractions (reciprocals of positive integers). We show that every rational number has Egyptian fraction representations where the number of terms is of the same order of magnitude as the largest denominator, improving a result from an earlier paper to best-possible form. We also settle, in best-possible form, the

Mina Teicher

The main result in this paper is as follows: Let S be the branch curve (in the projective plan) of a generic projection of a Veronese surface. Then the fundamental group of the complement of S is an extension of a solvable group by a symmetric group. A group with the property mentioned above is ``almost solvable&#39;&#39; in the sense that it contains a solv

Alexander Fel&#39;shtyn, Hector Sánchez-Morgado

In this paper we compute the Reidemeister torsion of a isoenergetic surface for the integrable Hamiltonian system on the four-dimensional symplectic manifold. We use the spectral sequence defined by the filtration and following Witten-Floer ideas we bring into play the orbits connecting the critical submanifolds.

Reinhold Huebl, Amnon Yekutieli

Let X be a variety over a field of characteristic 0. Given a vector bundle E on X we construct Chern forms c_{i}(E;\nabla) in Γ(X, \cal{A}^{2i}_{X}). Here \cal{A}^{.}_{X} is the sheaf Beilinson adeles and \nabla is an adelic connection. When X is smooth these adeles calculate the algebraic De Rham cohomology, and c_{i}(E) = [c_{i}(E;\nabla)] are the usual Ch

A. Yu. Olshanskii, M. Sapir

We survey recent results about asymptotic functions of groups, obtained by the authors in collaboration with J.-C.Birget, V. Guba and E. Rips. We also discuss methods used in the proofs of these results.

J. -C. Birget, A. Yu. Olshanskii, E. Rips, M. Sapir

We prove that the word problem of a finitely generated group $G$ is in NP (solvable in polynomial time by a non-deterministic Turing machine) if and only if this group is a subgroup of a finitely presented group $H$ with polynomial isoperimetric function. The embedding can be chosen in such a way that $G$ has bounded distortion in $H$.

Mark Sapir, Jean-Camille Birget, Eliyahu Rips

This is the first of two papers devoted to connections between asymptotic functions of groups and computational complexity. One of the main results of this paper states that if for every $m$ the first $m$ digits of a real number $α\ge 4$ are computable in time $\le C2^{2^{Cm}}$ for some constant $C>0$ then $n^α$ is equivalent (``big O&#39;&#39;) to the Dehn

Doron Zeilberger

The impact of the computer on present and especially future mathematics is illustrated by means of the iconic example of WZ theory.

T R Govindarajan

The existence of ring-like and knotted solitons in O(3) non-linear sigma model is analysed. The role of isotopy of knots/links in classifying such solitons is pointed out. Appearance of torus knot solitons is seen.

Marco Spaans

Observational diagnostics are constructed which reflect the underlying topology of Planckian space-time, and are directly related to phenomena on much larger scales. Specific predictions are made for the masses of elementary particles, coupling constants, quark confinement, black hole states, and the cosmological constant. In particular, a mass of 131.6 GeV

L. P. Horwitz

The problem of the classical non-relativistic electromagnetically kicked oscillator can be cast into the form of an iterative map on phase space. The original work of Zaslovskii {\it et al} showed that the resulting evolution contains a stochastic flow in phase space to unbounded energy. Subsequent studies have formulated the problem in terms of a relativist

M. C. Gonzalez-Garcia

I summarize our results on the attainable limits on the coefficients of dimension-6 operators from the analysis of Higgs boson phenomenology using data taken at Tevatron RUNI and LEPII. Our results show that the coefficients of Higgs-vector boson couplings can be determined with unprecedented accuracy. Assuming that the coefficients of all ``blind&#39;&#39;

O. J. P. Eboli, M. C. Gonzalez-Garcia, S. F. Novaes

We update the indirect bounds on anomalous triple gauge couplings coming from the non-universal one-loop contributions to the $Z \to b \bar{b}$ width. These bounds, which are independent of the Higgs boson mass, are in agreement with the standard model predictions for the gauge boson self-couplings since the present value of $R_b$ agrees fairly well with the

P. Desgrolard, L. Jenkovszky, F. Paccanoni

We suggest a formula interpolating between the known asymptotic regimes of the BFKL equation as the approximate solution of that equation. The parameters appearing in this interpolation are fitted to the data on deep inelastic scattering in a wide range of the kinematical variables. Care is taken of the large-$x$ domain as well, outside the HERA kinematical

P. Desgrolard, M. Giffon, E. Martynov, E. Predazzi

A detailed analysis of the existence of high energy secondary diffractive dips and structures in the extrapolations of the fits to the data is given. The existence of these dips and a fortiori their position is found to be rather model-dependent: present in all eikonalized models including Pomeron, Odderon and secondary Reggeons they disappear when an additi

L. P. Horwitz

A brief summary of the mathematical structure of the Lee-Friedrichs model is given, including the natural extension of its Hamiltonian to a Gel&#39;fand triple, containing a generalized eigenstate for the complex pole. Contains references to some physical applications and relativistic generalizations.

P. Aurenche, M. Fontannaz, J. Ph. Guillet, B. Kniehl

We discuss fixed target and ISR inclusive photon production and attempt a comparison between theory and experiments. The dependence of the theoretical predictions on the structure functions, and on the renormalization and factorization scales is investigated. The main result of this study is that the data cannot be simultaneously fitted with a single set of

P. Desgrolard, A. Lengyel, E. Martynov

A recently published soft Regge Dipole Pomeron model intended for all $x$ and $Q^2$ is proved to give a good agreement with (non fitted) recent HERA data from ZEUS (SVX95) on the protonstructure function $F_2^p(x,Q^2)$ at low $Q^2$ and low $x$. The model also reproduces (without fit) the recently estimated experimental derivatives ${\partial F_2^p\over\parti

Bert-Jan Nauta, Chris van Weert

We consider the extension of static dimensional reduction to real-time. For a scalar field theory it is shown that in the high-temperature limit this leads to an effective classical theory. Quantum corrections to the leading classical behavior are determined by an effective action which can be calculated perturbatively in the background of the classical fiel

H. Arthur Weldon

Conventional finite-temperature perturbation theory in which propagators have poles at $k^{2}=m^{2}$ is shown to break down at the two-loop level for self-interacting scalar fields. The breakdown is avoided by using free thermal propagators that have poles at the same energy as the exact thermal propagator. This quasiparticle energy ${\cal E}(\vec{k})$ is te

A. Hoferichter, E. Laermann, V. K. Mitrjushkin, M. Müller-Preussker

We investigate the limit of vanishing quark mass in quenched lattice QCD with unimproved Wilson fermions at $β=6.0$. Exploiting the correlations of propagators at different time slices we extract pion masses extremely close to the `chiral limit&#39;, despite the presence of `exceptional configurations&#39;. With this at hand, the existence of quenched chiral

Marina Artuso

We describe the two major components of CLEO III: the Silicon Vertex Detector and the Ring Imaging Cherenkov Detector (RICH). The Silicon Vertex Detector is a four layer barrel-style device which spans the radial distance from 2.5 cm to 10.1 cm and covers 93% of the solid angle. It is being constructed using double-sided silicon sensors read out by front end

The OPAL Collaboration, G. Abbiendi et al

Bose-Einstein correlations between like-charge pions are studied in hadronic final states produced by e+e- annihilations at center-of-mass energies of 172 and 183 GeV. Three event samples are studied, each dominated by one of the processes W+W- to qqlnu, W+W- to qqqq, or (Z/g)* to qq. After demonstrating the existence of Bose-Einstein correlations in W decay

F. Belgiorno, M. Martellini

We study some spectral features of the one-particle electron Hamiltonian obtained by separating the Dirac equation in a Kerr-Newman black hole background. We find that the essential spectrum includes the whole real line. As a consequence, there is no gap in the spectrum and discrete eigenvalues are not allowed for any value of the black hole charge $Q$ and a

J. Stockburger, C. H. Mak

An exact and efficient new method to simulate dynamics in dissipative quantum systems is presented. A stochastic Liouville equation, deduced from Feynman and Vernon&#39;s path-integral expression of the reduced density matrix, is used to describe the exact dynamics at any dissipative strength and for arbitrarily low temperatures. The utility of the method is

K. Nho, E. Manousakis

We use a hybrid Monte Carlo algorithm in which a single-cluster update is combined with the over-relaxation and Metropolis spin re-orientation algorithm. Periodic boundary conditions were applied in all directions. We have calculated the fourth-order cumulant in finite size lattices using the single-histogram re-weighting method. Using finite-size scaling th

J. J. Garcia-Ripoll, V. M. Perez-Garcia

We study the dynamics of the mean field model of a Bose-Einstein condensed atom cloud in a parametrically forced trap by using analytical and numerical techniques. The dynamics is related to a classical Mathieu oscillator in a singular potential. It is found that there are wide resonances which can strongly affect the dynamics even when dissipation is presen

V. N. Narozhnyi, J. Freudenberger, V. N. Kochetkov, K. A. Nenkov

The Hall resistivity rho_{xy} of LuNi_2B_2C is negative in the normal as well as in the mixed state and has no sign reversal typical for high-T_c superconductors. A distinct nonlinearity in the rho_{xy} dependence on field H was found in the normal state for T < 40K, accompanied by a large magnetoresistance reaching +90% for mu_0H=16T at T=20K. The scaling r

A. J. Fendrik, M. J. Sanchez

In the present article we perform analytical and numerical calculations related to persistent currents in 2D isolated mesoscopic annular cavities threaded by a magnetic flux. The system considered has a high number of open channels and therefore the single particle spectrum exhibits many level crossings as the flux varies. We determine the effect of the dist

V. N. Narozhnyi, D. Eckert, K. A. Nenkov, G. Fuchs

In Al-free PrBa_2Cu_3O_{7-y} single crystals the kink in the temperature dependence of magnetic susceptibility chi_{ab}(T), connected with Pr antiferromagnetic ordering, disappears after field cooling (FC) in a field H || ab-plane. The kink in chi_c(T) remains unchanged after FC in H || c-axis. As a possible explanation, freezing of the Cu magnetic moments,

A. S. Alexandrov, R. T. Giles

We show that bipolaron formation leads to a d-wave Bose-Einstein condensate in cuprates. It is the bipolaron energy dispersion rather than a particular pairing interaction which is responsible for the d-wave symmetry. The unusual low-temperature dependence of the magnetic field penetration depth in cuprates is explained by the localisation of bosons in the r

V. N. Narozhnyi, S. -L. Drechsler

Recently, Zou et al. (Phys. Rev. Lett. 80, 1074, 1998) reported the observation of bulk superconductivity (SC) for a PrBa_2Cu_3O_x (Pr123) single crystal grown by the traveling-solvent floating zone (TSFZ) method. The aim of this Comment is to show the inconsistency of the value of effective magnetic moment μ_{eff} reported by Zou et al. (2.92μ_B) with their

Ugo Bastolla, H. Eduardo Roman, Michele Vendruscolo

We simulate the evolution of model protein sequences subject to mutations. A mutation is considered neutral if it conserves 1) the structure of the ground state, 2) its thermodynamic stability and 3) its kinetic accessibility. All other mutations are considered lethal and are rejected. We adopt a lattice model, amenable to a reliable solution of the protein

T. Jarlborg

Local density calculations of the electronic structure of FeSi, FeSi_{1-x}Al_x and Fe_{1-x}Ir_xSi systems in the B20 structure are presented. Pure FeSi has a semi-conducting gap of 6 mRy at 0 K. Effects of temperature (T) in terms of electronic and vibrational excitations are included. Various measurable properties, such as magnetic susceptibility chi(T), el

Hai-cang Ren

This is an invited lecture at the XXII International School of Theoretical Physics, Ustron, Poland, 9/10-9/15, 1998. The boson-fermion model of high T_C superconductivity is reviewed. Its applications to the pseudo-gap and DC transport coefficients are discussed.

Michael D. Gladders, Tracy E. Clarke, Christopher R. Burns, Allen Attard

We present the first set of distance limits from the David Dunlap Observatory Intermediate Velocity Cloud (DDO IVC) distance project. Such distance measures are crucial to understanding the origins and dynamics of IVCs, as the distances set most of the basic physical parameters for the clouds. Currently there are very few IVCs with reliably known distances.

B. G. Elmegreen

Observations of normal galactic star-forming regions suggest there is widespread near-uniformity in the initial stellar mass function (IMF) in spite of diverse physical conditions. Fluctuations may come largely from statistical effects and observational selection. There are also tantalizing, but uncertain reports that the IMF shifts systematically in peculia

Suzanne M. Linder

Plots of equivalent width (or neutral hydrogen column density) versus impact parameter (between the galaxy and quasar line of sight) have been used to support a variety of conclusions about the relationship between galaxies and Lyαabsorbers. I &#39;observe&#39; my simulated galaxies again (as in Linder 1998 astro-ph/9810162) except using M_B<-18. It is shown