October 1998 arXiv papers — page 5

W. B. Burton, R. Braun, R. A. M. Walterbos, C. G. Hoopes

During the course of a search for compact, isolated gas clouds moving with anomalous velocities in or near our own Galaxy (Braun and Burton 1998 A&A, in press), we have discovered, in the data of the Leiden/Dwingeloo survey (Hartmann and Burton 1997, Atlas of Galactic Neutral Hydrogen, CUP) of Galactic hydrogen, the HI signature of a large galaxy, moving at

A. A. Starobinsky

It is shown that if a variable cosmological term in the present Universe is described by a scalar field with minimal coupling to gravity and with some phenomenological self-interaction potential $V(φ)$, then this potential can be unambiguously determined from the following observational data: either from the behaviour of density perturbations in dustlike mat

G. Giovannini, L. Feretti, T. Venturi, W. D. Cotton

We present here two epochs of Space VLBI observations at 18 cm of the BL-Lac type object Mkn 501. Thanks to the high resolution of these new data we have found that the inner jet is centrally brightened at its beginning but becomes extended and limb brightened at ~ 8 mas from the core. Moreover a comparison between the two epochs shows the presence of a poss

O. A. Kuznetsov, R. V. E. Lovelace, M. M. Romanova, V. M. Chechetkin

Hydrodynamic simulations have been used to study accretion disks consisting of counterrotating components with an intervening shear layer(s). Configurations of this type can arise from the accretion of newly supplied counterrotating matter onto an existing corotating disk. The grid-dependent numerical viscosity of our hydro code is used to simulate the influ

F. Hamann, K. Davidson, K. Ishibashi, T Gull

We describe some preliminary results from spatially-resolved spectroscopy of the compact ejection knots B and D in the Eta Carinae wind. We emphasize various line diagnostics of the abundances, kinematics and physical conditions. The data are from new STIS-HST observations described by Gull et al. elsewhere in this volume.

Bradley E. Schaefer

The nature of Gamma Ray Bursts (GRBs) remains a complete mystery, despite the recent breakthrough discovery of low energy counterparts, although it is now generally believed that at least most GRBs are at cosmological distances. Virtually all proposed cosmological models require bursters to reside in ordinary galaxies. This can be tested by looking inside th

Patrick Petitjean

It is difficult to describe in a few pages the numerous specific techniques used to study absorption lines seen in QSO spectra and to review even rapidly the field of research based on their observation and analysis. What follows is therefore a pale introduction to the invaluable contribution of these studies to our knowledge of the gaseous component of the

J. S. Thakur, D. Neilson

We calculate the dynamic effective electron-electron interaction potential for a low density disordered two-dimensional electron gas. The disordered response function is used to calculate the effective potential where the scattering rate is taken from typical mobilities from recent experiments. We investigate the development of an effective attractive pair p

P. V. Patanjali, P. Theule, Z. Zhai, N. Hakim

Radio frequency magneto-impedance measurements clearly reveal a pronounced anomaly at 260K besides the main MI transition at 125K in the double perovskite material $La_{1.2}Sr_{1.8}Mn_{2}O_{7}$. This feature is not seen clearly in static resistivity and magnetization measurements. We suggest that this anomaly represents short range magnetic correlations enha

T. M. Klapwijk, S. Das Sarma

We argue on the basis of experimental numbers that the B=0 metal-insulator transition in two dimensions, observed in Si-MOSFETs and in other two-dimensional systems, is likely to be due to a few strongly interacting electrons, which also interact strongly with the random positively ionized impurities. At the insulating side the electrons are all bound in pai

Joy Christian

After providing an extensive overview of the conceptual elements -- such as Einstein's `hole argument' -- that underpin Penrose's proposal for gravitationally induced quantum state reduction, the proposal is constructively criticised. Penrose has suggested a mechanism for objective reduction of quantum states with postulated collapse time T = h/E

Vincenzo Cirigliano, John F. Donoghue, Eugene Golowich

In kaon decay, electromagnetic radiative corrections can generate shifts in the apparent Delta I = 3/2 amplitude of order alpha A_0/A_2 ~ 22 alpha. In order to know the true Delta I = 3/2 amplitude for comparison with lattice calculations and phenomenology, one needs to subtract off this electromagnetic effect. We provide a careful estimate of the electromag

Jacques Distler, Frederic Zamora

We describe new non-supersymmetric conformal field theories in three and four dimensions, using the CFT/AdS correspondence. In order to believe in their existence at large N_c and strong 't Hooft coupling, we explicitly check the stability of the corresponding non-supersymmetric anti-de Sitter backgrounds. Cases of particular interest are the relevant de

Matteo Beccaria, Carlo Presilla, Gian Fabrizio De Angelis, Giovanni Jona-Lasinio

We present a simple derivation of a Feynman-Kac type formula to study fermionic systems. In this approach the real time or the imaginary time dynamics is expressed in terms of the evolution of a collection of Poisson processes. A computer implementation of this formula leads to a family of algorithms parametrized by the values of the jump rates of the Poisso

Carlo Angelantonj

We use the crosscap constraint to construct open descendants of the 0B string compactified on $T^6 /Z_3$ and on $T^4/Z_2$ free of tachyons both in the closed and in the open unoriented sectors. In four dimensions the construction results in a Chan-Paton gauge group $U(8)\otimes U(12)\otimes U(12)$ with three generations of chiral fermions in the representati

K. Iwamoto

We calculate radio-to-X-ray light curves for afterglows caused by non-thermal emission from a highly relativistic blast wave, which is inferred from the gamma-ray flux detected in GRB 980425 and from the very bright radio emission detected in SN 1998bw. We find that the observed gamma-ray and radio light curves are roughly reproduced by the synchrotron emiss

Sunil Mukhi

The SL(2,Z) anomaly recently derived for type IIB supergravity in 10 dimensions is shown to be a consequence of T-duality with the type IIA string, after compactification to 2 dimensions on an 8-fold. This explains the identity of the gravitational 8-forms appearing in different contexts in the effective actions of type IIA and IIB string theories. In this f

C. Charbonnel, W. Dappen, D. Schaerer, P. A. Bernasconi

We present stellar evolutionary models covering the mass range from 0.4 to 1 Msun calculated for metallicities Z=0.020 and 0.001 with the MHD equation of state (Hummer & Mihalas, 1988; Mihalas et al. 1988; Däppen et al. 1988). A parallel calculation using the OPAL (Rogers et al. 1996) equation of state has been made to demonstrate the adequacy of the MHD equ

C. Chryssomalakos, J. A. de Azcarraga, A. J. Macfarlane, J. C. Perez Bueno

After defining cohomologically higher order BRST and anti-BRST operators for a compact simple algebra {\cal G}, the associated higher order Laplacians are introduced and the corresponding supersymmetry algebra $Σ$ is analysed. These operators act on the states generated by a set of fermionic ghost fields transforming under the adjoint representation. In cont

Arne Jacobs, Reiner Kümmel, Hartmut Plehn

In the quasi-twodimensional (Q2D) electron gas of an InAs channel between an AlSb substrate and superconducting Niobium layers the proximity effect induces a pair potential so that a Q2D mesoscopic superconducting-normal-superconducting (SNS) junction forms in the channel. The pair potential is calculated with quasiclassical Green's functions in the clea

D. Drechsel, S. S. Kamalov, G. Krein, L. Tiator

The spin structure functions g1 and g2 have been calculated in the resonance region and for small and intermediate momentum transfer. The calculation is based on a gauge-invariant and unitary model for one-pion photo- and electroproduction. The predictions of the model agree with the asymmetries and the spin sturcture functions recently measured at SLAC, and

M. K. Volkov, V. L. Yudichev, D. Ebert

A chiral U(3)xU(3) Lagrangian, containing besides the usual meson fields their first radial excitations, is considered. The Lagrangian is derived by bosonization of the Nambu--Jona-Lasinio quark model with separable non-local interactions. The spontaneous breaking of chiral symmetry is governed by the NJL gap equation. The first radial excitations of the kao

K. Harigaya

Disorder effects on the density of states and electronic conduction in metallic carbon nanotubes are analyzed by a tight binding model with Gaussian bond disorder. Metallic armchair and zigzag nanotubes are considered. We obtain a conductance which becomes smaller by the factor 1/2 ~ 1/3 from that of the clean nanotube. This decrease mainly comes from lattic

J. Hisano, Daisuke Nomura

Taking the solar and the atmospheric neutrino experiments into account we discuss the lepton flavor violating processes, such as $τ\toμγ$ or $μ\to eγ$, in the minimal supersymmetric standard model with right-handed neutrinos (MSSMRN) and the supersymmetric SU(5) GUT with right-handed neutrinos (SU(5)RN). The predicted branching ratio of $μ\to eγ$ in the MSSM

H. Courtois, Ph. Gandit, B. Pannetier, D. Mailly

We review the mesoscopic transport in a diffusive proximity superconductor made of a normal metal (N) in metallic contact with a superconductor (S). The Andreev reflection of electrons on the N-S interface is responsible for the diffusion of electron pairs in N. Superconducting-like properties are induced in the normal metal. In particular, the conductivity

Yu. A. Kosevich, E. S. Syrkin

We predict an extreme sensitivity to the dissipative losses of the resonant interaction of bulk phonons with a 2D defect in a solid. We show that the total resonant reflection of the transverse phonon at the 2D defect, described earlier without an account for dissipation, occurs only in the limit of extremely weak dissipation and is changed into almost total

S. N. Molotkov, S. S. Nazin

We propose a simple non-linear crystal based optical scheme for experimental realization of the frequency entanglement swapping between the photons belonging to two independent biphotons.

Rajendra Bhandari

The geometric phase is usually treated as a quantity modulo 2π, a convention carried over from early work on the subject. The results of a series of optical interference experiments involving polarization of light, done by the present author (reviewed in R.Bhandari, Phys. Rep. 281 (1997) p.1) question the usefulness of such a definition of the geometric phas

H. Salehi, H. R. Sepangi

A variant of the divergence theory for vacuum-condensation developed in a previous communication is analyzed from the viewpoint of a 'time' asymmetric law in vacuum. This law is found to establish a substantial distinction between dynamically allowed vacuum-configurations related by signature changing duality transformations.

Ting-Wai Chiu

By exploiting the chiral symmetry, we derive analytic formulas for the massless and the massive Ginsparg-Wilson fermion propagators. Using these formulas, we derive an expression for the chiral condensate which is the order parameter for spontaneous chiral symmetry breaking in QCD. These formulas provide the proper way to compute the fermion propagators and

O. Martin, P. Hagler, A. Schafer

The evolution of orbital angular momentum distributions within the radiative parton model is studied. We use different scenarios for the helicity weighted parton distributions and consider a broad range of input distributions for orbital angular momentum. In all cases we are lead to the conclusion that the absolute value of the average angular momentum per p

Gregor Weihs, Thomas Jennewein, Christoph Simon, Harald Weinfurter

We observe strong violation of Bell's inequality in an Einstein, Podolsky and Rosen type experiment with independent observers. Our experiment definitely implements the ideas behind the well known work by Aspect et al. We for the first time fully enforce the condition of locality, a central assumption in the derivation of Bell's theorem. The necessar

David J. Fernandez C

We explain the meaning of dynamical manipulation, and we illustrate its mechanism by using a system composed of a charged particle in a Penning trap. It is shown that by means of appropriate electric shocks (delta-like pulses) applied to the trap walls one can induce the squeezing transformation. The geometric phases associated to some cyclic evolutions, ind

V. V. Dodonov

The problem of photon creation from vacuum due to the nonstationary Casimir effect in an ideal one-dimensional Fabry--Perot cavity with vibrating walls is solved in the resonance case, when the frequency of vibrations is close to the frequency of some unperturbed electromagnetic mode: $ω_w=p(πc/L_0)(1+δ)$, $|δ|\ll 1$, (p=1,2,...). An explicit analytical expr

W. J. Munro, G. J. Milburn

We present a potential realization of the Greenberger, Horne and Zeilinger ALL or NOTHING contradiction of quantum mechanics with local realism using phase measurement techniques in a simple photon number triplet. Such a triplet could be generated using nondegenerate parametric oscillation.

Robert V. Gentry

In late 1997 I reported (Mod. Phys. Lett. A 12 (1997) 2919; astro-ph/9806280) the discovery of A New Redshift Interpretation (NRI) of the Hubble relation and the 2.7K CBR, which showed for the first time that it was possible to explain these phenomena within the framework of a universe governed by Einstein's static-spacetime general relativity (GR) inste

Ross E. Larsen, Richard M. Stratt

Notwithstanding the long and distinguished history of studies of vibrational energy relaxation, exactly how it is that high frequency vibrations manage to relax in a liquid remains somewhat of a mystery. Both experimental and theoretical approaches seem to say that there is a natural frequency range associated with intermolecular motions in liquids, typicall

Chun-yu Ma, Danny Summers

A non-relativistic Fokker-Planck equation for the electron distribution function is formulated incorporating the effects of stochastic acceleration by whistler-mode waves and Coulomb collisions. The stationary solution $f$ to the equation, subject to a zero-flux boundary condition, is found to be a generalized Lorentzian (or kappa) distribution, which satisf

M. Kibler

The role of symmetry adaptation techniques in multi-photon spectroscopy of partly-filled shell ions in crystals is briefly reviewed. This leads to an intensity formula which is discussed from a qualitative point of view.

M. Daoud, M. Kibler

Symmetry adaptation techniques are applied to the determination of intensities of intra-configurational two-photon transitions for transition-metal ions in cubical symmetry. This leads to a simple model giving the polarization dependence of intensities of two-photon (electric dipolar) transitions between Stark levels of the configuration 3dN (N = even or odd

J. Haidenbauer, K. Nakayama, J. W. Durso, C. Hanhart

The reaction $pp \to pp ϕ$ is investigated within a relativistic meson-exchange model of hadronic interactions. The possibility of extracting the $NNϕ$ coupling constant from a study of this process is explored. A combined analysis of $ω-$ and $ϕ$-meson production in proton-proton collisions utilizing recent data on these reactions is carried out and yields

D. Karadjov, V. V. Voronov, F. Catara, M. Grinberg

A method to treat the ground state correlations beyond the RPA is presented. A set of nonlinear equations taking into account effects of the ground state correlations on the pairing and phonon-phonon coupling is derived. The influence of such correlations on properties of the vibrational states in spherical nuclei is studied.

M. Matsuo, S. Takami, K. Yabana

By performing a fully three dimensional Hartree-Fock calculation with use of the Skyrm forces, we demonstrate possibility of exotic deformations violating both the reflection and the axial symmetries of N=Z nuclei in $A \sim 60-80$ mass region. The \Ytwo tetrahedral shape predicted in excited \Zr arises from a shell gap at $N,Z = 40$ which is enhanced for th

M. Matsuo, K. Yoshida, T. Døssing, E. Vigezzi

The damping of collective rotational motion is studied microscopically, making use of shell model calculations based on the cranked Nilsson deformed mean-field and on residual two-body interactions, and focusing on the shape of the gamma-gamma correlation spectra and on its systematic behavior. It is shown that the spectral shape is directly related to the d

A. N. Ivanov, H. Oberhummer, N. I. Troitskaya, M. Faber

The relativistic field theory model of the deuteron (RFMD) is applied to the calculation of the astrophysical factor S_{pp}(0) for the process of the solar proton burning p + p -> D + e^+ + ν_e and the cross sections for the disintegration of the deuteron by photons gamma + D -> n + p and anti-neutrinos \barν_e + D -> e^+ + n + n. Our theoretical value of th

George A. Hagedorn, Bernhard Meller

We investigate a numerical method for studying resonances in quantum mechanics. We prove rigorously that this method yields accurate approximations to resonance energies and widths for shape resonances in the semiclassical limit.

M. J. Dunwoody

Bestvina and Feighn showed that a morphism S --> T between two simplicial trees that commutes with the action of a group G can be written as a product of elementary folding operations. Here a more general morphism between simplicial trees is considered, which allow different groups to act on S and T. It is shown that these morphisms can again be written as a

Daryl Cooper, Darren D. Long

We discuss techniques for analysing the structure of the group obtained by reducing the image of the Burau representation of the braid group modulo a prime. The main tools are a certain sesquilinear form first introduced by Squier and consideration of the action of the group on a Euclidean building.

Derek F. Holt

The history, definition and principal properties of automatic groups and their generalisations to subgroups and cosets are reviewed briefly, mainly from a computational perspective. A result about the asynchronous automaticity of an HNN extension is then proved and applied to an example that was proposed by Mark Sapir.

U. Bunke, M. Olbrich

We obtain the Plancherel theorem for the quotient of a simple Lie group of real rank one by a convex-cocompact discrete subgroup and its consequences for the spectrum of locally invariant differential operators on bundles over Kleinian manifolds. We develop a geometric version of scattering theory. The paper is an update of dg-ga/9609011, which is completely

A. Kempf

The set of space-time short-distance structures which can be described through linear operators is limited to a few basic cases. These are continua, lattices and a further short-distance structure which implies an ultraviolet cut-off. Under certain conditions, these cut-off degrees of freedom can reappear as internal degrees of freedom. We review the current

Alexios P. Polychronakos

We construct generalizations of the Calogero-Sutherland-Moser system by appropriately reducing a classical Calogero model by a subset of its discrete symmetries. Such reductions reproduce all known variants of these systems, including some recently obtained generalizations of the spin-Sutherland model, and lead to further generalizations of the elliptic mode

R. Dijkgraaf

We discuss two-dimensional sigma models on moduli spaces of instantons on K3 surfaces. These N=(4,4) superconformal field theories describe the near-horizon dynamics of the D1-D5-brane system and are dual to string theory on AdS_3. We derive a precise map relating the moduli of the K3 type IIB string compactification to the moduli of these conformal field th

B. G. Konopelchenko, G. Landolfi

The generalized Weierstrass representation for surfaces in $\Bbb{R}^{3}$ is used to study quantum effects for strings governed by Polyakov-Nambu-Goto action. Correlators of primary fields are calculated exactly in one-loop approximation for the pure extrinsic Polyakov action. Geometrical meaning of infrared singularity is discussed. The Nambu-Goto and sponta

H. T. Ozer

Starting from the well-known quantum Miura-like transformation for the non simply-laced Lie algebras B(3),we give an explicit construction of the Casimir WB(3) algebras.We reserve the notation WB(N) for the Casimir W algebras of type W(2,4,6,...,2N,N+1/2) which contains one fermionic field. It is seen that WB(3) algebra is closed an associative for all value

Patrick Dorey, Paolo Provero, Roberto Tateo, Stefano Vinti

We point out some problems with the previously-proposed phase diagram of the $Z_6$ spin models. Consideration of the diagram near to the decoupling surface using both exact and approximate arguments suggests a modification which remedies these deficiencies. With the aid of a new parametrisation of the phase space, we study the models numerically, with result

R. K. Ellis, S. Veseli

We calculate the strong radiative corrections to the process p pbar -> W(->e nu) g^*(->b bbar). At the Tevatron this process is the largest background to the associated Higgs boson production p pbar -> W(-> e nu) H(-> b bbar). The calculation is based on the subtraction procedure, and the corrections are found to be significant.

Thomas Mehen

I review the status of the extraction of NRQCD color-octet $J/ψ$ production matrix elements. Large theoretical uncertainties in current extractions from hadroproduction and photoproduction are emphasized. Leptoproduction of $J/ψ$ is calculated within the NRQCD factorization formalism. Color-octet contributions dominate the cross section, allowing for a relia

C. Spieles, R. Vogt, L. Gerland, S. A. Bass

We study J/psi suppression in AB collisions assuming that the charmonium states evolve from small, color transparent configurations. Their interaction with nucleons and nonequilibrated, secondary hadrons is simulated using the microscopic model UrQMD. The Drell-Yan lepton pair yield and the J/psi/Drell-Yan ratio are calculated as a function of the neutral tr

Gregory Mahlon

We summarize the Standard Model predictions for the three-body decays of the top quark t->WbX, where X = Z,H,g or gamma. Because of strong phase space suppression, we find that the branching ratios for the Z and H final states are of order a few times 10^{-7}, rendering them invisible at Tevatron Run II. On the other hand, the decays to g and gamma are suppr

X. Y. Pham

Neutrino oscillations, as recently reported by the Super-Kamiokande collaboration, imply that lepton numbers could be violated, and $τ^{\pm}\to μ^{\pm}+\ell^{+}+\ell^{-},τ^{\pm}\toμ^{\pm}+ρ^0$ are some typical examples. We point out that in these neutrinoless modes, the GIM cancelation is much milder with only a logarithmic behavior $\log (m_j /m_k)$ where $

D. B. Lichtenberg

Different mechanisms have been proposed to account for the spin-dependent interaction between quarks in ground-state hadrons. The first mechanism is the chromomagnetic interaction arising from one-gluon exchange, a second mechanism is an interaction arising from meson exchange, and a third from instanton effects. Some lattice calculations favor the first mec

Michael Gronau, Dan Pirjol, Tung-Mow Yan

We study the effects of electroweak penguin (EWP) amplitudes in $B$ meson decays into two charmless pseudoscalars in the approximation of retaining only the dominant EWP operators $Q_9$ and $Q_{10}$. Using flavor SU(3) symmetry, we derive a set of model-independent relations between EWP contributions and tree-level decay amplitudes one of which was noted rec

M. Stratmann

The theoretical framework for a next-to-leading order QCD analysis of the spin-dependent parton densities Delta f^{gamma}(x,Q^2) of the longitudinally polarized photon and of its structure function g_1^{gamma}(x,Q^2) is reviewed in some detail. Special emphasis is given to the specific features of different factorization schemes. Two conceivable scenarios fo

P. Colangelo, F. De Fazio, N. Paver

We review the role of the universal Isgur-Wise functions parameterizing the $B$ meson semileptonic matrix elements to charm states in the infinite heavy quark mass limit. We also discuss the determination of one of such form factors by QCD sum rules in the framework of the Heavy Quark Effective Theory.

S. V. Chekanov

The possibility to determine the gluon density inside the proton in deep inelastic ep collisions using current-target multiplicity correlations is discussed.

I. M. Dremin

Contents: 1. Pomeron physics 2. Multiplicities 3. Single-particle distributions 4. Correlations and fluctuations 5. Special final states and interaction mechanisms 6. Cosmic rays and forward detectors

Patricia Ball, V. M. Braun

We present a systematic study of twist-4 light-cone distribution amplitudes of vector mesons in QCD, which is based on conformal expansion. The structure of meson mass corrections is studied in detail. A complete set of distribution amplitudes is constructed, which satisfies all (exact) equations of motion and constraints from conformal expansion. Nonperturb

M. Pepe

A new method to compute observables at many values of the parameters λfor a model with lattice action {\cal{S}}(ϕ, λ) is described. After fixing a reference set λ^r of parameters, a single simulation is carried out by using a ``reference action'' {\cal{S}} (ϕ^r, λ^r) to generate configurations of the field ϕ^r. Then a suitable analytic transformation

R. D. Kenway

Recent results for the spectrum of light hadrons provide clear evidence for the failure of quenched QCD and encouraging signs that simulations with dynamical sea quarks rectify some of the discrepancies, although string breaking has not yet been observed. The use of perturbation theory to match lattice quark masses to continuum schemes remains questionable,

John W. Negele

A large body of evidence from lattice calculations indicates that instantons play a major role in the physics of light hadrons. This evidence is summarized, and recent results concerning the instanton content of the SU(3) vacuum, instanton contributions to the static potential, and a new class of instanton solutions at finite temperature are reviewed.

B. Anderson, A. Anjomshoaa, P. Dervan, J. A. Lauber

We describe here a proposal for a light injection calibration system for the MINOS detectors based on ultra bright blue LEDs as the light source. We have shown that these LEDs are bright enough to span over two orders of magnitude in light intensity, commensurate with that expected in a single scintillator strip in the MINOS neutrino detectors.

W. Krivan, R. H. Price

Realistic black hole collisions result in a rapidly rotating Kerr hole, but simulations to date have focused on nonrotating final holes. Using a new solution of the Einstein initial value equations we present here waveforms and radiation for an axisymmetric Kerr-hole-forming collision starting from small initial separation (the ``close limit'' approx

L. Herrera, Filipe M. Paiva, N. O. Santos

It is shown that the Levi-Civita metric can be obtained from a family of the Weyl metric, the Gamma metric, by taking the limit when the length of its Newtonian image source tends to infinity. In this process a relationship appears between two fundamental parameters of both metrics.

Yuri Gurevich, James K. Huggins

We give an evolving algebra solution for the well-known railroad crossing problem and use the occasion to experiment with agents that perform instantaneous actions in continuous time and in particular with agents that fire at the moment they are enabled.

James K. Huggins

We describe the architecture of an evolving algebra partial evaluator, a program which specializes an evolving algebra with respect to a portion of its input. We discuss the particular analysis, specialization, and optimization techniques used and show an example of its use.

Yuri Gurevich, James K. Huggins

We describe an automated partial evaluator for evolving algebras implemented at the University of Michigan.

Yuri Gurevich, James K. Huggins

In a recent provocative paper, Lamport points out "the insubstantiality of processes" by proving the equivalence of two different decompositions of the same intuitive algorithm by means of temporal formulas. We point out that the correct equivalence of algorithms is itself in the eye of the beholder. We discuss a number of related issues and, in part

James K. Huggins

We apply the Gurevich Abstract State Machine methodology to a benchmark specification problem of Broy and Lamport.

S. Bogdanovich, M. P. Sarachik, R. N. Bhatt

The low-temperature dc conductivities of barely metallic samples of p-type Si:B are compared for a series of samples with different dopant concentrations, n, in the absence of stress (cubic symmetry), and for a single sample driven from the metallic into the insulating phase by uniaxial compression, S. For all values of temperature and stress, the conductivi

N. V. Prokof'ev, P. C. E. Stamp

Recent theory and experiment in crystals of molecular magnets suggest that fundamental tests of the decoherence mechanisms of macroscopic quantum phenomena may be feasible in these systems (which are almost ideal quantum spin glasses). We review the results, and suggest new experiments.

P. C. E. Stamp

The low-energy physics of systems coupled to their surroundings is understood by truncating to effective Hamiltonians; these tend to reduce to a few canonical forms, involving coupling to "baths" of oscillators or spins. The method for doing this is demonstrated using examples from magnetism, superconductivity, and measurement theory, as is the way o

Z. Zhai, Patanjali V. Parimi, S. Sridhar

The non-linear dependence on applied $ac$ field ($b_ω$) or current ($% i_ω$) of the microwave (ac) impedance $R_ω+iX_ω$ of both short and long Josephson junctions is calculated under a variety of excitation conditions. The dependence on the junction width is studied, for both field symmetric (current anti-symmetric) and field anti-symmetric (current symmetri

G. Rose, P. C. E. Stamp

We calculate the magnetisation relaxation in the short-time regime for an ensemble of nanomagnets in the presence of a low-frequency external AC biasing field, at temperatures lower than the magnetic anisotropy energy of the individual nanomagnets. It is then found that the relaxation is strongly affected by AC fields with amplitude larger than that of the $

A. A. Aligia, G. Ortiz

We introduce a fundamental complex quantity, $z_{L}$, which allows us to discriminate between a conducting and non-conducting thermodynamic phase in extended quantum systems. Its phase can be related to the expectation value of the position operator, while its modulus provides an appropriate definition of a localization length. The expressions are valid for

A. V. Krasheninnikov, R. A. Koltsov

The effect of temperature on the operation of the elementary quantum-dot spin gates for single-electron computing is studied theoretically within the framework of the Hubbard model by the example of the NOT-AND gate. The calculated values of the uniform external magnetic field necessary to realize the whole truth table proved to be unreasonably high for the

V. Filinov, Yu. Lozovik, A. Filinov, I. Zacharov

The new numerical approach for consideration of quantum dynamics and calculations of the average values of quantum operators and time correlation functions in the Wigner representation of quantum statistical mechanics has been developed. The time correlation functions have been presented in the form of the integral of the Weyl's symbol of considered oper

L. A. Openov

The combined effect of both nonmagnetic and magnetic impurities on the superconducting transition temperature is studied theoretically within the BCS model. An expression for the critical temperature as a function of potential and spin-flip scattering rates is derived for a two-dimensional superconductor with arbitrary in-plane anisotropy of the superconduct

A. V. Kolesnikov, A. P. Silin

We study a motion of quantum particles, whose properties depend on one coordinate so that they can move freely in the perpendicular direction. A rotationally-symmetric Hamiltonian is derived and applied to study a general interface formed between two semiconductors. We predict a new type of electron states, localized at the interface. They appear whenever th

E. Sh. Mamasakhlisov, V. F. Morozov

The some dynamic properties of a random heteropolymer in the condensed state are studied in the mode coupling approximation. In agreement with recent report a dynamic friction increasing is predicted for the random heteropolymer with power-law correlations in comparison with exponential correlations. In the case of strong power-law correlations the dynamic f

Fernando Sols

I present an overview of the physics of the Josephson effect between Bose condensed systems, with emphasis on the recently achieved BEC's in trapped alkali gases. I focus mostly on those physical phenomena that are likely to be observed only (or more easily) in these novel systems. Thus I omit the discussion of problems which may be viewed as straightfor

V. Meden

The one-particle Green's function of the Tomonaga-Luttinger model for one-dimensional interacting Fermions is discussed. Far away from the origin of the plane of space-time coordinates the function falls off like a power law. The exponent depends on the direction within the plane. For a certain form of the interaction potential or within an approximated

J. Shiraishi, M. Kohmoto, K. Maki

Use is made of Onsager's hydrodynamic equation to derive the vibration spectrum of the vortex lattice in d-wave superconductor. In particular the rhombic lattice (i.e. the $45^\circ$ tilted square lattice) is found to be stable for $B>H_{cr}(t)$. Here $H_{cr}(t)$ denotes the critical field at which the vortex lattice transition takes place.

Nobuhiko Taniguchi

As a unified theory of integer and fractional quantum Hall plateau transitions, a nonperturbative theory of the two-parameter scaling renormalization group function is presented. By imposing global symmetries known as ``the law of corresponding states'', we seek a possible form of renormalization group flows. Asking for consistency with the result fr

A. S. Moskvin, Yu. D. Panov

The doped cuprates are considered to be a system of local spinless bosons moving in a lattice of the hole pseudo-Jahn-Teller centers CuO_{4}^{5-}. A detailed qualitative and quantitative description of the vibronic mechanism determining both the isotope substitution and the external pressure effect on T_c is given. This mechanism can properly interpret the p

Steven R. White

We present a new type of basis set which is local, compact, and orthogonal. The basis functions, called orthlets, are centered at the sites of a lattice and are specifically adapted to represent the system being studied. The adaptability includes the ability to have singular behavior within an orthlet, allowing a single orthlet to represent a function in the

P. Ruiz-Lapuente

While low-z Type Ia supernovae are used to measure the present rate of expansion of the Universe, high-z Type Ia measure its variation due to the cosmic matter-energy content. Results from those determinations imply a low matter density Universe with a non-zero cosmological constant (vacuum-energy component). The expansion rate of the Universe accelerates, a

Cristina Chiappini, Francesca Matteucci, Timothy Beers, Ken'ichi Nomoto

In this paper we study the very early phases of the evolution of our Galaxy by means of a chemical evolution model which reproduces most of the observational constraints in the solar vicinity and in the disk. We have restricted our analysis to the solar neighborhood and present the predicted abundances of several elements (C, N, O, Mg, Si, S, Ca, Fe) over an

Kathryn V. Johnston

If the Galaxy formed hierarchically through the accretion of smaller satellite galaxies we might hope to find signatures of this in the halo's phase-space distribution. I review theoretical ideas about what form these signatures should take, concentrating in particular on the characteristics of debris from the tidal disruption of satellites less than the

D. A. Fischer, G. W. Marcy, R. P. Butler, S. S. Vogt

We have enlarged the sample of stars in the planet search at Lick Observatory. Doppler measurements of 82 new stars observed at Lick Observatory, with additional velocities from Keck Observatory, have revealed two new planet candidates. The G3V/IV star, HD 195019, exhibits Keplerian velocity variations with a period of 18.27 d, an orbital eccentricity of 0.0