March 2000 arXiv papers — page 11

Mohammad Golshani, Saharon Shelah

We show if we use countable support iteration of forcing notions not adding reals that satisfy additional conditions, then the limit forcing does not add reals. As a result we prove that we can amalgamate two earlier methods and prove the consistency with ZFC + GCH of two statements gotten separately earlier: Souslin hypothesis and non-club guessing. We also

Miao Li

The recently proposed remarkable mechanism explaining ``stringy exclusion principle" on an Anti de Sitter space is shown to be another beautiful manifestation of spacetime uncertainty principle in string theory as well as in M theory. Put in another way, once it is realized that the graviton of a given angular momentum is represented by a spherical brane

J. E. Sonier, R. H. Heffner, D. E. MacLaughlin, G. J. Nieuwenhuys

Muon spin rotation measurements of the temperature dependence of the Knight shift in single crystals of U_{0.965}Th_{0.035}Be_{13} have been used to study the static spin susceptibility below the transition temperatures T_{c1} and T_{c2}. While an abrupt reduction of the susceptibility with decreasing temperature is observed below T_{c1}, the susceptibility

Igor Bandos, Alexei Nurmagambetov, Dmitri Sorokin

The kappa--invariant worldvolume action for the NS5--brane in a D=10 type IIA supergravity background is obtained by carrying out the dimensional reduction of the M5--brane action.

A. M. Steane

The nature of quantum computation is discussed. It is argued that, in terms of the amount of information manipulated in a given time, quantum and classical computation are equally efficient. Quantum superposition does not permit quantum computers to ``perform many computations simultaneously'' except in a highly qualified and to some extent misleadin

David Wands, Karim A. Malik, David H. Lyth, Andrew R. Liddle

We discuss the evolution of linear perturbations about a Friedmann-Robertson-Walker background metric, using only the local conservation of energy-momentum. We show that on sufficiently large scales the curvature perturbation on spatial hypersurfaces of uniform-density is conserved when the non-adiabatic pressure perturbation is negligible. This is the first

David Vitali, Mauro Fortunato, Paolo Tombesi

We present a scheme for the quantum teleportation of the polarization state of a photon employing a cross-Kerr medium. The experimental feasibility of the scheme is discussed and we show that, using the recently demonstrated ultraslow light propagation in cold atomic media, our proposal can be realized with presently available technology.

E. V. Deviatov, V. S. Khrapai, A. A. Shashkin, V. T. Dolgopolov

We employ magnetocapacitance measurements to study the spectrum of a double layer system with gate-voltage-tuned electron density distributions in tilted magnetic fields. For the dissipative state in normal magnetic fields at filling factor $ν=3$ and 4, a parallel magnetic field component is found to give rise to opening a gap at the Fermi level. We account

Bahram Mashhoon, Dietmar S. Theiss

The main general relativistic effects in the motion of the Moon are briefly reviewed. The possibility of detection of the solar gravitomagnetic contributions to the mean motions of the lunar node and perigee is discussed.

Katsuyuki Sugiyama

We study a central charge Z of a one parameter family of Calabi-Yau d-fold embedded in CP^{d+1}. For a d-fold case, we construct the Z concretely and analyze charge vectors of D-branes and intersection forms of associated cycles. We find the charges are described as some kinds of Mukai vectors. They are represented as products of Chern characters of coherent

R. Foot

We examine the maximal $ν_e --> ν_s$ and $ν_e --> ν_μ,τ$ oscillation solutions to the solar neutrino problem. These solutions lead to roughly a 50% solar flux reduction for the large parameter range $3\times 10^{-10} < δm^2/eV^2 < 10^{-3}$. It is known that the earth regeneration effect may cause a potentially large night-day asymmetry even for maximal neutr

Marek Czachor

Modification of the right-hand-side of canonical commutation relations (CCR) naturally occurs if one considers a harmonic oscillator with indefinite frequency. Quantization of electromagnetic field by means of such a non-CCR algebra naturally removes the infinite energy of vacuum but still results in a theory which is very similar to quantum electrodynamics.

Jin-Sheng Peng, Gao-Xiang Li, Peng Zhou, S. Swain

A cavity-modified master equation is derived for a coherently driven, V-type three-level atom coupled to a single-mode cavity in the bad cavity limit. We show that population inversion in both the bare and dressed-state bases may be achieved, originating from the enhancement of the atom-cavity interaction when the cavity is resonant with an atomic dressed-st

Peng Zhou

We show that cavity-induced interference may result in spectral line narrowing in the absorption spectrum of a $Ξ$-type atom coupled to a single-mode, frequency-tunable cavity field with a pre-selected polarization at finite temperature.

Choon-Lin Ho, V. R. Khalilov

The Dirac equation for an electron in two spatial dimensions in the Coulomb and homogeneous magnetic fields is discussed. For weak magnetic fields, the approximate energy values are obtained by semiclassical method. In the case with strong magnetic fields, we present the exact recursion relations that determine the coefficients of the series expansion of wav

B. Bagchi, F. Cannata, C. Quesne

The family of complex PT-symmetric sextic potentials is studied to show that for various cases the system is essentially quasi-solvable and possesses real, discrete energy eigenvalues. For a particular choice of parameters, we find that under supersymmetric transformations the underlying potential picks up a reflectionless part.

Johan Hansson

We propose that the mechanism responsible for the ``collapse of the wave function&#34; (or &#34;decoherence&#34; in its broadest meaning) in quantum mechanics is the nonlinearities already present in the theory via nonabelian gauge interactions. Unlike all other models of spontaneous collapse, our proposal is, to the best of our knowledge, the only one which

M. Znojil, G. Levai

We show that and how the Coulomb potential can be regularized and solved exactly at the imaginary couplings. The new spectrum of energies is real and bounded as expected, but its explicit form proves totally different from the usual real-coupling case.

Dong Pyo Chi, Jinsoo Kim, Soojoon Lee

We present a quantum algorithm for the f-conditioned phase transform which does not require any initialization of ancillary register. We also develop a quantum algorithm that can solve the generalized Deutsch-Jozsa problem by a single evaluation of a function.

Andrew Jones, Maxim Nazarov

We study a $q$-deformation for the semi-direct product of the symmetric group $S_n$ with the Clifford algebra on $n$ anticommuting generators. We obtain a $q$-version of the projective analogue for the classical Young symmetrizer found by the second author [Adv. Math. 127(1997), 190-257]. Our main tool is an analogue of the Hecke algebra of complex valued fu

Alexander Al-Hujaj, Peter Schmelcher

The lowest bound states of the hydrogen negative ion and negative donor systems in a homogeneous magnetic field are investigated theoretically via a full configuration interaction approach with an anisotropic Gaussian basis set. The broad magnetic field regime γ=0.0008 - 4000 is covered. Nonrelativistic total energies, electron detachment energies and transi

Michael B. Christiansen, Norman K. Glendenning, Jurgen Schaffner-Bielich

We calculate for the first time the surface tension and curvature coefficient of a first order phase transition between two possible phases of cold nuclear matter, a normal nuclear matter phase in equilibrium with a kaon condensed phase, at densities a few times the saturation density. We find the surface tension is proportional to the difference in energy d

Klaus Morawetz, Uwe Fuhrmann

We reanalyze the recently derived response function for interacting systems in relaxation time approximation respecting density, momentum and energy conservation. We find that momentum conservation leads exactly to the local field corrections for both cases respecting only density conservation and respecting density and energy conservation. This rewriting si

T. Gaitanos, H. H. Wolter, C. Fuchs

We investigate the thermodynamical properties of nuclear matter in heavy ion collisions, in particular with respect to questions of thermodynamical instability, phase transitions and fragmentation. For this we analyze results of relativistic transport calculations of Au+Au collisons at intermediate energies, separately for spectator and participant matter. O

G. Colo`, N. Van Giai, P. F. Bortignon, M. R. Quaglia

Isoscalar dipole strength distributions in spherical medium- and heavy-mass nuclei are calculated within random phase approximation (RPA) or quasiparticle RPA. Different Skyrme-type interactions corresponding to incompressibilities in the range 200 - 250 MeV are used. The results are discussed in comparison with existing data on isoscalar giant dipole resona

D. Vretenar, A. Wandelt, P. Ring

The isoscalar giant dipole resonance structure in $^{208}$Pb is calculated in the framework of a fully consistent relativistic random phase approximation, based on effective mean-field Lagrangians with nonlinear meson self-interaction terms. The results are compared with recent experimental data and with calculations performed in the Hartree-Fock plus RPA fr

Jochen Cleve, Martin Greiner

Markovian properties of a discrete random multiplicative cascade model of log-normal type are discussed. After taking small-scale resummation and breaking of the ultrametric hierarchy into account, qualitative agreement with Kramers-Moyal coefficients, recently deduced from a fully developed turbulent flow, is achieved.

M. Abel, L. Biferale, M. Cencini, M. Falcioni

We present a comprehensive investigation of $ε$-entropy, $h(ε)$, in dynamical systems, stochastic processes and turbulence. Particular emphasis is devoted on a recently proposed approach to the calculation of the $ε$-entropy based on the exit-time statistics. The advantages of this method are demonstrated in examples of deterministic diffusive maps, intermit

Jan Naudts

The notion of a multiplier of a group X is generalized to that of a C*-multiplier by allowing it to have values in an arbitrary C*-algebra A. On the other hand, the notion of the action of X in A is generalized to that of a projective action of X as linear transformations of the space of continuous functions with compact support in X and with values in A. It

J. S. Geronimo, H. Navelet

In a first part, we generalize a theorem for an holomorphic $\times $ anti-holomorphic integrand, in the case of 2 dimensional Fourier transform. In the second part, we derive p-uple conformal integrals the integrand of which are linear combination of holomorphic times holomorphic generalized hypergeometric functions. The specific case $p=3$ is relevant to d

R. Jaganathan

A very elementary introduction to quantum algebras is presented and a few examples of their physical applications are mentioned.

C. Daskaloyannis

The integrals of motion of the classical two dimensional superintegrable systems with quadratic integrals of motion close in a restrained quadratic Poisson algebra, whose the general form is investigated. Each classical superintegrable problem has a quantum counterpart, a quantum superintegrable system. The quadratic Poisson algebra is deformed to a quantum

Donu Arapura

This paper contains a Kawamata-Viehweg-Kollár type vanishing theorem for vector bundles. In order to formulate and prove this cleanly, we introduce a class of sheaves that automatically satisfies a vanishing theorem. This is obtained by closing up the subclass of sheaves of adjoint type under extensions, direct images, and taking direct summands.

Winfried Just, Saharon Shelah, Simon Thomas

It is well-known that the automorphism towers of infinite centreless groups of cardinality kappa terminate in less than (2^{kappa})^+ steps. But an easy counting argument shows that (2^{kappa})^+ is not the best possible bound. However, in this paper, we will show that it is impossible to find an explicit better bound using ZFC.

Mirna Džamonja, Saharon Shelah

The notion of stationary reflection is one of the most important notions of combinatorial set theory. We investigate weak reflection, which is, as the name suggests, a weak version of stationary reflection. This sort of reflection was introduced in [DjSh:545] (math.LO/9601219), where it was shown that weak reflection has applications to various guessing prin

Stephen D. Miller, Tonghai Yang

In the early 1980s, Rohrlich began a study of canonical Hecke characters, which are closely related to the simplest examples of CM elliptic curves. He and Montgomery showed the non-vanishing of the central value when the L-function has an even functional equation, and we now show the non-vanishing of the central derivative when the functional equation is odd

Guido Kings

In this paper we prove the Tamagawa number conjecture of Bloch and Kato for CM elliptic curves using a new explicit description of the specialization of the elliptic polylogarithm. The Tamagawa number conjecture describes the special values of the L-function of a CM elliptic curve in terms of the regulator maps of the K-theory of the variety into Deligne and

A. Losev, Yu. Manin

It is well known that formal solutions to the Associativity Equations are the same as cyclic algebras over the homology operad $(H_*(\bar{M}_{0,n+1}))$ of the moduli spaces of $n$--pointed stable curves of genus zero. In this paper we establish a similar relationship between the pencils of formal flat connections (or solutions to the Commutativity Equations)

I. Ya. Aref&#39;eva, D. M. Belov, A. S. Koshelev, O. A. Rytchkov

We consider noncommutative analogs of scalar electrodynamics and N=2 D=4 SUSY Yang-Mills theory. We show that one-loop renormalizability of noncommutative scalar electrodynamics requires the scalar potential to be an anticommutator squared. This form of the scalar potential differs from the one expected from the point of view of noncommutative gauge theories

Donam Youm

We study a general dilatonic p-brane solution in arbitrary dimensions in relation to the Randall-Sundrum scenario. When the p-brane is fully localized along its transverse directions, the Kaluza-Klein zero mode of bulk graviton is not normalizable. When the p-brane is delocalized along its transverse directions except one, the Kaluza-Klein zero mode of bulk

R. A. Bertlmann, E. Kohlprath

The gravitational anomalies in two dimensions, specifically the Einstein anomaly and the Weyl anomaly, are fully determined by means of dispersion relations. In this approach the anomalies originate from the peculiar infrared feature of the imaginary part of the relevant formfactor which approaches a $δ$-function singularity at zero momentum squared when $m

Boris Kors, Michael G. Schmidt

We present intermediate results of an ongoing investigation which attempts a generalization of the well known one-loop Bern Kosower rules of Yang-Mills theory to higher loop orders. We set up a general procedure to extract the field theoretical limit of bosonic open string diagrams, based on the sewing construction of higher loop world sheets. It is tested w

Xavier Bekaert, Bernard Knaepen, Christiane Schomblond

We classify all the first-order vertices of gravity consistently coupled to a system of 2-form gauge fields by computing the local BRST cohomology H(s|d) in ghost number 0 and form degree n. The consistent deformations are at most linear in the undifferentiated two-form, confirming the previous results of [1] that geometrical theories constructed from a nons

J. -P. Derendinger, R. Sauser

We present a general `off-shell&#39; description of the effective N=1 supergravity describing the low-energy limit of M-theory compactified on (Calabi-Yau) x S1/Z2. In our formulation, the M-theory Bianchi identities are imposed by the equations of motion of four-dimensional supermultiplets. Modifications of these identities (resulting for instance from cont

Ze-sen Yang, Xianhui Li, Weizhen Deng, Xiaolin Chen

We extend the previous work and study the renormalisability of the SU$_L$(2) $\times$ U$_Y$(1) electroweak theory with massive W Z fields and massive matter fields. We expound that with the constraint conditions caused by the W Z mass term and the additional condition chosen by us we can still performed the quantization in the same way as before. We also sho

Katsuyuki Sugiyama

We study a kaehler potential K in the large radius region of a Calabi-Yau d-fold M embedded in CP^{d+1}. It has a kaehler parameter t that describes a deformation of the A-model moduli. Also the metric, curvature and hermitian two-point functions in the large volume region are analyzed. We use a result of our previous paper in the B-model of the mirror. We p

Katsuyuki Sugiyama

We study a kaehler potential K of a one parameter family of Calabi-Yau d-fold embedded in CP^{d+1}. By comparing results of the topological B-model and the data of the CFT calculation at Gepner point, the K is determined unambiguously. It has a moduli parameter psi that describes a deformation of the CFT by a marginal operator. Also the metric, curvature and

Semyon Pol&#39;shin

Connection of the invariant Dirac equation over the de Sitter space with irreducible representations of the de Sitter group is ascertained. The set of solutions of this equation is obtained in the form of the product of two different systems of generalized coherent states for the de Sitter group. Using these solutions the quantized Dirac field over de Sitter

Semyon Pol&#39;shin

A system of generalized coherent states for the de Sitter group obeying Klein-Gordon equation and corresponding to the massive spin zero particles over the de Sitter space is considered. This allows us to construct the quantized scalar field by the resolution over these coherent states; the corresponding propagator can be computed by the method of analytic c

G. L. Kane, Lian-Tao Wang

We study the supersymmetry parameter region excluded if no Higgs is found at LEP, and the region allowed if a Higgs boson is found at LEP. We describe the full seven parameter structure of Higgs sector. When supersymmetry phases are included, $\tan β$ greater than or equal to 2 is always allowed, and the lower limit on lightest Higgs mass if no signal is fou

J. I. Kapusta, S. M. H. Wong

We calculate the order α_s finite temperature correction to dilepton production in quark-gluon plasma arising from the two-loop photon self-energy diagrams for high invariant mass M >> T.

R. Peschanski, C. Royon

A method allowing for a direct comparison of data with theoretical predictions is proposed for forward jet production at HERA and Mueller-Navelet jets at Tevatron and LHC. An application to the determination of the effective Pomeron intercept in the BFKL-LO parametrization from d sigma/dx data at HERA leads to a good fit with a significantly higher effective

J. -M. Levy, F. Vannucci

The Karmen anomaly can be interpreted as being due to a heavy neutrino of mass around 137 MeV produced in $π_{e 2}$ decays. This interpretation is consistent with the present limits on the couplings of such an object.

J. Smith

We compare parton densities for heavy quarks.

Apoorva Patel

Results for light quark masses obtained from lattice QCD simulations are compared and contrasted with other determinations. Relevance of these results to estimates of $ε&#39;/ε$ is discussed.

Ariel Zhitnitsky

It was argued recently that, in general, an arbitrary induced theta vacuum state would be created in the heavy ion collisions, similar to the creation of the disoriented chiral condensatewith an arbitrary isospin direction. It should be a large domain with a wrong theta orientation which will mimic the physics of the world when the fundamental theta is non-z

M. Joyce, T. Prokopec

Scalar fields can play a dominant role in the dynamics of the Universe until shortly before nucleosynthesis. Examples are provided by domination by a kinetic mode of a scalar field, which may be both the inflaton and the late time `quintessence&#39;, and also by more conventional models of reheating. The resultant modification to the pre-nucleosynthesis expa

T. M. Aliev, M. Savci

The most general model independent expressions for the CP-violating asymmetry, longitudinal, transversal and normal polarizations of leptons are derived. Application of these general results to the concrete models such as Standard model and three different types of two Higgs doublet model is discussed.

Marcela Carena, Katri Huitu, Tatsuo Kobayashi

We study a generalization of anomaly-mediated supersymmetry breaking (AMSB) scenarios, under the assumption that the effects of the high-scale theory do not completely decouple and D-term type contributions can be therefore present. We investigate the effect of such possible D-term additional contributions to soft scalar masses by requiring that, for non-van

Piotr Bialas, Philippe Blanchard, Santo Fortunato, Daniel Gandolfo

In the strong coupling limit the partition function of SU(2) gauge theory can be reduced to that of the continuous spin Ising model with nearest neighbour pair-interactions. The random cluster representation of the continuous spin Ising model in two dimensions is derived through a Fortuin-Kasteleyn transformation, and the properties of the corresponding clus

Ronald A. Poling

The status of heavy-quark decays as of summer 1999 is reviewed. New measurements of semileptonic B decays from LEP and from CLEO are reported and the status of determining the CKM parameters |Vcb| and |Vub| is assessed. Rare charmless hadronic B decays are reviewed, including the first observation of B->pi pi from CLEO. First attempts to measure CP asymmetri

Valery Telnov

High energy photon colliders based on laser backscattering are a very natural extension of a e+e- linear colliders and open new possibilities to study of the matter. This option has been included in the pre-conceptual designs of linear colliders and work on Technical Design Reports is in progress. The physics motivation for photon colliders is quite clear th

Frank J. Tipler, Jessica Graber, Matthew McGinley, Joshua Nichols-Barrer

We show it is possible for the information paradox in black hole evaporation to be resolved classically. Using standard junction conditions, we attach the general closed spherically symmetric dust metric to a spacetime satisfying all standard energy conditions but with a single point future c-boundary. The resulting Omega Point spacetime, which has NO event

Stanislav Tereshchenko

It is shown, that the radiation of the charge, moving with uniform acceleration or uniformly moving round a circle and also freely moving in a gravitational field, contradicts the principle of equivalence. It is also shown, that the interaction of the charges, moving with uniform acceleration or uniformly circling, which has been calculated within the framew

Alan Coley, Martin Goliath

Self-similar, spherically symmetric cosmological models with a perfect fluid and a scalar field with an exponential potential are investigated. New variables are defined which lead to a compact state space, and dynamical systems methods are utilised to analyse the models. Due to the existence of monotone functions global dynamical results can be deduced. In

De-Hai Zhang

A new &#39;&#39;twice loose shoe&#39;&#39; method in the Wheeler-DeWitt equation of the universe wave function on the cosmic scale factor a and a scalar field $ϕ$ is suggested in this letter. We analysis the both affects come from the tunneling effect of a and the potential well effect of $ϕ$, and obtain the initial values $a_0$ and $ϕ_0$ about a primary clo

Hiroko Koyama, Yasusada Nambu, Akira Tomimatsu

Vacuum polarization of massive scalar fields in a thermal state at arbitrary temperature is studied near the horizon of a Reissner-Nordström black hole. We derived an analytic form of $<ϕ^2>$ approximately in the large mass limit near the black hole horizon. We uses the zeroth order WKB approximation and power series expansion near the horizon for the Euclid

S. Etalle, J. Mountjoy

The possibility of translating logic programs into functional ones has long been a subject of investigation. Common to the many approaches is that the original logic program, in order to be translated, needs to be well-moded and this has led to the common understanding that these programs can be considered to be the ``functional part&#39;&#39; of logic progr

Nikolay Pelov, Maurice Bruynooghe

Proving failure of queries for definite logic programs can be done by constructing a finite model of the program in which the query is false. A general purpose model generator for first order logic can be used for this. A recent paper presented at PLILP98 shows how the peculiarities of definite programs can be exploited to obtain a better solution. There a p

Franck Selva, Jean-Louis Pichard

We study the difference between on site Hubbard and long range Coulomb repulsions for two interacting particles in a disordered chain. While Hubbard repulsion can only yield weak critical chaos with intermediate spectral statistics, Coulomb repulsion can drive the two particle system to quantum chaos with Wigner-Dyson spectral statistics. For intermediate st

R. Reigada, A. Sarmiento, A. H. Romero, J. M. Sancho

We present a model in which the immediate environment of a bistable system is a molecular chain which in turn is connected to a thermal environment of the Langevin form. The molecular chain consists of masses connected by harmonic or by anharmonic springs. The distribution, intensity, and mobility of thermal fluctuations in these chains is strongly dependent

Felix Ritort, Marta Sales

We study order-parameter fluctuations (OPF) in disordered systems by considering the behavior of some recently introduced paramaters $G,G_c$ which have proven very useful to locate phase transitions. We prove that both parameters G (for disconnected overlap disorder averages) and $G_c$ (for connected disorder averages) take the respective universal values 1/

J. E. Han, O. Gunnarsson

We consider a model which includes the electron-phonon coupling to Ag or Jahn-Teller Hg phonons, the Coulomb interaction U and an exchange integral K. We study the metal-insulator transition for the integer fillings n=3 and 4. We find that the coupling to Ag phonons increases the critical value Uc where the transition takes place, while the coupling to Hg ph

Stefan Bornholdt, Kim Sneppen

We suggest to simulate evolution of complex organisms constrained by the sole requirement of robustness in their expression patterns. This scenario is illustrated by evolving discrete logical networks with epigenetic properties. Evidence for dynamical features in the evolved networks is found that can be related to biological observables.

A. D. Mirlin, F. Evers

Critical fluctuations of wave functions and energy levels at the Anderson transition are studied for the family of the critical power-law random banded matrix ensembles. It is shown that the distribution functions of the inverse participation ratios (IPR) $P_q$ are scale-invariant at the critical point, with a power-law asymptotic tail. The IPR distribution,

G. Flossmann, R. Folk

We compare theoretical results for the characteristic frequency of the Rayleigh peak calculated in one-loop order within the field theoretical method of the renormalization group theory with experiments and other theoretical results. Our expressions describe the non-asymptotic crossover in temperature, density and wave vector. In addition we discuss the freq

Nam Kim, Hyun-Sik Chang, Hu-Jong Lee, Yong-Joo Doh

We observed that radio-frequency (rf) irradiation significantly enhances the $c$-axis resistance near and below the superconducting transition of the CuO$_{2}$ layer in contact with a normal-metal electrode on the surface of Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+x}$ single crystals. We attribute the resistance anomaly to the rf-induced charge-imbalance nonequilibr

G. Goll, J. Hagel, H. v. Loehneysen, T. Pietrus

Shubnikov--de Haas (SdH) and Hall-effect measurements of CeBiPt and LaBiPt reveal the presence of simple and very small Fermi surfaces with hole-like charge carriers for both semimetals. In the magnetic material, CeBiPt, we observe a strong temperature dependence of the SdH frequency. This highly unusual effect might be connected with an internal exchange fi

A. Ordemann, M. Porto, H. E. Roman, S. Havlin

The scaling behavior of linear polymers in disordered media modelled by self-avoiding random walks (SAWs) on the backbone of two- and three-dimensional percolation clusters at their critical concentrations p_c is studied. All possible SAW configurations of N steps on a single backbone configuration are enumerated exactly. We find that the moments of order q

Eyvind Aker, Knut Jorgen Maloy, Alex Hansen, Soumen Basak

We investigate the burst dynamics during drainage going from low to high injection rate at various fluid viscosities. The bursts are identified as pressure drops in the pressure signal across the system. We find that the statistical distribution of pressure drops scales according to other systems exhibiting self-organized criticality. The pressure signal was

A. Ordemann, G. Berkolaiko, S. Havlin, A. Bunde

We study the structural properties of self-attracting walks in d dimensions using scaling arguments and Monte Carlo simulations. We find evidence for a transition analogous to the Θtransition of polymers. Above a critical attractive interaction u_c, the walk collapses and the exponents νand k, characterising the scaling with time t of the mean square end-to-

Banu Ebru Özoğuz, Yiğit Gündüç, Meral Aydın

The critical behaviour in short time dynamics for the q=6 and 7 state Potts models in two-dimensions is investigated. It is shown that dynamic finite-size scaling exists for first-order phase transitions.

F. Yusef-Zadeh, Mark Shure, Mark Wardle, N. Kassim

The Trifid nebula (M20) is a well-known prominent optical HII region trisected by obscuring dust lanes. Radio continuum VLA observations of this Nebula show free-free emission at lambda 3.6 and 6cm from three stellar sources lying close to the O7V star at the center of the nebula. We argue that neutral material associated with these stars are photoionized ex

A. J. Barth, J. C. Shields

Motivated by the discovery of young, massive stars in the nuclei of some LINER/H II ``transition&#39;&#39; nuclei such as NGC 4569, we have computed photoionization models to determine whether some of these objects may be powered solely by young star clusters rather than by accretion-powered active nuclei. The models were calculated with the photoionization

Lynne A. Hillenbrand, John M. Carpenter

We present the results of a 0.5-0.9&#34; FWHM imaging survey at K (2.2 micron) and H (1.6 micron) covering 5.1&#39; x 5.1&#39; centered on Theta 1C Ori, the most massive star in the Orion Nebula Cluster (ONC). At the age and distance of this cluster, and in the absence of extinction, the hydrogen burning limit (0.08 Mo) occurs at K~13.5 mag while an object o

Adam J. Burgasser, J. Davy Kirkpatrick, I. Neill Reid, James Liebert

We report the detection of H{$α$} emission in the T dwarf (methane brown dwarf) 2MASSW J1237392+652615 over three days using the Keck Low Resolution Imaging Spectrograph. The measured line flux, log(L$_{Hα}$/L$_{bol}$) = $-$4.3, is roughly consistent with early M dwarf activity levels and inconsistent with decreasing activity trends in late M and L dwarfs. S

Mark Lacy, Andrew J. Bunker, Susan E. Ridgway

We present new near-infrared images of z>0.8 radio galaxies from the flux-limited 7C-III sample of radio sources for which we have recently obtained almost complete spectroscopic redshifts. The 7C objects have radio luminosities about 20 times fainter than 3C radio galaxies at a given redshift. The absolute magnitudes of the underlying host galaxies and thei

O. Laurent, I. F. Mirabel, V. Charmandaris, E. Le Floc&#39;h

We present mid-IR observations of the prototypical Seyfert 2 galaxy NGC 1068 obtained with ISOCAM between 5 and 16micron. The proximity of this galaxy coupled with the spectro-imaging capabilities of the instrument allow us to separate the mid-IR emission of the active galactic nucleus (AGN) from the distinctly different emission of the circumnuclear star fo

A. Rodriguez-Ardila, L. Binette, M. G. Pastoriza, C. J. Donzelli

This work studies the optical emission line properties and physical conditions of the narrow line region (NLR) of seven narrow-line Seyfert 1 galaxies (NLS1). Our results show that the flux carried out by the narrow component of H-beta is, on average, 50% of the total line flux. As a result, the [OIII] 5007/H-beta ratio emitted in the NLR varies from 1 to 5,

Paola Pietrini, Julian Krolik

We study radiation-hydrodynamical normal modes of radiation-supported accretion disks in the WKB limit. It has long been known that in the large optical depth limit the standard equilibrium is unstable to convection. We study how the growth rate depends on location within the disk, optical depth, disk rotation, and the way in which the local dissipation rate

Geoffrey C. Clayton, Karl D. Gordon, Michael J. Wolff

We have studied the UV extinction properties along 30 Galactic sightlines using data from the International Ultraviolet Explorer (IUE) archive that have never been previously examined. These distant (d > 1 kpc) sightlines were selected to investigate the distribution and physical conditions of gas located in low density regions of the Galactic disk and halo.

Zeljko Ivezic, Moshe Elitzur

Unbiased analysis shows that IRAS data reliably differentiate between the early and late stages of stellar evolution because objects at these stages clearly segregate in infrared color-color diagrams. Structure in these diagrams is primarily controlled by the density distribution of circumstellar dust. The density profile around older objects is the steepest

Jorg P. Rachen

The hypothesis that AGN jets might be the sources of the ultra-high energy cosmic rays has originally motivated the venture of TeV gamma ray astronomy. Surprisingly, after the discovery of TeV emission from blazars the attention has shifted to more traditional explanations which do not involve energetic hadrons, and there is even common believe that a hadron

N. G. Douglas, J. Gerssen, K. Kuijken, M. R. Merrifield

The planetary nebula populations of relatively nearby galaxies can be easily observed and provide both a distance estimate and a tool with which dynamical information can be obtained. Usually the requisite radial velocities are obtained by multi-object spectroscopy once the planetary nebulae have been located by direct imaging. Here we report on a technique

P. B. Alton, E. M. Xilouris, S. Bianchi, J. Davies

We compare 850um SCUBA images of NGC 891 with the corresponding V-band optical depth predicted from radiation transfer simulations. These two tracers of dust show a very similar distribution along the minor axis and a reasonable agreement along the major axis. Assuming that the grains responsible for optical extinction are also the source of 850um emission w

Suzanne Madden

Effects of young stellar clusters on their gas and dust environment are probed using mid-infrared (MIR) wavelengths. The strong MIR [NeIII]/[NeII] ratios (5 to 10) reveal the presence of current massive stars less than 5 Myr. Using MIR line ratios along with optical and NIR data from the literature, composite SEDs are constructed for NGC 1569, NGC 1140 and I

T. M. Tripp, B. D. Savage, E. B. Jenkins

FUV echelle spectroscopy of the radio-quiet QSO H1821+643 (z = 0.297), obtained with the Space Telescope Imaging Spectrograph (STIS) at 7 km/s resolution, reveals 4 definite O VI absorption line systems and one probable O VI absorber at 0.15 < z(abs) < 0.27. The four definite O VI absorbers are located near galaxies and are highly displaced from the quasar i

H. Heiselberg, V. Pandharipande

This review contains chapters discussing: Energy density fluctionals of nuclear matter, Many-body theory of nucleon matter, Hadronic and quark matter, Mixtures of phases in dense matter, Neutron star observations and predictions.

G. S. Bisnovatyi-Kogan, S. I. Blinnikov

Recently, there appeared many papers devoted to the modeling of X-ray properties of Cygnus X-1 and other black hole accretion disk candidates: e.g. J.Poutanen, J.Krolik, F.Ryde, MNRAS 292 (1997) L21; E.Agol, J.Krolik, ApJ 507 (1998) 304; A.Beloborodov, in ``High Energy Processes in Accreting Black Holes&#39;&#39;, ASP Conf. Series, 161, (1999), p.295. The go

J. Kumar

We demonstrate that under certain conditions a theory of conformal quantum mechanics will exhibit the symmetries of two half-Virasoro algebras. We further demonstrate the conditions under which these algebras combine to form a single Virasoro algebra, and comment on the connection between this result and the AdS/CFT correspondence.