January 2002 arXiv papers — page 22

F. Paccanoni

Constraints on the t-dependence of the hadronic scattering amplitude at asymptotic energies are derived by considering the exchange of the Pomeron, as a Regge pole, between off-shell gluons. Covariant reggeization ensures pure spin alpha exchange, where alpha is the Regge trajectory of the Pomeron. The structure of the amplitude, as a function of t, has been

Munshi G. Mustafa, Markus H. Thoma

Based on general arguments the in-medium quark propagator in a quark-gluon plasma leads to a quark dispersion relation consisting of two branches, of which one exhibits a minimum at some finite momentum. This results in a vanishing group velocity for collective quark modes. Important quantities such as the production rate of low mass lepton pairs and mesonic

Kakali Ray-Maity, Padmanabha Dasgupta

Evolution of structure functions and their moments at low and moderate $Q^2$ is studied in the chiral field theory. Evolution equations based on perturbation expansion in the coupling constant of the effective theory are derived and solved for the moments. The kernels of evolution arising from different processes have been calculated with contributions from

Apostolos D. Panagiotou, Panayotis Katsas, Elpida Gerodimou

We have studied the variation of a thermodynamic quantity, the strange chemical potential, in the phase diagram of nuclear matter, by employing the partition function in each domain and enforcing strangeness conservation. We propose that the change in the sign of the strange quark chemical potential, from positive in the hadronic phase to negative in the dec

Jihn E. Kim

I give a review on the self-tuning solution of the cosmological constant in a 5D RS-II model using a three index antisymmetric tensor field $A_{MNP}$. The three index antisymmetric tensor field can be the fundamental one appearing in 11D supergravity. Also, the dual of its field strength $H_{MNPQ}$, being a massless scalar, may be interpreted as a Goldstone

J. Ambjorn, J. Jurkiewicz, R. Loll

The model of Lorentzian three-dimensional dynamical triangulations provides a non-perturbative definition of three-dimensional quantum gravity. The theory has two phases: a weak-coupling phase with quantum fluctuations around a ``semiclassical'' background geometry which is generated dynamically despite the fact that the formulation is explicitly bac

J. Ambjorn

I review recent progress in understanding non-perturbative aspects of string theory, quantum gravity and non-commutative geometry using lattice methods.

Marco Battaglia, Ian Hinchliffe, John Jaros, James Wells

This report summarises the activity of the E3 working group "Experimental Approaches at Linear Colliders". The group was charged with examining critically the physics case for a linear collider of energy of order 1 TeV as well as the cases for higher energy machines, assessing the performance requirements and exploring the viability of several specia

M. Sioli

We report the measurement by the MACRO experiment of the ratio of double muon events over single muon events as a function of rock depth. Particular attention has been devoted to the analysis of high zenith angle events. Results are compared to the expectation of a detailed simulation performed with HEMAS-DPM Monte Carlo. No deviations with respect to ``stan

M. Sioli

An estimate of the energy of neutrino-induced muons in MACRO is provided by a multiple Coulomb scattering measurement. The MACRO original upward-muon data sample has been subdivided according to the reconstructed muon energy. Data in each subset are then compared with expected fluxes from atmospheric neutrinos. The results are interpreted in terms of neutrin

John C. Baez, S. Jay Olson

Ng and van Dam have argued that quantum theory and general relativity give a lower bound of L^{1/3} L_P^{2/3} on the uncertainty of any distance, where L is the distance to be measured and L_P is the Planck length. Their idea is roughly that to minimize the position uncertainty of a freely falling measuring device one must increase its mass, but if its mass

J. Podolsky

Exact solutions exist which describe impulsive gravitational waves propagating in Minkowski, de Sitter, or anti-de Sitter universes. These may be either nonexpanding or expanding. Both cases in each background are reviewed here from a unified point of view. All the main methods for their construction are described systematically: the Penrose "cut and pas

J. Ambjorn

One can try to define the theory of quantum gravity as the sum over geometries. In two dimensions the sum over {\it Euclidean} geometries can be performed constructively by the method of {\it dynamical triangulations}. One can define a {\it proper-time} propagator. This propagator can be used to calculate generalized Hartle-Hawking amplitudes and it can be u

U. Leonhardt

Laboratory-based optical analogs of astronomical objects such as black holes rely on the creation of light with an extremely low or even vanishing group velocity (slow light). These brief notes represent a pedagogical attempt towards elucidating this extraordinary form of light. This paper is a contribution to the book Artificial Black Holes edited by Mario

Jinlan Wang, Xiaoshuang Chen, Guanghou Wang, Baolin Wang

Surface melting temperature is well-known significantly lower than the bulk melting point. But we find that the interior melting temperature in ultrathin nanowires is lower than that of the surface melting . The thermal stability of helical multi-walled cylindrical gold nanowires is studied using molecular dynamics simulations. The melting temperature of gol

Efstratios Manousakis

Quantum systems with a large number of fermionic degrees of freedom are intractable by quantum simulations. In this paper we introduce the concept of a dedicated quantum simulator(DQS) which is an artificial system of quantum dots whose Hamiltonian maps exactly to the original many fermion problem. While the universal quantum simulator (UQS) introduced by Fe

Sven P. Rudin, M. D. Jones, C. W. Greeff, R. C. Albers

A tight-binding model is fit to first-principles calculations for copper that include structures distorted according to elastic constants and high-symmetry phonon modes. With the resulting model the first-principles-based phonon dispersion and the free energy are calculated in the quasi-harmonic approximation. The resulting thermal expansion, the temperature

Andrey V. Chubukov, David Pines, Joerg Schmalian

In this review we demonstrate that superconducting pairing, mediated by the exchange of spin fluctuations, is a viable alternative to conventional phonon-mediated pairing. We discuss in detail the normal state properties, the spin fluctuation induced d-wave pairing and the superconducting behavior of a material near an antiferromagnetic instability, when the

Marcelo A. Montemurro, Pedro A. Pury

In this paper we analyse the fractal structure of long human-language records by mapping large samples of texts onto time series. The particular mapping set up in this work is inspired on linguistic basis in the sense that is retains {\em the word} as the fundamental unit of communication. The results confirm that beyond the short-range correlations resultin

P. A. Netz, F. Starr, M. C. Barbosa, H. Eugene Stanley

We perform molecular dynamics simulations using the extended simple point charge SPC/E water model in order to investigate the dynamical behavior of supercooled-stretched water. We focus on the behavior of the translational diffusion coefficient, the orientational relaxation time, and the local hydrogen bond network. Decreasing density or pressure along an i

N. Puff, G. Debregeas, J. -M. di Meglio, D. Higgins

The growth dynamics of an air finger injected in a visco-elastic gel (a PVA/borax aqueous solution) is studied in a linear Hele-Shaw cell. Besides the standard Saffmann-Taylor instability, we observe - with increasing finger velocities - the existence of two new regimes: (a) a stick-slip regime for which the finger tip velocity oscillates between 2 different

G. Cuniberti, G. Fagas, K. Richter

Analytic results for the conductance of a molecular wire attached to mesoscopic tubule leads are obtained. They permit to study linear transport in presence of low dimensional leads in the whole range of parameters. In particular contact effects can be addressed in detail. By focusing on the specificity of the lead-wire contact, we show that the geometry of

Hugo Touchette

The difference between the terms additivity and extensivity, as well as their respective negations, is critically analyzed and illustrated with a few examples. The concepts of subadditivity, pseudo-additivity, and pseudo-extensivity are also defined.

Jens Jensen

A mean-field model explaining most of the details in the magnetic phase diagram of ErNi_2B_2C is presented. The low-temperature magnetic properties are found to be dominated by the appearance of long-period commensurate structures. The stable structure at low temperatures and zero field is found to have a period of 40 layers along the a direction, and upon c

S. Blanchard, T. Klein, J. Marcus, I. Joumard

Thermodynamic (specific heat, reversible magnetization, tunneling spectroscopy) and transport measurements have been performed on high quality (K,Ba)BiO$_3$ single crystals. The temperature dependence of the magnetic field $H_{Cp}$ corresponding to the onset of the specific heat anomaly presents a clear positive curvature. $H_{Cp}$ is significantly smaller t

J. Masek, F. Maca

We consider hypothetical Ga7MnAs8, Ga16MnAs16, and Ga14Mn3As16 crystals with Mn in a substitutional, interstitial, and both positions. Spin-polarized FPLAPW calculations were used to obtain their electronic structure. We show that the interstitial Mn acts as a double donor and compensates the holes created by two Mn atoms in substitutional positions. This ex

P. A. Netz, F. Starr, H. Eugene Stanley, M. C. Barbosa

We investigate the dynamics of the extended simple point charge (SPC/E) model of water in the supercooled region. The dynamics at negative pressures show a minimum in the diffusion constant $D$ when the density is decreased at constant temperature, complementary to the known maximum of $D$ at higher pressures. A similar trend in the rotational diffusion is a

K. P. Santo, K. L. Sebastian

We propose a simple model for the kinetics of packaging of viral DNA in to a capsid against an external force trying to prevent it. The model leads to a Butler-Volmer type dependence of the rate of packaging on the pulling force F.

S. B. Rutkevich

Nucleation in the two-dimensional q-state Potts model has been studied by means of Monte-Carlo simulations using the heat-bath dynamics. The initial metastable state has been prepared by magnetic quench of the ordered low-temperature phase. The magnetic field dependence of the nucleation time has been measured as the function of the magnetic field for differ

R. Burioni, D. Cassi, M. Rasetti, P. Sodano

The thermodynamic properties of non interacting bosons on a complex network can be strongly affected by topological inhomogeneities. The latter give rise to anomalies in the density of states that can induce Bose-Einstein condensation in low dimensional systems also in absence of external confining potentials. The anomalies consist in energy regions composed

Prabhakar P. Singh

Using density-functional-based methods, we show that the hole-doped Li_{x}BC and Na_{x}BC in P6_{3}/mmc crystal structure and C_{x} in graphite structure are capable of showing superconductivity, possibly with a T_{c} much higher than that of MgB_{2}. We use full-potential methods to obtain the optimized lattice constants a and c, coherent-potential approxim

H. Won, K. Maki

The Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state can be found in layered d-wave superconductors such as high $T_c$ cuprates and $κ$-(ET)$_2$ salts in a planar magnetic field. We show the superconducting order parameter forms two dimensional crystalline lattice in the FFLO state for d-wave superconductors. Also the quasiparticle density of states and the the

Y. B. Band, Marek Trippenbach

The criteria for validity of adiabaticity for nonlinear wave equations are considered within the context of atomic matter-waves tunneling from macroscopically populated optical standing-wave traps loaded from a Bose-Einstein condensate. We show that even when the optical standing wave is slowly turned on and the condensate behaves adiabatically during this t

I. N. Volovichev, G. Espejo, Yu. G. Gurevich, O. Yu. Titov

It is shown that the traditional approach for consideration of recombination under condition of steady-state current in the absence of external carrier generation is internally contradictory. Sometimes the approach leads to obviously incorrect results. Such situations are demonstrated and a new method for consideration of recombination is proposed.

Hidetoshi Nishimori

The gauge theory of spin glasses and statistical-mechanical formulation of error-correcting codes are reviewed with an emphasis on their similarities. For the gauge theory, we explain the functional identities on dynamical autocorrelation functions and on the distribution functions of order parameters. These functional identities restrict the possibilities o

R. Movshovich, E. G. Moshopoulou, M. Jaime, M. F. Hundley

In order to separate electronic and phonon mechanisms of thermal transport in high temperature superconducting Bi2212, we measured thermal conductivity of single crystals of Y-doped Bi2212, an insulating analogue of pure Bi2212, in the temperature range between 40 mK and 2 K. Temperature dependence of the thermal conductivity of insulating samples changes fr

M. R. Merrifield

This paper describes a framework for studying galaxy morphology, particularly bar strength, in a quantitative manner, and presents applications of this approach that reveal observational evidence for secular evolution in bar morphology. The distribution of bar strength in galaxies is quite strongly bimodal, suggesting that barred and unbarred systems are dis

Mark J. Neeser, Penny D. Sackett, Guido De Marchi, Francesco Paresce

We report the detection of a thick disk in the edge-on, low surface brightness (LSB), late-type spiral ESO 342-G017, based on ultra-deep images in the V and R bands obtained with the VLT Test Camera during Science Verification on UT1. All steps in the reduction procedure are fully described, which, together with an extensive analysis of systematic and statis

J. L. Hinz, D. W. McCarthy, D. A. Simons, T. J. Henry

A common proper motion survey of M dwarf stars within 8 pc of the Sun reveals no new stellar or brown dwarf companions at wide separations (~100-1400 AU). This survey tests whether the brown dwarf ``desert'' extends to large separations around M dwarf stars and further explores the census of the solar neighborhood. The sample includes 66 stars north

E. Moy, B. Rocca-Volmerange

We have analyzed the ultraviolet and optical emission line ratios of a large sample of extragalactic radio sources (QSOs and radio galaxies), with the help of models combining AGN photoionization and shocks. The results strongly suggest that the two ionizing mechanisms frequently coexist. The model sequences obtained by varying the balance between shocks and

J. Antonio Garcia-Barreto, Jose Franco, Larry Rudnick

We report new radio continuum observations with an angular resolution of 2''.1 at 1.4 GHz and 0''.28 at 8.4 GHz of the barred galaxy NGC 3367. In the map at 1.4 GHz the central nuclear region connects to the SW lobe, with a projected structure at a position angle of PA = 230 forming a jet-like structure. The map at 8.4 GHz shows a compact unr

S. Masi, P. A. R. Ade, J. J. Bock, J. R. Bond

We describe the BOOMERanG experiment and its main result, i.e. the measurement of the large scale curvature of the Universe. BOOMERanG is a balloon-borne microwave telescope with sensitive cryogenic detectors. BOOMERanG has measured the angular distribution of the Cosmic Microwave Background on $\sim 3%$ of the sky, with a resolution of $\sim 10$ arcmin and

Paolo Tozzi

The exploration of the end of the Dark Ages will be one of the most exciting field of the next decade. While most of the proposed observations must await the next-generation telescopes, the observational window of the redshifted 21cm line offers the possibility to investigate the physics of reheating and reionization on a short term. Here we describe several

P. Uttley, I. M. McHardy, I. E. Papadakis

We have developed a Monte Carlo technique to test models for the true power spectra of intermittently sampled lightcurves against the noisy, observed power spectra, and produce a reliable estimate of the goodness of fit of the given model. We apply this technique to constrain the broadband power spectra of a sample of four Seyfert galaxies monitored by the R

D. Pourbaix

Recent investigations (e.g. Han et al. 2001) have shown that fitting the Hipparcos observations with an orbital model when the astrometric wobble caused by the companion is below the noise level can have rather unexpected consequences. With new astrometric missions coming out within the next ten years, it is worth investigating the orbit reconstruction capab

Marco Fatuzzo, Fred C. Adams

Previous treatments of ambipolar diffusion in star-forming molecular clouds do not consider the effects of fluctuations in the fluid fields about their mean values. This paper generalizes the ambipolar diffusion problem in molecular cloud layers to include such fluctuations. Because magnetic diffusion is a nonlinear process, fluctuations can lead to an enhan

K. A. Postnov, D. I. Kosenko

Limitations on the multi-dimensional TeV-scale quantum gravity model by Arkani-Hamed, Dimopoulos and Dvali (1998) and on model by Dvali, Gabadadze, Porrati (2000) are obtained from an analysis of gamma-ray bursts at cosmological distances (relativistic fireball model).

F. Kemper, A. de Koter, L. B. F. M. Waters, J. Bouwman

We present a fit to the spectral energy distribution of OH 127.8+0.0, a typical asymptotic giant branch star with an optically thick circumstellar dust shell. The fit to the dust spectrum is achieved using non-spherical grains consisting of metallic iron, amorphous and crystalline silicates and water ice. Previous similar attempts have not resulted in a sati

G. Raimondo, V. Castellani, S. Cassisi, E. Brocato

We investigate the predicted Color-Magnitude distribution of metal-rich Horizontal Branch (HB) stars, discussing selected theoretical models computed under various assumptions about the star metallicity and the efficiency of super-adiabatic convection. We find that canonical Zero Age Horizontal Branches with metallicity larger or of the order of Z=0.002 shou

Stefan Jordan, Susanne Friedrich

We present highly time resolved circular-polarization and flux spectra of the magnetic white dwarf LP790-29 taken with the VLT UT1 in order to test the hypothesis that LP790-29 is a fast rotator with a period of the order of seconds to minutes. Due to low time resolution of former observations this might have been overlooked -- leading to the conclusion that

Heon-Young Chang, Cheongho Han

We investigate the pattern of anomalies in the light curves of caustic-crossing binary microlensing events induced by spot(s) on the lensed source star. For this purpose, we perform simulations of events with various models of spots. From these simulations, we find that the spot-induced anomalies take various forms depending on the physical state of spots, w

N. S. Dzhalilov, J. Staude, V. N. Oraevsky

Retrograde waves with frequencies much lower than the rotation frequency become trapped in the solar radiative interior. The eigenfunctions of the compressible, nonadiabatic, Rossby-like modes ($ε$-mechanism and radiative losses taken into account) are obtained by an asymptotic method assuming a very small latitudinal gradient of rotation, without an arbitra

Joel R. Primack

I discuss how measurements of the absorption of $γ$-rays from GeV to TeV energies via pair production on the extragalactic background light (EBL) can probe important issues in galaxy formation. We use semi-analytic models (SAMs) of galaxy formation, based on the flat LCDM hierarchical structure formation scenario with $Ω_m=0.3$ and Hubble parameter $h=0.65$,

N. P. Armitage, F. Ronning, D. H. Lu, C. Kim

We present an angle resolved photoemission (ARPES) doping dependence study of the n-type cuprate superconductor Nd_2-xCe_xCuO_4, from the half-filled Mott-insulator to the T_c=24K superconductor. In Nd2CuO4, we reveal the charge-transfer band (CTB) for the first time. As electrons are doped into the system, this feature's intensity decreases with the con

Guray Erkol, Gursevil Turan

We study the differential branching ratio, branching ratio and the forward-backward asymmetry for the exclusive $B \to π\ell^+ \ell^-$ and $B \to ρ\ell^+ \ell^-$ decays in the general two Higgs doublet model including the neutral Higgs boson effects. We analyze the dependencies of these quantities on the neutral Higgs boson contributions and the other model

Anzhong Wang

The embedding of a thick de Sitter 3-brane into a five-dimensional bulk is studied, assuming a scalar field with potential is present in the bulk. A class of solutions is found in closed form that can represent a thick de Sitter 3-brane interpolating either between two dynamical black holes with a $R \times S_{4}$ topology or between two Rindler-like spaceti

Soeren Koester

C denotes either the conformal group in 3+1 dimensions, or in one chiral dimension. Let U be a unitary, strongly continuous representation of C satisfying the spectrum condition and inducing, by its adjoint action, automorphisms of a v.Neumann algebra A. We construct the unique inner representation U^A of the universal covering group of C implementing these

Bayram Tekin

We show that the apparently periodic Charap-Duff Yang-Mills `instantons' in time-compactified Euclidean Schwarzschild space are actually time independent. For these solutions, the Yang-Mills potential is constant along the time direction (no barrier) and therefore, there is no tunneling. We also demonstrate that the solutions found to date are three dime

Yu Shi, Qian Niu

We study the transport of an overdamped particle adiabatically driven by an asymmetric potential which is periodic in both space and time. We develop an adiabatic perturbation theory after transforming the Fokker-Planck equation into a time-dependent hermitian problem, and reveal an analogy with quantum adiabatic particle transport. An analytical expression

J I Kapusta, S M H Wong

No conventional picture of nucleus-nucleus collisions has yet been able to explain the abundance of Omega and AntiOmega hadrons in central collisions between Pb nuclei at 158 A GeV at the CERN SPS. We argue that this is evidence that they are produced from topological defects in the form of skyrmions arising from the formation of disoriented chiral condensat

Paolo Zanardi, Xiaoguang Wang

We study pairwise quantum entanglement in systems of fermions itinerant in a lattice from a second-quantized perspective. Entanglement in the grand-canonical ensemble is studied, both for energy eigenstates and for the thermal state. Relations between entanglement and superconducting correlations are discussed in a BCS-like model and for $η$-pair superconduc

K. R. S. Balaji, W. Rodejohann

In the context of left-right symmetric models we study the connection of leptogenesis and low energy parameters such as neutrinoless double beta decay and leptonic CP violation. Upon imposition of a unitarity constraint, the neutrino parameters are significantly restricted and the Majorana phases are determined within a narrow range, depending on the kind of

C. Armendariz-Picon

It is known that Lorentzian wormholes must be threaded by matter that violates the null energy condition. We phenomenologically characterize such exotic matter by a general class of microscopic scalar field Lagrangians and formulate the necessary conditions that the existence of Lorentzian wormholes imposes on them. Under rather general assumptions, these co

Caslav Brukner, Anton Zeilinger

Young's experiment is the quintessential quantum experiment. It is argued here that quantum interference is a consequence of the finiteness of information. The observer has the choice whether that information manifests itself as path information or in the interference pattern or in both partially to the extent defined by the finiteness of information.

M. Birukou, V. Husain, G. Kunstatter, E. Vaz

We describe a formalism and numerical approach for studying spherically symmetric scalar field collapse for arbitrary spacetime dimension d and cosmological constant Lambda. The presciption uses a double null formalism, and is based on field redefinitions first used to simplify the field equations in generic two-dimensional dilaton gravity. The formalism is

Ming Li, John Tromp, Paul Vitanyi

We provide a new representation-independent formulation of Occam's razor theorem, based on Kolmogorov complexity. This new formulation allows us to: (i) Obtain better sample complexity than both length-based and VC-based versions of Occam's razor theorem, in many applications. (ii) Achieve a sharper reverse of Occam's razor theorem than previous

Yasuyuki Kawahigashi, Roberto Longo

We completely classify diffeomorphism covariant local nets of von Neumann algebras on the circle with central charge c less than 1. The irreducible ones are in bijective correspondence with the pairs of A-D_{2n}-E_{6,8} Dynkin diagrams such that the difference of their Coxeter numbers is equal to 1. We first identify the nets generated by irreducible represe

Martin Lopez-Corredoira

Doing research is fighting, what any other thing the human being could do? Fight against powers or to get powers, that depends on us. Science can be a revolution or deadlocked idleness. Still waters, without hitting the stones along their history, trend to form bogs.

Ferit Ozturk

A generalised Thurston-Bennequin invariant for a Q-singularity of a real algebraic variety is defined as a linking form on the homologies of the real link of the singularity. The main goal of this paper is to present a method to calculate the linking form in terms of the very good resolution graph of a real normal unibranch surface singularity. For such sing

A. V. Smilga

We calculate the subleading terms in the Born--Oppenheimer expansion for the effective zero-mode Hamiltonian of N = 1, d=4 supersymmetric Yang--Mills theory with any gauge group. The Hamiltonian depends on 3r abelian gauge potentials A_i, lying in the Cartan subalgebra, and their superpartners (r being the rank of the group). The Hamiltonian belongs to the c

E. Gabrielli, S. Khalil

We analyze the inclusive semileptonic decays B -> X_s l^+ l^- in the framework of the supersymmetric standard model with non-universal soft-breaking terms at GUT scale. We show that the general trend of universal and non-universal models is a decreasing of branching ratio (BR) and increasing of energy asymmetry (AS). However, only non--universal models can h

I. Cabrera-Carnero, J. F. Gomes, G. M. Sotkov, A. H. Zimerman

We introduce and study new integrable models of A_n^{(1)}-Non-Abelian Toda type which admit U(1)\otimes U(1) charged topological solitons. They correspond to the symmetry breaking SU(n+1) \to SU(2)\otimes SU(2)\otimes U(1)^{n-2} and are conjectured to describe charged dyonic domain walls of N=1 SU(n+1) SUSY gauge theory in large n limit. It is shown that thi

ALEPH Collaboration

The final results of the ALEPH search for the Standard Model Higgs boson at LEP, with data collected in the year 2000 at centre-of-mass energies up to 209 GeV, are presented. The changes with respect to the preceding publication are described and a complete study of systematic effects is reported. The findings of this final analysis confirm the preliminary r

P. O. Kazinski, S. L. Lyakhovich, A. A. Sharapov

The effective equations of motion for a point charged particle taking account of radiation reaction are considered in various space-time dimensions. The divergencies steaming from the pointness of the particle are studied and the effective renormalization procedure is proposed encompassing uniformly the cases of all even dimensions. It is shown that in any d

N. Arimitsu, T. Arimitsu

A theoretical formula for the probability density function (PDF) of velocity derivatives in a fully developed turbulent flow is derived with the multifractal aspect based on the generalized measures of entropy, i.e., the extensive Renyi entropy or the non-extensive Tsallis entropy, and is used, successfully, to analyze the PDF's observed in the direct nu

T. Renk, R. A. Schneider, W. Weise

We calculate dilepton production rates from a fireball adapted to the kinematical conditions realized in ultrarelativistic heavy ion collisions over a broad range of beam energies. The freeze-out state of the fireball is fixed by hadronic observables. We use this information combined with the initial geometry of the collision region to follow the space-time

Edward Malec, Marc Mars, Walter Simon

For asymptotically flat initial data of Einstein's equations satisfying an energy condition, we show that the Penrose inequality holds between the ADM mass and the area of an outermost apparent horizon, if the data are restricted suitably. We prove this by generalizing Geroch's proof of monotonicity of the Hawking mass under a smooth inverse mean cur

P. Jiji Thomas Joseph, Prabhakar P. Singh

Using Korringa-Kohn-Rostoker coherent-potential approximation in the atomic-sphere approximation (KKR-ASA CPA) method for taking into account the effects of disorder, Gaspari-Gyorffy formalism for calculating the electron-phonon coupling constant $λ$, and Allen-Dynes equation for calculating T_c, we have studied the variation of T_c in Mg_{1-x}Ta_{x}B_2 allo

H. Dannerbauer, M. D. Lehnert, D. Lutz, L. Tacconi

We have used the IRAM Plateau de Bure mm interferometer to locate with subarcsecond accuracy the dust emission of three of the brightest 1.2mm sources in the NTT Deep Field (NDF) selected from our 1.2mm MAMBO survey at the IRAM 30m telescope. We combine these results with deep B to K imaging and VLA interferometry. Strikingly, none of the three accurately lo

Wolfgang Schmitz, D. Adamova

During the 1999 lead run, CERES has measured hadron and electron-pair production at 40 A GeV/c beam momentum with the spectrometer upgraded by the addition of a radial TPC. Here the analysis of lambda and antilambda will be presented.

Thomas Laustsen, Klaus Molmer

In this paper we present an optimal protocol by which an unknown state on a Hilbert space of dimension $N$ can be approximately stored in an $M$-dimensional quantum system or be approximately teleported via an $M$-dimensional quantum channel. The fidelity of our procedure is determined for pure states as well as for mixed states and states which are entangle

Francesco Guerra, Fabio L. Toninelli

In a region above the Almeida-Thouless line, where we are able to control the thermodynamic limit of the Sherrington-Kirkpatrick model and to prove replica symmetry, we show that the fluctuations of the overlaps and of the free energy are Gaussian, on the scale N^{-1/2}, for N large. The method we employ is based on the idea, we recently developed, of introd

Francesco Guerra, Fabio L. Toninelli

We develop a simple method to study the high temperature, or high external field, behavior of the Sherrington-Kirkpatrick mean field spin glass model. The basic idea is to couple two different replicas with a quadratic term, trying to push out the two replica overlap from its replica symmetric value. In the case of zero external field, our results reproduce

Anatoli Kopylov, Valeri Petukhov

The presence of two monochromatic lines of approximately equal intensity: $^{7}$Be- and pep-neutrinos in the sensitivity plot of lithium detector makes the pattern of the seasonal variations of the effect from solar neutrinos very characteristic in case if the long-wave vacuum oscillations are realized. This can give the very high accuracy in the measurement

Dominic J. Lee, Igor F. Herbut

We consider the effective 2+1 dimensional electrodynamics (QED_3) of low-energy quasiparticles coupled to fluctuating vortex loops in the d-wave superconductor, with the velocity anisotropy: v_F not equal to v_Delta. This theory should be relevant to the quantum superconductor-insulator transition in underdoped cuprates. Working in the customary large-N appr

Vadim Borokhov

We show that any generally covariant coupling of matter fields to gravity gives rise to a conserved, on-shell symmetric energy-momentum tensor equivalent to the canonical energy-momentum tensor of the flat-space theory. For matter fields minimally coupled to gravity our algorithm gives the conventional Belinfante tensor. We establish that different matter-gr

Eun-Joo Ahn, Marco Cavaglia, Angela V. Olinto

We propose that higher-dimensional extended objects (p-branes) are created by super-Planckian scattering processes in theories with TeV scale gravity. As an example, we compute the cross section for p-brane creation in a (n+4)-dimensional spacetime with asymmetric compactification. We find that the cross section for the formation of a brane which is wounded

T. E. Humphrey, R. Newbury, R. P. Taylor, H. Linke

Brownian heat engines use local temperature gradients in asymmetric potentials to move particles against an external force. The energy efficiency of such machines is generally limited by irreversible heat flow carried by particles that make contact with different heat baths. Here we show that, by using a suitably chosen energy filter, electrons can be transf

Edward Farhi, Jeffrey Goldstone, Sam Gutmann

We explain why quantum adiabatic evolution and simulated annealing perform similarly in certain examples of searching for the minimum of a cost function of n bits. In these examples each bit is treated symmetrically so the cost function depends only on the Hamming weight of the n bits. We also give two examples, closely related to these, where the similarity

Hoi-Kwong Lo

Entanglement purification provides a unifying framework for proving the security of quantum key distribution schemes. Nonetheless, up till now, a local commutability constraint in the CSS code construction means that the error correction and privacy amplification procedures of BB84 are not fully decoupled. Here, I provide a method to decouple the two process

T. A. Osborn, M. F. Kondratieva

The Schrodinger and Heisenberg evolution operators are represented in quantum phase space by their Weyl symbols. Their semiclassical approximations are constructed in the short and long time regimes. For both evolution problems, the WKB representation is purely geometrical: the amplitudes are functions of a Poisson bracket and the phase is the symplectic are

Hongchen Fu, Allan I Solomon, Xiaoguang Wang

For a 3-qubit Heisenberg model in a uniform magnetic field, the pairwise thermal entanglement of any two sites is identical due to the exchange symmetry of sites. In this paper we consider the effect of a non-uniform magnetic field on the Heisenberg model, modeling a magnetic impurity on one site. Since pairwise entanglement is calculated by tracing out one

Qiong-gui Lin

It is well known that any cyclic solution of a spin 1/2 neutral particle moving in an arbitrary magnetic field has a nonadiabatic geometric phase proportional to the solid angle subtended by the trace of the spin. For neutral particles with higher spin, this is true for cyclic solutions with special initial conditions. For more general cyclic solutions, howe

G. Cattaneo, M. L. Dalla Chiara, R. Giuntini, R. Leporini

Logical gates studied in quantum computation suggest a natural logical abstraction that gives rise to a new form of unsharp quantum logic. We study the logical connectives corresponding to the following gates: the Toffoli gate, the NOT and the squareroot of NOT (which admit of natural physical models). This leads to a semantic characterization of a logic tha

A. Penaranda, C. E. Auguet, L. Ramirez-Piscina

The simulation of the transition sequence of superheated Type I superconducting granules (SSG) in disordered suspensions when an external magnetic field is slowly increased from zero has been studied. Simulation takes into account diamagnetic interactions and the presence of surface defects. Results have been obtained for the transition sequence and surface

Angom Dilip Singh, Bhanu Pratap Das

The atomic parity non-conservation(PNC) experiments has reached accuracies which have important implications for physics beyond the standard model. An optical rotation experiment to measure the atomic PNC of the 3P1(6s6p)--1P1(6s6p) in Yb was proposed recently. Our screened electron-electron coulomb potential multi-configuration Dirac-Fock calculation of th

S. Abbas Hosseini, A. Sharan, D. Goswami

Accurate knowledge of absorption coefficient of a sample is a prerequisite for measuring the third order optical nonlinearity of materials, which could become a serious limitation for unknown samples. We introduce a new method, which measures both the absorption coefficient and the third order optical nonlinearity of materials with high sensitivity in a sing

Th. A. Rijken, H. Polinder, J. Nagata

The partial wave projection of the Nijmegen soft-core potential model for Meson-Pair-Exchange (MPE) for NN-scattering in momentum space is presented. Here, nucleon-nucleon momentum space MPE-potentials are NN-interactions where either one or both nucleons contains a meson-pair vertex. Dynamically, the meson-pair vertices can be viewed as describing in an eff

M. Petraki, E. Mavrommatis, O. Benhar, J. W. Clark

Final-state interactions in the response of a many-body system to an external probe delivering large momentum are normally described using the eikonal approximation, for the trajectory of the struck particle, and the frozen approximation, for the positions of the spectators. We propose a generalization of this scheme, in which the initial momentum of the str

Th. A. Rijken, H. Polinder, J. Nagata

A momentum space representation is derived for the Nijmegen Extended-Soft-Core (ESC) interactions. The partial wave projection of this representation is carried through, in principle for Two-Meson-Exchange (TME) in general. Explicit results for the momentum space partial wave NN-potentials from PS-PS-Exchange are given.