July 2001 arXiv papers — page 8

D. Anselmi

I derive a procedure to generate sum rules for the trace anomalies a and a'. Linear combinations of Delta a = a_UV-a_IR and Delta a' = a'_UV-a'_IR are expressed as multiple flow integrals of the two-, three- and four-point functions of the trace of the stress tensor. Eliminating Delta a', universal flow invariants are obtained, in particular sum rules for De

Torsten A. Ensslin, Rashid A. Sunyaev

Most of the Universe's populations of low energy cosmic ray electrons in the energy range of 1-100 MeV still manage to elude from detection by our instruments, since their synchrotron emission is at too low frequencies. We investigate a mechanism which can lead to observable emission of such electron populations: synchrotron-self Comptonization (SSC). Th

S. D. Ganichev, S. N. Danilov, V. V. Bel'kov, E. L. Ivchenko

Spin sensitive bleaching of the absorption of far-infrared radiation has been observed in $p$-type GaAs/AlGaAs quantum well structures. The absorption of circularly polarized radiation saturates at lower intensities than that of linearly polarized light due to monopolar spin orientation in the first heavy hole subband. Spin relaxation times of holes in $p$-t

Motoki Kino, Fumio Takahara, Masaaki Kusunose

Using multi-frequency spectra from TeV blazars in quiescent states, we obtain the physical parameters of the emission region of blazars within the framework of the one-zone synchrotron self-Compton (SSC) model. We numerically calculate the steady-state energy spectra of electrons by self-consistently taking into account the effects of radiative cooling with

Aldo Deandrea, Antonio D. Polosa

We consider the hadronic B decays B0bar -> D0 eta, B0bar -> D*0 eta, B0bar -> D0 eta', B0bar -> D*0 eta' in the framework of a quark-flavour basis and factorization. The formalism allows to compute the decays to the eta meson and to relate them to those of the eta'. Measuring the branching ratios of these processes may shed light on the nature of

Kostyantyn Zheltukhin

We consider equations arising from rational Lax representations. A general method to construct recursion operators for such equations is given. Several examples are given, including a degenerate bi-Hamiltonian system with a recursion operator.

D. Clowe, P. Schneider

We present a mass profile for A1689 from 0.13 h^{-1} Mpc < r < 2 h^{-1} Mpc from a weak lensing analysis of a 34&#39;x34&#39; R-band image from the ESO/MPG Wide Field Imager. We detect the gravitational shearing of a 23<R<25.5 background galaxy population even at the edge of the image with a 4-sigma significance, and find a two-dimensional mass reconstructio

K. Abe, The Belle Collaboration

We present a measurement of the Standard Model CP violation parameter sin 2phi_1 based on a 29.1 fb^{-1} data sample collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider. One neutral B meson is fully reconstructed as a J/psi Ks, psi(2S) Ks, chi_c1 Ks, eta_c Ks, J/psi K_L or J/psi K^{*0} decay and the flav

J. R. Forshaw, D. A. Ross, B. E. White

We perform a global fit to high energy precision electroweak data in a Higgs model containing the usual isospin doublet plus a real isospin triplet. The analysis is performed in terms of the oblique parameters S, T and U and we show that the mass of the lightest Higgs boson can be as large as 2 TeV.

Subir Ghosh

A consistent framework has been put forward to quantize the isentropic, compressible and inviscid fluid model in the Hamiltonian framework, using the Clebsch parameterization. The naive quantization is hampered by the non-canonical (in particular field dependent) Poisson Bracket algebra. To overcome this problem, the Batalin-Tyutin \cite{12} quantization for

Masahide Yamaguchi

We investigate the scaling property of global monopoles in the expanding universe. By directly solving the equations of motion for scalar fields, we follow the time development of the number density of global monopoles in the radiation dominated (RD) universe and the matter dominated (MD) universe. It is confirmed that the global monopole network relaxes int

Yasuaki Hikida, Yuji Sugawara

We study D-branes in the Lorentzian AdS_3 background from the viewpoint of boundary states, emphasizing the role of open-closed duality in string theory. Employing the world sheet with Lorentzian signature, we construct the Cardy states with the discrete series. We show that they are compatible with (1) unitarity and normalizability, and (2) the spectral flo

I. L. Aleiner, D. Controzzi

We consider the problem of an heavy particle in a double well potential (DWP) interacting with an electron bath. Under general assumptions, we map the problem to a three-color logarithmic gas model, where the size of the core of the charged particles is proportional to the tunneling time, $τ_{tun}$, of the heavy particle between the two wells. For times larg

Asher Peres, Petra F. Scudo

Quantum particles, such as spins, can be used for communicating spatial directions to observers who share no common coordinate frame. We show that if the emitter&#39;s signals are the orbit of a group, then the optimal detection method may not be a covariant measurement (contrary to widespread belief). It may be advantageous for the receiver to use a differe

Wang-Chang Su

The Faddeev-Skyrme model, a modified O(3) nonlinear sigma model in three space dimensions, is known to admit topological solitons that are stabilized by the Hopf charge. The Faddeev-Skyrme model is also related to the low-energy limits of SU(2) Yang-Mills theory. Here, the model is reformulated into its gauge-equivalent expression, which turns out to be Skyr

P. J. Burke, J. P. Eisenstein, L. N. Pfeiffer, K. W. West

This paper describes a THz transmission spectrometer for the spectral range of 2-65 cm^-1 (100 GHz to 2 THz) with a spectral resolution of at least 1.8 cm^-1 (50 GHz) where the source, sample, and detector are all fully contained in a cryogenic environment. Cyclotron emission from a two-dimensional electron gas heated with an electrical current serves as a m

P. J. Burke, L. N. Pfeiffer, K. W. West

We measure the effect of externally applied broadband Nyquist noise on the intrinsic Nyquist dephasing rate of electrons in a two-dimensional electron gas at low temperatures. Within the measurement error, the phase coherence time is unaffected by the externally applied Nyquist noise, including applied noise temperatures of up to 300 K. The amplitude of the

Tohru Kawamoto, Takako Iizuka-Sakano, Yukihiro Shimoi, Shuji Abe

We calculated the Madelung energies of both the ground state and excited states in tetrathiafulvalene - p-chloranil (TTF-CA) by taking into account intramolecular charge distribution. The distribution is found to be significant in the neutral-ionic (NI) transition. In the ionic phase, the Madelung energy depends more strongly on the intermolecular distance p

Miloslav Dusek

The question of the discrimination of the Bell states of two qudits (i.e., d-dimensional quantum systems) by means of passive linear optical elements and conditional measurements is discussed. A qudit is supposed to be represented by d optical modes containing exactly one photon altogether. From recent results of Calsamiglia it follows that there is no way h

M. Genovese, C. Novero

We propose a quantum transmission based on bi-photons which are doubly-entangled both in polarisation and phase. This scheme finds a natural application in quantum cryptography, where we show that an eventual eavesdropper is bound to introduce a larger error on the quantum communication than for a single entangled bi-photon communication, when steeling the s

Jiri Soucek

The new interpretation of Quantum Mechanics is based on a complex probability theory. An interpretation postulate specifies events which can be observed and it follows that the complex probability of such event is, in fact, a real positive number. The two-slit experiment, the mathematical formulation of the complex probability theory, the density matrix, Bor

E. Ercolessi, G. Marmo, G. Morandi

We argue here that, as it happens in Classical and Quantum Mechanics, where it has been proven that alternative Hamiltonian descriptions can be compatible with a given set of equations of motion, the same holds true in the realm of Statistical Mechanics, i.e. that alternative Hamiltonian descriptions do lead to the same thermodynamical description of any phy

V. M. Tkachuk

Using supersymmetric quantum mechanics we construct the quasi-exactly solvable (QES) potentials with arbitrary two known eigenstates. The QES potential and the wave functions of the two energy levels are expressed by some generating function the properties of which determine the state numbers of these levels. Choosing different generating functions we presen

S. F. Huelga, M. B. Plenio, J. A. Vaccaro

We study the remote implementation of a unitary transformation on a qubit. We show the existence of non-trivial protocols (i.e., using less resources than bidirectional state teleportation) which allow the perfect remote implementation of certain continuous sets of quantum operations. We prove that, up to a local change of basis, only two subsets exist that

Maxim Raginsky

We propose a fidelity measure for quantum channels in a straightforward analogy to the corresponding mixed-state fidelity of Jozsa. We describe properties of this fidelity measure and discuss some applications of it to quantum information science.

N. J. Cerf, S. Iblisdir, G. Van Assche

The cloning of quantum variables with continuous spectra is investigated. We define a Gaussian 1-to-2 cloning machine, which copies equally well two conjugate variables such as position and momentum or the two quadrature components of a light mode. The resulting cloning fidelity for coherent states, namely $F=2/3$, is shown to be optimal. An asymmetric versi

Yuan-nan Young, Hermann Riecke

Weakly nonlinear hexagon convection patterns coupled to mean flow are investigated within the framework of coupled Ginzburg-Landau equations. The equations are in particular relevant for non-Boussinesq Rayleigh-Bénard convection at low Prandtl numbers. The mean flow is found to (1) affect only one of the two long-wave phase modes of the hexagons and (2) supp

Mason A. Porter, Richard L. Liboff

We classify the local bifurcations of one dov quantum billiards, showing that only saddle-center bifurcations can occur. We analyze the resulting planar system when there is no coupling in the superposition state. In so doing, we also consider the global bifurcation structure. Using a double-well potential as a representative example, we demonstrate how to l

Sudhir R. Jain, Benoit Gremaud, Avinash Khare

Even as we understand for long that the world is quantal and buried in it is classical dynamics which is chaotic, finding eigenfunctions analytically from the the Schroedinger equation has turned out to be a near-impossibility. Here, we discover a class of chaotic quantum systems for which we obtain some analytically exact eigenfunctions in closed form. This

Tetsu Masuda

We give an explicit determinant formula for a class of rational solutions of a q-analogue of the Painlevé V equation. The entries of the determinant are given by the continuous q-Laguerre polynomials.

A. K. Svinin

We report an infinite class of discrete hierarchies which naturally generalize familiar discrete KP one.

Bozidar Jovanovic

We consider nonholonomic geodesic flows of left-invariant metrics and left-invariant nonintegrable distributions on compact connected Lie groups. The equations of geodesic flows are reduced to the Euler-Poincare-Suslov equations on the corresponding Lie algebras. The Poisson and symplectic structures give raise to various algebraic constructions of the integ

Christian Fleischhack

It is indicated that the definition of physical measures via ``exponential of minus the action times kinematical measure&#39;&#39; contradicts properties of certain physical models. In particular, theories describing confinement typically cannot be gained this way. The results are rigorous within the Ashtekar approach to gauge field theories.

Alejandro Adem, Yongbin Ruan

We use equivariant methods to establish basic properties of orbifold K-theory. We introduce the notion of twisted orbifold K-theory in the presence of discrete torsion, and show how it can be explicitly computed for global quotients.

Tomek Bartoszynski, Lorenz Halbeisen

In a paper of 1929, Banach and Kuratowski proved, assuming the continuum hypothesis, a combinatorial theorem which implies that there is no non-vanishing sigma-additive finite measure on the real line which is defined for every set of reals. It will be shown that the combinatorial theorem is equivalent to the existence of a K-Lusin set of size the continuum

Ana Cristina Lopez

The compactified Jacobian of any projective curve $X$ is defined as the Simpson moduli space of torsion free rank one degree $d$ sheaves that are semistable with respect to a fixed polarization $H$ on $X$. In this paper we give explicitly the structure of this compactified Simpson Jacobian in the case where $X$ is a generalized tree-like curve, i.e., a proje

Yujiro Kawamata

We construct a cohomological mixed Hodge complex on a fiber of a weakly semistable fibration using logarithmic de Rham complex.

Richard Bean, E. S. Mahmoodian

A critical set in an n x n array is a set C of given entries, such that there exists a unique extension of C to an n x n Latin square and no proper subset of C has this property. The cardinality of the largest critical set in any Latin square of order n is denoted by lcs(n). In 1978 Curran and van Rees proved that lcs(n) <= n^2 - n. Here we show that lcs(n)

Iku Nakamura

We construct a canonical compactification $SQ^{toric}_{g,K}$ of the moduli of abelian varieties over $Z[ζ_N, 1/N]$ where $ζ_N$ is a primitive $N$-th root of unity. This is very similar to, but slightly diferent from the compactification constructed by the author in Inventiones vol. 136 (1999). Any degenerate abelian scheme on the boundary of $SQ^{toric}_{g,K

Stephen Montgomery-Smith, Shih-Chi Shen

For each 1 < p < infinity, there exists a positive constant c_p, depending only on p, such that the following holds. Let (d_k), (e_k) be real-valued martingale difference sequences. If for for all bounded nonnegative predictable sequences (s_k) and all positive integers k we have E[s_k vee |e_k|] le E[s_k vee |d_k|] then for all positive integers n we have |

Ali Nayeri, Adam Reynolds

In this paper we discuss a physical observable which is drastically different in a brane-world scenario. To date, the Randall-Sundrum model seems to be consistent with all experimental tests of general relativity. Specifically, we examine the so-called gravitomagnetic effect in the context of the Randall-Sundrum (RS) model. This treatment, of course, assumes

D. Ebert, V. Ch. Zhukovsky, M. V. Rogal

An exact time-dependent solution of field equations for the 3-d gauge field model with a Chern-Simons (CS) topological mass is found. Limiting cases of constant solution and solution with vanishing topological mass are considered. After Lorentz boost, the found solution describes a massive nonlinear non-abelian plane wave. For the more complicate case of gau

Rika Endo, Koichi Seo, Akio Sugamoto

Old fashioned duality used to derive the closed string field theory for magnetic vortex from the gauge theory with Higgs scalar, is applied to the string theories. The bosonic sring theory coupled to the Kalb-Ramond 2-form field is dually transformed to the 6-brane theory coupled to the 7-form field. The old fashioned dual transformation is also examined for

Dipankar Chakrabarti, A. Harindranath

We study the meson sector of 2+1 dimensional light-front QCD using a Bloch effective Hamiltonian in the first non-trivial order. The resulting two dimensional integral equation is converted into a matrix equation and solved numerically. We investigate the efficiency of Gaussian quadrature in achieving the cancellation of linear and logarithmic light-front in

E. Sezgin, P. Sundell

The AdS_5 superalgebra PSU(2,2|4) has an infinite dimensional extension, which we denote by hs(2,2|4). We show that the gauging of hs(2,2|4) gives rise to a spectrum of physical massless fields which coincides with the symmetric tensor product of two AdS_5 spin-1 doubletons (i.e. the N=4 SYM multiplets living on the boundary of AdS_5). This product decompose

Paul H. Frampton

We propose a model of soft CP violation that evades the strong CP problem and can describe observed CP violation in the neutral kaon sector, both direct and indirect. Our model requires two ``duark&#39;&#39; mesons carrying quark number two that have complex (CP-violating) bare masses and are coupled to quark pairs. Aside from the existence of these potentia

Zurab Berezhiani, Anupam Mazumdar, Abdel Pérez-Lorenzana

The onset of inflation in hybrid models require fine tuning in the initial conditions. The inflaton field should have an initial value close to the Planck scale $M_{P}$, whereas the auxiliary &#34;orthogonal&#34; field must be close to zero with an extreme accuracy. This problem can be alleviated if the orthogonal field fastly decays into some states not cou

Michael I. Eides, Howard Grotch, Valery A. Shelyuto

We calculate radiative-recoil corrections of order $α^2(Zα)(m/M)E_F$ to hyperfine splitting in muonium generated by the diagrams with electron and muon polarization loops. These corrections are enhanced by the large logarithm of the electron-muon mass ratio. The leading logarithm cubed and logarithm squared contributions were obtained a long time ago. The si

Zhou Yifei, Liu Qin, Tang Ying, Cheng Chun

The erraticity in the random-cascading $α$ model is revisited. It is found that in contrary to the previous expectation, even in the pure single-$α$ random-cascading model without putting in any particle there exists erraticity behavior and the corresponding entropy indices do not vanish. This means that the dynamical fluctuations in a pure single-$α$ model

A. V. Gulov, V. V. Skalozub

Model-independent search for the Abelian $Z&#39;$ gauge boson virtual state based on the new observable in the processes $e^+ e^- \to l^+ l^-$ is analyzed for the LEP data. The observable is introduced by using following from renormalizability of an underlying theory the correlations between the parameters of the low energy effective Lagrangian and kinematic

Evgeny Akhmedov, Augusto Barroso, Petteri Keränen

We study the effects of periodic matter in kaon regeneration, motivated by the possibility of parametric resonance in neutrino oscillations. The large imaginary parts of the forward kaon-nucleon scattering amplitudes and the decay width difference $ΔΓ$ prevent a sizable enhancement of the $K_L\to K_S$ transition probability. However, some interesting effects

A. Delgado, G. v. Gersdorff, M. Quiros

We perform an explicit two-loop computation of the Higgs mass in a five-dimensional supersymmetric theory compactified on the orbifold S^1/Z_2, with superpotential localized on a fixed-point brane and supersymmetry broken in the bulk of the extra dimension by Scherk-Schwarz boundary conditions. At one-loop, the Higgs mass is finite and proportional to 1/R^2,

B. Z. Kopeliovich, J. Nemchik, A. Schaefer, A. V. Tarasov

So far no theoretical tool for the comprehensive description of exclusive electroproduction of vector mesons off nuclei at medium energies has been developed. We suggest a light-cone QCD formalism which is valid at any energy and incorporates formation effects (color transparency), the coherence length and the gluon shadowing. At medium energies color transp

S. Luders

The 9600 channels of the multi-wire proportional chamber of the H1 experiment at HERA have to be read out within 96 ns and made available to the trigger system. The tight spatial conditions at the rear end flange require a compact bidirectional readout electronics with minimal power consumption and dead material. A solution using 40 identical optical link mo

P. J. Bussey

The production of prompt photons in photoproduction reactions in the ZEUS experiment is discussed. Cross sections for inclusive prompt photons and for prompt photons accompanied by jets are compared with theory, and the latter are used to determine the effective transverse momentum of the quarks in the proton.

P. D. Dauncey

Since May 1999 the BABAR detector has been taking data at the PEP-II asymmetric electron-positron collider at the Stanford Linear Accelerator Center, California. This experiment requires a very large data sample and the PEP-II accelerator uses intense beams to deliver the high collision rates needed. This poses a severe challenge to the BaBar trigger system,

V. M. Abazov

We present data on multiple jet production for transverse energies greater than 20 GeV in pbarp collisions at sqrt(s) = 1.8 TeV. QCD calculations in the parton shower approximation (PYTHIA) and in the next-to-leading order approximation (JETRAD) show discrepancies with data for three and four-jet production. This disagreement is especially apparent in multip

Ignacio Olabarrieta, Matthew W. Choptuik

We perform a numerical study of the critical regime at the threshold of black hole formation in the spherically symmetric, general relativistic collapse of collisionless matter. The coupled Einstein-Vlasov equations are solved using a particle-mesh method in which the evolution of the phase-space distribution function is approximated by a set of particles (o

Michael J. Pfenning

A quantum inequality for the quantized electromagnetic field is developed for observers in static curved spacetimes. The quantum inequality derived is a generalized expression given by a mode function expansion of the four-vector potential, and the sampling function used to weight the energy integrals is left arbitrary up to the constraints that it be a posi

M. Francaviglia, M. Raiteri

A general recipe to define, via Noether theorem, the Hamiltonian in any natural field theory is suggested. It is based on a Regge-Teitelboim-like approach applied to the variation of Noether conserved quantities. The Hamiltonian for General Relativity in presence of non-orthogonal boundaries is analysed and the energy is defined as the on-shell value of the

Zvika Marx, Ido Dagan, Joachim Buhmann

This paper proposes a new paradigm and computational framework for identification of correspondences between sub-structures of distinct composite systems. For this, we define and investigate a variant of traditional data clustering, termed coupled clustering, which simultaneously identifies corresponding clusters within two data sets. The presented method is

F. Marsiglio

Recent optical studies in c-axis oriented superconducting MgB$_2$ films indicate that the electron-phonon coupling is weak [tu01]. We reinforce this conclusion by examining the raw reflectance data; its frequency dependence is incompatible with strong electron-phonon scattering. This is further strengthened by analysis of the real part of the conductivity, a

O. Gulseren, T. Yildirim, S. Ciraci

We investigated the adsorption of a single atom, hydrogen and aluminum, on single wall carbon nanotubes from first-principles. The adsorption is exothermic, and the associated binding energy varies inversely as the radius of the zigzag tube. We found that the adsorption of a single atom and related properties can be modified continuously and reversibly by th

Ligang Chen, Michael W. Deem

By analogy with Monte Carlo algorithms, we propose new strategies for design and redesign of small molecule libraries in high-throughput experimentation, or combinatorial chemistry. Several Monte Carlo methods are examined, including Metropolis, three types of biased schemes, and composite moves that include swapping or parallel tempering. Among them, the bi

W. G. van der Wiel, Yu. V. Nazarov, S. De Franceschi, T. Fujisawa

We define a mesoscopic ring in a 2-dimensional electron gas (2DEG) interrupted by two tunnel barriers, enabling us to apply a well-defined potential difference between the two halves of the ring. The electron interference in the ring is modified using a perpendicular magnetic field and a bias voltage. We observe clear Aharonov-Bohm oscillations up to the qua

J. T. Devreese, V. M. Fomin, V. N. Gladilin, Y. Imanaka

Recent cyclotron resonance experiments in n-type CdS at ultra-high magnetic fields have revealed a pronounced maximum of the electron cyclotron mass as a function of temperature. In order to interpret these data, we calculate the magneto-absorption spectra of polarons in n-CdS using the arbitrary-coupling approach. We show that in high magnetic fields the po

J. Müller, M. Lang, F. Steglich, J. A. Schlueter

We present high-resolution measurements of the coefficient of thermal expansion $α(T)=\partial \ln l(T)/\partial T$ of the quasi-twodimensional (quasi-2D) salts $κ$-(BEDT-TTF)$_2$X with X = Cu(NCS)$_2$, Cu[N(CN)$_2$]Br and Cu[N(CN)$_2$]Cl. At intermediate temperatures (B), distinct anomalies reminiscent of second-order phase transitions have been found at $T

J. T. Devreese, V. M. Fomin, E. P. Pokatilov, E. A. Kotomin

We present a multilateral theoretical study of bound polarons in oxide compounds MgO and α-Al_2O_3 (corundum). A continuum theory at arbitrary electron-phonon coupling is used for calculation of the energies of thermal dissociation, photoionization (optically induced release of an electron (hole) from the ground self-consistent state), as well as optical abs

Y. Zhang, D. Kinion, J. Chen, D. G. Hinks

Point contact junctions made from two pieces of MgB2 can be adjusted to exhibit either superconductor-insulator-superconductor (SIS) or superconductor-normal metal-superconductor (SNS) current-voltage characteristics. The SIS characteristics are in good agreement with the standard tunneling model for s-wave superconductors, and yield an energy gap of (2.02 +

J. Dukelsky, C. Esebbag, P. Schuck

We present three classes of exactly solvable models for fermion and boson systems, based on the pairing interaction. These models are solvable in any dimension. As an example we show the first results for fermion interacting with repulsive pairing forces in a two dimensional square lattice. Inspite of the repulsive pairing force the exact results show attrac

Jesper Dall, Paolo Sibani

We discuss a rejectionless global optimization technique which, while being technically similar to the recently introduced method of Extremal Optimization, still relies on a physical analogy with a thermalizing system. Our waiting time method (WTM) is mathematically equivalent to the usual Metropolis algorithm, but considerably more efficient at low temperat

J. T. Devreese, V. M. Fomin, V. N. Gladilin, S. N. Klimin

A theory of photoluminescence in semiconductor quantum dots is developed which relies on two key ingredients. First, it takes into account non-adiabaticity of the exciton-phonon system. Second, it includes the multimode dielectric model of LO-phonons and of the electron-phonon interaction in confined systems. The role of non-adiabaticity is shown to be of pa

Konstantin Kikoin, Yshai Avishai

It is shown that the low-energy spin states of double quantum dots (DQD) with even electron occupation number $N$ possess the symmetry SO(4) similar to that of a rigid rotator familiar in quantum mechanics (rotational spectra of H$_2$ molecule, electron in Coulomb field, etc). The &#34;hidden symmetry&#34; of the rotator manifests itself in the tunneling pro

M. Schulz, S. Stepanow, S. Trimper

We study the behaviour of two Brownian particles coupled by an elastic harmonic force in a quenched disordered medium. We found that to first order in disorder strength, the relative motion weakens (with respect to the reference state of a Brownian particle with the double mass) the effect of the quenched forces on the centre of mass motion of the Brownian p

E. Sharon, G. Cohen, J. Fineberg

Crack front waves are localized waves that propagate along the leading edge of a crack. They are generated by the interaction of a crack with a localized material inhomogeneity. We show that front waves are nonlinear entities that transport energy, generate surface structure and lead to localized velocity fluctuations. Their existence locally imparts inertia

O. Calvo, I. Gomes, C. R. Mirasso, R. Toral

Stochastic and coherence resonances appear in nonlinear systems subjected to an external source of noise and are characterized by a maximum response at the optimal value of the noise intensity. This paper shows experimentally that it is possible to observe them in a chaotic system. To this end we have analysed an electronic Chua circuit running in the chaoti

Nazareno G. F. de Medeiros, Roberto N. Onody

Since its proposition in 1995, the Heumann-Hotzel model has remained as an obscure model of biological aging. The main arguments used against it were its apparent inability to describe populations with many age intervals and its failure to prevent a population extinction when only deleterious mutations are present. We find that with a simple and minor change

J-P Bouchaud, E. Pitard

We compute the dynamical structure factor S(q,tau) of an elastic medium where force dipoles appear at random in space and in time, due to `micro-collapses&#39; of the structure. Various regimes are found, depending on the wave vector q and the collapse time. In an early time regime, the logarithm of the structure factor behaves as (q tau)^{3/2}, as predicted

Francesca Zambelli, Sandro Stringari

Sum rules are used to calculate the corrections to the hydrodynamic collective frequencies of a harmonically trapped Bose gas at T=0, due to finite size effects. We show that, with logarithmic accuracy, the relative corrections behave like $(a_{ho}/R)^4\log(R/a_{ho})$, where $R$ is the Thomas-Fermi radius of the condensate and $a_{ho}$ is the oscillator leng

S. Heim, T. Nachtrab, M. Moessle, R. Kleiner

The most anisotropic high temperature superconductors like Bi2Sr2CaCu2O8, as well as the recently discovered layered manganite La1.4Sr1.6Mn2O7 are layered metallic systems where the interlayer current transport occurs via sequential tunneling of charge carriers. As a consequence, in Bi2Sr2CaCu2O8 adjacent CuO2 double layers form an intrinsic Josephson tunnel

Hua Wu

We have implemented a systematic LSDA and LSDA+U study of the double perovskites $A_{2}$FeReO$_{6}$ (A=Ba,Sr,Ca) and Sr$_{2}$$M$MoO$_{6}$ (M=Cr,Mn,Fe,Co) for understanding of their intriguing electronic and magnetic properties. The results suggest a ferrimagnetic (FiM) and half-metallic (HM) state of $A_{2}$FeReO$_{6}$ (A=Ba,Sr) due to a pdd-$π$ coupling bet

V. N. Gladilin, V. M. Fomin, J. T. Devreese

The theory of the surface-induced anisotropy is extended to the case of granular films of dilute magnetic alloys. Since the surface-induced blocking of a magnetic-impurity spin appears to be very sensitive to the specific polycrystalline structure, we speculate that the apparent discrepancy between the experimental results of different groups for the size de

Ludger Santen, Werner Krauth

We study the thermodynamic and dynamic phase transitions in two-dimensional polydisperse hard disks using Monte Carlo methods. A conventional local Monte Carlo algorithm allows us to observe a dynamic liquid-glass transition at a density, which depends very little on the degree of polydispersity. We furthermore apply Monte Carlo methods which sample the Bolt

R. Leturcq, D. L&#39;Hote, R. Tourbot, V. Senz

We study the resistivity vs. electric field dependence $ρ(E)$ of a 2D hole system in SiGe close to the B=0 metal-insulator transition. Using $ρ$ as a ``thermometer&#39;&#39; to obtain the effective temperature of the holes $T_e(E)$, we find that the $ρ(E)$ dependence can be attributed to hole heating. The hole-phonon coupling involves weakly screened piezoel

Massimo Mannarelli, Giuseppe Nardulli, Sebastiano Stramaglia

We consider the dynamics of diluted neural networks with clipped and adapting synapses. Unlike previous studies, the learning rate is kept constant as the connectivity tends to infinity: the synapses evolve on a time scale intermediate between the quenched and annealing limits and all orders of synaptic correlations must be taken into account. The dynamics i

J. Rembielinski, K. A. Smolinski, G. Duniec

The Lorentz covariant statistical physics and thermodynamics is formulated within the preferred frame approach. The transformation laws for geometrical and mechanical quantities such as volume and pressure as well as the Lorentz-invariant measure on the phase space are found using Lorentz transformation in absolute synchronization. Next, the probability dens

Scott M. Croom, S. J. Warren, K. Glazebrook

In this paper we present preliminary spectroscopic results from a small area faint K-excess (KX) survey, and compare KX selection against UVX selection. The aim of the KX method is to produce complete samples of QSOs flux-limited in the K band, in order to minimize any selection bias in samples of QSOs from the effects of reddening and extinction. Using the

Charles G. Hoopes, Rene A. M. Walterbos, Gregory D. Bothun

(Abridged) We have compared H-alpha and far ultraviolet (FUV) images of 10 nearby spirals, with the goal of understanding the contribution of field OB stars to the ionization of the diffuse ionized gas (DIG) in spiral galaxies. The FUV images were obtained by the Ultraviolet Imaging Telescope (UIT) and the H-alpha images were obtained using various ground-ba

M. A. Zwaan, F. H. Briggs, D. Sprayberry

We measure the z=0 B-band optical luminosity function (LF) for galaxies selected in a blind HI survey. The total LF of the HI selected sample is flat, with Schechter parameters M*=-19.38_{-0.62}^{+1.02} + 5 log h mag and alpha=-1.03_{-0.15}^{+0.25}, in good agreement with LFs of optically selected late-type galaxies. Bivariate distribution functions of sever

Cristiano Porciani, Mauro Giavalisco

We present a new measure of the angular two-point correlation function of Lyman-break galaxies (LBGs) at z~3, obtained from the variance of galaxy counts in 2-dimensional cells. By avoiding binning of the angular separations, this method is significantly less affected by shot noise than traditional measures, and allows for a more accurate determination of th

M. Sakano, H. Tomida, M. Matsuoka, S. Ueno

Monitor of All-sky X-ray Image (MAXI) on the International Space Station (ISS) has two kinds of X-ray detectors: the Gas Slit Camera (GSC) and the Solid-state Slit Camera (SSC). SSC is an X-ray CCD array, consisting of 16 chips, which has the best energy resolution as an X-ray all-sky monitor in the energy band of 0.5 to 10 keV. Each chip consists of 1024x10

Masaaki Sakano, Katsuji Koyama, Hiroshi Murakami, Yoshitomo Maeda

From the ASCA X-ray point-source list in the Galactic center 5x5 degree^2 region, we found the clear correlation between the position of the sources and the absorption. This fact implies that the major part of the absorption is due to the cold interstellar matter (ISM) in the line of sight. Using the correlation, we estimate the distribution of the cold ISM.

Bohdan Paczynski

In June 2003 the isolated neutron star RX J185635-3754 will pass within 0.3&#39;&#39; of a 26.5 mag star, changing its position by about 0.6 mas. The displacement, caused by gravitational lensing, will be proportional to the neutron star mass. The total event duration will be approximately 1 year.

Michael D. Gregg, Mark Lacy, Richard L. White, Eilat Glikman

In a survey of quasar candidates selected by matching the FIRST and 2MASS catalogs, we have found two extraordinarily red quasars. FIRST J013435.7-093102 is a 1 Jy source at z=2.216 and has B-K > 10, while FIRST J073820.1+275045 is a 2.5 mJy source at z=1.985 with B-K = 8.4. FIRST J073820.1+275045 has strong absorption lines of MgII and CIV in the rest frame

Noam Soker, Ron Hadar

We propose a scheme to classify planetary nebulae (PNe) according to their departure from axisymmetric structure. We consider only departure along and near the equatorial plane, i.e., between the two sides perpendicular to the symmetry axis of the nebula. We consider 6 types of departure from axisymmetry: (1) PNe whose central star is not at the center of th

Margarita Rosado, Eduardo de la Fuente, Lorena Arias, E. Le Coarer

We present a kinematic study of the Herbig-Haro objects HH 202, 203 and 204 using Halpha and [NII] Fabry-Perot velocity maps. For HH 202 we find new features that could belong to this HH object or that perhaps are associated with an outflow different from HH 202. Because of its high velocity (up to 100 km/seg) this outflow probably can be a HH flow not catal

Timothy M. Heckman

In this contribution I summarize our current knowledge of the nature and significance of starburst-driven galactic winds (``superwinds&#39;&#39;). Superwinds are complex multiphase outflows of cool, warm, and hot gas, dust, and magnetized relativistic plasma. The observational manifestations of superwinds result from the hydrodynamical interaction between th

Will J. Percival

Modelling the build-up of halos is important for linking the formation of galaxies with cosmological models. A simple model of halo growth is provided by Press-Schechter (PS) theory, where the initial field of density fluctuations is smoothed using spherically symmetric filters centred on a given position to obtain information about the likelihood of later c

Joshua N. Winn, James E. J. Lovell, Hsiao-Wen Chen, Andre B. Fletcher

The radio-loud quasar PMN J0134-0931 was discovered to have an unusual morphology during our search for gravitational lenses. In VLA and MERLIN images, there are 5 compact components with maximum separation 681 millarcseconds. All of these components have the same spectral index from 5 GHz to 43 GHz. In a VLBA image at 1.7 GHz, a curved arc of extended emiss

Spyros Basilakos

We attempt to put constraints on different cosmological and biasing models by combining the recent clustering results of X-ray sources in the local ($z\le 0.1$) and distant universe ($z\sim 1$).