February 2002 arXiv papers — page 11

Damien Le Borgne, Brigitte Rocca-Volmerange

Photometric redshifts are estimated on the basis of template scenarios with the help of the code ZPEG, an extension of the galaxy evolution model PEGASE.2 and available on the PEGASE web site. The spectral energy distribution (SED) templates are computed for nine spectral types including starburst, irregular, spiral and elliptical. Dust, extinction and metal

Nicholas E. White

The NASA program in X-ray astronomy has two long term goals: 1) to achieve sufficient angular resolution to image the event horizon of a black hole (0.1 micro arc sec) and 2) to achieve sufficient collecting area (50-150 sq m) and angular resolution (0.1-1.0 arc sec) to observe in detail the first black holes and galaxies at high redshift. These ambitous goa

Tim Adams, Melvyn B. Davies, Richard F. Jameson, Aylwyn Scally

We present the results of multiple simulations of open clusters, modelling the dynamics of a population of brown dwarf members. We consider the effects of a large range of primordial binary populations, including the possibilities of having brown dwarf members contained within a binary system. We also examine the effects of various cluster diameters and mass

Caleb A. Scharf

In this short paper I present the results of a calculation which seeks the maximum, or optimal, signal-to-noise energy band for galaxy group or cluster X-ray emission detected by the Chandra and XMM-Newton observatories. Using a background spectrum derived from observations and a grid of models I show that the "classical" 0.5-2 keV band is indeed clo

V. Braito, A. Franceschini, R. Della Ceca, L. Bassani

We present preliminary results of XMM-Newton observations of 5 Ultra-luminous Infrared Galaxies (ULIRGs), part of a mini-survey program dedicated to 10 ULIRGs selected from the bright IRAS sample. For 3 of them (IRAS 20551-4250, IRAS 19254-7245 and Mkn 231) we find strong evidence for the presence of a hidden AGN, while for two others (IRAS 20110-4156 IRAS 2

Indranil Chattopadhyay, Sandip K. Chakrabarti

Matter accreting onto black holes may develop shocks due to the centrifugal barrier. A part of inflowing matter in the post-shock flow is deflected along the axis in the form of jets. Post-shock flow which behaves like a Compton cloud has `hot' electrons emiting high energy photons. We study the effect of these `hot' photons on the outflowing matter.

Cesar Briceño, Nuria Calvet, Anna K. Vivas, L. Hartmann

We present recent results from our ongoing large scale variability survey of the Orion OB1 Association. In an area of ~ 25 square degrees we have unveiled new populations of low-mass young stars over a range of environments, and ages from 1-2 Myr in Ori OB 1b to roughly 10 Myr in Ori OB 1a. There is a lack of strong Ha emission and near-IR excesses in the yo

C. A. Haswell, R. I. Hynes, A. R. King, K. Schenker

We compare UV spectra of the recent soft X-ray transients XTE J1118+480 and XTE J1859+226. The emission line strengths in XTE J1118+480 strongly suggest that the accreting material has been CNO processed. We show that this system must have come into contact with a secondary star of about 1.5 solar masses, and an orbital period ~15hr, very close to the bifurc

Maxim Lyutikov

The dynamics of relativistic magnetized mass loaded outflows carrying toroidal magnetic field is analyzed in the context of Pulsar Wind Nebulae (PWNs). Mass loading is very efficient in slowing down super-relativistic magnetized flows and weakening of relativistic shocks. We suggest that weakening of relativistic reverse shocks by mass loading in PWNs is res

Sultana N. Nahar

A hot central star illuminating the surrounding ionized H II region usually produces very rich atomic spectra resulting from basic atomic processes: photoionization, electron-ion recombination, bound-bound radiative transitions, and collisional excitation of ions. Precise diagnostics of nebular spectra depend on accurate atomic parameters for these processes

Dimitrios Psaltis, M. Coleman Miller

The spin periods of the ten observed Anomalous X-ray Pulsars and Soft Gamma-ray Repeaters lie in the very narrow range 6-12 s. We use a point likelihood technique to assess the constraints this clustering imposes on the birth period and on the final period of such systems. We consider a general law for their spin evolution described by a constant braking ind

Tommaso Treu, Leon Koopmans

[Abridged] We combine our measurements of the velocity dispersion and the surface brightness profile of the lens galaxy D in the system MG2016+112 (z=1.004) with constraints from gravitational lensing to study its internal mass distribution. We find that: (i) dark matter accounts for >50% of the total mass within the Einstein radius (99% CL), excluding at th

Rusko Ruskov, Alexander N. Korotkov

We have developed a formalism suitable for calculation of the output spectrum of a detector continuously measuring quantum coherent oscillations in a solid-state qubit, starting from microscopic Bloch equations. The results coincide with that obtained using Bayesian and master equation approaches. The previous results are generalized to the cases of arbitrar

Mariana Graña

Using the kappa-symmetric action for a D3-brane, we study the interaction between its world-volume fermions and a bosonic type IIB supergravity background preserving 4-dimensional Lorentz invariance. We find that the renormalizable terms in the action include only coupling between the fermions and the 3-form flux in the combination *G_3-iG_3, which is zero f

Ikaros Bigi, Nikolai Uraltsev

Measuring the photon energy spectrum in radiative B decays provides essential help for gaining theoretical control over semileptonic B transitions. The hadronic recoil mass distribution in B -> X_u \ellνpromises the best environment for determining |V_ub|. The theoretical uncertainties are largest in the domain of low values of the lepton pair mass q^2. Univ

R. R. Metsaev, A. A. Tseytlin

We describe in detail the solution of type IIB superstring theory in the maximally supersymmetric plane-wave background with constant null Ramond-Ramond 5-form field strength. The corresponding light-cone Green-Schwarz action found in hep-th/0112044 is quadratic in both bosonic and fermionic coordinates. We find the spectrum of the light-cone Hamiltonian and

Kirill Krasnov

Using the recently proposed formalism for Lambda<0 quantum gravity in 2+1 dimensions we study the process of black hole production in a collision of two point particles. The creation probability for a BH with a simplest topology inside the horizon is given by the Liouville theory 4-point function projected on an intermediate state. We analyze in detail the s

L. Andrianopoli, R. D&#39;Auria, S. Ferrara, M. A. Lledo

We consider the reduction of supersymmetry in N-extended four dimensional supergravity via the super Higgs mechanism in theories without cosmological constant. We provide an analysis largely based on the properties of long and short multiplets of Poincare&#39; supersymmetry. Examples of the super Higgs phenomenon are realized in spontaneously broken N=8 supe

Adam K. Leibovich, David Rainwater

Light bottom squarks and gluinos have been invoked to explain the b quark pair production excess at the Tevatron. We investigate the associated production of ttbb at hadron colliders in this scenario, and find that the rates for this process are enhanced over the Standard Model prediction. If light gluinos exist, it may be possible to detect them at the Teva

Dirk Kreimer

We review the combinatorial structure of perturbative quantum field theory with emphasis given to the decomposition of graphs into primitive ones. The consequences in terms of unique factorization of Dyson--Schwinger equations into Euler products are discussed.

F. Ye, L. Zhou, S. Larochelle, L. Lu

The critical exponent beta =0.16 +- 0.02 for the random-field Ising model order parameter is determined using extinction-free magnetic x-ray scattering for Fe(0.85)Zn(0.15)F2 in magnetic fields of 10 and 11 T. The observed value is consistent with other experimental random-field critical exponents, but disagrees sharply with Monte Carlo and exact ground stat

P. Lira, M. J. Ward, A. Zezas, S. S. Murray

We present high spatial resolution X-ray Chandra HRC and HST WFPC2 Halpha observations of the prototypical infrared luminous galaxy NGC6240. The central region of this system shows a remarkably complex morphology, with filaments and loops observed in the optical and X-rays. The total X-ray luminosity is dominated by the extended emission. Both nuclei are cle

A. Udalski, B. Paczynski, K. Zebrun, M. Szymanski

We present results of an extensive photometric search for planetary and low-luminosity object transits in the Galactic disk stars commencing the third phase of the Optical Gravitational Lensing Experiment -- OGLE-III. Photometric observations of three fields in the direction of the Galactic center (800 epochs per field) were collected on 32 nights during tim

Karsten Jedamzik

It is widely believed that the cosmic baryon density may be obtained by inferring deuterium abundances in low-metallicity quasar absorption line systems. The implicit assumptions which enter this argument are critically assessed. In particular, the production of deuterium in non-standard Big Bang nucleosynthesis scenarios, the putative production of deuteriu

M. Cadoni, S. Mignemi

We investigate the cosmology of the two-dimensional Jackiw-Teitelboim model. Since the matter coupling is not defined uniquely, we consider two possible choices. The dilaton field plays an important role in the discussion of the properties of the solutions. In particular, the possibility of universes having a finite initial size emerges.

D. Maurin, M. Casse, E. Vangioni-Flam

A substantial increase of the mean logarithmic mass $<\ln A>$ of galactic cosmic rays {\em vs} energy has been observed . We study three effects that could explain this trend i) different source spectra for protons and heavy nuclei ii) a selective nuclear destruction in flight of heavies iii) a gradient of the source number and chemical composition in the ga

Christos Charmousis, Jean-Francois Dufaux

We consider 5-dimensional spacetimes of constant 3-dimensional spatial curvature in the presence of a bulk cosmological constant. We find the general solution of such a configuration in the presence of a Gauss-Bonnet term. Two classes of non-trivial bulk solutions are found. The first class is valid only under a fine tuning relation between the Gauss-Bonnet

E. Xanthopoulos, T. W. B. Muxlow, P. Thomasson, S. T. Garrington

We present MERLIN L-band images of the compact galaxy group, Stephan&#39;s Quintet. The Seyfert 2 galaxy, NGC 7319, the brightest member of the compact group, is seen to have a triple radio structure typical of many extra-galactic radio sources which have a flat spectrum core and two steep spectrum lobes with hot spots. The two lobes are asymmetrically distr

P. Heinamki, J. Einasto, M. Einasto, E. Saar

We have determined the mass function of loose groups of galaxies in the Las Campanas Redshift Survey. Loose groups of galaxies in the LCRS range in mass from $M \sim 10^{12} {\rm M}_{\sun}$ to $10^{15} {\rm M}_{\sun}$. We find that the sample is almost complete for masses in the interval $5\cdot 10^{13}-8\cdot 10^{14} {\rm M}_{\sun}$. Comparison of the obser

Shigeki Matsutani

The sine-Gordon equation has hyperelliptic al function solutions over a hyperelliptic Jacobian for $y^2 = f(x)$ of arbitrary genus $g$. This article gives an extension of the sine-Gordon equation to that over subvarieties of the hyperelliptic Jacobian. We also obtain the condition that the sine-Gordon equation in a proper subvariety of the Jacobian is define

Pasquale Calabrese, Andrea Pelissetto, Ettore Vicari

We study the combined effect of cubic anisotropy and quenched uncorrelated impurities on multicomponent spin models. For this purpose, we consider the field-theoretical approach based on the Ginzburg-Landau-Wilson $ϕ^4$ Hamiltonian with cubic-symmetric quartic interactions and quenched randomness coupled to the local energy density. We compute the renormaliz

M. C. Bento, O. Bertolami, A. A. Sen

We consider the scenario emerging from the dynamics of a generalized $d$-brane in a $(d+1, 1)$ spacetime. The equation of state describing this system is given in terms of the energy density, $ρ$, and pressure, $p$, by the relationship $p = - A/ρ^α$, where $A$ is a positive constant and $0 < α\le 1$. We discuss the conditions under which homogeneity arises a

E. Fiorani, G. Giachetta, G. Sardanashvily

A time-dependent completely integrable Hamiltonian system is quantized with respect to time-dependent action-angle variables near an instantly compact regular invariant manifold. Its Hamiltonian depends only on action variables, and has a time-independent countable energy spectrum.

G. Ferrari, M. Inguscio, W. Jastrzebski, G. Modugno

We determine the inter-species s-wave triplet scattering length a3 for all K-Rb isotopic mixtures by measuring the cross-section for collisions between 41K and 87Rb in different temperature regimes. The positive value a3=+163(+57,-12)a0 ensures the stability of binary 41K-87Rb Bose-Einstein condensates. For the fermion-boson mixture 40K-87Rb we obtain a larg

K. -I. Izawa, T. Watari, T. Yanagida

QCD in a five-dimensional sliced bulk with chiral extra-quarks on the boundaries is generically free from the strong CP problem. Accidental axial symmetry is naturally present except for suppressed breaking interactions, which plays a role of the Peccei-Quinn symmetry to make the strong CP phase sufficiently small.

Michael Gronau, Jonathan L. Rosner

Time-dependence in $B^0(t) \to π^+ π^-$ and $\ob(t) \to π^+ π^-$ is utilized to obtain a maximal set of information on strong and weak phases. One can thereby check theoretical predictions of a small strong phase $δ$ between penguin and tree amplitudes. A discrete ambiguity between $δ\simeq 0$ and $δ\simeq π$ may be resolved by comparing the observed charge-

Jin-Ho Cho, Phillial Oh, Jeong-Hyuck Park

We propose an exactly solvable Grassmannian sigma-model coupled to the Chern-Simons theory. In the presence of a novel topological term our model admits exact self-dual vortex solutions which are identical to those of pure Grassmannian model, but the topological charge has a physical meaning as a magnetic flux since the gauge field is no longer auxiliary. We

R. Kajimoto, K. Ishizaka, H. Yoshizawa, Y. Tokura

The charge ordering in La1.5Sr0.5NiO4 has been studied with neutron diffraction technique. An interesting rearrangement of the charge ordering was observed as a function of temperature. With decreasing temperature, a checkerboard-type charge order is formed below T{CO-C} ~ 480 K. It is, however, taken over by the stripe-type charge order with an incommensura

Ole E. Barndorff-Nielsen, Elena R. Loubenets

We develop the general quantum stochastic approach to the description of quantum measurements continuous in time. The framework, that we introduce, encompasses the various particular models for continuous-time measurements condsidered previously in the physical and the mathematical literature.

Stephen D. Bartlett, Barry C. Sanders, Samuel L. Braunstein, Kae Nemoto

We obtain sufficient conditions for the efficient simulation of a continuous variable quantum algorithm or process on a classical computer. The resulting theorem is an extension of the Gottesman-Knill theorem to continuous variable quantum information. For a collection of harmonic oscillators, any quantum process that begins with unentangled Gaussian states,

Kirill N. Alekseev, Aleksey V. Ponomarev

We examine a spatial evolution of lightwaves in a nonlinear photonic crystal with a quadratic nonlinearity when simultaneously a second harmonic and a sum-frequency generation are quasi-phase-matched. We find the conditions of a transition to Hamiltonian chaos for different amplitudes of lightwaves at the boundary of the crystal.

M. Antonelli, A. Mazzino, U. Rizza

Temperature fluctuations in an atmospheric convective boundary layer are investigated by means of Large Eddy Simulations (LES). A statistical characterization for both weak temperature fluctuations and strong temperature fluctuations has been found. Despite the nontriviality of the dynamics of temperature fluctuations, our data support the idea that the most

E. G. Bessonov

Methods of enhanced laser cooling of particle beams in storage rings and Robinson&#39;s damping criterion are discussed. The dynamics of amplitudes of betatron oscillations and instantaneous orbits of electrons interacting with laser beams being displaced in the radial direction is investigated.

V. P. Likhachev, J. Mesa, J. D. T. Arruda-Neto, B. V. Carlson

We present the result of a theoretical study of the quasi free electrofission of $^{238}$U. The exclusive differential cross sections for the quasi free scattering reaction stage have been calculated in PWIA, using a Macroscopic-Microscopic approach for the description of the proton bound states. The nuclear shape was parametrized in terms of cassinian ovalo

Mark Adler, Vadim B. Kuznetsov, Pierre van Moerbeke

The finite Pfaff lattice is given by commuting Lax pairs involving a finite matrix L (zero above the first subdiagonal) and a projection onto Sp(N). The lattice admits solutions such that the entries of the matrix L are rational in the time parameters t_1,t_2,..., after conjugation by a diagonal matrix. The sequence of polynomial tau-functions, solving the p

M. De Lucia, A. Mazzino, A. Vulpiani

Polymer transport is investigated for two paradigmatic laminar flows having open and closed streamlines, respectively. For both types of flows we find transport depletion owing to the action of the polymers elastic degree of freedom. For flows with closed streamlines the leading mechanism for the observed transport reduction is the (dynamical) formation of b

Pavel Grozman, Dimitry Leites, Irina Shchepochkina

We list defining relations for the four of the five exceptional simple Lie superalgebras some of which, as David Broadhurst conjectured and Kac demonstrated, may pertain to The Standard Model or Grand unified theories of elementary particles. For the fifth superalgebra the result is not final: there might be infinitely many relations. Contrariwise, for the s

Dimitry Leites

In mid 60s Bott proved that (1) the index theorem for homogeneous, G-invariant, elliptic differential operators acting in the spaces of sections of induced representations of G over G/H reduces to the Weyl character formula and (2) the index of an equivariant elliptic operator does not depend on the operator, but on the representations. Here the same theorem

Joan S. Birman, William W. Menasco

We give a new proof of Markov&#39;s classical theorem relating any two closed braid representations of the same knot or link. The proof is based upon ideas in a forthcoming paper by the authors, &#34;Stabilization in the braid groups&#34;. The new proof of the classical Markov theorem is used by Nancy Wrinkle in her forthcoming manuscript &#34;The Markov The

Dimitry Leites

In 1960&#39;s I. Gelfand posed a problem: describe indecomposable representations of any simple infinite dimensional Lie algebra of polynomial vector fields. Here, by applying the elementary technique of Gelfand and Ponomarev, a toy model of the problem is solved: finite dimensional indecomposable representations of vect(0|2), the Lie superalgebra of vector

Deepak Parashar

We study the quantum plane associated to the coloured quantum group GL_{q}^{λ,μ}(2) and solve the problem of constructing the corresponding differential geometric structure. This is achieved within the R-matrix framework generalising the Wess-Zumino formalism and leads to the concept of coloured quantum space. Both, the coloured Manin plane as well as the bi

Alexander Sergeev

Let A be an associative complex algebra and L an invariant linear functional on it (trace). Let i be an involutive antiautomorphism of A such that L(i(a))=L(a) for any a in A. Then A admits a symmetric invariant bilinear form (a, b)=L(a i(b)). For A=U(sl(2))/m, where m is any maximal ideal of U(sl(2)), Leites and I have constructed orthogonal basis whose ele

Dimitry Leites, Irina Shchepochkina

Howe&#39;s duality is considered from a unifying point of view based on Lie superalgebras. New examples are offered. In particular, we construct several simplest spinor-oscillator representations and compute their highest weights for the &#39;stringy&#39; Lie superalgebras (i.e., Lie superalgebras of complex vector fields (or their nontrivial central extensi

Dimitry Leites, Alexander Sergeev

Casimir operators -- the generators of the center of the enveloping algebra -- are described for simple or close to them ``classical&#39;&#39; finite dimensional Lie superalgebras with nondegenerate symmetric even bilinear form in Sergeev A., The invariant polynomials on simple Lie superalgebras. Represent. Theory 3 (1999), 250--280; math-RT/9810111 and for

Joel Hass, Jeffrey C. Lagarias

This paper considers affine analogues of the isoperimetric inequality in the sense of piecewise linear topology. Given a closed polygon P embedded in R^d having n edges, we give upper and lower bounds for the minimal number of triangles needed to forma triangulated embedded orientable surface in R^d having P as its geometric boundary. The most interesting ca

Pavel Grozman, Dimitry Leites

A class of simple filtered Lie algebras of polynomial growth with increasing filtration is distinguished and presentations of these algebras are explicitely described for the simplest examples. Lie (super)algebras of this class appear in relation with Calogero--Sutherland model, high-spin supergravity, etc.; they are associated with the associative algebras

Alberto S. Cattaneo, Juerg Froehlich, Bill Pedrini

The string bracket introduced by Chas and Sullivan [math.GT/9911159] is reinterpreted from the point of view of topological field theories in the Batalin-Vilkovisky or BRST formalisms. Namely, topological action functionals for gauge fields (generalizing Chern-Simons and BF theories) are considered together with generalized Wilson loops. The latter generate

Joerg Schuermann

We give a general formula for the defect appearing in the Verdier-type Riemann-Roch formula for Chern-Schwartz-MacPherson classes in the case of a regular embedding. Our proof of this formula uses the constructible function version of Verdier&#39;s specialization functor, together with a specialization property of Chern-Schwartz-MacPherson classes and the co

Eddy Godelle

Let $(A_S,S)$ be an Artin-Tits and $X$ a subset of $S$ ; denote by $A_X$ the subgroup of $A_S$ generated by $X$. When $A_S$ is of spherical type, we prove that the normalizer and the commensurator of $A_X$ in $A_S$ are equal and are the product of $A_X$ by the quasi-centralizer of $A_X$ in $A_S$. Looking to the associated monoids $A_S^+$ and $A_X^+$, we desc

Stefan Müller-Stach, Shuji Saito, Alberto Collino

We study the higher Chow groups $CH^2(X,1)$ and $CH^3(X,2)$ of smooth, projective algebraic surfaces over a field of char 0. We develop a theoretical framework to study them by using so-called higher normal functions and higher infinitesimal invariants when the cycles are supported on normal crossing divisors. Then we investigate their structure on hypersurf

I. G. Todorov

Generalizing a result of Arveson on finite width CSL algebras, we prove that finite width masa-bimodules satisfy spectral synthesis. Introducing a new class of masa-bimodules, we show that there exists a non-synthetic masa-bimodule, such that the maximal algebras over which it is a bimodule, are synthetic.

I. G. Todorov

We characterize the pairs of operator spaces which occur as pairs of Morita equivalence bimodules between non-selfadjoint operator algebras in terms of the mutual relation between the spaces. We obtain a characterization of the operator spaces which are completely isometrically isomorphic to imprimitivity bimodules between some strongly Morita equivalent (in

Jean-Francois Burnol

We establish a uniform upper estimate for the values of zeta(s)/zeta(s+A), 0<= A, on the critical line (conditionally on the Riemann Hypothesis). We use this to give a variant, purely complex analytic, to Baez-Duarte&#39;s proof of a strengthened Nyman-Beurling criterion for the validity of the Riemann Hypothesis.

Alexander Braverman

Let $k$ be an algebraically closed field of characteristic $p>0$ and let $\ell$ be another prime number. O. Gabber and F. Loeser proved that for any algebraic torus $T$ over $k$ and any perverse $\ell$-adic sheaf $\calF$ on $T$ the Euler characteristic $χ(\calF)$ is non-negative. We conjecture that the same result holds for any perverse sheaf $\calF$ on a re

Pavel Grozman, Dimitry Leites, Elena Poletaeva

The analogs of Chevalley generators are offered for simple (and close to them) Z-graded complex Lie algebras and Lie superalgebras of polynomial growth without Cartan matrix. We show how to derive the defining relations between these generators and explicitly write them for a &#34;most natural&#34; (&#34;distinguished&#34; in terms of Penkov and Serganova) s

Luis Baez-Duarte

Let $ρ(x)=x-[x]$, $χ=χ_{(0,1)}$. In $L_2(0,\infty)$ consider the subspace $\B$ generated by $\{ρ_a | a \geq 1\}$ where $ρ_a(x):=ρ(\frac{1}{ax})$. By the Nyman-Beurling criterion the Riemann hypothesis is equivalent to the statement $χ\in\bar{\B}$. For some time it has been conjectured, and proved in this paper, that the Riemann hypothesis is equivalent to th

Victor Nistor, Evgenij Troitsky

Let $\GR \to B$ be a bundle of compact Lie groups acting on a fiber bundle $Y \to B$. In this paper we introduce and study gauge-equivariant $K$-theory groups $K_\GR^i(Y)$. These groups satisfy the usual properties of the equivariant $K$-theory groups, but also some new phenomena arise due to the topological non-triviality of the bundle $\GR \to B$. As an ap

Dimitry Leites, Pavel Grozman

We introduce and completely describe the analogues of the Riemann curvature tensor for the curved supergrassmannian of the passing through the origin (0|2)-dimensional subsupermanifolds in the (0|4)-dimensional supermanifold with the preserved volume form. The underlying manifold of this supergrassmannian is the conventional Penrose&#39;s complexified and co

V. E. R. Lemes, M. Picariello, M. S. Sarandy, S. P. Sorella

The supersymmetric version of the descent equations following from the Wess-Zumino consistency condition is discussed. A systematic framework in order to solve them is proposed.

I. Nandori, K. Sailer, U. D. Jentschura, G. Soff

The renormalization group (RG) flow for the two-dimensional sine-Gordon model is determined by means of Polchinski&#39;s RG equation at next-to-leading order in the derivative expansion. In this work we have two different goals, (i) to consider the renormalization scheme-dependence of Polchinski&#39;s method by matching Polchinski&#39;s equation with the Weg

S. J. Gates

We discuss the problem of introducing background spacetimes of the de Sitter type (quintessential backgrounds) in the context of fundamental theories involving supersymmetry. The role of a model presented in 1984, showing that these backgrounds can occur as spontaneously broken phases of locally supersymmetric 4D, N-extended theories, is highlighted. The pre

Matthias Blau, José Figueroa-O&#39;Farrill, George Papadopoulos

We investigate the Penrose limits of classical string and M-theory backgrounds. We prove that the number of (super)symmetries of a supergravity background never decreases in the limit. We classify all the possible Penrose limits of AdS x S spacetimes and of supergravity brane solutions. We also present the Penrose limits of various other solutions: intersect

Shinji Mukohyama

We review the doubly gauge invariant formalism of cosmological perturbations in the Randall-Sundrum brane world. This formalism leads to four independent equations describing the evolution of scalar perturbations. Three of these equations are differential equations written in terms of gauge invariant variables on the brane only, and the other is an integro-d

H. C. de Godoy Caldas

In this paper we use Modified Self-Consistent Resummation (MSCR) in order to obtain the scalar dressed mass by evaluating the self-energy up to two loops in the neutral scalar $λϕ^4$ model at finite temperature. With this laboratory model we show that, if a theory is renormalizable at zero temperature, using the MSCR it is always possible to obtain a finite

Mark I. Gorenstein

A recently developed statistical coalescence model of the J/psi production is presented. The NA50 data on the J/psi suppression pattern and the transverse mass spectra in Pb+Pb collisions at the SPS are analyzed. The model predictions for the RHIC energies are formulated. The measurements of J/psi in Au+Au collisions at RHIC are crucial for disentangling the

M. Baldicchi, G. M. Prosperi

The perturbative expression of the running strong coupling constant α_{\rm s}(Q^{2}) has an unphysical singularity for Q^{2} = Λ^{2}_{\rm QCD}. Various modification have been proposed for the infrared region. The effect of some of such proposals on the quark-antiquark spectrum is tested on a Bethe-Salpeter (second order) formalism which was successfully appl

Irina Mocioiu, Maxim Pospelov

CPT violation in the neutrino sector, suggested as a new way to reconcile different neutrino anomalies, induces at the radiative level observable effects among charged leptons, where high-precision tests of the CPT symmetry are available. We show that, in the models with heavy right-handed Majorana neutrinos, constraints imposed by these experiments require

V. Barger, D. Marfatia, B. P. Wood

We dispel the misconception that data from SN 1987A favor the normal neutrino mass hierarchy over the inverted hierarchy for $\sin^2 θ_{13} \gsim 10^{-4}$. We find comparable fits for the two hierarchies. No bound can be placed on the mixing angle $θ_{13}$ even at the 1$σ$ level.

R. J. Wiltshire

A general class of solutions of Einstein&#39;s equation for a slowly rotating fluid source, with supporting internal pressure, is matched using Lichnerowicz junction conditions, to the Kerr metric up to and including first order terms in angular speed parameter. It is shown that the match applies to any previously known non-rotating fluid source made to rota

J. Alberto Lobo

This chapter is concerned with the question: how do gravitational waves (GWs) interact with their detectors? It is intended to be a theory review of the fundamental concepts involved in interferometric and acoustic (Weber bar) GW antennas. In particular, the type of signal the GW deposits in the detector in each case will be assessed, as well as its intensit

Alex Verstak, Naren Ramakrishnan, Layne T. Watson, Jian He

We describe a binding schema markup language (BSML) for describing data interchange between scientific codes. Such a facility is an important constituent of scientific problem solving environments (PSEs). BSML is designed to integrate with a PSE or application composition system that views model specification and execution as a problem of managing semistruct

Shai Berger, Daniel Lehmann, Karl Schlechta

We give a semantics to iterated update by a preference relation on possible developments. An iterated update is a sequence of formulas, giving (incomplete) information about successive states of the world. A development is a sequence of models, describing a possible trajectory through time. We assume a principle of inertia and prefer those developments, whic

Daniel Lehmann, Menachem Magidor, Karl Schlechta

A vast and interesting family of natural semantics for belief revision is defined. Suppose one is given a distance d between any two models. One may then define the revision of a theory K by a formula a as the theory defined by the set of all those models of a that are closest, by d, to the set of models of K. This family is characterized by a set of rationa

Daniel Lehmann

It is shown that Darwiche and Pearl&#39;s postulates imply an interesting property, not noticed by the authors.

Daniel Lehmann, Menachem Magidor

This paper presents a logical approach to nonmonotonic reasoning based on the notion of a nonmonotonic consequence relation. A conditional knowledge base, consisting of a set of conditional assertions of the type &#34;if ... then ...&#34;, represents the explicit defeasible knowledge an agent has about the way the world generally behaves. We look for a plaus

Sarit Kraus, Daniel Lehmann, Menachem Magidor

Many systems that exhibit nonmonotonic behavior have been described and studied already in the literature. The general notion of nonmonotonic reasoning, though, has almost always been described only negatively, by the property it does not enjoy, i.e. monotonicity. We study here general patterns of nonmonotonic reasoning and try to isolate properties that cou

C. Ortiz-Estrada, G. Luna-Barcenas, G. Ramirez-Santiago, I. C. Sanchez

My means of extensive Monte Carlo simulations the mean radius of gyration and the end-to-end distance are calculated for a single chain in a solvent over a broad range of volume fractions, pressures and temperatures. Our results indicate that in general, the chain collapses as temperature increases at constant pressure, or as density decreases at constant te

Ryo Maezono, Naoto Nagaosa

Jahn-Teller (JT) effect both in the absence and presence of the strong Coulomb correlation is studied theoretically focusing on the reduction $ΔK$ of the kinetic energy gain which is directly related to the spin wave stiffness. Without the Coulomb interaction, the perturbative analysis gives $ΔK / (g^2/MΩ^2) \cong 0.05-0.13$ depending on the electron number

Vito Latora, Massimo Marchiori

The mathematical study of the small-world concept has fostered quite some interest, showing that small-world features can be identified for some abstract classes of networks. However, passing to real complex systems, as for instance transportation networks, shows a number of new problems that make current analysis impossible. In this paper we show how a more

Romualdo Pastor-Satorras, Alessandro Vespignani

Many real networks present a bounded scale-free behavior with a connectivity cut-off due to physical constraints or a finite network size. We study epidemic dynamics in bounded scale-free networks with soft and hard connectivity cut-offs. The finite size effects introduced by the cut-off induce an epidemic threshold that approaches zero at increasing sizes.

Chun-Chung Chen, Marcel den Nijs

We describe a directed avalanche model; a slowly unloading sandbox driven by lowering a retaining wall. The directness of the dynamics allows us to interpret the stable sand surfaces as world sheets of fluctuating interfaces in one lower dimension. In our specific case, the interface growth dynamics belongs to the Kardar-Parisi-Zhang (KPZ) universality class

Cecile Monthus, Pierre Le Doussal

We consider the Sinai model describing a particle diffusing in a 1D random force field. As shown by Golosov, this model exhibits a strong localization phenomenon for the thermal packet: the disorder average of the thermal distribution of the relative distance y=x-m(t), with respect to the (disorder-dependent) most probable position m(t), converges in the lim

Yoshihiro Nishiyama

An elastic string embedded between rigid walls is simulated by means of the density-matrix renormalization group. The string collides against the walls owing to the quantum-mechanical zero-point fluctuations. Such ``quantum entropic&#39;&#39; interaction has come under thorough theoretical investigation in the context of the stripe phase observed experimenta

Sergey V. Kuplevakhsky

We present an exact mathematical description of the Meissner effect and of the vortex state in periodic thin-layer superconductor/insulator structures with an arbitrary number of identical junctions N-1 (N is the number of superconducting layers) in the presence of a static parallel external field H. Based on an analytical analysis of the coupled static sine

Mikhail V. Ivanov, Peter Schmelcher

A finite-difference solution of the Schroedinger equation for negative donor centers D^- in two dimensions is presented. Our approach is of exact nature and allows us to resolve a discrepancy in the literature on the ground state of a negative donor. Detailed calculations of the energies for a number of states show that for field strengths less than γ=0.117

O. Entin-Wohlman, Amnon Aharony

Adiabatically pumped charge, carried by non-interacting electrons through a quantum dot in a turnstile geometry, is studied as function of the strength of the two modulating potentials (related to the conductances of the two point-contacts to the leads) and of the phase shift between them. It is shown that the magnitude and sign of the pumped charge are dete

V. Dikovsky, Y. Yuzhelevski, V. Markovich, G. Gorodetsky

Deterministic oscillations of current-induced metastable resistivity in changing voltage have been detected in La$_{0.82}$Ca$_{0.18}$MnO$_3$ single crystals. At low temperatures, below the Curie point, application of specific bias procedures switches the crystal into metastable resistivity state characterized by appearance of pronounced reproducible and rand

M. W. Bautz, J. S. Arabadjis, G. P. Garmire

Chandra observations of lensing galaxy clusters have now provided accurate dark matter profiles for several objects in which the intracluster medium is likely to be in hydrostatic equilibrium. We discuss Chandra observations of the mass profile of one such cluster, EMSS1358+6245. We find no evidence for flattening of the mass density profile at radii greater

Amir Sagiv, Eli Waxman

We consider the effects of collective plasma processes on synchrotron emission from highly relativistic electrons. We find, in agreement with Sazonov (1970), that strong effects are possible also in the absence of a non-relativistic plasma component, due to the relativistic electrons (and protons) themselves. In contrast with Sazonov, who infers strong effec

Smita Mathur

Observations of warm absorbers provided new ways to study the nuclear environments of AGNs. I discuss basic properties of warm absorbers and early developments with ROSAT, ASCA and HST observations. I briefly touch upon recent advances made with Chandra and FUSE.