November 2004 arXiv papers — page 6

Bertrand Deroin

We show that for every $ε>0$, there exists a compact lamination by $ε$-holomorphic surfaces in the complex projective plane, minimal, and that carries hyperbolic holonomy. We call $ε$-holomorphic a real 2-dimensional surface $Σ$ in ${\bf C}P^2$ such that the angle between $TΣ$ and $iTΣ$ is uniformly bounded by $ε$. When $ε$ is sufficiently small, such surfac

Joel Merker

Let M be a smooth generic submanifold of C^n. Tumanov showed that the direction of CR extendability parallel propagates with respect to a certain differential geometric partial connection in a quotient bundle of the normal bundle to M. M is said to be globally minimal at a point z in M if the CR orbit of z contains a neighborhood of z in M. It is shown that

Luca M. Martinazzi

We study the problem of finding a minimal graph with prescribed boundary data in arbitrary dimension and codimension. Existence, uniqueness, stability and regularity are treated. We first present the well-known results for codimension one: Jenkins-Serrin's existence theorem, convexity properties of the area which give uniqueness and stability and De Gior

Keqin Liu

We introduce the notions of one-sided dirings, 3-irreducible left modules, 3-primitive left dirings, 3-semi-primitive left dirings, 3-primitive ideals and 3-radicals. The main results consists of two parts. The first part establishes two external characterizations of a 3-semi-primitive left diring. The second part characterizes the 3-radical of a left diring

Gabor Simonyi, Gabor Tardos

The local chromatic number of a graph was introduced by Erdos et al. in 1986. It is in between the chromatic and fractional chromatic numbers. This motivates the study of the local chromatic number of graphs for which these quantities are far apart. Such graphs include Kneser graphs, their vertex color-critical subgraphs, the Schrijver (or stable Kneser) gra

Luis Dieulefait, Mladen Dimitrov

In a previous article, the second author proved that the image of the Galois representation mod $λ$ attached to a Hilbert modular newform is large or all but finitely many primes $λ$, if the form is not a theta series. In this brief note, we give an explicit bound for this exceptional finite set of primes and determine the images in three different examples.

Hellmut Baumgärtel, Fernando Lledó

In the present paper we prove a duality theory for compact groups in the case when the C*-algebra A, the fixed point algebra of the corresponding Hilbert C*-system (F,G), has a nontrivial center Z and the relative commutant satisfies the minimality condition A.'\cap F = Z as well as a technical condition called regularity. The abstract characterization o

Charles Livingston

This is survey about the classical knot concordance group, prepared for an upcoming handbook of knot theory. Topics include: the basic definitions of concordance; the theory of algebraic concordance as developed by Levine; the theory of Casson-Gordon invariants; applications of topological surgery as developed by Freedman; smooth results based on differentia

J. F. Morales, H. Samtleben

We derive the spectrum of gauge invariant operators for maximally supersymmetric Yang-Mills theories in d dimensions. After subtracting the tower of BPS multiplets, states are shown to fall into long multiplets of a hidden SO(10,2) symmetry dressed by thirty-two supercharges. Their primaries organize into a universal, i.e. d-independent pattern. The results

M R Setare

The Casimir forces on two parallel plates moving by uniform proper acceleration in static de Sitter background due to conformally coupled massless scalar field satisfying Dirichlet boundary conditions on the plates is investigated. Static de Sitter space is conformally related to the Rindler space, as a result we can obtain vacuum expectation values of energ

Heng Fan, Bo-Yu Hou, Kang-Jie Shi, Rui-Hong Yue

In this paper, we give the general forms of the minimal $L$ matrix (the elements of the $L$-matrix are $c$ numbers) associated with the Boltzmann weights of the $A_{n-1}^1$ interaction-round-a-face (IRF) model and the minimal representation of the $A_{n-1}$ series elliptic quantum group given by Felder and Varchenko. The explicit dependence of elements of $L

V. A. Yerokhin, P. Indelicato, V. M. Shabaev

The two-loop self-energy correction is evaluated to all orders in Zαfor the ground-state Lamb shift of H-like ions with Z >= 10, where Z is the nuclear charge number and αis the fine structure constant. The results obtained are compared with the analytical values for the Zα-expansion coefficients. An extrapolation of the all-order numerical results to Z=1 is

C. S. Fischer, R. Alkofer

We summarise results for the propagators of Landau gauge QCD from the Green's functions approach and lattice calculations. The nonperturbative solutions for the ghost, gluon and quark propagators from a coupled set of Dyson-Schwinger equations agree almost quantitatively with corresponding lattice results. Similar unquenching effects are found in both ap

S. F. King

In this talk we show how a natural neutrino mass hierarchy can follow from the type I see-saw mechanism, and a natural neutrino mass degeneracy from the type II see-saw mechanism, where the bi-large mixing angles can arise from either the neutrino or charged lepton sector. We summarize the phenomenological implications of such natural models, and discuss the

Néstor Armesto, Carlos A. Salgado, Urs Achim Wiedemann

Data on low-pT hadronic spectra are widely regarded as evidence of a hydrodynamic expansion in nucleus-nucleus collisions. In this interpretation, different hadron species emerge from a common medium that has built up a strong collective velocity field. Here, we show that the existence of a collective flow field implies characteristic modifications of high-p

Hai-Yang Cheng

Final-state rescattering effects on the hadronic B decays and their impact on direct CP violation are examined. The phenomenology of the polarization anomaly in $B\toϕK^*$ decays is discussed.

Th. Lasserre

It is now widely accepted that a new middle baseline disappearance reactor neutrino experiment with multiple detectors could provide a clean measurement of the $θ_{13}$ mixing angle, free from any parameter degeneracies and correlations induced by matter effect and the unknown leptonic Dirac CP phase. The current best constraint on the third mixing angle com

F. Ambrosino

The phi-meson leptonic widths, Gee and Gmm, are obtained, respectively, from the e+e- forward-backward asymmetry and the muon cross section around the phi-mass energy. We find Gee=1.32⊕0.05⊕0.03 kev and sqrt(GeeGmm)= 1.320⊕0.018⊕0.017 kev. These results, compatible with Gee=Gmm, provide a precise test of lepton universality. Combining

Stefan E. Müller

The KLOE experiment at the Frascati $ϕ$-factory DA$Φ$NE has collected about 0.5 fb$^{-1}$ of data till the end of the year 2002. These data allow to perform a wide physics program, ranging from the physics of charged and neutral kaons to radiative $ϕ$-decays. Results are presented for the $K_L$ lifetime and the semileptonic processes $K_{S,L} \to πe ν$. From

Andre Schoning

Results of a general search for new phenomena at high transverse momentum and of a dedicated search for events with isolated leptons and missing transverse momentum are reported. These searches were performed on a data sample collected at HERA in e+-p collisions with the H1 detector in the period 1994-2004. The results obtained in the isolated lepton search

Joachim Moortgat, Jan Kuijpers

Gravitational waves (GWs) propagating through a uniformly magnetized plasma interact directly with the magnetic field and excite magnetohydrodynamic (MHD) waves with both electromagnetic and matter components. We study this process for arbitrary geometry in the MHD approximation and find that all three fundamental MHD modes -- slow and fast magnetosonic, and

D. J. Mulryne, N. J. Nunes, R. Tavakol, J. E. Lidsey

We study oscillatory universes within the context of Loop Quantum Cosmology. We make a comparative study of flat and positively curved universes sourced by scalar fields with either positive or negative potentials. We investigate how oscillating universes can set the initial conditions for successful slow-roll inflation, while ensuring that the semi-classica

James E. Lidsey

Within the framework of loop quantum cosmology, there exists a semi-classical regime where spacetime may be approximated in terms of a continuous manifold, but where the standard Friedmann equations of classical Einstein gravity receive non-perturbative quantum corrections. An approximate, analytical approach to studying cosmic dynamics in this regime is dev

D. Grumiller, D. Mayerhofer

Within the first order formalism static solutions of generic dilaton gravity in 2D with self-interacting (scalar) matter can be discussed with ease. The question of (non)existence of Killing horizons is addressed and the interplay with asymptotic conditions is investigated. Naturally, such an analysis has to be a global one. A central element in the discussi

J. P. Mbelek

Recently A. Rathke has argued that the KK$ψ$ model explanation of the discrepant measurements of Newton's constant is already ruled out due to Eötvös experiments by several orders of magnitude. The structure of the action of the KK$ψ$ model is even qualified as inconsistent in the sense that it would yield a negative energy of the electromagnetic field.

Christian Lavault

Owing to its nice properties, the pancake is one of the Cayley graphs that were proposed as alternatives to the hypercube for interconnecting processors in parallel computers. In this paper, we present embeddings of rings, grids and hypercubes into the pancake with constant dilation and congestion. We also extend the results to similar efficient embeddings i

Stefano Giovanazzi, Duncan H J O'Dell

We point out the possibility of having a roton-type excitation spectrum in a quasi-1D Bose-Einstein condensate with dipole-dipole interactions. Normally such a system is quite unstable due to the attractive portion of the dipolar interaction. However, by reversing the sign of the dipolar interaction using either a rotating magnetic field or a laser with circ

F. Larouche, J. Duquette, L. Cortelezzi, N. Nigam

A complete explanation of the synthesis of metal-catalyst nanoparticles, and the subsequent nucleation and growth of bundles of C-SWNTs is introduced using a novel model. It is shown that the synthesis process leads to the formation of a liquid layer supersaturated in carbon surrounding each metallic-catalyst nanoparticle. The onset of a solutal Bénard-Maran

R. Khasanov, D. G. Eshchenko, D. Di Castro, A. Shengelaya

Measurements of the magnetic field penetration depth λin the pyrochlore superconductor RbOs_2O_6 (T_c\simeq6.3 K) were carried out by means of the muon-spin-rotation (\muSR) technique. At low temperatures λ^{-2}(T) saturates and becomes constant below T\simeq 0.2T_c, in agreement with what is expected for weak-coupled s-wave BCS superconductors. The value of

J. Richter, J. Schulenburg, P. Tomczak, D. Schmalfuß

We discuss the ground state and the low-lying excitations of the spin-half Heisenberg antiferromagnet on the two-dimensional square-kagome lattice. This magnetic system belongs to the class of highly frustrated spin systems with an infinite non-trivial degeneracy of the classical ground state as it is known also for the Heisenberg antiferromagnet on the kago

Alexander Dmitriev, Michel Dyakonov, Remi Jullien

The classical correction to the velocity auto-correlation function of non-interacting particles due to memory effects, which are beyond the Boltzmann equation, is calculated both analytically and numerically for the case of isotropic scattering in two dimensions.

L. M. Fisher, A. V. Kalinov, I. F. Voloshin, N. A. Babushkina

Magnetic field induced step-like changes in magnetization and resistivity of SmSr manganites were studied. A strong dependence of these features on the cooling rate was observed. Magnetostriction, however, does not show the presence of large strain in our samples. From all these features we can rule out the conventional explanation of magnetization jumps as

J. -F. Berret, K. Yokota, M. Morvan

When polyelectrolyte-neutral block copolymers are mixed in solutions to oppositely charged species (e.g. surfactant micelles, macromolecules, proteins etc), there is the formation of stable supermicellar aggregates combining both components. The resulting colloidal complexes exhibit a core-shell structure and the mechanism yielding to their formation is elec

K. Yokota, M. Morvan, J. -F. Berret, J. Oberdisse

We report on the structural properties of mixed aggregates made from rare-earth inorganic nanoparticles (radius 20 Angstroms) and polyelectrolyte-neutral block copolymers in aqueous solutions. Using scattering experiments and Monte Carlo simulations, we show that these mixed aggregates have a hierarchical core-shell microstructure. The core is made of densel

Jens Kortus, Oleg V. Dolgov, Reinhard K. Kremer, Alexander A. Golubov

We argue, based on band structure calculations and Eliashberg theory, that the observed decrease of $T_c$ of Al and C doped MgB$_2$ samples can be understood mainly in terms of a band filling effect due to the electron doping by Al and C. A simple scaling of the electron-phonon coupling constant $λ$ by the variation of the density of states as function of el

A. Kunwar, A. John, K. Nishinari, A. Schadschneider

The traffic-like collective movement of ants on a trail can be described by a stochastic cellular automaton model. We have earlier investigated its unusual flow-density relation by using various mean field approximations and computer simulations. In this paper, we study the model following an alternative approach based on the analogy with the zero range proc

Mahn-Soo Choi, Rosa Lopez, Ramon Aguado

We investigate theoretically the non-equilibrium transport properties of carbon nanotube quantum dots. Owing to the two-dimensional band structure of graphene, a double orbital degeneracy plays the role of a pseudo-spin, which is entangled with the spin. Quantum fluctuations between these four degrees of freedom result in an SU(4) Kondo effect at low tempera

Baosheng Yuan, Bing-Hong Wang, Kan Chen

We investigate the dynamics of network minority games on Kauffman's NK networks (Kauffman nets), growing directed networks (GDNets), as well as growing directed networks with a small fraction of link reversals (GDRNets). We show that the dynamics and the associated phase structure of the game depend crucially on the structure of the underlying network. T

Rotha P. Yu, David M. Paganin, Michael J. Morgan

We give a means for measuring the equation of evolution of a complex scalar field that is known to obey an otherwise unspecified (2+1)-dimensional dissipative nonlinear parabolic differential equation, given field moduli over three closely-spaced planes. The formalism is tested by recovering nonlinear interactions and the associated equation of motion from s

Kenneth G. Libbrecht

I review published data relating to the growth of ice crystals from water vapor under various conditions, and I critically examine the different measurements to determine what useful information can be extracted from each. I show that most, and possibly all, of the existing growth data have been seriously distorted by systematic errors of one form or another

H. Ez-Zahraouy

The effect of the random quantum transverse field $Ω$

D. Beckmann, H. B. Weber, H. v. Löhneysen

We have measured the non-local resistance of aluminum-iron spin-valve structures fabricated by e-beam lithography and shadow evaporation. The sample geometry consists of an aluminum bar with two or more ferromagnetic wires forming point contacts to the aluminum at varying distances from each other. In the normal state of aluminum, we observe a spin-valve sig

Egor Babaev

We show that in two-gap Ginzburg-Landau model there is a wide range of parameters where the behaviour of the superconductor in external field can not be classified nor as type-I nor as type-II. In this regime the superconductor features a nonmonotonic interaction between vortices (which is attractive at a certain large length scale and repulsive at a shorter

Ashish Asgekar, Jayanne English, Samar Safi-Harb, Roland Kothes

Worms are defined to be dusty, atomic hydrogen (HI) structures which are observed in low resolution data to rise perpendicular to the Galactic plane. Data from the 1'-resolution Canadian Galactic Plane Survey (CGPS) were systematically searched for narrow vertical HI structures which could be resolved worms. Another motivation for the search was to explo

M. Chu, H. K. Eriksen, L. Knox, K. M. Gorski

We study the Blackwell-Rao (BR) estimator of the probability distribution of the angular power spectrum, P(C_l|d), by applying it to samples of full-sky no-noise CMB maps generated via Gibbs sampling. We find the estimator, given a set of samples, to be very fast and also highly accurate, as determined by tests with simulated data. We also find that the numb

Patrick De Laverny, Djamel Mekarnia

From VLT/NACO diffraction-limited images of RY~Sgr, we report the first direct detection of heterogeneities in the circumstellar envelope of a R Coronae Borealis variable star. Several bright and very large dust clouds are seen in various directions at several hundred stellar radii from RY Sgr, revealing high activity for the ejection of stellar material by

S. Ferraz-Mello, T. A. Michtchenko, C. Beaugé

The published orbits of the planets HD 82943b and HD 82943c correspond to a system bound to a catastrophic event in less than 100,000 years. Alternative sets of elements and masses, which fit the available observational data and correspond to regular motions, are presented in this paper. The planets HD 82943 c,b are in a 2/1 mean-motion resonance and are tra

B. Rocca-Volmerange, M. Remazeilles

The spectra of the powerful 3CR radio galaxies present a typical distribution in the far-infrared. From the observed radio to X-ray spectral energy distribution (SED) templates, we propose to subtract the typical energy distributions of, respectively, the elliptical galaxy host and the synchrotron radiation. The resulting SED reveals that the main dust emiss

Carlos De Breuck, Dennis Downes, Roberto Neri, Wil van Breugel

We have detected CO(4-3) in the z=3.8 radio galaxy 4C 41.17 with the IRAM Interferometer. The CO is in two massive (M_dyn ~ 6 x 10^10 M_Sun) systems separated by 1.8" (13 kpc), and by 400 km/s in velocity, which coincide with two different dark lanes in a deep Ly-alpha image. One CO component coincides with the cm-radio core of the radio galaxy, and its

P. Shtykovskiy, A. Lutovinov, M. Gilfanov, R. Sunyaev

We obtain photometric constraints on the luminosity of the stellar remnant in SNR1987A using XMM-Newton and INTEGRAL data. The upper limit in the 2--10 keV band based on the XMM-Newton data is L<5*10^{34}erg/s. We note, however, that the optical depth of the envelope is still high in the XMM-Newton band, therefore, this upper limit does not constrain the tru

J. S. Bagla, T. Padmanabhan

In this review we discuss Cosmological N-Body codes with a special emphasis on Particle Mesh codes. We present the mathematical model for each component of N-Body codes. We compare alternative methods for computing each quantity by calculating errors for each of the components. We suggest an optimum set of components that can be combined reduce overall error

Francesca Matteucci, Antonio Pipino

We have studied the effects of an hypothetical initial generation containing very massive stars (M > 100 Msun, pair-creation SNe) on the chemical and photometric evolution of elliptical galaxies. To this purpose, we have computed the evolution of a typical elliptical galaxy with luminous mass of the order of 10^11 Msun and adopted chemical evolution models a

Brian D. Fields, Keith A. Olive, Elisabeth Vangioni-Flam

Big bang nucleosynthesis (BBN) and the cosmic baryon density from cosmic microwave background anisotropies together predict a primordial Li7 abundance a factor of 2--3 higher than that observed in galactic halo dwarf stars. A recent analysis of Li7 observations in halo stars, using significantly higher surface temperature for these stars, found a higher Li p

V. Minier, M. G. Burton, T. Hill, M. R. Pestalozzi

We present a multiwavelength study of five methanol maser sites which are not directly associated with a strong ($>100$ mJy) radio continuum source: G 31.28+0.06, G 59.78+0.06, G 173.49+2.42 (S231, S233IR), G 188.95+0.89 (S252, AFGL5180) and G 192.60-0.05 (S255IR). These radio-quiet methanol maser sites are often interpreted as precursors of ultra-compact \i

Philip A. Hughes

Evidence that the magnetic fields of extragalactic jets have a significant fraction of their energy in a random component is briefly summarized, and a detailed model of evolving, jet polarization structures is constructed, based on this picture. The evolving magnetic field structure of an oblique shock complex that forms in a relativistic jet simulation is e

G. Kovacs, G. Bakos, R. W. Noyes

We show that various systematics related to certain instrumental effects and data reduction anomalies in wide field variability surveys can be efficiently corrected by a Trend Filtering Algorithm (TFA) applied to the photometric time series produced by standard data pipelines. Statistical tests, performed on the database of the HATNet project, show that by t

P. M. Marrese, U. Munari, R. Sordo, S. Dallaporta

The orbit and physical parameters of the double-lined eclipsing binary V570 Per, discovered by the Hipparcos satellite, are derived with formal errors better than 1% using high resolution Echelle spectroscopy and B, V photoelectric photometry. Atmospheric analysis is performed on spectra at quadrature using synthetic spectroscopy that indicates a [Fe/H]=+0.0

A. C. Katsiyannis, D. R. Williams, F. Murtagh, R. T. J. McAteer

SECIS observations of the June 2001 total solar eclipse were taken using an Fe {\sc xiv} 5303 Å filter. Automated tools based on wavelet analysis was used to detect intensity oscillations on various areas of the images. Statistical analysis of the detections found in the areas covered by the moon and the upper corona allowed us to estimate the atmospheric an

J. A. Stevens, M. Amure, W. K. Gear

We present and analyse high-quality SCUBA 850- and 450-um images of 14 local spiral galaxies, including the detection of dust well out into the extended disk in many cases. We use these data in conjunction with published far-IR flux densities from IRAS and ISO, and millimetre-wave measurements from ground-based facilities to deduce the global properties of t

Federica Govoni, Matteo Murgia, Luigina Feretti, Gabriele Giovannini

A deep radio observation of the A2255 cluster of galaxies has been carried out at 1.4 GHz with the Very Large Array synthesis telescope. Thanks to the excellent (u,v) coverage and sensitivity achieved by our observation, the low brightness diffuse extended sources in the cluster (radio halo and relic) have been imaged with unprecedented resolution and dynami

M. Kunert-Bajraszewska, A. Marecki, R. E. Spencer

We present VLBA 1.6, 5, 8.4 and 15 GHz observations of a new sample of weak, young, compact candidates for radio faders selected from the VLA FIRST survey. We claim that some, or even the majority of young sources, may be short-lived phenomena due to a lack of stable fuelling from the black hole and fade before evolving to large extended objects.

Marek A. Abramowicz

The familiar Newtonian version of the Rayleigh criterion demands that for dynamical stability the specific angular momentum should increase with the increasing circumferential radius of circular trajectories of matter. However, sufficiently close to a black hole the Rayleigh criterion reverses: in stable fluids, the angular momentum must decrease with the in

M. V. van der Sluys, F. Verbunt, O. R. Pols

A binary in which a slightly evolved star starts mass transfer to a neutron star can evolve towards ultra-short orbital periods under the influence of magnetic braking. This is called magnetic capture. We investigate in detail for which initial orbital periods and initial donor masses binaries evolve to periods less than 30-40 minutes within the Hubble time.

Rolf Nahnhauer

Several experimental techniques are currently under development, to measure the expected tiny fluxes of highest energy neutrinos above 10**18 eV. Projects in different stages of realisation are discussed here, which are based on optical and radio as well as acoustic detectors. For the detection of neutrino events in this energy range a combination of differe

Gerry Gilmore, Rosemary F. G. Wyse

Stellar chemical element ratios have well-defined systematic trends as a function of abundance, with an excellent correlation of these trends with stellar populations defined kinematically. This is remarkable, and has significant implications for Galactic evolution. The source function, the stellar Initial Mass Function, must be nearly invariant with time, p

T. Kuwabara, K. Shibata, T. Kudoh, R. Matsumoto

We analyzed the results of non-linear resistive magnetohydrodynamical (MHD) simulations of jet formation to study the acceleration mechanism of axisymmetric, resistive MHD jets. The initial state is a constant angular momentum, polytropic torus threaded by weak uniform vertical magnetic fields. The time evolution of the torus is simulated by applying the CIP

Zhen-Yu Wu, Xu Zhou, Jun Ma, Zhao-Ji Jiang

This paper presents 13 color CCD intermediate-band spectrophotometry of a field centered on the open cluster M48 (NGC 2548), from 400nm to nearly 1000nm, taken with Beijing-Arizona-Taiwan-Connecticut (BATC) Multi-Color Survey Photometric system. The fundamental parameters of this cluster are derived with a new method which based on the comparison between the

M. A. Abramowicz, W. Kluzniak

We present and discuss a short and simple derivation of orbital epicyclic frequencies for circular geodesic orbits in stationary and axially symmetric spacetimes. Such spacetimes include as special cases analytically known black hole Kerr and Schwarzschild spacetimes, as well as the analytic Hartle-Thorne spacetime and all numerically constructed spacetimes

M. J. Pereira, J. R. Kuhn

We report the discovery of a statistically significant radial alignment of cluster galaxies in a sample of 85 X-ray selected clusters observed in the Sloan Digital Sky Survey. The tendency for alignment is a robust feature of our sample and does not vary significantly with individual cluster or galaxy properties. We use dynamical arguments to show that a sig

Sung-Sik Lee, Xiao-Gang Wen

We consider the D2-brane probe action in the gravity background dual to N coincident Dp-branes by treating the separation between the D2- and Dp-branes as a nondynamical parameter for $p=2,4,6$. The gauge coupling, the core size of a non-BPS instanton and the mass gap of the compact U(1) gauge theory in the D2-brane are determined as a function of the separa

Zuo-Tang Liang, Xin-Nian Wang

We discuss the consequence of global polarization of the produced quarks in non-central heavy-ion collisions on the spin alignment of vector mesons. We show that the alignment is quite different for different hadronization scenarios. These results can be tested directly by measuring the vector mesons&#39; alignment through angular distributions of the decay

D. Arinkin, A. Borodin

We show that difference Painleve equations can be interpreted as isomorphisms of moduli spaces of d-connections on the projective line with given singularity structure. We also derive a new difference equation. It is the most general difference Painleve equation known so far, and it degenerates to both difference Painleve V and classical (differential) Painl

Jesús Casado-Pascual, José Gómez-Ordóñez, M. Morillo

A Markovian dichotomic system driven by a deterministic time-periodic force is analyzed in terms of the statistical properties of the switching events between the states. The consideration of the counting process of the switching events leads us to define a discrete phase. We obtain expressions for the instantaneous output frequency and phase diffusion assoc

Henrique Boschi-Filho, Nelson R. F. Braga

Inspired in the AdS/CFT correspondence one can look for dualities between string theory and non conformal field theories. Exact dualities in the non conformal case are intricate but approximations can be helpful in extracting physical results. A phenomenological approach consists in introducing a scale corresponding to the maximum value of the axial AdS coor

Kay Joerg Wiese

In this article, we study an elastic manifold in quenched disorder in the limit of zero temperature. Naively it is equivalent to a free theory with elasticity in Fourier-space proportional to k^4 instead of k^2, i.e. a model without disorder in two space-dimensions less. This phenomenon, called dimensional reduction, is most elegantly obtained using supersym

V. Chari, D. Jakelic, A. Moura

In this paper we describe a theory of (branched) crystals which is adapted to the study of representations in the BGG category $\cal O$ and which generalizes the theory of normal crystals of Kashiwara. In the case of $sl_2$ we show that one can associate (uniquely up to isomorphism) to every module in $\cal O$ a branched crystal . We show that the indecompos

Fergus Simpson, Sarah Bridle

One of the principal goals of modern cosmology is to constrain the properties of dark energy. At present, numerous surveys are aiming to determine the equation of state, which is assumed constant due to our poor understanding of its behaviour (and since higher order parameterisations lead to unwieldy errors). This raises the question - how does our &#34;best

O. Tsyplyatyev, Vladimir I. Fal&#39;ko

We propose a kinetic theory of transport in metals embedded with ferromagnetic nanoclusters, describing the dependence of the form of magnetoresistance on anisotropy characteristics of the ensemble of clusters and the influence of the electron spin depolarisation by clusters. We note that this effect is strongest when all the clusters have the same intrinsic

Leandro P. R. Pimentel

An Euclidean first-passage percolation (FPP) model describing the competing growth between $k$ different types of infection is considered. We focus on the long time behavior of this multi-type growth process and we derive multi-type shape results related to its morphology.

F. Colomo, A. G. Pronko

The six-vertex model with Domain Wall Boundary Conditions, or square ice, is considered for particular values of its parameters, corresponding to 1-, 2-, and 3-enumerations of Alternating Sign Matrices (ASMs). Using Hankel determinant representations for the partition function and the boundary correlator of homogeneous square ice, it is shown how the ordinar

Karim A. Malik, David Wands

We develop a gauge-invariant formalism for the study of density perturbations in a Friedmann-Robertson-Walker universe with multiple interacting fluids and/or scalar fields. We show how N scalar fields may be described by N kinetic fluids (with maximally stiff equation of state) interacting with a non-dynamical potential (with vacuum equation of state). We s

M. P. Almeida, S. P. Walborn, P. H. Souto Ribeiro

We investigate the utility of Einstein-Podolsky-Rosen correlations of the position and momentum of photon pairs from parametric down-conversion in the implementation of a secure quantum key distribution protocol. We show that security is guaranteed by the entanglement between downconverted pairs, and can be checked by either direct comparison of Alice and Bo

R. Peschanski, C. Royon, L. Schoeffel

We propose a phenomenological study of the Balitsky-Fadin-Kuraev-Lipatov (BFKL) approach applied to the data on the proton structure function F_2 measured at HERA in the small-x_{Bjorken} region. In a first part we use a simplified ``effective kernel&#39;&#39; approximation leading to few-parameter fits of F_2. It allows for a comparison between leading-logs

Fabio Giovi, Carlo Baccigalupi, Francesca Perrotta

We consider the distribution of the non-Gaussian signal induced by weak lensing on the primary total intensity cosmic microwave background (CMB) anisotropies. Our study focuses on the three point statistics exploiting an harmonic analysis based on the CMB bispectrum. By considering the three multipoles as independent variables, we reveal a complex structure

Florent Balacheff

We study some new isoperimetric inequalities on graphs. We etablish a relation between the volume entropy (or asymptotic volume), the systole and the first Betti number of weighted graphs. We also find bounds for the volume, associated to some special measure, of the unit ball for the stable norm of graphs.

S. E. Konstein, I. V. Tyutin

Cohomology spaces of the Poisson superalgebra realized on smooth Grassmann-valued functions with compact support on R^2 are investigated under suitable continuity restrictions on cochains. The zeroth, first, and second cohomology spaces in the adjoint representation of the Poisson superalgebra are found for the case of a nondegenerate constant Poisson superb

Frederic Bourgeois, Vincent Colin

We show that contact homology distinguishes infinitely many tight contact structures on any orientable, toroidal, irreducible 3-manifold. As a consequence of the contact homology computations, on a very large class of toroidal manifolds, all known examples of universally tight contact structures with nonvanishing torsion satisfy the Weinstein conjecture. ---

José C. M. Mombach, Damien Robert, François Graner, Germain Gillet

The influence of surface tension and size on rounding of cell aggregates are studied using chick embryonic cells and numerical simulations based on the cellular Potts model. Our results show exponential relaxation in both cases as verified in previous studies using 2D Hydra cell aggregates. The relaxation time decreases with higher surface tension as expecte

Anatole Castella

By underlying the commutation relation in a right-angled Coxeter group W, we recover the fact that right-angled Coxeter groups are rigid and we describe the second subgroup of Aut(W) that appears in the decomposition of Aut(W) into a semi-direct product established by J. Tits in &#34;Sur le groupe des automorphismes de certains groupes de Coxeter&#34; (Journ

A. Damiano, I. Sabadini, D. C. Struppa

This paper presents some algorithmic techniques to compute explicitly the noetherian operators associated to a class of ideals and modules over a polynomial ring. The procedures we include in this work can be easily encoded in computer algebra packages such as CoCoA and Singular.

S. Mereghetti, D. Gotz, I. F. Mirabel, K. Hurley

We report the discovery of persistent hard X-ray emission extending up to 150 keV from the soft gamma-ray repeater SGR 1806-20 using data obtained with the INTEGRAL satellite in 2003-2004. Previous observations of hard X-rays from objects of this class were limited to short duration bursts and rare transient episodes of strongly enhanced luminosity (``flares

Nobuyoshi Ohta

We review the recent developments in obtaining accelerating cosmologies and/or inflation from higher-dimensional gravitational theories, in particular superstring theories in ten dimensions and M-theory in eleven dimensions. We first discuss why it is difficult to obtain inflationary behavior in the effective low-energy theories of superstring/M-theory, i. e

E. B. Sonin

The Letter considers the ground state and the Tkachenko modes for a rapidly rotating Bose-Einstein condensate (BEC), when its macroscopic wave function is a coherent superposition of states analogous to the lowest Landau levels of a charge in a magnetic field. As well as in type II superconductors close to the critical magnetic field $H_{c2}$, this correspon

Mihai Tibar

We study the vanishing neighbourhood of non-isolated singularities of functions on singular spaces by associating a general linear function. We use the carrousel monodromy in order to show how to get a better control over the attaching of thimbles. For one dimensional singularities, we prove obstructions to integer (co)homology groups and to the eigenspaces

J. Klacka, P. Pastor

Spherical meteoroids orbiting the Sun experience orbital decay due to the Poynting-Robertson effect and can become trapped in commensurability resonances with a planet. Detail conditions for trapping in the planar circular restricted three-body problem with action of solar electromagnetic radiation on spherical grain are presented. The results are given in t

Gunnar Floystad

For a simplicial complex X on {1,2, ..., n} we define enriched homology and cohomology modules. They are graded modules over k[x_1, ..., x_n] whose ranks are equal to the dimensions of the reduced homology and cohomology groups. We characterize Cohen-Macaulay, l-Cohen-Macaulay, Buchsbaum, and Gorenstein* complexes X, and also orientable manifolds in terms of

J. R. Pelaez, F. J. Yndurain

We obtain reliable $ππ$ scattering amplitudes consistent with experimental data, both at low and high energies, and fulfilling appropriate analyticity properties. We do this by first fitting experimental low energy ($s^{1/2}\leq1.42 {\rm GeV}$) phase shifts and inelasticities with expressions that incorporate analyticity and unitarity. In particular, for the

Benjamin Dollet, Miguel Aubouy, Francois Graner

To understand the mechanics of a complex fluid such as a foam we propose a model experiment (a bidimensional flow around an obstacle) for which an external sollicitation is applied, and a local response is measured, simultaneously. We observe that an asymmetric obstacle (cambered airfoil profile) experiences a downards lift, opposite to the lift usually know

M. Leclerc

We will address the question of the consistency of teleparallel theories in presence of spinning matter which has been a controversial subject of discussion over the last twenty years. We argue that the origin of the problem is not simply the symmetry or asymmetry of the stress-energy tensor of the matter fields, which has been recently analyzed by several a

Enrico Rubiola

A frequency counter measures the input frequency $\barν$ averaged over a suitable time $τ$, versus the reference clock. High resolution is achieved by interpolating the clock signal. Further increased resolution is obtained by averaging multiple frequency measurements highly overlapped. In the presence of additive white noise or white phase noise, the square