June 2005 arXiv papers — page 5

Ben W. Reichardt, Lov K. Grover

Composite pulses are a quantum control technique for canceling out systematic control errors. We present a new composite pulse sequence inspired by quantum search. Our technique can correct a wider variety of systematic errors -- including, for example, nonlinear over-rotational errors -- than previous techniques. Concatenation of the pulse sequence can redu

Joerg B Goette, Sonja Franke-Arnold, Stephen M. Barnett

The violation of local uncertainty relations is a valuable tool for detecting entanglement, especially in multi-dimensional systems. The orbital angular momentum of light provides such a multi-dimensional system. We study quantum correlations for the conjugate variables of orbital angular momentum and angular position. We determine an experimentally testable

Sergei G. Matinyan, Berndt Müller

We continue our study of the quantum mechanical motion in the $x^2y^2$ potentials for $n=2,3$, which arise in the spatially homogeneous limit of the Yang-Mills (YM) equations. In the present paper, we develop a new approach to the calculation of the partition function $Z(t)$ beyond the Thomas-Fermi (TF) approximation by adding a harmonic (Higgs) potential an

M. Trupke, E. A. Hinds, S. Eriksson, E. A. Curtis

We present a novel microfabricated optical cavity, which combines a very small mode volume with high finesse. In contrast to other micro-resonators, such as microspheres, the structure we have built gives atoms and molecules direct access to the high-intensity part of the field mode, enabling them to interact strongly with photons in the cavity for the purpo

J. J. Longdell, E. Fraval, M. J. Sellars, N. B. Manson

We report on the demonstration of light storage for times greater than a second in praseodymium doped Y$_2$SiO$_5$ using electromagnetically induced transparency. The long storage times were enabled by the long coherence times possible for the hyperfine transitions in this material. The use of a solid state system also enabled operation with the probe and co

Geoffrey Hunter, Marian Kowalski, Camil Alexandrescu

The photon is modeled as a monochromatic solution of Maxwell's equations confined as a soliton wave by the principle of causality of special relativity. The soliton travels rectilinearly at the speed of light. The solution can represent any of the known polarization (spin) states of the photon. For circularly polarized states the soliton's envelope i

M. Kleinmann, H. Kampermann, D. Bruss

We investigate the unambiguous comparison of quantum states in a scenario that is more general than the one that was originally suggested by Barnett et al. First, we find the optimal solution for the comparison of two states taken from a set of two pure states with arbitrary a priori probabilities. We show that the optimal coherent measurement is always supe

J. C. Flores

We introduce a symbolic representation like set theory to consider ecologic interactions between species (ECOSET). The ecologic exclusion principle (Gause) is put in a symbolic way and used as operational tool to consider more complex cases like interaction with sterile species (SIT technique), two species with two superposed sources (niche differentiation)

O. Helene, M. T. Yamashita

A simple model based on the maximum energy that an athlete can produce in a small time interval is used to describe the high and long jump. Conservation of angular momentum is used to explain why an athlete should run horizontally to perform a vertical jump. Our results agree with world records.

Chuan-Yang Yin, Bing-Hong Wang, Wen-Xu Wang, Tao Zhou

In this letter, we propose a new routing strategy with a single free parameter $α$ only based on local information of network topology. In order to maximize the packets handling capacity of underlying structure that can be measured by the critical point of continuous phase transition from free flow to congestion, the optimal value of $α$ is sought out. By in

Germain Rousseaux

"Physical theories of fundamental significance tend to be gauge theories. These are theories in which the physical system being dealt with is described by more variables than there are physically independent degree of freedom. The physically meaningful degrees of freedom then reemerge as being those invariant under a transformation connecting the variabl

ALICE TRD Collaboration

We study the electron/pion identification performance of the ALICE Transition Radiation Detector (TRD) prototypes using a neural network (NN) algorithm. Measurements were carried out for particle momenta from 2 to 6 GeV/c. An improvement in pion rejection by about a factor of 3 is obtained with NN compared to standard likelihood methods.

Peter Chudinov

A classic problem of the motion of a point mass (projectile) thrown at an angle to the horizon is reviewed. The air drag force is taken into account with the drag factor assumed to be constant. Analytic approach is used for investigation. The problem of finding an optimal angle of launching a point mass in a medium with quadratic drag force is considered. An

Jose M. Diazdelacruz

Speckle photography can be used to monitor deformations of solid surfaces. The measuring characteristics, such as range or lateral resolution depend heavily on the optical recording and illumination set-up. This paper shows how, by the addition of two suitably perforated masks, the optical aperture of the system may vary from point to point, accordingly adap

A. Lezama, A. M. Akulshin, A. I. Sidorov, P. Hannaford

We present experimental evidence that light storage, i.e. the controlled release of a light pulse by an atomic sample dependent on the past presence of a writing pulse, is not restricted to small group velocity media but can also occur in a negative group velocity medium. A simple physical picture applicable to both cases and previous light storage experimen

James Finley

Using an approach based on many body perturbation theory, the correlation energy $\cEco$ is expressed as an explicit functional of $ρ_1$, $v$, and $v_s$, where $ρ_1$ is the one-particle density matrix from the noninteracting, or reference, determinantal-state; $v$ is the external potential from the interacting, or target, state; $v_s$ is the (kernel of the)

Natalya A. Zimbovskaya

It is shown that at low temperatures and moderate electron dephasing the electron transmission function reveales a structure containing information about donor/acceptor sites effectively participating in the electron transfer (ET) processes and primary pathways of electrons tunneling through molecular bridges in macromolecules. This important information can

F. Sammarruca, P. Krastev

We calculate nucleon-nucleon cross sections in the nuclear medium with unequal densities of protons and neutrons. We use the Dirac-Brueckner-Hartree-Fock approach together with realistic nucleon-nucleon potentials. We examine the effect of neutron/proton asymmetry and find that, although generally mild, it can be significant in specific regions of the phase

Matthias Brack

A short survey of the semiclassical periodic orbit theory, initiated by M. Gutzwiller and generalized by many other authors, is given. Via so-called semiclassical trace formmulae, gross-shell effects in bound fermion systems can be interpreted in terms of a few periodic orbits of the corresponding classical systems. In integrable systems, these are usually t

V. Baran, M. Colonna, M. Di Toro, M. Zielinska-Pfabe

In this paper we investigate isospin transport mechanisms in semi-peripheral collisions at Fermi energies. The effects of the formation of a low density region (neck) between the two reaction partners and of pre-equilibrium emission on the dynamics of isospin equilibration are carefully analyzed. We clearly identify two main contributions to the isospin tran

B. Cessac, J. A. Sepulchre

We discuss the ability of a network with non linear relays and chaotic dynamics to transmit signals, on the basis of a linear response theory developed by Ruelle \cite{Ruelle} for dissipative systems. We show in particular how the dynamics interfere with the graph topology to produce an effective transmission network, whose topology depends on the signal, an

Tooru Taniguchi, Gary P. Morriss

The dynamics of the localized region of the Lyapunov vector for the largest Lyapunov exponent is discussed in quasi-one-dimensional hard-disk systems at low density. We introduce a hopping rate to quantitatively describe the movement of the localized region of this Lyapunov vector, and show that it is a decreasing function of hopping distance, implying spati

E. Ahmed, A. S. Elgazzar, A. S. Hegazi

Almost every biological, economic and social system is a complex adaptive system (CAS). Mathematical and computer models are relevant to CAS. Some approaches to modeling CAS are given. Applications in vaccination and the immune system are studied. Mathematical topics motivated by CAS are discussed.

Victor S. L'vov, Anna Pomyalov, Itamar Procaccia, Sergej S. Zilitinkevich

We construct a simple analytic model for wall-bounded turbulence, containing only four adjustable parameters. Two of these parameters characterize the viscous dissipation of the components of the Reynolds stress-tensor and other two parameters characterize their nonlinear relaxation. The model offers an analytic description of the profiles of the mean veloci

Antonio Castaneda, Vladislav V. Kravchenko

In the present work we establish a simple relation between the Dirac equation with a scalar and an electromagnetic potentials in a two-dimensional case and a pair of decoupled Vekua equations. In general these Vekua equations are bicomplex. However we show that the whole theory of pseudoanalytic functions without modifications can be applied to these equatio

Stephen C. Anco, Dennis The

New nonlocal symmetries and conservation laws are derived for Maxwell's equations using a covariant system of joint vector potentials for the electromagnetic tensor field and its dual. A key property of this system, as well as of this class of new symmetries and conservation laws, is their invariance under the duality transformation that exchanges the el

Arturo Magidin

We consider the capability of $p$ groups of class two and odd prime exponent. We use linear algebra and counting arguments to establish a number of new results. In particular, we settle the 4-generator case, and prove a sufficient condition based on the ranks of $G/Z(G)$ and $[G,G]$.

Mark E. Huibregtse

Let k be an algebraically closed field. We study the cotangent space of a point t corresponding to a monomial ideal I of k[x_1, ..., x_r] in the Hilbert scheme of n points of affine r-space (so the k-dimension of k[x_1, ..., x_r]/I = colength of I = n). Since t lies in the closure of the locus corresponding to subschemes supported at n distinct points of A^r

W. N. Franzsen, R. B. Howlett, B. Mühlherr

Let $W$ be a Coxeter group and $r\in W$ a reflection. If the group of order 2 generated by $r$ is the intersection of all the maximal finite subgroups of $W$ that contain it, then any isomorphism from $W$ to a Coxeter group $W'$ must take $r$ to a reflection in $W'$. The aim of this paper is to show how to determine, by inspection of the Coxeter grap

Bernhard Mühlherr

By a recent result obtained by R. Howlett and the author considerable progress has been made towards a complete solution of the isomorphism problem for Coxeter groups. In this paper we give a survey on the isomorphism problem and explain in particular how the result mentioned above reduces it to its `reflection preserving' version. Furthermore we desrcib

Bernd Ammann, Emmanuel Humbert, Mohameden Ould Ahmedou

We prove a Pohozaev type identity for non-linear eigenvalue equations of the Dirac operator on Riemannian spin manifolds with boundary. As an application, we obtain that the mean curvature H of a conformal immersion S^{n}-> R^{n+1} satisfies $\int \partial_X H=0$ where X is a conformal vector field on S^{n} and where the integration is carried out with respe

Andras Juhasz

In this paper we define two regular homotopy invariants c and i for immersions of oriented 3-manifolds into R^5 in a geometric manner. The pair (c(f),i(f)) completely describes the regular homotopy class of the immersion f. The invariant i corresponds to the 3-dimensional obstruction that arises from Hirsch-Smale theory and extends the one defined in [10] fo

Andras Juhasz

Two locally generic maps f,g : M^n --> R^{2n-1} are regularly homotopic if they lie in the same path-component of the space of locally generic maps. Our main result is that if n is not 3 and M^n is a closed n-manifold then the regular homotopy class of every locally generic map f : M^n --> R^{2n-1} is completely determined by the number of its singular point

Andras Juhasz

In this paper we generalize the notion of regular homotopy of immersions of a closed connected n-manifold into R^{2n-1} to locally generic mappings. The main result is that if n=2 then two mappings with singularities are regularly homotopic if and only if they have the same number of cross-cap (or Whitney-umbrella) singularities. As an application, we get a

T. MacKenzie, A. J. Roberts

We analyse the nonlinear Kuramoto--Sivashinsky equation to develop accurate discretisations modeling its dynamics on coarse grids. The analysis is based upon centre manifold theory so we are assured that the discretisation accurately models the dynamics and may be constructed systematically. The theory is applied after dividing the physical domain into small

Christopher Jerdonek

We construct simple curves from immersed curves in the setting of handlebodies and Heegaard splittings. We define a measure of complexity we call girth for closed curves in a handlebody. We extend this complexity to Heegaard splittings and pose a conjecture about all Heegaard splittings. We prove a test case of this conjecture. Let S be a compact surface emb

L. Zsido

Notions of weak and uniformly weak mixing (to zero) are defined for bounded sequences in arbitrary Banach spaces. Uniformly weak mixing for vector sequences is characterized by mean ergodic convergence properties. For bounded sequences, which satisfy a certain domination condition, it is shown that weak mixing to zero is equivalent with uniformly weak mixing

G. J. Chaitin

In 1686 in his Discours de Metaphysique, Leibniz points out that if an arbitrarily complex theory is permitted then the notion of "theory" becomes vacuous because there is always a theory. This idea is developed in the modern theory of algorithmic information, which deals with the size of computer programs and provides a new view of Godel's work

T. M. Gendron

The fundamental germ is a generalization of $π_{1}$, first defined for laminations which arise through group actions in math.DG/0506270. In this paper, the fundamental germ is extended to any lamination having a dense leaf admitting a smooth structure. In addition, an amplification of the fundamental germ called the mother germ is constructed, which is, unli

Branko Malesevic

In this paper we consider alternating Kurepa's function $A(z)$ \cite{Petojevic_02}. We give some recurrent relations for alternating Kurepa's function via appropriate sequences of rational functions and gamma function. Also we give some inequalities for the real part of alternating Kurepa's function $A(x)$ for values of argument $x>-2$. The obtai

Pavel Okunev

We propose a fast algorithm for computing the expected tranche loss in the Gaussian factor model. We test it on a 125 name portfolio with a single factor Gaussian model and show that the algorithm gives accurate results. We choose a 125 name portfolio for our tests because this is the size of the standard DJCDX.NA.HY portfolio. The algorithm proposed here is

Paul Seidel, Ivan Smith

Ramanujam's surface M is a contractible affine algebraic surface which is not homeomorphic to the affine plane. For any m>1 the product M^m is diffeomorphic to Euclidean space R^{4m}. We show that, for every m>0, M^m cannot be symplectically embedded into a subcritical Stein manifold. This gives the first examples of exotic symplectic structures on Eucli

Gerard Maze, Lorenz Minder

This paper presents a new family of almost identities. These are based on series that sum to elements close to either rationals or rational multiples of pi. The explanation of the phenomenon takes its roots in the theory of Mellin transforms.

Kiran S. Kedlaya, Bjorn Poonen

We address several specific aspects of the following general question: can a field K have so many automorphisms that the action of the automorphism group on the elements of K has relatively few orbits? We prove that any field which has only finitely many orbits under its automorphism group is finite. We extend the techniques of that proof to approach a broad

Cristian Lenart, Alexander Postnikov

We give an explicit combinatorial Chevalley-type formula for the equivariant K-theory of generalized flag varieties G/P which is a direct generalization of the classical Chevalley formula. Our formula implies a simple combinatorial model for the characters of the irreducible representations of G and, more generally, for the Demazure characters. This model ca

M. Dine, Z. Sun

In the landscape, states with $R$ symmetries at the classical level form a distinct branch, with a potentially interesting phenomenology. Some preliminary analyses suggested that the population of these states would be significantly suppressed. We survey orientifolds of IIB theories compactified on Calabi-Yau spaces based on vanishing polynomials in weighted

Nick Mavromatos, Sarben Sarkar

We study in some detail the master equation, and its solution in a simplified case modelling flavour oscillations of a two-level system, stemming from the Liouville-string approach to quantum space time foam. In this framework we discuss the appearance of diffusion terms and decoherence due to the interaction of low-energy string matter with space-time defec

A. A. Saharian, E. R. Bezerra de Mello

We investigate the vacuum expectation value of the energy-momentum tensor associated with a massive fermionic field obeying the MIT bag boundary condition on a spherical shell in the global monopole spacetime. The asymptotic behavior of the vacuum densities is investigated near the sphere center and surface, and at large distances from the sphere. In the lim

Henning Samtleben, Martin Weidner

The general seven-dimensional maximal supergravity is presented. Its universal Lagrangian is described in terms of an embedding tensor which can be characterized group-theoretically. The theory generically combines vector, two-form and three-form tensor fields that transform into each other under an intricate set of nonabelian gauge transformations. The embe

Steven Weinberg

The ``in-in'' formalism is reviewed and extended, and applied to the calculation of higher-order Gaussian and non-Gaussian correlations in cosmology. Previous calculations of these correlations amounted to the evaluation of tree graphs in the in-in formalism; here we also consider loop graphs. It turns out that for some though not all theories, the c

Shigenori Seki, Katsuyuki Sugiyama

We formulate a gauged linear sigma model on a supermanifold. The structure of classical vacua is investigated and one-loop corrections are calculated for an auxiliary D-field. We find out a constraint for the one-loop divergence to vanish, which is consistent with a Ricci flatness condition for the supermanifold. Two types of D-branes are obtained by analysi

Nikolaos Kidonakis

I present universal master formulas for soft-gluon corrections to hard-scattering cross sections through next-to-next-to-next-to-leading order (NNNLO). I also briefly discuss applications to some processes where these corrections enhance the cross section and decrease the scale dependence.

Takeshi Fukuyama, Amon Ilakovac, Tatsuru Kikuchi

We consider the leptonic and semileptonic (SL) lepton flavour violating (LFV) decays of the charged leptons in the minimal supersymmetric standard model (MSSM). The formalism for evaluation of branching fractions for the SL LFV charged-lepton decays with one or two pseudoscalar mesons, or one vector meson in the final state, is given. Previous amplitudes for

Nick E. Mavromatos

In this review I classify the possible ways of CPT violation, and I describe briefly their phenomenology, in both terrestrial and astrophysical experiments, including antimatter factories, neutral mesons and neutrinos, and discuss the various sensitivities. I also pay attention to disentangling genuine quantum-gravity induced CPT violation from `fake' vi

A. H. Hoang, C. J. Reisser

In this talk electroweak corrections related to the finite top quark lifetime to the total top pair threshold e+e- cross section at NNLL order are discussed. We include the absorptive parts in electroweak matching conditions of the NRQCD operators related to the top decay and use the optical theorem. Gauge invariance is maintained. The corrections lead to ul

John Campbell, Francesco Tramontano

We present the results of a next-to-leading order calculation of Wt production, including the decays of both the top quark and the W boson. The effects of radiation in the decay of the top quark are also included. The separation of diagrams which appear in the real corrections, into singly- and doubly-resonant contributions, is performed using a b-jet veto w

V. J. Kolhinen

A brief overview of the global DGLAP analyses of the nuclear parton distribution functions is given. Although all the current global nPDF sets describe $R_{F_2}^A(x,Q^2)$ well in the large-$x$ region where the data exist, variations between their parton distributions can be substantial.

S. Groote, J. G. Körner, A. A. Pivovarov

We review recently developed new powerful techniques to compute a class of Feynman diagrams at any loop order, known as sunrise-type diagrams. These sunrise-type topologies have many important applications in many different fields of physics and we believe it to be timely to discuss their evaluation from a unified point of view. The method is based on the an

Matteo Beccaria

We review some peculiar features of Sudakov expansions in the calculation of electroweak radiative corrections in the MSSM at high energy. We give specific examples and consider in particular the process b g -> t W of single top quark production relevant for the top quark physics programme at LHC.

Luca Marotta, Fabio Siringo

A variational method is studied based on the minimum of energy variance. The method is tested on exactly soluble problems in quantum mechanics, and is shown to be a useful tool whenever the properties of states are more relevant than the eigenvalues. In quantum field theory the method provides a consistent second order extension of the gaussian effective pot

Nita Sinha, Rahul Sinha, Abner Soffer

We propose to measure the Cabibbo-Kobayashi-Maskawa parameter (2 beta+gamma) using B^0 decays involving several intermediate states, and describe a general formalism that applies to a broad class of decays. The main advantage of this method is that the ratios between the interfering amplitudes can be measured without requiring external input. In addition, di

Yu. A. Markov, M. A. Markova

In this work on the basis of Kadomtsev's kinetic fluctuation theory we present the more general expression for noise-noise correlation function in effective theory for ultrasoft field modes.

Ana M. Curiel, Maria J. Herrero

We compute the genuine SUSY one-loop quantum contributions to flavour-changing MSSM Higgs-boson decays into $b \bar s$ and $s \bar b$ using the full diagrammatic approach that is valid for all $\tan β$ values and do not rely on the mass-insertion approximation for the characteristic flavour-changing parameter. We analyze in full detail the dependence of thes

P. R. Crompton

We disprove the Vafa-Witten theorem on the impossibility of spontaneously breaking parity in vector-like gauge field theories, identifying a mechanism driven by quantum fluctuations. With the introduction of a meromorphic Lattice formulation, defined over 5 dimensions, we demonstrate that the minima of the free energy can be distinct from the maxima of the p

Stephan Durr, Christian Hoelbling, Urs Wenger

We investigate the overlap operator with a UV filtered Wilson kernel. The filtering leads to a better localization of the operator even on coarse lattices and with the untuned choice $ρ=1$. Furthermore, the axial-vector renormalization constant $Z_A$ is much closer to 1, reducing the mismatch with perturbation theory. We show that all these features persist

C. B. Lang, Pushan Majumdar, Wolfgang Ortner

We simulate Quantum Chromodynamics (QCD) in four Euclidean dimensions with two (degenerate mass) flavors of dynamical quarks. The Dirac operator we use is the so-called chirally improved Dirac operator. We discuss the algorithm used for the simulation as well as the checks and some results on lattices up to size 8**4 for fermion mass parameters down to 0.1.

B. Aubert, BABAR Collaboration

We report on searches for B- --> Ds- Phi and B- --> Ds*- Phi. In the context of the Standard Model, the branching fractions for these decays are expected to be highly suppressed, since they proceed through annhilation of the b and u-bar quarks in the B- meson. Our results are based on 234 million Upsilon(4S) --> B Bbar decays collected with the BaBar detecto

the ALEPH Collaboration

The full LEP-1 data set collected with the ALEPH detector at the $Z$ pole during 1991-1995 is analysed in order to measure the $τ$ decay branching fractions. Extensive systematic studies are performed, in order to match the large statistics of the data sample corresponding to over 300 000 measured and identified $τ$ decays. Branching fractions are obtained f

Ulrich Husemann

The HERA-B experiment at DESY has acquired a data set of approximately 300,000 decays J/psi -> l+l- during its 2002/2003 data-taking period. These data are used to analyze the production of heavy quarks in proton-nucleus interactions at a center-of-mass energy of 41.6 GeV. In this article, preliminary results of two measurements are discussed, a measurement

Martin Bojowald

Spherically symmetric space-times provide many examples for interesting black hole solutions, which classically are all singular. Following a general program, space-like singularities in spherically symmetric quantum geometry, as well as other inhomogeneous models, are shown to be absent. Moreover, one sees how the classical reduction from infinitely many ki

E. Minguzzi

We present some basic facts concerning simultaneity in both special and general relativity. We discuss Weyl's proof of the consistence of Einstein's synchronization convention and consider the general relativistic problem of assigning a time function to a congruence of timelike curves.

Steve Drasco, Eanna E. Flanagan, Scott A. Hughes

A key source for LISA will be the inspiral of compact objects into supermassive black holes. Recently Mino has shown that in the adiabatic limit, gravitational waveforms for these sources can be computed using for the radiation reaction force the gradient of one half the difference between the retarded and advanced metric perturbations. Using post-Newtonian

Yuval Shavitt, Eran Shir

Today's Internet maps, which are all collected from a small number of vantage points, are falling short of being accurate. We suggest here a paradigm shift for this task. DIMES is a distributed measurement infrastructure for the Internet that is based on the deployment of thousands of light weight measurement agents around the globe. We describe the rati

Hiroyasu Koizumi

We show that a stable spontaneous current appears in a system of a spin density wave order with merons, vortices in the spin configuration with winding number +1. A meron in the spin density wave order modifies the boundary condition for eigenfunctions around it to a sign-change one. As a consequence, two types of stable current states, one with a clockwise

Igor Zutic, Igor Mazin

Exotic superconducting properties of Sr$_{2}$RuO$_{4}$ have provided strong support for an unconventional pairing symmetry. However, the extensive efforts over the past decade have not yet unambiguously resolved the controversy about the pairing symmetry in this material. While recent phase-sensitive experiments using flux modulation in Josephson junctions c

A. Bertoni, M. Rontani, G. Goldoni, E. Molinari

We use a configuration-interaction approach and Fermi golden rule to investigate electron-phonon interaction in realistic multi-electron quantum dots. Lifetimes are computed in the low-density, highly correlated regime. We report numerical evidence that electron-electron interaction generally leads to reduced decay rates of excited electronic states in weakl

Peter J. Love, Bruce M. Boghosian, David A. Meyer

We present numerical results obtained using a lattice-gas model with dynamical geometry defined by Hasslacher and Meyer (Int. J. Mod. Phys. C. 9 1597 (1998)). The (irreversible) macroscopic behaviour of the geometry (size) of the lattice is discussed in terms of a simple scaling theory and obtained numerically. The emergence of irreversible behaviour from th

Matthew L. Wallace, Bela Joos

A phenomenon recently coined as ``overaging'' implies a slowdown in the collective (slow) relaxation modes of a glass when a transient shear strain is imposed. We are able to reproduce this behavior in simulations of a supercooled polymer melt by imposing instantaneous shear deformations. The increases in relaxation times $Δτ_{1/2}$ rise rapidly with

Ana Fariñas-Sanchez, Ricardo Paredes, Bertrand Berche

Simulations of nematic-isotropic transition of liquid crystals in two dimensions are performed using an O(2) vector model characterised by non linear nearest neighbour spin interaction governed by the fourth Legendre polynomial $P\_4$. The system is studied through standard Finite-Size Scaling and conformal rescaling of density profiles of correlation functi

Vassiliy Lubchenko, Robert J. Silbey, Peter G. Wolynes

Amorphous solids exhibit intrinsic, local structural transitions, that give rise to the well known quantum-mechanical two-level systems at low temperatures. We explain the microscopic origin of the electric dipole moment of these two-level systems: The dipole emerges as a result of polarization fluctuations between near degenerate local configurations, which

A. Mourachkine

The main purpose of this brief review is to present a sketch of the mechanism of high-Tc superconductivity based mainly on tunneling measurements in cuprates. In the review, we shall mostly discuss tunneling spectroscopy in Bi2212. Analysis of the data shows that the Cooper pairs in cuprates are topological excitations (e.g. quasi-one dimensional bisolitons,

A. I. Mares, J. M. van Ruitenbeek

We extend our previous shell effect observation in gold nanowires at room temperature under ultra high vacuum to the other two noble metals: silver and copper. Similar to gold, silver nanowires present two series of exceptionally stable diameters related to electronic and atomic shell filling. This observation is in concordance to what was previously found f

E. E. Takhtamirov, V. A. Volkov

It is developed a many-electron approach to explain the recently observed conductivity magnetooscillations in very high mobility 2D electron systems under microwave irradiation. For the first time a theory takes into account the microwave-induced renormalization of the screened impurity potential. As a result this potential has singular, dynamic and non-line

A. Ramsak, P. Prelovsek

Normal and superconducting state spectral properties of cuprates are theoretically described within the extended t-J model. The method is based on the equations of motion for projected fermionic operators and the mode-coupling approximation for the self-energy matrix. The dynamical spin susceptibility at various doping is considered as an input, extracted fr

Jacek Dziarmaga

A condensate initially prepared at finite temperature evolves under external time-dependent perturbation into a time-dependent mixed state. In these notes I use number-conserving time-dependent Bogoliubov theory to derive probability distribution for different outcomes of density measurement on the time-dependent excited state.

S. E. Korshunov

Different scenarios of the fluctuation-induced disordering of the striped phase which is formed at low temperatures in the triangular-lattice Ising model with the antiferromagnetic interaction of nearest and next-to-nearest neighbors are analyzed and compared. The dominant mechanism of the disordering is related to the formation of a network of domain walls,

Clecio C. de Souza Silva, J. Van de Vondel, B. Y. Zhu, M. Morelle

The vortex ratchet effect has been studied in Al films patterned with square arrays of submicron antidots. We have investigated the transport properties of two sets of samples: (i) asymmetrical antidots where vortices are driven by an unbiased ac current, and (ii) symmetrical antidots where in addition to the ac drive a dc bias was used. For each sample, the

V. I. Yukalov, K. -P. Marzlin, E. P. Yukalova, V. S. Bagnato

The report reviews the problem of topological coherent modes, which are nonlinear collective states of Bose-condensed atoms. Such modes can be generated by means of alternating external fields, whose frequencies are in resonance with the transition frequencies between the related modes. The Bose gas with generated topological coherent modes is a collective n

V. A. Brazhnyi, V. V. Konotop

Dynamics of vector dark solitons in two-component Bose-Einstein condensates is studied within the framework of the coupled one-dimensional nonlinear Schrödinger (NLS) equations. We consider the small amplitude limit in which the coupled NLS equations are reduced to the coupled Korteweg-de Vries (KdV) equations. For a specific choice of the parameters the obt

G. Mack, G. Palma, L. Vergara

Generalized universality, as recently proposed, postulates a universal non-Gaussian form of the probability density function (PDF) of certain global observables for a wide class of highly correlated systems of finite volume N. Studying the 2D XY -model, we link its validity to renormalization group properties. It would be valid if there were a single dimensi

Kirill Shtengel, Chetan Nayak, Waheb Bishara, Claudio Chamon

In this letter, we analyse the following apparent paradox: As has been recently proved by Hastings (cond-mat/0305505), under a general set of conditions, if a local Hamiltonian has a spectral gap above its (unique) ground state (GS), all connected equal-time correlation functions of local operators decay exponentially with distance. On the other hand, statis

Andreas Brzank, Sungchul Kwon, Gunter Schuetz

We study the conditions for reactivity enhancement of catalytic processes in porous solids by use of molecular traffic control (MTC) as a function of grain size. We extend a recently introduced two dimensional model system to three dimensions. With dynamic Monte-Carlo simulations and analytical solution of the associated Master equation we obtain a quantitat

M. A. Ambroso, R. D. Kamien, D. J. Durian

We present data for the time-dependence of wooden spheres penetrating into a loose non-cohesive packing of glass beads. The stopping time is a factor of three longer than the time $d/v_\circ$ needed to travel the total penetration distance $d$ at the impact speed $v_\circ$. The acceleration decreases monotonically throughout the impact. These kinematics are

A. Noriega-Crespo, A. Moro-Martin, S. Carey, P. W. Morris

New early release observations of the Cepheus E outflow and its embedded source, obtained with the Spitzer Space Telescope, are presented. We show the driving source is detected in all 4 IRAC bands, which suggests that traditional Class 0 classification, although essentially correct, needs to accommodate the new high sensitivity infrared arrays and their abi

B. Cameron Reed

The birthrate of stars of masses > 10 solar masses is estimated from a sample of just over 400 O3-B2 dwarfs within 1.5 kpc of the Sun and the result extrapolated to estimate the galactic supernova rate contributed by such stars. The solar-neighborhood galactic-plane massive star birthrate is estimated at 176 stars per cubic kpc per million years. Based on a

Ovidiu Vaduvescu, Marshall L. McCall, Michael G. Richer, Robin L. Fingerhut

A sample of 34 dwarf irregular galaxies in the Local Volume, most nearer than 5 Mpc, has been imaged in the near-infrared (NIR) in J and K_s at CFHT in Hawaii and OAN-SPM in Mexico. In CFHT images, stars brighter than M_Ks=-7.5 were resolved. In most cases, the resolved population represents less than 5% of the total NIR flux in K_s. Although exponential at

M. M. Hanson, R. -P. Kudritzki, M. A. Kenworthy, J. Puls

We present intermediate resolution (R ~ 8,000 - 12,000) high signal-to-noise H- and K-band spectroscopy of a sample of 37 optically visible stars, ranging in spectral type from O3 to B3 and representing most luminosity classes. Spectra of this quality can be used to constrain the temperature, luminosity and general wind properties of OB stars, when used in c

Amaya Moro-Martin, Renu Malhotra

We report several results related to the dynamical evolution of dust produced in the Kuiper Belt (KB). We show that its particle size frequency distribution in space is greatly changed from the distribution at production, as a results of the combined effects of radiation forces and the perturbations of the planets. We estimate the contribution of KB dust to

Jeremy D. Schnittman, Luciano Rezzolla

We use a relativistic ray-tracing code to analyze the X-ray emission from a pressure-supported oscillating relativistic torus around a black hole. We show that a strong correlation exists between the {\it intrinsic} frequencies of the torus normal modes and the {\it extrinsic} frequencies seen in the observed light curve power spectrum. This correlation demo

David A. Turnshek, Sandhya M. Rao, Daniel B. Nestor, Michele Belfort-Mihalyi

Sloan Digital Sky Survey (SDSS) quasar spectroscopy is yielding a database of strong low-ionization MgII absorbers over the redshift interval 0.36<z<2.28 which is over two orders of magnitude larger than anything previously assembled. HST UV spectroscopy has been used to measure neutral hydrogen column densities for a small subset of them. These data empiric