September 2003 arXiv papers — page 3

J. Vijande, F. Fernandez, A. Valcarce

The ${q}\bar{q}$ spectrum is studied within a chiral constituent quark model. It provides with a good fit of the available experimental data from light (vector and pseudoscalar) to heavy mesons including some recent results on charmonium. The $0^{++}$ light mesons and the new $D$ states measured at different factories cannot be described as $q\bar q$ pairs a

Subhendu Rakshit, Guy Raz, Sourov Roy, Yael Shadmi

Triplet-mediated proton decay in Grand Unified Theories (GUTs) is usually suppressed by arranging a large triplet mass. Here we explore instead a mechanism for suppressing the couplings of the triplets to the first and second generations compared to the Yukawa couplings, so that the triplets' mass can be below the GUT scale. This mechanism is based on a

Kenneth F. Nicholson

Given the dimensions (including thickness) of a galaxy, and its rotation profile, a method is shown that finds the mass and density distributions in the defined envelope that will cause that rotation profile with near-exact speed matches. Newton's law is unchanged. Surface-light intensity and dark matter are not needed. Results are presented in dimension

Michel Pleimling

Recently Mayer et al. [Phys. Rev. E {\bf 68}, 016116 (2003)] proposed a new way to compute numerically the fluctuation-dissipation ratios in nonequilibrium critical systems. Using well-known facts of nonequilibrium critical dynamics I show that the leading contributions of the quantities they consider are in fact one-time quantities which are independent of

M. Bialecki, A. Doliwa

We transfer the algebro-geometric method of construction of solutions of the discrete KP equation to the finite field case. We emphasize role of the Jacobian of the underlying algebraic curve in construction of the solutions. We illustrate in detail the procedure on example of a hyperelliptic curve.

The Belle Collaboration, K. Abe

K^+K^- production in two-photon collisions has been studied using a large data sample of 67 fb^{-1} accumulated with the Belle detector at the KEKB asymmetric e^+e^- collider. We have measured the cross section for the process gamma gamma -> K^+ K^- for center-of-mass energies between 1.4 and 2.4 GeV, and found three new resonant structures in the energy reg

Jiangbin Gong, Hans Jakob Worner, Paul Brumer

Control over the quantum dynamics of chaotic kicked rotor systems is demonstrated. Specifically, control over a number of quantum coherent phenomena is achieved by a simple modification of the kicking field. These include the enhancement of the dynamical localization length, the introduction of classical anomalous diffusion assisted control for systems far f

Jiangbin Gong, Paul Brumer

Quantum-classical correspondence in conservative chaotic Hamiltonian systems is examined using a uniform structure measure for quantal and classical phase space distribution functions. The similarities and differences between quantum and classical time-evolving distribution functions are exposed by both analytical and numerical means. The quantum-classical c

Fedor Herbut

An analogue of the mixing property of quantum entropy is derived for quantum relative entropy.It is applied to the final state of ideal measurement and to the spectral form of the second density operator. Three cases of states on a directed straight line of relative entropy are discussed.

Laurent Sanchez-Palencia, Gilbert Grynberg

We theoretically study the influence of the noise strength on the excitation of the Brillouin propagation modes in a dissipative optical lattice. We show that the excitation has a resonant behavior for a specific amount of noise corresponding to the precise synchronization of the Hamiltonian motion on the optical potential surfaces and the dissipative effect

Laurent Sanchez-Palencia, Michele Schiavoni, Francois-Regis Carminati, Ferruccio Renzoni

We present a theoretical and experimental study of the damping process of the atomic velocity in Sisyphus cooling. The relaxation rates of the atomic kinetic temperature are determined for a 3D lin$\perp$lin optical lattice. We find that the damping rates of the atomic temperature depend linearly on the optical pumping rate, for a given depth of the potentia

Michele Schiavoni, Laurent Sanchez-Palencia, Ferruccio Renzoni, Gilbert Grynberg

We demonstrate the phenomenon of directed diffusion in a symmetric periodic potential. This has been realized with cold atoms in a one-dimensional dissipative optical lattice. The stochastic process of optical pumping leads to a diffusive dynamics of the atoms through the periodic structure, while a zero-mean force which breaks the temporal symmetry of the s

Zafar Ahmed, Sudhir R. Jain

Employing the concept of time-delay, a relation is found which counts the number of quantal resonances supported by a potential. Several simple and advanced illustrations include a treatment of square-well, Dirac delta barrier, an interesting physical situation from neutron reflectometry, and the Delta resonance appearing in the scattering of πmeson from pro

Luc Bouten, Madalin Guta, Hans Maassen

A derivation of stochastic Schrodinger equations is given using quantum filtering theory. We study an open system in contact with its environment, the electromagnetic field. Continuous observation of the field yields information on the system: it is possible to keep track in real time of the best estimate of the system's quantum state given the observati

Norio Inui, Yoshinao Konishi, Norio Konno, Takahiro Soshi

Temporal fluctuations in the Hadamard walk on circles are studied. A temporal standard deviation of probability that a quantum random walker is positive at a given site is introduced to manifest striking differences between quantum and classical random walks. An analytical expression of the temporal standard deviation on a circle with odd sites is shown and

H. H. Adamyan, G. Yu. Kryuchkyan

We explore in detail the possibility of generation of continuous-variable (CV) entangled states of light fields with well-localized phases. We show that such quantum states, called entangled self-phase locked states, can be generated in nondegenerate optical parametric oscillator (NOPO) based on a type-II phase-matched down-conversion combined with polarizat

J. Chen, X. X. Yi, H. S. Song, L. Zhou

We discuss the generation of entangled states of two two-level atoms coupled simultaneously with a dissipated atom. The dissipation of the atom is supposed to come from its coupling to a noise with adjustable intensity. We describe how the entanglement between the atoms arise in such a situation, and wether a noise except the white one could help preparation

Himanshu Agrawal

We study counter expressed gene networks constructed from gene-expression data obtained from many types of cancers. The networks are synthesized by connecting vertices belonging to each others' list of K-farthest-neighbors, with K being an a priori selected non-negative integer. In the range of K corresponding to minimum homogeneity, the degree distribut

R. K. Nesbet

In the accompanying Comment [Phys. Rev. A {\bf 67}, 056501 (2003)], I. Lindgren and S. Salomonson claim to prove for the Kohn-Sham kinetic energy functional of ground state electron density that a Frëchet functional derivative exists, equivalent to a multiplicative local potential function. If true, this result would imply an exact Thomas-Fermi theory for gr

R. K. Nesbet

The accompanying Comment by A. Holas and N. H. March [Phys. Rev. A {\bf 66}, 066501 (2002)] is concerned with the issue of whether or not kinetic energy can be represented by an effective local potential, as required for an exact Thomas-Fermi theory equivalent to Kohn-Sham density-functional theory. They dispute [R.K. Nesbet, Phys. Rev. A {\bf 65}, 010502(R)

A. Xayaphoummine, T. Bucher, F. Thalmann, H. Isambert

Ab initio RNA secondary structure predictions have long dismissed helices interior to loops, so-called pseudoknots, despite their structural importance. Here, we report that many pseudoknots can be predicted through long time scales RNA folding simulations, which follow the stochastic closing and opening of individual RNA helices. The numerical efficacy of t

P. Zanca, F. Sattin, E. Martines

The equilibrium of a finite-beta cylindrical RFP plasma in the presence of saturated-amplitude tearing modes is investigated. The singularities arising from the perturbative analysis of the MHD force balance equation JxB=grad(p) are resolved through a proper regularization of the cylindrical symmetric component of the pressure and parallel current density pr

V. E. Oberacker, A. S. Umar, E. Teran, A. Blazkiewicz

Using the Hartree-Fock-Bogoliubov (HFB) mean field theory in coordinate space, we investigate ground state properties of the sulfur isotopes from the line of stability up to the two-neutron dripline ($^{34-52}S$). In particular, we calculate two-neutron separation energies, quadrupole moments, and rms-radii for protons and neutrons. Evidence for shape coexis

A. Belic, D. J. Dean, M. Hjorth-Jensen

We discuss several pairing-related phenomena in nuclear systems, ranging from superfluidity in neutron stars to the gradual breaking of pairs in finite nuclei. We describe recent experimental evidence that points to a relation between pairing and phase transitions (or transformations) in finite nuclear systems. A simple pairing interaction model is used in o

Mladen Martinis, Vesna Mikuta-Martinis

The posibility of large charge and isospin fluctuations in high-energy heavy ion-collisions is studied within the framework of the nonlinear $σ$-model with quark degrees of freedom. The multipion exchange potential between two quarks is derived. It is shown that the soft chiral pion bremsstralung leads to anomalously large fluctuations in the ratio of neutra

C. Albertus, J. E. Amaro, E. Hernandez, J. Nieves

We evaluate masses of bottom and charmed baryons using several non-relativistic quark potentials which parameters have been adjusted to the meson spectra. Heavy Quark Symmetry leads to important simplifications of the three body problem, which turns out to be easily solved by a simple variational ansatz. The wave functions obtained can be readily used to com

E. V. Prokhorova, E. A. Cherepanov, M. G. Itkis, N. A. Kondratiev

The capture-fission cross-sections in an energy range of 206-242 MeV of 48Ca-projectiles and mass-energy distributions (MEDs) of reaction products in an energy range of 211-242 MeV have been measured in the 48Ca+208Pb reaction using the double-arm time-of-flight spectrometer CORSET. The MEDs of fragments for heated fission were shown to consist of two compon

G. Ban

The transport and cooling of noble gas singly-charged ion beams by means of a Radio Frequency Quadrupole Cooler Buncher (RFQCB) have been studied at the LIMBE low energy beam line of the GANIL facility. Ions as light as $^{4}He^+$ have been cooled and stored before their extraction in bunches using $H_2$ as buffer gas. Bunches characteristics have been studi

Jen-Hsu Chang

We deform the Dorfman's and Sokolov's Hamiltonian operators by the quasi-Miura transformation coming from the topological field theory and investigate the deformed operators.

S. A. Darmanyan, A. M. Kamchatnov, M. Neviere

The joint influence of the polariton effect and Kerr-like nonlinearity on propagation of optical pulses is studied. The existence of different families of envelope solitary wave solutions in the vicinity of polariton gap is shown. The properties of solutions depend strongly on the carrier wave frequency. In particular, solitary waves inside and outside of th

A. I. Zenchuk

We represent the Fourier form of the dressing method, which is effective for construction of multidimensional integral-differential equations together with their solutions. Example of integrable (but non-physical) expansion of Intermediate Long Wave equation in (2+1)-dimensions is considered.

Yuri A. Kubyshin

We review the basic elements of the geometrical formalism for description of gauge fields and the theory of invariant connections, and their applications to the coset space dimensional reduction of Yang-Mills theories. We also discuss the problem of classification of principal fibre bundles, which is important for the quantization of gauge theories. Some res

Peter J. Forrester

The Hammersley process relates to the statistical properties of the maximum length of all up/right paths connecting random points of a given density in the unit square from (0,0) to (1,1). This process can also be interpreted in terms of the height of the polynuclear growth model, or the length of the longest increasing subsequence in a random permutation. T

Colin Adams

In 1978, W. Thurston revolutionized low diemsional topology with his work on hyperbolic 3-manifolds. In this paper, we discuss what is currently known about knots in the 3-sphere with hyperbolic complements. Then focus is on geometric invariants coming out of the hyperbolic structures. This is one of a collection of articles to appear in the Handbook of Knot

M. I. Merklen

We work with functions defined in R^n with values in a C^*- algebra A. We consider the set \Sa of the functions of Schwartz (the rapidly decreasing ones) with the usual l_2-norm. We denote \CB^{2n}A the set of functions of class C^\infty with bounded derivatives. We prove, generalizing a result in [10], that pseudodifferential operators with symbol in \CB^{2

Sergiu Klainerman, Igor Rodnianski

We develop a geometric invariant Littlewood-Paley theory for arbitrary tensors on a compact 2 dimensional manifold. We show that all the important features of the classical LP theory survive with estimates which depend only on very limited regularity assumptions on the metric. We give invariant descriptions of Sobolev and Besov spaces and prove some sharp pr

Claudio Bonanno

In this paper we prove estimates on the behaviour of the Kolmogorov-Sinai entropy relative to a partition for randomly perturbed dynamical systems. Our estimates use the entropy for the unperturbed system and are obtained using the notion of Algorithmic Information Content. The main result is an extension of known results to study time series obtained by the

Laurent Bonavero

Suppose $π: X \to Y$ is a smooth blow-up along a submanifold $Z$ of $Y$ between complex Fano manifolds $X$ and $Y$ of pseudo-indices $i_X$ and $i_Y$ respectively (recall that $i_X$ is defined by $i_X := \min \{-K_X \cdot C | C {is a rational curve of} X\}$). We prove that $i_X \leq i_Y$ if $2\dim (Z)< \dim(Y) + i_Y -1$ and show that this result is optimal by

Sergiu Klainerman, Igor Rodnianski

The main objective of the paper is to prove a geometric version of sharp trace and product estimates on null hypersurfaces with finite curvature flux. These estimates play a crucial role to control the geometry of such null hypersurfaces. The paper is based on an invariant version of the classical Littlewood -Paley theory, in a noncommutative setting, define

Jan Snellman

Bergeron, Bousquet-Melou and Dulucq enumerated paths in the Hasse diagram of the following poset: the underlying set is that of all compositions, and a composition μcovers another composition λif μcan be obtained from λby adding 1 to one of the parts of λ, or by inserting a part of size 1 into λ. We employ the methods they developed in order to study the sam

D. E. Yakovlev, D. N. Zhabin

The approach that allows find European option price on the assumption of hedging at discrete times is proposed. The routine allows find the option price not for lognormal distribution functions of underlying asset only but for wide enough classes of distribution functions too. It is shown that there exists a nonzero possibility that market parameters can tak

Guy Cohen, Stephane Gaubert, Jean-Pierre Quadrat

We consider subsemimodules and convex subsets of semimodules over semirings with an idempotent addition. We introduce a nonlinear projection on subsemimodules: the projection of a point is the maximal approximation from below of the point in the subsemimodule. We use this projection to separate a point from a convex set. We also show that the projection mini

Casim Abbas

In this paper we give a simple application of the filling methods developed earlier to the chord problem in three dimensional contact geometry.

Thomas Friedrich, Stefan Ivanov

We classify locally homogeneous quasi-Sasakian manifolds in dimension five that admit a parallel spinor $ψ$ of algebraic type $F \cdot ψ= 0$ with respect to the unique connection $\nabla$ preserving the quasi-Sasakian structure and with totally skew-symmetric torsion. We introduce a certain conformal transformation of almost contact metric manifolds and disc

Dominic Joyce

We introduce special Lagrangian submanifolds in C^m and in (almost) Calabi-Yau manifolds, and survey recent results on singularities of special Lagrangian submanifolds, and their application to the SYZ Conjecture. The paper is aimed at graduate students in Geometry, String Theorists, and others wishing to learn the subject. Special Lagrangian m-folds in C^m

Changrim Ahn, Rafael I. Nepomechie

We compute the boundary energy and the Casimir energy for both the spin-1/2 XXZ quantum spin chain and (by means of the light-cone lattice construction) the massive sine-Gordon model with both left and right boundaries. We also derive a nonlinear integral equation for the ground state of the sine-Gordon model on a finite interval. These results, which are ba

S. Sivasubramanian, G. Castellani, N. Fabiano, A. Widom

Employing Maxwell&#39;s equations as the field theory of the photon, quantum mechanical operators for spin, chirality, helicity, velocity, momentum, energy and position are derived. The photon ``Zitterbewegung&#39;&#39; along helical paths is explored. The resulting non-commutative geometry of photon position and the quantum version of the Pythagorean theore

B. de Carlos, J. M. Moreno

We study the localization of gravity on a string-like topological defect within a 6-dimensional space-time. Assuming zero cosmological constant we find complete numerical solutions to a set of first-order, Bogomol&#39;nyi-Prasad-Sommeferld (BPS)-like, equations for the metric and the scalar field, where the dynamics of the latter are dictated by a supergravi

Kazuo Fujikawa, Anton Rebhan, Peter van Nieuwenhuizen

We discuss the possibility to absorb all anomalies in the supersymmetry algebra of the N=(1,1) Wess-Zumino model in d=1+1 by a local counter term. This counter term corresponds to the change of the vacuum parameter $v_0^2$ in the model and the transition to an unconventional but admissible renormalization scheme. It does not modify the physical consequences

Sangyong Jeon, Guy D. Moore

We consider bremsstrahlung energy loss for hard partons traversing a quark-gluon plasma. Accounting correctly for the probabilistic nature of the energy loss, and making a leading-order accurate treatment of bremsstrahlung, we find that the suppression of the spectrum is nearly flat, with the most suppression at energies $E \sim 30 T$ ($T$ the QGP temperatur

V. M. Braun, D. Yu. Ivanov, G. P. Korchemsky

The B-meson distribution amplitude is calculated using QCD sum rules. In particular we obtain an estimate for the integral relevant to exclusive B-decays λ_B = 460 \pm 110 MeV at the scale 1 GeV. A simple QCD-motivated parametrization of the distribution amplitude is suggested.

Kazuo Fujikawa, Robert Shrock

We study a combination of amplitudes for neutrino scattering that can isolate a (gauge-invariant) difference of chirality-preserving neutrino electroweak radii for $ν_μ$ and $ν_τ$. This involves both photon and $Z_μ$ exchange contributions. It is shown that the construction singles out the contributions of the hypercharge gauge field $B_μ$ in the standard mo

Dmitry Semikoz, Guenter Sigl

We apply new upper limits on neutrino fluxes and the diffuse extragalactic component of the GeV gamma-ray flux to various scenarios for ultra high energy cosmic rays and neutrinos. As a result we find that extra-galactic top-down sources can not contribute significantly to the observed flux of highest energy cosmic rays. The Z-burst mechanism where ultra-hig

German Rodrigo, Frank Krauss

Expressions for Sudakov form factors for heavy quarks are presented. They are used to construct resummed jet rates in electron-positron annihilation. Predictions are given for production of bottom quarks at LEP and top quarks at the Linear Collider.

German Rodrigo, Frank Krauss

Expressions for Sudakov form factors for heavy quarks are presented. They are used to construct resummed jet rates in electron-positron annihilation. Predictions are given for production of bottom quarks at LEP and top quarks at the Linear Collider.

Antonio Dobado, Felipe J. Llanes-Estrada

We report a calculation of the shear viscosity in a relativistic multicomponent meson gas as a function of temperature and chemical potentials. We approximately solve the Uehling-Uhlenbeck transport equation of kinetic theory, appropriate for a boson gas, with relativistic kinematics. Since at low temperatures the gas can be taken as mostly composed of pions

H. Arthur Weldon

The retarded electron propagator S_{R}(p_{0},p) at high momentum p>>T was shown by Blaizot and Iancu to be an entire function of complex p_{0}. In this paper a specific form for S_{R}(p_{0},p) is obtained and checked by showing that its temporal Fourier transform S_{R}(t, p) has the correct behavior at large t. Potential infrared and collinear divergences fr

V. A. Saleev, D. V. Vasin

It is shown that the difference between the c-quark proton structure functions calculated in the k_T-factorization approach using different unintegrated gluon distribution functions is the same order as the difference between results obtained in the parton model and in the k_T-factorization approach.

Dipankar Chakrabarti, A. Harindranath, James P. Vary

In this work we investigate $q{\bar q}$ spectra and wavefunctions of light front transverse lattice Hamiltonians that result from different methods of formulating fermions on the transverse lattice. We adopt the one link approximation for the transverse lattice and Discrete Light Cone Quantization to handle longitudinal dynamics. We perform a detailed study

Jan van der Heide

We calculate the electromagnetic form factor of the pion in quenched lattice QCD. The non-perturbatively improved Sheikoleslami-Wohlert lattice action is used together with the ${\mathcal O}(a)$ improved current. We calculate form factor for pion masses down to $m_π= 360 MeV$. We compare the mean square radius for the pion extracted from our form factors to

R. Brower, S. Chandrasekharan, S. Riederer, U. -J. Wiese

D-theory is an alternative non-perturbative approach to quantum field theory formulated in terms of discrete quantized variables instead of classical fields. Classical scalar fields are replaced by generalized quantum spins and classical gauge fields are replaced by quantum links. The classical fields of a d-dimensional quantum field theory reappear as low-e

A. Shindler, M. Guagnelli, K. Jansen, F. Palombi

We compute non-perturbatively the evolution of the twist-2 operators corresponding to the average momentum of non-singlet quark densities. The calculation is based on a finite-size technique, using the Schrödinger Functional, in quenched QCD. We find that a careful choice of the boundary conditions, is essential, for such operators, to render possible the co

K. J. Juge, J. Kuti, F. Maresca, C. Morningstar

The excitations of gluonic flux tube in a periodic lattice are examined. Monte Carlo simulations from an anisotropic lattice are presented and the comparison with effective string models is discussed.

Takashi Umeda, Kouji Nomura, Hideo Matsufuru

We study the light hadron correlators near the deconfining transition by extracting the spectral function on quenched anisotropic lattices. We adopt the method successfully applied to the charmonium systems: the use of the smeared operators and the analysis method which is composed of the maximum entropy method and the $χ^2$ fitting assuming several forms. T

K. Sasaki, S. Sasaki, T. Hatsuda, M. Asakawa

We study excited states of the nucleon in quenched lattice QCD with the spectral analysis using the maximum entropy method. Our simulations are performed on three lattice sizes $16^3\times 32$, $24^3\times 32$ and $32^3\times 32$, at $β=6.0$ to address the finite volume issue. We find a significant finite volume effect on the mass of the Roper resonance for

Y. Mori, V. Bornyakov, H. Ichie, Y. Koma

We study the flux tube profile in the baryonic system in full QCD at finite temperature on $N_{t}=8$ lattice. We fix the maximally Abelian gauge and measure the monopole and the photon parts of the Abelian action density, the color electric field and the monopole current on both sides of the finite temperature transition. We demonstrate the disappearance of

Rainer Wanke

In the recent year many new results from kaon decays have been reported from both the NA48 experiment at CERN and the KTeV experiment at Fermilab. Both experiments have new and improved measurements of the parameter Re(epsilon&#39;/epsilon) of direct CP violation in the neutral kaon system. Also several new results on rare and very rare K_L decays were repor

Dumitru Astefanesei, Eugen Radu

We consider boson star solutions in a $D$-dimensional, asymptotically anti-de Sitter spacetime and investigate the influence of the cosmological term on their properties. We find that for $D>4$ the boson star properties are close to those in four dimensions with a vanishing cosmological constant. A different behavior is noticed for the solutions in the three

Katerina J. Argyraki, David R. Cheriton

Denial of Service (DoS) attacks are one of the most challenging threats to Internet security. An attacker typically compromises a large number of vulnerable hosts and uses them to flood the victim&#39;s site with malicious traffic, clogging its tail circuit and interfering with normal traffic. At present, the network operator of a site under attack has no ot

David A. Plaisted

A situation calculus is presented that provides a solution to the frame problem for hierarchical situations, that is, situations that have a modular structure in which parts of the situation behave in a relatively independent manner. This situation calculus is given in a relational, functional, and modal logic form. Each form permits both a single level hier

Boris Alexeev

We present and prove a theorem answering the question &#34;how many states does a minimal deterministic finite automaton (DFA) that recognizes the set of base-b numbers divisible by k have?&#34;

Kazumi Maki, Hyekyung Won, Stephan Haas

Recent experiments on single crystals of YNi$_2$B$_2$C have revealed the presence of point nodes in the superconducting energy gap Delta(k} at k = (1,0,0), (0,1,0), (-1,0,0), and (0,-1,0). In this paper we investigate the effects of impurity scattering on the quasiparticle spectrum in the vortex state of s+g-wave superconductors, which is found to be strongl

Massimo Rontani, L. J. Sham

We study the thermopower of a junction between a metal and a strongly correlated semiconductor. Both in the electronic ferroelectric regime and in the Kondo insulator regime the thermoelectric figures of merit, ZT, of these junctions are compared with that of the ordinary semiconductor. By inserting at the interface one or two monolayers of atoms different f

M. A. Avila, Y. Q. Wu, C. L. Condron, S. L. Bud&#39;ko

We address the nature of the ligandal disorder leading to local redistributions of Kondo temperatures, manifested as annealing-induced changes in the transport behavior of the heavy fermion system YbNi2B2C. The anomalous transport behavior was fully characterized by temperature dependent resistivity measurements in an extended range of 0.4 < T < 1000 K for a

Leonid Fedichkin, Arkady Fedorov, Vladimir Privman

We introduce new measures of decoherence appropriate for evaluation of quantum computing designs. Environment-induced deviation of a quantum system&#39;s evolution from controlled dynamics is quantified by a single numerical measure. This measure is defined as a maximal norm of the density matrix deviation. We establish the property of additivity: in the reg

C. I. Ventura, M. Acquarone

Well defined spin waves were observed when the spin dynamics of Tl2Mn2O7, the first pyrochlore compound found to exhibit colossal magnetoresistance, was measured [J.W.Lynn et al., Phys.Rev.Lett. 80,4582(1998)], in stark contrast with the experimental results on the larger family of magnetoresistive manganites with perovskite structure. In this work, we prese

Anna Okopińska

The effective action formalism of quantum field theory is used to study the properties of the non-relativistic interacting Bose gas. The Gaussian approximation is formulated by calculating the effective action to the first order of the optimized expansion. In the homogeneous limit the method respects the Hughenholz-Pines theorem, leading to the gapless spect

A. D. Drozdov

Kinetic equations are analyzed for thermal degradation of polymers. The governing relations are based on the fragmentation-annihilation concept. Explicit solutions to these equations are derived in two particular cases of interest. For arbitrary values of adjustable parameters, the evolution of the number-average and mass-average molecular weights of polymer

Nicholas P. Bailey, Jakob Schiøtz, Karsten W. Jacobsen

We have obtained effective medium theory (EMT) interatomic potential parameters suitable for studying Cu-Mg metallic glasses. We present thermodynamic and structural results from simulations of such glasses over a range of compositions. We have produced low-temperature configurations by cooling from the melt at as slow a rate as practical, using constant tem

S. B. Yuste, L. Acedo

The distribution of times $t_{j,N}$ elapsed until the first $j$ independent random walkers from a set of $N \gg 1$, all starting from the same site, are trapped by a quenched configuration of traps randomly placed on a disordered lattice is investigated. In doing so, the cumulants of the distribution of the territory explored by $N$ independent random walker

D. R. Lee, J. W. Freeland, G. Srajer, S. K. Sinha

A simple scheme to extract the magnetization reversals of characteristic magnetic domains on nanofabricated periodic arrays from soft x-ray resonant magnetic scattering (SXRMS) data is presented. The SXRMS peak intensities from a permalloy square ring array were measured with field cycling using circularly polarized soft x-rays at the Ni L$_3$ absorption edg

V. A. Moskalenko, M. E. Palistrant, V. M. Vakalyuk

The possibility is indicated of applying the theory of superconductors with overlapping energy bands to describe the thermodynamic and electromagnetic properties of the high-temperature compounds $La_{2-x}(Ba,Sr)_xCuO_4$ and $YBa_2Ci_3O_{7-δ}$. The two-band model was used to obtain high values of $T_c$, two energy gaps $2Δ_1/T_c > 3.5$ and $2Δ_2/T_c < 3.5$,

Amandine Aftalion, Ionut Danaila

We consider a rotating Bose-Einstein condensate confined in combined harmonic and quartic traps, following recent experiments [V. Bretin, S. Stock, Y. Seurin and J. Dalibard, cond-mat/0307464]. We investigate numerically the behavior of the wave function which solves the three-dimensional Gross Pitaevskii equation. When the harmonic part of the potential is

Kamil Walczak

Here we propose four-terminal molecular devices as functional logic gates (AND, NOR and XOR, respectively). Such devices are composed of single organic molecule connected to gold electrodes and located in between gate terminals. Specifically, the operation principle of molecular logic gates is discussed in detail. The input signal of the gate voltages can mo

Y. Xu, M. Khafizov, L. Satrapinsky, P. Kus

Femtosecond pump-probe studies show that carrier dynamics in MgB2 films is governed by the sub-ps electron-phonon (e-ph) relaxation present at all temperatures, the few-ps e-ph process well pronounced below 70 K, and the sub-ns superconducting relaxation below Tc. The amplitude of the superconducting component versus temperature follows the superposition of

Timothy B. Boykin, Gerhard Klimeck, M. A. Eriksson, Mark Friesen

A theory based on localized-orbital approaches is developed to describe the valley splitting observed in silicon quantum wells. The theory is appropriate in the limit of low electron density and relevant for proposed quantum computing architectures. The valley splitting is computed for realistic devices using the quantitative nanoelectronic modeling tool NEM

Julian Lee, Seung-Yeon Kim, Jooyoung Lee

We propose an automated protocol for designing the energy landscape of a protein energy function by optimizing its parameters. The parameters are optimized so that not only the global minimum energy conformation becomes native-like, but also the conformations distinct from the native structure have higher energies than those close to the native one. We succe

S. S. Gylfadottir, V. Gudmundsson, C. S. Tang, A. Manolescu

We investigate the difference in the response of a one-dimensional semiconductor quantum ring and a finite-width ring to a strong and short-lived time-dependent perturbation in the THz regime. In both cases the persistent current is modified through a nonadiabatic change of the many-electron states of the system, but by different mechanisms in each case.

J. M. Rubi, I. Santamaria-Holek, A. Perez-Madrid

We present a Fokker-Planck description of supercooled colloidal systems exhibiting slow relaxation dynamics. By assuming the existence of a local quasi-equilibrium state during the relaxation of the system, we derive a non-Markovian Fokker-Planck equation for the non-stationary conditional probability. A generalized Stokes-Einstein relation containing the te

Vito D. P. Servedio, Guido Caldarelli, Paolo Butta`

We study a recent model of random networks based on the presence of an intrinsic character of the vertices called fitness. The vertices fitnesses are drawn from a given probability distribution density. The edges between pair of vertices are drawn according to a linking probability function depending on the fitnesses of the two vertices involved. We study he

C. Degli Esposti Boschi, E. Ercolessi, G. Morandi

We review here some general properties of antiferromagnetic Heisenberg spin chains, emphasizing and discussing the role of hidden symmetries in the classification of the various phases of the models. We present also some recent results that have been obtained with a combined use of Conformal Field Theory and of numerical Density Matrix Renormalization Group

O. Benichou, M. Coppey, J. Klafter, M. Moreau

We study the behavior of several joint residence times of N independent Brownian particles in a disc of radius $R$ in two dimensions. We consider: (i) the time T_N(t) spent by all N particles simultaneously in the disc within the time interval [0,t]; (ii) the time T_N^{(m)}(t) which at least m out of N particles spend together in the disc within the time int

M. Coppey, O. Benichou, J. Klafter, M. Moreau

In this paper we analyze the effect of the bulk-mediated excursions (BME) of reactive species on the long-time behavior of the catalytic Langmuir-Hinshelwood-like A + B \to 0 reactions in systems in which a catalytic plane (CP) is in contact with liquid phase, containg concentrations of reactive particles. Such BME result from repeated particles desorption f

I. Pérez Castillo, N. S. Skantzos

We study the Hopfield model on a random graph in scaling regimes where the average number of connections per neuron is a finite number and where the spin dynamics is governed by a synchronous execution of the microscopic update rule (Little-Hopfield model).We solve this model within replica symmetry and by using bifurcation analysis we prove that the spin-gl

A. Agliolo Gallitto, M. Bonura, S. Fricano, M. Li Vigni

Field-induced variations of the microwave surface resistance, Rs(H), have been investigated in high-density ceramic MgB2. At low temperatures, several peculiarities of the Rs(H) curves cannot be justified in the framework of models reported in the literature. We suggest that they are ascribable to the unconventional vortex structure in MgB2, related to the p

Akira Onuki

We present a general Ginzburg-Landau theory of electrostatic interactions and electric field effects for the order parameter, the polarization, and the charge density. Electric field effects are then investigated in near-critical fluids and liquid crystals. Some new predictions are given on the liquid-liquid phase transition in polar binary mixtures with a s

A. P. Saiko, S. A. Markevich

We propose an explanation for the experimentally observed [JETP Lett. 74, 115 (2001)] giant temperature hysteresis of the ultrasound velocity and the internal friction in single crystals of lanthanum manganite (La0.8Sr0.2MnO3). The effect is interpreted within the framework of a phenomenological model based on the notion of two coexisting sublattices of the

Tetsufumi Tanamoto, Xuedong Hu

We solve the master equations of two charged qubits measured by a single-electron transistor (SET) consisted of two islands. We show that in the sequential tunneling regime the SET current can be used for reading out results of quantum calculations and providing evidences of two-qubit entanglement, especially when the interaction between the two qubits is we

Atsushi Yamashiro, Yukihiro Shimoi, Kikuo Harigaya, Katsunori Wakabayashi

In a nanographene ring with zigzag edges, the spin-polarized state and the charge-polarized state are stabilized by the on-site and the nearest neighbor Coulomb repulsions, U and V, respectively, within the extended Hubbard model under the mean field approximation. In a Moebius strip of the nanographene with a zigzag edge, U stabilizes two magnetic states, t

G. A. Ummarino, A. Calzolari, D. Daghero, R. S. Gonnelli

We present the results of point-contact spectroscopy measurements in polycrystalline RuSr_2GdCu_2O_8 samples previously characterized from both the structural and the electrical point of view. AC susceptibility and resistivity measurements, as well as SEM and optical microscopy, indicate that the polycrystalline material is made up of small, weakly connected