September 1998 arXiv papers

Tom Mehen, Iain W. Stewart

The OS and PDS renormalization schemes for the effective field theory with nucleons and pions are investigated. We explain in detail how the renormalization is implemented using local counterterms. Fits to the NN scattering data are performed in the 1S0 and 3S1 channels for different values of mu_R. An error analysis indicates that the range of the theory wi

P. Coleman

I review our incomplete understanding of non-Fermi liquid behavior in heavy fermion systems at a quantum critical point. General considerations suggest that critical antiferromagnetic fluctuations do not destroy the Fermi surface by scattering the heavy electrons- but by actually breaking up the internal structure of the heavy fermion. I contrast the weak, a

D. Becirevic, Ph. Boucaud, L. Giusti, J. P. Leroy

We present the results for light hadron spectrum, decay constants and the quark masses obtained with non-perturbatively improved Wilson fermions. We also give our preliminary results for the heavy-light decay constants.

Patricio S. Letelier, Samuel R. Oliveira

The static and stationary C-metric are revisited in a generic framework and their interpretations studied in some detail. Specially those with two event horizons, one for the black hole and another for the acceleration. We found that: i) The spacetime of an accelerated static black hole is plagued by either conical singularities or lack of smoothness and com

M. V. Cougo-Pinto, C. Farina, M. R. Negrao, A. C. Tort

We compute the influence of an external magnetic field on the Casimir energy of a massive charged scalar field confined between two parallel infinite plates. For this case the obtained result shows that the magnetic field inhibits the Casimir effect.

B. I. Shklovskii

A simple electrostatic theory of condensation of rod-like polyelectrolytes under influence of polyvalent ions is proposed. It is based on the idea that Manning condensation of ions results in formation of the Wigner crystal on a background of a bundle of rods. It is shown that, depending on a single dimensionless parameter, this can be the densely packed thr

Charles D. Dermer, Kurt E. Mitman

We have developed a computer model to calculate gamma ray burst (GRB) light curves and efficiencies from the interaction of a single, thin blast wave with clouds in the external medium. Large amplitude, spiky variability occurs when the clouds have radii r << R/Gamma, where R is the mean distance of a cloud from the GRB source and Gamma is the blast-wave Lor

Hernan A. Makse

We study segregation of granular mixtures in the continuous avalanche regime (for frequencies above ~ 1 rpm) in thin rotating drums using a continuum theory for surface flows of grains. The theory predicts profiles in agreement with experiments only when we consider a flux dependent velocity of flowing grains. We find the segregation of species of different

A. D. Dolgov, S. H. Hansen, S. Pastor, D. V. Semikoz

The impact of unstable Majorana tau neutrinos on primordial nucleosynthesis is considered. The mass and lifetime of nu_tau are taken in the intervals 0.1-20 MeV and 0.001-400 sec respectively. The studied decay modes are nu_tau -> nu_mu + phi and nu_tau -> nu_e + phi, where phi is a massless (or light) scalar. Integro-differential kinetic equations are solve

Piotr T. Chruściel

We prove non-existence of static, vacuum, appropriately regular, asymptotically flat black hole space-times with degenerate (not necessarily connected) components of the event horizon. This finishes the classification of static, vacuum, asymptotically flat domains of outer communication in an appropriate class of space-times, showing that the domains of oute

Paolo Pasti, Dmitri Sorokin, Mario Tonin

To construct actions for describing superbranes propagating in AdS x S superbackgrounds we propose a coset space realization of these superbackgrounds which results in a short polynomial fermionic dependence (up to the sixth power in Grassmann coordinates) of target superspace supervielbeins and superconnections. Gauge fixing kappa-symmetry in a way compatib

Jose Burillo, Sean Cleary, Melanie Stein

The distance from the origin in the word metric for generalizations F(p) of Thompson&#39;s group F is quasi-isometric to the number of carets in the reduced rooted tree diagrams representing the elements of F(p). This interpretation of the metric is used to prove that every F(p) admits a quasi-isometric embedding into every F(q), and also to study the behavi

Guido Altarelli, Ferruccio Feruglio

We discuss models of neutrino masses that lead to a large mixing angle for atmospheric neutrino oscillations. In particular we study a mechanism where a simple texture for the Dirac matrix leads to the observed pattern of mixings for a continuous range of Majorana matrices in a reasonably natural way. Both nearly maximal and small mixing solutions for solar

E. Elizalde, D. V. Vassilevich

We consider the four dimensional Euclidean Maxwell theory with a Chern-Simons term on the boundary. The corresponding gauge invariant boundary conditions become dependent on tangential derivatives. Taking the four-sphere as a particular example, we calculate explicitly a number of the first heat kernel coefficients and obtain the general formulas that yields

M. Knecht, S. Peris, E. de Rafael

The pi^+ - pi^0 mass difference generated by the electroweak interactions of the Standard Model is expressed, to lowest order in the chiral expansion and to leading order in alpha, in terms of an integral involving the same correlation function Pi_{LR}(Q^2) which governs the well known electromagnetic pi^+ - pi^0 mass difference. We calculate this contributi

Ruediger Scheibl, Ulrich Heinz

Using a density matrix approach to describe the process of coalescence, we calculate the coalescence probabilities and invariant momentum spectra for deuterons and antideuterons. We evaluate our expressions with a hydrodynamically motivated parametrization for the source at freeze-out which implements rapid collective expansion of the collision zone formed i

Anders Irbäck, Carsten Peterson, Frank Potthast, Erik Sandelin

Background: Designing amino acid sequences that are stable in a given target structure amounts to maximizing a conditional probability. A straightforward approach to accomplish this is a nested Monte Carlo where the conformation space is explored over and over again for different fixed sequences, which requires excessive computational demand. Several approxi

James J. Kelly

The sensitivity of momentum distributions, recoil polarization observables, and response functions for nucleon knockout by polarized electrons to channel coupling in final-state interactions is investigated using a model in which both the distorting and the coupling potentials are constructed by folding density-dependent effective interactions with nuclear t

Igor Batalin, Robert Marnelius

Recently it has been shown that antibrackets may be expressed in terms of Poisson brackets and vice versa for commuting functions in the original bracket. Here we also introduce generalized brackets involving higher antibrackets or higher Poisson brackets where the latter are of a new type. We give generating functions for these brackets for functions in arb

Robert J. Nemiroff, J. Bruce Rafert

It is currently feasible to start a continuous digital record of the entire sky sensitive to any visual magnitude brighter than 15 each night. Such a record could be created with a modest array of small telescopes, which collectively generate no more than a few Gigabytes of data daily. Alternatively, a few small telescopes could continually re-point to scan

Igor Batalin, Robert Marnelius

The recently presented quantum antibrackets are generalized to quantum Sp(2)-antibrackets. For the class of commuting operators there are true quantum versions of the classical Sp(2)-antibrackets. For arbitrary operators we have a generalized bracket structure involving higher Sp(2)-antibrackets. It is shown that these quantum antibrackets may be obtained fr

Hans-Juergen Matschull

When two point particles, coupled to three dimensional gravity with a negative cosmological constant, approach each other with a sufficiently large center of mass energy, then a BTZ black hole is created. An explicit solution to the Einstein equations is presented, describing the collapse of two massless particles into a non-rotating black hole. Some general

A. I. Davydychev, A. G. Grozin

The effect of non-zero c quark mass on b quark HQET Lagrangian, up to 1/m_b level, is calculated at two loops. The results are expressed in terms of dilogarithmic functions of m_c/m_b. This calculation involves on-shell two-loop propagator-type diagrams with two different masses, m_b and m_c. A general algorithm for reducing such Feynman integrals to the bas

C. Ford, T. Tok, A. Wipf

We consider Yang-Mills theories with general gauge groups $G$ and twists on the four torus. We find consistent boundary conditions for gauge fields in all instanton sectors. An extended Abelian projection with respect to the Polyakov loop operator is presented, where $A_0$ is independent of time and in the Cartan subalgebra. Fundamental domains for the gauge

Carlos Sopuerta, Roy Maartens, George Ellis, William Lesame

In a cold matter universe, the linearized gravito-magnetic tensor field satisfies a transverse condition (vanishing divergence) when it is purely radiative. We show that in the nonlinear theory, it is no longer possible to maintain the transverse condition, since it leads to a non-terminating chain of integrability conditions. These conditions are highly res

G. Battistoni

In view of the interpretation of data collected by large, deep underground experiments in terms of primary Cosmic Ray physics, this work is focused on the study of the production of of TeV muons in Extensive Air Showers. The review tries to point out those features of hadronic interactions that mostly affect the production of the high energy muons. A few dif

Kunihito Ioka, Takahiro Tanaka, Takashi Nakamura

The intensity of low frequency gravitational waves from black hole MACHO binaries is studied. First we estimate the gravitational wave background produced by black hole MACHO binaries in the Milky Way halo as well as the cosmological gravitational wave background produced by the extragalactic black hole MACHO binaries. It is found that the cosmological gravi

Alain Delgado, Lester Lavin, Roberto Capote, Augusto Gonzalez

A resonance behaviour of the far infrared absorption probability at a frequency \sim N^{1/4} is predicted for clusters of N electron-hole pairs (2\le N\le 110) confined in disk-shaped quantum dots. For radially symmetric dots, the absorption is dominated by a Giant Dipole Resonance, which accounts for more than 98 % of the energy-weighted photoabsorption sum

Bengt Friman, Mannque Rho, Chaejun Song

We discuss the Fermi-liquid properties of hadronic matter derived from a chiral Lagrangian field theory in which Brown-Rho (BR) scaling is incorporated. We identify the BR scaling as a contribution to Landau&#39;s Fermi liquid fixed-point quasiparticle parameter from &#34;heavy&#34; isoscalar meson degrees of freedom that are integrated out from a low-energy

Lubomir Gavrilov

Consider an ordinary differential equation which has a Lax pair representation A&#39;(x)= [A(x),B(x)], where A(x) is a matrix polynomial with a fixed regular leading coefficient and the matrix B(x) depends only onA(x). Such an equation can be considered as a completely integrable complex Hamiltonian system. We show that the generic complex invariant manifold

Michael Fleischhauer, Oliver Veits

We analyze the long-time quantum dynamics of degenerate parametric down-conversion from an initial sub-harmonic vacuum (spontaenous down-conversion). Standard linearization of the Heisenberg equations of motions fails in this case, since it is based on an expansion around an unstable classical solution and neglects pump depletion. Introducing a mean-field ap

Sigmund Kohler, Thomas Dittrich, Peter Hänggi

Using the parametrically driven harmonic oscillator as a working example, we study two different Markovian approaches to the quantum dynamics of a periodically driven system with dissipation. In the simpler approach, the driving enters the master equation for the reduced density operator only in the Hamiltonian term. An improved master equation is achieved b

A. Ambainis, R. Freivalds

We study 1-way quantum finite automata (QFAs). First, we compare them with their classical counterparts. We show that, if an automaton is required to give the correct answer with a large probability (over 0.98), then the power of 1-way QFAs is equal to the power of 1-way reversible automata. However, quantum automata giving the correct answer with smaller pr

Robert Beals, Harry Buhrman, Richard Cleve, Michele Mosca

We examine the number T of queries that a quantum network requires to compute several Boolean functions on {0,1}^N in the black-box model. We show that, in the black-box model, the exponential quantum speed-up obtained for partial functions (i.e. problems involving a promise on the input) by Deutsch and Jozsa and by Simon cannot be obtained for any total fun

R. M. Weiner

Invited talk at the CORR98 meeting on Correlations, Mátraháza, June 1998, to appear in the proceedings of the meeting in World Scientific. This talk is dedicated to the memory of Peter Carruthers.

Richard F. Lebed

Since QCD is believed to be the underlying theory of the strong interaction, it is appropriate to study techniques that take into account more features of its rich and complex structure. We begin by discussing aspects of physics that are ill-reproduced by the usual one- or two-meson exchange approaches and identify the source of the deficiencies of these mod

F. Cardarelli, E. Pace, G. Salme&#39;, S. Simula

The momentum distributions of the constituent quarks inside the nucleon and the prominent electroproduced nucleon resonances are investigated in the two most sophisticated, available quark potential models, based respectively on the assumption of the valence + gluon dominance and on the exchange of the pseudoscalar Goldstone-bosons arising from the spontaneo

Wojciech Satula

Various properties of single-particle Hartree-Fock ground-state solutions in $N\sim Z$ nuclei are investigated. The emphasis is on a role of single-particle mean-field in odd-even mass staggering. It is shown that, unlike in traditional scenario originating from the Fermi gas or macroscopic models, the symmetry energy contribution to odd-even mass staggering

Alain Messager, Bruno Nachtergaele

We review recent results as well as ongoing work and open problems concerning interface states in quantum spin systems at zero and finite temperature.

Kei Inoue, Masanori Ohya, Keiko Sato

Chaos degree defined through two complexities in information dynamics is applied to some deterministic dynamical models. It is shown that this degree well describes the chaostic feature of the models.

Toshiyasu Arai

In this paper we introduce a system AID (Alogtime Inductive Definitions) of bounded arithmetic. The main feature of AID is to allow a form of inductive definitions, which was extracted from Buss&#39; propositional consistency proof of Frege systems F. We show that AID proves the soundness of F, and conversely any Σ^b_0-theorem in AID yields boolean sentences

Rami Atar, Paul Dupuis

This paper considers the problem of rate function identification for multidimensional queueing models with feedback. A set of techniques are introduced which allow this identification when the model possesses certain structural properties. The main tools used are representation formulas for exponential integrals, weak convergence methods, and the regularity

Art M. Duval

\newcommand{\rhomi}[1]{\widetilde{H}_{#1}} \newcommand{\rbeti}[1]{β_{#1}} \newcommand{\kk}{\mathbf k} \newcommand{\dimk}{\dim_{\kk}} We show that algebraically shifting a pair of simplicial complexes weakly increases their relative homology Betti numbers in every dimension. More precisely, let $Δ(K)$ denote the algebraically shifted complex of simplicial com

Katarzyna Pietruska-Paluba

In this paper we identify the domain of the Dirichlet form associated with the Brownian motion on simple nested fractals with an integral Lipschitz space. This result generalizes such an identification on the Sierpiński gasket, carried on by Jonsson.

Philippe Biane

This is an introduction to some of the most probabilistic aspects of free probability theory.

Siye Wu

Consider a holomorphic torus action on a possibly non-compact Kähler manifold. We show that the higher cohomology groups appearing in the geometric quantization of the symplectic quotient are isomorphic to the invariant parts of the corresponding cohomology groups of the original manifold. For non-Abelian group actions on compact Kähler manifolds, this resul

Hirotaka Kikyo

For a theory $T$ in $L, T_σ$ is the theory of the models of $T$ with an automorphism $σ$. If $T$ is an unstable model complete theory without the independence property, then $T_σ$ has no model companion. If $T$ is an unstable model complete theory and $T_σ$ has the amalgamation property, then $T_σ$ has no model companion. If $T$ is model complete and has the

Ehud Hrushovski, Thomas Scanlon

We note here, in answer to a question of Poizat, that the Morley and Lascar ranks need not coincide in differentially closed fields. We approach this through the (perhaps) more fundamental issue of the variation of Morley rank in families.

Anand Pillay, Thomas Scanlon, Frank Wagner

It is proved that any supersimple field has trivial Brauer group, and more generally that any supersimple division ring is commutative. As prerequisites we prove several results about generic types in groups and fields whose theory is simple.

Thomas Scanlon, José Felipe Voloch

The work of Chatzidakis and Hrushovski on the model theory of difference fields in characteristic zero showed that groups defined by difference equations have a very restricted structure. Recent work of Chatzidakis, Hrushovski and Peterzil [CHP] extends the class of difference fields for which this sort of result is known to positive characteristic. In this

E. Mukhin, A. Varchenko

The quantized Knizhnik-Zamolodchikov equation is a difference equation defined in terms of rational $R$ matrices. We describe all singularities of hypergeometric solutions to the qKZ equations.

Denis R. Bell, Salah E. -A. Mohammed

Let $L$ be an infinitely degenerate second-order linear operator defined on a bounded smooth Euclidean domain. Under weaker conditions than those of Hörmander, we show that the Dirichlet problem associated with $L$ has a unique smooth classical solution. The proof uses the Malliavin calculus. At present, there appears to be no proof of this result using clas

Joseph M. Landsberg

This is an expanded and updated version of a lecture series I gave at Seoul National University in September 1997. It is in some sense an update of the 1979 Griffiths and Harris paper with a similar title. I discuss: Homogeneous varieties, Topology and consequences Projective differential invariants, Varieties with degenerate Gauss images, When can a unirule

J. Ginibre, G. Velo

We study the theory of scattering in the energy space for the Hartree equation in space dimension n>2. Using the method of Morawetz and Strauss, we prove in particular asymptotic completeness for radial nonnegative nonincreasing potentials satisfying suitable regularity properties at the origin and suitable decay properties at infinity. The results cover in

M. V. Cougo-Pinto, C. Farina, A. C. Tort

The influence of an external constant uniform magnetic field on the Casimir energy density of a Dirac field under antiperiodic (and periodic) boundary condition is computed by applying Schwinger&#39;s proper time method. The result thus obtained shows that in principle, under suitable conditions, the magnetic field can enhance the fermionic Casimir energy de

A. A. Rodrigues Sobreira, E. R. Bezerra de Mello

We study the classical and quantum motion of a relativistic charged particle on the spacetime produced by a global monopole. The self-potential, which is present in this spacetime, is considered as an external electrostatic potential. We obtain classical orbits and quantum states for a spin-1/2 and spin-0 particles.

Remo Garattini

We use variational methods to calculate quasilocal energy quantum corrections. A comparison with the effective potential calculated at quadratic order is made by means of gaussian wave functionals. The method is a particular case of the effective action for composite operators used in quantum field theory. In pure gravity the method is applied for the first

David Hochberg, Carmen Molina-Paris, Juan Perez-Mercader, Matt Visser

We demonstrate how to extract all the one-loop renormalization group equations for arbitrary quantum field theories from knowledge of an appropriate Seeley--DeWitt coefficient. By formally solving the renormalization group equations to one loop, we renormalization group improve the classical action, and use this to derive the leading-logarithms in the one-lo

Pawel O. Mazur, Andrzej Staruszkiewicz

The term $Θε^{μνρσ}F_{μν}F_{ρσ}$, when added to the electromagnetic Lagrangian $-{1\over 16π}F^{μν}F_{μν}$, does not change the signature of the Lagrangian. Actually, it increases the part with negative kinetic energy term at the spatial infinity. For this reason it does not change the conclusion, that at the spatial infinity the magnetic part of the electro

Robert Bluhm, Alan Kostelecky, Neil Russell

This talk discusses the sensitivity of electron-positron and proton-antiproton Penning-trap experiments to CPT- and Lorentz-violating effects in the context of an extension of the minimal standard model and quantum electrodynamics.

Carl E. Carlson

We review standard applications of perturbative QCD to baryon production, and argue by examining data that it is generally relevant at high but experimentally feasible momentum transfers. Then we consider some new initiatives, particularly meson photoproduction off baryons and the seeming quagmire of Delta(1232) electroproduction.

Liang Zuo-tang

We suggested that longitudinal polarization of Lambda produced in e+e- annihilation at LEP energies can provide useful information on hadronization mechanism in general and on testing the validity of different pictures for the spin content of baryon in describing the fragmentation process in particular. We present the results obtained from the calculations b

Michael Strickland

We present results of numerical solutions of Schwinger-Dyson equations for the finite-temperature quark and electron propagators. It is shown that both strongly coupled QED and QCD undergo a chiral symmetry restoring phase transition as the temperature is increased. We go beyond the bare vertex or &#34;rainbow&#34; approximation by applying the finite-temper

S. Kotkovsky, I. M. Narodetskii, K. A. Ter-Martirosyan, S. Simula

We derive a new parton formula for the inclusive B decays and briefly discuss its applications to semileptonic and weak radiative decays of the B-meson.

Marc Sher

The simplest extension of the standard model involves adding a scalar doublet--the so-called two-Higgs model. In general, the additional scalar will mediate tree-level flavor-changing neutral currents. Although one can arbitrarily impose a discrete symmetry to avoid these, it isn&#39;t necessary to do so; reasonable assumptions about the size of the flavor-c

S. T. Petcov

It is shown that the $\nu_2 \to \nu_{e}$ and $\nu_{\mu} \to \nu_{e}$ ($\nu_e \to \nu_{\mu (\tau)}$) transitions respectively of the solar and atmospheric neutrinos in the Earth in the case of $\nu_e - \nu_{\mu (\tau)}$ mixing in vacuum, are strongly enhanced by a new type of resonance when the neutrinos cross the Earth core. The resonance is operative at sma

P. Colangelo, F. De Fazio, N. Paver

We review several aspects of the phenomenology of P-wave $\bar q Q$ mesons: mass splittings, effective strong couplings and leptonic constants. We also describe a QCD sum rule determination to order $α_s$ of the form factor $τ_{1/2}(y)$ governing the semileptonic $B$ decays to the charm doublet with $J^P=(0^+_{1/2},1^+_{1/2})$.

Sh. Matsumoto, M. Yoshimura

Pair annihilation of heavy stable particles that occurs in the early universe is reconsidered including the off-shell effect not properly taken into account by the conventional Boltzmann equation approach. Our new calculation of the time evolution shows that the off-shell effect prolongs the freeze-out, always with a larger final relic abundance. The final y

R. Aloisio, V. Azcoiti, G. Di Carlo, A. Galante

In the large fermion mass limit of QCD at finite density the structure of the partition function greatly simplifies and can be studied analytically. We show that, contrary to general wisdom, the phase of the Dirac determinant is relevant only at finite temperature and can be neglected for zero temperature fields.

PACS Collaboration, S. Aoki, G. Boyd, R. Burkhalter

We report results on the static quark potential in two-flavor full QCD. The calculation is performed for three values of lattice spacing $a^{-1}\approx 0.9, 1.3$ and 2.5 GeV on $12^3{\times}24, 16^3{\times}32$ and $24^3{\times}48$ lattices respectively, at sea quark masses corresponding to $m_π/m_ρ\approx 0.8-0.6$. An RG-improved gauge action and a tadpole-i

Seyong Kim, Shigemi Ohta

We discuss chiral limit of light hadron mass from our quenched staggered calculations with a high lattice cutoff of (a^{-1})(\sim)3.7 GeV at (β)=6.5 and a large lattice volume of (48^3\times 64). We added six heavier quark mass values of (m_qa)=0.0075, 0.015, 0.02, 0.03, 0.04 and 0.05 to the previously existing 0.01, 0.005, 0.0025, and 0.00125. An interestin

The OPAL Collaboration, G. Abbiendi et al

A search for charginos and neutralinos, predicted by supersymmetric theories, has been performed using a data sample of 57 pb-1 at centre-of-mass energies of 181-184 GeV taken with the OPAL detector at LEP. No evidence for chargino or neutralino production has been found. Upper limits on chargino and neutralino pair production cross-sections are obtained as

H. W. Hamber

Accurate Quantum Gravity calculations, based on the simplicial lattice formulation, are computationally very demanding and require vast amounts of computer resources. A custom-made 64-node parallel supercomputer capable of performing up to $2 \times 10^{10}$ floating point operations per second has been assembled entirely out of commodity components, and has

T. Ootsuka, S. Miyagi, Y. Yasui, S. Zeze

Anti-self-dual (ASD) Maxwell solutions on 4-dimensional hyperkähler manifolds are constructed. The N=2 supersymmetric half-flat equations are derived in the context of the Ashtekar formulation of N=2 supergravity. These equations show that the ASD Maxwell solutions have a direct connection with the solutions of the reduced N=2 supersymmetric ASD Yang-Mills e

Edward D. Fackerell, David Hartley

We review the similarity solutions proposed by Waylen for a regular time-dependent axisymmetric vacuum space-time, and show that the key equation introduced to solve the invariant surface conditions is related by a Baecklund transform to a restriction on the similarity variables. We further show that the vacuum space-times produced via this path automaticall

James A. Hoagland, Raju Pandey, Karl N. Levitt

A security policy states the acceptable actions of an information system, as the actions bear on security. There is a pressing need for organizations to declare their security policies, even informal statements would be better than the current practice. But, formal policy statements are preferable to support (1) reasoning about policies, e.g., for consistenc

Carlos Domingo, Osamu Watanabe, Tadashi Yamazaki

In this paper we introduce a neural network model of self-organization. This model uses a variation of Hebb rule for updating its synaptic weights, and surely converges to the equilibrium status. The key point of the convergence is the update rule that constrains the total synaptic weight and this seems to make the model stable. We investigate the role of th

Carlos Domingo, Ricard Gavalda, Osamu Watanabe

One of the core applications of machine learning to knowledge discovery consists on building a function (a hypothesis) from a given amount of data (for instance a decision tree or a neural network) such that we can use it afterwards to predict new instances of the data. In this paper, we focus on a particular situation where we assume that the hypothesis we

Alexei V. Tkachenko

The theory of nematic-smectic phase transition in the system of uniform semi-flexible chains with hard-core repulsion is presented. Both the general density-functional formalism the tube-model calculation show that the flexibility of the chains results in a strong first-order transition, in contrast to the common weak-cristallization scenario of the nematic-

Amy J. Kolan, Edmund R. Nowak, Alexei V. Tkachenko

We present a theoretical discussion of the reversible parking problem, which appears to be one of the simplest systems exhibiting glassy behavior. The existence of slow relaxation, nontrivial fluctuations, and an annealing effect can all be understood by recognizing that two different time scales are present in the problem. One of these scales corresponds to

C. M. Arizmendi, J. R. Sanchez

Time correlated fluctuations interacting with a spatial asymmetry potential are sufficient conditions to give rise to transport of Brownian particles. The transfer of information coming from the nonequilibrium bath, viewed as a source of negentropy, give rise to the correlated noise. The algorithmic complexity of an object provides a means of quantitating it

Hernan A. Makse, Shlomo Havlin, Peter R. King, H. Eugene Stanley

Granular materials size segregate when exposed to external periodic perturbations such as vibrations. Moreover, mixtures of grains of different sizes spontaneously segregate in the absence of external perturbations: when a mixture is simply poured onto a pile, the large grains are more likely to be found near the base, while the small grains are more likely

Hernan A. Makse, Jose S. Andrade, Michael Batty, Shlomo Havlin

We propose and test a model that describes the morphology of cities, the scaling of the urban perimeter of individual cities, and the area distribution of systems of cities. The model is also consistent with observable urban growth dynamics, our results agreeing both qualitatively and quantitatively with urban data. The resulting growth morphology can be und

Pierre Cizeau, Hernan A. Makse, H. Eugene Stanley

Spontaneous stratification of granular mixtures has been reported by Makse et al. [Nature 386, 379 (1997)] when a mixture of grains differing in size and shape is poured in a quasi-two-dimensional heap. We study this phenomenon using two different approaches. First, we introduce a cellular automaton model that illustrates clearly the physical mechanism; the

Hernan A. Makse, Robin C. Ball, H. Eugene Stanley, Stephen Warr

Spontaneous stratification in granular mixtures has been recently reported by H. A. Makse et al. [Nature 386, 379 (1997)]. Here we study experimentally the dynamical processes leading to spontaneous stratification. Using a high-speed video camera, we study a rapid flow regime where the rolling grains size segregate during the avalanche. We characterize the d

Hernan A. Makse, Jose S. Andrade, H. Eugene Stanley

We analyze the transport properties of a neutral tracer in a carrier fluid flowing through percolation-like porous media with spatial correlations. We model convection in the mass transport process using the velocity field obtained by the numerical solution of the Navier-Stokes and continuity equations in the pore space. We show that the resulting statistica

Hernan A. Makse

We study the segregation of granular mixtures in two-dimensional silos using a set of coupled equations for surface flows of grains. We study the thick flow regime, where the grains are segregated in the rolling phase. We incorporate this dynamical segregation process, called kinematic sieving, free-surface segregation or percolation, into the theoretical fo

Hernan A. Makse, Hans J. Herrmann

We study segregation and stratification of mixtures of grains differing in size, shape and material properties poured in two-dimensional silos using a microscopic lattice model for surface flows of grains. The model incorporates the dissipation of energy in collisions between rolling and static grains and an energy barrier describing the geometrical asperiti

Hernan A. Makse

When a mixture of two kinds of grains differing in size and shape is poured in a vertical two-dimensional cell, the mixture spontaneously stratifies in alternating layers of small and large grains, whenever the large grains are more faceted than the small grains. Otherwise, the mixture spontaneously segregates in different regions of the cell when the large

Thomas Boutreux, Hernan A. Makse, Pierre-Gilles de Gennes

We present the generalization of the minimal model for surface flows of granular mixtures, proposed by Boutreux and de Gennes [J. Phys. I France 6, 1295 (1996)]. The minimal model was valid for grains differing only in their surface properties. The present model also takes into account differences in the size of the grains. We apply the model to study segreg

Hernan A. Makse, Pierre Cizeau, H. Eugene Stanley

We propose a mechanism to explain what occurs when a mixture of grains of different sizes and different shapes (i.e. different repose angles) is poured into a quasi-two-dimensional cell. Specifically, we develop a model that displays spontaneous stratification of the large and small grains in alternating layers. We find that the key requirement for stratific

Luis A. Nunes Amaral, Hernan A. Makse

We comment on a recent Letter by Maunuksela et al. [Phys. Rev. Lett. 79, 1515 (1997)].

Oscar Rodríguez de la Fuente, José M. Soler

Using molecular dynamics simulations, with a realistic many-body embedded-atom potential, and a novel method to characterize local order, we study the structure of pure nickel during the rapid quench of the liquid and in the resulting glass. In contrast with previous simulations with pair potentials, we find more crystalline order and fewer icosahedra for sl

P. Chandra, L. B. Ioffe, D. Sherrington

We present an analytic enumeration of the metastable states, $N_s$, in a periodic long-range Josephson array frustrated by a transverse field. We find that the configurational entropy, $S_{conf} \equiv \ln N_s$, is extensive and scales with frustration, confirming that the non-random system is glassy. We also find that $S_{conf}$ is different from that of it

Wolfgang B. Thimm, Johann Kroha, Jan von Delft

We study the Kondo effect generated by a single magnetic impurity embedded in an ultrasmall metallic grain, to be called a ``Kondo box&#39;&#39;. We find that the Kondo resonance is strongly affected when the mean level spacing in the grain becomes larger than the Kondo temperature, in a way that depends on the parity of the number of electrons on the grain.

J. Z. Sun, D. W. Abraham, R. A. Rao, C. B. Eom

To understand the near-interface magnetism in manganites, uniform, ultra-thin films of La_{0.67}Sr_{0.33}MnO_3 were grown epitaxially on single crystal (001) LaAlO_3 and (110) NdGaO_3 substrates. The temperature and magnetic field dependent film resistance is used to probe the film&#39;s structural and magnetic properties. A surface and/or interface related

Marie-Liesse Doublet, Marie-Bernadette Lepetit

The present work studies the quasi one-dimensional $Ni(dmit)_2$-based compounds within a correlated model. More specifically, we focus our attention on the composed influence of the electronic dimerization-factor and the repulsion, on the transport properties and the localization of the electronic density in the ground-state. Those properties are studied thr

Ubiraci P. C. Neves, J. R. Drugowich de Felicio

We investigate two-dimensional Ising systems with multisping interactions of three- (m=3) and four-body terms (m=4). The application of a new type of finite-size algorithm of de Oliveira allow us to clearly distinguish a first-order transition (in the m=4 case) from a continuous one (in the m=3 one). We also study the damage spreading in these systems. In th

R. A Broglia, G. Tiana, H. E. Roman, E. Vigezzi

The stability of model proteins with designed sequences is assessed in terms of the number of sequences (obtained from the designed sequence through mutations), which fold into 5the ``native&#39;&#39; conformation. By a complete enumeration of the total number of sequences obtained by introducing up to 4 point mutations and up to 7 composition--conserving mu

F. Della Sala, A. Di Carlo, P. Lugli, F. Bernardini

The free-carrier screening of macroscopic polarization fields in wurtzite GaN/InGaN quantum wells lasers is investigated via a self-consistent tight-binding approach. We show that the high carrier concentrations found experimentally in nitride laser structures effectively screen the built-in spontaneous and piezoelectric polarization fields, thus inducing a