January 1999 arXiv papers — page 7

Martin Treiber, Ansgar Hennecke, Dirk Helbing

We derive macroscopic traffic equations from specific gas-kinetic equations, dropping some of the assumptions and approximations made in previous papers. The resulting partial differential equations for the vehicle density and average velocity contain a non-local interaction term which is very favorable for a fast and robust numerical integration, so that se

Martin Treiber, Dirk Helbing

Based on simulations with the ``intelligent driver model'', a microscopic traffic model, we explain the recently discovered transition from free over ``synchronized'' traffic to stop-and-go patterns [B. S. Kerner, Phys. Rev. Lett. 81, 3797 (1998)]. We obtain a nearly quantitative agreement with empirical findings such as the ``pinch effect&#3

Vieri Mastropietro

In the context of the Anderson theory of high T_c cuprates, we develop a BCS theory for Luttinger liquids. If the Luttinger interaction is much stronger than the BCS potential we find that the BCS equation is quite modified compared to usual BCS equation for Fermi liquids. In particular T_c predicted by the BCS equation for Luttinger liquids is quite higher

Roland Faller, Alexander Kolb, Florian Müller-Plathe

Molecular dynamics simulation of a generic polymer model is applied to study melts of polymers with different types of intrinsic stiffness. Important static observables of the single chain such as gyration radius or persistence length are determined. Additionally we investigate the overall static melt structure including pair correlation function, structure

Z. F. Ezawa, K. Sasaki

An improved composite-boson theory of quantum Hall ferromagnets is proposed. It is tightly related with the microscopic wave-function theory. The characteristic feature is that the field operator describes solely the physical degrees of freedom representing the deviation from the ground state. It presents a powerful tool to analyze excited states within the

K. Tsutsui, W. Koshibae, S. Maekawa

We study the optical conductivity in doped nickelates, and find the dramatic difference of the spectrum in the gap ($ω$$\alt$4 eV) between one- (1D) and two-dimensional (2D) nickelates. The difference is shown to be caused by the dependence of hopping integral on dimensionality. The theoretical results explain consistently the experimental data in 1D and 2D

Xi Dai, Bin Chen, Zhao-Bin Su

An effective theory for the hole doped spin-1 antiferromagnetic chain is proposed in this paper. The two branches of low energy quasipaticle excitation is obtained by the diagrammic technique. In the large t limit(in which t is the hole hopping term), the lower band is essentially the bound state of one hole and one magnon and the other band is the sigle hol

M. Eschrig, D. Rainer, J. A. Sauls

We present the theory for the effects of superconducting pairing fluctuations on the nuclear spin-lattice relaxation rate, 1/T_1, and the NMR Knight shift for layered superconductors in high magnetic fields. These results can be used to clarify the origin of the pseudogap in high-T_c cuprates, which has been attributed to spin fluctuations as well as pairing

V. F. Mitrovi{ć}, H. N. Bachman, W. P. Halperin, M. Eschrig

In a recent Letter of Gorny et al. it was reported that the spin-lattice relaxation rate in YBCO_{7-d} is magnetic field independent. These authors point out that their results are inconsistent with prior reports of Borsa et al., Carretta et al., and Mitrovic et al., which concluded that there is a small but significant magnetic field dependence. In this com

V. F. Mitrovi{ć}, H. N. Bachman, W. P. Halperin, M. Eschrig

We report 63Cu(2) spin-lattice relaxation rate measurements of YBa_2Cu_3O_{6.95} in magnetic fields from 2.1 T to 27.3 T obtained from 17O(2,3) nuclear magnetic resonance spin-spin relaxation. For T < 120 K, the spin-lattice rate increases with increasing magnetic field. We identify this magnetic field dependence with the change in the low-energy spectral we

F. Hayot, C. Jayaprakash

We derive from the Navier-Stokes equation an exact equation satisfied by the dissipation rate correlation function. We exploit its mathematical similarity to the corresponding equation derived from the 1-dimensional stochastic Burgers equation to determine the intermittency exponents in terms of the exponents characterizing the behavior of the dynamical velo

H. R. Dullin, J. D. Meiss, D. Sterling

We show that in the neighborhood of the tripling bifurcation of a periodic orbit of a Hamiltonian flow or of a fixed point of an area preserving map, there is generically a bifurcation that creates a ``twistless&#39;&#39; torus. At this bifurcation, the twist, which is the derivative of the rotation number with respect to the action, vanishes. The twistless

Jay A. Frogel, Glenn P. Tiede, Leslie E. Kuchinski

We present a preliminary analysis of K, J-K color magnitude diagrams (CMDs) for 7 different positions on or close to the minor axis of the Milky Way at Galactic latitudes between +0.1^\circ and -2.8^\circ. From the slopes of the (linear) giant branches in these CMDs we derive a dependence of <[Fe/H]> on latitude for b between -0.8^\circ and -2.8^\circ of -0.

R. M. Bandyopadhyay, T. Shahbaz, P. A. Charles, T. Naylor

Using CGS4 on UKIRT, we have obtained 2.00-2.45 micron infrared spectra of a number of low-mass X-ray binaries including Sco X-1, Sco X-2, and GX13+1. Sco X-1 shows emission lines only, supporting our previous conclusion that the spectral type of the evolved secondary must be earlier than G5. Emission lines are also seen in the spectrum of Sco X-2, confirmin

A. Schröder, R. C. Kraan-Korteweg, G. A. Mamon

Roughly 25% of the optical extragalactic sky is obscured by the dust and stars of our Milky Way. Dynamically important structures might still lie hidden in this zone. Various surveys are presently being employed to uncover the galaxy distribution in the Zone of Avoidance (ZOA) but all suffer from (different) limitations and selection effects. We illustrate t

Charles D. Dermer

The kinetic energy of bulk relativistic plasma ejected from the central engine of blazars is converted into nonthermal particle energy in the comoving frame through a process of sweeping up material from the surrounding medium. The resulting deceleration of the bulk plasma introduces a number of effects which must be included in blazar modeling. For example,

R. Carballo, J. I. González-Serrano, C. R. Benn, S. F. Sánchez

UBVR photometry of a sample of B3-VLA radio quasars, about 80 per cent complete, is used to analyse their spectral energy distribution (SED). The SEDs are generally well fitted with power-laws, with an average slope alpha=-0.39 (S_nu propto nu^alpha). Two quasars appear clearly differenciated, exhibiting redder colours that the rest, and they have redshifts

James Annis

An astrophysical model is proposed to answer Fermi&#39;s question. Gamma-ray bursts have the correct rates of occurrence and plausibly the correct energetics to have consequences for the evolution of life on a galactic scale. If one assumes that they are in fact lethal to land based life throughout the galaxy, one has a mechanism that prevents the rise of in

Amancio C. S. Friaca, Roberto J. Terlevich

We investigate the nature of Lyman break galaxies (LBGs) using a chemodynamical model for evolution of galaxies. Our models predict an early (the first Gyr) stage of intense star formation in the evolution of massive spheroids which could be identified to the LBGs, observed at redshift $\sim 3$ with strong ongoing star formation. In particular, we are succes

P. A. Shaver, R. A. Windhorst, P. Madau, A. G. de Bruyn

The reionization of the Universe is expected to leave a signal in the form of a sharp step in the spectrum of the sky. If reionization occurs at 5 < z < 20, a feature should appear in the radio sky at 70 - 240 MHz due to redshifted HI 21-cm line emission, accompanied by another feature in the optical/near-IR at 0.7 - 2.6 micron due to hydrogen recombination

Leo Girardi

Based on the results of detailed population synthesis models, it was recently claimed that the clump of red giants in the colour-magnitude diagram (CMD) of composite stellar populations should present an extension to lower luminosities, which goes down to about 0.4 mag below the main clump. This feature is made of stars just massive enough for having ignited

A. D. Dolgov

A possibility that the universe may be strongly inhomogeneous chemically, while very smooth energetically, is considered. A possible mechanism which could lead to such a picture is a large and inhomogeneous lepton asymmetry. The model may explain possibly observed variation of primordial deuterium by an order of magnitude and predicts helium-rich and possibl

B. Stelzer, R. Neuhaeuser, S. Casanova, T. Montmerle

We present evidence for rotational modulation of X-ray flares by an analysis of four outbursts on late-type stars. Three of these flares have been observed on T Tauri Stars and one on Algol. The structure of the X-ray lightcurves observed in this selection of flare events is untypical in that the maximum emission extends over several hours producing a round

Glennys R. Farrar, Peter L. Biermann

We discuss the rationale for the energy cuts used in the previous study of directional correlation of the five highest energy cosmic ray events with compact, radio quasars. We check the consistency of the next three most energetic events which just missed those cuts, with the correlation hypothesis. Agreement between expected and observed properties of these

Motokazu Takizawa

We investigate the evolution of intracluster medium during a cluster merger, explicitly considering the relaxation process between the ions and electrons by N-body and hydrodynamical simulations. When two subclusters collide each other, a bow shock is formed between the centers of two substructures and propagate in both directions along the collision axis. T

Jeremy Kepner, Todd Tripp, Tom Abel, David Spergel

Recent observations and theoretical calculations suggest that some QSO absorption line systems may be due to gas in small dark matter halos with circular velocities on the order of 30 km/s. Additional observational evidence suggests that, in general, many absorption line systems may also be multi-phase in nature. Thus, computing the absorption lines of mini-

Travis S. Metcalfe

I have developed a procedure utilizing a Genetic-Algorithm-based optimization scheme to fit the observed light curves of an eclipsing binary star with a model produced by the Wilson-Devinney code. The principal advantages of this approach are the global search capability and the objectivity of the final result. Although this method can be more efficient than

Kevin E. Bassler, Maya Paczuski, George F. Reiter

Magnetic vortices intermittently flow through preferred channels when they are forced in or out of a superconductor. We study this behavior using a cellular model, and find that the vortex flow can make braided rivers strikingly similar to aerial photographs of braided fluvial rivers, such as the Brahmaputra. By developing an analysis technique suitable for

I. R. Klebanov, A. A. Tseytlin

We show that type 0B theory has a classical AdS_5 x S^5 solution and argue that it is stable at the string-theory level for small enough radius. The dual 4-d conformal field theory is the infrared limit of the theory on N electric D3-branes coincident with N magnetic D3-branes. We explicitly construct this SU(N) x SU(N) gauge theory with global SO(6) symmetr

S. Ettori, A. C. Fabian

We present a detailed and homogeneous analysis of the ROSAT PSPC surface brightness profiles of 36 clusters of galaxies with high X-ray luminosity (L_X > 10^{45} erg s^{-1}) and redshifts between 0.05 and 0.44. Using recent ASCA estimates of the temperature of the gas for most of the clusters in the sample, we apply both the deprojection technique and model

Robert H. Kraichnan

A putative powerlaw range of the probability density of velocity gradient in high-Reynolds-number forced Burgers turbulence is studied. In the absence of information about shock locations, elementary conservation and stationarity relations imply that the exponent $-α$ in this range satisfies $α\ge3$, if dissipation within the powerlaw range is due to isolate

B. Iványi, Z. Schram, K. Sailer, G. Soff

In this paper the Dynamical String Model is applied to the numerical simulation of the ultrarelativistic heavy-ion collision S(200 GeV/n)+S. The results are in qualitative agreement with experimental data.

B. Kleihaus

The regularity of static axially symmetric solutions in SU(2) Yang-Mills-dilaton theory is examined. We show that the solutions obtained previously within a singular Ansatz for the non-abelian gauge field can be gauge transformed into a regular form. The local form of the gauge transformation is given on the singular axis and at the origin.

Renata Kallosh

The main focus of this lecture is on extended objects in adS*S bosonic backgrounds with unbroken supersymmetry. The backgrounds are argued to be exact, special consideration are given to the non-maximal supersymmetry case. The near horizon superspace construction is explained. The superconformal symmetry appears in the worldvolume actions as the superisometr

I. Bigi

The narrative of these lectures contains three main threads: (i) CP violation despite having so far been observed only in the decays of neutral kaons has been recognized as a phenomenon of truly fundamental importance. The KM ansatz constitutes the minimal implementation of CP violation: without requiring unknown degrees of freedom it can reproduce the known

Ivan Horvath

Important recent discoveries suggest that Ginsparg-Wilson-Luscher (GWL) symmetry has analogous dynamical consequences for the theory on the lattice as chiral symmetry does in the continuum. While it is well known that inherent property of lattice chiral symmetry is fermion doubling, we show here that inherent property of GWL symmetry is that the infinitesima

Walter D. Neumann

We show that many 3-manifold groups have no nonabelian surface subgroups. For example, any link of an isolated complex surface singularity has this property. In fact, we determine the exact class of closed graph-manifolds which have no immersed pi_1-injective surface of negative Euler characteristic. We also determine the class of closed graph manifolds whic

R. Roussev, A. J. Millis

We show that recent resistivity data on SrRuO_3 for T->T_c are consistent with conventional theory when corrections to scaling are included and a small shift in T_c is allowed.

Aashish A. Clerk, Vinay Ambegaokar, Selman Hershfield

We examine the properties of an infinite-$U$ Anderson impurity coupled to both normal and superconducting metals. Both the cases of a quantum dot and a quantum point contact containing an impurity are considered; for the latter, we study both one and two-channel impurities. Using a generalization of the noncrossing approximation which incorporates multiple A

R. Beals, D. H. Sattinger, J. Szmigielski

The acoustic scattering operator on the real line is mapped to a Schrödinger operator under the Liouville transformation. The potentials in the image are characterized precisely in terms of their scattering data, and the inverse transformation is obtained as a simple, linear quadrature. An existence theorem for the associated Harry Dym flows is proved, using

G. F. Bonini, A. G. Cohen, C. Rebbi, V. A. Rubakov

We adapt the semiclassical technique, as used in the context of instanton transitions in quantum field theory, to the description of tunneling transmissions at finite energies through potential barriers by complex quantum mechanical systems. Even for systems initially in their ground state, not generally describable in semiclassical terms, the transmission p

Rudolf Friedrich, Joachim Peinke, Christoph Renner

It is shown that prize changes of the US dollar - German Mark exchange rates upon different delay times can be regarded as a stochastic Marcovian process. Furthermore we show that from the empirical data the Kramers-Moyal coefficients can be estimated. Finally, we present an explicite Fokker-Planck equation which models very precisely the empirical probabili

Gunn A. Quznetsov

All fermions and all interactions between fermions are expressed by the Cayley numbers in our space-time. PACS 02.50.Cw 04.20.Cz 11.10.Kk 12.10.Dm

Gunn A. Quznetsov

The probability behavior in the m+1 relativistic space-time is considered. The probability, which is defined by the relativistic m+1-vector of the probability density, is investigated.

F. Klingl, W. Weise

We discuss QCD sum rule constraints based on moments of vector meson spectral distributions in the vacuum and in a nuclear medium. Sum rules for the two lowest moments of these spectral distributions do not suffer from uncertainties related to QCD condensates of dimension higher than four. We exemplify these relations for the case of the omega meson and disc

William Browder, Jonathan Pakianathan

Studies among other things, the question of whether a Lie algebra over Z/(p^k)Z lifts to one over Z/(p^(k+1))Z. An obstruction theory is developed and examples of Fp-Lie algebras which don&#39;t lift to Lie algebras over Z/p^2Z are discussed. An example of an application of the result: A Fp-Lie algebra L with H^3(L, ad)=0 will lift to a p-adic Lie algebra.

William Browder, Jonathan Pakianathan

Studies the cohomology of p-central, powerful, p-groups with a certain extension property. These groups are naturally associated to Lie algebras. The paper develops a machinery that calculates the first few terms of the Bockstein spectral sequence in terms of the associated Lie algebras. This is then used to obtain results on the integral cohomology of these

Jonathan Pakianathan

Provides a counterexample to a long standing conjecture of A. Adem regarding the behaviour of the integral cohomology of a p-group.

Maciej Zworski

We consider scattering by an abstract compactly supported perturbation in R^n. To include the traditional cases of potential, obstacle and metric scattering without going into their particular nature we adopt the &#34;black box&#34; formalism developed jointly with Sjostrand [23]. It is quite likely that one could extend the results presented here to the cas

Youliang Tian, Weiping Zhang

We extend our earlier work in [TZ1], where an analytic approach to the Guillemin-Sternberg conjecture [GS] was developed, to cases where the Spin^c-complex under consideration is allowed to be further twisted by certain exterior power bundles of the cotangent bundle. The main result is a weighted quantization formula in the presence of commuting Hamiltonian

Amnon Neeman

This is the fourth installment of a series. The main point of the entire series is the following: given a triangulated category T, it is possible to attach to it a K-theory space.

Allan L. Edelson

This paper is concerned with the structure of the solutions to subcritical elliptic equations related to the Matukuma equation. In certain cases the complete structure of the solution set is known, and is comparable to that of the original Matukuma equation. Here we derive sufficient conditions for a more complicated solution set consisting of; (i) crossing

Robert H. Gilman, Derek F. Holt, Sarah Rees

A combing is a set of normal forms for a finitely generated group. This article investigates the language-theoretic and geometric properties of combings for nilpotent and polycyclic groups. It is shown that a finitely generated class 2 nilpotent group with cyclic commutator subgroup is real-time combable, as are also all 2 or 3-generated class 2 nilpotent gr

Ursula Gritsch

We prove that the space of gauge equivalence classes of U(1)-invariant connections on some SU(2)-principle bundles over the 4-sphere S^4 is weakly homotopy equivalent to a component of the second loop space of the 2-sphere S^2.

Chuu-Lian Terng, Karen Uhlenbeck

The geometric non-linear Schrodinger equation (GNLS) on the complex Grassmannian manifold M is the Hamiltonian equation for the energy functional on C(R,M) with respect to the symplectic form induced from the Kahler form on M. It has a Lax pair that is gauge equivalent to the Lax pair of the matrix non-linear Schrodinger equation (MNLS). We construct via gau

Sergey Yuzvinsky

In the paper we compute the ring strucure on the rational cohomology of a complex subspace complement. For that we construct a small differential graded subalgebra of the De Concini-Procesi wonderful model that is quasi isomorphic to this model. For two classes of arrangements explicit presentation of the ring is given.

Hitoshi Nishino

Starting with the ordinary ten-dimensional supersymmetric Yang-Mills theory for the gauge group U(N), we obtain a twelve-dimensional supersymmetric gauge theory as the large N limit. The two symplectic canonical coordinates parametrizing the unitary N X N matrices for U(N) are identified with the extra coordinates in twelve dimensions in the $N\to\infty$ lim

T. E. Clark, S. T. Love

The effects of extra space-time dimensions on the Wilsonian effective Kähler potential and the perturbative one loop effective Kähler potential are determined within the framework of an Abelian gauge theory with N=2 supersymmetric field content. The relation between the Kähler metric and the effective gauge couplings which leads to the absence of radiative c

Bugra Borasoy, Dean Lee

We introduce the spherical field formalism for free gauge fields. We discuss the structure of the spherical Hamiltonian for both general covariant gauge and radial gauge and point out several new features not present in the scalar field case. We then use the evolution equations to compute gauge-field and field-strength correlators.

G. K. Leontaris, J. Rizos

In the context of the free-fermionic formulation of the heterotic superstring, we construct a three generation N=1 supersymmetric SU(4)xSU(2)LxSU(2)R model supplemented by an SU(8) hidden gauge symmetry and five Abelian factors. The symmetry breaking to the standard model is achieved using vacuum expectation values of a Higgs pair in (4bar,2R)+(4,2R) at a hi

E. R. Berger, A. Donnachie, H. G. Dosch, W. Kilian

We investigate the reaction $e p \to e PS X$ where PS denotes a pseudoscalar meson $π^0, η, η&#39;$, or $η_c$ and X either a proton or resonance or continuum states into which the proton can go by diffractive excitation. At high energies photon and odderon exchange contribute to the reaction. The photon exchange contribution is evaluated exactly using data f

D. Kharzeev, H. Satz, A. Syamtomov, G. Zinovjev

Using short distance QCD methods based on the operator product expansion, we calculate the $J/ψ$ photoproduction cross section in terms of the gluon distribution function of the nucleon. Comparing the result with data, we show that experimental behaviour of the cross section correctly reflects the $x$-dependence of the gluon distribution obtained from deep i

J. L. Goity, R. Lewis, M. Schvellinger, L. Zhang

The Goldberger-Treiman discrepancy in SU(3) is analyzed in the framework of heavy baryon chiral perturbation theory (HBChPT). It is shown that the discrepancy at leading order is entirely given by counterterms from the order p^3 Lagrangian, and that the first subleading corrections are suppressed by two powers in the HBChPT expansion. These subleading correc

M. J. Ramsey-Musolf

I review the new physics sensitivity of low-energy parity-violating (PV) observables. I concentrate on signatures of new tree-level physics in atomic PV with a single isotope, ratios of atomic PV observables, and PV electron scattering. In addition to comparing the new physics sensitivities of these observables with those of high-energy colliders, I also dis

J. O. Eeg, K. Kumericki, I. Picek

We report on the calculation of the two-loop electroweak, two-photon mediated short-distance dispersive K_L \to μ^+μ^- decay amplitude. QCD corrections change the sign of this contribution and reduce it by an order of magnitude. The resulting amplitude enables us to provide a constraint on the otherwise uncertain long-distance dispersive amplitude.

E. Huguet, P. Peter

Bound states in monopoles are studied through a simplified, Witten-like model. As the overall structure is determined in full details, it is shown in particular that only those states having a vanishing angular momentum are allowed; for those, the energy spectrum is derived numerically and an approximation is set up that allows an easy description in terms o

Chao-Shang Huang, Xiao-Hong Wu, Shou-Hua Zhu

The flavor changing neutral current tcV (V=γ,Z) couplings in the production vertex for the process $e^+e^-\to t\bar c$ or $\bar t c$ in the standard model are investigated. The precise calculations keeping all quark masses non-zero are carried out. The total production cross section is found to be $1.84 \times 10^{-9}$ fb at $\sqrt s =200 GeV$ and $0.572 \ti

S. Y. Choi, J. S. Shim, H. S. Song, J. Song

We provide a detailed investigation of single-photon production processes in $e^+e^-$ collisions with missing momenta carried by neutrinos or neutralinos. The transition amplitudes for both processes can be organized into a generic simplified, factorized form; each neutral V$\pm$A vector current of missing energy carriers is factorized out and all the charac

Chong-shou Gao

Based on the general analysis of branching ratio of two pseudoscalar meson channels, discriminants between mesons and glueballs for $I=0, J^{PC}=even^{++}$ unflavored hadrons with mass between 1.2 GeV and 2.9 GeV are suggested. Known $I=0, J^{PC}=2^{++}, f_2(1525)$ particle is discriminated as a typical meson. The way to discriminate new $I=0, J^{PC}=even^{+

Howard E. Haber

The upper bound on the mass of the light CP-even Higgs boson of the minimal supersymmetric model (MSSM) depends on the supersymmetric particle spectrum via radiative loop effects. At present, complete one-loop results and partial two-loop results are known. Some simple analytic approximations have been obtained which are quite accurate over a large portion o

Ichio Fukui, Noriaki Setoh

The eigenvalue problem for the p-wave bound states formed by two unequal-mass scalar particles through the massive scalar particle exchange is analyzed numerically in the framework of the Bethe-Salpeter ladder model. As in the s-wave case, the eigenvalues of the coupling constant are found to become complex for some mass configurations in some range of the b

M. G. Schmidt

After some introductory remarks about the prospects of first order phase transitions in the early universe, we discuss in some detail the electroweak phase transition. In the standard model case a clear picture is arising including perturbative and nonperturbative effects. Since in this case the phase transition is not strongly first order as needed for bary

Yeong Gyun Kim, P. Ko, Jae Sik Lee

We consider possible new physics contributions to b\to s l^+ l^- assuming the new physics modifies (chromo)magnetic and electric form factors in b\to s γ^* and b\to s g with the same chirality structure as in the standard model. Parametrizing the new physics effects on b\to s γ^* and b\to s g in terms of four real parameters, one finds that there are enough

Robert G. Edwards, Urs M. Heller, Rajamani Narayanan

We investigate the approach to the continuum limit of the spectrum of the Hermitian Wilson-Dirac operator in the supercritical mass region for pure gauge SU(2) and SU(3) backgrounds. For this we study the spectral flow of the Hermitian Wilson-Dirac operator in the range $0\le m\le 2$. We find that the spectrum has a gap for $0 < m \le m_1$ and that the spect

ALEPH Collaboration, R. Barate

A study of events with photons and missing energy has been performed with the data sample obtained with the ALEPH detector at centre-of-mass energies from 161 to 184 GeV,corresponding to a total integrated luminosity of about 80 pb**-1. The measured distributions are in agreement with Standard Model predictions, leading to constraints on W W gamma gauge coup

H. Nikolic

In a nongeometrical interpretation of gravity, the metric $g_{μν}(x)=η_{μν}+Φ_{μν}(x)$ is interpreted as an {\em effective} metric, whereas $Φ_{μν}(x)$ is interpreted as a fundamental gravitational field, propagated in spacetime which is actually flat. Some advantages and disadvantages of such an interpretation are discussed. The main advantage is a natural

S. Yu. Ezhov, V. I. Anisimov, D. I. Khomskii, G. A. Sawatzky

We present the results of an LDA and LDA+U band structure study of the monoclinic and the corundum phases of V2O3 and argue that the most prominent (spin 1/2) models used to describe the semiconductor metal transition are not valid. Contrary to the generally accepted assumptions we find that the large on site Coulomb and exchange interactions result in a tot

Peter D. Olmsted

The past few years have seen many advances in our understanding of the dynamics of polymeric fluids. These include improvements on the successful reptation theory; an emerging molecular theory of semiflexible chain dynamics; and an understanding of how to calculate and classify ``phase diagrams&#39;&#39; for flow-induced transitions. Experimentalists have be

Peter D. Olmsted, C-Y David Lu

We present some results of recent calculations of rigid rod-like particles in shear flow, based on the Doi model. This is an ideal model system for exhibiting the generic behavior of shear-thinning fluids (polymer solutions, wormlike micelles, surfactant solutions, liquid crystals) in shear flow. We present calculations of phase coexistence under shear among

R. Baviera, M. Pasquini, M. Serva, D. Vergni

A quantitative check of weak efficiency in US dollar/German mark exchange rates is developed using high frequency data. We show the existence of long term return anomalies. We introduce a technique to measure the available information and show it can be profitable following a particular trading rule.

A. Yu. Cherny, A. A. Shanenko

As is known, the 1/q^2 theorem of Bogoliubov asserts that the mean density of the fermion pair states with the total momentum q obeys the inequality n_q > C/q^2 (q \to 0) in the case of the Fermi system taken at nonzero temperature and in the superconducting state provided the interaction term of its Hamiltonian is locally gauge invariant. With the principle

H. K. Janssen, O. Stenull, K. Oerding

We present a new view of Feynman diagrams for the field theory of transport on percolation clusters. The diagrams for random resistor networks are interpreted as being resistor networks themselves. This simplifies the field theory considerably as we demonstrate by calculating the fractal dimension $D_B$ of the percolation backbone to three loop order. Using

Osame Kinouchi, Carmen P. C. do Prado

A random neighbor extremal stick-slip model is introduced. In the thermodynamic limit, the distribution of states has a simple analytical form and the mean avalanche size, as a function of the coupling parameter, is exactly calculable. The system is critical only at a special point Jc in the coupling parameter space. However, the critical region around this

J. Osma, I. Sarria, E. V. Chulkov, J. M. Pitarke

The role of the intrinsic surface state ($n=0$) in the decay of the first image state ($n=1$) at the (111) surface of copper is investigated. Inelastic linewidths are evaluated from the knowledge of the imaginary part of the electron self-energy, which we compute, within the GW approximation of many-body theory, by going beyond a free-electron description of

A. E. Feiguin, Liliana Arrachea, A. A. Aligia

We consider the Kondo-Hubbard model with ferromagnetic exchange coupling $% J_{H}$, showing that it is an approximate effective model for late transition metal-O linear systems. We study the dependence of the charge and spin gaps $Δ_{C}$, $Δ_{S}$, and several spin-spin correlation functions, including the hidden order parameter $Z(π)$, as functions of $J_{H}

S. E. Barnes

Unlike that of SO(3) or SU(2), the Lie algebra for SO(2), which defines intermediate spin, comprises only $S_{z}$ and implies $S^{\pm}$ commute. In general, $S_{z}$ has a continuous spectrum. This intermediate spin scheme can realized for the low energy excitations of a wide class of large spin magnets. A magnetic field provides the necessary time reversal s

Sergey V. Kuplevakhsky

For the first time, we obtain the complete and exact analytical solution of the Lawrence-Doniach model for layered superconductors in external parallel magnetic fields. By solving a nontrivial mathematical problem of exact minimization of the free-energy functional, we derive a closed, self-consistent system of mean-field equations involving only two variabl

M. J. E. Richardson, John Cardy

The single-species reaction-diffusion process $A+A\to O$ is examined in the presence of an uncorrelated, quenched random velocity field. Utilising a field-theoretic approach, we find that in two dimensions and below the density decay is altered from the case of purely diffusing reactants. In two-dimensions the density amplitude is reduced in the presence of

A. Negadi, A. Sans-Penninckx, M. Bemouna, T. A. Vilgis

Theoretical aspects of polymers in mixed solvents are considered using the Edwards Hamiltonian formalism. Thermodynamic and structural properties are investigated and some predictions are made when the mixed solvent approaches criticality. Both the single and the many chain problems are examined. When the pure mixed solvent is near criticality, addition of a

Michele Vendruscolo, Eytan Domany

We present the development of the idea to use dynamics in the space of contact maps as a computational approach to the protein folding problem. We first introduce two important technical ingredients, the reconstruction of a three dimensional conformation from a contact map and the Monte Carlo dynamics in contact map space. We then discuss two approximations

M. A. Korotin, I. S. Elfimov, V. I. Anisimov, M. Troyer

We have performed ab-initio calculations of exchange couplings in the layered vanadates CaV2O5, MgV2O5, CaV3O7 and CaV4O9. The uniform susceptibility of the Heisenberg model with these exchange couplings is then calculated by quantum Monte Carlo method; it agrees well with the experimental measurements. Based on our results we naturally explain the unusual m

V. I. Yukalov

A model of a ferromagnet is considered, in which there arise mesoscopic fluctuations of paramagnetic phase. The presence of these fluctuations diminishes the magnetization of the ferromagnet, softens the spin-wave spectrum, increases the spin-wave attenuation, shortens the magnon free path, lowers the critical point, and can change the order of phase transit

Magnus Rattray, David Saad

Natural gradient descent is a principled method for adapting the parameters of a statistical model on-line using an underlying Riemannian parameter space to redefine the direction of steepest descent. The algorithm is examined via methods of statistical physics which accurately characterize both transient and asymptotic behavior. A solution of the learning d

M. Kubota, H. Fujioka, K. Ohoyama, K. Hirota

Systematic powder diffraction studies have been carried out to establish the magnetic phase diagram of La_{2-2x}Sr_{1+2x}Mn_2O_7 (LSMO327) in a wide hall concentration range ($0.30 \leq x \leq 0.50$), using the HERMES diffractometer. LSMO327 exhibits a planar ferromagnetic structure for $0.32\leq x\leq 0.38$ at low temperatures. A finite canting angle betwee

Seung-Pyo Hong, Choong-Seok Kim, Sung-Sik Lee, Sung-Ho Suck Salk

Using an exact diagonalization treatment of Ising and Heisenberg model Hamiltonians, we study field-induced phase transition for two-dimensional antiferromagnets. For the system of Ising antiferromagnet the predicted field-induced phase transition is of first order, while for the system of Heisenberg antiferromagnet it is the second-order transition. We find

Ranjan Chaudhury, Samir K. Paul

The possibility of existence of topological excitations in the anisotropic quantum Heisenberg model in one and two spatial dimensions is studied using coherent state method. It is found that a part of the Wess-Zumino term contributes to the partition function, as a topological term for ferromagnets in the long wavelength limit in both one and two dimensions.

Irene D&#39;Amico, Giovanni Vignale

We make use of continuum elasticity theory to investigate the collective modes that propagate along the edge of a two-dimensional electron liquid or crystal in a magnetic field. An exact solution of the equations of motion is obtained with the following simplifying assumptions: (i) The system is {\it macroscopically} homogeneous and isotropic in the half-pla

J. Delour, A. Kudrolli, J. P. Gollub

This paper has been withdrawn by the authors. It has been superceded by an improved investigation: &#34;Velocity statistics in vibrated granular media&#34; W. Losert, D.G.W. Cooper, J. Delour, A. Kudrolli, and J.P. Gollub (submitted to Chaos for a special issue on Granular Materials) cond-mat/9901203

Andrei Goryachev, Raymond Kapral

The structure of spiral waves is investigated in super-excitable reaction-diffusion systems where the local dynamics exhibits multi-looped phase space trajectories. It is shown that such systems support stable spiral waves with broken symmetry and complex temporal dynamics. The main structural features of such waves, synchronization defect lines, are demonst

James Liebert

The blue star reported in the field of the young LMC cluster NGC1818 by Elson et al. (1998) has the wrong luminosity and radius to be a &#34;luminous white dwarf&#34; member of the cluster. In addition, unless the effective temperature quoted by the authors is a drastic underestimate, the luminosity is much too low for it to be a cluster member in the post-A