May 1999 arXiv papers — page 7

Koji Hashimoto

We investigate various properties of classical configurations of the Born-Infeld theory in a uniform electric field. This system is involved with dynamics of (F,Dp) bound states, which are bound states of fundamental strings and Dp-branes. The uniform electric field can be treated as a constraint on the asymptotic behavior of the fields on the brane. BPS con

E. I. Chiang, M. E. Brown

We present the results of a pencil-beam survey of the Kuiper Belt using the Keck 10-m telescope. A single 0.01 square degree field is imaged 29 times for a total integration time of 4.8 hr. Combining exposures in software allows the detection of Kuiper Belt Objects (KBOs) having visual magnitude V < 27.9. Two new KBOs are discovered. One object having V = 25

Tycho Sleator, Paul R. Berman, Boris Dubetsky

We propose a set of experiments in which Ramsey-fringe techniques are tailored to probe transitions originating and terminating on the same ground state level. When pulses of resonant radiation, separated by a time delay $% T, $ interact with atoms, it is possible to produce Ramsey fringes having widths of order 1/T. If each pulse contains two counterpropaga

H. B. Nersisyan, S. S. Elbakian

The excitation of wake waves by a relativistic homogeneous electron bunch passing through cold magnetized plasma at equilibrium is studied for arbitrary values of the ratio of bunch density to plasma density. The analysis is based on the assumption that the magnetic field is sufficiently strong ($ω_B\gg ω_p$, where $ω_p$ and $ω_B$ are the electron plasma and

Elena A. Ostrovskaya, Yuri S. Kivshar, Dmitry V. Skryabin, William J. Firth

We demonstrate that, in contrast with what was previously believed, multi-hump solitary waves can be stable. By means of linear stability analysis and numerical simulations, we investigate the stability of two- and three-hump solitary waves governed by incoherent beam interaction in a saturable medium, providing a theoretical background for the experimental

S. Y. Panitkin

In this paper we present the preliminary results of the first study of the proton correlation function&#39;s dependence on the orientation of the reaction plane.

Haim Judah, Andrzej Roslanowski

We describe a method of building ``nice&#39;&#39; sigma-ideals from Souslin ccc forcing notions. [These notes were written down in 1992, but were not submitted to any journal. In a slightly modified form, they were incorporated to: T. Bartoszynski and H. Judah, Set Theory: on the structure of the real line, A K Peters, Wellesley, MA, 1995; pages 193-203.]

Steve Clark, Fritz Gesztesy, Helge Holden, Boris M. Levitan

A Borg-type uniqueness theorem for matrix-valued Schrödinger operators is proved. More precisely, assuming a reflectionless potential matrix and spectrum a half-line $[0,\infty)$, we derive triviality of the potential matrix. Our approach is based on trace formulas and matrix-valued Herglotz representation theorems. As a by-product of our techniques, we obta

Valery Alexeev

A short note that contains some Cliff&#39;s notes of the general theory (see math.AG/9905103) but concentrates on one of the stranger aspects of it - existence of other irreducible components.

Ola Bratteli, Akitaka Kishimoto

We prove that the automorphism group of a Cuntz algebra of finite order acts transitively on the set of pure states which are invariant under some gauge actions (which may depend on the states). The question of whether any pure state is invariant under some gauge action is left open, but for the senigroups of unital endomorphisms stronger transitivity proper

Mans Henningson, Kostas Skenderis

We consider a free two-form in six dimensions and calculate the conformal anomaly associated with a Wilson surface observable.

C. N. Pope, A. Sadrzadeh, S. R. Scuro

The usual T-duality that relates the type IIA and IIB theories compactified on circles of inversely-related radii does not operate if the dimensional reduction is performed on the time direction rather than a spatial one. This observation led to the recent proposal that there might exist two further ten-dimensional theories, namely type IIA^* and type IIB^*,

S. Jadach, B. F. L. Ward, Z. Was

We present a simple and flexible method of keeping track of the complex phases and spin quantization axes for half-spin initial- and final-state Weyl spinors in scattering amplitudes of Standard Model high energy physics processes. Both cases of massless and massive spinors are discussed. The method is demonstrated and checked numerically for spin correlatio

S. I. Polityko

It is shown that by realizing the project of intensive $γ$ beams with large energy (project PLC) an essential flux of light Goldstone particles (axions, arions, familons, majorons) will be generated. The light higgs can be observed via interaction with matter. The probability of light higgs - electron production by absorption of several laser photons simulta

G. Lazarides

Two moderate extensions of the minimal supersymmetric standard model are considered. The first one includes a U(1)_{B-L} gauge group, while the second is based on a left-right symmetric gauge group. In these models, hybrid inflation is `naturally&#39; realized and the mu problem is solved via a Peccei-Quinn symmetry. Baryon number conservation is an automati

E. Frlez, I. Supek, K. A. Assamagan, Ch. Br&#34;onnimann

Scintillation properties of pure CsI crystals used in the shower calorimeter being built for precise determination of the pi+ -> pi0 e+ nu decay rate are reported. Seventy-four individual crystals, polished and wrapped in Teflon foil, were examined in a multiwire drift chamber system specially designed for transmission cosmic muon tomography. Critical elemen

Masako Iwasaki, representing the SLD Collaboration

We present measurements of $Z^0$ to heavy-quark coupling electroweak parameters, $R_b$, $R_c$, and parity-violation parameter $A_c$, from SLD. The measurements are based on approximately 550k hadronic $Z^0$ events collected in 1993-98. Obtained preliminary results of $R_b$ and $R_c$ measurements are $R_b = 0.2159 \pm 0.0014 \pm 0.0014$ and $R_c = 0.1685 \pm

A. N. Petrov, J. Katz

Backgrounds are pervasive in almost every application of general relativity. Here we consider the Lagrangian formulation of general relativity for large perturbations with respect to a curved background spacetime. We show that Noether&#39;s theorem combined with Belinfante&#39;s &#34;symmetrization&#34; method applied to the group of displacements provide a

Rainer W. Kühne, Ute Löw

We performed a finite-temperature quantum Monte Carlo simulation of the one-dimensional spin-1/2 Heisenberg model with nearest-neighbor interaction coupled to Einstein phonons. Our method allows to treat easily up to 100 phonons per site and the results presented are practically free from truncation errors. We studied in detail the magnetic susceptibility, t

A. Milchev, J. P. Wittmer, D. P. Landau

We use an off-lattice microscopic model for solutions of equilibrium polymers (EP) in a lamellar shear flow generated by means of a self-consistent external field between parallel hard walls. The individual conformations of the chains are found to elongate in flow direction and shrink perpendicular to it while the average polymer length decreases with increa

J. A. Munoz, C. S. Kochanek, E. E. Falco

There are $\sim 1$, 0.1 and 0.01 gravitationally lensed X-ray sources per square degree with soft X-ray fluxes exceeding $10^{-15}, 10^{-14}$ and $10^{-13} ergs/s cm^{-2}$ respectively. These sources will be detected serendipitously with the Chandra X-ray Observatory at a rate of 1--3 lenses per year of high resolution imaging. The low detection rate is due

G. A. Sokol, T. A. Aibergenov, A. V. Kravtsov, A. I. L&#39;vov

We present preliminary results of an experiment performed at the 1-GeV electron synchrotron of the Lebedev Physical Institute. Using the bremsstrahlung photon beam with the end-point energy of 650-850 MeV and the carbon target, correlated pi+/n pairs with opening angle 180 deg and energies E_pi=300 MeV, E_n=100 MeV have been observed. They arise from the pro

Shigeki Sugimoto

We check some consistency conditions for the D9-anti-D9 system in type I string theory. The gravitational anomaly and gauge anomaly for SO(n) x SO(m) gauge symmetry are shown to be cancelled when n-m=32. In addition, we find that a string theory with USp(n) x USp(m) gauge symmetry also satisfies the anomaly cancellation conditions. After tachyon condensation

Shinji Mukohyama, Sean A. Hayward

A property well known as the first law of black hole is a relation among infinitesimal variations of parameters of stationary black holes. We consider a dynamical version of the first law, which may be called the first law of black hole dynamics. The first law of black hole dynamics is derived without assuming any symmetry or any asymptotic conditions. In th

E. Shuster, D. T. Son

Deryagin, Grigoriev, and Rubakov (DGR) have shown that in finite-density QCD at infinite Nc the Fermi surface is unstable with respect to the formation of chiral waves with wavenumber twice the Fermi momentum, while the BCS instability is suppressed. We show here that at large, but finite Nc, the DGR instability only occurs in a finite window of chemical pot

Leticia F. Cugliandolo, Daniel R. Grempel, Jorge Kurchan, Eric Vincent

We propose an indirect way of studying the fluctuation-dissipation relation in spin-glasses that only uses available susceptibility data. It is based on a dynamic extension of the Parisi-Toulouse approximation and a Curie-Weiss treatment of the average magnetic couplings. We present the results of the analysis of several sets of experimental data obtained fr

Lars Bergstrom, Thibault Damour, Joakim Edsjo, Lawrence M. Krauss

Recently, a new Solar System population of weakly interacting massive particle (WIMP) dark matter has been proposed to exist. We investigate the implications of this population on indirect signals in neutrino telescopes (due to WIMP annihilations in the Earth) for the case when the WIMP is the lightest neutralino of the MSSM, the minimal supersymmetric exten

Marco Billo', Ben Craps, Frederik Roose

We study how non-BPS type II D-branes couple to R-R potentials. Upon tachyon condensation the couplings we find give rise to the Wess-Zumino action of BPS D-branes.

J. Gutowski, G. Papadopoulos, P. K. Townsend

A static minimal energy configuration of a super p-brane in a supersymmetric (n+1)-dimensional spacetime is shown to be a `generalized calibrated&#39; submanifold. Calibrations in $\bE^{(1,n)}$ and $AdS_{n+1}$ are special cases. We present several M-brane examples.

Francesca Borzumati, Jean-Loic Kneur, Nir Polonsky

It is shown that the radiation of a charged Higgs boson off a third-generation quark (charged-Higgs-strahlung) provides an important channel for the discovery of the charged Higgs at hadron colliders. Equivalently, in supersymmetric models with explicit lepton-number (R-parity) violation, sleptons may also be produced in association with quarks (slepton-stra

Donam Youm

We construct partially localized supergravity counterpart solutions to the 1/2 supersymmetric non-threshold and the 1/4 supersymmetric threshold bound state BI dyons in the D3-brane Dirac-Born-Infeld theory. Such supergravity solutions have all the parameters of the BI dyons. By applying the IIA/IIB T-duality transformations to these supergravity solutions,

A. Ferroglia, G. Ossola, A. Sirlin

The FAC, PMS, and BLM optimization methods are applied to the QED corrections to the muon lifetime in the Fermi V-A theory. The FAC and PMS scales are close to m_e, while the BLM scale nearly concides with the geometric average \sqrt{m_e m_μ}. The optimized expressions are employed to estimate the third order coefficient in the α(m_μ) expansion and the theor

K. Takehana, T. Takamasu, M. Hase, G. Kido

Polarized far-infrared (FIR) spectroscopic measurements and FIR magneto-optical studies were performed on the inorganic spin-Peierls compound CuGeO_3. An absorption line, which was found at 98 cm$^{-1}$ in the dimerized phase (D phase), was assigned to a folded phonon mode of B$_{3u}$ symmetry. The splitting of the folded mode into two components in the inco

B. Stech

The mass matrices of charged fermions have a simple structure if expressed in powers of the small parameter sigma=(m_c/m_t)^{1/2}. It is suggested that the mass matrix of the three heavy neutrinos occuring in grand unified theories can be expressed in terms of the same parameter. The requirement that these heavy neutrinos carry different U(1) generation quan

G. E. Volovik

The status quo in our understanding of defect formation during a rapid transition into the broken symmetry state in condensed matter and cosmology is discussed. An observation of vortex nucleation in neutron absorption experiments in superfluid 3He-B is interpreted in terms of defect formation during inhomogeneous cooling through T_c. Due to the temperature

A. Jakovac, A. Patkos, P. Petreczky, Zs. Szep

The effective dynamics of the low-frequency modes is derived for the O(N) symmetric scalar field theory in the broken symmetry phase. The effect of the high-frequency fluctuations is taken into account at one-loop level exactly. A new length scale is shown to govern the long-time asymptotics of the linear response function of the Goldstone modes. The large t

N. I. Kochelev, V. Vento, A. V. Vinnikov

An enhancement for the $η$ production in proton-neutron collisions as compared with that in proton-proton scattering has been recently observed. We present a calculation for the production cross section, in proton-neutron collisions near threshold, within instanton model for the QCD vacuum and show that a specific flavor dependent nonperturbative quark-gluon

Chris Van Den Broeck

I show how a minor modification of the Alcubierre geometry can dramatically improve the total energy requirements for a `warp bubble&#39; that can be used to transport macroscopic objects. A spacetime is presented for which the total negative mass needed is of the order of a few solar masses, accompanied by a comparable amount of positive energy. This puts t

V. Yu. Grishina, L. A. Kondratyuk, M. Buescher, C. Hanhart

The two-step model with pi-, rho- and omega- exchanges taken into account is applied to investigate the reactions pn -> d eta and pn -> d eta-prime. The existing experimental data on the reaction pn -> d eta are analysed and predictions for the cross section of the reaction pn -> d eta-prime are presented. It is found that pi- as well as rho exchange yield s

ZEUS Collaboration

In a search for signatures of physics processes beyond the Standard Model, various eeqq vector contact-interaction hypotheses have been tested using the high-Q^2, deep inelastic neutral-current e^+p scattering data collected with the ZEUS detector at HERA. The data correspond to an integrated luminosity of 47.7pb-1 of e^+p interactions at 300GeV center-of-ma

Kirill. A. Kazakov, Petr. I. Pronin

The problem of gauge independent definition of the effective gauge field is considered. The Slavnov identities corresponding to a system of interacting quantum gauge and classical matter fields, playing the role of a measuring device, are obtained. With their help, in the case of power-counting renormalizable theories, gauge independence of the effective dev

Namiko Mitarai, Hiizu Nakanishi

We analyzed the stability of the uniform flow solution in the optimal velocity model for traffic and granular flow under the open boundary condition. It was demonstrated that, even within the linearly unstable region, there is a parameter region where the uniform solution is stable against a localized perturbation. We also found an oscillatory solution in th

D. Sornette, A. Sornette

The Gutenberg-Richter power law distribution of earthquake sizes is one of the most famous example illustrating self-similarity. It is well-known that the Gutenberg-Richter distribution has to be modified for large seismic moments, due to energy conservation and geometrical reasons. Several models have been proposed, either in terms of a second power law wit

Kenji Tomita

The observational behavior of spherically symmetric inhomogeneous cosmological models is studied, which consist of inner and outer homogeneous regions connected by a shell or an intermediate self-similar region. It is assumed that the present matter density parameter in the inner region is smaller than that in the outer region, and the present Hubble paramet

L. Gavrilov, A. Perelomov

Let $q_1,q_2,...,q_N$ be the coordinates of $N$ particles on the circle, interacting with the integrable potential $\sum_{j<k}^N\wp(q_j-q_k)$, where $\wp$ is the Weierstrass elliptic function. We show that every symmetric elliptic function in $q_1,q_2,...,q_N$ is a meromorphic function in time. We give explicit formulae for these functions in terms of genus

D. T. Alves, C. Farina, A. C. Tort

We compute the modification in the spontaneous emission rate for a two-level atom when it is located between two parallel plates of different nature: a perfectly conducting plate $(ε\to \infty)$ and an infinitely permeable one $(μ\to \infty)$. We also discuss the case of two infinitely permeable plates. We compare our results with those found in the literatu

H. Geiger, G. Obermair, Ch. Helm

The Bohmian formulation of quantum mechanics is used in order to describe the measurement process in an intuitive way without a reduction postulate in the framework of a deterministic single system theory. Thereby the motion of the hidden classical particle is chaotic during almost all nontrivial measurement processes. For the correct reproduction of experim

Özgür E. Müstecaplıoğlu, Alexander S. Shumovsky

A general fundamental relation connecting the correlation of Stokes and anti-Stokes modes to the quantum statistical behavior of vibration and pump modes in Raman-active materials is derived. We show that under certain conditions this relation can be used to determine the equilibrium number variance of phonons.Time and temperature ranges for which such condi

Fuminori Sakaguchi, Masahito Hayashi

The the over-complete eigenvector system of the operator Q^{-1}P (Q:position, P:momentum) which consists of the squeezed states |0; s, t > with various s and t are investigated from the viewpoint of the annihilation and creation relations related to the algebra su(1,1). We derive a positive operator-valued measure(POVM) for the simultaneous measurement betwe

Yuri A. Rylov

The Eulerian system of dynamic equations for the ideal fluid is closed but incomplete. The complete system of dynamic equations arises after appending Lin constraints which describe motion of fluid particles in a given velocity field. The complete system of dynamic equations for the ideal fluid can be integrated. Description in terms of hydrodynamic potentia

G. V. Grigoryan, R. P. Grigoryan

Spin dependencies of the intensity and polarization of the synchrotron radiation of the longitudinally polarized particle performing uniform circular motion in the magnetic field are investigated.

A. A. Ovchinnikov, S. Flach

We construct lattice Hamiltonians with homogeneous interaction potentials which allow for explicit breather solutions. Especially we obtain exponentially localized solutions for $d$-dimensional lattices with $d=2,3$.

Silas R. Beane

We discuss a recent computation of Compton scattering on the deuteron at photon energies of order the pion mass. An interaction kernel is computed in baryon chiral perturbation theory and sewn to phenomenological deuteron wave functions. As an appetizer, we consider a computation of the pion-deuteron scattering length using this method.

Y. Kanada-En&#39;yo, H. Horiuchi, A. Dote

We study structure of excited states of 10Be with the method of variation after spin parity projection in the framework of antisymmetrized molecular dynamics. Present calculations describe many excited states and reproduce the experimental data of E2 and E1 transitions and the new data of the $β$ transition strength successfully. We make systematic discussio

Harald Grosse, Gert Reiter

We study the graded derivation-based noncommutative differential geometry of the $Z_2$-graded algebra ${\bf M}(n| m)$ of complex $(n+m)\times(n+m)$-matrices with the ``usual block matrix grading&#39;&#39; (for $n\neq m$). Beside the (infinite-dimensional) algebra of graded forms the graded Cartan calculus, graded symplectic structure, graded vector bundles,

Michael Forger, Sebastian Sachse

Continuing our attempt to explain the degeneracy of the genetic code using basic classical Lie superalgebras, we present the branching schemes for the typical codon representations (typical 64-dimensional irreducible representations) of basic classical Lie superalgebras and find three schemes that do reproduce the degeneracies of the standard code, based on

Anna Opanowicz

All deformations of two dimensional centrally extended Galilei group are classified. The corresponding quantum Lie algebras are found.

Feng Luo

We give a characterization of the action of the mapping class group on Thurston&#39;s space of measured laminations.

Feng Luo

Given a 3-holed sphere decomposition of an orientable closed surface, it is shown that each orientation preserving homeomorphism of the surface is isotopic to a composition AB where A is a product of positive Dehn twists and B is a product of negative Dehn twists on the decomposition curves.

Feng Luo

We determine the characters of SL(2) representations of groups and surface groups.

Hajime Tsuji

We prove the birational boundedness of Q-Fano varieties with Picard number one and dimension $n$ for every $n$. We do not use Mori theory.

Korkut Bardakci

In this paper, a new approach to string dynamics is proposed. String coordinates are identified with a non-commuting set of operators familiar from free string quantization, and the dynamics follows from the Virasoro algebra. There is a very large gauge group operating on the non-commuting coordinates. The gauge has to be fixed suitably to make contact with

J. A. Espichan Carrillo, A. Maia

We study the influence of boundary conditions on energy levels of interacting fields in a box and discuss some consequences when we change the size of the box. In order to do this we calculate the energy levels of bound states of a scalar massive field $χ$ interacting with another scalar field $ϕ$ through the lagrangian ${\cal L}_{int} = 3/2 gϕ^{2}χ^{2}$ in

G W Gibbons

In pure Einstein theory, Ricci flat Lorentzian 4-metrics of Petrov types III or N have vanishing counter terms up to and including two loops. Moreover for pp-waves and type-N spacetimes of Kundt&#39;s class which admit a non-twisting, non expanding, null congruence all possible invariants formed from the Weyl tensor and its covariant derivatives vanish. Thus

J. Bellandi, J. R. Fleitas, J. Dias de Deus

We present in this paper a calculation of the average proton-nucleus inelasticity. Using an Iterative Leading Particle Model and the Glauber model, we relate the leading particle distribution in nucleon-nucleus interactions with the respective one in nucleon- proton collisions. To describe the leading particle distribution in nucleon-proton collisions, we us

J. C. Peng, P. L. McGaughey, J. M. Moss

Some recent results from several fixed-target dimuon production experiments at Fermilab are presented. In particular, we discuss the use of Drell-Yan data to determine the flavor structure of the nucleon sea, as well as to deduce the energy-loss of partons traversing nuclear medium. Future dilepton experiments at RHIC could shed more light on the flavor asym

C. D. Froggatt, H. B. Nielsen

The idea, following Michel and O&#39;Raifeartaigh, of assigning meaning to the (gauge) \underline{group} and not only the Lie algebra for a Yang Mills theory is reviewed. Hints from the group and the fermion spectrum of the Standard Model are used to suggest the putting forward of our AGUT-model, which gives a very good fit to the orders of magnitudes of the

Marta Losada

We incorporate the effects of mixing arising from the trilinear terms in the MSSM potential to the effective three dimensional theory for the MSSM at high temperature in the limit of large $m_{A}$. There are relevant one-loop effects that modify the 3D parameters of the effective theory. We calculate the two-loop effective potential of the 3D theory for the

Andrzej J. Buras

These lectures describe CP violation and rare decays of K and B mesons and consist of ten chapters: i) Grand view of the field including CKM matrix and the unitarity triangle, ii) General aspects of the theoretical framework, iii) Particle-antiparticle mixing and CP violation, iv) Standard analysis of the unitarity triangle, v) The ratio epsilon&#39;/epsilon

P. H. Chankowski, M. Krawczyk, J. Zochowski

We present an up-to-date analysis of the constraints imposed bythe precision data on the ($CP-$ conserving) Two-Higgs-Doublet Model of type II, with emphasis on the possible existence of very light neutral (pseudo)scalar Higgs boson with mass below 20--30 GeV. We show that even in the presence of such light particles, the 2HDM(II) can describe the electrowea

J. R. Pelaez, S. J. Brodsky, N. Toumbas

Inspired by the relation between the hadronic decay of the tau lepton and the electron-positron annihilation into hadrons, we derive new tests of perturbative QCD. We design a set of commensurate scale relations to test the self-consistency of leading-twist QCD predictions for any observable which defines an effective charge. This method provides renormaliza

Daniel de Florian

Jet production cross-sections in polarized proton-proton and electron-proton collisions are studied to next-to-leading order accuracy. Phenomenological results are presented for RHIC and HERA kinematics.

D. S. Hwang, Y. -Y. Keum

We calculate the decay constants of $D_s$ and $D_s^{*}$ with $\bar{B}^0 \ra D^{+}\ell^{-}ν$ and $\bar{B}^0 \ra D^{+}D_s^{-(*)}$ decays. In our analysis we take the factorization method including non-factorizable term contributions and used two different form factor behaviours (constant and monopole-type) for $F_0(q^2)$. We also consider the QCD-penguin and E

K. Harayama

Current experimental data suggest some relations between the Kobayashi-Maskawa Matrix and the quark mass ratios, namely $|V_{us}| \sim \sqrt{m_d / m_s}$, $|V_{ub} / V_{cb}| \sim \sqrt{m_u / m_c}$ and $|V_{cb}| \sim m_s / m_b$. We consider these relations seriously in this paper. As a result, they offer us some attractive relations among the elements of the m

Gela G. Devidze

The complete calculation of the lowest order short-distance contributions to the $B_{s}\toγγ$ decay in the SM are presented. The amplitude and branching ratio are calculated.

Tamas G. Kovacs, E. T. Tomboulis

We study the possible connection between centre vortices and P-vortices in SU(2) gauge theory. After briefly recalling some essential properties of centre vortices we point out that there is no known a priori connection between the gauge dependent P-vortices and the gauge invariant centre vortices. We then show by Monte Carlo simulations that the `centre pro

S. Aoki, R. Burkhalter, K. Kanaya, T. Yoshié

The CP-PACS is a massively parallel MIMD computer with the theoretical peak speed of 614 GFLOPS which has been developed for computational physics applications at the University of Tsukuba, Japan. We report on the performance of the CP-PACS computer measured during recent production runs using our Quantum Chromodynamics code for the simulation of quarks and

John C. Baez

In loop quantum gravity we now have a clear picture of the quantum geometry of space, thanks in part to the theory of spin networks. The concept of `spin foam&#39; is intended to serve as a similar picture for the quantum geometry of spacetime. In general, a spin network is a graph with edges labelled by representations and vertices labelled by intertwining

Alfredo E. Dominguez, Manuel H. Tiglio

We reconsider here the model where large quantum gravity effects were first found, but now in its Null Surface Formulation (NSF). We find that although the set of coherent states for $Z$, the basic variable of NSF, is as restricted as it is the one for the metric, while some type of small deviations from these states may cause huge fluctuations on the metric

Mariusz P. Dabrowski

Most of the observational claims in cosmology are based on the assumption that the universe is isotropic and homogeneous so they essentially test different types of Friedmann models. This also refers to recent observations of supernovae Ia, which, within the framework of Friedmann cosmologies give strong support to negative pressure matter and also weaken th

Reginald T. Cahill, Christopher M. Klinger

Noise is often used in the study of open systems, such as in classical Brownian motion and in Quantum Dynamics, to model the influence of the environment. However generalising results from Gödel and Chaitin in mathematics suggests that systems that are sufficiently rich that self-referencing is possible contain intrinsic randomness. We argue that this is rel

Sergio Dagach, Luis Dagach

We postulate that all the presently known kinematic effects on physical quantities related to a material particle (e.g., masss increase) are due to its velocity relative to surrounding matter, and not to the observer&#39;s reference frame. The minimal velocity (i.e., the velocity that minimizes these quantities) relative to a single large body being a functi

Thomas G. Dietterich

Many researchers have explored methods for hierarchical reinforcement learning (RL) with temporal abstractions, in which abstract actions are defined that can perform many primitive actions before terminating. However, little is known about learning with state abstractions, in which aspects of the state space are ignored. In previous work, we developed the M

Thomas G. Dietterich

This paper presents the MAXQ approach to hierarchical reinforcement learning based on decomposing the target Markov decision process (MDP) into a hierarchy of smaller MDPs and decomposing the value function of the target MDP into an additive combination of the value functions of the smaller MDPs. The paper defines the MAXQ hierarchy, proves formal results on

Alok Shukla, Michael Dolg, Peter Fulde, Hermann Stoll

We present a wavefunction-based approach to correlated ab initio calculations on crystalline insulators of infinite extent. It uses the representation of the occupied and the unoccupied (virtual) single-particle states of the infinite solid in terms of Wannier functions. Electron correlation effects are evaluated by considering virtual excitations from a sma

John J. Quinn, Arkadiusz Wojs

The mean field (MF) composite Fermion (CF) picture successfully predicts the band of low lying angular momentum multiplets of fractional quantum Hall systems for any value of the magnetic field. This success cannot be attributed to a cancellation between Coulomb and Chern--Simons interactions between fluctuations beyond the mean field. It results instead fro

Arkadiusz Wojs, Izabela Szlufarska, Kyung-Soo Yi, Pawel Hawrylak

Low lying states of a 2D electron-hole system contain electrons and one or more types of charged excitonic complexes. Binding energies and angular momenta of these excitonic ions, and the pseudopotentials describing their interactions with electrons and with one another are obtained from numerical studies of small systems. Incompressible fluid ground states

S. Sadewasser, J. S. Schilling, J. L. Wagner, O. Chmaissem

In previous studies on a number of under- and overdoped high temperature superconductors, including YBa_{2}Cu_{3}O_{7-y} and Tl_{2}Ba_{2}CuO_{6+δ}, the transition temperature T_c has been found to change with time in a manner which depends on the sample&#39;s detailed temperature and pressure history. This relaxation behavior in T_c is believed to originate

Stefan Wessel, Stephan Haas

Three-dimensional magnetic ordering transitions are studied theoretically in strongly anisotropic quantum magnets. An external magnetic field can drive quasi-one-dimensional subsystems with a spin gap into a gapless regime, thus inducing long-range three-dimensional magnetic ordering due to weak residual magnetic coupling between the subsystems. Compounds wi

Plamen Ch. Ivanov, Luís A. Nunes Amaral, Ary L. Goldberger, Shlomo Havlin

Recent evidence suggests that physiological signals under healthy conditions may have a fractal temporal structure. We investigate the possibility that time series generated by certain physiological control systems may be members of a special class of complex processes, termed multifractal, which require a large number of exponents to characterize their scal

S. Park, B. Kahng, H. Jeong, A. -L. Barabasi

Many morphological features of sputter eroded surfaces are determined by the balance between ion induced linear instability and surface diffusion. However, the impact of the nonlinear terms on the morphology is less understood. We demonstrate that while at short times ripple formation is described by the linear theory, after a characteristic time the nonline

B. Kahng, S. Park

We introduce an interface model with q-fold symmetry to study the nonequilibrium phase transition (NPT) from an active to an inactive state at the bottom layer. In the model, q different species of particles are deposited or are evaporated according to a dynamic rule, which includes the interaction between neighboring particles within the same layer. The NPT

Horacio E. Castillo, Paul M. Goldbart, Annette Zippelius

The question of the local stability of the (replica-symmetric) amorphous solid state is addressed for a class of systems undergoing a continuous liquid to amorphous-solid phase transition driven by the effect of random constraints. The Hessian matrix, associated with infinitesimal fluctuations around the stationary point corresponding to the amorphous solid

L. Roters, A. Hucht, S. Lubeck, U. Nowak

We analyze the depinning transition of a driven interface in the 3d random-field Ising model (RFIM) with quenched disorder by means of Monte Carlo simulations. The interface initially built into the system is perpendicular to the [111]-direction of a simple cubic lattice. We introduce an algorithm which is capable of simulating such an interface independent

John J. Quinn, Arkadiusz Wojs, Izabela Szlufarska, Kyung-Soo Yi

Two-dimensional systems containing Ne electrons and Nh holes (Ne>Nh) strongly correlated through Coulomb interactions in the presence of a large magnetic field are studied by exact numerical diagonalization. Low lying states are found to contain neutral (X0) and negatively charged (X-) excitons and higher charged exciton complexes (Xk-, a bound state of k ne

Cristian F. Moukarzel

Spreading according to simple rules (e.g. of fire or diseases), and shortest-path distances are studied on d-dimensional systems with a small density p per site of long-range connections (``Small-World&#39;&#39; lattices). The volume V(t) covered by the spreading quantity on an infinite system is exactly calculated in all dimensions. We find that V(t) grows

M. Kiselev, F. Bouis

In the recent letter [1] by H. Ikeda and Y. Ohashi, a new, very attractive idea is proposed for the explanation of the micromagnetism in U-based heavy fermion compounds. For this sake a nontrivial spin density wave (d-SDW) is introduced. Our goal is to claim, that in the model considered, the mean-field analysis is incomplete: the ferromagnetic state missed

D. Alfe`, G. Kresse, M. J. Gillan

First-principles molecular dynamics simulations based on density-functional theory and the projector augmented wave (PAW) technique have been used to study the structural and dynamical properties of liquid iron under Earth&#39;s core conditions. As evidence for the accuracy of the techniques, we present PAW results for a range of solid-state properties of lo

Hiroaki Ikeda, Yoji Ohashi

The possibility of the ferromagnetic state modifies the phase diagram in Phys.Rev.Lett.81,3723(1998), as Kiselev and Bouis have pointed out. However, the unconventional SDW that has been proposed in the letter above is still a candidate for the curious magnetism in URu_2Si_2.

Hiroaki Ikeda, Yoji Ohashi

We propose a novel spin density wave (SDW) state as a possible mechanism of the anomalous antiferromagnetism, so-called the micromagnetism, in URu_2Si_2 below 17.5[K]. In this new SDW, the electron-hole pair amplitude changes its sign in the momentum space as in the case of the unconventional superconductivity. It is shown that this state can be realized in