April 2000 arXiv papers — page 17

Aleksey D. Drozdov, Yitzhak Rabin

We analyze stability of a thin inextensible elastic rod which has non-vanishing spontaneous generalized torsions in its stress-free state. Two classical problems are studied, both involving spontaneously twisted rods: a rectilinear beam compressed by axial forces, and a circular ring subjected to uniform radial pressure on its outer perimeter. It is demonstr

K. N. Yugay, N. V. Blinov, I. V. Shirokov

Asymptotic states in long Josephson junctions are investigated in an external magnetic field. We show that a choice one of the solution of the stationary Ferrell-Prange equation can carry be out with use of an asymptotic solution of the sine-Gordon equation and that an evolution to that stable solution occurs by passing through metastable states, which is de

M. Ebrahim Fouladvand

A uni-directional two-lane road is approximated by a set of two parallel closed one-dimensional chains. Two types of car i.e. slow and fast ones are considered in the system. Based on the Nagel-Schreckenberg (Na-Sch) model of traffic flow, a set of reaction-diffusion processes are introduced to simulate the behaviour of the cars. Fast cars can pass the slow

Myung Gyoon Lee, Eunhyeuk Kim

We present a study of globular clusters in the inner region of the giant elliptical galaxy NGC 4472, based on the HST WFPC2 archive data. We have found about 1560 globular cluster candidates at the galactocentric radius r < 4 arcmin. V-(V-I) diagram of these objects shows a dominant vertical structure which consists obviously of two components: blue globular

Andrey Todorov

In this paper we will use our results about the local deformation theory of Calabi-Yau manifolds to define a Higgs field on the tangent bundle of the moduli space of CY threefolds. Combining this Higgs field with the Levi-Chevitta connection of the Weil-Petersson metrics on the moduli space of three dimensional CY manifolds, we construct a new $Sp(2h^{2,1}%

P. Colin, V. Avila-Reese, O. Valenzuela

We performed a series of high-resolution simulations designed to study the substructure of Milky Way-size galactic halos (host halos) and the density profiles of halos in a warm dark matter (WDM) scenario with a non-vanishing cosmological constant. The virial masses of the host halos range from 3.5 x 10^12 to 1.7 x 10^12 solar masses and they have more than

Pavel Etingof, David Kazhdan

This paper is a continuation of the series of papers "Quantization of Lie bialgebras (QLB) I-V". We show that the image of a Kac-Moody Lie bialgebra with the standard quasitriangular structure under the quantization functor defined in QLB-I,II is isomorphic to the Drinfeld-Jimbo quantization of this Lie bialgebra, with the standard quasitriangular structure.

Carlos Barcelo, Matt Visser

We sketch a particularly simple and compelling version of D-brane cosmology. Inspired by the semi-phenomenological Randall--Sundrum models, and their cosmological generalizations, we develop a variant that contains a single (3+1)-dimensional D-brane which is located on the boundary of a single bulk (4+1)-dimensional region. The D-brane boundary is itself to

S. E. Irvine, M. A. Walton

We show how the threshold level of affine fusion, the fusion of Wess-Zumino-Witten (WZW) conformal field theories, fits into the Schubert calculus introduced by Gepner. The Pieri rule can be modified in a simple way to include the threshold level, so that calculations may be done for all (non-negative integer) levels at once. With the usual Giambelli formula

Paul M. Fishbane

A layered material structure in a monochromatic neutrino beam produces interference effects that could be used for the measurement of features of the neutrino mass matrix. The phenomenon would be most useful at high energies.

Krishna Rajagopal, Eugene Shuster

Quark matter at asymptotically high baryon chemical potential is in a color superconducting state characterized by a gap Delta. We demonstrate that although present weak-coupling calculations of Delta are formally correct for mu -> Infinity, the contributions which have to this point been neglected are large enough that present results can only be trusted fo

P. Facchi, H. Nakazato, S. Pascazio, J. Perina

A quantum mechanical version of a classical inverted pendulum is analyzed. The stabilization of the classical motion is reflected in the bounded evolution of the quantum mechanical operators in the Heisenberg picture. Interesting links with the quantum Zeno effect are discussed.

Francesco Vissani

Narrow muon bundles in underground detectors permit to study muoproduction reactions that take place in the surrounding rock. We analyze the relevance of a QED+QCD reaction, muoproduction of &#34;open charm&#34;. The contribution to double muon events is estimated to be 4-8 % of the one due to QED &#34;trident&#34; process, for an ideal detector located unde

George Jikia, Avto Tkabladze

We present the next-to-leading-order cross sections of the heavy quark-antiquark pair production in polarized photon-photon collision for the general case of photon polarizations. The numerical results for top-antitop production cross sections together with production asymmetries are obtained for linearly polarized photon-photon collisions, including one-loo

D. Jaksch, J. I. Cirac, P. Zoller, S. L. Rolston

We propose several schemes for implementing a fast two-qubit quantum gate for neutral atoms with the gate operation time much faster than the time scales associated with the external motion of the atoms in the trapping potential. In our example, the large interaction energy required to perform fast gate operations is provided by the dipole-dipole interaction

D. Bailin, G. V. Kraniotis, A. Love

CP violation by soft supersymmetry-breaking terms in orbifold compactifications is investigated. We include the universal part of the moduli-dependent threshold corrections in the construction of the non-perturbative effective potential due to gaugino-condensation. This allows interpolation of the magnitude of CP violating phases between the weakly and stron

Adrian C. Ottewill, Elizabeth Winstanley

We derive constraints on the form of the renormalized stress tensor for states on Kerr space-time based on general physical principles: symmetry, the conservation equations, the trace anomaly and regularity on (sections of) the event horizon. This is then applied to the physical vacua of interest. We introduce the concept of past and future Boulware vacua an

I. F. Ginzburg, I. P. Ivanov

We discuss the potentialities of the study of CP-odd interactions of the Higgs boson with photons via its production at gamma-gamma and e-gamma colliders. Our treatment of H-gamma-gamma and H-Z-gamma anomalous interactions includes a set of parameters, whose impact on physical observables has not been considered before. We focus on two reactions - gamma+gamm

N. Ilieva, H. Narnhofer, W. Thirring

The anyon fields have trivial $α$-commutator for $α$ not integer. For integer $α$ the commutators become temperature-dependent operator valued distributions. The $n$-point functions do not factorize as for quasifree states.

A. Blasi, V. E. R. Lemes, N. Maggiore, S. P. Sorella

An algebraic proof of the nonrenormalization theorem for the perturbative beta function of the coupling constant of N=2 Super Yang-Mills theory is provided. The proof relies on a fundamental relationship between the N=2 Yang-Mills action and the local gauge invariant polynomial Tr phi^2, phi(x) being the scalar field of the N=2 vector gauge multiplet. The no

Thomas Besmer, Andreas Steffen

We investigate the influence of the R-parity violating couplings lambda, lambda&#39; and lambda&#39;&#39; on the branching ratio of b to s gamma in leading logarithmic approximation. The operator basis is enlarged and the corresponding gamma-matrix calculated. The matching conditions receive new contributions from the R-parity violating sector. The compariso

S. Massar

We give a complete analysis of covariant measurements on two spins. We consider the cases of two parallel and two antiparallel spins, and we consider both collective measurements on the two spins, and measurements which require only Local Quantum Operations and Classical Communication (LOCC). In all cases we obtain the optimal measurements for arbitrary fide

Katsuichi Higuchi, Katsuji Yamamoto

Aspects of the quark mixings and flavor changing interactions are investigated in electroweak models with singlet quarks. The effects on the ordinary quark mixing are determined in terms of the quark masses and the parameters describing the mixing between the ordinary quarks q and the singlet quarks Q (q-Q mixing). Some salient features arise in the flavor c

Yoshiyuki Fukumoto

By using the perturbation expansion up to the fifth order, we study the two-triplet-dimer excitation spectra in the Shastry-Sutherland model, where the localized nature of a triplet-dimer, the propagation of a triplet-dimer pair by the correlated hopping and the long-range interactions between triplet-dimers play an essential role. It is found that the dispe

Jean-Philippe Uzan, Francis Bernardeau

We reconsider the general properties of gravitational lensing effects induced by cosmic string systems, taking into account their equation of state and motion equations. We explicitly show that the deflection patterns induced by a string is equivalent to the one of a lineic and static distribution of matter. We then rigorously show that the convergence part

Francis Bernardeau, Jean-Philippe Uzan

We present a novel approach for investigating lens phenomenology of cosmic strings in order to elaborate detection strategies in galaxy deep field images. To account for the complexity of the projected energy distribution of string networks we assume their lens effects to be similar to those of a straight string carrying a {\em random} lineic energy distribu

S. Ansoldi, A. Aurilia, L. Marinatto, E. Spallucci

We study the vacuum functional for a system of p-branes interacting with Maxwell fields of higher rank. This system represents a generalization of the usual electrodynamics of point particles, with one essential difference: namely, that the world-history of a p-brane, due to the spatial extension of the object, may possess a physical boundary. Thus, the obje

E. J. Hackett-Jones, D. B. Leinweber, A. W. Thomas

We explore methods of extrapolating lattice calculations of hadronic observables to the physical regime, while respecting the constraints of chiral symmetry and heavy quark effective theory. In particular, we extrapolate lattice results for magnetic moments of the spin-1/2 baryon octet to the physical pion mass and compare with experimental measurements. The

Renyi Ma

In this article, we prove that there exists at least one chord which is characteristic of Reeb vector field connecting a given Legendre submanifold in a closed contact manifold with any contact form.

Alessandra Buonanno

We discuss the mapping of the conservative part of two-body electrodynamics onto that of a test charged particle moving in some external electromagnetic field, taking into account recoil effects and relativistic corrections up to second post-Coulombian order. Unlike the results recently obtained in general relativity, we find that in classical electrodynamic

Ola Tornkvist

I review a number of particle-physics models that lead to the creation of magnetic fields in the early universe and address the complex problem of evolving such primordial magnetic fields into the fields observed today. Implications for future observations of the Cosmic Microwave Background (CMB) are briefly discussed.

Renyi Ma

We study the $J-$holomorphic curves in the symplectization of the contact manifolds and prove that there exists at least one periodic Reeb orbits in any closed contact manifold with any contact form by using the well-known Gromov&#39;s nonlinear Fredholm alternative for $J-$holomorphic curves. As a corollary, we give a complete solution on the well-known Wei

Yehuda Sharf, Timothy F. Havel, David G. Cory

Control over spin dynamics has been obtained in NMR via coherent averaging, which is implemented through a sequence of RF pulses, and via quantum codes which can protect against incoherent evolution. Here, we discuss the design and implementation of quantum codes to protect against coherent evolution. A detailed example is given of a quantum code for protect

S. Antoci, L. Mihich

Some authors have raised the question whether the probabilities stemming from a quantum mechanical computation are entitled to enter the Bell and the Clauser-Horne inequalities. They have remarked that if the quantum probabilities are given the status of conditional ones and the statistics for the various settings of the detectors in a given experiment is pr

Oliver Rudolph, J. D. M. Wright

It is shown here that a strengthening of Wallach&#39;s Unentangled Gleason Theorem can be obtained by applying results of the present authors on generalised Gleason theorems for quantum multi-measures arising from investigations of quantum decoherence functionals.

G. Brida, M. Genovese, C. Novero, E. Predazzi

We report on a test of Bell inequalities using a non-maximally entangled state, which represents an important step in the direction of eliminating the detection loophole. The experiment is based on the creation of a polarisation entangled state via the superposition, by use of an appropriate optics, of the spontaneous fluorescence emitted by two non-linear c

G. Cassinelli, E. De Vito, A. Levrero, P. Lahti

We give necessary and sufficient conditions for the set of Neumark projections of a countable set of phase space observable to constitute a resolution of the identity, and we give a criteria for a phase space observable to be informationally complete. The results will be applied to the phase space observables arising from an irreducible representation of the

Yehuda Sharf, David G. Cory, Shyamal S. Somaroo, Timothy F. Havel

Quantum error correcting codes enable the information contained in a quantum state to be protected from decoherence due to external perturbations. Applied to NMR, quantum coding does not alter normal relaxation, but rather converts the state of a ``data&#39;&#39; spin into multiple quantum coherences involving additional ancilla spins. These multiple quantum

D. H. Rischke, R. D. Pisarski

We review what is different and what is similar in a color superconductor as compared to an ordinary BCS superconductor. The parametric dependence of the zero-temperature gap on the coupling constant differs in QCD from that in BCS theory. On the other hand, the transition temperature to the superconducting phase is related to the zero-temperature gap in the

E. Bauer, A. Polls, A. Ramos

The longitudinal and transverse nuclear responses to inclusive electron scattering reactions are analyzed within the Random Phase Approximation (RPA) framework. Several residual interactions are considered and it is shown that the exchange terms in the RPA make very difficult to find an effective residual interaction capable of reproducing simultaneously the

O. Dragoun, M. Rysavy, A. Spalek

The internal conversion coefficients (ICC) were calculated for all atomic subshells of the elements with 104<=Z<=126, the E1...E4, M1...M4 multipolarities and the transition energies between 10 and 1000 keV. The atomic screening was treated in the relativistic Hartree-Fock-Slater model. The Tables comprising almost 90000 subshell and total ICC were recently

C. Cetina, B. L. Berman, W. J. Briscoe, P. L. Cole

Total photofission cross sections for 238U, 235U, 233U, 237Np, 232Th, and natPb have been measured simultaneously, using tagged photons in the energy range Egamma=0.17-3.84 GeV. This was the first experiment performed using the Photon Tagging Facility in Hall B at Jefferson Lab. Our results show that the photofission cross section for 238U relative to that f

C. -Y. Liu, A. R. Young, S. K. Lamoreaux

A calculation of ultra-cold neutron (UCN) upscattering rates in molecular deuterium solids has been carried out, taking into account intra-molecular exictations and phonons. The different moelcular species ortho-D2 (with even rotational quantum number J) and para-D2 (with odd J) exhibit significantly different UCN-phonon annihilation cross-sections. Para- to

Ricardo Mansilla, Jose L. Gutierrez

A cellular automata model that describes as limit cases of his parameters the spread of contagious diseases modeled by systems of ordinary or partial differential equations is developed. Periodic features of the behavior of human settlement are considered. The model is built taking into account the range of motion of the elements of population. For small (la

Giampiero Esposito, Boris G. Konopelchenko

The Lax pseudo-differential operator plays a key role in studying the general set of KP equations, although it is normally treated in a formal way, without worrying about a complete characterization of its mathematical properties. The aim of the present paper is therefore to investigate the ellipticity condition. For this purpose, after a careful evaluation

G. J. Chaitin

Transcript of G.J. Chaitin&#39;s 2 March 2000 Carnegie Mellon University School of Computer Science Distinguished Lecture. The notion of randomness is taken from physics and applied to pure mathematics in order to shed light on the incompleteness phenomenon discovered by K. Godel.

Jens Bolte, Rainer Glaser

Quantum ergodicity, which expresses the semiclassical convergence of almost all expectation values of observables in eigenstates of the quantum Hamiltonian to the corresponding classical microcanonical average, is proven for non-relativistic quantum particles with spin 1/2. It is shown that quantum ergodicity holds, if a suitable combination of the classical

KunPeng Wang, Xianke Zhang

Here we study algebraic function fields K, give necessary and sufficient condition for the ideal class group $H(K)$ of any real quadratic function field $K$ to have a cyclic subgroup of order $n$, and obtain eight series of such fields $K$, with four of them NOT ERD-type or GERD-type.

Kunpeng Wang, Xianke Zhang

The theory of continued fractions of functions $ \sqrt D $ is used to give lower bound for class numbers $h(D)$ of general real quadratic function fields $K=k(\sqrt D)$ over $k={\bf F}_q(T)$. For five series of real quadratic function fields $K$, the bounds of $h(D)$ are given more explicitly, e.g., if $ D=F^2+c,$ \mbox{}\hspace{0.1cm} then $ h(D)\geq {deg}F

DeRong Qiu, Xianke Zhang

Let $p, q$ be twin prime numbers with $q-p=2$ . Consider the elliptic curves E=E_σ: y^2 = x (x+σp)(x+σq) . (σ=\pm 1). E=E_σis also denoted as E_+ or E_- when σ= +1or $-1.Here the Mordell-Weil group and the rank of the elliptic curve E over the Gauss field K=Q(\sqrt -1) (and over the rational field Q is determined in several cases; and results on solutions of

Andrey Todorov

In this paper we construct the analogue of Dedekind eta function for odd dimensional CY manifolds. We use the theory of determinant line bundles. We constructed a canonical holomorphic section $η^{N}$ of some power of the determinant line bundle on the moduli space of odd dimensional CY manifolds. According to Viehweg the moduli space of moduli space of pola

Johan Rade

Necessary and sufficient conditions are given for the Palais-Smale Condition C to hold for the Yang-Mills functional for connections that are invariant under a Lie group action on the manifold with orbits of codimension less than or equal to three. As an application the mountain pass lemma is used to give a simple proof of Wang&#39;s theorem on the existence

A. A. Glutsuk

We consider a polynomial h(x,y) in two complex variables of degree n+1>1 with a generic higher homogeneous part. The rank of the first homology group of its nonsingular level curve h(x,y)=t is n*n. To each 1- form in the variable space and a generator of the homology group one associates the (Abelian) integral of the form along the generator. The Abelian int

Hitoshi Murakami

I show various calculations of the limit of the colored Jones function for the figure-eight knot and confirm R. Kashaev&#39;s conjecture in this case.

Renyi Ma

In this paper we prove that there does not exists any closed Pre-Lagrangian submanifolds in any closed contact manifolds by using the $J-$holomorphic curves and Gromov&#39;s nonlinear Fredholm alternative.

Patrick Irwin

The energy radiated during the scattering of SU(3) monopoles is estimated as a function of their asymptotic velocity v. In a typical scattering process the total energy radiated is of order v^3 as opposed to v^5 for SU(2) monopoles. For charge (1,1) monopoles the dipole radiation produced is estimated for all geodesics on the moduli space. For charge (2,1) m

A. Alonso Izquierdo, M. A. Gonzalez Leon, J. Mateos Guilarte

The bosonic second invariant of SuperLiouville models in supersymmetric classical mechanics is described.

Marco Scandurra

We compute the ground state energy of a massive scalar field in the background of a cylindrical shell whose potential is given by a delta function. The zero point energy is expressed in terms of the Jost function of the related scattering problem, the renormalization is performed with the help of the heat kernel expansion. The energy is found to be negative

M. Burkardt

Issues that are specific for formulating fermions in light-cone quantization are discussed. Special emphasis is put on the use of parity invariance in the non-perturbative renormalization of light-cone Hamiltonians.

Xavier Bekaert, Marc Henneaux, Alexander Sevrin

We systematically study deformations of chiral forms with applications to string theory in mind. To first order in the coupling constant, this problem can be translated into the calculation of the local BRST cohomological group at ghost number zero. We completely solve this cohomology and present detailed proofs of results announced in a previous letter. In

C. Bizdadea, A. Constantin, S. O. Saliu

An irreducible canonical approach to reducible second-class constraints is given. The procedure is illustrated on gauge-fixed two-forms.

C. Bizdadea, E. M. Cioroianu, S. O. Saliu

An irreducible Hamiltonian BRST quantization method for reducible first-class systems is proposed. The general theory is illustrated on a two-stage reducible model, the link with the standard reducible BRST treatment being also emphasized.

C. Bizdadea, S. O. Saliu

Reducible constrained Hamiltonian systems are quantized accordingly an irreducible BRST manner. Our procedure is based on the construction of an irreducible theory which is physically equivalent with the original one. The equivalence between the two systems makes legitimate the substitution of the BRST quantization for the reducible theory by that of the irr

Y. Brihaye, M. Lubo

We consider the classical equations of the gravitating Abelian-Higgs model in an axially symmetric ansatz. More properties of the solutions of these equations (the Melvin and the sting branches) are presented. These solutions are also constructed for winding numbers N=2. It is shown that these vortices exist in attractive and repulsive phases, separated by t

R. Odorico

A simpler neural-network approach is presented for the analysis of the top quark non-leptonic decay channel in events of the D0 Collaboration. Results for the top quark signal are comparable to those found by the D0 Collaboration by a more elaborate handling of the event information used as input to the neural network.

Hsin-Chia Cheng, Bogdan A. Dobrescu, Christopher T. Hill

Electroweak symmetry breaking may be naturally induced by the observed quark and gauge fields in extra dimensions without a fundamental Higgs field. We show that a composite Higgs doublet can arise as a bound state of $(t, b)_L$ and a linear combination of the Kaluza-Klein states of $t_R$, due to QCD in extra dimensions. The top quark mass depends on the num

M. Ciafaloni, P. Ciafaloni, D. Comelli

Hard processes at the TeV scale exhibit enhanced (double log) EW corrections even for inclusive observables, leading to violation of the Bloch-Nordsieck theorem. This effect, previously related to the non abelian nature of free EW charges in the initial state (e- e+, e- p, p p ...), is here investigated for fermion initiated hard processes and to all orders

M. Boz, D. A. Demir, N. K. Pak

Q-balls generically exist in the supersymmetric extensions of the standard model. Taking into account the additional sources of CP violation, which are naturally accomodated by the supersymmetric models, it is shown that the Q-ball matter depends additively on individual CP phases, whereas mass per unit charge in the Q-ball depends only on the relative phase

Pierre Gauron, Basarab Nicolescu

We propose a QCD-inspired two-component Pomeron form which gives an excellent description of the proton-proton, pi-proton, kaon-proton, gamma-proton and gamma-gamma total cross sections. Our fit has a better CHI2/dof for a smaller number of parameters as compared with the PDG fit. Our 2-Pomeron form is fully compatible with weak Regge exchange-degeneracy, un

Hans Peter Nilles

We discuss the possible applications of string theory for the construction of generalizations of the $SU(3)\times SU(2)\times U(1)$ standard model of strong and electroweak interactions. This includes an investigation of effective $d=4$ dimensional supergravity theories that could be derived from higher dimensional string theories ($d=10$) and M-theory ($d=1

A. P. Burichenko

The &#34;recoil&#34; correction of order $m α^6$ to the hyperfine splitting of positronium ground state was found. The formalism employed is based on the noncovariant perturbation theory in QED. Equation for two-particle component of full (many-body) wave function is used, in which effective Hamiltonian depends on the energy of a system. The effective Hamilt

M. J. Ramsey-Musolf

Determinations of vuds with super-allowed Fermi beta-decay in nuclei and of the weak charge of the cesium in atomic parity-violation deviate from the Standard Model predicitions by 2 sigma or more. In both cases, the Standard Model over-predicts the magnitudes of the relevant observables. I discuss the implications of these results for R-parity violating (RP

J. Hisano, D. Nomura

The neutrino experiment results suggest that the neutrinos have finite masses and the lepton-flavor symmetries are violating in nature. In the supersymmetric models, the charged lepton-flavor violating processes, such as mu -> e gamma and tau -> mu gamma, may have the branching ratios accessible to the future experiments, depending on origins of the neutrino

S. Coutu, J. J. Beatty, M. A. DuVernois, S. W. Barwick

We present a new measurement of air shower muons made during atmospheric ascent of the High Energy Antimatter Telescope balloon experiment. The muon charge ratio mu+ / mu- is presented as a function of atmospheric depth in the momentum interval 0.3-0.9 GeV/c. The differential mu- momentum spectra are presented between 0.3 and about 50 GeV/c at atmospheric de

M. Cataldo, S. del Campo, A. Garcia

We propose an approach for constructing spatial slices of (3+1) spacetimes with cosmological constant but without a matter content, which yields (2+1) vacuum with $Λ$ solutions. The reduction mechanism from (3+1) to (2+1) gravity is supported on a criterion in which the Weyl tensor components are required to vanish together with a dimensional reduction via a

S. Sridhar, Z. Zhai

We show that a non-quasiparticle charge collective mode, in parallel and coincident with the d-wave pair conductivity, leads to a quantitative understanding of microwave surface impedance measurements on superconducting $Bi_{2}Sr_{2}CaCu_{2}O_{8+δ}$. The analysis suggests an inhomogeneous charge ground state in $Bi_{2}Sr_{2}CaCu_{2}O_{8+δ}$ and other HTS.

G. Barbero, A. K. Zvezdin

In the mean field approximation, we evaluate the temperature dependence of the anchoring energy strength of a nematic liquid crystal in contact with a solid substrate due to thermal fluctuations. Our study is limited to the weak anchoring case, where the microscopic surface energy is small with respect to the mean field energy due to the nematic phase. We as

F. Kh. Abdullaev, R. A. Kraenkel

We study the quantum coherent-tunneling between two Bose-Einstein condensates separated through an oscillating trap potential. The cases of slowly and rapidly varying in time trap potential are considered. In the case of a slowly varying trap we study the nonlinear resonances and chaos in the oscillations of the relative atomic population. Using the Melnikov

P. Kral, E. J. Mele, D. Tomanek

We show that an electrical shift current is generated when electrons are photoexcited from the valence to conduction bands on a BN nanotube. This photocurrent follows the light pulse envelope and its symmetry is controlled by the atomic structure of the nanotube. We find that the shift current has an intrinsic quantum mechanical signature in which the chiral

F. di Liberto, F. Peruggi

We present a mean field analysis of a fully frustrated Ising spin model on an Ising lattice gas. This is equivalent to a degenerate Blume-Emery-Griffiths model with frustration, which we analyze for different values of the quadrupolar interaction. This model might be useful in the study of structural glasses and related systems with disorder.

Michael Backhaus, Bodo Huckestein

We calculate numerically the spectrum of disordered electrons in the lowest Landau level at filling factor 1/5 using the self-consistent Hartree-Fock approximation for systems containing up to 400 flux quanta. Special attention is paid to the correct treatment of the q=0 component of the Coulomb interaction. For sufficiently strong disorder, the system is an

T. A. Vilgis, A. Johner, J. -F. Joanny

We study theoretically using scaling arguments the behavior of polyelectrolyte gels in poor solvents. Following the classical picture of Katchalsky, our approach is based on single chain elasticity but it accounts for the recently proposed pearl-necklace structure of polyelectrolytes in poor solvents. The elasticity both of gels at swelling equilibrium and o

G. Bilalbegovic

The temperature dependence of structural properties for infinitely long gold nanowires is studied. The molecular dynamics simulation method and the embedded-atom potential are used. The wires constructed at T=0 K with a face-centered cubic structure and oriented along the (111), (110), and (100) directions are investigated. It was found that multiwalled stru

V. Moldoveanu, A. Aldea, A. Manolescu, M. Nita

We investigate the transport properties of quantum dots placed in strong magnetic field using a quantum-mechanical &#39; approach based on the 2D tight-binding Hamiltonian with direct Coulomb interaction and the Landauer-Büttiker (LB) formalism. The electronic transmittance and the Hall resistance show Coulomb oscillations and also prove multiple addition pr

C. F. Chang, J. -Y. Lin, H. D. Yang

Very recently impurity scattering effects on quasiparticles in d-wave superconductors have attracted much attention. Especially, the thermodynamic properties in magnetic fields H are of interest. We have measured the low-temperature specific heat C(T,H) of La_1.78Sr_0.22Cu_1-xNi_xO4. For the first time, the impurity scattering effects on C(T,H) of cuprate su

A. Oosawa, T. Kato, H. Tanaka, H. Uekusa

Single-crystal neutron inelastic scattering was performed in order to investigate the magnetic excitations in the spin gap system TlCuCl$_3$. The constant-${\bf Q}$ energy scan profiles were collected in the $a^*-c^*$ plane. Three excitations are observed for $E{\leq}15$ meV. One of the excitations is identified to be magnetic excitation. The lowest magnetic

D. V. Fil

A piezoelectric mechanism of orientation of stripes in two-dimensional quantum Hall systems in GaAs heterostructures is considered. The anisotropy of the elastic moduli and the boundary of the sample are taken into account. It is found that in the average the stripes line up with the [110] axis. In double layer systems the wave vector of the stripe structure

D. S. Chow, F. Zamborszky, B. Alavi, D. J. Tantillo

Using one- and two-dimensional NMR spectroscopy applied to $^{13}$C spin-labeled (TMTTF)$_2$AsF$_6$ and (TMTTF)$_2$PF$_6$, we demonstrate the existence of an intermediate charge-ordered phase in the TMTTF family of charge-transfer salts. At ambient temperature, the spectra are characteristic of nuclei in equivalent environments, or molecules. Below a continu

Alexander S. Silbergleit, Robert V. Wagoner, Manuel Ortega-Rodriguez

We first briefly review how we investigate the modes of oscillation trapped within the inner region of accretion disks by the strong-field gravitational properties of a black hole (or a compact, weakly-magnetized neutron star). Then we focus on the `corrugation&#39;(c)-modes, nearly incompressible perturbations of the inner disk. The fundamental c-modes have

David A. Kornreich, Martha P. Haynes, R. V. E. Lovelace, Liese van Zee

New HI synthesis data have been obtained for six face-on galaxies with the Very Large Array. These data and reanalyses of three additional data sets make up a sample of nine face-on galaxies analyzed for deviations from axisymmetry in morphology and dynamics. This sample represents a subsample of galaxies already analyzed for morphological symmetry propertie

T. T. Takeuchi, H. Hirashita

We analyze the star formation history (SFH) of the Galactic disk by using an infall model. Based on the observed SFH of the Galactic disk, we first determine the timescales of the gas infall into the Galactic disk ($t_{\rm in}$) and that of the gas consumption to form stars ($t_{\rm sf}$). Since each of the two timescales does not prove to be determined inde

Paul J. Green, Babar Ali, Ralf Napiwotzki

We describe a near-IR photometric search for cool red dwarf companions to hot EUV-detected white dwarfs (WDs). While some composite systems have been found optically among WDs detected in recent EUV All-Sky Surveys, we develop an IR technique that probes farther down the main sequence, detecting yet more companions. We use detailed DA model atmosphere fits t

A. C. Robin, C. Reyle, M. Creze

As part of a global analysis of deep star counts to constrain scenarii of galaxy formation and evolution, we investigate possible links between the galactic spheroid and the dark matter halo. A wide set of deep star counts at high and intermediate galactic latitudes is used to determine the large scale density law of the spheroid. Assuming a power density la

D. Perez-Ramirez, J. H. Knapen, R. F. Peletier, S. Laine

We present sub-arcsecond resolution ground-based near-infrared images of the central regions of a sample of twelve barred galaxies with circumnuclear star formation activity, which is organized in ring-like regions typically one kiloparsec in diameter. We also present Hubble Space Telescope near-infrared images of ten of our sample galaxies, and compare them

Michael Feast, Patricia Whitelock

The Galactic kinematics of Mira variables have been studied using infrared photometry, radial velocities, and Hipparcos parallaxes and proper motions. For Miras in the period range 145 to 200 days (probably corresponding to [Fe/H] in the range -0.8 to -1.3) the major axes of the stellar orbits are concentrated in the first quadrant of Galactic longitude. Thi

Marek A. Abramowicz, Gunnlaugur Bjornsson, Igor V. Igumenshchev

We argue that the proper way to treat thin-thick accretion-disk transitions should take into account the 2-D nature of the problem. We illustrate the physical inconsistency of the 1-D vertically integrated approach by discussing a particular example of the convective transport of energy.

A. Ray, R. Petre, E. Schlegel

We report on the X-ray observation of the radio selected supernova SN1979C carried out with ASCA in December 1997. The supernova of type II$_{L}$ was first observed in the optical and occurred in the weakly barred, almost face on spiral galaxy NGC 4321 (M100) which is at a distance of 17.1 Mpc, and contains at least three other supernovae discovered in this

N. Ageorges, J. R. Walsh

The bipolar reflection nebula OH 231.8+4.2 (OH 0739-14), centred on the Mira variable star QX Pup, has been mapped at Ks in linear polarization using the ESO SOFI near-infrared multi-mode instrument. The large scale linear polarization features agree with previous studies, validating the polarimetric mode of the instrument. However the high spatial resolutio

E. Diolaiti, O. Bendinelli, D. Bonaccini, L. M. Close

StarFinder is a new code for the deep analysis of stellar fields, designed for well-sampled images with high and low Strehl ratio. It is organized in the form of a self-contained IDL widget-based application, with a &#39;user-friendly&#39; graphic interface. We give here a general description of the code along with some applications to real data with space-i

C. M. Wright, E. F. van Dishoeck, J. H. Black, H. Feuchtgruber

First detections of thermal water vapor absorption lines have been made toward Orion IRc2 using the Short Wavelength Spectrometer (SWS) on board the Infrared Space Observatory (ISO). Grating spectra covering wavelengths 25-45 micron yield 19 pure rotational lines, originating from energy levels 200-750 K above ground. Fabry-Perot spectra of 5 transitions res