September 1997 arXiv papers — page 15

R. Marc Kippen, James M. Ryan, Alanna Connors, Dieter H. Hartmann

The COMPTEL instrument on the Compton Gamma Ray Observatory is used to measure the locations of gamma-ray bursts through direct imaging of MeV photons. In a comprehensive search, we have detected and localized 29 bursts observed between 1991 April 19 and 1995 May 31. The average location accuracy of these events is 1.25$\arcdeg$ (1$σ$), including a systemati

Uffe Hellsten, Lars Hernquist, Neal Katz, David Weinberg

The metal absorption lines found in association with \lya absorbers of moderate to high HI column density contain valuable information about the metallicity and ionization conditions within the absorbers and offer a stronger test of models of the intergalactic medium at \sim 3$ than HI absorption lines alone. We have developed a method to predict the strengt

Jeff Secker, William E. Harris

Deep B- and R-band CCD images of the central ~700 arcmin^2 of the Coma cluster core have been used to measure the dwarf-galaxy population in Coma. In this paper, we describe a newly developed code for automated detection, photometry and classification of faint objects of arbitrary shape and size on digital images. Intensity-weighted moments are used to compu

M. Della Valle, N. Masetti, A. Bianchini

The spectrophotometric follow-up of the X-ray nova GU Mus (=GS 1124-68) is presented. We have analysed 128 B, V and R frames and 19 optical spectra, collected at ESO-La Silla, from the epoch of the discovery to January 1992. The optical lightcurve appears to be typical for a X-ray nova and exhibits secondary maxima in coincidence with the X-ray ones. The spe

S. C. Odewahn, D. Burstein, R. A. Windhorst

Surface photometry from 16 HST/WFPC2 fields in the I(F814W) filter is used to derive the distribution of apparent axis ratios for galaxies in progressively fainter magnitude intervals for I<25. We assess the systematic and accidental errors in ellipticity measurements as a function of image resolution and signal-to-noise ratio, and statistically correct for

M. Orlandini, D. Dal Fiume, L. Nicastro, E. Palazzi

Vela X-1 has been observed by the Italian/Dutch X-ray satellite BeppoSAX during its Science Verification Phase. During the ~ 50 ksec observation (orbital phases 0.27-0.34) two different intensity state are present, situation very common in this source. We report results from the pulse phase averaged and pulse phase resolved spectroscopy from the high-energy

David L. Band, Dieter H. Hartmann

If gamma-ray bursts originate in galaxies at cosmological distances, the host galaxy should be detected if a burst error box is searched deep enough; are the host galaxies present? We present and implement a statistical methodology which evaluates whether the observed galaxy detections in a burst&#39;s error box are consistent with the presence of the host g

Matthias Strauch, Yuri Tschinkel

We investigate analytic properties of height zeta functions of toric bundles over flag varieties.

H. F. Chau, K. K. Yan, K. Y. Wan, L. W. Siu

Given a (finite) string of zeros and ones, we report a way to determine if the number of ones is less than, greater than, or equal to a prescribed number by applying two sets of cellular automaton rules in succession. Thus, we solve the general density classification problem using cellular automaton.

J. A. Casas, Wai Yan Cheng, G. B. Gelmini

We present here a realistic model to produce a very large lepton asymmetry L of 0.1 to 1, without producing a large baryon asymmetry. The model is based on the Affleck and Dine scenario, in which the field acquiring a large vacuum expectation value during inflation is a s-neutrino right. We require $L$ to be large enough for the electroweak symmetry to be sp

Mark Trodden

I give a brief overview of a novel mechanism for generating the baryon asymmetry of the universe at the electroweak scale. This scenario circumvents the need for a strongly first order electroweak phase transition by utilizing gauged topological solitons to realize the requisite departure from thermal equilibrium.

E. Kiritsis

In these lecture notes, an introduction to superstring theory is presented. Classical strings, covariant and light-cone quantization, supersymmetric strings, anomaly cancelation, compactification, T-duality, supersymmetry breaking, and threshold corrections to low-energy couplings are discussed. A brief introduction to non-perturbative duality symmetries is

Robert B. Mann, Sergey N. Solodukhin

We consider the extremal limit of a black hole geometry of the Reissner-Nordstrom type and compute the quantum corrections to its entropy. Universally, the limiting geometry is the direct product of two 2-dimensional spaces and is characterized by just a few parameters. We argue that the quantum corrections to the entropy of such extremal black holes due to

J. F. Morales, C. A. Scrucca, M. Serone

We study the spin dependence of D-brane dynamics in the Green-Schwarz formalism of boundary states. In particular we show how to interpret insertion of supercharges on the boundary state as sources of non-universal spin effects in D-brane potentials. In this way we find for a generic (D)p-brane, potentials going like $v^{4-n}/r^{7-p+n}$ corresponding to inte

Edward W. Kolb, Anupam Singh, Mark Srednicki

We study the time evolution of the quantum fluctuations of the axion field for both the QCD axion as well as axions arising in the context of supergravity and string theories. We explicitly keep track not only of the coherently oscillating zero momentum mode of the axion but also of the higher non-zero momentum modes using the full axion potential. The full

Masashi Yamashiro, Yukio Tanaka, Satoshi Kashiwaya

A theory of tunneling conductance spectra for normal metal/insulator/Sr$_{2}$RuO$_{4}$ junction is studied theoretically. We assume several types of pair potentials with triplet symmetries that are promising candidates for Sr$_{2}$RuO$_{4}$. The calculated conductance spectra show either zero bias peaks or gap like structures depending on the orientations of

S. Scopetta, A. Yu. Umnikov, C. Ciofi degli Atti, L. P. Kaptari

Nuclear effects in polarized inelastic electron scattering off polarized $^3He$ and polarized $^2H$ are discussed; in the resonance region, Fermi motion effects are found to be much larger than in deep inelastic scattering. It is shown that improperly describing nuclear dynamics would lead to the extraction of unreliable neutron spin structure functions; on

Masashi Yamashiro, Yukio Tanaka, Yasunari Tanuma, Satoshi Kashiwaya

Tunneling conductance spectra of normal metal/insulator/triplet superconductor junctions are investigated theoretically. As triplet paring states we select several types of symmetries that are promising candidates for the superconducting states in UPt$_{3}$ and in Sr$_{2}$RuO$_{4}$. The calculated conductance spectra are sensitive to the orientation of the j

Nicola Manini, Erio Tosatti

We find the exact semiclassical (strong coupling) zero-point energy shifts applicable to the $e\otimes (n E)$ and $t\otimes (n H)$ dynamic Jahn-Teller problems, for an arbitrary number $n$ of discrete vibrational modes simultaneously coupled to one single electronic level. We also obtain an analytical formula for the frequency of the resulting normal modes,

Chong Sheng Li, C. --P. Yuan, Hong-Yi Zhou

In the supersymmetry (SUSY) models, because of the mass difference between the left- and right-top squarks, the supersymmetric QCD interactions can generate parity violating effects in the production of $ t \bar t$ pairs. We show that SUSY QCD radiative corrections to the parity violating asymmetry in the production rates of the left- and right-handed top qu

Yue Yu, Zhao-Bin Su, Xi Dai

The definitions of the effective mass of the composite fermion are discussed for the half-filled Landau level problem. In a recent work, Shankar and Murthy show a finite effective mass of the composite fermion by a canonical transformation while the perturbative calculation gives the logarithmic divergence of the effective mass at the Fermi surface. We will

A. S. Sachrajda, R. Ketzmerick, C. Gould, Y. Feng

Conductance fluctuations have been studied in a soft wall stadium and a Sinai billiard defined by electrostatic gates on a high mobility semiconductor heterojunction. These reproducible magnetoconductance fluctuations are found to be fractal confirming recent theoretical predictions of quantum signatures in classically mixed (regular and chaotic) systems. Th

Andreas E. Klinkmueller

Atomic negative ions are fragile quantum systems in which correlation among the valence electrons plays a very important role. For doubly excited states correlation becomes dominant. Photodetachment is the process where a negative ion absorbs a photon and as a consquence ejects the outermost electron. A new detection scheme has been developed. The residual a

E. Kiritsis, N. A. Obers

We continue our study of heterotic/type-I duality in D<10 dimensions. We consider the heterotic and type-I theories compactified on tori to lower dimensions. We calculate the special (``BPS saturated&#39;&#39;) F^4 and R^4 terms in the effective one-loop heterotic action. These terms are expected to be non-perturbatively exact for D>4. The heterotic result i

F. Farchioni, A. Papa

This work is organized in two independent parts. In the first part are presented some results concerning the surface tension in SU(3) obtained with a parametrized fixed point action. In the second part, a new, approximately scale-invariant, parametrized fixed point action is proposed which is suitable to study the topology in SU(3).

Jacques L. Rubin

Starting from a relativistic phenomenology of anyons in crystals, we discuss the concept of relativistic interaction and the need to unify electromagnetism and gravitation within the Spencer cohomology of Lie equations. Then, from the sophisticated non-linear Spencer complex of the Poincaré and conformal Lie pseudogroups, we build up a non-linear relative co

Gi-Chol Cho, Kaoru Hagiwara

The string theory predicts the unification of the gauge couplings and gravity. The minimal supersymmetric Standard Model, however, gives the unification scale $\sim 2\times 10^{16}$ GeV which is significantly smaller than the string scale $\sim 5\times 10^{17}$ GeV of the weak coupling heterotic string theory. We study the unification scale of the non-supers

Juliet Lee-Franzini, Paolo Franzini

CP violation in the K system is pedagogically reviewed. We discuss its manifestations in the neutral K meson systems, in rare K meson decays and in decays of charged K mesons. Results from classical experiments, and perspectives for upcoming experiments are included. We also briefly discuss the possibility of CPT tests.

H. Arfaei, M. M. Sheikh-Jabbari

In this article we consider open strings with mixed boundary conditions (a combination of Neumann and Dirichlet conditions at each end). We discuss how their end points show a $D_p$-brane with NS-NS charge, i.e. a bound state of a D-brane with a fundamental strings. We show that these branes are BPS saturated. In the case of one-branes, we show that their ma

Max Tegmark, Martin Rees

We explore the qualitative changes that would occur if the amplitude Q ~ 10^{-5} of cosmological density fluctuations were different. If is less than about 10^{-6}, the cosmological objects that form would have so low virial temperatures that they may be unable to cool and form stars, and would be so loosely bound that even if they could produce a supernova

De-Hone Lin

The path integral for relativistic spinless dionium atom is solved, and the energy spectra are extracted from the resulting amplitude.

Holger F. Hofmann

The spatiotemporal dynamics of photon emission into a non-local farfield channel and two local nearfield channels from a pair of coupled two level systems is analysed using a model for emission based on Wigner-Weisskopf theory. The local quantum beats can be observed in the two nearfield channels. However, the presence of the farfield causes decoherence in t

S. Stenholm, K. -A. Suominen

We summarize the theoretical description of wave packets on molecular energy levels. We review the various quantum mechanical effects which can be studied and the models that can be verified on this system. This justifies our claim that the wave packet constitutes a universal quantum object.

V. M. Tkachuk

The supersymmetry of the electron in both the nonstationary magnetic and electric fields in a two-dimensional case is studied. The supercharges which are the integrals of motion and their algebra are established. Using the obtained algebra the solutions of nonstationary Pauli equation are generated.

Arthur Jaffe

We develop from scratch a theory of invariants within the framework of non-commutative geometry. Given an operator Q (a supercharge in physics language) and an operator a (whose square equals the identity I), we derive a general formula for an invariant Z(Q,a) depending on Q and a. In case a=I, our formula reduces to the McKean-Singer representation of the i

Peter Moller, J. Rayford Nix

Beyond uranium heavy elements rapidly become increasingly unstable with respect to spontaneous fission as the proton number Z increases, because of the disruptive effect of the long-range Coulomb force. However, in the region just beyond Z = 100 magic proton and neutron numbers and the associated shell structure enhances nuclear stability sufficiently to all

S. G. Mashnik, A. J. Sierk, O. Bersillon, T. Gabriel

We have used an extended version of the Cascade-Exciton Model (CEM) to analyze more than 600 excitation functions for proton induced reactions on 19 targets ranging from C-12 to Au-197, for incident energies ranging from 10 MeV to 5 GeV. We have compared the calculations to available data, to calculations using approximately two dozen other models, and to pr

Shmuel Balberg, Nir Barnea

In this work we calculate the $^1S_0$ gap energies of $Λ$ hyperons in neutron star matter. The calculation is based on a solution of the BCS gap equation for an effective G-matrix parameterization of the $Λ-Λ$ interaction with a nuclear matter background, presented recently by Lanskoy and Yamamoto. We find that a gap energy of a few tenths of MeV is expected

F. de Jong, H. Lenske

In a relativistic Brueckner-Hartree-Fock calculation we include explicit negative-energy states in the two-body propagator. This is achieved by using the Gross spectator-equation, modified by medium effects. Qualitatively our results compare well with other RBHF calculations. In some details significant differences occur, e.g, our equation of state is stiffe

L. G. Moretto, L. Beaulieu, L. Phair, G. J. Wozniak

In a recent preprint by Tsang and Danielewicz, the authors attempt to give alternative or trivial explanations for the reducible and &#34;thermal&#34; nature of the intermediate mass fragment excitation functions reported previously (Phys. Rev. Lett. 74, 1530 (1995), Phys. Lett B 361, 25 (1995), Phys. Rep. 287, 249 (1997)). We demonstrate that their proposed

Nigel J. Kalton, Igor Emil Verbitsky

We study connections between the problem of the existence of positive solutions for certain nonlinear equations and weighted norm inequalities. In particular, we obtain explicit criteria for the solvability of the Dirichlet problem $$\aligned -& Δu = v \, u^q + w, \quad u \ge 0 \quad \text {on} \quad Ω, \\ &u = 0 \quad \text {on} \quad \partial Ω, \endaligne

Nigel J. Kalton, Mikhail I. Ostrovskii

The main object of the paper is to study the distance between Banach spaces introduced by Kadets. For Banach spaces $X$ and $Y$, the Kadets distance is defined to be the infimum of the Hausdorff distance $d(B_X,B_Y)$ between the respective closed unit balls over all isometric linear embeddings of $X$ and $Y$ into a common Banach space $Z.$ This is compared w

Nigel J. Kalton, Marius Mitrea

We investigate stability of Fredholm properties on interpolation scales of quasi-Banach spaces. This analysis is motivated by problems arising in PDE&#39;s and several applications are presented.

Nigel J. Kalton

Suppose $\Cal J$ is a two-sided quasi-Banach ideal of compact operators on a separable infinite-dimensional Hilbert space $\Cal H$. We show that an operator $T\in\Cal J$ can be expressed as finite linear combination of commutators $[A,B]$ where $A\in\Cal J$ and $B\in\Cal B(\Cal H)$ if and only its eigenvalues $(λ_n)$ (arranged in decreasing order of absolute

Kenneth J. Dykema, Nigel J. Kalton

For countably generated ideals, $\Jc$, of $B(\Hil)$, geometric stability is necessary for the canonical spectral characterization of sums of $(\Jc,B(\Hil))$--commutators to hold. This answers a question raised by Dykema, Figiel, Weiss and Wodzicki. There are some ideals, $\Jc$, having quasi--nilpotent elements that are not sums of $(\Jc,B(\Hil))$--commutator

Peter G. Casazza, Nigel J. Kalton

We extend the Paley-Wiener pertubation theory to linear operators mapping a subspace of one Banach space into another Banach space.

Costas Kounnas, Alok Kumar

The N = 3 string models are special solutions of the type II perturbative string theories. We present explicit expressions for the helicity supertraces,which count the number of the perturbative BPS multiplets. Assuming the non-perturbative duality $(S\leftrightarrow T)$ of the heterotic string on T^6 and type II on K_3 x T^2 valid in N = 4 theories, we deri

Jean Alexandre, Vincenzo Branchina, Janos Polonyi

The renormalization group is applied to the phi4 model in the symmetry broken phase in order to identify different scaling regimes. The new scaling laws reflect nonuniversal behavior at the phase transition. The extension of the analysis to finite temperature is briefly outlined. It is mentioned that the coupling constants can be found in the mixed phase by

George Jorjadze, Wlodzimierz Piechocki

A model of a relativistic particle moving in the Liouville field is investigated. Symmetry group of the system is $SL(2,R)/Z_2$. The corresponding dynamical integrals describe full set of classical trajectories. Dynamical integrals are used for the gauge-invariant Hamiltonian reduction. The new scheme is proposed for quantization of the reduced system. Obtai

Sahng-kyoon Yoo, D. K. Park

We calculate the second virial coefficient of spin-1/2 anyon gas in the various values of the self-adjoint extension parameter by incorporating the self-adjoint extension method into the Green&#39;s function formalism. Especially, the completely different cusp- and discontinuity-structures from the result of previous literature are obtained when the self-adj

Yu. Malyuta, T. Obikhod

The spectra of BPS states in F-theory on elliptic fibred fourfolds are investigated.

Marco Cavaglia

We derive a two-dimensional effective dilaton - gravity - matter action that describes the dynamics of an uncharged black p-brane in N dimensions. We show that this effective theory is completely integrable in the static sector and establish its general static solution. The solution includes, as a particular case, the boost symmetric p-brane solution investi

Yuval Grossman, Yosef Nir, Stephane Plaszczynski, Marie-Helene Schune

Fleischer and Mannel (FM) have shown that it may become possible to constrain the angle $γ$ of the unitarity triangle from measurements of various $B\toπK$ decays. This constraint is independent of hadronic uncertainties to the few percent level. We show that, within the Standard Model, the FM bound gives strong constraints on the CKM parameters. In particul

Antonio Riotto

We compute the baryon asymmetry generated at the electroweak phase transition by the Higgs scalar sector of the minimal supersymmetric standard model. Because of large enhancement effects from low momentum modes, Higgs particles may be responsible for the observed baryon asymmetry even though CP-violation in the Higgs sector only appears at the one-loop leve

W. Bernreuther, M. Flesch, P. Haberl

We analyze some signatures of neutral Higgs bosons, produced in high energy proton (anti)proton collisions, which decay primarily to top quarks. This channel is clouded by a large irreducible $t\bar t$ background. We investigate the $t\bar t$ invariant-mass distribution in the lepton+jets decay mode of $t\bar t$ and a $t\bar t$ spin-spin correlation in the d

A. Ballestrero, D. G. Charlton, G. Cowan, P. Dornan

The W Mass and QCD Working Group discussed a wide variety of topics relating to present and future measurements of M(W) at LEP2, including QCD backgrounds to W+W- production. Particular attention was focused on experimental issues concerning the direct reconstruction and threshold mass measurements, and on theoretical and experimental issues concerning the f

A. Brandenburg, W. Bernreuther, P. Uwer

We discuss a calculation of the next-to-leading order QCD corrections to the process $e^+e^-\to 3$ jets with massive quarks, and show numerical results for the three jet fraction and the differential two jet rate.

W. Bernreuther, A. Brandenburg, P. Uwer

The reaction $e^+e^-$ annihilation into three jets was recently computed for massive quarks at next-to-leading order in perturbative QCD. We discuss some results of our calculation for b jets produced at the Z resonance.

Berthold Stech

Exclusive non-leptonic two-body decays are discussed on the basis of a generalized factorization approach which also includes non-factorizeable contributions. Numerous decay processes can be described satisfactorily. The success of the method makes possible the determination of decay constants from non-leptonic decays. In particular, we obtain f_{D_s}=(234+-

B. Machet

I build a SU(2)left x U(1) electroweak gauge theory of J=0 mesons, which transform like sets of fermion-antifermion composite fields. SU(2)left x U(1) is embedded in a natural way, compatible with the Glashow-Salam-Weinberg model for quarks, into the chiral group U(N)left x U(N)right, N being the (even) number of ``flavours&#39;&#39;. The Lagrangian exhibits

Elena Accomando, Alessandro Ballestrero, Marco Pizzio

We compute several total and differential cross sections relevant to top, WWZ and Higgs physics at future $e^+e^-$ colliders taking into account the full set of Feynman diagrams for six fermion final states. We examine in particular charged current processes, in which final particles cannot be formed by three Z&#39;s decay. We include in our calculations ini

A. Bramon, Riazuddin, M. D. Scadron

We study the dynamical consequences imposed on effective chiral field theories such as the quark-level SU(2) linear $σ$ model (L$σ$M) due to the fundamental constraints of massless Goldstone pions, the normalization of the pion decay constant and form factor, and the pion charge radius. We discuss quark-level double counting L$σ$M ambiguities in the context

Attilio Cucchieri

We evaluate numerically the four-momentum-space gluon propagator in lattice Landau gauge, for pure SU(2) lattice gauge theory with periodic boundary conditions. Simulations are done in the strong-coupling regime, namely at $β= 0, 0.8, 1.2 and 1.6$, and for lattice sizes up to $30^4, 16^4, 20^4 and 24^4$ respectively. In the limit of large lattice volume, we

Rajamani Narayanan, Robert L. Singleton

Recent lattice measurements of the topological susceptibility of SU(2) gauge theory using improved cooling and inverse-blocking are in disagreement. We use the overlap method, which probes the fermionic sector of the theory directly, to help resolve this discrepancy.

F. Farchioni, V. Laliena

We compute the fixed point action for the Schwinger model through an expansion in the gauge field. The calculation allows a check of the locality of the action. We test its perfection by computing the 1-loop mass gap at finite spatial volume.

Marcel Demarteau

A review of recent electroweak results from hadron colliders is given. Properties of the W and Z gauge bosons using final states containing electrons and muons based on large integrated luminosities are presented. The emphasis is placed on the measurement of the mass of the W boson and the measurement of trilinear gauge boson couplings.

A. Maggiora

Surprisingly large polarization in hyperon production by unpolarized proton beam has been known since long time. Huge inclusive hyperon polarization data are available in literature, few data are disponible on spin observables and none on exclusive hyperon measurements. Evidence of relevant violation of the OZI rule in several reactions are also shown in rec

Helmut Rumpf

Application of the so-called refined algebraic quantization scheme for constrained systems to the relativistic particle provides an inner product that defines a unique Fock representation for a scalar field in curved space-time. The construction can be made rigorous for a general globally hyperbolic space-time, but the quasifree state so obtained turns out t

A. Bilge, M. Hortacsu, N. Ozdemir

Unruh&#39;s detector calculation is used to study the effect of the defect angle $β$ in a space-time with a cosmic string for both the excitation and deexcitation cases. It is found that a rotating detector results in a non-zero effect for both finite (small) and infinite (large) time.

Warren E. Pickett

We present results based on local spin density calculations of a computational search for half-metallic (HM) antiferromagnetic (AFM) materials within the class of double perovskite structure oxides LaM&#39;M&#39;&#39;O3 that incorporate open shell 3d (or 4d) transition metal ions M&#39;, M&#39;&#39;. The pairs M&#39;M&#39;&#39; = MnCo, CrFe, CrRu, CrNi, MnV,

D. I. Golosov, A. E. Ruckenstein, M. L. Horbach

We study correlation effects in a three-band extended Hubbard model of Cu -- O planes within the 1/N mean field approach, in the infinite U limit. We investigate the emerging phase diagram and discuss the low energy scales associated with each region. With increasing direct overlap between oxygen orbitals, $t_{pp} >0$, the solution displays a band crossing w

R. Kotlyar, C. A. Stafford, S. Das Sarma

Coherent charge transfer in a linear array of tunnel-coupled quantum dots, electrostatically coupled to external gates, is investigated using the Bethe ansatz for a symmetrically biased Hubbard chain. Charge polarization in this correlated system is shown to proceed via two distinct processes: formation of bound states in the metallic phase, and charge trans

Paolo De Los Rios, Nicola Manini

We show through selected examples, relevant to the physics of fullerene ions, that the presence of a Berry phase in dynamical Jahn-Teller systems does not guarantee the degeneracy of the ground state, contrary to what previously believed. Moreover, we introduce a new class of Jahn-Teller systems with no Berry phase, as a generalization of the basic icosahedr

Chen Zeng, J. Kondev, D. McNamara, A. A. Middleton

Statistical topography of two-dimensional interfaces in the presence of quenched disorder is studied utilizing combinatorial optimization algorithms. Finite-size scaling is used to measure geometrical exponents associated with contour loops and fully packed loops. We find that contour-loop exponents depend on the type of disorder (periodic ``vs&#39;&#39; non

D. N. Aristov, S. V. Maleyev

We present the results of analytical evaluation of the indirect RKKY interaction in a layered metal with nearly nested (almost squared) Fermi surface. The final expressions are obtained in closed form as a combination of Bessel functions. We discuss the notion of the ``2k_F&#39;&#39; oscillations and show that they occur as the far asymptote of our expressio

Francisco Vera, Zdenka Barticevic

We studied theoretically the excitonic energy levels and the optical absorption spectra for double quantum wells, both symmetric and asymmetric, in the presece of an homogeneous magnetic field. Within the effective mass approach, we expanded the excitonic wave function, in an orthogonal basis formed by products of electron and hole wave functions in the grow

Jacek Dziarmaga, Meik Hellmund

We prove that for a hard core interaction the ground state spin polarization in the low Zeeman energy limit is given by $P=2/ν-5$ for filling fractions in the range $ 1/3 \leqν\leq 2/5 $. The same result holds for a Coulomb potential except for marginally small magnetic fields. At the magnetic fields $B<20T$ unpolarized quasielectrons can manifest themselves

Jongbae Hong

A nonperturbative method to obtain on- and off-site one-particle Green&#39;s function is introduced and applied to noninteracting Hubbard model with next nearest neighbor hopping and interacting Hubbard model in large dimensions, for example. The former gives some lessons on the method and shows the advantage of the method compared with continued fraction fo

G. E. Volovik

Superconducting states with different internal topology are discussed for the layered high-T_c materials. If the time inversion symmetry is broken, the superconductivity is determined not only by the symmetry of the superconducting state, but also by the topology of the ground state. The latter is determined the integer-valued momentum-space topological inva

Peter Neuhaus, Norbert Broeker

Results of computational complexity exist for a wide range of phrase structure-based grammar formalisms, while there is an apparent lack of such results for dependency-based formalisms. We here adapt a result on the complexity of ID/LP-grammars to the dependency framework. Contrary to previous studies on heavily restricted dependency grammars, we prove that

Eurico Covas, Peter Ashwin, Reza Tavakol

We examine global dynamics and bifurcations occurring in a truncated model of a stellar mean field dynamo. This model has symmetry-forced invariant subspaces for the dynamics and we find examples of transient type I intermittency and blowout bifurcations to transient on-off intermittency, involving laminar phases in the invariant submanifold. In particular,

Albert Stebbins

Analytical expressions are presented for relativistic corrections to the Kompaneets equation and the Sunyaev-Zel&#39;dovich y-distortion. The latter provides a convenient method of inferring both the temperature and Thomson optical depth of the gas in clusters of galaxies using only observations of the spectrum of CMBR photons passing through the cluster. Th

Michel Fioc, Brigitte Rocca-Volmerange

The far-ultraviolet (UV) counts and the deep optical spectroscopic surveys have revealed an unexpected number of very blue galaxies (vBG). Using constraints from the UV and optical, we apply the galaxy evolution model PEGASE (Fioc & Rocca-Volmerange 1997, hereafter FRV) to describe this population with a cycling star formation. When added to normally evolvin

Joshua A. Frieman, Ioav Waga

Recent observations of high-redshift Type Ia supernovae have placed stringent constraints on the cosmological constant $Λ$. We explore the implications of these SNe observations for cosmological models in which a classically evolving scalar field currently dominates the energy density of the Universe. Such models have been shown to share the advantages of $Λ

Eurico Covas, Reza Tavakol, Andrew Tworkowski, Axel Brandenburg

We study axisymmetric mean field spherical and spherical shell dynamo models, with both dynamic and algebraic $α$--quenchings. Our results show that there are qualitative as well as quantitative differences and similarities between these models. Regarding similarities, both groups of models exhibit symmetric, antisymmetric and mixed modes of behaviour. As re

Jesper Sollerman, Robert J. Cumming, Peter Lundqvist

We present spectroscopic and photometric observations of the luminous narrow- line Type IIP (plateau) supernova 1994W. After the plateau phase (t >120 days), the light curve dropped by 3.5 mag in V in only 12 days. Between 125 and 197 days after explosion the supernova faded substantially faster than the decay rate of Co-56, and by day 197 it was 3.6 magnitu

P. M. Pizzochero, L. Viverit, R. A. Broglia

We calculate the force that pins vortices in the neutron superfluid to nuclei in the inner crust of rotating neutron stars, relying on a detailed microscopic description of both the vortex radial profile and the inner crust nuclear structure. The contribution to the pinning energy from pair condensation is estimated in the local density approximation with re

Liliya L. R. Williams, Paul L. Schechter

Gravitational lensing is now widely and successfully used to study a range of astronomical phenomena, from individual objects, like galaxies and clusters, to the mass distribution on various scales, to the overall geometry of the Universe. Here we describe and assess the use of gravitational lensing as ``gold standards&#39;&#39; in addressing one of the fund

Eduardo Esteves

We construct natural relative compactifications for the relative Jacobian over a family $X/S$ of reduced curves. In contrast with all the available compactifications so far, ours admit a universal sheaf, after an etale base change. Our method consists of considering the functor $F$ of relatively simple, torsion-free, rank 1 sheaves on $X/S$, and showing that

Eduardo Esteves

In a 1993 article, G. Faltings gave a new construction of the moduli space $U$ of semistable vector bundles on a smooth curve $X$, avoiding geometric invariant theory. Roughly speaking, Faltings showed that the normalisation $B$ of the ring $A$ of theta functions (associated with vector bundles on $X$) suffices to realize $U$ as a projective variety. Describ

S. A. Stanford, Richard Elston, Peter Eisenhardt, Hyron Spinrad

We report the discovery of a galaxy cluster at z=1.27. ClG J0848+4453 was found in a near-IR field survey as a high density region of objects with very red J-K colors. Optical spectroscopy of a limited number of 24 < R < 25 objects in the area shows that 6 galaxies within a 90 arcsec (0.49/h Mpc, q_O = 0.1) diameter region lie at z=1.273 +/- 0.002. Most of t

Einan Gardi

In this lecture I present some of the new developments concerning the use of Pade Approximants (PA&#39;s) for resumming perturbative series in QCD. It is shown that PA&#39;s tend to reduce the renormalization scale and scheme dependence as compared to truncated series. In particular it is proven that in the limit where the $β$ function is dominated by the 1-

H. M. Wiseman, J. A. Vaccaro

The stationary solution ρof a quantum master equation can be represented as an ensemble of pure states in a continuous infinity of ways. An ensemble which is physically realizable through monitoring the system&#39;s environment we call an `unraveling&#39;. The survival probability S(t) of an unraveling is the average probability for each of its elements to b

Louis H. Kauffman

The purpose of this paper is to present an introduction to a point of view for discrete foundations of physics. In taking a discrete stance, we find that the initial expression of physical theory must occur in a context of noncommutative algebra and noncommutative vector analysis. In this way the formalism of quantum mechanics occurs first, but not necessari

V. Zanchin, A. Maia, W. Craig, R. Brandenberger

Explosive particle production due to parametric resonance is a crucial feature of reheating in inflationary cosmology. Coherent oscillations of the inflaton field act as a periodically varying mass in the evolution equation for matter fields which couple to the inflaton. This in turn results in the parametric resonance instability. Thermal and quantum noise

Carles Bona, Joan Masso, Ed Seidel, Joan Stela

The causal structure of Einstein&#39;s evolution equations is considered. We show that in general they can be written as a first order system of balance laws for any choice of slicing or shift. We also show how certain terms in the evolution equations, that can lead to numerical inaccuracies, can be eliminated by using the Hamiltonian constraint. Furthermore

Masaru Siino

In our previous work, it was shown that the topology of an event horizon (EH) is determined by the past endpoints of the EH. A torus EH (the collision of two EH) is caused by the two-dimensional (one-dimensional) set of the endpoints. In the present article, we examine the stability of the topology of the EH. We see that a simple case of a single spherical E

Huai-Dong Cao, Ying Shen, Shunhui Zhu

We obtain a gradient estimate for the Gauss maps from complete spacelike constant mean curvature hypersurfaces in Minkowski space into the hyperbolic space. As applications, we prove a Bernstein theorem which says that if the image of the Gauss map is bounded from one side, then the spacelike constant mean curvature hypersurface must be linear. This result e

Minseok Park, Jongbae Hong

The extended Falicov-Kimball model which contains hybridization between localized level and conduction band has been studied using the exact diagonalization method. We obtain the single-particle density of states and the valency from this method and analyze the behaviors of valence transition and activation gap. We find that the valence transition is continu

Raul Jimenez, Chris Flynn

We have used the Hipparcos satellite colour magnitude diagram to determine the age of the Galactic disc. We first measure the metallicities of Hipparcos giants using DDO photometry (Høg & Flynn 1997). With accurate metallicities and distances we compute the minimum age of the Galactic disc as $11\pm1$ Gyr using the colour of the reddest clump stars as a func