bluuebunny/crossref_metadata_2025 huggingface dataset:
A HYBRID FINITE-ELEMENT SIMULATION OF SOLID FRACTURE
Authors: POTAPOV ALEXANDER V. , CAMPBELL CHARLES S.
Published: October 2004

This paper describes an extension to a computer simulation of solid fracture. In the original model, rigid elements are assembled into a simulated solid by "gluing" the elements together with compliant boundaries which fracture when the tensile strength of the glued joints is exceeded. The current extension applies portions of the finite element technique to allow changes in the shapes of elements. This is implemented at the element level and no global stiffness matrix is assembled; instead, the elements interact across the same compliant boundaries used in the rigid element simulation. As a result, the simulated material can conform to any desired shape and thus can handle large elastic and plastic deformation. This model is intended to study the propagation of multitudinous cracks through simulated solids to aid the understanding of problems such as the impact-induced fragmentation of particles.
GENERATING PARALLEL RANDOM NUMBER GENERATORS BY CELLULAR PROGRAMMING
Authors: SIPPER MOSHE , TOMASSINI MARCO
Published: October 2004

Random numbers are needed in a variety of applications, yet finding good random number generators is a difficult task. In this paper non-uniform cellular automata (CA) are studied, presenting the cellular programming algorithm for co-evolving such CAs to perform computations. The algorithm is applied to the evolution of random number generators; our results suggest that evolved generators are at least as good as previously described CAs, with notable advantages arising from the existence of a "tunable" algorithm for obtaining random number generators.
EFFECT OF GEOMETRY ON FLUXON WIDTH IN A JOSEPHSON JUNCTION
Authors: CAPUTO JEAN-GUY , FLYTZANIS NIKOS , VAVALIS EMMANUEL
Published: October 2004

We investigate the electromagnetic influence of the surrounding idle (no tunneling) region on static fluxons in window Josephson junctions. We calculated the fluxon width as a function of the size of the idle region for three different window (active tunneling area) geometries, namely elongated truncated rhombus, rectangular and bow-tie and derived approximate expressions for the case of small and large idle regions. The window geometry affects both the fluxon width and the fluxon stability. One can define an effective λJ which depends on the junction width, the idle region width and the inductance ratio and has important consequences on the static and dynamic properties of window Josephson junctions. We also show the effect of the idle region on the maximum tunneling current as a function of the external magnetic field.
POLYDISPERSITY EFFECT TO THE FLUID-SOLID TRANSITION
Authors: ITO NOBUYASU
Published: October 2004

The simulation results for polydisperse particle system are analyzed to study the polydispersity effect to liquid/fluid-solid transition. It is found that the transition density and the solid state are well described by the variance, σ2, of radius distribution. The critical polydispersity above which fluid-solid coexisting density region vanishes is estimated to be σ2 = 0.0073 ± 0.0005. A scaling plot for the solid pressure is shown.
UNIVERSAL FINITE-SIZE-SCALING FUNCTIONS
Authors: OKABE YUTAKA , KIKUCHI MACOTO
Published: October 2004

The idea of universal finite-size-scaling functions of the Ising model is tested by Monte Carlo simulations for various lattices. Not only regular lattices such as the square lattice but quasiperiodic lattices such as the Penrose lattice are treated. We show that the finite-size-scaling functions of the order parameter for various lattices are collapsed on a single curve by choosing two nonuniversal scaling metric factors. We extend the idea of the universal finite-size-scaling functions to the order-parameter distribution function. We pay attention to the effects of boundary conditions.
TESTS OF RANDOM NUMBER GENERATORS USING ISING MODEL SIMULATIONS
Authors: CODDINGTON P. D.
Published: October 2004

Large-scale Monte Carlo simulations require high-quality random number generators to ensure correct results. The contrapositive of this statement is also true — the quality of random number generators can be tested by using them in large-scale Monte Carlo simulations. We have tested many commonly-used random number generators with high precision Monte Carlo simulations of the 2-d Ising model using the Metropolis, Swendsen-Wang, and Wolff algorithms. This work is being extended to the testing of random number generators for parallel computers. The results of these tests are presented, along with recommendations for random number generators for high-performance computers, particularly for lattice Monte Carlo simulations.
TWO-TEMPERATURE NON-EQUILIBRIUM ISING MODELS
Authors: TAMAYO P. , GUPTA R. , ALEXANDER F. J.
Published: October 2004

We present results from a computational study of a class of 2D two-temperature non-equilibrium Ising models. In these systems the dynamics is a local competition of two equilibrium dynamics at different temperatures. We analyzed non-equilibrium versions of Metropolis, heat bath/Glauber and Swendsen-Wang dynamics and found strong evidence that some of these dynamics have the same critical exponents and belong to the same universality class as the equilibrium 2D Ising model.
SPIN DYNAMICS SIMULATIONS OF CLASSICAL, THREE-DIMENSIONAL HEISENBERG MAGNETS
Authors: LANDAU D. P. , BUNKER ALEX , CHEN KUN
Published: October 2004

Spin dynamics simulations have been used to study dynamic critical behavior of classical Heisenberg magnets. The temporal evolutions of the spin configurations were determined numerically from coupled equations of motion by a fourth-order predictor corrector method, with initial spin configurations generated by Monte-Carlo simulations. The neutron scattering function, S (q, ω), was calculated from the space and time displaced spin-spin correlation function and the dynamic critical exponent z was extracted using dynamic finite size scaling theory. For both ferromagnetic and antiferromagnetic models we find good agreement with theoretical predictions and experimental results.
CLUSTER MONTE CARLO STUDY OF THE QUANTUM XY MODEL IN TWO DIMENSIONS
Authors: KAWASHIMA N. , JARRELL MARK , GUBERNATIS J.E.
Published: October 2004

The recent generalization of the Fortuin-Kasteleyn percolation representation and the Swendsen-Wang (SW) cluster algorithm is reviewed. The new representation yields cluster algorithm for the XYZ model with arbitrary magnitude of spins, with arbitrary anisotropies, and in any dimensions. The new algorithm often reduces computational autocorrelation times by several orders of magnitude. By using the new algorithm together with methods of Bayesian statistical inference, we obtained the dynamical structure factor S (k, ω) for the S =1/2 XY model in two dimensions.
POWER LAWS ARE LOGARITHMIC BOLTZMANN LAWS
Authors: LEVY MOSHE , SOLOMON SORIN
Published: October 2004

Multiplicative random processes in (not necessarily equilibrium or steady state) stochastic systems with many degrees of freedom lead to Boltzmann distributions when the dynamics is expressed in terms of the logarithm of the elementary variables. In terms of the original variables this gives a power-law distribution. This mechanism implies certain relations between the constraints of the system, the power of the distribution and the dispersion law of the fluctuations. These predictions are validated by Monte Carlo simulations and experimental data. We speculate that stochastic multiplicative dynamics might be the natural origin for the emergence of criticality and scale hierarchies without fine-tuning.
HOW IS SYMPLECTIC INTEGRATOR APPLICABLE TO MOLECULAR DYNAMICS?
Authors: OKABE TSUNEYASU , YAMADA HIROAKI , GODA MASAKI
Published: October 2004

We systematically investigate how symplectic integrator schemes are effective when applied to molecular dynamics method. The performances are estimated from a point of view of the total energy conservation by investigating molecular dynamics of one-component Lennard–Jones system in constant volume and constant temperature and pressure. It is shown that numerical simulations by the symplectic integrator scheme are better than those by classical schemes for a long-time simulation even in the case of large step size. The performances of various orders of symplectic integrator are evaluated.
A THREE-DIMENSIONAL SIMULATION OF BRITTLE SOLID FRACTURE
Authors: POTAPOV ALEXANDER V. , CAMPBELL CHARLES S.
Published: October 2004

This paper describes an extension into three dimensions of an existing two-dimensional technique for simulating brittle solid fracture. The fracture occurs on a simulated solid created by "gluing" together space-filling polyhedral elements with compliant interelement joints. Such a material can be shown to have well-defined elastic properties. However, the "glue" can only support a specified tensile stress and breaks when that stress is exceeded. In this manner, a crack can propagate across the simulated material. A comparison with experiment shows that the simulation can accurately reproduce the size distributions for all fragments with linear dimensions greater than three element sizes.
AGE-OF-PARENT DEPENDENT MUTATION RATE AND WEAK CHILDREN IN THE PENNA MODEL IN BIOLOGICAL AGEING
Authors: BERNTSEN K. NIKOLAJ
Published: October 2004

We investigate the effect of an age-dependent mutation rate in the Penna model of ageing and then we observe that the high mortality for human babies can be reproduced by the model if one assumes babies to be weaker than adults.
PSEUDORECURRENCE AND CHAOS OF CUBIC-QUINTIC NONLINEAR SCHRÖDINGER EQUATION
Authors: ZHOU CANGTAO , LAI C. H.
Published: October 2004

Recurrence, pseudorecurrence, and chaotic solutions for a continuum Hamiltonian system in which there exist spatial patterns of solitary wave structures are investigated using the nonlinear Schrödinger equation (NSE) with cubic and quintic terms. The theoretical analyses indicate that there may exist Birkhoff's recurrence for the arbitrary parameter values. The numerical experiments show that there may be Fermi–Pasta–Ulam (FPU) recurrence, pseudorecurrence, and chaos when different initial conditions are chosen. The fact that the system energy is effectively shared by finite Fourier modes suggests that it may be possible to describe the continuum system in terms of some effective degrees of freedom.
EFFICIENCY OF DIFFERENT MATRIX INVERSION METHODS APPLIED TO WILSON FERMIONS
Authors: CELLA G. , HOFERICHTER A. , MITRJUSHKIN V. K. , MÜLLER-PREUSSKER M. , VICERÉ A.
Published: October 2004

We compare different conjugate gradient–like matrix inversion methods (CG, BiCGstab1 and BiCGstab2) employing for this purpose the compact lattice quantum electrodynamics (QED) with Wilson fermions. The main goals of this investigation are the CPU time efficiency of the methods as well as the influence of machine precision on the reliability of (physical) results especially close to the 'critical' line κc (β).
FRAGMENTATION OF COLLIDING DISCS
Authors: KUN FERENC , HERRMANN HANS J.
Published: October 2004

We study the phenomena associated with the low-velocity impact of two solid discs of equal size using a cell model of brittle solids. The fragment ejection exhibits a jet-like structure the direction of which depends on the impact parameter. We obtain the velocity and the mass distribution of the debris. Varying the radius and the initial velocity of the colliding particles, the velocity components of the fragments show anomalous scaling. The mass distribution follows a power law in the region of intermediate masses.
STUDYING PROBABILISTIC FAULTS IN EVOLVED NON-UNIFORM CELLULAR AUTOMATA
Authors: SIPPER MOSHE , TOMASSINI MARCO , BEURET OLIVIER
Published: October 2004

We study the effects of random faults on the behavior of one-dimensional, non-uniform cellular automata (CA), where the local update rule need not be identical for all grid sites. The CA systems examined were obtained via an approach known as cellular programming, which involves the evolution of non-uniform CAs to perform non-trivial computational tasks. Using the "system replicas" methodology, involving a comparison between a perfect, non-perturbed version of the CA and a faulty one, we find that our evolved systems exhibit graceful degradation in performance, able to tolerate a certain level of faults. We then "zoom" into the fault-tolerant zone, where "good" computational behavior is exhibited, introducing measures to fine-tune our understanding of the faulty CAs' operation. We study the error level as a function of time and space, as well as the recuperation time needed to recover from faults. Our investigation reveals an intricate interplay between temporal and spatial factors, with the presence of different rules in the grid giving rise to complex dynamics. Studies along this line may have applications to future computing systems that will contain thousands or even millions of computing elements, rendering crucial the issue of resilience.
KNOT THEORY, PARTITION FUNCTION AND FRACTALS
Authors: Ge Mo-Lin , Hu Liangzhong , Wang Yiwen
Published: October 2004

In this paper we first provide the open chain and the closed chain method to calculate the partition functions of the typical fractal lattices, i.e. a special kind of Sierpinski carpets(SC) and the triangular Sierpinski gaskets(SG). We then apply knot theory to fractal lattices by changing lattice graphs into link diagrams according to the interaction models, and explicitly obtain the partition functions of a special SC for the edge interaction models. These partition functions are also the knot invariants of the corresponding link diagrams. This is the first time that topology enters into fractals.
THE PLANARITY PROBLEM II
Authors: CAIRNS GRANT , ELTON DANIEL M.
Published: October 2004

C.F. Gauss gave a necessary condition for a word to be the intersection sequence of a closed normal planar curve and he gave an example which showed that his condition was not sufficient. Since then several authors have given algorithmic solutions to this problem. In a previous paper, along the lines of Gauss’s original condition, we gave a necessary and sufficient condition for the planarity of “signed” Gauss words. In this present paper we give a solution to the planarity problem for unsigned Gauss words.
WEAK UNKNOTTING NUMBER OF A COMPOSITE 2-KNOT
Authors: KANENOBU TAIZO
Published: October 2004

The weak unknotting number of a 2-knot K in a 4-sphere is the minimum number of elements g1, g2,…, gn of the knot group πK of K such that πK becomes the infinite cyclic group by adding the relations gix=xgi, where x is a meridian. We give an example of the nonadditivity of the weak unknotting number under connected sum of 2-knots.
GENERALIZED GAUSSIAN SUMS CHERN-SIMONS-WITTEN-JONES INVARIANTS OF LEN-SPACES
Authors: LI BANG-HE , LI TIAN-JUN
Published: October 2004

Starting from evaluating all Gaussian sums, we calculate {τr, r≥2} (in the 4r-th cyclotomic fields) and {ξr, r odd≥3} (in the r-th cyclotomic fields) for all lens spaces L(p, q). We prove that they are all algebraic integers and show that ξr determines the Dedekind sum s(q, p), and hence determines the generalized Casson invariant of lens space. We conjecture these two properties hold for more general 3-manifold, and some evidences are discussed. Though the formulae are not simple, we are able to give necessary and sufficient conditions for lens spaces to have the same CSWJ invariants. Examples of lens spaces with the same invariants but different topological types are given. Some applications in number theory are also included.
LOCAL MOVES ON A GRAPH IN R3
Authors: OHYAMA YOSHIYUKI
Published: October 2004

We extend a notion, an unknotting operation for knots, to a spatial embedding of a graph and study local moves on a diagram of a spatial graph.
QUANTUM PSU(2) INVARIANT AT A FIFTH ROOT OF UNITY
Authors: KAMADA N.
Published: October 2004

For Z/rZ-homology 3-spheres the Casson invariant is related to the quantum PSU (2) invariant at an rth root of unity with odd prime r. We prove a similar relationship between the Casson invariant and the quantum PSU (2) invariant at a fifth root of unity for a 3-manifold whose first Z /5 Z -Betti number is positive.
REPRESENTATIONS OF KNOT GROUPS AND VASSILIEV INVARIANTS
Authors: ALTSCHULER DANIEL
Published: October 2004

We show that the number of homomorphisms from a knot group to a finite group G cannot be a Vassiliev invariant, unless it is constant on the set of (2, 2p+1) torus knots. In several cases, such as when G is a dihedral or symmetric group, this implies that the number of homomorphisms is not a Vassiliev invariant.
ON ROBERTS’ PROOF OF THE TURAEV-WALKER THEOREM
Authors: BENEDETTI RICCARDO , PETRONIO CARLO
Published: October 2004

In this paper we discuss the beautiful idea of Justin Roberts [7] (see also [8]) to re-obtain the Turaev-Viro invariants [11] via skein theory, and re-prove elementarily the Turaev-Walker theorem [9], [10], [13]. We do this by exploiting the presentation of 3-manifolds introduced in [1], [4]. Our presentation supports in a very natural way a formal implementation of Roberts’ idea.

More specifically, what we show is how to explicitly extract from an o-graph (the object by which we represent a manifold, see below), one of the framed links in S3 which Roberts uses in the construction of his invariant, and a planar diagrammatic representation of such a link. This implies that the proofs of invariance and equality with the Turaev-Viro invariant can be carried out in a completely “algebraic” way, in terms of a planar diagrammatic calculus which does not require any interpretation of 3-dimensional figures. In particular, when proving the “term-by-term” equality of the expansion of the Roberts invariant with the state sum which gives the Turaev-Viro invariant, we simultaneously apply several times the “fusion rule” (which is formally defined, strictly speaking, only in diagrammatic terms), showing that the “braiding and twisting” which a priori may exist on tetrahedra is globally dispensable. In our point of view the success of this formal “algebraic” approach witnesses a certain efficiency of our presentation of 3-manifolds via o-graphs.

In this work we will widely use recoupling theory which was very clearly exposed in [2], and therefore we will avoid recalling notations. Actually, for the purpose of stating and proving our results we will need to slightly extend the class of trivalent ribbon diagrams on which the bracket can be computed. We also address the reader to the references quoted in [2], in particular for the fundamental contributions of Lickorish to this area.

In our approach it is more natural to consider invariants of compact 3-manifolds with non-empty boundary. The case of closed 3-manifolds is included by introducing a correction factor corresponding to boundary spheres, as explained in §2. Our main result is actually an extension to manifolds with boundary of the Turaev-Walker theorem: we show that the Turaev-Viro invariant of such a manifold coincides (up to a factor which depends on the Euler characteristic) with the Reshetikhin-Turaev-Witten invariant of the manifold mirrored in its boundary.
DERIVATION OF THE TOTAL TWIST FROM CHERN-SIMONS THEORY
Authors: HIRSHFELD ALLEN C. , SASSENBERG UWE
Published: October 2004

The total twist number, which represents on one hand the second coefficient of the Alexander-Conway polynomial and on the other hand the first non-trivial Vassiliev knot invariant, is derived from the second order expression of the Wilson loop expectation value in the Chern-Simons theory. Using the well-known fact that the analytical expression is an invariant, a combinatorial expression for the total twist based on the evaluation of knot diagrams is constructed by an appropriate deformation of the knot line in the three-dimensional Euclidian space. The relation to the original definition of the total twist is elucidated.
A CONJECTURE OF KAUFFMAN ON AMPHICHEIRAL ALTERNATING KNOTS
Authors: DASBACH OLIVER T. , HOUGARDY STEFAN
Published: October 2004

We give a counterexample to the following conjecture of Kauffman [2]:

Conjecture Let K be an amphicheiral alternating knot. Then there exists a reduced alternating knot-diagram D of K, such that G(D) is isomorphic to G* (D), where G(D) is a checkerboard-graph of D and G*(D) its dual.
GEOMETRIC OPERATIONS AND THE η-INVARIANTS OF HYPERBOLIC LINKS
Authors: OUYANG MINGQING
Published: October 2004

In this note we study how the η-invariant of a hyperbolic knot or link behaves under various geometric cuttings and pastings. Among other applications, we show that such an invariant is preserved under mutation and can be used to distinguish many links with homeomorphic complements.
VASSILIEV INVARIANTS FOR TORUS KNOTS
Authors: ALVAREZ M. , LABASTIDA J.M.F.
Published: October 2004

Vassiliev. invariants up to order six for arbitrary torus knots {n, m}, with n and m coprime integers, are computed. These invariants are polynomials in n and m whose degree coincide with their order. Furthermore, they turn out to be integer-valued in a normalization previously proposed by the authors.
EXPLICIT FORMULATION OF A THIRD ORDER FINITE KNOT INVARIANT DERIVED FROM CHERN-SIMONS THEORY
Authors: HIRSHFELD ALLEN C. , SASSENBERG UWE
Published: October 2004

An explicit formulation of a third order finite knot invariant is derived from the perturbative expression of the Wilson loop integral along a knotted line in Chern-Simons theory. This is achieved by an appropriate deformation of the knot line in three dimensional space. It is demonstrated that this formulation fulfils the axioms of the Vassiliev invariants. We use our formula in order to calculate the invariant for knots with up to nine crossings and for some torus knots.
SOME REMARKS ON TABACHNIKOV’S INVARIANTS OF PLANE CURVES
Authors: KHOVANOV MIKHAIL
Published: October 2004

We construct a generalization of the “free group valued” Tabachnikov’s invariant of long curves. We characterize Tabachnikov’s polynomial invariant of plane curves via a representation of the twin group. We also show that these invariants are combinations of finite type invariants.
A Braid Representation and Corresponding Closed Braid Invariant
Authors: MULLINS DAVID
Published: October 2004

In [5] Xiao Song Lin shows that “traceless” representations of a braid group into SU(2) counted with appropriate sign gives one half of the signature of the associated knot. This is done with a skein technique, comparing the behavior of the representations and the sign of the Conway polynomial of the knot evaluated at 2i. These results appear somewhat mysterious.

In this paper, we present a representation of the braid group into SL(2n,Z) where n+1 is the number of strands of the braid. This matrix arises naturally from considering the two-fold branched cover of a ball containing the braid. The lower right n×n block is basically the reduced Brauer representation evaluated at –1 while the lower left n×n block of this matrix has special significance. The absolute value of the determinant of this block corresponds to the determinant of the corresponding closed braid. If one defines C(η) to be the determinant of this block normalized properly one gets an invariant of the corresponding closed braid which is equal to the Conway polynomial of the corresponding closed braid evaluated at 2i. Therefore, one can use a skein technique to compute the signature of the knot from C(η). Since the absolute value of the Conway polynomial evaluated at 2i is the order of the homology of the two-fold branched cover of a link, C(η) also contains this homological information. It will be shown in [6] that the lower left n×n block is a presentation matrix of the first homology of the two-fold cover. This homology matrix is related to the traceless representations of Xiao Song Lin that come from the homology of the two-fold branched cover.
HOMOGENEOUS PERFECT FLUID IN BRANS-DICKE-BIANCHI TYPE V COSMOLOGICAL MODEL
Authors: CHAKRABORTY SUBENOY , NANDY GOPAL CH.
Published: October 2004

In this paper we have studied homogeneous perfect fluid for the Bianchi type V model in the Brans-Dicke theory. The equation of state is assumed to be [Formula: see text]. Some analytical solutions to the field equations are obtained for the radiation era.
SCALAR FIELD COSMOLOGIES WITH PERFECT FLUID IN ROBERTSON-WALKER METRIC
Authors: CHIMENTO LUIS P. , JAKUBI ALEJANDRO S.
Published: October 2004

Several isotropic, homogeneous cosmological models containing a self-interacting minimally coupled scalar field, a perfect fluid source and cosmological constant are solved. New exact, asymptotically stable solutions with an inflationary regime or a final Friedmann stage are found for some simple, interesting potentials. It is shown that the fluid and the curvature may determine how these models evolve for large times.
EXACT SOLUTIONS IN BRANS-DICKE MATTER COSMOLOGIES
Authors: CAPOZZIELLO S. , RITIS R. DE , RUBANO C. , SCUDELLARO P.
Published: October 2004

We investigate Brans-Dicke cosmology with perfect-fluid matter and give a method for selecting exact solutions parametrized by the constant γ of the state equation p=(γ−1)ρ and the parameter ξ of the nonminimal coupling in which the Brans-Dicke theory can be recast. In this sense, we can classify the solutions having and not having inflationary behavior in the presence of ordinary matter.
COSMIC NO-HAIR THEOREM IN ANISOTROPIC, NONMINIMALLY COUPLED COSMOLOGIES
Authors: CAPOZZIELLO S. , RITIS R. DE
Published: October 2004

The cosmic no-hair theorem is generalized for homogeneous and anisotropic spacetimes in which a scalar field is nonminimally coupled to the geometry. The result is that the Wald proof also holds here for all Bianchi-type universes except Bianchi type-IX. However, considering the asymptotic behaviour of parameters, it is possible to find a class of models where the conjecture holds for Bianchi-IX too.
THE WAVE EQUATIONS FOR THE WEYL TENSOR/SPINOR AND DIMENSIONALLY DEPENDENT TENSOR IDENTITIES
Authors: ANDERSSON FREDRIK , EDGAR S. BRIAN
Published: October 2004

By reconciling the wave equation for the Weyl tensor with the corresponding wave equation for the Weyl spinor, we establish a new tensor identity—involving the sum of terms each consisting of a product of the Weyl and Ricci tensors—valid in four (and only four) dimensions. This enables us to give, for the first time, the correct and simplest form of the wave equation for the Weyl tensor in four-dimensional nonvacuum spacetimes. The wave equation for the Weyl tensor in n(> 4) dimensional nonvacuum spaces is also presented for the first time; we show that there does not exist an analogous n-dimensional tensor identity matching the four-dimensional one, and so it follows that there does not exist an analogous simplification of the Weyl wave equation in the n-dimensional case. It is also shown how our new identity, and some other recently discovered identities, relate to a large class of dimensionally dependent identities found some time ago by Lovelock.
HAMILTONIAN FORMALISM FOR BLACK HOLES AND QUANTIZATION II
Authors: CAVAGLIÀ MARCO , ALFARO VITTORIO DE , FILIPPOV ALEXANDRE T.
Published: October 2004

We quantize by the Dirac-Wheeler-DeWitt method the canonical formulation of the Schwarzschild black hole developed in a previous paper. We investigate the properties of the operators that generate rigid symmetries of the Hamiltonian, establish the form of the invariant measure under the rigid transformations, and determine the gauge fixed Hilbert space of states. We also prove that the reduced quantization method leads to the same Hilbert space for a suitable gauge fixing.
ENERGY ASSOCIATED WITH CHARGED DILATON BLACK HOLES
Authors: CHAMORRO A. , VIRBHADRA K.S.
Published: October 2004

It is known that certain properties of charged dilaton black holes depend on a free parameter β which controls the strength of the coupling of the dilaton to the Maxwell field. We obtain the energy associated with static spherically symmetric charged dilaton black holes for arbitrary value of the coupling parameter and find that the energy distribution depends on the value of β. With increasing radial distance, the energy in a sphere increases for β=0 as well as for β<1, decreases for β>1, and remains constant for β=1. However, the total energy turns out to be the same for all values of β.
A PROPOSED SCALE-DEPENDENT COSMOLOGY FOR THE INHOMOGENEOUS UNIVERSE
Authors: KIM C.W. , SONG J.
Published: October 2004

We propose a scale-dependent cosmology with the stress-energy tensor of viscous fluid, in which the Robertson-Walker metric and the Einstein equation are generalized in such a way that Ω0, H0 and the age of the Universe all become scale-dependent. Its implications on the observational cosmology and possible modifications of the standard Friedmann cosmology are discussed. For example, since the age of the Universe in this model depends on the local values of Ω0 and the Hubble parameter, the age of the locally open Universe even with the high value of hubble parameter can be long enough to accommodate the measured ages of the oldest stars and globular clusters.
THE POST-BIANCHI IDENTITIES IN THE GHP FORMALISM
Authors: LUDWIG GARRY
Published: October 2004

As is well-known, when searching for Petrov type I vacuum solutions the imposition of tetrad conditions leads to integrability conditions on the Bianchi identities. Such post-Bianchi equations are simplest in GHP. They are exhibited explicitly for both a “canonical” frame and an “aligned” frame. Choosing a particular gauge, however, complicates the situation considerably; many more conditions are obtained. When this is done for the “canonical” case the resulting equations, when translated to NP, are the Brans-Edgar equations. How all such equations can be checked is reviewed in some detail.
TIME MACHINES AND THE PRINCIPLE OF SELF-CONSISTENCY AS A CONSEQUENCE OF THE PRINCIPLE OF STATIONARY ACTION (II): THE CAUCHY PROBLEM FOR A SELF-INTERACTING RELATIVISTIC PARTICLE
Authors: CARLINI A. , NOVIKOV I.D.
Published: October 2004

We consider the action principle to derive the classical, relativistic motion of a selfinteracting particle in a 4D Lorentzian spacetime containing a wormhole and which allows the existence of closed time-like curves. In particular, we study the case of a pointlike particle subject to a “hard-sphere” self-interaction potential and which can traverse the wormhole an arbitrary number of times, and show that the only possible trajectories for which the classical action is stationary are those which are globally self-consistent. Generically, the multiplicity of these trajectories (defined as the number of self-consistent solutions to the equations of motion beginning with given Cauchy data) is finite, and it becomes infinite if certain constraints on the same initial data are satisfied. This confirms the previous conclusions (for a nonrelativistic model) by Echeverria, Klinkhammer and Thorne that the Cauchy initial value problem in the presence of a wormhole “time machine” is classically “ill-posed” (far too many solutions). Our results further extend the recent claim by Novikov et al. that the “principle of self-consistency” is a natural consequence of the “principle of minimal action.”
TWISTORS IN CONFORMALLY FLAT EINSTEIN FOUR-MANIFOLDS
Authors: ESPOSITO GIAMPIERO , POLLIFRONE GIUSEPPE
Published: October 2004

This paper studies the two-component spinor form of massive spin-[Formula: see text] potentials in conformally flat Einstein four-manifolds. Following earlier work in the literature, a nonvanishing cosmological constant makes it necessary to introduce a supercovariant derivative operator. The analysis of supergauge transformations of primary and secondary potentials for spin-[Formula: see text] shows that the gauge freedom for massive spin-[Formula: see text] potentials is generated by solutions of the supertwistor equations. The supercovariant form of a partial connection on a nonlinear bundle is then obtained, and the basic equation of massive secondary potentials is shown to be the integrability condition on super β-surfaces of a differential operator on a vector bundle of rank 3. Moreover, in the presence of boundaries, a simple algebraic relation among some spinor fields is found to ensure the gauge invariance of locally supersymmetric boundary conditions relevant for quantum cosmology and supergravity.
RELATIVISTIC IONIZATION BY COMPRESSION OF ATOMS AND IONS: A PROPEDEUTICAL STUDY FOR DEGENERATE STELLAR STRUCTURES
Authors: MERLONI ANDREA , RUFFINI REMO
Published: October 2004

Following the relativistic generalization of the Fermi-Thomas equation proposed by Ferrerinho et al.1 we reconsider the Feynmann-Metropolis-Teller treatment2 for compressed atoms and ions. Explicit examples and numerical results are given for the Fermi energies and momenta for selected values of the compression; the ionization by compression curve is given as well. It is remarkable that, even in the most compressed and relativistic configurations, the enhancement of the electron density around the nucleus can never be neglected, so that the electron densities are always far from uniform. Derivation of the electronic distributions for selected values of the compression are given.
VANISHING OF THE COSMOLOGICAL CONSTANT, STABILITY OF THE DILATON AND INFLATION
Authors: MACORRA A. DE LA
Published: October 2004

We study the possibility of canceling the cosmological constant in supergravity string models. We show that with a suitable choice of superpotential the vacuum energy may vanish with the dilaton field at its minimum and supersymmetry broken with a large hierarchy. We derive the condition for which the introduction of a chiral potential, e.g. the inflaton potential, does not destabilize the dilaton field even in the region where the scalar potential takes positive values. This allows for an inflationary potential with the dilaton frozen at its minimum.
FIRST ORDER, 2D, EINSTEIN GRAVITIES
Authors: DESER S.
Published: October 2004

The Palatini variational method breaks down in 2D: First order forms of the Einstein action do not fix the affinity completely, as they possess an additional, Weyl, invariance absent in the second order versions.
SENSIBLE QUANTUM MECHANICS: ARE PROBABILITIES ONLY IN THE MIND?
Authors: PAGE DON N.
Published: October 2004

Quantum mechanics may be formulated as Sensible Quantum Mechanics (SQM) so that it contains nothing probabilistic except conscious perceptions. Sets of these perceptions can be deterministically realized with measures given by expectation values of positive-operator-valued awareness operators. Ratios of the measures for these sets of perceptions can be interpreted as frequency-type probabilities for many actually existing sets. These probabilities generally cannot be given by the ordinary quantum “probabilities” for a single set of alternatives. Probabilism, or ascribing probabilities to unconscious aspects of the world, may be seen to be an aesthemamorphic myth.
BLACK HOLE ENTROPY AND QUANTUM MECHANICS IN GENERIC 2-D DILATON GRAVITY
Authors: KUNSTATTER G.
Published: October 2004

We review some recent work concerning the classical thermodynamics and quantum mechanics of charged black holes in generic 2-D dilaton gravity. The main result that has emerged from this work is an intriguing connection between the classical black hole entropy and the imaginary part of the WKB phase of energy and charge eigenstates in the corresponding quantum theory.
MONOPOLES AS BIG AS A UNIVERSE AND THE UNIVERSE INSIDE A BUBBLE
Authors: LINDE A.
Published: October 2004

One of the most beautiful concepts in theoretical physics was the idea of fridmons, the semi-closed worlds which from the outside look like an elementary particle, but which may contain the whole universe in their heart. This idea was developed 25 years ago by Markov and his collaborators [1]. In this paper I will discuss some related ideas which have been developed very recently in the context of inflationary cosmology. The first one is the possibility that magnetic monopoles and other topological defects in a certain class of theories inflate, become exponentially large, and unceasingly produce other inflationary monopoles. The second idea is the possibility that an infinitely large open inflationary universe may fit into an interior of a single bubble of a finite size produced during the false vacuum decay.
THE PROBLEM OF CLASSICAL LIMIT IN QUANTUM COSMOLOGY: THE EFFECTIVE ACTION LANGUAGE
Authors: ALTSHULER B.L. , BOYARSKY A.M. , NERONOV A.YU.
Published: October 2004

The tool of functional averaging over some “large” diffeomorphisms is used to describe quantum systems with constraints, in particular quantum cosmology, in the language of quantum Effective. Action. Simple toy models demonstrate a supposedly general phenomenon: the presence of a constraint results in “quantum repel” from the classical mass shell.
TIME AND ENTROPY FROM SEMI-CLASSICAL TUNNELING OF THE COSMOLOGICAL SCALE FUNCTION
Authors: HORWITZ GERALD
Published: October 2004

Two major apparently unrelated problems, that of the origin of time in the universe associated with quantum gravity and of the entropy in de Sitter cosmological models, are found to have their origin in a single physical phenomenon: the semi-classical tunneling through a classically forbidden region of the cosmological scale factor. In this region there is a mixing of the states of quantum matter and those of the semi-classical gravity which produces a thermal mixture of the matter states and hence an “entropy;” this same mixing effect brings about the conversion of a parametric time variable into a physical intrinsic time.
INCLUSIVE TRITIUM STRIPPING REACTION THEORY
Authors: AKHIEZER A.I. , SOZNIK A.P. , BEREZHNOY YU. A.
Published: October 2004

The angular and energy distributions and the integrated cross-section of the inclusive two-nucleon transfer reaction with the participation of three-nucleon nucleus were calculated at intermediate energies.
POLARIZABILITY EFFECTS IN PION PHOTOPRODUCTION
Authors: WOLFE C.E. , NOZAWA S. , BUTLER M.N. , CASTEL B.
Published: October 2004

We investigate the pion photoproduction reaction γN→γNπ as a probe of pion electromagnetic polarizability. This reaction had been proposed as having the potential to resolve the long standing discrepancy between measurements of pion polarizabilities and the predictions of Chiral Perturbation Theory. We have carried out a series of calculations of ratios of substructure — related to background contributions for energies below the Δ resonance — but have to report that the largest values are found in the high-energy tail of the photon spectrum and that these are of the order of 0.1% for charged pions and 1% for neutral pions. We conclude that these sensitivities are not yet accessible experimentally, and that this regime of energy should be excluded from current consideration.
PHYSICS OF STRANGE MATTER FOR RELATIVISTIC HEAVY-ION COLLISIONS
Authors: GREINER CARSTEN , SCHAFFNER JÜRGEN
Published: October 2004

Relativistic heavy-ion collisions offer the possibility to produce exotic metastable or even absolutely stable states of nuclear matter containing (roughly) equal number of strangeness compared to the baryon number: Strangelets, small pieces of strange quark matter, were proposed as a signal of quark-gluon plasma formation. As their hadronic counterpart, also small pieces of strange hadronic matter may also show up with rather similar properties. The reasoning of both their stability and existence, the possible separation of strangeness necessary for their formation, and the chances for their detection, are reviewed.
STUDY OF EXCITATION FUNCTIONS IN Rh(α, xn) Ag REACTIONS
Authors: ANSARI M. AFZAL , SATHIK N.P.M. , SINGH B.P. , SANKARACHARYULU M.G.V. , PRASAD R.
Published: October 2004

The excitation functions for the reactions 103 Rh (α, n)106 m Ag , 103 Rh (α, 2n)105 Ag , and 103 Rh (α, 3n)104 Ag have been measured between 10 and 40 MeV alpha-particle energy, using the stacked foil activation technique. Excitation functions are also calculated theoretically using the Geometry Dependent Hybrid (GDH) model. The computer code ALICE/LIVERMORE-82 has been used which takes into account the pre-equilibrium contribution along with the equilibrium decay of the compound nucleus. It has been found that initial exciton number n0=4 gives a satisfactory reproduction of experimental data.
COLD NEUTRON AND NUCLEAR MATTER WITH EFFECTIVE AND REALISTIC INTERACTIONS
Authors: VENTURA J. , POLLS A. , VIÑAS X. , PI M.
Published: October 2004

A study of the equation of state (EOS) for cold asymmetric nuclear matter and beta-stable matter using effective interactions, of zero range (Skyrme type) and finite range type (D1-Gogny), is performed in the Hartree-Fock approach. The results are systematically compared with recent microscopic calculations. Two parametrizations of the energy of asymmetric nuclear matter in terms of the asymmetry parameter are tested in the case of effective interactions. While all forces agree rather well for nuclear matter, some discrepancies appear for neutron matter revealing the different spin-isospin contents of the interactions.
NUCLEAR SURFACE OSCILLATION MODEL IN HEAVY NUCLEI FISSION
Authors: GARISTOV VLADIMIR P.
Published: October 2004

The fission of many heavy nuclei shows a bimodal character, with both low and high-energy components in the kinetic energy distribution. These two components are thought to arise because the nucleus can choose two different paths to scission from the ground state; either a path leading to elongated scission shapes and low fission fragment kinetic energies or a path leading to the compact scission configuration of two touching spheres and high fission fragment kinetic energies. In the present paper we consider the second path. The vibration of the fragment surfaces leads to more realistic density distributions of the fragments. We consider that the neck density is responsible for the asymmetry and odd-even effects. Our results are compared with a large amount of experimental data in the cases of spontaneous fission of U, Pu, and Cf isotopes.
THE NUCLEON-NUCLEON FORCE FROM SKYRMIONS
Authors: EISENBERG J.M. , KÄLBERMANN G.
Published: October 2004

The applications of Skyrmions to the derivation of the nucleon-nucleon force is reviewed with attention to the use of the product ansatz, additional terms in the Lagrangian, baryon resonance admixtures, the instanton ansatz, dilatons, and exact two- or three-dimensional solutions for the B=2 system in order to find the sources of attraction in the central and spin-orbit potentials. We also discuss extensions to two-baryon systems with nonzero strangeness and address possible insights into the behavior of the nucleon in nuclei achieved from the Skyrmion approach.
SOME CONSEQUENCES OF DRESSING NUCLEONS
Authors: GEARHART C.C. , DICKHOFF W.H. , POLLS A. , RAMOS A.
Published: October 2004

A representation of nucleon spectral functions in nuclear matter is developed. Various contributions are identified including a quasiparticle term, broad background contributions below and above the Fermi energy, and a high-energy tail which has no significant momentum dependence. A convenient analytical energy dependence supplemented by a numerical dependence on momentum allows computationally tractable studies of the consequences associated with the considerable dressing of the nucleons. Applications are presented for high-momentum components as a function of energy, density of states, dressed particle-hole response, and the dressed particle-particle/hole-hole propagator.
ELASTIC SCATTERING OF 28Si–27Al IN A REALISTIC OPTICAL POTENTIAL
Authors: RASHDAN M.
Published: October 2004

Within a realistic model for the optical potential between nuclei based on the solution of the Bethe-Goldstone equation with the Reid soft-core potential, the differential cross-sections of the 28 Si –27 Al system, recently measured at energies around the Coulomb barrier, are calculated. The experimental data are well-reproduced over the entire energy range without any adjustable parameters to fit the cross-section.
NEGATIVE PARITY STATES IN 68Ge: EXPERIMENT AND THEORY
Authors: CHATURVEDI L. , BABU B.R.S. , HAMILTON J.H. , RAMAYYA A.V. , MA W.C. , ZHU S.J. , KORMICKI J. , PETROVICI A. , SCHMID K.W. , FAESSLER AMAND , JOHNSON N.R. , LEE I.Y. , BAKTASH C. , McGOWAN F.K. , HALBERT M.L. , RILEY M. , COLE J.D.
Published: October 2004

High spin negative parity states have been studied in 68 Ge via in-beam γ-ray spectroscopy at HHIRF. Several close-lying 7−, 9−, and 11− states are observed with a 13− to tentatively 17− cascade feeding them. Numerous E1 crossing transitions between the negative and positive parity levels are observed, along with possible M1 connecting transitions between the low lying negative parity bands. Previous microscopic calculations of the shape coexisting positive parity levels have been extended to the negative parity levels. The calculations used the EXCITED VAMPIR model based on complex HFB transformations with neutron-proton correlations and parity mixing in the mean field. The complex decay pattern and multiple high spin negative parity bands can be explained by a variable strength of mixing of the different deformed configurations which are bunched in small excitation intervals.
FIELD THEORETICAL STUDY OF 4He — A VARIATIONAL APPROACH
Authors: PANDA P.K. , PATRA S.K. , MISRA S.P. , SAHU R.
Published: October 2004

We developed a nonperturbative technique in field theory to obtain the ground state properties of 4 He nucleus. Here, the σ-meson effects are simulated through isosinglet scalar cloud of pairs of off-shell pions with a coherent state. The analysis de facto replaces the scalar isoscalar potential in nuclear physics by multipion condensates. Also, we discuss the two hard photons production from the off-shell π+π− pair as present through pion cloud within the framework of the model.
SINGULARITY-FREE BREIT EQUATION FROM CONSTRAINT TWO-BODY DIRAC EQUATIONS
Authors: CRATER HORACE W. , WONG CHUN WA , WONG CHEUK-YIN
Published: October 2004

We examine the relation between two approaches to the quantum relativistic two-body problem: (1) the Breit equation, and (2) the two-body Dirac equations derived from constraint dynamics. In applications to quantum electrodynamics, the former equation becomes pathological if certain interaction terms are not treated as perturbations. The difficulty comes from singularities which appear at finite separations r in the reduced set of coupled equations for attractive potentials even when the potentials themselves are not singular there. They are known to give rise to unphysical bound states and resonances. In contrast, the two-body Dirac equations of constraint dynamics do not have these pathologies in many nonperturbative treatments. To understand these marked differences we first express these contraint equations, which have an “external potential” form, similar to coupled one-body Dirac equations, in a hyperbolic form. These coupled equations are then recast into two equivalent equations: (1) a covariant Breit-like equation with potentials that are exponential functions of certain “generator” functions, and (2) a covariant orthogonality constraint on the relative momentum. This reduction enables us to show in a transparent way that finite-r singularities do not appear as long as the exponential structure is not tampered with and the exponential generators of the interaction are themselves nonsingular for finite r. These Dirac or Breit equations, free of the structural singularities which plague the usual Breit equation, can then be used safely under all circumstances, encompassing numerous applications in the fields of particle, nuclear, and atomic physics which involve highly relativistic and strong binding configurations.