A comment on spiral motions in projective relativity

Astronomical evidence has been inadequately invoked to support projective relativity. The spiral structure cannot be explained just by the existence of spiral orbits, and the use of Oort's constant to support the theory is also a missunderstanding. Besides, some mathematical inaccuracies make the application invalid.On a fellowship from the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina.     

Maximum mass of a Neutron star in metric theories of gravitation

A method is proposed of finding approximately the equilibrium configurations of nonrotating neutron stars without choosing any particular field equation for the metric. The method consists in choosing interpolation functions for the metric coefficients inside the star and matching them to that of the external metric at the body surface. In particular, the maximum mass a neutron star may have against gravitational collapse is studied, and a good agreement is found when compared with general relativistic results.On a fellowship from the Consejo Nacional de Investigaciones, Científicas y Técnicas de la República Argentina.     

Two-Dimensional Supergravity in the Canonical Exterior Formalism

The main features of the different linear gravity theories are reviewed. In particular, the supersymmetric extension of the Jackiw–Teitelboim (1+1) linear gravity is considered in detail within the canonical exterior formalism. In this context, the role of the several fields are analyzed. The constraints and the field equation are found. Finally, this supergravity model is treated in the second-order formalism.Member of the Consejo Nacional de Investigaciones Científicas y Técnicas, Argentina.     

A relation between the Szekeres quasispherical gravitational collapse solution and the Robinson-Trautman metrics

A form of the Robinson-Trautman metric for pure radiation is obtained by applying a limiting procedure to the quasispherical gravitational collapse solution of Szekeres. The procedure can be interpreted as that of allowing the particles making up the dust in the Szekeres solution to become massless.Research supported in part by a scholarship awarded to the author by the Consejo Nacional de Investigaciones Cintíficas y Técnicas of Argentina.     

A unified view of particles and fields in a simple model of a physical system

We start from the primitive concepts of preparticle and membership relation of set theory to obtain the derivative concepts of particle (already introduced in a previous work), field, and the interaction between systems of particles. We have explicitly stated, in addition, what the relationship between a system of particles and the field it produces is in the present model of physical systems. In order to discuss the motion of particles we have analyzed one of the possible definitions of a reference frame.On leave of absence from Instituto Venezolane de Investigaciones Científicas (I.V.I.C.).     

Exact vacuum solutions of 4-dimensional metric-affine gauge theories of gravitation

We presenttwo exact spherically symmetric vacuum solutions of gauge theories of gravity on a spacetime with non metric-compatible connection. One of them is defined on a Weyl-Cartan spacetime and the other on a general metric-affine space. We consider Lagrangians which include terms quadratic in the irreducible parts of the curvature, the torsion, and the nonmetricity. The metric part of both solutions is of the Reissner-Nordström type and includes a contribution of an effectivedilatation charge. A nontrivial Weyl 1-form is also common to both solutions. It resembles a Coulomb potential originating from thedilatation charge. The torsion is closely related to the nonmetricity.Supported by the Consejo Superior de Investigaciones Científicas, Serrano 123, E-28006 Madrid, Spain     

Convolution of Ultradistributions,Field Theory,Lorentz Invariance and Resonances

In this work, a general definition of convolution between two arbitrary Ultradistributions of Exponential type (UET) is given. The product of two arbitrary UET is defined via the convolution of its corresponding Fourier Transforms. Some examples of convolution of two UET are given. Expressions for the Fourier Transform of spherically symmetric (in Euclidean space) and Lorentz invariant (in Minkowskian space) UET in term of modified Bessel distributions are obtained (Generalization of Bochner’s theorem). The generalization to UET of dimensional regularization in configuration space is obtained in both, Euclidean and Minkowskian spaces As an application of our formalism, we give a solution to the question of normalization of resonances in Quantum Mechanics. General formulae for convolution of even, spherically symmetric and Lorentz invariant UET are obtained and several examples of application are given. This work was partially supported by Consejo Nacional de Investigaciones Científicas and Comisión de Investigaciones Científicas de la Pcia. de Buenos Aires; Argentina.     

A Topological Study of Contextuality and Modality in Quantum Mechanics

Kochen–Specker theorem rules out the non-contextual assignment of values to physical magnitudes. Here we enrich the usual orthomodular structure of quantum mechanical propositions with modal operators. This enlargement allows to refer consistently to actual and possible properties of the system. By means of a topological argument, more precisely in terms of the existence of sections of sheaves, we give an extended version of Kochen–Specker theorem over this new structure. This allows us to prove that contextuality remains a central feature even in the enriched propositional system. Graciela Domenech is a fellow of the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET). Hector Freytes is a fellow of the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET).     

Superspace gauge fixing of topological Yang-Mills theories

We revisit the construction of topological Yang-Mills theories of the Witten type with arbitrary space-time dimension and number of shift supersymmetry generators, using a superspace formalism. The super-BF structure of these theories is exploited in order to determine their actions uniquely, up to the ambiguities due to the fixing of the Yang-Mills and BF gauge invariance. UV finiteness to all orders of perturbation theory is proved in a gauge of the Landau type.Received: 29 October 2003, Published online: 18 February 2004Clisthenis P. Constantinidis: Supported in part by the Conselho Nacional de Desenvolvimento Científico e Tecnológico CNPq - BrazilOlivier Piguet: Supported in part by the Conselho Nacional de Desenvolvimento Científico e Tecnológico CNPq - BrazilWesley Spalenza: Supported in part by the Conselho Nacional de Desenvolvimento Científico e Tecnológico CNPq - Brazil     

The Heterotic Supersymmetric Sigma Model in the Canonical Exterior Formalism

Starting from a classical 2D superconformal theory described by the Wess–Zumino–Witten action, the canonical exterior formalism on group manifold for the heterotic supersymmetric sigma model is constructed. The motion equations of the dynamical field and the constraints are found and analyzed from the geometric point of view. It can be seen how the use of the canonical exterior formalism is more adequate and simple because of its manifest covariance in all the steps. The relationship between the form brackets defined in the canonical exterior formalism and the Poisson-brackets is written. Later on, the Dirac-brackets are written by using the second class constraints provided by the canonical exterior formalism. As it can be seen the canonical exterior formalism allows to show how the canonical quantization of the heterotic supersymmetric sigma model is facilitated. Member of the Consejo Nacional de Investigaciones Científicas y Técnicas, Argentina.     

Mössbauer study of hydrodemetallization clay catalysts of heavy oils: Role of pyrrhotites

The evolution of iron in clay catalysts employed in hydrodemetallization (HDM) of heavy oils has been studied by the Mossbauer effect. Pyrrhotites which appear during the process, were recognized as one of the active phases in HDM.Work partially supported by CDCH (Consejo de Desarrollo Científico y Humanistico de la Universidad Central de Venezuela).     

A Discussion on Particle Number and Quantum Indistinguishability

The concept of individuality in quantum mechanics shows radical differences from the concept of individuality in classical physics, as E. Schr?dinger pointed out in the early steps of the theory. Regarding this fact, some authors suggested that quantum mechanics does not possess its own language, and therefore, quantum indistinguishability is not incorporated in the theory from the beginning. Nevertheless, it is possible to represent the idea of quantum indistinguishability with a first-order language using quasiset theory (Q). In this work, we show that Q cannot capture one of the most important features of quantum non-individuality, which is the fact that there are quantum systems for which particle number is not well defined. An axiomatic variant of Q, in which quasicardinal is not a primitive concept (for a kind of quasisets called finite quasisets), is also given. This result encourages the searching of theories in which the quasicardinal, being a secondary concept, stands undefined for some quasisets, besides showing explicitly that in a set theory about collections of truly indistinguishable entities, the quasicardinal needs not necessarily be a primitive concept. Graciela Domenech — Fellow of the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET).     

On the perturbed angular correlation attenuation factor for relaxing systems

The attenuation factor of gamma-gamma perturbed angular correlation in the isotropic random-phase approximation is deduced for an axially symmetric quadrupole interaction and spins 1, 3/2, 2 and 5/2. It is shown that modifications to the usual expression are significant. Useful expressions for fitting procedures are obtained.Work supported in part by Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) and Financiadora de estudos e Projetos (FINEP).     

On the positive energy theorem involving mass and electromagnetic charges

A new theorem relating mass and charges is deduced, which can be applied to more general physical systems than those covered by the theorem of Gibbons and Hull [1].On leave from Instituto de Matématicas Astronomía y Física, Universidad Nacional de Córdoba, (5000) Córdoba, ArgentinaAlfred P. Sloan Fellow; supported in part by a grant from the National Science Foundation     

The Nonanuclear [Mo(IV){(CN)Fe(III)(3-ethoxy-saldptn)}8]Cl4 Complex Compound Exhibits Multiple Spin Transitions Observed by Mössbauer Spectroscopy

The hyperfine interactions at ¹⁸¹Ta ions on Fe³⁺ sites in α-Fe₂O₃ (hematite) were studied in the temperature range 11–1100 K by means of the perturbed angular correlation (PAC) technique. The ¹⁸¹Hf(β⁻)¹⁸¹Ta probe nuclei were introduced chemically into the sample during the preparation. The hyperfine interaction measurements allow to observe the magnetic phase transition and to characterize the supertransferred hyperfine magnetic field B_hf and the electric field gradient (EFG) at the impurity sites. The angles between B_hf and the principal axes of the EFG were determined. The Morin transition was also observed. The results are compared with those of similar experiments carried out using ¹¹¹Cd probe. ^aAlso at Comisión de Investigaciones Científicas de la Provincia de Buenos Aires, Argentina.     

The spiked harmonic oscillatorV(r)=r 2+λr −4 as a challenge to perturbation theory

The standard weak- and strong-coupling perturbation series are interpreted as extreme special cases of expansions obtainable within the framework of Rayleigh-Schroedinger perturbation theory with non-diagonal propagators and unspecified zero-order energies. The formalism of the latter type is then tested by our strongly singular example. It proves suitable for applications in the domain of virtually arbitrary couplings. A few related technicalities and especially the quadruple problem of convergence are also discussed.Dedicated to the memory of M. Gmitro.RG acknowledges support from the Comisión Interministerial de Ciencia y Tecnología, Spain, under contract 969/87. MFF acknowledges support via a fellowship from the Ministerio de Educación y Ciencia, Spain, under the program Estancias Temporales de Científicos y Tecnólogos Extranjeros. MZ acknowledges a partial support from the former resource during his short stay in Valencia, and a partial support from the Grant Agency of the Czechosl. Acad. Sci.     

The instrumental complexity of states

We apply a formalism developed previously to study the notion of the complexity of states in a general statistical theory. We identify the extreme points of the instrument sets as those instruments that view an intrinsic complexity of states and are uncontaminated by stochastic contributions of the experimenter. Various notions of entropy of a state are investigated.This work was financially supported by CNP_q (Conselho Nacional de Desenvolvimento Científico e Tecnológico) and FINEP (Financiadora de Estudos e Projetos) of the Brazilian government.     

Gauge fixing of Chern-Simons <Emphasis Type="Italic">N</Emphasis>-extended supergravity

We treat N-extended supergravity in 2 + 1 space-time dimensions as a Yang-Mills gauge field with Chern-Simons action associated to the N-extended Poincaré supergroup. We fix the gauge of this theory within the Batalin-Vilkovisky scheme.Received: 26 January 2004, Published online: 25 June 2004W. Spalenza: Supported in part by the Conselho Nacional de Desenvolvimento Científico e Tecnológico CNPq, Brazil