Jose Luis Flores

• National Polytechnic Institute

We identify, in spacetimes satisfying the null convergence condition, a certain natural class of null hypersurfaces that admit null sections with constant surface gravity. Our work is meant to offer complementary results to previous work on null hypersurfaces of zero expansion arising from the study of Cauchy and black hole horizons in general rela...

We identify certain general geometric conditions on a foliation of a spacetime (M, g) by timelike curves that will impede the existence of null geodesic lines, especially if (M, g) possesses a compact Cauchy hypersurface. The absence of such lines, in turn, yields well-known restrictions on the geometry of cosmological spacetimes, in the context of...

After publishing the research paper (Costa e Silva et al 2019 Class. Quantum Grav. 36 175002), we learned in private discussions with Müller that some central ideas therein were actually anticipated in a 1977 paper by Beem 1977 (Gen. Relativ. Gravit. 8 245–57). With a view to establishing Beem’s precedence where it is due, we present here a clear a...

Inspired by the results in a recent paper by Galloway and Vega (Lett Math Phys 108(10):2285–2292, 2018), we investigate a number of geometric consequences of the existence of a timelike conformal Killing vector field in a globally hyperbolic space-time with compact Cauchy hypersurfaces, especially in connection with the so-called Bartnik’s splittin...

Angular distributions for the inclusive He4 and He6 production cross sections in the He8+Pb208 system at incident energies of 16 and 22 MeV measured at the SPIRAL facility of the GANIL laboratory are presented. Using a combination of kinematical arguments and distorted wave Born approximation (DWBA) calculations, neutron transfer reactions were inf...

A bstract We give new definitions of null infinity and black hole in terms of causal boundaries, applicable to any strongly causal spacetime ( M , g ). These are meant to extend the standard ones given in terms of conformal boundaries, and use the new definitions to prove a classic result in black hole theory for this more general context: if the n...

p>En este trabajo se pretende mostrar cómo las características de la fuerza de trabajo se han ido adaptando a los distintos modelos de acumulación de capital que han existido en El Salvador desde el año de 1900 hasta la actualidad. La investigación y la exposición se realizó atendiendo a los tres modelos económicos identificados en El Salvador: mod...

In these notes we are going to briefly review some of the main ideas involved in the formulation and proof of the Riemannian and Lorentzian Splitting Theorems. We will try to emphasize the similarities and differences appeared when passing from the Riemannian to the Lorentzian case, and the way in which these difficulties are overcome by the author...

Dramatic differences in the elastic scattering of the neutron rich nuclei He-6 and He-8 are found when new high quality data for the He-8+Pb-208 system are compared with previously published He-6+Pb-208 data at the same laboratory frame incident energy. The new He-8 data are of the same level of detail as for stable beams. When comparing them with...

The new generation of nuclear physics detectors that used to study nuclear reactions is considering the use of digital pulse shape analysis techniques (DPSA) to obtain the (A,Z) values of the reaction products impinging in solid state detectors. This technique can be an important tool for selecting the relevant reaction channels at the HYDE (HYbrid...

We consider restrictions placed by geodesic completeness on spacetimes possessing a null parallel vector field, the so-called Brinkmann spacetimes. This class of spacetimes includes important idealized gravitational wave models in General Relativity, namely the plane-fronted waves with parallel rays, or pp-waves, which in turn have been intensely a...

We study the interplay between the global causal and geometric structures of a spacetime $(M,g)$ and the features of a given smooth $\mathbb{R}$-action $\rho$ on $M$ whose orbits are all causal curves, building on classic results about Lie group actions on manifolds described by Palais. In the first part of this paper, we prove that $\rho$ is free...

The information's systems have become in indispensable elements in different technology fields and health area has been a great beneficiary. This type of system allow timely delivery and accurate of medical information which converts an indispensable input for attendant a timely manner a medical emergency. This work is focused in the design and dev...

We discuss the geodesic connectedness problem in open subsets with convex boundary of globally hyperbolic spacetimes endowed with a complete, timelike or lightlike, Killing vector field. Furthermore, we furnish applications to generalized plane waves.

An important, if relatively less well known aspect of the singularity theorems in Lorentzian geometry, is to understand how their conclusions fare upon weakening or suppression of one or more of their hypotheses. Then, theorems with modified conclusion may arise, showing that those conclusions will fail only in special cases, at least some of which...

There are several ideal boundaries and completions in General Relativity sharing the topological property of being sequential, i.e., determined by the convergence of its sequences and, so, by some limit operator $L$. As emphasized in a classical article by Geroch, Liang and Wald, some of them have the property, commonly regarded as a drawback, that...

An important, if relatively less well known aspect of the singularity theorems in Lorentzian Geometry is to understand how their conclusions fare upon weakening or suppression of one or more of their hypotheses. Then, theorems with modified concusions may arise, showing that those conclusions will fail only in special cases, at least some of which...

Given a globally hyperbolic spacetime endowed with a complete lightlike Killing vector field and a complete Cauchy hypersurface, we characterize the points which can be connected by geodesics. A straightforward consequence is the geodesic connectedness of globally hyperbolic generalized plane waves with a complete Cauchy hypersurface.

The exotic nucleus 8He is investigated by means of the measurement of the angular distributions of the elastic channel and the 6He and 4He fragment yields produced in the collision with a 208Pb target at two energies around the Coulomb barrier, 16 and 22 MeV. The experiment was performed at the GANIL-SPIRAL facility, with the aim of extracting info...

We present some recent results in Flores et al. (ArXiv:1011.1154) about the relation between the causal boundary of standard stationary spacetimes (previously studied in Flores et al. (Memoirs A.M.S. ArXiv:1011.1154)) and that of a wide class of spacetimes which are isocausal to them.

An integrated circuit is provided with a set of sensors for scaling voltage based on performance of the integrated circuit. The set of sensors are monitored, and sensor provides an output value indicative of a performance metric of the integrated circuit. The output values from the set of sensors are combined using a calibrated model to determine w...

The skin nucleus 8 He is investigated by measuring the angular distribution of the elasticly scattered 8 He and the 6,4 He fragments produced in the collision with a 208 Pb target at 22 MeV, just above the Coulomb barrier. The experiment was carried out at SPIRAL/GANIL in 2010. Here we present preliminary results for the elastic sca...

Systems, methods, apparatus and computer-executable instructions stored on computer-readable media for communicating a modified hash message authentication code (HMAC) signed message between two endpoints are provided. The HMAC signature of the message may include a plurality of components. In some cases, the HMAC signature is a Server Message Bloc...

Recently, a new viewpoint on the classical c-boundary in Mathematical Relativity has been developed, the relations of this boundary with the conformal one and other classical boundaries have been analyzed, and its computation in some classes of spacetimes, as the standard stationary ones, has been carried out. In the present paper, we consider the...

The dynamics of He-8 around the Coulomb barrier is investigated- by measuring the energy and angular distribution of the elastic He-8 and the He and He-4 fragment yields in the collision process with a Pb-208 target. The experiment was carried out at SPIRAL/GANIL in October 2010. The experimental results will provide information about the relevant...

The aim of this chapter is to review and complete the study of geodesics on Gödel-type spacetimes from a variational viewpoint in the last decade (say, from [10] to [2]). In particular, we prove some new results on geodesic connectedness and geodesic completeness for these spacetimes.

The aim of this chapter is twofold. First, we review several results about the c-boundary of space-times and other boundaries in differential geometry, completing some points which were suggested in the original works. Second, we are going to apply these results to provide a precise description of the c-boundary of the stationary part of (slow rota...

Pulse shape analysis techniques for the identification of heavy ions produced in nuclear reactions have been recently proposed as an alternative to energy loss and time of flight methods. However this technique requires a large amount of memory for storing the shapes of charge and current signals. We have implemented a hardware solution for fast on...

We have measured the angular distributions of elastic scattering and He-6,He-4 fragments produced in the collisions of an exotic beam of He-8 on a Pb-208 target at laboratory energies of 18 and 22 MeV, just around the Coulomb barrier (19 MeV). The measurements were performed at the SPIRAL/GANIL facility in Caen, France. In this paper, we present pr...

The aim of this work is to explain the status and role of the so-called causal boundary of a spacetime in Mathematical Physics and Differential Geometry. This includes: (a) the consistency of its latest redefinition, (b) its role as an intrinsic conformally invariant boundary in the AdS/CFT correspondence, (c) its relation with the Gromov and Cauch...

The aim of this paper is to review and complete the study of geodesics on G\"odel type spacetimes initiated in [8] and improved in [2] of the References. In particular, we prove some new results on geodesic connectedness and geodesic completeness for these spacetimes.

Federation The dynamics of 8 He around the Coulomb barrier is investigated by measuring the energy and angular distribution of the elastic 8 He and the 6 He and 4 He fragment yields in the collision process with a 208 Pb target. The experiment was carried out at SPIRAL/GANIL in October 2010. The experimental results will provide information about t...

In this note we reduce the problem of geodesic connectedness in a wide class of Gödel type spacetimes to the search of critical points of a functional naturally involved in the study of geodesics in standard static spacetimes. Then, by using some known accurate results on the latter, we improve previous results on the former.

We construct an example which shows that two isocausal space-times, in the sense introduced recently in A. García-Parrado and J. M. M. Senovilla [Classical Quantum Gravity 20, No. 4, 625–664 (2003; Zbl 1026.83013)], may have c-boundaries which are not equal (more precisely, not equivalent, as no bijection between the completions can preserve all th...

The experimental study of the fusion of light neutron-rich nucleus 8 He with 206 Pb is reported in this work. A fusion stack of 206 Pb targets has been used for this study. The most prominent evaporation residue (210 Po), which has half-life of 138 days and decays by alpha emission, is populated in the reaction. Radiochemical analysis technique is...

In this note we reduce the problem of geodesic connectedness in a wide class of G\"odel type spacetimes to the search of critical points of a functional naturally involved in the study of geodesics in standard static spacetimes. Then, by using some known accurate results on the latter, we improve previous results on the former.

Drilling lags behind other industries in the implementation of automation. One reason for this is the variability of drilling operations and uncertainty in knowing what is being drilled at any given time. A closed-loop system that continually monitors drilling parameters and drilling performance in real time and constantly adjusts weight on bit (WO...

Recently, the old notion of causal boundary for a spacetime V has been redefined in a consistent way. The computation of this boundary $\partial V$ for a standard conformally stationary spacetime V = R x M, suggests a natural compactification $M_B$ associated to any Riemannian metric on M or, more generally, to any Finslerian one. The corresponding...

The research analyze the clusters of agroindustry fruits and vegetables from the state of Veracruz in its main products: orange, persian lemon, papaya, pineapple, banana, chayote and green chilli by location theory and economic geography (North y Krugman, 1995); the system value of the cluster (Porter, 1998) and the cluster type (Ramos, 1998; Alten...

In the present paper we provide new examples of marginally trapped surfaces and tubes in FLRW spacetimes by using a basic relation between these objects and CMC surfaces in 3-manifolds. We also provide a new method to construct marginally trapped surfaces in closed FLRW spacetimes, which is based on the classical Hopf map. The utility of this metho...

The notion of causal boundary $\partial M$ for a strongly causal spacetime $M$ has been a controversial topic along last decades: on one hand, some attempted definitions were not fully consistent, on the other, there were simple examples where an open conformal embedding $i:M\hookarrow M_{0}$ could be defined, but the corresponding conformal bounda...

The objective of this work is revising the reported literature in the state of art on environmental marketing and to describe those models which study consumer behavior which have found sustainable empirical evidence. After an extensive revision in all the international information banks, it were found 4 models of environmental marketing and a mode...

This work presents an analysis of the policies in the matter of tourism in Mexico since 1973 to 2003 and the three first years of Fox management. As a result of this has been demonstrates that in Mexico has not a state policy and that the strategy has changed every six years. Mexican model is not related to others models reported in literature. The...

We outline some recent results in the study of the causal boundary for two important classes of spacetimes: standard stationary and wave-type spacetimes. We briefly describe the procedure to compute this boundary for these spacetimes nad remark the mathematical tools involved.

In this paper we present a description of the causal boundary for the class of standard stationary spacetimes: With (M,g0) an arbitrary Riemannian manifold and omega a one-form on M, the causal boundary of (V = R×M,g = -dt2+omega⊗dt+dt⊗omega+g0) is given in terms of a Busemann boundary construction on manifolds (M,F+/-), with F+/- Finsler metrics a...

We study the geometry and the periodic geodesics of a compact Lorentzian manifold that has a Killing vector field which is timelike somewhere. Using a compactness argument for subgroups of the isometry group, we prove the existence of one timelike non self-intersecting periodic geodesic. If the Killing vector field is never vanishing, then there ar...

A complete and systematic approach to compute the causal boundary of wave-type spacetimes is carried out. The case of a 1-dimensional boundary is specially analyzed and its critical appearance in pp-wave type spacetimes is emphasized. In particular, the corresponding results obtained in the framework of the AdS/CFT correspondence for holography on...

This paper describes how to extend traditional Sky-hook which is used to isolate the vertical vibration in the chassis, in order to include the pitch vibration and the roll vibration for the stabilization of the semi-active suspension in a full vehicle model . A Magneto-Rheological (MR) damper will be used in the implementation of the system . This...

Dades estadístiques bàsiques del Baix Llobregat

Becoming a licensed Marriage, Family and Child Counselor (MFCC) in California is presented from a Chicano's perspective based on the author's own training. He reports that 1) there is a need for Chicanos trained extensively in marriage and family counseling to serve the large Mexican American population; 2) MFCC is a growing profession yet few Chic...

The new formulation of the causal completion of spacetimes suggested in [1], and modified later in [2], is tested by computing the causal boundary for product spacetimes of a Lorentz interval and a Riemannian manifold. This is particularized for two important families of spacetimes, conformal to the previous ones: (standard) static spacetimes and G...

El objetivo de este trabajo es revisar la literatura reportada en el estado del arte sobre marketing ambiental y describir aquellos modelos que estudian el comportamiento del consumidor que han encontrado evidencia empírica sustentable. Luego de una amplia revisión en todos los bancos internacionales de información fueron encontrados cuatro model...

In this paper we compare optimal skyhook, optimal ground hook and optimal hybrid control laws for the stabilization of the semi-active suspension in a quarter of a Renault Scenic 2001. A Magneto-Rheological (MR) damper will be used in the implementation of the system. This damper is modeled using a grey box structure based on a Bouc-Wen model and a...

In order to apply variational methods to the action functional for geodesics of a stationary spacetime, some hypotheses, useful to obtain classical Palais–Smale condition, are commonly used: pseudo-coercivity, bounds on certain coefficients of the metric, etc. We prove that these technical assumptions admit a natural interpretation for the conforma...

In the last fifteen years variational methods have been widely applied in the study of geodesic connectedness of stationary spacetimes. In this paper we introduce fine estimates which allow us to apply such methods to this problem in an optimal way, improving by far previous results on the subject. Our estimates also seem useful for extending the e...

We present a new development of the causal boundary of spacetimes, originally introduced by Geroch, Kronheimer and Penrose. Given a strongly causal spacetime (or, more generally, a chronological set), we reconsider the GKP ideas to construct a family of completions with a chronology and topology extending the original ones. Many of these completion...

The topology of the causal boundary for standard static spacetimes--spacetimes time-invariantly conformal to a metric product of the Lorentz line and a Riemannian manifold--is studied in depth. As this is given in terms of a set of real-valued functions on the Riemannian factor, one could use a function-space topology, but physical reasons recommen...

In this paper we look for periodic orbits for a Lagrangian system in a complete Riemannian manifold under the action of an eventually unbounded potential. An upper bound on the fixed period is obtained by means of variational tools involving penalization arguments and Morse theory.

In this note we study periodic trajectories in Plane Wave type spacetimes by applying some recent results about periodic orbits for a Lagrangian system in a Riemannian manifold under the action of an (eventually) unbounded potential.

The aim of this note is to study the existence and multiplicity of timelike geodesics in standard stationary Lorentzian manifolds with unbounded coefficients.

Global geometric properties of product manifolds ${\cal M}= M \times \R^2$, endowed with a metric type $<\cdot, \cdot > = < \cdot, \cdot >_R + 2 dudv + H(x,u) du^2$ (where $<\cdot, \cdot >_R$ is a Riemannian metric on $M$ and $H:M \times \R \to \R$ a function), which generalize classical plane waves, are revisited. Our study covers causality (causa...

Aim of this paper Is to give a full variational approach for the geodesic connectedness of a wide family of plane wave type spacetimes, including the case when its Riemannian part is not complete.

A complete study of the structure of Ricci collineations for type B warped spacetimes is carried out. This study can be used as a method to obtain these symetries in such spacetimes. Special cases as 2+2 reducible spacetimes, and plane and spherical symmetric spacetimes are considered specifically.

The aim of this paper is to study the geodesic connectedness of a complete static Lorentzian manifold (M, (·, ·)l) such that, if K is its irrotational timelike Killing vector field, the growth of β = -(K, K) l is (at most) quadratic. This is shown to be equivalent to a critical variational problem on a Riemannian manifold, where some geometrical in...

A classical nonlinear equation on a complete Riemannian manifold is considered. The existence of solutions connecting any two points is studied, i.e., for T>0 the critical points of the functional with x(0)=x0,x(T)=x1. When the potential V has a subquadratic growth with respect to x, JT admits a minimum critical point for any T>0 (infinitely many c...

A general class of Lorentzian metrics, M0 \mathbbR2 \mathcal{M}_0 \times \mathbb{R}^2 , á,ñz = á,ñx + 2dudv + H(x,u)du2\langle \cdot ,\; \cdot \rangle _z = \langle \cdot ,\; \cdot \rangle _x + 2\;\;du\;\;dv + H(x,u)\;du^2 , with (M0 ,á,ñx )(\mathcal{M}_0 ,\;\langle \cdot ,\; \cdot \rangle _x ) any Riemannian manifold, is introduced in order t...

Let = 0? ? be a pp-wave-type spacetime endowed with the metric , z = , x + 2du dv + H(x, u) du?, where (0, , x) is any Riemannian manifold and H(x, u) is an arbitrary function. We show that the behaviour of H(x, u) at spatial infinity determines the causality of , say: (a) if ?H(x, u) behaves subquadratically (i.e, essentially ?H(x, u) ? R1(u)|x|??...

The geodesic connectedness of outer Kerr space–time is proven by using a topo-logical method. The proof is based on arguments about Brouwer's degree for the solutions of functional equations. The applicability of these topological arguments for dealing with geodesics in space–times is stressed. © 2002 American Institute of Physics.

The Levi-Civita connection and geodesic equations for a stationary spacetime are studied in depth. General formulae which generalize those for warped products are obtained. These results are applicated to some regions of Kerr spacetime previously studied by using variational methods. We show that they are neither space-convex nor geodesically conne...

Given two points of a generalized Robertson–Walker space–time, the existence, multiplicity and causal character of geodesics connecting them is characterized. Conjugate points of such geodesics are related to conjugate points of geodesics on the fiber, and Morse-type relations are obtained. Applications to bidimensional space–times and to GRW space...

This work describes the deficiencies in health discovered by medical examination in professional ski-lift operators and attempts to relate incapacities for work to the conditions discovered. Possibilities for risk reduction were also sought. This was a cross-sectional epidemiological study carried out on a representative sample of 3910 workers. Hea...

A new technique for the study of geodesic connectedness in a class of Lorentzian manifolds is introduced. It is based on arguments of Brouwer's topological degree for the solution of functional equations. It is shown to be very useful for multiwarped spacetimes, which include different types of relativistic spacetimes. Connectedness by causal geode...

Ski-lifts and chair-lifts workers are exposed to particular occupational risks, especially in our countries where skiing has been well developed in the last ten years. Such a population does not move a lot, and is really preoccupied for the future: what about their functional capacities and professional prospects? The aim of this study was to measu...

This study evaluates ambulatory blood pressure ABP measurement as a technique for measuring the cardiovascular load in maintenance mechanics working on mechanical lifts at altitudes of over 2,500 meters (stress due to altitude and intensive static and dynamic work). 25 normotensive workers were studied during real working conditions. Each subject u...

Handicap is the result of a process initiated by an underlying disease, an accident or an abnormality, which leads to a functional deficit in various situations of everyday life. This definition, derived from the International Classification of Impairments, Disabilities, and Handicaps (ICIDH), reflects the desire of the elderly and the handicapped...

A survey of the total population of a small rural village was undertaken to discern the amount of impairment and disability present, using both questionnaire and examination techniques. It was confirmed that the concept of disability was applicable to such populations and that it was related to age, at both extremes of life. There was a good correl...

The study of the staff, services, and patient population of the East Los Angeles Mental Health Service seven years after its initial operations revealed that: 1 the staff remained predominately bilingual and bicultural; 2 there was a greater demand for direct treatment services than anticipated; 3 the majority (79%) of the patient population was Me...

RESUMEN Los principios de descentralización y desconcentración deben regir las actuaciones de la Administración Pública según la Constitución Española. Ello debe basarse en una reorgani-zación de la estructura territorial de España que tenga en cuenta los espacios a tres niveles: núcleos de población, comarcas y regiones. La clave del nuevo diseño...

Resumen En este trabajo se estudia el comportamiento de distintos compensadores de potencia de conexión paralela para la mitigación de armónicos de corriente en cargas trifásicas no lineales. Conocido el espectro armónico de la intensidad de una carga, el uso de filtros pasivos sintonizados a los armónicos de interés ofrecen una solución económica...

RESUMEN Antecedentes: la nefropatía por medio de contraste es uno de los factores etiológicos más importantes de insuficiencia renal aguda en pacientes hospitalizados, causa significativa de morbilidad y mortalidad, altos costos y estancias hospitalarias prolongadas. Objetivo: determinar la incidencia de nefropatía por medio de contraste en sujetos...

RESUMEN Los mecanismos flexibles tienen un gran potencial en el desarrollo de sistemas de posicionamiento de alta precisión como los sistemas de microensamble, micromanipulación y microcirugía. Este artículo presenta las capacidades de dos mecanismos flexibles de geometría no convencional, que se plantea como alternativa a mecanismos flexibles para...

Es presenta en aquesta monografia un avanç de l’explotació de l’Enquesta sobre els hàbits i les condicions de vida de la població a la regió metropolitana de Barcelona. Les dades corresponen a la tercera edició de l’Enquesta (1995) i permeten observar l’evolució de les dinàmiques metropolitanes en cinc camps: la mobilitat quotidiana de la població;...

Dades estadístiques bàsiques del Vallès Oriental

L’Enquesta sobre les condicions de vida i hàbits de la població de la regió de Barcelona (Enquesta de la Regió de Barcelona, ERB) es planteja quinquennalment reflectir i analitzar de manera exhaustiva la realitat social i econòmica de la població d’aquest territori. El document que el lector té a les mans presenta els primers resultats corresponent...