Results for "Marcelo Cárdenas"

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A priori estimates for nonlinear fourth order Schrödinger type equationsDec 15 2013We study the fourth order Schr\"odinger type differential inequality $-\Delta^2 u + \lambda V(x)u \geq a(x)u^q$ with $a,V\in L^1_{loc}(\mathbf{R}^N)$, both nonnegative, and $\lambda>0$. We consider nonnegative solutions without making any assumptions ... More
Stable Backward Diffusion Models that Minimise Convex EnergiesMar 08 2019Backward diffusion processes appear naturally in image enhancement and deblurring applications. However, the inverse problem of backward diffusion is known to be ill-posed and straightforward numerical algorithms are unstable. So far, existing stabilisation ... More
Existence Theory for the EED Inpainting ProblemJun 11 2019We establish an existence theory for an elliptic boundary value problem in image analysis known as edge-enhancing diffusion (EED) inpainting. The EED inpainting problem aims at restoring missing data in an image as steady state of a nonlinear anisotropic ... More
Spectral properties of Landau Hamiltonians with non-local potentialsJan 14 2019We consider the Landau Hamiltonian $H_0$, self-adjoint in $L^2({\mathbb R}^2)$, whose spectrum consists of an arithmetic progression of infinitely degenerate positive eigenvalues $\Lambda_q$, $q \in {\mathbb Z}_+$. We perturb $H_0$ by a non-local potential ... More
Atomic Effective Pseudopotentials for SemiconductorsJun 13 2012We derive an analytic connection between the screened self-consistent effective potential from density functional theory (DFT) and atomic effective pseudopotentials (AEPs). The motivation to derive AEPs is to address structures with thousands to hundred ... More
Cosmic slowing down of acceleration for several dark energy parametrizationsJul 07 2014Sep 08 2014We further investigate slowing down of acceleration of the universe scenario for five parametrizations of the equation of state of dark energy using four sets of supernovae data. In a maximal probability analysis we also use the baryon acoustic oscillation ... More
The Cauchy problem of scalar-tensor theories of gravityAug 31 2005Aug 07 2006The 3+1 formulation of scalar-tensor theories of gravity (STT) is obtained in the physical (Jordan) frame departing from the 4+0 covariant field equations. Contrary to the common belief (folklore), the new system of ADM-like equations shows that the Cauchy ... More
Oscillons in Scalar Field Theories: Applications in Higher Dimensions and InflationFeb 19 2006The basic properties of oscillons -- localized, long-lived, time-dependent scalar field configurations -- are briefly reviewed, including recent results demonstrating how their existence depends on the dimensionality of spacetime. Their role on the dynamics ... More
Reply to Comment on ``Dynamics of Weak First Order Phase Transitions''Nov 09 1995A reply to a Comment by Harris and Jungman (Phys. Rev. Lett. 75 (1995), 588), concerning my work on phase mixing and its implications to the dynamics of ``weak'' first order phase transitions.
Thermal Mixing of Phases: Numerical and Analytical StudiesJul 14 1995The dynamics of phase transitions plays a crucial r\^ole in the so-called interface between high energy particle physics and cosmology. Many of the interesting results generated during the last fifteen years or so rely on simplified assumptions concerning ... More
From Cosmos to Intelligent Life: The Four Ages of AstrobiologyFeb 22 2012Mar 02 2012The history of life on Earth and in other potential life-bearing planetary platforms is deeply linked to the history of the universe. Since life as we know it relies on chemical elements forged in dying heavy stars, the universe needs to be old enough ... More
Phase Transitions in the UniverseMar 09 1998During the past two decades, cosmologists turned to particle physics in order to explore the physics of the very early Universe. The main link between the physics of the smallest and largest structures in the Universe is the idea of spontaneous symmetry ... More
Right-Permutative Cellular Automata on Topological Markov ChainsMar 14 2006Jun 08 2007In this paper we consider cellular automata $(\mathfrak{G},\Phi)$ with algebraic local rules and such that $\mathfrak{G}$ is a topological Markov chain which has a structure compatible to this local rule. We characterize such cellular automata and study ... More
Proximal Markov chain Monte Carlo algorithmsJun 02 2013Apr 03 2015This paper presents a new Metropolis-adjusted Langevin algorithm (MALA) that uses convex analysis to simulate efficiently from high-dimensional densities that are log-concave, a class of probability distributions that is widely used in modern high-dimensional ... More
Black Hole Area Quantization rule from Black Hole Mass FluctuationsDec 06 2016We calculate the black hole mass distribution function that follows from the random emission of quanta by Hawking radiation and with this function we calculate the black hole mass fluctuation. From a complete different perspective we regard the black ... More
The random walks of a Schwarzschild black holeJun 19 1997We show that spinless and neutral black holes in thermal equilibrium with radiation undergo fluctuations of charge and angular momentum. The corresponding spreads for a black hole in contact with charged scalar particles is calculated. The angular momentum ... More
Extending Owen's integral table and a new multivariate Bernoulli distributionApr 16 2017Jun 21 2017We extend some equatilites in the Owen's table of normal integrals (A table of normal integrals in Communication in Statistics-Simulation and Computation, 1980). Furthermore a new probabilistic model for a vector of binary random variables is proposed. ... More
Pseudo-Stable BubblesAug 16 1993The evolution of spherically symmetric unstable scalar field configurations (``bubbles'') is examined for both symmetric (SDWP) and asymmetric (ADWP) double-well potentials. Bubbles with initial static energies $E_0\la E_{{\rm crit}}$, where $E_{{\rm ... More
Two Lectures On Phase MixingFeb 03 1998The dynamics of phase transitions plays a crucial r\^ole in the so-called interface between high energy particle physics and cosmology. Many of the interesting results generated during the last fifteen years or so rely on simplified assumptions concerning ... More
Dynamics of spherically symmetric spacetimes: hydrodynamics and radiationJan 18 2002Using the 3+1 formalism of general relativity we obtain the equations governing the dynamics of spherically symmetric spacetimes with arbitrary sources. We then specialize for the case of perfect fluids accompanied by a flow of interacting massless or ... More
Revisiting maximum-a-posteriori estimation in log-concave modelsDec 19 2016Jan 18 2019Maximum-a-posteriori (MAP) estimation is the main Bayesian estimation methodology in imaging sciences, where high dimensionality is often addressed by using Bayesian models that are log-concave and whose posterior mode can be computed efficiently by convex ... More
Charge Fluctuations of an Uncharged Black HoleAug 02 2016In this paper we calculate charge fluctuations of a Schwarzschild black-hole of mass $M$ confined within a perfectly reflecting cavity of radius R in thermal equilibrium with various species of radiation and fermions . Charge conservation is constrained ... More
Notes on the flexible manipulatorDec 04 2013The existence of solutions to the boundary tracking of the displacement at one end of a linear Timoshenko beam is discussed on the basis of the Cauchy problem with time and space interchanged.
Ill-distributed sets over global fields and exceptional sets in Diophantine GeometryJan 03 2019Let $K\subseteq \mathbb{R}$ be a number field. Using techniques of discrete analysis, we prove that for definable sets $X$ in $\mathbb{R}_{\exp}$ of dimension at most $2$ a conjecture of Wilkie about the density of rational points is equivalent to the ... More
Drake Equation for the Multiverse: From the String Landscape to Complex LifeFeb 08 2010It is argued that selection criteria usually referred to as "anthropic conditions" for the existence of intelligent (typical) observers widely adopted in cosmology amount only to preconditions for primitive life. The existence of life does not imply in ... More
What We Know and What We Don't Know About the UniverseJan 12 2004I present a non-technical and necessarily biased and incomplete overview of our present understanding of the physical universe and its constituents, emphasizing what we have learned from the explosive growth in cosmological and astrophysical data acquisition ... More
On the Strength of First Order Phase TransitionsMay 11 1994Electroweak baryogenesis may solve one of the most fundamental questions we can ask about the universe, that of the origin of matter. It has become clear in the past few years that it also poses a multi-faceted challenge. In order to compute the tiny ... More
Baryogenesis in BriefJul 25 1994In this talk I briefly review the main ideas and challenges involved in the computation of the baryon asymmetry of the Universe. (Invited talk given at ``The Birth of the Universe and Fundamental Physics'', Rome, May 18--21, 1994.)
Interplay between quasi-periodicity and disorder in quantum spin chains in a magnetic fieldJan 24 2002We study the interplay between disorder and a quasi periodic coupling array in an external magnetic field in a spin-1/2 XXZ chain. A simple real space decimation argument is used to estimate the magnetization values where plateaux show up. The latter ... More
A simple theorem to generate exact black hole solutionsApr 02 2003Oct 17 2003Under certain conditions imposed on the energy-momentum tensor, a theorem that characterizes a two-parameter family of static and spherically symmetric solutions to Einstein's field equations (black holes), is proved. A discussion on the asymptotics, ... More
Las antenas de espacio profundo en la ArgentinaMar 14 2018Since December 2012, the Deep Space Antenna DS3 of the European Space Agency was inaugurated in the province of Mendoza. The possibility of using this equipment for space and scientific activities was promoted by our country. Several scientific institutions ... More
Extending Description Logic EL++ with Linear Constraints on the Probability of AxiomsAug 27 2019One of the main reasons to employ a description logic such as EL or EL++ is the fact that it has efficient, polynomial-time algorithmic properties such as deciding consistency and inferring subsumption. However, simply by adding negation of concepts to ... More
Topological Quasi-Group ShiftsJan 14 2014In this work we characterize those shift spaces which can support a 1-block quasi-group operation and show the analogous of Kitchens result: any such shift is conjugated to a product of a full shift with a finite shift. Moreover, we prove that every expansive ... More
Hilbert bodies as quantum-classical continuaAug 24 2019A hybrid quantum-classical model is proposed whereby a micro-structured (Cosserat-type) continuum is construed as a principal Hilbert bundle
Compact Lie algebras, transversely Lie foliations and fibrationsOct 06 2009Jul 15 2010We study Lie foliations on compact manifolds, in case the Lie group is compact. Our main results improve Tischler classical result on the existence of fibration and, as an application, we study the case the manifold has an amenable fundamental group.
On the linear and weak-field limits of scalar-tensor theories of gravityFeb 21 2002The linear approximation of scalar-tensor theories of gravity is obtained in the physical (Jordan) frame under the 4+0 (covariant) and 3+1 formalisms. Then the weak-field limit is analyzed and the conditions leading to significant deviations of the $1/r^{2}$ ... More
The Origin of Baryonic Matter in the Universe: A Brief ReviewFeb 13 1996I briefly review the main ideas and challenges involved in the computation of the observed baryonic asymmetry of the Universe.
d-dimensional Oscillating Scalar Field Lumps and the Dimensionality of SpaceAug 28 2004Extremely long-lived, time-dependent, spatially-bound scalar field configurations are shown to exist in $d$ spatial dimensions for a wide class of polynomial interactions parameterized as $V(\phi) = \sum_{n=1}^h\frac{g_n}{n!}\phi^n$. Assuming spherical ... More
Dynamics of Weak First Order Phase TransitionsMar 18 1994The dynamics of weak vs. strong first order phase transitions is investigated numerically for 2+1 dimensional scalar field models. It is argued that the change from a weak to a strong transition is itself a (second order) phase transition, with the order ... More
Maximum-a-posteriori estimation with Bayesian confidence regionsFeb 27 2016Jul 11 2016Solutions to inverse problems that are ill-conditioned or ill-posed may have significant intrinsic uncertainty. Unfortunately, analysing and quantifying this uncertainty is very challenging, particularly in high-dimensional problems. As a result, while ... More
An Axiomatics and a Combinatorial Model of Creation/Annihilation OperatorsJun 21 2015A categorical axiomatic theory of creation/annihilation operators on bosonic Fock space is introduced and the combinatorial model that motivated it is presented. Commutation relations and coherent states are considered in both frameworks.
Analytic functors between presheaf categories over groupoidsMar 22 2013Jun 20 2013The paper studies analytic functors between presheaf categories. Generalising results of A. Joyal and of R. Hasegawa for analytic endofunctors on the category of sets, we give two characterisations of analytic functors between presheaf categories over ... More
Vlasov's beams and multivector Grassmann StaticsNov 10 2018A novel formulation of statics in terms of the exterior algebra of an affine space is shown to be the underlying mathematical structure of Vlasov's thin-walled beam theory in structural mechanics.
A Java Application to Characterize Biomolecules and Nanomaterials in Electrolyte Aqueous SolutionsJan 19 2018The electrostatic, entropic and surface interactions between a macroion (nanoparticle or biomolecule), surrounding ions and water molecules play a fundamental role in the behavior and function of colloidal systems. However, the molecular mechanisms governing ... More
The Inertial Polarization Principle: The Mechanism Underlying Sonoluminescence?Mar 11 2001In this paper we put forward a mechanism in which imploding shock waves emit electromagnetic radiation in the spectral region $\lambda_{0}\cong 2\pi R_{0}.$, where R$_{0}$ is the radius of the shock by the time it is first formed. The mechanism relies ... More
Charge Fluctuations of a Schwarzschild Black-HoleJul 09 2015Jul 12 2015In this paper we calculate charge fluctuations of a Schwarzschild black-hole of mass $M$ in thermal equilibrium with radiation and an electron-positron plasma confined within a vessel of radius R. We show that charge fluctuations are always present, even ... More
A bt-algebra of type BMar 26 2017We introduce a bt-algebra of type B. We define this algebra doing the natural analogy with the original construction of the bt-algebra. Notably we find a basis for it, a faithful tensorial representation, and we prove that it supports a Markov trace, ... More
Constrained ballistics and geometrical opticsApr 08 2014The problem of constant-speed ballistics is studied under the umbrella of non-linear non-holonomic constrained systems. The Newtonian approach is shown to be equivalent to the use of Chetaev's rule to incorporate the constraint within the initially unconstrained ... More
Standard decomposition of expansive ergodically supported dynamicsJan 30 2012Jun 04 2014In this work we introduce the notion of weak quasigroups, that are quasigroup operations defined almost everywhere on some set. Then we prove that the topological entropy and the ergodic period of an invertible expansive ergodically supported dynamical ... More
Right-Permutative Cellular Automata on Topological Markov ChainsMar 14 2006Feb 14 2017In this paper we consider cellular automata $(\mathfrak{G},\Phi)$ with algebraic local rules and such that $\mathfrak{G}$ is a topological Markov chain which has a structure compatible to this local rule. We characterize such cellular automata and study ... More
Asymmetric Spatiotemporal Evolution of Prebiotic HomochiralityJun 23 2006Nov 13 2006The role of asymmetry on the evolution of prebiotic homochirality is investigated in the context of autocatalytic polymerization reaction networks. A model featuring enantiometric cross-inhibition and chiral bias is used to study the diffusion equations ... More
On the Product Rule for Classification ProblemsJan 17 2013We discuss theoretical aspects of the product rule for classification problems in supervised machine learning for the case of combining classifiers. We show that (1) the product rule arises from the MAP classifier supposing equivalent priors and conditional ... More
Quantitative Logic ReasoningMay 14 2019In this paper we show several similarities among logic systems that deal simultaneously with deductive and quantitative inference. We claim it is appropriate to call the tasks those systems perform as Quantitative Logic Reasoning. Analogous properties ... More
Dilaton Gravity with a Non-Minimally Coupled Scalar FieldOct 11 1995We discuss the two-dimensional dilaton gravity with a scalar field as the source matter. The coupling between the gravity and the scalar, massless, field is presented in an unusual form. We work out two examples of these couplings, and solutions with ... More
Infinitesimal bialgebras, pre-Lie and dendriform algebrasNov 05 2002Nov 16 2002We introduce the categories of infinitesimal Hopf modules and bimodules over an infinitesimal bialgebra. We show that they correspond to modules and bimodules over the infinitesimal version of the double. We show that there is a natural, but non-obvious ... More
An Equational Metalogic for Monadic Equational SystemsSep 18 2013The paper presents algebraic and logical developments. From the algebraic viewpoint, we introduce Monadic Equational Systems as an abstract enriched notion of equational presentation. From the logical viewpoint, we provide Equational Metalogic as a general ... More
Objects of Categories as Complex NumbersDec 30 2002In many everyday categories (sets, spaces, modules, ...) objects can be both added and multiplied. The arithmetic of such objects is a challenge because there is usually no subtraction. We prove a family of cases of the following principle: if an arithmetic ... More
Social games in a social networkOct 05 2000We study an evolutionary version of the Prisoner's Dilemma game, played by agents placed in a small-world network. Agents are able to change their strategy, imitating that of the most successful neighbor. We observe that different topologies, ranging ... More
Small world effect in an epidemiological modelOct 05 2000A model for the spread of an infection is analyzed for different population structures. The interactions within the population are described by small world networks, ranging from ordered lattices to random graphs. For the more ordered systems, there is ... More
Hidden valence transition in URu2Si2?Feb 18 2019The term "hidden order" refers to an as yet unidentified form of broken-symmetry order parameter that is presumed to exist in the strongly correlated electron system URu2Si2 on the basis of the reported similarity of the heat capacity at its phase transition ... More
The Apparent Fractal Conjecture: Scaling Features in Standard CosmologiesApr 10 2001This paper presents an analysis of the smoothness problem in cosmology by focussing on the ambiguities originated in the simplifying hypotheses aimed at observationally verifying if the large-scale distribution of galaxies is homogeneous, and conjecturing ... More
Limited Frequency Range Observations of Cosmological Point SourcesOct 04 1999Jun 05 2002This paper advances a general proposal for testing non-standard cosmological models by means of observational relations of cosmological point sources in some specific waveband, and their use in the context of the data provided by the galaxy redshift surveys, ... More
A composition between risk and deviation measuresNov 22 2015May 24 2018The intuition of risk is based on two main concepts: loss and variability. In this paper, we present a composition of risk and deviation measures, which contemplate these two concepts. Based on the proposed Limitedness axiom, we prove that this resulting ... More
The role of curvature in quantum statistical mechanicsAug 06 2018In this manuscript, we calculate the scalar curvature of a two-dimensional thermodynamic space to study the properties of two thermodynamic systems. In particular, we study the stability and possible anyonic behavior of quantum group invariant systems ... More
Shear and Vorticity in an Accelerating Brans-Dicke Lambda-Universe with TorsionJul 11 2008Aug 06 2008We study accelerating Universes with power-law scale-factors. We include shear and vorticity, a cosmological "constant" term, and spin from torsion, as in Einstein-Cartan's theory when a scalar-field of Brans-Dicke type acts in the model. We find a "no-hair" ... More
Gravitomagnetism and Angular Momenta of Black-HolesAug 04 2006Aug 06 2008We review the energy contents formulae of Kerr-Newman black-holes, where gravitomagnetic energy term comes to play(Berman, 2006; 2006a; 2004). Then, we obtain the angular momenta formulae, which include the gravitomagnetic effect. Three theorems can be ... More
On the Zero-energy UniverseMay 11 2006Aug 16 2009We consider the energy of the Universe, from the pseudo-tensor point of view(Berman,1981). We find zero values, when the calculations are well-done.The doubts concerning this subject are clarified, with the novel idea that the justification for the calculation ... More
Information Dynamics at a Phase TransitionJun 30 2016Sep 01 2016We propose a new way of investigating phase transitions in the context of information theory. We use an information-entropic measure of spatial complexity known as configurational entropy (CE) to quantify both the storage and exchange of information in ... More
Information-Entropic Stability Bound for Compact Objects: Application to Q-Balls and the Chandrasekhar Limit of PolytropesJul 01 2013Nov 13 2013Spatially-bound objects across diverse length and energy scales are characterized by a binding energy. We propose that their spatial structure is mathematically encoded as information in their momentum modes and described by a measure known as configurational ... More
Cuntz-Krieger algebras for infinite matricesDec 18 1997Feb 01 1998Given an arbitrary infinite 0--1 matrix A having no identically zero rows, we define an algebra OA as the universal C*-algebra generated by partial isometries subject to conditions that generalize, to the infinite case, those introduced by Cuntz and Krieger ... More
On the Semisimplicty of the Action of the Frobenius on Etale CohomologySep 03 2010Jul 30 2011I give a proof of the semisimplicity of the action of the geometric frobenius on etale cohomology. This proof is based on the Weil Conjectures.
Series expansion analysis of a tetrahedral cluster spin chainSep 14 2005Using series expansion by continuous unitary transformations we study the magnetic properties of a frustrated tetrahedral spin-1/2 chain. Starting from the limit of isolated tetrahedra we analyze the evolution of the ground state energy and the elementary ... More
Quantum states of the spacetime, and formation of black holes in AdSMay 14 2012Oct 31 2012We argue that a non-perturbative description of quantum gravity should involve two (non-interacting) copies of a dual field theory on the boundary, and describe the states of the spacetimes accordingly. So, for instance, a complete description of the ... More
String Entanglement and D-branes as Pure StatesJun 17 2009Aug 17 2009We study the entanglement of closed strings degrees of freedom in order to investigate the microscopic structure and statistics of objects as D-branes. By considering the macroscopic pure state (MPS) limit, whenever the entanglement entropy goes to zero ... More
Area Operators in Holographic Quantum GravityApr 11 2014We argue that the holographic formula relating entanglement entropy and the area of a minimal surface is the key to define the area of surfaces in the (emergent) spacetime from the dual theory on the boundary. So we promote the entropy/area relation to ... More
On the Microscopical Structure of the Classical SpacetimeAug 19 2004Our purpose here is to introduce the idea of viewing the spacetime as a macroscopic complex system which, consequently, cannot be directly quantized. It should be thought of as a collection of more fundamental "microscopical" entities (atoms of geometry), ... More
Path Integral Solubility of a General Two-Dimensional ModelOct 05 1994The solubility of a general two dimensional model, which reduces to various models in different limits, is studied within the path integral formalism. Various subtleties and interesting features are pointed out.
Reacting to Variations in Product Demand: An Application for Conversion Rate (CR) Prediction in Sponsored SearchMay 25 2018In online internet advertising, machine learning models are widely used to compute the likelihood of a user engaging with product related advertisements. However, the performance of traditional machine learning models is often impacted due to variations ... More
Efficient spectroscopy of single embedded emitters using optical fiber taper waveguidesApr 17 2009Jun 11 2009A technique based on using optical fiber taper waveguides for probing single emitters embedded in thin dielectric membranes is assessed through numerical simulations. For an appropriate membrane geometry, photoluminescence collection efficiencies in excess ... More
Remarks on the Einstein-Euler-Entropy systemJan 23 2013We prove short-time existence for the Einstein-Euler-Entropy system for non-isentropic fluids with data in uniformly local Sobolev spaces. The cases of compact as well as non-compact Cauchy surfaces are covered. The method employed uses a Lagrangian description ... More
A note on the definition of sliding block codes and the Curtis-Hedlund-Lyndon TheoremJul 08 2015Sep 28 2015In this note we propose an alternative definition for sliding block codes between shift spaces. This definition coincides with the usual definition in the case that the shift space is defined on a finite alphabet, but it encompass a larger class of maps ... More
Positive topological entropy for Reeb flows on 3-dimensional Anosov contact manifoldsDec 10 2015Let $(M, \xi)$ be a compact contact 3-manifold and assume that there exists a contact form $\alpha_0$ on $(M, \xi)$ whose Reeb flow is Anosov. We show this implies that every Reeb flow on $(M, \xi)$ has positive topological entropy. Our argument builds ... More
Structure of the Loday-Ronco Hopf algebra of treesSep 02 2004Apr 05 2005Loday and Ronco defined an interesting Hopf algebra structure on the linear span of the set of planar binary trees. They showed that the inclusion of the Hopf algebra of non-commutative symmetric functions in the Malvenuto-Reutenauer Hopf algebra of permutations ... More
Representations of matched pairs of groupoids and applications to weak Hopf algebrasFeb 07 2004We introduce the category of set-theoretic representations of a matched pair of groupoids. This is a monoidal category endowed with a monoidal functor to the category of quivers over the common base of the groupoids in the matched pair (the forgetful ... More
Igusa-Todorov functions for Artin algebrasMay 31 2016In this paper we study the behaviour of the Igusa-Todorov functions for Artin algebras A with finite injective dimension, and Gorenstein algebras as a particular case. We show that the $\phi$-dimension and $\psi$-dimension are finite in both cases. Also ... More
The Tate Thomason ConjectureJul 02 2010Aug 29 2019We prove The Tate Thomason conjecture using K(l) localized spectra which is the localized spectrum of the complex topology spectrum at an odd prime l or equivalently E(1) localized spectra Fundamental to our proof are Theorem 2.2 and Theorem 2.3. The ... More
A fast algorithm for computing irreducible triangulations of closed surfaces in $E^d$Sep 21 2014Oct 27 2014We give a fast algorithm for computing an irreducible triangulation $T^\prime$ of an oriented, connected, boundaryless, and compact surface $S$ in $E^d$ from any given triangulation $T$ of $S$. If the genus $g$ of $S$ is positive, then our algorithm takes ... More
Legendrian contact homology and topological entropySep 12 2014Apr 23 2016In this paper we study the growth rate of a version of Legendrian contact homology, which we call strip Legendrian contact homology, in 3-dimensional contact manifolds and its relation to the topological entropy of Reeb flows. We show that: if for a pair ... More
An Objective Representation of the Gaussian IntegersNov 28 2002May 13 2004A rig is a riNg without Negatives. We analyse the free rig on a generator x subject to the equivalence x = 1 + x + x^2, showing that in it the non-constant polynomials form a ring. This ring can be identified with the Gaussian integers, which thus acquire ... More
Dynamical Emergence of Complex Structures in Field TheoriesSep 13 2007Nonlinear field theories can be used to study both standard physics questions, or to study questions such as the emergence of order and complexity. These theories are generally derived from the symmetries of a given problem and the interactions that respect ... More
Prebiotic Homochirality as a Critical PhenomenonJan 18 2006The development of prebiotic homochirality on early-Earth or another planetary platform may be viewed as a critical phenomenon. It is shown, in the context of spatio-temporal polymerization reaction networks, that environmental effects -- be them temperature ... More
Anisotropic Stars: Exact SolutionsDec 12 2000We study the effects of anisotropic pressure on the properties of spherically symmetric, gravitationally bound objects. We consider the full general relativistic treatment of this problem and obtain exact solutions for various form of equations of state ... More
Anisotropic Stars: Exact Solutions and StabilityJan 26 2004I report on recent work concerning the existence and stability of self-gravitating spheres with anisotropic pressure. After presenting new exact solutions, Chandrasekhar's variational formalism for radial perturbations is generalized to anisotropic objects ... More
Endomorphisms of B(H), extensions of pure states, and a class of representations of O_nSep 26 1997Let F_n be the fixed-point algebra of the gauge action of the circle on the Cuntz algebra O_n. For every pure state \rho of F_n and every representation \theta of C(T) we construct a representation of O_n, and we use the resulting class of representations ... More
The Geometry of Entanglement Sudden DeathMar 14 2007Jun 25 2007In open quantum systems, entanglement can vanish faster than coherence. This phenomenon is usually called sudden death of entanglement. In this paper sudden death of entanglement is discussed from a geometrical point of view, in the context of two qubits. ... More
New universality classes for generic higher character Lifshitz pointsMar 22 2004We describe new universality classes associated to generic higher character Lifshitz critical behaviors for systems with arbitrary short range competing interactions. New renormalization-group arguments are proposed for anisotropic and isotropic systems. ... More
The Social Behavior and the Evolution of Sexually Transmitted DiseasesDec 03 2002We introduce a model for the evolution of sexually transmitted diseases, in which the social behavior is incorporated as a determinant factor for the further propagation of the infection. The system may be regarded as a society of agents where in principle ... More
Long-Lived Localized Field Configurations in Small Lattices: Application to OscillonsAug 29 1999Long-lived localized field configurations such as breathers, oscillons, or more complex objects naturally arise in the context of a wide range of nonlinear models in different numbers of spatial dimensions. We present a numerical method, which we call ... More
A Case of Well-Defined Thermal Derivative Expansion to Lowest OrderDec 02 1998We examine a very simple model for which the leading contribution to the one-loop effective potential at finite temperature is uniquely defined despite the presence of the Landau terms. In addition we report on the usual non-analyticity at finite temperature ... More
Gravitational Waves from Collapsing Vacuum DomainsJul 24 1998Nov 10 1998The breaking of an approximate discrete symmetry, the final stages of a first order phase transition, or a post-inflationary biased probability distribution for scalar fields are possible cosmological scenarios characterized by the presence of unstable ... More