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The Cartan Matrix of a Brauer Configuration AlgebraAug 09 2018Using the combinatorial information of a Brauer configuration is possible to compute each entry of the Cartan matrix of the algebra associated to the Brauer configuration.

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

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

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

Stability of Lie group homomorphisms and Lie subgroupsDec 08 2018We discuss a Moser type argument to show when a deformation of a Lie group homomorphism and of a Lie subgroup is trivial. For compact groups we obtain stability results.

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

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

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

Frontiers of Condensed Matter Physics Explored with High-Field Specific HeatApr 06 2010Production of very high magnetic fields in the laboratory has relentlessly increased in quantity and quality over the last five decades, and a shift occurred from research focused in magnet technology to studies of the fundamental physics of novel materials ... More

On conserved charges and thermodynamics of the AdS$_{4}$ dyonic black holeMar 11 2016Four-dimensional gravity in the presence of a dilatonic scalar field and an Abelian gauge field is considered. This theory corresponds to the bosonic sector of a Kaluza-Klein dimensional reduction of eleven-dimensional supergravity which induces a determined ... 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

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

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

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

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

From endomorphisms to automorphisms and back: dilations and full cornersNov 18 1999When S is a discrete subsemigroup of a discrete group G such that G = S^{-1} S, it is possible to extend circle-valued multipliers from S to G; to dilate (projective) isometric representations of S to (projective) unitary representations of G; and 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

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

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

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

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

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.

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.

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

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

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

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

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

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

Chaos and PreheatingAug 31 2001Nov 26 2002We show evidence for a relationship between chaos and parametric resonance both in a classical system and in the semiclassical process of particle creation. We apply our considerations in a toy model for preheating after inflation.

Thermodynamics sheds light on black hole dynamicsDec 07 2017We propose to unify two a priori distinct aspects of black hole physics : their thermodynamics, and their effective dynamics when they are "skeletonized" as point particles (a useful procedure when tackling, for example, their motion in a coalescing binary ... More

On manifolds with nonhomogeneous factorsMar 19 2012Mar 20 2012We present simple examples of finite-dimensional connected homogeneous spaces (they are actually topological manifolds) with nonhomogeneous and nonrigid factors. In particular, we give an elementary solution of an old problem in general topology concerning ... More

Phase-Noise and Amplitude-Noise Measurement of DACs and DDSsJun 12 2019This article proposes a method for the measurement of Phase Noise (PN, or PM noise) and Amplitude Noise (AN, or AM noise) of Digital-to-Analog Converters (DAC) and Direct Digital Synthesizers (DDS) based on modulation-index amplification. The carrier ... 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

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

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

Entropy of the UniverseApr 20 2009After a discussion on several limiting cases where General Relativity turns into less sophisticated theories, we find that in the correct thermodynamical and cosmological weak field limit of Einstein's field equations the entropy of the Universe is R^(3/2) ... More

A General Relativistic Rotating Evolutionary Universe - Part IIJan 13 2008Aug 06 2008As a sequel to (Berman, 2008a), we show that the rotation of the Universe can be dealt by generalised Gaussian metrics, defined in this paper. Robertson-Walker's metric has been employed with proper-time, in its standard applications; the generalised ... More

Multimodal deep learning for short-term stock volatility predictionDec 25 2018Stock market volatility forecasting is a task relevant to assessing market risk. We investigate the interaction between news and prices for the one-day-ahead volatility prediction using state-of-the-art deep learning approaches. The proposed models are ... More

A theory for combinations of risk measuresJul 05 2018Mar 18 2019We study combinations of risk measures under no restrictive assumption on the set of alternatives. The main result is the representation for resulting risk measures from the properties of both alternative functionals and combination functions. To that, ... More

Invited review: Epidemics on social networksDec 12 2013Since its first formulations almost a century ago, mathematical models for disease spreading contributed to understand, evaluate and control the epidemic processes.They promoted a dramatic change in how epidemiologists thought of the propagation of infectious ... More

Realization of Einsteins Machian ProgramFeb 07 2013The Einsteins Machian Program is here accomplished.

Network-on-Chip with load balancing based on interleave of flits techniqueOct 23 2015This paper presents the evaluation of a Network-on-Chip (NoC) that offers load balancing for Systems-on-Chip (SoCs) dedicated for multimedia applications that require high traffic of variable bitrate communication. The NoC is based on a technique that ... More

Quantum histories without contrary inferencesMay 20 2014In the consistent histories formulation of quantum theory it was shown that it is possible to retrodict contrary properties. We show that this problem do not appear in our formalism of generalized contexts for quantum histories.

On the Geometry and Kinematics of Smoothly Distributed and Singular DefectsJan 14 2014A continuum mechanical framework for the description of the geometry and kinematics of defects in material structure is proposed. The setting applies to a body manifold of any dimension which is devoid of a Riemannian or a parallelism structure. In addition, ... More

A note on quantization in the presence of gravitational shock wavesApr 17 2013Sep 18 2013We study the quantization of a free scalar field when the background metric satisfies Einstein's equations and develops gravitational shock waves.

Explicit Error Bounds for Carleman LinearizationNov 07 2017We revisit the method of Carleman linearization for systems of ordinary differential equations with polynomial right-hand sides. This transformation provides an approximate linearization in a higher-dimensional space through the exact embedding of polynomial ... More

Hybrid gap modes induced by fiber taper waveguides: application in spectroscopy of single solid-state emitters deposited on thin filmsFeb 19 2010We show, via simulations, that an optical fiber taper waveguide can be an efficient tool for photoluminescence and resonant, extinction spectroscopy of single emitters, such as molecules or colloidal quantum dots, deposited on the surface of a thin dielectric ... More

Universal and deterministic manipulation of the quantum state of harmonic oscillators: a route to unitary gates for Fock State qubitsNov 10 2004We present a simple quantum circuit that allows for the universal and deterministic manipulation of the quantum state of confined harmonic oscillators. The scheme is based on the selective interactions of the referred oscillator with an auxiliary three-level ... More

Simplicity of Lyapunov spectra: a sufficient criterionJul 28 2006We exhibit an explicit sufficient condition for the Lyapunov exponents of a linear cocycle over a Markov map to have multiplicity 1. This builds on work of Guivarc'h-Raugi and Gol'dsheid-Margulis, who considered products of random matrices, and of Bonatti-Viana, ... More

A standard form for generator matrices with respect to the Niederreiter-Rosenbloom-Tsfasman metricMay 12 2011In this note, we present an analogue for codes in vector spaces with a Rosenbloom-Tsfasman metric of the well-known standard form of generator matrices for codes in spaces with the Hamming metric.

Lagrange's Theorem for Hopf Monoids in SpeciesMay 27 2011Jul 31 2012Following Radford's proof of Lagrange's theorem for pointed Hopf algebras, we prove Lagrange's theorem for Hopf monoids in the category of connected species. As a corollary, we obtain necessary conditions for a given subspecies K of a Hopf monoid H to ... More

Average sex ratio and population maintenance costApr 13 2010Feb 14 2017The ratio of males to females in a population is a meaningful characteristic of sexual species. The reason for this biological property to be available to the observers of nature seems to be a question never asked. Introducing the notion of historically ... More

Obstructions towards a generalization of no-hair theorems: I. Scalar clouds around Kerr black holesDec 14 2018We show that the integral method used to prove the no-hair theorem for Black Holes (BH's) in spherically symmetric and static spacetimes within the framework of general relativity with matter composed by a complex-valued scalar-field does not lead to ... More

Non-ideal rheology of semidilute bacterial suspensionsJan 11 2019Jan 29 2019The rheology of semidilute bacterial suspensions is studied with the tools of kinetic theory, considering binary interactions, going beyond the ideal gas approximation. Two models for the interactions are considered, which encompass both the steric and ... More

Self-injective right artinian rings and Igusa Todorov functionsJan 10 2011We show that a right artinian ring $R$ is right self-injective if and only if $\psi(M)=0$ (or equivalently $\phi(M)=0$) for all finitely generated right $R$-modules $M$, where $\psi, \phi : \mod R \to \mathbb N$ are functions defined by Igusa and Todorov. ... More

The Inverse Problem for Nested Polygonal Relative EquilibriaDec 07 2017We prove that for some potentials (including the Newtonian one, and the potential of Helmholtz vortices in the plane) relative equilibria consisting of two homothetic regular polygons of arbitrary size can only occur if the masses at each polygon are ... More

Legendrian contact homology and topological entropySep 12 2014May 08 2017In 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

THERMAL EFFECTS ON THE CATALYSIS BY A MAGNETIC FIELDApr 17 1995We show that the formation of condensates in the presence of a constant magnetic field in 2+1 dimensions is extremely unstable. It disappears as soon as a heat bath is introduced with or without a chemical potential. We point out some new nonanalytic ... More

DYNAMICAL SUPERSYMMETRYApr 10 1995We show, in a simple quantum mechanical model, how a theory can become supersymmetric in the presence of interactions even when the free theory is not. This dynamical generation of supersymmetry relaxes the condition on the equality of masses of the superpartners ... More

Local and global well-posedness for a quadratic Schrödinger system on spheres and Zoll manifoldsJun 07 2019We consider the initial value problem (IVP) associated to a quadratic Schr\"odinger system \begin{equation*} \begin{cases} i \partial_{t} v \pm \Delta_{g} v - v = \epsilon_{1} u \bar{v}, & t \in \mathbb{R},\; x \in M, \\[2ex] i \sigma \partial_{t} u \pm ... 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

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

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

A General Theory of Oscillon DynamicsOct 30 2009We present a comprehensive, nonperturbative analytical method to investigate the dynamics of time-dependent oscillating scalar field configurations. The method is applied to oscillons in a double well Klein-Gordon model in two and three spatial dimensions, ... 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

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