Searching Arxiv, refresh for possibly better results.

total 3221took 0.08s

Sliding Motions on SO(3), Sliding SubgroupsMay 14 2019We propose a sliding surface for systems on the Lie group $SO(3)\times \mathbb{R}^3$ . The sliding surface is shown to be a Lie subgroup. The reduced-order dynamics along the sliding subgroup have an almost globally asymptotically stable equilibrium. ... More

Coding the real locus of X_0+(N)Mar 05 2006Let X_0+(N) be the Atkin-Lehner quotient of the modular curve X_0(N) associated to the Fricke involution wN. Assume N > 3 prime and endow the real locus X+ 0 (N)(R) with the real topology. In this paper we revisit a special case of result due to Ogg on ... More

Finding the Topic of a Set of ImagesJun 25 2016In this paper we introduce the problem of determining the topic that a set of images is describing, where every topic is represented as a set of words. Different from other problems like tag assignment or similar, a) we assume multiple images are used ... More

On the 2-divisibility of certain Heenger pointsDec 28 2005Let E be an elliptic curve defined over the rationals and let N be its conductor. Assume N is prime. In this paper we give numerical evidence that suggests some conjectures on the 2-divisibility of certain sums of Heenger points on E of discriminant D ... More

Semi-global invariants of piecewise smooth Lagrangian fibrationsMar 21 2006We study certain types of piecewise smooth Lagrangian fibrations of smooth symplectic manifolds, which we call stitched Lagrangian fibrations. We extend the classical theory of action-angle coordinates to these fibrations by encoding the information on ... More

New supersymmetry-generated complex potentials with real spectraMay 19 2015Aug 24 2015A new form to construct complex superpotentials that produce real energy spectra in supersymmetric quantum mechanics is presented. This is based on the relation between the nonlinear Ermakov equation and a second order differential equation of the Schroedinger ... More

Quasi-Frobenius functors. ApplicationsDec 21 2006Sep 03 2008We investigate functors between abelian categories having a left adjoint and a right adjoint that are \emph{similar} (these functors are called \emph{quasi-Frobenius functors}). We introduce the notion of a \emph{quasi-Frobenius bimodule} and give a characterization ... More

A Matching Game for Data Trading in Operator-Supervised User-Provided NetworksFeb 16 2016In this paper, we consider a recent cellular network connection paradigm, known as user-provided network (UPN), where users share their connectivity and act as an access point for other users. To incentivize user participation in this network, we allow ... More

$b\to sγ$ Constraints on the Minimal Supergravity Model with Large $\tanβ$Dec 08 1997In the minimal supergravity model (mSUGRA), as the parameter $\tan\beta$ increases, the charged Higgs boson and light bottom squark masses decrease, which can potentially increase contributions from $tH^\pm$, $\tg\tb_j$ and $\tz_i\tb_j$ loops in the decay ... More

Selection rules in the double beta decay of deformed nucleiApr 30 2002The 2 nu double beta decay half-lives of six nuclei, whose decays were previously reported as theoretically forbidden, are calculated by including the pairing interaction, which mixes different occupations and opens up the possibility of the decay. All ... More

Theoretical description of the double beta decay of 160GdOct 08 2001Mar 25 2002The half-life of the 2 neutrino double-beta-decay of 160Gd, a process which was previously reported as theoretically forbidden, is estimated by including the pairing interaction, which mixes different occupations and opens channels for the decay. Explicit ... More

On Volterra quadratic stochastic operators of a two-sex population on $S^1\times S^1$Aug 06 2018Sep 11 2018We consider a four-parametric $(a, b, \alpha, \beta)$ family of Volterra quadratic stochastic operators for a bisexual population (i.e., each organism of the population must belong either to the female sex or the male sex). We show that independently ... More

Entanglement and Localization of a Two-Mode Bose-Einstein CondensateOct 17 2009A simple second quantization model is used to describe a two-mode Bose-Einstein condensate (BEC), which can be written in terms of the generators of a SU(2) algebra with three parameters. We study the behaviour of the entanglement entropy and localization ... More

Elastic forces that do no work and the dynamics of fast cracksJul 17 1995Jul 18 1995Elastic singularities such as crack tips, when in motion through a medium that is itself vibrating, are subject to forces orthogonal to the direction of motion and thus impossible to determine by energy considerations alone. This fact is used to propose ... More

Quantum Weibel InstabilityNov 06 2007The Weibel instability is analyzed for quantum plasmas described by the Wigner-Maxwell model. For a suitable class of electromagnetic potentials, the Wigner-Maxwell system is linearized yielding a general dispersion relation for transverse electromagnetic ... More

Josephson effect between Bose condensatesOct 26 1998I present an overview of the physics of the Josephson effect between Bose condensed systems, with emphasis on the recently achieved BEC's in trapped alkali gases. I focus mostly on those physical phenomena that are likely to be observed only (or more ... More

On the scaling property in fluctuation theory for stable Lévy processesJul 22 2010We find an expression for the joint Laplace transform of the law of $(T_{[x,+\infty[},X_{T_{[x,+\infty[}})$ for a L\'evy process $X$, where $T_{[x,+\infty[}$ is the first hitting time of $[x,+\infty[$ by $X$. When $X$ is an $\alpha$-stable L\'evy process, ... More

Quasi normal modes and the area spectrum of a near extremal de Sitter black hole with conformally coupled scalar fieldApr 14 2015In this paper we have studied a black hole in de Sitter space which has a conformally coupled scalar field in the background. This black hole is also known as the $MTZ$ black hole. We have obtained exact values for the quasi normal mode frequencies under ... More

On an Inequality of Dimension-like Invariants for Finite GroupsFeb 02 2015In this paper, we introduce several notions of "dimension" of a finite group, involving sizes of generating sets and certain configurations of maximal subgroups. We focus on the inequality $m(G) \leq \mathrm{MaxDim}(G)$, giving a family of examples where ... More

Enhanced $A$-infinity obstruction theoryOct 01 2015We define a new obstruction theory for the extension of truncated A-infinity algebra structures. Obstructions lie in the new terms of a spectral sequence which extends Bousfield-Kan's fringed spectral sequence of a certain tower of fibrations. The obstructions ... More

Wave dispersion derived from the square-root Klein-Gordon-Poisson systemJul 30 2013Recently there has been great interest around quantum relativistic models for plasmas. In particular striking advances have been obtained by means of the Klein-Gordon-Maxwell system, which provides a first order approach to the relativistic regimes of ... More

On the splitting ring of a polynomialApr 04 2015Oct 16 2015Let $f(Z)=Z^n-a_{1}Z^{n-1}+\cdots+(-1)^{n-1}a_{n-1}Z+(-1)^na_n$ be a monic polynomial with coefficients in a ring~$R$ with identity, not necessarily commutative. We study the ideal $I_f$ of $R[X_1,\dots,X_n]$ generated by $\sigma_i(X_1,\dots,X_n)-a_{i}$, ... More

Pseudo-Query ReformulationJul 14 2015Automatic query reformulation refers to rewriting a user's original query in order to improve the ranking of retrieval results compared to the original query. We present a general framework for automatic query reformulation based on discrete optimization. ... More

Born-Infeld-de Sitter gravity: Cold, ultracold and Nariai black holesDec 30 2013Aug 16 2014In this paper, we have presented interesting properties of the static charged Born-Infeld-de Sitter black hole. They can have time-like as well as space-like singularities depending on the parameters of the theory. The degenerate black holes lead to cold, ... More

Quasinormal modes of dilaton-de Sitter black holes: scalar perturbationsJan 24 2016Dilaton black hole solutions in low energy string theory (well known as GMGHS black holes) have analogue black holes with a cosmological constant derived by Gao and Zhang. Here, we study quasi normal modes of this dilaton-de Sitter black hole under neutral ... More

Hamilton-Dirac systems for charged particles in gauge fieldsOct 13 2014Apr 07 2015In this work, we use the Sternberg phase space (which may be considered as the classical phase space of particles in gauge fields) in order to explore the dynamics of such particles in the context of Hamilton-Dirac systems and their associated Hamilton-Pontryagin ... More

Superstring Phenomenology: An OverviewJul 22 1997The different aspects of superstring phenomenology before and after 1995 are briefly reviewed. (Contribution to the conference SUSY97)

Duality and Global SymmetriesJun 27 1997This is a general introduction to duality in field theories. The existence and breaking of global symmetries is used as a guideline to systematically prove duality between different field theories. Systems discussed include abelian and non-abelian T-duality ... More

The Deligne-Lusztig curve associated to the Suzuki groupJun 26 1997We give a characterization of the Deligne-Lusztig curve associated to the Suzuki group based on the genus and the number of rational points of the curve.

Equivalence and congruence of matrices under the action of standard parabolic subgroupsAug 21 2013We find necessary and sufficient conditions for $P$-equivalence of arbitrary matrices and $P$-congruence of symmetric and alternating matrices, where $P$ is standard parabolic subgroup of $GL_n(F)$ and $F$ is an arbitrary field.

Hyperbolic classification of natural numbers and Goldbach ConjectureJul 17 2005Jun 22 2007By means of a dynamical process we provide a characterization of the Goldbach Conjecture in an infinite set of even numbers that depends on time.

Reversed Dickson Polynomials of the Third KindFeb 15 2016Aug 08 2016Let $p$ be a prime and $q=p^e$. We discuss the properties of the reversed Dickson polynomial $D_{n,2}(1,x)$ of the third kind. We also give several necessary conditions for the reversed Dickson polynomial of the third kind $D_{n,2}(1,x)$ to be a permutation ... More

Sufficient conditions for the convergence of the Magnus expansionNov 15 2007Two different sufficient conditions are given for the convergence of the Magnus expansion arising in the study of the linear differential equation $Y' = A(t) Y$. The first one provides a bound on the convergence domain based on the norm of the operator ... More

P-V criticality in AdS black holes of massive gravityNov 16 2016Dec 14 2016In this paper we have studied the extended phase space thermodynamics in the canonical ensemble of black holes in massive gravity in AdS space. The black holes considered here belong to a theory of massive gravity where the graviton gain a mass due to ... More

Massive gravity with Lorentz symmetry breaking: black holes as heat enginesAug 26 2018In extended phase space, a static black hole in massive gravity is studied as a holographic heat engine. In the massive gravity theory considered, the graviton gain a mass due to Lorentz symmetry breaking. Exact efficiency formula is obtained for a rectangle ... More

The first passage time of a stable process conditioned to not overshootNov 15 2012Jan 07 2015Consider a stable L\'evy process $X=(X_t,t\geq 0)$ and let $T_x$, for $x>0$, denote the first passage time of $X$ above the level $x$. In this work, we give an alternative proof of the absolute continuity of the law of $T_x$ and we obtain a new expression ... More

On spectral approximation, Følner sequences and crossed productsAug 06 2010Oct 09 2012In this article we study Foelner sequences for operators and mention their relation to spectral approximation problems. We construct a canonical Foelner sequence for the crossed product of a discrete amenable group $\Gamma$ with a concrete C*-algebra ... More

Singular 2 webs and Polar CurvesApr 21 2013A 2-web in the plane is given by two everywhere transverse 1-foliations. In this paper we introduce the study of singular 2-webs, given by any two foliations, which may be tangent in some points. We show that such two foliations are tangent along a curve, ... More

Homotopy theory of non-symmetric operadsJan 09 2011We endow categories of non-symmetric operads with natural model structures. We work with no restriction on our operads and only assume the usual hypotheses for model categories with a symmetric monoidal structure. We also study categories of algebras ... More

On the unit of a monoidal model categoryNov 05 2014Nov 13 2014In this paper we show how to modify cofibrations in a monoidal model category so that the tensor unit becomes cofibrant while keeping the same weak equivalences. We obtain aplications to enriched categories and coloured operads in stable homotopy theory. ... More

Associativity of the Commutator Operation in GroupsMay 30 2008The study of associativity of the commutator operation in groups goes back to some work of Levi in 1942. In the 1960's Richard J. Thompson created a group F whose elements are representatives of the generalized associative law for an arbitrary binary ... More

The first obstructions to enhancing a triangulated categoryMar 06 2018In this paper we relate triangulated category structures to the cohomology of small categories and define initial obstructions to the existence of an algebraic or topological enhancement. We show that these obstructions do not vanish in an example of ... More

Enhanced finite triangulated categoriesOct 23 2018Feb 20 2019We give a necessary and sufficient condition for the existence of an enhancement of a finite triangulated category. Moreover, we show that enhancements are unique when they exist, up to Morita equivalence.

On the possibility of nonlinear de Broglie relations for very-high-energy photonsMay 20 2019While quantum field theory is at the heart of our understanding of a large variety of phenomena, there remains some discrepancies between theoretically predicted and observed quantities in the very-high-energy (VHE) domain. In this work, starting from ... More

Enveloping actions and Takai duality for partial actionsJul 17 2000We show that any continuous partial action on a topological space has a unique enveloping action, i.e. it is the restriction of a global action. In the case of C^*-algebras we prove that any partial action has an enveloping action up to Morita equivalence. ... More

Quantum MagnetohydrodynamicsMar 02 2005The quantum hydrodynamic model for charged particle systems is extended to the cases of non zero magnetic fields. In this way, quantum corrections to magnetohydrodynamics are obtained starting from the quantum hydrodynamical model with magnetic fields. ... More

On the relevance of quantum models for plasmasOct 01 2012Recently there has been a claim on the complete irrelevance of quantum modeling for plasmas. We address this subject from basic principles. Physical situations where quantum effects play a decisive role are identified.

The damped Pinney equation and its applications to dissipative quantum mechanicsDec 25 2007Dec 18 2009The work considers the damped Pinney equation, defined as the model arising when a linear in velocity damping term is included in the Pinney equation. In the general case the resulting equation does not admit Lie point symmetries or is reducible to a ... More

Aspects of quantum cooling in electron and atom systemsMay 18 2009Some features of nonadiabatic electron heat pumps are studied and connected to general questions of quantum cooling. Inelastic reflection is shown to contribute to heating if the external driving signal is time-symmetric. The quantum of cooling power, ... More

P-V criticality in AdS black holes of massive gravityNov 16 2016Nov 30 2016In this paper we have studied the extended phase space thermodynamics in the canonical ensemble of black holes in massive gravity in AdS space. The black holes considered here belong to a theory of massive gravity where the graviton gain a mass due to ... More

Phase transitions of black holes in massive gravityMay 16 2016May 19 2016In this paper we have studied thermodynamics of a black hole in massive gravity in the canonical ensemble. The massive gravity theory in consideration here has a massive graviton due to Lorentz symmetry breaking. The black hole studied here has a scalar ... More

A note on the automorphism group of Schubert varietiesMay 12 2016In this work we extend results on the automorphism group of Schubert varieties. We consider the Schubert conditions which define a Schubert variety. It turns out that an automorphism of the Grassmannian fixes a Schubert variety contained in it if and ... More

Nariai black holes with quintessenceAug 21 2014In this paper we study the properties of Schwarzschild black hole surrounded by quintessence matter. The main objective of the paper is to show the existence of Nariai type black hole for special values of the parameters in the theory. The Nariai black ... More

Extremal Surfaces in Asymptotically AdS Charged Boson Stars BackgroundsJan 18 2013In this paper, inspired by the holographic dual of the entanglement entropy, we consider the behaviour of extremal, codimension two, spacelike surfaces in the background of three and four dimensional charged boson stars in asymptotically anti-de Sitter ... More

Schwarzschild black hole surrounded by quintessence: Null geodesicsFeb 07 2012Aug 15 2014We have studied the null geodesics of the Schwarzschild black hole surrounded by quintessence matter. Quintessence matter is a candidate for dark energy. Here, we have done a detailed analysis of the geodesics and exact solutions are presented in terms ... More

Phase transitions of black holes in massive gravityMay 16 2016Dec 14 2016In this paper we have studied thermodynamics of a black hole in massive gravity in the canonical ensemble. The massive gravity theory in consideration here has a massive graviton due to Lorentz symmetry breaking. The black hole studied here has a scalar ... More

Counting Spanning trees in double nested graphsMay 16 2016In this paper we give a linear time algorithm for computing the number of spanninig trees in double nested graphs.

Lectures on Superstring PhenomenologyMar 12 1996Mar 26 1996The phenomenological aspects of string theory are briefly reviewed. Emphasis is given to the status of 4D string model building, effective Lagrangians, model independent results, supersymmetry breaking and duality symmetries.

On the proper homotopy type of locally compact A^2_n-polyhedraMay 08 2006In this paper we address the classification problem for locally compact (n-1)-connected CW-complexes with dimension less or equal than n+2 up to proper homotopy type. We obtain complete classification theorems in terms of purely algebraic data in those ... More

Modular reduction of the Steinberg lattice of the general linear groupAug 21 2013The modular reduction of the Steinberg lattice of the general linear group is studied

Dilations of interaction groups that extend actions of Ore semigroupsAug 05 2010We show that every interaction group extending an action of an Ore semigroup by injective unital endomorphisms of a C*-algebra, admits a dilation to an action of the corresponding enveloping group on another unital C*-algebra, of which the former is a ... More

Remarks on numerical semigroupsDec 19 1995We extend results on Weierstrass semigroups at ramified points of double covering of curves to any numerical semigroup whose genus is large enough. As an application we strengthen the properties concerning Weierstrass weights in \cited{To}.

On certain N--sheeted coverings and numerical semigroups which cannot be realized as Weierstrass semigroupsJul 26 1994Mar 06 1995A curve $X$ is said to be of type $(N,\gamma)$ if it is an $N$--sheeted covering of a curve of genus $\gamma$ with at least one totally ramified point. A numerical semigroup $H$ is said to be of type $(N,\gamma)$ if it has $\gamma$ positive multiples ... More

Operator algebras: an informal overviewJan 02 2009In this article we give a short and informal overview of some aspects of the theory of C*- and von Neumann algebras. We also mention some classical results and applications of these families of operator algebras.

Spinning dilaton black hole in 2+1 dimensions as a particle acceleratorMar 01 2017In this paper we have studied particle collision around a spinning dilaton black hole in 2 +1 dimensions. This black hole is a solution to the low energy string theory in 2+1 dimensions. Time-like geodesics are presented in detail and the center of mass ... More

Charged dilaton black hole in 2+1 dimensions as a particle acceleratorMar 29 2017In this paper we have studied particle collisions around a charged dilaton black hole in 2+1 dimensions. This black hole is a solution to the low energy string action in 2+1 dimensions. Time-like geodesics for charged particles are studied in detail. ... More

Is String Phenomenology an Oxymoron?Dec 05 2016Dec 13 2016A brief discussion is presented assessing the achievements and challenges of string phenomenology: the subfield dedicated to study the potential for string theory to make contact with particle physics and cosmology. Building from the well understood case ... More

Modeling of relativistic ion-acoustic waves in ultra-degenerate plasmasDec 14 2017We consider the relativistic ion-acoustic mode in a plasma composed by cold ions and an ultra-degenerate electron gas, described the relativistic Vlasov-Poisson system. A critical examination of popular fluid models for relativistic ion-acoustic waves ... More

Learning Entrepreneurship with Serious Games - A Classroom ApproachSep 18 2017The use of educational games for pedagogical practice can provide new conceptions of teaching-learning in an interactive environment stimulating the acquisition of new knowledge. The so-called serious games are focused on the goal of transmitting educational ... More

Systematic Derivation of Noether Point Symmetries in Special Relativistic Field TheoriesMar 03 2016Mar 16 2016A didactic and systematic derivation of Noether point symmetries and conserved currents is put forward in special relativistic field theories, without a priori assumptions about the transformation laws. Given the Lagrangian density, the invariance condition ... More

Representation theory of some infinite-dimensional algebras arising in continuously controlled algebra and topologyOct 21 2003In this paper we determine the representation type of some algebras of infinite matrices continuously controlled at infinity by a compact metrizable space. We explicitly classify their finitely presented modules in the finite and tame cases. The algebra ... More

Moduli spaces of algebras over non-symmetric operadsDec 21 2011Aug 19 2013In this paper we study spaces of algebras over an operad (non-symmetric) in symmetric monoidal model categories. We first compute the homotopy fiber of the forgetful functor sending an algebra to its underlying object, extending a result of Rezk. We then ... More

The deterministic limit of the Moran model: a uniform central limit theoremAug 21 2015We consider a Moran model with two allelic types, mutation and selection. In this work, we study the behaviour of the proportion of fit individuals when the size of the population tends to infinity, without any rescaling of parameters or time. We first ... More

New Parametrizations for the Photon Structure FunctionJan 07 2006In the last year four new parametrizations of the Hadronic Photon Structure Function at Next to Leading Order have appeared. In this talk, I briefly review the main features of three of them: the FFNS_CJK, CJK and AFG.

Geometric properties of RM vector fields along curves in Riemannian manifoldsSep 27 2016Rotation minimizing vector fields and frames were introduced by Bishop as an alternative to the Frenet frame. They are used in CAGD because they can be defined even the curvature vanishes. Nevertheless, many other geometric properties have not been studied. ... More

Black holes in massive gravity: quasinormal modes of Dirac field perturbationsJun 09 2015We have studied quasinormal modes of spinor $\frac{1}{2}$, massless Dirac field perturbations of a black hole in massive gravity. The parameters of the theory, such as the mass of the black hole, the scalar charge of the black hole, mode number and the ... More

Cold, ultracold and Nariai black holes with quintessenceJan 03 2014In this paper, we study the properties of the charged black hole surrounded by the quintessence. The solution space for the horizons for various values of the mass $M$, charge $Q$, and the quintessence parameter $\alpha$ are studied in detail. Special ... More

A Note on Permutation Binomials and Trinomials over Finite FieldsSep 22 2016Let $p$ be a prime and $e$ be a positive integer. We completely explain the permutation binomials and trinomials arising from the reversed Dickson polynomials of the $(k+1)$-th kind $D_{n,k}(1,x)$ over $\mathbb{F}_{p^e}$ when $n=p^l+2$, where $l\in \mathbb{N}$. ... More

Casimir effect around disclinationsMay 05 1995This communication concerns the structure of the electromagnetic quantum vacuum in a disclinated insulator. It is shown that a nonzero vacuum energy density appears when the rotational symmetry of a continuous insulating elastic medium is broken by a ... More

Enhancement of the magnetic moment of the electron due to a topological defectMay 23 1995In the framework of the theory of defects/three-dimensional gravitation, it is obtained a positive correction to the magnetic moment of the electron bound to a disclination in a dielectric solid.

Duality Beyond Global Symmetries: the Fate of the B_{μν} FieldJun 12 1995Duality between the `axion' field $a$ and the antisymmetric tensor field $B_{\mu\nu}$ is traced after a nonperturbative effect, gaugino condensation, breaks the Peccei-Quinn symmetry $a \rightarrow a +c$. Even though the PQ symmetry was at its origin, ... More

Abelian and Non-Abelian Dualities in String BacgroundsMay 13 1993We present a brief discussion of recent work on duality symmetries in non-trivial string backgrounds. Duality is obtained from a gauged non-linear sigma-model with vanishing gauge field strength. Standard results are reproduced for abelian gauge groups, ... More

Bounding the order of automorphisms of certain curvesNov 28 1994Aug 19 1995We study upper bounds on the order of automorphisms of non-singular curves $X$ satisfying at least one of the following hypothesis: 1) $X$ is an $m$-sheeted covering of exactly one non-singular curve of genus $\gamma$, where $m$ is prime; 2) the center ... More

Modular Theory by exampleJan 08 2009The present article contains a short introduction to Modular Theory for von Neumann algebras with a cyclic and separating vector. It includes the formulation of the central result in this area, the Tomita-Takesaki theorem, and several of its consequences. ... More

More on Equienergetic Threshold GraphsJul 02 2018The energy of a graph is defined as the sum the absolute values of the eigenvalues of its adjacency matrix. A threshold graph G on n vertices is coded by a binary sequence of length n. In this paper we answer a question posed by Jacobs et al. [Eigenvalues ... More

Enhanced $A$-infinity obstruction theoryOct 01 2015Mar 12 2018We extend the Bousfield-Kan spectral sequence for the computation of the homotopy groups of the space of minimal A-infinity algebra structures on a graded projective module. We use the new part to define obstructions to the extension of truncated minimal ... More

Cylinders for non-symmetric DG-operads via homological perturbation theoryMay 12 2015We construct small cylinders for cellular non-symmetric DG-operads over an arbitrary commutative ring by using the basic perturbation lemma from homological algebra. We show that our construction, applied to the A-infinity operad, yields the operad parametrizing ... More

A Note on Permutation Binomials and Trinomials over Finite FieldsSep 22 2016Feb 05 2017Let $p$ be an odd prime and $e$ be a positive integer. We completely explain the permutation binomials and trinomials arising from the reversed Dickson polynomials of the $(k+1)$-th kind $D_{n,k}(1,x)$ over $\mathbb{F}_{p^e}$ when $n=p^l+2$, where $l\in ... More

Non-Euclidean visibility problemsJul 27 2006We consider the analog of visibility problems in hyperbolic plane (represented by Poincar\'{e} half-plane model H), replacing the standard lattice $Z\times Z$ by the orbit $z=i$ under the full modular group $z$. We prove a visibility criterion and study ... More

A triangulated category without modelsMar 11 2007We exhibit a triangulated category which is neither the stable category of a Frobenius category nor a full triangulated subcategory of the homotopy category of a stable model category.

Conjugacy classes of p-cycles of type D in alternating groupsNov 27 2012Mar 04 2014We classify the conjugacy classes of p-cycles of type D in alternating groups. This finishes the open cases in arXiv:0812.4628. We also determine all the subracks of those conjugacy classes which are not of type D.

Design for a Darwinian Brain: Part 1. Philosophy and NeuroscienceMar 28 2013Physical symbol systems are needed for open-ended cognition. A good way to understand physical symbol systems is by comparison of thought to chemistry. Both have systematicity, productivity and compositionality. The state of the art in cognitive architectures ... More

Rotation Minimizing vector fields and frames in Riemannian manifoldsApr 27 2013We prove that a normal vector field along a curve in R3 is rotation minimizing (RM) if and only if it is parallel respect to the normal connection. This allows us to generalize all the results of RM vectors and frames to curves immersed in Riemannian ... More

Conformal covariance of massless free netsJun 16 2000In the present paper we review in a fibre bundle context the covariant and massless canonical representations of the Poincare' group as well as certain unitary representations of the conformal group (in 4 dimensions). We give a simplified proof of the ... More

Geometric properties of rotation minimizing vector fields along curves in Riemannian manifoldsSep 27 2016Mar 29 2017Rotation minimizing vector fields and frames were introduced by Bishop as an alternative to the Frenet frame. They are used in CAGD because they can be defined even the curvature vanishes. Nevertheless, many other geometric properties have not been studied. ... More

On quasi-Frobenius bimodules and coringsDec 21 2006It is proved here that any quasi-Frobenius bimodule produces a quasi-Frobenius comatrix coring

Low Momentum Classical Mechanics with Effective Quantum PotentialsMar 02 2005A recently introduced effective quantum potential theory is studied in a low momentum region of phase space. This low momentum approximation is used to show that the new effective quantum potential induces a space-dependent mass and a smoothed potential ... More

Uncertainty, incompleteness, chance, and designJan 29 2013Apr 09 2013The 20th century has revealed two important limitations of scientific knowledge. On the one hand, the combination of Poincar\'e's nonlinear dynamics and Heisenberg's uncertainty principle leads to a world picture where physical reality is, in many respects, ... More

String black hole: Can it be a particle accelerator ?Nov 06 2013Aug 21 2014In this paper we have studied the possibility of the center-of-mass energy of two particles colliding near the horizon of a static charged black hole in string theory. Various cases corresponding to the electric charge and the angular momentum of the ... More

Clifford theory for infinite dimensional modulesApr 28 2015Dec 29 2015Clifford theory of possibly infinite dimensional modules is studied