Results for "Eva Miranda"

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A note on symplectic and Poisson linearization of semisimple Lie algebra actionsMar 12 2015In this note we prove that an analytic symplectic action of a semisimple Lie algebra can be locally linearized in Darboux coordinates. This result yields simultaneous analytic linearization for Hamiltonian vector fields in a neighbourhood of a common ... More
Rigidity of infinitesimal momentum mapsOct 20 2014Sep 11 2015In this paper we prove rigidity theorems for Poisson Lie group actions on Poisson manifolds. In particular, we prove that close infinitesimal momentum maps associated to Poisson Lie group actions are equivalent using a normal form theorem for SCI spaces. ... More
Coupling symmetries with Poisson structuresJan 07 2013We study local normal forms for completely integrable systems on Poisson manifolds in the presence of additional symmetries. The symmetries that we consider are encoded in actions of compact Lie groups. The existence of Weinstein's splitting theorem for ... More
Equivariant normal form for nondegenerate singular orbits of integrable Hamiltonian systemsFeb 24 2003Jul 30 2004We consider an integrable Hamiltonian system with n-degrees of freedom whose first integrals are invariant under the symplectic action of a compact Lie group G. We prove that the singular Lagrangian foliation associated to this Hamiltonian system is symplectically ... More
A note on equivariant normal forms of Poisson structuresOct 25 2005Mar 17 2006We prove an equivariant version of the local splitting theorem for tame Poisson structures and Poisson actions of compact Lie groups. As a consequence, we obtain an equivariant linearization result for Poisson structures whose transverse structure has ... More
Symplectic and Poisson geometry on b-manifoldsJun 10 2012Feb 06 2014Let $M^{2n}$ be a Poisson manifold with Poisson bivector field $\Pi$. We say that $M$ is b-Poisson if the map $\Pi^n:M\to\Lambda^{2n}(TM)$ intersects the zero section transversally on a codimension one submanifold $Z\subset M$. This paper will be a systematic ... More
A note on symplectic topology of $b$-manifoldsDec 27 2013Nov 11 2015A Poisson manifold $(M^{2n},\p)$ is $b$-symplectic if $\bigwedge^n\p$ is transverse to the zero section. In this paper we apply techniques native to Symplectic Topology to address questions pertaining to $b$-symplectic manifolds. We provide constructions ... More
Action-angle coordinates for integrable systems on Poisson manifoldsMay 12 2008Jun 14 2008We prove the action-angle theorem in the general, and most natural, context of integrable systems on Poisson manifolds, thereby generalizing the classical proof, which is given in the context of symplectic manifolds. The topological part of the proof ... More
Cotangent models for group actions on $b$-Poisson manifoldsNov 29 2018Dec 13 2018In this article we give a normal form of a $b$-symplectic form in the neighborhood of a compact orbit of a Lie group action on a $b$-symplectic manifold. We establish cotangent models for Poisson actions on $b$-Poisson manifolds and a $b$-symplectic slice ... More
Codimension one symplectic foliations and regular Poisson structuresSep 06 2010Jun 21 2011In this short note we give a complete characterization of a certain class of compact corank one Poisson manifolds, those equipped with a closed one-form defining the symplectic foliation and a closed two-form extending the symplectic form on each leaf. ... More
Convexity for Hamiltonian torus actions on $b$-symplectic manifoldsDec 08 2014May 11 2016In [GMPS] we proved that the moment map image of a $b$-symplectic toric manifold is a convex $b$-polytope. In this paper we obtain convexity results for the more general case of non-toric hamiltonian torus actions on $b$-symplectic manifolds. The modular ... More
Toric actions on b-symplectic manifoldsSep 07 2013Mar 05 2014We study Hamiltonian actions on $b$-symplectic manifolds with a focus on the effective case of half the dimension of the manifold. In particular, we prove a Delzant-type theorem that classifies these manifolds using polytopes that reside in a certain ... More
Equivariant classification of $b^m$-symplectic surfaces and Nambu structuresJul 06 2016Mar 09 2017In this paper we extend the classification scheme in [S] for $b^m$-symplectic surfaces and, more generally, $b^m$-Nambu structures to the equivariant setting. When the compact group is the group of deck-transformations of an orientable covering, this ... More
Non-commutative integrable systems on $b$-symplectic manifoldsJun 08 2016In this paper we study non-commutative integrable systems on $b$-Poisson manifolds. One important source of examples (and motivation) of such systems comes from considering non-commutative systems on manifolds with boundary having the right asymptotics ... More
The geometry of E-manifoldsFeb 08 2018Motivated by the study of symplectic Lie algebroids, we study a describe a type of algebroid (called an $E$-tangent bundle) which is particularly well-suited to study of singular differential forms and their cohomology. This setting generalizes the study ... More
Integrable systems and closed one formsDec 21 2017Dec 27 2017In the first part of this paper we revisit a classical topological theorem by Tischler and deduce a topological result about compact manifolds admitting a set of independent closed forms proving that the manifold is a fibration over a torus. As an application ... More
On a Poincare lemma for foliationsJan 24 2013Apr 16 2013In this paper we revisit a Poincare lemma for foliated forms, with respect to a regular foliation, and compute the foliated cohomology for local models of integrable systems with singularities of nondegenerate type. A key point in this computation is ... More
Geometric Quantization of real polarizations via sheavesJan 11 2013Aug 06 2013In this article we develop tools to compute the Geometric Quantization of a symplectic manifold with respect to a regular Lagrangian foliation via sheaf cohomology and obtain important new applications in the case of real polarizations. The starting point ... More
A Poincare lemma in Geometric QuantisationJul 11 2013Jan 07 2014This article presents a Poincare lemma for the Kostant complex, used to compute geometric quantisation, when the polarisation is given by a Lagrangian foliation defined by an integrable system with nondegenerate singularities.
Cotangent models for integrable systemsJan 19 2016May 23 2016We associate cotangent models to a neighbourhood of a Liouville torus in symplectic and Poisson manifolds focusing on a special class called $b$-Poisson/$b$-symplectic manifolds. The semilocal equivalence with such models uses the corresponding action-angle ... More
On the volume elements of a manifold with transverse zeroesDec 10 2018Dec 18 2018Moser proved in 1965 in his seminal paper that two volume forms on a compact manifold can be conjugated by a diffeomorphism, that is to say they are equivalent, if and only if their associated cohomology classes in the top cohomology group of a manifold ... More
Contact structures and Reeb dynamics with singularitiesJun 14 2018Apr 05 2019We study singular contact structures, which are tangent to a given smooth hypersurface $Z$ and satisfy certain transversality conditions. These singular contact structures are determined by the kernel of non-smooth differential forms, called $b^m$-contact ... More
Equivariant classification of $b^m$-symplectic surfaces and Nambu structuresJul 06 2016In this paper we extend the classification scheme in [S] for $b^m$-symplectic surfaces, and more generally, $b^m$-Nambu structures to the equivariant setting. When the compact group is the group of deck-transformations of an orientable covering, this ... More
Contact structures with singularitiesJun 14 2018We study singular contact structures, which are tangent to a given smooth hypersurface $Z$ and satisfy certain transversality conditions. These singular contact structures are determined by the kernel of non-smooth differential forms, called $b^m$-contact ... More
Zeroth Poisson homology, foliated cohomology and perfect Poisson manifoldsSep 04 2017We prove that for regular Poisson manifolds, the zeroth homology group is isomorphic to the top foliated cohomology group and we give some applications. In particular, we show that for regular unimodular Poisson manifolds top Poisson and foliated cohomology ... More
Geometric quantization of integrable systems with hyperbolic singularitiesAug 03 2008Feb 04 2009We construct the geometric quantization of a compact surface using a singular real polarization coming from an integrable system. Such a polarization always has singularities, which we assume to be of nondegenerate type. In particular, we compute the ... More
Weakly Hamiltonian actionsFeb 10 2016May 03 2016In this paper we generalize constructions of non-commutative integrable systems to the context of weakly Hamiltonian actions on Poisson manifolds. In particular we prove that abelian weakly Hamiltonian actions on symplectic manifolds split into Hamiltonian ... More
A singular Poincare lemmaMay 23 2004We prove a Poincare lemma for a set of r smooth functions on a 2n-dimensional smooth manifold satisfying a commutation relation determined by r singular vector fields associated to a Cartan subalgebra of $\frak{sp}(2r,\mathbb R)$. This result has a natural ... More
Rigidity of Hamiltonian actions on Poisson manifoldsFeb 01 2011Oct 16 2011This paper is about the rigidity of compact group actions in the Poisson context. The main resut is that Hamiltonian actions of compact semisimple type are rigid. We prove it via a Nash-Moser normal form theorem for closed subgroups of SCI-type. This ... More
On geometric quantization of $b$-symplectic manifoldsAug 30 2016We study a notion of pre-quantization for $b$-symplectic manifolds. We use it to construct a formal geometric quantization of $b$-symplectic manifolds equipped with Hamiltonian torus actions with nonzero modular weight. We show that these quantizations ... More
Singular fibers of the Gelfand--Cetlin system on $\mathfrak{u}(n)^*$Mar 22 2018Apr 01 2018In this paper, we show that every singular fiber of the Gelfand--Cetlin system on coadjoint orbits of unitary groups is a smooth isotropic submanifold which is diffeomorphic to a $2$-stage quotient of a compact Lie group by free actions of two other compact ... More
Desingularizing $b^m$-symplectic structuresDec 16 2015A Poisson manifold $(M^{2n} ,\Pi)$ is said to be $b^m$-symplectic if it is symplectic on the complement of a hypersurface $Z$ and has a simple Darboux canonical form at points of $Z$ (which we will describe below). In this paper we will discuss a desingularization ... More
Geometric quantization of semitoric systems and almost toric manifoldsMay 02 2017May 23 2017Kostant gave a model for the real geometric quantization associated to polarizations via the cohomology associated to the sheaf of flat sections of a pre-quantum line bundle. This model is well-adapted for real polarizations given by integrable systems ... More
Examples of integrable and non-integrable systems on singular symplectic manifoldsDec 28 2015We present a collection of examples borrowed from celestial mechanics and projective dynamics. In these examples symplectic structures with singularities arise naturally from regularization transformations, Appell's transformation or classical changes ... More
Euler flows and singular geometric structuresJan 31 2019Mar 26 2019Tichler proved that a manifold admitting a smooth closed one-form fibers over a circle. More generally a manifold admitting $k$ independent closed one-forms fibers over a torus $T^k$. In this article we explain a version of this construction for manifolds ... More
Action-angle variables and a KAM theorem for b-Poisson manifoldsFeb 11 2015Mar 02 2015In this article we prove an action-angle theorem for b-integrable systems on b-Poisson manifolds improving the action-angle theorem contained in [LMV11] for general Poisson manifolds in this setting. As an application, we prove a KAM-type theorem for ... More
Euler flows and singular geometric structuresJan 31 2019Tichler proved that a manifold admitting a smooth closed one-form fibers over a circle. More generally a manifold admitting $k$ independent closed one-forms fibers over a torus $T^k$. In this article we explain a version of this construction for manifolds ... More
Desingularizing $b^m$-symplectic structuresDec 16 2015May 16 2017A $2n$-dimensional Poisson manifold $(M ,\Pi)$ is said to be $b^m$-symplectic if it is symplectic on the complement of a hypersurface $Z$ and has a simple Darboux canonical form at points of $Z$ which we will describe below. In this paper we will discuss ... More
On geometric quantization of $b^m$-symplectic manifoldsJan 11 2018We study the formal geometric quantization of $b^m$-symplectic manifolds equipped with Hamiltonian actions of a torus $T$ with nonzero leading modular weight. The resulting virtual $T-$modules are finite dimensional when $m$ is odd, as in \cite{gmw2}; ... More
Convexity of the moment map image for torus actions on $b^m$-symplectic manifoldsJan 03 2018We prove a convexity theorem for the image of the moment map of a Hamiltonian torus action on a $b^m$-symplectic manifold.
Connected components of closed affine Deligne-Lusztig varietiesJul 26 2006Jul 30 2007We determine the set of connected components of closed affine Deligne-Lusztig varieties for special maximal compact subgroups of split connected reductive groups. Especially, we show that such an affine Deligne-Lusztig variety has isolated points if and ... More
Rack invariants of links in $L(p,1)$Mar 01 2017Dec 18 2017We describe a presentation for the augmented fundamental rack of a link in the lens space $L(p,1)$. Using this presentation, the (enhanced) counting rack invariants that have been defined for the classical links are applied to the links in $L(p,1)$. In ... More
Large deviations for cascades of diffusions arising in oscillating systems of interacting Hawkes processesSep 27 2017We consider oscillatory systems of interacting Hawkes processes introduced in Ditlevsen and Loecherbach (2017) to model multi-class systems of interacting neurons together with the diffusion approximations of their intensity processes. This diffusion, ... More
The global structure of moduli spaces of polarized p-divisible groupsMar 28 2007We study the global structure of moduli spaces of quasi-isogenies of polarized p-divisible groups introduced by Rapoport and Zink. Using the corresponding results for non-polarized p-divisible groups from a previous paper, we determine their dimensions ... More
Particle Physics challenges to the Bohm Picture of Relativistic Quantum Field TheoryApr 29 2011I discuss topics in Particle Physics applying the novel ontological formulation of Relativistic Quantum Field Theory due to David Bohm. I argument that particle physicists might too benefit from this truly novel way of thinking Physics.
Torsion Sections of Semistable Elliptic SurfacesAug 21 1992Let S be a torsion section of an elliptic surface with only I_n fibers. This article addresses the question: which components of singular fibers can S pass through? We give necessary criteria for the "component numbers", and show an equidistribution result ... More
An Invitation to Singular Symplectic GeometryMay 10 2017In this paper we analyze in detail a collection of motivating examples to consider $b^m$-symplectic forms and folded-type symplectic structures. In particular, we provide models in Celestial Mechanics for every $b^m$-symplectic structure. At the end of ... More
Large-Small Equivalence in String TheoryJan 08 1992The simplest toroidally compactified string theories exhibit a duality between large and small radii: compactification on a circle, for example, is invariant under R goes to 1/R. Compactification on more general Lorentzian lattices (i.e. toroidal compactification ... More
Dimensional Mutation and Spacelike SingularitiesOct 05 2005Feb 27 2006I argue that string theory compactified on a Riemann surface crosses over at small volume to a higher dimensional background of supercritical string theory. Several concrete measures of the count of degrees of freedom of the theory yield the consistent ... More
Propagation of Gravitational Waves in Generalized TeVeSJan 11 2010Efforts are underway to improve the design and sensitivity of gravitational waves detectors, with the hope that the next generation of these detectors will observe a gravitational wave signal. Such a signal will not only provide information on dynamics ... More
Minimal geodesics and topological entropy on T^2Jul 04 2007Let (T^2, g) be a two-dimensional Riemannian torus. In this paper we prove that the topological entropy of the geodesic flow restricted to the set of initial conditions of minimal geodesics vanishes, independent of the choice of the Riemannian metric. ... More
AdS and dS Entropy from String JunctionsAug 26 2003Flux compactifications of string theory exhibiting the possibility of discretely tuning the cosmological constant to small values have been constructed. The highly tuned vacua in this discretuum have curvature radii which scale as large powers of the ... More
TASI/PiTP/ISS Lectures on Moduli and MicrophysicsMay 09 2004I review basic forces on moduli that lead to their stabilization, for example in the supercritical and KKLT models of de Sitter space in string theory, as well as an $AdS_4\times S^3\times S^3$ model I include which is not published elsewhere. These forces ... More
Double plumbings of disk bundles over spheresMar 24 2014Apr 25 2014We consider double plumbings of two disk bundles over spheres. We calculate the Heegaard-Floer homology with its absolute grading of the boundary of such a plumbing. Given a closed smooth 4-manifold $X$ and a suitable pair of classes in $H_{2}(X)$, we ... More
A Multiscale Analysis of Traveling Waves in Stochastic Neural FieldsAug 04 2015We analyze the effects of noise on the traveling wave dynamics in neural fields. The noise influences the dynamics on two scales: first, it causes fluctuations in the wave profile, and second, it causes a random shift in the phase of the wave. We formulate ... More
Eigensolutions and spectral analysis of a model for vertical gene transfer of plasmidsJun 28 2018Nov 19 2018Plasmids are autonomously replicating genetic elements in bacteria. At cell division plasmids are distributed among the two daughter cells. This gene transfer from one generation to the next is called vertical gene transfer. We study the dynamics of a ... More
Convergence to equilibrium for time inhomogeneous jump diffusions with state dependent jump intensityDec 10 2017Oct 30 2018We consider a time inhomogeneous jump Markov process $X = (X_t)_t$ with state dependent jump intensity, taking values in $R^d . $ Its infinitesimal generator is given by \begin{multline*} L_t f (x) = \sum_{i=1}^d \frac{\partial f}{\partial x_i } (x) b^i ... More
Radix and Pseudodigit Representations in Z^nFeb 22 2010We define radix representations for vectors in Z^n analogously with radix representations in Z, and give a sufficient condition for a matrix A:Z^n -> Z^n to yield a radix representation with a given canonical digit set. We relate our results to a sufficient ... More
Moduli spaces of p-divisible groupsFeb 15 2005Apr 27 2007We study the global structure of moduli spaces of quasi-isogenies of p-divisible groups introduced by Rapoport and Zink. We determine their dimensions and their sets of connected components and of irreducible components. If the isocrystals of the p-divisible ... More
Preferred frame parameters in the tensor-vector-scalar theory of gravity and its generalizationMay 25 2009Jul 01 2009The Tensor-Vector-Scalar theory of gravity, which was designed as a relativistic implementation to the modified dynamics paradigm, has fared quite well as an alternative to dark matter, on both galactic and cosmological scales. However, its performance ... More
Simple de Sitter SolutionsDec 07 2007Mar 18 2008We present a framework for de Sitter model building in type IIA string theory, illustrated with specific examples. We find metastable dS minima of the potential for moduli obtained from a compactification on a product of two Nil three-manifolds (which ... More
The topological Hochschild homology of algebraic $K$-theory of finite fieldsJun 07 2019Let $K(\mathbb{F}_q)$ be the algebraic $K$-theory spectrum of the finite field with $q$ elements and let $p \geq 5$ be a prime number coprime to $q$. In this paper we study the mod $p$ and $v_1$ topological Hochschild homology of $K(\mathbb{F}_q)$, denoted ... More
Radix Representations, Self-Affine Tiles, and Multivariable WaveletsFeb 22 2010We investigate the connection between radix representations for Z^n and self-affine tilings of R^n. We apply our results to show that Haar-like multivariable wavelets exist for all dilation matrices that are sufficie
Knot symmetries and the fundamental quandleJul 16 2017We establish a relationship between the knot symmetries and the automorphisms of the knot quandle. We identify the homeomorphisms of the pair $(S^{3},K)$ that induce the (anti)automorphisms of the fundamental quandle $Q(K)$. We show that every quandle ... More
A Cartan-Eilenberg spectral sequence for a non-normal extensionNov 13 2018Jan 19 2019Let $\Phi\to \Gamma\to \Sigma$ be a conormal extension of Hopf algebras over a commutative ring $k$, and let $M$ be a $\Gamma$-comodule. The Cartan-Eilenberg spectral sequence $$ E_2 = \mathrm{Ext}_\Phi(k,\mathrm{Ext}_\Sigma(k,M)) \implies \mathrm{Ext}_\Gamma(k,M)$$ ... More
Truncations of level 1 of elements in the loop group of a reductive groupJul 14 2009Sep 26 2013We generalize the notion of Ekedahl-Oort strata to elements in the loop group of any connected reductive group, and call the resulting discrete invariant the truncation of level 1 of the element. We give conditions for the Newton points occurring among ... More
Duality, Compactification, and $e^{-1/λ}$ Effects in the Heterotic String TheoryNov 24 1996Two classes of stringy instanton effects, stronger than standard field theory instantons, are identified in the heterotic string theory. These contributions are established using type IIA/heterotic and type I/heterotic dualities. They provide examples ... More
Gradient flow for the Boltzmann entropy and Cheeger's energy on time-dependent metric measure spacesNov 29 2016We introduce notions of dynamic gradient flows on time-dependent metric spaces as well as on time-dependent Hilbert spaces. We prove existence of solutions for a class of time dependent energy functionals in both settings. In particular we are interested ... More
Constructing biquandlesOct 06 2018We define biquandle structures on a given quandle, and show that any biquandle is given by some biquandle structure on its underlying quandle. We characterize all biquandles with a given underlying quandle. Using this characterization, we obtain a relationship ... More
Neuroevolutionary optimizationApr 20 2010This paper presents an application of evolutionary search procedures to artificial neural networks. Here, we can distinguish among three kinds of evolution in artificial neural networks, i.e. the evolution of connection weights, of architectures, and ... More
Nonsupersymmetric String SolitonsAug 21 1995We begin a search for nonsupersymmetric/supersymmetric dual string pairs by constructing candidate critical nonsupersymmetric strings as solitons in supersymmetric string theories. Using orbifold techniques, one can construct cosmic string solutions which ... More
The Survival of Planetary Nebulae in the Intracluster MediumJun 24 2005The stellar population stripped from galaxies in clusters evolve under the extreme conditions imposed by the intracluster (IC) medium. Intracluster stars generally suffer very high systemic velocities, and evolve within a rarefied and extremely hot IC ... More
Mott-Hubbard Insulator in Infinite DimensionsSep 28 2001Oct 16 2001We calculate the one-particle density of states for the Mott-Hubbard insulating phase of the Hubbard model on a Bethe lattice in the limit of infinite coordination number. We employ the Kato-Takahashi perturbation theory around the strong-coupling limit ... More
The saddle-point method for condensed Bose gasesJun 07 1999The application of the conventional saddle-point approximation to condensed Bose gases is thwarted by the approach of the saddle-point to the ground-state singularity of the grand canonical partition function. We develop and test a variant of the saddle-point ... More
Good $r$-divisions Imply Optimal Amortised Decremental BiconnectivityAug 07 2018We present a data structure that given a graph $G$ of $n$ vertices and $m$ edges, and a suitable pair of $r$-divisions of $G$, preprocesses $G$ in $O(m+n)$ time and handles any series of edge-deletions in $O(m)$ total time while answering queries to pairwise ... More
On the Alexander polynomial of links in lens spacesJun 10 2016Mar 15 2019We show how the Alexander polynomial of links in lens spaces is related to the classical Alexander polynomial of a link in the 3-sphere, obtained by cutting out the exceptional lens space fibre. It follows from these relationship that a certain normalization ... More
The Alexander polynomial for closed braids in lens spacesJan 04 2019We present a reduced Burau-like representation for the mixed braid group on one strand representing links in lens spaces and show how to calculate the Alexander polynomial of a link directly from the mixed braid.
Internal Kinematics of Microstructures and ImplicationsOct 14 2003High resolution images at different wavelengths show the common presence of structures and microstructures in planetary nebulae (PNe), which are not well incorporated to the existing models for the formation of these objects. We summarize how studies ... More
Entropy generation in a chemical reactionAug 10 2012Entropy generation in a chemical reaction is analyzed without using the general formalism of non-equilibrium thermodynamics at a level adequate for advanced undergraduates. In a first approach to the problem, the phenomenological kinetic equation of an ... More
Adiabatic reversible compression: a molecular viewAug 13 2012The adiabatic compression (or expansion) of an ideal gas has been analysed. Using the kinetic theory of gases the usual relation between temperature and volume is obtained, while textbooks follow a thermodynamic approach. In this way we show once again ... More
Conservative Inference Rule for Uncertain Reasoning under IncompletenessJan 15 2014In this paper we formulate the problem of inference under incomplete information in very general terms. This includes modelling the process responsible for the incompleteness, which we call the incompleteness process. We allow the process behaviour to ... More
Theoretical method for the study of the excited states of a systemJun 21 2012A novel, exact, theoretical method for the study of the excited states of a system is presented. It is demonstrated how to transform the excited state problem of one Hamiltonian into the ground state problem of an auxiliary one. From this, a new exact ... More
Path Cohomology of Locally Finite Digraphs,Hodge's Theorem and the $p$-Lazy Random WalkJun 11 2019In this paper we generalize the path cohomology of digraphs to a locally finite digraph $G=(V,E)$. We prove a Hodge Decomposition Theorem and show some relations with the $p$-lazy Random Walk.
Inflationary Steps in the Planck DataDec 03 2013We extend and improve the modeling and analysis of large-amplitude, sharp inflationary steps for second order corrections required by the precision of the Planck CMB power spectrum and for arbitrary Dirac-Born-Infeld sound speed. With two parameters, ... More
What lies between a free adiabatic expansion and a quasi-static one?Sep 26 2012An expression is found that relates the initial and final volumes and temperatures for any adiabatic process. It is given in terms of a parameter r that smoothly interpolates between a free adiabatic expansion (r = 0) and a quasi-static one (r = 1). The ... More
How to transform, with a capacitor, thermal energy into usable workAug 10 2012The temperature dependence of the dielectric permittivity is taken into account to study the energy change in a capacitor that follows a cycle between a cold and a hot thermal reservoirs. There is a net energy gain in the process that, in principle, can ... More
Possible Relevance of Odd Frequency Pairing to Heavy Fermion SuperconductivityOct 07 1994What is the character of the gapless quasiparticles in heavy fermion superconductors (HFSC)? We discuss an odd-frequency pairing interpretation of HFSC which leads to a two component model for the quasiparticle excitations. In this picture, line zeroes ... More
Positive Topological Entropy for Magnetic Flows on SurfacesJun 29 2006Jul 20 2007We study the topological entropy of the magnetic flow on a closed riemannian surface. We prove that if the magnetic flow has a non-hyperbolic closed orbit in some energy set T^cM= E^{-1}(c), then there exists an exact $ C^\infty$-perturbation of the 2-form ... More
Note on the representation of the gap formation probability for real and quaternion Wishart matricesJul 16 2016Wishart random matrices are often used to model multivariate systems in physics, finance, biology and wireless communication. Extreme value statistics, such as those of the smallest eigenvalue, can be used to test the accuracy of the model. In this article ... More
On non-smooth vector fields having a torus or a sphere as the sliding manifoldJul 02 2012In this paper we consider a non-smooth vector field $Z=(X,Y)$, where $X,Y$ are linear vector fields in dimension 3 and the discontinuity manifold $\Sigma$ of $Z$ is or the usual embedded torus or the unitary sphere at origin. We suppose that $\Sigma$ ... More
On the maximum efficiency of realistic heat enginesAug 10 2012In 1975, Courzon and Ahlborn studied a Carnot engine with thermal losses and got an expression for its efficiency that described better the performance of actual heat machines than the traditional result due to Carnot. In their original derivation, time ... More
Stochastic backgrounds of gravitational waves from cosmological sources - The role of dark energyAug 08 2012[Abridged] We investigate the detectability of the gravitational stochastic background produced by cosmological sources in scenarios of structure formation. The model considers the coalescences of three kind of binary systems: double neutron stars, the ... More
New M-theory Backgrounds with Frozen ModuliDec 17 1997Dec 22 1997We propose examples, which involve orbifolds by elements of the U-duality group, with M-theory moduli fixed at the eleven-dimensional Planck scale. We begin by reviewing asymmetric orbifold constructions in perturbative string theory, which fix radial ... More
Monodromy in the CMB: Gravity Waves and String InflationMar 21 2008Mar 23 2008We present a simple mechanism for obtaining large-field inflation, and hence a gravitational wave signature, from string theory compactified on twisted tori. For Nil manifolds, we obtain a leading inflationary potential proportional to phi^(2/3) in terms ... More
Characterization of geodesic flows on T^2 with and without positive topological entropyJul 04 2007Jun 30 2010In the present work we consider the behavior of the geodesic flow on the unit tangent bundle of the 2-torus $T^2$ for an arbitrary Riemannian metric. A natural non-negative quantity which measures the complexity of the geodesic flow is the topological ... More
Scalar Speed Limits and Cosmology: Acceleration from D-ccelerationOct 23 2003Jul 20 2004Causality on the gravity side of the AdS/CFT correspondence restricts motion on the moduli space of the N=4 super Yang Mills theory by imposing a speed limit on how fast the scalar field may roll. This effect can be traced to higher derivative operators ... More
Metal-poor Galaxies in the Local UniverseAug 14 2012A galaxy's mean metallicity is usually closely correlated with its luminosity and mass. Consequently the most metal-poor galaxies in the local universe are dwarf galaxies. Blue compact dwarfs and tidal dwarfs tend to deviate from the metallicity-luminosity ... More
Near-Field Cosmology with Local Group Dwarf SpheroidalsSep 06 2005The Local Group offers an excellent laboratory for near-field cosmology by permitting us to use the resolved stellar content of its constituent galaxies as probes of galaxy formation and evolution, which in turn is an important means for testing cosmological ... More
The Evolutionary History of Local Group Irregular GalaxiesMar 09 2004Irregular (Irr) galaxies are gas-rich objects with recent or ongoing star formation. In absence of spiral density waves, star formation occurs largely stochastically. The scattered star-forming regions tend to be long-lived and migrate slowly. Older populations ... More
Interstellar Media in the Magellanic Clouds and other Local Group Dwarf GalaxiesOct 21 2001I review the properties of the interstellar medium in the Magellanic Clouds and Local Group dwarf galaxies. The more massive, star-forming galaxies show a complex, multi-phase ISM full of shells and holes ranging from very cold phases (a few 10 K) to ... More