Results for "Sebastián A. Franchino-Viñas"

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Worldline Formalism and Noncommutative TheoriesOct 05 2015The objective of this Ph.D. thesis is the implementation of the Worldline Formalism in the frame of Noncommutative Quantum Field Theories. The result is a master formula for the 1-loop effective action that is applied to a number of scalar models -- among ... More
Propagator from Nonperturbative Worldline DynamicsAug 13 2019We use the worldline representation for correlation functions together with numerical path integral methods to extract nonperturbative information about the propagator to all orders in the coupling in the quenched limit (small-$N_{\text{f}}$ expansion). ... More
Worldline approach to the Grosse-Wulkenhaar modelJun 28 2014Dec 05 2014We apply the worldline formalism to the Grosse-Wulkenhaar model and obtain an expression for the one-loop effective action which provides an efficient way for computing Schwinger functions in this theory. Using this expression we obtain the quantum corrections ... More
Vacuum effective actions and mass-dependent renormalization in curved spaceFeb 08 2019Mar 02 2019We review past and present results on the non-local form-factors of the effective action of semiclassical gravity in two and four dimensions computed by means of a covariant expansion of the heat kernel up to the second order in the curvatures. We discuss ... More
Vacuum effective actions and mass-dependent renormalization in curved spaceFeb 08 2019We review past and present results on the non-local form-factors of the effective action of semiclassical gravity in two and four dimensions computed by means of a covariant expansion of the heat kernel up to the second order in the curvatures. We discuss ... More
Pumping current of a Luttinger liquid with finite lengthMar 16 2012We study transport properties in a Tomonaga-Luttinger liquid in the presence of two time-dependent point like weak impurities, taking into account finite-length effects. By employing analytical methods and performing a perturbation theory, we compute ... More
Form factors and decoupling of matter fields in four-dimensional gravityDec 02 2018Jan 31 2019We extend previous calculations of the non-local form factors of semiclassical gravity in $4D$ to include the Einstein-Hilbert term. The quantized fields are massive scalar, fermion and vector fields. The non-local form factor in this case can be seen ... More
Worldline Formalism in Snyder SpacesJun 29 2018We study the $\phi_{\star}^4$ model for a scalar field in a linearization of the Snyder model, using the methods of the Worldline Formalism. Our main result is a master equation for the 1-loop n-point function. From this we derive the renormalization ... More
Thermodynamics in the NC discMar 15 2018We study the thermodynamics of a scalar field on a noncommutative disc implementing the boundary as the limit case of an interaction with an appropriately chosen confining background. We explicitly obtain expressions for thermodynamic potentials of gases ... More
Robust Heteroclinic TangenciesMar 01 2019We construct diffeomorphisms in dimension $d\geq 2$ exhibiting $C^1$-robust heteroclinic tangencies.
Critical values of moment maps on quantizable manifoldsNov 02 2007Let $M$ be a quantizable symplectic manifold acted on by $T=(S^1)^r$ in a Hamiltonian fashion and $J$ a moment map for this action. Suppose that the set $M^{T}$ of fixed points is discrete and denote by ${\alpha}_{pj}\in{\mathbb Z}^r$ the weights of the ... More
Transverse Josephson vortices and localized states in stacked Bose-Einstein condensatesOct 14 2018Apr 13 2019The stacks of Bose-Einstein condensates coupled by long Josephson junctions present a rich phenomenology feasible to experimental realization and specially suitable for technological applications as the nonlinear-optics and superconducting analogues have ... More
Semi-transparent Boundary Conditions in the Worldline FormalismDec 13 2010The interaction of a quantum field with a background containing a Dirac delta function with support on a surface of codimension 1 represents a particular kind of matching conditions on that surface for the field. In this article we show that the worldline ... More
Quasiplatonic curves with symmetry group ${\mathbb Z}_{2}^{2} \rtimes {\mathbb Z}_{m}$ are definable over ${\mathbb Q}$Apr 03 2016Sep 15 2016It is well known that every closed Riemann surface $S$ of genus $g \geq 2$, admitting a group $G$ of conformal automorphisms so that $S/G$ has triangular signature, can be defined over a finite extension of ${\mathbb Q}$. It is interesting to know, in ... More
Magnetic properties of a Fermi gas in a noncommutative phase spaceJun 10 2016Motivated by the precision attained by SQUID devices in measuring magnetic fields, we study in this article the thermodynamic behaviour of a fermion gas in two and three dimen\-sional spatial space with noncommutative coordinates and momenta. An explicit ... More
Boundaries in the Moyal planeJul 17 2013Dec 20 2013We study the oscillations of a scalar field on a noncommutative disc implementing the boundary as the limit case of an interaction with an appropriately chosen confining background. The space of quantum fluctuations of the field is finite dimensional ... More
Worldline approach to noncommutative field theoryApr 04 2012Jan 25 2013The study of the heat-trace expansion in noncommutative field theory has shown the existence of Moyal nonlocal Seeley-DeWitt coefficients which are related to the UV/IR mixing and manifest, in some cases, the non-renormalizability of the theory. We show ... More
Monochromatic tree covers and Ramsey numbers for set-coloured graphsOct 18 2015May 28 2018We consider a generalisation of the classical Ramsey theory setting to a setting where each of the edges of the underlying host graph is coloured with a {\em set} of colours (instead of just one colour). We give bounds for monochromatic tree covers in ... More
Homological invariants relating the super Jordan plane to the Virasoro algebraJul 17 2017Aug 05 2017Nichols algebras are an important tool for the classification of Hopf algebras. Within those with finite GK dimension, we study homological invariants of the super Jordan plane, that is, the Nichols algebra $A=B(V(-1,2))$. These invariants are Hochschild ... More
Pointwise convergence of some multiple ergodic averagesSep 08 2016We show that for every ergodic system $(X,\mu,T_1,\ldots,T_d)$ with commuting transformations, the average \[\frac{1}{N^{d+1}} \sum_{0\leq n_1,\ldots,n_d \leq N-1} \sum_{0\leq n\leq N-1} f_1(T_1^n \prod_{j=1}^d T_j^{n_j}x)f_2(T_2^n \prod_{j=1}^d T_j^{n_j}x)\cdots ... More
The first determination of the viscosity parameter in the circumstellar disk of a Be StarNov 30 2011Be stars possess gaseous circumstellar decretion disks, which are well described using standard $\alpha$-disk theory. The Be star 28 CMa recently underwent a long outburst followed by a long period of quiescence, during which the disk dissipated. Here ... More
On the one-dimensional family of Riemann surfaces of genus $q$ with $4q$ automorphismsFeb 27 2018Bujalance, Costa and Izquierdo have recently proved that all those Riemann surfaces of genus $g \ge 2$ different from $3, 6, 12, 15$ and 30, with exactly $4g$ automorphisms form an equisymmetric one-dimensional family, denoted by $\mathcal{F}_g.$ In this ... More
Uniqueness of the AdS Spacetime among Static Vacua with prescribed Null infinityNov 24 2012We prove that an $(n+1)$-dimensional spin static vacuum with negative cosmological constant whose null infinity has a boundary admitting a non-trivial Killing spinor field is the AdS spacetime. As a consequence, we generalize previous uniqueness results ... More
A MegaCam Survey of Outer Halo Satellites. VII. A Single Sérsic Index v/s Effective Radius Relation for Milky Way Outer Halo SatellitesFeb 23 2019In this work we use structural properties of Milky Way's outer halo ($R_G > 25\,\mathrm{kpc}$) satellites (dwarf spheroidal galaxies, ultra-faint dwarf galaxies and globular clusters) derived from deep, wide-field and homogeneous data, to present evidence ... More
Mildly Suppressed Star Formation in Central Regions of MaNGA Seyfert GalaxiesSep 30 2018Negative feedback from accretion onto super-massive black holes (SMBHs), that is to remove gas and suppress star formation in galaxies, has been widely suggested. However, for Seyfert galaxies which harbor less active, moderately accreting SMBHs in the ... More
Study of spin polarized nuclear matter and finite nuclei with finite range simple effective interactionJan 12 2015The properties of spin polarized pure neutron matter and symmetric nuclear matter are studied using the finite range simple effective interaction, upon its parametrization revisited. Out of the total twelve parameters involved, we now determine ten of ... More
Performance of attack strategies on modular networksAug 08 2016Vulnerabilities of complex networks have became a trend topic in complex systems recently due to its real world applications. Most real networks tend to be very fragile to high betweenness adaptive attacks. However, recent contributions have shown the ... More
Pedestrian flows through a narrow doorway: Effect of individual behaviours on the global flow and microscopic dynamicsOct 19 2016Jan 09 2017We study the dynamics of pedestrian evacuations through a narrow doorway by means of controlled experiments. The influence of the pedestrians' behaviours is investigated by prescribing a selfish attitude to a fraction c\_s of the participants, while the ... More
Dynamical trapping through harmonic breathingFeb 13 2019Mar 13 2019A new strategy for trapping quantum particles is presented, which behaves like an effective harmonic oscillator potential trap wherever is desired. The approach is based on harmonic contraction and expansion of the system around a fixed point (trapping ... More
An extension of the Dirac and Gotay-Nester theories of constraints for Dirac dynamical systemsJun 16 2011Nov 21 2012This paper extends the Gotay-Nester and the Dirac theories of constrained systems in order to deal with Dirac dynamical systems in the integrable case. Integrable Dirac dynamical systems are viewed as constrained systems where the constraint submanifolds ... More
An extension of the Dirac and Gotay-Nester theories of constraints for Dirac dynamical systemsAug 09 2012Nov 14 2012This paper extends the Gotay-Nester and the Dirac theories of constrained systems in order to deal with Dirac dynamical systems in the integrable case. Integrable Dirac dynamical systems are viewed as constrained systems where the constraint submanifolds ... More
Revisiting the Jones eigenproblem in fluid-structure interactionJul 03 2018Aug 20 2019The Jones eigenvalue problem first described by D.S. Jones in 1983 concerns unusual modes in bounded elastic bodies: time-harmonic displacements whose tractions and normal components are both identically zero on the boundary. This problem is usually associated ... More
The index of exceptional symmetric spacesMay 15 2019The index of a Riemannian symmetric space is the minimal codimension of a proper totally geodesic submanifold (Onishchik, 1980). There is a conjecture by the first two authors for how to calculate the index. In this paper we give an affirmative answer ... More
Influence of temperature on the magnetic oscillations in graphene with spin splitting: a new approachJun 06 2018We analyze the magnetic oscillations (MO) in pristine graphene, under a perpendicular magnetic field, taking into account the Zeeman effect. We consider a constant Fermi energy, such that the valence band is always full and only the conduction band is ... More
Magnetic oscillations in siliceneJun 04 2018In this work the magnetic oscillations (MO) in pristine silicene at $T=0$ K are studied. Considering a constant electron density we obtain analytical expressions for the ground state internal energy and magnetization, under a perpendicular electric and ... More
The observable-state model and non-renormalizable theoriesMar 20 2013The aim of this work is to apply the observable-state model for the quantum field theory of a \phi^n self- interaction. We show how to obtain finite values for the 2-point and n-point correlation functions without introducing counterterms in the Lagrangian. ... More
Router-level community structure of the Internet Autonomous SystemsMar 25 2015Mar 27 2015The Internet is composed of routing devices connected between them and organized into independent administrative entities: the Autonomous Systems. The existence of different types of Autonomous Systems (like large connectivity providers, Internet Service ... More
Analytic solution for Gauged Dirac-Weyl equation in $(2+1)$-dimensionsOct 18 2016Jul 11 2017A gauged Dirac-Weyl equation in (2+1)-dimension is considered. This equation has the particularity to describe the states of a graphene Dirac matter. In particular we are interested in matter interacting with a Chern-Simons gauge fields. We show that ... More
Equivalence of relative Gibbs and relative equilibrium measures for actions of countable amenable groupsAug 31 2018We formulate and prove a very general relative version of the Dobrushin-Lanford-Ruelle theorem which gives conditions on constraints of configuration spaces over a finite alphabet such that for every absolutely summable relative interaction, every translation-invariant ... More
Differential Galois Theory and Isomonodromic DeformationsOct 19 2018Aug 05 2019We present a geometric setting for the differential Galois theory of $G$-invariant connections with parameters. As an application of some classical results on differential algebraic groups and Lie algebra bundles, we see that the Galois group of a connection ... More
On automorphism groups of Toeplitz subshiftsJan 04 2017Jun 14 2017In this article we study automorphisms of Toeplitz subshifts. Such groups are abelian and any finitely generated torsion subgroup is finite and cyclic. When the complexity is non superlinear, we prove that the automorphism group is, modulo a finite cyclic ... More
On automorphism groups of low complexity subshiftsJan 02 2015Jul 10 2015In this article we study the automorphism group ${\rm Aut}(X,\sigma)$ of subshifts $(X,\sigma)$ of low word complexity. In particular, we prove that Aut$(X,\sigma)$ is virtually $\mathbb{Z}$ for aperiodic minimal subshifts and certain transitive subshifts ... More
Geometric integrators for higher-order variational systems and their application to optimal controlOct 21 2014Nov 06 2014Numerical methods that preserve geometric invariants of the system, such as energy, momentum or the symplectic form, are called geometric integrators. In this paper we present a method to construct symplectic-momentum integrators for higher-order Lagrangian ... More
Poisson and symplectic reductions of 4-DOF isotropic oscillators. The van der Waals system as benchmarkFeb 07 2015This paper is devoted to studying Hamiltonian oscillators in 1:1:1:1 resonance with symmetries, which include several models of perturbed Keplerian systems. Normal forms are computed in Poisson and symplectic formalisms, by mean of invariants and Lie-transforms ... More
Long baseline observations of HD100546 with ALMA: a possible circumplanetary disk detected in dust continuum and gas kinematicsJun 14 2019Giant planets growing in a circumstellar disk interact dynamically with the whole disk, and planetary growth is thought to be regulated by the circumplanetary disk (CPD) and its immediate environment. How much dust is gathered in the CPD, in addition ... More
Relative drifts and temperature anisotropies of protons and $α$ particles in the expanding solar wind -- 2.5D hybrid simulationsOct 10 2014We perform 2.5D hybrid simulations to investigate the origin and evolution of relative drift speeds between protons and $\alpha$ particles in the collisionless turbulent low-$\beta$ solar wind plasma. We study the generation of differential streaming ... More
The Data Analysis Pipeline for the SDSS-IV MaNGA IFU Galaxy Survey: OverviewJan 03 2019Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) is acquiring integral-field spectroscopy for the largest sample of galaxies to date. By 2020, the MaNGA Survey --- one of three core programs in the fourth-generation Sloan Digital Sky Survey ... More
Optical Integral Field Spectroscopy observations applied to simulated galaxies: Testing the fossil record methodNov 12 2018Nov 27 2018By means of post-processed cosmological Hydrodynamics simulations we explore the ability of the fossil record method to recover the stellar mass, age gradients, and global/radial star formation and mass growth histories of galaxies observed with an optical ... More
A formula for the local metric pressureJan 22 2019In this note we present a formula for the local metric pressure that generalizes Brin-Katok result for the metric entropy. As an application, we give a straightforward proof of the fact that non-atomic weak-Gibbs invariant probability measures are equilibrium ... More
Equilibrium states for a class of skew-productsAug 06 2018We consider skew-products on $M\times \mathbb{T}^2$, where $M$ is the two-sphere or the two-torus, which are partially hyperbolic and semi-conjugate to an Axiom A diffeomorphism. This class of dynamics includes the open sets of $\Omega$-non-stable systems ... More
Ion Heating in Inhomogeneous Expanding Solar Wind Plasma: The Role of Parallel and Oblique Ion-Cyclotron WavesJul 17 2014Sep 30 2014Remote sensing observations of coronal holes show that heavy ions are hotter than protons and their temperature is anisotropic. In-situ observations of fast solar wind streams provide direct evidence for turbulent Alfv\'en wave spectrum, left-hand polarized ... More
Measurement of the muon inclusive cross section in pp collisions at $\sqrt{s}$ = 7 TeV with the ATLAS detectorNov 21 2011The measurement of the muon inclusive differential cross section dsigma/dpT in pp collisions at sqrt(s)=7 TeV with the ATLAS detector is presented. The analysis is performed in the pseudorapidity interval |eta|< 2.5 for muon of transverse momentum 4 < ... More
Geometric and physical properties of closed ever expanding dust modelsApr 18 2018Current observations suggest that our Universe is not incompatible with a small positive spatial curvature that can be associated with rest frames having a "closed" standard topology. We examine a toy model generalisation of the $\Lambda$CDM model in ... More
Cavity Polariton Condensate in a Disordered EnvironmentDec 30 2014Nov 16 2015We report on the influence of disorder on an exciton-polariton condensate in a ZnO based bulk planar microcavity and compare experimental results with a theoretical model for a non-equilibrium condensate. Experimentally, we detect intensity fluctuations ... More
Nuclear Symmetry Energy: constraints from Giant Quadrupole Resonances and Parity Violating Electron ScatteringJul 15 2013Experimental and theoretical efforts are being devoted to the study of observables that can shed light on the properties of the nuclear symmetry energy. We present our new results on the excitation energy [X. Roca-Maza et al., Phys. Rev. C 87, 034301 ... More
Periodic points and measures for a class of skew productsJul 30 2019We consider the open set constructed by M. Shub in [42] of partially hyperbolic skew products on the space $\mathbb{T}^2\times \mathbb{T}^2$ whose non-wandering set is not stable. We show that there exists an open set $\mathcal{U}$ of such diffeomorphisms ... More
Polarization-based Light-Atom Quantum Interface with an All-optical TrapDec 29 2008Feb 23 2009We describe the implementation of a system for studying light-matter interactions using an ensemble of $10^6$ cold rubidium 87 atoms, trapped in a single-beam optical dipole trap. In this configuration the elongated shape of the atomic cloud increases ... More
Pairing correlations of cold fermionic gases at overflow from a narrow to a wide harmonic trapSep 17 2014Nov 05 2014Within the context of Hartree-Fock-Bogoliubov theory, we study the behavior of superfluid Fermi systems when they pass from a small to a large container. Such systems can be now realized thanks to recent progress in experimental techniques. It will allow ... More
Bi-Directional Energy Cascades and the Origin of Kinetic Alfvénic and Whistler Turbulence in the Solar WindJul 09 2013Jan 01 2014The observed sub-proton scale turbulence spectrum in the solar wind raises the question of how that turbulence originates. Observations of keV energetic electrons during solar quite-time suggest them as possible source of free energy to drive the turbulence. ... More
Microscopic-Macroscopic Approach for Binding Energies with Wigner-Kirkwood MethodNov 24 2009The semi-classical Wigner-Kirkwood $\hbar$ expansion method is used to calculate shell corrections for spherical and deformed nuclei. The expansion is carried out up to fourth order in $\hbar$. A systematic study of Wigner-Kirkwood averaged energies is ... More
Pairing in exotic neutron rich nuclei around the drip line and in the crust of neutron starsMar 22 2013Exotic and drip-line nuclei as well as nuclei immersed in a low density gas of neutrons in the outer crust of neutron stars are systematically investigated with respect to their neutron pairing properties. This is done using Skyrme density-functional ... More
Higher-order symmetry energy and neutron star core-crust transition with Gogny forcesJun 08 2017Dec 19 2017We study the symmetry energy and the core-crust transition in neutron stars using the finite-range Gogny nuclear interaction and examine the deduced crustal thickness and crustal moment of inertia. We start by analyzing the second-, fourth- and sixth-order ... More
Characterizing the local relation between star formation rate and gas-phase metallicity in MaNGA spiral galaxiesApr 08 2019Jul 24 2019The role of gas accretion in galaxy evolution is still a matter of debate. The presence of inflows of metal-poor gas that trigger star formation bursts of low metallicity has been proposed as an explanation for the local anti-correlation between star ... More
The Origin of the Entropy in the UniverseOct 15 1996Mar 13 1997We discuss the entropy generation in quantum tunneling of a relativistic particle under the influence of a time varying force with the help of squeezing formalism. It is shown that if one associates classical coarse grained entropy to the phase space ... More
Controlling skyrmion helicity via engineered Dzyaloshinskii-Moriya interactionsNov 14 2015Single magnetic skyrmion dynamics in chiral magnets with a spatially inhomogeneous Dzyaloshinskii-Moriya interaction (DMI) is considered. Based on the relation between DMI coupling and skyrmion helicity, it is argued that the latter must be included as ... More
The Interaction Between PDE and Graphs in Multiscale ModelingMay 27 2015Apr 18 2016In this article an upscaled model is presented, for complex networks with highly clustered regions exchanging some abstract quantities in both, microscale and macroscale level. Such an intricate system is approximated by a partitioned open map in $\mathbb{R}^{2}$ ... More
Hénon-like families and blender-horseshoes at non-transverse heterodimensional cyclesJun 17 2018In dimension three and under certain regularity assumptions, we construct a renormalisation scheme at the heterodimensional tangency of a non-transverse heterodimensional cycle associated with a pair of saddle-foci whose limit dynamic is a center-unstable ... More
Inversion of nonsmooth maps between Banach spacesDec 02 2017May 15 2018We study the invertibility nonsmooth maps between infinite-dimensional Banach spaces. To this end, we introduce an analogue of the notion of pseudo-Jacobian matrix of Jeyakumar and Luc in this infinite-dimensional setting. Using this, we obtain several ... More
Blender-horseshoes in center-unstable Hénon-like familiesApr 07 2018A blender-horseshoe is a locally maximal transitive hyperbolic set that appears in dimension at least three carrying a distinctive geometrical property: its local stable manifold "behaves" as a manifold of topological dimension greater than the expected ... More
A Categorical Generalization of CounterpointSep 30 2018We extend Mazzola's counterpoint model in terms of category theory. One immediate outcome is the possibility of relaxing the "yes/no" character of the definitions of consonance, and stressing its dependence on context in general. A counterpoint model ... More
Fields of moduli of classical Humbert curvesSep 16 2016The computation of the field of moduli of a closed Riemann surface seems to be a very difficult problem and even more difficult is to determine if the field of moduli is a field of definition. In this paper we consider the family of closed Riemann surfaces ... More
Enhanced spin-orbit optical mirages from dual nanospheresJul 13 2018Spin-orbit interaction of light can lead to the so-called optical mirages, i.e. a perceived displacement in the position of a particle due to the spiraling structure of the scattered light. In electric dipoles, the maximum displacement is subwavelength ... More
Microscopic-Macroscopic Approach for Binding Energies with the Wigner-Kirkwood Method - IIJul 02 2012The binding energies of deformed even-even nuclei have been analysed within the framework of a recently proposed microscopic-macroscopic model. We have used the semiclassical Wigner - Kirkwood $\hbar$ expansion up to fourth - order, instead of the usual ... More
Exploring the Kibble-Zurek mechanism in a secondary bifurcationMar 08 2011We present new experimental results on the quenching dynamics of an extended thermo-convective system (a network array of approximately 100 convective oscillators) going through a secondary subcritical bifurcation. We characterize a dynamical phase transition ... More
Lifting Hamiltonian loops to isotopies in fibrationsFeb 22 2013Let $G$ be a Lie group, $H$ a closed subgroup and $M$ the homogeneous space $G/H$. Each representation $\Psi$ of $H$ determines a $G$-equivariant principal bundle ${\mathcal P}$ on $M$ endowed with a $G$-invariant connection. We consider subgroups ${\mathcal ... More
Particle Creation in the Bell-Szekeres SpacetimeNov 24 1995The quantization of a real massless scalar field in a spacetime produced in a collision of two electromagnetic plane waves with constant wave fronts is considered. The background geometry in the interaction region, the Bell-Szekeres solution, is locally ... More
Cohomological vertex operatorsJul 26 2016Given a Calabi-Yau manifold and considering the $B$-branes on it as objects in the derived category of coherent sheaves, we identify the vertex operators for strings between two branes with elements of the cohomology groups of Ext sheaves. We define the ... More
Branes on $G$-manifoldsJan 27 2017Let $X$ be Calabi-Yau manifold acted by a group $G$. We give a definition of $G$-equivariance for branes on $X$, and assign to each equivariant brane an element of the equivariant cohomology of $X$ that can be considered as a charge of the brane. We prove ... More
Spanning Class in the Category of BranesApr 11 2018Given a generic anticanonical hypersurface $Y$ of a toric variety determined by a reflexive polytope, we define a line bundle ${\mathcal L}$ on $Y$ that generates a spanning class in the bounded derivative category $D^b(Y)$. From this fact, we deduce ... More
Equivariant branesFeb 06 2015Feb 10 2015Given a Calabi-Yau manifold $X$ acted by a group $G$ and considering the $B$-branes on $X$ as objects in the derived category of coherent sheaves, we give a definition of equivariant branes, which generalizes the concept of equivariant sheaves. We also ... More
A characteristic number of bundles determined by mass linear pairsSep 09 2008Nov 13 2008Let $\Delta$ be a Delzant polytope in ${\mathbb R}^n$ and ${\bf b}\in{\mathbb Z}^n$. Let $E$ denote the symplectic fibration over $S^2$ determined by the pair $(\Delta, {\bf b})$. We prove the equivalence between the fact that $(\Delta, {\bf b})$ is a ... More
Structural and Dynamical Patterns on Online Social Networks: the Spanish May 15th Movement as a case studyJul 08 2011The number of people using online social networks in their everyday life is continuously growing at a pace never saw before. This new kind of communication has an enormous impact on opinions, cultural trends, information spreading and even in the commercial ... More
Invariants under deformation of the actions of topological groupsMay 20 2016Let $\varphi$ and $\varphi'$ be two homotopic actions of the topological group $G$ on the topological space $X$. To an object $A$ in the $G$-equivariant derived category $D_{\varphi}(X)$ of $X$ relative to the action $\varphi$ we associate an object $A'$ ... More
Action Integrals and discrete seriesAug 08 2011Let $G$ be a complex semisimple Lie group and ${G}_{\mathbb R}$ a real form that contains a compact Cartan subgroup $T_{\mathbb R}$. Let $\pi$ be a discrete series representation of $G_{\mathbb R}$. We present geometric interpretations in terms of concepts ... More
A Characteristic Number of Hamiltonian Bundles over $S^2$Jun 09 2005Dec 16 2005Each loop $\psi$ in the group $\text{Ham}(M)$ of Hamiltonian diffeomorphisms of a symplectic manifold $M$ determines a fibration $E$ on $S^2$, whose coupling class \cite{G-L-S} is denoted by $c$. If $VTE$ is the vertical tangent bundle of $E$, we relate ... More
Continuous families of Hamiltonian torus actionsMay 19 2008We determine conditions under which two Hamiltonian torus actions on a symplectic manifold $M$ are homotopic by a family of Hamiltonian torus actions, when $M$ is a toric manifold and when $M$ is a coadjoint orbit.
Charge of $D$-branes on singular varietiesNov 19 2018Considering the $D$-branes on a variety $Z$ as the objects of the derived category $D^b(Z)$, we propose a definition for the charge of $D$-branes on not necessarily smooth varieties. We define the charge $Q({\mathcal G})$ of ${\mathcal G}\in D^b(Z)$ as ... More
An effective decomposition approach and heuristics to generate spanning trees with a small number of branch verticesSep 22 2015Jun 30 2016Given a graph $G=(V,E)$, the minimum branch vertices problem consists in finding a spanning tree $T=(V,E')$ of $G$ minimizing the number of vertices with degree greater than two. We consider a simple combinatorial lower bound for the problem, from which ... More
Gas electron multiplier based on laser-perforated CVD diamond film: First testsJun 18 2016Gas electron multiplier (GEM) is widely used in modern gas detectors of ionizing radiation in experiments on high-energy physics at accelerators and in other fields of science. Typically the GEM devices are based on a dielectric foil with holes and electrodes ... More
All-carbon multi-electrode array for real-time in vitro measurements of oxidizable neurotransmittersAug 25 2016We report on the ion beam fabrication of all-carbon multi electrode arrays (MEAs) based on 16 graphitic micro-channels embedded in single-crystal diamond (SCD) substrates. The fabricated SCD-MEAs are systematically employed for the in vitro simultaneous ... More
Action integrals and infinitesimal charactersAug 14 2008Oct 26 2009Let $G$ be a reductive Lie group and ${\mathcal O}$ the coadjoint orbit of a hyperbolic element of ${\frak g}^*$. By $\pi$ is denoted the unitary irreducible representation of $G$ associated with ${\mathcal O}$ by the orbit method. We give geometric interpretations ... More
Hamiltonian diffeomorphisms of toric manifoldsJun 09 2005We prove that $\pi_1(\text{Ham}(M))$ contains an infinite cyclic subgroup, where $\text{Ham}(M)$ is the Hamiltonian group of the one point blow up of ${\Bbb C}P^3$. We give a sufficient condition for the group $\pi_1(\text{Ham}(M))$ to contain an infinite ... More
Characteristic number associated to mass linear pairsJun 15 2011Aug 09 2011Let $\Delta$ be a Delzant polytope in ${\mathbb R}^n$ and ${\mathbf b}\in{\mathbb Z}^n$. Let $E$ denote the symplectic fibration over $S^2$ determined by the pair $(\Delta,\,{\mathbf b})$. Under certain hypotheses, we prove the equivalence between the ... More
Cohomological vertex operatorsJul 26 2016Jan 12 2017Given a Calabi-Yau manifold and considering the $B$-branes on it as objects in the derived category of coherent sheaves, we identify the vertex operators for strings between two branes with elements of the cohomology groups of Ext sheaves. We define the ... More
Role of the absorption on the spin-orbit interactions of light with Si nano-particlesMar 09 2019The conservation of the photon total angular momentum in the incident direction in an axially symmetric scattering process is a very well known fact. Nonetheless, the re-distribution of this conserved magnitude into its spin and orbital components, an ... More
Transverse Josephson vortices and localized states in stacked Bose-Einstein condensatesOct 14 2018Stacks of Bose-Einstein condensates coupled by long Josephson junctions present a rich phenomenology susceptible of experimental realization. We show that transverse Bloch waves excited in an array of one-dimensional condensates can carry tunneling super ... More
Expansion-Free Cavity Evolution: Some exact Analytical ModelsMar 18 2011Nov 29 2011We consider spherically symmetric distributions of anisotropic fluids with a central vacuum cavity, evolving under the condition of vanishing expansion scalar. Some analytical solutions are found satisfying Darmois junction conditions on both delimiting ... More
Tuning the two-electron hybridization and spin states in parallel-coupled InAs quantum dotsMar 01 2018We study spin transport in the one- and two-electron regimes of parallel-coupled double quantum dots (DQDs). The DQDs are formed in InAs nanowires by a combination of crystal-phase engineering and electrostatic gating, with an interdot tunnel coupling ... More
A family of relativistic charged thin disks with an inner edgeJun 14 2009A new family of exact solutions of the Einstein-Maxwell equations for static axially symmetric spacetimes is presented. The metric functions of the solutions are explicitely computed and are simply written in terms of the oblate spheroidal coordinates. ... More
Exact Static Axially Symmetric Thin Annular Dust DisksJun 04 2009A new family of exact solutions of the Einstein field equations for static and axially simmetric spacetimes is presented. All the metric functions of the solutions are explicitly computed and the obtained expressions are simply written in terms of oblate ... More