Results for "Miguel Orszag"

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Ground-state cooling of a nanomechanical oscillator with N spinsJul 30 2018Oct 26 2018Typical of modern quantum technologies employing nanomechanical oscillators is to demand few mechanical quantum excitations, for instance, to prolong coherence times of a particular task or, to engineer a specific non-classical state. For this reason, ... More
Photon cooling by dispersive atom-field coupling with atomic postselectionApr 08 2019We propose, in a Ramsey interferometer, to cool the cavity field to its ground state, starting from a thermal distribution by a dispersive atom-field coupling followed by an atomic postselection. We also analyze the effect of the cavity and atomic losses. ... More
Optical qubit generation via atomic postselection in a Ramsey interferometerMay 03 2018Jul 24 2018We propose a realizable experimental scheme to prepare a superposition of the vacuum and one-photon states using a typical cavity QED-setup. This is different from previous schemes, where the superposition state of the field is generated by resonant atom-field ... More
Weak value amplification of photon number operators in the optomechanical interactionApr 26 2018Sep 27 2018An experimental proposal is presented in which dark port post-selection together with weak measurements are used to enlarge the radiation pressure effect of a single photon on a mechanical oscillator placed in the middle of a Fabry-Perot cavity and initialized ... More
Geometric quantum discord with Bures distanceApr 11 2013Dec 20 2013We define a new measure of quantum correlations in bipartite quantum systems given by the Bures distance of the system state to the set of classical states with respect to one subsystem, that is, to the states with zero quantum discord. Our measure is ... More
Determination of the maximum Global Quantum Discord via measurements of excitations in a cavity QED networkJan 13 2014Multipartite Quantum Correlations is one of the most relevant indicator of the quantumness of a system in many body systems. This remarkable feature is in general difficult to characterize and the known definitions are hard to measure. Besides the efforts ... More
Phonon maser stimulated by spin post-selectionFeb 08 2019In a sequence of single spins interacting dispersively with a mechanical oscillator, and using the micromaser model with random injection, we show that after an appropriate post-selection of each spin, a phonon laser analog with Poisson statistics is ... More
Geometric quantum discord with Bures distance: the qubit caseAug 22 2013Dec 23 2013The minimal Bures distance of a quantum state of a bipartite system AB to the set of classical states for subsystem A defines a geometric measure of quantum discord. When A is a qubit, we show that this geometric quantum discord is given in terms of the ... More
Decoherence versus disentanglement for two qubits in a squeezed bathJan 09 2008We study the relation between the sudden death and revival of the entanglement of two qubits in a common squeezed reservoir, and the normal decoherence, by getting closer to the Decoherence Free Subspace and calculating the effect on the death and revival ... More
Photon cooling by dispersive atom-field coupling with atomic postselectionApr 08 2019Apr 16 2019We propose, in a Ramsey interferometer, to cool the cavity field to its ground state, starting from a thermal distribution by a dispersive atom-field coupling followed by an atomic postselection. We also analyze the effect of the cavity and atomic losses. ... More
Fisher Information, Weak Values and Correlated Noise in InterferometryFeb 25 2019In this article we present an experimental proposal for quantum enhanced estimation of optomechanical parameters. The precision of the estimation is improved by using the technique of weak value amplification, which can enlarge the radiation pressure ... More
Propagation and Distribution of Quantum Correlations in a Cavity QED NetworkJun 05 2013We study the propagation and distribution of quantum correlations through two chains of atoms inside cavities joined by optical fibers. We consider an effective Hamiltonian for the system and cavity losses, in the dressed atom picture, using the Generalized ... More
Thermal effects on the sudden changes and freezing of correlations between remote atoms in cavity QED networkFeb 10 2014We investigate the thermal effects on the sudden changes and freezing of the quantum and classical correlations of remote qubits in a cavity quantum electrodynamics (CQED) network with losses. We find that the detrimental effect of the thermal reservoirs ... More
Selftrapping triggered by losses in cavity QEDDec 23 2014In a coupled cavity QED network model, we study the transition from a localized super fluid like state to a delocalized Mott insulator like state, triggered by losses. Without cavity losses, the transition never takes place. Further, if one measures the ... More
Instability and entanglement of the ground state of the Dicke modelMar 24 2005Using tools of quantum information theory we show that the ground state of the Dicke model exhibits an infinite sequence of instabilities (quantum-phase-like transitions). These transitions are characterized by abrupt changes of the bi-partite entanglement ... More
Thermally generated long-lived quantum correlations for two atoms trapped in fiber-coupled cavitiesNov 22 2011Apr 25 2012A theoretical model for driving a two qubit system to a stable long-lived entanglement is discussed. The entire system is represented by two atoms, initially in ground states and disentangled, each one coupled to a separate cavity with the cavities connected ... More
Generation and protection of Maximally Entangled State between many modes in an optical network with dissipationOct 03 2016We present a three-cavity network model with two modes in each cavity and a non-linear medium that generates a Kerr type interaction via both self-phase and cross-phase modulation processes. We have two main goals. The first one is to generate a multipartite ... More
Macroscopic non-classical state preparation via post-selectionDec 09 2016Dec 04 2017Macroscopic mechanical qubits are fundamental both to test the classical-quantum boundary and present suitable candidates for quantum information processing. Motivated by these, we propose a feasible probabilistic scheme to generate an on-demand mechanical ... More
Macroscopic oscillations locked and synchronized on fixed energy levels by two cooperating drivesAug 09 2019It was unknown whether the energy of a macroscopic object can be confined to a set of discrete values like the energy levels of microscopic systems. Here, through the numerical simulation and theoretical analysis based on an experimentally implementable ... More
The power of a control qubit in weak measurementsSep 28 2016In the late 80s, a curious effect suggested by Aharanov, Albert and Vaidman opened up new vistas regarding quantum measurements on weakly coupled systems. There, a combination of a "weak" finite interaction together with a "strong" post-selection measurement ... More
Harnessing synthetic gauge fields for maximally entangled state generationJan 21 2014We study the generation of entanglement between two species of neutral cold atoms living on an optical ring lattice, where each group of particles can be described by a $d$-dimensional Hilbert space (qu$d$it). Synthetic magnetic fields are exploited to ... More
Quantum Correlations in Cavity QED NetworksJul 21 2014We present a Review of the dynamical features such as generation, propagation, distribution, sudden transition and freezing of the various quantum correlation measures, as Concurrence, Entanglement of Formation, Quantum Discord, as well their geometrical ... More
Nonlinear mushy-layer convection with chimneys: stability and optimal solute fluxesMay 04 2012Dec 21 2012We model buoyancy-driven convection with chimneys -- channels of zero solid fraction -- in a mushy layer formed during directional solidification of a binary alloy in two-dimensions. A large suite of numerical simulations is combined with scaling analysis ... More
A note on stability and Cauchy time functionsApr 21 2013May 13 2013Since the solution of the so-called folk problems of smoothability, there has been a special interest in the properties of classical time and volume functions of spacetimes. Here we supply some information that complements the one provided in arXiv:1108.5120v3 ... More
Exchange Bias Theory: a ReviewJul 05 2001Research on the exchange bias (EB) phenomenon has witnessed a flurry of activity during recent years, which stems from its use in magnetic sensors and as stabilizers in magnetic reading heads. EB was discovered in 1956 but it attracted only limited attention ... More
$L^{2}$-homology for inclusions of von Neumann algebrasMar 24 2014Mar 25 2014In this paper we define $L^{2}$-homology and $L^{2}$-Betti numbers for tracial *-algebras $A$ with respect to a von Neumann subalgebra $B$. When $B$ is reduced to the field of complex numbers we recover the $L^{2}$-Betti numbers of $A$ as defined by A. ... More
Generation of the Single Precision BLAS library for the Parallella platform, with Epiphany co-processor acceleration, using the BLIS frameworkAug 18 2016The Parallella is a hybrid computing platform that came into existence as the result of a Kickstarter project by Adapteva. It is composed of the high performance, energy-efficient, manycore architecture, Epiphany chip (used as co-processor) and one Zynq-7000 ... More
Exact solution of Chern-Simons-matter matrix models with characteristic/orthogonal polynomialsJan 23 2016Apr 27 2016We solve for finite $N$ the matrix model of supersymmetric $U(N)$ Chern-Simons theory coupled to $N_{f}$ fundamental and $N_{f}$ anti-fundamental chiral multiplets of $R$-charge $1/2$ and of mass $m$, by identifying it with an average of inverse characteristic ... More
Constraints on a Class of Two-Higgs Doublet Models with tree level FCNCOct 28 2014We analyse a class of two Higgs doublet models where flavour-changing neutral currents (FCNC) are present at tree level in a mixing-suppressed manner. In this class of models, because of a discrete symmetry imposed on the lagrangian, the FCNC couplings ... More
Note on the phase space of asymptotically flat gravity in Ashtekar-Barbero variablesDec 17 2014We describe the canonical phase space of asymptotically flat gravity in Ashtekar-Barbero variables. We show that the Gauss constraint multiplier must fall off slower than previously considered in order to recover ADM phase space. The generators of the ... More
Epic substructures and primitive positive functionsJul 11 2016For $\mathbf{A}\leq\mathbf{B}$ first order structures in a class $\mathcal{K}$, say that $\mathbf{A}$ is an epic substructure of $\mathbf{B}$ in $\mathcal{K}$ if for every $\mathbf{C}\in\mathcal{K}$ and all homomorphisms $g,g^{\prime}:\mathbf{B}\rightarrow\mathbf{C}$, ... More
Forbidden Configurations: Finding the number predicted by the Anstee-Sali Conjecture is NP-hardOct 30 2012Jan 29 2013Let F be a hypergraph and let forb(m,F) denote the maximum number of edges a hypergraph with m vertices can have if it doesn't contain F as a subhypergraph. A conjecture of Anstee and Sali predicts the asymptotic behaviour of forb(m,F) for fixed F. In ... More
Mass-deformed ABJ and ABJM theory, Meixner-Pollaczek polynomials, and $su(1,1)$ oscillatorsApr 21 2016May 18 2016We give explicit analytical expressions for the partition function of $U(N)_{k}\times U(N+M)_{-k}$ ABJ theory at weak coupling ($k\rightarrow \infty )$ for finite and arbitrary values of $N$ and $M$ (including the ABJM case and its mass-deformed generalization). ... More
Kahler geometry of toric manifolds in symplectic coordinatesApr 19 2000A theorem of Delzant states that any symplectic manifold $(M,\om)$ of dimension $2n$, equipped with an effective Hamiltonian action of the standard $n$-torus $\T^n = \R^{n}/2\pi\Z^n$, is a smooth projective toric variety completely determined (as a Hamiltonian ... More
Are tiny gauge couplings out of the Swampland?Aug 07 2017There is significant evidence suggesting that continuous global symmetries are always gauged in quantum gravity. However, very weakly gauged symmetries seem global to an effective field theory expansion in powers of Newton's constant. We show that, at ... More
Kahler metrics on toric orbifoldsMay 14 2001A theorem of E.Lerman and S.Tolman, generalizing a result of T.Delzant, states that compact symplectic toric orbifolds are classified by their moment polytopes, together with a positive integer label attached to each of their facets. In this paper we ... More
An A-based cofibrantly generated model categoryMay 08 2014We develop a cofibrantly generated model category structure in the category of topological spaces in which weak equivalences are A-weak equivalences and such that the generalized CW(A)-complexes are cofibrant objects. With this structure the exponential ... More
Ultra High Energy Cosmic RaysNov 11 2011Ultra high energy particles arrive at Earth constantly. They provide a beam at energies higher than any man-made accelerator, but at a very low rate. Two large experiments, the Pierre Auger Observatory and the Telescope Array experiment, have been taking ... More
The Hybrid Activities of the Pierre Auger ObservatoryAug 30 2006The Pierre Auger Observatory detects ultra-high energy cosmic rays by implementing two complementary air-shower techniques. The combination of a large ground array and fluorescence detectors, known as the hybrid concept, means that a rich variety of measurements ... More
Atmospheric Monitoring for the Pierre Auger Fluorescence DetectorAug 25 2003Major uncertainties in the fluorescence energy measurement come from the precision of various atmospheric transmission, air Cerenkov subtraction, light multiple-scattering and cloud corrections. The Auger program for atmospheric monitoring, designed to ... More
On causality and closed geodesics of compact Lorentzian manifolds and static spacetimesFeb 15 2005Some results related to the causality of compact Lorentzian manifolds are proven: (1) any compact Lorentzian manifold which admits a timelike conformal vector field is totally vicious, and (2) a compact Lorentzian manifold covered regularly by a globally ... More
Generalized symmetries and invariant matter couplings in two-dimensional dilaton gravityFeb 20 1997Apr 04 1997New features of the generalized symmetries of generic two-dimensional dilaton models of gravity are presented and invariant gravity-matter couplings are introduced. We show that there is a continuum set of Noether symmetries, which contains half a de ... More
The group of isometries of a Banach space and dualitySep 22 2008We construct an example of a real Banach space whose group of surjective isometries has no uniformly continuous one-parameter semigroups, but the group of surjective isometries of its dual contains infinitely many of them. Other examples concerning numerical ... More
On the definition and examples of Finsler metricsNov 22 2011Oct 01 2012For a standard Finsler metric F on a manifold M, its domain is the whole tangent bundle TM and its fundamental tensor g is positive-definite. However, in many cases (for example, the well-known Kropina and Matsumoto metrics), these two conditions are ... More
Toric Kahler Metrics: Cohomogeneity One Examples of Constant Scalar Curvature in Action-Angle CoordinatesDec 02 2009In these notes, after an introduction to toric Kahler geometry, we present Calabi's family of U(n)-invariant extremal Kahler metrics in symplectic action-angle coordinates and show that it actually contains, as particular cases, many interesting cohomogeneity ... More
Polymer representations and geometric quantizationNov 02 2011Polymer representations of the Weyl algebra of linear systems provide the simplest analogues of the representation used in loop quantum gravity. The construction of these representations is algebraic, based on the Gelfand-Naimark-Segal construction. Is ... More
Null to time-like infinity Green's functions for asymptotic symmetries in Minkowski spacetimeSep 04 2015We elaborate on the Green's functions that appeared in [1,2] when generalizing, from massless to massive particles, various equivalences between soft theorems and Ward identities of large gauge symmetries. We analyze these Green's functions in considerable ... More
Universe made of baryonic gravitating particles behaves as a ΛCDM UniverseMay 02 2014Sep 10 2014Using an approximate solution to the $N$-body problem in general relativity, and the \emph{principle of local isotropy at any point}, we construct a cosmological model, with zero curvature, for a universe composed uniquely by collision-less gravitating ... More
Quantum Mechanics and Leggett's InequalitiesJun 27 2008Jul 08 2008We show that when the proper description of the behaviour of individual photons or spin 1/2 particles in a spherically symmetric entangled pair is done through the use of the density matrix, the Leggett's inequality is not violated by quantum mechanics. ... More
EPR, Bell, GHZ, and Hardy theorems, and quantum mechanicsAug 09 2005We review the theorems of Einstein-Podolsky-Rosen (EPR), Bell, Greenberger-Horne-Zeilinger (GHZ), and Hardy, and present arguments supporting the idea that quantum mechanics is a complete, causal, non local, and non separable theory.
Rhythms of the collective brain: Metastable synchronization and cross-scale interactions in connected multitudesNov 21 2016Jan 17 2018Crowd behaviour challenges our fundamental understanding of social phenomena. Involving complex interactions between multiple temporal and spatial scales of activity, its governing mechanisms defy conventional analysis. Using 1.5 million Twitter messages ... More
The CPT Group of the Dirac FieldApr 16 2004Aug 12 2004Using the standard representation of the Dirac equation we show that, up to signs, there exist only TWO SETS of consistent solutions for the matrices of charge conjugation (C), parity (P), and time reversal (T). In both cases, P^2=-1, and then two succesive ... More
Einstein-Cartan Theory and Gauge SymmetryDec 13 2012Mar 08 2013We argue that the non gauge invariant coupling between torsion and the Maxwell or Yang-Mills fields in Einstein-Cartan theory can not be ignored. Arguments based in the existence of normal frames in neighbourhoods, and an approximation to a \delta-function, ... More
Asymptotic Distribution Of The Roots Of The Ehrhart Polynomial Of The Cross-PolytopeDec 10 2010We use the method of steepest descents to study the root distribution of the Ehrhart polynomial of the $d$-dimensional cross-polytope, namely $\mathcal{L}_{d}$, as $d\rightarrow \infty$. We prove that the distribution function of the roots, approximately, ... More
Why old tires are still being preferred as dock bumpers in harboursMay 28 2012Sep 26 2012The usage of old tires as dock and tugboat bumpers has been a common practice from long ago, proving to be safe for docking even the largest freighters. The reaction force and stored energy of an axially compressed tire is studied in order to determine ... More
Hardy-Littlewood inequalities for norms of positive operators on sequence spacesAug 15 2012We consider estimates of Hardy and Littlewood for norms of operators on sequence spaces, and we apply a factorization result of Maurey to obtain improved estimates and simplified proofs for the special case of a positive operator.
The version for compact operators of Lindenstrauss properties A and BFeb 25 2015It has been very recently discovered that there are compact linear operators between Banach spaces which cannot be approximated by norm attaining operators. The aim of this expository paper is to give an overview of those examples and also of sufficient ... More
Recent progress on the notion of global hyperbolicityDec 12 2007Feb 25 2010Global hyperbolicity is a central concept in Mathematical Relativity. Here, we review the different approaches to this concept explaining both, classical approaches and recent results. The former includes Cauchy hypersurfaces, naked singularities, and ... More
The like-sign dimuon asymmetry and New PhysicsNov 14 2014The measurement by the D0 collaboration of a large like-sign dimuon asymmetry deviates significantly from Standard Model expectations. New Physics may be invoked to account for such a deviation. We analyse how generic extensions of the Standard Model ... More
Rhythms of the collective brain: Metastable synchronization and cross-scale interactions in connected multitudesNov 21 2016Collective social events operate at many levels of organization -- from individuals to crowds -- presenting a variety of temporal and spatial scales of activity, whose causal interactions challenge our understanding of social systems. Large data sets ... More
What can(not) be measured with ton-scale dark matter direct detection experimentsJun 03 2011Oct 31 2011Direct searches for dark matter have prompted in recent years a great deal of excitement within the astroparticle physics community, but the compatibility between signal claims and null results of different experiments is far from being a settled issue. ... More
The stochastic nature of stellar population modellingNov 29 2013Since the early 1970s, stellar population modelling has been one of the basic tools for understanding the physics of unresolved systems from observation of their integrated light. Models allow us to relate the integrated spectra (or colours) of a system ... More
Finding long simple paths in a weighted digraph using pseudo-topological orderingsSep 23 2016Given a weighted digraph D, finding the longest simple path is well known to be NP-hard. Furthermore, even giving an approximation algorithm is known to be NP-hard. In this paper we describe an efficient heuristic algorithm for finding long simple paths, ... More
From creation and annihilation operators to statisticsJun 06 2017A procedure to derive the partition function of non-interacting particles with exotic or intermediate statistics is presented. The partition function is directly related to the associated creation and annihilation operators that obey some specific commutation ... More
On different definitions of numerical rangeFeb 25 2015We study the relation between the intrinsic and the spatial numerical ranges with the recently introduced "approximated" spatial numerical range. As main result, we show that the intrinsic numerical range always coincides with the convex hull of the approximated ... More
Can our number system be improved?Dec 14 2001Our number system is a magnificent tool. But it is far from perfect. Can it be improved? In this paper some possibilities are discussed, including the use of a different base or directed (negative as well as positive) numerals. We also put forward some ... More
Character varieties for real formsOct 17 2016Oct 12 2017Let $\Gamma$ be a finitely generated group and $G$ a real form of $\mathrm{SL}_n(\mathbb{C})$. We propose a definition for the $G$-character variety of $\Gamma$ as a subset of the $\mathrm{SL}_n(\mathbb{C})$-character variety of $\Gamma$. We consider ... More
Smoothing of ribbons over curvesFeb 05 2003Apr 04 2005We prove that ribbons, i.e. double structures associated with a line bundle $\SE$ over its reduced support, a smooth irreducible projective curve of arbitrary genus, are smoothable if their arithmetic genus is greater than or equal to $3 $ and the support ... More
On the definition and examples of cones and Finsler spacetimesMay 17 2018Jun 17 2018We develop a systematic study of (smooth, strong) cone structures $\mathcal{C}$ and (smooth) Lorentz-Finsler metrics $L$ which includes: (a) to associate each $L$ (defined on some conic domain) with a $\mathcal{C}$, (b) to describe any $\mathcal{C}$ by ... More
Wind Riemannian spaceforms and Randers metrics of constant flag curvatureJan 05 2017Recently, wind Riemannian structures (WRS) have been introduced as a generalization of Randers and Kropina metrics. They are constructed from the natural data for Zermelo navigation problem, namely, a Riemannian metric $g_R$ and a vector field $W$ (the ... More
Some criteria for Wind Riemannian completeness and existence of Cauchy hypersurfacesMar 14 2017Jun 05 2017Recently, a link between Lorentzian and Finslerian Geometries has been carried out, leading to the notion of wind Riemannian structure (WRS), a generalization of Finslerian Randers metrics. Here, we further develop this notion and its applications to ... More
Kahler-Sasaki geometry of toric symplectic cones in action-angle coordinatesDec 02 2009Feb 17 2010In the same way that a contact manifold determines and is determined by a symplectic cone, a Sasaki manifold determines and is determined by a suitable Kahler cone. Kahler-Sasaki geometry is the geometry of these cones. This paper presents a symplectic ... More
From entanglement renormalisation to the disentanglement of quantum double modelsDec 26 2010Aug 16 2011We describe how the entanglement renormalisation approach to topological lattice systems leads to a general procedure for treating the whole spectrum of these models, in which the Hamiltonian is gradually simplified along a parallel simplification of ... More
Technical notes on a 2-d lattice O(N) model problemSep 28 2004Jan 18 2005This paper provides a technical companion to M. Aguado and E. Seiler, hep-lat/0406041, in which the fate of perturbation theory in the thermodynamic limit is discussed for the O(N) model on a 2d lattice and different boundary conditions. The techniques ... More
Fibre bundles, connections, general relativity, and Einstein-Cartan theoryOct 05 2011We present in the most natural way, that is, in the context of the theory of vector and principal bundles and connections in them, fundamental geometrical concepts related to General Relativity and one of its extensions, the Einstein-Cartan theory.
Charge Conjugation in the Galilean LimitMar 17 2006Strictly working in the framework of the nonrelativistic quantum mechanics of a spin 1/2 particle coupled to an external electromagnetic field, we show, by explicit construction, the existence of a charge conjugation operator matrix which defines the ... More
A Holographic Derivation of the Weak Gravity ConjectureDec 10 2018The Weak Gravity Conjecture (WGC) demands the existence of superextremal particles in any consistent quantum theory of gravity. The standard lore is that these particles are introduced to ensure that extremal black holes are either unstable or marginally ... More
Kahler geometry of toric varieties and extremal metricsNov 19 1997Recently Guillemin gave an explicit combinatorial way of constructing "toric" Kahler metrics on (symplectic) toric varieties, using only data on the moment polytope. In this paper, differential geometric properties of these metrics are investigated using ... More
Toward a finite-dimensional formulation of Quantum Field TheoryMay 04 1998Rules of quantization and equations of motion for a finite-dimensional formulation of Quantum Field Theory are proposed which fulfill the following properties: a) both the rules of quantization and the equations of motion are covariant; b) the equations ... More
The Alternative Daugavet Property of $C^*$-algebras and $JB^*$-triplesNov 24 2004A Banach space $X$ is said to have the alternative Daugavet property if for every (bounded and linear) rank-one operator $T:X\longrightarrow X$ there exists a modulus one scalar $\omega$ such that $\|Id + \omega T\|= 1 + \|T\|$. We give geometric characterizations ... More
Causal boundaries and holography on wave type spacetimesDec 01 2008Mar 14 2009The notion of a causal boundary for a spacetime has been a controversial topic during the last three decades. Moreover, recently the role of the boundary in the AdS/CFT correspondence for plane waves, have stimulated its redefinition with some possible ... More
On the foundations and necessity of classical gauge invarianceMar 10 2008We argue that, ideally, the ways to measure magnitudes in non-quantum theories of physics (spacetime, field theory), limit drastically their possible mathematical models. In particular, gauge invariance in the Yang-Mills framework, is a necessity of our ... More
Some remarks on Causality Theory and Variational Methods in Lorentzian manifoldsDec 04 2007Feb 29 2008In this conference published in 1997 some problems on the geodesics of a Lorentzian manifold concerning causality and infinite-dimensional variational methods, are pointed out. Even though a big progress on many of these questions have been carried out ... More
On the completeness of trajectories for some mechanical systemsMar 25 2013Sep 26 2013The classical tools which ensure the completeness of vector fields and second order differential equations for mechanical systems are revisited. Possible extensions in three directions are discussed: infinite dimensional Banach and Hilbert manifolds, ... More
Modeling the multiwavelength emission from G73.9+0.9: Gamma-rays from a SNR-MC interactionSep 12 2015G73.9+0.9 has been classified as a probable shell-type supernova remnant (SNR), although it has also been suggested that this object could be a pulsar wind nebula (PWN). Here, a broadband model of the non-thermal emission of G73.9+0.9 from radio to gamma-rays ... More
On the Eclipse of Thales, Cycles and ProbabilitiesJul 08 2013According to classical tradition, Thales of Miletus predicted the total solar eclipse that took place on 28 May 585 BCE. Even if some authors have flatly denied the possibility of such a prediction, others have struggled to find cycles which would justify ... More
Character varieties for real formsOct 17 2016Let $\Gamma$ be a finitely generated group and $G$ a real form of $\mathrm{SL}_n(\mathbb{C})$. We propose a definition for the $G$-character variety of $\Gamma$ as a subset of the $\mathrm{SL}_n(\mathbb{C})$-character variety of $\Gamma$. We consider ... More
On the non existence of non negative solutions to a critical Growth-Fragmentation EquationMar 22 2017A growth fragmentation equation with constant dislocation density measure is considered, in which growth and division rates balance each other. This leads to a simple example of equation where the so called Malthusian hypothesis $(M_+)$ of J. Bertoin ... More
Spherical CR Dehn SurgerySep 15 2015Consider a three dimensional cusped spherical $\mathrm{CR}$ manifold $M$ and suppose that the holonomy representation of $\pi_1(M)$ can be deformed in such a way that the peripheral holonomy is generated by a non-parabolic element. We prove that, in this ... More
Detection of GeV Gamma-rays from HESS J1534-571 and Multiwavelength Implications for the Origin of the Non-thermal EmissionMay 10 2017HESS J1534-571 is a very high energy gamma-ray source that was discovered by the H.E.S.S. observatory and reported as one of several new sources with a shell-like morphology at TeV energies, matching in size and location with the supernova remnant G323.7-1.0 ... More
twister - a P2P microblogging platformDec 26 2013This paper proposes a new microblogging architecture based on peer-to-peer networks overlays. The proposed platform is comprised of three mostly independent overlay networks. The first provides distributed user registration and authentication and is based ... More
Hybrid Detection of UHECR with the Pierre Auger ObservatoryJul 31 2006The Pierre Auger Observatory detects ultra-high energy cosmic rays by implementing two complementary air-shower techniques. The combination of a large ground array and fluorescence detectors, known as the "hybrid" concept, means that a rich variety of ... More
The High Altitude Water Cherenkov ObservatoryOct 27 2013The High Altitude Water Cherenkov (HAWC) observatory is a large field of view, continuously operated, TeV gamma-ray experiment under construction at 4,100 m a.s.l. in Mexico. The HAWC observatory will have an order of magnitude better sensitivity, angular ... More
Geodesic connectedness of semi-Riemannian manifoldsMay 04 2000Sep 12 2000The question whether a Riemannian manifold is geodesically connected can be studied from geometrical as well as variational methods, and accurate results can be obtained by using the associated distance and related properties of the positive-definiteness. ... More
Multiple-antenna fading coherent channels with arbitrary inputs: Characterization and optimization of the reliable information transmission rateOct 25 2012We investigate the constrained capacity of multiple-antenna fading coherent channels, where the receiver knows the channel state but the transmitter knows only the channel distribution, driven by arbitrary equiprobable discrete inputs in a regime of high ... More
Norm-attaining compact operatorsJun 05 2013Jun 13 2014We show examples of compact linear operators between Banach spaces which cannot be approximated by norm attaining operators. This is the negative answer to an open question posed in the 1970's. Actually, any strictly convex Banach space failing the approximation ... More
Quantum and Classical Fields in the Finite-Dimensional FormalismOct 09 2001The quantization rules recently proposed by M. Navarro (and independently I.V. Kanatchikov) for a finite-dimensional formulation of quantum field theory are applied to the Klein-Gordon and the Dirac fields to obtain the quantum equations of motion of ... More
Symmetries in two-dimensional dilaton gravity with matterJun 13 1997Sep 10 1997The symmetries of generic 2D dilaton models of gravity with (and without) matter are studied in some detail. It is shown that $\delta_2$, one of the symmetries of the matterless models, can be generalized to the case where matter fields of any kind are ... More
A Holographic Derivation of the Weak Gravity ConjectureDec 10 2018Apr 06 2019The Weak Gravity Conjecture (WGC) demands the existence of superextremal particles in any consistent quantum theory of gravity. The standard lore is that these particles are introduced to ensure that extremal black holes are either unstable or marginally ... More
Observability of molecular species in a nitrogen dominated atmosphere for 55 Cancri eSep 20 2018Oct 15 2018One of the key goals of exoplanet science is the atmospheric characterisation of super-Earths. Atmospheric abundances provide insight on the formation and evolution of those planets and help to put our own rocky planets in context. Observations on 55 ... More