Results for "L. Esposito"

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Best constants in Poincaré inequalities for convex domainsOct 13 2011We prove a Payne-Weinberger type inequality for the $p$-Laplacian Neumann eigenvalues ($p\ge 2$). The inequality provides the sharp upper bound on convex domains, in terms of the diameter alone, of the best constants in Poincar\'e inequality. The key ... More
Swift X-ray and ultraviolet observations of the shortest orbital period double-degenerate system RX J0806.3+1527 (HM Cnc)Nov 27 2013Dec 12 2013The system RX J0806.3+1527 (HM Cnc) is a pulsating X-ray source with 100 per cent modulation on a period of 321.5 s (5.4 min). This period reflects the orbital motion of a close binary consisting of two interacting white dwarfs. Here we present a series ... More
The longest shortest fence and sharp Poincaré-Sobolev inequalitiesNov 29 2010We prove a long standing conjecture concerning the fencing problem in the plane: among planar convex sets of given area, prove that the disc, and only the disc maximizes the length of the shortest area-bisecting curve. Although it may look intuitive, ... More
Discovery of a 6.4 h black hole binary in NGC 4490Sep 24 2013Oct 10 2013We report on the discovery with Chandra of a strong modulation (~90% pulsed fraction) at ~6.4 h from the source CXOU J123030.3+413853 in the star-forming, low-metallicity spiral galaxy NGC 4490, which is interacting with the irregular companion NGC 4485. ... More
XMM-Newton discovery of mHz quasi-periodic oscillations in the high mass X-ray binary IGRJ19140+0951May 20 2016We report on the discovery of mHz quasi-periodic oscillations (QPOs) from the high mass X-ray binary (HMXB) IGRJ19140+0951, during a 40 ks XMM-Newton observation performed in 201 5, which caught the source in its faintest state ever observed. At the start ... More
Five years of SGR 1900+14 observations with BeppoSAXSep 04 2006We present a systematic analysis of all the BeppoSAX data of the soft gamma-ray repeater SGR 1900+14: these observations allowed us to study the long term properties of the source quiescent emission. In the observation carried out before the 1998 giant ... More
Droplet minimizers for the Cahn Hilliard free energy functionalMay 11 2005We prove theorem characterizing the minimizers in a model for condensation based on the Cahn Hilliard free energy functional. In particular, we exactly determine the critical density for droplet formation.
Generating Solutions to the Einstein - Maxwell EquationsAug 07 2015The Einstein-Maxwell (E-M) equations in a curved spacetime that admits at least one Killing vector are derived, from a Lagrangian density adapted to symmetries. In this context, an auxiliary space of potentials is introduced, in which, the set of potentials ... More
Long term hard X-ray variability of the anomalous X-ray pulsar 1RXS J170849.0-400910 discovered with INTEGRALSep 24 2007We report on a multi-band high-energy observing campaign aimed at studying the long term spectral variability of the Anomalous X-ray Pulsar (AXP) 1RXS J170849.0-400910, one of the magnetar candidates. We observed 1RXS J170849.0-400910 in Fall 2006 and ... More
Majorana, Pauling and the quantum theory of the chemical bondJun 26 2013We discuss in detail very little known results obtained by Majorana as early as 1931, regarding the quantum theory of the chemical bond in homopolar molecules, based on the key concept of exchange interaction. After a brief historical overview of the ... More
Mildly obscured active galaxies and the cosmic X-ray backgroundMar 21 2016The diffuse cosmic X-ray background (CXB) is the sum of the emission of discrete sources, mostly massive black-holes accreting matter in active galactic nuclei (AGN). The CXB spectrum differs from the integration of the spectra of individual sources, ... More
Topological aspects in the photonic crystal analog of single-particle transport in quantum Hall systemsJul 10 2013We present a perturbative approach to derive the semiclassical equations of motion for the two-dimensional electron dynamics under the simultaneous presence of static electric and magnetic fields, where the quantized Hall conductance is known to be directly ... More
On sheets of conjugacy classes in good characteristicNov 26 2010Apr 01 2011We show that the sheets for a connected reductive algebraic group G over an algebraically closed field in good characteristic acting on itself by conjugation are in bijection with G-conjugacy classes of triples (M, Z(M)^\circ t, O) where M is the connected ... More
Affine hyperplane arrangements and Jordan classesJul 27 2018We study the geometry of the stratification induced by an affine hyperplane arrangement $H$ on the quotient of a complex affine space by the action of a group preserving $H$. We give conditions ensuring normality of strata. As an application, we determine ... 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
The longest observation of a low intensity state from a Supergiant Fast X-ray Transient: Suzaku observes IGRJ08408-4503Jul 07 2010We report here on the longest deep X-ray observation of a SFXT outside outburst, with an average luminosity level of 1E33 erg/s (assuming 3 kpc distance). This observation was performed with Suzaku in December 2009 and was targeted on IGRJ08408-4503, ... More
Solutions to the Boltzmann equation in the Boussinesq regimeSep 29 1997We consider a gas in a horizontal slab, in which the top and bottom walls are kept at different temperatures. The system is described by the Boltzmann equation (BE) with Maxwellian boundary conditions specifying the wall temperatures. We study the behavior ... More
The $Z_c^{(\prime)} \to η_c ρ$ decay as a discriminant between tetraquarks and meson moleculesAug 28 2015Sep 04 2015Understanding the nature of the exotic XYZ resonances is one of the open problems in hadronic spectroscopy. Despite the experimental efforts, the structure of these particles still lacks of an accepted theoretical framework. We propose to use the $Z_c^{(\prime)} ... More
Search for νμ {\to} ντ oscillations in appearance mode in the OPERA experimentMay 26 2011Jun 06 2011The OPERA experiment is aiming at the first direct detection of neutrino oscillations in appearance mode through the study of the {\nu}{\mu} {\tp} {\nu}{\tau} channel. The OPERA detector is placed in the CNGS long baseline {\nu}{\mu} beam 730 km away ... More
Mpemba effect and phase transitions in the adiabatic cooling of water before freezingApr 11 2007An accurate experimental investigation on the Mpemba effect (that is, the freezing of initially hot water before cold one) is carried out, showing that in the adiabatic cooling of water a relevant role is played by supercooling as well as by phase transitions ... More
Magnetars: a short review and some sparse considerationsMar 15 2018We currently know about 30 magnetars: seemingly isolated neutron stars whose properties can be (in part) comprehended only acknowledging that they are endowed with magnetic fields of complex morphology and exceptional intensity-at least in some components ... More
Detailed X-ray spectroscopy of the magnetar 1E 2259+586Apr 16 2019Magnetic field geometry is expected to play a fundamental role in magnetar activity. The discovery of a phase-variable absorption feature in the X-ray spectrum of SGR 0418+5729, interpreted as cyclotron resonant scattering, suggests the presence of very ... More
Probing the nature of Z_c states via the eta_c rho decaySep 11 2014Apr 27 2015The nature of the so-called XYZ states is a long-standing problem. It has been suggested that such particles may be described as compact four-quark states or loosely bound meson molecules. In the present work we analyze the Z_c(') -> eta_c rho decay using ... More
Long X-ray flares from the central source in RCW 103Apr 10 2019We observed the slowly revolving pulsar 1E 161348-5055 (1E 1613, spin period of 6.67 h) in the supernova remnant RCW 103 two times with XMM-Newton and one with the Very Large Telescope (VLT). The VLT observation was performed on 2016 June 30, about a ... More
Planets of young starsJan 10 2007Since the first massive planet in a short period orbit was discovered, the question arised how such an object could have formed. There are basically two formation scenarios: migration due to planet-disk or planet-planet interaction. Which of the two scenarios ... More
A high order $q$-difference equation for $q$-Hahn multiple orthogonal polynomialsOct 21 2009A high order linear $q$-difference equation with polynomial coefficients having $q$-Hahn multiple orthogonal polynomials as eigenfunctions is given. The order of the equation is related to the number of orthogonality conditions that these polynomials ... More
A $bb\bar b\bar b$ di-bottomonium at the LHC?Jul 16 2018Oct 01 2018We study the case of a di-bottomonium $bb\bar b\bar b$ particle at the LHC. Its mass and decay width are obtained within a new model of diquark-antidiquark interactions in tetraquarks. The same model solves several open problems on the phenomenology of ... More
Discovery of a 0.42-s pulsar in the ultraluminous X-ray source NGC 7793 P13Sep 21 2016Jan 04 2017NGC 7793 P13 is a variable (luminosity range ~100) ultraluminous X-ray source (ULX) proposed to host a stellar-mass black hole of less than 15 M$_{\odot}$ in a binary system with orbital period of 64 d and a 18-23 M$_{\odot}$ B9Ia companion. Within the ... More
High Resolution H alpha Images of the Binary Low-mass Proplyd LV 1 with the Magellan AO SystemAug 19 2013We utilize the new Magellan adaptive optics system (MagAO) to image the binary proplyd LV 1 in the Orion Trapezium at H alpha. This is among the first AO results in visible wavelengths. The H alpha image clearly shows the ionization fronts, the interproplyd ... More
Commissioning and operation of the Cherenkov detector for proton Flux Measurement of the UA9 ExperimentApr 12 2019The UA9 Experiment at CERN-SPS investigates channeling processes in bent silicon crystals with the aim to manipulate hadron beams. Monitoring and characterization of channeled beams in the high energy accelerators environment ideally requires in-vacuum ... More
A possibly inflated planet around the bright, young star DS Tuc AApr 02 2019The origin of the observed diversity of planetary system architectures is one of the main topic of the exoplanetary research. The detection of a statistically significant sample of planets around young stars allows us to study the early stages of planet ... More
Hydrodynamics of binary fluid phase segregationAug 21 2002Dec 06 2002Starting with the Vlasov-Boltzmann equation for a binary fluid mixture, we derive an equation for the velocity field $\bm{u}$ when the system is segregated into two phases (at low temperatures) with a sharp interface between them. $\bm{u}$ satisfies the ... More
The Neumann eigenvalue problem for the $\infty$-LaplacianMay 14 2014Sep 22 2014The first nontrivial eigenfunction of the Neumann eigenvalue problem for the $p$-Laplacian, suitable normalized, converges as $p$ goes to $\infty$ to a viscosity solution of an eigenvalue problem for the $\infty$-Laplacian. We show among other things ... More
Linearized theory for entire solutions of a singular Liouvillle equationJun 29 2010We discuss invertibility properties for entire finite-energy solutions of the regularized version of a singular Liouvillle equation.
A scalar invariant and the local geometry of a class of static spacetimesAug 21 2002Oct 23 2003The scalar invariant, I, constructed from the "square" of the first covariant derivative of the curvature tensor is used to probe the local geometry of static spacetimes which are also Einstein spaces. We obtain an explicit form of this invariant, exploiting ... More
The next to leading order effective potential in the 2+1 dimensional Nambu-Jona-Lasinio model at finite temperatureMar 03 1998Apr 10 1998The finite temperature effective potential in the 2+1 dimensional Nambu-Jona-Lasinio model is constructed up to the next to leading order in the large $N$ expansion, where $N$ is the number of flavors in the model. The distinctive feature of the analysis ... More
The discovery, monitoring and environment of SGR J1935+2154Jan 03 2016We report on the discovery of a new member of the magnetar class, SGR J1935+2154, and on its timing and spectral properties measured by an extensive observational campaign carried out between July 2014 and March 2015 with Chandra and XMM-Newton (11 pointings). ... More
Analysis of Droplets in Lattice Systems with Long-range Kac PotentialsApr 26 2011We investigate the geometry of typical equilibrium configurations for a lattice gas in a finite macroscopic domain with attractive, long range Kac potentials. We focus on the case when the system is below the critical temperature and has a fixed number ... More
Swift monitoring of IGR J16418-4532Sep 26 2012We report on the Swift observations of the candidate supergiant fast X-ray transient (SFXT) IGR J16418-4532, which has an orbital period of ~3.7 d. Our monitoring, for a total of ~43 ks, spans over three orbits and represents the most intense and complete ... More
Type IIB orientifolds with discrete torsionJan 29 2001Feb 16 2001We consider compact four-dimensional ${\bf Z_N}\times {\bf Z_M}$ type IIB orientifolds, for certain values of $N$ and $M$. We allow the additional feature of discrete torsion and discuss the modification of the consistency conditions arising from tadpole ... More
Cross Sections and Charged Pion Spectra in Proton-Carbon Interactions at 31 GeV/cMay 26 2011As neutrino long baseline experiments enter a new domain of precision, the careful study of systematic errors due to poor knowledge of production cross sections for pions and kaons require more dedicated measurements for precise neutrino flux predictions. ... More
Stability for Rayleigh-Benard convective solutions of the Boltzmann equationDec 19 2008We consider the Boltzmann equation for a gas in a horizontal slab, subject to a gravitational force. The boundary conditions are of diffusive type, specifying the wall temperatures, so that the top temperature is lower than the bottom one (Benard setup). ... More
Quantum phase excitations in Ginzburg-Landau superconductorsNov 15 2004We give a straightforward generalization of the Ginzburg-Landau theory for superconductors where the scalar phase field is replaced by an antisymmetric Kalb-Ramond field. We predict that at very low temperatures, where quantum phase effects are expected ... More
Sub-GeV Dark Matter in Superfluid He-4: an Effective Theory ApproachFeb 06 2019We employ an effective field theory to study the detectability of sub-GeV dark matter through its interaction with the gapless excitations of superfluid helium-4. In a quantum field theory language, the possible interactions between the dark matter and ... More
Fermionic reaction coordinates and their application to an autonomous Maxwell demon in the strong coupling regimeNov 24 2017Mar 23 2018We establish a theoretical method which goes beyond the weak coupling and Markovian approximations while remaining intuitive, using a quantum master equation in a larger Hilbert space. The method is applicable to all impurity Hamiltonians tunnel-coupled ... More
Binary Fluids with Long Range Segregating Interaction I: Derivation of Kinetic and Hydrodynamic EquationsApr 03 2001We study the evolution of a two component fluid consisting of ``blue'' and ``red'' particles which interact via strong short range (hard core) and weak long range pair potentials. At low temperatures the equilibrium state of the system is one in which ... More
Spectral variability in Swift and Chandra observations of the Ultraluminous source NGC 55 ULX1Jan 06 2015NGC 55 ULX1 is a bright Ultraluminous X-ray source located 1.78 Mpc away. We analysed a sample of 20 Swift observations, taken between 2013 April and August, and two Chandra observations taken in 2001 September and 2004 June. We found only marginal hints ... More
The gravitational mass carried by sound wavesJul 23 2018Mar 02 2019We show that the commonly accepted statement that sound waves do not transport mass is only true at linear order. Using effective field theory techniques, we confirm the result found in [1] for zero-temperature superfluids, and extend it to the case of ... More
Infinitesimal Automorphisms of VB-groupoids and algebroidsNov 21 2016Apr 04 2017VB-groupoids and algebroids are vector bundle objects in the categories of Lie groupoids and Lie algebroids respectively, and they are related via the Lie functor. VB-groupoids and algebroids play a prominent role in Poisson and related geometries. In ... More
Parabolic orbits of $2$-nilpotent elements for classical groupsFeb 18 2018Feb 08 2019We consider the conjugation-action of the Borel subgroup of the symplectic or the orthogonal group on the variety of nilpotent complex elements of nilpotency degree $2$ in its Lie algebra. We translate the setup to a representation-theoretic context in ... More
Thermodynamics of Chemical WavesApr 18 2019Chemical waves constitute a known class of dissipative structures emerging in reaction-diffusion systems. They play a crucial role in biology, spreading information rapidly to synchronize and coordinate biological events. We develop a rigorous thermodynamic ... More
A Landau-Zener Lindblad equation and work extraction from coherencesSep 26 2018We show that the dynamics of a driven quantum system weakly coupled to a finite reservoir can be approximated by a sequence of Landau-Zener transitions if the level spacing of the reservoir is large enough. This approximation can be formulated as a repeated ... More
Strengthened Information-theoretic Bounds on the Generalization ErrorMar 09 2019The following problem is considered: given a joint distribution $P_{XY}$ and an event $E$, bound $P_{XY}(E)$ in terms of $P_XP_Y(E)$ (where $P_XP_Y$ is the product of the marginals of $P_{XY}$) and a measure of dependence of $X$ and $Y$. Such bounds have ... More
Cosmological Constant and the Speed of LightJun 28 2000By exploring the relationship between the propagation of electromagnetic waves in a gravitational field and the light propagation in a refractive medium, it is shown that, in the presence of a positive cosmological constant, the velocity of light will ... More
An accreting pulsar with extreme properties drives an ultraluminous x-ray source in NGC 5907Sep 23 2016Feb 26 2017Ultraluminous x-ray sources (ULXs) in nearby galaxies shine brighter than any X-ray source in our Galaxy. ULXs are usually modeled as stellar-mass black holes (BHs) accreting at very high rates or intermediate-mass BHs. We present observations showing ... More
Swift observations of the ultraluminous X-ray source XMMU J004243.6+412519 in M31Oct 18 2012Nov 22 2012We report on a multi-wavelength study of the recently discovered X-ray transient XMMU J004243.6+412519 in M31, based on data collected with Swift and the 1.8-m Copernico Telescope at Cima Ekar in Asiago (Italy) between 2012 February and August. Undetected ... More
Observations of the unique X-ray emitting subdwarf stars HD49798 and BD+37 442Jun 28 2013We report on the results we obtained with XMM-Newton observations of HD49798 and BD+37 442, the only two sdO stars for which X-ray emission has been observed so far. HD is a single-lined spectroscopic binary with orbital period of 1.5 days. We could establish ... More
Magellan Adaptive Optics first-light observations of the exoplanet $β$ Pic b. I. Direct imaging in the far-red optical with MagAO+VisAO and in the near-IR with NICIMar 03 2014We present the first ground-based CCD ($\lambda < 1\mu$m) image of an extrasolar planet. Using MagAO's VisAO camera we detected the extrasolar giant planet (EGP) $\beta$ Pictoris b in $Y$-short ($Y_S$, 0.985 $\mu$m), at a separation of $0.470 \pm 0.010''$ ... More
Callen-like method for the classical Heisenberg ferromagnetNov 14 2011A study of the d-dimensional classical Heisenberg ferromagnetic model in the presence of a magnetic field is performed within the two-time Green function's framework in classical statistical physics. We extend the well known quantum Callen method to derive ... More
The observation of light nuclei at ALICE and the X(3872) conundrumAug 03 2015Aug 14 2015The new data reported by ALICE on the production of light nuclei with pT < 10 GeV in Pb-Pb collisions at sqrt(s_NN) = 2.76 TeV are used to compute an order-of-magnitude estimate of the expected production cross sections of light nuclei in proton-proton ... More
Field theoretic description of the abelian and non-abelian Josephson effectMay 14 2007We formulate the Josephson effect in a field theoretic language which affords a straightforward generalization to the non-abelian case. Our formalism interprets Josephson tunneling as the excitation of pseudo-Goldstone bosons. We demonstrate the formalism ... More
The abelian and non-abelian Josephson effect and pseudo-goldstone bosonsOct 16 2005We formulate the Josephson effect in a field theoretic language which affords a straightforward generalization to the non-abelian case. We give some examples and apply the formalism to the case of SO(5) superconductivity.
AX J1910.7+0917: the slowest X-ray pulsarMay 04 2017Pulsations from the high mass X-ray binary AXJ1910.7+0917 were discovered during Chandra observations performed in 2011 (Israel et al. 2016). We report here more details on this discovery and discuss the source nature. The period of the X-ray signal is ... More
The X-ray emission of the high mass X-ray binary IGR J17200-3116Apr 02 2014Apr 18 2014The source IGR J17200-3116 was discovered in the hard X-ray band by INTEGRAL. A periodic X-ray modulation at ~326 s was detected in its Swift light curves by our group (and subsequently confirmed by a Swift campaign). In this paper, we report on the analysis ... More
Energy deposition studies for the High-Luminosity Large Hadron Collider inner triplet magnetsApr 02 2015A detailed model of the High Luminosity LHC inner triplet region with new large-aperture Nb3Sn magnets, field maps, corrector packages, and segmented tungsten inner absorbers was built and implemented into the FLUKA and MARS15 codes. In the optimized ... More
X-ray emission from the luminous O-type subdwarf HD 49798 and its compact companionApr 05 2013The X-ray source RX J0648.0-4418 is the only confirmed binary system in which a compact object, most likely a massive white dwarf, accretes from a hot subdwarf companion, the bright sdO star HD 49798. The X-ray emission from this system is characterized ... More
The progenitor of a type Ia supernova with a short delay time?Sep 21 2011HD49798/RXJ0648.0-4418 is the only known X-ray binary composed of a hot subdwarf and a massive white dwarf (M=1.28+/-0.05 Msun). This system, with an orbital period of 1.55 days, is the outcome of a common envelope evolution, most likely of a pair of ... More
An ultra-massive fast-spinning white dwarf in a peculiar binary systemMar 04 2010White dwarfs typically have masses in a narrow range centered at about 0.6 solar masses (Msun). Only a few ultra-massive white dwarfs (M>1.2 Msun) are known. Those in binary systems are of particular interest because a small amount of accreted mass could ... More
The discovery of a massive white dwarf in the peculiar binary system HD 49798/RX J0648.0-4418Nov 19 2009An XMM-Mewton observation performed in May 2008 has confirmed that the 13 seconds pulsations in the X-ray binary HD 49798/RX J0648.0-4418 are due to a rapidly rotating white dwarf. From the pulse time delays induced by the 1.55 days orbital motion, and ... More
Lectures on Deformation quantization of Poisson manifoldsJul 13 2012Jul 18 2012These notes are based on the course given at the School of Geometry, University Kasdi Merbah (Ouargla) 2012. The aim of the course was the deformation quantization of Poisson Lie groups. In these notes we only review Kontsevich's formality theorem.
Poisson ReductionJun 20 2011Oct 09 2013In this paper we develope a theory of reduction for classical systems with Poisson Lie groups symmetries using the notion of momentum map introduced by Lu. The local description of Poisson manifolds and Poisson Lie groups and the properties of Lu's momentum ... More
A Personal Point of View about Scientific Discussions on Free WillFeb 15 2012I briefly present a personal view about alleged scientific results on free will.
Fermi at Los Alamos and the early Britain's way to nuclear energyMay 02 2008A novel recovery of some important documents related to the Fermi course on neutron physics, held at Los Alamos in 1945, is announced. Its relevance for the effective launch of a British nuclear programme in the early postwar period, independently of ... More
Four variations on Theoretical Physics by Ettore MajoranaApr 07 2006An account is given of some topical unpublished work by Ettore Majorana, revealing his very deep intuitions and skilfulness in Theoretical Physics. The relevance of the quite unknown results obtained by him is pointed out as well.
An unknown story: Majorana and the Pauli-Weisskopf scalar electrodynamicsOct 31 2007An account is given of an interesting but unknown theory by Majorana regarding scalar quantum electrodynamics, elaborated several years before the known Pauli-Weisskopf theory. Theoretical calculations and their interpretation are given in detail, together ... More
The action of neutrino ponderomotive force on supernova dynamicsFeb 16 1999Sep 02 1999Collective interactions of a beam of neutrinos/antineutrinos traversing a dense magnetized plasma of electrons/positrons, protons and neutrons are studied with particular reference to the case of a Supernova. We find that the ponderomotive force exerted ... More
Compact Tetraquark Interpretation of the XYZ StatesDec 14 2015The past decade witnessed the observation of several exotic charmonium-like resonances, some of which are manifestly non-qqbar mesons. We review one of the most popular interpretations of such states: the compact tetraquark in the constituent diquark-antidiquark ... More
Complex Parameters in Quantum MechanicsJul 21 1998Nov 04 1998The Schrodinger equation for stationary states in a central potential is studied in an arbitrary number of spatial dimensions, say q. After transformation into an equivalent equation, where the coefficient of the first derivative vanishes, it is shown ... More
Mathematical Structures of Space-TimeJul 01 1995At first we introduce the space-time manifold and we compare some aspects of Riemannian and Lorentzian geometry such as the distance function and the relations between topology and curvature. We then define spinor structures in general relativity, and ... More
Non-Fuchsian Singularities in Quantum MechanicsJan 02 1999Oct 13 1999A modification of the spiked harmonic oscillator is studied in the case for which the perturbation potential contains both an inverse power and a linear term. It is then possible to evaluate trial functions by solving an integral equation due to the occurrence ... More
Non-Local Boundary Conditions in Euclidean Quantum GravityJun 12 1998Dec 16 1998Non-local boundary conditions for Euclidean quantum gravity are proposed, consisting of an integro-differential boundary operator acting on metric perturbations. In this case, the operator P on metric perturbations is of Laplace type, subject to non-local ... More
Euclidean Maxwell Theory in the Presence of BoundariesJun 26 1995This paper describes recent progress in the analysis of relativistic gauge conditions for Euclidean Maxwell theory in the presence of boundaries. The corresponding quantum amplitudes are studied by using Faddeev-Popov formalism and zeta-function regularization, ... More
New Perspectives in Complex General RelativityJun 07 1995In complex general relativity, Lorentzian space-time is replaced by a four-complex-dimensional complex-Riemannian manifold, with holomorphic connection and holomorphic curvature tensor. A multisymplectic analysis shows that the Hamiltonian constraint ... More
On the classical and quantum momentum mapMar 19 2012In this thesis we study the classical and quantum momentum maps and the theory of reduction. We focus on the notion of momentum map in Poisson geometry and we discuss the classification of the momentum map in this framework. Furthermore, we describe the ... More
L'utilità di una teoria inutile-Crittografia, firma digitale e teoria dei numeriFeb 14 2011The theory of numbers was supposed to be the less useful branch of mathematics. At the same time, cryptography was thought to be a military or a diplomatic issue. In this note we show how the two concepts are today strictly related and how this link affects ... More
Debunking some myths about biometric authenticationMar 01 2012Biometric authentication systems are presented as the best way to reach high security levels in controlling access to IT systems or sensitive infrastructures. But several issues are often not taken properly into account. In order for the implementation ... More
Multibarrier tunnelingSep 02 2002We study the tunneling through an arbitrary number of finite rectangular opaque barriers and generalize earlier results by showing that the total tunneling phase time depends neither on the barrier thickness nor on the inter-barrier separation. We also ... More
Classical $v_{gr} \neq c$ solutions of Maxwell equations and the tunneling photon effectNov 21 1996We propose a very simple but general method to construct solutions of Maxwell equations propagating with a group velocity $v_{gr} \neq c$. Applications to wave guides and a possible description of the known experimental evidences on photonic tunneling ... More
On the indistinguishibility of Majorana- from Dirac-neutrino propagation in a stellar mediumJul 19 1996We study, in the framework of the Standard Model, the propagation of (pure) Majorana neutrinos in a typical stellar medium and show that Majorana neutrino matter oscillations are completely indistinguishable from Dirac ones, even if in the case of no ... More
Searching for an equation: Dirac, Majorana and the othersOct 31 2011We review the non-trivial issue of the relativistic description of a quantum mechanical system that, contrary to a common belief, kept theoreticians busy from the end of 1920s to (at least) mid 1940s. Starting by the well-known works by Klein-Gordon and ... More
Again on Majorana and the Thomas-Fermi model: a comment to physics/0511222Dec 28 2005We comment on a recent paper announcing the discovery of a previously unknown publication of Ettore Majorana on the Thomas-Fermi atomic model. In pointing out that such a publication was not written by Majorana, we correct some misunderstandings and clarify ... More
Il corso di Fisica teorica di Ettore Majorana: il ritrovamento del Documento MorenoNov 22 2004Mar 10 2005We analyze in some detail the course of Theoretical Physics held by Ettore Majorana at the University of Naples in 1938, just before his mysterious disappearance. In particular we give an account of the recently retrieved "Moreno Paper", where the lecture ... More
Some remarks concerning symmetry-breaking for the Ginzburg-Landau equationOct 23 2012The correlation term, introduced in [13] to describe the interaction between very far apart vortices, governs symmetry-breaking for the Ginzburg-Landau equation in R^2 or bounded domains. It is a homogeneous function of degree (-2), and then for 2\pi/N-symmetric ... More
Euclidean Quantum Gravity in Light of Spectral GeometryJul 23 2003A proper understanding of boundary-value problems is essential in the attempt of developing a quantum theory of gravity and of the birth of the universe. The present paper reviews these topics in light of recent developments in spectral geometry, i.e. ... More
Quantized Maxwell Theory in a Conformally Invariant GaugeOct 03 1996Jun 20 1997Maxwell theory can be studied in a gauge which is invariant under conformal rescalings of the metric, and first proposed by Eastwood and Singer. This paper studies the corresponding quantization in flat Euclidean 4-space. The resulting ghost operator ... More
Hamiltonian Structure of a Friedmann-Robertson-Walker Universe with TorsionSep 06 1995We study a $R^{2}$ model of gravity with torsion in a closed Friedmann-Robertson-Walker universe. The model is cast in Hamiltonian form subtracting from the original Lagrangian the total time derivative of $f_{K}f_{R}$, where $f_{K}$ is proportional to ... More
Alpha Surfaces for Complex Space-Times with TorsionJul 01 1995This paper studies necessary conditions for the existence of alpha-surfaces in complex space-time manifolds with nonvanishing torsion. For these manifolds, Lie brackets of vector fields and spinor Ricci identities contain explicitly the effects of torsion. ... More
Quantum Field Theory from First PrinciplesJun 06 2000When quantum fields are studied on manifolds with boundary, the corresponding one-loop quantum theory for bosonic gauge fields with linear covariant gauges needs the assignment of suitable boundary conditions for elliptic differential operators of Laplace ... More
A Theory of Quantum Gravity from First PrinciplesFeb 08 2000Apr 06 2000When quantum fields are studied on manifolds with boundary, the corresponding one-loop quantum theory for bosonic gauge fields with linear covariant gauges needs the assignment of suitable boundary conditions for elliptic differential operators of Laplace ... More
New Results in Heat-Kernel Asymptotics on Manifolds with BoundaryJul 17 1998A review is presented of some recent progress in spectral geometry on manifolds with boundary: local boundary-value problems where the boundary operator includes the effect of tangential derivatives; application of conformal variations and other functorial ... More