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Learning Symmetries of Classical Integrable SystemsJun 11 2019The solution of problems in physics is often facilitated by a change of variables. In this work we present neural transformations to learn symmetries of Hamiltonian mechanical systems. Maintaining the Hamiltonian structure requires novel network architectures ... More

Simple models of classical topological paramagnetismJun 01 2016Topological phases of matter are one of the hallmarks of quantum condensed matter physics. One of their striking features is a bulk-boundary correspondence wherein the topological nature of the bulk manifests itself on boundaries via exotic massless phases. ... More

Classical topological paramagnetismJun 01 2016Apr 01 2017Topological phases of matter are one of the hallmarks of quantum condensed matter physics. One of their striking features is a bulk-boundary correspondence wherein the topological nature of the bulk manifests itself on boundaries via exotic massless phases. ... More

Topological and symmetry broken phases of Z_N parafermions in one dimensionMar 22 2013Oct 31 2013We classify the gapped phases of Z_N parafermions in one dimension and construct a representative of each phase. Even in the absence of additional symmetries besides parafermionic parity, parafermions may be realized in a variety of phases, one for each ... More

Infinite Matrix Product States for long range SU(N) spin modelsMay 12 2014Jul 18 2014We construct 1D and 2D long-range SU(N) spin models as parent Hamiltonians associated with infinite matrix product states. The latter are constructed from correlators of primary fields in the SU(N) level 1 WZW model. Since the resulting groundstates are ... More

Classical topological paramagnetismJun 01 2016Nov 21 2016Topological phases of matter are one of the hallmarks of quantum condensed matter physics. One of their striking features is a bulk-boundary correspondence wherein the topological nature of the bulk manifests itself on boundaries via exotic massless phases. ... More

Rectangular amplitudes, conformal blocks, and applications to loop modelsJul 30 2012In this paper we continue the investigation of partition functions of critical systems on a rectangle initiated in [R. Bondesan et al, Nucl.Phys.B862:553-575,2012]. Here we develop a general formalism of rectangle boundary states using conformal field ... More

Critical Behaviour of Spanning Forests on Random Planar GraphsAug 09 2016As a follow-up of previous work of the authors, we analyse the statistical mechanics model of random spanning forests on random planar graphs. Special emphasis is given to the analysis of the critical behaviour. Exploiting an exact relation with a model ... More

Effective Edge State Dynamics in the Fractional Quantum Hall EffectMay 10 2018We consider the behaviour of quantum Hall edges away from the Luttinger liquid fixed point that occurs in the low energy, large system limit. Using the close links between quantum Hall wavefunctions and conformal field theories we construct effective ... More

On the Structure of Edge State Inner Products in the Fractional Quantum Hall EffectJan 15 2018We analyse the inner products of edge state wavefunctions in the fractional quantum Hall effect, specifically for the Laughlin and Moore-Read states. We use an effective description for these inner products given by a large-$N$ expansion ansatz proposed ... More

Critical Behaviour of Spanning Forests on Random Planar GraphsAug 09 2016Dec 16 2016As a follow-up of previous work of the authors, we analyse the statistical mechanics model of random spanning forests on random planar graphs. Special emphasis is given to the analysis of the critical behaviour. Exploiting an exact relation with a model ... More

On the Structure of Edge State Inner Products in the Fractional Quantum Hall EffectJan 15 2018Apr 06 2018We analyse the inner products of edge state wavefunctions in the fractional quantum Hall effect, specifically for the Laughlin and Moore-Read states. We use an effective description for these inner products given by a large-$N$ expansion ansatz proposed ... More

Edge states and conformal boundary conditions in super spin chains and super sigma modelsJan 23 2011May 07 2011The sigma models on projective superspaces CP^{N+M-1|N} with topological angle theta=pi mod 2pi flow to non-unitary, logarithmic conformal field theories in the low-energy limit. In this paper, we determine the exact spectrum of these theories for all ... More

Conformal boundary state for the rectangular geometryOct 31 2011May 16 2012We discuss conformal field theories (CFTs) in rectangular geometries, and develop a formalism that involves a conformal boundary state for the 1+1d open system. We focus on the case of homogeneous boundary conditions (no insertion of a boundary condition ... More

Exact exponents for the spin quantum Hall transition in the presence of multiple edge channelsSep 22 2011Mar 19 2012Critical properties of quantum Hall systems are affected by the presence of extra edge channels - present, in particular, at higher plateau transitions. We study this phenomenon for the case of the spin quantum Hall transition. Using supersymmetry we ... More

Stability of the spectral gap for the Boltzmann multi-species operator linearized around non-equilibrium Maxwell distributionsNov 20 2018We consider the Boltzmann operator for mixtures with cutoff Maxwellian, hard potentials, or hard spheres collision kernels. In a perturbative regime around the global Maxwellian equilibrium, the linearized Boltzmann multi-species operator $\mathbf{L}$ ... More

The Picard group of the universal abelian variety and the Franchetta conjecture for abelian varietiesMar 30 2016Apr 04 2016We compute the Picard group of the universal abelian variety over the moduli stack $\mathscr A_{g,n}$ of principally polarized abelian varieties over $\mathbb{C}$ with a symplectic principal level $n$-structure. We then prove that over $\mathbb{C}$ the ... More

The Brauer group of the universal moduli space of vector bundles over smooth curvesMay 14 2018Sep 24 2018We compute the Brauer group of the universal moduli stack of vector bundles on (possibly marked) smooth curves of genus at least three over the complex numbers. As consequence, we obtain an explicit description of the Brauer group of the smooth locus ... More

On the solutions of the Cartan equation in Metric Affine GravitySep 28 2000In the Tucker-Wang approach to Metric Affine gravity we review some particular solutions of the Cartan equation for the non-riemannian part of the connection. As application we show how a quite general non Riemannian model gives a Proca type equation ... More

Non-Invariant Ground States, Thermal Average, and generalized Fermionic StatisticsOct 11 1999Nov 09 1999We present an approach to generalised fermionic statistics which relates the existence of a generalised statistical behaviour to non-invariant ground states. Considering the thermal average of an operatorial generalization of the Heisenberg algebra, we ... More

The Prabhakar or three parameter Mittag--Leffler function: theory and applicationAug 24 2017Oct 11 2017The Prabhakar function (namely, a three parameter Mittag-Leffler function) is investigated. This function plays a fundamental role in the description of the anomalous dielectric properties in disordered materials and heterogeneous systems manifesting ... More

Numerical simulations of flow reversal in Rayleigh--Bénard convectionDec 20 2006We investigate numerically the statistical properties of the large scale flow in Rayleigh--B\'enard convection. By using an external random perturbation on the temperature field, we were able to decrease the effective Prandtl number of the flow while ... More

Superconformal Vacua in N=2 Usp(4) Gauge TheoriesFeb 26 2004We study the dynamics of a confining vacuum in N=2 USp(4) gauge theory with n_f=4. The vacuum appears to be a deformed conformal theory with nonabelian gauge symmetry. The low-energy degrees of freedom consist of four nonabelian magnetic monopole doublets ... More

Pure scaling operators at the integer quantum Hall plateau transitionDec 20 2013May 13 2014Stationary wave functions at the transition between plateaus of the integer quantum Hall effect are known to exhibit multi-fractal statistics. Here we explore this critical behavior for the case of scattering states of the Chalker-Coddington model with ... More

Nonclassical dynamics of Bose condensates in an optical lattice in the superfluid regimeJun 14 2007A condensate in an optical lattice, prepared in the ground state of the superfluid regime, is stimulated first by suddenly increasing the optical lattice amplitude and then, after a waiting time, by abruptly decreasing this amplitude to its initial value. ... More

Majorana and the Infinite Component Wave EquationsOct 23 2006I review the paper of Majorana about relativistic particles with arbitrary spin written in 1932. The main motivation for this papers was the dissatisfaction about the negative energy solutions of the Dirac equation. As such, the paper became immediately ... More

Color Superconductivity in High Density QCDDec 15 2005Jan 18 2006We describe the effects of the strange quark mass and of color and electric neutrality on the superconducing phases of QCD. We discuss various phases pointing out the corresponding problems, typically arising from a chromomagnetic instability. We show ... More

Neumark Operators and Sharp Reconstructions, the finite dimensional caseMay 17 2010A commutative POV measure $F$ with real spectrum is characterized by the existence of a PV measure $E$ (the sharp reconstruction of $F$) with real spectrum such that $F$ can be interpreted as a randomization of $E$. This paper focuses on the relationships ... More

Bounded cohomology of discrete groupsOct 26 2016Bounded cohomology of groups was first defined by Johnson and Trauber during the seventies in the context of Banach algebras. As an independent and very active research field, however, bounded cohomology started to develop in 1982, thanks to the pioneering ... More

Automorphisms of the UHF algebra that do not extend to the Cuntz algebraMar 09 2010Automorphisms of the canonical core UHF-subalgebra F_n of the Cuntz algebra O_n do not necessarily extend to automorphisms of O_n. Simple examples are discussed within the family of infinite tensor products of (inner) automorphisms of the matrix algebras ... More

New Physics at the LHC: Strong vs Weak symmetry breakingAug 25 2009What kind of New Physics, if any, we expect to discover at the LHC? I will try to address this formidable question by re-formulating it as follows: is the breaking of the electroweak symmetry strong or weak ?

Neutrino mass variability due to nonminimal coupling to spacetime curvature in neutrinophilic two-Higgs-doublet modelsOct 18 2013In neutrinophilic two-Higgs-doublet models, neutrinos acquire mass due to a Higgs field with vacuum expectation value of the order of 10^{-2} eV, corresponding to a Compton wavelength in the 10 micrometer range. This creates a situation in which nonminimal ... More

Are quantum measurements on macroscopic bodies feasible?Mar 26 2010Mar 29 2010The possibility to test quantum measurement theories is discussed in the more phenomenological framework of the quantum nondemolition theory. A simple test of the hypothesis of the state vector collapse is proposed by looking for deviations from the Boltzmann ... More

BlackfoldsJun 10 2011This is an introduction to the blackfold effective worldvolume theory for the dynamics of black branes, as well as its use as an approximate method for the construction of new black hole solutions. We also explain how the theory is useful for the analysis ... More

Black Hole Production at a TeVFeb 25 2003In this talk I briefly discuss some features of a striking signature of TeV quantum gravity/strings and large extra dimensions: the production of exotic objects such as black holes, and their stringy precursors, the string resonances at large masses which ... More

Black Hole Radiation On and Off the BraneSep 18 2000Sep 26 2000After a brief review of the description of black holes on branes, we examine the evaporation of a small black hole on a brane in a world with large extra dimensions. We show that, contrary to previous claims, most of the energy is radiated into the modes ... More

Black hole entropy as entanglement entropy: a holographic derivationMar 10 2006Apr 26 2006We study the possibility that black hole entropy be identified as entropy of entanglement across the horizon of the vacuum of a quantum field in the presence of the black hole. We argue that a recent proposal for computing entanglement entropy using AdS/CFT ... More

Probing dark energy with future surveysJul 21 2006I review the observational prospects to constrain the equation of state parameter of dark energy and I discuss the potential of future imaging and redshift surveys. Bayesian model selection is used to address the question of the level of accuracy on the ... More

Cosmic Microwave Background Anisotropies: Beyond Standard ParametersOct 05 2004In the first part of this work, I review the theoretical framework of cosmological perturbation theory necessary to understand the generation and evolution of cosmic microwave background (CMB) anisotropies. Using analytical and numerical techniques, in ... More

Optical correlation techniques for the investigation of colloidal systemsJun 06 2013This review aims to provide a simple introduction to the application of optical correlation methods in colloidal science. In particular, I plan to show that full appraisal of the intimate relation between light scattering and microscopy allows designing ... More

X-ray properties of spiral galaxiesNov 01 2002X-ray studies of nearby spiral galaxies with star formation allow us to investigate temperature and spatial distribution of the hot diffuse plasma, and to carry out individual and statistical studies of different classes of discrete sources (low- and ... More

The optical emission lines as a probe of state transitions in black-hole candidatesJan 17 2001Optical spectroscopic studies of emission lines in black-hole candidates can help us investigate state transitions in those systems. Changes in the optical line profiles reflect changes in the geometry of the accretion flow, usually associated with X-ray ... More

Galactic positrons and electrons from astrophysical sources and dark matterOct 14 2009A very interesting puzzle about the origin of electron and positron cosmic rays is deduced from the latests experimental results. We model the propagation of such cosmic rays in terms of a successfully tested two--zone propagation model. Several theoretical ... More

Power Consumption of Virtualization Technologies: an Empirical InvestigationNov 04 2015Virtualization is growing rapidly as a result of the increasing number of alternative solutions in this area, and of the wide range of application field. Until now, hypervisor-based virtualization has been the de facto solution to perform server virtualization. ... More

Computing Quasidegrees of A-graded ModulesOct 26 2015We describe the main functions of the Macaulay2 package Quasidegrees. The purpose of this package is to compute the quasidegree set of a finitely generated A-graded module presented as the cokernel of a monomial matrix. We provide examples with motivation ... More

Relaxation models for Single Helical Reversed Field Pinch plasmasSep 24 2015Oct 26 2016In this paper a relaxation theory, proposed several years ago for plasmas where a single dominant mode is present, is revisited. The solutions of the related eigenvalue problem are numerically calculated and discussed. Although these solutions are very ... More

Measuring Inequality and SegregationAug 05 2015In this paper, I introduce the Divergence Index, a conceptually intuitive and methodologically rigorous measure of inequality and segregation. The index measures the difference between a distribution of interest and another empirical, theoretical, or ... More

Cosmic Rays: What Gamma Rays Can SayDec 23 2014We will review the main channels of gamma ray emission due to the acceleration and propagation of cosmic rays, discussing the cases of both galactic and extra-galactic cosmic rays and their connection with gamma rays observations.

High-energy density implications of a gravitoweak unification scenarioDec 15 2014We discuss how a scenario recently proposed for the morphing of macroscopic gravitation into weak interactions at the attometer scale affects our current understanding of high-energy density phenomena. We find that the Yukawa couplings of the fundamental ... More

Cohomological invariants of hyperelliptic curves of genus 3Sep 08 2016We compute the cohomological invariants with coefficients in $\mathbb{Z}/p\mathbb{Z}$ of the stack $\mathscr{H}_3$ of hyperelliptic curves of genus $3$ over an algebraically closed field.

The Principle of Minimal Resistance in Non-Equilibrium ThermodynamicsJan 21 2015Analytical models describing the motion of colloidal particles in given velocity fields are presented. In addition to local approaches, leading to well known master equations such as the Langevin and the Fokker-Planck equations, a global description based ... More

On symmetries of N=(4,4) sigma models on T^4Mar 10 2014Aug 08 2014Motivated by an analogous result for K3 models, we classify all groups of symmetries of non-linear sigma models on a torus T^4 that preserve the N=(4,4) superconformal algebra. The resulting symmetry groups are isomorphic to certain subgroups of the Weyl ... More

Entropy of Coherent ExcitationsJan 08 2019We provide a rigorous, explicit formula for the vacuum relative entropy of a coherent state on wedge local von Neumann algebras associated with a free, neutral quantum field theory on the Minkowski spacetime of arbitrary spacetime dimension. The second ... More

Random generation of optimal saturated designsMar 26 2013Mar 28 2013Efficient algorithms for searching for optimal saturated designs are widely available. They maximize a given efficiency measure (such as D-optimality) and provide an optimum design. Nevertheless, they do not guarantee a \emph{global} optimal design. Indeed, ... More

Bn-generalized geometry and G2(2)-structuresJan 15 2013Jul 29 2013We introduce the concept of G2(2)-structure on an orientable 3-manifold M using the setting of generalized geometry of type Bn, study their local deformation by making use of a Moser-type argument, and give a description of the cone of G2(2)-structures. ... More

A study of the apsidal angle and a proof of monotonicity in the logarithmic potential caseSep 06 2013This paper concerns the behaviour of the apsidal angle for orbits of central force system with homogenous potential of degree $-2\leq \alpha\leq 1$ and logarithmic potential. We derive a formula for the apsidal angle as a fixed-end points integral and ... More

Hyperbolicity for log canonical pairs and the cone theoremOct 09 2014Oct 01 2017Given a log canonical pair $(X, \Delta)$, we show that $K_X+\Delta$ is nef assuming there is no non constant map from the affine line with values in the open strata of the stratification induced by the non-klt locus of $\Delta$. This implies a generalization ... More

A Multispin Algorithm for the Kob-Andersen Stochastic Dynamics on Regular LatticesOct 14 2017The aim of the paper is to propose an algorithm based on the Multispin Coding technique for the Kob-Andersen glassy dynamics. We first give motivations to speed up the numerical simulation in the context of spin glass models [M. Mezard, G. Parisi, M. ... More

Bubbles and Knots in the Kinematical Structure of the Bipolar Planetary Nebula NGC 2818Mar 27 2012High-resolution Hubble Space Telescope (HST) archive imaging and high-dispersion spectroscopy are used to study the complex morphological and kinematical structure of the planetary nebula, NGC 2818. We analyze narrow band H{\alpha}, [O III], [N II], [S ... More

Microcanonical Entropy and Dynamical Measure of Temperature for Systems with Two First IntegralsApr 30 2010Jul 19 2011We consider a generic classical many particle system described by an autonomous Hamiltonian $H(x^{_1},...,x^{_{N+2}})$ which, in addition, has a conserved quantity $V(x^{_1},...,x^{_{N+2}})=v$, so that the Poisson bracket $\{H,V \}$ vanishes. We derive ... More

A topological approach to leading monomial idealsAug 02 2010Jun 01 2011We introduce a very natural topology on the set of total orderings of monomials of any algebra having a countable basis over a field. This topological space and some notable subspaces are compact. This topological framework allows us to deduce some finiteness ... More

Critical behaviour of a non-local φ^{4} field theory and asymptotic freedomJul 10 2018The critical behaviour of a non-local scalar field theory is studied. This theory has a non-local kinetic term which involves a real power 1-2\alpha of the Laplacian. The interaction term is the usual local \phi^{4} interaction. The lowest order Feynman ... More

Matching electroweak fermion loops onto the Fermi theory without higher dimensional operatorsFeb 05 2019We match, at the one-fermion-loop accuracy, the electroweak theory onto the nonrenormalizable four-fermion Fermi model. The matching is performed without introducing higher dimensional interaction terms in the Fermi Lagrangian. As a result, an effective ... More

On the Picard numbers of abelian varieties in positive characteristicMar 23 2018In this paper, we study the set $R_g^{(p)}$ of possible Picard numbers of abelian varieties of dimension $g$ over algebraically closed fields of characteristic $p>0$. We show that many of the results for complex abelian varieties have analogues in positive ... More

Entropy distribution of localised statesSep 10 2018Sep 18 2018We study the geometric distribution of the relative entropy of a charged localised state in Quantum Field Theory. With respect to translations, the second derivative of the vacuum relative entropy is zero out of the charge localisation support and positive ... More

Scaling Distances on Finitely Ramified FractalsAug 31 2015Nov 06 2015In previous papers by A. Kameyama and by J. Kigami distances on fractals have been discussed having two different but similar properties. One property is that the maps defining the fractal are Lipschitz of prescribed constants less than 1, the other is ... More

A Lie based 4-dimensional higher Chern-Simons theoryDec 18 2015Feb 22 2016We present and study a model of 4-dimensional higher Chern-Simons theory, special Chern-Simons (SCS) theory, instances of which have appeared in the string literature, whose symmetry is encoded in a skeletal semistrict Lie 2-algebra constructed from a ... More

On higher holonomy invariants in higher gauge theory IMay 08 2015This is the first of a series of two technical papers devoted to the analysis of holonomy invariants in strict higher gauge theory with end applications in higher Chern--Simons theory. For a flat 2--connection, we define the 2-holonomy of surface knots ... More

Exact renormalization group and effective action: a Batalin--Vilkovisky algebraic formulationNov 21 2017Dec 27 2017In the present paper, which is a mathematical follow--up of [16] taking inspiration from [11], we present an abstract formulation of exact renormalization group (RG) in the framework of Batalin--Vilkovisky (BV) algebra theory. In the first part, we work ... More

Ultra High Energy Cosmic Rays and the Highest Energies UniverseMay 20 2019We will discuss the main relevant aspects of the physics of ultra high energy cosmic rays. After a short recap of the experimental evidences, we will review theoretical models aiming at describing the sources of these extremely energetic particles opening ... More

Search for Antimatter in Space with the Alpha Magnetic SpectrometerJul 12 1999The Alpha Magnetic Spectrometer (AMS) is a state of the art particle physics experiment for the extraterrestrial study of antimatter, matter and missing matter. AMS successfully completed the precursor STS91 Discovery flight (June 2nd-12th, 1998), completing ... More

Superelliptic Josephson Tunnel JunctionsNov 07 2016The most important practical characteristic of a Josephson junction is its critical current. The shape of the junction determines the specific form of the magnetic-field dependence of the its Josephson current. Here we address the magnetic diffraction ... More

Bounded cohomology of discrete groupsOct 26 2016Nov 03 2016Bounded cohomology of groups was first defined by Johnson and Trauber during the seventies in the context of Banach algebras. As an independent and very active research field, however, bounded cohomology started to develop in 1982, thanks to the pioneering ... More

Muonic hydrogen as a quantum gravimeterSep 01 2015High precision spectroscopy of muonic hydrogen has recently led to an anomaly in the Lamb shift, which has been parametrized in terms of a proton charge radius differing by seven standard deviations from the CODATA value. We show how this anomaly may ... More

On weak interactions as short-distance manifestations of gravityDec 15 2014We conjecture that weak interactions are peculiar manifestations of quantum gravity at the Fermi scale, and that the Fermi constant is related to the Newtonian constant of gravitation.In this framework one may understand the violations of fundamental ... More

The Spatial Context of Residential SegregationSep 11 2015Feb 15 2016Residential segregation is defined in a variety of ways to address a common concern: to what extent do social groups reside in separate or distinct places. The spatial pattern of segregation varies widely across cities, and distinct spatial patterns can ... More

Mathieu Moonshine and symmetries of K3 sigma modelsJan 30 2012A recent observation by Eguchi, Ooguri and Tachikawa (EOT) suggests a relationship between the largest Mathieu group M24 and the elliptic genus of K3. This correspondence would be naturally explained by the existence of a non-linear sigma-model on K3 ... More

The isocurvature fraction after WMAP 3-year dataAug 04 2006Mar 02 2007I revisit the question of the adiabaticity of initial conditions for cosmological perturbations in view of the 3-year WMAP data. I focus on the simplest alternative to pure adiabatic conditions, namely a superposition of the adiabatic mode and one of ... More

Gravitational collapse of a macroscopic string by a Newtonian description including the effect of gravitational radiationFeb 12 2007Feb 16 2007We make an attempt to dynamically study, in four space-time dimensions, the classical gravitational collapse of a macroscopic circular fundamental string, by a truncation of the Einstein equations that suppresses retarded features but keeps the main self-gravity ... More

Stochastic Resonance: from climate to biologyFeb 05 2007In this paper I will review some basic aspects of the mechanism of stochastic resonance. Stochastic resonance was first introduced as a possible mechanism to explain long term climatic variation. Since then, there have been many applications of stochastic ... More

Flow reversal in a simple dynamical model of turbulenceOct 21 2004In this paper, we study a simple hydrodynamical model showing abrupt flow reversals at random times. For a suitable range of parameters, we show that the dynamics of flow reversal is accurately described by stochastic differential equations, where the ... More

A holographic composite Higgs modelSep 15 2006If the Higgs boson has a composite nature, it might be the 4-dimensional hologram of a gauge field living in a warped extra dimension. In this talk I discuss a minimal, calculable model that passes all electroweak precision tests, included that from Z->bb, ... More

Black diholesJun 21 1999Mar 24 2000We present and analyze exact solutions of the Einstein-Maxwell and Einstein-Maxwell-Dilaton equations that describe static pairs of oppositely charged extremal black holes, i.e., black diholes. The holes are suspended in equilibrium in an external magnetic ... More

Exact Gravitational Shockwaves and Planckian Scattering on BranesApr 02 2001Apr 30 2001We obtain a solution describing a gravitational shockwave propagating along a Randall-Sundrum brane. The interest of such a solution is twofold: on the one hand, it is the first exact solution for a localized source on a Randall-Sundrum three-brane. On ... More

Born-Infeld Strings Tunneling to D-branesNov 14 1997Recent work on solutions to the Born-Infeld theory used to describe D-branes suggests that fundamental strings can be viewed, in a certain limit, as D-branes whose worldvolumes have collapsed to string-like configurations. Here we address the possibility ... More

Proton radius puzzle and quantum gravity at the Fermi scaleDec 12 2013We show how the "proton radius puzzle" emerging from the measurement of the Lamb shift in muonic hydrogen may be solved by means of a binding energy contribution due to an effective Yukawian gravitational potential related to charged weak interactions. ... More

The cosmic X-ray background: abundance and evolution of hidden black holesApr 12 2013The growth of supermassive black holes across cosmic time leaves a radiative imprint recorded in the X-ray background (XRB). The XRB spectral shape suggests that a large population of distant, hidden nuclei must exist, which are now being revealed at ... More

Recipes for ULX formation: necessary ingredients and garnishmentsNov 05 2006I summarize the main observational features that seem to recur more frequently in the ULX population. I speculate that two of the most important physical requirements for ULX formation are low metal abundance, and clustered star formation triggered by ... More

Eccentricity of HLX-1Oct 15 2012I compare the outer radius of the accretion disc in the intermediate-mass black hole candidate HLX-1 as estimated from the UV/optical continuum, with the values estimated from its outburst decline timescales. I fit the Swift 2010 outburst decline lightcurve ... More

Voids and overdensities of coupled Dark EnergyMar 03 2009We investigate the clustering properties of dynamical Dark Energy even in association of a possible coupling between Dark Energy and Dark Matter. We find that within matter inhomogeneities, Dark Energy migth form voids as well as overdensity depending ... More

Bayesian Methods in CosmologyJan 05 2017These notes aim at presenting an overview of Bayesian statistics, the underlying concepts and application methodology that will be useful to astronomers seeking to analyse and interpret a wide variety of data about the Universe. The level starts from ... More

Induced Action for Conformal Higher Spins from Worldline Path IntegralsSep 04 2017Nov 29 2017Conformal higher spin (CHS) fields, despite being non unitary, provide a remarkable example of a consistent interacting higher spin theory in flat space background, that is local to all orders. The non-linear action is defined as the logarithmically UV ... More

An infinite family of hyperbolic graph complements in S^3Sep 23 2003For any g>1 we construct a graph G_g in S^3 whose exterior M_g supports a complete finite-volume hyperbolic structure with one toric cusp and a connected geodesic boundary of genus g. We compute the canonical decomposition and the isometry group of M_g, ... More

Slow decay of Gibbs measures with heavy tailsNov 17 2008We consider Glauber dynamics reversible with respect to Gibbs measures with heavy tails. Spins are unbounded. The interactions are bounded and finite range. The self potential enters into two classes of measures, $\kappa$-concave probability measure and ... More

Mathematical consistence of the surface entropyNov 30 2018In a recent paper, we have suggested to use of the surface entropy, namely the logarithm of the area of a hypersurface of constant energy in the phase space, as an expression for the thermodynamic microcanonical entropy, in place of the standard definition ... More

Quotients of the square of a curve by a mixed action, further quotients and Albanese morphismsAug 05 2017May 21 2018We study mixed surfaces, the minimal resolution S of the singularities of a quotient of the "square" of a curve by a finite group G of automorphisms that contains elements not preserving the factors. We study them through the "further quotients" by G' ... More

Some comments on symmetric orbifolds of K3Feb 28 2019May 21 2019We consider two dimensional $\mathcal{N}=(4,4)$ superconformal field theories in the moduli space of symmetric orbifolds of K3. We complete a classification of the discrete groups of symmetries of these models, conditional to a series of assumptions and ... More

Small systems at the LHCApr 10 2018In these proceedings, I report on a selection of recent LHC results in small systems from ALICE, ATLAS and CMS experiments. Due to the fact that the investigation of QCD in small systems at high multiplicity is becoming an increasingly large subject, ... More

Current with "wrong" sign and phase transitionsOct 10 2018We prove that under certain conditions, phase separation is enough to sustain a regime in which current flows along the concentration gradient, a phenomenon which is known in the literature as \textit{uphill diffusion}. The model we consider here is a ... More

Back-of-the-envelope swaptions in a very parsimonious multicurve interest rate modelDec 18 2017We propose an elementary model to price European physical delivery swaptions in multicurve setting with a simple exact closed formula. The proposed model is very parsimonious: it is a three-parameter multicurve extension of the two-parameter Hull-White ... More