Results for "Fabio Riccioni"

total 3312took 0.12s
Low-energy structure of six-dimensional open-string vacuaMar 18 2002This dissertation reviews some properties of the low-energy effective actions for six dimensional open-string models. The first chapter is a pedagogical introduction about supergravity theories. In the second chapter closed strings are analyzed, with ... More
Tensor Multiplets in Six-Dimensional (2,0) SupergravityDec 17 1997We construct the complete coupling of $(2,0)$ supergravity in six dimensions to $n$ tensor multiplets, extending previous results to all orders in the fermi fields. The truncation to $(1,0)$ supergravity coupled to tensor multiplets exactly reproduces ... More
The very-extended tromboneJan 11 2010Mar 24 2010Starting from the very-extended Kac-Moody algebra $E_{11}$, we consider the algebra $E_{11,D}^{local}$, obtained by adding to the non-negative level $E_{11}$ generators the $D$-dimensional momentum operator and an infinite set of additional generators ... More
Abelian Vectors and Self-Dual Tensors in Six-Dimensional SupergravityOct 29 1999Nov 27 2000In this note we describe the most general coupling of {\it abelian} vector and tensor multiplets to six-dimensional $(1,0)$ supergravity. As was recently pointed out, it is of interest to consider more general Chern-Simons couplings to abelian vectors ... More
Local E(11) and the gauging of the trombone symmetryJan 08 2010Mar 17 2010In any dimension, the positive level generators of the very-extended Kac-Moody algebra $E_{11}$ with completely antisymmetric spacetime indices are associated to the form fields of the corresponding maximal supergravity. We consider the local $E_{11}$ ... More
Truncations of the D9-brane action and type-I stringsJan 06 2003Jan 17 2003The low-energy effective action of type-I superstring theory in ten dimensions is obtained performing a truncation of type-IIB supergravity in a background where D9-branes are present. The open sector corresponds to the first order in the low-energy expansion ... More
All Couplings of Minimal Six-dimensional SupergravityJan 11 2001We describe the complete coupling of $(1,0)$ six-dimensional supergravity to tensor, vector and hypermultiplets. The generalized Green-Schwarz mechanism implies that the resulting theory embodies factorized gauge and supersymmetry anomalies, to be disposed ... More
E(11)-extended spacetime and gauged supergravitiesDec 11 2007Feb 19 2008We formulate all the five dimensional gauged maximal supergravity theories as non-linear realisations of the semi-direct product of E_{11} and a set of generators which transform according to the first fundamental representation l of E_{11}. The latter ... More
Self-dual Tensors in Six-Dimensional SupergravityDec 04 1998Jan 25 1999We review some properties of the field equations of six-dimensional (1,0) supergravity coupled to tensor and vector multiplets, and in particular their relation to covariant and consistent anomalies and a peculiar Noether identity for the energy-momentum ... More
The E_{11} origin of all maximal supergravitiesMay 07 2007Starting from the eleven dimensional E_{11} non-linear realisation of M-theory we compute all possible forms, that is objects with totally antisymmetrised indices, that occur in four dimensions and above as well as all the 1-forms and 2-forms in three ... More
Dual fields and E_{11}Dec 01 2006We show that the adjoint representation of E_{11} contains generators corresponding to the infinite possible dual descriptions of the bosonic on-shell degrees of freedom of eleven dimensional supergravity. We also give an interpretation for the fields ... More
Non-geometric orbifolds and wrapping rulesJul 21 2014We show that the number of half-supersymmetric p-branes in the Type II theories compactified on orbifolds is determined by the wrapping rules recently introduced, provided that one accounts correctly for both geometric and non-geometric T-dual configurations. ... More
Local E(11)Feb 26 2009Mar 16 2009We give a method of deriving the field-strengths of all massless and massive maximal supergravity theories in any dimension starting from the Kac-Moody algebra $E_{11}$. Considering the subalgebra of $E_{11}$ that acts on the fields in the non-linear ... More
Consistent and covariant anomalies in six-dimensional supergravityJun 16 1998Jul 03 1998In this note we clarify some issues in six-dimensional (1,0) supergravity coupled to vector and tensor multiplets. In particular, we show that, while the low-energy equations embody tensor-vector couplings that contribute only to gauge anomalies, the ... More
Some Properties of Tensor Multiplets in Six-Dimensional SupergravityNov 11 1997We review some results on the complete coupling between tensor and vector multiplets in six-dimensional $(1,0)$ supergravity.
Massive higher spins and holographyJan 11 2006We review recent progress towards the understanding of higher spin gauge symmetry breaking in AdS space from a holographic vantage point. According to the AdS/CFT correspondence, N=4 SYM theory at vanishing coupling constant should be dual to a theory ... More
Geometric Couplings and Brane Supersymmetry BreakingJul 11 2001Sep 20 2001Orientifold vacua allow the simultaneous presence of supersymmetric bulks, with one or more gravitinos, and non-supersymmetric combinations of BPS branes. This ``brane supersymmetry breaking'' raises the issue of consistency for the resulting gravitino ... More
Dual doubled geometryJun 01 2011We probe doubled geometry with dual fundamental branes, i.e. solitons. Restricting ourselves first to solitonic branes with more than two transverse directions we find that the doubled geometry requires an effective wrapping rule for the solitonic branes ... More
The D-brane U-scanSep 08 2011We consider the D-branes that occur in IIA/IIB string theory compactified on a torus. We review how a general expression for the Wess-Zumino term of such branes is derived. We also review the method to determine the D-brane Wess-Zumino term in a U-duality ... More
Branes and wrapping rulesAug 25 2011We show that the branes of ten-dimensional IIA/IIB string theory must satisfy, upon toroidal compactification, specific wrapping rules in order to reproduce the number of supersymmetric branes that follows from a supergravity analysis. The realization ... More
Heterotic wrapping rulesOct 04 2012Oct 18 2012We show that the same wrapping rules that have been derived for the branes of IIA and IIB string theory also apply to the branes of the toroidally compactified heterotic string theory. Moreover, we show that applying these wrapping rules to the IIA theory ... More
String Solitons and T-dualityFeb 04 2011Jun 23 2011We construct for arbitrary dimensions a universal T-duality covariant expression for the Wess-Zumino terms of supersymmetric String Solitons in toroidally compactified string theories with 32 supercharges. The worldvolume fields occurring in the effective ... More
D-Brane Wess-Zumino Terms and U-DualitySep 23 2010Oct 20 2010We construct gauge-invariant and U-duality covariant expressions for Wess-Zumino terms corresponding to general Dp-branes (for any p<D) in arbitrary 2<D<11 dimensions. A distinguishing feature of these Wess-Zumino terms is that they contain twice as many ... More
On the fermionic Grande Bouffe: more on higher spin symmetry breaking in AdS/CFTAug 11 2005Aug 25 2005We discuss fermionic higher spin gauge symmetry breaking in AdS space from a holographic perspective. Analogously to the recently discussed bosonic case, the higher spin Goldstino mode responsible for the symmetry breaking has a non-vanishing mass in ... More
Real weights, bound states and duality orbitsJan 27 2015Nov 13 2015We show that the duality orbits of extremal black holes in supergravity theories with symmetric scalar manifolds can be derived by studying the stabilizing subalgebras of suitable representatives, realized as bound states of specific weight vectors of ... More
Real forms of very extended Kac-Moody algebras and theories with eight supersymmetriesJan 17 2008Feb 19 2008We consider all theories with eight supersymmetries whose reduction to three dimensions gives rise to scalars that parametrise symmetric manifolds. We conjecture that these theories are non-linear realisations of very-extended Kac-Moody algebras for suitable ... More
Brane orbitsJan 27 2012We complete the classification of half-supersymmetric branes in toroidally compactified IIA/IIB string theory in terms of representations of the T-duality group. As a by-product we derive a last wrapping rule for the space-filling branes. We find examples ... More
Exceptional ReductionsDec 28 2010Mar 11 2011Starting from basic identities of the group E8, we perform progressive reductions, namely decompositions with respect to the maximal and symmetric embeddings of E7xSU(2) and then of E6xU(1). This procedure provides a systematic approach to the basic identities ... More
Branes, Weights and Central ChargesMar 01 2013Dec 18 2014We study the properties of half-supersymmetric branes in string theory with 32 supercharges from a purely group-theoretical point of view using the U-duality symmetry of maximal supergravity and the R-symmetry of the corresponding supersymmetry algebra. ... More
Exotic Dual of Type II Double Field TheoryDec 08 2016We perform an exotic dualization of the Ramond-Ramond fields in type II double field theory, in which they are encoded in a Majorana-Weyl spinor of O(D,D). Starting from a first-order master action, the dual theory in terms of a tensor-spinor of O(D,D) ... More
Towards a classification of branes in theories with eight superchargesFeb 11 2014We provide a classification of half-supersymmetric branes in quarter-maximal supergravity theories with scalars parametrising coset manifolds. Guided by the results previously obtained for the half-maximal theories, we are able to show that half-supersymmetric ... More
The E(11) origin of all maximal supergravities - the hierarchy of field-strengthsJun 05 2009Oct 01 2009Starting from $E_{11}$ and the space-time translations we construct an algebra that promotes the global $E_{11}$ symmetries to local ones, and consider all its possible massive deformations. The Jacobi identities imply that such deformations are uniquely ... More
Duality Symmetries and G^{+++} TheoriesJun 25 2007Feb 26 2008We show that the non-linear realisations of all the very extended algebras G^{+++}, except the B and C series which we do not consider, contain fields corresponding to all possible duality symmetries of the on-shell degrees of freedom of these theories. ... More
$P$ fluxes and exotic branesOct 25 2016We consider the ${\cal N}=1$ superpotential generated in type-II orientifold models by non-geometric fluxes. In particular, we focus on the family of $P$ fluxes, that are related by T-duality transformations to the S-dual of the $Q$ flux. We determine ... More
Supersymmetric Domain WallsJun 25 2012We classify the half-supersymmetric "domain walls", i.e. branes of codimension one, in toroidally compactified IIA/IIB string theory and show to which gauged supergravity theory each of these domain walls belong. We use as input the requirement of supersymmetric ... More
Dual Double Field TheoryMar 23 2016Jun 02 2016We present the dual formulation of double field theory at the linearized level. This is a classically equivalent theory describing the duals of the dilaton, the Kalb-Ramond field and the graviton in a T-duality or O(D,D) covariant way. In agreement with ... More
The different faces of branes in Double Field TheoryMar 13 2019We show how the Wess-Zumino terms of the different branes in string theory can be embedded within double field theory. Crucial ingredients in our construction are the identification of the correct brane charge tensors {and the use of the} double field ... More
IIB Supergravity RevisitedJun 01 2005Jan 17 2006We show in the SU(1,1)-covariant formulation that IIB supergravity allows the introduction of a doublet and a quadruplet of ten-form potentials. The Ramond-Ramond ten-form potential which is associated with the SO(32) Type I superstring is in the quadruplet. ... More
SL(2,R)-invariant IIB Brane ActionsNov 03 2006Jan 18 2007We give a universal SL(2,R)-invariant expression for all IIB p-brane actions with p=-1,1,3,5,7,9. The Wess-Zumino terms in the brane actions are determined by requiring (i) target space gauge invariance and (ii) the presence of a single Born-Infeld vector. ... More
Dual Gravity and MatterMar 13 2008Mar 27 2008We consider the problem of finding a dual formulation of gravity in the presence of non-trivial matter couplings. In the absence of matter a dual graviton can be introduced only for linearised gravitational interactions. We show that the coupling of linearised ... More
IIA Ten-forms and the Gauge Algebras of Maximal Supergravity TheoriesFeb 27 2006Jul 11 2006We show that IIA supergravity can be extended with two independent 10-form potentials. These give rise to a single BPS IIA 9-brane. We investigate the bosonic gauge algebra of both IIA and IIB supergravity in the presence of 10-form potentials and point ... More
IIB Nine-branesJan 18 2006Jul 11 2006We calculate the tensions of all half-supersymmetric nine-branes in IIB string theory. In particular, we point out the existence of a solitonic IIB nine-brane. We find that the D9-brane and its duality transformations parametrize a two-dimensional surface ... More
Spacetime-Filling Branes in Ten and Nine DimensionsOct 18 2004Mar 11 2005Type-IIB supergravity in ten dimensions admits two consistent $Z_2$ truncations. After the insertion of D9-branes, one of them leads to the low-energy action of type-I string theory, and it can be performed in two different ways, in correspondence with ... More
Decomposition of geodesics in the Wasserstein space and the globalization propertySep 26 2012Aug 20 2013We will prove a decomposition for Wasserstein geodesics in the following sense: let $(X,d,m)$ be a non-branching metric measure space verifying $\mathsf{CD}_{loc}(K,N)$ or equivalently $\mathsf{CD}^{*}(K,N)$. We prove that every geodesic $\mu_{t}$ in ... More
Heavy-flavour production in pp collisions and correlations in pp and p-Pb collisions measured with ALICE at the LHCSep 27 2016Thanks to its excellent tracking and particle identification performance, the ALICE detector is capable of measuring D mesons at central rapidity via their hadronic decay channels down to very low transverse momentum. We show an extension of the prompt ... More
A non trivial extension of the two-dimensional Ising model: the d-dimensional "molecular" modelMay 24 2000A recently proposed molecular model is discussed as a non-trivial extension of the Ising model. For d=2 the two models are shown to be equivalent, while for d>2 the molecular model describes a peculiar second order transition from an isotropic high temperature ... More
A variational study of bound states in the Higgs modelAug 03 2000The possible existence of Higgs-Higgs bound states in the Higgs sector of the Standard Model is explored using the |hh>+|hhh> variational ansatz of Di Leo and Darewych. The resulting integral equations can be decoupled exactly, yielding a one-dimensional ... More
Measuring Chemical Abundances in Extragalactic Metal-Rich HII RegionsAug 19 2006The analysis of metal-rich HII regions has a profound impact on the calibration of abundance diagnostics widely used to measure the chemical content of star-forming galaxies, both locally and at high redshift. I review the main difficulties that affect ... More
Clues on the rejuvenation of the S0 galaxy NGC 404 from the chemical abundance of its outer diskJun 13 2013The oxygen abundance of the outer disk of the nearby S0 galaxy NGC 404, a prototypical early-type galaxy with extended star formation, has been derived from the analysis of HII region spectra. The high mean value found, 12+log(O/H)=8.6 \pm 0.1, equivalent ... More
Quarkonium Decays and Production in NRQCDJul 02 2000Some examples of the most recent applications of the NRQCD factorization approach to quarkonium phenomenology are presented. In the first part of the talk the NLO calculations for $\chicj$ and $\Upsilon$ decays rates are compared to the data and the results ... More
Invariant bipartite random graphs on $\mathbb{R}^d$Feb 23 2012Suppose that red and blue points occur in $\mathbb{R}^d$ according to two simple point process with finite intensities $\lambda_{\mathcal{R}}$ and $\lambda_{\mathcal{B}}$, respectively. Furthermore, let $\nu$ and $\mu$ be two probability distributions ... More
An idea for detecting capture dominated Dark StarsJun 22 2009I discuss an idea which could lead to a methodology for testing the effects of WIMP DM scattering and capture onto primordial stars. It relies on the effects of "life-prolongation" of affected Population III stars, that can slow down nuclear reactions ... More
Toward an invariant matrix model for the Anderson TransitionMar 11 2015We consider invariant matrix models with log-normal (asymptotic) weight. It is known that their eigenvalue distribution is intermediate between Wigner-Dyson and Poissonian, which candidates these models for describing a system intermediate between the ... More
An operator view on alliances in politicsJan 23 2015We introduce the concept of an {\em operator decision making technique} and apply it to a concrete political problem: should a given political party form a coalition or not? We focus on the situation of three political parties, and divide the electorate ... More
On the Spontaneous Breaking of U(N) symmetry in invariant Matrix ModelsDec 19 2014Jul 28 2015Matrix Models are the most effective way to describe strongly interacting systems with many degrees of freedom. They have proven successful in describing very different settings, from nuclei spectra to conduction in mesoscopic systems, from holographic ... More
The axiom of choice, co-comprehension schema and redundancies in triposesFeb 12 2016We study the role of the axiom of choice and co-comprehention in second order encoding of first order predicates logic
Ramified Galois covers via monoidal functorsJul 19 2015May 08 2016We interpret Galois covers in terms of particular monoidal functors, extending the correspondence between torsors and fiber functors. As applications we characterize tame $G$-covers between normal varieties for finite and \'etale group schemes and we ... More
Transition probabilities for non self-adjoint Hamiltonians in infinite dimensional Hilbert spacesAug 11 2015In a recent paper we have introduced several possible inequivalent descriptions of the dynamics and of the transition probabilities of a quantum system when its Hamiltonian is not self-adjoint. Our analysis was carried out in finite dimensional Hilbert ... More
Convergence in $L^p$ for Feynman path integralsMar 19 2015Mar 22 2015We consider a class of Schrodinger equations with time-dependent smooth magnetic and electric potentials having a growth at infinity at most linear and quadratic, respectively. We study the convergence in $L^p$ with loss of derivatives, $1<p<\infty$, ... More
Some results on the dynamics and transition probabilities for non self-adjoint hamiltoniansFeb 25 2015We discuss systematically several possible inequivalent ways to describe the dynamics and the transition probabilities of a quantum system when its hamiltonian is not self-adjoint. In order to simplify the treatment, we mainly restrict our analysis to ... More
Trace map and regularity of finite extensions of a DVRJun 13 2015We interpret the regularity of a finite and flat extension of a discrete valuation ring in terms of the trace map of the extension.
Homogeneous Hermitian manifolds and special metricsAug 29 2016We consider non-Kaehler compact complex manifolds which are homogeneous under the action of a compact Lie group of biholomorphisms and we investigate the existence of special (invariant) Hermitian metrics on these spaces. We focus on a particular class ... More
Non self-adjoint Hamiltonians with complex eigenvaluesMar 07 2016Motivated by what one observes dealing with PT-symmetric quantum mechanics, we discuss what happens if a physical system is driven by a diagonalizable Hamiltonian with not all real eigenvalues. In particular, we consider the functional structure related ... More
Hilbertian Toposes Epsilon ToposesMar 02 2016We study Hilbert's epsilon calculus and Hilbert's partial epsilon calculus in toposes.
Remarks on the Tripos To Topos Construction: extensionality, comprehensions, quotients and cauchy-complete objectsJan 30 2014Feb 24 2014We give a description of the Tripos To Topos construction in terms of four free constructions. We prove that these compose up to give a free construction from the category of triposes and logical morphisms to the category of toposes and logical functors. ... More
Universal scaling of gluon and ghost propagators in the infraredJul 07 2016A universal behavior is predicted for ghost and gluon propagators in the infrared. The universal behavior is shown to be a signature of a one-loop approximation and emerges naturally by the massive expansion that predicts universal analytical functions ... More
Dual Affine Quantum GroupsDec 03 1997Sep 13 1999Let $\hat{\frak g}$ be an untwisted affine Kac-Moody algebra, with its Sklyanin-Drinfel'd structure of Lie bialgebra, and let $\hat{\frak h}$ be the dual Lie bialgebra. By dualizing the quantum double construction - via formal Hopf algebras - we construct ... More
Quantization of Poisson GroupsNov 24 1995Jan 29 1996The quantization of well-known pairs of Poisson groups of a wide class is studied by means of Drinfeld's double construction and dualization via formal Hopf algebras; new quantized enveloping algebras $ U_{q,\varphi}^{M,\infty} (\frak h) $ and quantum ... More
The quantum duality principleSep 14 1999Jun 07 2001The "quantum duality principle" states that the quantization of a Lie bialgebra - via a quantum universal enveloping algebra (QUEA) - provides also a quantization of the dual Lie bialgebra (through its associated formal Poisson group) - via a quantum ... More
Multidimensional Hahn polynomials, intertwining functions on the symmetric group and Clebsch-Gordan coefficientsMay 06 2008We generalize a construction of Dunkl, obtaining a wide class intertwining functions on the symmetric group and a related family of multidimensional Hahn polynomials. Following a suggestion of Vilenkin and Klymik, we develop a tree-method approach for ... More
Generalization of the linear r-matrix formulation through Loop coproductsOct 06 2009A new method for the construction of classical integrable systems, that we call loop coproduct formulation, is presented. We show that the linear r-matrix formulation, the Sklyanin algebras and the reflection algebras can be obtained as particular subcases ... More
Loop coproductsJul 28 2009In this paper we show that if $A$ is a Poisson algebra equipped with a set of maps $\Delta^{(i)}_\la:A \to A^{\otimes N}$ satisfying suitable conditions, then the images of the Casimir functions of $A$ under the maps $\Delta^{(i)}_\la$ (that we call "loop ... More
Quantum corrections to broken N=8 supergravityFeb 08 2013The discovery of the Higgs boson and the non-discovery (so far) of additional particles at the TeV scale underline our poor understanding of the hierarchy problems in the physics of the fundamental interactions. Loosely motivated by this consideration, ... More
Supersymmetry and gauge symmetry breaking with naturally vanishing vacuum energyNov 13 1995We review the construction of $N=1$ supergravity models where the Higgs and super-Higgs effects are simultaneously realized, with naturally vanishing classical vacuum energy and goldstino components along gauge-non-singlet directions: this situation is ... More
The Crystal Duality Principle: from Hopf Algebras to Geometrical SymmetriesApr 14 2003Jan 14 2005We give functorial recipes to get, out of any Hopf algebra over a field, two pairs of Hopf algebras which have some geometrical content. When the ground field has characteristic zero, the first pair is made by a function algebra over a connected Poisson ... More
Quantifying the Evolutionary Self Structuring of Embodied Cognitive NetworksDec 07 2012We outline a possible theoretical framework for the quantitative modeling of networked embodied cognitive systems. We notice that: 1) information self structuring through sensory-motor coordination does not deterministically occur in Rn vector space, ... More
On the radical of Brauer algebrasJun 20 2006Dec 14 2007The radical of the Brauer algebra B_f^x is known to be non-trivial when the parameter x is an integer subject to certain conditions (with respect to f). In these cases, we display a wide family of elements in the radical, which are explicitly described ... More
The tree method for multidimensional q-Hahn and q-Racah polynomialsDec 22 2009We develop a tree method for multidimensional q-Hahn polynomials. We define them as eigenfunctions of a multidimensional q-difference operator and we use the factorization of this operator as a key tool. Then we define multidimensional q-Racah polynomials ... More
Yang-Mills ghost propagator in linear covariant gaugesMar 02 2019From first principles, using a screened expansion, a simple one-loop analytical expression is provided for the ghost propagator of pure SU(3) Yang-Mills theory in a generic linear covariant gauge. At variance with the Landau gauge, the ghost dressing ... More
Moving closer: contractive maps on discrete metric spaces and graphsNov 18 2010We consider discrete metric spaces and we look for non-constant contractions. We introduce the notion of contractive map and we characterize the spaces with non-constant contractive maps. We provide some examples to discussion the possible relations between ... More
Lie supergroups vs. super Harish-Chandra pairs: a new equivalenceSep 09 2016Oct 30 2018It is known that there exists a natural functor $\Phi$ from Lie supergroups to super Harish-Chandra pairs. A functor going backwards, that associates a Lie supergroup with each super Harish-Chandra pair, yielding an equivalence of categories, was found ... More
Poisson geometrical symmetries associated to non-commutative formal diffeomorphismsSep 09 2003Dec 03 2004Let G be the group of all formal power series starting with x with coefficients in a field k of zero characteristic (with the composition product), and let F[G] be its function algebra. C. Brouder and A. Frabetti introduced a non-commutative, non-cocommutative ... More
PBW theorems and Frobenius structures for quantum matricesOct 23 2006Dec 14 2007Let G be either of Mat(n), GL(n) or SL(n), let O_q(G) be the quantum function algebra - over Z[q,q^{-1}] - associated to G, and let O_e(G) be the specialisation of O_q(G) at a root of unity, of odd order l. Then O_e(G) is a module over the corresponding ... More
Presentation by Borel subalgebras and Chevalley generators for quantum enveloping algebrasMar 22 2004Dec 14 2007We provide an alternative approach to the Faddeev-Reshetikhin-Takhtajan presentation of the quantum group U_q(g), with L-operators as generators and relations ruled by an R-matrix. We look at U_q(g) as being generated by the quantum Borel subalgebras ... More
A note on toric Deligne-Mumford stacksMay 25 2007Apr 08 2008We give a new description of the data needed to specify a morphism from a scheme to a toric Deligne-Mumford stack. The description is given in terms of a collection of line bundles and sections which satisfy certain conditions. As applications, we characterize ... More
On General Duality Principles for Non-Convex Variational Optimization with Applications to the Ginzburg-Landau System in SuperconductivityApr 17 2018Oct 10 2018This article develops duality principles applicable to non-convex models in the calculus of variations. The results here developed are applied to Ginzburg-Landau type equations. For the first and second duality principles, through an optimality criterion ... More
Variations of the stellar Initial Mass Function in Semi-Analytic Models: implications for the mass assembly of galaxies in the GAEA modelMar 08 2019A wealth of observations recently challenged the notion of a universal stellar initial mass function (IMF) by showing evidences in favour of a variability of this statistical indicator as a function of galaxy properties. I present predictions from the ... More
Analytic structure of QCD propagators in Minkowski spaceMay 24 2016Analytical functions for the propagators of QCD, including a set of chiral quarks, are derived by a one-loop massive expansion in the Landau gauge, deep in the infrared. By analytic continuation, the spectral functions are studied in Minkowski space, ... More
Variational Quantum ElectrodynamicsAug 13 2013Jan 09 2014A variational method is discussed, based on the principle of minimal variance. The method seems to be suited for gauge interacting fermions, and the simple case of quantum electrodynamics is discussed in detail. The issue of renormalization is addressed, ... More
Higher order extensions of the Gaussian effective potentialAug 08 2013Sep 21 2013A variational method is discussed, extending the Gaussian effective potential to higher orders. The single variational parameter is replaced by trial unknown two-point functions, with infinite variational parameters to be optimized by the solution of ... More
The Principle of Stationary Variance in Quantum Field TheoryAug 19 2013The principle of stationary variance is advocated as a viable variational approach to quantum field theory. The method is based on the principle that the variance of energy should be at its minimum when the state of a quantum system reaches its best approximation ... More
Some Results about FramesJan 30 1997In this paper we discuss some topics related to the general theory of frames. In particular we focus our attention to the existence of different 'reconstruction formulas' for a given vector of a certain Hilbert space and to some refinement of the perturbative ... More
Multi-Resolution Analysis in Arbitrary Hilbert SpacesJan 30 1997We discuss the possibility of introducing a multi-resolution in a Hilbert space which is not necessarily a space of functions. We investigate which of the classical properties can be translated to this more general framework and the way in which this ... More
Study of a Class of Four Dimensional Nonsingular Cosmological BouncesJul 07 2003We study a novel class of nonsingular time-symmetric cosmological bounces. In this class of four dimensional models the bounce is induced by a perfect fluid with a negative energy density. Metric perturbations are solved in an analytic way all through ... More
The lithium problem, a phenomenologist's perspectiveJun 11 2012Jul 09 2012Thirty years after the first observation of the 7Li isotope in the atmosphere of metal-poor halo stars, the puzzle about its origin persists. Do current observations still support the existence of a "plateau": a single value of lithium abundance, constant ... More
The global quantum duality principleDec 22 1999The "quantum duality principle" states that the quantization of a Lie bialgebra --- via a quantum universal enveloping algebra (QUEA) --- provides also a quantization of the dual Lie bialgebra (through its associated formal Poisson group) --- via a quantum ... More
Geometrical Meaning of R-matrix Action for Quantum Groups at Roots of 1Apr 12 1996Nov 06 1996The present work splits in two parts: first, we perform a straightforward generalization of results from [Re], proving autoquasitriangularity of quantum groups U_q(g) and their unrestricted specializations at roots of 1, in particular the function algebra ... More
Quantization of Poisson groups -- IIApr 10 1996Nov 07 1997Let $ G^\tau $ be a connected simply connected semisimple algebraic group, endowed with generalized Sklyanin-Drinfeld structure of Poisson group; let $ H^\tau $ be its dual Poisson group. By means of Drinfeld's double construction and dualization via ... More
An improved model of alliances between political partiesFeb 29 2016We consider an operatorial model of alliances between three political parties which interact with their electors, with the undecided voters, and with the electors of the other parties. This extends what was done in a previous paper, where this last type ... More
Perturbative study of Yang-Mills theory in the infraredSep 19 2015Mar 31 2016Pure Yang-Mills SU(N) theory is studied in four dimensional space and Landau gauge by a double perturbative expansion based on a massive free-particle propagator. By dimensional regularization, all diverging mass terms cancel exactly in the double expansion, ... More