Results for "Massimiliano Sala"

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Several Proofs of Security for a Tokenization AlgorithmSep 01 2016Feb 01 2017In this paper we propose a tokenization algorithm of Reversible Hybrid type, as defined in PCI DSS guidelines for designing a tokenization solution, based on a block cipher with a secret key and (possibly public) additional input. We provide some formal ... More
A proof of security for a key-policy RS-ABE schemeMar 21 2016A revocable-storage attribute-based encryption (RS-ABE) scheme is an encryption scheme which extends attribute-based encryption by intro- ducing user revocation. A key-policy RS-ABE scheme links each key to an access structure. We propose a new key-policy ... More
Several Proofs of Security for a Tokenization AlgorithmSep 01 2016In this paper we propose a tokenization algorithm of the Reversible Hybrid type, based on a block cipher with a secret key and (possibly public) additional input. We provide some formal proofs of security for it.
Postulation of general quintuple fat point schemes in P^3Mar 28 2011We study the postulation of a general union Y of double, triple, quartuple and quintuple points of P^3. In characteristic 0, we prove that Y has good postulation in degree $d\ge 11$. The proof is based on the combination of the Horace differential lemma ... More
On differential uniformity of maps that may hide an algebraic trapdoorJan 17 2015Jun 11 2015We investigate some differential properties for permutations in the affine group, of a vector space V over the binary field, with respect to a new group operation $\circ$, inducing an alternative vector space structure on $V$ .
A generalization of bounds for cyclic codes, including the HT and BS boundsJun 20 2013We use the algebraic structure of cyclic codes and some properties of the discrete Fourier transform to give a reformulation of several classical bounds for the distance of cyclic codes, by extending techniques of linear algebra. We propose a bound, whose ... More
A deterministic algorithm for the distance and weight distribution of binary nonlinear codesMay 04 2015May 05 2015Given a binary nonlinear code, we provide a deterministic algorithm to compute its weight and distance distribution, and in particular its minimum weight and its minimum distance, which takes advantage of fast Fourier techniques. This algorithm's performance ... More
Generalized AG codes as evaluation codesDec 23 2012We extend the construction of GAG codes to the case of evaluation codes. We estimate the minimum distance of these extended evaluation codes and we describe the connection to the one-point GAG codes.
Intersections between the norm-trace curve and some low degree curvesDec 20 2018In this paper we analyze the intersection between the norm-trace curve over $\mathbb{F}_{q^3}$ and the curves of the form $y=ax^3+bx^2+cx+d$, giving a complete characterization of the intersection between the curve and the parabolas, as well as sharp ... More
A bound on the size of linear codesFeb 10 2009Jun 27 2012We present a bound on the size of linear codes. This bound is independent of other known bounds, e.g. the Griesmer bound.
Several Proofs of Security for a Tokenization AlgorithmSep 01 2016Oct 13 2016In this paper we propose a tokenization algorithm of Reversible Hybrid type, as defined in PCI DSS guidelines for designing a tokenization solution, based on a block cipher with a secret key and (possibly public) additional input. We provide some formal ... More
On the Hermitian curve and its intersections with some conicsFeb 16 2014We classify completely the intersections of the Hermitian curve with parabolas in the affine plane. To obtain our results we employ well-known algebraic methods for finite fields and geometric properties of the curve automorphisms. In particular, we provide ... More
On the Hermitian curve, its intersections with some conics and their applications to affine-variety codes and Hermitian codesAug 08 2012Sep 12 2012For any affine-variety code we show how to construct an ideal whose solutions correspond to codewords with any assigned weight. We classify completely the intersections of the Hermitian curve with lines and parabolas (in the $\mathbb{F}_{q^2}$ affine ... More
Code generator matrices as RNG conditionersFeb 05 2015Mar 02 2017We quantify precisely the distribution of the output of a binary random number generator (RNG) after conditioning with a binary linear code generator matrix by showing the connection between the Walsh spectrum of the resulting random variable and the ... More
Hilbert quasi-polynomial for order domains and application to coding theoryJul 25 2016Feb 02 2018We present an application of Hilbert quasi-polynomials to order domains, allowing the effective check of the second order-domain condition in a direct way. We also provide an improved algorithm for the computation of the related Hilbert quasi-polynomials. ... More
Abelian regular subgroups of the affine group and radical ringsOct 08 2005Apr 20 2006We establish a link between abelian regular subgroup of the affine group, and commutative, associative algebra structures on the underlying vector space that are (Jacobson) radical rings. As an application, we show that if the underlying field has positive ... More
Quasi-cyclic LDPC codes with high girthJun 18 2009We study a class of quasi-cyclic LDPC codes. We provide precise conditions guaranteeing high girth in their Tanner graph. Experimentally, the codes we propose perform no worse than random LDPC codes with their same parameters, which is a significant achievement ... More
Do AES encryptions act randomly?Nov 11 2010The Advanced Encryption Standard (AES) is widely recognized as the most important block cipher in common use nowadays. This high assurance in AES is given by its resistance to ten years of extensive cryptanalysis, that has shown no weakness, not even ... More
A weight-distribution bound for entropy extractors using linear binary codesMay 12 2014We consider a bound on the bias reduction of a random number generator by processing based on binary linear codes. We introduce a new bound on the total variation distance of the processed output based on the weight distribution of the code generated ... More
Improved decoding of affine-variety codesFeb 21 2011Dec 20 2011General error locator polynomials are polynomials able to decode any correctable syndrome for a given linear code. Such polynomials are known to exist for all cyclic codes and for a large class of linear codes. We provide some decoding techniques for ... More
An algorithmic approach using multivariate polynomials for the nonlinearity of Boolean functionsOct 19 2016The nonlinearity of a Boolean function is a key property in deciding its suitability for cryptographic purposes, e.g. as a combining function in stream ciphers, and so the nonlinearity computation is an important problem for applications. Traditional ... More
Hilbert quasi-polynomial for order domain codesJul 25 2016We present an application of Hilbert quasi-polynomials to order domain codes, allowing the effective computation of the order domain condition in a direct way. We also provide an improved and specialized algorithm for the computation of the related Hilbert ... More
Complexity of multivariate polynomial evaluationJun 14 2011We describe a method to evaluate multivariate polynomials over a finite field and discuss its multiplicative complexity.
Permutation equivalent maximal irreducible Goppa codesJun 10 2008We consider the problem of finding the number of permutation non-equivalent classical irreducible maximal Goppa codes having fixed parameters q, n and r from a group theory point of view.
On optimal nonlinear systematic codesJun 10 2015Feb 11 2016Most bounds on the size of codes hold for any code, whether linear or not. Notably, the Griesmer bound holds only in the linear case and so optimal linear codes are not necessarily optimal codes. In this paper we identify code parameters $(q,d,k)$, namely ... More
Computing the distance distribution of systematic non-linear codesSep 09 2009The most important families of non-linear codes are systematic. A brute-force check is the only known method to compute their weight distribution and distance distribution. On the other hand, it outputs also all closest word pairs in the code. In the ... More
Some bounds on the size of codesJun 26 2012Dec 27 2012We present some upper bounds on the size of non-linear codes and their restriction to systematic codes and linear codes. These bounds are independent of other known theoretical bounds, e.g. the Griesmer bound, the Johnson bound or the Plotkin bound, and ... More
A possible intrinsic weakness of AES and other cryptosystemsJun 30 2010Nov 11 2010It has been suggested that the algebraic structure of AES (and other similar block ciphers) could lead to a weakness exploitable in new attacks. In this paper, we use the algebraic structure of AES-like ciphers to construct a cipher embedding where the ... More
Code generator matrices as entropy extractorsFeb 05 2015We show the connection between the Walsh spectrum of the output of a binary random number generator (RNG) and the bias of individual bits, and use this to show how previously known bounds on the performance of linear binary codes as entropy extractors ... More
A note on an infeasible linearization of some block ciphersNov 07 2015Nov 20 2015A block cipher can be easily broken if its encryption functions can be seen as linear maps on a small vector space. Even more so, if its round functions can be seen as linear maps on a small vector space. We show that this cannot happen for the AES. More ... More
Key-Policy Multi-Authority Attribute-Based EncryptionDec 13 2014Feb 04 2016Bilinear groups are often used to create Attribute-Based Encryption (ABE) algorithms. In particular, they have been used to create an ABE system with multi authorities, but limited to the ciphertext-policy instance. Here, for the first time, we propose ... More
The role of Boolean functions in hiding sums as trapdoors for some block ciphersNov 27 2014Jan 16 2015Most modern block ciphers are built using components whose cryptographic strength is evaluated in terms of their resistance to attacks on the whole cipher. In particular, differential properties of vectorial Boolean functions are studied for the S-Boxes ... More
A note on an infeasible linearization of some block ciphersNov 07 2015Feb 02 2017A block cipher can be easily broken if its encryption functions can be seen as linear maps on a small vector space. Even more so, if its round functions can be seen as linear maps on a small vector space. We show that this cannot happen for the AES. More ... More
Study of the transition from the hard to the soft Pomeron in the small x region using optimal renormalizationDec 04 2012We show that it is possible to describe the effective Pomeron intercept using NLO BFKL evolution together with collinear improvements. In order to obtain a good description over the whole range of Q^2 we use a non-Abelian physical renormalization scheme ... More
On Prime Reciprocals in the Cantor SetJun 02 2009Nov 11 2011The middle-third Cantor set C_3 is a fractal consisting of all the points in [0, 1] which have non-terminating base-3 representations involving only the digits 0 and 2. It is easily shown that the reciprocals of all prime numbers p > 3 satisfying an equation ... More
A bound on the charm chromo-EDM and its implicationsDec 09 2013Sep 09 2014We derive bounds on the electric and chromo-electric dipole moments of the charm quark. The second one turns out to be particularly strong, and we quantify its impact on models that allow for a sizeable flavour violation in the up quark sector, like flavour ... More
On causality of extreme eventsJan 26 2016May 19 2016Multiple metrics have been developed to detect causality relations between data describing the elements constituting complex systems, all of them considering their evolution through time. Here we propose a metric able to detect causality within static ... More
Flexoelectricity from density-functional perturbation theoryJun 18 2013Sep 20 2013We derive the complete flexoelectric tensor, including electronic and lattice-mediated effects, of an arbitrary insulator in terms of the microscopic linear response of the crystal to atomic displacements. The basic ingredient, which can be readily calculated ... More
A new approach to non-commutative inflationAug 13 2009Mar 24 2011We propose an inflationary scenario inspired by a recent formulation, in terms of coherent states, of non-commutative quantum field theory. We consider the semiclassical Einstein equations, and we exploit the ultraviolet finiteness of the non-commutative ... More
Superluminal dispersion relations and the Unruh effectFeb 05 2008May 26 2008In the context of quantum gravity phenomenology, we study the Unruh effect in the presence of superluminal dispersion relations. In particular, we estimate the response function and the probability rate for an accelerated detector coupled to a massless ... More
Toroidal Black Holes and T-dualityAug 03 2002Aug 19 2002We consider the toroidal black holes that arise as a generalization of the AdS_5 times S^5 solution of type IIB supergravity. The symmetries of the horizon space allow T-duality transformations that can be exploited to generate new inequivalent black ... More
Dark energy as a fixed point of the Einstein Yang-Mills Higgs EquationsAug 19 2015Sep 17 2015We study the Einstein Yang-Mills Higgs equations in the $SO(3)$ representation on a isotropic and homogeneous flat Universe, in the presence of radiation and matter fluids. We map the equations of motion into an autonomous dynamical system of first-order ... More
Quasi Scale-Invariant Inflationary AttractorsJul 21 2015Dec 21 2015We show that pure quadratic gravity with quantum loop corrections yields a viable inflationary scenario. We also show that a large family of models in the Jordan frame, with softly-broken scale invariance, corresponds to the same theory with linear inflaton ... More
On the unirationality of 3-fold conic bundlesMar 27 2014A variety is unirational if it is dominated by a rational variety. A variety is rationally connected if two general points can be joined by a rational curve. This paper aims to show that the two notions can cooperate and, building on Graber-Harris-Starr ... More
Low--Temperature Series for Renormalized Operators: the Ferromagnetic Square--Lattice Ising Model.Sep 19 1994Mar 23 1995A method for computing low--temperature series for renormalized operators in the two--dimensional Ising model is proposed. These series are applied to the study of the properties of the truncated renormalized Hamiltonians when we start at very low temperature ... More
The 3-State Potts Antiferromagnet on the Hexagonal LatticeFeb 13 1998We study the 3-state hexagonal-lattice Potts antiferromagnet by a Monte Carlo simulation using the Wang-Swendsen-Kotecky cluster algorithm. We study the staggered susceptibility and the correlation length, and we confirm that this model is disordered ... More
Measurement of airborne 131I, 134Cs, and 137Cs nuclides due to the Fukushima reactors accident in air particulate in Milan (Italy)Jun 21 2011After the earthquake and the tsunami occurred in Japan on 11th March 2011, four of the Fukushima reactors had released in air a large amount of radioactive isotopes that had been diffused all over the world. The presence of airborne 131I, 134Cs, and 137Cs ... More
On the shape of the general error locator polynomial for cyclic codesFeb 10 2015Dec 24 2015A general result on the explicit form of the general error locator polynomial for all cyclic codes is given, along with several results for infinite classes of cyclic codes with $t=2$ and $t=3$. From these, a theoretically justification of the sparsity ... More
On the Griesmer bound for nonlinear codesJan 18 2015Most bounds on the size of codes hold for any code, whether linear or nonlinear. Notably, the Griesmer bound, holds only in the linear case. In this paper we characterize a family of systematic nonlinear codes for which the Griesmer bound holds. Moreover, ... More
On the provable security of BEAR and LION schemesMay 02 2011BEAR, LION and LIONESS are block ciphers presented by Biham and Anderson (1996), inspired by the famous Luby-Rackoff constructions of block ciphers from other cryptographic primitives (1988). The ciphers proposed by Biham and Anderson are based on one ... More
Two-tier blockchain timestamped notarization with incremental securityFeb 08 2019Digital notarization is one of the most promising services offered by modern blockchain-based solutions. We present a digital notary design with incremental security and cost reduced with respect to current solutions. A client of the service receives ... More
Wave-Shaped Round Functions and Primitive GroupsAug 29 2017Sep 21 2018Round functions used as building blocks for iterated block ciphers, both in the case of Substitution-Permutation Networks and Feistel Networks, are often obtained as the composition of different layers which provide confusion and diffusion, and key additions. ... More
The neutron EDM vs up and charm flavour violationMay 21 2014We derive a strong bound on the chromo-electric dipole moment of the charm quark, and we quantify its impact on models that allow for a sizeable flavour violation in the up quark sector. In particular we show how the constraints coming from the charm ... More
Chiral symmetry and the axial nucleon to Delta(1232) transition form factorsMar 29 2008We study the momentum and the quark mass dependence of the axial nucleon to Delta(1232) transition form factors in the framework of non-relativistic chiral effective field theory to leading-one-loop order. The outcome of our analysis provides a theoretical ... More
Existence of good divisors on Mukai varietiesMay 09 1997A Mukai variety is a Fano n-fold of index n-2. In this paper we study the fundamental divisor of a Mukai variety with at worst log terminal singularities. The main result is a complete classification of log terminal Mukai varieties which have not good ... More
Unified ab initio formulation of flexoelectricity and strain-gradient elasticityApr 27 2016The theories of flexoelectricity and that of nonlocal elasticity are closely related, and are often considered together when modeling strain-gradient effects in solids. Here I show, based on a first-principles lattice-dynamical analysis, that their relationship ... More
Global calibrations for the non-homogeneous Mumford-Shah functionalMay 16 2001Using a calibration method we prove that, if $\Gamma\subset \Omega$ is a closed regular hypersurface and if the function $g$ is discontinuous along $\Gamma$ and regular outside, then the function $u_{\beta}$ which solves $$ \begin{cases} \Delta u_{\beta}=\beta(u_{\beta}-g)& ... More
Singularities of linear systems and the Waring ProblemJun 15 2004Waring problem for homogeneus forms asks for additive decomposition of a form $f$ into powers of linear forms. A classical problem is to determine when such a decomposition is unique. In this paper I answer this question when the degree of $f$ is greater ... More
Approximation of the first passage time density of a Wiener process to an exponentially decaying threshold by two-piecewise linear threshold. Application to neuronal spiking activityJul 04 2015Feb 17 2016The first passage time density of a diffusion process to a time varying threshold is of primary interest in different fields. Here we consider a Brownian motion in presence of an exponentially decaying threshold to model the neuronal spiking activity. ... More
On weakly APN functions and 4-bit S-BoxesFeb 17 2011Aug 02 2011S-Boxes are important security components of block ciphers. We provide theoretical results on necessary or sufficient criteria for an (invertible) 4-bit S-Box to be weakly APN. Thanks to a classification of 4-bit invertible S-Boxes achieved independently ... More
On the security of the Blockchain Bix Protocol and CertificatesJul 28 2016The BIX protocol is a blockchain-based protocol that allows distribution of certificates linking a subject with his public key, hence providing a service similar to that of a PKI but without the need of a CA. In this paper we analyze the security of the ... More
A momentum-space representation of Green's functions with modified dispersion relations on general backgroundsMar 26 2008Jun 04 2008We consider the problem of calculating the Green's functions associated to a massive scalar field with modified dispersion relations. We analyze the case when dispersion is modified by higher derivative spatial operators acting on the field orthogonally ... More
Mimicking dark matter in Horndeski gravityAug 12 2016Since the rediscovery of Horndeski gravity, a lot of work has been devoted to the exploration of its properties, especially in the context of dark energy. However, one sector of this theory, namely the one containing the coupling of the Einstein tensor ... More
Higgs Dark EnergyApr 02 2014Jan 20 2015We study the classical dynamics of a non-abelian Higgs theory coupled to gravity in an isotropic and homogeneous Universe. For non-minimal coupling, this theory leads to a model of cosmic inflation that is very attractive due to its simplicity and consistency ... More
Self-T-Dual Brane CosmologyOct 23 2006Oct 24 2006We show how T-duality can be implemented with brane cosmology. As a result, we obtain a smooth bouncing cosmology with features similar to the ones of the pre-Big Bang scenario. Also, by allowing T-duality transformations along the time-like direction, ... More
Effect of neutrino asymmetry on the estimation of cosmological parametersFeb 18 2004The recent analysis of the cosmic microwave background data carried out by the WMAP team seems to show that the sum of the neutrino masses is <0.7 eV. However, this result is not model-independent, depending on precise assumptions on the cosmological ... More
Equivalent Birational Embeddings III: conesJul 30 2014Two divisors in $\mathbb P^n$ are said to be Cremona equivalent if there is a Cremona modification sending one to the other. In this paper I study irreducible cones in $\mathbb P^n$ and prove that two cones are Cremona equivalent if their general hyperplane ... More
Free loop space and the cyclic bar constructionFeb 29 2016Aug 29 2016Using the $E_\infty-$structure on singular cochains, we construct a homotopy coherent map from the cyclic bar construction of the differential graded algebra of cochains on a space to a model for the cochains on its free loop space. This fills a gap in ... More
Free loop spaces and dihedral homologyAug 29 2016We prove an $O(2)$-equivariant version of the Jones isomorphism relating the Borel $O(2)$-equivariant cohomology of the free loop space to the dihedral homology of the cochain algebra. We discuss polynomial forms and a variation of the de Rham isomorphism ... More
Existence of good divisors on Mukai manifoldsNov 20 1996A normal projective variety X is called Fano if a multiple of the anticanonical Weil divisor, -K_X, is an ample Cartier divisor, the index of a Fano variety is the number i(X):=sup{t: -K_X= tH, for some ample Cartier divisor H}. Mukai announced, the classification ... More
The dark aftermath of Higgs inflationSep 27 2013Mar 11 2014In this letter we study the dynamics of the late Universe when a nonminimally coupled Higgs field is present. In general, the nonminimal coupling leads to a nontrivial mixing between the gravitational degrees of freedom and the Goldstone massless bosons. ... More
Black holes with non-minimal derivative couplingAug 01 2012Nov 06 2012We study the gravitational field equations in the presence of a coupling between the derivative of a massless scalar field and the Einstein tensor. This configuration is motivated by Galileon gravity as it preserves shift invariance in the scalar sector. ... More
Aspects of Quantum Gravity in CosmologyJan 22 2012Feb 13 2012We review some aspects of quantum gravity in the context of cosmology. In particular, we focus on models with a phenomenology accessible to current and near-future observations, as the early Universe might be our only chance to peep through the quantum ... More
Modified Dispersion Relations and trans-Planckian PhysicsNov 06 2007Nov 08 2007We consider modified dispersion relations in quantum field theory on curved space-time. Such relations, despite breaking the local Lorentz invariance at high energy, are considered in several phenomenological approaches to quantum gravity. Their existence ... More
Advances on CNN-based super-resolution of Sentinel-2 imagesFeb 07 2019Thanks to their temporal-spatial coverage and free access, Sentinel-2 images are very interesting for the community. However, a relatively coarse spatial resolution, compared to that of state-of-the-art commercial products, motivates the study of super-resolution ... More
Noise effect on Grover algorithmJan 08 2008The decoherence effect on Grover algorithm has been studied numerically through a noise modelled by a depolarizing channel. Two types of error are introduced characterizing the qubit time evolution and gate application, so the noise is directly related ... More
Simple fault-tolerant encoding over q-ary CSS quantum codesDec 19 2007CSS codes are a subfamily of stabilizer codes especially appropriate for fault-tolerant quantum computations. A very simple method is proposed to encode a general qudit when a Calderbank-Shor-Steane quantum code, defined over a q-ary alphabet, is used. ... More
Homotopy of ringed finite spacesNov 19 2015A ringed finite space is a ringed space whose underlying topological space is finite. The category of ringed finite spaces contains, fully faithfully, the category of finite topological spaces and the category of affine schemes. Any ringed space, endowed ... More
Ringed Finite SpacesSep 16 2014Oct 10 2014A ringed finite space is a ringed space whose underlying topological space is finite. The category of ringed finite spaces contains, fully faithfully, the category of finite topological spaces and the category of affine schemes. Any ringed space, endowed ... More
Variational principles and approximation of dynamical indicators for systems with nonuniformly hyperbolic behaviorMar 20 2013Nov 20 2013This note is concerned with approximation of dynamical indicators as pressures, Lyapunov exponents and dimension-like quantities, in systems with nonuniformly hyperbolic behavior. For this we let $P^*(\Phi) := \sup_{\mu}\{h(\mu) + \mu(\Phi)\}$ be a variational ... More
Framed sheaves on projective stacksNov 12 2013Nov 05 2014Given a normal projective irreducible stack $\mathscr X$ over an algebraically closed field of characteristic zero we consider framed sheaves on $\mathscr X$, i.e., pairs $(\mathcal E,\phi_{\mathcal E})$, where $\mathcal E$ is a coherent sheaf on $\mathscr ... More
Phase changes in delay propagation networksNov 02 2016The analysis of the dynamics of delays propagation is one of the major topics inside Air Transport Management research. Delays are generated by the elements of the system, but their propagation is a global process fostered by relationships inside the ... More
Excitation spectrum of the two-dimensional attractive Hubbard modelSep 25 1998We calculate the one-particle spectral functions above the superconducting transition temperature $T_{C}$, in the framework of a functional integral approach. The coupling of the electronic self-energy to pair fluctuations, which are treated by means ... More
A Novel Nanoporous Graphite Based on Graphynes: First Principles Structure and Carbon Dioxide Preferential PhysisorptionOct 05 2016Ubiquitous graphene is a stricly 2D material representing an ideal adsorbing platform due to its large specific surface area as well as its mechanical strength and resistance to both thermal and chemical stresses. However, graphene as a bulk material ... More
The automorphisms group of $\overline{M}_{0,n}$Jun 04 2010In this paper we study fiber type morphisms between moduli spaces of pointed rational curves. Via Kapranov's description we are able to prove that the only such morphisms are forgetful maps. This allow us to show that the Automorphism group of $\overline{M}_{0,n}$ ... More
First-Principles Modeling of Pt/LaAlO3/SrTiO3 Capacitors Under an External Bias PotentialDec 14 2011We study the electrical properties of Pt/LaAlO3/SrTiO3 capacitors under the action of an external bias potential, using first-principles simulations performed at constrained electric displacement field. A complete set of band diagrams, together with the ... More
Pre-Big Bang Scenario on Self-T-Dual Bouncing BranesNov 20 2004Mar 15 2005We consider a new class of 5-dimensional dilatonic actions which are invariant under T-duality transformations along three compact coordinates, provided that an appropriate potential is chosen. We show that the invariance remains when we add a boundary ... More
Status of neutrino properties and future prospects - Cosmological and astrophysical constraintsDec 19 2017Cosmological observations are a powerful probe of neutrino properties, and in particular of their mass. In this review, we first discuss the role of neutrinos in shaping the cosmological evolution at both the background and perturbation level, and describe ... More
4-manifolds as covers of the 4-sphere branched over non-singular surfacesMar 09 2002Jul 23 2002We prove the long-standing Montesinos conjecture that any closed oriented PL 4-manifold M is a simple covering of S^4 branched over a locally flat surface (cf [J M Montesinos, 4-manifolds, 3-fold covering spaces and ribbons, Trans. Amer. Math. Soc. 245 ... More
Faceted Semantic Search for Personalized Social SearchFeb 29 2012Actual social networks (like Facebook, Twitter, Linkedin, ...) need to deal with vagueness on ontological indeterminacy. In this paper is analyzed the prototyping of a faceted semantic search for personalized social search using the "joint meaning" in ... More
On some fibrations of $\overline{M}_{0,n}$May 17 2011The paper is a second step in the study of $\overline{M}_{0,n}$ started in arXiv:1006.0987 [math.AG]. We study fiber type morphisms of this moduli space via Kapranov's beautiful description. Our final goal is to understand if any dominant morphism $f: ... More
Cascade of minimizers for a nonlocal isoperimetric problem in thin domainsSep 03 2013Apr 11 2014For $\Omega_\e=(0,\e)\times (0,1)$ a thin rectangle, we consider minimization of the two-dimensional nonlocal isoperimetric problem given by \[ \inf_u E^{\gamma}_{\Omega_\e}(u)\] where \[ E^{\gamma}_{\Omega_\e}(u):= P_{\Omega_\e}(\{u(x)=1\})+\gamma\int_{\Omega_\e}\abs{\nabla{v}}^2\,dx ... More
Non-embeddability of certain classes of Levi flat manifoldsMar 08 2010On the basis of a result of Barrett, we show that members of certain classes of abstract Levi flat manifolds with boundary, whose Levi foliation contains a compact leaf with contracting, flat holonomy, admit no $CR$ embedding as a hypersurface of a complex ... More
The Turn-off of Classical Novae Observed Through X-rays: Models versus ROSAT Observations of V1974 CygOct 05 2004Detection of X-ray emission from classical novae in their post-outburst stages provides crucial information about the nova phenomenon. The soft X-ray emission gives a direct insight into the remaining hot nuclear burning shell. A numerical model for steady ... More
X-ray observations of classical novae. Theoretical implicationsOct 24 2009Detection of X-rays from classical novae, both in outburst and post-outburst, provides unique and crucial information about the explosion mechanism. Soft X-rays reveal the hot white dwarf photosphere, whenever hydrogen (H) nuclear burning is still on ... More
Envelope models for the supersoft X-ray emission of V1974 CygFeb 04 2005The evolution of the soft X-ray emission of V1974 Cyg has been simulated by a white dwarf envelope model with steady hydrogen burning. The comparison of the results obtained from ROSAT observations with the results of our envelope models indicates that ... More
Non-exact Integral FunctorsFeb 18 2011We give a natural notion of (non-exact) integral functor in the context of k-linear and graded categories. In this broader sense, we prove that every k-linear and graded functor is integral.
Exact T=0 Partition Functions for Potts Antiferromagnets on Sections of the Simple Cubic LatticeFeb 10 2001We present exact solutions for the zero-temperature partition function of the $q$-state Potts antiferromagnet (equivalently, the chromatic polynomial $P$) on tube sections of the simple cubic lattice of fixed transverse size $L_x \times L_y$ and arbitrarily ... More
XMM-Newton Observations of Recent Galactic NovaeOct 05 2004We report on the observations of five recent galactic classical novae, performed with XMM-Newton. Some of them show emission in the whole range from 0.2 to 8.0 keV, up to 3 years after the explosion. Nova Oph 1998 shows clear evidence of resumed accretion ... More
Liouville-type theorems for foliations with complex leavesAug 11 2007We discuss various problems regarding the structure of the foliation of some foliated submanifolds S of C^n, in particular Levi flat ones. As a general scheme, we suppose that S is bounded along a coordinate (or a subset of coordinates), and prove that ... More