Results for "Silvia Bianchi"

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An all order identity between ABJM and N=4 SYM four-point amplitudesDec 15 2011We derive an exact algebraic identity between the two-loop four-point amplitude in ABJM theory and the corresponding one-loop amplitude in N=4 SYM theory. This identity generalizes previous partial results to an exact relation valid at all orders in the ... More
On dominating set polyhedra of circular interval graphsDec 19 2017Feb 20 2018Clique-node and closed neighborhood matrices of circular interval graphs are circular matrices. The stable set polytope and the dominating set polytope on these graphs are therefore closely related to the set packing polytope and the set covering polyhedron ... More
Circuits and circulant minorsFeb 08 2019Circulant contraction minors play a key role for characterizing ideal circular matrices in terms of minimally non ideal structures. In this article we prove necessary and sufficient conditions for a circular matrix $A$ to have circulant contraction minors ... More
Scattering in ABJ theoriesOct 04 2011We study the correspondence between scattering amplitudes and Wilson loops in three-dimensional Chern-Simons matter theories. In particular, using N=2 superspace formalism, we compute at one loop the whole spectrum of four-point superamplitudes for generic ... More
The Conformal Manifold of Chern-Simons Matter TheoriesSep 30 2010Oct 25 2010We determine perturbatively the conformal manifold of N=2 Chern-Simons matter theories with the aim of checking in the three dimensional case the general prescription based on global symmetry breaking, recently introduced. We discuss in details few remarkable ... More
Infrared stability of ABJ-like theoriesOct 27 2009Nov 11 2009We consider marginal deformations of the superconformal ABJM/ABJ models which preserve N=2 supersymmetry. We determine perturbatively the spectrum of fixed points and study their infrared stability. We find a closed line of fixed points which is IR stable. ... More
Some advances on the set covering polyhedron of circulant matricesMay 28 2012Working on the set covering polyhedron of consecutive ones circulant matrices, Argiroffo and Bianchi found a class of facet defining inequalities, induced by a particular family of circulant minors. In this work we extend these results to inequalities ... More
Infrared Stability of N=2 Chern-Simons Matter TheoriesDec 22 2009Feb 04 2010According to the AdS4/CFT3 correspondence, N=2 supersymmetric Chern-Simons matter theories should have a stable fixed point in the infrared. In order to support this prediction we study RG flows of two-level Chern-Simons matter theories with/without flavors ... More
Minimally helicity violating, maximally simple scalar amplitudes in N=4 SYMAug 01 2012Nov 21 2012In planar N=4 SYM we study a particular class of helicity preserving amplitudes. These are scalar amplitudes whose flavor configuration is chosen in such a way that only a limited number of diagrams is allowed, which exhibit an iterative structure. For ... More
Correctors and Field Fluctuations for the $p_ε(x)$-Laplacian with Rough Exponents: The Sublinear Growth CaseJul 15 2011Jun 14 2012A corrector theory for the strong approximation of gradient fields inside periodic composites made from two materials with different power law behavior is provided. Each material component has a distinctly different exponent appearing in the constitutive ... More
Techniques to study cosmic ray anisotropiesFeb 20 2009These lectures review some of the techniques used to analyze the arrival direction distribution of Cosmic Rays, and some relevant results on the field.
Asymptotic properties of adaptive maximum likelihood estimators in latent variable modelsJun 25 2012Jul 04 2014Latent variable models have been widely applied in different fields of research in which the constructs of interest are not directly observable, so that one or more latent variables are required to reduce the complexity of the data. In these cases, problems ... More
Umbral Calculus, a Different Mathematical LanguageFeb 24 2018This thesis is intended to provide an account of the theory and applications of Operational Methods that allow the "translation" of the theory of special functions and polynomials into a "different" mathematical language. The language we are referring ... More
Modelling the Far-Infrared emission in spyral galaxiesNov 22 1999This thesis presents an original model for the FIR emission in spirals, developed from an existing radiative transfer code (Bianchi, Ferrara & Giovanardi, 1996, ApJ, 465, 127). The model's main features are: a complete treatment of multiple scattering ... More
Dust Extinction and Emission in a Clumpy Galactic Disk. An Application of the Radiative Transfer Code TRADINGJul 18 2008Jul 24 2008AIMS: I present the Monte Carlo radiative transfer code TRADING (Transfer of RAdiation through Dust In Galaxies). The code computes self-consistently the extinction of radiation in a dusty medium (including absorption and scattering) and the dust emission. ... More
The covariogram and Fourier-Laplace transform in $\mathbb{C}^n$Dec 30 2013Apr 29 2016The covariogram $g_{K}$ of a convex body $K$ in $\mathbb{R}^n$ is the function which associates to each $x\in\mathbb{R}^n$ the volume of the intersection of $K$ with $K+x$. Determining $K$ from the knowledge of $g_K$ is known as the Covariogram Problem. ... More
The 1/2 BPS Wilson loop in ABJ(M) at two loops: The detailsJul 02 2013Jul 14 2013We compute the expectation value of the 1/2 BPS circular Wilson loop operator in ABJ(M) theory at two loops in perturbation theory. Our result turns out to be in exact agreement with the weak coupling limit of the prediction coming from localization, ... More
Light-like Wilson loops in ABJM and maximal transcendentalityApr 22 2013We revisit the computation of the two-loop light-like tetragonal Wilson loop for three dimensional pure Chern-Simons and N=6 Chern-Simons-matter theory, within dimensional regularization with dimensional reduction scheme. Our examination shows that, contrary ... More
The 1/2 BPS Wilson loop in ABJM theory at two loopsMar 27 2013We compute the expectation value of the 1/2 BPS circular Wilson loop in ABJM theory at two loops in perturbation theory. The result shows perfect agreement with the prediction from localization and the proposed framing factor.
Lovász-Schrijver PSD-operator on Claw-Free GraphsDec 06 2016The subject of this work is the study of $\LS_+$-perfect graphs defined as those graphs $G$ for which the stable set polytope $\stab(G)$ is achieved in one iteration of Lov\'asz-Schrijver PSD-operator $\LS_+$, applied to its edge relaxation $\estab(G)$. ... More
Detection of Gamma-Ray Bursts in the 1 GeV - 1 TeV energy range by ground based experimentsApr 23 1999Sep 29 1999Ground based extensive air showers arrays can observe GRBs in the 1-1000 GeV energy range using the "single particle" techique. The sensitivity to detect a GRB as a function of the burst parameters and the detector characteristics are discussed. The rate ... More
A characterization of two classes of locally truncated diagram geometriesNov 27 2007We study locally truncated geometries that are parapolar spaces locally of type A_{n-1,j}(K) with n>6 and j=3,4. Residually connected sheaves over these geometries are constructed. It is proved that these geometries are residually connected diagram geometries ... More
Clusters of galaxies and variation of the fine structure constantDec 05 2012We propose a new method to probe for variations in the fine structure constant alpha using clusters of galaxies, opening up a window on a new redshift range for such constraints. Hot clusters shine in the X-ray mainly due to bremsstrahlung, while they ... More
Asymptotics of the occupancy scheme in a random environment and its applications to triesSep 11 2016Consider $ m $ copies of an irreducible, aperiodic Markov chain $ Y $ taking values in a finite state space. The asymptotics as $ m $ tends to infinity, of the first time from which on the trajectories of the $ m $ copies differ, have been studied by ... More
On the Chern numbers and the Hilbert polynomial of an almost complex manifold with a circle actionNov 24 2014Feb 15 2016Let $(M,J)$ be a compact, connected, almost complex manifold of dimension $2n$ endowed with a $J$-preserving circle action with isolated fixed points. In this note we analyse the `geography problem' for such manifolds, deriving equations relating the ... More
Asymptotics of the occupancy scheme in a random environment and its applications to triesSep 11 2016Aug 03 2017Consider $ m $ copies of an irreducible, aperiodic Markov chain $ Y $ taking values in a finite state space. The asymptotics as $ m $ tends to infinity, of the first time from which on the trajectories of the $ m $ copies differ, have been studied by ... More
Worldsheet scattering for the GKP stringAug 28 2015We initiate the perturbative study of the S-matrix for the excitations on top of the GKP vacuum at strong coupling. Using the string sigma model action expanded around the null cusp classical solution, we compute the tree-level S-matrix elements and compare ... More
Perturbation theory for string sigma modelsApr 06 2016Apr 07 2016In this thesis we investigate quantum aspects of the Green-Schwarz superstring in various AdS backgrounds relevant for the AdS/CFT correspondence, providing several examples of perturbative computations in the corresponding integrable sigma-models. We ... More
Higher Spins and Stringy AdS5xS5Sep 29 2004In this lecture I review recent work on higher spin holography. After a notational flash on the AdS/CFT correspondence, I will discuss HS symmetry enhancement and derive the spectrum of perturbative type IIB superstring excitations on AdS5 in this limit. ... More
Duality Symmetries in String TheoryNov 24 1995Dec 21 1995We review the status of duality symmetries in superstring theories. These discrete symmetries mark the striking differences between theories of pointlike objects and theories of extended objects. They prove to be very helpful in understanding non-perturbative ... More
Type I Superstrings without D-branesFeb 12 1997Notwithstanding the central role of D-branes in many recently proposed string dualities, several interesting type I vacua have been found without resorting directly to D-brane technology. In this talk, we analyze a three-generation SO(8)xU(12) chiral ... More
Parabolic implosion for endomorphisms of $\mathbb{C}^2$Jul 27 2016We give an estimate of the discontinuity of the large Julia set for a perturbation of a class of maps tangent to the identity, by means of a two-dimensional Lavaurs Theorem. We adapt to our situation a strategy due to Bedford, Smillie and Ueda in the ... More
Nonanticommutative U(1) SYM theories: Renormalization, fixed points and infrared stabilityApr 21 2009Renormalizable nonanticommutative SYM theories with chiral matter in the adjoint representation of the gauge group have been recently constructed in [arXiv:0901.3094]. In the present paper we focus on the U*(1) case with matter interacting through a cubic ... More
The Minor inequalities in the description of the Set Covering Polyhedron of Circulant MatricesJun 06 2012In this work we give a complete description of the set covering polyhedron of circulant matrices $C^k_{sk}$ with $s = 2,3$ and $k\geq 3 $ by linear inequalities. In particular, we prove that every non boolean facet defining inequality is associated with ... More
Radiative Transfer in Spiral GalaxiesSep 16 2003The internal dust extinction in spiral galaxies can affect our understanding of their structure and morphology, as well as our perception of the distant universe in the background. The intrinsic properties of the stellar and dust components can be studied ... More
On R^4 terms and MHV amplitudes in N = 5,6 supergravity vacua of Type II superstringsOct 22 2010We compute one-loop threshold corrections to R^4 terms in N= 5,6 supergravity vacua of Type II superstrings. We then discuss non-perturbative corrections generated by asymmetric D-brane instantons. Finally we derive generating functions for MHV amplitudes ... More
Higher spin symmetry (breaking) in N=4 SYM theory and holographySep 29 2004I concisely review the results of recent work done in collaboration with N. Beisert, H. Samtleben, and J. F. Morales, that shed some light on ``La Grande Bouffe'', the Pantagruelic Higgs mechanism whereby higher spin gauge fields in the AdS bulk eat lower ... More
The covariogram determines three-dimensional convex polytopesMay 12 2008The cross covariogram g_{K,L} of two convex sets K, L in R^n is the function which associates to each x in R^n the volume of the intersection of K with L+x. The problem of determining the sets from their covariogram is relevant in stochastic geometry, ... More
Vindicating single-T modified blackbody fits to Herschel SEDs (Research Note)Feb 22 2013I show here that the bulk of the dust mass in a galaxy can be equivalently estimated from: i) the full spectral energy distribution of dust emission, using the approach of Draine & Lee (2007) that includes a distribution of dust grains and a range of ... More
Consequences of the functional equation of the $p$-adic $L$-function of an elliptic curveNov 09 2016We prove that the first two coefficients in the series expansion around $s=1$ of the $p$-adic $L$-function of an elliptic curve over $\mathbb{Q}$ are related by a formula involving the conductor of the curve. This is analogous to a recent result of Wuthrich ... More
Quantum dispersion relations for the $AdS_4 \times CP^3$ GKP stringMay 04 2015Nov 04 2015We compute the one-loop correction to the dispersion relations of the excitations of the $AdS_4 \times CP^3$ sigma model dual to ABJM theory, expanded around the cusp background. The results parallel those of N = 4 SYM. As in that case, the dispersion ... More
On the scattering of gluons in the GKP stringNov 03 2015We compute the one-loop S-matrix for the light bosonic excitations of the GKP string at strong coupling. These correspond, on the gauge theory side, to gluon insertions in the GKP vacuum. We perform the calculation by Feynman diagrams in the worldsheet ... More
Non-planarity through unitarity in ABJMNov 25 2013May 21 2014We use unitarity techniques to compute the two-loop non-planar corrections to the Sudakov form factor and the four-point amplitude in ABJM theory. We start by reconstructing non-planar integrals from two-particle cuts in three dimensions. This causes ... More
The dust distribution in edge-on galaxies. Radiative transfer fits of V and K'-band imagesMay 10 2007Aims: I have analyzed a sample of seven nearby edge-on galaxies observed in the V and K'-band, in order to infer the properties of the dust distribution. Methods: A radiative transfer model, including scattering, have been used to decompose each image ... More
From Twists and Shifts to L-R asymmetric D-branesFeb 04 2009In the first part of the talk, we discuss non-geometric twists and shifts and briefly review asymmetric orbifolds and free fermion constructions. These allow us to build Type IIB models with N = 1_L + 1_R and N = 1_L + 0_R models having few or no moduli. ... More
Recent Trends in Superstring PhenomenologySep 09 2009We review for non-experts possible phenomenological scenari in String Theory. In particular we focus on vacuum configurations with intersecting and/or magnetized unoriented D-branes. We will show how a TeV scale tension may be compatible with the existence ... More
Bound-states of D-branes in L-R asymmetric superstring vacuaMay 21 2008We discuss bound-states of D-branes in truly L-R asymmetric and thus non-geometric Type II vacuum configurations with extended supersymmetry. We argue for their stability as a result of residual supersymmetry and coupling to R-R potentials surviving in ... More
(Non-)perturbative tests of the AdS/CFT correspondenceMar 14 2001Apr 04 2001I summarize perturbative and non-perturbative field theory tests of the holographic correspondence between type IIB superstring on AdS_5xS^5 and N=4 SYM theory. The holographic duality between D-instantons and YM instantons is briefly described. Non renormalization ... More
Open Strings and DualitiesDec 02 1997In the fruitful interplay between gauge fields and strings and in many conjectured M-theory dualities, open strings play a prominent role. We review the construction of open-string descendants (un-orientifolds) of closed-string theories admitting a generalized ... More
A Note on Toroidal Compactifications of the Type I Superstring and Other Superstring Vacuum Configurations with 16 SuperchargesNov 28 1997Aug 07 1998We show that various disconnected components of the moduli space of superstring vacua with 16 supercharges admit a rationale in terms of BPS un-orientifolds, i.e. type I toroidal compactifications with constant non-vanishing but quantized vacuum expectation ... More
Ergodic convergence of a stochastic proximal point algorithmApr 21 2015Jul 25 2016The purpose of this paper is to establish the almost sure weak ergodic convergence of a sequence of iterates $(x_n)$ given by $x_{n+1} = (I+\lambda_n A(\xi_{n+1},\,.\,))^{-1}(x_n)$ where $(A(s,\,.\,):s\in E)$ is a collection of maximal monotone operators ... More
Entropy of Non-Extremal Black Holes from Loop GravityApr 23 2012We compute the entropy of non-extremal black holes using the quantum dynamics of Loop Gravity. The horizon entropy is finite, scales linearly with the area A, and reproduces the Bekenstein-Hawking expression S = A/4 with the one-fourth coefficient for ... More
Misiurewicz parameters and dynamical stability of polynomial-like maps of large topological degreeDec 08 2016Given a family of polynomial-like maps of large topological degree, we relate the presence of Misiurewicz parameters to a growth condition of the postcritical volume. This allows us to generalize to this setting the theory of stability and bifurcation ... More
On some logical and algebraic properties of axiomatic extensions of the monoidal t-norm based logic MTL related with single chain completenessMay 21 2012In [Mon11] are studied, for the axiomatic extensions of the monoidal t-norm based logic ([EG01]), the properties of single chain completeness. On the other side, in [GJKO07, Chapter 5] are studied many logical and algebraic properties (like Halld\'en ... More
The Effects of Galaxy Shape and Rotation on the X-ray Haloes of Early-Type GalaxiesApr 15 2013May 20 2013We present a detailed diagnostic study of the observed temperatures of the hot X-ray coronae of early-type galaxies. By extending the investigation carried out in Pellegrini (2011) with spherical models, we focus on the dependence of the energy budget ... More
The effects of flattening and rotation on the temperature of the X-ray halos of elliptical galaxiesFeb 27 2013Elliptical galaxies have hot coronae with X-ray luminosities and mean gas temperatures that span over wide ranges. This variation can be partially due to the energy budget of the hot gas, that depends on the host galaxy structure and internal kinematics. ... More
A comparison of some criteria for states selection in the latent Markov model for longitudinal dataDec 03 2012We compare different selection criteria to choose the number of latent states of a multivariate latent Markov model for longitudinal data. This model is based on an underlying Markov chain to represent the evolution of a latent characteristic of a group ... More
Modeling and Querying Data Cubes on the Semantic WebDec 18 2015The web is changing the way in which data warehouses are designed, used, and queried. With the advent of initiatives such as Open Data and Open Government, organizations want to share their multidimensional data cubes and make them available to be queried ... More
A Direct Proof of Schwichtenberg's Bar Recursion Closure TheoremJul 18 2016In 1979 Schwichtenberg showed that a rule-like version Spector's bar recursion of lowest type levels $0$ and $1$ is closed under system $\text{T}$. More precisely, if the functional $Y$ which controls the stopping condition of Spector's bar recursor is ... More
The local power of the gradient testApr 30 2010Jul 12 2010The asymptotic expansion of the distribution of the gradient test statistic is derived for a composite hypothesis under a sequence of Pitman alternative hypotheses converging to the null hypothesis at rate $n^{-1/2}$, $n$ being the sample size. Comparisons ... More
A multidimensional latent class IRT model for non-ignorable missing responsesOct 17 2014We propose a structural equation model, which reduces to a multidimensional latent class item response theory model, for the analysis of binary item responses with non-ignorable missingness. The missingness mechanism is driven by two sets of latent variables: ... More
Profiles of Strong Permitted Lines in Classical T Tauri StarsJan 18 2000We present a spectral analysis of 30 T Tauri stars observed with the Hamilton echelle spectrograph over more than a decade. One goal is to test magnetospheric accretion model predictions. Observational evidence previously published supporting the model, ... More
Automorphisms of trivalent graphsNov 15 2011Let $G_{g,b}$ be the set of all uni/trivalent graphs representing the combinatorial structures of pant decompositions of the oriented surface of genus $g$ with $b$ boundary components. We describe the set $A_{g,b}$ of all automorphisms of graphs in $G_{g,b}$ ... More
Evaluation of two interaction techniques for visualization of dynamic graphsAug 31 2016Several techniques for visualization of dynamic graphs are based on different spatial arrangements of a temporal sequence of node-link diagrams. Many studies in the literature have investigated the importance of maintaining the user's mental map across ... More
Avoiding substrings in compositonsMar 30 2009Jun 23 2009A classical result by Guibas and Odlyzko obtained in 1981 gives the generating function for the number of strings that avoid a given set of substrings with the property that no substring is contained in any of the others. In this paper, we give an analogue ... More
Multiple $\mathbb{S}^{1}$-orbits for the Schrödinger-Newton systemApr 29 2013We prove existence and multiplicity of symmetric solutions for the \emph{Schr\"odinger-Newton system} in three dimensional space using equivariant Morse theory.
A dynamical model of the adaptive immune system: effects of cells promiscuity, antigens and B-B interactionsMay 14 2015We analyse a minimal model for the primary response in the adaptive immune system comprising three different players: antigens, T and B cells. We assume B-T interactions to be diluted and sampled locally from heterogeneous degree distributions, which ... More
Associative networks with diluted patterns: dynamical analysis at low and medium loadMay 10 2014In this work we solve the dynamics of pattern diluted associative networks, evolving via sequential Glauber update. We derive dynamical equations for the order parameters, that quantify the simultaneous pattern recall of the system, and analyse the nature ... More
Overview of the Heisenberg--Weyl Algebra and Subsets of Riordan SubgroupsApr 07 2014Jan 21 2016In a first part, we are concerned with the relationships between polynomials in the two generators of the algebra of Heisenberg--Weyl, its Bargmann--Fock representation with differential operators and the associated one-parameter group.Upon this basis, ... More
Size and power properties of some tests in the Birnbaum-Saunders regression modelMay 18 2010The Birnbaum-Saunders distribution has been used quite effectively to model times to failure for materials subject to fatigue and for modeling lifetime data. In this paper we obtain asymptotic expansions, up to order $n^{-1/2}$ and under a sequence of ... More
Proceedings Combined 21st International Workshop on Expressiveness in Concurrency and 11th Workshop on Structural Operational SemanticsAug 06 2014This volume contains the proceedings of the Combined 21st International Workshop on Expressiveness in Concurrency and the 11th Workshop on Structural Operational Semantics (EXPRESS/SOS 2014) which was held on 1st September 2014 in Rome, Italy, as an affiliated ... More
Algebraic Properties of Codimension Series of PI-AlgebrasNov 01 2011For a PI-algebra R over a field of characteristic 0 let T(R) be the T-ideal of the polynomial identities of R and let c(R,t) be the codimension series of R (i.e., the generating function of the codimension sequence of R). Let A, B and R be PI-algebras ... More
The complex of pant decompositions of a surfaceOct 08 2007Oct 27 2007We exhibit a set of edges (moves) and 2-cells (relations) making the complex of pant decompositions on a surface a simply connected complex. Our construction, unlike the previous ones, keeps the arguments concerning the structural transformations independent ... More
A characteristic subgroup for fusion systemsNov 22 2008As a counterpart for the prime 2 to Glauberman's $ZJ$-theorem, Stellmacher proves that any nontrivial 2-group $S$ has a nontrivial characteristic subgroup $W(S)$ with the following property. For any finite $\Sigma_4$-free group $G$, with $S$ a Sylow 2-subgroup ... More
Approximated structured pseudospectraNov 14 2016Pseudospectra and structured pseudospectra are important tools for the analysis of matrices. Their computation, however, can be very demanding for all but small matrices. A new approach to compute approximations of pseudospectra and structured pseudospectra, ... More
On a homotopy relation between the 2-local geometry and the Bouc complex for the sporadic group McLOct 26 2005Nov 29 2007We study the homotopy relation between the standard 2-local geometry and the Bouc complex for the sporadic finite simple group McL.
Fast nonnegative least squares through flexible Krylov subspacesNov 19 2015Aug 11 2016Constrained least squares problems arise in a variety of applications, and many iterative methods are already available to compute their solutions. This paper proposes a new efficient approach to solve nonnegative linear least squares problems. The associated ... More
FBOTs and AT2018cow following electron-capture collapse of merged white dwarfsDec 18 2018We suggest that fast-rising blue optical transients (FBOTs), and the brightest event of the class AT2018cow, result from electron-capture collapse following a merger of a massive ONeMg white dwarf (WD) with another WD. Two distinct evolutionary channels ... More
Using simple elastic bands to explain quantum mechanics: a conceptual review of two of Aert's machine-modelsDec 17 2011Aug 21 2012From the beginning of his research, the Belgian physicist Diederik Aerts has shown great creativity in inventing a number of concrete machine-models that have played an important role in the development of general mathematical and conceptual formalisms ... More
God may not play dice, but human observers surely doAug 03 2012We investigate indeterminism in physical observations. For this, we introduce a distinction between genuinely indeterministic (creation-1 and discovery-1) observational processes, and fully deterministic (creation-2 and discovery-2) observational processes, ... More
Comment on "The quantum mechanics of electric conduction in crystals," by R. J. Olsen and G. Vignale [Am. J. Phys. 78 (9), 954-960 (2010)]Apr 25 2011In this note we use the notion of time-delay to explain the physical content of the transformation properties of transmission and reflection amplitudes, as a result of a displacement of the potential. Then, we reconsider the recent analysis of the scattering ... More
From permanence to total availability: a quantum conceptual upgradeOct 24 2010Jun 14 2011We consider the classical concept of time of permanence and observe that its quantum equivalent is described by a bona fide self-adjoint operator. Its interpretation, by means of the spectral theorem, reveals that we have to abandon not only the idea ... More
Notes on unoriented D-brane instantonsSep 11 2009In the first lecture, we discuss basic aspects of worldsheet and penta-brane instantons as well as (unoriented) D-brane instantons, which is our main focus here, and threshold corrections to BPS-saturated couplings. The second lecture is devoted to non-perturbative ... More
Non-renormalisation of extremal correlators in N=4 SYM theoryOct 01 1999Oct 19 1999We show that extremal correlators of chiral primary operators in N=4 supersymmetric Yang-Mills theory with SU(N) gauge group are neither renormalised at first order in perturbation theory nor receive contribution from any instanton sector at leading order ... More
Non-perturbative and Flux superpotentials for Type I strings on the Z_3 orbifoldFeb 01 2007Apr 04 2007Non-perturbative effects are studied for Type I strings on the Z_3 orbifold with Chan-Paton symmetry broken by Wilson lines. Generalizing previous analyses that have focussed on (bi)fundamentals, it is argued that (anti)symmetric representations of the ... More
The Effective Temperatures of O-type Stars from UV spectroscopyAug 14 2013We present an analysis of high resolution spectra in the far-UV -- UV range (~905-2000\AA) with non-LTE, spherical, hydrodynamical, line-blanketed models, of three O-type Galactic stars, and derive their photospheric and wind parameters. These data extend ... More
DDF operators, open string coherent states and their scattering amplitudesFeb 19 2019We study interactions of string coherent states in the DDF (after Di Vecchia, Del Giudice, Fubini) formalism. For simplicity we focus on open bosonic strings. After reviewing basic properties of DDF operators and of excited open strings, we compute various ... More
Framing and localization in Chern-Simons theories with matterApr 01 2016Jun 23 2016Supersymmetric localization provides exact results that should match QFT computations in some regularization scheme. The agreement is particularly subtle in three dimensions where complex answers from localization procedure sometimes arise. We investigate ... More
ABJM amplitudes and WL at finite NJun 13 2013Jul 25 2013We evaluate ABJM observables at two loops, for any value of the rank N of the gauge group. We compute the color subleading contributions to the four-point scattering amplitude in ABJM at two loops. Contrary to the four dimensional case, IR divergent N-subleading ... More
Scattering Amplitudes/Wilson Loop Duality In ABJM TheoryJul 15 2011Oct 05 2011For N=6 superconformal Chern-Simons-matter theories in three dimensions, by a direct superspace Feynman diagram approach, we compute the two-loop four-point scattering amplitude with external chiral matter fields. We find that the result is in perfect ... More
The quantum 1/2 BPS Wilson loop in ${\cal N}=4$ Chern-Simons-matter theoriesJun 22 2016In three dimensional ${\cal N}=4$ Chern-Simons-matter theories two independent fermionic Wilson loop operators can be defined, which preserve half of the supersymmetry charges and are cohomologically equivalent at classical level. We compute their three-loop ... More
One Loop Amplitudes In ABJMApr 19 2012Jul 10 2012For three dimensional N=6 superconformal field theories we compute one-loop scattering amplitudes for any number of external particles. We focus on a particular subsector of N=2 invariant superamplitudes for which the ordinary perturbative evaluation ... More
Interplay between charge-order, ferroelectricity and ferroelasticity: tungsten bronze structures as a playground for multiferroicityDec 10 2009Large electron-electron Coulomb-interactions in correlated systems can lead to a periodic arrangement of localized electrons, the so called "charge-order". The latter is here proposed as a driving force behind ferroelectricity in iron fluoride K0.6FeF3. ... More
Operators ideals and approximation propertiesNov 30 2012Dec 13 2012We use the notion of $\A$-compact sets, which are determined by a Banach operator ideal $\A$, to show that most classic results of certain approximation properties and several Banach operator ideals can be systematically studied under this framework. ... More
Low-mode averaging for baryon correlation functionsOct 03 2005The low-mode averaging technique is a powerful tool for reducing large fluctuations in correlation functions due to low-mode eigenvalues of the Dirac operator. In this work we propose a generalization to baryons and test our method on two-point correlation ... More
Semiclassical analysis for pseudo-relativistic Hartree equationsJan 26 2015In this paper we study the semiclassical limit for the pseudo-relativistic Hartree equation $\sqrt{-\varepsilon^2 \Delta + m^2}u + V u = (I_\alpha * |u|^{p}) |u|^{p-2}u$ in $\mathbb{R}^N$ where $m>0$, $2 \leq p < \frac{2N}{N-1}$, $V \colon \mathbb{R}^N ... More
Cocharacters of polynomial identities of upper triangular matricesJan 24 2011We give an easy algorithm which calculates the generating function of the cocharacter sequence of the T-ideal of the polynomial identities of the algebra of upper triangular matrices over a field of characteristic zero. Applying this algorithm we have ... More
Ferroelectricity induced by cooperative orbital ordering and Peierls instabilityApr 23 2012A general mechanism by which orbital ordering, coupled to Peierls-like lattice distortions, can induce an electronic switchable polarization is discussed within a model Hamiltonian approach in the context of the modern theory of polarization. By using ... More
Orbital degrees of freedom as origin of magnetoelectric coupling in magnetiteOct 06 2010Oct 07 2010A microscopic understanding of magnetoelectricity, i.e. the coupling between magnetic (electric) properties and external electric (magnetic) fields, is a crucial milestone for future generations of electrically-controlled spintronic devices. Here, we ... More
Dynamic programming for infinite horizon boundary control problems of PDE's with age structureJun 26 2008We develop the dynamic programming approach for a family of infinite horizon boundary control problems with linear state equation and convex cost. We prove that the value function of the problem is the unique regular solution of the associated stationary ... More