total 83343took 0.14s

SCUBA observations of NGC 6946Dec 01 1999We present sub-millimetre images of the spiral galaxy NGC 6946 at 450 and 850 um. The observations have been carried out using the scan/map imaging mode of the Sub-millimetre Common User Bolometer Array (SCUBA) at the James Clark Maxwell Telescope (JCMT). ... More

D-strings in unconventional type I vacuum configurationsNov 02 1998Apr 12 1999We determine the spectrum of D-string bound states in various classes of generalized type I vacuum configurations with sixteen and eight supercharges. The precise matching of the BPS spectra confirms the duality between unconventional type IIB orientifolds ... More

(Unoriented) T-folds with few T'sDec 31 2008Mar 10 2009We use the combined action of Z_2-chiral reflections (T-dualities) and shifts to build N=1,2 supersymmetric four-dimensional string compactifications with few moduli. In particular, we consider Z_2^4 asymmetric orbifolds of Type IIB on the maximal torus ... More

Black hole entropy from graviton entanglementNov 02 2012Jan 07 2013We argue that the entropy of a black hole is due to the entanglement of matter fields and gravitons across the horizon. While the entanglement entropy of the vacuum is divergent because of UV correlations, we show that low-energy perturbations of the ... More

Black Hole Entropy, Loop Gravity, and Polymer PhysicsNov 25 2010Loop Gravity provides a microscopic derivation of Black Hole entropy. In this paper, I show that the microstates counted admit a semiclassical description in terms of shapes of a tessellated horizon. The counting of microstates and the computation of ... 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

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 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

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

Anomalies, RG-flows and Open/Closed String DualityJan 16 2001We discuss the interplay between IR and UV divergences in vacuum configurations with open and unoriented strings. We establish a general one-to-one correspondence between anomalies and R-R tadpoles associated to sectors with non-trivial Witten index. ... More

RG-flows and Open/Closed String DualityJun 22 2000Aug 28 2000We discuss the interpaly between IR and UV divergences in theories with open and unoriented strings in view of the AdS/CFT correspondence. We start by deriving general formulas for the computation of threshold corrections to gauge couplings in generic ... More

Unoriented D-brane Instantons vs Heterotic worldsheet InstantonsDec 12 2007Feb 01 2008We discuss Fermi interactions of four hyperini generated by ``stringy'' instantons in a Type I / Heterotic dual pair on T^4/Z_2.

Testing warm Comptonization models for the origin of the soft X-ray excess in AGNOct 13 2017The X-ray spectra of many active galactic nuclei (AGN) show a soft X-ray excess below 1-2 keV on top of the extrapolated high- energy power law. The origin of this component is uncertain. It could be a signature of relativistically blurred, ionized reflection, ... More

First order superconducting phase transition in CeCoIn$_5$Mar 14 2002We investigated the magnetic field dependence of the superconducting phase transition in heavy fermion CeCoIn_5 (T_c = 2.3 K) using specific heat, magneto-caloric effect, and thermal expansion measurements. The superconducting transition becomes first ... More

Anomalies & TadpolesFeb 17 2000We show that massless RR tadpoles in vacuum configurations with open and unoriented strings are always related to anomalies. RR tadpoles arising from sectors of the internal SCFT with non-vanishing Witten index are in one-to-one correspondence with conventional ... More

A deep X-ray view of the bare AGN Ark 120. VI. Geometry of the hot corona from spectroscopic and polarization signaturesNov 19 2018The spectral shape of the hard X-ray continuum of Active Galactic Nuclei (AGN) can be ascribed to inverse Compton scattering of optical/UV seed photons from the accretion disc by a hot corona of electrons. This physical process produces a polarization ... More

The Blaschke-Santalo InequalityDec 01 2013Aug 04 2014The Blaschke-Santal\'o Inequality is the assertion that the volume product of a centrally symmetric convex body in Euclidean space is maximized by (and only by) ellipsoids. In this paper we give a Fourier analytic proof of this fact.

Horizon energy as the boost boundary term in general relativity and loop gravityMay 24 2012We show that the near-horizon energy introduced by Frodden, Ghosh and Perez arises from the action for general relativity as a horizon boundary term. Spin foam variables are used in the analysis. The result provides a derivation of the horizon boost Hamiltonian ... More

The perturbative Regge-calculus regime of Loop Quantum GravitySep 13 2007Dec 11 2007The relation between Loop Quantum Gravity and Regge calculus has been pointed out many times in the literature. In particular the large spin asymptotics of the Barrett-Crane vertex amplitude is known to be related to the Regge action. In this paper we ... More

Identities and isomorphisms of finite-dimensional graded simple algebrasApr 04 2018Jun 07 2018Let $\mathbb F$ be an algebraically closed field, $G$ be an abelian group, and let $A$ and $B$ be arbitrary finite-dimensional $G$-graded simple algebras over $\mathbb F$. We prove that $A$ and $B$ are isomorphic if, and only if, they satisfy the same ... More

Holomorphic motion for Julia sets of holomorphic families of endomorphisms of CP(k)Jan 14 2015We build measurable holomorphic motions for Julia sets of holomorphic families of endomorphisms of CP(k) under various equivalent notions of stability.

The recent star formation in NGC 6822 from HST imagingMay 14 2006We present HST WFPC2 and STIS imaging of the low metallicity galaxy NGC 6822, performed as part of a study of the young stellar populations in the galaxies of the Local Group. Eleven WFPC2 pointings, with some overlap, cover two regions, extending over ... More

Are multi-factor Gaussian term structure models still useful? An empirical analysis on Italian BTPsMay 25 2018In this paper, we empirically study models for pricing Italian sovereign bonds under a reduced form framework, by assuming different dynamics for the short-rate process. We analyze classical Cox-Ingersoll-Ross and Vasicek multi-factor models, with a focus ... More

Neutron Majorana mass from exotic instantonsJul 10 2014Jul 30 2014We show how a Majorana mass for the Neutron could result from non-perturbative quantum gravity effects peculiar to string theory. In particular, "exotic instantons" in un-oriented string compactifications with D-branes extending the (supersymmetric) standard ... More

Unoriented D-brane instantonsFeb 29 2012We give a pedagogical introduction to D-brane instanton effects in vacuum configurations with open and unoriented strings. We focus on quiver gauge theories for unoriented D-branes at orbifold singularities and describe in some detail the Z_3 case, where ... More

Ephemeral properties and the illusion of microscopic particlesAug 14 2010Feb 20 2011Founding our analysis on the Geneva-Brussels approach to quantum mechanics, we use conventional macroscopic objects as guiding examples to clarify the content of two important results of the beginning of twentieth century: Einstein-Podolsky-Rosen's reality ... More

Enriques and Octonionic Magic Supergravity ModelsDec 18 2007We reconsider the Enriques Calabi Yau (FHSV) model and its string derivation and argue that the Octonionic magic supergravity theory admits a string interpretation closely related to the Enriques model. The uplift to D=6 of the Octonionic magic model ... More

The open story of the magnetic fluxesFeb 16 2005Feb 24 2005We discuss the effects of oblique internal magnetic fields on the spectrum of type I superstrings compactified on tori. In particular we derive general formulae for the magnetic shifts and multiplicities of open strings connecting D9-branes with arbitrary ... More

More on La Grande Bouffe: towards higher spin symmetry breaking in AdSApr 19 2005Aug 09 2005We discuss higher spin gauge symmetry breaking in AdS space from a holographic prespective. Indeed, the AdS/CFT correspondence implies that N=4 SYM theory at vanishing coupling constant is dual to a theory in AdS which exhibits higher spin gauge symmetry ... More

Probing Fuzzballs with Particles, Waves and StringsNov 28 2017Feb 24 2018We probe D1D5 micro-state geometries with massless particles, waves and strings. To this end, we study geodetic motion, Klein-Gordon equation and string scattering in the resulting gravitational background. Due to the reduced rotational symmetry, even ... More

Dynamical supersymmetry breaking from unoriented D-brane instantonsApr 14 2009We study the non-perturbative dynamics of an unoriented Z_5-quiver theory of GUT kind with gauge group U(5) and chiral matter. At strong coupling the non-perturbative dynamics is described in terms of set of baryon/meson variables satisfying a quantum ... More

On stringy AdS_5 x S^5 and higher spin holographyMay 07 2003Jun 13 2003We derive the spectrum of Kaluza-Klein descendants of string excitations on AdS_5 x S^5. String states are organized in long multiplets of the AdS supergroup SU(2,2|4,R) with a rich pattern of shortenings at the higher spin enhancement point \lambda=0. ... More

Organic molecules in the protoplanetary disk of DG Tau revealed by ALMAFeb 07 2019Planets form in protoplanetary disks and inherit their chemical compositions. It is thus crucial to map the distribution and investigate the formation of simple organics, such as formaldehyde and methanol, in protoplanetary disks. We analyze ALMA observations ... More

Multiple phase transitions in Ce(Rh,Ir,Co)In5 heavy-fermion superconductorsJul 12 2001Jul 17 2001Magnetic susceptibility, electrical resistivity and heat capacity data for single crystals of Ce(Rh,Ir)1-x(Co,Ir)xIn5 (0 < x < 1) have allowed us to construct a detailed phase diagram for this new family of heavy-fermion superconductors(HFS). CeRh1-xIrxIn5 ... More

Discrete torsion in non-geometric orbifolds and their open-string descendantsOct 28 1999Dec 09 1999We discuss some Z_N^L x Z_N^R orbifold compactifications of the type IIB superstring to D= 4,6 dimensions and their type I descendants. Although the Z_N^L x Z_N^R generators act asymmetrically on the chiral string modes, they result into left-right symmetric ... More

Measuring the Universe with galaxy redshift surveysMar 28 2018Galaxy redshift surveys are one of the pillars of the current standard cosmological model and remain a key tool in the experimental effort to understand the origin of cosmic acceleration. To this end, the next generation of surveys aim at achieving sub-percent ... More

D-brane Instantons on the T^6/Z_3 orientifoldApr 05 2007May 31 2007We give a detailed microscopic derivation of gauge and stringy instanton generated superpotentials for gauge theories living on D3-branes at Z_3-orientifold singularities. Gauge instantons are generated by D(-1)-branes and lead to Affleck, Dine and Seiberg ... More

Novel calibrations of virial black hole mass estimators in active galaxies based on X-ray luminosity and optical/NIR emission linesOct 11 2016Accurately weigh the masses of SMBH in AGN is currently possible for only a small group of local and bright broad-line AGN through reverberation mapping (RM). Statistical demographic studies can be carried out considering the empirical scaling relation ... More

Water and interstellar complex organics associated with the HH 212 protostellar disc - On disc atmospheres, disc winds, and accretion shocksJun 20 2018The HH 212 protostellar system, in Orion B, has been mapped thanks to ALMA-Band 7 Cycle 1 and Cycle 4 observations of dueterated water (HDO) and acetaldehyde (CH$_3$CHO) emission with an angular resolution down to $\sim$0.15 arcsec (60 au). Many emission ... More

Discreteness of the volume of space from Bohr-Sommerfeld quantizationFeb 26 2011Jun 06 2011A major challenge for any theory of quantum gravity is to quantize general relativity while retaining some part of its geometrical character. We present new evidence for the idea that this can be achieved by directly quantizing space itself. We compute ... More

The WISSH quasars Project: II. Giant star nurseries in hyper-luminous quasarsJun 13 2017Jun 15 2017Studying the coupling between the energy output produced by the central quasar and the host galaxy is fundamental to fully understand galaxy evolution. Quasar feedback is indeed supposed to dramatically affect the galaxy properties by depositing large ... More

RealPen: Providing Realism in Handwriting Tasks on Touch Surfaces using Auditory-Tactile FeedbackMar 06 2018We present RealPen, an augmented stylus for capacitive tablet screens that recreates the physical sensation of writing on paper with a pencil, ball-point pen or marker pen. The aim is to create a more engaging experience when writing on touch surfaces, ... More

Luminous star-forming galaxies in the SDSS-GALEX databaseFeb 17 2014We use the combined photometric SDSS + GALEX database to look for populations of luminous blue star-forming galaxies. These were initially identified from such a sample at redshifts near 0.4, using SDSS spectra. We make use of the colour index previously ... More

On the soft limit of open string disk amplitudes with massive statesMay 21 2015Aug 24 2015We discuss the soft behaviour of open string amplitudes with gluons and massive states in any dimension. Notwithstanding non-minimal couplings of massive higher spin states to gluons, relying on OPE and factorization, we argue that the leading and sub-leading ... More

Open Strings on the Neveu-Schwarz PentabraneNov 10 1997We analyze the propagation of open and unoriented strings on the Neveu-Schwarz pentabrane (N5-brane) along the lines of a similar analysis for the SU(2) WZNW models. We discuss the two classes of open descendants of the diagonal models and a series of ... More

Nustar Measurement Of Coronal Temperature In Two Luminous, High Redshift QsosApr 09 2019X-ray emission from AGN is believed to be produced via Comptonization of optical/UV seed photons emitted by the accretion disk, up-scattered by hot electrons in a corona surrounding the black hole. A critical compactness vs. temperature threshold is predicted ... More

Electronic inhomogeneity in a Kondo latticeApr 28 2011Inhomogeneous electronic states resulting from entangled spin, charge, and lattice degrees of freedom are hallmarks of strongly correlated electron materials; such behavior has been observed in many classes of d-electron materials, including the high-Tc ... More

Self-Assembly of Patchy Particles into Polymer Chains: A Parameter-Free Comparison between Wertheim Theory and Monte Carlo SimulationJan 22 2007We numerically study a simple fluid composed of particles having a hard-core repulsion, complemented by two short-ranged attractive (sticky) spots at the particle poles, which provides a simple model for equilibrium polymerization of linear chains. The ... More

One-dimensional spin texture of Bi(441); Quantum Spin Hall properties without a topological insulatorJun 26 2015The high index (441) surface of bismuth has been studied using Scanning Tunnelling Microscopy (STM), Angle Resolved Photoemission Spectroscopy (APRES) and spin-resolved ARPES. The surface is strongly corrugated, exposing a regular array of (110)-like ... More

The Suzaku X-ray spectrum of NGC 3147. Further insights on the best "true" Seyfert 2 galaxy candidateApr 04 2012NGC 3147 is so far the most convincing case of a "true" Seyfert 2 galaxy, i.e. a source genuinely lacking the Broad Line Regions. We obtained a Suzaku observation with the double aim to study in more detail the iron line complex, and to check the Compton-thick ... More

The Dark Side of FuzzballsNov 06 2018Black holes absorb any particle impinging with an impact parameter below a critical value. We show that 2- and 3-charge fuzzball geometries exhibit a similar trapping behaviour for a selected choice of the impact parameter of incoming massless particles. ... More

On the spectrum of AdS/CFT beyond supergravityOct 31 2003We test the spectrum of string theory on AdS_5 x S^5 derived in hep-th/0305052 against that of single-trace gauge invariant operators in free N=4 super Yang-Mills theory. Masses of string excitations at critical tension are derived by extrapolating plane-wave ... More

ALE Instantons in String TheorySep 20 1994In this talk we will describe a string solution which contains a self-dual (instantonic) metric and study its properties. Talk given by M.Bianchi at the Seventh Marcel Grossmann Meeting, Stanford July 24-30, 1994.

XMM-Newton broad-band observations of NGC 7582: Nh variations and fading out of the active nucleusFeb 21 2007We present results from two XMM-Newton observations of the bright classical Seyfert 2 galaxy NGC 7582 taken four years apart (2001 May and 2005 April). We present the analysis of the high-resolution (0.3-1 keV) RGS and low-resolution (0.3-10 keV) EPIC ... More

N=4 Superconformal Characters and Partition FunctionsSep 26 2006Character formulae for positive energy unitary representations of the N=4 superconformal group are obtained through use of reduced Verma modules and Weyl group symmetry. Expansions of these are given which determine the particular representations present ... More

Polar features in the flagellar propulsion of E. coli bacteriaJun 30 2015E. coli bacteria swim following a run and tumble pattern. In the run state all flagella join in a single helical bundle that propels the cell body along approximately straight paths. When one or more flagellar motors reverse direction the bundle unwinds ... More

Radio/X-ray monitoring of the broad-line radio galaxy 3C 382. High-energy view with XMM-Newton and NuSTARMay 16 2018We present the analysis of five joint XMM-Newton/NuSTAR observations, 20 ks each and separated by 12 days, of the broad-line radio galaxy 3C 382. The data were obtained as part of a campaign performed in September-October 2016 simultaneously with VLBA. ... More

String Theory and ALE InstantonsOct 28 1994We show that the classical equations of motion of the low-energy effective field theory describing the massless modes of the heterotic (or type I) string admit two classes of supersymmetric self--dual backgrounds. The first class, which was already considered ... More

Higher Spin Symmetry and N=4 SYMMay 07 2004Sep 10 2004We assemble the spectrum of single-trace operators in free N=4 SU(N) SYM theory into irreducible representations of the Higher Spin symmetry algebra hs(2,2|4). Higher Spin representations or YT-pletons are associated to Young tableaux (YT) corresponding ... More

Instanton Effects in Supersymmetric Yang-Mills Theories on ALE Gravitational BackgroundsJul 03 1995In this letter we report on the computation of instanton-dominated correlation functions in supersymmetric YM theories on ALE spaces. Following the approach of Kronheimer and Nakajima, we explicitly construct the self-dual connection on ALE spaces necessary ... More

ALE Instantons in String Effective TheorySep 07 1994We show that the classical equations of motion of the low-energy effective field theory describing the massless modes of the heterotic (or type I) string admit two classes of supersymmetric self--dual backgrounds. The first class, which was already considered ... More

The role of magnetic field for quiescence-outburst models in CVsDec 19 2014In this paper we present the elementary assumptions of our research on the role of the magnetic field in modelling the quiescence-outbursts cycle in Cataclysmic Variables (CVs). The behaviour of the magnetic field is crucial not only to integrate the ... More

XMM-Newton observations of 4 luminous radio-quiet AGN, and the soft X-ray excess problemJan 30 2008The nature and origin of the soft X-ray excess in radio quiet AGN is still an open issue. The interpretation in terms of thermal disc emission has been challanged by the discovery of the constancy of the effective temperature despite the wide range of ... More

Linear growth of the entanglement entropy and the Kolmogorov-Sinai rateSep 01 2017Feb 26 2018The rate of entropy production in a classical dynamical system is characterized by the Kolmogorov-Sinai entropy rate $h_{\mathrm{KS}}$ given by the sum of all positive Lyapunov exponents of the system. We prove a quantum version of this result valid for ... More

The boundary is mixedJun 21 2013We show that Oeckl's boundary formalism incorporates quantum statistical mechanics naturally, and we formulate general-covariant quantum statistical mechanics in this language. We illustrate the formalism by showing how it accounts for the Unruh effect. ... More

Towards Spinfoam CosmologyMar 17 2010We compute the transition amplitude between coherent quantum-states of geometry peaked on homogeneous isotropic metrics. We use the holomorphic representations of loop quantum gravity and the Kaminski-Kisielowski-Lewandowski generalization of the new ... More

Metastability in the reversible inclusion processMay 17 2016We study the condensation regime of the finite reversible inclusion process, i.e., the inclusion process on a finite graph $S$ with an underlying random walk that admits a reversible measure. We assume that the random walk kernel is irreducible and its ... More

Forward-looking portfolio selection with multivariate non-Gaussian models and the Esscher transformMay 15 2018May 25 2018In this study we suggest a portfolio selection framework based on option-implied information and multivariate non-Gaussian models. The proposed models incorporate skewness, kurtosis and more complex dependence structures among stocks log-returns than ... More

The contribution of galaxies to the UV ionising background and the evolution of the Lyman forestJun 28 2001We have modelled the evolution of the number of Ly_alpha absorbers with redshift, resulting from the evolution of the ionising background and the Hubble expansion. The contribution of quasars (QSOs) and galaxies to the HI-ionising UV background has been ... More

On Demazure and local Weyl modules for affine hyperalgebrasJul 16 2013Sep 22 2014We establish the existence of Demazure flags for graded local Weyl modules for hyper current algebras in positive characteristic. If the underlying simple Lie algebra is simply laced, the flag has length one, i.e., the graded local Weyl modules are isomorphic ... More

Continuous-time random walk between Lévy-spaced targets in the real lineJun 06 2018We consider a continuous-time random walk which is defined as an interpolation of a random walk on a point process on the real line. The distances between neighboring points of the point process are i.i.d. random variables in the normal domain of attraction ... More

Tumor-induced neoneurogenesis and perineural tumor growth: a mathematical approachJul 13 2015Primary tumors infrequently lead to demise of cancer patients; instead, mortality and a significant degree of morbidity result from the growth of secondary tumors in distant organs (metastasis). It is well-known that malignant tumors induce the formation ... More

Efficient Linear Bandits through Matrix SketchingSep 28 2018Feb 21 2019We prove that two popular linear contextual bandit algorithms, OFUL and Thompson Sampling, can be made efficient using Frequent Directions, a deterministic online sketching technique. More precisely, we show that a sketch of size $m$ allows a $\mathcal{O}(md)$ ... More

Majorization under constraints and bounds of the second Zagreb indexMay 10 2011In this paper we present a theoretical analysis in order to establish maximal and minimal vectors with respect to the majorization order of particular subsets of \Re ^n: Afterwards we apply these issues to the calcula- tion of bounds for a topological ... More

Observations on Arithmetic Invariants and U-Duality Orbits in N =8 SupergravityDec 01 2009Jun 24 2010We establish a relation between time-like, light-like and space-like orbits of the non-compact E{7(7)}(R)symmetry and discrete E{7(7)}(Z) invariants. We discuss the U-duality invariant formula for the degeneracy of states d(Q) which in the approximation ... More

Continuous-time random walk between Lévy-spaced targets in the real lineJun 06 2018Mar 26 2019We consider a continuous-time random walk which is defined as an interpolation of a random walk on a point process on the real line. The distances between neighboring points of the point process are i.i.d. random variables in the normal domain of attraction ... More

Strangeness production as a function of charged particle multiplicity in proton-proton collisionsApr 22 2016Apr 26 2016Recent measurements performed in high-multiplicity proton-proton (pp) and proton-lead (p-Pb) collisions have shown features that are reminiscent of those observed in lead-lead (Pb-Pb) collisions. These observations warrant a comprehensive measurement ... More

Brane instantons and fluxes in F-theoryNov 30 2012Sep 23 2013We study the combined effect of world-volume and background fluxes on Euclidean D3-brane instantons in F-theory compactifications. We derive an appropriate form of the fermionic effective action, in which the fermions are topologically twisted and the ... More

A note on drastic product logicJun 27 2014The drastic product $*_D$ is known to be the smallest $t$-norm, since $x *_D y = 0$ whenever $x, y < 1$. This $t$-norm is not left-continuous, and hence it does not admit a residuum. So, there are no drastic product $t$-norm based many-valued logics, ... More

Coding with Scrambling, Concatenation, and HARQ for the AWGN Wire-Tap Channel: A Security Gap AnalysisAug 29 2013This study examines the use of nonsystematic channel codes to obtain secure transmissions over the additive white Gaussian noise (AWGN) wire-tap channel. Unlike the previous approaches, we propose to implement nonsystematic coded transmission by scrambling ... More

Light stringy statesOct 25 2011Aug 07 2014We carefully study the spectrum of open strings localized at the intersections of D6-branes and identify the lowest massive 'twisted' states and their vertex operators, paying particular attention to the signs of the intersection angles. We argue that ... More

Magnetized E3-brane instantons in F-theoryJul 19 2011Feb 13 2012We discuss E3-brane instantons in N=1 F-theory compactifications to four dimensions and clarify the structure of E3-E3 zero modes for general world-volume fluxes. We consistently incorporate SL(2,Z) monodromies and highlight the relation between F-theory ... 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

On closed-string twist-field correlators and their open-string descendantsOct 24 2011In a recent paper we have proposed the possibility that the lightest massive string states could be identified with open strings living at intersections of D-branes forming small angles. In this note, we reconsider the relevant twist-field correlation ... More

On stable higher spin states in Heterotic String TheoriesOct 06 2010We study properties of 1/2 BPS Higher Spin states in heterotic compactifications with extended supersymmetry. We also analyze non BPS Higher Spin states and give explicit expressions for physical vertex operators of the first two massive levels. We then ... More

Non-Systematic Codes for Physical Layer SecurityApr 26 2010This paper is a first study on the topic of achieving physical layer security by exploiting non-systematic channel codes. The chance of implementing transmission security at the physical layer is known since many years in information theory, but it is ... More

New Results on Holographic Three-Point FunctionsOct 14 2003Dec 18 2003We exploit a gauge invariant approach for the analysis of the equations governing the dynamics of active scalar fluctuations coupled to the fluctuations of the metric along holographic RG flows. In the present approach, a second order ODE for the active ... More

Generating Tree Amplitudes in N=4 SYM and N=8 SGMay 06 2008May 22 2008We study n-point tree amplitudes of N=4 super Yang-Mills theory and N=8 supergravity for general configurations of external particles of the two theories. We construct generating functions for n-point MHV and NMHV amplitudes with general external states. ... More

Instanton corrections to circular Wilson loops in N=4 Supersymmetric Yang-MillsFeb 01 2002Feb 03 2002It is argued that whereas supersymmetry requires the instanton contribution to the expectation value of a straight Wilson line in the N=4 supersymmetric SU(2) Yang-Mills theory to vanish, it is not required to vanish in the case of a circular Wilson loop. ... More

Symmetrization in GeometryMar 02 2016Oct 21 2016The concept of an $i$-symmetrization is introduced, which provides a convenient framework for most of the familiar symmetrization processes on convex sets. Various properties of $i$-symmetrizations are introduced and the relations between them investigated. ... More

Ongoing Formation of Bulges and Black Holes in the Local Universe: New Insights from GALEXSep 15 2006We analyze a volume-limited sample of massive bulge-dominated galaxies with data from both the Sloan Digital Sky Survey and the Galaxy Evolution Explorer (GALEX) satellite. The galaxies have central velocity dispersions greater than 100 km/s and stellar ... More

Investigating the complex X-ray spectrum of a broad-line 2MASS red quasar: XMM-Newton observation of FTM 0830+3759Jan 14 2010We report results from a 50 ks XMM-Newton observation of the dust-reddened broad-line quasar FTM 0830+3759 (z=0.413) selected from the FIRST/2MASS Red Quasar survey. For this AGN, a very short 9 ks Chandra exposure had suggested a feature-rich X-ray spectrum ... More

Anatomy of the AGN in NGC 5548: III. The high-energy view with NuSTAR and INTEGRALJan 14 2015We describe the analysis of the seven broad-band X-ray continuum observations of the archetypal Seyfert 1 galaxy NGC 5548 that were obtained with XMM-Newton or Chandra, simultaneously with high-energy (> 10 keV) observations with NuSTAR and INTEGRAL. ... More

The Chandra High Resolution Spectra of Mkn 421Feb 26 2001Mkn 421 was observed by Chandra twice, on November 5, 1999 as part of the Chandra calibration program, with the ACIS-HETG configuration, and on May 29, 2000 following our Target Of Opportunity request aimed to catch the source in an ultra-high state, ... More

Number Counts of GALEX Sources in FUV (1530A) and NUV (2310A) BandsNov 12 2004Number Counts of galaxies in two GALEX bands (FUV: 1530A and NUV: 2310A, both in AB magnitudes) are reported. They provide for the first time in the literature homogeneously calibrated number counts of UV galaxies covering continuously a very wide range ... More

Ultraviolet-to-Far Infrared Properties of Lyman Break Galaxies and Luminous Infrared Galaxies at z ~ 1Jan 06 2006We present the first large, unbiased sample of Lyman Break Galaxies (LBGs) at z ~ 1. Far ultraviolet-dropout (1530 A) galaxies in the Chandra Deep Field South have been selected using GALEX data. This first large sample in the z ~ 1 universe provides ... More

The Galaxy Evolution Explorer: A Space Ultraviolet Survey MissionNov 11 2004We give an overview of the Galaxy Evolution Explorer (GALEX), a NASA Explorer Mission launched on April 28, 2003. GALEX is performing the first space UV sky-survey, including imaging and grism surveys in two bands (1350-1750 Angstroms and 1750-2750 Angstroms). ... More

Flux and spectral variations in the Circinus GalaxySep 27 2002We report on a dramatic flux (50 % increase in the LECS and MECS band) and spectral variation between two BeppoSAX observations of the Circinus Galaxy performed almost three years apart. Through the analysis of all Chandra observations available in the ... 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