Results for "Marta Betcke"

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Choose your path wisely: gradient descent in a Bregman distance frameworkDec 11 2017Nov 02 2018We propose an extension of a special form of gradient descent --- in the literature known as linearised Bregman iteration --- to a larger class of non-convex functions. We replace the classical (squared) two norm metric in the gradient descent setting ... More
On the Adjoint Operator in Photoacoustic TomographyFeb 05 2016Aug 01 2016Photoacoustic Tomography (PAT) is an emerging biomedical "imaging from coupled physics" technique, in which the image contrast is due to optical absorption, but the information is carried to the surface of the tissue as ultrasound pulses. Many algorithms ... More
Acoustic Wave Field Reconstruction from Compressed Measurements with Application in Photoacoustic TomographySep 09 2016We present a method for the recovery of compressively sensed acoustic fields using patterned, instead of point-by-point, detection. From a limited number of such compressed measurements, we propose to reconstruct the field on the sensor plane in each ... More
Multi-Contrast MRI Reconstruction with Structure-Guided Total VariationNov 20 2015Magnetic resonance imaging (MRI) is a versatile imaging technique that allows different contrasts depending on the acquisition parameters. Many clinical imaging studies acquire MRI data for more than one of these contrasts---such as for instance T1 and ... More
Quantum mushroom billiardsNov 29 2006Sep 07 2007We report the first large-scale statistical study of very high-lying eigenmodes (quantum states) of the mushroom billiard proposed by L. Bunimovich in this journal, vol. 11, 802 (2001). The phase space of this mixed system is unusual in that it has a ... More
Stability and convergence of the Method of Fundamental Solutions for Helmholtz problems on analytic domainsAug 27 2007The Method of Fundamental Solutions (MFS) is a popular tool to solve Laplace and Helmholtz boundary value problems. Its main drawback is that it often leads to ill-conditioned systems of equations. In this paper we investigate for the interior Helmholtz ... More
A priorconditioned LSQR algorithm for linear ill-posed problems with edge-preserving regularizationAug 30 2013This article presents a method for solving large-scale linear inverse problems regular- ized with a nonlinear, edge-preserving penalty term such as the total variation or Perona-Malik. In the proposed scheme, the nonlinearity is handled with lagged diffusivity ... More
Enhancing Compressed Sensing Photoacoustic Tomography by Simultaneous Motion EstimationFeb 14 2018A crucial limitation of current high-resolution 3D photoacoustic tomography (PAT) devices that employ sequential scanning is their long acquisition time. In previous work, we demonstrated how to use compressed sensing techniques to improve upon this: ... More
Gradient descent in a generalised Bregman distance frameworkDec 08 2016Dec 27 2016We discuss a special form of gradient descent that in the literature has become known as the so-called linearised Bregman iteration. The idea is to replace the classical (squared) two norm metric in the gradient descent setting with a generalised Bregman ... More
Accelerated High-Resolution Photoacoustic Tomography via Compressed SensingApr 30 2016Sep 28 2016Current 3D photoacoustic tomography (PAT) systems offer either high image quality or high frame rates but are not able to deliver high spatial and temporal resolution simultaneously, which limits their ability to image dynamic processes in living tissue. ... More
Gradient descent in a generalised Bregman distance frameworkDec 08 2016We discuss a special form of gradient descent that in the literature has become known as the so-called linearised Bregman iteration. The idea is to replace the classical (squared) two norm metric in the gradient descent setting with a generalised Bregman ... More
Model based learning for accelerated, limited-view 3D photoacoustic tomographyAug 31 2017Recent advances in deep learning for tomographic reconstructions have shown great potential to create accurate and high quality images with a considerable speed-up. In this work we present a deep neural network that is specifically designed to provide ... More
High Temperature Dimensional Reduction of the MSSM and other Multi-Scalar ModelsMay 09 1996Using dimensional reduction we construct an effective 3D theory of the Minimal Supersymmetric Standard Model at finite temperature. The final effective theory is obtained after three successive stages of integration out of massive particles. We obtain ... More
A new estimator for the tail-dependence coefficientSep 26 2011Recently, the concept of tail dependence has been discussed in financial applications related to market or credit risk. The multivariate extreme value theory is a proper tool to measure and model dependence, for example, of large loss events. A common ... More
Linear Connections on Normal Almost Contact Manifolds with Norden MetricApr 28 2011Families of linear connections are constructed on almost contact manifolds with Norden metric. An analogous connection to the symmetric Yano connection is obtained on a normal almost contact manifold with Norden metric and closed structural 1-form. The ... More
The early evolution of massive black holesDec 02 2009Massive black holes are nowadays believed to reside in most local galaxies. Studies have also established a number of relations between the MBH mass and properties of the host galaxy such as bulge mass and velocity dispersion. These results suggest that ... More
B Physics Prospects at LHCJun 22 2005Future Experiments at LHC will have the opportunity to pursue an extensive program on B Physics and CP violation. The expected performance are presented here.
On Periodic Points of Symplectomorphisms on SurfacesAug 10 2016We construct a symplectic flow on a surface of genus g greater than one with exactly 2g-2 hyperbolic fixed points and no other periodic orbits. Moreover, we prove that a (strongly non-degenerate) symplectomorphism of a surface (with genus g greater than ... More
Isoperimetric problem for exponential measure on the plane with l_1-metricJun 10 2016We give a solution to the isoperimetric problem for the exponential measure on the plane with the $\ell_1$-metric. As it turns out, among all sets of a given measure, the simplex or its complement (i.e. the ball in the $\ell_1$-metric or its complement) ... More
The Electroweak Phase Transition in the MSSMAug 27 1998The construction of an effective 3D theory at high temperatures for the MSSM as a model of electroweak baryogenesis is discussed. The analysis for a single light scalar field shows, that given the experimental constraints, there is no value of the Higgs ... More
The Two-Loop Finite-Temperature Effective Potential of the MSSM and BaryogenesisJun 29 1998We construct an effective three dimensional theory for the MSSM at high temperatures in the limit of large-$m_{A}$. We analyse the two-loop effective potential of the 3D theory for the case of a light right handed stop to determine the precise region ... More
Galois groups and an obstruction to principal graphs of subfactorsMay 12 2006Jun 15 2006The Galois group of the minimal polymonal of a Jones index value gives a new type of obstruction to a principal graph, thanks to a recent result of P.Etingof, D.Nikshych, and V.Ostrik. We show that the sequence of the graphs given by Haagerup as candidates ... More
Almost complex connections on almost complex manifolds with Norden metricApr 29 2011A four-parametric family of linear connections preserving the almost complex structure is defined on an almost complex manifold with Norden metric. Necessary and sufficient conditions for these connections to be natural are obtained. A two-parametric ... More
On the penultimate tail behavior of Weibull-type modelsSep 14 2011Sep 26 2011The Gumbel max-domain of attraction corresponds to a null tail index which do not distinguish the different tail weights that might exist between distributions within this class. The Weibull-type distributions form an important subgroup of this latter ... More
Mixing Effects in the Finite-Temperature Effective Potential of the MSSM with a Light StopMay 21 1999We incorporate the effects of mixing arising from the trilinear terms in the MSSM potential to the effective three dimensional theory for the MSSM at high temperature in the limit of large $m_{A}$. There are relevant one-loop effects that modify the 3D ... More
The Electroweak Phase Transition in the Minimal Supersymmetric Standard ModelDec 12 1996Using dimensional reduction we construct an effective 3D theory of the Minimal Supersymmetric Standard Model at finite temperature. The final effective theory is obtained after three successive stages of integration out of massive particles. We obtain ... More
From practical geometry to the laboratory method: the search for an alternative to Euclid in the history of teaching geometryFeb 29 2016This paper wants to show how practical geometry, created to give a concrete help to people involved in trade, in land-surveying and even in astronomy, underwent a transformation that underlined its didactical value and turned it first into a way of teaching ... More
Bifurcations of critical orbits of invariant potentials with applications to bifurcations of central configurations of the N-body problemJan 29 2015In this article we study topological bifurcations of critical orbits of equivariant gradient equations. We give necessary and sufficient conditions for the existence of global bifurcations of solutions of these equations. Moreover, we apply these abstract ... More
Track structure modelling for ion radiotherapyOct 20 2014In its broadest terms, doctoral dissertation entitled "Track structure modelling for ion radiotherapy" is part of the supporting research background in the development of the ambitious proton radiotherapy project currently under way at the Institute of ... More
Inheriting of chaos in nonautonomous dynamical systemsNov 16 2013We consider nonautonomous discrete dynamical systems $\{ f_n\}_{n\ge 1}$, where every $f_n$ is a surjective continuous map $[0,1]\to [0,1]$ such that $f_n$ converges uniformly to a map $f$. We show, among others, that if $f$ is chaotic in the sense of ... More
Basic deformation theory of smooth formal schemesJan 18 2008We provide the main results of a deformation theory of smooth formal schemes. First we deal with the case of global lifting of smooth morphisms. We prove that the obstruction to the existence of a global lifting lies in a Ext^1 group. Then we study uniqueness ... More
Inclusive diffraction with the ZEUS detector at HERA: a comparison among selection methodsAug 06 2008The diffractive dissociation of virtual photons, gamma*p -> Xp, has been studied with the ZEUS detector at HERA by requiring a large rapidity gap between X and the outgoing proton, by analysing the mass distribution, M_X, of the hadronic final state, ... More
Gravitational recoil: signatures on the massive black hole populationMar 08 2007May 07 2007In the last stages of a black hole merger, the binary can experience a recoil due to asymmetric emission of gravitational radiation. Recent numerical relativity simulations suggest that the recoil velocity can be as high as a few thousands kilometers ... More
Experimental review on moment analysesJul 16 2003Jul 18 2003Moments of the photon energy spectrum in B -> Xs gamma decays, of the hadronic mass spectrum and of the lepton energy spectrum in B -> Xc l nu decays are sensitive to the masses of the heavy quarks as well as to the non-perturbative parameters of the ... More
The search for Higgs particles at LEPJul 26 1999The results of the experimental searches for Higgs particles at LEP, using the data collected at centre-of-mass energies up to 189 GeV, are reviewed and the prospects for the near future outlined.
On hyperbolic points and periodic orbits of symplectomorphismsOct 08 2013Sep 02 2014We prove the existence of infinitely many periodic orbits of symplectomorphisms isotopic to the identity if they admit at least one hyperbolic periodic orbit and satisfy some condition on the flux. Our result is proved for a certain class of closed symplectic ... More
Slow motion of internal shock layers for the Jin-Xin system in one space dimensionJul 09 2012May 15 2014This paper considers the slow motion of the shock layer exhibited by the solution to the initial-boundary value problem for a scalar hyperbolic system with relaxation. Such behavior, known as metastable dynamics, is related to the presence of a first ... More
The minimal resolution conjecture for points on the cubic surfaceNov 06 2006In this paper we prove that the generalized version of the Minimal Resolution Conjecture stated by Mustata holds for certain general sets of points on a smooth cubic surface $X \subset \mathbb{P}^3$. The main tool used is Gorenstein liaison theory and, ... More
Complex connections on conformal Kähler manifolds with Norden metricApr 28 2011An eight-parametric family of complex connections on a class complex manifolds with Norden metric is introduced. The form of the curvature tensor with respect to each of these connections is obtained. The conformal group of the considered connections ... More
On dilatation factors of braids on three strandsJul 26 2013In this work we present a natural surjective map from rigid braids in B_3 (in Garside sense) to SL_2(N). This map provides an upper and a lower bound for the dilatation factor of a pseudo-Anosov 3-strand braid. These bounds only depend on the canonical ... More
Imaginary quadratic points on toric varieties via universal torsorsMay 21 2015Jun 16 2015Inspired by a paper of Salberger we give a new proof of Manin's conjecture for toric varieties over imaginary quadratic number fields by means of universal torsor parameterizations and elementary lattice point counting.
Estimates of norms of log-concave random matrices with dependent entriesFeb 04 2019We prove estimates for $\mathbb{E} \| X: \ell_{p'}^n \to \ell_q^m\|$ for $p,q\ge 2$ and any random matrix $X$ having the entries of the form $a_{ij}Y_{ij}$, where $Y=(Y_{ij})_{1\le i\le m, 1\le j\le n}$ has i.i.d. isotropic log-concave rows. This generalises ... More
The Formation and Evolution of Massive Black HolesAug 06 2012The past 10 years have witnessed a change of perspective in the way astrophysicists think about massive black holes (MBHs), which are now considered to have a major role in the evolution of galaxies. This appreciation was driven by the realization that ... More
A note on convergence of low energy critical points of nonlinear elasticity functionals, for thin shells of arbitrary geometryJul 07 2009We prove that the critical points of the 3d nonlinear elasticity functional on shells of small thickness $h$ and around the mid-surface $S$ of arbitrary geometry, converge as $h\to 0$ to the critical points of the von K\'arm\'an functional on $S$, recently ... More
On the metastable behavior of solutions to a class of parabolic systemsJul 04 2014In this paper we describe the metastable behavior of solutions to a class of parabolic systems. In particular, we improve some results contained in \cite{MS} by using different techniques to describe the slow motion of the internal layers. Numerical simulations ... More
Maturity of the Internet of Things Research Field: Or Why Choose Rigorous KeywordsJun 05 2016Periodically researchers examine their fields of research in order to test the fields maturity, to determine theories and methods used, and to uncover areas of research emphasis. Research articles for these studies are generally located through keyword ... More
Embedding of the rank 1 DAHA into Mat(2,Tq) and its automorphismsMar 11 2016In this review paper we show how the Cherednik algebra of type $\check{C_1}C_1$ appears naturally as quantisation of the group algebra of the monodromy group associated to the sixth Painlev\'e equation. This fact naturally leads to an embedding of the ... More
Persistent currents in coherently coupled Bose-Einstein condensates in a ring trapNov 12 2015We study the stability of persistent currents in a coherently coupled quasi-2D Bose-Einstein condensate confined in a ring trap at T=0. By numerically solving Gross-Pitaevskii equations and by analyzing the excitation spectrum obtained from diagonalization ... More
On non-contractible hyperbolic periodic orbits and periodic points of symplectomorphismsJul 15 2015Aug 26 2015We prove the existence of infinitely many periodic points of symplectomorphisms isotopic to the identity if they admit at least one (non-contractible) hyperbolic periodic orbit and satisfy some condition on its flux. The obtained periodic points correspond ... More
Evolution of supermassive black holesFeb 28 2006Supermassive black holes (SMBHs) are nowadays believed to reside in most local galaxies, and the available data show an empirical correlation between bulge luminosity - or stellar velocity dispersion - and black hole mass, suggesting a single mechanism ... More
A Test of CP Symmetry in PositroniumApr 29 2004The aim of this CP symmetry test in positronium is to measure the CP violation amplitude parameter \ccp. This is derived from the measurement of the asymmetry in an angular distribution of the photons from the decay of the ortho-positronium in a magnetic ... More
On a Class Almost Contact Manifolds with Norden MetricApr 28 2011Certain curvature properties and scalar invariants of the manifolds belonging to one of the main classes almost contact manifolds with Norden metric are considered. An example illustrating the obtained results is given and studied.
Slow dynamics in reaction-diffusion systemsJun 24 2016We consider a system of reaction-diffusion equations in a bounded interval of the real line, with emphasis on the metastable dynamics, whereby the time-dependent solution approaches the steady state in an asymptotically exponentially long time interval ... More
Comparison of radiative energy loss models in a hot QCD mediumDec 03 2010The suppression of high $p_{T}$ hadron production in heavy ion collisions is thought to be due to energy loss by gluon radiation off hard partons in a QCD medium. Existing models of QCD radiative energy loss in a color-charged medium give estimates of ... More
Comment on "Interplanetary coronal mass ejections that are undetected by solar coronagraphs" by T. A. Howard and G. M. SimnettJan 02 2009Howard and Simnett (HS) employed a new technique for associating LASCO CMEs to SMEI ICMEs. In order to extrapolate the SMEI data back to the LASCO field of view they used nonlinear trajectories, dependent on a speed and direction, what is more realistic ... More
Evolution of massive black holesSep 12 2007Sep 16 2007Supermassive black holes are nowadays believed to reside in most local galaxies. Accretion of gas and black hole mergers play a fundamental role in determining the two parameters defining a black hole: mass and spin. I briefly review here some of the ... More
Supermassive black hole mergers and cosmological structure formationSep 27 2006Massive black holes (MBHs), with masses in the range 10^3-10^8 Msolar, which merge with a companion black hole of similar mass are expected to be the most powerful source of gravitational radiation in the frequency range probed by LISA. MBH binaries can ... More
Confluences of the Painleve equations, Cherednik algebras and q-Askey schemeJul 23 2013Oct 19 2015In this paper we produce seven new algebras as confluences of the Cherednik algebra of type \check{C_1}C_1 and we characterise their spherical-sub-algebras. The limit of the spherical sub-algebra of the Cherednik algebra of type \check{C_1}C_1 is the ... More
Hydrogen bond models for the simulation of protein folding and aggregationAug 10 2012Hydrogen bonds are a common feature in protein folding and aggregation. Due to their chemical peculiarities in terms of strength and directionality, a particular attention must be paid to the definition of the hydrogen bond potential itself. This global ... More
On the rigidity of the coisotropic Maslov index on certain rational symplectic manifoldsOct 07 2011Nov 11 2011We revisit the definition of the Maslov index of loops in coisotropic submanifolds tangent to the characteristic foliation of this submanifold. This Maslov index is given by the mean index of a certain symplectic path which is a lift of the holonomy along ... More
The geometry of the classical solutions of the Garnier systemsJun 25 2001Jul 09 2001Our aim is to find a general approach to the theory of classical solutions of the Garnier system in $n$-variables, ${\cal G}_n$, based on the Riemann-Hilbert problem and on the geometry of the space of isomonodromy deformations. Our approach consists ... More
Quantum multiple construction of subfactorsFeb 13 2006May 23 2006We construct the quantum s-tuple subfactors for an AFD II_1 subfactor with finite index and depth, for an arbitrary natural number s. This is a generalization of the quantum multiple subfactors by J.Erlijman and H.Wenzl, which generalizes the quantum ... More
Lie groups as four-dimensional special complex manifolds with Norden metricApr 28 2011An example of a four-dimensional special complex manifold with Norden metric of constant holomorphic sectional curvature is constructed via a two-parametric family of solvable Lie algebras. The curvature properties of the obtained manifold are studied. ... More
Gonality of complete graphs with a small number of omitted edgesMar 04 2015Feb 22 2016Let $K_d$ be the complete metric graph on $d$ vertices. We compute the gonality of graphs obtained from $K_d$ by omitting edges forming a $K_h$, or general configurations of at most $d-2$ edges. We also investigate if these graphs can be lifted to curves ... More
Theta characteristics of hyperelliptic graphsNov 23 2015Feb 22 2016We study theta characteristics of hyperelliptic metric graphs of genus $g$ with no bridge edges. These graphs have a harmonic morphism of degree two to a metric tree that can be lifted to morphism of degree two of a hyperelliptic curve $X$ over $K$ to ... More
Conjugate connections and statistical structures on almost Norden manifoldsDec 11 2018Relations between conjugate connections with respect to the pair of Norden metrics and to the almost complex structure on almost Norden manifolds are studied. Conjugate connections of the Levi-Civita connections induced by the Norden metrics are obtained. ... More
The gonality sequence of complete graphsMay 12 2016The gonality sequence $(d_r)_{r\geq1}$ of a finite graph / metric graph / algebraic curve comprises the minimal degrees $d_r$ of linear systems of rank $r$. For the complete graph $K_d$, we show that $d_r = kd - h$ if $r<g=\frac{(d-1)(d-2)}{2}$, where ... More
Color Octet LeptogenesisSep 03 2009Sep 11 2009We study the implications for generating the cosmological baryon asymmetry through leptogenesis in the recent model of Fileviez Perez and Wise, which provides a new mechanism for generating neutrino masses at one-loop by introducing new color octet fermion ... More
Leptogenesis with four gauge singletsJun 19 2003We consider a generic type of leptogenesis model which can successfully produce the correct value of the observed baryon number to entropy ratio. The main feature of this model is that it is a simple TeV scale model, a scale accessible in near future ... More
Neutrino masses in the R-parity violating MSSMMay 09 2000Nov 06 2000We compute one loop neutrino masses in the R-parity violating Minimal Supersymmetric Model, including the bilinear R-parity violating masses in the mass insertion approximation. To the order we calculate, our results are independent of the Higgs-lepton ... More
Node seniority rankingFeb 25 2014Recent advances in graph theory suggest that is possible to identify the oldest nodes of a network using only the graph topology. Here we report on applications to heterogeneous real world networks. To this end, and in order to gain new insights, we propose ... More
EM for phylogenetic topology reconstruction on non-homogeneous dataNov 21 2013Jun 18 2014Background: The reconstruction of the phylogenetic tree topology of four taxa is, still nowadays, one of the main challenges in phylogenetics. Its difficulties lie in considering not too restrictive evolutionary models, and correctly dealing with the ... More
O-minimality on twisted universal torsors and Manin's conjecture over number fieldsDec 23 2013Jul 20 2015Manin's conjecture predicts the distribution of rational points on Fano varieties. Using explicit parameterizations of rational points by integral points on universal torsors and lattice-point-counting techniques, it was proved for several specific varieties ... More
Dirichlet boundary conditions for degenerate and singular nonlinear parabolic equationsDec 05 2014We study existence and uniqueness of solutions to a class of nonlinear degenerate parabolic equations, in bounded domains. We show that there exists a unique solution which satisfies possibly inhomogeneous Dirichlet boundary conditions. To this purpose ... More
An invariance principle for maps with polynomial decay of correlationsAug 13 2004We give a general method of deriving statistical limit theorems, such as the central limit theorem and its functional version, in the setting of ergodic measure preserving transformations. This method is applicable in situations where the iterates of ... More
Multidimensional extremal dependence coefficientsJan 05 2017Jan 13 2017Extreme values modeling has attracting the attention of researchers in diverse areas such as the environment, engineering, or finance. Multivariate extreme value distributions are particularly suitable to model the tails of multidimensional phenomena. ... More
Quasi-uniform Convergence in Dynamical Systems Generated by an Amenable Group ActionOct 30 2016We study properties of the Weyl pseudometric associated with an action of a countable amenable group on a compact metric space. We prove that the topological entropy and the number of minimal subsets of the closure of an orbit are both lower semicontinuous ... More
Empar: EM-based algorithm for parameter estimation of Markov models on treesJul 05 2012The goal of branch length estimation in phylogenetic inference is to estimate the divergence time between a set of sequences based on compositional differences between them. A number of software is currently available facilitating branch lengths estimation ... More
Poisson algebras of block-upper-triangular bilinear forms and braid group actionDec 23 2010Nov 18 2011In this paper we study a quadratic Poisson algebra structure on the space of bilinear forms on $C^{N}$ with the property that for any $n,m\in N$ such that $n m =N$, the restriction of the Poisson algebra to the space of bilinear forms with block-upper-triangular ... More
Convergence to Lévy stable processes under some weak dependence conditionsJul 07 2009Jul 06 2010For a strictly stationary sequence of random vectors in $\mathbb{R}^d$ we study convergence of partial sum processes to L\'evy stable process in the Skorohod space with $J_1$-topology. We identify necessary and sufficient conditions for such convergence ... More
Substochastic semigroups and densities of piecewise deterministic Markov processesApr 30 2008May 14 2009Necessary and sufficient conditions are given for a substochastic semigroup on $L^1$ obtained through the Kato--Voigt perturbation theorem to be either stochastic or strongly stable. We show how such semigroups are related to piecewise deterministic Markov ... More
Notes on link homologyApr 08 2008This article consists of six lectures on the categorification of the Burau representation and on link homology groups which categorify the Jones and the HOMFLY-PT polynomial. The notes are based on the lecture course at the PCMI 2006 summer school in ... More
Cosmological black hole spin evolution by mergers and accretionJan 31 2008May 27 2008Using recent results from numerical relativity simulations of black hole mergers, we revisit previous studies of cosmological black hole spin evolution. We show that mergers are very unlikely to yield large spins, unless alignment of the spins of the ... More
Charm-Anticharm Kinematical Correlations in Photon-Proton ScatteringAug 04 2004$c-\bar c$ correlations are calculated in the $k_t$-factorization approach. Different unintegrated gluon distributions (uGDF) from the literature are used. The results are compared with recent results of the FOCUS collaboration. The recently developed ... More
Canonical structure and symmetries of the Schlesinger equationsNov 16 2003Jan 10 2007The Schlesinger equations $S_{(n,m)}$ describe monodromy preserving deformations of order $m$ Fuchsian systems with $n+1$ poles. They can be considered as a family of commuting time-dependent Hamiltonian systems on the direct product of $n$ copies of ... More
Prepotential and Instanton Corrections in N=2 Supersymmetric SU(N_1)xSU(N_2) Yang Mills TheoriesJan 16 2003Jan 28 2003In this paper we analyse the non-hyperelliptic Seiberg-Witten curves derived from M-theory that encode the low energy solution of N=2 supersymmetric theories with product gauge groups. We consider the case of a SU(N_1)xSU(N_2) gauge theory with a hypermultiplet ... More
Bianchi I cosmology in the presence of a causally regularized viscous fluidSep 29 2016Oct 01 2016We analyze the dynamics of a Bianchi I cosmology in the presence of a viscous fluid, causally regularized according to the Lichnerowicz approach. We show how the effect induced by shear viscosity is still able to produce a matter creation phenomenon, ... More
Basis independent neutrino masses in the $R_p$ violating MSSMOct 27 2000Mar 11 2001We calculate the neutrino mass matrix up to one loop order in the MSSM without R-parity, including the bilinears in the mass insertion approximation. This introduces additional diagrams usually neglected in the literature. We systematically consider the ... More
On Haagerup's list of potential principal graphs of subfactorsNov 27 2007We show that any graph, in the sequence given by Haagerup in 1991 as that of candidates of principal graphs of subfactors, is not realized as a principal graph except for the smallest two. This settles the remaining case of a previous work of the first ... More
Properties of the density for a three dimensional stochastic wave equationFeb 12 2008We consider a stochastic wave equation in space dimension three driven by a noise white in time and with an absolutely continuous correlation measure given by the product of a smooth function and a Riesz kernel. Let $p_{t,x}(y)$ be the density of the ... More
A dual Simplex-type algorithm for the smallest enclosing ball of balls and related problemsDec 04 2018We define the notion of infimum of a set of points with respect to the second order cone. This problem can be showed to be equivalent to the minimum ball containing a set of balls problem and to the maximum intersecting ball problem, as well as others. ... More
Cox rings over nonclosed fieldsAug 22 2014Sep 04 2018We give a definition of Cox rings and Cox sheaves for varieties over nonclosed fields that is compatible with torsors under quasitori, including universal torsors. We study their existence and classification, we make the relation to torsors precise, and ... More
Inferences on the Relations Between Central Black Hole Mass and Total Galaxy Stellar Mass in the high-redshift UniverseFeb 18 2016At the highest redshifts, z>6, several tens of luminous quasars have been detected. The search for fainter AGN, in deep X-ray surveys, has proven less successful, with few candidates to date. An extrapolation of the relationship between black hole (BH) ... More
Teichmüller spaces as degenerated symplectic leaves in Dubrovin--Ugaglia Poisson manifoldsMay 23 2011In this paper we study the Goldman bracket between geodesic length functions both on a Riemann surface $\Sigma_{g,s,0}$ of genus $g$ with $s=1,2$ holes and on a Riemann sphere $\Sigma_{0,1,n}$ with one hole and $n$ orbifold points of order two. We show ... More
The mass function of black holes at 1<z<4.5: comparison of models with observationsJul 25 2011Feb 18 2012In this paper, we compare the observationally derived black hole mass function (BHMF) of luminous broad-line quasars (BLQSOs) at 1<z<4.5 drawn from the Sloan Digital Sky Survey (SDSS) presented in Kelly et al. (2010), with models of merger driven BH growth ... More
Journey to the M_BH -sigma relation: the fate of low mass black holes in the UniverseMar 12 2009Aug 21 2009In this paper, we explore the establishment and evolution of the empirical correlation between black hole mass and velocity dispersion with redshift. We track the growth and accretion history of massive black holes starting from high redshift using two ... More
The CMS High Level Trigger: Commissioning and First Operation with LHC BeamsMay 05 2009The CMS experiment will collect data from the proton-proton collisions delivered by the Large Hadron Collider (LHC) at a centre-of-mass energy up to 14 TeV. The CMS trigger system is designed to cope with unprecedented luminosities and LHC bunch-crossing ... More
Relative Role of Stars and Quasars in Cosmic ReionizationMay 01 2009Aug 21 2009We revisit the classical view that quasar contribution to the reionization of hydrogen is unimportant. When secondary ionization are taken into account, in many plausible scenarios for the formation and growth of supermassive black holes quasars contribute ... More
Towards a Combined HERA Diffractive Deep Inelastic Scattering MeasurementMar 17 2009The diffractive dissociation of virtual photons, gamma*p -> Xp, has been studied with the H1 and ZEUS detectors at HERA using various complementary techniques. Events have been selected by direct tagging of the outgoing proton or by requiring a large ... More
Formation of the first nuclear clusters and massive black holes at high redshiftOct 06 2008Dec 11 2008We present a model for the formation of massive black holes ($\sim 1000 \msun$) due to stellar-dynamical processes in the first stellar clusters formed at early cosmic times ($z\sim10-20$). The high redshift black hole seeds form as a result of multiple ... More