Results for "Marta Betcke"

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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
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
Hamilton-Green solver for the forward and adjoint problems in photoacoustic tomographyOct 31 2018The majority of the solvers for the acoustic problem in Photoacoustic Tomography (PAT) rely on full solution of the wave equation which makes them less suitable for real-time and dynamic applications where only partial data is available. This is in contrast ... 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
Overresolving in the Laplace domain for convolution quadrature methodsMar 05 2016Convolution quadrature (CQ) methods have enjoyed tremendous interest in recent years as an efficient tool for solving time-domain wave problems in unbounded domains via boundary integral equation techniques. In this paper we consider CQ type formulations ... More
Simple and efficient GPU parallelization of existing H-Matrix accelerated BEM codeNov 06 2017In this paper, we demonstrate how GPU-accelerated BEM routines can be used in a simple black-box fashion to accelerate fast boundary element formulations based on Hierarchical Matrices (H-Matrices) with ACA (Adaptive Cross Approximation). In particular, ... 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
Approximate k-space models and Deep Learning for fast photoacoustic reconstructionJul 09 2018We present a framework for accelerated iterative reconstructions using a fast and approximate forward model that is based on k-space methods for photoacoustic tomography. The approximate model introduces aliasing artefacts in the gradient information ... More
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
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
Enhancing Compressed Sensing 4D Photoacoustic Tomography by Simultaneous Motion EstimationFeb 14 2018Jun 15 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
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
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
Model based learning for accelerated, limited-view 3D photoacoustic tomographyAug 31 2017Mar 26 2018Recent 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
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
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.
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
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
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 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
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
The geometric phase of Z$_n$- and T-symmetric nanomagnets as a classification toolkitMay 11 2016Jul 21 2016We derive the general form of the non-trivial geometric phase resulting from the unique combination of point group and time reversal symmetries. This phase arises e.g. when a magnetic adatom is adsorbed on a non-magnetic C$_n$ crystal surface, where $n$ ... More
Status and Physics Reach of LHCbMar 13 2009LHCb is the experiment at the Large Hadron Collider devoted to studies of new phenomena in CP violation and in rare decays. This review summarizes the status of the experiment in the imminence of the data taking, the prospects for the first measurements ... More
Metastable dynamics of internal interfaces for a convection-reaction-diffusion equationDec 03 2013Apr 09 2015We study a one dimensional metastable dynamics of internal interfaces for the initial boundary value problem for the following convection-reaction-diffusion equation \begin{equation*} \partial_t u = \varepsilon \partial_x^2 u -\partial_x f(u)+ f'(u). ... More
The Double Pulsar System in its 8th anniversaryOct 03 2012The double pulsar system J0737-3039A/B, discovered with the Parkes radio telescope in 2003, is one of the most intriguing pulsar findings of the last decade. This binary system, with an orbital period of only 2.4-hr and with the simultaneous presence ... More
The first massive black holesSep 06 2012I briefly outline recent theoretical developments on the formation of the first massive black holes (MBHs) that may grow into the population of MBHs powering quasars and inhabiting galactic centers today. I also touch upon possible observational tests ... 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
Formation of Supermassive Black HolesMar 23 2010Evidence shows that massive black holes 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 central ... More
Evolution of massive black hole spinsFeb 19 2010Oct 05 2010Black hole spins affect the efficiency of the "classical" accretion processes, hence the radiative output from quasars. Spins also determine how much energy is extractable from the hole itself. Recently it became clear that massive black hole spins also ... More
The geometric phase of Z$_n$- and T-symmetric nanomagnets as a classification toolkitMay 11 2016Feb 07 2017We derive the general form of the non-trivial geometric phase resulting from the unique combination of point group and time reversal symmetries. This phase arises e.g. when a magnetic adatom is adsorbed on a non-magnetic C$_n$ crystal surface, where $n$ ... More
History of Mathematics Education - ItalyFeb 29 2016Starting from the Italian unification in 1861, we describe the role of mathematics teaching in the Italian system of education giving an account of the main features of Italian mathematics education, and referring to the official syllabi, to the used ... More
Guido Castelnuovo e l'insegnamento della matematicaFeb 29 2016At the beginning of the 900s Guido Castelnuovo turned his attention toward methodological, didactical, historical and applicative issues. He was an active member of the ICMI (International Commission on Mathematical Instruction) and of the Mathesis, an ... More
Production of W+W- pairs via subleading processes at the LHCOct 21 2014Oct 27 2014We discuss many new subleading processes for inclusive production of W+W- pairs generally not included in the literature so far. We focus mainly on photon-photon induced processes. We include elastic-elastic, elastic-inelastic, inelastic-elastic and inelastic-inelastic ... 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
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
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
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
On Galois descent of complete intersectionsMay 01 2019We introduce a notion of strict complete intersections with respect to Cox rings and we prove Galois descent for this new notion.
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
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
Torsion normal generators of the mapping class group of a non-orientable surfaceMar 25 2019We show that the normal closure of any periodic element of the mapping class group of a non-orientable surface whose order is greater than 2 contains the commutator subgroup, which for $g\geq 7$ is equal to the twist subgroup, and provide necessary and ... 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
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
On Galois descent of complete intersectionsMay 01 2019May 09 2019We introduce a notion of strict complete intersections with respect to Cox rings and we prove Galois descent for this new notion.
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
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.
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
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
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
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
On rationally connected varieties over $C_1$ fields of characteristic $0$May 06 2019We use birational geometry to show that the existence of rational points on proper rationally connected varieties over fields of characteristic $0$ is a consequence of the existence of rational points on terminal Fano varieties. We discuss several consequences ... 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
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
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
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
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
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
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.
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
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
Constraining the supermassive black holes evolution through continuity equationMar 02 2016The population of supermassive black holes (SMBHs) is composed by quiescent SMBHs, such as those seen in local galaxies including the Milky Way's, and active ones, resulting in quasars and active galactic nuclei (AGN). Outside our neighbourhood, all the ... More
Colliding holes in Riemann surfaces and quantum cluster algebrasSep 23 2015May 24 2016We introduce the notion of bordered cusped Teichm\"uller space, as the Teichm\"uller space of Riemann surfaces with at least one hole and at least one bordered cusp on the boundary. We propose a combinatorial graph description of this bordered cusped ... 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
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
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
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
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
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
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
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
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
Generating the mapping class group of a nonorientable surface by crosscap transpositionsMar 10 2017A crosscap transposition is an element of the mapping class group of a nonorientable surface represented by a homeomorphism supported on a one-holed Klein bottle and swapping two crosscaps. We prove that the mapping class group of a compact nonorientable ... 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
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
On a Poisson space of bilinear forms with a Poisson Lie actionApr 03 2014Mar 20 2015We consider the space of bilinear forms on a complex N-dimensional vector space endowed with the quadratic Poisson bracket studied in our previous paper arXiv:1012.5251. We classify all possible quadratic brackets on the set of pairs of matrices A and ... More
An algorithm to determine Hopf Galois structuresApr 01 2017Jul 25 2017A Hopf Galois structure on a finite field extension L/K is given by a finite cocommutative K-Hopf algebra and a Hopf action. In this paper we present an algorithm written in the computational algebra system Magma which gives all Hopf Galois structures ... 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
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
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
Invariant functionals on completely distributive latticesNov 04 2009Apr 19 2010In this paper we are interested in functionals defined on completely distributive lattices and which are invariant under mappings preserving {arbitrary} joins and meets. We prove that the class of nondecreasing invariant functionals coincides with the ... 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
Scaling approach to order-parameter fluctuations in disordered frustrated systemsNov 21 2000Apr 25 2001We present a constructive approach to obtain information about the compactness and shape of large-scale lowest excitations in disordered systems by studying order-parameter fluctuations (OPF) at low temperatures. We show that the parameter $G$ which measures ... More
A conjectured scenario for order-parameter fluctuations in spin glassesMar 20 2000We study order-parameter fluctuations (OPF) in disordered systems by considering the behavior of some recently introduced paramaters $G,G_c$ which have proven very useful to locate phase transitions. We prove that both parameters G (for disconnected overlap ... More
Fragility of the glassy state of a directed polymer in random media: a replica approachDec 20 2001We study the stability of the glassy equilibrium state of a directed polymer in random media against weak perturbations including the intriguing problem of temperature-chaos. The statistical correlation of two real replica systems under perturbations, ... More
Confluence on the Painlevé Monodromy Manifolds, their Poisson Structure and QuantisationDec 30 2012In this paper we obtain a system of flat coordinates on the monodromy manifold of each of the Painlev\'e equations. This allows us to quantise such manifolds. We produce a quantum confluence procedure between cubics in such a way that quantisation and ... 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