Results for "André Hofmeister Serra"

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The failure of the Classical Nucleation Theory at low temperatures resolvedFeb 08 2019A relevant observation about crystal nucleation kinetics in glass-forming substances has been a matter of intense debate for several decades. The Classical Nucleation Theory (CNT) allegedly fails to describe the temperature dependence of the homogeneous ... More
The relation between radio and X-ray luminosity of black hole binaries: affected by inner cool disks?Jan 29 2014Observations of the black hole X-ray binaries GX 339-4 and V404 Cygni have brought evidence of a strong correlation between radio and X-ray emission during the hard spectral state; however, now more and more sources, the so-called `outliers', are found ... More
Black hole X-ray transients: mass accumulation in the disk - constraints for the viscosityMar 12 2001The outburst cycles of black hole X-ray transients are now generally understood as caused by a thermal instability in the accretion disk, the same mechanism as in dwarf novae outbursts. During quiescence the accretion occurs via a cool disk in the outer ... More
Black hole soft X-ray transients: evolution of the cool disk and mass supply for the ADAFJun 18 1999Using the black hole transient X-ray source A0620-00 as an example we study the physical interplay of three theoretical constituents for modelling these transient sources: (1) the advection-dominated accretion flow (ADAF) onto the central black hole, ... More
On the source of viscosity in cool binary accretion disksJan 18 1999We suggest that the low viscosity in close binary accretion disks during quiescence is due to magnetic fields from the companion star. In very late evolutionary phase the companion stars become brown dwarfs and have cooled down to such low a temperature ... More
A self-regulating braking mechanism in black hole X-ray binariesMar 30 2001The outbursts of black hole X-ray transients can be understood as caused by a limit cycle instability in the accretion disk, similar to dwarf nova outbursts. For adequately low mass overflow rates from the companion star long outburst recurrence times ... More
On the ultimate fate of AM Her starsMay 06 1999We suggest, that the magnetic field of the white dwarf in AM Her systems loses coupling to the secondary star when the latter becomes non-magnetic at the transition from a late main sequence star to a cool degenerate brown dwarf. This leads to spin-up ... More
Better Alternative to "Astronomical Silicate": Laboratory-Based Optical Functions of Chondritic/Solar Abundance Glass With Application to HD161796Jun 09 2015"Astronomical" or "circumstellar" silicate optical functions (real and imaginary indices of refraction n and k have been previously derived from compositionally and structurally disparate samples; past values were compiled from different sources in the ... More
Coronae above accretion disks around black holes: The effect of Compton coolingAug 01 2012The geometry of the accretion flow around stellar mass and supermassive black holes depends on the accretion rate. Broad iron emission lines originating from the irradiation of cool matter can indicate that there is an inner disk below a hot coronal flow.These ... More
Radial symmetry of solutions to diffusion equations with discontinuous nonlinearitiesJan 26 2011We prove a radial symmetry result for bounded nonnegative solutions to the $p$-Laplacian semilinear equation $-\Delta_p u=f(u)$ posed in a ball of $\mathbb R^n$ and involving discontinuous nonlinearities $f$. When $p=2$ we obtain a new result which holds ... More
A higgs-like dilaton: viability and implicationsDec 01 2013We re-examine the feasibility of the higgs-like particle discovered at the LHC being a dilaton: the Goldstone boson of spontaneous breaking of scale invariance. We review the expected phenomenological deviations from the SM higgs and compare with other ... More
Beyond the Minimal Top Partner DecayJun 16 2015Jan 13 2016Light top partners are the prime sign of naturalness in composite Higgs models. We explore here the possibility of non-standard top partner phenomenology. We show that even in the simplest extension of the minimal composite Higgs model, featuring an extra ... More
Electromagnetic Induction and the Conservation of Momentum in the Spiral ParadoxDec 05 2000The inversion of cause and effect in the classic description of electromagnetism, gives rise to a conceptual error which is at the bottom of many paradoxes and exceptions. At present, the curious fact that unipolar induction or the Faraday Disc constitutes ... More
Depicting qudit quantum mechanics and mutually unbiased qudit theoriesApr 04 2014Dec 30 2014We generalize the ZX calculus to quantum systems of dimension higher than two. The resulting calculus is sound and universal for quantum mechanics. We define the notion of a mutually unbiased qudit theory and study two particular instances of these theories ... More
Can Four-fermion Contact Interactions at One-loop Explain the New Atomic Parity Violation Results?Feb 07 2000We investigate the possibility that four-fermion contact interactions give rise to the observed deviation from the Standard Model prediction for the weak charge of Cesium, through one-loop contributions. We show that the presence of loops involving the ... More
Riemann Hypothesis and Random Walks: the Zeta caseJan 05 2016Feb 05 2016In previous work it was shown that if certain series based on sums over primes of non-principal Dirichlet characters have a conjectured random walk behavior, then the Euler product formula for its $L$-function is valid to the right of the critical line ... More
Representations of surface groups in the projective general linear groupJan 15 2009Aug 14 2010Given a closed, oriented surface X of genus g>1, and a semisimple Lie group G, let R_G be the moduli space of reductive representations of the fundamental group of X in G. We determine the number of connected components of R_PGL(n,R), for n>=4 even. In ... More
On large gaps between zeros of $L$-functions from branchesApr 19 2017May 26 2017It is commonly believed that the normalized gaps between consecutive ordinates $t_n$ of the zeros of the Riemann zeta function on the critical line can be arbitrarily large. In particular, drawing on analogies with random matrix theory, it has been conjectured ... More
Quadric bundles applied to non-maximal Higgs bundlesAug 01 2016We present a survey on the moduli spaces of rank 2 quadric bundles over a compact Riemann surface X. These are objects which generalise orthogonal bundles and which naturally occur through the study of the connected components of the moduli spaces of ... More
The Froissart bound for inelastic cross-sectionsApr 23 2009Aug 14 2009We prove that while the total cross{}-section is bounded by $(\pi/m_\pi^2) \ln^2 s$, where $s$ is the square of the c.m. energy and $m_\pi$ the mass of the pion, the total inelastic cross{}-section is bounded by $(1/4)(\pi/m_\pi^2) \ln^2 s$, which is ... More
Poincaré and log-Sobolev inequalities for mixturesDec 16 2018This work studies mixtures of probability measures on $\mathbb{R}^n$ and gives bounds on the Poincar\'e and the log-Sobolev constant of two-component mixtures provided that each component satisfies the functional inequality, and both components are close ... More
Algebraic Relations and Triangulation of Unlabeled Image PointsJul 27 2017In multiview geometry when correspondences among multiple views are unknown the image points can be understood as being unlabeled. This is a common problem in computer vision. We give a novel approach to handle such a situation by regarding unlabeled ... More
Groupes de Galois motivques et périodesJun 12 2016In the mid sixties, A. Grothendieck envisioned a vast generalization of Galois theory to systems of polynomials in several variables, motivic Galois theory, and introduced tannakian categories on this occasion. In characteristic zero, various unconditional ... More
Function call overhead benchmarks with MATLAB, Octave, Python, Cython and CFeb 13 2012We consider the overhead of function calls in the programming languages MATLAB/Octave, Python, Cython and C. In many applications a function has to be called very often inside a loop. One such application in numerical analysis is the finite element method ... More
Energy loss mechanism for suspended micro- and nanoresonators due to the Casimir forceMay 11 2011A so far not considered energy loss mechanism in suspended micro- and nanoresonators due to noncontact acoustical energy loss is investigated theoretically. The mechanism consists on the conversion of the mechanical energy from the vibratory motion of ... More
The Herschel View of Star FormationSep 30 2013Recent studies of the nearest star-forming clouds of the Galaxy at submillimeter wavelengths with the Herschel Space Observatory have provided us with unprecedented images of the initial conditions and early phases of the star formation process. The Herschel ... More
On nef and semistable hermitian lattices, and their behaviour under tensor productAug 09 2010We study the behaviour of semistability under tensor product in various settings: vector bundles, euclidean and hermitian lattices (alias Humbert forms or Arakelov bundles), multifiltered vector spaces. One approach to show that semistable vector bundles ... More
Local functional principal component analysisFeb 21 2007Covariance operators of random functions are crucial tools to study the way random elements concentrate over their support. The principal component analysis of a random function X is well-known from a theoretical viewpoint and extensively used in practical ... More
Weak convergence in the functional autoregressive modelSep 12 2005The functional autoregressive model is a Markov model taylored for data of functional nature. It revealed fruitful when attempting to model samples of dependent random curves and has been widely studied along the past few years. This article aims at completing ... More
An electrostatic depiction of the validity of the Riemann Hypothesis and a formula for the N-th zero at large NMay 12 2013Sep 18 2013We construct a vector field E from the real and imaginary parts of an entire function xi (z) which arises in the quantum statistical mechanics of relativistic gases when the spatial dimension d is analytically continued into the complex z plane. This ... More
Interacting Bose and Fermi gases in low dimensions and the Riemann hypothesisNov 17 2006Sep 18 2007We apply the S-matrix based finite temperature formalism to non-relativistic Bose and Fermi gases in 1+1 and 2+1 dimensions. In the 2+1 dimensional case, the free energy is given in terms of Roger's dilogarithm in a way analagous to the relativistic 1+1 ... More
Stellar rotation: Evidence for a large horizontal turbulence and its effects on evolutionJan 14 2003We derive a new expression for the coefficient $D_{\mathrm{h}}$ of diffusion by horizontal turbulence in rotating stars. This new estimate can be up to two orders of magnitude larger than given by a previous expression. As a consequence the differential ... More
Baryons made of heavy quarks at the LHCSep 29 2014Oct 08 2014Baryons made of heavy quarks are extremely interesting and could be seen at the LHC.
Differential Hybrid GamesJul 17 2015Feb 24 2017This article introduces differential hybrid games, which combine differential games with hybrid games. In both kinds of games, two players interact with continuous dynamics. The difference is that hybrid games also provide all the features of hybrid systems ... More
A note related to the CS decomposition and the BK inequality for discrete determinantal processesMay 09 2019We prove that for a discrete determinantal process the BK inequality occurs for increasing events generated by simple points. We give also some elementary, but nonetheless appealing relationship, between a discrete determinantal process and the well-known ... More
A sharpening of Li's criterion for the Riemann HypothesisApr 10 2004Apr 15 2004Exact and asymptotic formulae are displayed for the coefficients $\lambda_n$ used in Li's criterion for the Riemann Hypothesis. In particular, we argue that if (and only if) the Hypothesis is true, $\lambda_n \sim n(A \log n +B)$ for $n \to \infty$ (with ... More
Viterbi Algorithm Generalized for n-Tape Best-Path SearchDec 07 2006We present a generalization of the Viterbi algorithm for identifying the path with minimal (resp. maximal) weight in a n-tape weighted finite-state machine (n-WFSM), that accepts a given n-tuple of input strings (s_1,... s_n). It also allows us to compile ... More
Acronym-Meaning Extraction from Corpora Using Multi-Tape Weighted Finite-State MachinesDec 06 2006The automatic extraction of acronyms and their meaning from corpora is an important sub-task of text mining. It can be seen as a special case of string alignment, where a text chunk is aligned with an acronym. Alternative alignments have different cost, ... More
Noncommutative polynomial mapsAug 01 2012Polynomial maps attached to polynomials of an Ore extension are naturally defi ned. In this setting we show the importance of pseudo-linear transformations and give some applications. In particular, factorizations of polynomials in an Ore extension over ... More
Usage-based vs. Citation-based Methods for Recommending Scholarly Research ArticlesMar 28 2013Mar 29 2013There are two principal data sources for collaborative filtering recommenders in scholarly digital libraries: usage data obtained from harvesting a large, distributed collection of Open URL web logs and citation data obtained from the journal articles. ... More
Structure des connexions méromorphes formelles de plusieurs variables et semi-continuité de l'irrégularitéJan 30 2007We prove Malgrange's conjecture on the absence of confluence phenomena for integrable meromorphic connections. More precisely, if $ Y\to X$ is a complex-analytic fibration by smooth curves, $Z$ a hypersurface of $Y$ finite over $X$, and $\nabla$ an integrable ... More
Riemann Hypothesis and Random Walks: the Zeta caseJan 05 2016May 23 2017In previous work it was shown that if certain series based on sums over primes of non-principal Dirichlet characters have a conjectured random walk behavior, then the Euler product formula for its $L$-function is valid to the right of the critical line ... More
Critical points of 2d disordered Dirac fermions: the Quantum Hall Transitions revisitedOct 22 2007May 30 2008We propose a resolution of the renormalization group flow for the disordered Dirac fermion theories describing the quantum Hall transition (QHT) and spin Quantum Hall transition (SQHT), which previously revealed no perturbative fixed points at 1-loop ... More
The gl(1|1) super-current algebra: the role of twist and logarithmic fieldsOct 16 2007A free field representation of the gl(1|1)_k current algebra at arbitrary level k is given in terms of two scalar fields and a symplectic fermion. The primary fields for all representations are explicitly constructed using the twist and logarithmic fields ... More
RFID et nouvelles technologies de communication; enjeux économiques incontournables et problèmes d'éthique RFID and new communication technologies - economic challenges and ethic problemsJan 04 2010Auto ID technologies such RFID are more and more commonly used in industry and in distribution. Human are identify thanks to this technology, too. A lot of people have highlighted ethic problems relative to their utilization. This paper present first ... More
Exploiting Modern Hardware for High-Dimensional Nearest Neighbor SearchDec 08 2017Many multimedia information retrieval or machine learning problems require efficient high-dimensional nearest neighbor search techniques. For instance, multimedia objects (images, music or videos) can be represented by high-dimensional feature vectors. ... More
Macroscopic limit of the Becker-Döring equation via gradient flowsJul 29 2016Feb 26 2018This work considers gradient structures for the Becker-D\"oring equation and its macroscopic limits. The result of Niethammer [17] is extended to prove the convergence not only for solutions of the Becker-D\"oring equation towards the Lifshitz-Slyozov-Wagner ... More
Zeta-regularisation for exact-WKB resolution of a general 1D Schrödinger equationFeb 14 2012Apr 06 2012We review an exact analytical resolution method for general one-dimensional (1D) quantal anharmonic oscillators: stationary Schr\"odinger equations with polynomial potentials. It is an exact form of WKB treatment involving spectral (usual) vs "classical" ... More
On octahedraliy and Müntz spacesNov 05 2018We show that every M\"untz space can be written as a direct sum of Banach spaces X and Y , where Y is almost isometric to a subspace of c and X is finite dimensional. We apply this to show that no M\"untz space is locally octahedral or almost square.
Dynamic Logics of Dynamical SystemsMay 22 2012We survey dynamic logics for specifying and verifying properties of dynamical systems, including hybrid systems, distributed hybrid systems, and stochastic hybrid systems. A dynamic logic is a first-order modal logic with a pair of parametrized modal ... More
On a geometric description of $Gal(\bar{\bf Q}_p/{\bf Q}_p)$ and a p-adic avatar of $\hat{GT}$Mar 18 2002Oct 24 2002We develop a $p$-adic version of the so-called Grothendieck-Teichm\"uller theory (which studies $Gal(\bar{\bf Q}/{\bf Q})$ by means of its action on profinite braid groups or mapping class groups). For every place $v$ of $\bar{\bf Q}$, we give some geometrico-combinatorial ... More
Séries Gevrey de type arithmétique, II. Transcendance sans transcendanceMar 01 2000In this second part, we study the Diophantine properties of values of arithmetic Gevrey series of non-zero order at algebraic points. We rely on the fact, proved in the first part, that the minimal differential operator (with polynomial coefficients) ... More
A new convergence proof for the higher-order power method and generalizationsJul 17 2014Jan 23 2015A proof for the point-wise convergence of the factors in the higher-order power method for tensors towards a critical point is given. It is obtained by applying established results from the theory of \L{}ojasiewicz inequalities to the equivalent, unconstrained ... More
Period mappings and differential equations. From $\bf C$ to $\bf C_p$Mar 19 2002This is an introduction to $p$-adic geometry and $p$-adic analysis focusing on the theme of $p$-adic period mappings. We follow as closely as possible the development of the classical theory of complex period mappings, blending differential equations, ... More
On the Kodaira-Spencer map of abelian schemesJun 12 2016Let $A$ be an abelian scheme over a smooth affine complex variety $S$, $\varOmega_A$ the $\sO_S$-module of $1$-forms of the first kind on $A$, $\sD_S\varOmega_A$ the $\sD_S$-module spanned by $\varOmega_A$ in the first algebraic De Rham cohomology module, ... More
Interstellar filaments and star formationOct 03 2017Recent studies of the nearest star-forming clouds of the Galaxy at submillimeter wavelengths with the Herschel Space Observatory have provided us with unprecedented images of the initial conditions and early phases of the star formation process. The Herschel ... More
Uniform sheaves and differential equationsJul 14 2012Real blow-ups and more refined "zooms" play a key role in the analysis of singularities of complex-analytic differential modules. They do not change the underlying topology, but the uniform structure. This suggests to revisit the cohomology theory of ... More
Differential Game LogicAug 08 2014Jul 24 2015Differential game logic (dGL) is a logic for specifying and verifying properties of hybrid games, i.e. games that combine discrete, continuous, and adversarial dynamics. Unlike hybrid systems, hybrid games allow choices in the system dynamics to be resolved ... More
A Complete Uniform Substitution Calculus for Differential Dynamic LogicJan 22 2016Jul 27 2016This article introduces a relatively complete proof calculus for differential dynamic logic (dL) that is entirely based on uniform substitution, a proof rule that substitutes a formula for a predicate symbol everywhere. Uniform substitutions make it possible ... More
Discretized Keiper/Li approach to the Riemann HypothesisMar 08 2017Jul 17 2017The Keiper--Li sequence $\{ \lambda _n \}$ is most sensitive to the Riemann Hypothesis asymptotically ($n \to \infty$), but highly elusive both analytically and numerically. We deform it to fully explicit sequences, simpler to analyze and to compute (up ... More
Simplifications of the Keiper/Li approach to the Riemann HypothesisFeb 10 2016The Keiper/Li constants $\{\lambda_n\}_{n=1,2,\ldots}$ are asymptotically ($n \to \infty$) sensitive to the Riemann Hypothesis, but highly elusive analytically and difficult to compute numerically. We present quite explicit variant sequences that stay ... More
Lyapunov Exponents of Rank 2-Variations of Hodge Structures and Modular EmbeddingsMar 05 2013Aug 22 2013If the monodromy representation of a VHS over a hyperbolic curve stabilizes a rank two subspace, there is a single non-negative Lyapunov exponent associated with it. We derive an explicit formula using only the representation in the case when the monodromy ... More
Phenomenological modeling of long range noncontact friction in micro- and nanoresonatorsApr 14 2011Oct 05 2011Motivated by the results of an experiment using atomic force microscopy performed by Gotsmann and Fuchs [Phys. Rev. Lett. {\bf 86}, 2597 (2001)], where a strong energy loss due to the tip-sample interaction was measured, we investigate the potential implications ... More
Extensions of the Schwarzschild solution into regions of non-zero energy density and pressureMay 10 2019We present solutions of the Einstein equations that extend the static Schwarzschild solution in empty space to regions of non-zero energy density $\rho$ and radial pressure $p= w \rho$, where $w$ is a constant equation of state parameter. For simplicity ... More
A Bäcklund transformation for elliptic four-point conformal blocksMar 09 2018We apply an integral transformation to solutions of a partial differential equation for five-point correlation functions in Liouville theory on a sphere with one degenerate field $V_{-\frac{1}{2b}}$. By repeating this transformation, we can reach a whole ... More
A benchmark library for parametric timed model checkingDec 20 2018Verification of real-time systems involving hard timing constraints and concurrency is of utmost importance. Parametric timed model checking allows for formal verification in the presence of unknown timing constants or uncertainty (e.g. imprecision for ... More
Early inflation based on an aboriginal black holeJul 01 2019It has been recently proposed that the interior of a black hole is vacuum energy, and this offers a possible explanation for the dark energy of the current observable universe. In this article we explore the idea that black holes are a source of vacuum ... More
Formalizing Time4sys using parametric timed automataMay 23 2019Critical real-time systems must be verified to avoid the risk of dramatic consequences in case of failure. Thales developed an open formalism Time4sys to model real-time systems, with expressive features such as periodic or sporadic tasks, task dependencies, ... More
An introduction to motivic zeta functions of motivesDec 19 2008It oftens occurs that Taylor coefficients of (dimensionally regularized) Feynman amplitudes $I$ with rational parameters, expanded at an integral dimension $D= D_0$, are not only periods (Belkale, Brosnan, Bogner, Weinzierl) but actually multiple zeta ... More
Zeta functions over zeros of Zeta functions and an exponential-asymptotic view of the Riemann HypothesisMar 18 2014Jul 26 2014We review generalized zeta functions built over the Riemann zeros (in short: "superzeta" functions). They are symmetric functions of the zeros that display a wealth of explicit properties, fully matching the much more elementary Hurwitz zeta function. ... More
Sharpenings of Li's criterion for the Riemann HypothesisJun 16 2005Jan 25 2006Exact and asymptotic formulae are displayed for the coefficients $\lambda_n$ used in Li's criterion for the Riemann Hypothesis. For $n \to \infty$ we obtain that if (and only if) the Hypothesis is true, $\lambda_n \sim n(A \log n +B)$ (with $A>0$ and ... More
Preconditioning of interplanetary space due to transient CME disturbancesDec 19 2016Interplanetary space is characteristically structured mainly by high-speed solar wind streams emanating from coronal holes and transient disturbances such as coronal mass ejections (CMEs). While high-speed solar wind streams pose a continuous outflow, ... More
Identification of coronal holes and filament channels in SDO/AIA 193Å images via geometrical classification methodsAug 12 2014In this study, we describe and evaluate shape measures for distinguishing between coronal holes and filament channels as observed in Extreme Ultraviolet (EUV) images of the Sun. For a set of well-observed coronal hole and filament channel regions extracted ... More
3-Phase Evolution of a Coronal Hole, Part II: The Magnetic FieldJun 26 2018Jul 04 2019We investigate the magnetic characteristics of a persistent coronal hole (CH) extracted from EUV imagery using HMI filtergrams over the timerange February 2012-October 2012. The magnetic field, its distribution as well as the magnetic fine structure in ... More
Characteristics of Low-Latitude Coronal Holes near the Maximum of Solar cycle 24Feb 07 2017We investigate the statistics of 288 low-latitude coronal holes extracted from SDO/AIA-193 filtergrams over the time range 2011/01/01 to 2013/12/31. We analyse the distribution of characteristic coronal hole properties, such as the areas, mean AIA-193 ... More
Cold gas and young stars in tidally-disturbed ellipticals at z=0Oct 13 2009We present an analysis of the neutral hydrogen and stellar populations of elliptical galaxies in the Tal et al. (2009) sample. Our aim is to test their conclusion that the continuing assembly of these galaxies at z~0 is essentially gas-free and not accompanied ... More
Impact of Secondary non-Gaussianities on the Search for Primordial Non-Gaussianity with CMB MapsJan 21 2008When constraining the primordial non-Gaussianity parameter f_NL with cosmic microwave background anisotropy maps, the bias resulting from the covariance between primordial non-Gaussianity and secondary non-Gaussianities to the estimator of f_NL is generally ... More
Symmetry breaking results for problems with exponential growth in the unit diskApr 13 2005We investigate some asymptotic properties of extrema to a two-dimensional variational problem in the unit disk. Some results about non-radialicity of solutions are given.
Understanding Human-Centric Images: From Geometry to FashionDec 14 2015Understanding humans from photographs has always been a fundamental goal of computer vision. In this thesis we have developed a hierarchy of tools that cover a wide range of topics with the objective of understanding humans from monocular RGB image: from ... More
Large sets with small doubling modulo p are well covered by an arithmetic progressionApr 06 2008We prove that there is a small but fixed positive integer e such that for every prime larger than a fixed integer, every subset S of the integers modulo p which satisfies |2S|<(2+e)|S| and 2(|2S|)-2|S|+2 < p is contained in an arithmetic progression of ... More
Identification of potential Music Information Retrieval technologies for computer-aided jingju singing trainingNov 02 2017Music Information Retrieval (MIR) technologies have been proven useful in assisting western classical singing training. Jingju (also known as Beijing or Peking opera) singing is different from western singing in terms of most of the perceptual dimensions, ... More
Topological suppression of magnetoconductance oscillations in NS junctionsJan 11 2017Jan 15 2017We show that the magnetoconductance oscillations of laterally-confined 2D NS junctions are completely suppressed when the superconductor side enters a topological phase. This suppression can be attributed to the modification of the vortex structure of ... More
Quantitative stability of the free boundary in the obstacle problemAug 04 2017We prove some detailed quantitative stability results for the contact set and the solution of the classical obstacle problem in $\mathbb{R}^n$ ($n \ge 2$) under perturbations of the obstacle function, which is also equivalent to studying the variation ... More
The Existence of Inner Cool Disks in the Low Hard State of Accreting Black HolesSep 03 2007The condensation of matter from a corona to a cool, optically thick inner disk is investigated for black hole X-ray transient systems in the low hard state. A description of a simple model for the exchange of energy and mass between corona and disk originating ... More
3-Phase Evolution of a Coronal Hole, Part I: 360° remote sensing and in-situ observationsJun 25 2018We investigate the evolution of a well-observed, long-lived, low-latitude coronal hole (CH) over 10 solar rotations in the year 2012. By combining EUV imagery from STEREO-A/B and SDO we are able to track and study the entire evolution of the CH having ... More
The Dependence of the Peak Velocity of High-Speed Solar Wind Streams as Measured in the Ecliptic by ACE and the STEREO satellites on the Area and Co-Latitude of their Solar Source Coronal HolesApr 25 2018Apr 26 2018We study the properties of 115 coronal holes in the time-range from 2010/08 to 2017/03, the peak velocities of the corresponding high-speed streams as measured in the ecliptic at 1 AU, and the corresponding changes of the Kp index as marker of their geo-effectiveness. ... More
On stable solutions for boundary reactions: a De Giorgi-type result in dimension 4+1May 08 2017We prove that every bounded stable solution of \[ (-\Delta)^{1/2} u + f(u) =0 \qquad \mbox{in }\mathbb R^3\] is a 1D profile, i.e., $u(x)= \phi(e\cdot x)$ for some $e\in \mathbb S^2$, where $\phi:\mathbb R\to \mathbb R$ is a nondecreasing bounded stable ... More
Correlation among runners and some results on the Lonely Runner ConjectureJul 12 2014Sep 12 2015The Lonely Runner Conjecture was posed independently by Wills and Cusick and has many applications in different mathematical fields, such as diophantine approximation. This well-known conjecture states that for any set of runners running along the unit ... More
On the tree-depth of Random GraphsApr 12 2011Feb 15 2012The tree-depth is a parameter introduced under several names as a measure of sparsity of a graph. We compute asymptotic values of the tree-depth of random graphs. For dense graphs, p>> 1/n, the tree-depth of a random graph G is a.a.s. td(G)=n-O(sqrt(n/p)). ... More
A minimization approach to hyperbolic Cauchy problemsOct 25 2013Developing an original idea of De Giorgi, we introduce a new and purely variational approach to the Cauchy Problem for a wide class of defocusing hyperbolic equations. The main novel feature is that the solutions are obtained as limits of functions that ... More
Localization of the valence electron of endohedrally confined hydrogen, lithium and sodium in fullerene cagesMar 08 2016The localization of the valence electron of $H$, $Li$ and $Na$ atoms enclosed by three different fullerene molecules is studied. The structure of the fullerene molecules is used to calculate the equilibrium position of the endohedrally atom as the minimum ... More
On the fine structure of the free boundary for the classical obstacle problemSep 12 2017Nov 25 2017In the classical obstacle problem, the free boundary can be decomposed into "regular" and "singular" points. As shown by Caffarelli in his seminal papers \cite{C77,C98}, regular points consist of smooth hypersurfaces, while singular points are contained ... More
On the number of monochromatic solutions of integer linear systems on Abelian groupsMar 11 2012Let $G$ be a finite abelian group with exponent $n$, and let $r$ be a positive integer. Let $A$ be a $k\times m$ matrix with integer entries. We show that if $A$ satisfies some natural conditions and $|G|$ is large enough then, for each $r$--coloring ... More
Rainbow Matchings: existence and countingApr 14 2011A perfect matching M in an edge-colored complete bipartite graph K_{n,n} is rainbow if no pair of edges in M have the same color. We obtain asymptotic enumeration results for the number of rainbow matchings in terms of the maximum number of occurrences ... More
Life time evolution of coronal holesJul 05 2019Jul 16 2019We investigate the evolution of eight well-observed persistent coronal holes (CHs) with life spans of 5--12 solar rotations, that were observed between 2010 and 2015. The aim is to increase our understanding of the evolution of CHs, as well as to investigate ... More
Verification of high-speed solar wind stream forecasts using operational solar wind modelsJul 24 2016High-speed solar wind streams emanating from coronal holes are frequently impinging on the Earth's magnetosphere causing recurrent, medium-level geomagnetic storm activity. Modeling high-speed solar wind streams is thus an essential element of successful ... More
Modules over Monads and LinearityAug 11 2006May 07 2007Inspired by the classical theory of modules over a monoid, we give a first account of the natural notion of module over a monad. The associated notion of morphism of left modules ("Linear" natural transformations) captures an important property of compatibility ... More
Some Riemann Hypotheses from Random Walks over PrimesSep 11 2015Apr 17 2016The aim of this article is to investigate how various Riemann Hypotheses would follow only from properties of the prime numbers. To this end, we consider two classes of $L$-functions, namely, non-principal Dirichlet and those based on cusp forms. The ... More
Robust minimal matching rules for quasicrystalsSep 27 2018We propose a unified framework for dealing with matching rules of quasiperiodic patterns, relevant for both tiling models and real world quasicrystals. The approach is intended for extraction and validation of a minimal set of matching rules, directly ... More
Improved Algorithms for MST and Metric-TSP InterdictionMay 31 2017We consider the {\em MST-interdiction} problem: given a multigraph $G = (V, E)$, edge weights $\{w_e\geq 0\}_{e \in E}$, interdiction costs $\{c_e\geq 0\}_{e \in E}$, and an interdiction budget $B\geq 0$, the goal is to remove a set $R\subseteq E$ of ... More