Results for "Stella Chariton"

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High-performance stock index trading: making effective use of a deep LSTM neural networkFeb 07 2019We present a deep long short-term memory (LSTM)-based neural network for predicting asset prices, together with a successful trading strategy for generating profits based on the model's predictions. Our work is motivated by the fact that the effectiveness ... More
High-pressure synthesis of ultraincompressible hard rhenium nitride pernitride Re$_{2}$(N$_{2}$)N$_{2}$ stable at ambient conditionsFeb 25 2019Here we report the synthesis of metallic, ultraincompressible (bulk modulus $K_{0}$ = 428(10) GPa) and very hard (nanoindentation hardness 36.7(8) GPa) rhenium (V) nitride pernitride Re$_{2}$(N$_{2}$)N$_{2}$. While the empirical chemical formula of the ... More
B1-B2 phase transition in MgO at ultra-high static pressureMar 31 2019Studies of the behaviour of solids at ultra-high pressures, those beyond 200 GPa, contribute to our fundamental understanding of materials properties and allow an insight into the processes happening at such extreme conditions relevant for terrestrial ... More
On the algebraic K-theory of Spec Z^NJul 17 2012In his thesis, N. Durov develops a theory of algebraic geometry in which schemes are locally determined by commutative algebraic monads. In this setting, one is able to construct the Arakelov geometric compactification of the spectrum of the ring of integers ... More
Polyhedral models for generalized associahedra via Coxeter elementsNov 07 2011Aug 28 2012Motivated by the theory of cluster algebras, F. Chapoton, S. Fomin and A. Zelevinsky associated to each finite type root system a simple convex polytope called \emph{generalized associahedron}. They provided an explicit realization of this polytope associated ... More
The Relativistic Precession Model for QPOs in Low Mass X-ray BinariesNov 21 2000The relativistic precession model for quasi periodic oscillations, QPOs, in low mass X-ray binaries is reviewed. The behaviour of three simultaneous types of QPOs is well matched in terms of the fundamental frequencies for geodesic motion in the strong ... More
A first study of the semi-leptonic decay of the $Λ_b$ baryonJul 29 1996We present the preliminary results of the first Lattice study of the baryonic Isgur and Wise function obtained from the matrix element of the weak current between $\Lambda$-baryon external states. Its dependence on the heavy and light quark masses is ... More
Heavy Baryon SpectroscopyNov 30 1994We present the preliminary results of an exploratory study of heavy baryon spectroscopy, using the $O(a)$-improved fermionic action. Estimates of masses and splittings at the charm and beauty physical limit are reported.
Reconstructing the spectrum of F_1 from the stable homotopy categoryMar 07 2011Jun 23 2011The finite stable homotopy category S_0 has been suggested as a candidate for a category of perfect complexes over the monoid scheme Spec F_1. We apply a reconstruction theorem from algebraic geometry to S_0, and show that one recovers the one point topological ... More
Reconstruction of quasi-compact quasi-separated schemes from categories of perfect complexesAug 05 2011We show how to recover the underlying topological space of a quasi-compact quasi-separated scheme from the tensor triangulated structure on its category of perfect complexes.
Pressure induced Hydrogen-Hydrogen interaction in metallic FeH revealed by NMRFeb 08 2019Knowledge of the behavior of hydrogen in metal hydrides is the key for understanding their electronic properties. So far, no experimental methods exist to access these properties beyond 100 GPa, where high-Tc superconductivity emerges. Here, we present ... More
Mental Lexicon Growth Modelling Reveals the Multiplexity of the English LanguageApr 05 2016In this work we extend previous analyses of linguistic networks by adopting a multi-layer network framework for modelling the human mental lexicon, i.e. an abstract mental repository where words and concepts are stored together with their linguistic patterns. ... More
Matrix geometric approach for random walks: stability condition and equilibrium distributionMar 15 2016Sep 17 2016In this manuscript, the authors consider a sub-class of the two-dimensional homogeneous nearest neighbor (simple) random walk restricted on the lattice. In particular, the sub-class of random walks with equilibrium distributions given as series of product-forms ... More
CTBNCToolkit: Continuous Time Bayesian Network Classifier ToolkitApr 18 2014Continuous time Bayesian network classifiers are designed for temporal classification of multivariate streaming data when time duration of events matters and the class does not change over time. This paper introduces the CTBNCToolkit: an open source Java ... More
A k-deformed Model of Growing Complex Networks with FitnessApr 12 2014The Barab\'asi-Bianconi (BB) fitness model can be solved by a mapping between the original network growth model to an idealized bosonic gas. The well-known transition to Bose-Einstein condensation in the latter then corresponds to the emergence of "super-hubs" ... More
The action of a Coxeter element on an affine root systemAug 15 2018Aug 16 2018The characterization of orbits of roots under the action of a Coxeter element is a fundamental tool in the study of finite root systems and their reflection groups. This paper develops the analogous tool in the affine setting.
A new instability of accretion disks around compact magnetic starsMar 09 1998Aperiodic variability and Quasi Periodic Oscillations (QPOs) are observed from accretion disks orbiting white dwarfs, neutron stars, and black holes, suggesting that the flow is universally broken up into discrete blobs. We consider the interaction of ... More
SupraNova Events from Spun-up Neutron Stars: an Explosion in Search of an ObservationOct 01 1999We consider a formation scenario for supramassive neutron stars (SMNSs) taking place through mass and angular momentum transfer from a close companion during a Low Mass X-ray Binary (LMXB) phase, with the ensuing suppression of the magnetic field. We ... More
Cluster lens reconstruction using only observed local data -- an improved finite-field inversion techniqueMar 27 1995Gravitational light deflection can distort the images of distant sources by its tidal effects. The population of faint blue galaxies is at sufficiently high redshift so that their images are distorted near foreground clusters, with giant luminous arcs ... More
Mean-field Games for Bio-inspired Collective Decision-making in Dynamical NetworksFeb 09 2018Given a large number of homogeneous players that are distributed across three possible states, we consider the problem in which these players have to control their transition rates, while minimizing a cost. The optimal transition rates are based on the ... More
Mean Field Renormalization Group for the Boundary Magnetization of Strip ClustersJul 13 1993We analyze in some detail a recently proposed transfer matrix mean field approximation which yields the exact critical point for several two dimensional nearest neighbor Ising models. For the square lattice model we show explicitly that this approximation ... More
A Finiteness Property of Torus InvariantsOct 28 2015In this paper the invariant subring $R_n$ of an algebraic torus $T=(\mathbb{C}^\times)^r$ acting on the multi-homogenous polynomial ring $$S^{\boxtimes n}=\bigoplus_{d=0}^\infty (S^{(d)})^{\otimes n},$$ where $S^{(d)}$ is the $d$th graded piece of the ... More
Bayesian Model comparison of Higgs couplingsNov 18 2014Oct 01 2015We investigate the possibility of contributions from physics beyond the Standard Model (SM) to the Higgs couplings, in the light of the LHC data. The work is performed within an interim framework where the magnitude of the Higgs production and decay rates ... More
An affine almost positive roots modelJul 02 2017Aug 20 2018We generalize the almost positive roots model for cluster algebras from finite type to a uniform finite/affine type model. We define the almost positive Schur roots $\Phi_c$ and a compatibility degree, given by a formula that is new even in finite type. ... More
Some consequences of categorificationDec 22 2017Several conjectures on acyclic skew-symmetrizable cluster algebras are proven as direct consequences of their categorification via valued quivers. These include conjectures of Fomin-Zelevinsky, Reading-Speyer, and Reading-Stella related to d-vectors, ... More
A new finite-field mass reconstruction algorithmFeb 04 1998A new method for the reconstruction of the projected mass distribution of clusters of galaxies from the image distortion of background galaxies is discussed. This method is essentially equivalent to the one we developed previously, i.e., the noise-filtering ... More
Reverberation by a Relativistic Accretion DiskSep 19 1994We calculate the response of a line emitted from a relativistic accretion disk to a continuum variation of the central illuminating source. This model might be relevant to the very broad and sometimes redshifted emission lines which have been observed ... More
Exchange Relations for Finite Type Cluster Algebras with Acyclic Initial Seed and Principal CoefficientsApr 21 2016Jul 09 2016We give an explicit description of all the exchange relations in any finite type cluster algebra with acyclic initial seed and principal coefficients.
An expansion for the number of partitions of an integerJan 21 2019We obtain an asymptotic expansion for $p(n)$, the number of partitions of a natural number $n$, starting from a formula that relates its generating function $f(t), t\in (0,1)$ with the characteristic functions of a family of sums of independent random ... More
Patterns in the English Language: Phonological Networks, Percolation and Assembly ModelsOct 16 2014Mar 23 2015In this paper we provide a quantitative framework for the study of phonological networks (PNs) for the English language by carrying out principled comparisons to null models, either based on site percolation, randomization techniques, or network growth ... More
Nonequilibrium Dynamics with Finite-Time Repeated InteractionsSep 13 2018In the thermodynamics of elementary quantum systems, repeated interactions with environmental probes can be used as a template to model relaxation in various reservoir types. We formulate a coarse-grained master equation that spans arbitrary interaction ... More
The interplay between representable functionals and derivations on Banach quasi *-algebrasSep 03 2018This note aims to highlight the link between representable functionals and derivations on a Banach quasi *-algebra, i.e. a mathematical structure that can be seen as the completion of a normed *-algebra in the case the multiplication is only separately ... More
Initial-seed recursions and dualities for d-vectorsSep 16 2014Jul 26 2017We present an initial-seed-mutation formula for d-vectors of cluster variables in a cluster algebra. We also give two rephrasings of this recursion: one as a duality formula for d-vectors in the style of the g-vectors/c-vectors dualities of Nakanishi ... More
An affine almost positive roots modelJul 02 2017Apr 09 2019We generalize the almost positive roots model for cluster algebras from finite type to a uniform finite/affine type model. We define the almost positive Schur roots $\Phi_c$ and a compatibility degree, given by a formula that is new even in finite type. ... More
Bio-inspired Evolutionary Game Dynamics on Complex Networks under Uncertain Cross-inhibitory SignalsJun 05 2017Given a large population of players, each player has three possible choices between option 1 or 2 or no option. The two options are equally favorable and the population has to reach consensus on one of the two options quickly and in a distributed way. ... More
Theoretic Shaping Bounds for Single Letter Constraints and Mismatched DecodingAug 27 2013Shaping gain is attained in schemes where a shaped subcode is chosen from a larger codebook by a codeword selection process. This includes the popular method of Trellis Shaping (TS), originally proposed by Forney for average power reduction. The decoding ... More
The Self-Organization of Grid Cells in 3DDec 02 2014What sort of grid cells do we expect to see in bats exploring a three-dimensional environment? How long will it take for them to emerge? We address these questions within our self-organization model based on firing-rate adaptation. The model indicates ... More
Young Crab-like pulsars and luminous X-ray sources in starbursts and optically dull galaxiesJul 08 2004Recent Chandra observations of nearby galaxies have revealed a number of ultraluminous X-ray sources (ULXs) with super-Eddington luminosities, away from the central regions of non-active galaxies. The nature of these sources is still debated. We argue ... More
On the relationship between the periodic and aperiodic variability of accreting X-ray pulsarsSep 04 1996Besides the narrow peaks originating from the periodic signal, the power spectra of accreting X-ray pulsars display continuum components usually increasing towards low frequencies; these arise from the source aperiodic variability. Most studies so far ... More
On the bolometric quiescent luminosity and luminosity swing of black hole candidate and neutron star low mass X-ray transientsMay 07 2000Low mass X-ray transients (LMXRTs) hosting black hole candidates (BHCs) display on average a factor of ~100 larger swing in the minimum (quiescent) to maximum (outburst) X-ray luminosity than neutron stars (NSs), despite the fact that the swing in the ... More
New results on neutron star low mass transients in the quiescenceSep 30 2003We review the main observational properties of neutron star low mass transients in quiescence. We first survey the discoveries of BeppoSAX. We then focus on recent discoveries by Chandra and XMM-Newton, with special emphsasis on the detection of the quiescent ... More
The action of a Coxeter element on an affine root systemAug 15 2018Mar 18 2019The characterization of orbits of roots under the action of a Coxeter element is a fundamental tool in the study of finite root systems and their reflection groups. This paper develops the analogous tool in the affine setting, adding detail and uniformity ... More
Neural Networks on GroupsJun 13 2019Jul 09 2019Although neural networks traditionally are typically used to approximate functions defined over $\mathbb{R}^n$, the successes of graph neural networks, point-cloud neural networks, and manifold deep learning among other methods have demonstrated the clear ... More
Wonder of sine-Gordon Y-systemsDec 31 2012Jan 23 2016The sine-Gordon Y-systems and the reduced sine-Gordon Y-systems were introduced by Tateo in the 90's in the study of the integrable deformation of conformal field theory by the thermodynamic Bethe ansatz method. The periodicity property and the dilogarithm ... More
Dust Continuum Observations of Protostars: Constraining Properties with SimulationsAug 06 2012The properties of unresolved protostars and their local environment (e.g., disk, envelope and outflow characteristics) are frequently inferred from spectral energy distributions (SEDs) through comparison with idealized model SEDs. However, if it is not ... More
Initial-seed recursions and dualities for d-vectorsSep 16 2014Cluster variables in a cluster algebra can be parametrized by two families of integer vectors: d-vectors and g-vectors. While g-vectors satisfy two recursive formulas (one for initial-seed-mutations and one for final-seed-mutations), d-vectors admit only ... More
kHz Quasi Periodic Oscillations in Low Mass X-ray Binaries as Probes of General Relativity in the Strong Field RegimeDec 07 1998We consider the interpretation of a pair of kHz Quasi Periodic Oscillations (QPOs) in the Fourier spectra of two Low Mass X-Ray Binaries, Sco X-1 and 4U1608-52, hosting an old accreting neutron star. The observed frequency difference of these QPOs decreaseas ... More
A gamma ray burst with small contaminationAug 31 1998We present a scenario (SupraNova) for the formation of GRBs occurring when a supramassive neutron star (SMNS) loses so much angular momentum that centrifugal support against self--gravity becomes impossible, and the star implodes to a black hole. This ... More
Lense-Thirring Precession and QPOs in Low Mass X-Ray BinariesSep 10 1997We show in this Letter that relativistic dragging of inertial frames around fast rotating collapsed stars is substantial and can give rise to observable effects. We apply this to the kHz quasi periodic oscillations (QPOs) sources, low mass X-ray binaries ... More
Short Gamma-Ray Bursts and Gravitational Waves from Dynamically Formed Merging BinariesNov 05 2008Nov 10 2008Merging binary systems consisting of two collapsed objects are among the most promising sources of high frequency gravitational wave, GW, signals for ground based interferometers. Double neutron star or black hole/neutron star mergers are also believed ... More
The Density of 1-Jansky Sources Around Zwicky ClustersAug 30 1994In a recent paper by Rodrigues-Williams \& Hogan (RH94), a correlation between high-redshift, optically-selected QSOs and Zwicky clusters was reported at a very high significance level. Due to the fairly bright flux threshold of the cluster sample, these ... More
The evolution of the high energy tail in the quiescent spectrum of the soft X-ray transient Aql X-1Jul 10 2003A moderate level of variability has been detected in the quiescent luminosity of several neutron star soft X-ray transients. Spectral variability was first revealed by Chandra observations of Aql X-1 in the four months that followed the 2000 X-ray outburst. ... More
Diagrammatic description of c-vectors and d-vectors of cluster algebras of finite typeOct 23 2012Jan 13 2014We provide an explicit Dynkin diagrammatic description of the c-vectors and the d-vectors (the denominator vectors) of any cluster algebra of finite type with principal coefficients and any initial exchange matrix. We use the surface realization of cluster ... More
Quantum annealing of an Ising spin-glass by Green's function Monte CarloAug 18 2006We present an implementation of Quantum Annealing (QA) via lattice Green's function Monte Carlo (GFMC), focusing on its application to the Ising spin-glass in transverse field. In particular, we study whether or not such method is more effective than ... More
Dynamic Multi-level Privilege Control in Behavior-based Implicit Authentication Systems Leveraging Mobile DevicesAug 02 2018Implicit authentication (IA) is gaining popularity over recent years due to its use of user behavior as the main input, relieving users from explicit actions such as remembering and entering passwords. However, such convenience comes at a cost of authentication ... More
Role of scaling in the statistical modeling of financeApr 02 2008Modeling the evolution of a financial index as a stochastic process is a problem awaiting a full, satisfactory solution since it was first formulated by Bachelier in 1900. Here it is shown that the scaling with time of the return probability density function ... More
Boundary effects in a random neighbor model of earthquakesJan 07 1998We introduce spatial inhomogeneities (boundaries) in a random neighbor version of the Olami, Feder and Christensen model [Phys. Rev. Lett. 68, 1244 (1992)] and study the distributions of avalanches starting both from the bulk and from the boundaries of ... More
Scaling and efficiency determine the irreversible evolution of a marketJul 16 2008In setting up a stochastic description of the time evolution of a financial index, the challenge consists in devising a model compatible with all stylized facts emerging from the analysis of financial time series and providing a reliable basis for simulating ... More
C^{k,α}-regularity of solutions to quasilinear equations structured on Hörmander's vector fieldsApr 18 2013For a linear nonvariational operator structured on smooth H\"ormander's vector fields, with H\"older continuous coefficients, we prove a regularity result in the spaces of H\"older functions. We deduce an analogous regularity result for nonvariational ... More
A category for the adjoint representationFeb 08 2000Jul 03 2001We construct an abelian category C and exact functors in C which on the Grothendieck group descend to the action of a simply-laced quantum group in its adjoint representation. The braid group action in the adjoint representation lifts to an action in ... More
Categorification of some level two representations of sl(n)Apr 28 2002We categorify representations of quantum sl(n) whose highest weight is twice a fundamental weight.
Gluing semigroups and strongly indispensable free resolutionsOct 25 2017Oct 02 2018We study strong indispensability of minimal free resolutions of semigroup rings. We focus on two operations, gluing and extending, used in literature to produce more examples with a special property from the existing ones. We give a naive condition to ... More
Pseudoknots in a HomopolymerDec 19 2003After a discussion of the definition and number of pseudoknots, we reconsider the self-attracting homopolymer paying particular attention to the scaling of the number of pseudoknots at different temperature regimes in two and three dimensions. Although ... More
Fast variability from black-hole binariesJul 28 2014Currently available information on fast variability of the X-ray emission from accreting collapsed objects constitutes a complex phenomenology which is difficult to interpret. We review the current observational standpoint for black-hole binaries and ... More
Relativistic precession around rotating neutron stars: Effects due to frame-dragging and stellar oblatenessAug 21 1998General relativity predicts that a rotating body produces a frame-dragging (or Lense-Thirring) effect: the orbital plane of a test particle in a non-equatorial orbit precesses about the body's symmetry axis. In this paper we compute the precession frequencies ... More
Under Augustus sign: the role of Astronomy in the foundation of Augusta Praetoria SalassorumNov 28 2013Augusta Praetoria Salassorum, modern Aosta, was founded around 25 BC to celebrate the victory of Augustus army on the Salassi. Aosta is a city of the founder under many respects; for instance, one of the two twin temples of the forum was devoted to Augustus, ... More
Mugeetion: Musical Interface Using Facial Gesture and EmotionSep 14 2018Oct 07 2018People feel emotions when listening to music. However, emotions are not tangible objects that can be exploited in the music composition process as they are difficult to capture and quantify in algorithms. We present a novel musical interface, Mugeetion, ... More
The local sharp maximal function and BMO on locally homogeneous spacesNov 07 2015We prove a local version of Fefferman-Stein inequality for the local sharp maximal function, and a local version of John-Nirenberg inequality for locally BMO functions, in the framework of locally homogeneous spaces, in the sense of Bramanti-Zhu [Manuscripta ... More
Asymptotic analysis of microscopic impenetrability constraints for atomistic systemsMay 12 2015In this paper we analyze a two-dimensional discrete model of nearest-neighbour Lennard-Jones interactions under the microscopical constraint that points on a lattice triangle maintain their order. This can be understood as a microscopical non-interpenetration ... More
Theta-point universality of polyampholytes with screened interactionsJul 09 1998Sep 06 1998By an efficient algorithm we evaluate exactly the disorder-averaged statistics of globally neutral self-avoiding chains with quenched random charge $q_i=\pm 1$ in monomer i and nearest neighbor interactions $\propto q_i q_j$ on square (22 monomers) and ... More
Newborn Magnetars as sources of Gravitational Radiation: constraints from High Energy observations of Magnetar CandidatesFeb 02 2007Soft Gamma Repeaters and the Anomalous X-ray Pulsars are believed to contain slowly spinning "magnetars". The enormous energy liberated in the 2004 Dece 27 giant flare from SGR 1806-20, together with the likely recurrence time of such events, points to ... More
A new technique for the detection of periodic signals in ``coloured'' power spectraMar 11 1996The light curves from a variety of celestial objects display aperiodic variations, often giving rise to red-noise components in their power spectra. Searching for a narrow power spectrum peak resulting from a periodic modulation over the frequency range ... More
Central limit theorem for anomalous scaling due to correlationsOct 10 2005Feb 28 2007We derive a central limit theorem for the probability distribution of the sum of many critically correlated random variables. The theorem characterizes a variety of different processes sharing the same asymptotic form of anomalous scaling and is based ... More
BMO estimates for nonvariational operators with discontinuous coefficients structured on Hormander's vector fields on Carnot groupsSep 17 2012We consider a class of nonvariational linear operators formed by homogeneous left invariant Hormander's vector fields with respect to a structure of Carnot group. The bounded coefficients of the operators belong to "vanishing logarithmic mean oscillation" ... More
A scale-free network hidden in the collapsing polymerSep 22 2004Sep 23 2004We show that the collapsed globular phase of a polymer accommodates a scale-free incompatibility graph of its contacts. The degree distribution of this network is found to decay with the exponent $\gamma = 1/(2-c)$ up to a cut-off degree $d_c \propto ... More
Level convexity as a necessary condition for the relaxation of $L^\infty$-functionalsFeb 19 2018We consider a supremal functional of the form $$F(u)= \supess_{x \in \Omega} f(x,Du(x))$$ where $\Omega\subseteq \R^N$ is a regular bounded open set, $u\in \wi$ and $f$ is a Borel function. Under a mild assumption on the sublevel sets of $F$, we show ... More
High Energy Radiation from Neutron Star BinariesJul 10 2002This paper surveys our current knowledge of the hard X-ray emission properties of old accreting neutron stars in low mass X-ray binaries. Hard X-ray components extending up to energies of a few hundred keV have been clearly detected in sources of both ... More
Unbounded derivations and *-automorphisms groups of Banach quasi *-algebrasJul 30 2018This paper is devoted to the study of unbounded derivations on Banach quasi *-algebras with a particular emphasis to the case when they are infinitesimal generators of one parameter automorphisms groups. Both of them, derivations and automorphisms are ... More
Anomalous scaling due to correlations: Limit theorems and self-similar processesSep 04 2009Dec 23 2009We derive theorems which outline explicit mechanisms by which anomalous scaling for the probability density function of the sum of many correlated random variables asymptotically prevails. The results characterize general anomalous scaling forms, justify ... More
The asymptotic expansion for the factorial and Lagrange inversion formulaFeb 20 2010We obtain an explicit simple formula for the coefficients of the asymptotic expansion for the factorial of a natural number,in terms of derivatives of powers of an elementary function. The unique explicit expression for the coefficients that appears to ... More
The Gluon Propagator on a Large Volume, at $β=6.0$Oct 20 1994Oct 21 1994We present the results of a high statistics lattice study of the gluon propagator, in the Landau gauge, at $\beta=6.0$. As suggested by previous studies, we find that, in momentum space, the propagator is well described by the expression $G(k^2)= \Big[ ... More
New Primal-Dual Proximal Algorithm for Distributed OptimizationMay 06 2016Dec 03 2016We consider a network of agents, each with its own private cost consisting of the sum of two possibly nonsmooth convex functions, one of which is composed with a linear operator. At every iteration each agent performs local calculations and can only communicate ... More
Approximate analytical calculations of photon geodesics in the Schwarzschild metricAug 16 2016Aug 30 2016We develop a method for deriving approximate analytical formulae to integrate photon geodesics in a Schwarzschild spacetime. Based on this, we derive the approximate equations for light bending and propagation delay that have been introduced empirically. ... More
Scaling of a collapsed polymer globule in 2DJun 28 2005Oct 18 2005Extensive Monte Carlo data analysis gives clear evidence that collapsed linear polymers in two dimensions fall in the universality class of athermal, dense self-avoiding walks, as conjectured by B.Duplantier [Phys.Rev.Lett. 71, 4274 (1993)]. However, ... More
Peculiar scaling of self-avoiding walk contactsApr 11 2001May 31 2001The nearest neighbor contacts between the two halves of an N-site lattice self-avoiding walk offer an unusual example of scaling random geometry: for N going to infinity they are strictly finite in number but their radius of gyration Rc is power law distributed, ... More
Dynamics, CO depletion, and deuterium fractionation of the dense condensations within the fragmented prestellar core Orion B9-SMM 6May 10 2013We present APEX observations of C17O(2-1), N2H+(3-2), and N2D+(3-2) towards the subfragments inside the prestellar core SMM 6 in Orion B9. We combined these spectral line data with our previous SABOCA 350-{\mu}m dust continuum map of the source. The subfragments ... More
Scaling law for seismic hazard after a main shockMar 01 2004After a large earthquake, the likelihood of successive strong aftershocks needs to be estimated. Exploiting similarities with critical phenomena, we introduce a scaling law for the decay in time following a main shock of the expected number of aftershocks ... More
Excitation-transport in open quantum networks: The effects of configurationsAug 24 2017We study the environment-assisted enhancement of the excitation-transport efficiency across a network of interacting quantum particles or sites. Our study reveals a crucial influence of the network configuration - and especially its degree of connectivity ... More
Neutron star bulk viscosity, "spin-flip" and GW emission of newly born magnetarsJun 28 2018The viscosity-driven "spin-flip" instability in newborn magnetars with interior toroidal magnetic fields is re-examined. We calculate the bulk viscosity coefficient ($\zeta$) of cold, $npe \mu$ matter in neutron stars (NS), for selected values of the ... More
NuSTAR J095551+6940.8: a highly magnetised neutron star with super-Eddington mass accretionDec 04 2014Jan 23 2015The identification of the Ultraluminous X-ray source (ULX) X-2 in M82 as an accreting pulsar has shed new light on the nature of a subset of ULXs, while rising new questions on the nature of the super-Eddington accretion. Here, by numerically solving ... More
Hunting for Magnetars in High Mass X-ray Binaries. The Case of SuperGiant Fast X-Ray TransientsNov 06 2008In this paper we summarize some aspects of the wind accretion theory in high mass X-ray binaries hosting a magnetic neutron star and a supergiant companion. In particular, we concentrate on the different types of interaction between the inflowing wind ... More
Correlations in the QPO Frequencies of Low Mass X-Ray Binaries and the Relativistic Precession ModelJul 26 1999A remarkable correlation between the centroid frequencies of quasi periodic oscillations, QPOs, (or peaked noise components) from low mass X-ray binaries, has been recently discovered by Psaltis, Belloni and van der Klis (1999). This correlation extends ... More
New limits on the orbital parameters of 1E1048.1-5937 and 1E2259+586 from RossiXTE observationsOct 29 1997We report on two RossiXTE observations of the anomalous X-ray pulsars 1E 1048.1-5937 and 1E 2259+586. Both sources have continued their almost constant spin-down during 1995/96. We carried out a search for orbital Doppler shifts, in their observed spin ... More
Magic: The Gathering is Turing CompleteMar 24 2019Apr 23 2019$\textit{Magic: The Gathering}$ is a popular and famously complicated trading card game about magical combat. In this paper we show that optimal play in real-world $\textit{Magic}$ is at least as hard as the Halting Problem, solving a problem that has ... More
Better than Real: Complex-valued Neural Nets for MRI FingerprintingJul 01 2017The task of MRI fingerprinting is to identify tissue parameters from complex-valued MRI signals. The prevalent approach is dictionary based, where a test MRI signal is compared to stored MRI signals with known tissue parameters and the most similar signals ... More
Light Propagation in Arbitrary Spacetimes and the Gravitational Lens ApproximationMar 24 1994We reformulate the transport equation which determines the size, shape and orientation of infinitesimal light beams in arbitrary spacetimes. The behaviour of such light beams near vertices and conjugate points is investigated, with special attention to ... More
A BeppoSAX view of transient black hole candidates in quiescenceApr 04 2001We report on BeppoSAX observations of five transient black hole candidates during their quiescent phase. We confirm these sources are X-ray faint, improving on and complementing existing upper limits. We derive 1-10 keV upper limits for GRO J0422+32, ... More
Bots increase exposure to negative and inflammatory content in online social systemsFeb 20 2018Feb 28 2019Societies are complex systems which tend to polarize into sub-groups of individuals with dramatically opposite perspectives. This phenomenon is reflected -- and often amplified -- in online social networks where, however, humans are no more the only players, ... More
Affine cluster monomials are generalized minorsDec 25 2017We study the realization of acyclic cluster algebras as coordinate rings of Coxeter double Bruhat cells in Kac-Moody groups. We prove that all cluster monomials with g-vector lying in the doubled Cambrian fan are restrictions of principal generalized ... More
The Generalized Langevin Equation: An efficient approach to non-equilibrium molecular dynamics of open systemsDec 17 2013Mar 18 2014The Generalized Langevin Equation (GLE) has been recently suggested to simulate the time evolution of classical solid and molecular systems when considering general non-equilibrium processes. In this approach, a part of the whole system (an open system), ... More