Results for "Alessandro B. Romeo"

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Astrophysical Dynamics 1999/2000: Merging Research and EducationJun 09 2000The workshop `Astrophysical Dynamics 1999/2000' followed a homonymous advanced research course, and both activities were organized by me. In this opening paper of the proceedings book, I describe them and document their strong impact on the academic life ... More
Modelling Gravity in N-Body Simulations of Disc Galaxies: Optimal Types of Softening for Given Dynamical RequirementsApr 27 1998Modelling gravity is a fundamental problem that must be tackled in N-body simulations of stellar systems, and satisfactory solutions require a deep understanding of the dynamical effects of softening. In a previous paper (Romeo 1997), we have devised ... More
Dynamical Effects of Softening in N-Body Simulations of Disc GalaxiesFeb 03 1997Two questions that naturally arise in N-body simulations of stellar systems are: (1) How can we compare experiments that employ different types of softened gravity? (2) Given a particular type of softened gravity, which choices of the softening length ... More
From spirals to dwarf irregulars: a new tight scaling relation linking the gas and stellar content of galaxies to disc gravitational instabilityMay 14 2019We present a new galaxy scaling relation that predicts the mass fractions of atomic gas, molecular gas and stars as a function of fundamental physical properties such as mass and specific angular momentum. Our scaling relation stretches across two orders ... More
A simple and accurate approximation for the Q stability parameter in multi-component and realistically thick discsFeb 18 2013May 08 2013In this paper, we propose a Q stability parameter that is more realistic than those commonly used, and is easy to evaluate [see Eq. (19)]. Using our Q_N parameter, you can take into account several stellar and/or gaseous components as well as the stabilizing ... More
The effective stability parameter for two-component galactic discs: Is 1/Q ~ 1/Q_stars + 1/Q_gas ?Jan 24 2011May 23 2011The Wang-Silk approximation, 1/Q ~ 1/Q_stars + 1/Q_gas, is frequently used for estimating the effective Q parameter in two-component discs of stars and gas. Here we analyse this approximation in detail, and show how its accuracy depends on the radial ... More
Larson's scaling laws, and the gravitational instability of clumpy discs at high redshiftMar 04 2014May 13 2014Gravitational instabilities play a primary role in shaping the clumpy structure and powering the star formation activity of gas-rich high-redshift galaxies. Here we analyse the stability of such systems, focusing on the size and mass ranges of unstable ... More
Characterizing gravitational instability in turbulent multi-component galactic discsFeb 19 2015Gravitational instabilities play an important role in galaxy evolution and in shaping the interstellar medium (ISM). The ISM is observed to be highly turbulent, meaning that observables like the gas surface density and velocity dispersion depend on the ... More
N-body simulations with two-orders-of-magnitude higher performance using waveletsFeb 18 2003Noise is a problem of major concern for N-body simulations of structure formation in the early Universe, of galaxies and plasmas. Here for the first time we use wavelets to remove noise from N-body simulations of disc galaxies, and show that they become ... More
Chemodynamic evolution of dwarf galaxies in tidal fieldsAug 24 2016The mass-metallicity relation shows that the galaxies with the lowest mass have the lowest metallicities. As most dwarf galaxies are in group environments, interaction effects such as tides could contribute to this trend. We perform a series of smoothed ... More
A wavelet add-on code for new-generation N-body simulations and data de-noising (JOFILUREN)Aug 10 2004Wavelets are a new and powerful mathematical tool, whose most celebrated applications are data compression and de-noising. In Paper I (Romeo, Horellou & Bergh 2003, astro-ph/0302343), we have shown that wavelets can be used for removing noise efficiently ... More
The stellar velocity dispersion in nearby spirals: radial profiles and correlationsApr 26 2018The stellar velocity dispersion, $\sigma$, is a quantity of crucial importance for spiral galaxies, where it enters fundamental dynamical processes such as gravitational instability and disc heating. Here we analyse a sample of 34 nearby spirals from ... More
A Toomre-like stability criterion for the clumpy and turbulent interstellar mediumJan 26 2010May 07 2010We explore the gravitational instability of clumpy and turbulent gas discs, taking into account the Larson-type scaling laws observed in giant molecular clouds (GMCs) and HI, as well as more general scaling relations. This degree of freedom is of special ... More
Physical properties and scaling relations of molecular clouds: the effect of stellar feedbackJan 09 2018Jun 21 2018Using hydrodynamical simulations of entire galactic discs similar to the Milky Way, reaching 4.6pc resolution, we study the origins of observed physical properties of giant molecular clouds (GMCs). We find that efficient stellar feedback is a necessary ... More
Reply to Melott's Comment on ``Discreteness Effects in Lambda Cold Dark Matter Simulations: A Wavelet-Statistical View'' by Romeo et alMay 05 2008Melott has made pioneering studies of the effects of particle discreteness in N-body simulations, a fundamental point that needs careful thought and analysis since all such simulations suffer from numerical noise arising from the use of finite-mass particles. ... More
Discreteness Effects in Lambda Cold Dark Matter Simulations: A Wavelet-Statistical ViewApr 02 2008Jun 27 2008The effects of particle discreteness in N-body simulations of Lambda Cold Dark Matter (LambdaCDM) are still an intensively debated issue. In this paper we explore such effects, taking into account the scatter caused by the randomness of the initial conditions, ... More
Online Permutation Routing in Partitioned Optical Passive Star NetworksFeb 26 2005This paper establishes the state of the art in both deterministic and randomized online permutation routing in the POPS network. Indeed, we show that any permutation can be routed online on a POPS network either with $O(\frac{d}{g}\log g)$ deterministic ... More
On the Observed Diversity of Star Formation Efficiencies in Giant Molecular CloudsFeb 01 2019Apr 30 2019Observations find a median star formation efficiency per free-fall time in Milky Way Giant Molecular Clouds (GMCs) on the order of $\epsilon_{\rm ff}\sim 1\%$ with dispersions of $\sim0.5\,{\rm dex}$. The origin of this scatter in $\epsilon_{\rm ff}$ ... More
Large scale galactic turbulence: can self-gravity drive the observed HI velocity dispersions?Oct 09 2008Dec 17 2008Observations of turbulent velocity dispersions in the HI component of galactic disks show a characteristic floor in galaxies with low star formation rates and within individual galaxies the dispersion profiles decline with radius. We carry out several ... More
The impact of stellar feedback on the density and velocity structure of the interstellar mediumAug 30 2016We study the role of stellar feedback in shaping the density and velocity structure of neutral hydrogen (HI) in disc galaxies. For our analysis, we carry out $\sim 4.6$ pc resolution $N$-body+adaptive mesh refinement (AMR) hydrodynamic simulations of ... More
On the Observed Diversity of Star Formation Efficiencies in Giant Molecular CloudsFeb 01 2019Observations find a median star formation efficiency per free-fall time in Milky Way Giant Molecular Clouds (GMCs) on the order of $\epsilon_{\rm ff}\sim 1\%$ and a four order of magnitude spread in values ($0.01\%-100\%$). The origin of the large range ... More
Orbital Stabilization of Nonlinear Systems via the Immersion and Invariance TechniqueOct 01 2018Immersion and Invariance is a technique for the design of stabilizing and adaptive controllers and state observers for nonlinear systems recently proposed in the literature. In all these applications the problem is translated into stabilization of equilibrium ... More
MY LIFE AS TUTOR: Reflections on Two Recent ExperiencesJun 14 1999In this final report, I briefly reflect on two parallel teaching experiences as tutor. Besides, I briefly view such experiences in interaction with my research work, private life and new teaching position. In harmony with my conception of teaching, I ... More
Local instability signatures in ALMA observations of dense gas in NGC7469Jun 03 2015We present an unprecedented measurement of the disc stability and local instability scales in the luminous infrared Seyfert 1 host, NGC7469, based on ALMA observations of dense gas tracers and with a synthesized beam of 165 x 132 pc. While we confirm ... More
Modified energy-momentum conservation laws and vacuum Cherenkov radiationSep 29 2014Dec 22 2014We present a general parametrization for the leading order terms in a momentum power expansion of a non-universal Lorentz-violating, but rotational invariant, kinematics and its implications for two-body decay thresholds. The considered framework includes ... More
What powers the starburst activity of NGC 1068? Star-driven gravitational instabilities caught in the actFeb 09 2016May 11 2016We explore the role that gravitational instability plays in NGC 1068, a nearby Seyfert galaxy that exhibits unusually vigorous starburst activity. For this purpose, we use the Romeo-Falstad disc instability diagnostics and data from BIMA SONG, SDSS and ... More
A double molecular disc in the triple-barred starburst galaxy NGC 6946: structure and stabilityMar 04 2015May 29 2015The late-type spiral galaxy NGC 6946 is a prime example of molecular gas dynamics driven by "bars within bars". Here we use data from the BIMA SONG and HERACLES surveys to analyse the structure and stability of its molecular disc. Our radial profiles ... More
The effect of ISM turbulence on the gravitational instability of galactic discsMar 06 2012Jul 07 2012We investigate the gravitational instability of galactic discs, treating stars and cold interstellar gas as two distinct components, and taking into account the phenomenology of turbulence in the interstellar medium (ISM), i.e. the Larson-type scaling ... More
Non-universal relativistic kinematicsDec 19 2014We present a systematic derivation of the constraints that the relativity principle imposes between coefficients of a deformed (but rotational invariant) momentum composition law, dispersion relation, and momentum transformation laws, at first order in ... More
Cross-Language Question Re-RankingOct 04 2017We study how to find relevant questions in community forums when the language of the new questions is different from that of the existing questions in the forum. In particular, we explore the Arabic-English language pair. We compare a kernel-based system ... More
From Grad-Shafranov equations set to a pseudo-general form of the non-linear Schroedinger equationJul 10 2008In the year 2003 a paper by G. Lapenta demonstrated that there is a new class of soliton-like solutions for the Grad-Shafranov Equations (GSE).The author determined an appropriate pair of transformations of the free fields p (fluid field of hydrodynamical ... More
Amplification phenomena of Casimir force fluctuations on close scatterers coupled via a coherent fermionic fluidMar 21 2016We study the mechanical actions affecting close scatterers immersed in a coherent fermionic fluid. Using a scattering field theory, we theoretically analyse the single-scatterer and the two-scatterer case. Concerning the single-scatterer case, we find ... More
An elementary proof of a congruence by Skula and GranvilleAug 11 2011Let $p\ge 5$ be a prime, and let $q_p(2):=(2^{p-1}-1)/p$ be the Fermat quotient of $p$ to base 2. The following curious congruence was conjectured by L. Skula and proved by A. Granville $$ q_p(2)^2\equiv -\sum_{k=1}^{p-1}\frac{2^k}{k^2}\pmod{p}. $$ In ... More
On the distribution of primes in the alternating sums of concecutive primesMay 26 2018Quite recently, in [8] the authoor of this paper considered the distribution of primes in the sequence $(S_n)$ whose $n$th term is defined as $S_n=\sum_{k=1}^{2n}p_k$, where $p_k$ is the $k$th prime. Some heuristic arguments and the numerical evidence ... More
Euclid's theorem on the infinitude of primes: a historical survey of its proofs (300 B.C.--2017) and another new proofFeb 16 2012Jun 16 2018In this article, we provide a comprehensive historical survey of 183 different proofs of famous Euclid's theorem on the infinitude of prime numbers. The author is trying to collect almost all the known proofs on infinitude of primes, including some proofs ... More
Angular momentum and local gravitational instability in galaxy discs: does $Q$ correlate with $j$ or $M\,$?May 15 2018Jun 27 2018We introduce a new diagnostic for exploring the link between angular momentum and local gravitational instability in galaxy discs. Our diagnostic incorporates the latest developments in disc instability research, is fully consistent with approximations ... More
SWIPE: a bolometric polarimeter for the Large-Scale Polarization ExplorerAug 01 2012The balloon-borne LSPE mission is optimized to measure the linear polarization of the Cosmic Microwave Background at large angular scales. The Short Wavelength Instrument for the Polarization Explorer (SWIPE) is composed of 3 arrays of multi-mode bolometers ... More
A simple model of energy expenditure in human locomotionSep 06 2006A simple harmonic oscillator model is proposed to describe the mechanical power involved in human locomotion. In this framework, by taking into account the anthropometric parameters of a standard individual, we are able to calculate the speed-power curves ... More
On the mod $p^2$ determination of $\sum_{k=1}^{p-1}H_k/(k\cdot 2^k)$: another proof of a conjecture by SunAug 16 2011Aug 18 2011For a positive integer $n$ let $H_n=\sum_{k=1}^{n}1/k$ be the $n$th harmonic number. Z. W. Sun conjectured that for any prime $p\ge 5$, $$ \sum_{k=1}^{p-1}\frac{H_k}{k\cdot 2^k} \equiv7/24pB_{p-3}\pmod{p^2}. $$ This conjecture is recently confirmed by ... More
Several generalizations and variations of Chu-Vandermonde identityJul 23 2018In this paper we prove some combinatorial identities which can be considered as generalizations and variations of remarkable Chu-Vandermonde identity. These identities are proved by using an elementary combinatorial-probabilistic approach to the expressions ... More
Ideals in some Rings of Nevanlinna-Smirnov TypeApr 09 2018Let $N^p$ $(1<p<\infty)$ denote the algebra of holomorphic functions in the open unit disk, introduced by I.~I.~Privalov with the notation $A_q$ in [8]. Since $N^p$ becomes a ring of Nevanlinna--Smirnov type in the sense of Mortini [7], the results from ... More
Variations of Lucas' Theorem Modulo Prime PowersDec 29 2012Let $p$ be a prime, and let $k,n,m,n_0$ and $m_0$ be nonnegative integers such that $k\ge 1$, and $_0$ and $m_0$ are both less than $p$. K. Davis and W. Webb established that for a prime $p\ge 5$ the following variation of Lucas' Theorem modulo prime ... More
Variations of Kurepa's left factorial hypothesisDec 26 2013Jan 06 2014Kurepa's hypothesis asserts that for each integer $n\ge 2$ the greatest common divisor of $!n:=\sum_{k=0}^{n-1}k!$ and $n!$ is $2$. Motivated by an equivalent formulation of this hypothesis involving derangement numbers, here we give a formulation of ... More
A primality criterion based on a Lucas' congruenceJul 29 2014Let $p$ be a prime. In 1878 \'{E}. Lucas proved that the congruence $$ {p-1\choose k}\equiv (-1)^k\pmod{p}$$ holds for any nonnegative integer $k\in\{0,1,\ldots,p-1\}$. The converse statement was given in Problem 1494 of {\it Mathematics Magazine} proposed ... More
An Extension of a Congruence by TaurasoSep 14 2011For a positive integer $n$ let $H_n=\sum_{k=1}^{n}1/n$ be the $n$th harmonic number. In this note we prove that for any prime $p\ge 7$, $$ \sum_{k=1}^{p-1}\frac{H_k}{k^2}\equiv \sum_{k=1}^{p-1}\frac{H_k^2}{k} \equiv\frac{3}{2p}\sum_{k=1}^{p-1}\frac{1}{k^2}\pmod{p^2}. ... More
Curious conjectures on the distribution of primes among the sums of the first $2n$ primesApr 06 2018Let $p_n$ be $n$th prime, and let $(S_n)_{n=1}^\infty:=(S_n)$ be the sequence of the sums of the first $2n$ consecutive primes, that is, $S_n=\sum_{k=1}^{2n}p_k$ with $n=1,2,\ldots$. Heuristic arguments supported by the corresponding computational results ... More
A characterization of maximal ideals in the Fréchet algebras of holomorphic functions $F^p$ $(1<p<\infty$Dec 25 2018The space $F^p$ ($1<p<\infty$) consists of all holomorphic functions $f$ on the open unit disk $\Bbb D$ for which $\lim_{r\to 1}(1-r)^{1/q}\log^+M_{\infty}(r,f)=0,$ where $M_{\infty}(r,f)=\max_{\vert z\vert\le r}\vert f(z)\vert$ with $0<r<1$. Stoll [5, ... More
A note on some sub-Gaussian random variablesMar 07 2018In [8] the author of this paper continued the research on the complex-valued discrete random variables $X_l(m,N)$ ($0\le l\le N-1$, $1\le M\le N)$ recently introduced and studied in [24]. Here we extend our results by considering $X_l(m,N)$ as sub-Gaussian ... More
Some aspects of the Hadamard's ill-posedness in the hydrodynamical problemJul 09 2010Jul 29 2010Navier-Stokes equations establish the hydrodynamical problem by definition. The importance of these equations is quite natural to understand if we focus on the role they assume in a large spectrum of dynamical problems which involve 'fluids'. Neverthless, ... More
A generalization of some random variables involving in certain compressive sensing problemsJun 26 2018Jul 03 2018In this paper we give a generalization of the discrete complex-valued random variable defined and investigated in \cite{ssa} and \cite{m8}. We prove the statements concerning the expressions for the excepted value and the variance of this random variable. ... More
Millimetric Ground Based Observation of CMBR Anisotropy at $δ =+28^{\lowercase{o}}$Nov 11 2000Results from the third campaign of a ground-based multi-band observation of the millimeter emission of the sky from Tenerife (Canary Islands) are presented. The instrument consists of a 0.45 meter diameter off-axis telescope equipped with a 4-band multi-mode ... More
Subgap states in dirty superconductors and their effect on dephasing in Josephson qubitsOct 21 2004We present a theory of the subgap tails of the density of states in a diffusive superconductor containing magnetic impurities. We show that the subgap tails have two contributions: one arising from mesoscopic gap fluctuations, previously discussed by ... More
Relative resilience to noise of standard and sequential approaches to measurement-based quantum computationDec 15 2017May 30 2018A possible alternative to the standard model of measurement-based quantum computation (MBQC) is offered by the sequential model of MBQC -- a particular class of quantum computation via ancillae. Although these two models are equivalent under ideal conditions, ... More
Addressing Community Question Answering in English and ArabicOct 18 2016This paper studies the impact of different types of features applied to learning to re-rank questions in community Question Answering. We tested our models on two datasets released in SemEval-2016 Task 3 on "Community Question Answering". Task 3 targeted ... More
Properties of galaxy halos in Clusters and VoidsSep 29 2000Dec 12 2001We use the results of a high resolution N-body simulation to investigate the role of the environment on the formation and evolution of galaxy-sized halos. Starting from a set of constrained initial conditions, we have produced a final configuration hosting ... More
Finite density 2d O(3) sigma model: dualization and numerical simulationsAug 23 2018Dec 03 2018The action of the 2d O(3) non-linear sigma model on the lattice in a bath of particles, when expressed in terms of standard O(3) degrees of freedom, is complex. A reformulation of the model in terms of new variables that makes the action real is presented. ... More
An Improved Upper Bound on Maximal Clique Listing via Rectangular Fast Matrix MultiplicationJun 02 2015Aug 24 2015The first output-sensitive algorithm for the Maximal Clique Listing problem was given by Tsukiyama et.al. in 1977. As any algorithm falling within the Reverse Search paradigm, it performs a DFS visit of a directed tree (the RS-tree) having the objects ... More
Time of occurrence observable in quantum mechanicsOct 24 2002We propose a general construction of an observable measuring the time of occurence of an effect in quantum theory. Time delay in potential scattering is computed as a straightforward application.
Linear-Time Algorithm for Update Games via Trap-Alternating-Strongly-Connected ComponentsOct 30 2016An arena is a finite directed graph whose vertices are divided into two classes, $V_{\square}$ and $V_{\ocircle}$; this forms the basic playground for a plethora of 2-players pebble games. We introduce and study a notion of connectivity for arenas, named ... More
Influence of a magnetic fluxon on the vacuum energy of quantum fields confined by a bagDec 11 1996We study the simultaneous influence of boundary conditions and external fields on quantum fluctuations by considering vacuum zero-point energies for quantum fields in the presence of a magnetic fluxon confined by a bag, circular and spherical for bosons ... More
Interaction effects in non-equilibrium transport properties of a four-terminal topological corner junctionJun 18 2014We study the transport properties of a four-terminal corner junction made by etching a two- dimensional topological insulator to form a quantum point contact (QPC). The QPC geometry enables inter-boundary tunneling processes allowing for the coupling ... More
On the uniqueness of minimizers for a class of variational problems with Polyconvex integrandFeb 05 2017We prove existence and uniqueness of minimizers for a family of energy functionals that arises in Elasticity and involves polyconvex integrands over a certain subset of displacement maps. This work extends previous results by Awi and Gangbo to a larger ... More
Beyond Homophily: Incorporating Actor Variables in Actor-oriented Network ModelsMar 19 2018Sep 11 2018We consider the specification of effects of numerical actor attributes in statistical models for directed social networks. A fundamental mechanism is homophily or assortativity, where actors have a higher likelihood to be tied with others having similar ... More
Routing Permutations in Partitioned Optical Passive Star NetworksSep 18 2001It is shown that a POPS network with g groups and d processors per group can efficiently route any permutation among the n=dg processors. The number of slots used is optimal in the worst case, and is at most the double of the optimum for all permutations ... More
When is a Parameterized Controller Suitable for Adaptive Control?May 30 2014In this paper we investigate when a parameterized controller, designed for a plant depending on unknown parameters, admits a realization which is independent of the parameters. It is argued that adaptation is unnecessary for this class of parameterized ... More
Superselection Sectors and General Covariance.INov 21 2005Dec 21 2005This paper is devoted to the analysis of charged superselection sectors in the framework of the locally covariant quantum field theories. We shall analize sharply localizable charges, and use net-cohomology of J.E. Roberts as a main tool. We show that ... More
Minimal model of point contact Andreev reflection spectroscopy of multiband superconductorsJul 28 2014We formulate a minimal model of point contact Andreev reflection spectroscopy of a normal- metal/multiband superconductor interface. The theory generalizes the Blonder-Tinkham-Klapwijk (BTK) formulation to a multiband superconductor and it is based on ... More
Quantum pumping in deformable quantum dotsSep 02 2009The charge current pumped adiabatically through a deformable quantum dot is studied within the Green's function approach. Differently from the non-deformable case, the current shows an undefined parity with respect to the pumping phase \phi. The unconventional ... More
Parasitic pumping currents in an interacting quantum dotOct 06 2010We analyze the charge and spin pumping in an interacting dot within the almost adiabatic limit. By using a non-equilibrium Green's function technique within the time-dependent slave boson approximation, we analyze the pumped current in terms of the dynamical ... More
Dynamic Controllability of Conditional Simple Temporal Networks is PSPACE-completeAug 30 2016Even after the proposal of various solution algorithms, the precise computational complexity of checking whether a Conditional Temporal Network is Dynamically Controllable had still remained widely open. This issue gets settled in this paper which provides ... More
Some results on more flexible versions of Graph MotifFeb 23 2012Sep 10 2014The problems studied in this paper originate from Graph Motif, a problem introduced in 2006 in the context of biological networks. Informally speaking, it consists in deciding if a multiset of colors occurs in a connected subgraph of a vertex-colored ... More
Checking Dynamic Consistency of Conditional Hyper Temporal Networks via Mean Payoff Games (Hardness and (pseudo) Singly-Exponential Time Algorithm)Feb 19 2016In this work we introduce the \emph{Conditional Hyper Temporal Network (CHyTN)} model, which is a natural extension and generalization of both the \CSTN and the \HTN model. Our contribution goes as follows. We show that deciding whether a given \CSTN ... More
A multi-scale limit of a randomly forced rotating $3$-D compressible fluidJan 29 2018We study a singular limit of a scaled compressible Navier--Stokes--Coriolis system driven by both a deterministic and stochastic forcing terms in three dimensions. If the Mach number is comparable to the Froude number with both proportional to say $\varepsilon\ll ... More
Microlocal Analysis and Interacting Quantum Field Theories: Renormalization on Physical BackgroundsMar 12 1999We present a perturbative construction of interacting quantum field theories on any smooth globally hyperbolic manifold. We develop a purely local version of the Stueckelberg-Bogoliubov-Epstein-Glaser method of renormalization using techniques from microlocal ... More
Eigenmodes of a Laplacian on Some Laakso SpacesMar 26 2009We analyze the spectrum of a self-adjoint operator on a Laakso space using the projective limit construction originally given by Barlow and Evans. We will use the hierarchical cell structure induced by the choice of approximating quantum graphs to calculate ... More
An Improved Pseudo-Polynomial Upper Bound for the Value Problem and Optimal Strategy Synthesis in Mean Payoff GamesMar 15 2015Apr 24 2016In this work we offer an $O(|V|^2 |E|\, W)$ pseudo-polynomial time deterministic algorithm for solving the Value Problem and Optimal Strategy Synthesis in Mean Payoff Games. This improves by a factor $\log(|V|\, W)$ the best previously known pseudo-polynomial ... More
Towards a Background Independent Formulation of Perturbative Quantum GravityMar 20 2006Jun 21 2006The recent formulation of locally covariant quantum field theory may open the way towards a background independent perturbative formulation of Quantum Gravity.
Remarks on time-energy uncertainty relationsJul 09 2002Using a recent construction of observables characterizing the time of occurence of an effect in quantum theory, we present a rigorous derivation of the standard time-energy uncertainty relation. In addition, we prove an uncertainty relation for time measurements ... More
Interacting Quantum Fields on a Curved BackgroundSep 01 1997A renormalized perturbative expansion of interacting quantum fields on a globally hyperbolic spacetime is performed by adapting the Bogoliubov Epstein Glaser method to a curved background. The results heavily rely on techniques from microlocal analysis, ... More
Dynamic Consistency of Conditional Simple Temporal Networks via Mean Payoff Games: a Singly-Exponential Time DC-CheckingMay 04 2015Jul 17 2015Conditional Simple Temporal Network (CSTN) is a constraint-based graph-formalism for conditional temporal planning. It offers a more flexible formalism than the equivalent CSTP model of Tsamardinos, Vidal and Pollack, from which it was derived mainly ... More
On Restricted Disjunctive Temporal Problems: Faster Algorithms and Tractability FrontierMay 06 2018Aug 04 2018In 2005 Kumar studied the Restricted Disjunctive Temporal Problem (RDTP), a restricted but very expressive class of disjunctive temporal problems (DTPs). It was shown that that RDTPs are solvable in deterministic strongly-polynomial time by reducing them ... More
Poisson (co)homology of polynomial Poisson algebras in dimension four : Sklyanin's caseMar 11 2008In this paper, we compute the Poisson (co)homology of a polynomial Poisson structure given by two Casimir polynomial functions which define a complete intersection with an isolated singularity.
On the Hochschild homology of elliptic Sklyanin algebrasMay 19 2008Apr 21 2010In this paper, we compute the Hochschild homology of elliptic Sklyanin algebras. These algebras are deformations of polynomial algebra with a Poisson bracket called the Sklyanin Poisson bracket.
Modular dynamics in diamondsSep 25 2010We investigate the relation between the actions of Tomita-Takesaki modular operators for local von Neumann algebras in the vacuum for free massive and massless bosons in four dimensional Minkowskian spacetime. In particular, we prove a long-standing conjecture ... More
Quantum Field Theory on Curved BackgroundsJan 14 2009We review the status of (scalar) quantum field theory on curved spacetimes using a novel formulation in terms of non linear functionals over the smooth configuration fields. In particular, this entails also a new foundation of locally covariant classical ... More
Regularized Casimir energy for an infinite dielectric cylinder subject to light-velocity conservationDec 22 1999The Casimir energy of a dilute dielectric cylinder, with the same light-velocity as in its surrounding medium, is evaluated exactly to first order in $\xi^2$ and numerically to higher orders in $\xi^2$. The first part is carried out using addition formulas ... More
Complete zeta-function approach to the electromagnetic Casimir effect for spheres and circlesMay 03 1996A technique for evaluating the electromagnetic Casimir energy in situations involving spherical or circular boundaries is presented. Zeta function regularization is unambiguously used from the start and the properties of Bessel and related zeta functions ... More
Adaptation is Unnecessary in L1-"Adaptive" ControlSep 08 2014We show in the paper that the, so--called, "new architecture of L_1-Adaptive Control" is, indeed, different from classical model reference adaptive control. Alas, it is not new, since it exactly coincides with a full--state feedback, linear time--invariant ... More
The Aharonov-Bohm-Casher ring-dot as a flux-tunable resonant tunneling diodeMay 18 2008A mesoscopic ring subject to the Rashba spin-orbit interaction and sequentially coupled to an interacting quantum dot, in the presence of Aharonov-Bohm flux, is proposed as a flux tunable tunneling diode. The analysis of the conductance by means of the ... More
Persistent spin and charge currents and magnification effects in open ring conductors subject to Rashba couplingJan 18 2007We analyze the effect of Rashba spin-orbit coupling and of a local tunnel barrier on the persistent spin and charge currents in a one-dimensional conducting Aharonov-Bohm (AB) ring symmetrically coupled to two leads. First, as an important consequence ... More
The Complexity of Simulation and Matrix MultiplicationMay 07 2016Aug 30 2016Computing the simulation preorder of a given Kripke structure (i.e., a directed graph with $n$ labeled vertices) has crucial applications in model checking of temporal logic. It amounts to solving a specific two-players reachability game, called simulation ... More
Linear Time Algorithm for Update Games via Strongly-Trap-Connected ComponentsOct 30 2016Nov 28 2016An arena is a finite directed graph whose vertices are divided into two classes, i.e $V=V_{\square}\cup V_{\bigcirc}$; this forms the basic playground for a plethora of 2-player infinite pebble-games. We introduce and study a refined notion of reachability ... More
Spin-torque generation by dc or ac voltages in magnetic layered structuresSep 02 2009A general expression of the current induced spin torque in a magnetic layered structure in the presence of external dc or ac voltages is derived in the framework of the scattering matrix approach. A detailed analysis is performed for a magnetic-nonmagnetic-magnetic ... More
Super-magnetoresistance effect in triplet spin valvesMar 02 2013We study a triplet spin valve obtained by intercalating a triplet superconductor spacer between two ferromagnetic regions with non-collinear magnetizations. We demonstrate that the magnetoresitance of the triplet spin valve depends on the relative orientations ... More
Convergence of finite difference schemes to the Aleksandrov solution of the Monge-Ampere equationJul 30 2015We present a technique for proving convergence to the Aleksandrov solution of the Monge-Ampere equation of a stable and consistent finite difference scheme. We also require a notion of discrete convexity with a stability property and a local equicontinuity ... More
Conformal Sector in $D=6$ Quantum GravityOct 26 1994We discuss the conformal factor dynamics in $D=6$. Accepting the proposal that higher-derivative dimensionless terms in the anomaly-induced effective action may be dropped, we obtain a superrenormalizable (like in $D=4$) effective theory for the conformal ... More
Single-molecule enhanced spin-flip detectionNov 02 2016We studied the spin-flip excitations of a double-decker nickelocene molecule (Nc) adsorbed on Cu(100) by means of inelastic tunneling spectroscopy (IETS), X-ray magnetic circular dichroism (XMCD) and density functional theory calculations (DFT). The results ... More
Persistent Currents in Superconducting Quantum Interference DevicesApr 04 2007Jul 26 2007Starting from the reduced dynamical model of a two-junction quantum interference device, a quantum analog of the system has been exhibited, in order to extend the well known properties of this device to the quantum regime. By finding eigenvalues of the ... More
Casimir Energy for a Purely Dielectric Cylinder by the Mode Summation MethodApr 25 2005We use the mode summation method together with zeta-function regularization to compute the Casimir energy of a dilute dielectric cylinder. The method is very transparent, and sheds light on the reason the resulting energy vanishes.
Stochastic compressible Euler equations and inviscid limitsFeb 20 2018Jan 30 2019We prove the existence of a unique local strong solution to the stochastic compressible Euler system with nonlinear multiplicative noise. This solution exists up to a positive stopping time and is strong in both the PDE and probabilistic sense. Based ... More