Results for "Alessandro B. Romeo"

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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
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
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
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
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
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
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 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
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
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
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
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
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
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
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
The impact of stellar feedback on the density and velocity structure of the interstellar mediumAug 30 2016Dec 01 2016We study the impact 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 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
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
Adversarial Domain Adaptation for Duplicate Question DetectionSep 07 2018We address the problem of detecting duplicate questions in forums, which is an important step towards automating the process of answering new questions. As finding and annotating such potential duplicates manually is very tedious and costly, automatic ... More
Winter long duration stratospheric balloons from Polar regionsOct 12 2018A new opportunity for astronomy, cosmology, physics, and atmospheric observations is the possibility to fly stratospheric payloads at 30 - 40 km of altitude during the polar night. The absence of solar irradiation for long periods, and the extremely low ... 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
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
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
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 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
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
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 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
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 $p\ge 7$, $$ \sum_{k=1}^{p-1}\frac{H_k}{k^2}\equiv \sum_{k=1}^{p-1}\frac{H_k^2}{k} \equiv\frac{3}{2p}\sum_{k=1}^{p-1}\frac{1}{k^2}\pmod{p^2}. ... More
Angular momentum and local gravitational instability in galaxy discs: does $Q$ correlate with $j$ or $M\,$?May 15 2018Jun 27 2018We introduce a new diagnostic for exploring the link between angular momentum and local gravitational instability in galaxy discs. Our diagnostic incorporates the latest developments in disc instability research, is fully consistent with approximations ... More
N-body simulations with two-orders-of-magnitude higher performance using waveletsFeb 18 2003Noise is a problem of major concern for N-body simulations of structure formation in the early Universe, of galaxies and plasmas. Here for the first time we use wavelets to remove noise from N-body simulations of disc galaxies, and show that they become ... More
SWIPE: a bolometric polarimeter for the Large-Scale Polarization ExplorerAug 01 2012The balloon-borne LSPE mission is optimized to measure the linear polarization of the Cosmic Microwave Background at large angular scales. The Short Wavelength Instrument for the Polarization Explorer (SWIPE) is composed of 3 arrays of multi-mode bolometers ... More
A simple model of energy expenditure in human locomotionSep 06 2006A simple harmonic oscillator model is proposed to describe the mechanical power involved in human locomotion. In this framework, by taking into account the anthropometric parameters of a standard individual, we are able to calculate the speed-power curves ... More
A characterization of some prime ideals in certain $F$-algebras of holomorphic functionsFeb 21 2019The class $M^p$ $(1<p<\infty)$ consists of all holomorphic functions $f$ on the open unit disk $\Bbb D$ for which $$ \int_0^{2\pi}\left(\log^+Mf(\theta)\right)^p\,\frac{d\theta}{2\pi}<\infty, $$ where $Mf(\theta)=\sup_{0\leqslant r<1}\big\lvert f\big(re^{i\theta}\big)\big ... More
Different classes of binary necklaces and a combinatorial method for their enumerationsMar 31 2018In this paper we investigate enumeration of some classes of $n$-character strings and binary necklaces. Recall that binary necklaces are necklaces in two colors with length $n$. We prove three results (Theorems 1, 1' and 2) concerning the numbers of three ... More
A search for primes $p$ such that Euler number $E_{p-3}$ is divisible by $p$Dec 14 2012Let $p>3$ be a prime. Euler numbers $E_{p-3}$ first appeared in H. S. Vandiver's work (1940) in connection with the first case of Fermat Last Theorem. Vandiver proved that $x^p+y^p=z^p$ has no solution for integers $x,y,z$ with $\gcd(xyz,p)=1$ if $E_{p-3}\equiv ... More
Congruences for Wolstenholme primesAug 21 2011A prime number $p$ is said to be a Wolstenholme prime if it satisfies the congruence ${2p-1\choose p-1} \equiv 1 \,\,(\bmod{\,\,p^4})$. For such a prime $p$, we establish the expression for ${2p-1\choose p-1}\,\,(\bmod{\,\,p^8})$ given in terms of the ... More
A congruence modulo $n^3$ involving two consecutive sums of powers and its applicationsNov 17 2012For various positive integers $k$, the sums of $k$th powers of the first $n$ positive integers, $S_k(n+1)=1^k+2^k+...+n^k$, have got to be some of the most popular sums in all of mathematics. In this note we prove that for each $k\ge 2 $$ 2S_{2k+1}(n)- ... 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
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
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
Euclid's theorem on the infinitude of primes: a historical survey of its proofs (300 B.C.--2012) and another new proofFeb 16 2012Jun 05 2012In this article, we provide a comprehensive historical survey of different proofs of famous Euclid's theorem on the infinitude of prime numbers. The Bibliography of this article contains 99 references consisting of 24 textbooks and monographs, 73 articles ... More
An elemetary proof of an estimate for a number of primes less than the product of the first $n$ primesNov 17 2012Let $\alpha$ be a real number such that $1< \alpha <2$ and let $x_0=x_0(\alpha)$ be a {\rm(}unique{\rm)} positive solution of the equation $$ x^{\alpha-1} -\frac{\pi}{e^2\sqrt{3}}x +1=0. $$ Then we prove that for each positive integer $n>x_0$ there exist ... More
Goldbach's like conjectures arising from arithmetic progressions whose first two terms are primesJan 20 2019For two odd primes $p$ and $q$ such that $p<q$, let $A(p,q):=(a_k)_{k=1}^{\infty}$ be the arithmetic progression whose $k$th term is given by $a_k=(k-1)(q-p)+p$ (i.e., with $a_1=p$ and $a_2=q$). Here we conjecture that for every positive integer $a>1$ ... More
An Extension of a Congruence by KohnenSep 11 2011Oct 19 2011Let $p>3$ be a prime, and let $q_p(2)=(2^{p-1}-1)/p$ be the Fermat quotient of $p$ to base 2. Recently, Z. H. Sun proved that \sum_{k=1}^{p-1}\frac{1}{k\cdot 2^k}\equiv q_p(2)-\frac{p}{2}q_p(2)^2 \pmod{p^2} which is a generalization of a congruence due ... More
Wolstenholme's theorem: Its Generalizations and Extensions in the last hundred and fifty years (1862--2012)Nov 13 2011Dec 25 2011In 1862 Wolstenholme proved that for any prime $p\ge 5$ the numerator of the fraction $$ 1+\frac 12 +\frac 13+...+\frac{1}{p-1} $$ written in reduced form is divisible by $p^2$, $(2)$ and the numerator of the fraction $$ 1+\frac{1}{2^2} +\frac{1}{3^2}+...+\frac{1}{(p-1)^2} ... More
A generalization of some random variables involving in certain compressive sensing problemsJun 26 2018Jul 03 2018In this paper we give a generalization of the discrete complex-valued random variable defined and investigated in \cite{ssa} and \cite{m8}. We prove the statements concerning the expressions for the excepted value and the variance of this random variable. ... More
Lucas' theorem: its generalizations, extensions and applications (1878--2014)Sep 06 2014In 1878 \'E. Lucas proved a remarkable result which provides a simple way to compute the binomial coefficient ${n\choose m}$ modulo a prime $p$ in terms of the binomial coefficients of the base-$p$ digits of $n$ and $m$: {\it If $p$ is a prime, $n=n_0+n_1p+\cdots ... More
Generalizations of Carmichael numbers IMay 04 2013A composite positive integer $n$ is said to be a {\it weak Carmichael number} if $$ \sum_{\gcd(k,n)=1\atop 1\le k\le n-1}k^{n-1}\equiv \varphi(n) \pmod{n}. \leqno(1) $$ It is proved that a composite positive integer $n$ is a weak Carmichael number if ... More
Closed maximal ideals ideals in some Fréchet algebras of holomorphic functionsMar 26 2019The space $F^p$ ($1<p<\infty$) consists of all holomorphic functions $f$ on the open unit disk $\Bbb D$ such that $ \lim_{r\to 1}(1-r)^{1/q}\log^+M_{\infty}(r,f)=0,$ where $M_{\infty}(r,f)=\max_{\vert z\vert\le r}\vert f(z)\vert$ with $0<r<1$. Stoll [5, ... More
From Grad-Shafranov equations set to a pseudo-general form of the non-linear Schroedinger equationJul 10 2008In the year 2003 a paper by G. Lapenta demonstrated that there is a new class of soliton-like solutions for the Grad-Shafranov Equations (GSE).The author determined an appropriate pair of transformations of the free fields p (fluid field of hydrodynamical ... More
Amplification phenomena of Casimir force fluctuations on close scatterers coupled via a coherent fermionic fluidMar 21 2016We study the mechanical actions affecting close scatterers immersed in a coherent fermionic fluid. Using a scattering field theory, we theoretically analyse the single-scatterer and the two-scatterer case. Concerning the single-scatterer case, we find ... More
On the distribution of primes in the alternating sums of concecutive primesMay 26 2018Quite recently, in [8] the authoor of this paper considered the distribution of primes in the sequence $(S_n)$ whose $n$th term is defined as $S_n=\sum_{k=1}^{2n}p_k$, where $p_k$ is the $k$th prime. Some heuristic arguments and the numerical evidence ... More
Clarkson's type inequalities for positive $l_p$ sequences with $p\ge 2$Sep 23 2011For a fixed $1\le p<+\infty$ denote by $\Vert\cdot\Vert_p$ the usual norm in the space $l_p$ (or $L_p$). In this paper we prove that for all real numbers $p$ and $q$ such that $2\le p\le q$ holds $$ 2(\Vert x\Vert_p^q+\Vert y\Vert_p^q)\le \Vert x+y\Vert_p^q ... More
Lucas Type Theorem Modulo Prime PowersDec 29 2012In this note we prove that {equation*} {np^s\choose mp^s+r}\equiv (-1)^{r-1}r^{-1}(m+1){n\choose m+1}p^s \pmod{p^{s+1}} {equation*} where $p$ is any prime, $n$, $m$, $s$ and $r$ are nonnegative integers such that $n\ge m$, $s\ge 1$, $1\le r\le p^s-1$ ... More
On the mod $p^7$ determination of ${2p-1\choose p-1}$Aug 04 2011In this paper we prove that for any prime $p\ge 11$ holds $$ {2p-1\choose p-1}\equiv 1 -2p \sum_{k=1}^{p-1}\frac{1}{k} +4p^2\sum_{1\le i<j\le p-1}\frac{1}{ij}\pmod{p^7}. $$ This is a generalization of the famous Wolstenholme's theorem which asserts that ... More
Proof of a congruence for harmonic numbers conjectured by Z.-W. SunAug 04 2011Mar 25 2012For a positive integer $n$ let $H_n=\sum_{k=1}^{n}1/k$ be the $n$th harmonic number. In this note we prove that for any prime $p\ge 7$, $$ \sum_{k=1}^{p-1}\frac{H_k^2}{k^2} \equiv4/5pB_{p-5}\pmod{p^2}, $$ which confirms the conjecture recently proposed ... 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
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
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
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
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
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
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
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
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
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
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
Energy of the vacuum with a perfectly conducting and infinite cylindrical surfaceSep 29 1998Values for the vacuum energy of scalar fields under Dirichlet and Neuman boundary conditions on an infinite clylindrical surface are found, and they happen to be of opposite signs. In contrast with classical works, a complete zeta function regularization ... 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
Uniqueness of Minimizers of Some Variational Problems Arising in Image ProcessingJul 28 2018Dec 09 2018We will study an open problem pertaining to the uniqueness of minimizers for a class of variational problems emanating from Meyer's model for the decomposition of an image into a geometric part and a texture part. Mainly, we are interested in the uniqueness ... More
On some metric topologies on Privalov spaces on the unit diskNov 21 2018Let $N^p$ $(1<p<\infty)$ be the Privalov class $N^p$ of holomorphic functions on the open unit disk $\Bbb D$ in the complex plane. In 1977 M. Stoll proved that the class $N^p$ equipped with the topology given by the metric $\lambda_p$ defined by $$\lambda_p(f,g) ... More