Results for "G. Cossu"

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Factorizations into idempotent factors of matrices over Prüfer domainsOct 01 2018A classical problem, that goes back to the 1960's, is to characterize the integral domains R satisfying the property (IDn): "every singular nxn matrix over R is a product of idempotent matrices". Significant results, which describe this property in the ... More
Minimal Prüfer-Dress rings and products of idempotent matricesNov 22 2018We investigate a special class of Pr\"ufer domains, firstly introduced by Dress in 1965. The {\it minimal Dress ring} $D_K$, of a field $K$, is the smallest subring of $K$ that contains every element of the form $1/(1+x^2)$, with $x\in K$. We show that, ... More
On self-sustaining processes in Rayleigh-stable rotating plane Couette flows and subcritical transition to turbulence in accretion disksDec 07 2006Subcritical transition to turbulence in Keplerian accretion disks is still a controversial issue and some theoretical progress is required in order to determine whether or not this scenario provides a plausible explanation for the origin of angular momentum ... More
Non-perturbative renormalization of bilinear operators with Möbius domain-wall fermions in the coordinate spaceNov 25 2014We study the non-perturbative determination of the renormalization constants of flavor non-singlet quark bilinear operators on the lattice. The renormalization condition is imposed on correlation functions of bilinear operators in the coordinate space. ... More
Surface antiferromagnetism and incipient metal-insulator transition in strained manganite filmsDec 20 2012Jun 18 2013Using first-principles calculations, we show that the (001) surface of the ferromagnet La$_{1-x}$Sr$_{x}$MnO$_{3}$ under epitaxial compression favors antiferromagnetic ordering in the first few surface layers, coexisting with ferromagnetic bulk order. ... More
Stochastic calculation of the QCD Dirac operator spectrum with Mobius domain-wall fermionJan 05 2016We calculate the spectral function of the QCD Dirac operator using the four-dimensional effective operator constructed from the Mobius domain-wall implementation. We utilize the eigenvalue filtering technique combined with the stochastic estimate of the ... More
A test of first order scaling in Nf=2 QCDSep 30 2007We complete our analysis of Nf=2 QCD based on the lattice staggered fermion formulation. Using a series of Monte Carlo simulations at fixed (amq*Ls^yh) one is able to test the universality class with given critical exponent yh. This strategy has been ... More
Two flavor QCD and confinement - IIJun 29 2007This paper is part of a program of investigation of the chiral transition in Nf=2 QCD, started in Phys.Rev.D72:114510,2005. Progress is reported on the understanding of some possible systematic errors. A direct test of first order scaling is presented. ... More
Phase diagram of the lattice SU(2) Higgs modelNov 09 2009Jan 07 2010We perform a detailed study of the phase diagram of the lattice Higgs SU(2) model with fixed Higgs field length. Consistently with previsions based on the Fradkin Shenker theorem we find a first order transition line with an endpoint whose position we ... More
Extracting the $η^\prime$ meson mass from gluonic correlators in lattice QCDNov 12 2015Calculation of the eta-prime meson mass is a notoriously difficult problem, as it requires evaluation of the disconnected diagram which is costly and noisy. In this work, we use a gluonic operator to extract the eta-prime state after smearing the link ... More
On the stabilizing mechanism of 2D absolute and global instabilities by 3D streaksApr 11 2014Global and local absolute instabilities of 2D wakes are known to be stabilized by spanwise periodic modulations of the wake profile. The present study shows that this stabilizing effect is of general nature and can be mimicked by enforcing spanwise periodic ... More
Monopole condensation in two-flavour Adjoint QCDSep 26 2006Two distinct phase transitions occur at different temperatures in QCD with adjoint fermions (aQCD): deconfinement and chiral symmetry restoration. In this model, quarks do no explicitely break the center Z(3) symmetry and therefore the Polyakov loop is ... More
Magnetorotational dynamo chimeras. The missing link to turbulent accretion disk dynamo models?Jul 11 2016In Keplerian accretion disks, turbulence and magnetic fields may be jointly excited through a subcritical dynamo process involving the magnetorotational instability (MRI). High-resolution simulations exhibit a tendency towards statistical self-organization ... More
Periodic magnetorotational dynamo action as a prototype of nonlinear magnetic field generation in shear flowsSep 08 2011The nature of dynamo action in shear flows prone to magnetohydrodynamic instabilities is investigated using the magnetorotational dynamo in Keplerian shear flow as a prototype problem. Using direct numerical simulations and Newton's method, we compute ... More
Dissipative effects on the sustainment of a magnetorotational dynamo in Keplerian shear flowOct 13 2014The magnetorotational (MRI) dynamo has long been considered one of the possible drivers of turbulent angular momentum transport in astrophysical accretion disks. However, various numerical results suggest that this dynamo may be difficult to excite in ... More
Global bifurcations to subcritical magnetorotational dynamo action in Keplerian shear flowJun 14 2013Magnetorotational dynamo action in Keplerian shear flow is a three-dimensional, nonlinear magnetohydrodynamic process whose study is relevant to the understanding of accretion and magnetic field generation in astrophysics. Transition to this form of dynamo ... More
Analysis of short-distance current correlators using OPENov 30 2015We investigate the correlators of flavor non-singlet bilinear operators calculated on the lattice at short distances. In the continuum theory, non-perturbative effects are encoded in the form of the operator product expansion (OPE). We test the prediction ... More
Evidence of effective axial U(1) symmetry restoration at high temperature QCDDec 06 2016We study the axial U(1) symmetry at finite temperature in two-flavor lattice QCD. Employing the Mobius domain-wall fermions, we generate gauge configurations slightly above the critical temperature Tc with different lattice sizes L = 2-4 fm. Our action ... More
Overlap/Domain-wall reweightingNov 19 2013We investigate the eigenvalues of nearly chiral lattice Dirac operators constructed with five-dimensional implementations. Allowing small violation of the Ginsparg-Wilson relation, the HMC simulation is made much faster while the eigenvalues are not significantly ... More
Monopole condensation in two-flavour Adjoint QCDFeb 13 2008Mar 05 2008In QCD with adjoint fermions (aQCD) the deconfining transition takes place at a lower temperature than the chiral transition. We study the two transitions by use of the Polyakov Loop, the monopole order parameter and the chiral condensate. The deconfining ... More
An update in monopole condensation in two-flavour Adjoint QCDOct 09 2007QCD with fermions in the adjoint representation (aQCD) is a model for which a deconfinement and a chiral phase transition take place at different temperatures. In this work, we present a study of the deconfinement transition in the dual superconductor ... More
A test of first order scaling in Nf =2 QCD: a progress reportJan 21 2009We present the status of our analysis on the order of the finite temperature transition in QCD with two flavors of degenerate fermions. Our new simulations on large lattices support the hypothesis of the first order nature of the transition, showing a ... More
$η^\prime$ meson mass from topological charge density correlator in QCDSep 03 2015Nov 20 2015The flavor-singlet component of the eta prime meson is related to the topological structure of the SU(3) gauge field through the chiral anomaly. We perform a 2+1-flavor lattice QCD calculation and demonstrate that the two-point function of a gluonically ... More
Light meson form factors in N_f=2+1 QCD with dynamical overlap quarksDec 01 2010We report on our calculation of pion and kaon form factors in three-flavor QCD using the overlap quark action. Gauge ensembles are generated on a 16^3 \times 48 lattice at a lattice spacing of 0.11 fm with pion masses down to 310 MeV. Connected and disconnected ... More
Dual Superconductivity in G2 groupSep 28 2006We investigate the dual superconductivity mechanism in the exceptional group $G_2$. This is a centerless group (no 't Hooft flux vortices are allowed) and we check for the presence of a magnetic monopole condensate in the confined phase by measuring on ... More
Meson correlation functions at high temperature QCD: $SU(2)_{CS}$ symmetry vs. free quarksSep 01 2018Oct 05 2018We report on the progress of understanding spatial correlation functions in high temperature QCD. We study isovector meson operators in $N_f=2$ QCD using domain-wall fermions on lattices of $N_s=32$ and different quark masses. It has previously been found ... More
Decay constants and spectroscopy of mesons in lattice QCD using domain-wall fermionsDec 29 2015We report results of masses and decay constants of light and charmed pseudo-scalar mesons using lattice QCD with M\"obius domain-wall fermions. Using this formulation we are able to compute pseudo-scalar decay constants through the pseudo-scalar density ... More
Study of the conformal region of the SU(3) gauge theory with domain-wall fermionsNov 20 2015We investigate the phase structure of the SU(3) gauge theory with $N_f=8$ by numerical simulations employing the massless Domain-Wall fermions.Our aim is to study directly the massless quark region, since it is the most important region to clarify the ... More
Renormalization of domain-wall bilinear operators with short-distance current correlatorsApr 29 2016We determine the renormalization constants for flavor non-singlet fermion bilinear operators of M\"obius domain-wall fermions. The renormalization condition is imposed on the correlation functions in the coordinate space, such that the non-perturbative ... More
Topology density correlator on dynamical domain-wall ensembles with nearly frozen topological chargeNov 06 2014Nov 13 2014Global topological charge decorrelates very slowly or even freezes in fine lattice simulations. On the other hand, its local fluctuations are expected to survive and lead to the correct physical results as long as the volume is large enough. We investigate ... More
Large-scale simulations with chiral symmetryNov 27 2013We carry out a comparative study among five-dimensional formulations of chirally symmetric fermions about the algorithmic performance, chiral symmetry violation and topological tunneling to find a computationally inexpensive formulation with good chiral ... More
Light meson electromagnetic form factors from three-flavor lattice QCD with exact chiral symmetryOct 22 2015We study the chiral behavior of the electromagnetic (EM) form factors of pion and kaon in three-flavor lattice QCD. In order to make a direct comparison of the lattice data with chiral perturbation theory (ChPT), we employ the overlap quark action that ... More
Fe clusters (Fe$_n$, n=1-6) chemisorbed on vacancy defects in graphene: Stability, spin-dipole moment and magnetic anisotropyApr 26 2014May 06 2014In this work, we have studied the chemical and magnetic interactions of Fe$_n$ ; n=1-6 clusters with vacancy defects (monovacancy to correlated vacancies with six missing C atoms) in a graphene sheet by ab-initio density functional calculations combined ... More
On the phase diagram of the Higgs SU(2) modelJan 28 2009The Higgs SU(2) model with fixed Higgs length is usually believed to have two different phases at high gauge coupling (\beta), separated by a line of first order transitions but not distinuguished by any typical symmetry associated with a local order ... More
Subcritical dynamos in shear flowsMay 09 2008Identifying generic physical mechanisms responsible for the generation of magnetic fields and turbulence in differentially rotating flows is fundamental to understand the dynamics of astrophysical objects such as accretion disks and stars. In this paper, ... More
PRINC domains and comaximal factorization domainsJan 16 2019The notion of PRINC domain was introduced by Salce and Zanardo (2014), motivated by the investigation of the products of idempotent matrices with entries in a commutative domain. An integral domain R is a PRINC domain if every two-generated invertible ... More
Anderson Localization in high temperature QCD: background configuration properties and Dirac eigenmodesApr 04 2016Apr 13 2016We investigate the properties of the background gauge field configurations that act as disorder for the Anderson localization mechanism in the Dirac spectrum of QCD at high temperatures. We compute the eigenmodes of the M\"obius domain-wall fermion operator ... More
A note on the stability of slip channel flowsMar 30 2005We consider the influence of slip boundary conditions on the modal and non-modal stability of pressure-driven channel flows. In accordance with previous results by Gersting (1974) (Phys. Fluids, 17) but in contradiction with the recent investigation of ... More
On a self-sustained process at large scale in the turbulent channel flowApr 23 2010Large-scale motions, important in turbulent shear flows, are frequently attributed to the interaction of structures at smaller scale. Here we show that, in a turbulent channel at Re_{\tau} \approx 550, large-scale motions can self-sustain even when smaller-scale ... More
Chiral behavior of light meson form factors in 2+1 flavor QCD with exact chiral symmetryJan 28 2016We present a study of chiral behavior of light meson form factors in QCD with three flavors of overlap quarks. Gauge ensembles are generated at single lattice spacing 0.12 fm with pion masses down to 300 MeV. The pion and kaon electromagnetic form factors ... More
Symmetries of spatial meson correlators in high temperature QCDFeb 08 2019Based on a complete set of $J = 0$ and $J=1$ spatial isovector correlation functions calculated with $N_F = 2$ domain wall fermions we identify an intermediate temperature regime of $T \sim 250 - 550$ MeV where chiral symmetry is restored but the correlators ... More
Approximate degeneracy of $J=1$ spatial correlators in high temperature QCDJul 06 2017Feb 08 2019We study spatial isovector meson correlators in $N_f=2$ QCD with dynamical domain-wall fermions on $32^3\times 8$ lattices at temperatures $T=220-380$ MeV. We measure the correlators of spin-one ($J=1$) operators including vector, axial-vector, tensor ... More
Chiral behavior of kaon semileptonic form factors in lattice QCD with exact chiral symmetryNov 27 2012We calculate the kaon semileptonic form factors in lattice QCD with three flavors of dynamical overlap quarks. Gauge ensembles are generated at pion masses as low as 290 MeV and at a strange quark mass near its physical value. We precisely calculate relevant ... More
Kaon semileptonic form factors in QCD with exact chiral symmetryDec 22 2011We report on our calculation of the kaon semileptonic form factors in Nf=2+1 lattice QCD. Chiral symmetry is exactly preserved by using the overlap quark action for a straightforward comparison with chiral perturbation theory (ChPT). We simulate three ... More
Chiral behavior of $K \to πl ν$ decay form factors in lattice QCD with exact chiral symmetryMay 02 2017We calculate the form factors of the $K \to \pi l \nu$ semileptonic decays in three-flavor lattice QCD, and study their chiral behavior as a function of the momentum transfer and the Nambu-Goldstone boson masses. Chiral symmetry is exactly preserved by ... More
Unveiling hidden charge density waves in single-layer NbSe$_2$ by impuritiesAug 05 2018Nov 15 2018We employ {\it{ab-initio}} calculations to investigate the charge density waves in single-layer NbSe$_2$, and we explore how they are affected by transition metal atoms. Our calculations reproduce the observed orthorhombic phase in single-layer NbSe$_2$ ... More
Finite size phase transitions in QCD with adjoint fermionsApr 08 2009May 25 2009We perform a lattice investigation of QCD with three colors and 2 flavors of Dirac (staggered) fermions in the adjoint representation, defined on a 4d space with one spatial dimension compactified, and study the phase structure of the theory as a function ... More
Analysis of topological structure of the QCD vacuum with overlap-Dirac operator eigenmodeNov 01 2013Using the eigenmodes of the overlap-Dirac operator, we study the topological structure of the QCD vacuum. We investigate the space-time profile of the low-lying eigenmodes and their contribution to the vacuum action density and chiral condensate under ... More
A Review of Features for the Discrimination of Twitter Users: Application to the Prediction of Offline InfluenceSep 22 2015Jul 29 2016Many works related to Twitter aim at characterizing its users in some way: role on the service (spammers, bots, organizations, etc.), nature of the user (socio-professional category, age, etc.), topics of interest , and others. However, for a given user ... More
Detecting Real-World Influence Through TwitterJun 19 2015Jul 20 2015In this paper, we investigate the issue of detecting the real-life influence of people based on their Twitter account. We propose an overview of common Twitter features used to characterize such accounts and their activity, and show that these are inefficient ... More
Forcing large-scale coherent streaks in a zero pressure gradient turbulent boundary layerApr 26 2010Large scale coherent streaks are artificially forced in a well developed turbulent boundary layer at $\Redstar \approx 1000$ using an array of cylindrical roughness elements. Measures of the velocity field with particle image velocimetry reveal the presence ... More
PRoST: Distributed Execution of SPARQL Queries Using Mixed Partitioning StrategiesFeb 16 2018The rapidly growing size of RDF graphs in recent years necessitates distributed storage and parallel processing strategies. To obtain efficient query processing using computer clusters a wide variety of different approaches have been proposed. Related ... More
Partial restoration of chiral symmetry inside hadronsDec 07 2014By using the overlap-Dirac operator eigenmodes, we investigate spatial distribution of the chiral condensate around static color sources for both quark-antiquark and three quark systems. In the presence of color sources, a characteristic flux-tube structure ... More
Drag reduction in pipe flow by optimal forcingAug 27 2009In most settings, from international pipelines to home water supplies, the drag caused by turbulence raises pumping costs many times higher than if the flow were laminar. Drag reduction has therefore long been an aim of high priority. In order to achieve ... More
Lattice QCD study of partial restoration of chiral symmetry in the flux-tubeJan 17 2014Using the overlap-Dirac eigenmodes, we study the spatial distribution of the chiral condensate around static color sources in lattice QCD. Between the color sources, there appears a color-flux tube, which leads a linear confining potential. By measuring ... More
Coherent structures in fully-developed pipe turbulenceAug 25 2009A turbulent mean profile for pipe flow is prescribed which closely matches experimental observations. The nature of perturbations superimposed upon this profile is then considered. Optimal growth calculations predict two distinct classes of structures, ... More
Partial restoration of chiral symmetry in the color flux tubeFeb 17 2015May 07 2015Using the quark eigenmodes computed on the lattice with the overlap-Dirac operator, we investigate the spatial distribution of the chiral condensate around static color sources corresponding to quark-antiquark and three-quark systems. A flux structure ... More
Travelling-wave solutions bifurcating from relative periodic orbits in plane Poiseuille flowJan 06 2016Travelling-wave solutions are shown to bifurcate from relative periodic orbits in plane Poiseuille flow at Re = 2000 in a saddle-node infinite period bifurcation. These solutions consist in self-sustaining sinuous quasi-streamwise streaks and quasi- streamwise ... More
Staggered fermions simulations on GPUsOct 26 2010We present our implementation of the RHMC algorithm for staggered fermions on Graphics Processing Units using the NVIDIA CUDA programming language. While previous studies exclusively deal with the Dirac matrix inversion problem, our code performs the ... More
Polyakov loops and the Hosotani mechanism on the latticeSep 17 2013Jun 10 2014We explore the phase structure and symmetry breaking in four-dimensional SU(3) gauge theory with one spatial compact dimension on the lattice ($16^3 \times 4$ lattice) in the presence of fermions in the adjoint representation with periodic boundary conditions. ... More
Violation of chirality of the Möbius domain-wall Dirac operator from the eigenmodesOct 26 2015We investigate the effects of the violation of the Ginsparg-Wilson (GW) relation in the M\"obius domain-wall fermion formulation on the lattice with finite fifth dimension. Using a decomposion in terms of the eigenmodes of its four-dimensional effective ... More
FDG kinetics in cells and tissues: a biochemically-driven compartmental approachMar 13 2018The radioactive glucose analogue 2-deoxy-2-[18F]fluoro-D-glucose (FDG) is widely used to reconstruct glucose metabolism and other biological functions in cells and tissues. The analysis of data on the time course of FDG tracer distribution is performed ... More
Toward a well defined monopole creation operatorOct 26 2010Jan 03 2011The lattice implementation of monopole creation operator proves to have problems related to bulk transitions that can possibly affect the interpretation of its mean value as an order parameter for monopole condensation. Preliminary evidence is presented ... More
Active learning in annotating micro-blogs dealing with e-reputationJun 16 2017Sep 25 2017Elections unleash strong political views on Twitter, but what do people really think about politics? Opinion and trend mining on micro blogs dealing with politics has recently attracted researchers in several fields including Information Retrieval and ... More
Strong dynamics with matter in multiple representations: SU(4) gauge theory with fundamental and sextet fermionsApr 18 2019We present a non-perturbative lattice study of SU(4) gauge theory with two flavors of fermions in the fundamental representation and two in the two-index antisymmetric representation: a theory closely related to a minimal partial-compositeness model for ... More
The Roberge-Weiss endpoint in N_f = 2 QCDNov 19 2010Jul 08 2011We present the results of extensive simulations regarding the critical behavior at the endpoint of the Roberge-Weiss transition for N_f = 2 QCD. We confirm early evidence, presented in arXiv:0909.0254, according to which the Roberge-Weiss endpoint is ... More
How to merge three different methods for information filtering ?Oct 26 2015Twitter is now a gold marketing tool for entities concerned with online reputation. To automatically monitor online reputation of entities , systems have to deal with ambiguous entity names, polarity detection and topic detection. We propose three approaches ... More
The disorder parameter of dual superconductivity in QCD revisitedNov 07 2011Mar 05 2012We discover the origin of the pathologies of the disorder parameter used in previous papers to detect dual superconductivity of QCD vacuum, and we remove them by defining an improved disorder parameter. A check of the approach is made by numerical simulations ... More
Effects of near-zero Dirac eigenmodes on axial U(1) symmetry at finite temperatureDec 23 2014We study the axial U(1)A symmetry of Nf = 2 QCD at finite temperature using the Dirac eigenvalue spectrum. The gauge configurations are generated employing the Mobius domain-wall fermion action on 16^3x8 and 32^3x8 lattices. The physical spatial size ... More
Grid: A next generation data parallel C++ QCD libraryDec 10 2015In this proceedings we discuss the motivation, implementation details, and performance of a new physics code base called Grid. It is intended to be more performant, more general, but similar in spirit to QDP++\cite{QDP}. Our approach is to engineer the ... More
On the self-sustained nature of large-scale motions in turbulent Couette flowSep 15 2015Large-scale motions in wall-bounded turbulent flows are frequently interpreted as resulting from an aggregation process of smaller-scale structures. Here, we explore the alternative possibility that such large-scale motions are themselves self-sustained ... More
QCD simulations with staggered fermions on GPUsJun 28 2011Dec 28 2011We report on our implementation of the RHMC algorithm for the simulation of lattice QCD with two staggered flavors on Graphics Processing Units, using the NVIDIA CUDA programming language. The main feature of our code is that the GPU is not used just ... More
On the relevance of Reynolds stresses in resolvent analyses of turbulent wall-bounded flowsJan 14 2019The ability of linear stochastic response analysis to estimate coherent motions is investigated in turbulent channel flow at friction Reynolds number Re$_\tau$ = 1007. The analysis is performed for spatial scales characteristic of buffer-layer and large-scale ... More
Ergodicity of the LLR method for the Density of StatesOct 17 2017The LLR method is a novel algorithm that enables us to evaluate the density of states in lattice gauge theory. We present our study of the ergodicity properties of the LLR algorithm for the model of Yang Mills SU(3). We show that the use of the replica ... More
On the axial $U(1)$ symmetry at finite temperatureNov 18 2015We study the $U(1)_A$ anomaly in two-flavor lattice QCD at finite temperature with the M\"obius domain-wall Dirac operator. We generate gauge configurations in the temperature range $(0.9, 1.2) T_c$ on different physical volumes, $L=$ 2--4 fm, and lattice ... More
Finite temperature study of the axial U(1) symmetry on the lattice with overlap fermion formulationApr 23 2013We examine the axial U(1) symmetry near and above the finite temperature phase transition in two-flavor QCD using lattice QCD simulations. Although the axial U(1) symmetry is always violated by quantization, (i.e.) the chiral anomaly, the correlation ... More
Testing algorithms for critical slowing downOct 19 2017We present the preliminary tests on two modifications of the Hybrid Monte Carlo (HMC) algorithm. Both algorithms are designed to travel much farther in the Hamiltonian phase space for each trajectory and reduce the autocorrelations among physical observables ... More
Hosotani mechanism on the latticeNov 01 2013Nov 18 2013We explore the phase structure and symmetry breaking in four-dimensional SU(3) gauge theory with one spatial compact dimension on the lattice in the presence of fermions in the adjoint and fundamental representations with general boundary conditions. ... More
Axial U(1) symmetry at finite temperature with Möbius domain-wall fermionsDec 18 2014We investigate the axial $U(1)$ symmetry restoration at finite temperature in two flavor QCD. We employ the M\"obius domain-wall formalism that is designed to achieve good chiral symmetry. We show the measurements of a difference of meson susceptibilities, ... More
Topological susceptibility and axial symmetry at finite temperatureApr 20 2012We consider the simulation of finite temperature QCD with two flavors of dynamical overlap fermions in order to study the suppression of the axial U(1) symmetry breaking at the chiral phase transition point. As a preliminary study, pure gauge simulations ... More
Stochastic calculation of the Dirac spectrum on the lattice and a determination of chiral condensate in 2+1-flavor QCDJul 05 2016Aug 19 2016We compute the chiral condensate in 2+1-flavor QCD through the spectrum of low-lying eigenmodes of Dirac operator. The number of eigenvalues of the Dirac operator is evaluated using a stochastic method with an eigenvalue filtering technique on the background ... More
Effective $θ$ term by CP-odd electromagnetic background fieldsDec 10 2013We discuss our study of QCD in the presence of CP-odd electromagnetic (e.m.) background fields. We investigate the propagation of the CP-odd term from the e.m. sector to the strong sector, inducing an effective $\theta$ term. We discuss the method we ... More
Confinement: $G_2$ group caseOct 02 2007The gauge group being centreless, $G_2$ gauge theory is a good laboratory for studying the role of the centre of the group for colour confinement in Yang-Mills gauge theories. In this paper, we investigate $G_2$ pure gauge theory at finite temperature ... More
JLQCD IroIro++ lattice code on BG/QNov 01 2013We describe our experience on the multipurpose C++ code IroIro++ designed for JLQCD to run on the BG/Q installation at KEK. We discuss some details on the performance improvements specific for the IBM Blue Gene Q.
G_2 gauge theory at finite temperatureSep 05 2007The gauge group being centreless, $G_2$ gauge theory is a good laboratory for studying the role of the centre of the group for colour confinement in Yang-Mills gauge theories. In this paper, we investigate $G_2$ pure gauge theory at finite temperature ... More
Accelerating HPC codes on Intel(R) Omni-Path Architecture networks: From particle physics to Machine LearningNov 13 2017We discuss practical methods to ensure near wirespeed performance from clusters with either one or two Intel(R) Omni-Path host fabric interfaces (HFI) per node, and Intel(R) Xeon Phi(TM) 72xx (Knight's Landing) processors, and using the Linux operating ... More
Degeneracy of vector-channel spatial correlators in high temperature QCDOct 20 2017We study spatial isovector meson correlators in $N_f=2$ QCD with dynamical domain-wall fermions on $32^3\times 8$ lattices at temperatures up to 380 MeV with various quark masses. We measure the correlators of spin-one isovector operators including vector, ... More
Finite temperature QCD at fixed Q with overlap fermionsNov 01 2010We present some preliminary results of the project on finite temperature QCD with overlap fermions at KEK. We performed a series of simulations to assess the effects of fixing the topological sector at finite temperature and we will show the first calculations ... More
Systèmes du LIA à DEFT'13Feb 21 2017The 2013 D\'efi de Fouille de Textes (DEFT) campaign is interested in two types of language analysis tasks, the document classification and the information extraction in the specialized domain of cuisine recipes. We present the systems that the LIA has ... More
Comment on Neutrino Radiative Decay Limits from the Infrared BackgroundAug 26 1998Recent observations of TeV gamma rays from distant sources provide new limits on the cosmic infrared background and thus on radiative decays of background neutrinos. I translate these limits into bounds on transition dipole moments and compare them with ... More
Astro-Particle PhysicsDec 31 1997Recent developments of those areas of astro-particle physics are discussed that were represented at the HEP97 conference. In particular, the current status of direct and indirect dark-matter searches and of TeV neutrino and gamma-ray astronomy will be ... More
Dark Matter: Motivation, Candidates and SearchesDec 29 1997The physical nature of most of the gravitating mass in the universe is completely mysterious. The astrophysical evidence for the presence of this dark matter and astrophysical constraints on its properties will be reviewed. The most popular dark-matter ... More
Internal mobility edge in doped graphene: frustration in a renormalized latticeJul 06 2007We show that an internal localization mobility edge can appear around the Fermi energy in graphene by introducing impurities in the split-band regimen, or by producing vacancies in the lattice. The edge appears at the center of the spectrum and not at ... More
Symmetry allowed, but unobservable, phases in renormalizable Gauge Field Theory ModelsMay 03 2004In Quantum Field Theory models with spontaneously broken gauge invariance, renormalizability limits to four the degree of the Higgs potential, whose minima determine the vacuum state at tree-level. In many models, this bound has the intriguing consequence ... More
Characteristic Polynomials of Complex Random Matrix ModelsDec 04 2002Dec 12 2002We calculate the expectation value of an arbitrary product of characteristic polynomials of complex random matrices and their hermitian conjugates. Using the technique of orthogonal polynomials in the complex plane our result can be written in terms of ... More
New Critical Matrix Models and Generalized UniversalityJan 21 2002Mar 06 2002We study a class of one-matrix models with an action containing nonpolynomial terms. By tuning the coupling constants in the action to criticality we obtain that the eigenvalue density vanishes as an arbitrary real power at the origin, thus defining a ... More
Macroscopic and Microscopic (Non-)Universality of Compact Support Random Matrix TheoryFeb 17 2000Jun 07 2000A random matrix model with a sigma-model like constraint, the restricted trace ensemble (RTE), is solved in the large-n limit. In the macroscopic limit the smooth connected two-point resolvent G(z,w) is found to be non-universal, extending previous results ... More
Non-Keplerian rotation in the nucleus of NGC 1068: evidence for a massive accretion disk?Nov 06 2002The nucleus of the Seyfert galaxy NGC 1068 is believed to host a supermassive black hole. Evidence for the presence of a massive central object is provided by water maser emission, which displays a linear pattern in the sky, suggestive of a rotating disk. ... More
A class of self-gravitating accretion disksAug 09 1999We consider a class of steady-state self-gravitating accretion disks for which efficient cooling mechanisms are assumed to operate so that the disk is self-regulated at a condition of approximate marginal Jeans stability. In an earlier paper, this scenario ... More
Delocalised states in a 1D diagonally disordered systemOct 07 20031D diagonally disordered chain with Frenkel exciton and long range exponential intersite interaction is considered. It is shown that some states of this disordered system are delocalised contrary to the popular statement that all states in 1D disordered ... More