Results for "C. Simenel"

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Time-dependent Hartree-Fock Study of Octupole Vibrations in doubly magic nucleiJan 20 2016Feb 10 2016Octupole vibrations are studied in some doubly magic nuclei using the time-dependent Hartree-Fock (TDHF) theory with a Skyrme energy density functional. Through the use of the linear response theory, the energies and transition amplitudes of the low-lying ... More
Non-Linear Vibrations in NucleiSep 23 2002Jul 21 2004We have perfomed Time Dependant Hartree-Fock (TDHF) calculations on the non linear response of nuclei. We have shown that quadrupole (and dipole) motion produces monopole (and quadrupole) oscillations in all atomic nuclei. We have shown that these findings ... More
Effect of shell structure on the fission of sub-lead nucleiApr 02 2019Fission of atomic nuclei often produces mass asymmetric fragments. However, the origin of this asymmetry was believed to be different in actinides and in the sub-lead region [A. Andreyev et al., Phys. Rev. Lett. 105, 252502 (2010)]. It has recently been ... More
Formation and dynamics of fission fragmentsDec 17 2013Mar 13 2014Although the overall time-scale for nuclear fission is long, suggesting a slow process, rapid shape evolution occurs in its later stages near scission. Theoretical prediction of the fission fragments and their characteristics are often based on the assumption ... More
Influence of entrance-channel magicity and isospin on quasi-fissionNov 11 2011Mar 26 2012The role of spherical quantum shells in the competition between fusion and quasi-fission is studied for reactions forming heavy elements. Measurements of fission fragment mass distributions for different reactions leading to similar compound nuclei have ... More
Quantum Calculation of Dipole Excitation in Fusion ReactionNov 10 2000Jul 21 2004The excitation of the giant dipole resonance by fusion is studied with N/Z asymmetry in the entrance channel. the TDHF solution exhibits a strong dipole vibration which can be associated with a giant vibration along the main axis of a fluctuating prolate ... More
Isospin coupling in time-dependent-mean-field theories and decay of isovector excitationsApr 15 2005We show that isospin non-diagonal terms should appear in the mean field Hamiltonian when neutron-proton symmetry is broken. They give rise to charge mixing in the single-particle wave-functions. We study the Time Dependent Hartree-Fock response of a charge-exchange ... More
Dependence of fusion on isospin dynamicsSep 27 2016We introduce a new microscopic approach to calculate the dependence of fusion barriers and cross-sections on isospin dynamics. The method is based on the time-dependent Hartree-Fock theory and the isoscalar and isovector properties of the energy density ... More
Equilibration dynamics and isospin effects in nuclear reactionsApr 12 2019We discuss equilibration times and isospin effect for various quantities in low-energy heavy-ion reactions. These include equilibration of mass, isospin, and total kinetic energy (TKE) in quasifission and deep-inelastic reactions. The calculations are ... More
Dynamical effects in fusion with exotic nucleiJun 24 2016[Background] Reactions with stable beams have demonstrated a strong interplay between nuclear structure and fusion. Exotic beam facilities open new perspectives to understand the impact of neutron skin, large isospin, and weak binding energies on fusion. ... More
Isovector properties of the nuclear energy density functional from the quark-meson coupling modelApr 26 2017Background: The Skyrme energy density functional is widely used in mean-field calculations of nuclear structure and dynamics. However, its reliance on phenomenology may compromise its isovector properties and its performance for exotic nuclear systems. ... More
Energy dependence of potential barriers and its effect on fusion cross-sectionsJan 28 2014Couplings between relative motion and internal structures are known to affect fusion barriers by dynamically modifying the densities of the colliding nuclei. The effect is expected to be stronger at energies near the barrier top, where changes in density ... More
Microscopic approach to coupled-channels effects on fusionOct 24 2013Dec 01 2013Background: Near-barrier fusion can be strongly affected by the coupling between relative motion and internal degrees of freedom of the collision partners. The time-dependent Hartree-Fock (TDHF) theory and the coupled-channels (CC) method are standard ... More
Superfluid fission dynamics with microscopic approachesJan 19 2016Recent progresses in the description of the latter stage of nuclear fission are reported. Dynamical effects during the descent of the potential towards scission and in the formation of the fission fragments are studied with the time-dependent Hartree-Fock ... More
Fusion and quasifission dynamics in the reactions $^{48}$Ca+$^{249}$Bk and $^{50}$Ti+$^{249}$Bk using TDHFJun 02 2016Background: Synthesis of superheavy elements (SHE) with fusion-evaporation reactions is strongly hindered by the quasifission (QF) mechanism which prevents the formation of an equilibrated compound nucleus and which depends on the structure of the reactants. ... More
Dynamics of quasifissionJul 30 2015Quasifission is the primary reaction mechanism that limits the formation of superheavy nuclei and consequently an important ingredient for choosing the best target-projectile combinations for the heavy element searches. Quasifission is characterized by ... More
Microscopic study of $^{16}$O+$^{16}$O fusionJun 24 2013Aug 31 2013We perform a study of $^{16}$O+$^{16}$O fusion at above and below the interaction barrier energies using three-dimensional time-dependent Hartree-Fock (TDHF) calculations at above barrier energies and density-constrained TDHF calculations for the entire ... More
Dissipative dynamics in quasi-fissionSep 10 2014Quasi-fission is the primary reaction mechanism that prevents the formation of superheavy elements in heavy-ion fusion experiments. Employing the time-dependent density functional theory approach we study quasi-fission in the systems $^{40,48}$Ca+$^{238}$U. ... More
Quasifission dynamics in TDHFAug 19 2015For light and medium mass systems the capture cross-section may be considered to be the same as that for complete fusion, whereas for heavy systems leading to superheavy formations the evaporation residue cross-section is dramatically reduced due to the ... More
Shape evolution and collective dynamics of quasifission in TDHFJun 23 2015Background: At energies near the Coulomb barrier, capture reactions in heavy-ion collisions result either in fusion or in quasifission. The former produces a compound nucleus in statistical equilibrium, while the second leads to a reseparation of the ... More
Microscopic study of $^{40}$Ca+$^{58,64}$Ni fusion reactionsFeb 17 2016Background: Heavy-ion fusion reactions at energies near the Coulomb barrier are influenced by couplings between the relative motion and nuclear intrinsic degrees of freedom of the colliding nuclei. The time-dependent Hartree-Fock (TDHF) theory, incorporating ... More
Particle transfer reactions with the time-dependent Hartree-Fock theory using a particle number projection techniqueAug 18 2010Nov 08 2010A particle-number projection technique is used to calculate transfer probabilities in the $^{16}$O+$^{208}$Pb reaction below the fusion barrier. The time evolution of the many-body wave function is obtained with the time-dependent Hartree-Fock (TDHF) ... More
Nuclear Quantum Many-Body Dynamics: From Collective Vibrations to Heavy-Ion CollisionsSep 15 2012Nov 08 2012A summary of recent researches on nuclear dynamics with realistic microscopic quantum approaches is presented. The Balian-V\'en\'eroni variational principle is used to derive the time-dependent Hartree-Fock (TDHF) equation describing the dynamics at the ... More
Particle number fluctuations and correlations in transfer reactions obtained using the Balian-Vénéroni variational principleNov 10 2010Feb 21 2011The Balian-V\'en\'eroni (BV) variational principle, which optimizes the evolution of the state according to the relevant observable in a given variational space, is used at the mean-field level to determine the particle number fluctuations in fragments ... More
The Role of Tensor Force in Heavy-Ion Fusion DynamicsMay 24 2018Jul 18 2018The tensor force is implemented into the time-dependent Hartree-Fock (TDHF) theory so that both exotic and stable collision partners, as well as their dynamics in heavy-ion fusion, can be described microscopically. The role of tensor force on fusion dynamics ... More
From light to hyper-heavy molecules and neutron-star crusts in a dynamical mean-field approachNov 11 2012The richness of phenomena occurring in heavy-ion collisions calls for microscopic approaches where the motion of each nucleon is treated quantum mechanically. The most popular microscopic approach for low-energy collisions between atomic nuclei is the ... More
Probing quantum many-body dynamics in nuclear systemsAug 23 2013Aug 31 2013Quantum many-body nuclear dynamics is treated at the mean-field level with the time-dependent Hartree-Fock (TDHF) theory. Low-lying and high-lying nuclear vibrations are studied using the linear response theory. The fusion mechanism is also described ... More
Microscopic study of the effect of intrinsic degrees of freedom on fusionApr 11 2014Fusion cross-sections are computed for the $^{40}$Ca$+^{40}$Ca system over a wide energy range with two microscopic approaches where the only phenomenological input is the Skyrme energy density functional. The first method is based on the coupled-channels ... More
How the Pauli exclusion principle affects fusion of atomic nucleiOct 09 2016The Pauli exclusion principle induces a repulsion between composite systems of identical fermions such as colliding atomic nuclei. Our goal is to study how heavy-ion fusion is impacted by this "Pauli repulsion". We propose a new microscopic approach, ... More
Coupled collective motion in nuclear reactionsSep 15 2003In this paper, we review the roles of collective modes in nuclear reactions. We emphaize the strong couplings of various collective states with the monopole and quadrupole motions. In inelastic excitation, these couplings can be seen as an important source ... More
On the origin of asymmetric fission of actinidesApr 10 2018Nov 03 2018Background: Nuclear fission of most actinides near the valley of stability is dominated by asymmetric modes with a heavy fragment charge distribution centred around $Z\approx52-55$ protons. Although spherical shell effects in the $^{132}$Sn are often ... More
Time-Depentent Hartree-Fock description of heavy ions fusionNov 06 2007A microscopic mean-field description of heavy ions fusion is performed in the framework of the Time-Dependent Hartree-Fock (TDHF) theory using a Skyrme interaction with the SLy4d parametrization. A good agreement with experiments is obtained on the position ... More
Couplings between dipole and quadrupole vibrations in tin isotopesSep 11 2009Dec 11 2009We study the couplings between collective vibrations such as the isovector giant dipole and isoscalar giant quadrupole resonances in tin isotopes in the framework of the time-dependent Hartree-Fock theory with a Skyrme energy density functional. These ... More
Collision dynamics of two $^{238}$U atomic nucleiApr 20 2009Jun 02 2009Collisions of actinide nuclei form, during very short times of few $10^{-21}$ s, the heaviest ensembles of interacting nucleons available on Earth. Such very heavy ions collisions have been proposed as an alternative way to produce heavy and superheavy ... More
Novel insights into transfer processes in the reaction 16O+208Pb at sub-barrier energiesJan 07 2011The collision of the doubly-magic nuclei $^{16}$O+$^{208}$Pb is a benchmark in nuclear reaction studies. Our new measurements of back-scattered projectile-like fragments at sub-barrier energies show show that transfer of 2 protons ($2p$) is much more ... More
Interplay between quantum shells and orientation in quasi-fissionJun 23 2014Oct 08 2014The quasi-fission mechanism hinders fusion in heavy systems through breakup within zeptoseconds into two fragments with partial mass equilibration. Its dependence on the structure of both the collision partners and the final fragments is a key question. ... More
Effects of Nuclear Structure on Quasi-fissionOct 03 2012The quasi-fission mechanism hinders fusion of heavy systems because of a mass flow between the reactants, leading to a re-separation of more symmetric fragments in the exit channel. A good understanding of the competition between fusion and quasi-fission ... More
Investigation of the role of shell structure in quasi-fission mass distributionsNov 21 2011Systematic measurements of mass-ratio distributions for fission following collisions of $^{48}$Ti projectiles with even-even target nuclei from $^{144}$Sm to $^{208}$Pb have been made at sub-barrier energies. They show the presence of quasifission, and ... More
Quantum calculations of Coulomb reorientation for sub-barrier fusionJan 21 2004Jul 28 2004Classical mechanics and Time Dependent Hartree-Fock (TDHF) calculations of heavy ions collisions are performed to study the rotation of a deformed nucleus in the Coulomb field of its partner. This reorientation is shown to be independent on charges and ... More
Pairing Vibrations Study with the Time-Dependent Hartree-Fock-Bogoliubov theoryAug 26 2008Sep 26 2008We study pairing vibrations in $^{18,20,22}$O and $^{42,44,46}$Ca nuclei solving the time-dependent Hartree-Fock-Bogoliubov equation in coordinate space with spherical symmetry. We use the SLy4 Skyrme functional in the normal part of the energy density ... More
Microscopic description of heavy ion collisions around the barrierApr 17 2009A microscopic mean-field description of heavy ion collisions is performed in the framework of the time dependent Hartree-Fock theory using a Skyrme energy density functional. A good agreement with experiments is obtained on the position of the fusion ... More
Actinide collisions for QED and superheavy elements with the time-dependent Hartree-Fock theory and the Balian-Vénéroni variational principleAug 11 2011Collisions of actinide nuclei form, during very short times of few zs ($10^{-21}$ s), the heaviest ensembles of interacting nucleons available on Earth. Such collisions are used to produce super-strong electric fields by the huge number of interacting ... More
Quantum microscopic approach to low-energy heavy ion collisionsSep 04 2012Oct 03 2012The Time-dependent Hartree-Fock (TDHF) theory is applied to the study of heavy ion collisions at energies around the Coulomb barrier. The competition between fusion and nucleon transfer mechanisms is investigated. For intermediate mass systems such as ... More
Fusion process studied with preequilibrium giant dipole resonance in time dependent Hartree-Fock theoryApr 04 2007Aug 24 2007The equilibration of macroscopic degrees of freedom during the fusion of heavy nuclei, like the charge and the shape, are studied in the Time-Dependent Hartree-Fock theory. The pre-equilibrium Giant Dipole Resonance (GDR) is used to probe the fusion path. ... More
Exploring Zeptosecond Quantum Equilibration Dynamics: From Deep-Inelastic to Fusion-Fission Outcomes in $^{58}$Ni+$^{60}$Ni ReactionsDec 26 2017Energy dissipative processes play a key role in how quantum many-body systems dynamically evolve towards equilibrium. In closed quantum systems, such processes are attributed to the transfer of energy from collective motion to single-particle degrees ... More
Microscopic approaches for nuclear Many-Body dynamics: applications to nuclear reactionsJun 17 2008Apr 20 2009These lecture notes are addressed to PhD student and/or researchers who want a general overview of microscopic approaches based on mean-field and applied to nuclear dynamics. Our goal is to provide a good description of low energy heavy-ion collisions. ... More
Dynamical description of the fission process using the TD-BCS theoryAug 05 2015The description of fission remains a challenge for nuclear microscopic theories. The time-dependent Hartree-Fock approach with BCS pairing is applied to study the last stage of the fission process. A good agreement is found for the one-body observables: ... More
Superfluid dynamics of 258Fm fissionJan 15 2015Theoretical description of nuclear fission remains one of the major challenges of quantum many-body dynamics. The slow, mostly adiabatic motion through the fission barrier is followed by a fast, non-adiabatic descent of the potential between the fragments. ... More
Microscopic description of large amplitude collective motion in the nuclear astrophysics contextMay 13 2015In the last 10 years, we have observed an important increase of interest in the application of time-dependent energy density functional theory (TD-EDF). This approach allows to treat nuclear structure and nuclear reaction from small to large amplitude ... More
Reduced quasifission competition in fusion reactions forming neutron-rich heavy elementsApr 13 2015Measurements of mass-angle distributions (MADs) for Cr + W reactions, providing a wide range in the neutron-to-proton ratio of the compound system, (N/Z)CN, have allowed for the dependence of quasifission on the (N/Z)CN to be determined in a model-independent ... More
Study of $^{124}$Sn+$^{136}$Xe fusion-evaporation: analysis of a rare-event experimentNov 12 2011Nov 22 2011Fusion-evaporation in the $^{124}$Sn+$^{136}$Xe system is studied using a high intensity xenon beam provided by the Ganil accelerator and the LISE3 wien filter for the selection of the products. Due to the mass symmetry of the entrance system, the rejection ... More
Gamow-Teller strengths in 24Na using the 24Mg(t,3He) reaction at 115 AMeVJul 15 2008Gamow-Teller transitions from 24Mg to 24Na were studied via the (t,3He) reaction at 115 AMeV using a secondary triton beam produced via fast fragmentation of 150 AMeV 16O ions. Compared to previous (t,3He) experiments at this energy that employed a primary ... More
On the extraction of weak transition strengths via the (3He,t) reaction at 420 MeVJul 19 2007Mar 27 2008Differential cross sections for transitions of known weak strength were measured with the (3He,t) reaction at 420 MeV on targets of 12C, 13C, 18O, 26Mg, 58Ni, 60Ni, 90Zr, 118Sn, 120Sn and 208Pb. Using this data, it is shown the proportionalities between ... More
Quantum calculation of Coulomb reorientation and near-barrier fusionMay 08 2006We investigate the role of deformation on the fusion probability around the barrier using the Time-Dependent Hartree-Fock theory with a full Skyrme force. We obtain a distribution of fusion probabilities around the nominal barrier due to the different ... More
Generating functional analysis of Minority Games with real market historiesOct 13 2004It is shown how the generating functional method of De Dominicis can be used to solve the dynamics of the original version of the minority game (MG), in which agents observe real as opposed to fake market histories. Here one again finds exact closed equations ... More
Statistical Mechanics of Recurrent Neural Networks II. DynamicsJun 01 2000A lecture notes style review of the non-equilibrium statistical mechanics of recurrent neural networks with discrete and continuous neurons (e.g. Ising, graded-response, coupled-oscillators). To be published in the Handbook of Biological Physics (North-Holland). ... More
Non-equilibrium statistical mechanics of Minority GamesMay 13 2002In this paper I give a brief introduction to a family of simple but non-trivial models designed to increase our understanding of collective processes in markets, the so-called Minority Games, and their non-equilibrium statistical mathematical analysis. ... More
NSV 13983: A New Dwarf Nova in the Period GapJun 17 2008Aims. NSV 13983 is catalogued as a dwarf nova based on a reported outburst from 2005. The system has not yet been studied spectroscopically. We attempt to confirm its nature as a dwarf nova and determine its orbital period. Methods. We derive the orbital ... More
Computation of the topological type of a real Riemann surfaceApr 21 2012We present an algorithm for the computation of the topological type of a real compact Riemann surface associated to an algebraic curve, i.e., its genus and the properties of the set of fixed points of the anti-holomorphic involution $\tau$, namely, the ... More
Scaling of the superfluid density in severely underdoped YBa2Cu3O6+yNov 20 2009Recent measurements on extremely-underdoped YBa2Cu3O6+y [Phys. Rev. Lett. 99, 237003 (2007)] have allowed the critical temperature (T_c), superfluid density [rho_0 (T << T_c)] and dc conductivity [sigma_dc (T ~ T_c)] to be determined for a series of electronic ... More
Quantum-mechanical picture of peripheral chiral dynamicsMar 06 2015The nucleon's peripheral transverse charge and magnetization densities are computed in chiral effective field theory. The densities are represented in first-quantized form, as overlap integrals of chiral light-front wave functions describing the transition ... More
Eclipsing Binary PulsarsApr 05 2004The first eclipsing binary pulsar, PSR B1957+20, was discovered in 1987. Since then, 13 other eclipsing low-mass binary pulsars have been found, 12 of these are in globular clusters. In this paper we list the known eclipsing binary pulsars and their properties, ... More
The Pulsar Population in Globular Clusters and in the GalaxyOct 15 2012Oct 23 2012In this paper, I review some of the basic properties of the pulsar population in globular clusters (GCs) and compare it with the the Galactic disk population. The neutron stars (NSs) in GCs were likely formed - and appear to continue forming - in highly ... More
A theorem of Mislin for cohomology of fusion systems and applications to block algebras of finite groupsNov 15 2013Dec 10 2014We give an algebraic proof for a theorem of Mislin in the case of cohomology of saturated fusion systems defined on p-groups when p is odd. Some applications of this theorem to block algebras of finite groups are also given.
Stückelberg Field Shiftting Quantization of Free-Particle on D-Dimensional SphereAug 11 2000In this paper we quantize the free-particle on a D-dimensional sphere in an unambiguous way by converting the second-class constraint using St\"uckelberg field shiftting formalism. Further, we argument that this formalism is equivalent to the BFFT constraint ... More
Entanglement and topological entropy of the toric code at finite temperatureApr 27 2007Nov 01 2007We calculate exactly the von Neumann and topological entropies of the toric code as a function of system size and temperature. We do so for systems with infinite energy scale separation between magnetic and electric excitations, so that the magnetic closed ... More
Dynamical shift conditions for the Z4 and BSSN hyperbolic formalismsJan 07 2004Mar 22 2004A class of dynamical shift conditions is shown to lead to a strongly hyperbolic evolution system, both in the Z4 and in the BSSN Numerical Relativity formalisms. This class generalizes the harmonic shift condition, where light speed is the only non-trivial ... More
Auger recombination and carrier multiplication in embedded silicon and germanium nanocrystalsSep 10 2007Apr 16 2008For Si and Ge nanocrystals (NCs) embedded in wide band-gap matrices, Auger recombination (AR) and carrier multiplication (CM) lifetimes are computed exactly in a three-dimensional real space grid using empirical pseudopotential wave functions. Our results ... More
Theoretical study of the insulating oxides and nitrides: SiO2, GeO2, Al2O3, Si3N4, and Ge3N4Oct 06 2006Jul 23 2007An extensive theoretical study is performed for wide bandgap crystalline oxides and nitrides, namely, SiO_{2}, GeO_{2}, Al_{2}O_{3}, Si_{3}N_{4}, and Ge_{3}N_{4}. Their important polymorphs are considered which are for SiO_{2}: $\alpha$-quartz, $\alpha$- ... More
Staggered Chiral Perturbation TheoryAug 28 2003We discuss how to formulate a staggered chiral perturbation theory. This amounts to a generalization of the Lee-Sharpe Lagrangian to include more than one flavor (i.e. multiple staggered fields), which turns out to be nontrivial. One loop corrections ... More
Dark Matter in a single-metric universeJan 04 2016Mar 01 2016A few years ago Baker proposed a metric, implementing the Bona-Stela construction, which interpolates smoothly between the Schwarzschild metric at small scales and the Friedmann-Robertson-Walker (FRW) metric at large scales. As it stands, by enforcing ... More
Light-front representation of chiral dynamics in peripheral transverse densitiesMar 16 2015The nucleon's electromagnetic form factors are expressed in terms of the transverse densities of charge and magnetization at fixed light-front time. At peripheral transverse distances $b = O(M_\pi^{-1})$ the densities are governed by chiral dynamics and ... More
Understanding Convolutional Neural Networks with A Mathematical ModelSep 14 2016Nov 02 2016This work attempts to address two fundamental questions about the structure of the convolutional neural networks (CNN): 1) why a non-linear activation function is essential at the filter output of every convolutional layer? 2) what is the advantage of ... More
Detection of Optical Synchrotron Emission from the Radio Jet of 3C279Oct 08 2002Nov 05 2002We report the detection of optical and ultraviolet emission from the kiloparsec scale jet of the well-known quasar 3C~279. A bright knot, discovered in archival V and U band {\it Hubble Space Telescope} Faint Object Camera images, is coincident with a ... More
On the density of the sum of two independent Student t-random vectorsJun 16 2009In this paper, we find an expression for the density of the sum of two independent $d-$dimensional Student $t-$random vectors $\mathbf{X}$ and $\mathbf{Y}$ with arbitrary degrees of freedom. As a byproduct we also obtain an expression for the density ... More
Eccentric Binary Millisecond PulsarsJul 18 2009In this paper we review the recent discovery of several millisecond pulsars (MSPs) in eccentric binary systems. Timing these MSPs we were able to estimate (and in one case precisely measure) their masses. These results suggest that, as a class, MSPs have ... More
Understanding Convolutional Neural Networks with A Mathematical ModelSep 14 2016This work attempts to address two fundamental questions about the structure of the convolutional neural networks (CNN): 1) why a non-linear activation function is essential at the filter output of every convolutional layer? 2) what is the advantage of ... More
Threshold effects in open-string theoryMay 05 1996May 14 1996We analyze the one-loop effective gauge-field action in $Z_2$-orbifold compactifications of type-I theory. We show how, for non-abelian group factors, the threshold effects are ultraviolet finite though given entirely by a six-dimensional field theory ... More
Hidden Symmetry of a Fluid Dynamical ModelMay 28 2001A connection between solutions of the relativistic d-brane system in (d+1) dimensions with the solutions of a Galileo invariant fluid in d-dimensions is by now well established. However, the physical nature of the light-cone gauge description of a relativistic ... More
A quantum topological phase transition at the microscopic levelJul 13 2007Mar 01 2008We study a quantum phase transition between a phase which is topologically ordered and one which is not. We focus on a spin model, an extension of the toric code, for which we obtain the exact ground state for all values of the coupling constant that ... More
Explicit Gravitational Radiation in Hyperbolic Systems for Numerical RelativityFeb 14 2002Feb 28 2002A method for studying the causal structure of space-time evolution systems is presented. This method, based on a generalization of the well known Riemann problem, provides intrinsic results which can be interpreted from the geometrical point of view. ... More
Flux Limiter Methods in 3D Numerical RelativityFeb 28 2002New numerical methods have been applied in relativity to obtain a numerical evolution of Einstein equations much more robust and stable. Starting from 3+1 formalism and with the evolution equations written as a FOFCH (first-order flux conservative hyperbolic) ... More
Staggered Chiral Perturbation Theory for Heavy-Light MesonsOct 18 2005Jan 25 2006We incorporate heavy-light mesons into staggered chiral perturbation theory, working to leading order in 1/m_Q, where m_Q is the heavy quark mass. At first non-trivial order in the chiral expansion, staggered taste violations affect the chiral logarithms ... More
Replica methods for loopy sparse random graphsJan 29 2016I report on the development of a novel statistical mechanical formalism for the analysis of random graphs with many short loops, and processes on such graphs. The graphs are defined via maximum entropy ensembles, in which both the degrees (via hard constraints) ... More
Statistical Mechanics of Recurrent Neural Networks I. StaticsJun 01 2000A lecture notes style review of the equilibrium statistical mechanics of recurrent neural networks with discrete and continuous neurons (e.g. Ising, coupled-oscillators). To be published in the Handbook of Biological Physics (North-Holland). Accompanied ... More
Observational constraints upon quintessence models arising from moduli fieldsApr 14 2000Jun 12 2000We study observational constraints on cosmological models with a quintessence arising from moduli fields. The scalar field potential is given by a double exponential potential V=V_0 exp(-A e^{sqrt{2} kappa phi}). After reviewing the properties of the ... More
Light-front representation of chiral dynamics with Delta isobar and large-N_c relationsMar 29 2016Transverse densities describe the spatial distribution of electromagnetic current in the nucleon at fixed light-front time. At peripheral distances b = O(M_pi^{-1}) the densities are governed by chiral dynamics and can be calculated model-independently ... More
Radio Identification of the X-ray Jet in the z=4.3 Quasar GB 1508+5714Oct 25 2003Dec 01 2003The recent discovery of an X-ray jet in the z=4.3 quasar GB 1508+5714 by Yuan et al. (astro-ph/0309318) and Siemiginowska et al. (astro-ph/0310241) prompted a search for its radio counterpart. Here, we report the successful discovery of faint radio emission ... More
CNN as Guided Multi-layer RECOS TransformJan 30 2017Feb 19 2017There is a resurging interest in developing a neural-network-based solution to the supervised machine learning problem. The convolutional neural network (CNN) will be studied in this note. To begin with, we introduce a RECOS transform as a basic building ... More
Multi-scale RenormalizationDec 18 1996The Standard MS renormalization prescription is inadequate for dealing with multi-scale problems. To illustrate this we consider the computation of the effective potential in the Higgs-Yukawa model. It is argued that it is natural to employ a two-scale ... More
Electroweak standard model at finite temperature in presence of a bosonic chemical potentialMar 15 2007Dec 30 2010We study the electroweak standard model at finite temperature in presence of a bosonic chemical potential associated with the conserved electromagnetic current. To preserve the thermodynamic equilibrium of the system, the thermal medium is neutralized ... More
The classical overdetermined Serrin problemNov 29 2017Nov 30 2017In this survey we consider the classical overdetermined problem which was studied by Serrin in 1971. The original proof relies on Alexandrov's moving plane method, maximum principles, and a refinement of Hopf's boundary point Lemma. Since then other approaches ... More
Basic Morita equivalences and a conjecture of Sasaki for cohomology of block algebras of finite groupsJun 14 2015We show, using basic Morita equivalences between block algebras of finite groups, that the Conjecture of H. Sasaki from [9] is true for a new class of blocks called nilpotent covered blocks. When this Conjecture is true we define some transfer maps between ... More
Small-x QCD effects in forward-jet and Mueller-Navelet jet productionOct 20 2005Mar 07 2006We investigate small-x QCD effects in forward-jet production in deep inelastic scattering in the kinematic regime where the virtuality of the photon and the transverse momentum of the jet are two hard scales of about the same magnitude. We show that the ... More
The Gravitational Radiaton degrees of freedom in Hyperbolic Systems for Numerical RelativityAug 06 2002The gravitational radiation degrees of freedom of freedom are described in the framework of the 3+1 decomposition of spacetime. The relationship with eigenfields of the Kidder-Scheel-Teukolsky (KST) equations is established. This relationship is used ... More
Bound-free $\mathbf{e}^+ \mathbf{e}^-$ pair creation with a linearly polarized laser field and a nuclear fieldJul 28 2008The process of bound-free pair production of electrons and positrons in combined laser and Coulomb fields is investigated. It is assumed that an ion collides at relativistic speed with an intense x-ray laser beam of linear polarization. The process proceeds ... More
Approximate solutions for N-body Hamiltonians with identical particles in D dimensionsJul 19 2013Nov 13 2013A method based on the envelope theory is presented to compute approximate solutions for $N$-body Hamiltonians with identical particles in $D$ dimensions ($D\ge 2$). In some favorable cases, the approximate eigenvalues can be analytically determined and ... More
Schur-finiteness in $λ$-ringsNov 05 2010Nov 17 2011We introduce the notion of a Schur-finite element in a $\lambda$-ring.
Pion and Kaon masses in Staggered Chiral Perturbation TheoryApr 21 2003Jul 07 2003We show how to compute chiral logarithms that take into account both the $\cO(a^2)$ taste-symmetry breaking of staggered fermions and the fourth-root trick that produces one taste per flavor. The calculation starts from the Lee-Sharpe Lagrangian generalized ... More