Results for "J. M. Brader"

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Nonlinear rheology of colloidal dispersionsAug 27 2010Colloidal dispersions are commonly encountered in everyday life and represent an important class of complex fluid. Of particular significance for many commercial products and industrial processes is the ability to control and manipulate the macroscopic ... More
Structural precursor to freezing: An integral equation studyAug 01 2008Recent simulation studies have drawn attention to the shoulder which forms in the second peak of the radial distribution function of hard-spheres at densities close to freezing and which is associated with local crystalline ordering in the dense fluid. ... More
Density profiles of a colloidal liquid at a wall under shear flowOct 13 2010Using a dynamical density functional theory we analyze the density profile of a colloidal liquid near a wall under shear flow. Due to the symmetries of the system considered, the naive application of dynamical density functional theory does not lead to ... More
Local phase transitions in driven colloidal suspensionsNov 30 2017Using dynamical density functional theory and Brownian dynamics simulations we investigate the influence of a driven tracer particle on the density distribution of a colloidal suspension at a thermodynamic statepoint close to the liquid side of the binodal. ... More
Green-Kubo approach to the average swim speed in active Brownian systemsAug 29 2016We develop an exact Green-Kubo formula relating nonequilibrium averages in systems of interacting active Brownian particles to equilibrium time-correlation functions. The method is applied to calculate the density-dependent average swim speed, which is ... More
Escape rate of transiently active Brownian particle in one dimensionFeb 08 2019Activity significantly enhances the escape rate of a Brownian particle over a potential barrier. Whereas constant activity has been extensively studied in the past, little is known about the effect of time-dependent activity on the escape rate of the ... More
Density Functional approach to Nonlinear RheologyJan 22 2013We present a density functional based closure of the pair Smoluchowski equation for Brownian particles under shear flow. Given an equilibrium free energy functional as input the theory provides first-principles predictions for the flow-distorted pair ... More
Microrheology close to an equilibrium phase transitionFeb 24 2014We investigate the microstructural and microrheological response to a tracer particle of a two- dimensional colloidal suspension under thermodynamic conditions close to a liquid-gas phase bound- ary. On the liquid side of the binodal, increasing the velocity ... More
Escape rate of transiently active Brownian particle in one dimensionFeb 08 2019Jun 13 2019Activity significantly enhances the escape rate of a Brownian particle over a potential barrier. Whereas constant activity has been extensively studied in the past, little is known about the effect of time-dependent activity on the escape rate of the ... More
Shear-induced migration in colloidal suspensionsDec 19 2017Using Brownian dynamics simulations we perform a systematic investigation of the shear-induced migration of colloidal particles subject to Poiseuille flow in both cylindrical and planar geometry. We find that adding an attractive component to the interparticle ... More
Effect of mixing and spatial dimension on the glass transitionJul 14 2009We study the influence of composition changes on the glass transition of binary hard disc and hard sphere mixtures in the framework of mode coupling theory. We derive a general expression for the slope of a glass transition line. Applied to the binary ... More
Structure and phase equilibria of the Widom-Rowlinson modelAug 01 2008The Widom-Rowlinson model plays an important role in the statistical mechanics of second order phase transitions and yet there currently exists no theoretical approach capable of accurately predicting both the microscopic structure and phase equilibria. ... More
Dynamics and rheology of active glassesMar 04 2014Mar 07 2014Within the framework of mode-coupling theory, we present a simple model for describing dense assemblies of active (self-propelled) spherical colloidal particles. For isotropic suspensions, we demonstrate that the glass transition is shifted to higher ... More
Three Dimensional Flow of Colloidal GlassesSep 02 2011Jan 09 2012Recent experiments performed on a variety of soft glassy materials have demonstrated that any imposed shear flow serves to simultaneously fluidize these systems in all spatial directions [Ovarlez \textit{et al.} (2010)]. When probed with a second shear ... More
Escape rate of active particles in the effective equilibrium approachNov 11 2016The escape rate of a Brownian particle over a potential barrier is accurately described by the Kramers theory. A quantitative theory explicitly taking the activity of Brownian particles into account has been lacking due to the inherently out-of-equilibrium ... More
First-Principles Constitutive Equation for Suspension RheologyMay 09 2012We provide a detailed derivation of a recently developed first-principles approach to calculating averages in systems of interacting, spherical Brownian particles under time-dependent flow. Although we restrict ourselves to flows which are both homogeneous ... More
A First-Principles Constitutive Equation for Suspension RheologyAug 11 2008Using mode-coupling theory, we derive a constitutive equation for the nonlinear rheology of dense colloidal suspensions under arbitrary time-dependent homogeneous flow. Generalizing previous results for simple shear, this allows the full tensorial structure ... More
A First-Principles Constitutive Equation for Suspension Rheology: Supplementary MaterialAug 11 2008Additional supplementary material for the paper `A First-Principles Constitutive Equation for Suspension Rheology'.
Schematic Mode Coupling Theory of Glass Rheology: Single and Double Step StrainsMar 28 2012Mode coupling theory (MCT) has had notable successes in addressing the rheology of hard-sphere colloidal glasses, and also soft colloidal glasses such as star-polymers. Here, we explore the properties of a recently developed MCT-based schematic constitutive ... More
Dense colloidal suspensions under time-dependent shearSep 01 2006We consider the nonlinear rheology of dense colloidal suspensions under a time-dependent simple shear flow. Starting from the Smoluchowski equation for interacting Brownian particles advected by shearing (ignoring fluctuations in fluid velocity) we develop ... More
Normal-stress coefficients and rod climbing in colloidal dispersionsOct 07 2013We calculate tractable microscopic expressions for the low-shear normal-stress coefficients of colloidal dispersions. Although restricted to the low rate regime, the presented formulas are valid for all volume fractions below the glass transition and ... More
Dynamical density functional theory analysis of the laning instability in sheared soft matterNov 02 2017Nov 29 2017Using dynamical density functional theory (DDFT) methods we investigate the laning instability of a sheared colloidal suspension. The nonequilibrium ordering at the laning transition is driven by non-affine particle motion arising from interparticle interactions. ... More
Effective Interactions in Active Brownian SuspensionsApr 01 2015Apr 20 2015Active colloids exhibit persistent motion, which can lead to motility-induced phase separation (MIPS). However, there currently exists no microscopic theory to account for this phenomenon. We report a first-principles theory, free of fit parameters, for ... More
From Equilibrium to Steady State: The Transient Dynamics of Colloidal Liquids under ShearJul 24 2008We investigate stresses and particle motion during the start up of flow in a colloidal dispersion close to arrest into a glassy state. A combination of molecular dynamics simulation, mode coupling theory and confocal microscopy experiment is used to investigate ... More
Power functional theory for Brownian dynamicsJan 11 2013Sep 05 2013Classical density functional theory (DFT) provides an exact variational framework for determining the equilibrium properties of inhomogeneous fluids. We report a generalization of DFT to treat the non-equilibrium dynamics of classical many-body systems ... More
Glass Rheology: From mode-coupling theory to a dynamical yield criterionSep 28 2009The mode coupling theory (MCT) of glasses, while offering an incomplete description of glass transition physics, represents the only established route to first-principles prediction of rheological behavior in nonergodic materials such as colloidal glasses. ... More
Flow induced crystallization of penetrable particlesNov 06 2017For a system of Brownian particles interacting via a soft exponential potential we investigate the interaction between equilibrium crystallization and spatially varying shear flow. For thermodynamic state points within the liquid part of the phase diagram, ... More
Nonequilibrium Ornstein-Zernike relation for Brownian many-body dynamicsMay 16 2013Oct 30 2013We derive a dynamic Ornstein-Zernike equation for classical fluids undergoing overdamped Brownian motion and driven out of equilibrium. Inhomogeneous two-time correlation functions are obtained from functional differentiation of the one-body density and ... More
Active Brownian particles at interfaces: An effective equilibrium approachFeb 02 2017A simple theoretical approach is used to investigate active colloids at the free interface and near repulsive substrates. We employ dynamical density functional theory to determine the steady-state density profiles in an effective equilibrium system [Farage ... More
Controlling colloidal sedimentation using time dependent shearSep 10 2011Employing a recently developed dynamical density functional theory we study the response of a colloidal sediment above a wall to shear, demonstrating the time dependent changes of the density distribution and its center-of-mass after switching shear either ... More
Dynamic correlations in Brownian many-body systemsOct 30 2013Jan 17 2014For classical Brownian systems driven out of equilibrium we derive inhomogeneous two-time correlation functions from functional differentiation of the one-body density and current with respect to external fields. In order to allow for appropriate freedom ... More
Nonlinear response of dense colloidal suspensions under oscillatory shear: Mode-coupling theory and FT-rheology experimentsOct 13 2010Using a combination of theory, experiment and simulation we investigate the nonlinear response of dense colloidal suspensions to large amplitude oscillatory shear flow. The time-dependent stress response is calculated using a recently developed schematic ... More
Phase separation on the sphere: Patchy particles and self-assemblyJul 12 2016Motivated by observations of heterogeneous domain structure on the surface of cells, we consider a minimal model to describe the dynamics of phase separation on the surface of a spherical particle. Finite-size effects on the curved particle surface lead ... More
Pressure, surface tension and curvature in active systems: a touch of equilibriumDec 20 2018We explore the pressure of active particles on curved surfaces and its relation to other interfacial properties. We use both direct simulations of the active systems as well as simulations of an equilibrium system with effective (pair) interactions designed ... More
Dynamic Glass Transition in Two DimensionsMar 07 2007The question about the existence of a structural glass transition in two dimensions is studied using mode coupling theory (MCT). We determine the explicit d-dependence of the memory functional of mode coupling for one-component systems. Applied to two ... More
Nonequilibrium phase behaviour from minimization of free power dissipationSep 30 2016We develop a general theory for describing phase coexistence between nonequilibrium steady states in Brownian systems, based on power functional theory (J. Chem. Phys. 138, 214101 (2013)). We apply the framework to the special case of fluid-fluid phase ... More
Nonequilibrium phase behaviour from minimization of free power dissipationSep 30 2016Nov 17 2016We develop a general theory for describing phase coexistence between nonequilibrium steady states in Brownian systems, based on power functional theory (M. Schmidt and J.M. Brader, J. Chem. Phys. 138, 214101 (2013)). We apply the framework to the special ... More
Pressure, surface tension and curvature in active systems: A touch of equilibriumDec 20 2018May 13 2019We explore the pressure of active particles on curved surfaces and its relation to other interfacial properties. We use both direct simulations of the active systems as well as simulations of an equilibrium system with effective (pair) interactions designed ... More
Particle-conserving dynamics on the single-particle levelJan 08 2019We generalize the particle-conserving dynamics method of de las Heras et al. [J. Phys. Condens. Matter: 28, 24404 (2016).] to binary mixtures and apply this to hard rods in one dimension. Considering the case of one species consisting of only one particle ... More
Rheology, Structure and Dynamics of Colloid-Polymer Mixtures: from Liquids to GelsDec 04 2008We investigated the viscoelastic properties of colloid-polymer mixtures at intermediate colloid volume fraction and varying polymer concentrations, thereby tuning the attractive interactions. Within the examined range of polymer concentrations, the samples ... More
Residual Stresses in GlassesFeb 16 2013The history dependence of the glasses formed from flow-melted steady states by a sudden cessation of the shear rate $\dot\gamma$ is studied in colloidal suspensions, by molecular dynamics simulations, and mode-coupling theory. In an ideal glass, stresses ... More
Superadiabatic forces in Brownian many-body dynamicsAug 05 2014Theoretical approaches to nonequilibrium many-body dynamics generally rest upon an adiabatic assumption, whereby the true dynamics is represented as a sequence of equilibrium states. Going beyond this simple approximation is a notoriously difficult problem. ... More
Effective equilibrium states in the colored-noise model for active matter I. Pairwise forces in the Fox and unified colored noise approximationsJan 31 2017Nov 29 2017The equations of motion of active systems can be modeled in terms of Ornstein-Uhlenbeck processes (OUPs) with appropriate correlators. For further theoretical studies, these should be approximated to yield a Markovian picture for the dynamics and a simplified ... More
Isotropic-nematic transition of self-propelled rods in three dimensionsJan 26 2018Using overdamped Brownian dynamics simulations we investigate the isotropic-nematic (IN) transition of self-propelled rods in three spatial dimensions. For two well-known model systems (Gay-Berne potential and hard spherocylinders) we find that turning ... More
Particle Conservation in Dynamical Density Functional TheoryNov 26 2015Jan 07 2016We present the exact adiabatic theory for the dynamics of the inhomogeneous density distribution of a classical fluid. Erroneous particle number fluctuations of dynamical density functional theory are absent, both for canonical and grand canonical initial ... More
Effective equilibrium states in the colored-noise model for active matter II. A unified framework for phase equilibria, structure and mechanical propertiesFeb 01 2017Nov 29 2017Active particles driven by colored noise can be approximately mapped onto a system that obeys detailed balance. The effective interactions which can be derived for such a system allow to describe the structure and phase behavior of the active fluid by ... More
Effective equilibrium states in mixtures of active particles driven by colored noiseNov 06 2017Jan 16 2018We consider the steady-state behavior of pairs of active particles having different persistence times and diffusivities. To this purpose we employ the active Ornstein-Uhlenbeck model, where the particles are driven by colored noises with exponential correlation ... More
Isotropic-nematic transition of self-propelled rods in three dimensionsJan 26 2018Jun 28 2018Using overdamped Brownian dynamics simulations we investigate the isotropic-nematic (IN) transition of self-propelled rods in three spatial dimensions. For two well-known model systems (Gay-Berne potential and hard spherocylinders) we find that turning ... More
Brownian systems with spatially inhomogeneous activityMay 03 2017We generalize the Green-Kubo approach, previously applied to bulk systems of spherically symmetric active particles [J. Chem. Phys. 145, 161101 (2016)], to include spatially inhomogeneous activity. The method is applied to predict the spatial dependence ... More
Dynamics of localized particles from density functional theoryNov 23 2011A fundamental assumption of the dynamical density functional theory (DDFT) of colloidal systems is that a grand-canonical free energy functional may be employed to generate the thermodynamic driving forces. Using one-dimensional hard-rods as a model system ... More
Effect of anisotropic diffusion on spinodal decompositionOct 03 2018We study the phase transition dynamics of a fluid system in which the particles diffuse anisotropically in space. The motivation to study such a situation is provided by systems of interacting magnetic colloidal particles subject to the Lorentz force. ... More
Langevin equation for a particle in magnetic field is inconsistent with equilibriumDec 04 2018We study the stochastic motion of a particle subject to spatially varying Lorentz force in the small-mass limit. Using existing literature on the small-mass limit of Langevin equations, we obtain the overdamped equation of motion of a Brownian particle ... More
Lorentz forces induce inhomogeneity and fluxes in active systemsAug 07 2019We consider the nonequilibrium dynamics of a charged active Brownian particle in the presence of a space dependent magnetic field. It has recently been shown that the Lorentz force induces a particle flux perpendicular to density gradients, thus preventing ... More
Nondiffusive Fluxes in Brownian System with Lorentz ForceAug 08 2019The Fokker-Planck equation provides complete statistical description of a particle undergoing random motion in a solvent. In the presence of Lorentz force due to an external magnetic field, the Fokker-Planck equation picks up a tensorial coefficient, ... More
Linear response approach to active Brownian particles in time-varying activity fieldsFeb 12 2018In a theoretical and simulation study, active Brownian particles (ABPs) in three-dimensional bulk systems are exposed to time-varying sinusoidal activity waves that are running through the system. A linear response (Green-Kubo) formalism is applied to ... More
Rational streams coalgebraicallyJul 25 2008Sep 19 2008We study rational streams (over a field) from a coalgebraic perspective. Exploiting the finality of the set of streams, we present an elementary and uniform proof of the equivalence of four notions of representability of rational streams: by finite dimensional ... More
The global properties of all variety of AGNDec 13 2004Active Galactic Nuclei (AGN) have been a challenging field of research for the past six decades. Nevertheless, many questions still remain unanswered today, regardless of the tremendous theoretical and technological advances. In this brief review I propose ... More
Visualising a FuseOct 27 2010Nov 09 2010In this brief article I describe an experiment to illustrate how a fuse works. I have used this as part of lessons for my year 11 classes to demonstrate how an electrical fuse 'blows' when too high a current passes through it.
Trapped surfaces, horizons and exact solutions in higher dimensionsMar 30 2002May 18 2002A very simple criterion to ascertain if (D-2)-surfaces are trapped in arbitrary D-dimensional Lorentzian manifolds is given. The result is purely geometric, independent of the particular gravitational theory, of any field equations or of any other conditions. ... More
Applications of Super-Energy TensorsDec 13 1999In this contribution I intend to give a summary of the new relevant results obtained by using the general superenergy tensors. After a quick review of the definition and properties of these tensors, several of their mathematical and physical applications ... More
Super-energy tensorsJun 21 1999A purely algebraic construction of super-energy tensors for arbitrary fields is presented in any dimensions. These tensors have good mathematical and physical properties, and they can be used in any theory having as basic arena an n-dimensional manifold ... More
(Super)^n-Energy for arbitrary fields and its interchange: Conserved quantitiesMay 17 1999Inspired by classical work of Bel and Robinson, a natural purely algebraic construction of super-energy tensors for arbitrary fields is presented, having good mathematical and physical properties. Remarkably, there appear quantities with mathematical ... More
Remarks on Superenergy TensorsJan 07 1999We define super-energy tensors for arbitrary physical fields, including the gravitational, electromagnetic and massless scalar fields. We also define super-super-energy tensors, and so on. All these tensors satisfy the so-called "Dominant Superenergy ... More
Superenergy tensors and their applicationsFeb 20 2002In Lorentzian manifolds of any dimension the concept of causal tensors is introduced. Causal tensors have positivity properties analogous to the so-called ``dominant energy condition''. Further, it is shown how to build, from ANY given tensor $A$, a new ... More
Mobile Phone Faraday CageDec 23 2011A Faraday cage is an interesting physics phenomena where an electromagnetic wave can be excluded from a volume of space by enclosure with an electrically conducting material. The practical application of this in the classroom is to block the signal to ... More
The Wonders of LevitationOct 27 2010I discuss some interesting classroom demonstrations of diamagnetism and how this effect can produce levitation. The possibilities for hands-on demonstrations of diamagnetic and superconducting levitation are discussed. To conclude I discuss some practical ... More
Effects on Amorphous Silicon Photovoltaic Performance from High-temperature Annealing Pulses in Photovoltaic Thermal Hybrid DevicesMar 06 2012There is a renewed interest in photovoltaic solar thermal (PVT) hybrid systems, which harvest solar energy for heat and electricity. Typically, a main focus of a PVT system is to cool the photovoltaic (PV) cells to improve the electrical performance, ... More
LEP1 vs. Future Colliders: Effective Operators And Extended Gauge GroupJul 24 1992In an effective Lagrangian approach to physics beyond the Standard Model, it has been argued that imposing $SU(2) \times U(1)$ invariance severely restricts the discovery potential of future colliders. We exhibit a possible way out in an extended gauge ... More
Gravitational waves from the collapse and bounce of a stellar core in tensor-scalar gravityNov 16 1999Tensor-scalar theory of gravity allows the generation of gravitational waves from astrophysical sources, like Supernov\ae{}, even in the spherical case. That motivated us to study the collapse of a degenerate stellar core, within tensor-scalar gravity, ... More
The Domino EffectJan 07 2004The physics of a row of toppling dominoes is discussed. In particular the forces between the falling dominoes are analyzed and with this knowledge, the effect of friction has been incorporated. A set of limiting situations is discussed in detail, such ... More
Spin Waves in Canted Phases: An Application to Doped ManganitesNov 29 1999Dec 12 2000We present the effective lagrangian for low energy and momentum spin waves in canted phases at next to leading order in the derivative expansion. The symmetry breaking pattern SU(2) --> 1 of the internal spin group and that of the crystallographic space ... More
Elastic s-wave scattering phase shifts and |Vub| from lattice calculations of form factors for exclusive semileptonic decaysNov 21 2007Omnes dispersion relations make a connection between form factors for exclusive semileptonic decays and phase shifts in the corresponding elastic scattering channels. We describe two applications. In the first, we use lattice form factor calculations ... More
Breakdown of Landau Fermi liquid properties in the $2D$ Boson-Fermion modelDec 07 1995We study the normal state spectral properties of the fermionic excitations in the Boson-Fermion model. The fermionic single particle excitations show a flattening of the dispersion as the Fermi vector ${\bf k}_{_F}$ is approached from below, forshadowing ... More
The Spin Gap in the Context of the Boson-Fermion Model for High $T_c$ SuperconductivityDec 18 1996The issue of the spin gap in the magnetic susceptibility $\chi''(q,\omega)$ in high T_c superconductors is discussed within a scenario of a mixture of localized tightly bound electron pairs in singlet states (bi-polarons) and itinerant electrons. Due ... More
Trace anomalies and the $ΔI = 1/2$ ruleNov 30 2000Trace Anomaly Dominance in weak $K$-decays successfully reproduces the $\Delta I = {1\over 2}$ selection rule results, as observed in $K_S \to \pi\pi, K_L \to \pi\pi\pi, K_S \to \gamma\gamma$ and $K_L \to \pi^0 \gamma\gamma$.
On the analyticity of the trajectories of the particles in the patch problem for $2$D Euler and aggregation equationsJul 31 2019We give a proof of the analiticity in time for the particle trajectories associated with the solutions of some transport equations when the initial datum is a patch. These results are obtained from a precise study of the Beurling transform, which provides ... More
Stochastic MultiresonanceMar 02 1997We present a class of systems for which the signal-to-noise ratio as a function of the noise level may display a multiplicity of maxima. This phenomenon, referred to as stochastic multiresonance, indicates the possibility that periodic signals may be ... More
All tree-level amplitudes in N=4 SYMAug 19 2008Mar 16 2009We give an explicit formula for all tree amplitudes in N=4 SYM, derived by solving the recently presented supersymmetric tree-level recursion relations. The result is given in a compact, manifestly supersymmetric form and we show how to extract from it ... More
Revealing the extended radio emission from the gamma-ray binary HESS J0632+057Aug 01 2011Sep 04 2011Context. After the detection of a 321-days periodicity in X-rays, HESS J0632+057 can be robustly considered a new member of the selected group of gamma-ray binaries. These sources are known to show extended radio structure at scales of milliarcseconds ... More
X-ray properties of active M dwarfs as observed by XMM-NewtonApr 06 2005We present a comparative study of X-ray emission from a sample of active M dwarfs with spectral types \hbox{M3.5 - M4.5} using XMM-Newton observations of two single stars, AD Leonis and EV Lacertae, and two unresolved binary systems, AT Microscopii and ... More
X-ray emission from the remarkable A-type star HR 8799Apr 08 2010We present a Chandra observation of the exceptional planet bearing A5V star HR 8799, more precisely classified as a kA5hF0mA5 star and search for intrinsic X-ray emission. We clearly detect HR 8799 at soft X-ray energies with the ACIS-S detector in a ... More
Stability of string defects in models of non-Abelian symmetry breakingJul 09 1998Aug 12 1998In this paper we describe a new type of topological defect, called a homilia string, which is stabilized via interactions with the string network. Using analytical and numerical techniques, we investigate the stability and dynamics of homilia strings, ... More
Optical Control of Donor Spin Qubits in SiliconJul 28 2015Oct 26 2015We show how to achieve optical, spin-selective transitions from the ground state to excited orbital states of group-V donors (P, As, Sb, Bi) in silicon. We consider two approaches based on either resonant, far-infrared (IR) transitions of the neutral ... More
O(alpha_s) Spin-Spin Correlations for Top and Bottom Quark Production in e+ e- AnnihilationJun 23 1997Oct 15 1997We present the full O(alpha_s) longitudinal spin-spin correlations for heavy-quark pair production at e+ e- high-energy colliders in closed analytical form. In such reactions, quark and antiquark have strongly correlated spins, and the longitudinal components ... More
Shades of Hyperbolicity for HamiltoniansDec 19 2012We prove that a C2 Hamiltonian system H in M is globally hyperbolic if any of the following statements holds: H is robustly topologically stable; H is stably shadowable; H is stably expansive; and H has the stable weak specification property. Moreover, ... More
Form Factors for Semileptonic B -> pi and D -> pi Decays from the Omnes RepresentationJul 24 2000Feb 27 2001We use the Omnes representation to obtain the q-squared dependence of the form factors f+ and f0 for semileptonic H -> pi decays from the elastic pi H -> pi H scattering amplitudes, where H denotes a B or D meson. The scattering amplitudes used satisfy ... More
Free-volume kinetic models of granular matterJun 08 2000We show that the main dynamical features of granular media can be understood by means of simple models of fragile-glass forming liquid provided that gravity alone is taken into account. In such lattice-gas models of cohesionless and frictionless particles, ... More
Theory of projections with non-orthogonal basis sets: Partitioning techniques and effective HamiltoniansApr 08 2014Jul 31 2014Here we present a detailed account of the fundamental problems one encounters in projection theory when non-orthogonal basis sets are used for representation of the operators. In particular, we re-examine the use of projection operators in connection ... More
Investigating the rotational evolution of very low-mass stars and brown dwarfs in young clusters using Monte Carlo simulationsNov 19 2016Context. Very low-mass (VLM) stars and brown dwarfs (BDs) present a different rotational behaviour from their solar mass counter-parts. Aims. We investigate the rotational evolution of young VLM stars and BDs using Monte Carlo simulations under the hypothesis ... More
Massive String States as Extreme Black HolesJun 15 1994Dec 12 1994We consider the Schwarz-Sen spectrum of elementary electrically charged massive $N_R=1/2$ states of the four-dimensional heterotic string and show the maximum spin $1$ supermultiplets to correspond to extreme black hole solutions. The $N_L=1$ states and ... More
Hyperfine structure of alkali-metal diatomic moleculesAug 18 2017Sep 18 2017We present calculations of the hyperfine coupling constants for all the heteronuclear alkali-metal diatomic molecules at the equilibrium geometry of the electronic ground state. These constants are important in developing methods to control ultracold ... More
Violation of causality in f(R) gravityJul 08 2010We examine the question as to whether the f(R) gravity theories, in both metric and in Palatini formalisms, permit space-times in which the causality is violated. We show that the field equations of these f(R) gravity theories admit solutions with violation ... More
Gödel-type universes in f(R) gravityJun 29 2009Sep 21 2009The $f(R)$ gravity theories provide an alternative way to explain the current cosmic acceleration without a dark energy matter component. If gravity is governed by a $f(R)$ theory a number of issues should be reexamined in this framework, including the ... More
Octupole correlations in low-lying states of 150Nd and 150Sm and their impact on neutrinoless double-beta decayApr 21 2016Jul 07 2016We present a generator-coordinate calculation, based on a relativistic energy-density functional, of the low-lying spectra in the isotopes $^{150}$Nd and $^{150}$Sm and of the nuclear matrix element that governs the neutrinoless double-beta decay of the ... More
Super Curves, their Jacobians, and super KP equationsJan 15 1996We study the geometry and cohomology of algebraic super curves, using a new contour integral for holomorphic differentials. For a class of super curves (``generic SKP curves'') we define a period matrix. We show that the odd part of the period matrix ... More
Critical phenomena from the two-particle irreducible 1/N expansionApr 06 2004The 1/N expansion of the two-particle irreducible (2PI) effective action is employed to compute universal properties at the second-order phase transition of an O(N)-symmetric N-vector model directly in three dimensions. At next-to-leading order the approach ... More
Spatiotemporal Stochastic Resonance in the Swift-Hohenberg EquationFeb 22 1997We show the appearance of spatiotemporal stochastic resonance in the Swift-Hohenberg equation. This phenomenon emerges when a control parameter varies periodically in time around the bifurcation point. By using general scaling arguments and by taking ... More
Composition Dependence of the Structure and Electronic Properties of Liquid Ga-Se Alloys Studied by Ab Initio Molecular Dynamics SimulationOct 02 1995Ab initio molecular dynamics simulation is used to study the structure and electronic properties of the liquid Ga-Se system at the three compositions Ga$_2$Se, GaSe and Ga$_2$Se$_3$, and of the GaSe and Ga$_2$Se$_3$ crystals. The calculated equilibrium ... More
The Ab-Initio Simulation of the Liquid Ga-Se SystemJul 12 1995Ab-initio dynamical simulation is used to study the liquid Ga-Se system at the three concentrations Ga$_2$Se, GaSe and Ga$_2$Se$_3$ at the temperature 1300~K. The simulations are based on the density functional pseudopotential technique, with the system ... More
Bosonic Partition Functions at Nonzero (Imaginary) Chemical PotentialOct 07 2016We consider bosonic random matrix partition functions at nonzero chemical potential and compare the chiral condensate, the baryon number density and the baryon number susceptibility to the result of the corresponding fermionic partition function. We find ... More