Results for "J. M. Brader"

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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
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
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
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
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
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
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
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
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
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
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
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'.
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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 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
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
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
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
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
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
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
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
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
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
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
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
Effective Operators and Extended SymmetryJul 30 1993In this note we expand on our previous study of the implications of LEP1 results for future colliders. We extend the effective operator-based analysis of De R\'ujula et al. to a larger symmetry group, and show at which cost their expectations can be relaxed. ... 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
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
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
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 $K_L \to \pi^0 \gamma\gamma$.
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
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
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
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
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
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
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
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
Diffuse flux of galactic neutrinos and gamma raysOct 08 2016We calculate the fluxes of neutrinos and gamma rays from interactions of cosmic rays with interstellar matter in our galaxy. We use EPOS-LHC, SIBYLL and GHEISHA to obtain the yield of these particles in proton, helium and iron collisions at kinetic energies ... More
How to separate the low amplitude delta Scuti variation from the instrumental ones in CoRoT data?Apr 01 2016Rich regular frequency patterns were found in the Fourier spectra of low-amplitude delta Scuti stars observed by CoRoT satellite (see Papar\'o et al. 2016a,b). The CoRoT observations are, however, influenced by the disturbing effect of the South Atlantic ... More
Good rotationsMay 20 1998Numerical integrations in celestial mechanics often involve the repeated computation of a rotation with a constant angle. A direct evaluation of these rotations yields a linear drift of the distance to the origin. This is due to roundoff in the representation ... More
Breathers in the weakly coupled topological discrete sine-Gordon systemFeb 19 1998Jul 06 1998Existence of breather (spatially localized, time periodic, oscillatory) solutions of the topological discrete sine-Gordon (TDSG) system, in the regime of weak coupling, is proved. The novelty of this result is that, unlike the systems previously considered ... More
Classical information capacity of a class of quantum channelsDec 16 2004Apr 14 2005We consider the additivity of the minimal output entropy and the classical information capacity of a class of quantum channels. For this class of channels the norm of the output is maximized for the output being a normalized projection. We prove the additivity ... 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
Theory of Exciton Migration and Field-Induced Dissociation in Conjugated PolymersJul 08 1996The interplay of migration, recombination, and dissociation of excitons in disordered media is studied theoretically in the low temperature regime. An exact expression for the photoluminescence spectrum is obtained. The theory is applied to describe the ... More
Isospin amplitudes and CP violation in $(B \to Kπ)$ decaysNov 25 1997We present a simple isospin invariant parametrization for $(B \to K\pi)$ decay amplitudes which consistently includes CP violation and (quasi-elastic) hadronic final states interactions. We find that the observed $(B \to K\pi)$ decays do not lead to a ... More
Phases and Amplitudes in Inclusive $Ψ$ and $Ψ'$ DecaysJun 14 1999In inclusive decays of the $\Psi$ (3097), electromagnetic and gluonic annihilation amplitudes add incoherently, namely they are 90$^\circ$ out of phase. We argue that this incoherence must persist in each exclusive decay channel. For inclusive $\Psi'$ ... More
Testing various polarized parton distributions at RHICJun 03 1997Jun 06 1997A very promising spin physics programme will be soon on the way at the BNL Relativistic Heavy Ion Collider (RHIC). By studying the spin asymmetries for various processes (single photon, single-jet and $W^{\pm}$ production), we will compare the different ... More
Effects of Fermion Flavor on Exciton Condensation in Double Layer SystemsAug 31 2011We use fermionic path integral quantum Monte Carlo to study the effects of fermion flavor on the physical properties of dipolar exciton condensates in double layer systems. We find that by including spin in the system weakens the effective interlayer ... More
Kovacs effect in facilitated spin models of strong and fragile glassesAug 18 2004Nov 29 2004We investigate the Kovacs (or crossover) effect in facilitated $f$-spin models of glassy dynamics. Although the Kovacs hump shows a behavior qualitatively similar for all cases we have examined (irrespective of the facilitation parameter $f$ and the spatial ... More
Bound States of Black Holes and Other $P$-BranesMay 13 1996May 24 1996In the process of identifying heterotic and Type $II$ BPS string states with extremal dilaton black holes, it has been suggested that solutions with scalar/Maxwell parameters $a=\sqrt{3}$, $1$, $1/\sqrt{3}$ and $0$ correspond to $1-$, $2-$, $3-$ and $4$-particle ... More
Connecting Berry's phase and the pumped charge in a Cooper pair pumpMar 10 2003Apr 30 2003The properties of the tunnelling-charging Hamiltonian of a Cooper pair pump are well understood in the regime of weak and intermediate Josephson coupling, i.e. when $E_{\mathrm{J}}\lesssim E_{\mathrm{C}}$. It is also known that Berry's phase is related ... More
An Asymptotic Analysis of a 2-D Model of Dynamically Active Compartments Coupled by Bulk DiffusionNov 10 2015A class of coupled cell-bulk ODE-PDE models is formulated and analyzed in a two-dimensional domain, which is relevant to studying quorum sensing behavior on thin substrates. In this model, spatially segregated dynamically active signaling cells of a common ... More
Laplacian operators and Radon transforms on Grassmann graphsApr 01 2004Aug 26 2005Let $\Omega$ be a vector space over a finite field with q elements. Let G denote the general linear group of endomorphisms of $\Omega$ and let us consider the left regular representation $\rho: G \to B(L_2(X))$ associated to the natural action of G on ... More
New X-ray observations of IQ Aurigae and alpha2 Canum Venaticorum - Probing the magnetically channelled wind shock model in A0p starsMay 18 2011We present new X-ray observations of the A0p stars alpha^2 CVn (log Lx < 26.0 erg/s) and IQ Aur (log Lx = 29.6 erg/s) and find that their X-ray luminosities differ by at least three orders of magnitude. IQ Aur possesses a strong cool plasma component ... More
Hyperbolicity and Stability for Hamiltonian flowsApr 05 2012We prove that a Hamiltonian star system, defined on a 2d-dimensional symplectic manifold M, is Anosov. As a consequence we obtain the proof of the stability conjecture for Hamiltonians. This generalizes the 4-dimensional results in [6].
Periodic morphological changes in gamma-ray binariesOct 29 2012Gamma-ray binaries allow us to study physical processes such as particle acceleration up to very-high energies and gamma-ray emission and absorption with changing geometrical configurations on a periodic basis. They produce outflows of radio-emitting ... More
Double Gate Bias Dependency of Low Temperature Conductivity of SiO2-Si-SiO2 Quantum WellsNov 28 2006The gate bias dependency of conductivity is examined in two Si quantum wells with well thickness tw = 7 nm and tw = 14 nm. The conductivity of the thinner device behaves smoothly whereas the thicker device shows strong non-monotonic features as a function ... More
Highly optimized tolerance and power laws in dense and sparse resource regimesApr 20 2005Power law cumulative frequency $(P)$ vs. event size $(l)$ distributions $P(\geq l)\sim l^{-\alpha}$ are frequently cited as evidence for complexity and serve as a starting point for linking theoretical models and mechanisms with observed data. Systems ... 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
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
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