Results for "August Evrard"

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The Tully--Fisher Relation : A Numerical Simulator's PerspectiveMar 26 1997In this brief contribution, I outline hopes of understanding the origin of galaxy scaling relations using numerical simulations as a tool to gain understanding. The case of the Tully--Fisher relation for disk galaxies is used as an example to illustrate ... More
Simulations of Clusters of GalaxiesJun 11 1994The degree of complexity and, to a somewhat lesser degree, realism in simulations has advanced rapidly in the past few years. The simplest approach - modeling a cluster as collisionless dark matter and collisonal, non--radiative gas is now fairly well ... More
The Lx-T Relation and Intracluster Gas Fractions of X-ray ClustersJun 26 1998Jan 19 1999We re-examine the X-ray luminosity-temperature relation using a nearly homogeneous data set of 24 clusters selected for statistically accurate temperature measurements and absence of strong cooling flows. The data exhibit a remarkably tight power-law ... More
Four Measures of the Intracluster Medium Temperature and Their Relation to a Cluster's Dynamical StateApr 21 2000We employ an ensemble of hydrodynamic cluster simulations to create spatially and spectrally resolved images of quality comparable to Chandra's expected performance. Emission from simulation mass elements is represented using the XSPEC mekal program assuming ... More
Structure in a Loitering UniverseDec 10 1992We study the formation of structure for a universe that undergoes a recent loitering phase. We compare the nonlinear mass distribution to that in a standard, matter dominated cosmology. The statistical aspects of the clustered matter are found to be robust ... More
Influence of Projection in Cluster Cosmology StudiesJun 15 2011Jun 24 2011Projection tends to skew the mass-observable relation of galaxy clusters by creating a small fraction of severely blended systems, those for which the measured observable property of a cluster is strongly boosted relative to the value of its primary host ... More
Confusion of Diffuse Objects in the X-ray SkyDec 08 2000Most of the baryons in the present-day universe are thought to reside in intergalactic space at temperatures of 10^5-10^7 K. X-ray emission from these baryons contributes a modest (~10%) fraction of the ~ 1 keV background whose prominence within the large-scale ... More
Clustering of dark matter halos on the light-cone: scale-, time- and mass-dependence of the halo biasing in the Hubble volume simulationsOct 02 2001Oct 05 2001We develop a phenomenological model to predict the clustering of dark matter halos on the light-cone by combining several existing theoretical models. Assuming that the velocity field of halos on large scales is approximated by linear theory, we propose ... More
The Cosmological Dependence of Cluster Density ProfilesApr 15 1994We use N-body simulations to study the shape of mean cluster density and velocity profiles formed via gravitational instability. The dependence of the final structure on both cosmology and initial density field is examined, using a grid of cosmologies ... More
The Asymptotic Form of Cosmic Structure: Small Scale Power and Accretion HistoryNov 30 2006We explore the effects of small scale structure on the formation and equilibrium of dark matter halos in a universe dominated by vacuum energy. We present the results of a suite of four N-body simulations, two with a LCDM initial power spectrum and two ... More
Simulating Large-scale StructureDec 21 1998After two decades of direct dynamical simulation of large-scale structure in the universe, it is safe to say the subject is now mature. Still, there are parts of the problem that are less well developed than others. In general, the collisionless dynamics ... More
The Intracluster Gas Fraction in X-ray Clusters : Constraints on the Clustered Mass DensityJan 21 1997The mean intracluster gas fraction of X-ray clusters within their hydrostatic regions is derived from recent observational compilations of David, Jones & Forman and White & Fabian. At radii encompassing a mean density 500 times the critical value, the ... More
Dynamics of Clusters of GalaxiesNov 17 1993The abundance and internal characteristics of rich clusters of galaxies can provide useful constraints on models of large--scale structure formation. This article will review some recent three dimensional, multi--fluid simulations of cluster dynamics ... More
Optically-Selected Cluster Catalogs as a Precision Cosmology ToolMar 21 2007We introduce a framework for describing the halo selection function of optical cluster finders. We treat the problem as being separable into a term that describes the intrinsic galaxy content of a halo (the Halo Occupation Distribution, or HOD) and a ... More
Effects of Mergers and Core Structure on the Bulk Properties of Nearby Galaxy ClustersOct 03 2005Dec 10 2005We use morphological measurements and the scatter of clusters about observed and simulated scaling relations to examine the impact of merging and core-related phenomena on the structure of galaxy clusters. All relations constructed from emission-weighted ... More
The Ultimate Halo Mass in a LCDM UniverseDec 07 2004In the far future of an accelerating LCDM cosmology, the cosmic web of large-scale structure consists of a set of increasingly isolated halos in dynamical equilibrium. We examine the approach of collisionless dark matter to hydrostatic equilibrium using ... More
Future Evolution of Structure in an Accelerating UniverseMay 12 2003Current cosmological data indicate that our universe contains a substantial component of dark vacuum energy that is driving the cosmos to accelerate. We examine the immediate and longer term consequences of this dark energy (assumed here to have a constant ... More
Cluster-Supercluster AlignmentsAug 31 2006Nov 17 2006We study correlations in spatial orientation between galaxy clusters and their host superclusters using a Hubble Volume N-body realization of a concordance cosmology and an analytic model for tidally-induced alignments. We derive an analytic form for ... More
A Comparison of Cosmological Hydrodynamic CodesApr 07 1994We present a detailed comparison of the simulation results of various cosmological hydrodynamic codes. Starting with identical initial conditions based on the Cold Dark Matter scenario for the growth of structure, we integrate from redshift $z=20$ to ... More
A Simulation of the Intracluster Medium with Feedback from Cluster GalaxiesSep 29 1993The formation and evolution of an X--ray cluster is studied using a 3--D N-body + hydrodynamical simulation which includes feedback of energy and iron from cluster galaxies. The differences in evolution and final state between the simulation and a similar ... More
The temperature-mass relation in magnetized galaxy clustersJan 17 2001We use cosmological, magneto-hydrodynamic simulations of galaxy clusters to quantify the dynamical importance of magnetic fields in these clusters. The set-up of initial magnetic field strengths at high redshifts is chosen such that observed Faraday-rotation ... More
Simulations Of Galaxy Clusters With And Without Winds: I. The Structure Of ClustersOct 28 1997We use gas dynamic simulations to explore the effects of galactic winds on galaxy clusters. Two ensembles of 18 realizations, spanning a decade in temperature, are evolved with and without winds in an underlying biased CDM cosmology. Galaxies are identified ... More
An X-ray Size-Temperature Relation for Galaxy Clusters: Observation and SimulationJul 16 1997We show that galaxy clusters conform to a tight relation between X-ray isophotal size R_I and emission weighted intracluster medium (ICM) temperature T_X. The best fit relation for 41 members of an X-ray flux limited cluster sample is: $log{R_I}= (0.93\pm0.11) ... More
Sensitivity of galaxy cluster dark energy constraints to halo modeling uncertaintiesAug 04 2009Mar 16 2010We perform a sensitivity study of dark energy constraints from galaxy cluster surveys to uncertainties in the halo mass function, bias and the mass-observable relation. For a set of idealized surveys, we evaluate cosmological constraints as priors on ... More
Late reionization by supernova-driven windsJun 23 1993Sep 08 1996A model is presented in which supernova-driven winds from early galaxies reionize the intergalactic medium by z=5. This scenario can explain the observed absence of a Gunn-Peterson trough in the spectra of high-redshift quasars providing that the bulk ... More
The Future Landscape of High-Redshift Galaxy Cluster ScienceMar 13 2019Modern galaxy cluster science is a multi-wavelength endeavor with cornerstones provided by X-ray, optical/IR, mm, and radio measurements. In combination, these observations enable the construction of large, clean, complete cluster catalogs, and provide ... More
A High Throughput Workflow Environment for Cosmological SimulationsOct 11 2012Nov 13 2012The next generation of wide-area sky surveys offer the power to place extremely precise constraints on cosmological parameters and to test the source of cosmic acceleration. These observational programs will employ multiple techniques based on a variety ... More
LoCuSS: A Comparison of Cluster Mass Measurements from XMM-Newton and Subaru - Testing Deviation from Hydrostatic Equilibrium and Non-Thermal Pressure SupportJan 05 2010Feb 23 2010We compare X-ray hydrostatic and weak-lensing mass estimates for a sample of 12 clusters that have been observed with both XMM-Newton and Subaru. At an over-density of \Delta=500, we obtain 1-M^{X}/M^{WL}=0.01+/-0.07 for the whole sample. We also divided ... More
Detecting Intracluster Gas Motion in Galaxy Clusters: Mock Astro-E2 ObservationsMar 12 2005May 19 2005We explore the detectability of bulk motions in the X-ray emitting intracluster medium (ICM) using a catalog of 1,836 mock Astro-E2 observations of simulated clusters of galaxies. We generate high resolution mock spectra for two observing strategies: ... More
Galaxy Tracers and Velocity BiasMay 17 1995This paper examines several methods of tracing galaxies in N-body simulations and their effects on the derived galaxy statistics, especially measurements of velocity bias. Using two simulations with identical initial conditions, one following dark matter ... More
Properties of Simulated Compact Groups of GalaxiesApr 24 1996We analyze compact groups of galaxies appearing in a galaxy formation simulation dominated by cold dark matter (omega_0=1, omega_{baryon}=0.1). The simulation uses an N-body code to model the behavior of the non-baryonic matter and smoothed particle hydrodynamics ... More
Effects of Preheating on X-ray Scaling Relations in Galaxy ClustersOct 30 2000Feb 20 2001The failure of purely gravitational models of X-ray cluster formation to reproduce basic observed properties of the local cluster population suggests the need for one or more additional physical processes operating on the intracluster medium (ICM). We ... More
A Morphology--Cosmology Connection for X--Ray ClustersOct 01 1993We employ N--body/$3D$ gas dynamic simulations of the formation of galaxy clusters to determine whether cluster X--ray morphologies can be used as cosmological constraints. Confirming the analytic expectations of Richstone, Loeb, \& Turner, we demonstrate ... More
Radial Temperature Profiles of X-Ray--Emitting Gas Within Clusters of GalaxiesJan 29 1999Previous analyses of ASCA data of clusters of galaxies have found conflicting results regarding the slope of the temperature profile of the hot X-ray gas within clusters, mainly because of the large, energy-dependent point spread function (PSF) of the ... More
A Cold Front in a Preheated Galaxy ClusterJul 08 2002We present a simulated cluster of galaxies, modeled with a pre-heated intracluster medium, that exhibits X-ray features similar to the `cold fronts' seen in Chandra observations. Mock observations at a particular epoch show factor two discontinuities ... More
A Model for Multi-property Galaxy Cluster StatisticsMar 06 2014The massive dark matter halos that host groups and clusters of galaxies have observable properties that appear to be log-normally distributed about power-law mean scaling relations in halo mass. Coupling this assumption with either quadratic or cubic ... More
Mass Estimates of X-Ray ClustersOct 10 1995We use cosmological gas dynamic simulations to investigate the accuracy of galaxy cluster mass estimates based on X-ray observations. The experiments follow the formation of clusters in different cosmological models and include the effects of gravity, ... More
Cosmological Parameters from Observations of Galaxy ClustersMar 24 2011Jun 10 2011Studies of galaxy clusters have proved crucial in helping to establish the standard model of cosmology, with a universe dominated by dark matter and dark energy. A theoretical basis that describes clusters as massive, multi-component, quasi-equilibrium ... More
Dark Energy Studies: Challenges to Computational CosmologyOct 06 2005The ability to test the nature of dark mass-energy components in the universe through large-scale structure studies hinges on accurate predictions of sky survey expectations within a given world model. Numerical simulations predict key survey signatures ... More
ROSAT Observations of Compact Groups of GalaxiesJan 03 1995We have systematically analyzed a sample of 13 new and archival ROSAT PSPC observations of compact groups of galaxies: 12 Hickson Compact Groups plus the NCG 2300 group. We find that approximately two-thirds of the groups have extended X-ray emission ... More
Evaluation of the Casimir Force for a Dielectric-diamagnetic Cylinder with Light Velocity Conservation Condition and the Analogue of Sellmeir's Dispersion LawJan 28 2006May 11 2007We study the Casimir pressure for a dielectric-diamagnetic cylinder subject to light velocity conservation and with a dispersion law analogous to Sellmeir's rule. Similarities to and differences from the spherical case are pointed out.
Transformation Semigroup and Complex Topology: a study of inversion with increasing complexityAug 11 2010This paper is a continuation of our 2005 paper on complex topology and its implication on invertibility (or non-invertibility). In this paper, we will try to classify the complexity of inversion into 3 different classes. We will use synthetic models based ... More
Model structure on operads in orthogonal spectraMar 28 2007We generalize Berger and Moerdijk's results on axiomatic homotopy theory for operads to the setting of enriched symmetric monoidal model categories, and show how this theory applies to orthogonal spectra. In particular, we provide a symmetric fibrant ... More
Polar Coordinates and Noncommutative Phase SpaceOct 22 2016The so-called Weyl transform is a linear map from a commutative algebra of functions to a noncommutative algebra of linear operators, characterized by an action on Cartesian coordinate functions of the form $(x, y) \mapsto (X, Y)$ such that $XY -YX = ... More
Quantitative and Qualitative Seismic Imaging and Seismic InversionJun 16 2017We consider seismic imaging to include seismic inversion. Imaging could use approximate operator or time instead of depth. Processing in time is an important part of seismic imaging as well as processing in depth. We can classify seismic imaging as quantitative ... More
Seismic Solvability ProblemsDec 06 2012Classical approach of solvability problem has shed much light on what we can solve and what we cannot solve mathematically. Starting with quadratic equation, we know that we can solve it by the quadratic formula which uses square root. Polynomial is a ... More
Geometric theory of inversion and seismic imagingJun 01 2015The goal of inversion is to estimate the model which generates the data of observations with a specific modeling equation. One general approach to inversion is to use optimization methods which are algebraic in nature to define an objective function. ... More
L0+L1+L2 mixed optimization: a geometric approach to seismic imaging and inversion using concepts in topology and semigroupJul 12 2010The mathematical interpretation of L0, L1 and L2 is needed to understand how we should use these norms for optimization problems. The L0 norm is combinatorics which is counting certain properties of an object or an operator. This is the least amplitude ... More
Using Recurrent Neural Networks to Optimize Dynamical Decoupling for Quantum MemoryApr 01 2016Sep 17 2016We utilize machine learning models which are based on recurrent neural networks to optimize dynamical decoupling (DD) sequences. DD is a relatively simple technique for suppressing the errors in quantum memory for certain noise models. In numerical simulations, ... More
Involutions on $S[ΩM]$Oct 11 2005The contribution of this PhD thesis is to construct for each vector bundle $\xi$ an orthogonal ring spectrum $R$, weakly equivalent to $S[\Omega M]$, together with an involution on $R$. On the homotopy groups $\pi_*S[\Omega M]$ our involution corresponds ... More
Influence of a magnetic fluxon on the vacuum energy of quantum fields confined by a bagDec 11 1996We study the simultaneous influence of boundary conditions and external fields on quantum fluctuations by considering vacuum zero-point energies for quantum fields in the presence of a magnetic fluxon confined by a bag, circular and spherical for bosons ... More
On the Landau-gauge adjoint quark propagatorApr 16 2013Quarks in the adjoint representation have been a subject of study for both conceptual and practical purposes. Conceptually, their differences when it comes to confining and chiral symmetry properties has long been suspected to hold important information ... More
Direct and indirect seismic inversion: interpretation of certain mathematical theoremsNov 04 2017Quantitative methods are more familiar to most geophysicists with direct inversion or indirect inversion. We will discuss seismic inversion in a high level sense without getting into the actual algorithms. We will stay with meta-equations and argue pros ... More
Accretion Shocks in Clusters of Galaxies and their SZ Signature from Cosmological SimulationsFeb 19 2009Cold dark matter (CDM) hierarchical structure formation models predict the existence of large-scale accretion shocks between the virial and turnaround radii of clusters of galaxies. Kocsis et al. (2005) suggest that the Sunyaev-Zel'dovich (SZ) signal ... More
The X-ray Cluster Normalization of the Matter Power SpectrumSep 23 2008The number density of galaxy clusters provides tight statistical constraints on the matter fluctuation power spectrum normalization, traditionally phrased in terms of sigma_8, the root mean square mass fluctuation in spheres with radius 8 h^-1 Mpc. We ... More
The X-ray Size-Temperature Relation for Intermediate Redshift Galaxy ClustersApr 18 2000Jul 02 2000We present the first measurements of the X-ray size-temperature (ST) relation in intermediate redshift (z~0.30) galaxy clusters. We interpret the local ST relation (z~0.06) in terms of underlying scaling relations in the cluster dark matter properties, ... More
RHAPSODY-G simulations II - Baryonic growth and metal enrichment in massive galaxy clustersOct 02 2015Apr 14 2016We study the evolution of the stellar component and the metallicity of both the intracluster medium and of stars in massive ($M_{\rm vir}\approx 6\times 10^{14}$ M$_{\odot}/h$) simulated galaxy clusters from the Rhapsody-G suite in detail and compare ... More
Persistent, Global Identity for Scientists via ORCIDFeb 22 2015Scientists have an inherent interest in claiming their contributions to the scholarly record, but the fragmented state of identity management across the landscape of astronomy, physics, and other fields makes highlighting the contributions of any single ... More
Problem Roulette: Studying Introductory Physics in the CloudSep 30 2013Problem Roulette (PR) is a web-based study service at the University of Michigan that offers random-within-topic access to a large library of past exam problems in introductory physics courses. Built on public-private cloud computing infrastructure, PR ... More
Cosmological Simulations with Scale-Free Initial Conditions I: Adiabatic HydrodynamicsMay 14 1997Apr 24 1998We analyze hierarchical structure formation based on scale-free initial conditions in an Einstein-de Sitter universe, including a baryonic component. We present three independent, smoothed particle hydrodynamics (SPH) simulations, performed with two different ... More
Cluster Cosmology at a Crossroads: Neutrino MassesFeb 20 2013Mar 05 2013Galaxy clusters --- in combination with CMB and BAO data --- can provide precise constraints on the sum of neutrino masses. However, these constraints depend on the calibration of the mass--observable relation. For instance, the mass calibration employed ... More
A Comparative Study of Local Galaxy Clusters: I. Derived X-ray ObservablesApr 27 2012We examine systematic differences in the derived X-ray properties of galaxy clusters as reported by three different groups: Vikhlinin et al. (2009a), Mantz et al. (2010b), and Planck Collaboration (2011b). The sample overlap between any two pairs of works ... More
Galaxy Cluster Mass Estimation from Stacked Spectroscopic AnalysisJan 21 2016We use simulated galaxy surveys to study: i) how galaxy membership in redMaPPer clusters maps to the underlying halo population, and ii) the accuracy of a mean dynamical cluster mass, $M_\sigma(\lambda)$, derived from stacked pairwise spectroscopy of ... More
Rhapsody-G simulations: galaxy clusters as baryonic closed boxes and the covariance between hot gas and galaxiesMar 13 2015Jul 22 2015Within a sufficiently large cosmic volume, conservation of baryons implies a simple `closed box' view in which the sum of the baryonic components must equal a constant fraction of the total enclosed mass. We present evidence from Rhapsody-G hydrodynamic ... More
Virial scaling of galaxies in clusters: bright to faint is cool to hotJun 28 2013Sep 19 2013By combining galaxy tracers from high-resolution N-body and hydrodynamical simulations, we present a consistent picture of the behaviour of galaxy velocities in massive clusters. In haloes above ~ 10^14 Msun, the brightest satellite galaxies are slightly ... More
The Evolution of Radio Galaxies and X-ray Point Sources in Coma Cluster Progenitors Since z~1.2Jul 10 2011Using Chandra imaging spectroscopy and Very Large Array (VLA) L-band radio maps, we have identified radio sources at P_{1.4GHz} >=5x10^{23} W Hz^{-1} and X-ray point sources (XPSs) at L_{0.3-8keV}>=5x10^{42} erg s^{-1} in L>L* galaxies in 12 high-redshift ... More
Extrinsic Sources of Scatter in the Richness-Mass Relation of Galaxy ClustersApr 11 2011Maximizing the utility of upcoming photometric cluster surveys requires a thorough understanding of the richness-mass relation of galaxy clusters. We use Monte Carlo simulations to study the impact of various sources of observational scatter on this relation. ... More
Rhapsody-G simulations I: the cool cores, hot gas and stellar content of massive galaxy clustersSep 14 2015We present the Rhapsody-G suite of cosmological hydrodynamic AMR zoom simulations of ten massive galaxy clusters at the $M_{\rm vir}\sim10^{15}\,{\rm M}_\odot$ scale. These simulations include cooling and sub-resolution models for star formation and stellar ... More
The Asymptotic Structure of Space-TimeAug 13 2003Astronomical observations strongly suggest that our universe is now accelerating and contains a substantial admixture of dark vacuum energy. Using numerical simulations to study this newly consolidated cosmological model (with a constant density of dark ... More
Scaling Rrelation in two situations of extreme mergersDec 17 2010Clusters of galaxies are known to be dynamically active systems, yet X-ray studies of the low redshift population exhibit tight scaling laws. In this work, we extend previous studies of this apparent paradox using numerical simulations of two extreme ... More
The Merger in Abell 576: A Line of Sight Bullet Cluster?Jun 08 2007Using a combination of Chandra and XMM observations, we confirmed the presence of a significant velocity gradient along the NE/E-W/SW direction in the intracluster gas of the cluster Abell 576. The results are consistent with a previous ASCA SIS analysis ... More
Studying Dark Energy with Galaxy Cluster SurveysAug 05 2002Galaxy cluster surveys provide a powerful means of studying the density and nature of the dark energy. The redshift distribution of detected clusters in a deep, large solid angle SZE or X-ray survey is highly sensitive to the dark energy equation of state. ... More
Expectations For an Interferometric Sunyaev-Zel'dovich Effect Survey for Galaxy ClustersDec 17 1999Dec 22 2000Non-targeted surveys for galaxy clusters using the Sunyaev-Zel'dovich effect (SZE) will yield valuable information on both cosmology and evolution of the intra-cluster medium (ICM). The redshift distribution of detected clusters will constrain cosmology, ... More
Closing the Loop: A Self-Consistent Model of Optical, X-ray, and SZ Scaling Relations for Clusters of GalaxiesApr 27 2012Jun 14 2012We demonstrate that optical data from SDSS, X-ray data from ROSAT and Chandra, and SZ data from Planck, can be modeled in a fully self-consistent manner. After accounting for systematic errors and allowing for property covariance, we find that scaling ... More
A Comparative Study of Local Galaxy Clusters: II: X-ray and SZ Scaling RelationsApr 27 2012Jun 14 2012We compare cluster scaling relations published for three different samples selected via X-ray and Sunyaev-Zel'dovich (SZ) signatures. We find tensions driven mainly by two factors: i) systematic differences in the X-ray cluster observables used to derive ... More
Perturbative zero-point energy for a cylinder of elliptical sectionJul 25 2006We examine the Casimir effect for a perfectly conducting cylinder of elliptical section, taking as reference the known case of circular section. The zero-point energy of this system is evaluated by the mode summation method, using the ellipticity as a ... More
Vacuum densities and zero-point energy for fields obeying Robin conditions on cylindrical surfacesJan 24 2001The Casimir effect for general Robin conditions on the surface of a cylinder in $D$-spacetime dimensions is studied for massive scalar field with general curvature coupling. The energy distribution and vacuum stress are investigated. We separate volumic ... More
Getting the Measure of the Flatness ProblemJul 06 1995The problem of estimating cosmological parameters such as $\Omega$ from noisy or incomplete data is an example of an inverse problem and, as such, generally requires a probablistic approach. We adopt the Bayesian interpretation of probability for such ... More
Nonlinear Sturm Oscillation: from the interval to a starOct 22 2016The so-called Sturm oscillation property, e.g. that the $n$-th eigenfunction of a Sturm-Liouville operator on a line segment has $n -1$ zeros (nodes), has been well studied. This result is known to hold when the interval is replaced by a tree graph. We ... More
Structure of Noncommutative Solitons: Existence and Spectral TheoryNov 16 2014We consider the Schr\"odinger equation with a Hamiltonian given by a second order difference operator with nonconstant growing coefficients, on the half one dimensional lattice. This operator appeared first naturally in the construction and dynamics of ... More
Casimir Energy for a Purely Dielectric Cylinder by the Mode Summation MethodApr 25 2005We use the mode summation method together with zeta-function regularization to compute the Casimir energy of a dilute dielectric cylinder. The method is very transparent, and sheds light on the reason the resulting energy vanishes.
Nonlinear Sturm Oscillation: from the interval to a starOct 22 2016May 16 2017The Sturm oscillation property, i.e. that the $n$-th eigenfunction of a Sturm-Liouville operator on an interval has $n -1$ zeros (nodes), has been well studied. This result is known to hold when the interval is replaced by a metric (quantum) tree graph. ... More
Dynamics of Noncommutative Solitons I: Spectral Theory and Dispersive EstimatesNov 16 2014We consider the Schr\"odinger equation with a Hamiltonian given by a second order difference operator with nonconstant growing coefficients, on the half one dimensional lattice. This operator appeared first naturally in the construction and dynamics of ... More
Conformal Sector in $D=6$ Quantum GravityOct 26 1994We discuss the conformal factor dynamics in $D=6$. Accepting the proposal that higher-derivative dimensionless terms in the anomaly-induced effective action may be dropped, we obtain a superrenormalizable (like in $D=4$) effective theory for the conformal ... More
Efficient approximation for global functions of matrix product operatorsApr 10 2018Apr 13 2018Building on a previously introduced block Lanczos method, we demonstrate how to approximate any operator function of the form Trf (A) when the argument A is given as a Hermitian matrix product operator. This gives access to quantities that, depending ... More
The Role of Machine Learning in the Next Decade of CosmologyFeb 26 2019In recent years, machine learning (ML) methods have remarkably improved how cosmologists can interpret data. The next decade will bring new opportunities for data-driven cosmological discovery, but will also present new challenges for adopting ML methodologies ... More
Effective potential for a covariantly constant gauge field in curved spacetimeJul 24 1996We discuss the influence of gravitational effects on the stabilization of the chromomagnetic vacuum. The one-loop effective potential for a covariantly constant SU(2) gauge field in ${\bf S}^2 \times {\bf R}^2$ and ${\bf T}^2 \times {\bf R}^2$ is calculated. ... More
Manifestations of Quantum Gravityin Scalar QED PhenomenaOct 05 1994Quantum gravitational corrections to the effective potential, at one-loop level and in the leading-log approximation, for scalar quantum electrodynamics with higher-derivative gravity ---which is taken as an effective theory for quantum gravity (QG)--- ... More
The influence of local field corrections on Thomson scattering in non-ideal two-component plasmasJun 19 2009Thomson scattering in non-ideal (collision-dominated) two-component plasmas is calculated accounting for electron-ion collisions as well as electron-electron correlations. This is achieved by using a novel interpolation scheme for the electron-electron ... More
Amoebas of complex hypersurfaces in statistical thermodynamicsDec 19 2011The amoeba of a complex hypersurface is its image under a logarithmic projection. A number of properties of algebraic hypersurface amoebas are carried over to the case of transcendental hypersurfaces. We demonstrate the potential that amoebas can bring ... More
A Dynamical Model of Lipoprotein MetabolismOct 28 2006We present a dynamical model of lipoprotein metabolism derived by combining a cascading process in the blood stream and cellular level regulatory dynamics. We analyse the existence and stability of equilibria and show that this low-dimensional, nonlinear ... More
Autoionizing Resonances in Time-Dependent Density Functional TheoryFeb 11 2009Jun 30 2009Autoionizing resonances that arise from the interaction of a bound single-excitation with the continuum can be accurately captured with the presently used approximations in time-dependent density functional theory (TDDFT), but those arising from a bound ... More
Bondi Accretion in Trumpet GeometriesJul 11 2016The Bondi solution, which describes the radial inflow of a gas onto a non-rotating black hole, provides a powerful test for numerical relativistic codes. However, the Bondi solution is usually derived in Schwarzschild coordinates, which are not well suited ... More
Optical properties and one-particle spectral function in non-ideal plasmasOct 28 2006A basic concept to calculate physical features of non-ideal plasmas, such as optical properties, is the spectral function which is linked to the self-energy. We calculate the spectral function for a non-relativistic hydrogen plasma in $GW$-approximation. ... More
Singularities of Nonconfluent Hypergeometric Functions in Several VariablesMay 13 2004The paper deals with singularities of nonconfluent hypergeometric functions in several variables. Typically such a function is a multi-valued analytic function with singularities along an algebraic hypersurface. We describe such hypersurfaces in terms ... More
On the Approximation of Functionals of Very Large Hermitian Matrices represented as Matrix Product OperatorsOct 19 2016We present a method to approximate functionals $\text{Tr} \, f(A)$ of very high-dimensional hermitian matrices $A$ represented as Matrix Product Operators (MPOs). Our method is based on a reformulation of a block Lanczos algorithm in tensor network format. ... More
Improved Effective Potential in Curved Spacetime and Quantum Matter - Higher Derivative Gravity TheoryOct 17 1994\noindent{\large\bf Abstract.} We develop a general formalism to study the renormalization group (RG) improved effective potential for renormalizable gauge theories ---including matter-$R^2$-gravity--- in curved spacetime. The result is given up to quadratic ... More
Zeta-Regularization of the O(N) Non-Linear Sigma Model in D dimensionsMay 17 1995Nov 24 1995The O(N) non-linear sigma model in a $D$-dimensional space of the form ${\bf R}^{D-M} \times {\bf T}^M$, ${\bf R}^{D-M} \times {\bf S}^M$, or ${\bf T}^M \times {\bf S}^P$ is studied, where ${\bf R}^M$, ${\bf T}^M$ and ${\bf S}^M$ correspond to flat space, ... More
Cross-correlation Weak Lensing of SDSS galaxy Clusters II: Cluster Density Profiles and the Mass--Richness RelationSep 09 2007We interpret and model the statistical weak lensing measurements around 130,000 groups and clusters of galaxies in the Sloan Digital Sky Survey presented by Sheldon et al. 2007 (Paper I). We present non-parametric inversions of the 2D shear profiles to ... More
MaxBCG: A Red Sequence Galaxy Cluster FinderJan 09 2007Measurements of galaxy cluster abundances, clustering properties, and mass to- light ratios in current and future surveys can provide important cosmological constraints. Digital wide-field imaging surveys, the recently-demonstrated fidelity of red-sequence ... More