Results for "Anja von der Linden"

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Center-Excised X-ray Luminosity as an Efficient Mass Proxy for Future Galaxy Cluster SurveysMay 25 2017Oct 26 2017The cosmological constraining power of modern galaxy cluster catalogs can be improved by obtaining low-scatter mass proxy measurements for even a small fraction of sources. In the context of large upcoming surveys that will reveal the cluster population ... More
How special are Brightest Group and Cluster Galaxies?Nov 07 2006May 07 2007We use the Sloan Digital Sky Survey to construct a sample of 625 brightest group and cluster galaxies (BCGs) together with control samples of non-BCGs matched in stellar mass, redshift, and color. We investigate how the systematic properties of BCGs depend ... More
Cluster Galaxies Die HardDec 14 2009Apr 16 2010We investigate how the specific star formation rates of galaxies of different masses depend on cluster-centric radius and on the central/satellite dichotomy in both field and cluster environments. Recent data from a variety of sources, including the cluster ... More
Cold dark energy constraints from the abundance of galaxy clustersJan 25 2017Nov 22 2017We constrain cold dark energy of negligible sound speed using galaxy cluster abundance observations. In contrast to standard quasi-homogeneous dark energy, negligible sound speed implies clustering of the dark energy fluid at all scales, allowing us to ... More
Cosmology and Astrophysics from Relaxed Galaxy Clusters I: Sample SelectionFeb 20 2015This is the first in a series of papers studying the astrophysics and cosmology of massive, dynamically relaxed galaxy clusters. Here we present a new, automated method for identifying relaxed clusters based on their morphologies in X-ray imaging data. ... More
Angular Momenta, Dynamical Masses, and Mergers of Brightest Cluster GalaxiesOct 28 2013Using the VIMOS Integral Field Unit (IFU) spectrograph on the Very Large Telescope (VLT), we have spatially mapped the kinematic properties of 10 nearby Brightest Cluster Galaxies (BCGs) and 4 BCG companion galaxies located within a redshift of $z=0.1$. ... More
Revealing the properties of dark matter in the merging cluster MACSJ0025.4-1222Jun 13 2008Jul 23 2008We constrain the physical nature of dark matter using the newly identified massive merging galaxy cluster MACSJ0025.4-1222. As was previously shown by the example of the Bullet Cluster (1E0657-56), such systems are ideal laboratories for detecting isolated ... More
New constraints on $f(R)$ gravity from clusters of galaxiesNov 29 2014Aug 08 2015The abundance of massive galaxy clusters is a powerful probe of departures from General Relativity (GR) on cosmic scales. Despite current stringent constraints placed by stellar and galactic tests, on larger scales alternative theories of gravity such ... More
Cl 1103.7-1245 at z=0.96: the highest redshift galaxy cluster in the EDisCS surveyJul 06 2012We present new spectroscopic observations in a field containing the highest redshift cluster of the ESO Distant Cluster Survey (EDisCS). We measure galaxy redshifts and determine the velocity dispersions of the galaxy structures located in this field. ... More
Cosmology and Astrophysics from Relaxed Galaxy Clusters II: Cosmological ConstraintsFeb 25 2014Mar 21 2014We present cosmological constraints from measurements of the gas mass fraction, $f_{gas}$, for massive, dynamically relaxed galaxy clusters. Our data set consists of Chandra observations of 40 such clusters, identified in a comprehensive search of the ... More
The accretion histories of brightest cluster galaxies from their stellar population gradientsMar 04 2015We analyse the spatially-resolved stellar populations of 9 local ($z<0.1$) Brightest Cluster Galaxies (BCGs) observed with VIMOS in IFU mode. Our sample is composed of 7 slow-rotating and 2 fast-rotating BCGs. We do not find a connection between stellar ... More
The evolution of the density of galaxy clusters and groups: denser environments at higher redshiftsFeb 18 2010We show that, observationally, the projected local density distribution in high-z clusters is shifted towards higher values compared to clusters at lower redshift. To search for the origin of this evolution, we analyze a sample of haloes selected from ... More
Sausage Instabilities on Top of Kinking Lengthening Current-Carrying Magnetic Flux TubesMar 26 2017Jun 22 2018We theoretically explore the possibility of sausage instabilities developing on top of a kink instability in lengthening current-carrying magnetic flux tubes. Observations indicate that the dynamics of magnetic flux tubes in our cosmos and terrestrial ... More
Robust Weak-lensing Mass Calibration of Planck Galaxy ClustersFeb 11 2014Oct 09 2014In light of the tension in cosmological constraints reported by the Planck team between their SZ-selected cluster counts and Cosmic Microwave Background (CMB) temperature anisotropies, we compare the Planck cluster mass estimates with robust, weak-lensing ... More
Thermoelectric properties of a strongly correlated layerApr 10 2017Sep 06 2017In this paper we investigate the effect of strong electronic interactions on the thermoelectric properties of a simple generic system, consisting of a single correlated layer sandwiched between two metallic leads. Results will be given for the linear ... More
Resonance Effects in Correlated Multilayer HeterostructuresJul 18 2016Dec 29 2016We study the occurrence of negative differential conductance induced by resonance effects in a model for a multilayer heterostructure. In particular, we consider a system consisting of several correlated and non-correlated monoatomic layers, sandwiched ... More
The Grism Lens-Amplified Survey from Space (GLASS). V. Extent and spatial distribution of star formation in z~0.5 cluster galaxiesNov 02 2015We present the first study of the spatial distribution of star formation in z~0.5 cluster galaxies. The analysis is based on data taken with the Wide Field Camera 3 as part of the Grism Lens-Amplified Survey from Space (GLASS). We illustrate the methodology ... More
The Rest-Frame Optical Luminosity Function of Cluster Galaxies at z<0.8 and the Assembly of the Cluster Red SequenceMay 27 2009We present the rest-frame optical luminosity function (LF) of red sequence galaxies in 16 clusters at 0.4<z<0.8 drawn from the ESO Distant Cluster Survey (EDisCS). We compare our clusters to an analogous sample from the Sloan Digital Sky Survey (SDSS) ... More
Weighing the Giants II: Improved Calibration of Photometry from Stellar Colors and Accurate Photometric RedshiftsAug 02 2012Apr 19 2014We present improved methods for using stars found in astronomical exposures to calibrate both star and galaxy colors as well as to adjust the instrument flat field. By developing a spectroscopic model for the SDSS stellar locus in color-color space, synthesizing ... More
Weighing the Giants - I. Weak-lensing masses for 51 massive galaxy clusters: project overview, data analysis methods and cluster imagesAug 02 2012Apr 18 2014This is the first in a series of papers in which we measure accurate weak-lensing masses for 51 of the most X-ray luminous galaxy clusters known at redshifts 0.15<z<0.7, in order to calibrate X-ray and other mass proxies for cosmological cluster experiments. ... More
Quantum Monte Carlo and variational approaches to the Holstein modelMay 16 2003Jan 24 2004Based on the canonical Lang-Firsov transformation of the Hamiltonian we develop a very efficient quantum Monte Carlo algorithm for the Holstein model with one electron. Separation of the fermionic degrees of freedom by a reweighting of the probability ... More
Effect of the exchange hole on the Gutzwiller approximation in one dimensionJun 16 2009Jul 27 2009The Gutzwiller approximate solution to the Gutzwiller wavefunction yields exact results for the Gutzwiller wavefunction in the infinite dimensional limit. Implicit in the Gutzwiller approximation is an approximate local form of the fermion exchange hole. ... More
Holstein polaron in two and three dimensions by quantum Monte CarloJan 30 2004A recently developed quantum Monte Carlo approach to the Holstein model with one electron [PRB 69, 024301 (2004)] is extended to two and three dimensional lattices. A moderate sign problem occurs, which is found to diminish with increasing system size ... More
Current characteristics of a one-dimensional Hubbard chain: The role of correlation and dissipationJun 16 2015We study the electronic transport in an infinite one-dimensional Hubbard chain, driven by a homogeneous electric field. The physical chain is coupled to fermion bath chains, in order to account for dissipation and to prevent the occurrence of Bloch Oscillations. ... More
Nested sampling, statistical physics and the Potts modelMar 08 2016Dec 08 2017We present a systematic study of the nested sampling algorithm based on the example of the Potts model. This model, which exhibits a first order phase transition for $q>4$, exemplifies a generic numerical challenge in statistical physics: The evaluation ... More
Prediction of High-Tc conventional Superconductivity in the Ternary Lithium Borohydride SystemMay 19 2017We investigate the superconducting ternary lithium borohydride phase diagram at pressures of 0 and 200$\,$GPa using methods for evolutionary crystal structure prediction and linear-response calculations for the electron-phonon coupling. Our calculations ... More
Measurements of the Canonical Helicity of a Gyrating KinkMar 14 2018Jul 19 2018Conversions between magnetic and kinetic energy occur over a range of plasma scales in astrophysical and solar dynamos and reconnection in the solar corona and the laboratory. Canonical flux tubes reconcile all plasma regimes with concepts of twists, ... More
Precise weak lensing constraints from deep high-resolution $K_\mathrm{s}$ images: VLT/HAWK-I analysis of the super-massive galaxy cluster RCS2$J$232727.7$-$020437 at $z=0.70$Nov 01 2017Apr 04 2018We demonstrate that deep good-seeing VLT/HAWK-I $K_\mathrm{s}$ images complemented with $g$+$z$-band photometry can yield a sensitivity for weak lensing studies of massive galaxy clusters at redshifts \mbox{$0.7\lesssim z \lesssim 1.1$}, which is almost ... More
Spitzer UltRa Faint SUrvey Program (SURFS UP). II. IRAC-Detected Lyman-Break Galaxies at 6 < z < 10 Behind Strong-Lensing ClustersApr 08 2015Jan 05 2016We study the stellar population properties of the IRAC-detected $6 \lesssim z \lesssim 10$ galaxy candidates from the Spitzer UltRa Faint SUrvey Program (SURFS UP). Using the Lyman Break selection technique, we find a total of 16 new galaxy candidates ... More
Nonequilibrium, spatio-temporal formation of the Kondo screening-cloud on a latticeSep 02 2014Mar 03 2015We study the nonequilibrium formation of a spin screening cloud that accompanies the quenching of a local magnetic moment immersed in a Fermi sea at zero temperature. Based on high precision density matrix renormalization group results for the interacting ... More
Effective spinless fermions in the strong coupling Kondo modelJun 05 2002Nov 21 2002Starting from the two-orbital Kondo-lattice model with classical t_2g spins, an effective spinless fermion model is derived for strong Hund coupling J_H with a projection technique. The model is studied by Monte Carlo simulations and analytically using ... More
Non-equilibrium Green's functions and their relation to the negative differential conductance in the interacting resonant level modelDec 20 2018Jan 23 2019We evaluate the non-equilibrium single particle Green's functions in the steady state of the interacting resonant level model (IRLM) under the effect of an applied bias voltage. Employing the so-called auxiliary master equation approach, we present accurate ... More
Charge redistribution in correlated heterostuctures within nonequilibrium real-space dynamical mean-field theoryMay 02 2018Aug 13 2018We address the steady-state behavior of a system consisting of several correlated monoatomic layers sandwiched between two metallic leads under the influence of a bias voltage. In particular, we investigate the effect of the local Hubbard and of the long-range ... More
RCS2 J232727.6-020437: An Efficient Cosmic Telescope at $z=0.6986$Mar 09 2015We present a detailed gravitational lens model of the galaxy cluster RCS2 J232727.6-020437. Due to cosmological dimming of cluster members and ICL, its high redshift ($z=0.6986$) makes it ideal for studying background galaxies. Using new ACS and WFC3/IR ... More
Weighing the Giants IV: Cosmology and Neutrino MassJul 16 2014Nov 26 2014We employ robust weak gravitational lensing measurements to improve cosmological constraints from measurements of the galaxy cluster mass function and its evolution, using X-ray selected clusters detected in the ROSAT All-Sky Survey. Our lensing analysis ... More
The relation between star formation, morphology and local density in high redshift clusters and groupsMay 08 2008We investigate how the [OII] properties and the morphologies of galaxies in clusters and groups at z=0.4-0.8 depend on projected local galaxy density, and compare with the field at similar redshifts and clusters at low-z. In both nearby and distant clusters, ... More
Deep Multi-object Spectroscopy to Enhance Dark Energy Science from LSSTMar 22 2019Community access to deep (i ~ 25), highly-multiplexed optical and near-infrared multi-object spectroscopy (MOS) on 8-40m telescopes would greatly improve measurements of cosmological parameters from LSST. The largest gain would come from improvements ... More
Emission characteristics of laser-driven dissipative coupled-cavity systemsNov 11 2010Feb 25 2011We consider a laser-driven and dissipative system of two coupled cavities with Jaynes-Cummings nonlinearity. In particular, we investigate both incoherent and coherent laser driving, corresponding to different experimental situations. We employ Arnoldi ... More
Magnetic Polarons in the 1D FM Kondo ModelJan 20 2003Jan 23 2003The ferromagnetic Kondo model with classical corespins is studied via unbiased Monte-Carlo simulations. We show that with realistic parameters for the manganites and at low temperatures, the double-exchange mechanism does not lead to phase separation ... More
Auxiliary master equation approach within matrix product states: Spectral properties of the nonequilibrium Anderson impurity modelJul 10 2015Dec 09 2015Within the recently introduced auxiliary master equation approach it is possible to address steady state properties of strongly correlated impurity models, small molecules or clusters efficiently and with high accuracy. It is particularly suited for dynamical ... More
Steady-state and quench dependent relaxation of a quantum dot coupled to one-dimensional leadsJan 14 2013Jul 30 2013We study the time evolution and steady state of the charge current in a single-impurity Anderson model, using matrix product states techniques. A nonequilibrium situation is imposed by applying a bias voltage across one-dimensional tight-binding leads. ... More
Spatial kinematics of Brightest Cluster Galaxies and their close companions from Integral Field Unit spectroscopyApr 07 2011We present Integral Field Unit (IFU) spectroscopy of four brightest cluster galaxies (BCGs) at z~0.1. Three of the BCGs have close companions within a projected radius of 20 kpc and one has no companion within that radius. We calculate the dynamical masses ... More
Uniform hopping approach to the FM Kondo Model at finite temperatureNov 28 2002Nov 29 2002We study the ferromagnetic Kondo model with classical corespins via unbiased Monte-Carlo simulations and derive a simplified model for the treatment of the corespins at any temperature. Our simplified model captures the main aspects of the Kondo model ... More
Low Temperature Lanczos MethodNov 08 2002We present a modified finite temperature Lanczos method for the evaluation of dynamical and static quantities of strongly correlated electron systems that complements the finite temperature method (FTLM) introduced by Jaklic and Prelovsek for low temperatures. ... More
Analysis of femtosecond pump-probe photoelectron-photoion coincidence measurements applying Bayesian probability theorySep 13 2017Jun 08 2018Ultrafast dynamical processes in photoexcited molecules can be observed with pump-probe measurements, in which information about the dynamics is obtained from the transient signal associated with the excited state. Background signals provoked by pump ... More
First-principles molecular transport calculation for the benzenedithiolate moleculeMay 05 2017Oct 09 2017A first-principles approach based on Density Functional Theory and Non-Equilibrium Green's functions is used to study the molecular transport system consisting of benzenedithiolate connected with monoatomic gold and platinum electrodes. Using symmetry ... More
Thermoelectric response of a correlated impurity in the nonequilibrium Kondo regimeAug 19 2016Mar 19 2017We study nonequilibrium thermoelectric transport properties of a correlated impurity connected to two leads for temperatures below the Kondo scale. At finite bias, for which a current flows across the leads, we investigate the differential response of ... More
Master equation based steady-state cluster perturbation theoryMay 07 2015A simple and efficient approximation scheme to study electronic transport characteristics of strongly correlated nano devices, molecular junctions or heterostructures out of equilibrium is provided by steady-state cluster perturbation theory. In this ... More
Auxiliary master equation approach within stochastic wave functions: Application to the Interacting Resonant Level ModelDec 05 2018Dec 11 2018We present further developments of the auxiliary master equation approach (AMEA), a numerical method to simulate many-body quantum systems in as well as out of equilibrium, and apply it to the Interacting Resonant Level Model (IRLM) to benchmark the new ... More
Homology and homotopy in semi-abelian categoriesJul 04 2006The theory of abelian categories proved very useful, providing an axiomatic framework for homology and cohomology of modules over a ring and, in particular, of abelian groups. For many years, a similar categorical framework has been lacking for non-abelian ... More
Simplicial homotopy in semi-abelian categoriesJul 04 2006We study Quillen's model category structure for homotopy of simplicial objects in the context of Janelidze, Marki and Tholen's semi-abelian categories. This model structure exists as soon as the base category A is regular Mal'tsev and has enough regular ... More
Multiple Images of a Highly Magnified Supernova Formed by an Early-Type Cluster Galaxy LensNov 21 2014Mar 05 2015In 1964, Refsdal hypothesized that a supernova whose light traversed multiple paths around a strong gravitational lens could be used to measure the rate of cosmic expansion. We report the discovery of such a system. In Hubble Space Telescope imaging, ... More
The ESO Distant Cluster Sample: galaxy evolution and environment out to z=1Apr 29 2009The ESO Distant Cluster Survey (EDisCS, P.I. Simon D.M. White, LP 166.A-0162) is an ESO large programme aimed at studying clusters and cluster galaxies at z=0.4-1. How different is the evolution of the star formation activity in clusters, in groups and ... More
Steady-state spectra, current and stability diagram of a quantum dot: a non-equilibrium Variational Cluster ApproachJul 24 2012Oct 16 2012We calculate steady-state properties of a strongly correlated quantum dot under voltage bias by means of non-equilibrium Cluster Perturbation Theory and the non-equilibrium Variational Cluster Approach, respectively. Results for the steady-state current ... More
WFIRST Science Investigation Team "Cosmology with the High Latitude Survey" Annual Report 2017Apr 10 2018Cosmic acceleration is the most surprising cosmological discovery in many decades. Testing and distinguishing among possible explanations requires cosmological measurements of extremely high precision probing the full history of cosmic expansion and structure ... More
Scientific Synergy Between LSST and EuclidOct 23 2017Nov 29 2017Euclid and the Large Synoptic Survey Telescope (LSST) are poised to dramatically change the astronomy landscape early in the next decade. The combination of high cadence, deep, wide-field optical photometry from LSST with high resolution, wide-field optical ... More
Measuring cosmic distances with galaxy clustersJul 30 2013In addition to cosmological tests based on the mass function and clustering of galaxy clusters, which probe the growth of cosmic structure, nature offers two independent ways of using clusters to measure cosmic distances. The first uses measurements of ... More
X-ray bright active galactic nuclei in massive galaxy clusters III: New insights into the triggering mechanisms of cluster AGNJul 30 2014We present the results of a new analysis of the X-ray selected Active Galactic Nuclei (AGN) population in the vicinity of 135 of the most massive galaxy clusters in the redshift range of 0.2 < z < 0.9 observed with Chandra. With a sample of more than ... More
X-ray Bright Active Galactic Nuclei in Massive Galaxy Clusters I: Number Counts and Spatial DistributionSep 10 2012Dec 14 2012We present an analysis of the X-ray bright point source population in 43 massive clusters of galaxies observed with the Chandra X-ray Observatory. We have constructed a catalog of 4210 rigorously selected X-ray point sources in these fields, which span ... More
A decomposition formula for the weighted commutatorApr 04 2013We decompose the weighted subobject commutator of M. Gran, G. Janelidze and A. Ursini as a join of a binary and a ternary commutator.
On the "three subobjects lemma" and its higher-order generalisationsMar 30 2019We solve a problem mentioned in an article of Berger and Bourn: we prove that in the context of an algebraically coherent semi-abelian category, two natural definitions of the lower central series coincide. In a first, "standard" approach, nilpotency ... More
A comonadic interpretation of Baues-Ellis homology of crossed modulesMay 20 2018We introduce and study a homology theory of crossed modules with coefficients in an abelian crossed module. We discuss the basic properties of these new homology groups and give some applications. We then restrict our attention to the case of integral ... More
Categories vs. groupoids via generalised Mal'tsev propertiesJun 13 2012Aug 18 2014We study the difference between internal categories and internal groupoids in terms of generalised Mal'tsev properties---the weak Mal'tsev property on the one hand, and $n$-permutability on the other. In the first part of the article we give conditions ... More
A characterisation of Lie algebras via algebraic exponentiationNov 02 2017Oct 22 2018In this article we describe varieties of Lie algebras via algebraic exponentiation, a concept introduced by Gray in his Ph.D. thesis. For $\mathbb{K}$ an infinite field of characteristic different from $2$, we prove that the variety of Lie algebras over ... More
Further remarks on the "Smith is Huq" conditionJan 22 2014We compare the 'Smith is Huq' condition (SH) with three commutator conditions in semi-abelian categories: first an apparently weaker condition which arose in joint work with Bourn and turns out to be equivalent with (SH), then an apparently equivalent ... More
Higher extensions in exact Mal'tsev categories: distributivity of congruences and the $3^n$-LemmaJul 09 2018The aim of this article is to better understand the correspondence between $n$-cubic extensions and $3^n$-diagrams, which may be seen as non-abelian Yoneda extensions, useful in (co)homology of non-abelian algebraic structures. We study a higher-dimensional ... More
A comparison theorem for simplicial resolutionsJul 24 2007Oct 08 2007It is well known that Barr and Beck's definition of comonadic homology makes sense also with a functor of coefficients taking values in a semi-abelian category instead of an abelian one. The question arises whether such a homology theory has the same ... More
A relative theory of universal central extensionsAug 26 2009Oct 11 2012Basing ourselves on Janelidze and Kelly's general notion of central extension, we study universal central extensions in the context of semi-abelian categories. Thus we unify classical, recent and new results in one conceptual framework. The theory we ... More
Relative Commutator Theory in Semi-Abelian CategoriesAug 19 2011Basing ourselves on the concept of double central extension from categorical Galois theory, we study a notion of commutator which is defined relative to a Birkhoff subcategory B of a semi-abelian category A. This commutator characterises Janelidze and ... More
On the second cohomology group in semi-abelian categoriesNov 14 2005May 07 2007We develop some new aspects of cohomology in the context of semi-abelian categories: we establish a Hochschild-Serre 5-term exact sequence extending the classical one for groups and Lie algebras; we prove that an object is perfect if and only if it admits ... More
The Yoneda isomorphism commutes with homologyMay 20 2015Sep 06 2015We show that, for a right exact functor from an abelian category to abelian groups, Yoneda's isomorphism commutes with homology and, hence, with functor derivation. Then we extend this result to semiabelian domains. An interpretation in terms of satellites ... More
Higher central extensions and cohomologyFeb 18 2015We establish a Galois-theoretic interpretation of cohomology in semi-abelian categories: cohomology with trivial coefficients classifies central extensions, also in arbitrarily high degrees. This allows us to obtain a duality, in a certain sense, between ... More
Universal central extensions in semi-abelian categoriesFeb 22 2013Basing ourselves on Janelidze and Kelly's general notion of central extension, we study universal central extensions in the context of semi-abelian categories. We consider a new fundamental condition on composition of central extensions and give examples ... More
The ternary commutator obstruction for internal crossed modulesJul 05 2011Jun 19 2012In finitely cocomplete homological categories, co-smash products give rise to (possibly higher-order) commutators of subobjects. We use binary and ternary co-smash products and the associated commutators to give characterisations of internal crossed modules ... More
A note on split extensions of bialgebrasJan 03 2017Mar 13 2017We prove a universal characterization of Hopf algebras among cocommutative bialgebras over a field: a cocommutative bialgebra is a Hopf algebra precisely when every split extension over it admits a join decomposition. We also explain why this result cannot ... More
Context-Aware Proactive Content Caching with Service Differentiation in Wireless NetworksJun 14 2016Dec 16 2016Content caching in small base stations or wireless infostations is considered to be a suitable approach to improve the efficiency in wireless content delivery. Placing the optimal content into local caches is crucial due to storage limitations, but it ... More
Context-Aware Hierarchical Online Learning for Performance Maximization in Mobile CrowdsourcingMay 10 2017Nov 08 2018In mobile crowdsourcing (MCS), mobile users accomplish outsourced human intelligence tasks. MCS requires an appropriate task assignment strategy, since different workers may have different performance in terms of acceptance rate and quality. Task assignment ... More
Dark Matter Distribution of Four Low-z Clusters of GalaxiesDec 20 2018We present here the methods and first results of our systematic study of $\sim 10^{14}\ M_{\odot}$ mass substructure in low-redshift ($z<0.12$) clusters. This work capitalizes on the wide field of view of the Dark Energy Camera at the Cerro Tololo Inter-American ... More
Maximizing Science in the Era of LSST: A Community-Based Study of Needed US CapabilitiesOct 05 2016The Large Synoptic Survey Telescope (LSST) will be a discovery machine for the astronomy and physics communities, revealing astrophysical phenomena from the Solar System to the outer reaches of the observable Universe. While many discoveries will be made ... More
The nature of filamentary cold gas in the core of the Virgo ClusterNov 28 2012Mar 06 2013We present a multi-wavelength study of the emission-line nebulae located southeast of the nucleus of M87, the central dominant galaxy of the Virgo Cluster. We report the detection of far-infrared (FIR) [CII] line emission from the nebulae using observations ... More
Probing the extreme realm of AGN feedback in the massive galaxy cluster, RX J1532.9+3021Jun 04 2013Sep 15 2013We present a detailed Chandra, XMM-Newton, VLA and HST analysis of one of the strongest cool core clusters known, RX J1532.9+3021 (z=0.3613). Using new, deep 90 ks Chandra observations, we confirm the presence of a western X-ray cavity or bubble, and ... More
Feedback under the microscope II: heating, gas uplift, and mixing in the nearest cluster coreMar 28 2010Using a combination of deep 574ks Chandra data, XMM-Newton high-resolution spectra, and optical Halpha+NII images, we study the nature and spatial distribution of the multiphase plasma in M87. Our results provide direct observational evidence of `radio ... More
Global three-dimensional simulations of magnetic field evolution in a galactic disk. II. Gas rich galaxiesJan 30 1998A fully three-dimensional computation of induction processes in a disk is performed to investigate the evolution of a large-scale magnetic field in gas-rich barred and spiral galaxies in the presence of field diffusion. As input parameters we use time ... More
Molecular Clouds Close to the Galactic CenterMay 12 1993We demonstrate that the accretion disk model for the Galactic Center region by Linden et al (1993a) is applicable for at least one order of magnitude in radius from the Galactic Center (10 ... 100 pc). The viscosity $\nu$ is shown to be weakly dependent ... More
Recent Developments of NEMO: Detection of Solar Eruptions CharacteristicsMar 23 2011The recent developments in space instrumentation for solar observations and telemetry have caused the necessity of advanced pattern recognition tools for the different classes of solar events. The Extreme ultraviolet Imaging Telescope (EIT) of solar corona ... More
Deep Learning and Data Assimilation for Real-Time Production Prediction in Natural Gas WellsFeb 14 2018Feb 15 2018The prediction of the gas production from mature gas wells, due to their complex end-of-life behavior, is challenging and crucial for operational decision making. In this paper, we apply a modified deep LSTM model for prediction of the gas flow rates ... More
Sunspot number second differences as a precursor of the following 11-year sunspot cycleDec 15 2017Forecasting the strength of the sunspot cycle is highly important for many space weather applications. Our previous studies have shown the importance of sunspot number variability in the declining phase of the current 11-year sunspot cycle to predict ... More
Two characterisations of groups amongst monoidsJun 28 2016Apr 26 2017The aim of this paper is to solve a problem proposed by Dominique Bourn: to provide a categorical-algebraic characterisation of groups amongst monoids and of rings amongst semirings. In the case of monoids, our solution is given by the following equivalent ... More
A criterion for reflectiveness of normal extensionsFeb 08 2016We give a new sufficient condition for the normal extensions in an admissible Galois structure to be reflective. We then show that this condition is indeed fulfilled when X is the (protomodular) reflective subcategory of S-special objects of a Barr-exact ... More
Phase diagram of selectively cross-linked block copolymers shows chemically microstructured gelSep 29 2014We study analytically the intricate phase behavior of cross-linked $AB$ diblock copolymer melts, which can undergo two main phase transitions due to quenched random constraints: Gelation, i.e., spatially random localization of polymers forming a system-spanning ... More
Tangent-point repulsive potentials for a class of non-smooth $m$-dimensional sets in $\R^n$. Part I: Smoothing and self-avoidance effectsFeb 17 2011We consider repulsive potential energies $\E_q(\Sigma)$, whose integrand measures tangent-point interactions, on a large class of non-smooth $m$-dimensional sets $\Sigma$ in $\R^n.$ Finiteness of the energy $\E_q(\Sigma)$ has three sorts of effects for ... More
Automated LASCO CME catalog for solar cycle 23: are CMEs scale invariant?Oct 07 2008In this paper we present the first automatically constructed LASCO CME catalog, a result of the application of the Computer Aided CME Tracking software (CACTus) on the LASCO archive during the interval September 1997 - January 2007. We have studied the ... More
The fundamental group functor as a Kan extensionJun 29 2013Sep 17 2013We prove that the fundamental group functor from categorical Galois theory may be computed as a Kan extension.
An observation on n-permutabilityJun 27 2013We prove that in a regular category all reflexive and transitive relations are symmetric if and only if every internal category is an internal groupoid. In particular, these conditions hold when the category is n-permutable for some n.
Peri-abelian categories and the universal central extension conditionApr 11 2014Aug 08 2014We study the relation between Bourn's notion of peri-abelian category and conditions involving the coincidence of the Smith, Huq and Higgins commutators. In particular we show that a semi-abelian category is peri-abelian if and only if for each normal ... More
A framework for torsion theory computations on elliptic threefoldsSep 27 2018We give a list of statements on the geometry of elliptic threefolds phrased only in the language of topology and homological algebra. Using only notions from topology and homological algebra, we recover existing results and prove new results on torsion ... More
State-dependence of climate sensitivity: attractor constraints and palaeoclimate regimesApr 12 2016Equilibrium climate sensitivity is a frequently used measure to predict long-term climate change. However, both climate models and observational data suggest a rather large uncertainty on climate sensitivity (CS). The reasons for this include: the climate ... More
Symmetric critical knots for O'Hara's energiesSep 20 2017We prove the existence of symmetric critical torus knots for O'Hara's knot energy family $E_\alpha$, $\alpha\in (2,3)$ using Palais' classic principle of symmetric criticality. It turns out that in every torus knot class there are at least two smooth ... More
On minimal immersions in Finsler spacesMar 31 2014Apr 01 2014We explore a connection between the Finslerian area functional and well-investigated Cartan functionals to prove new Bernstein theorems, uniqueness and removability results for Finsler-minimal graphs, as well as enclosure theorems and isoperimetric inequalities ... More
On sphere-filling ropesMay 25 2010What is the longest rope on the unit sphere? Intuition tells us that the answer to this packing problem depends on the rope's thickness. For a countably infinite number of prescribed thickness values we construct and classify all solution curves. The ... More