Results for "Arjen van Elteren"
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The signatures of the parental cluster on field planetary systemsNov 03 2017Nov 23 2017Due to the high stellar densities in young clusters, planetary systems formed in these environments are likely to have experienced perturbations from encounters with other stars. We carry out direct $N$-body simulations of multi-planet systems in star ... More Cosmogenic photons strongly constrain UHECR source modelsSep 12 2016With the newest version of our Monte Carlo code for ultra-high-energy cosmic ray (UHECR) propagation, CRPropa 3, the flux of neutrinos and photons due to interactions of UHECRs with extragalactic background light can be predicted. Together with the recently ... More Multi-scale and multi-domain computational astrophysicsFeb 19 2014Astronomical phenomena are governed by processes on all spatial and temporal scales, ranging from days to the age of the Universe (13.8,Gyr) as well as from km size up to the size of the Universe. This enormous range in scales is contrived, but as long ... More Determining neutrino absorption spectra at Ultra-High EnergiesJan 22 2008Apr 16 2008A very efficient method to measure the flux of Ultra-high energy (UHE) neutrinos is through the detection of radio waves which are emitted by the particle shower in the lunar regolith. The highest acceptance is reached for radio waves in the frequency ... More PeV Neutrinos from Ultra-High-Energy Cosmic RaysJul 24 2014We investigate the possibility that the recently detected TeV-PeV neutrino events by IceCube can originate from extragalactic ultra-high-energy cosmic ray interactions with the cosmic microwave background or the UV/optical/IR background. This is done ... More Runtime Optimizations for Prediction with Tree-Based ModelsDec 11 2012Apr 26 2013Tree-based models have proven to be an effective solution for web ranking as well as other problems in diverse domains. This paper focuses on optimizing the runtime performance of applying such models to make predictions, given an already-trained model. ... More Ultra-deep Ks-band Imaging of the Hubble Frontier FieldsJun 23 2016We present an overview of the "KIFF" project, which provides ultra-deep Ks-band imaging of all six of the Hubble Frontier Fields clusters Abell 2744, MACS-0416, Abell S1063, Abell 370, MACS-0717 and MACS-1149. All of these fields have recently been observed ... More The Astrophysical Multipurpose Software EnvironmentJul 11 2013We present the open source Astrophysical Multi-purpose Software Environment (AMUSE, www.amusecode.org), a component library for performing astrophysical simulations involving different physical domains and scales. It couples existing codes within a Python ... More On the Masses of Galaxies in the Local UniverseSep 08 2010We compare estimates of stellar mass, Mstar, and dynamical mass,Mdyn,for a sample of galaxies from the Sloan Digital Sky Survey (SDSS). We assume dynamical homology (i.e., Mdyn = dispersion**2 * Reff, and we find a tight but strongly non-linear relation: ... More Spontaneous Charging and Crystallization of Water Droplets in OilJul 29 2008Jul 31 2008We study the spontaneous charging and the crystallization of spherical micron-sized water-droplets dispersed in oil by numerically solving, within a Poisson-Boltzmann theory in the geometry of a spherical cell, for the density profiles of the cations ... More Stellar Masses and SFRs for 1M Galaxies from SDSS and WISEJun 01 2015We combine SDSS and WISE photometry for the full SDSS spectroscopic galaxy sample, creating SEDs that cover lambda=0.4-22 micron for an unprecedented large and comprehensive sample of 858,365 present-epoch galaxies. Using MAGPHYS we then model simultaneously ... More The Pair Fraction of Massive Galaxies at 0 < z < 3Sep 13 2011Using a mass-selected ($M_{\star} \ge 10^{11} M_{\odot}$) sample of 198 galaxies at 0 < z < 3.0 with HST/NICMOS $H_{160}$-band images from the COSMOS survey, we find evidence for the evolution of the pair fraction above z ~ 2, an epoch in which massive ... More Major Merging: The Way to Make a Massive, Passive GalaxyOct 21 2009Nov 10 2009We analyze the projected axial ratio distribution, p(b/a), of galaxies that were spectroscopically selected from the Sloan Digital Sky Survey (DR6) to have low star-formation rates. For these quiescent galaxies we find a rather abrupt change in p(b/a) ... More A simple SVD algorithm for finding hidden partitionsApr 15 2014Finding a hidden partition in a random environment is a general and important problem, which contains as subproblems many famous questions, such as finding a hidden clique, finding a hidden coloring, finding a hidden bipartition etc. In this paper, we ... More Sum-product estimates via directed expandersMay 04 2007Let $\F_q$ be a finite field of order $q$ and $P$ be a polynomial in $\F_q[x_1, x_2]$. For a set $A \subset \F_q$, define $P(A):=\{P(x_1, x_2) | x_i \in A \}$. Using certain constructions of expanders, we characterize all polynomials $P$ for which the ... More A structural approach to subset-sum problemsApr 20 2008We discuss a structural approach to subset-sum problems in additive combinatorics. The core of this approach are Freiman-type structural theorems, many of which will be presented through the paper. These results have applications in various areas, such ... More Singular vectors under random perturbationApr 12 2010Computing the first few singular vectors of a large matrix is a problem that frequently comes up in statistics and numerical analysis. Given the presence of noise, exact calculation is hard to achieve, and the following problem is of importance: \vskip2mm ... More A Parallel-pulling Protocol for Free-Energy EvaluationMay 24 2011Feb 14 2012Jarzynski's equality (JE) allows us to compute free energy differences from distributions of work. In molecular dynamics simulations, the traditional way of constructing work distributions is to perform as many pulling simulations as possible. But reliable ... More The merger-driven evolution of massive galaxiesFeb 22 2010Jun 29 2010We explore the rate and impact of galaxy mergers on the massive galaxy population using the amplitude of the two-point correlation function on small scales for M > 5e10 M_sun galaxies from the COSMOS and COMBO-17 surveys. Using a pair fraction derived ... More Weakly nonlocal continuum physics - the Ginzburg-Landau equationOct 18 2002May 13 2003Some peculiarities of the exploitation of the entropy inequality in case of weakly nonlocal continuum theories are investigated and refined. As an example it is shown that the proper application of the Liu procedure leads to the Ginzburg-Landau equation ... More Weakly nonlocal irreversible thermodynamicsDec 12 2001Jan 10 2003Weakly nonlocal thermodynamic theories are critically revisited. A relocalized, irreversible thermodynamic theory of nonlocal phenomena is given, based on a modified form of the entropy current and new kind of internal variables, the so called current ... More The Majority of Compact Massive Galaxies at z~2 are Disk DominatedJan 12 2011Mar 10 2011We investigate the stellar structure of massive, quiescent galaxies at z~2, based on Hubble Space Telescope/WFC3 imaging from the Early Release Science program. Our sample of 14 galaxies has stellar masses of M* > 10^{10.8} Msol and photometric redshifts ... More Cosmic ray propagation with CRPropa 3Oct 20 2014Solving the question of the origin of ultra-high energy cosmic rays (UHECRs) requires the development of detailed simulation tools in order to interpret the experimental data and draw conclusions on the UHECR universe. CRPropa is a public Monte Carlo ... More Optical probes of electron correlations in solidsJul 21 2008Classically the interaction between light and matter is given by the Maxwell relations. These are briefly reviewed and will be used as a basis to discuss several techniques that are used in optical spectroscopy. We then discuss the quantum mechanical ... More Orbital-Peierls State in NaTiSi2O6Dec 22 2005Dec 23 2005Does the quasi one-dimensional titanium pyroxene NaTiSi2O6 exhibit the novel {\it orbital-Peierls} state? We calculate its groundstate properties by three methods: Monte Carlo simulations, a spin-orbital decoupling scheme and a mapping onto a classical ... More Theory of indirect resonant inelastic X-ray scatteringNov 19 2003We express the cross section for indirect resonant inelastic X-ray scattering in terms of an intrinsic dynamic correlation function of the system that is studied with this technique. The cross section is a linear combination of the charge response function ... More Monodromy calculatons of fourth order equations of Calabi-Yau typeDec 30 2004Mar 20 2005This paper contains a preliminary study of the monodromy of certain fourth order differential equations, that were called of Calabi-Yau type in math.NT/0402386. Some of these equations can be interpreted as the Picard-Fuchs equations of a Calabi-Yau manifold ... More Towards an automated query modification assistantApr 01 2011Users who need several queries before finding what they need can benefit from an automatic search assistant that provides feedback on their query modification strategies. We present a method to learn from a search log which types of query modifications ... More Spontaneous Symmetry Breaking and Decoherence in SuperconductorsJun 13 2007Jun 15 2007We show that superconductors have a thin spectrum associated with spontaneous symmetry breaking similar to that of antiferromagnets, while still being in full agreement with Elitzur's theorem, which forbids the spontaneous breaking of local (gauge) symmetries. ... More Shock Waves in Weakly Compressed Granular MediaApr 23 2013We experimentally probe nonlinear wave propagation in weakly compressed granular media, and observe a crossover from quasi-linear sound waves at low impact, to shock waves at high impact. We show that this crossover grows with the confining pressure $P_0$, ... More Zooming-in on the SU(2) fundamental domainOct 05 1993Oct 08 1993For SU(2) gauge theories on the three-sphere we analyse the Gribov horizon and the boundary of the fundamental domain in the 18 dimensional subspace that contains the tunnelling path and the sphaleron and on which the energy functional is degenerate to ... More Bayesian inference with rescaled Gaussian process priorsOct 19 2007We use rescaled Gaussian processes as prior models for functional parameters in nonparametric statistical models. We show how the rate of contraction of the posterior distributions depends on the scaling factor. In particular, we exhibit rescaled Gaussian ... More