Results for "Lars Buesing"

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Credit Assignment Techniques in Stochastic Computation GraphsJan 07 2019Stochastic computation graphs (SCGs) provide a formalism to represent structured optimization problems arising in artificial intelligence, including supervised, unsupervised, and reinforcement learning. Previous work has shown that an unbiased estimator ... More
Temporal Difference Variational Auto-EncoderJun 08 2018Jan 02 2019To act and plan in complex environments, we posit that agents should have a mental simulator of the world with three characteristics: (a) it should build an abstract state representing the condition of the world; (b) it should form a belief which represents ... More
Black box variational inference for state space modelsNov 23 2015Latent variable time-series models are among the most heavily used tools from machine learning and applied statistics. These models have the advantage of learning latent structure both from noisy observations and from the temporal ordering in the data, ... More
Bayesian Manifold Learning: The Locally Linear Latent Variable Model (LL-LVM)Oct 24 2014Dec 01 2015We introduce the Locally Linear Latent Variable Model (LL-LVM), a probabilistic model for non-linear manifold discovery that describes a joint distribution over observations, their manifold coordinates and locally linear maps conditioned on a set of neighbourhood ... More
Learning model-based planning from scratchJul 19 2017Conventional wisdom holds that model-based planning is a powerful approach to sequential decision-making. It is often very challenging in practice, however, because while a model can be used to evaluate a plan, it does not prescribe how to construct a ... More
Learning and Querying Fast Generative Models for Reinforcement LearningFeb 08 2018A key challenge in model-based reinforcement learning (RL) is to synthesize computationally efficient and accurate environment models. We show that carefully designed generative models that learn and operate on compact state representations, so-called ... More
Imagination-Augmented Agents for Deep Reinforcement LearningJul 19 2017Feb 14 2018We introduce Imagination-Augmented Agents (I2As), a novel architecture for deep reinforcement learning combining model-free and model-based aspects. In contrast to most existing model-based reinforcement learning and planning methods, which prescribe ... More
Woulda, Coulda, Shoulda: Counterfactually-Guided Policy SearchNov 15 2018Learning policies on data synthesized by models can in principle quench the thirst of reinforcement learning algorithms for large amounts of real experience, which is often costly to acquire. However, simulating plausible experience de novo is a hard ... More
Fast amortized inference of neural activity from calcium imaging data with variational autoencodersNov 06 2017Calcium imaging permits optical measurement of neural activity. Since intracellular calcium concentration is an indirect measurement of neural activity, computational tools are necessary to infer the true underlying spiking activity from fluorescence ... More
Geometric Analysis and General RelativityDec 23 2005This article discusses methods of geometric analysis in general relativity, with special focus on the role of "critical surfaces" such as minimal surfaces, marginal surface, maximal surfaces and null surfaces.
Maximal supersymmetry and exceptional groupsJun 08 2010The article is a tribute to my old mentor, collaborator and friend Murray Gell-Mann. In it I describe work by Pierre Ramond, Sung-Soo Kim and myself where we describe the N = 8 Supergravity in the light-cone formalism. We show how the Cremmer-Julia E7(7) ... More
Dissipation for Euler's Disk and a Desktop Demonstration of Coalescing Neutron StarsFeb 11 2001I show that the recent calculation of Moffatt's regarding the viscous dissipation of a spinning coin overlooked the importance of the finite width of the viscous boundary layer. My new estimates are more in accord with that observed. I also point out ... More
Slow ultrafilters and asymptotic cones of proper metric spacesOct 08 2010In this paper I present an elementary construction to prove that any proper metric space can arise as the asymptotic cone of another proper metric space. Furthermore I answer a question of Drutu and Sapir concerning slow ultrafilters.
Recent multi-wavelength campaigns in the Fermi-GST eraJul 02 2010Since 2008 the Fermi/LAT instrument has delivered highly time-resolved gamma-ray spectra and detailed variability curves for a steadily increasing number of AGN. For detailed AGN studies the Fermi/LAT data have to be combined with, and accompanied by, ... More
Algorithm Selection for Combinatorial Search Problems: A SurveyOct 30 2012The Algorithm Selection Problem is concerned with selecting the best algorithm to solve a given problem on a case-by-case basis. It has become especially relevant in the last decade, as researchers are increasingly investigating how to identify the most ... More
The MSSM with large tan(beta) beyond the decoupling limitOct 02 2009For large values of tan(beta) interesting effects arise in the MSSM due to the enhancement of down-quark self-energies. These effects are well-studied within the decoupling limit, i.e. in the limit of supersymmetric masses far above the electroweak scale. ... More
Measurement of CP violation phase phi_s and charge asymmetries in B^0_(s) decays at D0Sep 23 2008Sep 25 2008The CP violation phase phi_s and charge asymmetries in B^0_s decays have been measured by the D0 experiment in Run II of the Fermilab Tevatron Collider where proton anti-proton collisions take place at a center of mass energy of sqrt{s}=1.96 TeV. The ... More
Algebraic approach to solve $t\bar{t}$ dilepton equationsOct 07 2005Jun 18 2011The set of non-linear equations describing the Standard Model kinematics of the top quark antiqark production system in the dilepton decay channel has at most a four-fold ambiguity due to two not fully reconstructed neutrinos. Its most precise solution ... More
Searches for New Phenomena at the LHCJun 26 2012Searches for physics beyond the Standard Model (SM) with the CMS and ATLAS experiments in pp collisions at a centre of mass energy of sqrt(s)=7 TeV at the LHC are presented. The discussed results are based on data taken in 2011, making use of integrated ... More
Analytical solution of ttbar dilepton equationsMar 01 2006Jun 18 2011The top quark antiquark production system in the dilepton decay channel is described by a set of equations which is nonlinear in the unknown neutrino momenta. Its most precise and least time consuming solution is of major importance for measurements of ... More
CDF and D0 top quark cross section measurementsOct 13 2004Nov 03 2004Preliminary results of ttbar cross section measurements and single top exclusion limits of the Tevatron experiments CDF and D0 are presented. The different measurements are based on a dataset between 140 and 200 inverse pb corresponding to a data taking ... More
The D0 Silicon Track TriggerSep 01 2004The Level-2 Silicon Track Trigger preprocessor (L2 STT) of the D0 detector in Run II is described. It performs a precise reconstruction of charged particle tracks in the Central Fiber Tracker (CFT) and the Silicon Microstrip Tracker (SMT). Events with ... More
Ideal depth of QF extensionsDec 08 2010A minimum depth d^I(S --> R) is assigned to a ring homomorphism S --> R and a R-R-bimodule I. The recent notion of depth of a subring d(S,R)in a paper by Boltje-Danz-Kuelshammer is recovered when I = R and S --> R is the inclusion mapping. Ideal depth ... More
The big de Rham-Witt complexJun 16 2010Dec 07 2014This paper gives a new and direct construction of the multi-prime big de Rham-Witt complex which is defined for every commutative and unital ring; the original construction by the author and Madsen relied on the adjoint functor theorem and accordingly ... More
An approach to quasi-Hopf algebras via Frobenius coordinatesAug 18 2004We study quasi-Hopf algebras and their subobjects over certain commutative rings from the point of view of Frobenius algebras. We introduce a type of Radford formula involving an anti-automorphism and the Nakayama automorphism of a Frobenius algebra, ... More
Normal Hopf subalgebras, depth two and Galois extensionsNov 06 2004Apr 06 2005Let $S$ be the left $R$-bialgebroid of a depth two extension with centralizer $R$ as defined in math.QA/0108067. We show that the left endomorphism ring of depth two extension, not necessarily balanced, is a left $S$-Galois extension of $A^{\rm op}$. ... More
Skew Hopf algebras, irreducible extensions and the pi-methodJan 15 2007Dec 28 2007To a depth two extension A | B, we associate the dual bialgebroids S := \End {}_BA_B and T := (A \o_B A)^B over the centralizer R=C_A(B). In the set-up where R is a subalgebra of B, which is quite common, two nondegenerate pairings of S and T will define ... More
On the Whitehead spectrum of the circleOct 15 2007May 22 2008The seminal work of Waldhausen, Farrell and Jones, Igusa, and Weiss and Williams shows that the homotopy groups in low degrees of the space of homeomorphisms of a closed Riemannian manifold of negative sectional curvature can be expressed as a functor ... More
Drift velocity and pressure monitoring of the CMS muon drift chambersJul 02 2011The drift velocity in drift tubes of the CMS muon chambers is a key parameter for the muon track reconstruction and trigger. It needs to be monitored precisely in order to detect any deviation from its nominal value. A change in absolute pressure, a variation ... More
The trapped regionJan 17 2009Jan 20 2009I will discuss some recent results on marginally outer trapped surfaces, apparent horizons, and the trapped region. A couple of applications of the results developed for marginally outer trapped surfaces to coalescence of black holes and to the characterization ... More
On the relation between mathematical and numerical relativityJul 17 2006The large scale binary black hole effort in numerical relativity has led to an increasing distinction between numerical and mathematical relativity. This note discusses this situation and gives some examples of succesful interactions between numerical ... More
The global existence problem in general relativityNov 09 1999Apr 28 2006We survey some known facts and open questions concerning the global properties of 3+1 dimensional spacetimes containing a compact Cauchy surface. We consider spacetimes with an $\ell$-dimensional Lie algebra of space-like Killing fields. For each $\ell ... More
Gravitational Radiation and Rotation of Accreting Neutron StarsApr 29 1998Recent discoveries by the Rossi X-Ray Timing Explorer indicate that most of the rapidly accreting and weakly magnetic neutron stars in the Galaxy are rotating at spin frequencies greater than 250 Hz. Remarkably, they all rotate in a narrow range of frequencies. ... More
The Angular Momentum of Accreting Neutron StarsJan 07 1998I review the rotation measurements of accreting neutron stars. Many of the highly magnetic accreting X-ray pulsars have been continuously observed with the Burst and Transient Source Experiment (BATSE) aboard the Compton Gamma-Ray Observatory (CGRO) since ... More
Thermonuclear Burning on Rapidly Accreting Neutron StarsSep 10 1997Neutron stars in mass-transferring binaries are accreting the hydrogen and helium rich matter from the surfaces of their companions. This article simply explains the physics associated with how that material eventually fuses to form heavier nuclei and ... More
Cosmological models and stabilityOct 07 2013Principles in the form of heuristic guidelines or generally accepted dogma play an important role in the development of physical theories. In particular, philosophical considerations and principles figure prominently in the work of Albert Einstein. As ... More
Dust in the early Universe: Evidence for non-stellar dust production or observational errors?Feb 02 2011Observations have revealed unexpectedly large amounts of dust in high-redshift galaxies and its origin is still much debated. Valiante et al. (2009, MNRAS, 397, 1661) suggested the net stellar dust production of the quasar host galaxy SDSS J1148+5251 ... More
Decoupling of beams previously coupled by effective stand-alone solenoid fringe fieldsMar 27 2014Oct 23 2014Beams passing through a solenoid fringe field experience x-y coupling and change of their eigen-emittances. As reported previously (C.~Xiao et al., Phys. Rev. ST Accel. Beams 044201, {\bf 16} 2013) constant settings of a subsequent decoupling section ... More
A Generic Framework for Diamond LemmasDec 07 2007This paper gives a generic form of the diamond lemma, which includes support for additive and topological structures of the base set, and which does not require any further structure (e.g. an associative multiplication operation) to be present. This result ... More
The Picard Group of Simply Connected Regular Varieties and Stratified Line BundlesApr 12 2011We prove that the Picard group of a regular simply connected variety over an algebraically closed field of arbitrary characteristic is finitely generated. The main difficulty to overcome is the unavailability of resolution of singularities. From this ... More
Chern classes of tropical vector bundlesNov 15 2009We introduce tropical vector bundles, morphisms and rational sections of these bundles and define the pull-back of a tropical vector bundle and of a rational section along a morphism. Afterwards we use the bounded rational sections of a tropical vector ... More
The tower of K-theory of truncated polynomial algebrasFeb 28 2007Aug 12 2007Let A a regular F_p-algebra. The relative K-groups K_q(A[x]/(x^m),(x)) and the Nil-groups Nil_q(A[x]/(x^m)) were evaluated earlier by the author and Madsen in terms of the big de Rham-Witt groups of the ring A. In this paper, we evaluate the maps of relative ... More
A tower condition characterizing normalityOct 18 2013Jan 27 2014We define left relative H-separable tower of rings and continue a study of these begun by Sugano. It is proven that a progenerator extension has right depth two if and only if the ring extension together with its right endomorphism ring is a left relative ... More
Depth three towers of rings and groupsMar 12 2007May 11 2007Depth three and finite depth are notions known for subfactors via diagrams and Frobenius extensions of rings via centralizers in endomorphism towers. From the point of view of depth two ring extensions, we provide a clear definition of depth three for ... More
A note on Galois theory for bialgebroidsJan 01 2005In this note we reduce certain proofs in \cite{KS, Karl, AMA} to depth two quasibases from one side only. This minimalistic approach leads to a characterization of Galois extensions for finite projective bialgebroids without the Frobenius extension property: ... More
Uniquely separable extensionsAug 14 2018The separability tensor element of a separable extension of noncommutative rings is an idempotent when viewed in the correct endomorphism ring; so one speaks of a separability idempotent, as one usually does for separable algebras. It is proven that this ... More
Dirichlet-to-Robin Operators via Composition SemigroupsSep 06 2017We show well-posedness for an evolution problem associated with the Dirichlet-to-Robin operator for certain Robin boundary data. Moreover, it turns out that the semigroup generated by the Dirichlet-to-Robin operator is closely related to a weighted semigroup ... More
Intersections of Class FieldsSep 04 2017Nov 27 2017Using class field theory, we prove a restriction on the intersection of the maximal abelian extensions associated with different number fields. This restriction is then used to improve a result of Rosen and Silverman about the linear independence of Heegner ... More
ICON Challenge on Algorithm SelectionNov 12 2015We present the results of the ICON Challenge on Algorithm Selection.
Small-scale clustering of nano-dust grains in turbulent interstellar molecular clouds [Extended version]Nov 23 2018Clustering and dynamics of nano-sized particles (nano dust) is investigated using high-resolution ($1024^3$) simulations of compressible isothermal hydrodynamic turbulence, intended to mimic the conditions inside cold molecular clouds in the interstellar ... More
A Homogeneous Function Constant along the Leaves of a FoliationJul 03 2018Given a smooth foliation by complex curves (locally around a point $x\in\mathbb{C}^2\setminus\{0\}$) which is "compatible" with the foliation by spheres centered at the origin, we construct a smooth real-valued function $g$ in a neighborhood of said point, ... More
A Parameter Version of Forstnerič's Splitting LemmaFeb 05 2018We construct solution operators to the $\overline{\partial}$-equation that depend continuously on the domain. This is applied to derive a parameter version of Forstneri\v{c}'s splitting lemma: If both the maps and the domains they are defined on vary ... More
Separable equivalence of rings and symmetric algebrasOct 25 2017Nov 04 2018We continue a study of separable equivalence from Hokkaido Mathematical Journal 24 (1995), 527-549. We prove that symmetric separable equivalent rings $A$ and $B$ are linked by a Frobenius bimodule ${}_AP_B$ such that $A$ is $P$-separable over $B$. Separably ... More
Report on GRG18, Session A3, Mathematical Studies of the Field EquationsMar 31 2008Apr 01 2008In this report I will give a summary of some of the main topics covered in Session A3, mathematical studies of the field equations, at GRG18, Sydney. Unfortunately, due to length constraints, some of the topics covered at the session will be very briefly ... More
Construction of hyperboloidal initial dataMay 18 2002I describe the conformal method for constructing solutions of the hyperboloidal constraint equations as well as the conditions needed on the free data in order to have regularity up to boundary for the solutions to the constraint equations. A brief discussion ... More
Arresting Accretion Torques with Gravitational RadiationNov 30 2002Recent theoretical work has made it plausible for neutron stars (NSs) to lose angular momentum via gravitational radiation on long timescales (around Myrs) while actively accreting. The gravitational waves (GWs) can either be emitted via the excitation ... More
Hot White Dwarf Donors in Ultracompact X-Ray BinariesAug 07 2002The discovery of two accreting millisecond X-ray pulsars in binaries with 43 minute orbital periods allows for a new probe of the donor's structure. For XTE J1751-305, only a hot white dwarf (WD) can fill the Roche Lobe. A cold He WD is a possible solution ... More
Theory and Observations of Type I X-Ray Bursts from Neutron StarsJan 08 2000I review our understanding of the thermonuclear instabilities on accreting neutron stars that produce Type I X-Ray bursts. I emphasize those observational and theoretical aspects that should interest the broad audience of this meeting. The easily accessible ... More
N/O-trends in Late-Type Galaxies: AGB-stars, IMFs, Abundance Gradients and the Origin of NitrogenAug 15 2008Models of galactic chemical evolution (CEMs) show that the shape of the stellar initial mass function (IMF) and other assumptions regarding star formation affect the resultant abundance gradients in models of late-type galaxies. Furthermore, intermediate ... More
Measuring NUMA effects with the STREAM benchmarkMar 16 2011Modern high-end machines feature multiple processor packages, each of which contains multiple independent cores and integrated memory controllers connected directly to dedicated physical RAM. These packages are connected via a shared bus, creating a system ... More
Quantum-Critical transport at a semimetal-to-insulator transition on the honeycomb latticeDec 01 2010Jan 25 2012In this paper we study transport properties of electrons on the two-dimensional honeycomb lattice. We consider a half-filled system in the vicinity of a symmetry-breaking transition from a semimetallic phase towards an insulating phase with either charge ... More
Ranking Algorithms by PerformanceNov 18 2013A common way of doing algorithm selection is to train a machine learning model and predict the best algorithm from a portfolio to solve a particular problem. While this method has been highly successful, choosing only a single algorithm has inherent limitations ... More
Saas-Fee Lecture Notes: Multi-messenger Astronomy and Dark MatterFeb 06 2012Feb 10 2012Notes of lectures given at the Saas-Fee School 2010 in Les Diablerets, Switzerland. These notes are of introductory nature and should be suitable for graduate students and postdocs wanting to learn the basics of astroparticle physics and cosmology, with ... More
Evolutionary Extortion and Mischief: Zero Determinant strategies in iterated 2x2 gamesAug 12 2013This paper studies the mechanisms, implications, and potential applications of the recently discovered class of Zero Determinant (ZD) strategies in iterated 2x2 games. These strategies were reported to successfully extort pure economic maximizers, and ... More
Measurement of the charge ratio of atmospheric muons with the CMS detectorSep 01 2010A measurement is presented of the flux ratio of positive and negative muons from cosmic ray interactions in the atmosphere, using data collected by the CMS detector at ground level and in the underground experimental cavern. The excellent performance ... More
Heavy flavour jet abundances and tagging rates analytically determinedMay 13 2009Heavy flavour jet tagging is widely used in the determination of cross sections including the production of heavy flavoured quarks. This requires the knowledge of heavy and light flavour jet tagging efficiencies and their uncertainties. A system of eight ... More
Higgs searches at TevatronJul 09 2007SM and MSSM Higgs Searches at the proton anti-proton collider Tevatron in Run II are presented. The performance of the collider and the two experiments D0 and CDF is shown. No deviation from SM background expectation and no MSSM Higgs signal has been ... More
Odd H-depth and H-separable extensionsOct 06 2011Jun 26 2012A subring pair B < A has right depth 2n if the n+1'st relative Hochschild bar resolution group is isomorphic to a direct summand of a multiple of the n'th relative Hochschild bar resolution group as A-B-bimodules; depth 2n+1 if the same condition holds ... More
On the K-theory of planar cuspical curves and a new family of polytopesMar 25 2013Oct 26 2013Let k be a regular F_p-algebra, let A = k[x,y]/(x^b - y^a) be the coordinate ring of a planar cuspical curve, and let I = (x,y) be the ideal that defines the cusp point. We give a formula for the relative K-groups K_q(A,I) in terms of the groups of de ... More
On the topological cyclic homology of the algebraic closure of a local fieldAug 17 2005The cyclotomic trace provides a comparison of the algebraic K-theory spectrum and a pro-spectrum TR that is built from the cyclic fixed points of topological Hochschild homology. In a previous paper with Ib Madsen, we used this comparison and an approximate ... More
Periodic topological cyclic homology and the Hasse-Weil zeta functionFeb 05 2016We propose a definition of periodic topological cyclic homology and show that, for schemes smooth and proper over a finite field, the infinite dimensional cohomology theory that results provides a natural vessel for Deninger's cohomological interpretation ... More
Simplicial Hochschild cochains as an Amitsur complexNov 23 2007It is shown that the cochain complex of relative Hochschild A-valued cochains of a depth two extension A | B under cup product is isomorphic as a differential graded algebra with the Amitsur complex of the coring S = End {}_BA_B over the centralizer R ... More
Interactive Simplifier Tracing and Debugging in IsabelleJun 02 2014The Isabelle proof assistant comes equipped with a very powerful tactic for term simplification. While tremendously useful, the results of simplifying a term do not always match the user's expectation: sometimes, the resulting term is not in the form ... More
On the Zeta Function of Forms of Fermat EquationsJan 17 2003We study ``forms of the Fermat equation'' over an arbitrary field $k$, i.e. homogenous equations of degree $m$ in $n$ unknowns that can be transformed into the Fermat equation $X_1^m+...+X_n^m$ by a suitable linear change of variables over an algebraic ... More
Non-Realizable Minimal Vertex Triangulations of Surfaces: Showing Non-Realizability using Oriented Matroids and Satisfiability SolversJan 16 2008We show that no minimal vertex triangulation of a closed, connected, orientable 2-manifold of genus 6 admits a polyhedral embedding in R^3. We also provide examples of minimal vertex triangulations of closed, connected, orientable 2-manifolds of genus ... More
Hopf algebroids and Galois extensionsSep 07 2004To a finite Hopf-Galois extension $A | B$ we associate dual bialgebroids $S := \End_BA_B$ and $T := (A \o_B A)^B$ over the centralizer $R$ using the depth two theory in math.RA/0108067. First we extend results on the equivalence of certain properties ... More
A Note on the Eigenvalues of the Google MatrixJan 15 2004The Google matrix is a positive, column-stochastic matrix that is used to compute the pagerank of all the web pages on the Internet: the eigenvector corresponding to the eigenvalue 1 is the pagerank vector. Due to its huge dimension, of the order of billions, ... More
An action-free characterization of weak Hopf-Galois extensionsSep 29 2004Dec 11 2004We define comodule algebras and Galois extensions for actions of bialgebroids. Using just module conditions we characterize the Frobenius extensions that are Galois as depth two and right balanced extensions. As a corollary, we obtain characterizations ... More
Depth three towers and Jacobson-Bourbaki correspondenceJun 08 2007We introduce a notion of depth three tower of three rings C < B < A as a useful generalization of depth two ring extension. If A = End B_C and B | C is a Frobenius extension, this also captures the notion of depth three for a Frobenius extension in math.RA/0107064 ... More
The Endomorphism Ring Theorem for Galois and D2 extensionsMar 10 2005Apr 01 2005Let $S$ be the left bialgebroid $\End {}_BA_B$ over the centralizer $R$ of a right D2 algebra extension $A \| B$, which is to say that its tensor-square is isomorphic as $A$-$B$-bimodules to a direct summand of a finite direct sum of $A$ with itself. ... More
Galois theory for bialgebroids, depth two and normal Hopf subalgebrasFeb 09 2005We reduce certain proofs in math.RA/0108067, math.RA/0408155, and math.QA/0409589 to depth two quasibases from one side only, a minimalistic approach which leads to a characterization of Galois extensions for finite projective bialgebroids without the ... More
Infinite index subalgebras of depth twoJul 14 2006Aug 17 2006An algebra extension $A \| B$ is right depth two in this paper if its tensor-square is $A$-$B$-isomorphic to a direct summand of any (not necessarily finite) direct sum of $A$ with itself. For example, normal subgroups of infinite groups, infinitely generated ... More
Integrability of generalized pluriharmonic mapsFeb 11 2015In this paper we provide examples of maps from almost complex domains into pseudo-Riemannian symmetric targets, which are pluriharmonic and not integrable, i.e. do not admit an associated family. More precisely, for one class of examples the source has ... More
Topological Hochschild homology and the Hasse-Weil zeta functionFeb 05 2016Sep 16 2017We consider the Tate cohomology of the circle group acting on the topological Hochschild homology of schemes. We show that in the case of a scheme smooth and proper over a finite field, this cohomology theory naturally gives rise to the cohomological ... More
Algebra depth in tensor categoriesNov 07 2015Nov 27 2015Study of the quotient module of a finite-dimensional Hopf subalgebra pair in order to compute its depth yields a relative Maschke Theorem, in which semisimple extension is characterized as being separable, and is therefore an ordinary Frobenius extension. ... More
Self-gravitating elastic bodiesJul 30 2014Extended objects in GR are often modelled using distributional solutions of the Einstein equations with point-like sources, or as the limit of infinitesimally small "test" objects. In this note, I will consider models of finite self-gravitating extended ... More
The Bounded Height Conjecture for Semiabelian VarietiesMar 11 2017Mar 12 2019The Bounded Height Conjecture of Bombieri, Masser, and Zannier states that for any sufficiently generic algebraic subvariety of a semiabelian $\overline{\mathbb{Q}}$-variety $G$ there is an upper bound on the Weil height of the points contained in its ... More
An analytical test case for dust dynamics during a shock-wave passageNov 23 2016An exact solution of a forced Burgers' equation representing the dynamics of a "dust fluid" in a one-dimensional flow is presented. The test case considered starts with a steady (time independent) two-fluid flow in one dimension, where the two fluid components ... More
On Effective Degrees of Freedom in the Early UniverseSep 16 2016Jan 26 2017We explore the effective degrees of freedom in the early universe, from before the electroweak scale at a few femtoseconds after the Big Bang, until the last positrons disappeared a few minutes later. We first look at the established concepts of effective ... More
Points of Small Height on Semiabelian VarietiesAug 02 2018Mar 14 2019The Equidistribution Conjecture is proved for general semiabelian varieties over number fields. Previously, this conjecture was only known in the special case of almost split semiabelian varieties through work of Chambert-Loir. The general case has remained ... More
Dynamical multifractal zeta-functions, multifractal pressure and fine multifractal spectraSep 30 2013We introduce multifractal pressure and dynamical multifractal zeta-functions providing precise information of a very general class of multifractal spectra, including, for example, the fine multifractal spectra of self-conformal measures and the fine multifractal ... More
Report on GR16, Session A3: Mathematical Studies of the Field EquationsApr 29 2002May 17 2002In this report, which is an extended version of that appearing in the Proceedings of GR16, I will give a summary of the main topics covered in Session A.3. on mathematical relativity at GR16, Durban. The summary is mainly based on extended abstracts submitted ... More
The origin of carbon: Low-mass stars and an evolving, initially top-heavy IMF?Mar 17 2010Multi-zone chemical evolution models (CEMs), differing in the nucleosynthesis prescriptions (yields) and prescriptions of star formation, have been computed for the Milky Way. All models fit the observed O/H and Fe/H gradients well and reproduce the main ... More
The 130 GeV Fingerprint of Right-Handed Neutrino Dark MatterAug 30 2012Sep 03 2012Recently, an interesting indication for a dark matter signal in the form of a narrow line, or maybe two lines and/or an internal bremsstrahlung feature, has been found in data from the Fermi-LAT satellite detector. As recent analyses have also shown that ... More
Dark Matter Evidence, Particle Physics Candidates and Detection MethodsMay 22 2012Jun 14 2012The problem of the dark matter in the universe is reviewed. A short history of the subject is given, and several of the most obvious particle candidates for dark matter are identified. Particular focus is given to weakly interacting, massive particles ... More
Side Effects in Steering FragmentsSep 10 2011In this thesis I will give a formal definition of side effects. I will do so by modifying a system for modelling program instructions and program states, Quantified Dynamic Logic, to a system called DLAf (for Dynamic Logic with Assignments as Formulas), ... More
Determination of the strong coupling constant from inclusive jet cross section in ppbar collisions at sqrt(s)=1.96 TeV with the D0 experimentJun 14 2010The strong coupling constant alpha_s and its dependence on the momentum scale is determined from the p_T dependence of the inclusive jet cross section in ppbar collisions at sqrt(s)=1.96 TeV measured with the D0 experiment. The jet transverse momentum ... More
CP-conserving and CP-violating properties in semileptonic Bs decays with the D0 experimentAug 16 2009A search for CP violation has been performed in a sample of semileptonic Bs decays corresponding to approximately 5fb^-1 of data collected by the D0 detector in Run II at the Fermilab Tevatron collider. A time-dependent fit to the distributions of Bs ... More
Photon plus Jet Cross Sections at the TevatronApr 03 2008Photon plus jet production has been studied by the D0 and CDF experiments in Run II of the Fermilab Tevatron Collider at a center of mass energy of sqrt{s}=1.96 TeV. Measurements of the inclusive photon plus jet, di-photon and photon plus b jet cross ... More
CMS: Cosmic muons in simulation and measured dataJul 03 2011A dedicated cosmic muon Monte-Carlo event generator CMSCGEN has been developed for the CMS experiment. The simulation relies on parameterisations of the muon energy and the incidence angle, based on measured and simulated data of the cosmic muon flux. ... More