Results for "Max N. Markmeyer"

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Formation of Acetaldehyde on CO-rich IcesApr 12 2019The radicals HCO and CH$_3$ on carbon monoxide ice surfaces were simulated using density functional theory. Their binding energy on amorphous CO ice shows broad distributions, with approximative average values of 500 K for HCO and 200 K for CH$_3$. If ... More
A componentwise version of Terao's conjectureJan 22 2009Aug 25 2009This paper has been withdrawn by the authors due to crucial error in the main proof (located in Section 2.4). The authors apologize for any inconveniences.
The thermal Hall effect of spin excitations in a Kagome magnetFeb 19 2015At low temperatures, the thermal conductivity of spin excitations in a magnetic insulator can exceed that of phonons. However, because they are charge neutral, the spin waves are not expected to display a thermal Hall effect in a magnetic field. Recently, ... More
Extending the ergodic convergence rate of the proximal ADMMNov 09 2016Pointwise and ergodic iteration-complexity results for the proximal alternating direction method of multipliers (ADMM) for any stepsize in(0,(1+\sqrt{5})/2) have been recently established in the literature. In addition to giving alternative proofs of ... More
Improved pointwise iteration-complexity of a regularized ADMM and of a regularized non-Euclidean HPE frameworkJan 06 2016Jan 06 2017This paper describes a regularized variant of the alternating direction method of multipliers (ADMM) for solving linearly constrained convex programs. It is shown that the pointwise iteration-complexity of the new method is better than the corresponding ... More
Geometric Cycles in Floer TheorySep 03 2014We construct a version of Hamiltonian Floer Homology based on the notion of a semi-infinite cycle. As an application, we provide a new proof for the existence of critical points of the action functional.
Geometric HomologySep 03 2014The purpose of this paper is to introduce a version of singular homology based on smooth mappings of manifolds with corners. Although variants of such a theory exists in the literature, we felt that certain points were not adequately addressed. In particular, ... More
Asymptotic Symmetry Algebras in Non-Anti-de-Sitter Higher-Spin Gauge TheoriesOct 24 2012We analyze asymptotic symmetry algebras in (2+1)-dimensional non-AdS higher-spin gravity with a focus on AdS$_2\times\mathbb{R}$ and $\mathbb{H}_2\times\mathbb{R}$. We find a consistent set of boundary conditions for spin-3 gravity in the non-principal ... More
On the Choice of Regions for Generalized Belief PropagationJul 11 2012Generalized belief propagation (GBP) has proven to be a promising technique for approximate inference tasks in AI and machine learning. However, the choice of a good set of clusters to be used in GBP has remained more of an art then a science until this ... More
Taking Inspiration from Quantum-Wave Analogies --- Recent Results for Photonic CrystalsApr 04 2018Similarities between quantum systems and analogous systems for classical waves have been used to great effect in the physics community, be it to gain an intuition for quantum systems or to anticipate novel phenomena in classical waves. This proceeding ... More
Filters and Ultrafilters in Real AnalysisDec 22 2012We study free filters and their maximal extensions on the set of natural numbers. We characterize the limit of a sequence of real numbers in terms of the Frechet filter, which involves only one quantifier as opposed to the three non-commuting quantifiers ... More
Limit theorems for projections of random walk on a hypersphereAug 25 2009We show that almost any one-dimensional projection of a suitably scaled random walk on a hypercube, inscribed in a hypersphere, converges weakly to an Ornstein-Uhlenbeck process as the dimension of the sphere tends to infinity. We also observe that the ... More
Nonhyperbolicity of invariant measures on maximal attractorJul 30 2008The article states that for every compact manifold M of dimension 4 or higher there is an area U in a set of smooth diffeomorphisms over M such that every map f from U has local maximal partially hyperbolic attractor and nonatomic ergodic invariant measure ... More
Moduli of twisted sheavesNov 15 2004Jul 08 2005We study moduli of semistable twisted sheaves on smooth proper morphisms of algebraic spaces. In the case of a relative curve or surface, we prove results on the structure of these spaces. For curves, they are essentially isomorphic to spaces of semistable ... More
Tunnelling dominates the reactions of hydrogen atoms with unsaturated alcohols and aldehydes in the dense mediumJun 15 2018Hydrogen addition and abstraction reactions play an important role as surface reactions in the buildup of complex organic molecules in the dense interstellar medium. Addition reactions allow unsaturated bonds to be fully hydrogenated, while abstraction ... More
Covariance in Physics and Convolutional Neural NetworksJun 06 2019In this proceeding we give an overview of the idea of covariance (or equivariance) featured in the recent development of convolutional neural networks (CNNs). We study the similarities and differences between the use of covariance in theoretical physics ... More
Thermal elastic-wave attenuation in low-dimensional SiN$_{x}$ bars at low temperaturesMay 26 2017At low temperatures, < 200 mK, the thermal flux through low-dimensional amorphous dielectric bars, < 2 $\mu$m wide and 200 nm thick, is transported by a small number of low-order elastic modes. For long bars, L > 400 $\mu$m, it is known that the conductance ... More
Correlations between user voting data, budget, and box office for films in the Internet Movie DatabaseDec 14 2013Jan 16 2014The Internet Movie Database (IMDb) is one of the most-visited websites in the world and the premier source for information on films. Like Wikipedia, much of IMDb's information is user contributed. IMDb also allows users to voice their opinion on the quality ... More
Numerical Solution of the Simple Monge-Ampère Equation with Non-convex Dirichlet Data on Non-convex DomainsMay 12 2017Jun 01 2017The existence of a unique numerical solution of the semi-Lagrangian method for the simple Monge-Amp\`ere equation is known independently of the convexity of the domain or Dirichlet boundary data -- when the Monge-Amp\`ere equation is posed as Bellman ... More
A Two-Phase Free Boundary Problem for Harmonic MeasureSep 15 2014Sep 27 2016We study a 2-phase free boundary problem for harmonic measure first considered by Kenig and Toro and prove a sharp H\"older regularity result. The central difficulty is that there is no a priori non-degeneracy in the free boundary condition. Thus we must ... More
Family size decomposition of genealogical treesMar 07 2019We study the path of family size decompositions of varying depth of genealogical trees. We prove that this decomposition as a function on (equivalence classes of) ultra-metric measure spaces to the Skorohod space describing the family sizes at different ... More
General Boundary Quantum Field Theory in Anti de Sitter SpacetimesFeb 03 2016Jun 09 2016We mainly study real Klein-Gordon theory on Anti de Sitter spacetimes, and apply the General Boundary Formulation (GBF) of Quantum Theory in order to compute a radial S-matrix. We consider first the classical theory, giving a complete list of Klein-Gordon ... More
A zero point energy explanation of a peak in liquid helium's dynamic structure factorMay 27 1997Recent high resolution experiments show a strong peak at Q = 1.9 Ang^{-1} in liquid helium's dynamic structure factor that exhibits a singular dependence on temperature. The theoretical situation is briefly reviewed, and the comment is made that the simplest ... More
Towards a q-analogue of the Harer-Zagier formula via rook placementsDec 10 2014In 1986 Harer and Zagier computed a certain matrix integral to determine an influential closed-form formula for the number of (orientable) one-face maps on n vertices colored from N colors. Kerov (1997) provided a proof which computed the same matrix ... More
Characterizations of countably $n$-rectifiable Radon measures by higher-dimensional Menger curvaturesApr 07 2018May 05 2018In the late `90s there was a flurry of activity relating $1$-rectifiable sets, boundedness of singular integral operators, the analytic capacity of a set, and the integral Menger curvature in the plane. In `99 Leger extended the results for Menger curvature ... More
Twisted sheaves and the period-index problemNov 09 2005May 25 2007We use twisted sheaves and their moduli spaces to study the Brauer group of a scheme. In particular, we (1) show how twisted methods can be efficiently used to re-prove the basic facts about the Brauer group and cohomological Brauer group (including Gabber's ... More
Integrated-optics heralded controlled-NOT gate for polarization-encoded qubitsAug 22 2017Feb 21 2018Recent progress in integrated-optics technology has made photonics a promising platform for quantum networks and quantum computation protocols. Integrated optical circuits are characterized by small device footprints and unrivalled intrinsic interferometric ... More
Evidence for massive bulk Dirac Fermions in Pb$_{1-x}$Sn$_x$Se from Nernst and thermopower experimentsJul 15 2013Sep 10 2013The lead chalcogenides (Pb,Sn)Te and (Pb,Sn)Se are the first examples of topological crystalline insulators (TCI) predicted \cite{Fu,Hsieh} (and confirmed \cite{Hasan,Story,Takahashi}) to display topological surface Dirac states (SDS) that are protected ... More
On uniqueness of JSJ decompositions of finitely generated groupsOct 17 2001May 22 2003We give an example of two JSJ decompositions of a group that are not related by conjugation, conjugation of edge-inclusions, and slide moves. This answers the question of Rips and Sela stated in "Cyclic splittings of finitely presented groups and the ... More
Return Probabilities of Random WalksDec 14 2015Associated to a random walk on $\mathbb{Z}$ and a positive integer $n$, there is a return probability of the random walk returning to the origin after $n$ steps. An interesting question is when the set of return probabilities uniquely determines the random ... More
Splittings of generalized Baumslag-Solitar groupsFeb 02 2005Mar 11 2006We study the structure of generalized Baumslag-Solitar groups from the point of view of their (usually non-unique) splittings as fundamental groups of graphs of infinite cyclic groups. We find and characterize certain decompositions of smallest complexity ... More
Partial flag incidence algebrasMay 05 2016The $n^{th}$ partial flag incidence algebra of a poset $P$ is the set of functions from $P^n$ to some ring which are zero on non-partial flag vectors. These partial flag incidence algebras for $n>2$ are not commutative, not unitary, and not associative. ... More
Semiclassical Dynamics and Magnetic Weyl CalculusFeb 20 2012Aug 16 2015Weyl quantization and related semiclassical techniques can be used to study conduction properties of crystalline solids subjected to slowly-varying, external electromagnetic fields. The case where the external magnetic field is constant, is not covered ... More
Classical Klein-Gordon solutions, symplectic structures and isometry actions on AdS spacetimesDec 12 2012Dec 21 2012We study classical, real Klein-Gordon theory on Lorentzian Anti de Sitter (AdS_{1,d}) spacetimes with spatial dimension d. We give a complete list of well defined and bounded Klein-Gordon solutions for three types of regions on AdS: slice (time interval ... More
The Least-Perimeter Partition of a Sphere into Four Equal AreasMar 24 2009Jun 19 2009We prove that the least-perimeter partition of the sphere into four regions of equal area is a tetrahedral partition.
The Devron propertyDec 24 2013Jul 17 2014We introduce a criterion called the Devron property that a discrete dynamical system can possess. The Devron property is said to occur when a class of highly singular inputs of a mapping F are carried by some iterate of $F^{-1}$ to a class of highly singular ... More
$L^2(H^1_γ)$ Finite Element Convergence for Degenerate Isotropic Hamilton-Jacobi-Bellman EquationsJul 01 2015In this paper we study the convergence of monotone $P1$ finite element methods for fully nonlinear Hamilton-Jacobi-Bellman equations with degenerate, isotropic diffusions. The main result is strong convergence of the numerical solutions in a weighted ... More
Error estimates for variational normal derivatives and Dirichlet control problems with energy regularizationAug 03 2018This article deals with error estimates for the finite element approximation of variational normal derivatives and, as a consequence, error estimates for the finite element approximation of Dirichlet boundary control problems with energy regularization. ... More
Constructing Superelliptic Curves with non-trivial rational Torsion on their JacobiansJul 13 2017In this paper, we describe the construction of superelliptic curves with a rational point of prescribed order on their jacobians. The construction is based on Hensel's Lemma and produces for a given integer $N$ a superelliptic curve of genus linear in ... More
The period-index problem for fields of transcendence degree 2Sep 24 2009Jan 05 2015Using geometric methods we prove the standard period-index conjecture for the Brauer group of a field of transcendence degree 2 over a finite field.
Correlation of Crystal Quality and Extreme Magnetoresistance of WTe$_2$Jun 16 2015High quality single crystals of WTe$_2$ were grown using a Te flux followed by a cleaning step involving self-vapor transport. The method is reproducible and yields consistently higher quality single crystals than are typically obtained via halide assisted ... More
Automatic segmentation of MR brain images with a convolutional neural networkApr 11 2017Automatic segmentation in MR brain images is important for quantitative analysis in large-scale studies with images acquired at all ages. This paper presents a method for the automatic segmentation of MR brain images into a number of tissue classes using ... More
Anomalous Nernst Effect in Dirac Semimetal Cd3As2Oct 08 2016Sep 20 2017Dirac and Weyl semimetals display a host of novel properties. In Cd$_3$As$_2$, the Dirac nodes lead to a protection mechanism that strongly suppresses backscattering in zero magnetic field, resulting in ultrahigh mobility ($\sim$ 10$^7$ cm$^2$ V$^{-1}$ ... More
A Equação de Euler e a Análise Assintótica de GevreyApr 09 2014In this work, we introduce the notion of Gevrey asymptotic expansion and we show how the classical concept of a convergent power series can be generalized to include the case in which the radius of convergence is zero. This technique can be useful in ... More
Extended Dependency Structures and their Formal InterpretationApr 29 1996May 09 1996We describe two ``semantically-oriented'' dependency-structure formalisms, U-forms and S-forms. U-forms have been previously used in machine translation as interlingual representations, but without being provided with a formal interpretation. S-forms, ... More
A unified treatment of cubic invariants at fixed and arbitrary energyNov 09 1998Dec 20 1999Cubic invariants for two-dimensional Hamiltonian systems are investigated using the Jacobi geometrization procedure. This approach allows for a unified treatment of invariants at both fixed and arbitrary energy. In the geometric picture the invariant ... More
The Krein-Schrödinger Formalism of Bosonic BdG and Certain Classical Systems and Their Topological ClassificationMar 15 2019To understand recent works on classical and quantum spin equations and their topological classification, we develop a unified mathematical framework for bosonic BdG systems and associated classical wave equations; it applies not just to equations that ... More
On the large N expansion in hyperbolic sigma-modelsNov 23 2007Jun 27 2008Invariant correlation functions for ${\rm SO}(1,N)$ hyperbolic sigma-models are investigated. The existence of a large $N$ asymptotic expansion is proven on finite lattices of dimension $d \geq 2$. The unique saddle point configuration is characterized ... More
Length functions of 2-dimensional right-angled Artin groupsMar 28 2011Apr 08 2011Morgan and Culler proved that a minimal action of a free group on a tree is determined by its translation length function. We prove an analogue of this theorem for 2-dimensional right-angled Artin groups acting on CAT(0) rectangle complexes.
Snowflake geometry in CAT(0) groupsFeb 26 2016Aug 15 2017We construct CAT(0) groups containing subgroups whose Dehn functions are given by $x^s$, for a dense set of numbers $s \in [2, \infty)$. This significantly expands the known geometric behavior of subgroups of CAT(0) groups.
Convergent semi-Lagrangian methods for the Monge-Ampère equation on unstructured gridsFeb 15 2016Sep 06 2016This paper is concerned with developing and analyzing convergent semi-Lagrangian methods for the fully nonlinear elliptic Monge-Amp\`ere equation on general triangular grids. This is done by establishing an equivalent (in the viscosity sense) Hamilton-Jacobi-Bellman ... More
Inference for Empirical Wasserstein Distances on Finite SpacesOct 11 2016Apr 26 2017The Wasserstein distance is an attractive tool for data analysis but statistical inference is hindered by the lack of distributional limits. To overcome this obstacle, for probability measures supported on finitely many points, we derive the asymptotic ... More
Ptychography for pulse-to-pulse wavefront sensing at free-electron lasersJan 24 2019The growing interest in the wavefront of ultra-bright and ultra-short pulses produced by free-electron lasers (FELs) brought to the development of several complementary approaches to characterize them. Ptychography has been proposed as a suitable method ... More
Multiscale Analysis for a Vector-Borne Epidemic ModelAug 09 2011Feb 27 2013Traditional studies about disease dynamics have focused on global stability issues, due to their epidemiological importance. We study a classical SIR-SI model for arboviruses in two different directions: we begin by describing an alternative proof of ... More
A characterization of shortest geodesics on surfacesJun 24 2001Any finite configuration of curves with minimal intersections on a surface is a configuration of shortest geodesics for some Riemannian metric on the surface. The metric can be chosen to make the lengths of these geodesics equal to the number of intersections ... More
Computing the inverses, their power sums, and extrema for Euler's totient and other multiplicative functionsJan 23 2014May 17 2016We propose a generic algorithm for computing the inverses of a multiplicative function under the assumption that the set of inverses is finite. More generally, our algorithm can compute certain functions of the inverses, such as their power sums (e.g., ... More
Partitioning edge-coloured infinite complete bipartite graphs into monochromatic pathsAug 29 2018In 1978, Richard Rado showed that every edge-coloured complete graph of countably infinite order can be partitioned into monochromatic paths of different colours. He asked whether this remains true for uncountable complete graphs and a notion of \emph{generalised ... More
The Jacobian ideal of a hyperplane arrangementJul 18 2007The Jacobian ideal of a hyperplane arrangement is an ideal in the polynomial ring whose generators are the partial derivatives of the arrangements defining polynomial. In this article, we prove that an arrangement can be reconstructed from its Jacobian ... More
Derivations of an effective divisor on the complex projective lineJul 15 2005Nov 11 2005In this paper we consider an effective divisor on the complex projective line and associate with it the module D consisting of all the derivations $\theta$ such that $\theta(I_i)\subset I_i^{m_i}$ for every $i$, where $I_i$ is the ideal of $p_i$. The ... More
Fourier-Mukai partners of K3 surfaces in positive characteristicDec 21 2011Aug 12 2014We study Fourier-Mukai equivalence of K3 surfaces in positive characteristic and show that the classical results over the complex numbers all generalize. The key result is a positive-characteristic version of the Torelli theorem that uses the derived ... More
Perfect points on genus one curves and consequences for supersingular K3 surfacesApr 09 2019Apr 22 2019We describe a method to show that certain elliptic surfaces do not admit purely inseparable multisections (equivalently, that genus one curves over function fields admit no points over the perfect closure of the base field) and use it to show that any ... More
Weak Lensing: Prospects for Measuring Cosmological ParametersNov 11 1998Weak lensing of galaxies by large scale structure can potentially measure cosmological quantities as accurately as the cosmic microwave background (CMB). However, the relation between observables and fundamental parameters is more complex and degenerate, ... More
Reionization in an open cdm universe: implications for cosmic microwave background fluctuationsMay 17 1994Sep 08 1996We generalize previous work on early photoionization to CDM models with Omega<1. Such models have received recent interest because the excess power in the large-scale galaxy distribution is phenomenologically fit if the ``shape parameter" Gamma=h Omega_0 ... More
Instantons and infinite distancesApr 09 2019May 28 2019We consider geodesics of infinite length in the (classical) hypermultiplet moduli space of type II Calabi-Yau compactifications. When approaching such infinite distance points, a large amount of D-instantons develop an exponentially suppressed action, ... More
Edge colored hypergraphic arrangementsMar 25 2009A subspace arrangement defined by intersections of hyperplanes of the braid arrangement can be encoded by an edge colored hypergraph. It turns out that the characteristic polynomial of this type of subspace arrangement is given by a generalized chromatic ... More
Whitehead moves for G-treesOct 10 2007Aug 29 2008We generalize the familiar notion of a Whitehead move from Culler and Vogtmann's Outer space to the setting of deformation spaces of G-trees. Specifically, we show that there are two moves, each of which transforms a reduced G-tree into another reduced ... More
Circuits through prescribed edgesOct 22 2018We prove that a connected graph contains a circuit---a closed walk that repeats no edges---through any $k$ prescribed edges if and only if it contains no odd cut of size at most $k$.
Positive-Instance Driven Dynamic Programming for Graph SearchingMay 03 2019Research on the similarity of a graph to being a tree - called the treewidth of the graph - has seen an enormous rise within the last decade, but a practically fast algorithm for this task has been discovered only recently by Tamaki (ESA 2017). It is ... More
$n$-arc and $n$-circle connected graph-like spacesJul 05 2018A space $X$ is $n$-arc connected (respectively, $n$-circle connected) if for any choice of at most $n$ points there is an arc (respectively, a circle) in $X$ containing the specified points. We study $n$-arc connectedness and $n$-circle connectedness ... More
Eulerian SpacesApr 04 2019We develop a unified theory of Eulerian spaces by combining the combinatorial theory of infinite, locally finite Eulerian graphs as introduced by Diestel and K\"uhn with the topological theory of Eulerian continua defined as irreducible images of the ... More
The construction of finite solvable groups revisitedJun 18 2013Sep 20 2013We describe a new approach towards the systematic construction of finite groups up to isomorphism. This approach yields a practical algorithm for the construction of finite solvable groups up to isomorphism. We report on a GAP implementation of this method ... More
Poincaré, modified logarithmic Sobolev and isoperimetric inequalities for Markov chains with non-negative Ricci curvatureDec 01 2016We study functional inequalities for Markov chains on discrete spaces with entropic Ricci curvature bounded from below. Our main results are that when curvature is non-negative, but not necessarily positive, the spectral gap, the Cheeger isoperimetric ... More
Non-Asymptotic Gap-Dependent Regret Bounds for Tabular MDPsMay 09 2019This paper establishes that optimistic algorithms attain gap-dependent and non-asymptotic logarithmic regret for episodic MDPs. In contrast to prior work, our bounds do not suffer a dependence on diameter-like quantities or ergodicity, and smoothly interpolate ... More
Decomposing edge-coloured complete symmetric digraphs into monochromatic pathsNov 23 2017Confirming and extending a conjecture by Guggiari, we show that every countable $(r+1)$-edge-coloured complete symmetric digraph containing no directed paths of edge-length $\ell_i$ for any colour $i\leq r$ can be covered by $\prod_{i\leq r} \ell_i$ pairwise ... More
Index reduction for Brauer classes via stable sheaves (with an appendix by Bhargav Bhatt)Jun 07 2007Dec 26 2007We use twisted sheaves to study the problem of index reduction for Brauer classes. In general terms, this problem may be phrased as follows: given a field $k$, a $k$-variety $X$, and a class $\alpha \in \Br(k)$, compute the index of the class $\alpha_{k(X)} ... More
Splitting Brauer classes using the universal AlbaneseMay 31 2018Nov 12 2018We prove that every Brauer class over a field splits over a torsor under an abelian variety. If the index of the class is not congruent to 2 modulo 4, we show that the Albanese variety of any smooth curve of positive genus that splits the class also splits ... More
Construction of normal numbers with respect to Generalized Lüroth Series from equidistributed sequencesSep 28 2015Generalized L\"uroth series generalize $b$-adic representations as well as L\"uroth series. Almost all real numbers are normal, but it is not easy to construct one. In this paper, a new construction of normal numbers with respect to Generalized L\"uroth ... More
Particle-vortex duality of 2d Dirac fermion from electric-magnetic duality of 3d topological insulatorsMay 19 2015Particle-vortex duality is a powerful theoretical tool that has been used to study bosonic systems. Here we propose an analogous duality for Dirac fermions in 2+1 dimensions. The physics of a single Dirac cone is proposed to be described by a dual theory, ... More
Improving Variational Auto-Encoders using convex combination linear Inverse Autoregressive FlowJun 07 2017Jun 14 2017In this paper, we propose a new volume-preserving flow and show that it performs similarly to the linear general normalizing flow. The idea is to enrich a linear Inverse Autoregressive Flow by introducing multiple lower-triangular matrices with ones on ... More
Graduality from Embedding-projection Pairs (Extended Version)Jul 08 2018Gradually typed languages allow statically typed and dynamically typed code to interact while maintaining benefits of both styles. The key to reasoning about these mixed programs is Siek-Vitousek-Cimini-Boyland's (dynamic) gradual guarantee, which says ... More
An Introduction to Variational AutoencodersJun 06 2019Variational autoencoders provide a principled framework for learning deep latent-variable models and corresponding inference models. In this work, we provide an introduction to variational autoencoders and some important extensions.
Semi- and Non-relativistic Limit of the Dirac Dynamics with External FieldsApr 16 2012Aug 17 2012We show how to approximate Dirac dynamics for electronic initial states by semi- and non-relativistic dynamics. To leading order, these are generated by the semi- and non-relativistic Pauli hamiltonian where the kinetic energy is related to $\sqrt{m^2 ... More
Complex structures for an S-matrix of Klein-Gordon theory on AdS spacetimesJan 19 2015While the standard construction of the S-matrix fails on Anti-de Sitter (AdS) spacetime, a generalized S-matrix makes sense, based on the hypercylinder geometry induced by the boundary of AdS. In contrast to quantum field theory in Minkowski spacetime, ... More
A Unified Model of Phantom Energy and Dark MatterJan 30 2008To explain the acceleration of the cosmological expansion researchers have considered an unusual form of mass-energy generically called dark energy. Dark energy has a ratio of pressure over mass density which obeys $w=p/\rho <-1/3$. This form of mass-energy ... More
Gale-Robinson quivers: from representations to combinatorial formulasOct 26 2017We investigate a family of representations of Gale-Robinson quivers that are geared towards providing concrete information about the corresponding cluster algebras. In this way, we provide a representation theoretic explanation for known combinatorial ... More
CNN-based Cost Volume Analysis as Confidence Measure for Dense MatchingMay 17 2019Due to its capability to identify erroneous disparity assignments in dense stereo matching, confidence estimation is beneficial for a wide range of applications, e.g. autonomous driving, which needs a certain degree of confidence as mandatory prerequisite. ... More
Multiple universes, cosmic coincidences, and other dark mattersSep 07 2004Dec 21 2004Even when completely and consistently formulated, a fundamental theory of physics and cosmological boundary conditions may not give unambiguous and unique predictions for the universe we observe; indeed inflation, string/M theory, and quantum cosmology ... More
Born in an Infinite Universe: a Cosmological Interpretation of Quantum MechanicsAug 05 2010Jun 12 2012We study the quantum measurement problem in the context of an infinite, statistically uniform space, as could be generated by eternal inflation. It has recently been argued that when identical copies of a quantum measurement system exist, the standard ... More
The Real Graded Brauer groupJan 14 2019We introduce a version of the Brauer--Wall group for Real vector bundles of algebras (in the sense of Atiyah), and compare it to the topological analogue of the Witt group. For varieties over the reals, these invariants capture the topological parts of ... More
Generalized spin representations. Part 2: Cartan-Bott periodicity for the split real En seriesMar 18 2014In this article we analyze the quotients of the maximal compact subalgebras of the split real Kac-Moody algebras of the En series resulting from the generalized spin representations introduced in part 1. It turns out that these quotients satisfy a Cartan-Bott ... More
On Enumeration of Dyck--Schröder PathsJan 22 2016Oct 12 2018We address the problem of enumerating paths in square lattices, where allowed steps include (1,0) and (0,1) everywhere, and (1,1) above the diagonal y=x. We consider two such lattices differing in whether the (1,1) steps are allowed along the diagonal ... More
On the Convergence of Finite Element Methods for Hamilton-Jacobi-Bellman EquationsNov 23 2011In this note we study the convergence of monotone P1 finite element methods on unstructured meshes for fully non-linear Hamilton-Jacobi-Bellman equations arising from stochastic optimal control problems with possibly degenerate, isotropic diffusions. ... More
Fans in the Theory of Real Semigroups I. Algebraic TheoryMar 21 2017In a previous paper we introduced the notion of a {\it real semigroup} (RS) as an axiomatic framework to study diagonal quadratic forms with arbitrary entries over (commutative, unitary) semi-real rings. Two important classes of RSs were studied at length ... More
Stable Crank-Nicolson Discretisation for Incompressible Miscible Displacement Problems of Low RegularityOct 08 2009In this article we study the numerical approximation of incompressible miscible displacement problems with a linearised Crank-Nicolson time discretisation, combined with a mixed finite element and discontinuous Galerkin method. At the heart of the analysis ... More
Wild examples of rectifiable setsMay 05 2019We study the geometry of sets based on the behavior of the Jones function, $J_{E}(x) = \int_{0}^{1} \beta_{E;2}^{1}(x,r)^{2} \frac{dr}{r}$. We construct two examples of countably $1$-rectifiable sets in $\mathbb{R}^{2}$ with positive and finite $\mathcal{H}^1$-measure ... More
Cross-correlation of Tenerife data with Galactic templates - evidence for spinning dust?Apr 22 1999Jan 31 2000The recent discovery of dust-correlated diffuse microwave emission has prompted two rival explanations: free-free emission and spinning dust grains. We present new detections of this component at 10 and 15 GHz by the switched-beam Tenerife experiment. ... More
Elliptical Galaxy in the Making: The Dual Active Galactic Nuclei and Metal-enriched Halo of Mrk 273Jan 14 2019A systematic analysis of the X-ray emission from the nearby ultraluminous infrared galaxy Mrk 273 was carried out by combining new 200 ksec Chandra data with archived 44 ksec data. The active galactic nucleus (AGN) associated with the Southwest nucleus ... More
CASSOWARY 20: a Wide Separation Einstein Cross Identified with the X-shooter SpectrographSep 17 2009Nov 24 2009We have used spectra obtained with X-shooter, the triple arm optical-infrared spectrograph recently commissioned on the Very Large Telescope of the European Southern Observatory, to confirm the gravitational lens nature of the CASSOWARY candidate CSWA ... More
Second-order topological insulators and superconductors with an order-two crystalline symmetryJan 30 2018Jul 04 2018Second-order topological insulators and superconductors have a gapped excitation spectrum in bulk and along boundaries, but protected zero modes at corners of a two-dimensional crystal or protected gapless modes at hinges of a three-dimensional crystal. ... More
Model Selection for Treatment Choice: Penalized Welfare MaximizationSep 11 2016This paper studies a new statistical decision rule for the treatment assignment problem. Consider a utilitarian policy maker who must use sample data to allocate one of two treatments to members of a population, based on their observable characteristics. ... More