Results for "David C. McKay"

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Slow Thermalization Between a Lattice and Free Bose GasNov 20 2012Jul 27 2013Using a 3D spin-dependent optical lattice, we study thermalization and energy exchange between two ultracold Bose gases, one of which is bound to the lattice and another that is free from the lattice potential. Disruption of inter-species thermalization ... More
Aplicacion de la descomposicion racional univariada a monstrous moonshine (in Spanish)May 15 2008This paper shows how to use Computational Algebra techniques, namely the decomposition of rational functions in one variable, to explore a certain set of modular functions, called replicable functions, that arise in Monstrous Moonshine. In particular, ... More
Decomposing replicable functionsMar 24 2008Mar 25 2008We describe an algorithm to decompose rational functions from which we determine the poset of groups fixing these functions.
High contrast qubit interactions using multimode cavity QEDFeb 27 2014Oct 22 2014We introduce a new multimode cavity QED architecture for superconducting circuits which can be used to implement photonic memories, more efficient Purcell filters, and quantum simulations of photonic materials. We show that qubit interactions mediated ... More
Efficient Z-Gates for Quantum ComputingDec 02 2016For superconducting qubits, microwave pulses drive rotations around the Bloch sphere. Here we show that the phase of these drives can be used to generate zero-duration arbitrary Z-gates which, combined with two $X_{\pi/2}$ gates, can generate any SU(2) ... More
Efficient Z-Gates for Quantum ComputingDec 02 2016Jun 28 2017For superconducting qubits, microwave pulses drive rotations around the Bloch sphere. The phase of these drives can be used to generate zero-duration arbitrary "virtual" Z-gates which, combined with two $X_{\pi/2}$ gates, can generate any SU(2) gate. ... More
A universal gate for fixed-frequency qubits via a tunable busApr 11 2016Aug 18 2016A challenge for constructing large circuits of superconducting qubits is to balance addressability, coherence and coupling strength. High coherence can be attained by building circuits from fixed-frequency qubits, however, leading techniques cannot couple ... More
Evolution of condensate fraction during rapid lattice rampsJan 16 2012Combining experiments and numerical simulations, we investigate the redistribution of quasi-momentum in a gas of atoms trapped in an optical lattice when the lattice depth is rapidly reduced. We find that interactions lead to significant momentum redistribution ... More
A universal gate for fixed-frequency qubits via a tunable busApr 11 2016Dec 19 2016A challenge for constructing large circuits of superconducting qubits is to balance addressability, coherence and coupling strength. High coherence can be attained by building circuits from fixed-frequency qubits, however, leading techniques cannot couple ... More
Three Qubit Randomized BenchmarkingDec 18 2017Dec 12 2018As quantum circuits increase in size, it is critical to establish scalable multiqubit fidelity metrics. Here we investigate three-qubit randomized benchmarking (RB) with fixed-frequency transmon qubits coupled to a common bus with pairwise microwave-activated ... More
Defining the frame of minimum nonlinear Hubble expansion variationMar 13 2015Dec 29 2016We characterize a cosmic rest frame in which the monopole variation of the spherically averaged nonlinear Hubble expansion is most uniform, under arbitrary local Lorentz boosts of the central observer. Using the COMPOSITE sample of 4534 galaxies, we identify ... More
Exact Statistical Characterization of $2\times2$ Gram Matrices with Arbitrary Variance ProfileApr 12 2017This paper is concerned with the statistical properties of the Gram matrix $\mathbf{W}=\mathbf{H}\mathbf{H}^\dagger$, where $\mathbf{H}$ is a $2\times2$ complex central Gaussian matrix whose elements have arbitrary variances. With such arbitrary variance ... More
Defining the frame of minimum nonlinear Hubble expansion variationMar 13 2015Jan 15 2016We characterize a cosmic rest frame in which the monopole variation of the spherically averaged nonlinear Hubble expansion is most uniform, under arbitrary local Lorentz boosts of the central observer. Using the COMPOSITE sample of 4534 galaxies, we identify ... More
Principal moduli and class fieldsNov 12 2003We study the values taken by Gamma_0(n) modular functions at elliptic points of order 2 for the Fricke extension that lie outside Gamma_0(n). In the case of a principal modulus (`Hauptmodul') for Gamma_0(n) or its Fricke extension, we determine the class ... More
Morphological Classification of Galaxies by Shapelet Decomposition in the Sloan Digital Sky SurveyJul 22 2003Oct 16 2003We describe application of the `shapelet' linear decomposition of galaxy images to morphological classification using images of $\sim$ 3000 galaxies from the Sloan Digital Sky Survey. After decomposing the galaxies we perform a principal component analysis ... More
Morphological Classification of Galaxies by Shapelet Decomposition in the Sloan Digital Sky Survey II: Multiwavelength ClassificationJan 21 2004Dec 15 2004We describe the application of the `shapelet' linear decomposition of galaxy images to multi-wavelength morphological classification using the $u,g,r,i,$ and $z$-band images of 1519 galaxies from the Sloan Digital Sky Survey. We utilize elliptical shapelets ... More
Asymptotic enumeration of symmetric integer matrices with uniform row sumsAug 23 2011Jan 21 2013We investigate the number of symmetric matrices of non-negative integers with zero diagonal such that each row sum is the same. Equivalently, these are zero diagonal symmetric contingency tables with uniform margins, or loop-free regular multigraphs. ... More
Verifying Multipartite Entangled GHZ States via Multiple Quantum CoherencesMay 14 2019The ability to generate and verify multipartite entanglement is an important benchmark for near-term quantum devices devices. We develop a scalable entanglement metric based on multiple quantum coherences, and demonstrate experimentally on a 20-qubit ... More
Large Dimensional Analysis of Robust M-Estimators of Covariance with OutliersMar 04 2015A large dimensional characterization of robust M-estimators of covariance (or scatter) is provided under the assumption that the dataset comprises independent (essentially Gaussian) legitimate samples as well as arbitrary deterministic samples, referred ... More
Extreme Eigenvalue Distributions of Jacobi Ensembles: New Exact Representations, Asymptotics and Finite Size CorrectionsJun 09 2019Let $\mathbf{W}_1$ and $\mathbf{W}_2$ be independent $n\times n$ complex central Wishart matrices with $m_1$ and $m_2$ degrees of freedom respectively. This paper is concerned with the extreme eigenvalue distributions of double-Wishart matrices $(\mathbf{W}_1+\mathbf{W}_2)^{-1}\mathbf{W}_1$, ... More
Signal Characteristics from Electromagnetic Cascades in IceJan 18 2001Feb 26 2002We investigate the development of electromagnetic cascades in ice using a GEANT Monte Carlo simulation. We examine the Cherenkov pulse that is generated by the charge excess that develops and propagates with the shower. This study is important for the ... More
Large-dimensional behavior of regularized Maronna's M-estimators of covariance matricesApr 26 2018Robust estimators of large covariance matrices are considered, comprising regularized (linear shrinkage) modifications of Maronna's classical M-estimators. These estimators provide robustness to outliers, while simultaneously being well-defined when the ... More
Metastable Bose-Einstein Condensation in a Strongly Correlated Optical LatticeNov 20 2014Nov 25 2014We experimentally and theoretically study the peak fraction of a Bose-Einstein condensate loaded into a cubic optical lattice as the lattice potential depth and entropy per particle are varied. This system is well-described by the superfluid regime of ... More
Coherent Radio Pulses From GEANT Generated Electromagnetic Showers In IceDec 20 2001Feb 25 2002Radio Cherenkov radiation is arguably the most efficient mechanism for detecting showers from ultra-high energy particles of 1 PeV and above. Showers occuring in Antarctic ice should be detectable at distances up to 1 km. We report on electromagnetic ... More
Problem Roulette: Studying Introductory Physics in the CloudSep 30 2013Problem Roulette (PR) is a web-based study service at the University of Michigan that offers random-within-topic access to a large library of past exam problems in introductory physics courses. Built on public-private cloud computing infrastructure, PR ... More
Summary of progress on the Blaschke conjectureSep 05 2013Aug 03 2015The Blaschke conjecture claims that every compact Riemannian manifold whose injectivity radius equals its diameter is, up to constant rescaling, a compact rank one symmetric space. We summarize the intuition behind this problem, the proof that such manifolds ... More
Holomorphic Cartan geometries on uniruled surfacesMay 24 2011We classify holomorphic Cartan geometries on every compact complex curve, and on every compact complex surface which contains a rational curve.
Characteristic forms of complex Cartan geometriesApr 19 2007Dec 09 2008We calculate relations on characteristic classes which are obstructions preventing closed K\"ahler manifolds from carrying holomorphic Cartan geometries. We apply these relations to give global constraints on the phase spaces of complex analytic determined ... More
The Hartogs extension phenomenon for holomorphic parabolic and reductive geometriesFeb 23 2013Jul 25 2016Every holomorphic effective parabolic or reductive geometry on a domain over a Stein manifold extends uniquely to the envelope of holomorphy of the domain. This result completes the open problems of my earlier paper on extension of holomorphic geometric ... More
Hydrogen on graphene under stress: Molecular dissociation and gap openingJun 02 2011Density functional calculations are employed to study the molecular dissociation of hydrogen on graphene, the diffusion of chemisorbed atomic species, and the electronic properties of the resulting hydrogen on graphene system. Our results show that applying ... More
On the Equivalence between Interference and Eavesdropping in Wireless CommunicationsJul 31 2014Feb 25 2015We show that the problem of analyzing the outage probability in cellular systems affected by co-channel interference and background noise is mathematically equivalent to the problem of analyzing the wireless information-theoretic security in terms of ... More
Power Allocation Schemes for Multicell Massive MIMO SystemsJun 10 2015This paper investigates the sum-rate gains brought by power allocation strategies in multicell massive multipleinput multiple-output systems, assuming time-division duplex transmission. For both uplink and downlink, we derive tractable expressions for ... More
Nonuniversality and finite dissipation in decaying magnetohydrodynamic turbulenceFeb 23 2015May 12 2015A model equation for the Reynolds number dependence of the dimensionless dissipation rate in freely decaying homogeneous magnetohydrodynamic turbulence in the absence of a mean magnetic field is derived from the real-space energy balance equation, leading ... More
Asymptotics of eigenstructure of sample correlation matrices for high-dimensional spiked modelsOct 24 2018Mar 12 2019Sample correlation matrices are employed ubiquitously in statistics. However, quite surprisingly, little is known about their asymptotic spectral properties for high-dimensional data, particularly beyond the case of "null models" for which the data is ... More
Analysis and Design of Multiple-Antenna Cognitive Radios with Multiple Primary User SignalsMay 25 2014Apr 23 2015We consider multiple-antenna signal detection of primary user transmission signals by a secondary user receiver in cognitive radio networks. The optimal detector is analyzed for the scenario where the number of primary user signals is no less than the ... More
Asymptotics of eigenstructure of sample correlation matrices for high-dimensional spiked modelsOct 24 2018Oct 25 2018Sample correlation matrices are employed ubiquitously in statistics. However, quite surprisingly, little is known about their asymptotic spectral properties for high-dimensional data, particularly beyond the case of "null models" for which the data is ... More
Cross-Correlation Lensing: Determining Galaxy and Cluster Mass Profiles from Statistical Weak Lensing MeasurementsJul 20 2005We present a new non-parametric method for determining mean 3D density and mass profiles from weak lensing measurements around stacked samples of galaxies or clusters, that is, from measurement of the galaxy-shear or cluster-shear correlation functions. ... More
Sussmann's orbit theorem and mapsAug 06 2005A map between manifolds which matches up families of complete vector fields is a fiber bundle mapping on each orbit of those vector fields.
Rational curves and ordinary differential equationsJul 05 2005Mar 26 2007The systems of complex analytic second order ordinary differential equations whose solutions close up to become rational curves (after analytic continuation) are characterized by the vanishing of an explicit differential invariant, and turn out to provide ... More
Lagrangian submanifolds in affine symplectic geometryAug 06 2005We uncover the lowest order differential invariants of Lagrangian submanifolds under affine symplectic maps, and find out what happens when they are constant.
Introduction to exterior differential systemsJun 29 2017A brief introduction to exterior differential systems for graduate students familiar with manifolds and differential forms.
The Blaschke conjecture and great circle fibrations of spheresDec 03 2001Oct 13 2016We construct an explicit diffeomorphism taking any fibration of a sphere by great circles into the Hopf fibration, using elementary geometry--indeed the diffeomorphism is a local (differential) invariant, algebraic in derivatives.
Complex homogeneous surfacesJun 10 2014Jul 22 2015We classify the transitive, effective, holomorphic actions of connected complex Lie groups on complex surfaces.
Almost complex rigidity of the complex projective planeMar 09 2004Aug 06 2005An isomorphism of symplectically tame smooth pseudocomplex structures on the complex projective plane which is a homeomorphism and differentiable of full rank at two points is smooth.
Semi-affine Coxeter-Dynkin graphs and $G \subseteq SU_2(C)$Jul 14 1999These graphs generalize both affine and finite type and provide an explanation for some quantum properties of roots of unity.
Complete complex parabolic geometriesSep 28 2004Aug 31 2011Complete complex parabolic geometries (including projective connections and conformal connections) are flat and homogeneous. This is the first global theorem on parabolic geometries.
Exotic geometric structures on Kodaira surfacesJan 20 2012Oct 16 2012On all compact complex surfaces (modulo finite unramified coverings), we classify all of the locally homogeneous geometric structures which are locally isomorphic to the exotic homogeneous surfaces of Lie.
Morphisms of Cartan connectionsFeb 11 2008Sep 28 2010We define what we call morphisms of Cartan connections. We generalize the main theorems on Cartan connections to theorems on morphisms. Many of the known constructions involving Cartan connections turn out to be examples of morphisms. We prove some basic ... More
G2 manifolds of cohomogeneity twoNov 25 2003Aug 06 2005This paper has been withdrawn by the author, due to errors in Groebner basis calculations in the cases of five and six dimensional groups.
Rigid geometry on projective varietiesMar 12 2006Nov 25 2010We prove rigidity of various types of holomorphic parabolic geometry on smooth complex projective varieties.
Complete projective connectionsApr 05 2005May 27 2006The first examples of complete projective connections are uncovered: normal projective connections on surfaces whose geodesics are all closed and embedded are complete, as are normal projective connections induced from complete affine connections with ... More
Holomorphic geometric structures on Kaehler-Einstein manifoldsAug 07 2013Nov 23 2013We prove that the compact Kaehler manifolds with first Chern class nonnegative that admit holomorphic parabolic geometries are the flat bundles of rational homogeneous varieties over complex tori. We also prove that the compact Kaehler manifolds with ... More
Extension Phenomena for Holomorphic Geometric StructuresDec 12 2008Jun 08 2009The most commonly encountered types of complex analytic G-structures and Cartan geometries cannot have singularities of complex codimension 2 or more.
Smooth projective planesDec 27 2004Mar 04 2008Using symplectic topology and the Radon transform, we prove that smooth 4-dimensional projective planes are diffeomorphic to $\mathbb{CP}^2$. We define the notion of a plane curve in a smooth projective plane, show that plane curves in high dimensional ... More
On better-quasi-ordering classes of partial ordersAug 01 2014Oct 01 2014We provide a method of constructing better-quasi-orders by generalising a technique for constructing operator algebras that was developed by Pouzet. We then generalise the notion of $\sigma$-scattered to partial orders, and use our method to prove that ... More
Holomorphic Parabolic Geometries and Calabi-Yau ManifoldsDec 09 2008Sep 20 2011We prove that the only complex parabolic geometries on Calabi-Yau manifolds are the homogeneous geometries on complex tori. We also classify the complex parabolic geometries on homogeneous compact K\"ahler manifolds.
Dual curves and pseudoholomorphic curvesJan 02 2001Aug 06 2005A notion of dual curve for pseudoholomorphic curves in 4--manifolds turns out to be possible only if the notion of almost complex structure structure is slightly generalized. The resulting structure is as easy (perhaps easier) to work with, and yields ... More
Analogues of Complex GeometryJul 10 2001May 10 2006We prove that there are no pseudoholomorphic theories of anything other than curves, even if one allows more general spaces than almost complex manifolds. The proof is elementary, except for theories of pseudoholomorphic hypersurfaces, where topological ... More
Summary of progress on the Blaschke conjectureSep 05 2013Nov 15 2016The Blaschke conjecture claims that every compact Riemannian manifold whose injectivity radius equals its diameter is, up to constant rescaling, a compact rank one symmetric space. We summarize the intuition behind this problem, the proof that such manifolds ... More
Lifting locally homogeneous geometric structuresAug 16 2011We prove that under some purely algebraic conditions every locally homogeneous structure modelled on some homogeneous space is induced by a locally homogeneous structure modelled on a different homogeneous space.
Neutral Hydrogen in Galaxy GroupsDec 10 2002We present preliminary results from a study of the neutral hydrogen (HI) properties of an X-ray selected sample of nearby loose galaxy groups. This forms part of a multi-wavelength investigation (X-ray, optical and radio) of the formation and evolution ... More
Searching for Needles in Haystacks - Looking for GRB gamma-rays with the Fermi/LAT DetectorOct 07 2010Oct 23 2010Since the launch of the Fermi Gamma-ray Space Telescope on June 11, 2008, 55 gamma-ray bursts (GRBs) have been observed at coordinates that fall within 66^\circ of the Fermi Large Area Telescope (LAT) boresight with precise localizations provided by the ... More
Searching for Needles in Haystacks - Using the Fermi/GBM to find GRB gamma-rays with the Fermi/LAT DetectorOct 08 2010Oct 26 2010From the launch of the Fermi Gamma-ray Space Telescope to July 9, 2010, the Gamma-ray Burst Monitor (GBM) has detected 497 probable GRB events. Twenty-two of these satisfy the simultaneous requirements of an estimated burst direction within 52^\circ of ... More
The radio flaring behaviour of GRO J1655-40: an analogy with extragalactic radio sources?Feb 25 2003At radio frequencies, the current evidence for the microquasar-quasar connection is based on imaging observations showing that relativistic outflows/jets are found in both classes of objects. Some microquasars also display superluminal motion, further ... More
Weak Lensing from Space III: Cosmological ParametersApr 23 2003Mar 12 2004Weak gravitational lensing provides a unique method to directly map the dark matter in the universe and measure cosmological parameters. Current weak lensing surveys are limited by the atmospheric seeing from the ground and by the small field of view ... More
ArborZ: Photometric Redshifts Using Boosted Decision TreesAug 27 2009Precision photometric redshifts will be essential for extracting cosmological parameters from the next generation of wide-area imaging surveys. In this paper we introduce a photometric redshift algorithm, ArborZ, based on the machine-learning technique ... More
Intrinsic Alignment of Cluster Galaxies: the Redshift EvolutionMar 17 2011Jul 12 2011We present measurements of two types of cluster galaxy alignments based on a volume limited and highly pure ($\ge$ 90%) sample of clusters from the GMBCG catalog derived from SDSS DR7. We detect a clear BCG alignment (the alignment of major axis of the ... More
Cosmological Constraints from the Clustering of the Sloan Digital Sky Survey DR7 Luminous Red GalaxiesJul 09 2009Jul 13 2009We present the power spectrum of the reconstructed halo density field derived from a sample of Luminous Red Galaxies (LRGs) from the Sloan Digital Sky Survey Seventh Data Release (DR7). The halo power spectrum has a direct connection to the underlying ... More
Baryon Acoustic Oscillations in the Sloan Digital Sky Survey Data Release 7 Galaxy SampleJul 10 2009Nov 02 2009The spectroscopic Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7) galaxy sample represents the final set of galaxies observed using the original SDSS target selection criteria. We analyse the clustering of galaxies within this sample, including both ... More
Galaxy Mass and Luminosity Scaling Laws Determined by Weak Gravitational LensingAug 01 2001We present new measurements of scaling laws relating the luminosity of galaxies to the amplitude and shape of their dark matter halos. Early imaging and spectroscopic data from the Sloan Digital Sky Survey are used to make weak lensing measurements of ... More
Qiskit Backend Specifications for OpenQASM and OpenPulse ExperimentsSep 10 2018As interest in quantum computing grows, there is a pressing need for standardized API's so that algorithm designers, circuit designers, and physicists can be provided a common reference frame for designing, executing, and optimizing experiments. There ... More
Weak Lensing Measurements of 42 SDSS/RASS Galaxy ClustersMar 02 2001We present a lensing study of 42 galaxy clusters imaged in Sloan Digital Sky Survey (SDSS) commissioning data. Cluster candidates are selected optically from SDSS imaging data and confirmed for this study by matching to X-ray sources found independently ... More
Thermometry with spin-dependent latticesNov 20 2009Mar 03 2010We propose a method for measuring the temperature of strongly correlated phases of ultracold atom gases confined in spin-dependent optical lattices. In this technique, a small number of "impurity" atoms--trapped in a state that does not experience the ... More
Two-loop mass splittings in electroweak multiplets: winos and minimal dark matterDec 04 2017Apr 01 2018The radiatively-induced splitting of masses in electroweak multiplets is relevant for both collider phenomenology and dark matter. Precision two-loop corrections of $\mathcal{O}$(MeV) to the triplet mass splitting in the wino limit of the minimal supersymmetric ... More
Formal Groups, Witt vectors and Free ProbabilityApr 29 2012The set of non-commutative probability distributions with mean one can be endowed with the structure of a unital ring, which is isomorphic to the Grothendieck $\lambda$-ring. Voiculescu's multiplicative and additive free convolution, $\boxtimes$ and $\boxplus$, ... More
A class of Ramsey-extremal hypergraphsAug 28 2016In 1991, McKay and Radziszowski proved that, however each 3-subset of a 13-set is assigned one of two colours, there is some 4-subset whose four 3-subsets have the same colour. More than 25 years later, this remains the only non-trivial classical Ramsey ... More
A note on the history of the four-colour conjectureJan 13 2012Feb 21 2012The four-colour conjecture was brought to public attention in 1854, most probably by Francis or Frederick Guthrie. This moves back by six years the date of the earliest known publication.
Symmetries of holomorphic geometric structures on toriSep 03 2015Jan 14 2016We prove that any holomorphic locally homogeneous geometric structure on a complex torus, modelled on a complex homogeneous surface, is translation invariant. We conjecture that this result is true is any dimension. In higher dimension we prove it here ... More
Imaging and addressing of individual fermionic atoms in an optical latticeOct 15 2015We demonstrate fluorescence microscopy of individual fermionic potassium atoms in a 527-nm-period optical lattice. Using electromagnetically induced transparency (EIT) cooling on the 770.1-nm D$_1$ transition of $^{40}$K, we find that atoms remain at ... More
Low-temperature, high-density magneto-optical trapping of potassium using the open 4S-5P transition at 405 nmOct 18 2011We report the laser cooling and trapping of neutral potassium on an open transition. Fermionic 40K is captured using a magneto-optical trap (MOT) on the closed 4S-4P transition at 767 nm and then transferred, with unit efficiency, to a MOT on the open ... More
Affine connections on complex manifolds of algebraic dimension zeroAug 03 2015Sep 24 2015We prove that any compact complex manifold with finite fundamental group and algebraic dimension zero admits no holomorphic affine connection.
Modular Invariants and Generalized Halphen SystemsFeb 17 1999Generalized Halphen systems are solved in terms of functions that uniformize genus zero Riemann surfaces, with automorphism groups that are commensurable with the modular group. Rational maps relating these functions imply subgroup relations between their ... More
Modular Solutions to Equations of Generalized Halphen TypeApr 09 1998Apr 28 1998Solutions to a class of differential systems that generalize the Halphen system are determined in terms of automorphic functions whose groups are commensurable with the modular group. These functions all uniformize Riemann surfaces of genus zero and have ... More
On the edit distance from $K_{2,t}$-free graphs II: Cases $t\geq 5$Dec 03 2010Feb 19 2011The edit distance between two graphs on the same vertex set is defined to be size of the symmetric difference of their edge sets. The edit distance function of a hereditary property, $\mathcal{H}$, is a function of $p$ and measures, asymptotically, the ... More
Holomorphic Cartan geometries and Calabi--Yau manifoldsDec 21 2008We prove that the only Calabi--Yau projective manifolds which bear holomorphic Cartan geometries are precisely the abelian varieties. (Nous d\'emontrons que les seules vari\'et\'es projectives de Calabi--Yau qui poss\`edent des g\'eom\'etrie holomorphes ... More
Affine connections on complex manifolds of algebraic dimension zeroAug 03 2015Mar 24 2018We prove that any compact complex manifold with finite fundamental group and algebraic dimension zero admits no holomorphic affine connection.
Inhomogeneous supersymmetric bilinear formsDec 30 2016Sep 20 2017We consider inhomogeneous supersymmetric bilinear forms, i.e., forms that are neither even nor odd. We classify such forms up to dimension seven in the case when the restrictions of the form to the even and odd parts of the superspace are nondegenerate. ... More
Radio Emission from GRO J1655-40 during the 1994 Jet Ejection EpisodesMar 31 2000We report multifrequency radio observations of GRO J1655-40 obtained with the Australia Telescope Compact Array, the Molonglo Observatory Synthesis Telescope and the Hartebeesthoek Radio Astronomy Observatory at the time of the major hard X-ray and radio ... More
Locally homogeneous structures on Hopf surfacesOct 02 2009Nov 11 2009We study holomorphic locally homogeneous geometric structures modelled on line bundles over the projective line. We classify these structures on primary Hopf surfaces. We write out the developing map and holonomy morphism of each of these structures explicitly ... More
Twisted logarithmic modules of free field algebrasApr 01 2016Jun 16 2016Given a non-semisimple automorphism $\varphi$ of a vertex algebra $V$, the fields in a $\varphi$-twisted $V$-module involve the logarithm of the formal variable, and the action of the Virasoro operator $L_0$ on such module is not semisimple. We construct ... More
Cooling in strongly correlated optical lattices: prospects and challengesOct 01 2010Dec 23 2010Optical lattices have emerged as ideal simulators for Hubbard models of strongly correlated materials, such as the high-temperature superconducting cuprates. In optical lattice experiments, microscopic parameters such as the interaction strength between ... More
Holomorphic Cartan geometries and rational curvesMay 10 2010Mar 07 2016We prove that any compact K\"ahler manifold bearing a holomorphic Cartan geometry contains a rational curve just when the Cartan geometry is inherited from a holomorphic Cartan geometry on a lower dimensional compact K\"ahler manifold.
Subgraphs of dense random graphs with specified degreesFeb 16 2010Nov 27 2010Let d = (d1, d2, ..., dn) be a vector of non-negative integers with even sum. We prove some basic facts about the structure of a random graph with degree sequence d, including the probability of a given subgraph or induced subgraph. Although there are ... More
Hypohamiltonian planar cubic graphs with girth fiveJul 26 2015A graph is called hypohamiltonian if it is not hamiltonian but becomes hamiltonian if any vertex is removed. Many hypohamiltonian planar cubic graphs have been found, starting with constructions of Thomassen in 1981. However, all the examples found until ... More
Twisted logarithmic modules of lattice vertex algebrasAug 28 2017Sep 14 2018Twisted modules over vertex algebras formalize the relations among twisted vertex operators and have applications to conformal field theory and representation theory. A recent generalization, called twisted logarithmic module, involves the logarithm of ... More
Holomorphic Cartan geometries, Calabi--Yau manifolds and rational curvesSep 29 2010We prove that if a Calabi--Yau manifold $M$ admits a holomorphic Cartan geometry, then $M$ is covered by a complex torus. This is done by establishing the Bogomolov inequality for semistable sheaves on compact K\"ahler manifolds. We also classify all ... More
Observing the dark matter density profile of isolated galaxiesJan 17 2003Using the Sloan Digital Sky Survey (SDSS), we probe the halo mass distribution by studying the velocities of satellites orbiting isolated galaxies. In a subsample that covers 2500 sq. degrees on the sky, we detect about 3000 satellites with absolute blue ... More
Cosmological Constraints from SDSS maxBCG Cluster AbundancesMar 21 2007We perform a maximum likelihood analysis of the cluster abundance measured in the SDSS using the maxBCG cluster finding algorithm. Our analysis is aimed at constraining the power spectrum normalization $\sigma_8$, and assumes flat cosmologies with a scale ... More
Weak Lensing from Space II: Dark Matter MappingApr 23 2003Mar 12 2004We study the accuracy with which weak lensing measurements could be made from a future space-based survey, predicting the subsequent precisions of 3-dimensional dark matter maps, projected 2-dimensional dark matter maps, and mass-selected cluster catalogues. ... More
Cross-correlation Weak Lensing of SDSS galaxy Clusters II: Cluster Density Profiles and the Mass--Richness RelationSep 09 2007We interpret and model the statistical weak lensing measurements around 130,000 groups and clusters of galaxies in the Sloan Digital Sky Survey presented by Sheldon et al. 2007 (Paper I). We present non-parametric inversions of the 2D shear profiles to ... More