Results for "Richard Mann"

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Learning Sparse Wavelet RepresentationsFeb 08 2018In this work we propose a method for learning wavelet filters directly from data. We accomplish this by framing the discrete wavelet transform as a modified convolutional neural network. We introduce an autoencoder wavelet transform network that is trained ... More
Minorities report: optimal incentives for collective intelligenceNov 11 2016Collective intelligence is the ability of a group to perform more effectively than any individual alone. Diversity among group members is a key condition for the emergence of collective intelligence, but maintaining diversity is challenging in the face ... More
Towards a fully predictive model of flight paths in pigeons navigating in the familiar area: prediction across differing individualsApr 20 2016This paper will detail the basis of our previously developed predictive model for pigeon flight paths based on observations of the specific individual being predicted. We will then describe how this model can be adapted to predict the flight of a new, ... More
The entropic basis of collective behaviourSep 24 2014In this paper, we identify a radically new viewpoint on the collective behaviour of groups of intelligent agents. We first develop a highly general abstract model for the possible future lives that these agents may encounter as a result of their decisions. ... More
A New Approach to Black Hole MicrostatesMay 30 1998If one encodes the gravitational degrees of freedom in an orthonormal frame field there is a very natural first order action one can write down (which in four dimensions is known as the Goldberg action). In this essay we will show that this action contains ... More
A note on the duality between interaction responses and mutual positions in flocking and schoolingApr 28 2014Jul 04 2014Background: Recent research in animal behaviour has contributed to determine how alignment, turning responses, and changes of speed mediate flocking and schooling interactions in different animal species. Here, we address specifically the problem of what ... More
Deep Reinforcement Learning in Large Discrete Action SpacesDec 24 2015Apr 04 2016Being able to reason in an environment with a large number of discrete actions is essential to bringing reinforcement learning to a larger class of problems. Recommender systems, industrial plants and language models are only some of the many real-world ... More
Complex Spinors and Unified TheoriesJun 19 2013In this paper delivered by Murray Gell-Mann at the Stony Brook Supergravity Workshop in 1979, several paths to unification are discussed, from N=8 supergravity to $SU_5$, $SO_{10}$, and $E_6$. Generalizations of $SO_{10}$ to spinor representations of ... More
Measuring Unrecorded MeasurementApr 14 2016Projective (Von Neumann) Measurement of an operator (i.e. a dynamical variable) selected from a prescribed set of operators is termed unrecorded measurement (URM) when both the selected operator and the measurement outcome are unknown, i.e. "lost". Within ... More
Megaton Modular Multi-Purpose Neutrino DetectorAug 21 2001This brief note outlines a detector for the Homestake Laboratory and the physics experiments that might be done with it. The note might go on record as a letter of intent to be converted to a formal proposal at a later time.
Deconstructing the Welch Equation Using $p$-adic MethodsAug 21 2016The Welch map $x \rightarrow g^{x-1+c}$ is similar to the discrete exponential map $x \rightarrow g^x$, which is used in many cryptographic applications including the ElGamal signature scheme. This paper analyzes the number of solutions to the Welch equation: ... More
Finite Linear Spaces, Plane Geometries, Hilbert spaces and Finite Phase SpaceAug 03 2015Finite plane geometry is associated with finite dimensional Hilbert space. The association allows mapping of q-number Hilbert space observables to the c-number formalism of quantum mechanics in phase space. The mapped entities reflect geometrically based ... More
"Iff" is not expressible in independence-friendly logicJun 29 2008Ordinary first-order logic has the property that two formulas \phi and \psi have the same meaning in a structure if and only if the formula ``\phi iff \psi'' is true in the structure. We prove that independence-friendly logic does not have this property. ... More
Efficient exploration of discrete energy landscapesOct 14 2009Jan 18 2011Many physical and chemical processes, such as folding of biopolymers, are best described as dynamics on large combinatorial energy landscapes. A concise approximate description of dynamics is obtained by partitioning the micro-states of the landscape ... More
On black strings & branes in Lovelock gravityMar 21 2006Mar 27 2006It is well known that black strings and branes may be constructed in pure Einstein gravity simply by adding flat directions to a vacuum black hole solution. A similar construction holds in the presence of a cosmological constant. While these constructions ... More
Quantum D-modules for toric nef complete intersectionsDec 07 2011On a smooth projective variety with k ample line bundles, we denote by Z the complete intersection subvariety defined by generic sections. We define the twisted quantum D-module which is a vector bundle with a flat connection, a flat pairing and a natural ... More
Group orderings, dynamics, and rigidityJun 30 2016Let G be a countable group. We prove several results on the (topological) relationship between the space CO(G) of circular orders on G, and the moduli space of actions of G on the circle. Similar results hold for spaces of left orders and actions on the ... More
Which finitely generated Abelian groups admit equal growth functions?Sep 13 2013We show that finitely generated Abelian groups admit equal growth functions with respect to symmetric generating sets if and only if they have the same rank and the torsion parts have the same parity. In contrast, finitely generated Abelian groups admit ... More
Nanodust in the Interstellar Medium in Comparison to the Solar SystemOct 30 2012Nanodust, which undergoes stochastic heating by single starlight photons in the interstellar medium, ranges from angstrom-sized large molecules containing tens to thousands of atoms (e.g. polycyclic aromatic hydrocarbon molecules) to grains of a couple ... More
Rigid motion revisited: rigid quasilocal framesOct 01 2008Nov 30 2008We introduce the notion of a rigid quasilocal frame (RQF) as a geometrically natural way to define a "system" in general relativity. An RQF is defined as a two-parameter family of timelike worldlines comprising the worldtube boundary of the history of ... More
On the Existence and Utility of Rigid Quasilocal FramesJul 07 2013The notion of a rigid quasilocal frame (RQF) provides a geometrically natural way to define a system in general relativity, and a new way to analyze the problem of motion. An RQF is defined as a two-parameter family of timelike worldlines comprising the ... More
Quasilocal Conservation Laws: Why We Need ThemJun 27 2012We argue that conservation laws based on the local matter-only stress-energy-momentum tensor (characterized by energy and momentum per unit volume) cannot adequately explain a wide variety of even very simple physical phenomena because they fail to properly ... More
M Dwarf Activity in the Pan-STARRS 1 Medium-Deep Survey: First Catalog and Rotation PeriodsAug 02 2016We report on an ongoing project to investigate activity in the M dwarf stellar population observed by the Pan-STARRS 1 Medium Deep Survey (PS1-MDS). Using a custom-built pipeline, we refine an initial sample of $\approx$ 4 million sources in PS1-MDS to ... More
Bayesian Optimal Active Search and SurveyingJun 27 2012We consider two active binary-classification problems with atypical objectives. In the first, active search, our goal is to actively uncover as many members of a given class as possible. In the second, active surveying, our goal is to actively query points ... More
Momentum in General Relativity: Local versus Quasilocal Conservation LawsJun 24 2013We construct a general relativistic conservation law for linear and angular momentum for matter and gravitational fields in a finite volume of space that does not rely on any spacetime symmetries. This work builds on our previous construction of a general ... More
Charged Rotating AdS Black Holes with Chern-Simons couplingOct 17 2016Oct 29 2016We obtain a perturbative solution for rotating charged black holes in 5-dimensional Einstein-Maxwell-Chern-Simons theory with a negative cosmological constant. We start from a small undeformed Kerr-AdS solution and use the electric charge as a perturbative ... More
Light Cone Current AlgebraJan 17 2003This talk follows by a few months a talk by the same authors on nearly the same subject at the Coral Gables Conference. The ideas presented here are basically the same, but with some amplification, some change of viewpoint, and a number of new questions ... More
Lattice model refinement of protein structuresMay 10 2010To find the best lattice model representation of a given full atom protein structure is a hard computational problem. Several greedy methods have been suggested where results are usually biased and leave room for improvement. In this paper we formulate ... More
Dynamic Mode Decomposition for Financial Trading StrategiesAug 18 2015We demonstrate the application of an algorithmic trading strategy based upon the recently developed dynamic mode decomposition (DMD) on portfolios of financial data. The method is capable of characterizing complex dynamical systems, in this case financial ... More
Thermodynamics and phases in quantum gravityDec 02 2008Jun 30 2009We give an approach for studying quantum gravity effects on black hole thermodynamics. This combines a quantum framework for gravitational collapse with quasi-local definitions of energy and surface gravity. Our arguments suggest that (i) the specific ... More
Mirror fibrations and root stacks of weighted projective spacesMar 15 2008We show that the orbifold Chow ring of a root stack over a well-formed weighted projective space can be naturally seen as the Jacobian algebra of a function on a singular variety given by a partial compactification of its Ginzburg-Landau model.
Current Algebra: Quarks and What Else?Aug 01 2002After receiving many requests for reprints of this article, describing the original ideas on the quark gluon gauge theory, which we later named QCD, we decided to place the article in the e-Print archive.
SUSY Searches for Inclusive Squark and Gluino Production at the LHCMay 15 2013A selection of recent searches for Supersymmetry conducted by the ATLAS and CMS collaborations is presented, summarizing the relevant results for inclusive squark and gluino production at the LHC. No indication for the existence of Supersymmetry in terms ... More
Casimir Effect: The Classical LimitAug 23 1999Jun 01 2000We analyze the high temperature (or classical) limit of the Casimir effect. A useful quantity which arises naturally in our discussion is the ``relative Casimir energy", which we define for a configuration of disjoint conducting boundaries of arbitrary ... More
Adiabatic Analysis of Gravitationally-Induced Three-Flavor Neutrino OscillationsJan 19 1995Some implications of the proposal that flavor nondiagonal couplings of neutrinos to gravity might resolve the solar neutrino problem are considered in the context of three neutrino flavours. Using an adiabatic approximation iso-SNU curves are calculated ... More
Gravitationally--Induced Three--Flavor Neutrino Oscillations as a Possible Solution to the Solar Neutrino ProblemJul 20 1995Neutrinos can undergo flavor--oscillations if they possess flavor--dependent couplings to the surrounding gravitational field (the VEP mechanism). The neutrino fields can be massless, in accord with the Minimal Standard Model, but at the expense of the ... More
Choice of measurement as signalNov 30 2012Jun 28 2013In classical mechanics, performing a measurement without reading the measurement outcome is equivalent to not exploiting the measurement at all. A non-selective measurement in the classical realm carries no information. Here we show that the situation ... More
Generalized coherent states are unique Bell states of quantum systems with Lie group symmetriesJul 09 1997We consider quantum systems, whose dynamical symmetry groups are semisimple Lie groups, which can be split or decay into two subsystems of the same symmetry. We prove that the only states of such a system that factorize upon splitting are the generalized ... More
Parity-dependent squeezing of lightApr 20 1996A parity-dependent squeezing operator is introduced which imposes different SU(1,1) rotations on the even and odd subspaces of the harmonic oscillator Hilbert space. This operator is used to define parity-dependent squeezed states which exhibit highly ... More
A Family of Weyl-Wigner Transforms for Discrete Variables Defined in a Finite-Dimensional Hilbert SpaceJul 11 2015Nov 23 2016We study the Weyl-Wigner transform in the case of discrete variables defined in a Hilbert space of finite prime-number dimensionality $N$. We define a family of Weyl-Wigner transforms as function of a phase parameter. We show that it is only for a specific ... More
Inside a Spinning Black StringSep 16 1994We show that mass inflation occurs inside spinning black cosmic string, which is a solution of a low-energy effective string theory in $(3+1)$-dimensions. This confirms Poisson and Israel's conjecture that the inner mass parameter diverges even if spacetime ... More
Dynamic scaling behavior of an interacting monomer--dimer modelAug 18 1995We study the dynamic scaling behavior of a monomer-dimer model with repulsive interactions between the same species in one dimension. With infinitely strong interactions the model exhibits a continuous transition from a reactive phase to an inactive phase ... More
Post-Newtonian Conservation Laws in Rigid Quasilocal FramesDec 12 2013Jan 10 2014In recent work we constructed completely general conservation laws for energy and linear and angular momentum of extended systems in general relativity based on the notion of a rigid quasilocal frame (RQF). We argued at a fundamental level that these ... More
Quantum ThermometryMay 22 2014In this review article we revisit and spell out the details of previous work on how Berry phase can be used to construct a precision quantum thermometer. An important advantage of such a scheme is that there is no need for the thermometer to acquire thermal ... More
Decomposition During Search for Propagation-Based Constraint SolversDec 14 2007Jun 11 2008We describe decomposition during search (DDS), an integration of And/Or tree search into propagation-based constraint solvers. The presented search algorithm dynamically decomposes sub-problems of a constraint satisfaction problem into independent partial ... More
Thermodynamics of Lovelock-Lifshitz Black BranesJun 17 2010Sep 16 2010We investigate the thermodynamics of Lovelock-Lifshitz black branes. We begin by introducing the finite action of third order Lovelock gravity in the presence of a massive vector field for a flat boundary, and use it to compute the energy density of these ... More
Characterising the optical properties of galaxy clusters with GMPhoRCCNov 26 2016We introduce the Gaussian Mixture full Photometric Red sequence Cluster Characteriser (GMPhoRCC), an algorithm for determining the redshift and richness of a galaxy cluster candidate. By using data from a multi-band sky survey with photometric redshifts, ... More
Geoids in General Relativity: Geoid Quasilocal FramesOct 10 2015Nov 30 2015We develop, in the context of general relativity, the notion of a geoid -- a surface of constant "gravitational potential". In particular, we show how this idea naturally emerges as a specific choice of a previously proposed, more general and operationally ... More
LHS 2803B: A very wide mid-T dwarf companion to an old M dwarf identified from Pan-STARRS1Aug 01 2012Aug 23 2012We report the discovery of a wide (approximately 400 AU projected separation), common proper motion companion to the nearby M dwarf LHS 2803 (PSO J207.0300-13.7422). This object was discovered during our census of the local T dwarf population using Pan-STARRS1 ... More
Escape path complexity and its context dependency in Pacific blue-eyes (Pseudomugil signifer)Feb 26 2015The escape trajectories animals take following a predatory attack appear to show high degrees of apparent 'randomness' - a property that has been described as 'protean behaviour'. Here we present a method of quantifying the escape trajectories of individual ... More
Discovery of the host galaxy of HDF850.1, the brightest sub-mm source in the Hubble Deep FieldMay 28 2002Despite extensive observational efforts, the brightest sub--mm source in the Hubble Deep Field, HDF850.1, has failed to yield a convincing optical/infrared identification almost 4 years after its discovery. This failure is all the more notable given the ... More
Wide, Cool and Ultracool Companions to Nearby Stars from Pan-STARRS1Jul 10 2014Jul 16 2014We present the discovery of 61 wide (>5 arcsecond) separation, low-mass (stellar and substellar) companions to stars in the solar neighborhood identified from Pan-STARRS\,1 (PS1) data and the spectral classification of 27 previously known companions. ... More
Mass inflation in (1+1)-dimensional Dilaton GravityJun 14 1994We investigate the phenomenon of mass inflation in two-dimensional dilaton theories of gravity. We consider two distinct black hole spacetimes and construct the mass-inflation solution for each. Our analysis is extended to include multi-horizon spacetimes. ... More
Gravitation and Cosmology in Generalized (1+1)-dimensional dilaton gravityAug 25 1994The actions of the ``$R=T$'' and string-inspired theories of gravity in (1+1) dimensions are generalized into one single action which is characterized by two functions. We discuss differing interpretations of the matter stress-energy tensor, and show ... More
Black hole chemistry: thermodynamics with LambdaAug 22 2016We review recent developments on the thermodynamics of black holes in extended phase space, where the cosmological constant is interpreted as thermodynamic pressure and treated as a thermodynamic variable in its own right. In this approach, the mass of ... More
Classical Models of Subatomic ParticlesJul 21 1993We look at the program of modelling a subatomic particle---one having mass, charge, and angular momentum---as an interior solution joined to a classical general-relativistic Kerr-Newman exterior spacetime. We find that the assumption of stationarity upon ... More
The clustering of warm and cool IRAS galaxiesNov 08 1995We use a series of statistical techniques to compare the clustering of samples of IRAS galaxies selected on the basis of their far-infrared emission temperature, to see whether a temperature-dependent effect, such as might be produced by interaction-induced ... More
Dissipative dynamics of a quantum two-state system in presence of nonequilibrium quantum noiseOct 10 2016We analyze the real-time dynamics of a quantum two-state system in the presence of nonequilibrium quantum fluctuations. The latter are generated by a coupling of the two-state system to a single electronic level of a quantum dot which carries a nonequilibrium ... More
Transport of energetic electrons through the solar corona and the interplanetary spaceDec 22 2011During solar flares fast electron beams generated in the solar corona are non-thermal radio sources in terms of type III bursts. Sometimes they can enter into the interplanetary space, where they can be observed by in-situ measurements as it is done e.g. ... More
Governing dynamics by squeezing in a system of cold trapped ionsSep 17 1998We consider a system of laser-cooled ions in a linear harmonic trap and study the phenomenon of squeezing exchange between their internal and motional degrees of freedom. An interesting relation between the quantum noise reduction (squeezing) and the ... More
The Graph Grammar Library - a generic framework for chemical graph rewrite systemsApr 04 2013Graph rewrite systems are powerful tools to model and study complex problems in various fields of research. Their successful application to chemical reaction modelling on a molecular level was shown but no appropriate and simple system is available at ... More
Equivalence Classes of Optimal Structures in HP Protein Models Including Side ChainsOct 20 2009Lattice protein models, as the Hydrophobic-Polar (HP) model, are a common abstraction to enable exhaustive studies on structure, function, or evolution of proteins. A main issue is the high number of optimal structures, resulting from the hydrophobicity-based ... More
Thermodynamics of Rotating Charged Black Branes in Third Order Lovelock Gravity and the Counterterm MethodFeb 23 2006May 08 2006We generalize the quasilocal definition of the stress energy tensor of Einstein gravity to the case of third order Lovelock gravity, by introducing the surface terms that make the action well-defined. We also introduce the boundary counterterm that removes ... More
NUT-Charged Black Holes in Gauss-Bonnet GravityOct 11 2005Nov 30 2005We investigate the existence of Taub-NUT/bolt solutions in Gauss-Bonnet gravity and obtain the general form of these solutions in $d$ dimensions. We find that for all non-extremal NUT solutions of Einstein gravity having no curvature singularity at $r=N$, ... More
Quasilocal Thermodynamics of Kerr and Kerr-anti-de Sitter Spacetimes and the AdS/CFT CorrespondenceFeb 01 2001Jun 29 2001We consider the quasilocal thermodynamics of rotating black holes in asymptotically flat and asymptotically anti de Sitter spacetimes. Using the minimal number of intrinsic boundary counterterms inspired by the AdS/CFT correspondence, we find that we ... More
Realizing All Free Homotopy Classes for the Newtonian Three-Body ProblemDec 06 2014The configuration space of the planar three-body problem when collisions are excluded has a rich topology which supports a large set of free homotopy classes. Most classes survive modding out by rotations. Those that survive are called the reduced free ... More
Higgs Factory and 100 TeV Hadron Collider: Opportunity for a New World Laboratory within a DecadeFeb 24 2014Suggestions have been made for a 80-100 km circumference Future Circular Collider (FCC) that could ultimately contain a circular e+e- ring collider operating as a Higgs Factory as well as a 100 TeV hadron collider. Those suggestions have motivated us ... More
Diffeomorphism groups of balls and spheresApr 09 2013In this paper we discuss the relationship between groups of diffeomorphisms of spheres and balls. We survey results of a topological nature and then address the relationship as abstract (discrete) groups. We prove that the identity component Diff_0(S^{2n-1}) ... More
RNA Secondary Structures: Complex Statics and Glassy DynamicsOct 30 2007Feb 02 2008Models for RNA secondary structures (the topology of folded RNA) without pseudo knots are disordered systems with a complex state-space below a critical temperature. Hence, a complex dynamical (glassy) behavior can be expected, when performing Monte Carlo ... More
Classical limit of the Casimir entropy for scalar massless fieldAug 12 2007We study the Casimir effect at finite temperature for a massless scalar field in the parallel plates geometry in N spatial dimensions, under various combinations of Dirichlet and Neumann boundary conditions on the plates. We show that in all these cases ... More
Maximal Bell's Inequality Violation for Non Maximal EntanglementNov 19 2003Bell's inequality violation (BIQV) for correlations of polarization is studied for a {\it product} state of two two-mode squeezed vacuum (TMSV) states. The violation allowed is shown to attain its maximal limit for all values of the squeezing parameter, ... More
Factorizations and Physical RepresentationsAug 25 2005A Hilbert space in M dimensions is shown explicitly to accommodate representations that reflect the prime numbers decomposition of M. Representations that exhibit the factorization of M into two relatively prime numbers: the kq representation (J. Zak, ... More
Casimir energy of a dilute dielectric ball with uniform velocity of light at finite temperatureJan 05 2000Jan 07 2000The Casimir energy, free energy and Casimir force are evaluated, at arbitrary finite temperature, for a dilute dielectric ball with uniform velocity of light inside the ball and in the surrounding medium. In particular, we investigate the classical limit ... More
Cohomologie quantique orbifolde des espaces projectifs a poidsOct 16 2005In 2001, S. Barannikov showed that the Frobenius manifold coming from the quantum cohomology of the complex projective space is isomorphic to the Frobenius manifold attached to some Laurent polynomial. The purpose of this thesis is to generalize this ... More
Superfluid Black HolesSep 08 2016We present what we believe is the first example of a "$\lambda$-line" phase transition in black hole thermodynamics. This is a line of (continuous) second order phase transitions which in the case of liquid $^4$He marks the onset of superfluidity. The ... More
Planetary Embryo Bow Shocks as a Mechanism for Chondrule FormationMay 16 2016We use radiation hydrodynamics with direct particle integration to explore the feasibility of chondrule formation in planetary embryo bow shocks. The calculations presented here are used to explore the consequences of a Mars-size planetary embryo traveling ... More
Discussion of: A statistical analysis of multiple temperature proxies: Are reconstructions of surface temperatures over the last 1000 years reliable?May 11 2011Discussion of "A statistical analysis of multiple temperature proxies: Are reconstructions of surface temperatures over the last 1000 years reliable?" by B.B. McShane and A.J. Wyner [arXiv:1104.4002]
Vortex HolographyMay 14 2001Jan 11 2002We show that the Abelian Higgs field equations in the four dimensional anti de Sitter spacetime have a vortex line solution. This solution, which has cylindrical symmetry in AdS$_4$, is a generalization of the flat spacetime Nielsen-Olesen string. We ... More
Avatar-independent scripting for real-time gesture animationFeb 10 2015When animation of a humanoid figure is to be generated at run-time, instead of by replaying pre-composed motion clips, some method is required of specifying the avatar's movements in a form from which the required motion data can be automatically generated. ... More
Stationary product measures for conservative particle systems and ergodicity criteriaDec 06 2012We study conservative particle systems on W^S, where S is countable and W = {0, ..., N} or the natural numbers. The rate of a particle moving from site x to site y is given by p(x,y) b(eta_x, eta_y), where eta_z is the number of particles at site z. Under ... More
Automorphism groups of sporadic groupsJun 19 2011Among the simplest invariants of the sporadic finite simple groups are their outer automorphism groups. For 12 of the 26 possible isomorphism types of a sporadic simple group G, the outer automorphism group Out(G) has order 2, and in the remaining 14 ... More
A characterisation of algebraic exactnessSep 01 2011An algebraically exact category in one that admits all of the limits and colimits which every variety of algebras possesses and every forgetful functor between varieties preserves, and which verifies the same interactions between these limits and colimits ... More
Causality and chance in relativistic quantum field theoriesMay 13 2014Bell appealed to the theory of relativity in formulating his principle of local causality. But he maintained that quantum field theories do not conform to that principle, even when their field equations are relativistically covariant and their observable ... More
Charge Transfer Inefficiency in the Hubble Space Telescope since Servicing Mission 4Sep 22 2010We update a physically-motivated model of radiation damage in the Hubble Space Telescope Advanced Camera for Surveys/Wide Field Channel, using data up to mid 2010. We find that Charge Transfer Inefficiency increased dramatically before shuttle Servicing ... More
Digging into dark matter with weak gravitational lensingJun 08 2009Ordinary baryonic particles (such as protons and neutrons) account for only one-sixth of the total matter in the Universe. The remainder is a mysterious "dark matter" component, which does not interact via the electromagnetic force and thus neither emits ... More
A Note on the Cohomology of Moduli of Rank Two Stable BundlesMar 12 1996Aug 13 1996The rational cohomology of the moduli space of rank two, odd degree stable bundles over a curve (of genus g > 1) has been studied intensely in recent years and in particular the invariant subring generated by Newstead's generators alpha, beta, gamma. ... More
On the absence of shear from perfect Einstein rings and the stability of geometryDec 14 2007Concordance cosmology points to a Universe of zero mean curvature, due to the inflation mechanism which occurred soon after the Big Bang, while along a relatively small number of lower redshift light paths where lensing events are observed, space is positively ... More
Time delay for an abstract quantum scattering processMar 20 2011In this short review paper, we discuss the concept of time delay for an abstract quantum scattering system. Its definition in terms of sojourn times is explained as well as its identity with the so-called Eisenbud-Wigner time delay. Necessary and natural ... More
How are AGN Found?May 07 2004We discuss the very different methods in each wavelength band for selecting and finding Active Galactic Nuclei (AGN). We briefly review the history of the different techniques for finding AGN and compare and contrast the advantages and difficulties of ... More
X-ray Observations of Groups and Clusters - A Relic of the High Redshift UniverseDec 29 1999I review the evidence from clusters and groups of galaxies for `relic' evidence of the high redshift universe. Contrary to the received wisdom, clusters are old. Their x-ray emitting intergalactic medium in massive clusters is a reservoir of metal and ... More
A proposal for measuring photon temporal coherence in continuum radiationOct 24 2013Oct 06 2015A technique complementary to those for spectral lines is proposed for the observation of continuum radiation. As, quantum mechanically, the radiation is a mixture of pure states, it should be possible to measure the temporal coherence of the states as ... More
Approximation of the Quadratic Knapsack ProblemSep 06 2015May 23 2016For any given $\epsilon>0$ we provide an algorithm for the Quadratic Knapsack Problem that has an approximation ratio within $O(n^{2/5+\epsilon})$ and a run time within $O(n^{9/\epsilon})$.
The Lorentz Force Law and Spacetime SymmetriesApr 04 2005Assume that arc length is measured with the flat spacetime metric. Then, for the most general Poincare group representation for translating 4-vectors, curves with parallel translated tangent vectors must have accelerations that are the scalar product ... More
Embedding classical into quantum computationDec 24 2008We describe a simple formalism for generating classes of quantum circuits that are classically efficiently simulatable and show that the efficient simulation of Clifford circuits (Gottesman-Knill theorem) and of matchgate circuits (Valiant's theorem) ... More
On the simulation of quantum circuitsMar 19 2006We consider recent works on the simulation of quantum circuits using the formalism of matrix product states and the formalism of contracting tensor networks. We provide simplified direct proofs of many of these results, extending an explicit class of ... More
Searching in Grover's AlgorithmJan 09 1999Grover's algorithm is usually described in terms of the iteration of a compound operator of the form $Q = - H I_{0} H I_{x_0}$. Although it is quite straightforward to verify the algebra of the iteration, this gives little insight into why the algorithm ... More
Critical sets in the elementary abelian 2- and 3- groupsFeb 28 2004In 1998, Khodkar showed that the minimal critical set in the Latin square corresponding to the elementary abelian 2-group of order 16 is of size at most 124. Since the paper was published, improved methods for solving integer programming problems have ... More
Eulerian cube complexes and reciprocitySep 26 2013Feb 25 2014Let $G$ be the fundamental group of a compact nonpositively curved cube complex $Y$. With respect to a basepoint $x$, one obtains an integer-valued length function on $G$ by counting the number of edges in a minimal length edge-path representing each ... More
First Measurement of the Photon Structure Function F_2,c^gammaOct 11 2000The first measurement of F_2,c^gamma is presented. At low x the measurement indicates a non-zero hadron-like component to F_2,c^gamma. At large x the measurement constitutes a test of perturbative QCD at next-to-leading order, with only m_c and alpha_s ... More
The Photon Structure from Deep Inelastic Electron-Photon ScatteringDec 21 1999The present knowledge of the structure of the photon is presented with emphasis on measurements of the photon structure obtained from deep inelastic electron-photon scattering at e+e- colliders. This review covers the leptonic and hadronic structure of ... More