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On a model for the Navier--Stokes equations using magnetization variablesJan 19 2016Aug 04 2016The Navier--Stokes equations can be reformulated in terms of so-called magnetization variables $w$ that satisfy \begin{equation}\label{Abs_magform} \partial_tw + (\mathbb{P} w \cdot\nabla)w + (\nabla \mathbb{P} w)^\top w - \mathrm{\Delta} w =0, \end{equation} ... More

On a model for the Navier--Stokes equations using magnetization variablesJan 19 2016Jan 09 2018It is known that in a classical setting, the Navier--Stokes equations can be reformulated in terms of so-called magnetization variables $w$ that satisfy \begin{equation}\label{Abs_magform} \partial_tw + (\mathbb{P} w \cdot\nabla)w + (\nabla \mathbb{P} ... More

Well-posedness for the diffusive 3D Burgers equations with initial data in $H^{1/2}$Jan 19 2016In this note we discuss the diffusive, vector-valued Burgers equations in a three-dimensional domain with periodic boundary conditions. We prove that given initial data in $H^{1/2}$ these equations admit a unique global solution that becomes classical ... More

An Eulerian-Lagrangian Form for the Euler Equations in Sobolev SpacesMar 27 2014Jan 19 2016In 2000 Constantin showed that the incompressible Euler equations can be written in an "Eulerian-Lagrangian" form which involves the back-to-labels map (the inverse of the trajectory map for each fixed time). In the same paper a local existence result ... More

Asymptotics for vortex filaments using a modified Biot-Savart kernelMar 18 2019We consider a family of approximations to the Euler equations obtained by adding $(-\Delta)^{-\alpha/2}$ to the non-locality in the Biot-Savart kernel together with a mollification (with parameter $\varepsilon$). We consider the evolution of a thin vortex ... More

Leray's fundamental work on the Navier-Stokes equations: a modern review of "Sur le mouvement d'un liquide visqueux emplissant l'espace"Aug 31 2017This article offers a modern perspective which exposes the many contributions of Leray in his celebrated work on the Navier--Stokes equations from 1934. Although the importance of his work is widely acknowledged, the precise contents of his paper are ... More

Non-conservation of dimension in divergence-free solutions of passive and active scalar systemsMay 14 2019For any $h\in(1,2]$, we give an explicit construction of a compactly supported, uniformly continuous, and (weakly) divergence-free velocity field in $\mathbb{R}^2$ that weakly advects a measure whose support is initially the origin but for positive times ... More

Interface Width and Bulk Stability: requirements for the simulation of Deeply Quenched Liquid-Gas SystemsJun 11 2007Simulations of liquid-gas systems with extended interfaces are observed to fail to give accurate results for two reasons: the interface can get ``stuck'' on the lattice or a density overshoot develops around the interface. In the first case the bulk densities ... More

Swimming with a friend at low Reynolds numberMay 24 2007We investigate the hydrodynamic interactions between microorganisms swimming at low Reynolds number. By considering simple model swimmers, and combining analytic and numerical approaches, we investigate the time-averaged flow field around a swimmer. At ... More

An integral monitoring of GRS1915+105: simultaneous observations with INTEGRAL, RXTE, the Ryle and Nancay radio telescopesNov 07 2006Since the launch of INTEGRAL in late 2002 we have monitored the Galactic microquasar GRS 1915+105 with long exposures (~100 ks) pointings. All the observations have been conducted simultaneously with other instruments, in particular RXTE and the Ryle ... More

The orbital modulation in the radio emission of Cygnus X-1Jun 26 2002We present model lightcurves which have been created in order to explain the orbital modulation observed in the radio emission of Cyg X-1. We invoke variable absorption by the stellar wind as the black hole jet orbits around the OB companion star and ... More

Orbital modulation and longer-term variability in the radio emission from Cygnus X-1Sep 24 199820 months of observations of the radio emission at 15 GHz from Cygnus X-1, starting in 1996 October, show variations at the binary period of 5.6 days, but with a phase offset from those at X-ray wavelengths. There are also longer-term variations on a ... More

Background Independence, Diffeomorphism Invariance, and the Meaning of CoordinatesJun 10 2015Diffeomorphism invariance is sometimes taken to be a criterion of background independence. This claim is commonly accompanied by a second, that the genuine physical magnitudes (the "observables") of background-independent theories and those of background-dependent ... More

The Distortion of the Cosmic Microwave Background by the Milky WayJul 21 2014The Milky Way can act as a large-scale weak gravitational lens of the cosmic microwave background (CMB). We study this effect using a photon ray-tracing code and a Galactic mass distribution with disk, bulge and halo components. For an observer at the ... More

Radio and X-ray observations of an exceptional radio flare in the extreme z=4.72 blazar GB B1428+4217Feb 15 2006We report on the extreme behaviour of the high redshift blazar GB B1428+4217 at z=4.72. A continued programme of radio measurements has revealed an exceptional flare in the lightcurve, with the 15.2 GHz flux density rising by a factor ~3 from ~140 mJy ... More

The very flat radio - millimetre spectrum of Cygnus X-1Oct 11 1999We present almost-simultaneous detections of Cygnus X-1 in the radio and mm regimes, obtained during the low/hard X-ray state. The source displays a flat spectrum between 2 and 220 GHz, with a spectral index flatter than 0.15 (3sigma). There is no evidence ... More

Capillary filling in patterned channelsMay 27 2008We show how the capillary filling of microchannels is affected by posts or ridges on the sides of the channels. Ridges perpendicular to the flow direction introduce contact line pinning which slows, or sometimes prevents, filling; whereas ridges parallel ... More

Modeling microscopic swimmers at low Reynolds numberJan 22 2007We employ three numerical methods to explore the motion of low Reynolds number swimmers, modeling the hydrodynamic interactions by means of the Oseen tensor approximation, lattice Boltzmann simulations and multiparticle collision dynamics. By applying ... More

GMRT radio observations of microquasar GRS 1915+105Aug 01 2002We have observed microquasar GRS 1915+105 at 1.28 GHz for 8 days from June 18 to July 1, 2001 using Giant Metrewave Radio Telescope (GMRT). We have seen several isolated radio baby flares of varying intensity and duration. We have also observed broad ... More

Posterior-based proposals for speeding up Markov chain Monte CarloMar 25 2019Markov chain Monte Carlo (MCMC) is widely used for Bayesian inference in models of complex systems. Performance, however, is often unsatisfactory in models with many latent variables due to so-called poor mixing, necessitating development of application ... More

9C spectral-index distributions and source-count estimates from 15 to 93 GHz - a re-assessmentMar 06 2018In an earlier paper (2007), we used follow-up observations of a sample of sources from the 9C survey at 15.2 GHz to derive a set of spectral-index distributions up to a frequency of 90 GHz. These were based on simultaneous measurements made at 15.2 GHz ... More

Avoiding the Global Sort: A Faster Contour Tree AlgorithmNov 11 2014Dec 10 2015We revisit the classical problem of computing the \emph{contour tree} of a scalar field $f:\mathbb{M} \to \mathbb{R}$, where $\mathbb{M}$ is a triangulated simplicial mesh in $\mathbb{R}^d$. The contour tree is a fundamental topological structure that ... More

Quantum Computing with Globally Controlled Exchange-type InteractionsApr 24 2001If the interaction between qubits in a quantum computer has a non-diagonal form (e.g. the Heisenberg interaction), then one must be able to "switch it off" in order to prevent uncontrolled propagation of states. Therefore, such QC schemes typically demand ... More

The Hardness-Intensity Diagram of Cygnus X-3: Revisiting the Radio/X-Ray StatesMar 23 2010Cygnus X-3 is one of the brightest X-ray and radio sources in the Galaxy, and is well known for its erratic behaviour in X-rays as well as in the radio, occasionally producing major radio flares associated with relativistic ejections. However, even after ... More

A bright off-nuclear X-ray source: A bright off-nuclear X-ray source: a type IIn supernova, a bright ULX or a recoiling super-massive black hole in CXO J122518.6+144545Apr 29 2010In this Paper we report the discovery of CXO J122518.6+144545; a peculiar X-ray source with a position 3.6+-0.2",off-nuclear from an SDSS DR7 z=0.0447 galaxy. The 3.6" offset corresponds to 3.2 kpc at the distance of the galaxy. The 0.3-8 keV X-ray flux ... More

Discovery of Radio Outbursts in the Active Nucleus of M81May 06 1999The low-luminosity active galactic nucleus of M81 has been monitored at centimeter wavelengths since early 1993 as a by-product of radio programs to study the radio emission from Supernova 1993J. The extensive data sets reveal that the nucleus experienced ... More

X-ray and optical observations of M55 and NGC 6366: evidence for primordial binariesJul 02 2008We present Chandra X-ray Observatory ACIS-S3 X-ray imaging observations and VLT/FORS2 and Hubble Space Telescope optical observations of two low-density Galactic globular clusters; NGC 6366 and M55. We detect 16 X-ray sources with 0.5-6.0 keV luminosities ... More

Some estimates of the source counts at Planck Surveyor frequencies, using the 9C survey at 15 GHzJun 08 2007We have used multi-frequency follow-up observations of a sample of extragalactic sources from the 9C survey at 15 GHz to make deductions about the expected source population at higher radio frequencies, such as those in the lower frequency bands of the ... More

Computation in Self-assembled Nanometre Scale ArraysMar 14 2005Apr 05 2006Ordered nanoarrays, i.e. regular patterns of quantum structures at the nanometre scale, have recently been synthesized in a wide range of systems. Here I explore a possible route to technological exploitation: assuming a simple form of bistability for ... More

Gravitationally Focused Dark Matter Around Compact StarsDec 11 2011If dark matter self-annihilates then it may produce an observable signal when its density is high. The details depend on the intrinsic properties of dark matter and how it clusters in space. For example, the density profile of some dark matter candidates ... More

Rapid infrared flares in GRS 1915+105 : evidence for infrared synchrotron emissionJul 29 1997We report imaging photometry of the radio-jet black hole candidate source GRS 1915+105 in the infrared K band. The observations reveal rapid infrared flare events on timescales of less than an hour. These events are strikingly similar to those regularly ... More

Was the Narrow Line Seyfert 1 RGB J0044+193 ever radio loud?Dec 16 2004We show new radio data and a re-analysis of old data for the Narrow Line Seyfert 1 (NLSy1) galaxy RGB J0044+193. This galaxy has previously been suggested to be both radio loud, and highly variable in the radio. As most NLSy 1 galaxies are radio quiet, ... More

The radio source counts at 15 GHz and their implications for cm-wave CMB imagingFeb 28 2001We present the preliminary results of a new survey of radio sources using the Ryle telescope at 15.2 GHz. This is the highest frequency at which a survey has been done that is relevant to the issue of radio source contamination in CMB experiments. The ... More

Efficient Graph State Construction Under the Barrett and Kok SchemeApr 14 2005Sep 25 2005Recently Barrett and Kok (BK) proposed an elegant method for entangling separated matter qubits. They outlined a strategy for using their entangling operation (EO) to build graph states, the resource for one-way quantum computing. However by viewing their ... More

Multi-Qubit Gates in Arrays Coupled by 'Always On' InteractionsMar 09 2004May 12 2004Recently there has been interest in the idea of quantum computing without control of the physical interactions between component qubits. This is highly appealing since the 'switching' of such interactions is a principal difficulty in creating real devices. ... More

Schemes for Parallel Quantum Computation Without Local Control of QubitsSep 02 1999Sep 18 1999Typical quantum computing schemes require transformations (gates) to be targeted at specific elements (qubits). In many physical systems, direct targeting is difficult to achieve; an alternative is to encode local gates into globally applied transformations. ... More

Intertwining for semi-direct product operadsJan 03 2018This paper shows that the semi-direct product construction for G-operads and the levelwise Borel construction for G-cooperads are intertwined by the topological operadic bar construction.

Hyper-commutative algebras and cyclic cohomologyJan 26 2016This paper investigates a chain model for the Deligne-Mumford operad formed by homotopically trivializing the circle in a chain model for the framed little disks. The latter acts on the deformation complex of a multiplicative cyclic operad and under degeneration ... More

Simple Pulses for Universal Quantum Computation with a Heisenberg ABAB ChainApr 07 2001Recently Levy has shown that quantum computation can be performed using an ABAB.. chain of spin-1/2 systems with nearest-neighbor Heisenberg interactions. Levy notes that all necessary elementary computational `gates' can be achieved by using spin-resonance ... More

Massey products for graph homologyMar 28 2019This paper shows that the operad encoding modular operads is Koszul. Using this result we construct higher composition operations on (hairy) graph homology which characterize its rational homotopy type.

Disentangling jet and disc emission from the 2005 outburst of XTE J1118+480Jan 12 2010The black hole X-ray transient, XTE J1118+480, has now twice been observed in outburst - 2000 and 2005 - and on both occasions remained in the low/hard X-ray spectral state. Here we present radio, infrared, optical, soft X-ray and hard X-ray observations ... More

Spectral state dependence of the 0.4-2 MeV polarized emission in Cygnus X-1 seen with INTEGRAL/IBIS, and links with the AMI radio dataMay 11 2015Polarization of the >~400 keV hard tail of the microquasar Cygnus X-1 has been independently reported by INTEGRAL/IBIS, and INTEGRAL/SPI and interpreted as emission from a compact jet. These conclusions were, however, based on the accumulation of all ... More

A superburst candidate in EXO 1745--248 as a challenge to thermonuclear ignition modelsJul 23 2012We report on Chandra, RXTE, Swift/BAT and MAXI observations of a ~1 day X-ray flare and subsequent outburst of a transient X-ray source observed in October-November 2011 in the globular cluster Terzan 5. We show that the source is the same as the transient ... More

Low frequency radio monitoring of Cygnus X-1 and Cygnus X-3Sep 19 2005We present results of monitoring observations of the micro-quasars CygnusX-1 and Cygnus X-3 at 0.61 and 1.28 GHz. The observations were performed with Giant Meter-wave Radio Telescope, GMRT, between 2003 June and 2005 January. Variable, unresolved sources ... More

Merger-driven Fueling of Active Galactic Nuclei: Six Dual and Offset Active Galactic Nuclei Discovered with Chandra and Hubble Space Telescope ObservationsApr 06 2015Dual active galactic nuclei (AGNs) and offset AGNs are kpc-scale separation supermassive black holes pairs created during galaxy mergers, where both or one of the black holes are AGNs, respectively. These dual and offset AGNs are valuable probes of the ... More

Radio, Infrared and X-ray observations of GRS 1915+105Dec 10 1996We present multiwavelength observations of the superluminal jet source GRS 1915+105 in 1996 April-May, over which period a variety of phenomena, including radio QPO, strong infrared emission lines and rapid X-ray flickering and outbursts were observed. ... More

Evidence for deceleration in the radio jets of GRS1915+105?Dec 08 2006There is currently a clear discrepancy in the proper motions measured on different angular scales in the approaching radio jets of the black hole X-ray binary GRS1915+105. Lower velocities were measured with the Very Large Array (VLA) prior to 1996 than ... More

X-ray Swift observations of SN 2018cowJul 17 2018Apr 01 2019Supernova (SN) 2018cow (or AT2018cow) is an optical transient detected in the galaxy CGCG 137-068. It has been classified as a SN due to various characteristics in its optical spectra. The transient is also a bright X-ray source. We present results of ... More

Opacity effects and shock-in-jet modelling of low-level activity in Cygnus X-3Nov 20 2008We present simultaneous dual-frequency radio observations of Cygnus X-3 during a phase of low-level activity. We constrain the minimum variability timescale to be 20 minutes at 43 GHz and 30 minutes at 15 GHz, implying source sizes of 2 to 4 AU. We detect ... More

A far-ultraviolet variable with an 18-minute period in the globular cluster NGC 1851May 16 2016May 17 2016We present the detection of a variable star with an $18.05$ minute period in far-ultraviolet (FUV) images of the globular cluster NGC 1851 taken with the Hubble Space Telescope (HST). A candidate optical counterpart lies on the red horizontal branch or ... More

Is the cosmic microwave background really non-Gaussian?Apr 20 1999Aug 08 1999Two recent papers have claimed detection of non-Gaussian features in the COBE DMR sky maps of the cosmic microwave background. We confirm these results, but argue that Gaussianity is still not convincingly ruled out. Since a score of non-Gaussianity tests ... More

Distance rationalization of social rulesOct 06 2016The concept of distance rationalizability of social choice rules has been explored in recent years by several authors. We deal here with several foundational questions, and unify, correct, and generalize previous work. For example, we study a new question ... More

Distance rationalization of anonymous and homogeneous voting rulesOct 06 2016Jun 07 2018The concept of distance rationalizability of voting rules has been explored in recent years by several authors. Roughly speaking, we first choose a consensus set of elections (defined via preferences of voters over candidates) for which the result is ... More

SU(3) Corrections to B -> D l nu Form Factors at O(1/M)Feb 16 1995We compute the O(1/M,m_s) heavy quark and SU(3) corrections to B_s -> D_s e nu form factors. In the limit of vanishing light quark mass, B_s -> D_s e nu form factors are given in terms of the the B -> D e nu form factors, the leading order chiral parameter ... More

X-rays from the Globular Cluster G1: Intermediate Mass Black Hole or Low Mass X-ray Binary?May 02 2006The globular cluster G1 (Mayall II) in M31 is the most massive (~10^7 M_sun) stellar cluster in the Local Group, and it has the highest central velocity dispersion (~28 km/s). It has been claimed to host a central ~20,000 M_sun black hole, but these claims ... More

X-ray and Optical Eclipses in ULXs as Possible Indicators of Black Hole MassSep 20 2005Ultraluminous X-ray sources (ULXs) with 10^39 < L_x < 10^41 erg/s have been discovered in great numbers in external galaxies with ROSAT, Chandra, and XMM-Newton. The central question regarding this important class of sources is whether they represent ... More

Synchrotron flaring behaviour of CygnusX-3 during the February-March 1994 and September 2001 outburstsJul 18 2007Aims: In this paper we study whether the shock-in-jet model, widely used to explain the outbursting behaviour of quasars, can be used to explain the radio flaring behaviour of the microquasar Cygnus X-3. Method: We have used a method developed to model ... More

Variability of the extreme z=4.72 blazar, GB 1428+4217Jul 02 1999We report X-ray and radio variability of GB 1428+4217 which confirm its blazar nature. IR observations reveal a powerful optical-UV component, not obscured by dust, which is suggestive of the presence of a billion solar mass black hole, already formed ... More

Faint X-ray Sources in the Globular Cluster Terzan 5Jun 11 2006Jun 13 2006We report our analysis of a Chandra X-ray observation of the rich globular cluster Terzan 5, in which we detect 50 sources to a limiting 1.0-6 keV X-ray luminosity of 3*10^{31} ergs/s within the half-mass radius of the cluster. Thirty-three of these have ... More

Panglossian Prospects for Detecting Neutralino Dark Matter in Light of Natural PriorsJun 11 2008Sep 22 2008In most global fits of the constrained minimal supersymmetric model (CMSSM) to indirect data, the a priori likelihoods of any two points in tan beta are treated as equal, and the more fundamental mu and B Higgs potential parameters are fixed by potential ... More

Hierarchical surface code for network quantum computing with modules of arbitrary sizeSep 25 2015The network paradigm for quantum computing involves interconnecting many modules to form a scalable machine. Typically it is assumed that the links between modules are prone to noise while operations within modules have significantly higher fidelity. ... More

High threshold distributed quantum computing with three-qubit nodesApr 02 2012May 05 2012In the distributed quantum computing paradigm, well-controlled few-qubit `nodes' are networked together by connections which are relatively noisy and failure prone. A practical scheme must offer high tolerance to errors while requiring only simple (i.e. ... More

Quantum Computing in Arrays Coupled by 'Always On' InteractionsJan 12 2004It has recently been shown that one can perform quantum computation in a Heisenberg chain in which the interactions are 'always on', provided that one can abruptly tune the Zeeman energies of the individual (pseudo-)spins. Here we provide a more complete ... More

Quantum Computing with an 'Always On' Heisenberg InteractionOct 23 2002May 22 2003Many promising ideas for quantum computing demand the experimental ability to directly switch 'on' and 'off' a physical coupling between the component qubits. This is typically the key difficulty in implementation, and precludes quantum computation in ... More

Relativistic Iron Emission and Disk Reflection in Galactic Microquasar XTE J1748-288Aug 08 2000Aug 24 2000We report evidence for an Fe K-alpha fluorescence line feature and disk reflection in the Very High, High, and Low State X-ray spectra of the galactic microquasar XTE J1748-288 during its June~1998 outburst. Spectral analyses are made on data gathered ... More

X-ray Swift observations of SN 2018cowJul 17 2018Aug 03 2018Supernova (SN) 2018cow is an optical transient detected in the galaxy CGCG 137-068. It has been classified as a SN due to various characteristics in its optical spectra. The transient is also a bright X-ray source. We present results of the analysis of ... More

Limits on thermal variations in a dozen quiescent neutron stars over a decadeJul 14 2015In quiescent low-mass X-ray binaries (qLMXBs) containing neutron stars, the origin of the thermal X-ray component may be either release of heat from the core of the neutron star, or continuing low-level accretion. In general, heat from the core should ... More

Hamiltonian domain wall fermions at strong couplingDec 14 1999Feb 24 2000We apply strong-coupling perturbation theory to gauge theories containing domain-wall fermions in Shamir's surface version. We construct the effective Hamiltonian for the color-singlet degrees of freedom that constitute the low-lying spectrum at strong ... More

Observational evidence for stochastic biasingSep 25 1998Apr 17 1999We show that the galaxy density in the Las Campanas Redshift Survey (LCRS) cannot be perfectly correlated with the underlying mass distribution since various galaxy subpopulations are not perfectly correlated with each other, even taking shot noise into ... More

Distance rationalization of anonymous and homogeneous voting rulesOct 06 2016The concept of distance rationalizability of voting rules has been explored in recent years by several authors. Most previous work has dealt with a definition in terms of preference profiles. However, most voting rules in common use are anonymous and ... More

Quantum compilation and circuit optimisation via energy dissipationNov 07 2018Dec 19 2018We describe a method for automatically recompiling a quantum circuit A into a target circuit B, with the goal that both circuits have the same action on a specific input i.e. A|in> = B|in>. This is of particular relevance to hybrid, NISQ-era algorithms ... More

Gravity FormalityJul 03 2017We show that Willwacher's cyclic formality theorem can be extended to preserve natural Gravity operations on cyclic multivector fields and cyclic multidifferential operators. We express this in terms of a homotopy Gravity quasi-isomorphism with explicit ... More

Bayesian semiparametric analysis of multivariate continuous responses, with variable selectionMay 21 2019We develop models for multivariate Gaussian responses with nonparametric models for the means, the variances and the correlation matrix, with automatic variable selection based on spike-slab priors. We use the separation strategy to factorize the covariance ... More

Quantifying the Strategyproofness of Mechanisms via Metrics on Payoff DistributionsMay 09 2012Strategyproof mechanisms provide robust equilibrium with minimal assumptions about knowledge and rationality but can be unachievable in combination with other desirable properties such as budget-balance, stability against deviations by coalitions, and ... More

The radio source population at high frequency: follow-up of the 15-GHz 9C surveyJul 12 2004We have carried out extensive radio and optical follow-up of 176 sources from the 15 GHz 9th Cambridge survey. Optical identifications have been found for 155 of the radio sources; optical images are given with radio maps overlaid. The continuum radio ... More

Deep spectroscopy of 9C J1503+4528: a very young CSS radio source at z=0.521May 18 2006May 23 20069C J1503+4528 is a very young CSS radio galaxy, with an age of order 10^4 years. This source is therefore an ideal laboratory for the study ofthe intrinsic host galaxy/IGM properties, interactions between the radio source and surrounding ISM, links between ... More

Follow-up of the 9C survey: Initial resultsFeb 18 2003We present initial results from a follow-up of the 9C survey, complete to 25 mJy at 15 GHz, designed to assemble and investigate a sample of young radiosources. We have made radio continuum maps of 111 sources at frequencies spanning 1.4-43 GHz, and classified ... More

Supernova Remnants in High DefinitionMar 22 2019Supernova remnants (SNRs) offer the means to study SN explosions, dynamics, and shocks at sub-parsec scales. X-ray observations probe the hot metals synthesized in the explosion and the TeV electrons accelerated by the shocks, and thus they are key to ... More

The origin of the spacetime metric: Bell's `Lorentzian pedagogy' and its significance in general relativityAug 17 1999Oct 19 1999The purpose of this paper is to evaluate the `Lorentzian pedagogy' defended by J.S. Bell in his essay ``How to teach special relativity'', and to explore its consistency with Einstein's thinking from 1905 to 1952. Some remarks are also made in this context ... More

On the Role of the Accretion Disk in Black Hole Disk-Jet ConnectionsJul 16 2012Models of jet production in black hole systems suggest that the properties of the accretion disk - such as its mass accretion rate, inner radius, and emergent magnetic field - should drive and modulate the production of relativistic jets. Stellar-mass ... More

A transient relativistic radio jet from Cygnus X-1Feb 14 2006We report the first observation of a transient relativistic jet from the canonical black hole candidate, Cygnus X-1, obtained with the Multi-Element Radio-Linked Interferometer Network (MERLIN). The jet was observed in only one of six epochs of MERLIN ... More

Orbital, precessional and flaring variability of Cygnus X-1Jun 23 1999We present the results of a 2.5-year multiwavelength monitoring programme of Cygnus X-1, making use of hard and soft X-ray data, optical spectroscopy, UBVJHK photometry and radio data. In particular we confirm that the 5.6-day orbital period is apparent ... More

Minkowski space-time: a glorious non-entityMar 17 2004Einstein distinguished between ``principle'' and ``constructive'' theories in physics, and although he thought the latter were more explanatory than the former, he regarded his 1905 formulation of special relativity theory as a principle theory. Some ... More

A Chandra X-ray observation of the globular cluster Terzan 1Dec 06 2005Mar 14 2006We present a 19 ks Chandra ACIS-S observation of the globular cluster Terzan 1. Fourteen sources are detected within 1.4 arcmin of the cluster center with 2 of these sources predicted to be not associated with the cluster (background AGN or foreground ... More

First e-VLBI observations of Cygnus X-3Nov 02 2006We report the results of the first two 5 GHz e-VLBI observations of the X-ray binary Cygnus X-3 using the European VLBI Network. Two successful observing sessions were held, on 2006 April 20, when the system was in a quasi-quiescent state several weeks ... More

Simultaneous multi-wavelength observations of microquasars (the MINE collaboration)Dec 15 2003We present the international collaboration MINE (Multi-lambda INTEGRAL NEtwork) aimed at conducting multi-wavelength observations of microquasars simultaneously with the INTEGRAL satellite. The first results on GRS 1915+105 are encouraging and those to ... More

Chandra and Hubble Space Telescope Study of the Globular Cluster NGC 288Mar 14 2006Apr 28 2006We report on the Chandra X-ray Observatory observations of the globular cluster NGC 288. We detect four X-ray sources within the core radius and seven additional sources within the half-mass radius down to a limiting luminosity of Lx=7e30 erg/s (assuming ... More

Searching for the expelled hydrogen envelope in Type I supernovae via late-time H-alpha emissionFeb 16 2017We report the first results from our long-term observational survey aimed at discovering late-time interaction between the ejecta of hydrogen-poor Type I supernovae and the hydrogen-rich envelope expelled from the progenitor star several decades/centuries ... More

Continued Neutron Star Crust Cooling of the 11 Hz X-Ray Pulsar in Terzan 5: A Challenge to Heating and Cooling Models?Jun 10 2013Aug 23 2013The transient neutron star low-mass X-ray binary and 11 Hz X-ray pulsar IGR J17480-2446 in the globular cluster Terzan 5 exhibited an 11-week accretion outburst in 2010. Chandra observations performed within five months after the end of the outburst revealed ... More

Discovery of the Third Transient X-ray Binary in the Galactic Globular Cluster Terzan 5Nov 18 2013We report and study the outburst of a new transient X-ray binary (XRB) in Terzan 5, the third detected in this globular cluster, Swift J174805.3-244637 or Terzan 5 X-3. We find clear spectral hardening in Swift/XRT data during the outburst rise to the ... More

Detection of a CMB decrement towards the z = 3.8 quasar pair PC1643+4631A&BNov 26 1996In a 15-GHz Ryle-Telescope observation of PC1643+4631 A & B, a pair of quasars at redshifts z = 3.79 and 3.83 separated by 198 arcsec on the sky, we find a decrement in the cosmic microwave background (CMB) of -380 +/- 64 uJy in a 110 arcsec x 175 arcsec ... More

Universal behaviour of four-boson systems from a functional renormalisation groupApr 19 2013Sep 12 2013We apply a functional renormalisation group to systems of four bosonic atoms close to the unitary limit. We work with a local effective action that includes a dynamical trimer field and we use this field to eliminate structures that do not correspond ... More

Exact Performance of Concatenated Quantum CodesJun 11 2002When a logical qubit is protected using a quantum error-correcting code, the net effect of coding, decoherence (a physical channel acting on qubits in the codeword) and recovery can be represented exactly by an effective channel acting directly on the ... More

Sampling using a `bank' of cluesMay 03 2007Nov 26 2007An easy-to-implement form of the Metropolis Algorithm is described which, unlike most standard techniques, is well suited to sampling from multi-modal distributions on spaces with moderate numbers of dimensions (order ten) in environments typical of investigations ... More

Effective Lagrangian for strongly coupled domain wall fermionsMay 17 2001Aug 03 2001We derive the effective Lagrangian for mesons in lattice gauge theory with domain-wall fermions in the strong-coupling and large-N_c limits. We use the formalism of supergroups to deal with the Pauli-Villars fields, needed to regulate the contributions ... More

A New Hybrid N-Body-Coagulation Code for the Formation of Gas Giant PlanetsDec 02 2010Feb 18 2011We describe an updated version of our hybrid N-body-coagulation code for planet formation. In addition to the features of our 2006-2008 code, our treatment now includes algorithms for the 1D evolution of the viscous disk, the accretion of small particles ... More

On Noncontextual, Non-Kolmogorovian Hidden Variable TheoriesAug 11 2016One implication of Bell's theorem is that there cannot in general be hidden variable models for quantum mechanics that both are noncontextual and retain the structure of a classical probability space. Thus, some hidden variable programs aim to retain ... More

Making Planet Nine: A Scattered Giant in the Outer Solar SystemMar 25 2016Correlations in the orbits of several minor planets in the outer solar system suggest the presence of a remote, massive Planet Nine. With at least ten times the mass of the Earth and a perihelion well beyond 100 AU, Planet Nine poses a challenge to planet ... More

Making Planet Nine: Pebble Accretion at 250--750 AU in a Gravitationally Unstable RingMar 25 2016We investigate the formation of icy super-Earth mass planets within a gravitationally unstable ring of solids orbiting at 250-750 AU around a 1 solar mass star. Coagulation calculations demonstrate that a system of a few large oligarchs and a swarm of ... More

Magnet field sensing beyond the standard quantum limit under the effect of decoherenceJan 13 2011Entangled states can potentially be used to outperform the standard quantum limit which every classical sensor is bounded by. However, entangled states are very susceptible to decoherence, and so it is not clear whether one can really create a superior ... More