Results for "D. P. Hamilton"

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Preparation and detection of states with simultaneous spin alignment and molecular orientation in PbOJul 30 2008We are pursuing an experiment to measure the electric dipole moment of the electron using the molecule PbO. This measurement requires the ability to prepare quantum states with orientation of the molecular axis and, simultaneously, alignment of the electron ... More
The quantization of a toric manifold is given by the integer lattice points in the moment polytopeAug 21 2007Feb 13 2008We describe a very nice argument, which we learned from Sue Tolman, that the dimension of the quantization space of a toric manifold, using a Kaehler polarization, is given by the number of integer lattice points in the moment polytope.
The minimal genus problem for elliptic surfacesJun 06 2012Sep 26 2013We solve a certain case of the minimal genus problem for embedded surfaces in elliptic 4-manifolds. The proofs involve a restricted transitivity property of the action of the orientation preserving diffeomorphism group on the second homology. In the case ... More
Generalized fibre sums of 4-manifolds and the canonical classJul 15 2009May 02 2013In this paper we determine the integral homology and cohomology groups of a closed 4-manifold X obtained as the generalized fibre sum of two closed 4-manifolds M and N along embedded surfaces of genus g and self-intersection zero. If the homologies of ... More
The closure of the symplectic cone of elliptic surfacesOct 03 2012May 04 2014The symplectic cone of a closed oriented 4-manifold is the set of cohomology classes represented by symplectic forms. A well-known conjecture describes this cone for every minimal Kaehler surface. We consider the case of the elliptic surfaces E(n) and ... More
Cyclic group actions and embedded spheres in 4-manifoldsJun 11 2014Jan 20 2015In this note we derive an upper bound on the number of 2-spheres in the fixed point set of a smooth and homologically trivial cyclic group action of prime order on a simply-connected 4-manifold. This improves the a priori bound which is given by one half ... More
The field and Killing spinor equations of M-theory and type IIA/IIB supergravity in coordinate-free notationJun 30 2016Jul 19 2016We review the actions of the supergravity theory in eleven dimensions as well as the type IIA and IIB supergravities in ten dimensions and derive the bosonic equations of motion in a coordinate-free notation. We also consider the existence of supersymmetries ... More
Inequivalent contact structures on Boothby-Wang 5-manifoldsJan 12 2010Nov 13 2012We consider contact structures on simply-connected 5-manifolds which arise as circle bundles over simply-connected symplectic 4-manifolds and show that invariants from contact homology are related to the divisibility of the canonical class of the symplectic ... More
Representing homology classes by symplectic surfacesSep 23 2011Mar 23 2013We derive an obstruction to representing a homology class of a symplectic 4-manifold by an embedded, possibly disconnected, symplectic surface.
On the geography of symplectic 4-manifolds with divisible canonical classJan 19 2009In this article we consider a version of the geography question for simply-connected symplectic 4-manifolds that takes into account the divisibility of the canonical class as an additional parameter. We also find new examples of 4-manifolds admitting ... More
Homology classes of negative square and embedded surfaces in 4-manifoldsJan 16 2013Sep 26 2013Let X be a simply-connected closed oriented 4-manifold and A an embedded surface of genus g and negative self-intersection -N. We show that for fixed genus g there is an upper bound on N if the homology class of A is divisible or characteristic. In particular, ... More
Locally toric manifolds and singular Bohr-Sommerfeld leavesSep 26 2007Jun 24 2009When geometric quantization is applied to a manifold using a real polarization which is "nice enough", a result of Sniatycki says that the quantization can be found by counting certain objects, called Bohr-Sommerfeld leaves. Subsequently, several authors ... More
On certain exotic 4-manifolds of Akhmedov and ParkFeb 07 2011Feb 22 2011In an article from 2008, A. Akhmedov and B. D. Park constructed irreducible symplectic 4-manifolds homeomorphic but not diffeomorphic to the manifolds CP^2#3CP^2bar and 3CP^2#5CP^2bar. These manifolds are constructed by using generalized fibre sums. In ... More
On the conformal systoles of four-manifoldsDec 06 2005Nov 16 2006We extend a result of M. Katz on conformal systoles to all four-manifolds with b^+=1 which have odd intersection form. The same result holds for all four-manifolds with b^+=1 with even intersection form and which are symplectic or satisfy the so-called ... More
The Higgs boson for mathematicians. Lecture notes on gauge theory and symmetry breakingDec 08 2015Dec 14 2015These notes form part of a lecture course on gauge theory. The material covered is standard in the physics literature, but perhaps less well-known to mathematicians. The purpose of these notes is to make spontaneous symmetry breaking and the Higgs mechanism ... More
Iterated fibre sums of algebraic Lefschetz fibrationsSep 12 2012Oct 15 2013Let M denote the total space of a Lefschetz fibration, obtained by blowing up a Lefschetz pencil on an algebraic surface. We consider the n-fold fibre sum M(n), generalizing the construction of the elliptic surfaces E(n). For a Lefschetz pencil on a simply-connected ... More
Observation of the Kondo Effect in a Spin-3/2 Hole Quantum DotMar 02 2011Jul 20 2011We report the observation of Kondo physics in a spin- 3/2 hole quantum dot. The dot is formed close to pinch-off in a hole quantum wire defined in an undoped AlGaAs/GaAs heterostructure. We clearly observe two distinctive hallmarks of quantum dot Kondo ... More
Mechanisms for strong anisotropy of in-plane g-factors in hole based quantum point contactsDec 02 2016In-plane hole g-factors measured in quantum point contacts based on p-type heterostructures, strongly depend on the orientation of the magnetic field with respect to the electric current. This effect, first reported a decade ago and confirmed in a number ... More
Rotation sensing with trapped ionsSep 02 2016We present a protocol for using trapped ions to measure rotations via matter-wave Sagnac interferometry. The trap allows the interferometer to enclose a large area in a compact apparatus through repeated round-trips in a Sagnac geometry. We show how a ... More
Geometric quantization of integrable systems with hyperbolic singularitiesAug 03 2008Feb 04 2009We construct the geometric quantization of a compact surface using a singular real polarization coming from an integrable system. Such a polarization always has singularities, which we assume to be of nondegenerate type. In particular, we compute the ... More
Convergence of Kähler to real polarizations on flag manifolds via toric degenerationsMay 04 2011In this paper we construct a family of complex structures on a complex flag manifold that converge to the real polarization coming from the Gelfand-Cetlin integrable system, in the sense that holomorphic sections of a prequantum line bundle converge to ... More
Dynamical Instabilities in High-Obliquity SystemsNov 30 2012High-inclination circumplanetary orbits that are gravitationally perturbed by the central star can undergo Kozai oscillations---large-amplitude, coupled variations in the orbital eccentricity and inclination. We first study how this effect is modified ... More
Search for the electron electric dipole moment using $Ω$-doublet levels in PbO$^*$Mar 13 2013May 01 2013We present results of the first experiment to probe for the electric dipole moment (EDM) of the electron using an $\Omega$-doublet state in a polar molecule. If the molecule is both massive and has a large molecular-fixed frame dipole moment, then the ... More
The three-dimensional structure of Saturn's E ringNov 10 2011Jan 05 2012Saturn's diffuse E ring consists of many tiny (micron and sub-micron) grains of water ice distributed between the orbits of Mimas and Titan. Various gravitational and non-gravitational forces perturb these particles' orbits, causing the ring's local particle ... More
Extreme sensitivity of the spin-splitting and 0.7 anomaly to confining potential in one-dimensional nanoelectronic devicesAug 23 2012Quantum point contacts (QPCs) have shown promise as nanoscale spin-selective components for spintronic applications and are of fundamental interest in the study of electron many-body effects such as the 0.7 x 2e^2/h anomaly. We report on the dependence ... More
Of Horseshoes and Heliotropes: Dynamics of Dust in the Encke GapNov 20 2012Feb 14 2013The Encke Gap is a 320-km-wide opening in Saturn's outer A ring that contains the orbit of the small moon Pan and an array of dusty features composed of particles less than 100 microns across. In particular, there are three narrow ringlets in this region ... More
Herwig++ 2.0 Release NoteSep 29 2006A new release of the Monte Carlo program Herwig++ (version 2.0) is now available. This is the first version of the program which can be used for hadron-hadron physics and includes the full simulation of both initial- and final-state QCD radiation.
Scaling of the Kondo zero bias peak in a hole quantum dot at finite temperaturesMay 07 2013We have measured the zero bias peak in differential conductance in a hole quantum dot. We have scaled the experimental data with applied bias and compared to real time renormalization group calculations of the differential conductance as a function of ... More
Electrometry using the quantum Hall effect in a bilayer 2D electron systemMar 25 2010We discuss the development of a sensitive electrometer that utilizes a two-dimensional electron gas (2DEG) in the quantum Hall regime. As a demonstration, we measure the evolution of the Landau levels in a second, nearby 2DEG as the applied perpendicular ... More
Metal-insulator transition at B=0 in a dilute two dimensional GaAs-AlGaAs hole gasSep 22 1997Oct 12 1997We report the observation of a metal insulator transition at B=0 in a high mobility two dimensional hole gas in a GaAs-AlGaAs heterostructure. A clear critical point separates the insulating phase from the metallic phase, demonstrating the existence of ... More
Weak localisation, hole-hole interactions and the "metal"-insulator transition in two dimensionsOct 22 1999Oct 24 1999A detailed investigation of the metallic behaviour in high quality GaAs-AlGaAs two dimensional hole systems reveals the presence of quantum corrections to the resistivity at low temperatures. Despite the low density ($r_{s}>10$) and high quality of these ... More
Origin of the hysteresis in bilayer 2D systems in the quantum Hall regimeSep 28 2010The hysteresis observed in the magnetoresistance of bilayer 2D systems in the quantum Hall regime is generally attributed to the long time constant for charge transfer between the 2D systems due to the very low conductivity of the quantum Hall bulk states. ... More
Re-entrant insulator-metal-insulator transition at B=0 in a two dimensional hole gasAug 11 1998We report the observation of a re-entrant insulator--metal--insulator transition at B=0 in a two dimensional (2D) hole gas in GaAs at temperatures down to 30mK. At the lowest carrier densities the holes are strongly localised. As the carrier density is ... More
Minimality and irreducibility of symplectic four-manifoldsSep 09 2005Jan 02 2006We prove that all minimal symplectic four-manifolds are essentially irreducible. We also clarify the relationship between holomorphic and symplectic minimality of K\"ahler surfaces. This leads to a new proof of the deformation-invariance of holomorphic ... More
Herwig++ 2.3 Release NoteDec 02 2008A new release of the Monte Carlo program Herwig++ (version 2.3) is now available. This version includes a number of improvements including: the extension of the program to lepton-hadron collisions; the inclusion of several processes accurate at next-to-leading ... More
Algebraic bounds for heterogeneous site percolation on directed and undirected graphsMay 15 2015Oct 15 2016We analyze site percolation on directed and undirected graphs with site-dependent open-site probabilities. We construct upper bounds on cluster susceptibilities, vertex connectivity functions, and the expected number of simple open cycles through a chosen ... More
Tight lower bound for percolation threshold on a quasi-regular graphApr 30 2014We construct an exact expression for the site percolation threshold p_c on a quasi-regular tree, and a related exact lower bound for a quasi-regular graph. Both are given by the inverse spectral radius of the appropriate Hashimoto matrix used to count ... More
The Fate of Sub-micron Circumplanetary Dust Grains II: Multipolar FieldsJun 05 2012We study the radial and vertical stability of dust grains launched with all charge-to-mass ratios at arbitrary distances from rotating planets with complex magnetic fields. We show that the aligned dipole magnetic field model analyzed by Jontof-Hutter ... More
The physics of the relativistic counter-streaming instability that drives mass inflation inside black holesNov 12 2008Jun 15 2010If you fall into a real astronomical black hole (choosing a supermassive black hole, to make sure that the tidal forces don't get you first), then you will probably meet your fate not at a central singularity, but rather in the exponentially growing, ... More
The river model of black holesNov 12 2004Aug 31 2006This paper presents an under-appreciated way to conceptualize stationary black holes, which we call the river model. The river model is mathematically sound, yet simple enough that the basic picture can be understood by non-experts. %that can by understood ... More
Secular Orbital Evolution of Compact Planet SystemsFeb 07 2013Oct 24 2013Recent observations have shown that at least some close-in exoplanets maintain eccentric orbits despite tidal circularization timescales that are typically shorter than stellar ages. We explore gravitational interactions with a distant planetary companion ... More
Production of Intermediate-Mass Black Holes in Globular ClustersJun 11 2001The discovery of numerous non-nuclear X-ray point sources with luminosities L>10^39 erg/s in several starburst galaxies has stimulated speculation about their nature and origin. The strong variability seen in several sources points to massive black holes ... More
Fisher Information and Kinetic-energy Functionals: A Dequantization ApproachMay 21 2009We strengthen the connection between Information Theory and quantum-mechanical systems using a recently developed dequantization procedure whereby quantum fluctuations latent in the quantum momentum are suppressed. The dequantization procedure results ... More
On the origin of the Trojan asteroids: Effects of Jupiter's mass accretion and radial migrationJul 19 2000We present analytic and numerical results which illustrate the effects of Jupiter's accretion of nebular gas and the planet's radial migration on its Trojan companions. Initially, we approximate the system by the planar circular restricted three-body ... More
Four-Body Effects in Globular Cluster Black Hole CoalescenceFeb 15 2002In the high density cores of globular clusters, multibody interactions are expected to be common, with the result that black holes in binaries are hardened by interactions. It was shown by Sigurdsson & Hernquist (1993) and others that 10 solar mass black ... More
Information content of the non-linear power spectrum: the effect of beat-coupling to large scalesNov 14 2005Jun 21 2006We measure the covariance of the non-linear matter power spectrum from N-body simulations using two methods. In the first case, the covariance of power is estimated from the scatter over many random realizations of the density field. In the second, we ... More
Information content of the non-linear matter power spectrumFeb 03 2005Apr 12 2005We use an ensemble of N-body simulations of the currently favoured (concordance) cosmological model to measure the amount of information contained in the non-linear matter power spectrum about the amplitude of the initial power spectrum. Two surprising ... More
Lyman Limit Imaging of High Redshift Galaxies. III. New Observations of 4 QSO FieldsSep 18 1995We present the results of deep Lyman limit imaging in four new fields as part of a continuing search for galaxies at $3.0 \le z \le 3.5$. The technique uses a custom broad--band filter set ($U_n G {\cal R}$) designed to isolate objects having Lyman continuum ... More
Exponential decay of connectivity and uniqueness in percolation on finite and infinite graphsOct 16 2016We give an upper bound for the uniqueness transition on an arbitrary locally finite graph ${\cal G}$ in terms of the limit of the spectral radii $\rho\left[ H({\cal G}_t)\right]$ of the non-backtracking (Hashimoto) matrices for an increasing sequence ... More
The Fate of Sub-Micron Circumplanetary Dust Grains I: Aligned Dipolar Magnetic FieldsJan 17 2012We study the stability of charged dust grains orbiting a planet and subject to gravity and the electromagnetic force. Our numerical models cover a broad range of launch distances from the planetary surface to beyond synchronous orbit, and the full range ... More
Spectral bounds for percolation on directed and undirected graphsMar 02 2015We give several algebraic bounds for percolation on directed and undirected graphs: proliferation of strongly-connected clusters, proliferation of in- and out-clusters, and the transition associated with the number of giant components.
Proceedings of the Fourth International Workshop on Verification and Program TransformationJul 06 2016This volume contains the revised versions of papers presented at the Fourth International Workshop on Verification and Program Transformation (VPT 2016) on April 2, 2016 in Eindhoven, The Netherlands. The workshop is an event of the European Joint Conferences ... More
Implications of the PSR 1257+12 Planetary System for Isolated Millisecond PulsarsDec 02 2000The first extrasolar planets were discovered in 1992 around the millisecond pulsar PSR 1257+12. We show that recent developments in the study of accretion onto magnetized stars, plus the existence of the innermost, moon-sized planet in the PSR 1257+12 ... More
Flavor Changing Neutral Currents in a Realistic Composite Technicolor ModelNov 20 1992We consider the phenomenology of a composite technicolor model proposed recently by Georgi. Composite technicolor interactions produce four-quark operators in the low energy theory that contribute to flavor changing neutral current processes. While we ... More
Excitonic Superfluidity and Screening in Electron-Hole Bilayer SystemsAug 01 2013Feb 24 2014Superfluidity in e-h bilayers in graphene and GaAs has been predicted many times but not observed. A key problem is how to treat the screening of the Coulomb interaction for pairing. Different mean-field theories give dramatically different conclusions, ... More
Fabrication and characterisation of ambipolar devices on an undoped AlGaAs/GaAs heterostructureApr 03 2012We have fabricated AlGaAs/GaAs heterostructure devices in which the conduction channel can be populated with either electrons or holes simply by changing the polarity of a gate bias. The heterostructures are entirely undoped, and carriers are instead ... More
Using a tunable quantum wire to measure the large out-of-plane spin splitting of quasi two-dimensional holes in a GaAs nanostructureJan 31 2013The out-of-plane g-factor g_perp for quasi-2D holes in a (100) GaAs heterostructure is studied using a variable width quantum wire. A direct measurement of the Zeeman splitting is performed in a magnetic field applied perpendicular to the 2D plane. We ... More
Observation of orientation- and $k$-dependent Zeeman spin-splitting in hole quantum wires on (100)-oriented AlGaAs/GaAs heterostructuresSep 29 2009We study the Zeeman spin-splitting in hole quantum wires oriented along the $[011]$ and $[01\bar{1}]$ crystallographic axes of a high mobility undoped (100)-oriented AlGaAs/GaAs heterostructure. Our data shows that the spin-splitting can be switched `on' ... More
Herwig++ 2.5 Release NoteFeb 08 2011A new release of the Monte Carlo program Herwig++ (version 2.5) is now available. This version comes with a number of improvements including: new next-to-leading order matrix elements, including weak boson pair production; a colour reconnection model; ... More
Radio-frequency reflectometry on large gated 2-dimensional systemsOct 29 2008We have embedded an AlGaAs/GaAs based, gated 2D hole system (2DHS) into an impedance transformer $LC$ circuit, and show that by using radio-frequency reflectometry it is possible to perform sensitive, large bandwidth, electrical resistance measurements ... More
Determining the stability and activation energy of Si acceptors in AlGaAs using quantum interference in an open hole quantum dotDec 06 2013Apr 07 2014We fabricated an etched hole quantum dot in a Si-doped (311)A AlGaAs/GaAs heterostructure to study disorder effects via magnetoconductance fluctuations (MCF) at millikelvin temperatures. Recent experiments in electron quantum dots have shown that the ... More
Herwig++ 2.6 Release NoteMay 22 2012A new release of the Monte Carlo event generator Herwig++ (version 2.6) is now available. This version comes with a number of improvements including: a new structure for the implementation of next-to-leading order matrix elements; an improved treatment ... More
Memory beyond memory in heart beating: an efficient way to detect pathological conditionsJul 30 2001We study the long-range correlations of heartbeat fluctuations with the method of diffusion entropy. We show that this method of analysis yields a scaling parameter $\delta$ that apparently conflicts with the direct evaluation of the distribution of times ... More
Self-aligned fabrication process for silicon quantum computer devicesAug 20 2002Aug 28 2002We describe a fabrication process for devices with few quantum bits (qubits), which are suitable for proof-of-principle demonstrations of silicon-based quantum computation. The devices follow the Kane proposal to use the nuclear spins of 31P donors in ... More
Single-Shot Readout with the Radio Frequency Single Electron Transistor in the Presence of Charge NoiseApr 16 2003Sep 22 2004The radio frequency single electron transistor (rf-SET) possesses key requirements necessary for reading out a solid state quantum computer. This work explores the use of the rf-SET as a single-shot readout device in the presence of 1/f and telegraph ... More
Non-extensive diffusion entropy analysis: non-stationarity in teen birth phenomenaMay 24 2002A complex process is often a balance between non-stationary and stationary components. We show how the non-extensive Tsallis q-entropy indicator may be interpreted as a measure of non-stationarity in time series. This is done by applying the non-extensive ... More
Herwig++ 2.1 Release NoteNov 20 2007A new release of the Monte Carlo program Herwig++ (version 2.1) is now available. This version includes a number of significant improvements including: an eikonal multiple parton-parton scattering model of the underlying event; the inclusion of Beyond ... More
Zeeman splitting in ballistic hole quantum wiresJul 14 2006We have studied the Zeeman splitting in ballistic hole quantum wires formed in a (311)A quantum well by surface gate confinement. Transport measurements clearly show lifting of the spin degeneracy and crossings of the subbands when an in-plane magnetic ... More
Observing sub-microsecond telegraph noise with the radio frequency single electron transistorSep 22 2004Telegraph noise, which originates from the switching of charge between meta-stable trapping sites, becomes increasingly important as device sizes approach the nano-scale. For charge-based quantum computing, this noise may lead to decoherence and loss ... More
Ultra-shallow quantum dots in an undoped GaAs/AlGaAs 2D electron gasDec 21 2011Mar 16 2013We report quantum dots fabricated on very shallow 2-dimensional electron gases, only 30 nm below the surface, in undoped GaAs/AlGaAs heterostructures grown by molecular beam epitaxy. Due to the absence of dopants, an improvement of more than one order ... More
Anisotropic Zeeman splitting in ballistic one-dimensional hole systemsJul 14 2006We have studied the effect of an in-plane magnetic field B on a one-dimensional hole system in the ballistic regime created by surface gate confinement. We observed clearly the lifting of the spin degeneracy due to the Zeeman effect on the one dimensional ... More
Conductance quantization and the 0.7x2e2/h conductance anomaly in one-dimensional hole systemsJul 25 2005We have studied ballistic transport in a 1D channel formed using surface gate techniques on a back-gated, high-mobility, bilayer 2D hole system. At millikelvin temperatures, robust conductance quantization is observed in the quantum wire formed in the ... More
Herwig++ Status ReportSep 11 2008Herwig++ is the successor of the event generator HERWIG. In its present version 2.2.1 it provides a program for full LHC event generation which is superior to the previous program in many respects. We briefly summarize its features and describe present ... More
Herwig++ 2.2 Release NoteApr 18 2008A new release of the Monte Carlo program Herwig++ (version 2.2) is now available. This version includes a number of improvements including: matrix elements for the production of an electroweak gauge boson, W and Z, in association with a jet; several new ... More
The Structure of Rh$_8^+$ in the Gas PhaseSep 30 2009The geometric structure of the Rh$_8^+$ cation is investigated using a combination of far-infrared multiple photon dissociation spectroscopy and density functional theory (DFT) calculations. The energetic ordering of the different structural motifs is ... More
Development and operation of the twin radio frequency single electron transistor for solid state qubit readoutFeb 04 2003Apr 08 2004Ultra-sensitive detectors and readout devices based on the radio frequency single electron transistor (rf-SET) combine near quantum-limited sensitivity with fast operation. Here we describe a twin rf-SET detector that uses two superconducting rf-SETs ... More
Evolution of the bilayer nu = 1 quantum Hall state under charge imbalanceMar 19 2004We use high-mobility bilayer hole systems with negligible tunneling to examine how the bilayer nu = 1 quantum Hall state evolves as charge is transferred from one layer to the other at constant total density. We map bilayer nu = 1 state stability versus ... More
Compressibility measurements of quasi-one-dimensional quantum wiresAug 05 2011We report measurements of the compressibility of a one-dimensional (1D) quantum wire, defined in the upper well of a GaAs/AlGaAs double quantum well heterostructure. A wire defined simultaneously in the lower well probes the ability of the upper wire ... More
The effect of screening long-range Coulomb interactions on the metallic behavior in two-dimensional hole systemsApr 25 2008We have developed a technique utilizing a double quantum well heterostructure that allows us to study the effect of a nearby ground-plane on the metallic behavior in a GaAs two-dimensional hole system (2DHS) in a single sample and measurement cool-down, ... More
0.7 Structure and Zero Bias Anomaly in Ballistic Hole Quantum WiresFeb 08 2007Jul 01 2008We study the anomalous conductance plateau around $G = 0.7(2e^{2}/h)$ and the zero-bias anomaly in ballistic hole quantum wires with respect to in-plane magnetic fields applied parallel $B_{\parallel}$ and perpendicular $B_{\perp}$ to the quantum wire. ... More
Herwig++ Physics and ManualMar 06 2008Dec 02 2008In this paper we describe Herwig++ version 2.3, a general-purpose Monte Carlo event generator for the simulation of hard lepton-lepton, lepton-hadron and hadron-hadron collisions. A number of important hard scattering processes are available, together ... More
Manifestation of a non-abelian gauge field in a p-type semiconductor systemApr 21 2016Jun 01 2016Gauge theories, while describing fundamental interactions in nature, also emerge in a wide variety of physical systems. Abelian gauge fields have been predicted and observed in a number of novel quantum many-body systems, topological insulators, ultracold ... More
The origin of gate hysteresis in p-type Si-doped AlGaAs/GaAs heterostructuresJul 12 2012Sep 15 2012Gate instability/hysteresis in modulation-doped p-type AlGaAs/GaAs heterostructures impedes the development of nanoscale hole devices, which are of interest for topics from quantum computing to novel spin physics. We present an extended study conducted ... More
The Impact of Small-Angle Scattering on Ballistic Transport in Quantum DotsApr 01 2012Disorder increasingly affects performance as electronic devices are reduced in size. The ionized dopants used to populate a device with electrons are particularly problematic, leading to unpredictable changes in the behavior of devices such as quantum ... More
Probing the Sensitivity of Electron Wave Interference to Disorder-Induced Scattering in Solid-State DevicesJun 28 2011May 07 2012The study of electron motion in semiconductor billiards has elucidated our understanding of quantum interference and quantum chaos. The central assumption is that ionized donors generate only minor perturbations to the electron trajectories, which are ... More
Variational approach to dequantizationNov 08 2005Mar 28 2006We present a dequantization procedure based on a variational approach whereby quantum fluctuations latent in the quantum momentum are suppressed. This is done by adding generic local deformations to the quantum momentum operator which give rise to a deformed ... More
Using Formal Specifications to Support Model Based Testing ASDSpec: A Tool Combining the Best of Two TechniquesMar 28 2014Formal methods and testing are two important approaches that assist in the development of high quality software. For long time these approaches have been seen as competitors and there was very little interaction between the two communities. In recent ... More
Chaotic dust dynamics and implications for the hemispherical color asymmetries of the Uranian satellitesJun 17 2013Dust grains generated by the Uranian irregular satellites will undergo chaotic large-amplitude eccentricity oscillations under the simultaneous action of radiation forces and the highly misaligned quadrupole potentials of the oblate planet and distant ... More
Classical kinetic energy, quantum fluctuation terms and kinetic-energy functionalsSep 17 2006Apr 08 2007We employ a recently formulated dequantization procedure to obtain an exact expression for the kinetic energy which is applicable to all kinetic-energy functionals. We express the kinetic energy of an N-electron system as the sum of an N-electron classical ... More
A Generic Multi-node State Monitoring SubsystemMay 30 2003The BaBar online data acquisition (DAQ) system includes approximately fifty Unix systems that collectively implement the level-three trigger. These systems all run the same code. Each of these systems has its own state, and this state is expected to change ... More
A high resolution UV absorption spectrum of supernova ejecta in SN1006Feb 25 2006We report a high resolution, far-ultraviolet, STIS E140M spectrum of the strong, broad Si II, III, and IV features produced by the ejecta of SN1006 seen in absorption against the background Schweizer-Middleditch star. The spectrum confirms the extreme ... More
Growth of Intermediate-Mass Black Holes in Globular ClustersFeb 23 2004We present results of numerical simulations of sequences of binary-single scattering events of black holes in dense stellar environments. The simulations cover a wide range of mass ratios from equal mass objects to 1000:10:10 solar masses and compare ... More
On measuring the covariance matrix of the nonlinear power spectrum from simulationsNov 14 2005Jun 21 2006We show how to estimate the covariance of the power spectrum of a statistically homogeneous and isotropic density field from a single periodic simulation, by applying a set of weightings to the density field, and by measuring the scatter in power spectra ... More
The Absence of X-ray Flashes from Nearby Galaxies and the Gamma-Ray Burst Distance ScaleJul 31 1996If typical gamma-ray bursts (GRBs) have X-ray counterparts similar to those detected by Ginga, then sensitive focusing X-ray telescopes will be able to detect GRBs three orders of magnitude fainter than the detection limit of the Burst and Transient Source ... More
Charge shelving and bias spectroscopy for the readout of a charge-qubit on the basis of superposition statesAug 15 2003Jul 27 2004Charge-based qubits have been proposed as fundamental elements for quantum computers. One commonly proposed readout device is the single-electron transistor (SET). SETs can distinguish between localized charge states, but lack the sensitivity to directly ... More
Old open clusters: UBGVRI photometry of NGC 2506Jul 07 1997UBGVRI photometry for the open cluster NGC 2506 is presented. From comparison of the observed colour-magnitude diagrams with simulations based on stellar evolutionary models we derive in a self consistent way reddening, distance, and age of the cluster: ... More
The EINSTEIN Observatory Detection of Faint X-Ray FlashesJul 31 1996We report on the result of an extensive search for X-ray counterparts to Gamma Ray Bursts (GRB) using data acquired with the Imaging Proportional Counter (IPC) on-board the Einstein Observatory. We examine background sky fields from all pointed observations ... More
Multiband Mechanism for the Sign Reversal of Coulomb Drag Observed in Double Bilayer Graphene HeterostructuresJun 28 2018Coupled 2D sheets of electrons and holes are predicted to support novel quantum phases. Two experiments of Coulomb drag in electron-hole (e-h) double bilayer graphene (DBLG) have reported an unexplained and puzzling sign reversal of the drag signal. However, ... More
An Improved Process for Fabricating High-Mobility Organic Molecular Crystal Field-Effect TransistorsJun 21 2007In this paper we present an improved process for producing elastomer transistor stamps and high-mobility organic field-effect transistors (FETs) based on semiconducting acene molecular crystals. In particular, we have removed the need to use a silanized ... More
Galileo In-Situ Dust Measurements in Jupiter's Gossamer RingsMar 19 2008During its late orbital mission at Jupiter the Galileo spacecraft made two passages through the giant planet's gossamer ring system. The impact-ionization dust detector on board successfully recorded dust impacts during both ring passages and provided ... More