Results for "J. R. Petta"

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Dispersive readout of valley splittings in cavity-coupled silicon quantum dotsJul 29 2016The bandstructure of bulk silicon has a six-fold valley degeneracy. Strain in the Si/SiGe quantum well system partially lifts the valley degeneracy, but the materials factors that set the splitting of the two lowest lying valleys are still under intense ... More
Hyperfine-Enhanced Gyromagnetic Ratio of a Nuclear Spin in DiamondMar 25 2015Nuclear spins in the solid state environment of diamond are highly coherent, but difficult to rapidly control due to the small nuclear gyromagnetic ratio. Here we demonstrate a more than 50-fold enhancement of the effective nuclear gyromagnetic ratio ... More
High-quality quantum point contact in two-dimensional GaAs (311)A hole systemSep 29 2008We studied ballistic transport across a quantum point contact (QPC) defined in a high-quality, GaAs (311)A two-dimensional (2D) hole system using shallow etching and top-gating. The QPC conductance exhibits up to 11 quantized plateaus. The ballistic one-dimensional ... More
Harnessing the GaAs quantum dot nuclear spin bath for quantum controlFeb 24 2010Dec 20 2011We theoretically demonstrate that nuclear spins can be harnessed to coherently control two-electron spin states in a double quantum dot. Hyperfine interactions lead to an avoided crossing between the spin singlet state and the ms = +1 triplet state, T_+ ... More
Optimized cavity-mediated dispersive two-qubit gates between spin qubitsFeb 20 2019The recent realization of a coherent interface between a single electron in a silicon quantum dot and a single photon trapped in a superconducting cavity opens the way for implementing photon-mediated two-qubit entangling gates. In order to couple a spin ... More
Interplay of charge and spin coherence in Landau-Zener-Stückelberg-Majorana interferometryOct 06 2012Jul 16 2013We study Landau-Zener dynamics in a double quantum dot filled with two electrons, where the spin states can become correlated with charge states and the level velocity can be tuned in a time-dependent fashion. We show that a correct interpretation of ... More
Protocol for a resonantly-driven three-qubit Toffoli gate with silicon spin qubitsMay 16 2019The three-qubit Toffoli gate plays an important role in quantum error correction and complex quantum algorithms such as Shor's factoring algorithm, motivating the search for efficient implementations of this gate. Here we introduce a Toffoli gate suitable ... More
Controlled MOCVD growth of Bi2Se3 topological insulator nanoribbonsJun 14 2012Topological insulators are a new class of materials that support topologically protected electronic surface states. Potential applications of the surface states in low dissipation electronic devices have motivated efforts to create nanoscale samples with ... More
Correlating the nanostructure and electronic properties of InAs nanowiresDec 08 2009Oct 04 2010The electronic properties and nanostructure of InAs nanowires are correlated by creating multiple field effect transistors (FETs) on nanowires grown to have low and high defect density segments. 4.2 K carrier mobilities are ~4X larger in the nominally ... More
A quadrupolar exchange-only spin qubitJul 27 2018We propose a quadrupolar exchange-only spin (QUEX) qubit that is highly robust against charge noise and nuclear spin dephasing, the dominant decoherence mechanisms in quantum dots. The qubit consists of four electrons trapped in three quantum dots, and ... More
Measurements of strongly-anisotropic g-factors for spins in single quantum statesJun 22 2002We have measured the full angular dependence, as a function of the direction of magnetic field, for the Zeeman splitting of individual energy states in copper nanoparticles. The g-factors for spin splitting are highly anisotropic, with angular variations ... More
Studies of spin-orbit scattering in noble-metal nanoparticles using energy level tunneling spectroscopyJun 21 2001The effects of spin-orbit scattering on discrete electronic energy levels are studied in copper, silver, and gold nanoparticles. Level-to-level fluctuations of the effective $g$-factor for Zeeman splitting are characterized, and the statistics are found ... More
Probing electron-phonon interactions in the charge-photon dynamics of cavity-coupled double quantum dotsNov 03 2017Electron-phonon coupling is known to play an important role in the charge dynamics of semiconductor quantum dots. Here we explore its role in the combined charge-photon dynamics of cavity-coupled double quantum dots. Previous work on these systems has ... More
Phase locking of a semiconductor double quantum dot single atom maserJul 24 2017We experimentally study the phase stabilization of a semiconductor double quantum dot (DQD) single atom maser by injection locking. A voltage-biased DQD serves as an electrically tunable microwave frequency gain medium. The statistics of the maser output ... More
Spin-dependent transport in molecular tunnel junctionsApr 30 2004We present measurements of magnetic tunnel junctions made using a self-assembled-monolayer molecular barrier. Ni/octanethiol/Ni samples were fabricated in a nanopore geometry. The devices exhibit significant changes in resistance as the angle between ... More
A coherent beam splitter for electronic spin statesOct 04 2010Rapid coherent control of electron spin states is required for implementation of a spin-based quantum processor. We demonstrate coherent control of electronic spin states in a double quantum dot by sweeping an initially prepared spin singlet state through ... More
MOCVD synthesis of compositionally tuned topological insulator nanowiresJul 22 2015Device applications involving topological insulators (TIs) will require the development of scalable methods for fabricating TI samples with sub-micron dimensions, high quality surfaces, and controlled compositions. Here we use Bi-, Se-, and Te-bearing ... More
Superconductor-semiconductor hybrid cavity quantum electrodynamicsMay 03 2019Light-matter interactions at the single particle level have generally been explored in the context of atomic, molecular, and optical physics. Recent advances motivated by quantum information science have made it possible to explore coherent interactions ... More
Fast Room-Temperature Phase Gate on a Single Nuclear Spin in DiamondMar 13 2014Jul 14 2014Nuclear spins support long lived quantum coherence due to weak coupling to the environment, but are difficult to rapidly control using nuclear magnetic resonance (NMR) as a result of the small nuclear magnetic moment. We demonstrate a fast ~ 500 ns nuclear ... More
Large anomalous Hall effect in ferromagnetic insulator-topological insulator heterostructuresJul 05 2014Aug 25 2014We demonstrate the van der Waals epitaxy of the topological insulator compound Bi2Te3 on the ferromagnetic insulator Cr2Ge2Te6. The layers are oriented with (001) of Bi2Te3 parallel to (001) of Cr2Ge2Te6 and (110) of Bi2Te3 parallel to (100) of Cr2Ge2Te6. ... More
Phonon-Assisted Gain in a Semiconductor Double Quantum Dot MaserJan 14 2015Apr 13 2015We develop a microscopic model for the recently demonstrated double quantum dot (DQD) maser. In characterizing the gain of this device we find that, in addition to the direct stimulated emission of photons, there is a large contribution from the simultaneous ... More
Microwave detection of electron-phonon interactions in a cavity-coupled double quantum dotNov 13 2017Quantum confinement leads to the formation of discrete electronic states in quantum dots. Here we probe electron-phonon interactions in a suspended InAs nanowire double quantum dot (DQD) that is electric-dipole coupled to a microwave cavity. We apply ... More
Fast charge sensing of a cavity-coupled double quantum dot using a Josephson parametric amplifierFeb 04 2015We demonstrate fast readout of a double quantum dot (DQD) that is coupled to a superconducting resonator. Utilizing parametric amplification in a nonlinear operational mode, we improve the signal-to-noise ratio (SNR) by a factor of 2000 compared to the ... More
Polarized Temperature Dependent Raman Study of Bi2Te3-Cr2Ge2Te6 heterostructure and the Ferromagnetic Insulator Cr2Ge2Te6Oct 07 2014Cr2Ge2Te6 has been of interest for decades, as it is one of only a few ferromagnetic insulators. Recently, this material has been revisited due to its potential as a substrate for Bi2Te3, a topological insulator. This enables the possibility of studying ... More
Circuit Quantum Electrodynamics Architecture for Gate-Defined Quantum Dots in SiliconOct 18 2016We demonstrate a hybrid device architecture where the charge states in a double quantum dot (DQD) formed in a Si/SiGe heterostructure are read out using an on-chip superconducting microwave cavity. A quality factor Q = 5,400 is achieved by selectively ... More
Single charge sensing and transport in double quantum dots fabricated from commercially grown Si/SiGe heterostructuresDec 13 2011Mar 21 2012We perform quantum Hall measurements on three types of commercially available modulation doped Si/SiGe heterostructures to determine their suitability for depletion gate defined quantum dot devices. By adjusting the growth parameters, we are able to achieve ... More
Photon Emission from a Cavity-Coupled Double Quantum DotJan 30 2014Jul 28 2014We study a voltage biased InAs double quantum dot (DQD) that is coupled to a superconducting transmission line resonator. Inelastic tunneling in the DQD is mediated by electron phonon coupling and coupling to the cavity mode. We show that electronic transport ... More
Injection Locking of a Semiconductor Double Quantum Dot MicromaserAug 17 2015Emission linewidth is an important figure of merit for masers and lasers. We recently demonstrated a semiconductor double quantum dot (DQD) micromaser where photons are generated through single electron tunneling events. Charge noise directly couples ... More
Sisyphus Thermalization of Photons in a Cavity-Coupled Double Quantum DotDec 03 2015Oct 11 2016We investigate the non-classical states of light that emerge in a microwave resonator coupled to a periodically-driven electron in a nanowire double quantum dot (DQD). Under certain drive configurations, we find that the resonator approaches a thermal ... More
Semiconductor double quantum dot micromaserJul 22 2015The coherent generation of light, from masers to lasers, relies upon the specific structure of the individual emitters that lead to gain. Devices operating as lasers in the few-emitter limit provide opportunities for understanding quantum coherent phenomena, ... More
Highly-tunable formation of nitrogen-vacancy centers via ion implantationJul 05 2014Aug 26 2014We demonstrate highly-tunable formation of nitrogen-vacancy (NV) centers using 20 keV 15N+ ion implantation through arrays of high-resolution apertures fabricated with electron beam lithography. By varying the aperture diameters from 80 to 240 nm, as ... More
The Role of Multilevel Landau-Zener Interference in Extreme Harmonic GenerationJul 27 2016Motivated by the observation of multiphoton electric dipole spin resonance processes in InAs nanowires, we theoretically study the transport dynamics of a periodically driven five-level system, modeling the level structure of a two-electron double quantum ... More
Extreme Harmonic Generation in Electrically Driven Spin ResonanceDec 13 2013Jul 03 2014We report the observation of multiple harmonic generation in electric dipole spin resonance in an InAs nanowire double quantum dot. The harmonics display a remarkable detuning dependence: near the interdot charge transition as many as eight harmonics ... More
On-Chip Quantum Dot Light Source for Quantum State ReadoutJul 27 2017We use microwave radiation generated by a semiconductor double quantum dot (DQD) micromaser for charge state detection. A cavity is populated with n_c ~ 6000 photons by driving a current through an emitter DQD. These photons are used to sense the charge ... More
Input-output theory for spin-photon coupling in Si double quantum dotsOct 06 2017The interaction of qubits via microwave frequency photons enables long-distance qubit-qubit coupling and facilitates the realization of a large-scale quantum processor. However, qubits based on electron spins in semiconductor quantum dots have proven ... More
Nonadiabatic quantum control of a semiconductor charge qubitJul 25 2011Mar 25 2012We demonstrate multipulse quantum control of a single electron charge qubit. The qubit is manipulated by applying nonadiabatic voltage pulses to a surface depletion gate and readout is achieved using a quantum point contact charge sensor. We observe Ramsey ... More
Spins in few-electron quantum dotsOct 16 2006Jun 05 2007This review describes the physics of spins in quantum dots containing one or two electrons, from an experimentalist's viewpoint. Various methods for extracting spin properties from experiment are presented, restricted exclusively to electrical measurements. ... More
Charge Relaxation in a Single Electron Si/SiGe Double Quantum DotApr 09 2013Apr 15 2013We measure the interdot charge relaxation time T_1 of a single electron trapped in an accumulation mode Si/SiGe double quantum dot. The energy level structure of the charge qubit is determined using photon assisted tunneling, which reveals the presence ... More
Manipulation of a single charge in a double quantum dotAug 06 2004We manipulate a single electron in a fully tunable double quantum dot using microwave excitation. Under resonant conditions, microwaves drive transitions between the (1,0) and (0,1) charge states of the double dot. Local quantum point contact charge detectors ... More
Coherent Adiabatic Spin Control in the Presence of Charge Noise Using Tailored PulsesJul 12 2012Mar 02 2013We study finite-time Landau-Zener transitions at a singlet-triplet level crossing in a GaAs double quantum dot, both experimentally and theoretically. Sweeps across the anticrossing in the high driving speed limit result in oscillations with a small visibility. ... More
A Radio Frequency Charge Parity MeterSep 18 2012We demonstrate a total charge parity measurement by detecting the radio frequency signal that is reflected by a lumped element resonator coupled to a single InAs nanowire double quantum dot. The high frequency response of the circuit is used to probe ... More
A Reconfigurable Gate Architecture for Si/SiGe Quantum DotsFeb 05 2015We demonstrate a reconfigurable quantum dot gate architecture that incorporates two interchangeable transport channels. One channel is used to form quantum dots and the other is used for charge sensing. The quantum dot transport channel can support either ... More
Single-Spin Relaxation in a Synthetic Spin-Orbit FieldNov 02 2018Strong magnetic field gradients can produce a synthetic spin-orbit interaction that allows for high fidelity electrical control of single electron spins. We investigate how a field gradient impacts the spin relaxation time T_1 by measuring T_1 as a function ... More
Field Tuning the G-Factor in InAs Nanowire Double Quantum DotsMay 07 2011Mar 21 2012We study the effects of magnetic and electric fields on the g-factors of spins confined in a two-electron InAs nanowire double quantum dot. Spin sensitive measurements are performed by monitoring the leakage current in the Pauli blockade regime. Rotations ... More
Electron Spin Resonance at the Level of 10000 Spins Using Low Impedance Superconducting ResonatorsAug 17 2016We report on electron spin resonance (ESR) measurements of phosphorus donors localized in a 200 square micron area below the inductive wire of a lumped element superconducting resonator. By combining quantum limited parametric amplification with a low ... More
Long-Range Microwave Mediated Interactions Between Electron SpinsMay 02 2019Entangling gates for electron spins in semiconductor quantum dots are generally based on exchange, a short-ranged interaction that requires wavefunction overlap. Coherent spin-photon coupling raises the prospect of using photons as long-distance interconnects ... More
Comment on `Vacuum Rabi Splitting in a Semiconductor Circuit QED System' by Toida et al., Phys. Rev. Lett. 110, 066802 - Published 6 February 2013Apr 12 2013Toida et al. claim in their recent article [Phys. Rev. Lett. 110, 066802 (2013)] that they `report a direct observation of vacuum Rabi splitting in a GaAs/AlGaAs double quantum dot (DQD) based charge qubit coupled with a superconducting coplanar waveguide ... More
Quantum Coherence in a One-Electron Semiconductor Charge QubitAug 18 2010May 07 2011We study quantum coherence in a semiconductor charge qubit formed from a GaAs double quantum dot containing a single electron. Voltage pulses are applied to depletion gates to drive qubit rotations and non-invasive state readout is achieved using a quantum ... More
Singlet-triplet spin blockade and charge sensing in a few-electron double quantum dotOct 26 2004Singlet-triplet spin blockade in a few-electron lateral double quantum dot is investigated using simultaneous transport and charge-sensing measurements. Transport from the (1,1) to the (0,2) electron occupancy states is strongly suppressed relative to ... More
Scalable gate architecture for densely packed semiconductor spin qubitsJul 24 2016We demonstrate a 12 quantum dot device fabricated on an undoped Si/SiGe heterostructure as a proof-of-concept for a scalable, linear gate architecture for semiconductor quantum dots. The device consists of 9 quantum dots in a linear array and 3 single ... More
Radio frequency charge sensing in InAs nanowire double quantum dotsMay 29 2012We demonstrate charge sensing of an InAs nanowire double quantum dot (DQD) coupled to a radio frequency (rf) circuit. We measure the rf signal reflected by the resonator using homodyne detection. Clear single dot and DQD behavior are observed in the resonator ... More
Development and operation of research-scale III-V nanowire growth reactorsNov 04 2009Oct 04 2010III-V nanowires are useful platforms for studying the electronic and mechanical properties of materials at the nanometer scale. However, the costs associated with commercial nanowire growth reactors are prohibitive for most research groups. We developed ... More
Flopping-mode electric dipole spin resonanceMay 01 2019Traditional approaches to controlling single spins in quantum dots require the generation of large electromagnetic fields to drive many Rabi oscillations within the spin coherence time. We demonstrate "flopping-mode" electric dipole spin resonance, where ... More
Shuttling a single charge across a one-dimensional array of silicon quantum dotsSep 11 2018Significant advances have been made towards fault-tolerant operation of silicon spin qubits, with single qubit fidelities exceeding 99.9%, several demonstrations of two-qubit gates based on exchange coupling, and the achievement of coherent single spin-photon ... More
Landau-Zener-Stuckelberg Interferometry of a Single Electron Charge QubitMay 28 2012Sep 17 2012We perform Landau-Zener-Stuckelberg interferometry on a single electron GaAs charge qubit by repeatedly driving the system through an avoided crossing. We observe coherent destruction of tunneling, where periodic driving with specific amplitudes inhibits ... More
Exchange Control of Nuclear Spin Diffusion in a Double Quantum DotMar 20 2008Coherent two-level systems, or qubits, based on electron spins in GaAs quantum dots are strongly coupled to the nuclear spins of the host lattice via the hyperfine interaction. Realizing nuclear spin control would likely improve electron spin coherence ... More
Suppressing Spin Qubit Dephasing by Nuclear State PreparationJul 09 2008Coherent spin states in semiconductor quantum dots offer promise as electrically controllable quantum bits (qubits) with scalable fabrication. For few-electron quantum dots made from gallium arsenide (GaAs), fluctuating nuclear spins in the host lattice ... More
High-fidelity quantum gates in Si/SiGe double quantum dotsNov 02 2017Motivated by recent experiments of Zajac et al. [arXiv:1708.03530], we theoretically describe high-fidelity two-qubit gates using the exchange interaction between the spins in neighboring quantum dots subject to a magnetic field gradient. We use a combination ... More
Quantum CNOT Gate for Spins in SiliconAug 11 2017Single qubit rotations and two-qubit CNOT operations are crucial ingredients for universal quantum computing. While high fidelity single qubit operations have been achieved using the electron spin degree of freedom, realizing a robust CNOT gate has been ... More
Threshold Dynamics of a Semiconductor Single Atom MaserApr 06 2017We demonstrate a single-atom maser consisting of a semiconductor double quantum dot (DQD) that is embedded in a high quality factor microwave cavity. A finite bias drives the DQD out of equilibrium, resulting in sequential single electron tunneling and ... More
Site-selective quantum control in an isotopically enriched 28Si/SiGe quadruple quantum dotMar 14 2019Silicon spin qubits are a promising quantum computing platform offering long coherence times, small device sizes, and compatibility with industry-backed device fabrication techniques. In recent years, high fidelity single-qubit and two-qubit operations ... More
Structural and Electrical Characterization of Bi2Se3 Nanostructures Grown by Metalorganic Chemical Vapor DepositionAug 25 2011Sep 17 2012We characterize nanostructures of Bi2Se3 that are grown via metalorganic chemical vapor deposition using the precursors diethyl selenium and trimethyl bismuth. By adjusting growth parameters, we obtain either single-crystalline ribbons up to 10 microns ... More
Investigation of Mobility Limiting Mechanisms in Undoped Si/SiGe HeterostructuresMar 19 2015We perform detailed magnetotransport studies on two-dimensional electron gases (2DEGs) formed in undoped Si/SiGe heterostructures in order to identify the electron mobility limiting mechanisms in this increasingly important materials system. By analyzing ... More
Relaxation, dephasing, and quantum control of electron spins in double quantum dotsFeb 20 2006Mar 14 2007Recent experiments have demonstrated quantum manipulation of two-electron spin states in double quantum dots using electrically controlled exchange interactions. Here, we present a detailed theory for electron spin dynamics in two-electron double dot ... More
A Coherent Spin-Photon Interface in SiliconOct 09 2017Electron spins in silicon quantum dots are attractive systems for quantum computing due to their long coherence times and the promise of rapid scaling using semiconductor fabrication techniques. While nearest neighbor exchange coupling of two spins has ... More
Circuit Quantum Electrodynamics with a Spin QubitMay 30 2012Circuit quantum electrodynamics allows spatially separated superconducting qubits to interact via a "quantum bus", enabling two-qubit entanglement and the implementation of simple quantum algorithms. We combine the circuit quantum electrodynamics architecture ... More
Cavity-Mediated Entanglement Generation Via Landau-Zener InterferometryDec 04 2012We demonstrate quantum control and entanglement generation using a Landau-Zener beam splitter formed by coupling two transmon qubits to a superconducting cavity. Single passage through the cavity-mediated qubit-qubit avoided crossing provides a direct ... More
Effect of Exchange Interaction on Spin Dephasing in a Double Quantum DotDec 05 2005Jul 03 2006We measure singlet-triplet dephasing in a two-electron double quantum dot in the presence of an exchange interaction which can be electrically tuned from much smaller to much larger than the hyperfine energy. Saturation of dephasing and damped oscillations ... More
Pulsed-gate measurements of the singlet-triplet relaxation time in a two-electron double quantum dotDec 02 2004Dec 05 2004A pulsed-gate technique with charge sensing is used to measure the singlet-triplet relaxation time for nearly-degenerate spin states in a two-electron double quantum dot. Transitions from the (1,1) charge occupancy state to the (0,2) state, measured as ... More
Double Quantum Dot Floquet Gain MediumJul 27 2016Strongly driving a two-level quantum system with light leads to a ladder of Floquet states separated by the photon energy. Nanoscale quantum devices allow the interplay of confined electrons, phonons, and photons to be studied under strong driving conditions. ... More
Measurement of Temporal Correlations of the Overhauser Field in a Double Quantum DotDec 24 2007Oct 20 2008In quantum dots made from materials with nonzero nuclear spins, hyperfine coupling creates a fluctuating effective Zeeman field (Overhauser field) felt by electrons, which can be a dominant source of spin qubit decoherence. We characterize the spectral ... More
Charge and spin manipulation in a few-electron double dotOct 06 2005We demonstrate high speed manipulation of a few-electron double quantum dot. In the one-electron regime, the double dot forms a charge qubit. Microwaves are used drive transitions between the (1,0) and (0,1) charge states of the double dot. A local quantum ... More
Triplet-Singlet Spin Relaxation via Nuclei in a Double Quantum DotMar 29 2005Jun 07 2005The spin of a confined electron, when oriented originally in some direction, will lose memory of that orientation after some time. Physical mechanisms leading to this relaxation of spin memory typically involve either coupling of the electron spin to ... More
Dynamic Nuclear Polarization with Single Electron SpinsSep 06 2007Sep 07 2007We polarize nuclear spins in a GaAs double quantum dot by controlling two-electron spin states near the anti-crossing of the singlet (S) and m_S=+1 triplet (T+) using pulsed gates. An initialized S state is cyclically brought into resonance with the T+ ... More
Electrical control and decoherence of the flopping-mode spin qubitApr 30 2019We propose and analyze a novel "flopping-mode" mechanism for electric dipole spin resonance based on the delocalization of a single electron across a double quantum dot confinement potential. Delocalization of the charge maximizes the electronic dipole ... More
Perspective for resonances in p-p collisions with the ALICE detectorOct 14 2008The capability of the ALICE detector to reconstruct short-lived resonances from the very beginning of the LHC p-p program start-up was investigated, considering about 300,000 minimum bias p-p PYTHIA events at 900 GeV and 10 TeV, fully reconstructed under ... More
Understanding the dynamics of biological colloids to elucidate cataract formation towards the development of methodology for its early diagnosisDec 19 2008The eye lens is the most characteristic example of mammalian tissues exhibiting complex colloidal behaviour. In this paper we briefly describe how dynamics in colloidal suspensions can help addressing selected aspects of lens cataract which is ultimately ... More
Tiny Descriptors for Image Retrieval with Unsupervised Triplet HashingNov 10 2015A typical image retrieval pipeline starts with the comparison of global descriptors from a large database to find a short list of candidate matches. A good image descriptor is key to the retrieval pipeline and should reconcile two contradictory requirements: ... More
Group Invariant Deep Representations for Image Instance RetrievalJan 09 2016Jan 13 2016Most image instance retrieval pipelines are based on comparison of vectors known as global image descriptors between a query image and the database images. Due to their success in large scale image classification, representations extracted from Convolutional ... More
The late time structure of high density contrast, single mode Richtmyer-Meshkov flowJul 19 2016We study the late time flow structure of Richtmyer-Meshkov instability. Recent numerical work has suggested a self-similar collapse of the development of this instability at late times, independent of the initial surface profile. Using the form of collapse ... More
An addendum to `A rigidity property for the set of all characters induced by valuations'May 28 2013This corrects and amplifies some comments made in a paper by Robert Bieri and the author with the above title.
Subdirect products of finitely presented metabelian groupsJun 13 2011Jul 15 2011There has been substantial investigation in recent years of subdirect products of limit groups and their finite presentability and homological finiteness properties. To contrast the results obtained for limit groups, Baumslag, Bridson, Holt and Miller ... More
Using Annular Josephson Tunnel Junctions to Monitor Causal HorizonMar 29 2005If systems change as fast as possible as they pass through a phase transition then the initial domain structure is constrained by causality. We shall show how we can trace these causal horizons by measuring the spontaneous production of flux in annular ... More
The effective potential at finite temperature in the left-right symmetric modelOct 09 1992We obtain the effective potential at finite temperature within the left-right symmetric model. We take the Higgs sector to consist of two doublets and calculate its finite temperature effective potential up to the order of ``ring-diagrams'', using analogous ... More
Real Higgs singlet and the electroweak phase transition in the standard model, (UM-P-93/80, OZ-93/20)Aug 06 1993Aug 13 1993The effective potential at finite temperature is constructed within the minimal standard model when a real Higgs singlet is added on. We find that a region of parameter space exists for which one can find a first order transition strong enough to prevent ... More
Modelling the application of integrated photonic spectrographs to astronomyJul 23 2012One of the well-known problems of producing instruments for Extremely Large Telescopes is that their size (and hence cost) scales rapidly with telescope aperture. To try to break this relation alternative new technologies have been proposed, such as the ... More
Effects for atmospheric neutrino experiments from electron neutrino oscillationsFeb 26 1997Sep 10 1997The minimal interpretation of the atmospheric neutrino data suggests that the muon neutrino oscillates into another species with a mixing angle close to the maximal $\pi/4$. In the Exact Parity Symmetric Model, both the muon and electron neutrinos are ... More
Structure of large random hypergraphsMar 22 2005The theme of this paper is the derivation of analytic formulae for certain large combinatorial structures. The formulae are obtained via fluid limits of pure jump-type Markov processes, established under simple conditions on the Laplace transforms of ... More
Diffractive rho production with an AdS/QCD holographic wavefunction for the rho mesonNov 20 2012We report on the results of our recent research published in [1] that shows that AdS/QCD generates predictions for the rate of diffractive \rho-meson electroproduction that are in agreement with data collected at the HERA electron-proton collider [2,3]. ... More
Planetary Torques as the Viscosity of Protoplanetary DisksOct 27 2000We revisit the idea that density-wave wakes of planets drive accretion in protostellar disks. The effects of many small planets can be represented as a viscosity if the wakes damp locally, but the viscosity is proportional to the damping length. Damping ... More
Backscattering-Induced Crossover in Deterministic DiffusionJul 07 1996We study diffusion in a one-dimensional periodic array of scatterers modeled by a simple map. The chaotic scattering process for this map can be changed by a control parameter and exhibits the dynamics of a crisis in chaotic scattering. We show that the ... More
Spectroscopy of diffuse ionized gas in halos of selected edge-on galaxiesAug 22 2000In order to examine the excitation and ionization mechanism of extraplanar diffuse ionized gas (DIG) we have obtained optical longslit spectra of seven edge-on spiral galaxies. In four objects the brightest emission lines can be traced out to distances ... More
An AdS/QCD holographic wavefunction for the rho mesonJul 18 2012We use an AdS/QCD holographic wavefunction to generate predictions for the rate of diffractive {\rho}-meson electroproduction that are in reasonable agreement with data collected at the HERA electron-proton collider.
Extracting the rho meson wavefunction from HERA dataJul 12 2010Oct 07 2010We extract the light-cone wavefunctions of the rho meson using the HERA data on diffractive rho photoproduction. We find good agreement with predictions for the distribution amplitude based on QCD sum rules and from the lattice. We also find that the ... More
On the 2D Ising Wulff crystal near criticalityMar 08 2006Jan 26 2010We study the behavior of the two-dimensional Ising model in a finite box at temperatures that are below, but very close to, the critical temperature. In a regime where the temperature approaches the critical point and, simultaneously, the size of the ... More
Hard thermal loops in long wave-length and static external gravitational fieldsJan 10 2013We study, in the long wave-length and static limits, the structure of the n-point graviton functions at high temperature. Using the gauge and Weyl invariance of the theory, we derive a simple expression for the hard thermal amplitudes in these two limits. ... More
An AdS/QCD holographic wavefunction for the rho meson and diffractive rho meson electroproductionMar 27 2012Jul 18 2012We show that AdS/QCD generates predictions for the rate of diffractive rho meson electroproduction that are in agreement with data collected at the HERA electron-proton collider.
Phenomenology of Distribution Amplitudes for the rho mesonDec 23 2011We report on a successful extraction of the twist-2 and twist-3 Distribution Amplitudes (DAs) of the rho meson using the HERA data on diffractive rho photoproduction. We extract these DAs using several Colour Glass Condensate (CGC) inspired and a Regge ... More
Constraining the rho meson wavefunctionDec 22 2010Diffractive rho meson production has been identified as one of the important processes where saturation can be probed at a future Electron-Ion Collider (EIC). A source of uncertainty in making predictions for this process lies within the assumed form ... More
Scaling Laws for Fluxon Formation in Annular Josephson Tunnel JunctionsJan 16 2003It has been argued by Zurek and Kibble that the likelihood of producing defects in a continuous phase transition depends in a characteristic way on the quench rate. In this paper we discuss our experiment for measuring the Zurek-Kibble scaling exponent ... More