Results for "Felix A. Pollock"

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Non-Markovian memory in IBMQX4Feb 21 2019We measure and quantify non-Markovian effects in IBM's Quantum Experience. Specifically, we analyze the temporal correlations in a sequence of gates by characterizing the performance of a gate conditioned on the gate that preceded it. With this method, ... More
Quantum Batteries - Review ChapterMay 15 2018Book chapter in "Thermodynamics in the quantum regime - Recent Progress and Outlook" -- This chapter is a survey of the published literature on quantum batteries -- ensembles of non-degenerate quantum systems on which energy can be deposited, and from ... More
Tightening Quantum Speed Limits for Almost All StatesSep 26 2017Oct 10 2017Conventional quantum speed limits perform poorly for mixed quantum states: They are generally not tight and often significantly underestimate the fastest possible evolution speed. To remedy this, for unitary driving, we derive two quantum speed limits ... More
Almost Markovian processes from closed dynamicsFeb 28 2018Apr 29 2019It is common, when dealing with quantum processes involving a subsystem of a much larger composite closed system, to treat them as effectively memory-less (Markovian). While open systems theory tells us that non-Markovian processes should be the norm, ... More
Equilibration on average of temporally non-local observables in quantum systemsMay 21 2019Temporally non-local observables can evade equilibration on average in quantum systems. Equilibration on average refers to the evolution of a system's time-dependent properties towards a constant value and remaining close to it for most times. We generalize ... More
Enhancing the charging power of quantum batteriesDec 15 2016Apr 19 2017Can collective quantum effects make a difference in a meaningful thermodynamic operation? Focusing on energy storage and batteries, we demonstrate that quantum mechanics can lead to an enhancement in the amount of work deposited per unit time, i.e., the ... More
Noisy frequency estimation with noisy probesDec 21 2017Aug 18 2018We consider frequency estimation in a noisy environment with noisy probes. This builds on previous studies, most of which assume that the initial probe state is pure, while the encoding process is noisy, or that the initial probe state is mixed, while ... More
Quantum Markov OrderMay 29 2018Nov 10 2018We formally extend the notion of Markov order to open quantum processes by accounting for the instruments used to probe the system of interest at different times. Our description recovers the classical Markov order property in the appropriate limit: when ... More
Operational Markov condition for quantum processesJan 30 2018We derive a necessary and sufficient condition for a quantum process to be Markovian which coincides with the classical one in the relevant limit. Our condition unifies all previously known definitions for quantum Markov processes by accounting for all ... More
Tomographically reconstructed master equations for any open quantum dynamicsApr 20 2017Jul 06 2018Memory effects in open quantum dynamics are often incorporated in the equation of motion through a superoperator known as the memory kernel, which encodes how past states affect future dynamics. However, the usual prescription for determining the memory ... More
Discussion of "Sequential Quasi-Monte-Carlo Sampling" by M. Gerber and N. ChopinFeb 04 2015In this comment we consider whether QMC methods can be further embedded within SMC schemes in settings in which the transition density of the latent process is intractable and pseudo-marginal methods are deployed.
Pseudo-time regularization for PDE with solution-dependent diffusionNov 12 2016Nov 27 2016This work unifies pseudo-time and inexact regularization techniques for nonmonotone classes of partial differential equations, into a regularized pseudo-time framework. Convergence of the residual at the predicted rate is investigated through the idea ... More
An improved method for solving quasilinear convection diffusion problems on a coarse meshFeb 09 2015A method is developed for solving quasilinear convection diffusion problems starting on a coarse mesh where the data and solution-dependent coefficients are unresolved, the problem is unstable and approximation properties do not hold. The Newton-like ... More
Reconstructing open quantum system dynamics with limited controlOct 07 2016Jul 06 2018The dynamics of an open quantum system can be fully described and tomographically reconstructed if the experimenter has complete control over the system of interest. Most real-world experiments do not fulfill this assumption, and the amount of control ... More
Stabilized and inexact adaptive methods for capturing internal layers in quasilinear PDEJul 24 2015Feb 14 2016A method is developed within an adaptive framework to solve quasilinear diffusion problems with internal and possibly boundary layers starting from a coarse mesh. The solution process is assumed to start on a mesh where the problem is badly resolved, ... More
A regularized Newton-like method for nonlinear PDEDec 19 2014Jan 25 2015An adaptive regularization strategy for stabilizing Newton-like iterations on a coarse mesh is developed in the context of adaptive finite element methods for nonlinear PDE. Existence, uniqueness and approximation properties are known for finite element ... More
Tight, robust, and feasible quantum speed limits for open dynamicsJun 22 2018Feb 22 2019Starting from a geometric perspective, we derive a quantum speed limit for arbitrary open quantum evolution, which could be Markovian or non-Markovian, providing a fundamental bound on the time taken for the most general quantum dynamics. Our methods ... More
Exploiting the causal tensor network structure of quantum processes to efficiently simulate non-Markovian path integralsFeb 01 2019In the path integral formulation of the evolution of an open quantum system coupled to a Gaussian, non-interacting environment, the dynamical contribution of the latter is encoded in an object called the influence functional. Here, we relate the influence ... More
Reconstructing open quantum system dynamics with limited controlOct 07 2016The dynamics of an open quantum system can be fully described and tomographically reconstructed if the experimenter has complete control over the system of interest. Most real-world experiments do not fulfill this assumption, and the amount of control ... More
Emergence of a fluctuation relation for heat in typical open quantum processesOct 28 2015In a generalisation of the Landauer erasure protocol, we study bounds on the heat generated in typical open quantum processes. We derive a fluctuation relation for this heat, implying that it is almost always positive when either the system or reservoir ... More
An introduction to operational quantum dynamicsAug 02 2017In the summer of 2016, physicists gathered in Torun, Poland for the 48th annual Symposium on Mathematical Physics. This Symposium was special; it celebrated the 40th anniversary of the discovery of the Gorini-Kossakowski-Sudarshan-Lindblad master equation, ... More
The 155-day X-ray cycle of the very massive Wolf-Rayet star Melnick 34 in the Large Magellanic CloudMar 02 2018The Wolf-Rayet star Mk 34 was observed more than 50 times as part of the deep T-ReX Chandra ACIS-I X-ray imaging survey of the Tarantula Nebula in the Large Magellanic Cloud conducted between 2014 May and 2016 January. Its brightness showed one bright ... More
An ultraluminous supersoft source with a 4 hour modulation in NGC 4631Jul 06 2007Context. Supersoft X-ray sources (SSSs) are characterised by very low temperatures (< 100 eV). Classical SSSs have bolometric luminosities in the range of 10^36-10^38 erg/s and are modelled with steady nuclear burning of hydrogen on the surfaces of white ... More
A Wolf-Rayet/black-hole X-ray binary candidate in NGC 300Nov 14 2006Context. Wolf Rayet/black hole binaries are believed to exist as a later evolutionary product of high-mass X-ray binaries. Hundreds of such binaries may exist in galaxies, but only a few of them are close enough to be observed as X-ray binaries. Only ... More
The Conspicuous Absence of X-ray Emission from Carbon-Enriched Wolf-Rayet StarsMar 03 2003The carbon-rich WC5 star WR 114 was not detected during a 15.9 ksec XMM-Newton observation, implying an upper limit to the X-ray luminosity of Lx < 2.5*10^{30} erg/s and to the X-ray to bolometric luminosity ratio of Lx/Lbol < 4*10^{-9}. This confirms ... More
Analytic Framework for Students' Use of Mathematics in Upper-Division PhysicsJul 02 2013Oct 14 2014Many students in upper-division physics courses struggle with the mathematically sophisticated tools and techniques that are required for advanced physics content. We have developed an analytical framework to assist instructors and researchers in characterizing ... More
Towards an understanding of the Of?p star HD191612: Phase-resolved multiwavelength observationsNov 07 2006We present the analysis of phase-resolved X-ray and optical observations of the peculiar hot star HD191612 (Of?p). This star is known to display line-profile variations that are recurrent with a period of 538d and its spectrum was found to present the ... More
Photon polarization tensor in circularly polarized Hermite- and Laguerre-Gaussian beamsDec 24 2017We derive analytical expressions for the photon polarization tensor in circularly polarized Hermite- and Laguerre-Gaussian beams, complementing the corresponding results for linearly polarized beams obtained recently. As they are based upon a locally ... More
The photon polarization tensor in pulsed Hermite- and Laguerre-Gaussian beamsNov 16 2017In this article, we provide analytical expressions for the photon polarization tensor in pulsed Hermite- and Laguerre-Gaussian laser beams. Our results are based on a locally constant field approximation of the one-loop Heisenberg-Euler effective Lagrangian ... More
Kähler quantization and entanglementJun 26 2018For a very ample line bundle L on a compact connected complex manifold X, with a real structure, we discuss entanglement properties of certain sequences of vectors in tensor products of spaces of holomorphic sections of powers of L.
Using a biased qubit to probe complex systemsJul 17 2015Sep 15 2016Complex mesoscopic systems play increasingly important roles in modern science -- from understanding biological functions at the molecular level, to designing solid-state information processing devices. The operation of these systems typically depends ... More
Almost Markovian processes from closed dynamicsFeb 28 2018Jan 29 2019It is common, when dealing with quantum processes involving a subsystem of a much larger composite closed system, to treat them as effectively memory-less (Markovian). While open systems theory tells us that non-Markovian processes should be the norm, ... More
Non-Markovian quantum control as coherent stochastic trajectoriesFeb 09 2018Sep 19 2018We develop a notion of stochastic quantum trajectories. First, we construct a basis set of trajectories, called elementary trajectories, and go on to show that any quantum dynamical process, including those that are non-Markovian, can be expressed as ... More
The Structure of Quantum Stochastic Processes with Finite Markov OrderOct 25 2018Nov 10 2018Non-Markovian quantum processes exhibit different memory effects when measured in different ways; an unambiguous characterization of memory length requires accounting for the sequence of instruments applied to probe the system dynamics. This instrument-specific ... More
NGC 300 X-1 is a Wolf-Rayet/Black-Hole binaryJan 26 2010We present VLT/FORS2 time-series spectroscopy of the Wolf-Rayet star #41 in the Sculptor group galaxy NGC 300. We confirm a physical association with NGC 300 X-1, since radial velocity variations of the HeII 4686 line indicate an orbital period of 32.3 ... More
Dissipation enhanced vibrational sensing in an olfactory molecular switchMar 25 2014Feb 11 2015Motivated by a proposed olfactory mechanism based on a vibrationally-activated molecular switch, we study electron transport within a donor-acceptor pair that is coupled to a vibrational mode and embedded in a surrounding environment. We derive a polaron ... More
CP divisibility does not mean MarkovianityJan 16 2019In the classical domain, it is well-known that divisibility does not imply that a stochastic process is Markovian. However, for quantum processes, divisibility is often considered to be synonymous with Markovianity. We show that completely positive (CP) ... More
How does interference fall?Oct 07 2016We study how single- and double-slit interference patterns fall in the presence of gravity. First, we demonstrate that universality of free fall still holds in this case, i.e., interference patterns fall just like classical objects. Next, we explore lowest ... More
Analytic influence functionals for numerical Feynman integrals in most open quantum systemsMar 20 2012Fully analytic formulas, which do not involve any numerical integration, are derived for the discretized influence functionals of a very extensive assortment of spectral distributions. For Feynman integrals derived using the Trotter splitting and Strang ... More
Optimal representation of the bath response function & fast calculation of influence functional coefficients in open quantum systems with BATHFIT 1May 21 2012May 27 2012Today's most popular techniques for accurately calculating the dynamics of the reduced density operator in an open quantum system, either require, or gain great computational benefits, from representing the bath response function a(t) in the form a(t)={\Sigma}_k^K ... More
Almost Markovian processes from closed dynamicsFeb 28 2018Apr 24 2019It is common, when dealing with quantum processes involving a subsystem of a much larger composite closed system, to treat them as effectively memory-less (Markovian). While open systems theory tells us that non-Markovian processes should be the norm, ... More
Kolmogorov extension theorem for (quantum) causal modelling and general probabilistic theoriesDec 07 2017Jul 07 2018In classical physics, the Kolmogorov extension theorem lays the foundation for the theory of stochastic processes. It has been known for a long time that, in its original form, this theorem does not hold in quantum mechanics. More generally, it does not ... More
Kolmogorov extension theorem for general (quantum) stochastic processesDec 07 2017In classical physics, the Kolmogorov extension theorem provides the foundation for the definition and investigation of stochastic processes. In its original form, it does not hold in quantum mechanics. More generally, it does not hold in any theory -- ... More
Non-Markovian quantum control as coherent stochastic trajectoriesFeb 09 2018Feb 12 2018We develop a notion of stochastic quantum trajectories. First, we construct a basis set of trajectories, called elementary trajectories, and go on to show that any quantum dynamical process, including those that are non-Markovian, can be expressed as ... More
The Structure of Quantum Stochastic Processes with Finite Markov OrderOct 25 2018Apr 10 2019Non-Markovian quantum processes exhibit different memory effects when measured in different ways; an unambiguous characterization of memory length requires accounting for the sequence of instruments applied to probe the system dynamics. This instrument-specific ... More
A matrix analysis approach to discrete comparison principles for nonmonotone PDENov 20 2017Mar 16 2018We consider a linear algebra approach to establishing a discrete comparison principle for a nonmonotone class of quasilinear elliptic partial differential equations. In the absence of a lower order term, we require local conditions on the mesh to establish ... More
Discrete comparison principles for quasilinear elliptic PDEAug 07 2017Oct 31 2017Comparison principles are developed for discrete quasilinear elliptic partial differential equations. We consider the analysis of a class of nonmonotone Leray-Lions problems featuring both nonlinear solution and gradient dependence in the principal coefficient, ... More
Estimation of the XUV radiation onto close planets and their evaporationMay 03 2011Context: The current distribution of planet mass vs. incident stellar X-ray flux supports the idea that photoevaporation of the atmosphere may take place in close-in planets. Integrated effects have to be accounted for. A proper calculation of the mass ... More
SNR 1E 0102.2-7219 as an X-ray Calibration Standard in the 0.5-1.0 keV Bandpass and Its Application to the CCD Instruments aboard Chandra, Suzaku, Swift and XMM-NewtonJul 11 2016We desire a simple comparison of the absolute effective areas of the current generation of CCD instruments onboard the following observatories: Chandra ACIS-S3, XMM-Newton (EPIC-MOS and EPIC-pn), Suzaku XIS, and Swift XRT and a straightforward comparison ... More
Reduction of light shifts in Ramsey spectroscopy with a combined error signalMar 01 2019Light-induced frequency shifts can be a key limiting contribution to the mid and long-term frequency instability in atomic clocks. In this letter, we demonstrate the experimental implementation of the combined error signal interrogation protocol to a ... More
The spectral dimension controls the decay of the quantum first detection probabilityFeb 15 2018Mar 05 2018We consider a quantum system that is initially localized at $x_{in}$ and that is repeatedly projectively probed with a fixed period $\tau$ at position $x_d$. We ask for the probability that the system is detected in $x_d$ for the very first time, $F_n$, ... More
Robust multiple comparisons against a control group with application in toxicologyMay 06 2019The Dunnett procedure compares several treatment or dose groups with a control group, while controlling the familywise error rate. When deviations from the normal distribution and heterogeneous variances occur, the nominal $\alpha$ level may be violated, ... More
The haptic paradigm in education: Challenges and case studiesNov 29 2018The process of learning involves interaction with the learning environment through our five senses (sight, hearing, touch, smell, and taste). Until recently, distance education focused only on the first two of those senses, sight and sound. Internet-based ... More
Variational Density Matrix Method for Warm Condensed Matter and Application to Dense HydrogenOct 08 1999A new variational principle for optimizing thermal density matrices is introduced. As a first application, the variational many body density matrix is written as a determinant of one body density matrices, which are approximated by Gaussians with the ... More
The Orbital Period of the Wolf-Rayet Binary IC 10 X-1; Dynamic Evidence that the Compact Object is a Black HoleSep 18 2007IC 10 X-1 is a bright (Lx=10^38 ergs/s) variable X-ray source in the local group starburst galaxy IC 10. The most plausible optical counterpart is a luminous Wolf-Rayet star, making IC 10 X-1 a rare example of a Wolf-Rayet X-ray binary. In this paper, ... More
On the limits to mobility in InAs quantum wells with nearly lattice-matched barriersOct 12 2016Oct 13 2016The growth and the density dependence of the low temperature mobility of a series of two-dimensional electron systems confined to un-intentionally doped, low extended defect density InAs quantum wells with Al$_{1-x}$Ga$_{x}$Sb barriers are reported. The ... More
A Simple Test of the Equivalence Principle(s) for Quantum SuperpositionsNov 10 2015We propose a simple experimental test of the quantum equivalence principle introduced by Zych and Brukner [arXiv:1502.00971], which generalises the Einstein equivalence principle to superpositions of internal energy states. We consider a harmonically-trapped ... More
A multi-site variational master equation approach to dissipative energy transferDec 22 2012Jul 23 2013Unitary transformations can allow one to study open quantum systems in situations for which standard, weak-coupling type approximations are not valid. We develop here an extension of the variational (polaron) transformation approach to open system dynamics, ... More
Non-Markovian quantum processes: complete framework and efficient characterisationDec 02 2015Jan 31 2018Currently, there is no systematic way to describe a quantum process with memory solely in terms of experimentally accessible quantities. However, recent technological advances mean we have control over systems at scales where memory effects are non-negligible. ... More
Energy-efficient quantum frequency estimationDec 21 2017Jun 13 2018The problem of estimating the frequency of a two-level atom in a noisy environment is studied. Our interest is to minimise both the energetic cost of the protocol and the statistical uncertainty of the estimate. In particular, we prepare a probe in a ... More
Divisible quantum dynamics satisfies temporal Tsirelson's boundOct 15 2015We show that divisibility of qubit quantum processes implies temporal Tsirelson's bound. We also prove that the classical bound of the temporal Bell's inequality holds for dynamics that can be described by entanglement-breaking channels---a more general ... More
Complete framework for efficient characterisation of non-Markovian processesDec 02 2015Oct 18 2016A non-Markovian process is one that retains 'memory' of its past. A systematic understanding of these processes is necessary to fully describe and harness a vast range of complex phenomena; however, no such general characterisation currently exists. This ... More
Quantum Markov OrderMay 29 2018Apr 10 2019We formally extend the notion of Markov order to open quantum processes by accounting for the instruments used to probe the system of interest at different times. Our description recovers the classical Markov order property in the appropriate limit: when ... More
Divisible quantum dynamics satisfies temporal Tsirelson's boundOct 15 2015Jan 08 2017We give strong evidence that divisibility of qubit quantum processes implies temporal Tsirelson's bound. We also give strong evidence that the classical bound of the temporal Bell's inequality holds for dynamics that can be described by entanglement-breaking ... More
Spatial statistics and attentional dynamics in scene viewingMay 13 2014Dec 04 2014In humans and in foveated animals visual acuity is highly concentrated at the center of gaze, so that choosing where to look next is an important example of online, rapid decision making. Computational neuroscientists have developed biologically-inspired ... More
Spin-chain model of a many-body quantum batteryDec 10 2017Recently, it has been shown that energy can be deposited on a collection of quantum systems at a rate that scales super-extensively. Some of these schemes for `quantum batteries' rely on the use of global many-body interactions that take the batteries ... More
Entanglement, non-Markovianity, and causal non-separabilityNov 11 2017Quantum mechanics, in principle, allows for processes with indefinite causal order. However, most of these causal anomalies have not yet been detected experimentally. We show that every such process can be simulated experimentally by means of non-Markovian ... More
Tracing dense and diffuse neutral hydrogen in the halo of the Milky WayNov 25 2016Nov 28 2016We have combined observations of Galactic high-velocity HI from two surveys: a very sensitive survey from the Green Bank 140ft Telescope with limited sky coverage, and the less sensitive but complete Galactic All Sky Survey from the 64m Parkes Radio Telescope. ... More
Theory of the Franck-Condon blockade regimeJun 20 2006Dec 01 2006Strong coupling of electronic and vibrational degrees of freedom entails a low-bias suppression of the current through single-molecule devices, termed Franck-Condon blockade. In the limit of slow vibrational relaxation, transport in the Franck-Condon-blockade ... More
Gamma-ray flares from red giant/jet interactions in AGNMay 28 2010Sep 03 2010Non-blazar AGN have been recently established as a class of gamma-ray sources. M87, a nearby representative of this class, show fast TeV variability on timescales of a few days. We suggest a scenario of flare gamma-ray emission in non-blazar AGN based ... More
Towards the observation of phase locked Bloch oscillations in arrays of small Josephson junctionsJun 27 2011Sep 09 2011We have designed an experiment and performed extensive simulations and preliminary measurements to identify a set of realistic circuit parameters that should allow the observation of constant-current steps at I=2ef in short arrays of small Josephson junctions ... More
Yang-Mills instantons and dyons on homogeneous G_2-manifoldsJun 11 2010We consider Lie G-valued Yang-Mills fields on the space R x G/H, where G/H is a compact nearly K"ahler six-dimensional homogeneous space, and the manifold R x G/H carries a G_2-structure. After imposing a general G-invariance condition, Yang-Mills theory ... More
Operators in Machine Learning: Response Properties in Chemical SpaceJul 23 2018Aug 23 2018The role of response operators is well established in quantum mechanics. We investigate their use for universal quantum machine learning models of response properties in molecules. After introducing a theoretical basis, we present and discuss numerical ... More
Planning with Information-Processing Constraints and Model Uncertainty in Markov Decision ProcessesApr 07 2016Information-theoretic principles for learning and acting have been proposed to solve particular classes of Markov Decision Problems. Mathematically, such approaches are governed by a variational free energy principle and allow solving MDP planning problems ... More
Surface Compression Using Dynamic Color PalettesJan 19 2019Off-chip memory traffic is a major source of power and energy consumption on mobile platforms. A large amount of this off-chip traffic is used to manipulate graphics framebuffer surfaces. To cut down the cost of accessing off-chip memory, framebuffer ... More
Efficient control of transient wave forms to prevent spreading depolarizationsMay 23 2007Sep 27 2007In various neurological disorders spatio-temporal excitation patterns constitute examples of excitable behavior emerging from pathological pathways. During migraine, seizure, and stroke an initially localized pathological state can temporarily spread ... More
Controlling the onset of traveling pulses in excitable media by nonlocal spatial coupling and time-delayed feedbackDec 18 2008The onset of pulse propagation is studied in a reaction-diffusion (RD) model with control by augmented transmission capability that is provided either along nonlocal spatial coupling or by time-delayed feedback. We show that traveling pulses occur primarily ... More
On the Lq(Lp)-regularity and Besov smoothness of stochastic parabolic equations on bounded Lipschitz domainsJan 07 2013We investigate the regularity of linear stochastic parabolic equations with zero Dirichlet boundary condition on bounded Lipschitz domains $O \subset R^d$ with both theoretical and numerical purpose. We use N.V. Krylov's framework of stochastic parabolic ... More
Experimental Verification of Below-Cutoff Propagation in Miniaturized Circular Waveguides Using Anisotropic ENNZ Metamaterial LinersOct 26 2015This paper presents experimental verification of below-cutoff transmission through miniaturized waveguides whose interior is coated with a thin anisotropic metamaterial liner possessing epsilon-negative and near-zero (ENNZ) properties. These liners are ... More
Monte Carlo FusionJan 01 2019This paper proposes a new theory and methodology to tackle the problem of unifying distributed analyses and inferences on shared parameters from multiple sources, into a single coherent inference. This surprisingly challenging problem arises in many settings ... More
Assessing Student Learning in Middle-Division Classical Mechanics/Math MethodsJun 12 2013Reliable and validated assessments of introductory physics have been instrumental in driving curricular and pedagogical reforms that lead to improved student learning. As part of an effort to systematically improve our sophomore-level Classical Mechanics ... More
Essentially No Barriers in Neural Network Energy LandscapeMar 02 2018Feb 22 2019Training neural networks involves finding minima of a high-dimensional non-convex loss function. Knowledge of the structure of this energy landscape is sparse. Relaxing from linear interpolations, we construct continuous paths between minima of recent ... More
Shaping in Practice: Training Wheels to Learn Fast Hopping Directly in HardwareSep 29 2017Mar 07 2018Learning instead of designing robot controllers can greatly reduce engineering effort required, while also emphasizing robustness. Despite considerable progress in simulation, applying learning directly in hardware is still challenging, in part due to ... More
Interpretation of the flares of M87 at TeV energies in the cloud-jet interaction scenarioFeb 27 2012Jun 27 2012Active galactic nuclei with misaligned jets have been recently established as a class of high-energy gamma-ray sources. M87, a nearby representative of this class, shows fast TeV variability on timescales less than one day. We present calculations performed ... More
TeV AstronomyFeb 22 2013With the successful realization of the current-generation of ground-based detectors, TeV Astronomy has entered into a new era. We review recent advances in VHE astronomy, focusing on the potential of Imaging Atmospheric Cherenkov Telescopes (IACTs), and ... More
An information-theoretic on-line update principle for perception-action couplingApr 16 2018Inspired by findings of sensorimotor coupling in humans and animals, there has recently been a growing interest in the interaction between action and perception in robotic systems [Bogh et al., 2016]. Here we consider perception and action as two serial ... More
Failure of feedback as a putative common mechanism of spreading depolarizations in migraine and strokeMar 16 2008The stability of cortical function depends critically on proper regulation. Under conditions of migraine and stroke a breakdown of transmembrane chemical gradients can spread through cortical tissue. A concomitant component of this emergent spatio-temporal ... More
DNA hybridization to mismatched templates: a chip studyNov 27 2001High-density oligonucleotide arrays are among the most rapidly expanding technologies in biology today. In the {\sl GeneChip} system, the reconstruction of the target concentration depends upon the differential signal generated from hybridizing the target ... More
Induced Cycles in GraphsJun 03 2014The maximum cardinality of an induced $2$-regular subgraph of a graph $G$ is denoted by $c_{\rm ind}(G)$. We prove that if $G$ is an $r$-regular graph of order $n$, then $c_{\rm ind}(G) \geq \frac{n}{2(r-1)} + \frac{1}{(r-1)(r-2)}$ and we prove that if ... More
A new $κ$-deformed parametric model for the size distribution of wealthMay 17 2018It has been pointed out by Patriarca et al. (2005) that the power-law tailed equilibrium distribution in heterogeneous kinetic exchange models with a distributed saving parameter can be resolved as a mixture of Gamma distributions corresponding to particular ... More
Anderson-accelerated convergence of Picard iterations for incompressible Navier-Stokes equationsOct 19 2018We propose, analyze and test Anderson-accelerated Picard iterations for solving the incompressible Navier-Stokes equations (NSE). Anderson acceleration has recently gained interest as a strategy to accelerate linear and nonlinear iterations, based on ... More
A new paradigm for the X-ray emission of O stars from XMM-Newton observations of the O9.7 supergiant zeta OrionisDec 18 2006XMM-Newton observations of the O supergiant zeta Orionis (O9.7 Ib) extend knowledge of its high-resolution spectrum beyond the CVI line at 33.7 Angstroms and suggest a new framework for the interpretation of the X-ray spectra of single hot stars. All ... More
Collisionless shock acceleration of narrow energy spread ion beams from mixed species plasmas using 1 $μ$m lasersOct 18 2018Collisionless shock acceleration of protons and C$^{6+}$ ions has been achieved by the interaction of a 10$^{20}$ W/cm$^2$, 1 $\mu$m laser with a near-critical density plasma. Ablation of the initially solid density target by a secondary laser allowed ... More
The SMC SNR 1E0102.2-7219 as a Calibration Standard for X-ray Astronomy in the 0.3-2.5 keV BandpassJul 14 2008The flight calibration of the spectral response of CCD instruments below 1.5 keV is difficult in general because of the lack of strong lines in the on-board calibration sources typically available. We have been using 1E 0102.2-7219, the brightest supernova ... More
A new non-convex model of the binary asteroid (809) Lundia obtained with the SAGE modelling techniqueMay 20 2019We present a new non-convex model of the binary asteroid (809) Lundia. A SAGE (Shaping Asteroids with Genetic Evolution) method using disc-integrated photometry only was used for deriving physical parameters of this binary system. The model of (809) Lundia ... More
Multiple Asteroid Systems: Dimensions and Thermal Properties from Spitzer Space Telescope and Ground-Based ObservationsApr 19 2016Photometric lightcurves were also obtained for 14 of them during the Spitzer observations to provide the context of the observations and reliable estimates of their absolute magnitudes. The extracted mid-IR spectra were analyzed using a modified standard ... More
Spin correlations in $\vec{p}\vec{p}\to pnπ^{+}$ pion production near thresholdAug 20 2001A first measurement of longitudinal as well as transverse spin correlation coefficients for the reaction $\vec{p}\vec{p}\to pn\pi^+$ was made using a polarized proton target and a polarized proton beam. We report kinematically complete measurements for ... More
Initial singlet and triplet spin state contributions to pp -> pp pi0Aug 31 1999The PINTEX facility at the IUCF Cooler ring, dedicated to the study of spin dependence in nucleon-nucleon interactions, has been used to measure polarization observables of the reaction pp -> pp pi0 at beam energies between 325 and 400 MeV. The stored ... More
Measurement of Partial-Wave Contributions in pp --> pp pi^0Jul 26 1999Jul 27 1999We report a measurement of the spin-dependent total cross section ratios delta_sigma_T/sigma_tot and delta_sigma_L/sigma_tot of the pp --> pp pi^0 reaction between 325 MeV and 400 MeV. The experiment was carried out with a polarized internal target in ... More
Definition of the Dirac Sea in the Presence of External FieldsMay 02 1997Jan 06 2009It is shown that the Dirac sea can be uniquely defined for the Dirac equation with general interaction, if we impose a causality condition on the Dirac sea. We derive an explicit formula for the Dirac sea in terms of a power series in the bosonic potentials. ... More