Results for "P. H. Keys"

total 173688took 0.14s
Nanoflare Activity in the Solar ChromosphereSep 23 2014We use ground-based images of high spatial and temporal resolution to search for evidence of nanoflare activity in the solar chromosphere. Through close examination of more than 10^9 pixels in the immediate vicinity of an active region, we show that the ... More
The Influence of the Magnetic Field on Running Penumbral Waves in the Solar ChromosphereOct 29 2013We use images of high spatial and temporal resolution, obtained using both ground- and space-based instrumentation, to investigate the role magnetic field inclination angles play in the propagation characteristics of running penumbral waves in the solar ... More
Propagating Wave Phenomena Detected in Observations and Simulations of the Lower Solar AtmosphereJan 10 2012We present high-cadence observations and simulations of the solar photosphere, obtained using the Rapid Oscillations in the Solar Atmosphere imaging system and the MuRAM magneto-hydrodynamic code, respectively. Each dataset demonstrates a wealth of magneto-acoustic ... More
Tracking Magnetic Bright Point Motions Through the Solar AtmosphereOct 22 2012High cadence, multi-wavelength observations and simulations are employed for the analysis of solar photospheric magnetic bright points (MBPs) in the quiet Sun. The observations were obtained with the Rapid Oscillations in the Solar Atmosphere (ROSA) imager ... More
Dynamic properties of bright points in an active regionMay 15 2014Context. Bright points (BPs) are small-scale, magnetic features ubiquitous across the solar surface. Previously, we have observed and noted their properties for quiet Sun regions. Here, we determine the dynamic properties of BPs using simultaneous quiet ... More
Chromospheric Velocities of a C-class FlareMar 22 2011We use high spatial and temporal resolution observations from the Swedish Solar Telescope to study the chromospheric velocities of a C-class flare originating from active region NOAA 10969. A time-distance analysis is employed to estimate directional ... More
A Search for High-Frequency Coronal Brightness Variations in the 21 August 2017 Total Solar EclipseMar 14 2019We report on a search for short-period intensity variations in the green-line FeXIV 530.3 nm emission from the solar corona during the 21 August 2017 total eclipse viewed from Idaho in the United States. Our experiment was performed with a much more sensitive ... More
Time-dependent suppression of oscillatory power in evolving solar magnetic fieldsApr 19 2016Oscillation amplitudes are generally smaller within magnetically active regions like sunspots and plage, when compared to their surroundings. Such magnetic features, when viewed in spatially-resolved powermaps, appear as regions of suppressed power due ... More
The Source of Three-minute Magneto-acoustic Oscillations in Coronal FansAug 15 2012We use images of high spatial, spectral and temporal resolution, obtained using both ground- and space-based instrumentation, to investigate the coupling between wave phenomena observed at numerous heights in the solar atmosphere. Intensity oscillations ... More
The Dynamics of Rapid Redshifted and Blueshifted Excursions in the Solar Halpha lineJan 25 2015We analyse high temporal and spatial resolution time-series of spectral scans of the Halpha line obtained with the CRisp Imaging SpectroPolarimeter (CRISP) instrument mounted on the Swedish Solar Telescope. The data reveal highly dynamic, dark, short-lived ... More
The Origin of Type I Spicule OscillationsNov 23 2011We use images of high spatial and temporal resolution, obtained with the Rapid Oscillations in the Solar Atmosphere instrument at the Dunn Solar Telescope, to reveal how the generation of transverse waves in Type I spicules is a direct result of longitudinal ... More
A failed filament eruption inside a coronal mass ejection in active region 11121Feb 24 2013We study the formation and evolution of a failed filament eruption observed in NOAA active region 11121 near the southeast limb on November 6, 2010. We use a time series of SDO/AIA 304, 171, 131, 193, 335, 94 {\AA} images, SDO/HMI magnetograms, plus ROSA ... More
The Velocity Distribution of Solar Photospheric Magnetic Bright PointsSep 16 2011We use high spatial resolution observations and numerical simulations to study the velocity distribution of solar photospheric magnetic bright points. The observations were obtained with the Rapid Oscillations in the Solar Atmosphere instrument at the ... More
Vorticity in the solar photosphereOct 27 2010Aims. We use magnetic and non-magnetic 3D numerical simulations of solar granulation and G-band radiative diagnostics from the resulting models to analyse the generation of small-scale vortex motions in the solar photosphere. Methods. Radiative MHD simulations ... More
Propagating Spectropolarimetric Disturbances in a Large SunspotOct 30 2018We present results derived from the analysis of spectropolarimetric measurements of active region AR12546, which represents one of the largest sunspots to have emerged onto the solar surface over the last $20$ years. The region was observed with full-Stokes ... More
Applicability of dynamic facilitation theory to binary hard disk systemsApr 10 2016Sep 02 2016We investigate numerically the applicability of dynamic facilitation (DF) theory for glass-forming binary hard disk systems where supercompression is controlled by pressure. By using novel efficient algorithms for hard disks, we are able to generate equilibrium ... More
Using the s-Ensemble to Probe Glasses Formed by Cooling and AgingJan 28 2014Mar 30 2014From length scale distributions characterizing frozen amorphous domains, we relate the s-ensemble method with standard cooling and aging protocols for forming glass. We show that in a general class of models, where space-time scaling is in harmony with ... More
Calorimetric glass transition explained by hierarchical dynamic facilitationNov 14 2012Mar 25 2013The glass transition refers to the non-equilibrium process by which an equilibrium liquid is transformed to a non-equilibrium disordered solid, or vice versa. Associated response functions, such as heat capacities, are markedly different on cooling than ... More
Alfvén Wave Dissipation in the Solar ChromosphereOct 17 2018Magneto-hydrodynamic (MHD) Alfv\'en waves have been a focus of laboratory plasma physics and astrophysics for over half a century. Their unique nature makes them ideal energy transporters, and while the solar atmosphere provides preferential conditions ... More
Solar coronal magnetic fields derived using seismology techniques applied to omnipresent sunspot wavesMay 19 2016Sunspots on the surface of the Sun are the observational signatures of intense manifestations of tightly packed magnetic field lines, with near-vertical field strengths exceeding 6,000 G in extreme cases. It is well accepted that both the plasma density ... More
Photospheric observations of surface and body modes in solar magnetic poresMar 05 2018Over the past number of years, great strides have been made in identifying the various low-order magnetohydrodynamic wave modes observable in a number of magnetic structures found within the solar atmosphere. However, one aspect of these modes that has ... More
Wave Damping Observed in Upwardly Propagating Sausage-mode Oscillations contained within a Magnetic PoreMay 06 2015May 11 2015We present observational evidence of compressible magnetohydrodynamic wave modes propagating from the solar photosphere through to the base of the transition region in a solar magnetic pore. High cadence images were obtained simultaneously across four ... More
Excitations are localized and relaxation is hierarchical in glass-forming liquidsJul 19 2011May 07 2014For several atomistic models of glass formers, at conditions below their glassy dynamics onset temperatures, ${T_\mathrm{o}}$, we use importance sampling of trajectory space to study the structure, statistics and dynamics of excitations responsible for ... More
Continuum emission enhancements and penumbral changes observed during flares by IRIS, ROSA, and HinodeJan 07 2019In this paper we describe observations acquired by satellite instruments (Hinode/SOT and IRIS) and ground-based telescopes (ROSA@DST) during two consecutive C7.0 and X1.6 flares occurred in active region NOAA 12205 on 2014 November 7. The analysis of ... More
Cone-Guided Fast Ignition with no Imposed Magnetic FieldsNov 22 2011Sep 10 2012Simulations of ignition-scale fast ignition targets have been performed with the new integrated Zuma-Hydra PIC-hydrodynamic capability. We consider an idealized spherical DT fuel assembly with a carbon cone, and an artificially-collimated fast electron ... More
A Workshop that WorksApr 15 2014The main goal of a scientific workshop is to bring together experts in a specific field or related fields to collaborate, to discuss, and to creatively make progress in a particular area. The organizational aspects of such a meeting play a critical role ... More
Fast-ignition design transport studies: realistic electron source, integrated PIC-hydrodynamics, imposed magnetic fieldsMay 08 2012Transport modeling of idealized, cone-guided fast ignition targets indicates the severe challenge posed by fast-electron source divergence. The hybrid particle-in-cell [PIC] code Zuma is run in tandem with the radiation-hydrodynamics code Hydra to model ... More
An Inside Look at Sunspot Oscillations with Higher Azimuthal WavenumbersMay 17 2017Solar chromospheric observations of sunspot umbrae offer an exceptional view of magneto-hydrodynamic wave phenomena. In recent years, a wealth of wave signatures related to propagating magneto-acoustic modes have been presented, which demonstrate complex ... More
H$α$ and H$β$ emission in a C3.3 solar flare: comparison between observations and simulationsOct 11 2017The Hydrogen Balmer series is a basic radiative loss channel from the flaring solar chromosphere. We report here on the analysis of an extremely rare set of simultaneous observations of a solar flare in the H${\alpha}$ and H${\beta}$ lines at high spatial ... More
The proximal distance algorithmJul 27 2015The MM principle is a device for creating optimization algorithms satisfying the ascent or descent property. The current survey emphasizes the role of the MM principle in nonlinear programming. For smooth functions, one can construct an adaptive interior ... More
CfA4: Light Curves for 94 Type Ia SupernovaeMay 21 2012We present multi-band optical photometry of 94 spectroscopically-confirmed Type Ia supernovae (SN Ia) in the redshift range 0.0055 to 0.073, obtained between 2006 and 2011. There are a total of 5522 light curve points. We show that our natural system ... More
Application of Mutual Information Methods in Time-Distance HelioseismologyJan 22 2015Jun 09 2015We apply a new technique, the mutual information (MI) from information theory, to time-distance helioseismology, and demonstrate that it can successfully reproduce several classic results based on the widely used cross-covariance method. MI quantifies ... More
On Parrondo's paradox: how to construct unfair games by composing fair gamesJun 15 2002We construct games of chance from simpler games of chance. We show that it may happen that the simpler games of chance are fair or unfavourable to a player andyet the new combined game is favourable -- this is a counter-intuitive phenomenoknown as Parrondo's ... More
The Virtual Ring Shear-Slip Mesh Update MethodApr 10 2018A novel method - the Virtual Ring Shear-Slip Mesh Update Method (VR-SSMUM) - for the efficient and accurate modeling of moving boundary or interface problems in the context of the numerical analysis of fluid flow is presented. We focus on cases with periodic ... More
Proximal Distance Algorithms: Theory and PracticeApr 19 2016Proximal distance algorithms combine the classical penalty method of constrained minimization with distance majorization. If $f(\boldsymbol{x})$ is the loss function, and $C$ is the constraint set in a constrained minimization problem, then the proximal ... More
Comparing Terminal Performance of .357 SIG and 9mm Bullets in Ballistic Gelatin Using Retarding Force Analysis from High Speed VideoAug 21 2015High-speed video has emerged as an valuable tool for quantifying bullet performance in ballistic gelatin. This paper presents the results of testing four .357 SIG bullets using high-speed video of bullet impacts in ballistic gelatin to determine retarding ... More
Fixed and Market Pricing for Cloud ServicesJan 26 2012This paper considers two simple pricing schemes for selling cloud instances and studies the trade-off between them. We characterize the equilibrium for the hybrid system where arriving jobs can choose between fixed or the market based pricing. We provide ... More
Efficient Advert AssignmentApr 10 2014Jun 02 2016We develop a framework for the analysis of large-scale Ad-auctions where adverts are assigned over a continuum of search types. For this pay-per-click market, we provide an efficient mechanism that maximizes social welfare. In particular, we show that ... More
Proximal Distance Algorithms: Theory and ExamplesApr 19 2016Aug 30 2018Proximal distance algorithms combine the classical penalty method of constrained minimization with distance majorization. If $f(\boldsymbol{x})$ is the loss function, and $C$ is the constraint set in a constrained minimization problem, then the proximal ... More
Statistical Signatures of Nanoflare Activity. I. Monte Carlo Simulations and Parameter Space ExplorationDec 17 2018Small-scale magnetic reconnection processes, in the form of nanoflares, have become increasingly hypothesized as important mechanisms for the heating of the solar atmosphere, for driving propagating disturbances along magnetic field lines in the Sun's ... More
Statistical Signatures of Nanoflare Activity. I. Monte Carlo Simulations and Parameter-space ExplorationDec 17 2018Feb 27 2019Small-scale magnetic reconnection processes, in the form of nanoflares, have become increasingly hypothesized as important mechanisms for the heating of the solar atmosphere, for driving propagating disturbances along magnetic field lines in the Sun's ... More
Manifestations of Dynamical Facilitation in Glassy MaterialsFeb 24 2012Jun 21 2012By characterizing the dynamics of idealized lattice models with a tunable kinetic constraint, we explore the different ways in which dynamical facilitation manifests itself within the local dynamics of glassy materials. Dynamical facilitation is characterized ... More
The NANOGrav 11-Year Data Set: Limits on Gravitational Waves from Individual Supermassive Black Hole BinariesDec 30 2018Observations indicate that nearly all galaxies contain supermassive black holes (SMBHs) at their centers. When galaxies merge, their component black holes form SMBH binaries (SMBHBs), which emit low-frequency gravitational waves (GWs) that can be detected ... More
Renormalization of the Polyakov loop with gradient flowSep 25 2015Nov 24 2015We use the gradient flow for the renormalization of the Polyakov loop in various representations. Using 2+1 flavor QCD with highly improved staggered quarks and lattices with temporal extents of $N_\tau=6$, $8$, $10$ and $12$ we calculate the renormalized ... More
Microscopic study of superdeformation in the A=150 mass regionOct 06 1995The cranked Hartree-Fock-Bogoliubov method presented in previous studies of superdeformed bands in Hg and Pb isotopes is applied to the study of superdeformed bands in Gd150, Dy152, Dy151 and Tb151. The same density-dependent zero-range pairing interaction ... More
On the Analytic Structure of the Quark Self-Energy in Nambu-Jona- Lasinio ModelsAug 25 1993The self-energy of quarks is investigated for various models which are inspired by the Nambu--Jona-Lasinio (NJL) model. Including, beyond the Hartree-Fock approximation, terms up to second-order in the quark interaction, the real and imaginary parts of ... More
Low energy threshold corrections to neutrino masses and mixing anglesOct 17 2001We compute the low energy threshold corrections to neutrino masses and mixing in the Standard Model (SM) and its minimal supersymmetric version, using the effective theory technique. We demonstrate that they stabilize the renormalization group (RG) running ... More
An Overdensity of Extremely Red Objects Around Faint Mid-IR galaxiesMay 04 2004We have searched for Extremely Red Objects (EROs) around faint mid-IR selected galaxies in ELAIS fields. We find a significant overdensity, by factors of 2 to 5, of these EROs compared to field EROs in the same region and literature random field ERO counts. ... More
Number Counts of Bright Extremely Red Objects: Evolved Massive Galaxies at z~1Apr 06 2004We present results on number counts of Extremely Red Objects (EROs) in a 2850 arcmin^2 near-infrared survey performed in European Large Area ISO Survey (ELAIS) fields at K<17.5. Counts of EROs are extended to brighter levels than available previously, ... More
Significance Tests in Climate ScienceMar 15 2010A large fraction of papers in the climate literature includes erroneous uses of significance tests. A Bayesian analysis is presented to highlight the meaning of significance tests and why typical misuse occurs. It is concluded that a significance test ... More
Neutrino Mass Differences and Nonunitarity of Neutrino Mixing Matrix from Interfering Recoil IonsMar 20 2008Oct 06 2009We show that the recent observation of the time modulation of two-body weak decays of heavy ions reveals the mass content of the electron neutrinos via interference patterns in the recoiling ion wave function. From the modulation period we derive the ... More
Large sample-to-sample fluctuations of the nonequilibrium critical current through mesoscopic Josephson junctionsApr 12 2000We present a theory for the nonequilibrium current in a mesoscopic Josephson junction which is coupled to a normal electron reservoir, and apply it to a chaotic junction. Large sample-to-sample fluctuations of the critical current $I_{\rm c}$ are found, ... More
Theory of Coherent Raman Superradiance Imaging of Condensed Bose GasesFeb 14 2006Oct 17 2006We model the off-resonant superradiant Raman scattering of light from a cigar-shaped atomic Bose-Einstein condensate. Absorption images of transmitted light serve as a direct probe of long range coherence in the condensate. Our multimode theory is in ... More
Creating macroscopic atomic EPR states from Bose condensatesJul 05 2000We present a scheme for creating quantum entangled atomic states through the coherent spin-exchange collision of a spinor Bose-Einstein condensate. The state generated possesses macroscopic Einstein-Podolsky-Roson correlation and the fluctuation in one ... More
Giant outflows in z~2 radio galaxies: The smoking gun of AGN feedback in the early universeJun 16 2009Jun 19 2009AGN feedback is now a major component of models of galaxy evolution. Using near-infrared imaging spectroscopy on the VLT we identify kpc-sized outflows of few x 10^10 M_s of ionized gas in powerful radio galaxies at z~2-3. Velocity fields are consistent ... More
Strangeness Production in AA and pp CollisionsJan 07 2016Boost-invariant hadron production in high energy collisions occurs in causally disconnected regions of finite space-time size. As a result, globally conserved quantum numbers (charge, strangeness, baryon number) are conserved locally in spatially restricted ... More
Causality Constraints on Hadron Production In High Energy CollisionsOct 25 2013For hadron production in high energy collisions, causality requirements lead to the counterpart of the cosmological horizon problem: the production occurs in a number of causally disconnected regions of finite space-time size. As a result, globally conserved ... More
Spin-Wave Resonance Model of Surface Pinning in Ferromagnetic Semiconductor (Ga,Mn)As Thin FilmsNov 22 2013Jan 08 2014The source of spin-wave resonance (SWR) in thin films of the ferromagnetic semiconductor (Ga,Mn)As is still under debate: does SWR stem from the \emph{surface} anisotropy (in which case the surface inhomogeneity (SI) model would apply), or does it originate ... More
Scattering states of coupled valence-band holes in point defect potential derived from variable phase theoryOct 31 2006In this article we present a method to compute the scattering states of holes in spherical bands in the strong spin-orbit coupling regime. More precisely, we calculate scattering phase shifts and amplitudes of holes induced by defects in a semiconductor ... More
Topology and the Dirac Operator Spectrum in Finite-Volume Gauge TheoriesMar 11 1999Mar 17 1999The interplay between between gauge-field winding numbers, theta-vacua, and the Dirac operator spectrum in finite-volume gauge theories is reconsidered. To assess the weight of each topological sector, we compare the mass-dependent chiral condensate in ... More
AC susceptibility of YBa2Cu3O7-d superconducting thin film in a perpendicular fieldNov 30 2002The temperature dependence of ac susceptibility of YBCO thin film was measured as a function of frequency and ac field amplitude in a field perpendicular to the film plane. We show that all measured ac susceptibility curves can be caled into a single ... More
Constraints on low energy supersymmetryNov 25 1997We review the available constraints on the low energy supersymmetry. The bulk of the electroweak data is well screened from supersymmetric loop effects, due to the structure of the theory, even with superpartners generically light, ${\cal O}(M_Z)$. The ... More
Probability distribution of the order parameter in the directed percolation universality classSep 09 2012The probability distributions of the order parameter for two models in the directed percolation universality class were evaluated. Monte Carlo simulations have been performed for the one-dimensional generalized contact process and the Domany-Kinzel cellular ... More
Exact perturbative solution of the Kondo problemJun 22 1995We explicitly evaluate the infinite series of integrals that appears in the "Anderson-Yuval" reformulation of the anisotropic Kondo problem in terms of a one-dimensional Coulomb gas. We do this by developing a general approach relating the anisotropic ... More
Numerical calculation of linear modes in stellar disksMar 18 1996We present a method for solving the two-dimensional linearized collisionless Boltzmann equation using Fourier expansion along the orbits. It resembles very much solutions present in the literature, but it differs by the fact that everything is performed ... More
Quiver Gauge Theory and Unification at About 4 TeVFeb 08 2003The use of the AdS/CFT correspondence to arrive at quiver gauge field theories is dicussed, focusing on the orbifolded case without supersymmetry. An abelian orbifold with the finite group $Z_{p}$ can give rise to a $G = SU(N)^p$ gauge group with chiral ... More
Application of Conformal Gauge Theories Derived from Field-String DualityAug 25 1999In this article I first give an abbreviated history of string theory and then describe the recently-conjectured field-string duality. This suggests a class of nonsupersymmetric gauge theories which are conformal (CGT) to leading order of 1/N and some ... More
ADS/CFT String Duality and Conformal Gauge Field TheoriesDec 14 1998Compactification of Type IIB superstring on an $AdS_5 \times S^5/\Gamma$ background leads to SU(N) gauge field theories with prescribed matter representations. In the 't Hooft limit of large N such theories are conformally finite. For finite N and broken ... More
Dark Matter Candidate from ConformalityJul 17 2006Sep 26 2006Abelian quiver gauge theories provide candidates for the conformality approach to physics beyond the standard model which possess novel cancellation mechanisms for quadratic divergences. A $Z_2$ symmetry (R parity) can be imposed and leads naturally to ... More
Probing Matter Radii of Neutron-Rich Nuclei by Antiproton ScatteringFeb 21 2005We propose to use antiprotons to investigate the sizes of stable and neutron-rich exotic nuclei by measurements of the $\pbar A$ absorption cross section along isotopic chains in inverse kinematics. The expected effects are studied theoretically in a ... More
Flops, Type III contractions and Gromov-Witten invariants on Calabi-Yau threefoldsJul 09 1997Jul 20 1998We investigate Gromov-Witten invariants associated to exceptional classes for primitive birational contractions on a Calabi-Yau threefold X. It was observed in a previous paper that these invariants are locally defined, in that they can be calculated ... More
Star formation in grand-design, spiral galaxies. Young, massive clusters in the near-infraredApr 25 2012Deep, near-infrared JHK-maps were observed for 10 nearby, grand-design, spiral galaxies using HAWK-I/VLT to study the distribution of young stellar clusters in them and thereby determine whether strong spiral perturbations can influence star formation. ... More
Iteratively algebraic ordersOct 26 2008Jan 02 2010A short proof of a theorem of M.H. Albert, and its application to lattices.
Boundedness questions for Calabi-Yau threefoldsJun 05 2017May 09 2018In this paper, we study boundedness questions for (simply-connected) smooth Calabi-Yau threefolds. The diffeomorphism class of such a threefold is known to be determined up to finitely many possibilities by the integral middle cohomology and two integral ... More
Budget Optimization for Sponsored Search: Censored Learning in MDPsOct 16 2012We consider the budget optimization problem faced by an advertiser participating in repeated sponsored search auctions, seeking to maximize the number of clicks attained under that budget. We cast the budget optimization problem as a Markov Decision Process ... More
Neutron Stars and Gamma Ray Bursts with LOFARSep 17 2009LOFAR, the Low Frequency Array, is an innovative new radio telescope currently under construction in the Netherlands. With its continuous monitoring of the radio sky we expect LOFAR will detect many new transient events, including GRB afterglows and pulsating/single-burst ... More
Ranking and Tradeoffs in Sponsored Search AuctionsApr 29 2013In a sponsored search auction, decisions about how to rank ads impose tradeoffs between objectives such as revenue and welfare. In this paper, we examine how these tradeoffs should be made. We begin by arguing that the most natural solution concept to ... More
Iterative Hard Thresholding for Model Selection in Genome-Wide Association StudiesAug 04 2016Nov 16 2016A genome-wide association study (GWAS) correlates marker variation with trait variation in a sample of individuals. Each study subject is genotyped at a multitude of SNPs (single nucleotide polymorphisms) spanning the genome. Here we assume that subjects ... More
Self-Assembly of Patchy Particles into Diamond Structures through Molecular MimicryJan 17 2012Fabrication of diamond structures by self-assembly is a fundamental challenge in making three-dimensional photonic crystals. We simulate a system of model hard particles with attractive patches and show that they can self-assemble into a diamond structure ... More
The scientific potential of LOFAR for time-domain astronomyDec 12 2011LOFAR is a groundbreaking low-frequency radio telescope currently nearing completion across northern europe. As a software telescope with no moving parts, enormous fields of view and multi-beaming, it has fantastic potential for the exploration of the ... More
Strong-coupling expansion for the Hubbard model in arbitrary dimension using slave bosonsJan 17 1996A strong-coupling expansion for the antiferromagnetic phase of the Hubbard model is derived in the framework of the slave-boson mean-field approximation. The expansion can be obtained in terms of moments of the density of states of freely hopping electrons ... More
A Field-Effect-Transistor from Graphite: No Effect of Low Gate FieldsApr 04 2003Inspired by the striking similarities between the metal-insulator transitions in graphite and Si-MOSFET's and the recent attention to charge doping in carbon-based materials, we have made attempts to fabricate a field-effect transistor based on graphite. ... More
The Simple Ree groups ${}^2F_4(q^2)$ are determined by the set of their character degreesMar 21 2011May 29 2011Let $G$ be a finite group. Let ${\rm{cd}}(G)$ be the set of all complex irreducible character degrees of $G.$ In this paper, we will show that if ${\rm{cd}}(G)={\rm{cd}}(H),$ where $H$ is the simple Ree group ${}^2F_4(q^2),q^2\geq 8,$ then $G\cong H\times ... More
Completing Continuum Coulomb Gauge in the Functional FormalismNov 19 2007It is argued that within the continuum functional formalism, there is no need to supply a further (spatially independent) gauge constraint to complete the Coulomb gauge of Yang-Mills theory. It is shown explicitly that a natural completion of the gauge-fixing ... More
Dyson-Schwinger Equations and Coulomb Gauge Yang-Mills TheoryOct 20 2006Coulomb gauge Yang-Mills theory is considered within the first order formalism. It is shown that the action is invariant under both the standard BRS transform and an additional component. The Ward-Takahashi identity arising from this non-standard transform ... More
The QCD Dirac Operator Spectrum and Finite-Volume ScalingAug 25 1998Random matrix theory and chiral Lagrangians offer a convenient tool for the exact calculation of microscopic spectral correlators of the Dirac operator in a well-defined finite-volume scaling regime.
The Microscopic Dirac Operator SpectrumOct 24 2001We review the exact results for microscopic Dirac operator spectra based on either Random Matrix Theory, or, equivalently, chiral Lagrangians. Implications for lattice calculations are discussed.
The Dirac Operator Spectrum and Effective Field TheoryAug 24 2000Aug 28 2000When chiral symmetry is spontaneously broken, the low-energy part of the Dirac operator spectrum can be computed analytically in the chiral limit. The tool is effective field theory or, equivalently in this case, Random Matrix Theory.
Beyond The Colour-Singlet Model For Inelastic J/ψPhotoproductionNov 17 1995Bound-state corrections to $J/\psi$ production from almost real photons are calculated in the colour-singlet model. A systematic, gauge-invariant, theory of hard quarkonium processes is used upto $O(v^2)$, where $v$ is the relative velocity of the quarks. ... More
Frequentist vs Bayesian statistics - a non-statisticians viewAug 10 2012People who by training end up dealing with probabilities ("statisticians") roughly fall into one of two camps. One is either a frequentist or a Bayesian. To a scientist, who needs to use probabilities to make sense of the real world, this division seems ... More
Temperature structure of the intergalactic medium within seven nearby and bright clusters of galaxies observed with XMM-NewtonFeb 13 2008Aims. We map the temperature structure of the intra-cluster medium (ICM) within a nearly complete X-ray flux limited sample of galaxy clusters in the redshift range z=[0.045,0.096]. Our sample contains seven bright clusters of galaxies observed with XMM-Newton: ... More
How unconditionally secure quantum bit commitment is possibleSep 13 2001Nov 20 2001Bit commitment involves the submission of evidence from one party to another so that the evidence can be used to confirm a later revealed bit value by the first party, while the second party cannot determine the bit value from the evidence alone. It is ... More
Quantum states for Heisenberg-limited interferometryFeb 16 2007Jul 19 2007The phase resolution of interferometers is limited by the so-called Heisenberg limit, which states that the optimum phase sensitivity is inversely proportional to the number of interfering particles N, a 1/sqrt{N} improvement over the standard quantum ... More
Density perturbations in warm inflation and COBE normalizationFeb 13 2002Starting from a gauge invariant treatment of perturbations an analytical expression for the spectrum of long wavelength density perturbations in warm inflation is derived. The adiabatic and entropy modes are exhibited explicitly. As an application of ... More
Simulating Cosmic Structure at High Resolution: Towards a Billion Particles?Sep 30 1997Cosmic structure simulations have improved enormously over the past decade, both in terms of the resolution which can be achieved, and with the addition of hydrodynamic and other techniques to formerly purely gravitational methods. This is an informal, ... More
Effect of deoxygenation on the weak link behavior of YBCO superconductorsNov 27 2002A systematic study of the weak- link behavior for YBa2Cu3O7-d polycrystalline samples has been done using the electrical resistivity and AC susceptibility techniques.The experiments were performed with two samples of similar grain, a sample of well-coupled ... More
NIR view on young stellar clusters in nearby spiralsSep 20 2011Observations in the near-infrared (NIR) allow a detailed study of young stellar clusters in grand-design spiral galaxies which in visual bands often are highly obscured by dust lanes along the arms. Deep JHK-maps of 10 spirals were obtained with HAWK-I/VLT. ... More
Learning Identity Mappings with Residual GatesNov 04 2016We propose a technique to augment network layers by adding a linear gating mechanism, which provides a way to learn identity mappings by optimizing only one parameter. We also introduce a new metric which served as basis for the technique. It captures ... More
Chain of impacting pendulums as non-analytically perturbed sine-Gordon systemJan 06 2005We investigate a mechanical system consisting of infinite number of harmonically coupled pendulums which can impact on two rigid rods. Because of gravitational force the system has two degenerate ground states. The related topological kink - likely the ... More
Some geometry and combinatorics for the S-invariant of ternary cubicsJul 14 2004Jun 20 2006Given a real cubic form f(x,y,z), there is a pseudo-Riemannian metric given by its Hessian matrix, defined on the open subset of R^3 where the Hessian determinant h is non-zero. We determine the full curvature tensor of this metric in terms of h and the ... More