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Results for "D. Hessman"

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Measurements of strain and bandgap of coherently epitaxially grown wurtzite InAsP-InP core-shell nanowiresApr 12 2019We report on experimental determination of the strain and bandgap of InAsP in epitaxially grown InAsP-InP core-shell nanowires. The core-shell nanowires are grown via metal-organic vapor phase epitaxy. The as-grown nanowires are characterized by transmission ... More
Evidence for an oscillation of the magnetic axis of the white dwarf in the polar DP LeonisJan 08 2014From 1979 to 2001, the magnetic axis of the white dwarf in the polar DP Leo slowly rotated by 50 deg in azimuth, possibly indicating a small asynchronism between the rotational and orbital periods of the magnetic white dwarf. We have obtained phase-resolved ... More
The quest for companions to post-common envelope binaries. II. NSVS14256825 and HS0705+6700Feb 27 2012We report new mid-eclipse times of the two close binaries NSVS14256825 and HS0705+6700, harboring an sdB primary and a low-mass main-sequence secondary. Both objects display clear variations in the measured orbital period, which can be explained by the ... More
A long-term optical and X-ray ephemeris of the polar EK Ursae MajorisNov 06 2009We searched for long-term period changes in the polar EK UMa using new optical data and archival X-ray/EUV data. An optical ephemeris was derived from data taken remotely with the MONET/N telescope and compared with the X-ray ephemeris based on Einstein, ... More
The difficulty of measuring the local dark matter densityJun 01 2015The analysis of the vertical velocity dispersion of disc stars is the most direct astronomical means of estimating the local dark matter density, $\rho_{DM}$. Current estimates based on the mid-plane dynamic density use a local baryonic correction that ... More
HS0907+1902: a new 4.2hr eclipsing dwarf novaMar 22 2000We report on follow-up spectroscopy and photometry of the cataclysmic variable candidate HS0907+1902 selected from the Hamburg Quasar Survey. B, V, and R photometry obtained during the first observed outburst of HS0907+1902 (V~13) reveals deep eclipses ... More
The Bosma effect revisited - I. HI and stellar disc scaling modelsJun 28 2011The observed proportionality between the centripetal contribution of the dynamically insignificant HI gas in the discs of spiral galaxies and the dominant contribution of DM - the "Bosma effect" - has been repeatedly mentioned in the literature but largely ... More
On the naming convention used for multiple star systems and extrasolar planetsDec 03 2010The present naming convention for extrasolar planets used by the vast majority of researchers in the field is based upon an interpretation of the provisional I.A.U. standard for multiple star systems. With the existence of hundreds of exoplanets around ... More
The Patchy Accretion Disc in HT CassiopeiaeDec 19 2001We have reconstructed the temperatures and surface densities in the quiescent accretion disc in HT Cas by performing a "Physical Parameter Eclipse Mapping" analysis of archival UBVR observations. Using a simple hydrogen slab model and demanding a smooth, ... More
Second generation planet formation in NN Serpentis?Dec 29 2013In this paper, we study the general impact of stellar mass-ejection events in planetary orbits in post-common envelope binaries with circumbinary planets like those around NN Serpentis. We discuss a set of simple equations that determine upper and lower ... More
The quest for companions to post-common envelope binaries IV: The 2:1 mean-motion resonance of the planets orbiting NN SerpentisMay 28 2013We present 69 new mid-eclipse times of the young post-common envelope binary (PCEB) NN Ser, which was previously suggested to possess two circumbinary planets. We have interpreted the observed eclipse-time variations in terms of the light-travel time ... More
Detecting circumstellar disks around gravitational microlensesApr 07 2009We investigate the chance of detecting proto-planetary or debris disks in stars that induce microlensing events (lenses). The modification of the light curves shapes due to occultation and extinction by the disks as well as the additional gravitational ... More
Optimising Optimal Image SubtractionNov 20 2006Difference imaging is a technique for obtaining precise relative photometry of variable sources in crowded stellar fields and, as such, constitutes a crucial part of the data reduction pipeline in surveys for microlensing events or transiting extrasolar ... More
The giant planet orbiting the cataclysmic binary DP LeonisNov 17 2010Planets orbiting post-common envelope binaries provide fundamental information on planet formation and evolution, especially for the yet nearly unexplored class of circumbinary planets. We searched for such planets in \odp, an eclipsing short-period binary, ... More
Two planets orbiting the recently formed post-common envelope binary NN SerpentisOct 18 2010Planets orbiting post-common envelope binaries provide fundamental information on planet formation and evolution. We searched for such planets in NN Ser ab, an eclipsing short-period binary that shows long-term eclipse time variations. Using published, ... More
The Planets around the Post-Common Envelope Binary NN SerpentisFeb 02 2011We have detected 2 circumbinary planets around the close binary system NN Serpentis using the orbital time delay effect measured via the sharp eclipses of the white dwarf primary. The present pre-cataclysmic binary was formed when the original - 2 M primary ... More
The response of a dwarf nova disc to real mass transfer variationsApr 19 2000We present simulations of dwarf nova outbursts taking into account realistic variations of the mass loss rate from the secondary. The mass transfer variation has been derived from 20 years of visual monitoring and from X-ray observations covering various ... More
Reengineering observatory operations for the time domainJul 28 2014Observatories are complex scientific and technical institutions serving diverse users and purposes. Their telescopes, instruments, software, and human resources engage in interwoven workflows over a broad range of timescales. These workflows have been ... More
The quest for companions to post-common envelope binaries: III. A reexamination of HW VirginisJun 14 2012We report new mid-eclipse times of the short-period sdB/dM binary HW Vir, which differ substantially from the times predicted by a previous model. The proposed orbits of the two planets in that model are found to be unstable. We present a new secularly ... More
A Giant Planet beyond the Snow Line in Microlensing Event OGLE-2011-BLG-0251Mar 05 2013We present the analysis of the gravitational microlensing event OGLE-2011-BLG-0251. This anomalous event was observed by several survey and follow-up collaborations conducting microlensing observations towards the Galactic Bulge. Based on detailed modelling ... More
A sub-Saturn Mass Planet, MOA-2009-BLG-319LbOct 09 2010Dec 10 2010We report the gravitational microlensing discovery of a sub-Saturn mass planet, MOA-2009-BLG-319Lb, orbiting a K or M-dwarf star in the inner Galactic disk or Galactic bulge. The high cadence observations of the MOA-II survey discovered this microlensing ... More
High angular resolution imaging and infrared spectroscopy of CoRoT candidatesJul 05 2013Jul 19 2013Studies of transiting extrasolar planets are of key importance for understanding the nature of planets outside our solar system because their masses, diameters, and bulk densities can be measured. An important part of transit-search programmes is the ... More
Physical properties of the 0.94-day period transiting planetary system WASP-18Oct 26 2009We present high-precision photometry of five consecutive transits of WASP-18, an extrasolar planetary system with one of the shortest orbital periods known. Through the use of telescope defocussing we achieve a photometric precision of 0.47 to 0.83 mmag ... More
AstroImageJ: Image Processing and Photometric Extraction for Ultra-Precise Astronomical Light Curves (Expanded Edition)Jan 17 2017ImageJ is a graphical user interface (GUI) driven, public domain, Java-based, software package for general image processing traditionally used mainly in life sciences fields. The image processing capabilities of ImageJ are useful and extendable to other ... More
Microlensing Binaries Discovered through High-Magnification ChannelSep 15 2011Nov 29 2011Microlensing can provide a useful tool to probe binary distributions down to low-mass limits of binary companions. In this paper, we analyze the light curves of 8 binary lensing events detected through the channel of high-magnification events during the ... More
The spectral type of CHS7797 - an intriguing very low mass periodic variable in the Orion Nebula ClusterJan 24 2013We present the spectroscopic characterization of the unusual high-amplitude very low mass pre-main-sequence periodic variable CHS7797. This study is based on optical medium-resolution (R=2200) spectroscopy in the 6450-8600 A range, carried out with GMOS-GEMINI-S ... More
Zeeman tomography of magnetic white dwarfs: General method and application to EF EridaniMar 14 2003We have developed a new method to derive the magnetic field distribution on the surfaces of rotating magnetic white dwarfs from phase-resolved flux and circular polarization spectra. An optimization code based on an evolutionary strategy is used to fit ... More
I. Flux and color variations of the quadruply imaged quasar HE 0435-1223Jan 19 2011Feb 16 2011aims: We present VRi photometric observations of the quadruply imaged quasar HE 0435-1223, carried out with the Danish 1.54m telescope at the La Silla Observatory. Our aim was to monitor and study the magnitudes and colors of each lensed component as ... More
AstroImageJ: Image Processing and Photometric Extraction for Ultra-Precise Astronomical Light CurvesJan 11 2016Jan 17 2017ImageJ is a graphical user interface (GUI) driven, public domain, Java-based, software package for general image processing traditionally used mainly in life sciences fields. The image processing capabilities of ImageJ are useful and extendable to other ... More
Planet formation in post-common-envelope binariesJan 07 2015To understand the evolution of planetary systems, it is important to investigate planets in highly evolved stellar systems, and to explore the implications of their observed properties with respect to potential formation scenarios. Observations suggest ... More
EMCCD photometry reveals two new variable stars in the crowded central region of the globular cluster NGC 6981Apr 08 2013Sep 02 2013Two previously unknown variable stars in the crowded central region of the globular cluster NGC 6981 are presented. The observations were made using the Electron Multiplying CCD (EMCCD) camera at the Danish 1.54m Telescope at La Silla, Chile.The two variables ... More
An unusual very low-mass high-amplitude pre-main sequence periodic variableJul 10 2012We have investigated the nature of the variability of CHS7797, an unusual periodic variable in the Orion Nebula Cluster. An extensive I-band photometric data set of CHS7797 was compiled between 2004-2010 using various telescopes. Further optical data ... More
IVOA Recommendation: Vocabularies in the Virtual Observatory Version 1.19Oct 03 2011This document specifies a standard format for vocabularies based on the W3C's Resource Description Framework (RDF) and Simple Knowledge Organization System (SKOS). By adopting a standard and simple format, the IVOA will permit different groups to create ... More
A detailed census of variable stars in the globular cluster NGC 6333 (M9) from CCD differential photometryJun 13 2013We report CCD $V$ and $I$ time-series photometry of the globular cluster NGC 6333 (M9). The technique of difference image analysis has been used, which enables photometric precision better than 0.05 mag for stars brighter than $V \sim 19.0$ mag, even ... More
The eclipsing post-common envelope binary CSS21055: a white dwarf with a probable brown-dwarf companionDec 18 2013We report photometric observations of the eclipsing close binary CSS21055 (SDSS J141126+200911) that strongly suggest that the companion to the carbon-oxygen white dwarf is a brown dwarf with a mass between 0.030 and 0.074 Msun. The measured orbital period ... More
The quest for companions to post-common envelope binaries: I. Searching a sample of stars from the CSS and SDSSJan 10 2012As part of an ongoing collaboration between student groups at high schools and professional astronomers, we have searched for the presence of circum-binary planets in a bona-fide unbiased sample of twelve post-common envelope binaries (PCEBs) from the ... More
OGLE-2015-BLG-0479LA,B: Binary Gravitational Microlens Characterized by Simultaneous Ground-based and Space-based ObservationJun 30 2016We present a combined analysis of the observations of the gravitational microlensing event OGLE-2015-BLG-0479 taken both from the ground and by the {\it Spitzer Space Telescope}. The light curves seen from the ground and from space exhibit a time offset ... More
OGLE-2009-BLG-092/MOA-2009-BLG-137: A Dramatic Repeating Event With the Second Perturbation Predicted by Real-Time AnalysisSep 02 2010We report the result of the analysis of a dramatic repeating gravitational microlensing event OGLE-2009-BLG-092/MOA-2009-BLG-137, for which the light curve is characterized by two distinct peaks with perturbations near both peaks. We find that the event ... More
Pathway to the Galactic Distribution of Planets: Combined Spitzer and Ground-Based Microlens Parallax Measurements of 21 Single-Lens EventsNov 26 2014Feb 24 2015We present microlens parallax measurements for 21 (apparently) isolated lenses observed toward the Galactic bulge that were imaged simultaneously from Earth and Spitzer, which was ~1 AU West of Earth in projection. We combine these measurements with a ... More
VLT observations of GRB 990510 and its environmentSep 02 1999We present BVRI photometry and spectrophotometry of GRB990510 obtained with the ESO VLT/Antu telescope during the late decline phase. Between days 8 and 29 after the burst, the afterglow faded from R=24.2 to ~26.4. The spectral flux distribution and the ... More
MOA-2010-BLG-477Lb: constraining the mass of a microlensing planet from microlensing parallax, orbital motion and detection of blended lightMay 29 2012Microlensing detections of cool planets are important for the construction of an unbiased sample to estimate the frequency of planets beyond the snow line, which is where giant planets are thought to form according to the core accretion theory of planet ... More
Cen A persistence and Virgo absence versus updated maps to understand UHECR natureDec 31 2010Ultra High Cosmic Rays (UHECR) should be tracing their sources, making a new astronomy. Their events counting are finally growing, by Auger experiment, into cosmic sky. Their map should follow the mass distribution in a narrow cosmic volume (the GZK cut ... More
Deep Core muon neutrino rate and anisotropy by mixing and CPT violationDec 23 2010Neutrinos are allowed to mix and to oscillate among their flavor. Muon and tau in particular oscillate at largest values.Last Minos experiment claimed possible difference among their matter and anti-matter masses, leading to a first violation of the most ... More
Achievements and Mirages in Uhecr and Neutrino AstronomyMay 11 2009Photon Astronomy ruled the last four centuries while wider photon band ruled last radio-X-Gamma century of discovery. Present decade may see the rise and competition of UHECR and UHE Neutrino Astronomy. Tau Neutrino may win and be the first flavor revealed. ... More
An apparent GRBs evolution around us or a sampling of thin GRB beaming jets?Oct 13 2009Oct 14 2009The gamma ray burst apparent average isotropic power versus their red-shift of all known GRB (Sept.2009) is reported. It calls for an unrealistic Gamma Ray Burst Evolution around us or it just probe the need of a very thin gamma precession-jet model. ... More
IVOA Recommendation: Sky Event Reporting Metadata Version 2.0Oct 03 2011VOEvent defines the content and meaning of a standard information packet for representing, transmitting, publishing and archiving information about a transient celestial event, with the implication that timely follow-up is of interest. The objective is ... More
GRB 021004: a Massive Progenitor Star Surrounded by ShellsNov 09 2002Feb 18 2003We present spectra of the optical transient of GRB021004 obtained with the Hobby-Eberly telescope starting 15.48, 20.31 hours, and 4.84 days after the burst and a spectrum obtained with the H. J. Smith 2.7 m Telescope starting 14.31 hours after the burst. ... More
Inconsistence of super-luminal Cern-Opera neutrino speed with observed SN1987A burst and neutrino mixing for any imaginary neutrino massSep 25 2011Mar 05 2012We tried to fit in any way the recent Opera-Cern claims of a neutrino super-luminal speed with observed Supernova SN1987A neutrino burst and all (or most) neutrino flavor oscillation. We considered three main frame-works: (1) A tachyon imaginary neutrino ... More
MOA-2010-BLG-523: "Failed Planet" = RS CVn StarOct 22 2012Oct 26 2012The Galactic bulge source MOA-2010-BLG-523S exhibited short-term deviations from a standard microlensing lightcurve near the peak of an Amax ~ 265 high-magnification microlensing event. The deviations originally seemed consistent with expectations for ... More
Neutrino oscillations along the Earth to probe flavor parameters: a NeuWorldJan 11 2013Mar 12 2013On 2010 MINOS experiment was showing an hint of possible different mass splitting and mixing angles for neutrinos and anti-neutrinos, suggesting a charge-parity-time (CPT) violation in the lepton sector; last year 2012 a second result from MINOS showed ... More
Beaming Selection and SN-GRB-Jets EvolutionFeb 19 2009After a decade of Fireball reign there is a hope for thin collimated Jet to solve the Supernova-GRB mystery
MOA-2010-BLG-073L: An M-Dwarf with a Substellar Companion at the Planet/Brown Dwarf BoundaryNov 16 2012Dec 11 2012We present an analysis of the anomalous microlensing event, MOA-2010-BLG-073, announced by the Microlensing Observations in Astrophysics survey on 2010-03-18. This event was remarkable because the source was previously known to be photometrically variable. ... More
MOA-2010-BLG-311: A planetary candidate below the threshold of reliable detectionOct 22 2012Oct 10 2013We analyze MOA-2010-BLG-311, a high magnification (A_max>600) microlensing event with complete data coverage over the peak, making it very sensitive to planetary signals. We fit this event with both a point lens and a 2-body lens model and find that the ... More
Campaign 9 of the $K2$ Mission: Observational Parameters, Scientific Drivers, and Community Involvement for a Simultaneous Space- and Ground-based Microlensing SurveyDec 30 2015Mar 07 2016$K2$'s Campaign 9 ($K2$C9) will conduct a $\sim$3.7 deg$^{2}$ survey toward the Galactic bulge from 7/April through 1/July of 2016 that will leverage the spatial separation between $K2$ and the Earth to facilitate measurement of the microlens parallax ... More
Intrinsic Properties of the <z>=2.7 Lyman Alpha Forest from Keck Spectra of QSO HS 1946+7658Jan 27 1997Feb 20 1997We present the highest quality Lyman Alpha forest spectra published to date, from the QSO HS 1946+7658. The distribution of H I column densities is a power law of slope -1.5 from Log N = 12.1 - 14. This power law can extend to N = 0, because lines weaker ... More
Possible flakes of molecular hydrogen in the early UniverseNov 18 2002The thermochemistry of H2 and HD in non-collapsed, non-reionized primordial gas up to the end of the dark age is investigated with recent radiation-matter and chemical reaction rates taking into account the efficient coolant HD, and the possibility of ... More
The category of singularities as a crystal and global Springer fibersDec 14 2014May 12 2015We prove the "Gluing Conjecture" on the spectral side of the categorical geometric Langlands correspondence. The key tool is the structure of crystal on the category of singularities, which allows to reduce the conjecture to the question of homological ... More
The spin-1 ladder : A bosonization studyAug 16 1999We construct a field-theoretic description of two coupled spin-1 Heisenberg chains, starting with the known representation of a single spin-1 chain in terms of Majorana fermions (or Ising models). After reexamining the bosonization rules for two Ising ... More
Ginzburg-Landau equations for superconducting quark matter in neutron starsJun 19 2000May 18 2002We investigate magnetic properties of color superconducting quark matter within a Ginzburg-Landau approach. The simultaneous coupling of the quark fields to gluonic and electromagnetic gauge fields leads to rotated electromagnetism with a massive (Higgsed) ... More
13CO(1-0) and 12CO(2-1) in the center of the barred galaxy NGC 1530Apr 26 1999We present 13CO(1-0) and 12CO(2-1) aperture synthesis maps of the barred spiral galaxy NGC1530. The angular resolutions are respectively 3''.1 and 1''.6. Both transitions show features similar to the 12CO(1-0) map, with a nuclear feature (a ring or unresolved ... More
Production of complex particles in low energy spallation and in fragmentation reactions by in-medium random clusterizationMay 18 2005Rules for in-medium complex particle production in nuclear reactions are proposed. These rules have been implemented in two models to simulate nucleon-nucleus and nucleus-nucleus reactions around the Fermi energy. Our work emphasizes the effect of randomness ... More
OGLE-2011-BLG-0265Lb: a Jovian Microlensing Planet Orbiting an M DwarfOct 30 2014Feb 24 2015We report the discovery of a Jupiter-mass planet orbiting an M-dwarf star that gave rise to the microlensing event OGLE-2011-BLG-0265. Such a system is very rare among known planetary systems and thus the discovery is important for theoretical studies ... More
Anisotropies of Cosmic Rays and Search for Intergalactic Cascades from the direction of the Highest Energetic Cosmic Ray Events with the HEGRA Scintillator ArraySep 07 1999Data taken with the HEGRA Scintillator Array have been used to search for spatial anisotropies in the arrival directions of cosmic rays above 20 TeV. In this paper results on the search for TeV gamma-ray emission from the Galactic plane and the Gould ... More
Perturbative BPS-algebras in superstring theoryFeb 27 1997This paper investigates the algebraic structure that exists on perturbative BPS-states in the superstring, compactified on the product of a circle and a Calabi-Yau fourfold. This structure was defined in a recent article by Harvey and Moore. It shown ... More
Solid State Quantum BitsMay 27 2005We present the solid-state quantum circuits that have been developed in order to implement quantum bits suitable for a quantum processor. These qubits are either based on the quantum state of a single particle (semiconductor qubits), or on the quantum ... More
Applying MVC and PAC patterns in mobile applicationsJan 20 2010Additional requirements are set for mobile applications in relation to applications for desktop computers. These requirements primarily concern the support to different platforms on which such applications are performed, as well as the requirement for ... More
Bound States and Superconductivity in Dense Fermi SystemsDec 02 2008A quantum field theoretical approach to the thermodynamics of dense Fermi systems is developed for the description of the formation and dissolution of quantum condensates and bound states in dependence of temperature and density. As a model system we ... More
Gravity as an effective theoryOct 21 2009Using as inspiration the well known chiral effective lagrangian describing the interactions of pions at low energies, in these lectures we review the quantization procedure of Einstein gravity in the spirit of effective field theories. As has been emphasized ... More
Superconductivity in the 2D Hubbard model: Electron doping is differentAug 04 2008A variational Monte Carlo calculation is used for studying the ground state of the two-dimensional Hubbard model, including hopping between both nearest and next-nearest neighbor sites. Superconductivity with d-wave symmetry is found to be restricted ... More
Classical Functional Bethe Ansatz for $SL(N)$: separation of variables for the magnetic chainMar 04 1994The Functional Bethe Ansatz (FBA) proposed by Sklyanin is a method which gives separation variables for systems for which an $R$-matrix is known. Previously the FBA was only known for $SL(2)$ and $SL(3)$ (and associated) $R$-matrices. In this paper I ... More
A new class of magnetic materials: Sr2FeMoO6 and related compoundsFeb 27 2001Ordered double perovskite oxides of the general formula, A2BB'O6, have been known for several decades to have interesting electronic and magnetic properties. However, a recent report of a spectacular negative magnetoresistance effect in a specific member ... More
A locally symmetric Kaehler Einstein structure on the cotangent bundle of a space formAug 25 2003We obtain a locally symmetric Kaehler Einstein structure on the cotangent bundle of a Riemannian manifold of negative constant sectional curvature. Similar results are obtained on a tube around zero section in the cotangent bundle, in the case of a Riemannian ... More
Existence, multiplicity and stability of endemic states for an age-structured S-I epidemic modelJun 20 2008Feb 25 2010We study an S--I type epidemic model in an age-structured population, with mortality due to the disease. A threshold quantity is found that controls the stability of the disease-free equilibrium and guarantees the existence of an endemic equilibrium. ... More
Deformation effects on the coexistence between neutron-proton and particle like pairing in N=Z medium mass nucleiNov 07 2014A model combining self-consistent mean-field and shell-model techniques is used to study the competition between particle like and proton-neutron pairing correlations in fp-shell even-even self-conjugate nuclei. Results obtained using constant two-body ... More
The accretion-diffusion scenario for metals in cool white dwarfsMar 08 2006We calculated diffusion timescales for Ca, Mg, Fe in hydrogen atmosphere white dwarfs with temperatures between 5000 and 25000 K. With these timescales we determined accretion rates for a sample of 38 DAZ white dwarfs from the recent studies of Zuckerman ... More
The elliptic genus of Calabi-Yau 3- and 4-folds, product formulae and generalized Kac-Moody algebrasJul 03 1996In this paper the elliptic genus for a general Calabi-Yau fourfold is derived. The recent work of Kawai calculating N=2 heterotic string one-loop threshold corrections with a Wilson line turned on is extended to a similar computation where K3 is replaced ... More
Spherical varieties and Langlands dualityNov 10 2006Aug 07 2007Let G be a connected reductive complex algebraic group. This paper is devoted to the space Z of meromorphic quasimaps from a curve into an affine spherical G-variety X. The space Z may be thought of as an algebraic model for the loop space of X. In this ... More
Chemical evolution of turbulent protoplanetary disks and the Solar nebulaApr 21 2011Aug 23 2011This is the second paper in a series where we study the influence of transport processes on the chemical evolution of protoplanetary disks. Our analysis is based on a flared alpha-model of the DM Tau system, coupled to a large gas-grain chemical network. ... More
Uniform Kazhdan groupsJun 01 2006We construct first examples of infinite groups having property (T) whose Kazhdan constants admit a lower bound independent of the choice of a finite generating set.
A locally symmetric Kaehler Einstein structure on a tube in the nonzero cotangent bundle of a space formAug 29 2003We obtain a locally symmetric Kaehler Einstein structure on a tube in the nonzero cotangent bundle of a Riemannian manifold of positive constant sectional curvature. The obtained Kaehler Einstein structure cannot have constant holomorphic sectional curvature. ... More
Semi-classical description of the frustrated antiferromagnetic chainSep 21 1994The antiferromagnetic Heisenberg model on a chain with nearest and next nearest neighbor couplings is mapped onto the $SO(3)$ nonlinear sigma model in the continuum limit. In one spatial dimension this model is always in its disordered phase and a gap ... More
GSC 2314-0530: the shortest-period eclipsing system with dMe componentsMay 03 2010CCD photometric observations in VRI colors and spectroscopic observations of the newly discovered eclipsing binary GSC 2314-0530 (NSVS 6550671) with dMe components and very short period of P=0.192636 days are presented. The simultaneous light-curve solution ... More
Non-existence of a dilaton gravity action for the exact string black holeOct 07 2002Nov 07 2002We prove that no local diffeomorphism invariant two-dimensional theory of the metric and the dilaton without higher derivatives can describe the exact string black hole solution found a decade ago by Dijkgraaf, Verlinde and Verlinde. One of the key points ... More
eta and eta' mesons and dimension 2 gluon condensate <A^2>Dec 05 2005The study of light pseudoscalar quark-antiquark bound states in the Dyson-Schwinger approach with the effective QCD coupling enhanced by the interplay of the dimension 2 gluon condensate <A^2> and dimension 4 gluon condensate <F^2>, is extended to the ... More
Supersymmetric AdS(4) compactifications of IIA supergravityDec 21 2004Jan 25 2005We derive necessary and sufficient conditions for N=1 compactifications of (massive) IIA supergravity to AdS(4) in the language of SU(3) structures. We find new solutions characterized by constant dilaton and nonzero fluxes for all form fields. All fluxes ... More
A Selection of Giant Radio Sources from NVSSMar 22 2016May 10 2016Results of the application of pattern recognition techniques to the problem of identifying Giant Radio Sources (GRS) from the data in the NVSS catalog are presented and issues affecting the process are explored. Decision-tree pattern recognition software ... More
Comparing Pattern Recognition Feature Sets for Sorting Triples in the FIRST DatabaseMay 03 2006Pattern recognition techniques have been used with increasing success for coping with the tremendous amounts of data being generated by automated surveys. Usually this process involves construction of training sets, the typical examples of data with known ... More
Topological Dependence of Universal Correlations in Multi-Parameter HamiltoniansDec 03 1996Universality of correlation functions obtained in parametric random matrix theory is explored in a multi-parameter formalism, through the introduction of a diffusion matrix $D_{ij}(R)$, and compared to results from a multi-parameter chaotic model. We ... More
A class of locally symmetric Kaehler Einstein structures on the cotangent bundle of a space formJul 14 2004We obtain a class of locally symmetric Kaehler Einstein structures on the cotangent bundle of a Riemannian manifold of negative sectional curvature. Similar results are obtained in the case of a Riemannian manifold of positive sectional curvature. The ... More
Quantitative determination of the level of cooperation in the presence of punishment in three public good experimentsOct 25 2006Nov 21 2007Strong reciprocity is a fundamental human characteristic associated with our extraordinary sociality and cooperation. Laboratory experiments on social dilemma games and many field studies have quantified well-defined levels of cooperation and propensity ... More
Representations of algebraic groups over a 2-dimensional local fieldFeb 14 2003Jun 14 2004We introduce a categorical framework for the study of representations of $G_F$, where $G$ is a reductive group, and $\bF$ is a 2-dimensional local field, i.e. $F=K((t))$, where $K$ is a local field. Our main result says that the space of functions on ... More
Hecke operators on quasimaps into horospherical varietiesNov 11 2004Nov 10 2006Let $G$ be a connected reductive complex algebraic group. This paper is part of a project devoted to the space $Z$ of meromorphic quasimaps from a curve into an affine spherical $G$-variety $X$. The space $Z$ may be thought of as an algebraic model for ... More
Controlled dynamics of qubits in the presence of decoherenceJun 19 2007An exactly solvable model for the decoherence of one and two-qubit states interacting with a spin-bath, in the presence of a time-dependent magnetic field is studied. The magnetic field is static along $\hat{z}$ direction and oscillatory in the transverse ... More
Morphological Annotations for Groups in the FIRST DatabaseApr 19 2011The morphology of selected groups of sources in the FIRST (Faint Images of the Radio Sky at Twenty Centimeters) survey and catalog is examined. Sources in the FIRST catalog (April 2003 release, 811117 entries) were sorted into singles, doubles, triples ... More
Superconductivity and antiferromagnetism in the two-dimensional Hubbard model: a variational studyAug 21 2007A variational ground state of the repulsive Hubbard model on a square lattice is investigated numerically for an intermediate coupling strength (U = 8t) and for moderate sizes (from 6 x 6 to 10 x 10). Our ansatz is clearly superior to other widely used ... More
Relaxation measurements in the regime of the second magnetization peak in Nb filmsNov 05 2004We report on magnetic measurements as a function of field, temperature and time (relaxation) in superconducting Nb films of critical temperature Tc = 9.25 K. The magnetic measurements as a function of field exhibited a second magnetization peak (SMP) ... More
Hadronic resonances, strange and multi-strange particle production in Xe-Xe and Pb-Pb collisions with ALICE at the LHCJul 23 2018We present measurements of hadronic resonance, strange and multi-strange particle production in collisions of Xe-Xe and Pb-Pb at the center-of-mass energies of $\sqrt{s_{NN}}=5.44$ and $5.02$ TeV, respectively, by the ALICE collaboration at the LHC. Particle ... More
A class of locally symmetric Kaehler Einstein structures on the nonzero cotangent bundle of a space formJul 21 2004We obtain a class of locally symetric Kaehler Einstein structures on the nonzero cotangent bundle of a Riemannian manifold of positive constant sectional curvature. The obtained class of Kaehler Einstein structures depends on one essential parameter and ... More
A Kaehler Einstein structure on the nonzero cotangent bundle of a space formMay 07 2004We obtain a Kaehler Einstein structure on the nonzero cotangent bundle of a Riemannian manifold of positive constant sectional curvature. The obtained Kaehler Einstein structure cannot have constant holomorphic sectional curvature and is not locally symmetric. ... More
On the Representations of Leavitt path algebrasJun 14 2010Oct 08 2013Given a graph E we define E-algebraic branching systems, show their existence and how they induce representations of the associated Leavitt path algebra. We also give sufficient conditions to guarantee faithfulness of the representations associated to ... More