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Constraining multiple systems with GAIAApr 26 2012GAIA will provide observations of some multiple asteroid and dwarf systems. These observations are a way to determine and improve the quantification of dynamical parameters, such as the masses and the gravity fields, in these multiple systems. Here we ... More

Compositional characterisation of the Themis familyJan 11 2016Context. It has recently been proposed that the surface composition of icy main-belt asteroids (B-,C-,Cb-,Cg-,P-,and D-types) may be consistent with that of chondritic porous interplanetary dust particles (CPIDPs). Aims. In the light of this new association, ... More

Spectral and Spin Measurement of Two Small and Fast-Rotating Near-Earth AsteroidsAug 21 2012In May 2012 two asteroids made near-miss "grazing" passes at distances of a few Earth-radii: 2012 KP24 passed at nine Earth-radii and 2012 KT42 at only three Earth-radii. The latter passed inside the orbital distance of geosynchronous satellites. From ... More

The Spectrum of Pluto, 0.40 - 0.93 $μ$m I. Secular and longitudinal distribution of ices and complex organicsSep 01 2015Context. During the last 30 years the surface of Pluto has been characterized, and its variability has been monitored, through continuous near-infrared spectroscopic observations. But in the visible range only few data are available. Aims. The aim of ... More

The Compositional Structure of the Asteroid BeltJun 16 2015The past decade has brought major improvements in large-scale asteroid discovery and characterization with over half a million known asteroids and over 100,000 with some measurement of physical characterization. This explosion of data has allowed us to ... More

Multiple and Fast: The Accretion of Ordinary Chondrite Parent BodiesMay 27 2014Although petrologic, chemical and isotopic studies of ordinary chondrites and meteorites in general have largely helped establish a chronology of the earliest events of planetesimal formation and their evolution, there are several questions that cannot ... More

Rotationally Resolved Spectroscopy of Asteroid Pairs: No Spectral Variation Suggests Fission is followed by Settling of DustAug 12 2014We examine the spectral properties of asteroid pairs that were disrupted in the last 2 Myrs to examine whether the site of the fission can be revealed. We studied the possibility that the sub-surface material, perhaps on one hemisphere, has spectral characteristics ... More

Mars Encounters cause fresh surfaces on some near-Earth asteroidsSep 19 2013All airless bodies are subject to the space environment, and spectral differences between asteroids and meteorites suggest many asteroids become weathered on very short (<1My) timescales. The spectra of some asteroids, particularly Q-types, indicate surfaces ... More

Comet 162P/Siding Spring: A Surprisingly Large NucleusAug 17 2006We present an analysis of thermal emission from comet 162P/Siding Spring (P/2004 TU12) measured during its discovery apparition in 2004 December. The comet showed no dust coma at this time, so we have sampled emission from the comet's nucleus. Observations ... More

Ultra-Low Delta-v Objects and the Human Exploration of AsteroidsMay 20 2011Jun 15 2011Missions to near-Earth objects (NEOs) are key destinations in NASA's new "Flexible Path" approach. NEOs are also of interest for science, for the hazards they pose, and for their resources. We emphasize the importance of ultra-low delta-v from LEO to ... More

Near-infrared thermal emission from near-Earth asteroids: Aspect-dependent variabilityNov 10 2016Here we explore a technique for constraining physical properties of near-Earth asteroids (NEAs) based on variability in thermal emission as a function of viewing aspect. We present case studies of the low albedo, near-Earth asteroids (285263) 1998 QE2 ... More

The Mission Accessible Near-Earth Objects Survey (MANOS): first photometric resultsJul 12 2016The Mission Accessible Near-Earth Objects Survey (MANOS) aims to physically characterize sub-km Near-Earth Objects (NEOs). We report first photometric results from the survey which began in August, 2013. Photometric observations were performed using 1 ... More

A 2 km-size asteroid challenging the rubble-pile spin barrier - a case for cohesionDec 22 2015The rubble pile spin barrier is an upper limit on the rotation rate of asteroids larger than ~200-300 m. Among thousands of asteroids with diameters larger than ~300 m, only a handful of asteroids are known to rotate faster than 2.0 h, all are in the ... More

Similar origin for low- and high-albedo Jovian Trojans and Hilda asteroids ?Jul 25 2014Hilda asteroids and Jupiter Trojans are two low-albedo (p$_{\rm v}$ ~ 0.07) populations for which the Nice model predicts an origin in the primordial Kuiper Belt region. However, recent surveys by WISE and the Spitzer Space Telescope (SST) have revealed ... More

Modeling the Expected Performance of the REgolith X-ray Imaging Spectrometer (REXIS)Oct 12 2014Oct 18 2014OSIRIS-REx is the third spacecraft in the NASA New Frontiers Program and is planned for launch in 2016. OSIRIS-REx will orbit the near-Earth asteroid (101955) Bennu, characterize it, and return a sample of the asteroid's regolith back to Earth. The Regolith ... More

Unexpected D-type Interlopers in the Inner Main BeltDec 10 2013Very red featureless asteroids (spectroscopic D-types) are expected to have formed in the outer solar system far from the sun. They comprise the majority of asteroids in the Jupiter Trojan population, and are also commonly found in the outer main belt ... More

Physical characterization and origin of binary near-Earth asteroid (175706) 1996 FG3Mar 21 2012The near-Earth asteroid (NEA) (175706) 1996 FG3 is a particularly interesting spacecraft target: a binary asteroid with a low-DeltaV heliocentric orbit. The orbit of its satellite has provided valuable information about its mass density while its albedo ... More

Observations of "Fresh" and Weathered Surfaces on Asteroid Pairs and Their Implications on the Rotational-Fission MechanismJan 17 2014The rotational-fission of a rubble-pile asteroid can result in an "asteroid pair", two un-bound asteroids sharing similar orbits. This mechanism might exposes material that previously had never have been exposed to the weathering conditions of space. ... More

The CH4 cycles on Pluto over seasonal and astronomical timescalesMar 05 2019New Horizons observations suggest that CH4 on Pluto has a complex history, involving reservoirs of different composition, thickness and stability controlled by volatile processes occurring on different timescales. In order to interpret these observations, ... More

Modeling glacial flow on and onto Pluto's Sputnik PlanumJun 18 2016Observations of Pluto's surface made by the New Horizons spacecraft indicates present-day nitrogen ice glaciation in and around the basin known as Sputnik Planum. Motivated by these observations, we have developed an evolutionary glacial flow model of ... More

The Puzzling Detection of X-rays From Pluto by ChandraOct 25 2016Using Chandra ACIS-S, we have obtained imaging Xray spectrophotometry of the Pluto system in support of the New Horizons flyby on 14 July 2015. 174 ksec of observations were obtained on 4 visits in Feb 2014 to Aug 2015. We measured a net signal of 6.8 ... More

Composition of the L5 Mars Trojans: Neighbors, not SiblingsSep 12 2007Mars is the only terrestrial planet known to have Tro jan (co-orbiting) asteroids, with a confirmed population of at least 4 objects. The origin of these objects is not known; while several have orbits that are stable on solar-system timescales, work ... More

Near-IR spectroscopy of asteroids 21 Lutetia, 89 Julia, 140 Siwa, 2181 Fogelin, and 5480 (1989YK8), potential targets for the Rosetta mission; remote observations campaign on IRTFDec 29 2003In the frame of the international campaign to observe potential target asteroids for the Rosetta mission, remote observations have been carried out between Observatoire de Paris, in Meudon-France, and the NASA Infrared Telescope Facility on Mauna Kea. ... More

Modeling glacial flow on and onto Pluto's Sputnik PlanitiaJun 18 2016Jul 26 2018Observations of Pluto's surface made by the New Horizons spacecraft indicates present-day nitrogen ice glaciation in and around the basin known as Sputnik Planum. Motivated by these observations, we have developed an evolutionary glacial flow model of ... More

Pluto's global surface composition through pixel-by-pixel Hapke modeling of New Horizons Ralph/LEISA dataApr 28 2016On July 14th 2015, NASA's New Horizons mission gave us a first view of the Pluto system. The complex compositional diversity of Pluto's encounter hemisphere was revealed by the Ralph/LEISA infrared spectrometer on board of New Horizons. We present compositional ... More

Early Observations and Analysis of the Type Ia SN 2014J in M82May 15 2014We present optical and near infrared (NIR) observations of the nearby Type Ia SN 2014J. Seventeen optical and twenty-three NIR spectra were obtained from 10 days before ($-$10d) to 10 days after (+10d) the time of maximum $B$-band brightness. The relative ... More

Impact Craters on Pluto and Charon Indicate a Deficit of Small Kuiper Belt ObjectsFeb 27 2019The flyby of Pluto and Charon by the New Horizons spacecraft provided high-resolution images of cratered surfaces embedded in the Kuiper belt, an extensive region of bodies orbiting beyond Neptune. Impact craters on Pluto and Charon were formed by collisions ... More

The small binary asteroid (939) IsbergaNov 04 2014In understanding the composition and internal structure of asteroids, their density is perhaps the most diagnostic quantity. We aim here to characterize the surface composition, mutual orbit, size, mass, and density of the small main-belt binary asteroid ... More

The compositional diversity of non-Vesta basaltic asteroidsMay 17 2017We present near-infrared (0.78-2.45 {\mu}m) reflectance spectra for nine middle and outer main belt (a > 2.5 AU) basaltic asteroids. Three of these objects are spectrally distinct from all classifications in the Bus-DeMeo system and could represent spectral ... More

Analysis of the First Disk-Resolved Images of Ceres from Ultraviolet Observations with the Hubble Space TelescopeOct 10 2001We present HST Faint Object Camera observations of the asteroid 1 Ceres at near-, mid-, and far-UV wavelengths (lambda = 3636, 2795, and 1621 A, respectively) obtained on 1995 June 25. The disk of Ceres is well-resolved for the first time, at a scale ... More

Olivine-dominated A-type asteroids in the Main Belt: Distribution, Abundance and Relation to FamiliesJan 09 2019Differentiated asteroids are rare in the main asteroid belt despite evidence for ~100 distinct differentiated bodies in the meteorite record. We have sought to understand why so few main-belt asteroids differentiated and where those differentiated bodies ... More

New Horizons: Anticipated Scientific Investigations at the Pluto SystemSep 26 2007The New Horizons spacecraft will achieve a wide range of measurement objectives at the Pluto system, including color and panchromatic maps, 1.25-2.50 micron spectral images for studying surface compositions, and measurements of Pluto's atmosphere (temperatures, ... More

Pluto's global surface composition through pixel-by-pixel Hapke modeling of New Horizons Ralph/LEISA dataApr 28 2016Nov 30 2016On July 14th 2015, NASA's New Horizons mission gave us an unprecedented detailed view of the Pluto system. The complex compositional diversity of Pluto's encounter hemisphere was revealed by the Ralph/LEISA infrared spectrometer on board of New Horizons. ... More

2011 HM102: Discovery of a High-Inclination L5 Neptune Trojan in the Search for a post-Pluto New Horizons TargetOct 16 2012Feb 21 2013We present the discovery of a long-term stable L5 (trailing) Neptune Trojan in data acquired to search for candidate Trans-Neptunian objects for the New Horizons spacecraft to fly by during an extended post-Pluto mission. This Neptune Trojan, 2011 HM102, ... More

A spectral comparison of (379) Huenna and its satelliteFeb 08 2011We present near-infrared spectral measurements of Themis family asteroid (379) Huenna (D~98 km) and its 6 km satellite using SpeX on the NASA IRTF. The companion was farther than 1.5" from the primary at the time of observations and was approximately ... More

Surface Compositions Across Pluto and CharonApr 18 2016The New Horizons spacecraft mapped colors and infrared spectra across the encounter hemispheres of Pluto and Charon. The volatile ices CH$_4$, CO, and N$_2$, that dominate Pluto's surface, have complicated spatial distributions resulting from sublimation, ... More

Great Expectations: Plans and Predictions for New Horizons Encounter with Kuiper Belt Object 2014 MU69 ('Ultima Thule')Aug 06 2018The New Horizons encounter with the cold classical Kuiper Belt object (KBO) 2014 MU69 (informally named 'Ultima Thule,' hereafter Ultima) on 1 January 2019 will be the first time a spacecraft has ever closely observed one of the free-orbiting small denizens ... More

The REgolith X-Ray Imaging Spectrometer (REXIS) for OSIRIS-REx: Identifying Regional Elemental Enrichment on AsteroidsSep 25 2013The OSIRIS-REx Mission was selected under the NASA New Frontiers program and is scheduled for launch in September of 2016 for a rendezvous with, and collection of a sample from the surface of asteroid Bennu in 2019. 101955 Bennu (previously 1999 RQ36) ... More

The Mission Accessible Near-Earth Objects Survey: Four years of photometrySep 10 2018Over 4.5 years, the Mission Accessible Near-Earth Object Survey (MANOS) assembled 228 Near-Earth Object (NEO) lightcurves. We report rotational lightcurves for 82 NEOs, constraints on amplitudes and periods for 21 NEOs, lightcurves with no detected variability ... More

The Small Satellites of Pluto as Observed by New HorizonsApr 18 2016The New Horizons mission has provided resolved measurements of Pluto's moons Styx, Nix, Kerberos, and Hydra. All four are small, with equivalent spherical diameters of $\approx$40 km for Nix and Hydra and ~10 km for Styx and Kerberos. They are also highly ... More

OSIRIS-REx: Sample Return from Asteroid (101955) BennuFeb 22 2017In May of 2011, NASA selected the Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) asteroid sample return mission as the third mission in the New Frontiers program. The other two New Frontiers missions ... More

Formation of Charon's Red Poles From Seasonally Cold-Trapped VolatilesMar 09 2019A unique feature of Pluto's large satellite Charon is its dark red northern polar cap. Similar colours on Pluto's surface have been attributed to organic macromolecules produced by energetic radiation processing of hydrocarbons. The polar location of ... More

Reorientation of Sputnik Planitia implies a Subsurface Ocean on PlutoMar 13 2019The deep nitrogen-covered Sputnik Planitia (SP; informal name) basin on Pluto is located very close to the longitude of Pluto's tidal axis[1] and may be an impact feature [2], by analogy with other large basins in the solar system[3,4]. Reorientation[5-7] ... More

Pluto's Haze as a Surface MaterialMar 09 2019Pluto's atmospheric haze settles out rapidly compared with geological timescales. It needs to be accounted for as a surface material, distinct from Pluto's icy bedrock and from the volatile ices that migrate via sublimation and condensation on seasonal ... More

A Spectroscopic Comparison of HED Meteorites and V-type Asteroids in the Inner Main BeltMar 12 2010V-type asteroids in the inner Main Belt (a < 2.5 AU) and the HED meteorites are thought to be genetically related to one another as collisional fragments from the surface of the large basaltic asteroid 4 Vesta. We investigate this relationship by comparing ... More

The Geology of Pluto and Charon Through the Eyes of New HorizonsApr 19 2016NASA's New Horizons spacecraft has revealed the complex geology of Pluto and Charon. Pluto's encounter hemisphere shows ongoing surface geological activity centered on a vast basin containing a thick layer of volatile ices that appears to be involved ... More

Convection in a volatile nitrogen-ice-rich layer drives Pluto's geological vigorMar 13 2019The vast, deep, volatile-ice-filled basin informally named Sputnik Planum is central to Pluto's geological activity[1,2]. Composed of molecular nitrogen, methane, and carbon monoxide ices[3], but dominated by N2-ice, this ice layer is organized into cells ... More

The Design Reference Asteroid for the OSIRIS-REx Mission Target (101955) BennuSep 16 2014The Design Reference Asteroid (DRA) is a compilation of all that is known about the OSIRIS-REx mission target, asteroid (101955) Bennu. It contains our best knowledge of the properties of Bennu based on an extensive observational campaign that began shortly ... More

A White Paper on Pluto Follow On Missions: Background, Rationale, and New Mission RecommendationsAug 22 2018Nov 19 2018The exploration of the binary Pluto-Charon and its small satellites during the New Horizons flyby in 2015 revealed not only widespread geologic and compositional diversity across Pluto, but surprising complexity, a wide range of surface unit ages, evidence ... More

Valence Bond Glass Phase in the Diluted Kagome AntiferromagnetsFeb 27 2010We present a theory for site dilution in the Valence Bond Crystal Phase of the Kagome Lattice Heisenberg Model. The presence of an empty site leads to strong singlet bond across the impurity. It also creates a free spin, which delocalizes inside the unit ... More

The Pluto system: Initial results from its exploration by New HorizonsOct 26 2015The Pluto system was recently explored by NASA's New Horizons spacecraft, making closest approach on 14 July 2015. Pluto's surface displays diverse landforms, terrain ages, albedos, colors, and composition gradients. Evidence is found for a water-ice ... More

Two-magnon Raman scattering in insulating cuprates: Modifications of the effective Raman operatorMar 14 2000May 24 2000Calculations of Raman scattering intensities in spin 1/2 square-lattice Heisenberg model, using the Fleury-Loudon-Elliott theory, have so far been unable to describe the broad line shape and asymmetry of the two magnon peak found experimentally in the ... More

Efficient generation of series expansions for $\pm J$ Ising spin-glasses in a classical or a quantum (transverse) fieldSep 11 2017We discuss generation of series expansions for Ising spin-glasses with a symmetric $\pm J$ (i.e. bimodal) distribution on d-dimensional hypercubic lattices using linked-cluster methods. Simplifications for the bimodal distribution allow us to go to higher ... More

Covariance Properties of Reflection Equation AlgebrasDec 01 1992The reflection equations (RE) are a consistent extension of the Yang-Baxter equations (YBE) with an addition of one element, the so-called reflection matrix or $K$-matrix. For example, they describe the conditions for factorizable scattering on a half ... More

de Almeida-Thouless instability in short-range Ising spin-glassesMay 02 2017Jul 17 2017We use high temperature series expansions to study the $\pm J$ Ising spin-glass in a magnetic field in $d$-dimensional hypercubic lattices for $d=5, 6, 7$ and $8$, and in the infinite-range Sherrington-Kirkpatrick (SK) model. The expansions are obtained ... More

Critical and Griffiths-McCoy singularities in quantum Ising spin-glasses on d-dimensional hypercubic lattices: A series expansion studyJul 05 2017Nov 01 2017We study the $\pm J$ transverse-field Ising spin glass model at zero temperature on d-dimensional hypercubic lattices and in the Sherrington-Kirkpatrick (SK) model, by series expansions around the strong field limit. In the SK model and in high-dimensions ... More

BRST analysis of topologically massive gauge theory: novel observationsApr 07 2011Jul 14 2011A dynamical non-Abelian 2-form gauge theory (with B \wedge F term) is endowed with the "scalar" and "vector" gauge symmetry transformations. In our present endeavor, we exploit the latter gauge symmetry transformations and perform the Becchi-Rouet-Stora-Tyutin ... More

13/2 ways of counting curvesNov 07 2011May 09 2016In the past 20 years, compactifications of the families of curves in algebraic varieties X have been studied via stable maps, Hilbert schemes, stable pairs, unramified maps, and stable quotients. Each path leads to a different enumeration of curves. A ... More

Notes on the proof of the KKV conjectureNov 04 2014May 09 2016The Katz-Klemm-Vafa conjecture expresses the Gromov-Witten theory of K3 surfaces (and K3-fibred 3-folds in fibre classes) in terms of modular forms. Its recent proof gives the first non-toric geometry in dimension greater than 1 where Gromov-Witten theory ... More

Two-magnon Raman scattering in spin-ladder geometries and the ratio of rung and leg exchange constantsApr 27 2000Jul 20 2000We discuss ways in which the ratio of exchange constants along the rungs and legs of a spin-ladder material influences the two-magnon Raman scattering spectra and hence can be determined from it. We show that within the Fleury-Loudon-Elliott approach, ... More

Stable pairs and BPS invariantsNov 25 2007Oct 12 2008We define the BPS invariants of Gopakumar-Vafa in the case of irreducible curve classes on Calabi-Yau 3-folds. The main tools are the theory of stable pairs in the derived category and Behrend's constructible function approach to the virtual class. We ... More

The 3-fold vertex via stable pairsSep 24 2007May 24 2008The theory of stable pairs in the derived category yields an enumerative geometry of curves in 3-folds. We evaluate the equivariant vertex for stable pairs on toric 3-folds in terms of weighted box counting. In the toric Calabi-Yau case, the result simplifies ... More

Almost closed 1-formsApr 18 2012We construct an algebraic almost closed 1-form with zero scheme not expressible (even locally) as the critical locus of a holomorphic function on a nonsingular variety. The result answers a question of Behrend-Fantechi. We correct here an error in our ... More

Stable pairs and BPS invariantsNov 25 2007May 23 2017We define the BPS invariants of Gopakumar-Vafa in the case of irreducible curve classes on Calabi-Yau 3-folds. The main tools are the theory of stable pairs in the derived category and Behrend's constructible function approach to the virtual class. We ... More

Curve counting via stable pairs in the derived categoryJul 16 2007May 09 2016For a nonsingular projective 3-fold $X$, we define integer invariants virtually enumerating pairs $(C,D)$ where $C\subset X$ is an embedded curve and $D\subset C$ is a divisor. A virtual class is constructed on the associated moduli space by viewing a ... More

Surface Composition of (99942) ApophisMar 14 2018On April 13, 2029, near-Earth asteroid (NEA) (99942) Apophis will pass at a distance of 6 Earth radii from Earth. This event will provide researchers with a unique opportunity to study the effects of tidal forces experienced by an asteroid during a close ... More

Particle creation and decay in nonminimally coupled models of gravityJan 18 2019Mar 29 2019In extended models of gravity a nonminimal coupling to matter has been assumed to lead to irreversible particle creation. In this paper we challenge this assumption. We argue that a non-minimal coupling of the matter and gravitational sectors results ... More

Observer dependence of the quasi-local energy and momentum in Schwarzschild space-timeJan 23 2008Sep 03 2008The observer dependence of the quasi-local energy (QLE) and momentum in the Schwarzschild geometry is illustrated. Using the Brown-York prescription, the QLE for families of non-geodesic and geodesic observers penetrating the event horizon is obtained. ... More

Logarithmic rate dependence in deforming granular materialsOct 08 2002Rate-independence for stresses within a granular material is a basic tenet of many models for slow dense granular flows. By contrast, logarithmic rate dependence of stresses is found in solid-on-solid friction, in geological settings, and elsewhere. In ... More

Violation of action--reaction and self-forces induced by nonequilibrium fluctuationsApr 18 2008Jun 17 2008We show that the extension of Casimir-like forces to fluctuating fluids driven out of equilibrium can exhibit two interrelated phenomena forbidden at equilibrium: self-forces can be induced on single asymmetric objects and the action--reaction principle ... More

Supersymmetric Oscillator: Novel SymmetriesOct 01 2011Mar 10 2012We discuss various continuous and discrete symmetries of the supersymmetric simple harmonic oscillator (SHO) in one (0 + 1)-dimension of spacetime and show their relevance in the context of mathematics of differential geometry. We show the existence of ... More

Entanglement in the symmetric sector of $n$ qubitsJan 14 2011We discuss the entanglement properties of symmetric states of $n$ qubits. The Majorana representation maps a generic such state into a system of $n$ points on a sphere. Entanglement invariants, either under local unitaries (LU) or stochastic local operations ... More

Andreev tunnelling in quantum dots: A slave-boson approachJun 05 1998We study a strongly interacting quantum dot connected to a normal and to a superconducting lead. By means of the slave-boson technique we investigate the low temperature regime and discuss electrical transport through the dot. We find that the zero bias ... More

On resonant and non-resonant origin of double-mode Cepheid pulsationJul 16 2009Double-mode Cepheid behaviour may arise either from non-resonant or resonant mode interaction. Inclusion of turbulent convection into pulsation codes by Kollath et al. (1998) led to stable double-mode F+1O Cepheid pulsation. However, our recent computations ... More

A near-solar metallicity damped Lyman-alpha system toward the BAL quasar Tol 1037-2703May 10 2001We report the detection of a Broad Absorption Line (BAL) outflow in the spectrum of Tol 1037-2703 with three main BALs at 36000, 25300 and 22300~\kms outflow velocities. Although the overall flow is dominated by high ionization lines like and C IV, the ... More

Brownian motion in a magnetic fieldMay 22 2000We derive explicit forms of Markovian transition probability densities for the velocity space, phase-space and the Smoluchowski configuration-space Brownian motion of a charged particle in a constant magnetic field. By invoking a hydrodynamical formalism ... More

Some Inconvenient TruthsJun 13 2015A recent paper by Fr\"ob employs the linearized Weyl-Weyl correlator to construct the tensor power spectrum. Although his purpose was to argue that infrared divergences and secular growth in the graviton propagator are gauge artefacts, a closer examination ... More

Fermion Self-Energy during InflationJul 13 2003I report on work done with Tomislav Prokopec (Heidelberg, CERN). We computed the one loop self-energy of a massless fermion during inflation. When the fermion is free it experiences only a small amount of inflationary particle production owing to the ... More

The Ostrogradskian Instability of Lagrangians with Nonlocality of Finite ExtentJul 21 2002I reply to the objections recently raised by J. Llosa to my constructive proof that Lagrangians with nonlocality of finite extent inherit the full Ostrogradskian instability.

Light Cone QED in a Homogeneous Electric BackgroundOct 22 2001I present an exact solution for the Heisenberg picture, Dirac electron in the presence of an electric field which depends arbitrarily upon the light cone time parameter $x^+ = (t+x)/\sqrt{2}$. This is the largest class of background fields for which the ... More

A Canonical Formalism For Lagrangians With Nonlocality Of Finite ExtentJun 27 2000Jul 10 2000I consider Lagrangians which depend nonlocally in time but in such a way that there is no mixing between times differing by more than some finite value $\Delta t$. By considering these systems as the limits of ever higher derivative theories I obtain ... More

Particles As Bound States In Their Own PotentialsMar 31 1998I consider the problem of computing the mass of a charged, gravitating particle in quantum field theory. It is shown how solving for the first quantized propagator of a particle in the presence of its own potentials reproduces the gauge and general coordinate ... More

Avoiding Dark Energy with 1/R Modifications of GravityJan 30 2006Feb 06 2006Scalar quintessence seems epicyclic because one can choose the potential to reproduce any cosmology (I review the construction) and because the properties of this scalar seem to raise more questions than they answer. This is why there has been so much ... More

The ages and distances of globular clusters with the luminosity function method: the case of M5 and M55Jan 20 1997We present new age and distance determinations for the Galactic Globular Clusters M55 and M5, using the luminosity function method (Jimenez & Padoan 1996, Padoan & Jimenez 1997). We find an age of $11.8 \pm 1.5$ Gyr for M55 and $11.1 \pm 0.7$ Gyr for ... More

Core excitation in Coulomb breakup reactionsFeb 08 2001Within the pure Coulomb breakup mechanism, we investigate the one-neutron removal reaction of the type A(a,b$\gamma$)X with $^{11}$Be and $^{19}$C projectiles on a heavy target nucleus $^{208}$Pb at the beam energy of 60 MeV/nucleon. Our intention is ... More

A theoretical framework for the detection of point-sources in Cosmic Microwave Background mapsOct 27 2008Jul 14 2009The detection of point-sources in microwave maps is a critical step in the analysis of the Cosmic Microwave Background (CMB) data. If not properly removed, these sources have adverse effects on the estimation of the power-spectrum and/or the test of Gaussianity ... More

Theoretical energy level spectra and transition data for 4p$^6$4d$^2$, 4p$^6$4d4f and 4p$^5$4d$^3$ configurations of W$^{36+}$ ionApr 08 2015The ab initio quasirelativistic Hartree-Fock method developed specifically for the calculation of spectral parameters of heavy atoms and highly charged ions is used to derive transition data for multicharged tungsten ion. The configuration interaction ... More

Identified Particle Spectra and Jet Interactions with the MediumOct 17 2005Through a combination of detector upgrades and advancements in analysis techniques, physicist at RHIC are extending their ability to identify particles at high pT . With these new capabilities some outstanding questions are being addressed: particularly ... More

Hamiltonian structure of thermodynamics with gaugeJul 18 2000Mar 01 2001The state of a thermodynamic system being characterized by its set of extensive variables $q^{i}(i=1,...,n) ,$ we write the associated intensive variables $\gamma_{i},$ the partial derivatives of the entropy $ S(q^{1},...,q^{n}) \equiv q_{0},$ in the ... More

Excitons in Mott insulatorsOct 27 2001Motivated by recent Raman and resonant inelastic X-ray scattering experiments performed for Mott insulators, which suggest formation of excitons in these systems, we present a theory of exciton formation in the upper Hubbard band. The analysis based on ... More

Persistence of energy-dependent localization in the Anderson-Hubbard model with increasing system size and dopingJan 12 2016Non-interacting systems with bounded disorder have been shown to exhibit sharp density of states peaks at the band edge which coincide with an energy range of abruptly suppressed localization. Recent work has shown that these features also occur in the ... More

Observations of Extrasolar Planets Enabled by a Return to the MoonMar 13 2007Ambitious studies of Earth-like extrasolar planets are outlined in the context of an exploration initiative for a return to the Earth's Moon. Two mechanism for linearly polarizing light reflected from Earth-like planets are discussed: 1) Rayleigh-scattering ... More

The element abundance FIP effect in the quiet SunMar 02 2005The Mg/Ne abundance ratio in the quiet Sun is measured in both network and supergranule cell centre regions through EUV spectra from the Coronal Diagnostic Spectrometer on SOHO. Twenty four sets of data over the period 1996 March to 1998 June (corresponding ... More

Ole Romer's method still on the stage. The study of two bound eclipsing binaries in quintuple system V994 HerFeb 18 2013More than three hundred years ago, Ole Romer measured the speed of light only by observing the periodic shifting of the observed eclipse arrival times of Jupiter's moons arising from the varying Earth-Jupiter distance. The same method of measuring the ... More

Large-scale second RPA calculations with finite-range interactionsOct 09 2009Second RPA (SRPA) calculations of nuclear response are performed and analyzed. Unlike in most other SRPA applications, the ground state, approximated by the Hartree-Fock (HF) ground state, and the residual couplings are described by the same Hamiltonian ... More

Supersymmetry in quantum mechanics: An extended viewJan 23 2004The concept of supersymmetry in a quantum mechanical system is extended, permitting the recognition of many more supersymmetric systems, including very familiar ones such as the free particle. Its spectrum is shown to be supersymmetric, with space-time ... More

Neutron Star Astronomy with the E-ELTAug 30 2010So far, 24 Isolated neutron stars (INSs) of different types have been identified at optical wavelengths, from the classical radio pulsars to more peculiar objects, like the magnetars. Most identifications have been obtained in the last 20 years thanks ... More

Multi-wavelength identification of high-energy sourcesFeb 03 2009The nature of most of the ~300 high-energy gamma-ray sources discovered by the EGRET instrument aboard the Gamma-ray Observatory (GRO) between 1991 and 1999 is one of the greatest enigmas in high-energy astrophysics. While about half of the extragalactic ... More

Back-Reaction: A Cosmological PanaceaOct 18 2005We present a solution to the dark energy problem in terms of the Effective Energy Momentum Tensor (EMT) of cosmological perturbations. The approach makes use of the gravitational back-reaction of long wavelength (super-Hubble) fluctuation modes on the ... More

Moment maps, monodromy and mirror manifoldsApr 19 2001Via considerations of symplectic reduction, monodromy, mirror symmetry and Chern-Simons functionals, a conjecture is proposed on the existence of special Lagrangians in the hamiltonian deformation class of a given Lagrangian submanifold of a Calabi-Yau ... More