Results for "R. T. Garrod"

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A new modified-rate approach for gas-grain chemical simulationsSep 17 2008Understanding grain-surface processes is crucial to interpreting the chemistry of the ISM. However, accurate surface chemistry models are computationally expensive and are difficult to integrate with gas-phase simulations. A new modified-rate method for ... More
Modeling CO, CO$_2$ and H$_2$O ice abundances in the envelopes of young stellar objects in the Magellanic CloudsJan 24 2018Massive young stellar objects in the Magellanic Clouds show infrared absorption features corresponding to significant abundances of CO, CO$_2$ and H$_2$O ice along the line of sight, with the relative abundances of these ices differing between the Magellanic ... More
Formation of methyl formate and other organic species in the warm-up phase of hot molecular coresJul 25 2006Aims: The production of saturated organic molecules in hot cores and corinos is not well understood. The standard approach is to assume that, as temperatures heat up during star formation, methanol and other species evaporate from grain surfaces and undergo ... More
Non-thermal desorption from interstellar dust grains via exothermic surface reactionsMar 08 2007Aims: The gas-phase abundance of methanol in dark quiescent cores in the interstellar medium cannot be explained by gas-phase chemistry. In fact, the only possible synthesis of this species appears to be production on the surfaces of dust grains followed ... More
Kinetic Monte Carlo simulations of the grain-surface back-diffusion effectApr 19 2017Rate-equation models are a widely-used and inexpensive tool for the simulation of interstellar chemistry under a range of physical conditions. However, their application to grain-surface chemical systems necessitates a number of simplifying assumptions, ... More
Kinetic Monte Carlo simulations of the grain-surface back-diffusion effectNov 08 2017Back-diffusion is the phenomenon by which random walkers revisit binding sites on a lattice. This phenomenon must occur on interstellar dust particles, slowing down dust-grain reactions, but it is not accounted for by standard rate-equation models. Microscopic ... More
Molecular Clouds as Ensembles of Transient CoresOct 20 2005We construct models of molecular clouds that are considered as ensembles of transient cores. Each core is assumed to develop in the background gas of the cloud, grow to high density and decay into the background. The chemistry in each core responds to ... More
Dense and diffuse gas in dynamically active cloudsOct 13 2006We investigate the chemical and observational implications of repetitive transient dense core formation in molecular clouds. We allow a transient density fluctuation to form and disperse over a period of 1 Myr, tracing its chemical evolution. We then ... More
Three-dimensional off-lattice Monte Carlo kinetics simulations of interstellar grain chemistry and ice structureOct 09 2013The first off-lattice Monte Carlo kinetics model of interstellar dust-grain surface chemistry is presented. The positions of all surface particles are determined explicitly, according to the local potential minima resulting from the pair-wise interactions ... More
Simulations of ice chemistry in cometary nucleiSep 08 2019The first computational model of solid-phase chemistry in cometary nuclear ices is presented. An astrochemical kinetics model, MAGICKAL, is adapted to trace the chemical evolution in multiple layers of cometary ice, over a representative period of 5 Gyr. ... More
A three-phase chemical model of hot cores: the formation of glycineFeb 04 2013A new chemical model is presented that simulates fully-coupled gas-phase, grain-surface and bulk-ice chemistry in hot cores. Glycine (NH2CH2COOH), the simplest amino acid, and related molecules such as glycinal, propionic acid and propanal, are included ... More
On the Formation of CO2 and Other Interstellar IcesJun 03 2011We investigate the formation and evolution of interstellar dust-grain ices under dark-cloud conditions, with a particular emphasis on CO2. We use a three-phase model (gas/surface/mantle) to simulate the coupled gas--grain chemistry, allowing the distinction ... More
The Effects of Grain Size and Temperature Distributions on the Formation of Interstellar Ice MantlesDec 21 2015Computational models of interstellar gas-grain chemistry have historically adopted a single dust-grain size of 0.1 micron, assumed to be representative of the size distribution present in the interstellar medium. Here, we investigate the effects of a ... More
Complex organic molecules in diffuse clouds along the line of sight to Sgr B2Aug 24 2017Up to now, mostly relatively simple molecules have been detected in interstellar diffuse molecular clouds in our galaxy, but more complex species have been reported in the diffuse/translucent medium of a z = 0.89 spiral galaxy. We aim at searching for ... More
The Effective Surface Area of Amorphous Solid Water Measured by the Infrared Absorption of Carbon MonoxideMay 02 2019The need to characterize ices coating dust grains in dense interstellar clouds arises from the importance of ice morphology in facilitating the diffusion and storage of radicals and reaction products in ices, a well-known place for the formation of complex ... More
Formation rates of complex organics in UV irradiated CH3OH-rich ices I: ExperimentsAug 08 2009(Abridged) Gas-phase complex organic molecules are commonly detected in the warm inner regions of protostellar envelopes. Recent models show that photochemistry in ices followed by desorption may explain the observed abundances. This study aims to experimentally ... More
Exploring Molecular Complexity with ALMA (EMoCA): Deuterated complex organic molecules in Sagittarius B2(N2)Nov 18 2015Deuteration is a powerful tracer of the history of the cold prestellar phase in star forming regions. Apart from methanol, little is known about deuterium fractionation of complex organic molecules in the interstellar medium, especially in high mass star ... More
Star formation in Chamaeleon I and III: a molecular line study of the starless core populationNov 13 2014The Chamaeleon clouds are excellent targets for low-mass star formation studies. Cha I and II are actively forming stars while Cha III shows no sign of ongoing star formation. We aim to determine the driving factors that have led to the very different ... More
Increased complexity in interstellar chemistry: Detection and chemical modeling of ethyl formate and n-propyl cyanide in Sgr B2(N)Feb 26 2009In recent years, organic molecules of increasing complexity have been found toward the prolific Galactic center source Sagittarius B2. We wish to explore the degree of complexity that the interstellar chemistry can reach in star-forming regions. We carried ... More
Exploring molecular complexity with ALMA (EMoCA): Detection of three new hot cores in Sagittarius B2(N)Mar 28 2017The SgrB2 molecular cloud contains several sites forming high-mass stars. SgrB2(N) is one of its main centers of activity. It hosts several compact and UCHII regions, as well as two known hot molecular cores (SgrB2(N1) and SgrB2(N2)), where complex organic ... More
Spectroscopic study and astronomical detection of doubly 13C-substituted ethyl cyanideApr 12 2016We have performed a spectral line survey called EMoCA toward Sagittarius B2(N) between 84 and 114 GHz with ALMA. Line intensities of the main isotopic species of ethyl cyanide and its singly 13C-substituted isotopomers observed toward the hot molecular ... More
Interstellar Glycolaldehyde, Methyl Formate, and Acetic Acid I: A Bi-modal Abundance Pattern in Star Forming RegionsJul 31 2019The relative column densities of the structural isomers methyl formate, glycolaldehyde, and acetic acid are derived for a dozen positions towards the massive star-forming regions MM1 and MM2 in the NGC 6334I complex, which are separated by $\sim$4000 ... More
The complex chemistry of hot cores in Sagittarius B2(N): Influence of cosmic-ray ionization and thermal historyJun 11 2019As the number of complex organic molecules (COMs) detected in the interstellar medium increases, it becomes important to place meaningful constraints on the formation pathways of these species. The molecular cloud SgrB2(N) is host to several hot molecular ... More
Re-exploring Molecular Complexity with ALMA (ReMoCA): Interstellar detection of ureaJun 11 2019Urea, NH2C(O)NH2, is a molecule of great importance in organic chemistry and biology. Two searches for urea in the interstellar medium were reported in the past, but neither were conclusive. We want to take advantage of the increased sensitivity and angular ... More
Re-exploring Molecular Complexity with ALMA (ReMoCA): Interstellar detection of ureaJun 11 2019Jun 17 2019Urea, NH2C(O)NH2, is a molecule of great importance in organic chemistry and biology. Two searches for urea in the interstellar medium were reported in the past, but neither were conclusive. We want to take advantage of the increased sensitivity and angular ... More
Exploring molecular complexity with ALMA (EMoCA): Alkanethiols and alkanols in Sagittarius B2(N2)Dec 16 2015Over the past five decades, radio astronomy has shown that molecular complexity is a natural outcome of interstellar chemistry, in particular in star forming regions. However, the pathways that lead to the formation of complex molecules are not completely ... More
Rotational spectroscopy, tentative interstellar detection, and chemical modelling of N-methylformamideJan 17 2017N-methylformamide, CH3NHCHO, may be an important molecule for interstellar pre-biotic chemistry because it contains a peptide bond. The rotational spectrum of the most stable trans conformer of CH3NHCHO is complicated by strong torsion-rotation interaction ... More
Probing the physical and chemical structure of the CS core in LDN 673. Multitransitional and continuum observationsJun 13 2012High-angular resolution observations of dense molecular cores show that these cores can be clumpier at smaller scales, and that some of these clumps can also be unbound or transient. The use of chemical models of the evolution of the molecular gas provides ... More
Complex Chemistry in Star-Forming Regions: An Expanded Gas-Grain Warm-up Chemical ModelMar 08 2008Gas-phase processes were long thought to be the key formation mechanisms for complex organic molecules in star-forming regions. However, recent experimental and theoretical evidence has cast doubt on the efficiency of such processes. Grain-surface chemistry ... More
Science with an ngVLA: Prebiotic MoleculesOct 15 2018Extraterrestrial amino acids, the chemical building blocks of the biopolymers that comprise life as we know it on Earth are present in meteoritic samples. More recently, glycine (NH$_2$CH$_2$COOH), the simplest amino acid, was detected by the Rosetta ... More
Modeling the Lukewarm Corino Phase - is L1527 unique?Mar 12 2008Sakai et al. have observed long-chain unsaturated hydrocarbons and cyanopolyynes in the low-mass star-forming region L1527, and have attributed this result to a gas-phase ion-molecule chemistry, termed ``Warm Carbon Chain Chemistry'', which occurs during ... More
Molecular Evolution and Star Formation: From Prestellar Cores to Protostellar CoresOct 03 2007We investigate molecular evolution in a star-forming core that is initially a hydrostatic starless core and collapses to form a low-mass protostar. The results of a one-dimensional radiation-hydrodynamics calculation are adopted as a physical model of ... More
Effects of population growth on the success of invading mutantsSep 21 2016Mar 28 2017Understanding if and how mutants reach fixation in populations is an important question in evolutionary biology. We study the impact of population growth has on the success of mutants. To systematically understand the effects of growth we decouple competition ... More
Small-scale physical and chemical structure of diffuse and translucent molecular clouds along the line of sight to Sgr B2Jan 10 2019The diffuse and translucent molecular clouds traced in absorption along the line of sight to strong background sources have so far been investigated mainly in the spectral domain because of limited angular resolution or small sizes of the background sources. ... More
Effects of population growth on the success of invading mutantsSep 21 2016Understanding if and how mutants reach fixation in populations is an important question in evolutionary biology. We study the impact of population growth has on the success of mutants. To systematically understand the effects of growth we decouple competition ... More
Formation of hydroxylamine on dust grains via ammonia oxidationJan 20 2015The quest to detect prebiotic molecules in space, notably amino acids, requires an understanding of the chemistry involving nitrogen atoms. Hydroxylamine (NH$_2$OH) is considered a precursor to the amino acid glycine. Although not yet detected, NH$_2$OH ... More
The ALMA-PILS survey: first detection of methyl isocyanide (CH$_3$NC) in a solar-type protostarJul 09 2018Methyl isocyanide (CH$_3$NC) is the isocyanide with the largest number of atoms confirmed in the interstellar medium (ISM), but it is not an abundant molecule, having only been detected towards a handful of objects. Conversely, its isomer, methyl cyanide ... More
The ALMA-PILS survey: Complex nitriles towards IRAS 16293--2422Apr 24 2018Complex organic molecules are readily detected in the inner regions of the gaseous envelopes of forming protostars. In particular, molecules that contain nitrogen are interesting due to the role nitrogen plays in the development of life and the compact ... More
ALMA Detection of Interstellar Methoxymethanol (CH$_3$OCH$_2$OH)Dec 08 2017We report the detection of interstellar methoxymethanol (CH$_3$OCH$_2$OH) in ALMA Bands 6 and 7 toward the MM1 core in the high-mass star-forming region NGC 6334I at ~0.1" - 1" spatial resolution. A column density of 4(2) x $10^{18}$ cm$^{-2}$ at $T_{ex}$ ... More
First Results of an ALMA Band 10 Spectral Line Survey of NGC 6334I: Detections of Glycolaldehyde (HC(O)CH$_2$OH) and a New Compact Bipolar Outflow in HDO and CSAug 16 2018We present the first results of a pilot program to conduct an ALMA Band 10 spectral line survey of the high-mass star-forming region NGC 6334I. The observations were taken in exceptional weather conditions (0.19 mm precipitable water) with typical system ... More
Science with an ngVLA: Deuteration in starless and prestellar coresOct 16 2018In dense starless and protostellar cores, the relative abundance of deuterated species to their non-deuterated counterparts can become orders of magnitude greater than in the local interstellar medium. This enhancement proceeds through multiple pathways ... More
The ALMA-PILS survey: Detection of CH$_{3}$NCO toward the low-mass protostar IRAS 16293-2422 and laboratory constraints on its formationMar 09 2017May 04 2017Methyl isocyanate (CH$_{3}$NCO) belongs to a select group of interstellar molecules considered to be relevant precursors in the formation of larger organic compounds, including those with peptide bonds. The molecule has only been detected in a couple ... More
From Prestellar to Protostellar Cores II. Time Dependence and Deuterium FractionationOct 09 2012Oct 16 2012We investigate the molecular evolution and D/H abundance ratios that develop as star formation proceeds from a dense-cloud core to a protostellar core, by solving a gas-grain reaction network applied to a 1-D radiative hydrodynamic model with infalling ... More
Detection of a branched alkyl molecule in the interstellar medium: iso-propyl cyanideOct 09 2014The largest non-cyclic molecules detected in the interstellar medium (ISM) are organic with a straight-chain carbon backbone. We report an interstellar detection of a branched alkyl molecule, iso-propyl cyanide (i-C3H7CN), with an abundance 0.4 times ... More
Complex organic molecules in organic-poor massive young stellar objectsJan 13 2015Massive young stellar objects (MYSOs) with hot cores are classic sources of complex organic molecules. The origins of these molecules in such sources, as well as the small- and large-scale differentiation between nitrogen- and oxygen-bearing complex species, ... More
Complex Organic Molecules Towards Embedded Low-Mass ProtostarsMay 15 2017Complex organic molecules (COMs) have been observed towards several low-mass young stellar objects (LYSOs). Small and heterogeneous samples have so far precluded conclusions on typical COM abundances, as well as the origin(s) of abundance variations between ... More
The secretary problem on an unknown posetJul 07 2011Jun 28 2012We consider generalizations of the classical secretary problem, also known as the problem of optimal choice, to posets where the only information we have is the size of the poset and the number of maximal elements. We show that, given this information, ... More
A ring/disk/outflow system associated with W51 North: a very massive star in the makingApr 02 2009Sensitive and high angular resolution ($\sim$ 0.4\arcsec) SO$_2$[22$_{2,20}$ $\to$ 22$_{1,21}$] and SiO[5$\to$4] line and 1.3 and 7 mm continuum observations made with the Submillimeter Array (SMA) and the Very Large Array (VLA) towards the young massive ... More
First detection of cyanamide (NH$_2$CN) towards solar-type protostarsDec 27 2017Searches for the prebiotically-relevant cyanamide (NH$_2$CN) towards solar-type protostars have not been reported in the literature. We here present the first detection of this species in the warm gas surrounding two solar-type protostars, using data ... More
The Spatial Distribution of Organics toward the High-Mass YSO NGC 7538 IRS9May 14 2013Based on astrochemical theory, the complex molecular composition around high-mass YSOs should evolve from the outer envelope in toward the central hot region as a sequence of temperature dependent chemical pathways are activated in ices and in the gas-phase. ... More
Forming an Early O-type Star Through Gas Accretion?Nov 30 2007Dec 03 2007We present high angular resolution ($\sim$ 3$''$) and sensitive 1.3 mm continuum, cyanogen (CN) and vinyl cyanide (C$_2$H$_3$CN) line observations made with the Submillimeter Array (SMA) toward one of most highly obscured objects of the W51 IRS2 region, ... More
The ALMA-PILS survey: First detections of deuterated formamide and deuterated isocyanic acid in the interstellar mediumMay 09 2016May 12 2016Formamide (NH$_2$CHO) has previously been detected in several star-forming regions and is thought to be a precursor for different prebiotic molecules. Its formation mechanism is still debated, however. Observations of formamide, related species and their ... More
The ALMA-PILS survey: First detections of ethylene oxide, acetone and propanal toward the low-mass protostar IRAS 16293-2422Nov 22 2016One of the open questions in astrochemistry is how complex organic and prebiotic molecules are formed. Aims. Our aim is to start the process of compiling an inventory of oxygen-bearing complex organic molecules toward the solar-type Class 0 protostellar ... More
The ALMA Protostellar Interferometric Line Survey (PILS): First results from an unbiased submillimeter wavelength line survey of the Class 0 protostellar binary IRAS 16293-2422 with ALMAJul 29 2016The inner regions of the envelopes surrounding young protostars are characterised by a complex chemistry, with prebiotic molecules present on the scales where protoplanetary disks eventually may form. This paper introduces a systematic survey, "Protostellar ... More
Large algebraic connectivity fluctuations in spatial network ensembles imply a predictive advantage from node location informationMay 17 2018Nov 02 2018A Random Geometric Graph (RGG) ensemble is defined by the disordered distribution of its node locations. We investigate how this randomness drives sample-to-sample fluctuations in the dynamical properties of these graphs. We study the distributional properties ... More
Laboratory spectroscopic study and astronomical detection of vibrationally excited n-propyl cyanideAug 29 2016We performed a spectral line survey called Exploring Molecular Complexity with ALMA (EMoCA) toward Sagittarius~B2(N) between 84.1 and 114.4 GHz with the Atacama Large Millimeter/submillimeter Array (ALMA) in its Cycles 0 and 1. We determined line intensities ... More
Laboratory rotational spectroscopy of isotopic acetone, CH$_3^{13}$C(O)CH$_3$ and $^{13}$CH$_3$C(O)CH$_3$, and astronomical search in Sagittarius B2(N2)Jul 18 2019We want to study the rotational spectra of CH$_3^{13}$C(O)CH$_3$ and $^{13}$CH$_3$C(O)CH$_3$ and search for them in Sagittarius B2(N2). We investigated the laboratory rotational spectrum of isotopically enriched CH$_3^{13}$C(O)CH$_3$ between 40 GHz and ... More
Examples of interacting particle systems on $\mathbb{Z}$ as Pfaffian point processes II - coalescing branching random walks and annihilating random walks with immigrationMay 31 2016Two classes of interacting particle systems on $\mathbb{Z}$ are shown to be Pfaffian point processes at fixed times, and for all deterministic initial conditions. The first comprises coalescing and branching random walks, the second annihilating random ... More
Submillimeter spectroscopy and astronomical searches of vinyl mercaptan, C$_2$H$_3$SHFeb 15 2019We have extended the pure rotational investigation of the two isomers syn and anti vinyl mercaptan to the millimeter domain using a frequency-multiplication spectrometer. The species were produced by a radiofrequency discharge in 1,2-ethanedithiol. Additional ... More
Rotational and high-resolution infrared spectrum of HC$_3$N: global ro-vibrational analysis and improved line catalogue for astrophysical observationsNov 23 2017HC$_3$N is an ubiquitous molecule in interstellar environments, from external galaxies, to Galactic interstellar clouds, star forming regions, and planetary atmospheres. Observations of its rotational and vibrational transitions provide important information ... More
Examples of interacting particle systems on $\mathbb{Z}$ as Pfaffian point processes: annihilating and coalescing random walksJul 07 2015Jul 04 2018A class of interacting particle systems on $\mathbb{Z}$, involving instantaneously annihilating or coalescing nearest neighbour random walks, are shown to be Pfaffan point processes for all deterministic initial conditions. As diffusion limits, explicit ... More
Interacting particle systems on Z as Pfaffian point processes I - annihilating and coalescing random walksJul 07 2015A class of interacting particle systems on Z, involving instantaneously annihilating or coalescing random walks, are shown to be Pfaffian point processes for all deterministic initial conditions.
Two New and Remarkable Sightlines through the Galactic Center's Molecular GasDec 19 2009Dec 31 2009Until now the known sources in the Galactic center with sufficiently smooth spectra and of sufficient brightness to be suitable for high resolution infrared absorption spectroscopy of interstellar gas occupied a narrow range of longitudes, from the central ... More
Quantum Hall-like effect on strips due to geometryMar 16 2004In this Letter we present an exact calculation of the effective potential which appears on a helicoidal strip. This potential leads to the appearance of lcalized states at a distance \xi_0 from the central axis. The twist \omega of the strip plays the ... More
Magnetic and metal-insulator transitions in coupled spin-fermion systemsAug 14 2014Sep 29 2014We use quantum Monte Carlo to determine the magnetic and transport properties of coupled square lattice spin and fermionic planes as a model for a metal-insulator interface. Specifically, layers of Ising spins with an intra-layer exchange constant $J$ ... More
How Dense is Your Gas? On the recoverability of LVG model parametersFeb 02 2016Feb 23 2016We explore the recoverability of gas physical conditions with the Large Velocity Gradient (LVG) model, using the public code RADEX and the molecules HCN and CO. Examining a wide parameter range with a series of models of increasing complexity we use both ... More
The Effect of Pion Exchange in a Relativistic Quark Model of BaryonsJan 15 2008We examine the effect of adding pion exchange between quarks and pion self-energy corrections to the Los Alamos Relativistic Quark model with a short distance cutoff of the Bethe form. The contributions to the nucleon and the Delta-baryon are small. We ... More
The ISM in Distant GalaxiesJan 12 2009The interstellar medium (ISM) is a key ingredient in galaxy formation and evolution as it provides the molecular gas reservoir which fuels star formation and supermassive black hole accretion. Yet the ISM is one of the least studied aspects of distant ... More
Fractal fractal dimensions of deterministic transport coefficientsJan 27 2003If a point particle moves chaotically through a periodic array of scatterers the associated transport coefficients are typically irregular functions under variation of control parameters. For a piecewise linear two-parameter map we analyze the structure ... More
Double white dwarfs and LISAJan 25 2011Close pairs of white dwarfs are potential progenitors of Type~Ia supernovae and they are common, with of order 100 -- 300 million in the Galaxy. As such they will be significant, probably dominant, sources of the gravitational waves detectable by LISA. ... More
Gravitational lensing in eclipsing binary starsDec 18 2000I consider the effect of the gravitational deflection of light upon the light curves of eclipsing binary stars, focussing mainly upon systems containing at least one white dwarf component. In absolute terms the effects are small, however they are strongest ... More
Universality of the saturation scale and the initial eccentricity in heavy ion collisionsSep 11 2006Recent estimates that Color Glass Condensate initial conditions may generate a larger initial eccentricity for noncentral relativistic heavy ion collisions (relative to the initial eccentricity assumed in earlier hydrodynamic calculations) have raised ... More
Optimal Measurements of Magnetic Flux in Superconducting Circuits and Macroscopic Quantum MechanicsFeb 01 1995A model of repeated quantum measurements of magnetic flux in superconducting circuits manifesting tunneling is discussed. The perturbation due to the previous measurements of magnetic flux is always present unless quantum nondemolition measurements are ... More
Discovery of Eight Recycled Pulsars - The Swinburne Intermediate Latitude Pulsar SurveyNov 12 1999Nov 19 1999We have conducted a pulsar survey of intermediate Galactic latitudes (15deg < |b| < 5deg) at 20 cm. The survey has been highly successful, discovering 58 new pulsars, eight of which are recycled, in only ~14 days of integration time. One pulsar has a ... More
Composite particles in the Theory of Quantum Hall EffectMar 13 1998The formation of composite particles in the electron liquid under QHE conditions discussed by Jain in generalizing Laughlins many-particle state is considered by using a model for two-dimensional guiding center configurations. Describing the self-consistent ... More
Exact SU(2)*U(1) Stringy Black HolesSep 11 1994Nov 08 1994Extreme magnetic dilaton black holes are promoted to exact solutions of heterotic string theory with unbroken supersymmetry. With account taken of alpha' corrections this is accomplished by supplementing the known solutions with SU(2) Yang-Mills vectors ... More
Chiral Gepner Model OrientifoldsAug 19 2004We summarize recent progress in constructing orientifolds of Gepner models, a phenomenologically interesting class of exactly solvable string compactifications with viable gauge groups and chiral matter.
Statistical mechanics of secondary structures formed by random RNA sequencesJul 10 2001The formation of secondary structures by a random RNA sequence is studied as a model system for the sequence-structure problem omnipresent in biopolymers. Several toy energy models are introduced to allow detailed analytical and numerical studies. First, ... More
Critical Properties of an Ising Model with Dilute Long-range InteractionsSep 08 2004Statistical mechanical models with local interactions in $d>1$ dimension can be regarded as $d=1$ dimensional models with regular long range interactions. In this paper we study the critical properties of Ising models having $V$ sites, each having $z$ ... More
Modeling age and metallicity in globular clusters: a comparison of theoretical giant branch isochronesMay 26 1999In view of the important contributions of red giants to the integrated light in evolutionary synthesis calculations of old stellar populations in clusters and galaxies, we provide a comparison of theoretical isochrones computed from the Padova, Geneva, ... More
Improved Quark Actions for Lattice QCDDec 06 1996I present a brief summary of the status and prospects of improved Wilson-type quark actions for coarse lattice simulations. My conclusions are optimistic.
The symmetric Square of the Theta Divisor in Genus 4Sep 10 2011Nov 15 2013We discuss variations of Hodge structures on abelian varieties that arise from intersecting translates of theta divisors with a special focus on the case of abelian varieties of dimension 4
The complement of proper power graphs of finite groupsJan 14 2016For a finite group $G$, the proper power graph $\mathscr{P}^*(G)$ of $G$ is a graph whose vertices are non-trivial elements of $G$ and two vertices $u$ and $v$ are adjacent if and only if $u \neq v$ and $u^m=v$ or $v^m=u$ for some positive integer $m$. ... More
Enhanced Pinning of Vortices in Thin Film Superconductors by Magnetic Dot ArraysMar 29 2000We study the pinning of vortices in thin film superconductors by magnetic dots in the London approximation. A single dot is in general able to pin multiple field-induced vortices, up to a saturation number n_s, which can be much larger than one. However, ... More
Pricing formulas, model error and hedging derivative portfoliosAug 31 2001We propose a method for extending a given asset pricing formula to account for two additional sources of risk: the risk associated with future changes in market--calibrated parameters and the remaining risk associated with idiosyncratic variations in ... More
Perturbative quantum gauge fields on the noncommutative torusMar 22 1999Mar 23 1999Using standard field theoretical techniques, we survey pure Yang-Mills theory on the noncommutative torus, including Feynman rules and BRS symmetry. Although in general free of any infrared singularity, the theory is ultraviolet divergent. Because of ... More
Angle dependence of the integrated intensity in thin film x-ray diffractionDec 05 2016A new length scale, the linear regime, is shown to exist for very thin films in x-ray diffraction. In this regime, the integrated intensity is independent of the absorption coefficient and the angle dependence is also different when compared to bulk materials ... More
Baryon superfluidity and neutrino emissivity of neutron starsFeb 03 2004For neutron stars with hyperon-mixed core, neutrino emissivity is studied under the equation of state, obtained by introducing repulsive three-body force universal for all baryons so as to assure the maximum mass compatible with the observation. By paying ... More
Methods of Supersymmetry BreakingOct 12 1995This is a review of basic ideas and mechanisms encountered in the supersymmetry breaking problem at the global level, in supergravity models, and in superstring theory.
Low-Energy Effective Action of Superstring TheoryNov 24 1992A fundamental task for the heterotic superstring theory is the determination of the effective action describing the physics of massless string excitations at low energies. This is necessary for the phenomenological applications of string theory, in particular ... More
Evolution of the stellar-merger red nova V1309 Scorpii: SED analysisJun 30 2016Jul 06 2016One very important object for understanding the nature of red novae is V1309 Sco. Its pre-outburst observations showed that, before its red-nova eruption in 2008, it was a contact binary quickly evolving to the merger of the components. It thus provided ... More
Advanced simulation code for alpha spectrometryMay 04 2005A Monte Carlo code, known as AASI, is developed for simulating energy spectra in alpha spectrometry. The code documented here is a comprehensive package where all the major processes affecting the spectrum are included. A unique feature of the code is ... More
Lattice Calculation of Thermal Properties of Low-Density Neutron Matter with Pionless NN Effective Field TheoryAug 19 2007May 12 2009Thermal properties of low-density neutron matter are investigated by determinantal quantum Monte Carlo lattice calculations on 3+1 dimensional cubic lattices. Nuclear effective field theory (EFT) is applied using the pionless single- and two-parameter ... More
Rational and global forms of certain Chiral Conformal Field Theories; Vertex Algebras IJan 09 2014We present explicit global constructions - avoiding power series - of certain chiral CFTs, including current algebras on the projective line. We outline an approach to vertex algebras, inspired by this construction. We construct natural pairings on state ... More
Algebraic methods for computing smallest enclosing and circumscribing cylinders of simplicesNov 21 2002We provide an algebraic framework to compute smallest enclosing and smallest circumscribing cylinders of simplices in Euclidean space $\E^n$. Explicitly, the computation of a smallest enclosing cylinder in $\mathbb{E}^3$ is reduced to the computation ... More
VY Scl-Type Star V504 CenJun 02 2003V504 Cen was classified as a possible R CrB-type star. Although this object has been spectroscopically confirmed to be a cataclysmic variable, no detailed study has been yet published. We show, from long-term visual observations and ASAS-3 public CCD ... More
Light Quark Masses and the CP violation parameter $ε'/ε$Sep 28 1996We present estimates of light quarks masses using lattice data. Our main results are based on a global analysis of all the published data for Wilson and Staggered fermions, both in the quenched approximation and with $n_f=2$ dynamical flavors. The Wilson ... More
Detection of H3+ in the interstellar medium of IRAS 08572+3915Sep 11 2001The first detection of the molecular ion H3+ in an extragalactic object has been made toward the highly obscured ultraluminous galaxy, IRAS 08572+3915. Two absorption features near 3.9 microns in its spectrum are identified as the redshifted 3.668 microns ... More
Modeling of Photoionized PlasmasSep 23 2010In this paper I review the motivation and current status of modeling of plasmas exposed to strong radiation fields, as it applies to the study of cosmic X-ray sources. This includes some of the astrophysical issues which can be addressed, the ingredients ... More
The variable 6307A emission line in the spectrum of Eta Carinae: blueshifted [S III] 6313A from the interacting windsOct 07 2009Oct 09 2009The 6307A emission line in the spectrum of Eta Car (Martin et al. 2006) is blue-shifted [S III] 6313A emission originating from the outer wind structures of the massive binary system. We realized the identification while analyzing multiple forbidden emission ... More