Results for "L. Fortson"

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Atomic Parity Nonconservation: Electroweak Parameters and Nuclear StructureNov 05 1992There have been suggestions to measure atomic parity nonconservation (PNC) along an isotopic chain, by taking ratios of observables in order to cancel complicated atomic structure effects. Precise atomic PNC measurements could make a significant contribution ... More
Modeling with the Crowd: Optimizing the Human-Machine Partnership with ZooniverseMar 19 2019LSST and Euclid must address the daunting challenge of analyzing the unprecedented volumes of imaging and spectroscopic data that these next-generation instruments will generate. A promising approach to overcoming this challenge involves rapid, automatic ... More
Precision measurement of light shifts in a single trapped Ba$^+$ ionFeb 22 2005Using a single trapped barium ion we have developed an rf spectroscopy technique to measure the ratio of the off-resonant vector ac Stark effect (or light shift) in the 6S_{1/2} and 5D_{3/2} states to 0.1% precision. We find R = Delta_S / Delta_D = -11.494(13) ... More
Gamma-ray Signatures of Ultra High Energy Cosmic Ray Line-of-sight InteractionsMay 01 2013Sep 29 2013Ultra High Energy Cosmic Rays (UHECRs) interact en route to Earth, producing secondary gamma-rays. For the case of high cosmic ray power and weak intergalactic magnetic fields, the deflections of these UHECRs may be small leading to detectable gamma-ray ... More
Radio Galaxy Zoo: host galaxies and radio morphologies derived from visual inspectionJul 27 2015We present results from the first twelve months of operation of Radio Galaxy Zoo, which upon completion will enable visual inspection of over 170,000 radio sources to determine the host galaxy of the radio emission and the radio morphology. Radio Galaxy ... More
A Measurement of the Cosmic Ray Spectrum and Composition at the KneeMar 14 2000Jun 22 2000The energy spectrum and primary composition of cosmic rays with energy between $3\times 10^{14}$ and $3\times10^{16}\unit{eV}$ have been studied using the CASA-BLANCA detector. CASA measured the charged particle distribution of air showers, while BLANCA ... More
CASA-BLANCA: A Large Non-imaging Cherenkov Detector at CASA-MIAJul 02 1997The lateral distribution of Cherenkov light at ground level records important information on the development of the cosmic ray air shower which produces it. We have constructed an array of 144 non-imaging Cherenkov detectors at the CASA-MIA experiment ... More
Galaxy Zoo: Bars in Disk GalaxiesMar 01 2010Oct 09 2010We present first results from Galaxy Zoo 2, the second phase of the highly successful Galaxy Zoo project ( Using a volume-limited sample of 13665 disk galaxies (0.01< z < 0.06 and M_r<-19.38), we study the fraction of galaxies with ... More
Muon Hunter: a Zooniverse projectFeb 24 2018The large datasets and often low signal-to-noise inherent to the raw data of modern astroparticle experiments calls out for increasingly sophisticated event classification techniques. Machine learning algorithms, such as neural networks, have the potential ... More
Galaxy Zoo: the effect of bar-driven fueling on the presence of an active galactic nucleus in disc galaxiesFeb 03 2015We study the influence of the presence of a strong bar in disc galaxies which host an active galactic nucleus (AGN). Using data from the Sloan Digital Sky Survey and morphological classifications from the Galaxy Zoo 2 project, we create a volume-limited ... More
Galaxy Zoo: Evidence for Diverse Star Formation Histories through the Green ValleyJan 23 2015Does galaxy evolution proceed through the green valley via multiple pathways or as a single population? Motivated by recent results highlighting radically different evolutionary pathways between early- and late-type galaxies, we present results from a ... More
Integrating human and machine intelligence in galaxy morphology classification tasksFeb 23 2018Quantifying galaxy morphology is a challenging yet scientifically rewarding task. As the scale of data continues to increase with upcoming surveys, traditional classification methods will struggle to handle the load. We present a solution through an integration ... More
Galaxy Zoo: the dependence of the star formation-stellar mass relation on spiral disk morphologyFeb 11 2015We measure the stellar mass-star formation rate relation in star-forming disk galaxies at z<0.085, using Galaxy~Zoo morphologies to examine different populations of spirals as classified by their kiloparsec-scale structure. We examine the number of spiral ... More
Measurement of the Iron Spectrum in Cosmic Rays by VERITASJul 20 2018We present a new measurement of the energy spectrum of iron nuclei in cosmic rays from 20 to 500 TeV. The measurement makes use of a template-based analysis method, which, for the first time, is applied to the energy reconstruction of iron-induced air ... More
Direct measurement of stellar angular diameters by the VERITAS Cherenkov TelescopesApr 12 2019The angular size of a star is a critical factor in determining its basic properties. Direct measurement of stellar angular diameters is difficult: at interstellar distances stars are generally too small to resolve by any individual imaging telescope. ... More
Galaxy Zoo: Finding offset discs and bars in SDSS galaxiesApr 28 2017We use multi-wavelength SDSS images and Galaxy Zoo morphologies to identify a sample of $\sim$$270$ late-type galaxies with an off-centre bar. We measure offsets in the range 0.2-2.5 kpc between the photometric centres of the stellar disc and stellar ... More
A Search for Pulsed Very High-Energy Gamma Rays from Thirteen Young Pulsars in Archival VERITAS DataApr 19 2019We conduct a search for periodic emission in the very high-energy gamma-ray band (VHE; E > 100 GeV) from a total of 13 pulsars in an archival VERITAS data set with a total exposure of over 450 hours. The set of pulsars includes many of the brightest young ... More
The Green Valley is a Red Herring: Galaxy Zoo reveals two evolutionary pathways towards quenching of star formation in early- and late-type galaxiesFeb 19 2014We use SDSS+\textit{GALEX}+Galaxy Zoo data to study the quenching of star formation in low-redshift galaxies. We show that the green valley between the blue cloud of star-forming galaxies and the red sequence of quiescent galaxies in the colour-mass diagram ... More
The impact of astrophysical particle acceleration on searches for beyond-the-Standard-Model physicsMay 01 2013Jul 28 2013A brief white paper is provided, discussing how the particle acceleration mechanisms taking place within astrophysical sources may mimic or mask signatures of new physics and the role that will be played by next-generation gamma-ray observatories, such ... More
Frequency doubling and stabilization of a Tm,Ho:YLF laser at 2051 nm to a high finesse optical cavityMay 23 2011Light from a Tm,Ho:YLF laser operating at 2051 nm is frequency doubled then coupled into a high Fabry-Perot cavity with manufacturer quoted finesse in excess of 300,000. The frequency of the laser is stabilized using the Pound-Drever-Hall (PDH) method. ... More
Citizen Science: Contributions to Astronomy ResearchFeb 12 2012The contributions of everyday individuals to significant research has grown dramatically beyond the early days of classical birdwatching and endeavors of amateurs of the 19th century. Now people who are casually interested in science can participate directly ... More
A Search for Brief Optical Flashes Associated with the SETI Target KIC 8462852Feb 02 2016Feb 03 2016The F-type star KIC 8462852 has recently been identified as an exceptional target for SETI (search for extraterrestrial intelligence) observations. We describe an analysis methodology for optical SETI, which we have used to analyse nine hours of serendipitous ... More
The Composition of Cosmic Rays at the KneeFeb 07 2002The observation of a small change in spectral slope, or 'knee' in the fluxes of cosmic rays near energies 10^15 eV has caused much speculation since its discovery over 40 years ago. The origin of this feature remains unknown. A small workshop to review ... More
Optimizing the Human-Machine Partnership with ZooniverseSep 25 2018Over the past decade, Citizen Science has become a proven method of distributed data analysis, enabling research teams from diverse domains to solve problems involving large quantities of data with complexity levels which require human pattern recognition ... More
Optical clocks based on ultra-narrow three-photon resonances in alkaline earth atomsSep 09 2004A sharp resonance line that appears in three-photon transitions between the $^{1}S_{0}$ and $^{3}P_{0}$ states of alkaline earth and Yb atoms is proposed as an optical frequency standard. This proposal permits the use of the even isotopes, in which the ... More
Precision measurement of light shifts at two off-resonant wavelengths in a single trapped Ba+ ion and determination of atomic dipole matrix elementsAug 13 2008We define and measure the ratio (R) of the vector ac-Stark effect (or light shift) in the 6S_1/2 and 5D_3/2 states of a single trapped barium ion to 0.2% accuracy at two different off-resonant wavelengths. We earlier found R = -11.494(13) at 514.531nm ... More
A new limit on the permanent electric dipole moment of ^{199}HgDec 01 2000We present the first results of a new search for a permanent electric dipole moment of the ^{199}Hg atom using a UV laser. Our measurements give d(Hg)= - (1.06 +/- 0.49 +/- 0.40) 10^{-28} e cm. We interpret the result as an upper limit |d(Hg)| < 2.1 10^{-28} ... More
Dark Matter Constraints from a Joint Analysis of Dwarf Spheroidal Galaxy Observations with VERITASMar 15 2017May 08 2017We present constraints on the annihilation cross section of WIMP dark matter based on the joint statistical analysis of four dwarf galaxies with VERITAS. These results are derived from an optimized photon weighting statistical technique that improves ... More
Galaxy Zoo: Morphological Classifications for 120,000 Galaxies in HST Legacy ImagingOct 10 2016Oct 14 2016We present the data release paper for the Galaxy Zoo: Hubble (GZH) project. This is the third phase in a large effort to measure reliable, detailed morphologies of galaxies by using crowdsourced visual classifications of colour composite images. Images ... More
Galaxy Zoo 2: detailed morphological classifications for 304,122 galaxies from the Sloan Digital Sky SurveyAug 15 2013Aug 19 2013We present the data release for Galaxy Zoo 2 (GZ2), a citizen science project with more than 16 million morphological classifications of 304,122 galaxies drawn from the Sloan Digital Sky Survey. Morphology is a powerful probe for quantifying a galaxy's ... More
Galaxy Zoo: Are Bars Responsible for the Feeding of Active Galactic Nuclei at 0.2 < z < 1.0?Sep 18 2014Dec 19 2014We present a new study investigating whether active galactic nuclei (AGN) beyond the local universe are preferentially fed via large-scale bars. Our investigation combines data from Chandra and Galaxy Zoo: Hubble (GZH) in the AEGIS, COSMOS, and GOODS-S ... More
A Very High Energy $γ$-Ray Survey towards the Cygnus Region of the GalaxyMay 15 2018We present results from deep observations towards the Cygnus region using 300 hours of very-high-energy (VHE) $\gamma$-ray data taken with the VERITAS Cherenkov telescope array and over seven years of high-energy $\gamma$-ray data taken with the Fermi ... More
Galaxy Zoo SupernovaeNov 09 2010Nov 15 2010This paper presents the first results from a new citizen science project: Galaxy Zoo Supernovae. This proof of concept project uses members of the public to identify supernova candidates from the latest generation of wide-field imaging transient surveys. ... More
Constraints on Gamma-ray Emission from the Galactic Plane at 300 TeVMar 10 1997We describe a new search for diffuse ultrahigh energy gamma-ray emission associated with molecular clouds in the galactic disk. The Chicago Air Shower Array (CASA), operating in coincidence with the Michigan muon array (MIA), has recorded over 2.2 x 10^{9} ... More
The Real-Time Analysis of the Cherenkov Telescope Array ObservatoryJul 24 2013The Cherenkov Telescope Array (CTA) Observatory must be capable of issuing fast alerts on variable and transient sources to maximize the scientific return. This will be accomplished by means of a Real-Time Analysis (RTA) pipeline, a key system of the ... More
Deep Broadband Observations of the Distant Gamma-ray Blazar PKS 1424+240Mar 18 2014We present deep VERITAS observations of the blazar PKS 1424+240, along with contemporaneous Fermi Large Area Telescope, Swift X-ray Telescope and Swift UV Optical Telescope data between 2009 February 19 and 2013 June 8. This blazar resides at a redshift ... More
An Upper Bound on the Strongly Forbidden $6S_{1/2} \leftrightarrow 5D_{3/2}$ Magnetic Dipole Transition Moment in {Ba}$^{+}$Oct 14 2016We report the results from our first-generation experiment to measure the magnetic-dipole transition moment (M1) between the $6S_{1/2}$ and $5D_{3/2}$ manifolds in Ba$^{+}$. Knowledge of M1 is crucial for the proposed parity-nonconservation experiment ... More
Nuclear magnetic octupole moment and the hyperfine structure of the $5D_{3/2,5/2}$ states of the Ba$^+$ ionApr 28 2008The hyperfine structure of the long-lived $5D_{3/2}$ and $5D_{5/2}$ levels of Ba$^+$ ion is analyzed. A procedure for extracting relatively unexplored nuclear magnetic moments $\Omega$ is presented. The relevant electronic matrix elements are computed ... More
Studies of the $^{1}$S$_{0}$--$^3$P$_0$ transition in atomic ytterbium for optical clocks and qubit arraysApr 28 2005We report an observation of the weak $6^{1}$S$_{0}$-$6^3$P$_0$ transition in $^{171,173}$Yb as an important step to establish Yb as a primary candidate for future optical frequency standards, and to open up a new approach for qubits using the $^{1}$S$_{0}$ ... More
A transient search using combined human and machine classificationsJul 17 2017Large modern surveys require efficient review of data in order to find transient sources such as supernovae, and to distinguish such sources from artefacts and noise. Much effort has been put into the development of automatic algorithms, but surveys still ... More
Coherent Excitation of the 6S1/2 to 5D3/2 Electric Quadrupole Transition in 138Ba+Mar 09 2012The electric dipole-forbidden, quadrupole 6S1/2 <-> 5D3/2 transition in Ba+ near 2051 nm, with a natural linewidth of 13 mHz, is attractive for potential observation of parity non-conservation, and also as a clock transition for a barium ion optical frequency ... More
A Method for Measuring the $6S_{1/2} \leftrightarrow 5D_{3/2}$ Magnetic Dipole Transition Moment in {Ba}$^{+}$Jun 01 2013We propose a method for measuring the magnetic dipole (M1) transition moment of the $6S_{1/2} \big(\mathrm{m}=-1/2\big)\leftrightarrow 5D_{3/2}\big(\mathrm{m}=-1/2\big)$ transition in single trapped Ba$^{+}$ by exploiting different symmetries in the electric ... More
Progress on indium and barium single ion optical frequency standardsApr 01 2005Apr 01 2005We report progress on 115In+ and 137Ba+ single ion optical frequency standards using all solid-state sources. Both are free from quadrupole field shifts and together enable a search for drift in fundamental constants.
First NuSTAR Observations of Mrk 501 within a Radio to TeV Multi-Instrument CampaignSep 16 2015Sep 24 2015We report on simultaneous broadband observations of the TeV-emitting blazar Markarian 501 between 1 April and 10 August 2013, including the first detailed characterization of the synchrotron peak with Swift and NuSTAR. During the campaign, the nearby ... More
TeV Gamma-Ray Observations of the Perseus and Abell 2029 Galaxy ClustersFeb 13 2006Galaxy clusters might be sources of TeV gamma rays emitted by high-energy protons and electrons accelerated by large scale structure formation shocks, galactic winds, or active galactic nuclei. Furthermore, gamma rays may be produced in dark matter particle ... More
Galaxy Zoo: CANDELS Barred Disks and Bar FractionsSep 03 2014The formation of bars in disk galaxies is a tracer of the dynamical maturity of the population. Previous studies have found that the incidence of bars in disks decreases from the local Universe to z ~ 1, and by z > 1 simulations predict that bar features ... More
Measurement of Linear Stark Interference in 199HgNov 24 2010Jun 24 2011We present measurements of Stark interference in the 6$^1S_0$ $\rightarrow$ 6$^3P_1$ transition in $^{199}$Hg, a process whereby a static electric field $E$ mixes magnetic dipole and electric quadrupole couplings into an electric dipole transition, leading ... More
Galaxy Zoo: Morphological Classification and Citizen ScienceApr 28 2011We provide a brief overview of the Galaxy Zoo and Zooniverse projects, including a short discussion of the history of, and motivation for, these projects as well as reviewing the science these innovative internet-based citizen science projects have produced ... More
Periastron Observations of TeV Gamma-Ray Emission from a Binary System with a 50-year PeriodOct 11 2018We report on observations of the pulsar / Be star binary system PSR J2032+4127 / MT91 213 in the energy range between 100 GeV and 20 TeV with the VERITAS and MAGIC imaging atmospheric Cherenkov telescope arrays. The binary orbit has a period of approximately ... More
Improved limit on the permanent electric dipole moment of 199HgJan 15 2009Mar 10 2009We report the results of a new experimental search for a permanent electric dipole moment of 199Hg utilizing a stack of four vapor cells. We find d(199Hg) = (0.49 \pm 1.29_stat \pm 0.76_syst) x 10^{-29} e cm, and interpret this as a new upper bound, |d(199Hg)| ... More
Search for Dark Matter Subhalos in the High-Energy Gamma-ray Band with Fermi and the Cherenkov Telescope ArrayMay 01 2013May 04 2013We discuss the potential for the detection of dark matter and the characterization of its particle nature via the observation of dark matter subhalos. Specifically, we discuss the search for dark matter Galactic subhalos in the gamma-ray band with the ... More
Radio frequency spectroscopy measurement of the Landé g factor of the 5D5/2 state of Ba+ with a single trapped ionJun 14 2013We report an improved measurement of the Land\'e g factor of the 5D5/2 state of singly ionized barium. Measurements were performed on single Doppler-cooled 138Ba+ ions in linear Paul traps using two similar, independent apparatuses. Transitions between ... More
Testing a Novel Self-Assembling Data Paradigm in the Context of IACT DataSep 07 2015The process of gathering and associating data from multiple sensors or sub-detectors due to a common physical event (the process of event-building) is used in many fields, including high-energy physics and $\gamma$-ray astronomy. Fault tolerance in event-building ... More
Anisotropy of the superconducting fluctuations in multiband superconductors: the case of LiFeAsJul 08 2014Nov 14 2014Between the different families of pnictide multiband superconductors, LiFeAs is probably one of the less understood. Indeed, despite the large amount of experiments performed in the last few years on this material, no consensus has been reached yet on ... More
On the measure of Lagrangian invariant tori in nearly--integrable mechanical systems (draft)Mar 27 2015Consider a real--analytic nearly--integrable mechanical system with potential $f$, namely, a Hamiltonian system, having a real-analytic Hamiltonian $$ H(y,x)=\frac12 | y |^2 +\e f(x)\ , $$ $y,x$ being $n$--dimensional standard action--angle variables ... More
On the Evaluation and Comparison of Taggers: The Effect of Noise in Testing CorporaSep 28 1998This paper addresses the issue of {\sc pos} tagger evaluation. Such evaluation is usually performed by comparing the tagger output with a reference test corpus, which is assumed to be error-free. Currently used corpora contain noise which causes the obtained ... More
Poisson-Lie T-plurality of three-dimensional conformally invariant sigma models II: Nondiagonal metrics and dilaton puzzleAug 17 2004Sep 29 2005We look for 3-dimensional Poisson-Lie dualizable sigma models that satisfy the vanishing beta-function equations with constant dilaton field. Using the Poisson-Lie T-plurality we then construct 3-dimensional sigma models that correspond to various decompositions ... More
Classification of 6-dimensional real Manin triplesFeb 21 2002Mar 27 2002We present a complete list of 6-dimensional Manin triples or, equivalently, of 3-dimensional Lie bialgebras. We start from the well known classification of 3-dimensional real Lie algebras and assume the canonical bilinear form on the 6-dimensional Drinfeld ... More
Renormalizability of semiquantized fieldsOct 03 1994Sep 21 1995A definition is given, in the framework of stochastic quantization, for the dynamics of a system composed of classical and quantum degrees of freedom mutually interacting. It is found that the theory breaks reflection positivity, and hence it is unphysical. ... More
Quantum Bounded Symmetric DomainsMar 26 2008Oct 13 2010This is Leonid Vaksman's monograph "Quantum bounded symmetric domains" (in Russian), preceded with an English translation of the table of contents and (a part) of the introduction. Quantum bounded symmetric domains are interesting from several points ... More
On a multidimentional Brownian motion with partly reflecting membrane on a hyperplaneOct 30 2012A multidimensional Brownian motion with partial reflection on a hyperplane $S$ in the direction $qN+\alpha $, where $N$ is the conormal vector to the hyperplane and $q\in [-1,1], \alpha \in S$ are given parametres, is constructed and this construction ... More
Reply to Comment on "Statistical mechanics of developable ribbons"Nov 09 2011Starostin and van der Heijden [arXiv:1111.2029] question the validity of the results reported in our Letter [Phys. Rev. Lett. 104, 238104 (2010)] regarding the existence of spontaneous helical structure in finite-temperature developable ribbons. According ... More
Multistability of free spontaneously-curved anisotropic stripsApr 20 2011Dec 07 2011Multistable structures are objects with more than one stable conformation, exemplified by the simple switch. Continuum versions are often elastic composite plates or shells, such as the common measuring tape or the slap bracelet, both of which exhibit ... More
VZ Velorum: 116 years of a Mira starJun 01 2006Using the Harvard College Observatory Photographic Plate Collection and recent CCD observations by the ASAS project we have reconstructed the light variations of the southern pulsating red giant star VZ Velorum between 1890 and early 2006. Contrary to ... More
Results on D+-->lv and Ds+-->lv decays at Charm factoryMay 07 2013Jun 07 2013In this article, we reviewed the results on D+-->lv and Ds+-->lv decays at Charm factory.
Wireless Josephson Junction Arrays as Tunable Metamaterials: Inducing Discrete Frequency Steps with Microwave RadiationJan 23 2015We report low temperature, microwave transmission measurements on a new switchable and tunable class of nonlinear metamaterials. A wireless two dimensional array of Josephson junctions (JJ) is probed as a metamaterial where each plaquette in the array ... More
The Effect of Weak Gravitational Lensing on the Angular Distribution of Gamma-Ray BurstsJun 10 1996If Gamma-Ray Bursts (GRBs) are cosmologically distributed standard candles and are associated with the luminous galaxies, then the observed angular distribution of all GRBs is altered due to weak gravitational lensing of bursts by density inhomogeneities. ... More
Theory of charge fluctuations and domain relocation times in semiconductor superlatticesDec 07 2004Shot noise affects differently the nonlinear electron transport in semiconductor superlattices depending on the strength of the coupling among the superlattice quantum wells. Strongly coupled superlattices can be described by a miniband Boltzmann-Langevin ... More
New AdS(3) x G/H compactifications of chiral IIB supergravityMar 13 2000May 30 2000We present a new class of solutions of D=10, N=2 chiral supergravity. A nonvanishing background for the field strength G_{MNR} of the complex two-form triggers AdS_3 x M_7 compactifications, where M_7 is a 7-dimensional compact manifold. When M_7 is a ... More
Detailed analysis of quantum phase transitions within the $u(2)$ algebraOct 13 2009We analyze in detail the quantum phase transitions that arise in models based on the $u(2)$ algebraic description for bosonic systems with two types of scalar bosons. First we discuss the quantum phase transition that occurs in hamiltonians that admix ... More
Recent Results on $\psip$ Decays at BesMay 16 2005Recent results on $\psip$ decays, including 10 Vector + Pseudoscalar (VP) modes and $p\bar{p}\pi^0(\eta)$, are reported with $14\times10^6$ $\psip$ events collected with the BESII detector. Cross sections and form factors for $e^+e^- \to \wpi$, $\rho\eta$, ... More
Statistical consistency of quantum-classical hybridsJan 20 2012After formulating a no-go theorem for perfect quantum-classical hybrid systems, a new consistency requirement based on standard statistical considerations is noted. It is shown that such requirement is not fulfilled by the mean-field approach, nor by ... More
Derivative expansion of the heat kernel in curved spaceJun 13 2007Jul 02 2007The heat kernel in curved space-time is computed to fourth order in a strict expansion in the number of covariant derivatives. The computation is made for arbitrary non abelian gauge and scalar fields and for the Riemann connection in the coordinate sector. ... More
Phase space localization of antisymmetric functionsNov 05 2002Upper and lower bounds are written down for the minimum information entropy in phase space of an antisymmetric wave function in any number of dimensions. Similar bounds are given when the wave function is restricted to belong to any of the proper subspaces ... More
On the uniqueness of the expected stress-energy tensor in renormalizable field theoriesMar 15 1999Sep 17 1999It is argued that the ambiguity introduced by the renormalization in the effective action of a four-dimensional renormalizable quantum field theory is at most a local polynomial action of canonical dimension four. The allowed ambiguity in the expected ... More
Direct construction of the effective action of chiral gauge fermions in the anomalous sectorApr 14 2008Jul 25 2008The anomaly implies an obstruction to a fully chiral covariant calculation of the effective action in the abnormal parity sector of chiral theories. The standard approach then is to reconstruct the anomalous effective action from its covariant current. ... More
The induced Chern-Simons term at finite temperatureJan 09 2002It is argued that the derivative expansion is a suitable method to deal with finite temperature field theory, if it is restricted to spatial derivatives only. Using this method, a simple and direct calculation is presented for the radiatively induced ... More
Expansion of a Bose-Einstein Condensate in an atomic waveguideNov 15 2001The expansion of a Bose-Einstein condensate in an atomic waveguide is analyzed. We study different regimes of expansion, and identify a transient regime between one-dimensional and three-dimensional dynamics, in which the properties of the condensate ... More
Constraints on star formation theories from the Serpens molecular cloud and protoclusterJul 10 2002We have mapped the large-scale structure of the Serpens cloud core using moderately optically thick (13CO(1--0) and CS(2--1)) and optically thin tracers (C18O(1--0), C34S(2--1), and N2H+(1--0)), using the 16-element focal plane array operating at a wavelength ... More
Classification of Poisson-Lie T-dual models with two-dimensional targetsOct 16 2001Dec 20 2001Four-dimensional Manin triples and Drinfeld doubles are classified and corresponding two-dimensional Poisson-Lie T-dual sigma models on them are constructed. The simplest example of a Drinfeld double allowing decomposition into two nontrivially different ... More
Statistical Mechanics of Developable RibbonsFeb 24 2010Jun 11 2010We investigate the statistical mechanics of long developable ribbons of finite width and very small thickness. The constraint of isometric deformations in these ribbon-like structures that follows from the geometric separation of scales introduces a coupling ... More
A bracket polynomial for graphsAug 25 2008Jan 14 2009A knot diagram has an associated looped interlacement graph, obtained from the intersection graph of the Gauss diagram by attaching loops to the vertices that correspond to negative crossings. This construction suggests an extension of the Kauffman bracket ... More
Chapman-Enskog method and synchronization of globally coupled oscillatorsJun 12 2000Jul 10 2000The Chapman-Enskog method of kinetic theory is applied to two problems of synchronization of globally coupled phase oscillators. First, a modified Kuramoto model is obtained in the limit of small inertia from a more general model which includes ``inertial'' ... More
A Dynamical Cross-over Regime in the Transmission and Reflection Spectra of Evanescent Waves with 2D Arrays of Josephson JunctionsFeb 18 2013A dynamical cross-over regime is revealed when exposing a classical two-dimensional ordered Josephson junction (JJ) array to evanescent waves and tuning the incident microwave power. At the lowest possible temperature for these experiments, 1.1 K, and ... More
Population Models With Delay in Dynamic EnvironmentJan 05 2006Mar 15 2006We study the combined effects of periodically varying carrying capacity and survival rates on the fish population in the ocean (sea). We introduce the Getz type delay differential equation model with a control parameter which describes how fish are harvested. ... More
The invariant factor of the chiral determinantJul 10 2008The coupling of spin 0 and spin 1 external fields to Dirac fermions defines a theory which displays gauge chiral symmetry. Quantum mechanically, functional integration of the fermions yields the determinant of the Dirac operator, known as the chiral determinant. ... More
Derivative expansion for the effective action of chiral gauge fermions. The abnormal parity componentDec 19 2000Mar 01 2001Explicit exact formulas are presented, for the leading order term in a strict chiral covariant derivative expansion, for the abnormal parity component of the effective action of two- and four-dimensional Dirac fermions in presence of scalar, pseudo-scalar, ... More
Representation of Complex ProbabilitiesJul 19 1996Let a ``complex probability'' be a normalizable complex distribution $P(x)$ defined on $\R^D$. A real and positive probability distribution $p(z)$, defined on the complex plane $\C^D$, is said to be a positive representation of $P(x)$ if $\langle Q(x)\rangle_P ... More
Gibbs sampling of complex valued distributionsOct 30 2015Sep 26 2016A new technique is explored for the Monte Carlo sampling of complex-valued distributions. The method is based on a heat bath approach where the conditional probability is replaced by a positive representation of it on the complex plane. Efficient ways ... More
Existence of positive representations for complex weightsJun 29 2007The necessity of computing integrals with complex weights over manifolds with a large number of dimensions, e.g., in some field theoretical settings, poses a problem for the use of Monte Carlo techniques. Here it is shown that very general complex weight ... More
Derivative expansion for the effective action of chiral gauge fermions. The normal parity componentDec 19 2000Mar 01 2001Explicit exact formulas are presented, up to fourth order in a strict chiral covariant derivative expansion, for the normal parity component of the Euclidean effective action of even-dimensional Dirac fermions. The bosonic background fields considered ... More
Parity breaking in 2+1 dimensions and finite temperatureFeb 11 1998Mar 17 1999An expansion in the number of spatial covariant derivatives is carried out to compute the $\zeta$-function regularized effective action of 2+1-dimensional fermions at finite temperature in an arbitrary non-Abelian background. The real and imaginary parts ... More
Absence of classical and quantum mixingSep 15 1995It is shown, under mild assumptions, that classical degrees of freedom dynamically coupled to quantum ones do not inherit their quantum fluctuations. It is further shown that, if the assumptions are strengthen by imposing the existence of a canonical ... More
Optical Calibration For Jefferson Lab HKS SpectrometerNov 04 2005In order to accept very forward angle scattering particles, Jefferson Lab HKS experiment uses an on-target zero degree dipole magnet. The usual spectrometer optics calibration procedure has to be modified due to this on-target field. This paper describes ... More
Skew braces and the Yang-Baxter equationNov 10 2015Mar 16 2016Braces were introduced by Rump to study non-degenerate involutive set-theoretic solutions of the Yang-Baxter equation. We generalize Rump's braces to the non-commutative setting and use this new structure to study not necessarily involutive non-degenerate ... More
Bounds on the Quenched Pressure and Main Eigenvalue of the Ruelle Operator for Brownian Type PotentialsMar 02 2016Jun 23 2016In this paper we consider a random potential derived from the Brownian motion. We obtain upper and lower bounds for the expected value of the main eigenvalue of the associated Ruelle operator and for its quenched topological pressure. We also exhibit ... More
Supersymmetric domain wall x G/H solutions of IIB supergravityApr 23 20011-brane nonmaximally supersymmetric solutions of D=10 chiral supergravity are discussed. In the dual frame, their near brane geometry is the product of a 3-dimensional domain wall spacetime and a 7-dimensional homogeneous Einstein space G/H.
Hawking Radiation and Back-ReactionMar 20 1992The puzzles of black hole evaporation can be studied in the simplified context of 1+1 dimensional gravity. The semi-classical equations of Callan, Giddings, Harvey and Strominger provide a consistent description of the evaporation process which we describe ... More
Optical Doppler shift measurement using a rotating mirrorJul 24 2006Sep 22 2006Optical Doppler shift demonstration experiments are not a simple task since the light source cannot usually be moved in a sufficiently smooth and uniform manner to keep the level of noise well below of that of the signal. For that reason most demonstration ... More
Minimal surfaces bounded by elastic linesAug 02 2011May 30 2012In mathematics, the classical Plateau problem consists of finding the surface of least area that spans a given rigid boundary curve. A physical realization of the problem is obtained by dipping a stiff wire frame of some given shape in soapy water and ... More