Results for "Duncan R. Lorimer"

total 122339took 0.13s
The pulsar spectral index distributionFeb 08 2013Feb 11 2013The flux density spectra of radio pulsars are known to be steep and, to first order, described by a power-law relationship of the form S_{\nu} \propto \nu^{\alpha}, where S_{\nu} is the flux density at some frequency \nu and \alpha is the spectral index. ... More
Multifrequency Observations of Radio Pulse Broadening and Constraints on Interstellar Electron Density MicrostructureJan 07 2004We have made observations of 98 low-Galactic-latitude pulsars to measure pulse broadening caused by multipath propagation through the interstellar medium. Data were collected with the 305-m Arecibo telescope at four radio frequencies between 430 and 2380 ... More
Towards deeper neural networks for Fast Radio Burst detectionFeb 17 2019With the upcoming commensal surveys for Fast Radio Bursts (FRBs), and their high candidate rate, usage of machine learning algorithms for candidate classification is a necessity. Such algorithms will also play a pivotal role in sending real-time triggers ... More
GMRT Galactic Plane Pulsar and Transient Survey and the Discovery of PSR J1838+1523May 14 2018We report the results of a blind pulsar survey carried out with the Giant Metrewave Radio Telescope (GMRT) at 325 MHz. The survey covered about 10\% of the region between Galactic longitude 45$^{\circ} < l <$ 135$^{\circ}$ and Galactic latitude 1$^{\circ} ... More
Testing the universality of free fall by tracking a pulsar in a stellar triple systemJul 05 2018Einstein's theory of gravity, general relativity, has passed stringent tests in laboratories, elsewhere in the Solar Sytem, and in pulsar binaries. Nevertheless it is known to be incompatible with quantum mechanics and must differ from the true behaviour ... More
SETIBURST: A Robotic, Commensal, Realtime Multi-Science Backend for the Arecibo TelescopeJan 17 2017Radio astronomy has traditionally depended on observatories allocating time to observers for exclusive use of their telescopes. The disadvantage of this scheme is that the data thus collected is rarely used for other astronomy applications, and in many ... More
Discovery of Five New Pulsars in Archival DataJun 13 2012May 11 2013Reprocessing of the Parkes Multibeam Pulsar Survey has resulted in the discovery of five previously unknown pulsars and several as-yet-unconfirmed candidates. PSR J0922-52 has a period of 9.68 ms and a DM of 122.4 pc cm^-3. PSR J1147-66 has a period of ... More
The Galactic Millisecond Pulsar PopulationOct 09 2012Among the current sample of over 2000 radio pulsars known primarily in the disk of our Galaxy, millisecond pulsars now number almost 200. Due to the phenomenal success of blind surveys of the Galactic field, and targeted searches of Fermi gamma-ray sources, ... More
ALFABURST: A commensal search for Fast Radio Bursts with AreciboOct 30 2017Nov 22 2017ALFABURST has been searching for Fast Radio Bursts (FRBs) commensally with other projects using the Arecibo L-band Feed Array (ALFA) receiver at the Arecibo Observatory since July 2015. We describe the observing system and report on the non-detection ... More
How else can we detect Fast Radio Bursts?May 05 2016May 26 2016We discuss possible electromagnetic signals accompanying Fast Radio Bursts (FRBs) that are expected in the scenario where FRBs originate in neutron star magnetospheres. For models involving Crab-like giant pulses, no appreciable contemporaneous emission ... More
Flares from Galactic centre pulsars: a new class of X-ray transients?Mar 17 2016Despite intensive searches, the only pulsar within 0.1 pc of the central black hole in our Galaxy, Sgr A*, is a radio-loud magnetar. Since magnetars are rare among the Galactic neutron star population, and a large number of massive stars are already known ... More
The luminosity function of cluster pulsarsDec 21 2010We study luminosities of millisecond pulsars in globular clusters by fitting the observed luminosity distribution with single and double power laws. We use simulations to model the observed distribution as the brighter part of some parent distribution ... More
Verifying and Reporting Fast Radio BurstsAug 23 2018Fast Radio Bursts (FRBs) are a class of short-duration transients at radio wavelengths with inferred astrophysical origin. The prototypical FRB is a broadband signal that occurs over the extent of the receiver frequency range, is narrow in time, and is ... More
The Probability Distribution of the Double Neutron Star Coalescence Rate and Predictions for More DetectionsDec 02 2002We present an analysis method that allows us to estimate the Galactic formation of radio pulsar populations based on their observed properties and our understanding of survey selection effects. More importantly, this method allows us to assign a statistical ... More
Isolated pulsar spin evolution on the P-Pdot DiagramJan 14 2010We look at two contrasting spin-down models for isolated radio pulsars and, accounting for selection effects, synthesize observable populations. While our goal is to reproduce all of the observable characteristics, in this paper we pay particular attention ... More
GREENBURST: a commensal fast radio burst search back-end for the Green Bank TelescopeMar 13 2019We describe the design and deployment of GREENBURST, a commensal Fast Radio Burst (FRB) search system at the Green Bank Telescope. GREENBURST uses the dedicated L-band receiver tap to search over the 960$-$1920 MHz frequency range for pulses with dispersion ... More
PSR J1907+0918 - a young radio pulsar near SGR 1900+14 and G42.8+0.6May 19 2000Jul 12 2000We have extensively searched for periodic signals from the soft-gamma repeater SGR 1900+14, at 430 and 1410 MHz with the Arecibo telescope. Our observations did not reveal the 5.16-s periodicity discovered at X-ray wavelengths by Hurley et al. (1998). ... More
Luminosities of recycled radio pulsars in globular clustersJul 22 2011Using Monte Carlo simulations, we model the luminosity distribution of recycled pulsars in globular clusters as the brighter, observable part of an intrinsic distribution and find that the observed luminosities can be reproduced using either log-normal ... More
On the detectability of eccentric binary pulsarsFeb 20 2013Mar 27 2013By generalizing earlier work of Johnston & Kulkarni, we present a detailed description of the reduction in the signal-to-noise ratio for observations of binary pulsars. We present analytical expressions, and provide software, to calculate the sensitivity ... More
Unidentified FRBs in archival dataMar 01 2019Recently Zhang et al. (2019) reported the discovery of FRB 010312 in a dataset previously searched for FRBs. Here we explain how and why this FRB was initially missed, and highlight several caveats relevant to FRB search completeness. It is possible that ... More
Effect of PSR J0737-3039 on the DNS Merger Rate and Implications for GW DetectionAug 14 2006We present the current estimates of the Galactic merger rate of double-neutron-star (DNS) systems. Using a statistical analysis method, we calculate the probability distribution function (PDF) of the rate estimates, which allows us to assign confidence ... More
The detectability of eccentric binary pulsarsJan 15 2014Studies of binary pulsars provide insight into various theories of physics. Detection of such systems is challenging due to the Doppler modulation of the pulsed signal caused by the orbital motion of the pulsar. We investigated the loss of sensitivity ... More
Arecibo timing observations of 17 pulsars along the Galactic planeDec 05 2001We present phase-coherent timing solutions obtained for the first time for 17 pulsars discovered at Arecibo by Hulse & Taylor (1975ab) in a 430-MHz survey of the Galactic plane. This survey remains the most sensitive of the Galactic plane at 430 MHz and ... More
Ordinary X-rays from Three Extraordinary Millisecond Pulsars: XMM-Newton Observations of PSRs J0337+1715, J0636+5129, and J0645+5158Feb 01 2016Mar 14 2016We present the first X-ray observations of three recently discovered millisecond pulsars (MSPs) with interesting characteristics: PSR J0337+1715, PSR J0636+5129, and PSR J0645+5158. PSR J0337+1715 is a fast-spinning, bright, and so-far unique MSP in a ... More
Gauge Invariant Effective Potentials and Higgs Mass BoundsApr 28 1997May 12 1997The problem of defining a gauge invariant effective potential with a strict energetic interpretation is examined in the context of spontaneously broken gauge theories. It is shown that such a potential can be defined in terms of a composite gauge invariant ... More
Observations of 20 millisecond pulsars in 47 Tucanae at 20 cmNov 12 1999We have used a new observing system on the Parkes radio telescope to carry out a series of pulsar observations of the globular cluster 47 Tucanae at 20-cm wavelength. We detected all 11 previously known pulsars, and have discovered nine others, all of ... More
The NANOGrav 11-Year Data Set: Arecibo Observatory Polarimetry And Pulse MicrocomponentsJul 02 2018We present the polarization pulse profiles for 28 pulsars observed with the Arecibo Observatory by the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) timing project at 2.1 GHz, 1.4 GHz, and 430 MHz. These profiles represent some ... More
Variability of the Pulsed Radio Emission from the Large Magellanic Cloud Pulsar PSR J0529-6652Nov 19 2012We have studied the variability of PSR J0529-6652, a radio pulsar in the LMC, using observations conducted at 1390 MHz with the Parkes 64-m telescope. PSR J0529-6652 is detectable as a single pulse emitter, with amplitudes that classify the pulses as ... More
The Probability Distribution of Binary Pulsar Coalescence Rate Estimates. II. Neutron Star-White Dwarf BinariesFeb 06 2004Aug 10 2004We consider the statistics of pulsar binaries with white dwarf companions (NS-WD). Using the statistical analysis method developed by Kim et al. (2003) we calculate the Galactic coalescence rate of NS-WD binaries due to gravitational-wave emission. We ... More
Detecting fast radio bursts at decametric wavelengthsSep 04 2016Nov 07 2016Fast radio bursts (FRBs) are highly dispersed, sporadic radio pulses that are likely extragalactic in nature. Here we investigate the constraints on the source population from surveys carried out at frequencies $<1$~GHz. All but one FRB has so far been ... More
On gigahertz spectral turnovers in pulsarsOct 06 2015Pulsars are known to emit non-thermal radio emission that is generally a power-law function of frequency. In some cases, a turnover is seen at frequencies around 100~MHz. Kijak et al. have reported the presence of a new class of ''Gigahertz Peaked Spectrum'' ... More
Detecting fast radio bursts at decametric wavelengthsSep 04 2016Sep 13 2016Fast radio bursts (FRBs) are highly dispersed, sporadic radio pulses that are likely extragalactic in nature. Here we investigate the constraints on the source population from surveys carried out at frequencies $<1$~GHz. All but one FRB has so far been ... More
An Upper Limit on the Coalescence Rate of Double Neutron-Star Binaries in the GalaxyJul 29 1999Sep 30 1999In the context of assessing the detectability of the coalescence of two neutron stars (NS) by currently built gravitational-wave experiments, we present a way of obtaining an upper limit to the coalescence rate in the Galaxy. We consider the NS/NS progenitors ... More
Jumping the energetics queue: Modulation of pulsar signals by extraterrestrial civilizationsNov 19 2013Aug 14 2014It has been speculated that technological civilizations evolve along an energy consumption scale first formulated by Kardashev, ranging from human-like civilizations that consume energy at a rate of $\sim 10^{19}$ erg s$^{-1}$ to hypothetical highly advanced ... More
Pulsar science with the Five hundred metre Aperture Spherical TelescopeAug 12 2009Aug 17 2009With a collecting area of 70 000 m^2, the Five hundred metre Aperture Spherical Telescope (FAST) will allow for great advances in pulsar astronomy. We have performed simulations to estimate the number of previously unknown pulsars FAST will find with ... More
Initial Results from the ALFABURST SurveyOct 25 2017Here, we present initial results from the ALFABURST radio transient survey, which is currently running in a commensal mode with the ALFA receiver at the Arecibo telescope. We observed for a total of 1400 hours and have detected single pulses from known ... More
The Largest Mathieu Group and (Mock) Automorphic FormsJan 19 2012We review the relationship between the largest Mathieu group and various modular objects, including recent progress on the relation to mock modular forms. We also review the connections between these mathematical structures and string theory on K3 surfaces. ... More
Optimal Mock Jacobi Theta FunctionsMay 14 2016Mar 02 2017We classify the optimal mock Jacobi forms of weight one with rational coefficients. The space they span is thirty-four-dimensional, and admits a distinguished basis parameterized by genus zero groups of isometries of the hyperbolic plane. We show that ... More
The hunt for new pulsars with the Green Bank TelescopeMar 21 2013The Green Bank Telescope (GBT) is the largest fully steerable radio telescope in the world and is one of our greatest tools for discovering and studying radio pulsars. Over the last decade, the GBT has successfully found over 100 new pulsars through large-area ... More
Derived categories of centrally-symmetric smooth toric Fano varietiesDec 21 2018We exhibit full exceptional collections of vector bundles on any smooth, Fano arithmetic toric variety whose split fan is centrally symmetric.
The Giant Flare of 1998 August 27 from SGR 1900+14: I. An Interpretive Study of BeppoSAX and Ulysses ObservationsOct 24 2000The giant flare of 1998 August 27 from SGR 1900+14 was extraordinary in many ways: it was the most intense flux of gamma rays ever detected from a source outside our solar system; it was longer than any previously detected burst from a soft gamma repeater ... More
A Survey of the Galactic Plane for Dispersed Pulses with the Australian Square Kilometre Array PathfinderMar 12 2019We report the results from a survey of the Galactic plane for dispersed single pulses using the Australian SKA Pathfinder (ASKAP). We searched for rare bright dispersed radio pulses comprising 160 pointings covering 4800 deg$^2$ of the Galactic plane ... More
Discovery of two pulsars towards the Galactic CentreJun 20 2006We report the discovery of two highly dispersed pulsars in the direction of the Galactic Centre made during a survey at 3.1 GHz with the Parkes radio telescope. Both PSRs J1745-2912 and J1746-2856 have an angular separation from the Galactic Centre of ... More
A Population of Non-Recycled Pulsars Orginating in Globular ClustersJul 09 2012Jul 10 2012We explore the enigmatic population of long-period, apparently non-recycled pulsars in globular clusters, building on recent work by Boyles et al (2011). This population is difficult to explain if it formed through typical core collapse supernovae, leading ... More
A Study of Single Pulses in the Parkes Multibeam Pulsar SurveyJun 30 2018We reprocessed the Parkes Multibeam Pulsar Survey, searching for single pulses out to a DM of 5000 pc cm$^{-3}$ with widths of up to one second. We recorded single pulses from 264 known pulsars and 14 Rotating Radio Transients. We produced amplitude distributions ... More
Millisecond Pulsars in 47 TucanaeNov 19 1999Recent observations of the globular cluster 47 Tuc, made with the Parkes telescope at a wavelength of 20 cm, have resulted in the discovery of nine new millisecond pulsars, all in binary systems. The number of timing solutions available has risen from ... More
The Galactic Double-Neutron-Star Merger Rate: Most Current EstimatesMay 27 2004Aug 11 2004We summarize our results on the Galactic merger rate of double neutron stars (DNS) in view of the recent discovery of PSR J0737-3039. We also present previously unpublished results for the 'global' probability distribution of merger rate values that incorporate ... More
The Galactic Formation Rate of Eccentric Neutron Star-White Dwarf BinariesAug 13 2004In this paper we consider the population of eccentric binaries with a neutron star and a white dwarf that has been revealed in our galaxy in recent years through binary pulsar observations. We apply our statistical analysis method (Kim, Kalogera, & Lorimer ... More
Magnetospheric Switching in PSR B1828-11Mar 04 2019PSR B1828-11 is a young pulsar once thought to be undergoing free precession and recently found instead to be switching magnetospheric states in tandem with spin-down changes. Here we show the two extreme states of the mode-changing found for this pulsar ... More
Mode switching and oscillations in PSR B1828-11Mar 04 2019The young pulsar PSR B1828-11 has long been known to show correlated shape and spin-down changes with timescales of roughly 500 and 250 days, perhaps associated with large-scale magnetospheric switching. Here we present multi-hour observations with the ... More
PSR J1833-1034: Discovery of the Central Young Pulsar in the Supernova Remnant G21.5-0.9Sep 27 2005We have discovered the pulsar associated with the supernova remnant G21.5-0.9. PSR J1833-1034, with spin period P = 61.8 ms and dispersion measure 169 pc/cc, is very faint, with pulse-averaged flux density of approximately 70 microJy at a frequency of ... More
Discovery of a 136 millisecond radio and X-ray pulsar in SNR G54.1+0.3Jun 13 2002We report the discovery of a pulsar with period P = 136 ms and dispersion measure 308 pc/cc in a deep observation of the supernova remnant (SNR) G54.1+0.3 with the Arecibo radio telescope. Timing measurements of the new pulsar, J1930+1852, reveal a characteristic ... More
X-Ray Emission from the Double Pulsar System J0737-3039Feb 22 2004We report on a 10 ksec observation of the double pulsar system J0737-3039 obtained with the Chandra X-ray Observatory's Advanced CCD Imaging Spectrometer. We detect the system as a point source with coordinates (J2000) RA = 07:37:51.23, Decl. = -30:39:40.9, ... More
Detecting pulsars in the Galactic centreNov 21 2016Although high-sensitivity surveys have revealed a number of highly dispersed pulsars in the inner Galaxy, none have so far been found in the Galactic centre (GC) region, which we define to be within a projected distance of 1~pc from Sgr~A*. This null ... More
Twisted forms of toric varietiesAug 18 2014Jan 19 2016We consider the set of forms of a toric variety over an arbitrary field: those varieties which become isomorphic to a toric variety after base field extension. In contrast to most previous work, we also consider arbitrary isomorphisms rather than just ... More
Equivariant unirationality of del Pezzo surfaces of degree 3 and 4Oct 30 2014Oct 03 2016A variety X with an action of a finite group G is said to be G-unirational if there is a G-equivariant dominant rational map V -> X where V is a faithful linear representation of G. This generalizes the usual notion of unirationality. We determine when ... More
Bursting emission from B0611+22Feb 07 2014Over the past decade it has become apparent that a class of `bursting pulsars' exist with the discovery of PSR J1752+2359 and PSR J1938+2213. In these pulsars, a sharp increase in the emission is observed that then tends to systematically drop-off from ... More
Population modelling of FRBs from intrinsic propertiesFeb 26 2019We develop a formalism to estimate the intrinsic properties of FRBs from observations by assuming a fixed DM contribution from a MW-like host galaxy, pulse temporal broadening models for turbulent plasma and a flat FRB energy spectrum. We then perform ... More
SDSS J102347.6+003841: A Millisecond Radio Pulsar Binary That Had A Hot Disk During 2000-2001May 24 2009Aug 20 2009The Sloan Digital Sky Survey (SDSS) source J102347.6+003841 was recently revealed to be a binary 1.69 millisecond radio pulsar with a 4.75 hr orbital period and a ~0.2 M_sun companion. Here we analyze the SDSS spectrum of the source in detail. The spectrum ... More
Equivariant K3 InvariantsAug 09 2015In this note, we describe a connection between the enumerative geometry of curves in K3 surfaces and the chiral ring of an auxiliary superconformal field theory. We consider the invariants calculated by Yau--Zaslow (capturing the Euler characters of the ... More
Precision Ephemerides For Gravitational Wave Searches: II. Cyg X-2Apr 12 2016Accreting neutron stars in low-mass X-ray binaries (LMXBs) are candidate high-frequency persistent gravitational wave sources. These may be detectable with next generation interferometers such as Advanced LIGO/VIRGO within this decade. However, the search ... More
Weight One Jacobi Forms and Umbral MoonshineMar 11 2017We analyze holomorphic Jacobi forms of weight one with level. One such form plays an important role in umbral moonshine, leading to simplifications of the statements of the umbral moonshine conjectures. We prove that non-zero holomorphic Jacobi forms ... More
Mock Modular Mathieu Moonshine ModulesJun 20 2014Aug 10 2015We construct super vertex operator algebras which lead to modules for moonshine relations connecting the four smaller sporadic simple Mathieu groups with distinguished mock modular forms. Starting with an orbifold of a free fermion theory, any subgroup ... More
The Millisecond Pulsars in NGC 6760Nov 06 2004Jan 22 2005We present the results of recent Arecibo and Green Bank observations of the globular cluster NGC 6760. Using Arecibo, a phase-coherent timing solution has been obtained for the previously known binary pulsar in this cluster, PSR J1911+0102A. We have also ... More
Non-Recycled Pulsars in Globular ClustersJan 04 2011We place limits on the population of non-recycled pulsars originating in globular clusters through Monte Carlo simulations and frequentist statistical techniques. We set upper limits on the birth rates of non-recycled cluster pulsars and predict how many ... More
Simultaneous radio and X-ray observations of PSR B0611+22Jul 26 2016We report results from simultaneous radio and X-ray observations of PSR B0611+22 which is known to exhibit bursting in its single-pulse emission. The pulse phase of the bursts vary with radio frequency. The bursts are correlated in 327/150~MHz datasets ... More
Radio Properties of Rotating Radio Transients I: searches for periodicities and randomness in pulse arrival timesJul 05 2011We have analysed the long- and short-term time dependence of the pulse arrival times and the pulse detection rates for eight Rotating Radio Transient (RRAT) sources from the Parkes Multi-beam Pulsar Survey (PMPS). We find significant periodicities in ... More
Blind surveys for radio pulsars and transientsDec 21 2010Dec 22 2010The main reasons for searching for pulsars are to: (i) get an accurate census of the neutron star population and its origin and evolution; (ii) connect neutron stars to other stellar populations in the Galaxy and globular clusters; (iii) study Galactic ... More
Recent discoveries of energetic young radio pulsarsJan 16 2003The observed population of young radio pulsars has grown substantially in recent years due to a combination of large-scale surveys and deep targeted searches. Many of the pulsars are associated with supernova remnants and/or unidentified gamma-ray sources. ... More
Binary and Millisecond PulsarsNov 05 2008We review the main properties, demographics and applications of binary and millisecond radio pulsars. Our knowledge of these exciting objects has greatly increased in recent years, mainly due to successful surveys which have brought the known pulsar population ... More
Neutron Star Birth RatesNov 30 1999A crucial test any proposed evolutionary scenario must pass is can the birth rate of the sources we see be sustained by the proposed progenitor population? In this review, I investigate the methods used to determine the birth rates of normal and millisecond ... More
Binary and Millisecond Pulsars at the New MillenniumApr 24 2001We review the properties and applications of binary and millisecond pulsars. Our knowledge of these exciting objects has greatly increased in recent years, mainly due to successful surveys which have brought the known pulsar population to over 1300. There ... More
IAU 177 - A week in reviewNov 15 1999Nov 17 1999A look back at the recent IAU meeting "Pulsar Astronomy 2000 and beyond" held in Bonn.
Age constraints in the double pulsar system J0737-3039May 23 2007We investigate the age constraints that can be placed on the double pulsar system using models for the spin-down of the first-born 22.7-ms pulsar A and the 2.77-s pulsar B with characteristic ages of 210 and 50 Myr respectively. Standard models assuming ... More
Discovery of Three Wide-orbit Binary Pulsars: Implications for Binary Evolution and Equivalence PrinciplesJun 08 2005Jun 27 2005We report the discovery of three binary millisecond pulsars during the Parkes Multibeam Pulsar Survey of the Galactic Plane. The objects are highly recycled and are in orbits of many tens of days about low-mass white-dwarf companions. The eccentricity ... More
Yet MORE PM Survey Discoveries....?Jan 17 2003The Parkes Multibeam (PM) survey has found nearly 50% of the >1400 known pulsars and detected 20% of the pulsars in binary systems (75% within the survey area), few of these are millisecond pulsars with orbits of less than one day. It is known that the ... More
Pulsar Birthrate from Parkes Multi-beam SurveyOct 08 2003We report on calculations of the pulsar birthrate based on the results of the Parkes multibeam survey. From the observed sample of more than 800 pulsars, we compute the pulsar current, accounting as accurately as possible for all known selection effects. ... More
Compressive optical imaging with a photonic lanternMar 01 2019The thin and flexible nature of optical fibres often makes them the ideal technology to view biological processes in-vivo, but current microendoscopic approaches are limited in spatial resolution. Here, we demonstrate a new route to high resolution microendoscopy ... More
Binary and Millisecond PulsarsNov 09 2005We review the main properties, demographics and applications of binary and millisecond radio pulsars. Our knowledge of these exciting objects has greatly increased in recent years, mainly due to successful surveys which have brought the known pulsar population ... More
Radio Pulsars - An Observer's PerspectiveNov 17 1999Dec 01 1999Pulsar astronomy is currently enjoying one of the most productive phases in its history. In this review, I outline some of the basic observational aspects and summarise some of the latest results of searches for pulsars in the disk of our Galaxy and its ... More
Pulsar Searches - Tricks of the TradeJan 12 1998The study of pulsars has come a long way since their accidental discovery as ``scruff'' on pen chart recordings of the radio sky at 81 MHz by Jocelyn Bell and Anthony Hewish at Cambridge some thirty years ago. The present sample of almost 800 objects ... More
Radio pulsar populationsAug 11 2010The goal of this article is to summarize the current state of play in the field of radio pulsar statistics. Simply put, from the observed sample of objects from a variety of surveys with different telescopes, we wish to infer the properties of the underlying ... More
The Galactic population and birth rate of radio pulsarsAug 28 2003We review current understanding of the underlying, as opposed to the observed, pulsar population. The observed sample is heavily biased by selection effects, so that surveys see less than 10% of all potentially observable pulsars. We compare various techniques ... More
Online storage ring optimization using dimension-reduction and genetic algorithmsJul 27 2018Oct 19 2018Particle storage rings are a rich application domain for online optimization algorithms. The Cornell Electron Storage Ring (CESR) has hundreds of independently powered magnets, making it a high-dimensional test-problem for algorithmic tuning. We investigate ... More
Gravitational waves from intermediate-mass-ratio inspirals for ground-based detectorsDec 11 2006Mar 13 2008We explore the prospects for Advanced LIGO to detect gravitational waves from neutron stars and stellar mass black holes spiraling into intermediate-mass ($M\sim 50 M_\odot$ to $350 M_\odot$) black holes. We estimate an event rate for such \emph{intermediate-mass-ratio ... More
Mathieu Moonshine and N=2 String CompactificationsJun 20 2013Sep 11 2013There is a `Mathieu moonshine' relating the elliptic genus of K3 to the sporadic group M_{24}. Here, we give evidence that this moonshine extends to part of the web of dualities connecting heterotic strings compactified on K3 \times T^2 to type IIA strings ... More
Attractive Strings and Five-Branes, Skew-Holomorphic Jacobi Forms and MoonshineAug 24 2017Jul 23 2018We show that certain BPS counting functions for both fundamental strings and strings arising from fivebranes wrapping divisors in Calabi--Yau threefolds naturally give rise to skew-holomorphic Jacobi forms at rational and attractor points in the moduli ... More
Homogenization of lateral diffusion on a random surfaceJan 22 2014Jan 30 2014We study the problem of lateral diffusion on a static, quasi-planar surface generated by a stationary, ergodic random field possessing rapid small-scale spatial fluctuations. The aim is to study the effective behaviour of a particle undergoing Brownian ... More
Predator-Prey Behaviour in Self-Replicating Interstellar ProbesMar 02 2019The concept of a rapid spread of self-replicating interstellar probes (SRPs) throughout the Milky Way adds considerable strength to Fermi's Paradox. A single civilisation creating a single SRP is sufficient for a fleet of SRPs to grow and explore the ... More
Near Real-time Hippocampus Segmentation Using Patch-based Canonical Neural NetworkJul 15 2018Over the past decades, state-of-the-art medical image segmentation has heavily rested on signal processing paradigms, most notably registration-based label propagation and pair-wise patch comparison, which are generally slow despite a high segmentation ... More
Automorphisms of cubic surfaces in positive characteristicDec 04 2017Oct 12 2018We classify all possible automorphism groups of smooth cubic surfaces over an algebraically closed field of arbitrary characteristic. As an intermediate step we also classify automorphism groups of quartic del Pezzo surfaces. We show that the moduli space ... More
Pattern avoidance in ascent sequencesSep 16 2011Oct 30 2011Ascent sequences are sequences of nonnegative integers with restrictions on the size of each letter, depending on the number of ascents preceding it in the sequence. Ascent sequences have recently been related to (2+2)-free posets and various other combinatorial ... More
Asymptotic zero distribution of random orthogonal polynomialsJan 30 2018Mar 22 2018We consider random polynomials of the form $H_n(z)=\sum_{j=0}^n\xi_jq_j(z)$ where the $\{\xi_j\}$ are i.i.d non-degenerate complex random variables, and the $\{q_j(z)\}$ are orthonormal polynomials with respect to a compactly supported measure $\tau$ ... More
The Pulsar Search CollaboratoryMay 06 2010The Pulsar Search Collaboratory [PSC, NSF #0737641] is a joint project between the National Radio Astronomy Observatory (NRAO) and West Virginia University (WVU) designed to interest high school students in science, technology, engineering, and mathematics ... More
Pebble accretion in self-gravitating protostellar discsFeb 14 2019Pebble accretion has become a popular component to core accretion models of planet formation, and is especially relevant to the formation of compact, resonant terrestrial planetary systems. Pebbles initially form in the inner protoplanetary disc, sweeping ... More
High-Precision Dark Halo Virial Masses from Globular Cluster Numbers: Implications for Globular Cluster Formation and Galaxy AssemblyJan 03 2019We confirm that the number of globular clusters (GC) N$_{GC}$ is an excellent tracer of their host's dark halo virial mass M$_{vir}$. The simple linear relation M$_{vir} = 5 \times 10^9$ M$_{\odot} \times$ N$_{GC}$ fits the data perfectly from M$_{vir} ... More
Orientable and non-orientable genus $n$ Wicks forms over hyperbolic groupsSep 03 2015Sep 24 2015In 1962 M.J. Wicks gave a precise description of the form a commutator could take in a free group or a free product and in 1973 extended this description to cover a product of two squares. Subsequently, lists of "Wicks forms" were found for arbitrary ... More
Learning Multiple Categories on Deep Convolution NetworksFeb 21 2018Deep convolution networks have proved very successful with big datasets such as the 1000-classes ImageNet. Results show that the error rate increases slowly as the size of the dataset increases. Experiments presented here may explain why these networks ... More
Batch Normalization and the impact of batch structure on the behavior of deep convolution networksFeb 21 2018Batch normalization was introduced in 2015 to speed up training of deep convolution networks by normalizing the activations across the current batch to have zero mean and unity variance. The results presented here show an interesting aspect of batch normalization, ... More
On the nonlinearity of quantum dynamical entropyOct 12 2018Oct 20 2018Linearity of a dynamical entropy means that the dynamical entropy of the n-fold composition of a dynamical map with itself is equal to n times the dynamical entropy of the map for every positive integer n. We show that the quantum dynamical entropy introduced ... More