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Carbon Monoxide Clouds at Low-Metallicity in the WLM GalaxyOct 16 2013Carbon monoxide (CO) is the primary tracer for interstellar clouds where stars form, yet CO has never been detected in galaxies with an Oxygen abundance relative to Hydrogen less than 20% of solar, even though such low metallicity galaxies often form ... More

The Stellar Population and Star Clusters in the Unusual Local Group Galaxy IC 10May 25 2001We present analysis of HST U,V,I, and Halpha images of the peculiar Local Group irregular galaxy IC 10. The images are used to determine the nature of the stellar products in a portion of the recent starburst in this galaxy. We identified 13 stellar associations ... More

Dust and Gas as Seeds for Metal-Poor Star FormationOct 28 2008I address the issue of dust and gas as seeds for metal-poor star formation by reviewing what we know about star formation in nearby dwarf galaxies and its relationship to the gas and dust. I (try to) speculate on the extent to which processes in nearby ... More

Star Formation Properties of a Large Sample of Irregular GalaxiesAug 12 2004We present the results of Halpha imaging of 94 irregular galaxies, including types Im, BCD, and Sm. The sample spans a large range in galactic parameters including integrated absolute magnitude (MV=-9 to -19), average surface brightness (20 to 27 mag/arcsec2), ... More

The Distribution of Atomic Hydrogen Around Two Irregular GalaxiesFeb 07 2002We present radio interferometric observations of two irregular galaxies that were candidates for having unusually extended HI emission. The galaxies, UGC 199 and DDO 26, otherwise appeared to be normal, low-luminosity systems with modest star-formation ... More

In-spiraling Clumps in Blue Compact Dwarf GalaxiesJan 17 2012Giant star-formation clumps in dwarf irregular galaxies can have masses exceeding a few percent of the galaxy mass enclosed inside their orbital radii. They can produce sufficient torques on dark matter halo particles, halo stars, and the surrounding ... More

On the Disruption of Star Clusters in a Hierarchical Interstellar MediumFeb 15 2010The distribution of the number of clusters as a function of mass M and age T suggests that clusters get eroded or dispersed in a regular way over time, such that the cluster number decreases inversely as an approximate power law with T within each fixed ... More

Radial Profiles of Star Formation in the Far Outer Regions of Galaxy DisksSep 07 2005Star formation in galaxies is triggered by a combination of processes, including gravitational instabilities, spiral wave shocks, stellar compression, and turbulence compression. Some of these persist in the far outer regions where the column density ... More

Broad-Band Imaging of a Large Sample of Irregular GalaxiesSep 07 2005We present the results of UBV imaging of a large sample of irregular galaxies: 94 Im systems, 24 Blue Compact Dwarfs (BCDs), and 18 Sm galaxies. We also include JHK imaging of 41 of these galaxies. The sample spans a large range in galactic parameters. ... More

A Star Formation Law for Dwarf Irregular GalaxiesMar 15 2015The radial profiles of gas, stars, and far ultraviolet radiation in 20 dwarf Irregular galaxies are converted to stability parameters and scale heights for a test of the importance of two-dimensional (2D) instabilities in promoting star formation. A detailed ... More

The Star Clusters in the Irregular Galaxy NGC 4449Oct 25 2000We examine the star clusters in the irregular galaxy NGC 4449. We use a near-infrared spectrum and broad-band images taken with the HST to place a limit of 8--15 Myrs on the age of the bright central ojbect in NGC 4449. Its luminosity and size suggest ... More

The Relationship Between Gas, Stars, and Star Formation in Irregular Galaxies: A Test of Simple ModelsDec 31 1997We explore various instability models for the onset of star formation in irregular galaxies. Critical gas densities are calculated for gravitational instabilities with a thin, pure-gas disk, and with a thick disk composed of gas and a star-like fluid. ... More

Compact Star Clusters in Nearby Dwarf Irregular GalaxiesDec 12 2001Nearby dwarf irregular galaxies were searched for compact star clusters using data from the HST archives. Three of the galaxies were found to host both populous clusters (M_V<-9.5 at a fiducial age of 10 Myr) and super-star clusters (M_V<-10.5 at 10 Myr). ... More

Discovery of Recent Star Formation in the Extreme Outer Regions of Disk GalaxiesAug 14 1998We present deep Halpha images of three nearby late-type spiral galaxies (NGC628, NGC1058 and NGC6946), which reveal the presence of HII regions out to, and beyond, two optical radii (defined by the 25th B-band isophote). The outermost HII regions appear ... More

A High-Resolution Study of the HI Content of Local Group Dwarf Irregular Galaxy WLMFeb 21 2007Dwarf irregular galaxies are unique laboratories for studying the interaction between stars and the interstellar medium in low mass environments. We present the highest spatial resolution observations to date of the neutral hydrogen content of the Local ... More

Power Spectra in V-band and Halpha of Nine Irregular GalaxiesMar 14 2005Fourier transform power spectra of major axis cuts in V and Halpha images were made for a sample of 9 irregular galaxies. These power spectra reveal structure over a wide range of scales. For 6 of the galaxies the power spectrum slopes at intermediate ... More

GALEX Ultraviolet Imaging of Dwarf Galaxies and Star FormationNov 23 2009We present ultraviolet integrated and azimuthally-averaged surface photometric properties of a sample of 44 dIm, BCD, and Sm galaxies measured from archival NUV and FUV images obtained with GALEX. We compare the UV to Halpha and V-band properties and ... More

Turbulence and Star Formation in a Sample of Spiral GalaxiesAug 08 2016We investigate turbulent gas motions in spiral galaxies and their importance to star formation in far outer disks, where the column density is typically far below the critical value for spontaneous gravitational collapse. Following the methods of Burkhart ... More

Surface Brightness Profiles of Dwarf Galaxies: II. Color Trends and Mass ProfilesJun 02 2016In this second paper of a series, we explore the B-V, U-B, and FUV-NUV radial color trends from a multi-wavelength sample of 141 dwarf disk galaxies. Like spirals, dwarf galaxies have three types of radial surface brightness profiles: (I) single exponential ... More

Young star clusters in the outer disks of LITTLE THINGS dwarf irregular galaxiesMar 01 2016We examine FUV images of the LITTLE THINGS sample of nearby dwarf irregular (dIrr) and Blue Compact Dwarf (BCD) galaxies to identify distinct young regions in their far outer disks. We use these data, obtained with the Galaxy Evolution Explorer satellite, ... More

Shrinking Galaxy Disks with Fountain-Driven Accretion from the HaloNov 02 2014Star formation in most galaxies requires cosmic gas accretion because the gas consumption time is short compared to the Hubble time. This accretion presumably comes from a combination of infalling satellite debris, cold flows, and condensation of hot ... More

Mid-Infrared Images of Stars and Dust in Irregular GalaxiesApr 05 2006We present mid-infrared to optical properties of 22 representative irregular galaxies: 18 Im, 3 BCDs, and one Sm. The mid-IR is based on images from the Spitzer Space Telescope archives. The 3.6 and 4.5 micron bands and the UBVJHK images are used to examine ... More

Identifying Old Tidal Dwarf IrregularsMay 11 2000We examine the observational consequences of the two possible origins for irregular galaxies: formation from collapse of a primordial cloud of gas early in the age of the Universe, and formation from tidal tails in an interaction that could have occured ... More

DDO 88: A Galaxy-Sized Hole in the Interstellar MediumSep 29 2004We present an HI and optical study of the gas-rich dwarf irregular galaxy DDO 88. Although DDO 88's global optical and HI parameters are normal for its morphological type, it hosts a large (3 kpc diameter) and unusually complete ring of enhanced HI emission. ... More

Ongoing Massive Star Formation in NGC 604Oct 19 2012Oct 24 2012NGC 604 is the second most massive H II region in the Local Group, thus an important laboratory for massive star formation. Using a combination of observational and analytical tools that include Spitzer spectroscopy, Herschel photometry, Chandra imaging, ... More

HI Power Spectra and the Turbulent ISM of Dwarf Irregular GalaxiesMay 16 2012HI spatial power spectra (PS) were determined for a sample of 24 nearby dwarf irregular galaxies selected from the LITTLE THINGS (Local Irregulars That Trace Luminosity Extremes - The HI Nearby Galaxy Survey) sample. The two-dimensional (2D) power spectral ... More

Surface Brightness Profiles of Dwarf Galaxies: I. Profiles and StatisticsAug 30 2013Radial surface brightness profiles of spiral galaxies are classified into three types: (I) single exponential, or the light falls off with one exponential to a break before falling off (II) more steeply, or (III) less steeply. Profile breaks are also ... More

DDO 43: A Prototypical Dwarf Irregular Galaxy?Jun 06 2005We present sensitive and high resolution 21 cm observations of the dwarf irregular (dIm) galaxy DDO 43, in conjunction with optical broad and narrow band images in U, B, V, and Halpha. The observations are used to examine the relationship between its ... More

The Nature of Low-Density Star FormationMar 13 2019How do stars manage to form within low-density, HI-dominated gas? Such environments provide a laboratory for studying star formation with physical conditions distinct from starbursts and the metal-rich disks of spiral galaxies where most effort has been ... More

Outside-in Shrinking of the Star-forming Disk of Dwarf Irregular GalaxiesNov 14 2011We have studied multi-band surface brightness profiles of a representative sample of 34 nearby dwarf irregular galaxies (dIrrs). Our data include GALEX FUV/NUV, UBV, H\alpha, and Spitzer 3.6 \mum images. These galaxies constitute the majority of the LITTLE ... More

The Stellar and Gas Kinematics of Several Irregular GalaxiesJul 23 2002We present long-slit spectra of three irregular galaxies from which we determinethe stellar kinematics in two of the galaxies (NGC 1156 and NGC 4449) and ionized-gas kinematics in all three (including NGC 2366). We compare this to the optical morphology ... More

Diffuse Ionized Gas in Spiral Galaxies: Probing Photon Leakage from HII Regions?Feb 14 1996As part of a large study to map the distribution of star formation across galactic disks, we have obtained deep Halpha images of the nearby Sculptor Group spirals NGC 247 and NGC 7793. These images are of sufficiently high quality that they allow identification ... More

Bright Ultraviolet Regions and Star Formation Characteristics in Nearby Dwarf GalaxiesAug 20 2009We compare star formation in the inner and outer disks of 11 dwarf Irregular galaxies (dIm) within 3.6 Mpc. The regions are identified on GALEX near-UV images, and modeled with UV, optical, and near-IR colors to determine masses and ages. A few galaxies ... More

Dense cloud cores revealed by CO in the low metallicity dwarf galaxy WLMMar 15 2016Understanding stellar birth requires observations of the clouds in which they form. These clouds are dense and self-gravitating, and in all existing observations, they are molecular with H_2 the dominant species and CO the best available tracer. When ... More

Reachability in succinct one-counter gamesJul 08 2014Jul 18 2014We consider the reachability problem on transition systems corresponding to succinct one-counter machines, that is, machines where the counter is incremented or decremented by a value given in binary.

The expressiveness of MTL with countingSep 04 2012It is well known that MTL with integer endpoints is unable to express all of monadic first-order logic of order and metric (FO(<,+1)). Indeed, MTL is unable to express the counting modalities $C_n$ that assert a properties holds $n$ times in the next ... More

VC density and dp rankAug 22 2011Aug 25 2011We derive that dpR(n) \leq dens(n) \leq dpR(n)+1, where dens(n) is the supremum of the VC density of all formulas in n parameters, and dpR(n) is the maximum depth of an ICT pattern in n variables. Consequently, strong dependence is equivalent to finite ... More

Nonnegative Eigenvectors of Symmetric MatricesAug 28 2018For matrices with all nonnegative entries, the Perron-Frobenius theorem guarantees the existence of an eigenvector with all nonnegative components. We show that the existence of such an eigenvector is also guaranteed for a very different class of matrices, ... More

Modified diagonals and linear relations between small diagonalsOct 01 2018We prove that the vanishings of the modified diagonal cycles of Gross and Schoen govern the $\mathbb{Z}$-linear relations between small $m$-diagonals $\text{pt}^{\{1,\ldots,n\}\setminus A}\times\Delta_A$ in the rational Chow ring of $X^n$ for $A$ ranging ... More

Belief Revision and TrustApr 30 2014Belief revision is the process in which an agent incorporates a new piece of information together with a pre-existing set of beliefs. When the new information comes in the form of a report from another agent, then it is clear that we must first determine ... More

LIFO-search on digraphs: A searching game for cycle-rankMar 30 2011Aug 04 2011We consider the extension of the last-in-first-out graph searching game of Giannopoulou and Thilikos to digraphs. We show that all common variations of the game require the same number of searchers, and the minimal number of searchers required is one ... More

Some new maximum VC classesSep 08 2013Set systems of finite VC dimension are frequently used in applications relating to machine learning theory and statistics. Two simple types of VC classes which have been widely studied are the maximum classes (those which are extremal with respect to ... More

Maximum VC familiesJun 01 2011Jun 02 2011Maximum VC classes which are stable in the sense of model theory are characterized.

Mapping the Extended HI Distribution of Three Dwarf GalaxiesSep 13 2011We present large field HI-line emission maps obtained with the single-dish Green Bank Telescope centered on the dwarf irregular galaxies Sextans A, NGC 2366, and WLM. We do not detect the extended skirts of emission associated with the galaxies that were ... More

The stellar velocity dispersion in the inner 1.3 disk scale-lengths of the irregular galaxy NGC 4449Aug 13 2005We present measurements of the stellar velocity dispersion in the inner 1 arcmin radius (1.3 disk scale-lengths) of the irregular galaxy NGC 4449 determined from long-slit absorption-line spectra. The average observed dispersion is 29 +/-2 km/s, the same ... More

Measuring Inconsistency in Argument GraphsAug 09 2017There have been a number of developments in measuring inconsistency in logic-based representations of knowledge. In contrast, the development of inconsistency measures for computational models of argument has been limited. To address this shortcoming, ... More

Expected Number of Vertices of a Hypercube SliceAug 28 2018Given a random k-dimensional cross-section of a hypercube, what is its expected number of vertices? We show that, for a suitable distribution of random slices, the answer is $2^k$, independent of the dimension of the hypercube.

Dp-rank and forbidden configurationsAug 31 2011Nov 07 2011A theory $T$ is shown to have an ICT pattern of depth $k$ in variables $\xbar$ iff it interprets some $k$-maximum VC class in $|\xbar|$ parameters.

Orthogonal Symmetric Chain Decompositions of HypercubesJun 26 2017Jun 28 2017In 1979, Shearer and Kleitman conjectured that there exist $\lfloor n/2 \rfloor+1$ orthogonal chain decompositions of the hypercube $Q_n$, and constructed two orthogonal chain decompositions. In this paper, we make the first non-trivial progress on this ... More

Local Maxima of Quadratic Boolean FunctionsOct 06 2013How many strict local maxima can a real quadratic function on $\{0,1\}^n$ have? Holzman conjectured a maximum of $n \choose \lfloor n/2 \rfloor$. The aim of this paper is to prove this conjecture. Our approach is via a generalization of Sperner's theorem ... More

Analysis of Dialogical Argumentation via Finite State MachinesApr 29 2014Dialogical argumentation is an important cognitive activity by which agents exchange arguments and counterarguments as part of some process such as discussion, debate, persuasion and negotiation. Whilst numerous formal systems have been proposed, there ... More

Ordinal Conditional Functions for Nearly Counterfactual RevisionMar 31 2016We are interested in belief revision involving conditional statements where the antecedent is almost certainly false. To represent such problems, we use Ordinal Conditional Functions that may take infinite values. We model belief change in this context ... More

Reconciling MPEG-7 and MPEG-21 Semantics through a Common Event-Aware Metadata ModelOct 22 2002The "event" concept appears repeatedly when developing metadata models for the description and management of multimedia content. During the typical life cycle of multimedia content, events occur at many different levels - from the events which happen ... More

Monge-Ampère IterationDec 07 2017In a recent paper, Darvas-Rubinstein proved a convergence result for the Kahler-Ricci iteration, which is a sequence of recursively defined complex Monge-Ampere equations. We introduce the Monge-Ampere iteration to be an analogous, but more general, sequence ... More

Non-monotonic Reasoning in Deductive ArgumentationSep 04 2018Argumentation is a non-monotonic process. This reflects the fact that argumentation involves uncertain information, and so new information can cause a change in the conclusions drawn. However, the base logic does not need to be non-monotonic. Indeed, ... More

The Outer Disks of Dwarf Irregular GalaxiesJul 27 2011To explore the properties of extreme outer stellar disks, we obtained ultra-deep V and GALEX UV images of 4 dwarf irregular galaxies and one Blue Compact Dwarf galaxy and ultra-deep B images of 3 of these. Our V-band surface photometry extends to 29.5 ... More

A study of two dwarf irregular galaxies with asymmetrical star formation distributionsFeb 06 2018Two dwarf irregular galaxies DDO 187 and NGC 3738 exhibit a striking pattern of star formation: intense star formation is taking place in a large region occupying roughly half of the inner part of the optical galaxy. We use data on the HI distribution ... More

The Stellar and Gas Kinematics of the LITTLE THINGS Dwarf Irregular Galaxy NGC 1569Sep 11 2012In order to understand the formation and evolution of dIm galaxies, one needs to understand their three-dimensional structure. We present measurements of the stellar velocity dispersion in NGC 1569, a nearby post-starburst dIm galaxy. The stellar vertical ... More

The Shape of LITTLE THINGS Dwarf Galaxies DDO 46 and DDO 168: Understanding the stellar and gas kinematicsApr 25 2015We present the stellar and gas kinematics of DDO 46 and DDO 168 from the LITTLE THINGS survey and determine their respective Vmax/sigma_z,0 values. We used the KPNO's 4-meter telescope with the Echelle spectrograph as a long-slit spectrograph. We acquired ... More

A Radio Continuum Study of Dwarf Galaxies: 6 cm imaging of Little ThingsJan 16 2018In this paper we examine to what extent the radio continuum can be used as an extinction free probe of star formation in dwarf galaxies. To that aim we observe $40$ nearby dwarf galaxies with the Very Large Array at 6 cm ($4$-$8$ GHz) in C-configuration. ... More

Star Formation in Two Luminous Spiral GalaxiesJul 26 2013We have examined star formation in two very luminous (M_V=-22 to -23) Sc-type spiral galaxies, NGC 801 and UGC 2885, using ultra-deep Halpha images. We combine these with UBV and 2MASS JHK images and HI maps to explore the star formation characteristics ... More

Performance Analysis of Spectral Clustering on Compressed, Incomplete and Inaccurate MeasurementsNov 03 2010Spectral clustering is one of the most widely used techniques for extracting the underlying global structure of a data set. Compressed sensing and matrix completion have emerged as prevailing methods for efficiently recovering sparse and partially observed ... More

Cell-cycle regulated transcription associates with DNA replication timing in yeast and humanAug 08 2013Eukaryotic DNA replication follows a specific temporal program, with some genomic regions consistently replicating earlier than others, yet what determines this program is largely unknown. Highly transcribed regions have been observed to replicate in ... More

Distributed Protocols for Interference Management in Cooperative NetworksSep 21 2011In scenarios where devices are too small to support MIMO antenna arrays, symbol-level cooperation may be used to pool the resources of distributed single-antenna devices to create a virtual MIMO antenna array. We address design fundamentals for distributed ... More

Short-Time Existence for Scale-Invariant Hamiltonian WavesNov 02 2005We prove short-time existence of smooth solutions for a class of nonlinear, and in general spatially nonlocal, Hamiltonian evolution equations that describe the self-interaction of weakly nonlinear scale-invariant waves. These equations include ones that ... More

Vapnik-Chervonenkis density on indiscernible sequences, stability, and the maximum propertyFeb 21 2013Aug 08 2013This paper presents some finite combinatorics of set systems with applications to model theory, particularly the study of dependent theories. There are two main results. First, we give a way of producing lower bounds on VC_ind-density, and use it to compute ... More

Tuning turbine rotor design for very large wind farmsMar 11 2018Nov 17 2018A new theoretical method is presented for future multi-scale aerodynamic optimisation of very large wind farms. The new method combines a recent two-scale coupled momentum analysis of ideal wind turbine arrays with the classical blade-element-momentum ... More

Kemeny's Function for Markov Chains and Markov Renewal ProcessesFeb 22 2018Feb 26 2018Extensions of Kemeny's constant, as derived for irreducible finite Markov chains in discrete time, to Markov renewal processes and Markov chains in continuous time are discussed. Three alternative Kemeny's functions and their variants are considered. ... More

Incidence strata of affine varieties with complex multiplicitiesMar 12 2019To each affine variety $X$ and $m_1,\ldots,m_k\in \mathbb{C}$ such that no subset of the $m_i$ add to zero, we construct a variety which for $m_1,\ldots,m_k \in \mathbb{N}$ specializes to the closed $(m_1,\ldots,m_k)$-incidence stratum of $Sym^{m_1+\ldots+m_k}X$. ... More

The classification of Hamiltonian stationary Lagrangian tori in the complex projective plane by their spectral dataApr 12 2010Jan 12 2011It is known that all weakly conformal Hamiltonian stationary Lagrangian immersions of tori in the complex projective plane may be constructed by methods from integrable systems theory. This article describes the precise details of a construction which ... More

Model theory and combinatorics of banned sequencesJan 23 2018We set up a general context in which one can prove Sauer-Shelah type lemmas. We apply our general results to answer a question of Bhaskar and give a slight improvement to a result of Malliaris and Terry. We also prove a new Sauer-Shelah type lemma in ... More

An Expectation-Maximization Algorithm for the Matrix Normal DistributionSep 25 2013Dramatic increases in the size and dimensionality of many recent data sets make crucial the need for sophisticated methods that can exploit inherent structure and handle missing values. In this article we derive an expectation-maximization (EM) algorithm ... More

The Computation of Key Properties of Markov Chains via PerturbationsFeb 17 2016Oct 09 2016Computational procedures for the stationary probability distribution, the group inverse of the Markovian kernel and the mean first passage times of an irreducible Markov chain, are developed using perturbations. The derivation of these expressions involves ... More

The non-thermal superbubble in IC 10: the generation of cosmic ray electrons caught in the actNov 06 2014Nov 24 2014Superbubbles are crucial for stellar feedback, with supposedly high (of the order of 10 per cent) thermalization rates. We combined multiband radio continuum observations from the Very Large Array (VLA) with Effelsberg data to study the non-thermal superbubble ... More

Accurate calculations of stationary distributions and mean first passage times in Markov renewal processes and Markov chainsOct 05 2015Feb 15 2016This article describes an accurate procedure for computing the mean first passage times of a finite irreducible Markov chain and a Markov renewal process. The method is a refinement to the Kohlas, Zeit fur Oper Res, 30,197-207, (1986) procedure. The technique ... More

Encoding monotonic multi-set preferences using CI-nets: preliminary reportNov 09 2016CP-nets and their variants constitute one of the main AI approaches for specifying and reasoning about preferences. CI-nets, in particular, are a CP-inspired formalism for representing ordinal preferences over sets of goods, which are typically required ... More

Generalized inverses of Markovian kernels in terms of properties of the Markov chainSep 17 2012All one-condition generalized inverses of the Markovian kernel I - P, where P is the transition matrix of a finite irreducible Markov chain, can be uniquely specified in terms of the stationary probabilities and the mean first passage times of the underlying ... More

The Distribution of Mixing Times in Markov ChainsNov 01 2011The distribution of the "mixing time" or the "time to stationarity" in a discrete time irreducible Markov chain, starting in state i, can be defined as the number of trials to reach a state sampled from the stationary distribution of the Markov chain. ... More

The Computation of the Mean First Passage Times for Markov ChainsJan 15 2017Mar 16 2018A survey of a variety of computational procedures for finding the mean first passage times in Markov chains is presented. The author recently developed a new accurate computational technique, an Extended GTH Procedure, Hunter (Special Matrices, 2016) ... More

A Moduli Space of the Quaternionic Hopf Surface Encodes Standard Model PhysicsSep 13 2012The quaternionic Hopf surface, HL, is associated with a non-compact moduli space, ML, of stable holomorphic SL(2,C) bundles. ML is open in MLc, the corresponding compact moduli space of holomorphic SL(2,C) bundles, and naturally fibers over an open set ... More

The Action of Instantons with Nut ChargeJul 05 1998We examine the effect of a non-trivial nut charge on the action of non-compact four-dimensional instantons with a U(1) isometry. If the instanton action is calculated by dimensionally reducing along the isometry, then the nut charge is found to make an ... More

Model Theory and Machine LearningJan 19 2018About 25 years ago, it came to light that a single combinatorial property determines both an important dividing line in model theory (NIP) and machine learning (PAC-learnability). The following years saw a fruitful exchange of ideas between PAC learning ... More

The Derivation of Markov Chain Properties using Generalized Matrix InversesDec 15 2011The analysis of many problems of interest associated with Markov chains, e.g. stationary distributions, moments of first passage time distributions and moments of occupation time random variables, involves the solution of a system of linear equations ... More

Markov chain properties in terms of column sums of the transition matrixNov 01 2011Questions are posed regarding the influence that the column sums of the transition probabilities of a stochastic matrix (with row sums all one) have on the stationary distribution, the mean first passage times and the Kemeny constant of the associated ... More

Judiciously 3-partitioning 3-uniform hypergraphsOct 03 2018Bollob\'as, Reed and Thomason proved every $3$-uniform hypergraph $\mathcal{H}$ with $m$ edges has a vertex-partition $V(\mathcal{H})=V_1 \sqcup V_2 \sqcup V_3$ such that each part meets at least $\frac{1}{3}(1-\frac{1}{e})m$ edges, later improved to ... More

$PGL_2$-equivariant strata of point configurations in $\mathbb{P}^1$Aug 17 2018Sep 04 2018We compute the integral Chow ring of the quotient stack $[(\mathbb{P}^1)^n/PGL_2]$, which contains $\mathcal{M}_{0,n}$ as a dense open, and determine a natural $\mathbb{Z}$-basis for the Chow ring in terms of certain ordered incidence strata. We further ... More

Probabilistic Argumentation with Epistemic Extensions and Incomplete InformationMay 14 2014Abstract argumentation offers an appealing way of representing and evaluating arguments and counterarguments. This approach can be enhanced by a probability assignment to each argument. There are various interpretations that can be ascribed to this assignment. ... More

Enhanced Lifespan of Smooth Solutions of a Burgers-Hilbert EquationDec 05 2011We consider an initial value problem for a quadratically nonlinear inviscid Burgers-Hilbert equation that models the motion of vorticity discontinuities. We use a normal form transformation, which is implemented by means of a near-identity coordinate ... More

Empirical Evaluation of Abstract Argumentation: Supporting the Need for Bipolar and Probabilistic ApproachesJul 28 2017Dec 08 2017In dialogical argumentation it is often assumed that the involved parties always correctly identify the intended statements posited by each other, realize all of the associated relations, conform to the three acceptability states (accepted, rejected, ... More

The Role of Kemeny's Constant in Properties of Markov ChainsAug 23 2012In a finite state irreducible Markov chain with stationary probabilities \pi_i and mean first passage times m_(ij) (mean recurrence time when i = j) it was first shown by Kemeny and Snell (1960) that \sum_j \pi_j m_(ij) is a constant K, not depending ... More

Herschel Spectroscopic Observations of LITTLE THINGS Dwarf GalaxiesSep 29 2015We present far-infrared spectral line observations of five galaxies from the LITTLE THINGS sample: DDO 69, DDO 70, DDO 75, DDO 155, and WLM. While most studies of dwarfs focus on bright systems or starbursts due to observational constraints, our data ... More

Unstable Bar and Spiral Modes of Disk GalaxiesMar 11 2005We study bisymmetric modes of angular wavenumber 2 for flat stellar disks in potentials with smooth cores. Stars either all circulate in the same direction or a small fraction may counter-rotate. The bisymmetric modes are unstable unless there is a sufficiently ... More

Large amplitude gravitational wavesDec 04 1998We derive an asymptotic solution of the Einstein field equations which describes the propagation of a thin, large amplitude gravitational wave into a curved space-time. The resulting equations have the same form as the colliding plane wave equations without ... More

Why the Kemeny Time is a ConstantOct 02 2015Nov 03 2015We present a new fundamental intuition for why the Kemeny feature of a Markov chain is a constant. This new perspective has interesting further implications

Local versus Global Search in Channel GraphsApr 15 2010Previous studies of search in channel graphs has assumed that the search is global; that is, that the status of any link can be probed by the search algorithm at any time. We consider for the first time local search, for which only links to which an idle ... More

The impact of the phase-space density on the indirect detection of dark matterJun 27 2013We study the indirect detection of dark matter when the local dark matter velocity distribution depends upon position, as expected for the Milky Way and its dwarf spheroidal satellites, and the annihilation cross-section is not purely s-wave. Using a ... More

Clustering Via Finite Nonparametric ICA Mixture ModelsOct 28 2015Sep 10 2018We propose an extension of non-parametric multivariate finite mixture models by dropping the standard conditional independence assumption and incorporating the independent component analysis (ICA) structure instead. We formulate an objective function ... More

Iterated Belief Change Due to Actions and ObservationsJan 16 2014In action domains where agents may have erroneous beliefs, reasoning about the effects of actions involves reasoning about belief change. In this paper, we use a transition system approach to reason about the evolution of an agents beliefs as actions ... More

Quantitative games with interval objectivesApr 18 2014Traditionally quantitative games such as mean-payoff games and discount sum games have two players -- one trying to maximize the payoff, the other trying to minimize it. The associated decision problem, "Can Eve (the maximizer) achieve, for example, a ... More

Diffractive Nonlinear Geometrical Optics for Variational Wave Equations and the Einstein EquationsNov 02 2005We derive an asymptotic solution of the vacuum Einstein equations that describes the propagation and diffraction of a localized, large-amplitude, rapidly-varying gravitational wave. We compare and contrast the resulting theory of strongly nonlinear geometrical ... More