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Eternal Inflation and the Refined Swampland ConjectureNov 28 2018Nov 30 2018I apply recently proposed "Swampland" conjectures to eternal inflation in single-scalar field theories. Eternal inflation is a phase of infinite self-reproduction of a quasi-de Sitter universe which has been argued to be a generic consequence of cosmological ... More

Non-canonical generalizations of slow-roll inflation modelsOct 01 2008Oct 29 2008We consider non-canonical generalizations of two classes of simple single-field inflation models. First, we study the non-canonical version of "ultra-slow roll" inflation, which is a class of inflation models for which quantum modes do not freeze at horizon ... More

Monte Carlo reconstruction of the inflationary potentialOct 15 2002Nov 07 2002We present Monte Carlo reconstruction, a new method for ``inverting'' observational data to constrain the form of the scalar field potential responsible for inflation. This stochastic technique is based on the flow equation formalism and has distinct ... More

Attractor Solutions in Tachyacoustic CosmologyJun 13 2012Sep 22 2012We study the dynamical stability of "tachyacoustic" cosmological models, in which primordial perturbations are generated by a shrinking sound horizon during a period of decelerating expansion. Such models represent a potential alternative to inflationary ... More

Measuring the cosmological lepton asymmetry through the CMB anisotropyMar 23 1999Apr 23 1999A large lepton asymmetry in the Universe is still a viable possibility and leads to many interesting phenomena such as gauge symmetry nonrestoration at high temperature. We show that a large lepton asymmetry changes the predicted cosmic microwave background ... More

The Ultimate Fate of Life in an Accelerating UniverseMay 17 2002May 24 2002The ultimate fate of life in a universe with accelerated expansion is considered. Previous work showed that life cannot go on indefinitely in a universe dominated by a cosmological constant. In this paper we consider instead other models of acceleration ... More

A Signature of Inflation from Dynamical Supersymmetry BreakingFeb 27 1998In models of cosmological inflation motivated by dynamical supersymmetry breaking, the potential driving inflation may be characterized by inverse powers of a scalar field. These models produce observables similar to those typical of the hybrid inflation ... More

Negative running prevents eternal inflationApr 17 2014Jun 04 2014Current data from the Planck satellite and the BICEP2 telescope favor, at around the $2 \sigma$ level, negative running of the spectral index of curvature perturbations from inflation. We show that for negative running $\alpha < 0$, the curvature perturbation ... More

Theoretical Uncertainties in Inflationary PredictionsNov 04 2005Mar 09 2006With present and future observations becoming of higher and higher quality, it is timely and necessary to investigate the most significant theoretical uncertainties in the predictions of inflation. We show that our ignorance of the entire history of the ... More

Back reaction of a long range force on a Friedmann-Robertson-Walker backgroundJun 07 2000It is possible that there may exist long-range forces in addition to gravity. In this paper we construct a simple model for such a force based on exchange of a massless scalar field and analyze its effect on the evolution of a homogeneous Friedmann-Robertson-Walker ... More

Slow roll in simple non-canonical inflationJan 11 2007Jan 16 2007We consider inflation using a class of non-canonical Lagrangians for which the modification to the kinetic term depends on the field, but not its derivatives. We generalize the standard Hubble slow roll expansion to the non-canonical case and derive expressions ... More

Natural Inflation: Consistency with Cosmic Microwave Background Observations of Planck and BICEP2Mar 20 2014May 29 2014Natural inflation is a good fit to all cosmic microwave background (CMB) data and may be the correct description of an early inflationary expansion of the Universe. The large angular scale CMB polarization experiment BICEP2 has announced a major discovery, ... More

Dynamical Supersymmetric InflationApr 23 1997We propose a new class of inflationary models in which the scalar field potential governing inflation is generated by the same non-perturbative gauge dynamics that may lead to supersymmetry breaking. Such models satisfy constraints from cosmic microwave ... More

Short Distance Physics and the Consistency Relation for Scalar and Tensor Fluctuations in the Inflationary UniverseSep 07 2001May 30 2002Recent discussions suggest the possibility that short distance physics can significantly modify the behavior of quantum fluctuations in the inflationary universe, and alter the standard large scale structure predictions. Such modifications can be viewed ... More

On: Natural InflationApr 01 2004Sep 27 2004We re-examine the original model of Natural inflation, in which the inflaton is a pseudo Nambu-Goldstone boson with potential of the form $ V(\phi) = \Lambda^4 [1 \pm \cos(\phi/f)]$, in light of recent data. We find that the model is alive and well. Successful ... More

An attempt to do without dark matterJun 30 2000The discrepancy between dynamical mass measures of objects such as galaxies and the observed distribution of luminous matter in the universe is typically explained by invoking an unseen ``dark matter'' component. Dark matter must necessarily be non-baryonic. ... More

Observing Trans-Planckian Signatures in the Cosmic Microwave BackgroundDec 23 2004Mar 11 2005We examine the constraints cosmological observations can place on any trans-Planckian corrections to the primordial spectrum of perturbations underlying the anisotropies in the Cosmic Microwave Background. We focus on models of trans-Planckian physics ... More

Natural Inflation: the status after WMAP 3-year dataFeb 02 2008The model of Natural Inflation is examined in light of recent 3-year data from the Wilkinson Microwave Anisotropy Probe and shown to provide a good fit. The inflaton potential is naturally flat due to shift symmetries, and in the simplest version takes ... More

Gravitational wave production by Hawking radiation from rotating primordial black holesNov 18 2015Oct 11 2016In this paper we analyze in detail a rarely discussed question of gravity wave production from evaporating primordial black holes. These black holes emit gravitons which are, at classical level, registered as gravity waves. We use the latest constraints ... More

The zoo plot meets the swampland: mutual (in)consistency of single-field inflation, string conjectures, and cosmological dataAug 20 2018Apr 16 2019We consider single-field inflation in light of string-motivated "swampland" conjectures suggesting that effective scalar field theories with a consistent UV completion must have field excursion $\Delta \phi \lesssim M_{\rm Pl}$, in combination with a ... More

Inflationary potentials in DBI modelsJul 07 2009Aug 05 2009We study DBI inflation based upon a general model characterized by a power-law flow parameter $\epsilon(\phi)\propto\phi^{\alpha}$ and speed of sound $c_s(\phi)\propto\phi^{\beta}$, where $\alpha$ and $\beta$ are constants. We show that in the slow-roll ... More

Flow in Cyclic CosmologyJul 05 2010Jul 14 2010In this paper, we use a known duality between expanding and contracting cosmologies to construct a dual of the inflationary flow hierarchy applicable to contracting cosmologies such as Ekpyrotic and Cyclic models. We show that the inflationary flow equations ... More

Cosmology with a long range repulsive forceOct 12 2001Apr 16 2002We consider a class of cosmological models in which the universe is filled with a (non-electric) charge density that repels itself by means of a force carried by a vector boson with a tiny mass. When the vector's mass depends upon other fields, the repulsive ... More

Planck Limits on Non-canonical Generalizations of Large-field Inflation ModelsSep 28 2016In this paper, we consider two case examples of Dirac-Born-Infeld (DBI) generalizations of canonical large-field inflation models, characterized by a reduced sound speed, $c_{S} < 1$. The reduced speed of sound lowers the tensor-scalar ratio, improving ... More

Large-$η$ Constant-Roll Inflation Is Never An AttractorApr 05 2018Apr 25 2018Slow roll solutions to inflationary potentials have been widely believed to be the only universal attractor. Over the last few years there has been growing interest in a new class of inflationary models known as Constant-Roll Inflation. Constant roll ... More

Cosmology with a long-range repulsive forceMay 06 2002We discuss the properties of a cosmology dominated by a charged scalar field with a repulsive, long-range self-interaction. The interaction, in the form of a vector field with a tiny mass, can have a dramatic effect on the evolution of the universe, with ... More

The pre-inflationary vacuum in the cosmic microwave backgroundNov 30 2006Aug 09 2007We consider the effects on the primordial power spectrum of a period of radiation-dominated expansion prior to the inflationary era. If inflation lasts a total of only 60 e-folds or so, the boundary condition for quantum modes cannot be taken in the short-wavelength ... More

Boundary Effective Field Theory and Trans-Planckian Perturbations: Astrophysical ImplicationsMay 20 2005Jul 01 2005We contrast two approaches to calculating trans-Planckian corrections to the inflationary perturbation spectrum: the New Physics Hypersurface [NPH] model, in which modes are normalized when their physical wavelength first exceeds a critical value, and ... More

Symmetron InflationJul 16 2013Apr 01 2014We define a new inflationary scenario in which inflation starts naturally after the Big Bang when the energy density drops below some critical value. As a model, we use recently proposed symmetron field whose effective potential depends on the energy ... More

Consistency of Tachyacoustic Cosmology with de Sitter Swampland ConjecturesDec 11 2018Jan 10 2019Recent studies show that there is tension between the de Sitter swampland conjectures proposed by Obeid, et al. and inflationary cosmology. In this paper, we consider an alternative to inflation, `tachyacoustic' cosmology, in light of swampland conjectures. ... More

Phantom Dirac-Born-Infeld Dark EnergyOct 12 2017Mar 09 2018Motivated by the apparent discrepancy between Cosmic Microwave Background measurements of the Hubble constant and measurements from Type-Ia supernovae, we construct a model for Dark Energy with equation of state $w = p / \rho < -1$, violating the Null ... More

The Phantom Bounce: A New Proposal for an Oscillating CosmologyFeb 19 2008Feb 27 2008An oscillating universe cycles through a series of expansions and contractions. We propose a model in which ``phantom'' energy with a supernegative pressure ($p < - \rho$) grows rapidly and dominates the late-time expanding phase. The universe's energy ... More

The Phantom Bounce: A New Oscillating CosmologyMay 18 2004Feb 20 2008An oscillating universe cycles through a series of expansions and contractions. We propose a model in which ``phantom'' energy with $p < -\rho$ grows rapidly and dominates the late-time expanding phase. The universe's energy density is so large that the ... More

Dynamical Analysis of Attractor Behavior in Constant Roll InflationApr 12 2019May 29 2019There has been considerable recent interest in a new class of non-slow roll inflationary solutions known as \textit{constant roll} inflation. Constant roll solutions are a generalization of the ultra-slow roll (USR) solution, where the first Hubble slow ... More

Latest inflation model constraints from cosmic microwave background measurementsMay 19 2008Sep 26 2008In this addendum to Phys.Rev. D74 (2006) 023502, we present an update of cosmological constraints on single-field inflation in light of the Wilkinson Microwave Ansiotropy Probe satellite mission five-year results (WMAP5). We find that the cosmic microwave ... More

Inflation as a Probe of Short Distance PhysicsApr 11 2001May 18 2001We show that a string-inspired Planck scale modification of general relativity can have observable cosmological effects. Specifically, we present a complete analysis of the inflationary perturbation spectrum produced by a phenomenological Lagrangian that ... More

General conditions for scale-invariant perturbations in an expanding universeJul 06 2011We investigate the general properties of expanding cosmological models which generate scale-invariant curvature perturbations in the presence of a variable speed of sound. We show that in an expanding universe, generation of a super-Hubble, nearly scale-invariant ... More

Cosmic Microwave Background Observations as a Way to Discriminate Among Inflation ModelsApr 03 1998The upcoming satellite missions MAP and Planck will measure the spectrum of fluctuations in the Cosmic Microwave Background with unprecedented accuracy. We discuss the prospect of using these observations to distinguish among proposed models of inflationary ... More

The Lyth Bound and the End of InflationJan 12 2006Jul 07 2006We derive an extended version of the well-known Lyth Bound on the total variation of the inflaton field, incorporating higher order corrections in slow roll. We connect the field variation $\Delta\phi$ to both the spectral index of scalar perturbations ... More

Flavor versus mass eigenstates in neutrino asymmetries: implications for cosmologySep 11 2016We show that, if they exist, lepton number asymmetries ($L_\alpha$) of neutrino flavors should be distinguished from the ones ($L_i$) of mass eigenstates, since Big Bang Nucleosynthesis (BBN) bounds on the flavor eigenstates cannot be directly applied ... More

Measuring the cosmological bulk flow using the peculiar velocities of supernovaeFeb 03 2011Apr 14 2011We study large-scale coherent motion in our universe using the existing Type IA supernovae data. If the recently observed bulk flow is real, then some imprint must be left on supernovae motion. We run a series of Monte Carlo Markov Chain runs in various ... More

Dynamical Analysis of Attractor Behavior in Constant Roll InflationApr 12 2019There has been considerable recent interest in a new class of non-slow roll inflationary solutions known as \textit{constant roll} inflation. Constant roll solutions are a generalization of the ultra-slow roll (USR) solution, where the first Hubble slow ... More

Inflation model constraints from the Wilkinson Microwave Anisotropy Probe three-year dataMay 13 2006We extract parameters relevant for distinguishing among single-field inflation models from the Wilkinson Microwave Anisotropy Probe (WMAP) three-year data set, and also from WMAP in combination with the Sloan Digital Sky Survey (SDSS) galaxy power spectrum. ... More

A generic estimate of trans-Planckian modifications to the primordial power spectrum in inflationApr 16 2002We derive a general expression for the power spectra of scalar and tensor fluctuations generated during inflation given an arbitrary choice of boundary condition for the mode function at a short distance. We assume that the boundary condition is specified ... More

Imprints of Short Distance Physics On Inflationary CosmologyOct 24 2001Apr 16 2002We analyze the impact of certain modifications to short distance physics on the inflationary perturbation spectrum. For the specific case of power-law inflation, we find distinctive -- and possibly observable -- effects on the spectrum of density perturbations. ... More

Tensors, non-Gaussianities, and the future of potential reconstructionDec 09 2008Jan 15 2009We present projections for reconstruction of the inflationary potential expected from ESA's upcoming Planck Surveyor CMB mission. We focus on the effects that tensor perturbations and the presence of non-Gaussianities have on reconstruction efforts in ... More

Inflaton or Curvaton? Constraints on Bimodal Primordial Spectra from Mixed PerturbationsMar 03 2012Jun 19 2012We consider Cosmic Microwave Background constraints on inflation models for which the primordial power spectrum is a mixture of perturbations generated by inflaton fluctuations and fluctuations in a curvaton field. If future experiments do not detect ... More

Tachyacoustic Cosmology: An Alternative to InflationAug 26 2009Sep 25 2009We consider an alternative to inflation for the generation of superhorizon perturbations in the universe in which the speed of sound is faster than the speed of light. We label such cosmologies, first proposed by Armendariz-Picon, {\it tachyacoustic}, ... More

Resurrection of large lepton number asymmetries from neutrino flavor oscillationsSep 06 2016We numerically solve the evolution equations of neutrino three-flavor density matrices, and show that, even if neutrino oscillations mix neutrino flavors, large lepton number asymmetries are still allowed in certain limits by Big Bang Nucleosynthesis ... More

Eternal Hilltop InflationJan 29 2016May 11 2016We consider eternal inflation in hilltop-type inflation models, favored by current data, in which the scalar field in inflation rolls off of a local maximum of the potential. Unlike chaotic or plateau-type inflation models, in hilltop inflation the region ... More

The History of Inflation from Microwave Background Polarimetry and Laser InterferometrySep 10 2014May 08 2015A period of inflation in the early universe produces a nearly scale-invariant spectrum of gravitational waves over a huge range in wavelength. If the amplitude of this gravitational wave background is large enough to be detectable with microwave background ... More

Cosmic microwave background measurements can discriminate among inflation modelsFeb 19 1997Quantum fluctuations during inflation may be responsible for temperature anisotropies in the cosmic microwave background (CMB). Observations of CMB anisotropies can be used to falsify many currently popular models. In this paper we discuss the prospectus ... More

Reionization history and CMB parameter estimationNov 29 2012We study how uncertainty in the reionization history of the universe affects estimates of other cosmological parameters from the Cosmic Microwave Background. We analyze WMAP7 data and synthetic Planck-quality data generated using a realistic scenario ... More

Flavor versus mass eigenstates in neutrino asymmetries: implications for cosmologySep 11 2016Sep 19 2017We show that, if they exist, lepton number asymmetries ($L_\alpha$) of neutrino flavors should be distinguished from the ones ($L_i$) of mass eigenstates, since Big Bang Nucleosynthesis (BBN) bounds on the flavor eigenstates cannot be directly applied ... More

Cosmological data and indications for new physicsMar 18 2013Data from the Atacama Cosmology Telescope (ACT) and the South Pole Telescope (SPT), combined with the nine-year data release from the WMAP satellite, provide very precise measurements of the cosmic microwave background (CMB) angular anisotropies down ... More

Jet directions in Seyfert galaxies: B and I imaging dataFeb 06 2000We present the results of broad-band B and I imaging observations for a sample of 88 Seyfert galaxies (29 Seyfert 1's and 59 Seyfert 2's), selected from a mostly isotropic property, the flux at 60$\mu$m. We also present the B and I imaging results for ... More

Homogeneous and Isotropic Charge Densities to Accelerate the UniverseMay 18 2001Aug 02 2001Various theoretical obstacles are associated with a homogeneous and isotropic distribution of ``charge'' which is subject to a repulsive, long-range force. We show how these can be overcome, for all practical purposes, by the simple device of endowing ... More

New Constraints on inflation from the Cosmic Microwave BackgroundJul 25 2000Aug 03 2000The recent data from the Boomerang and MAXIMA-1 balloon flights have marked the beginning of the precision era of Cosmic Microwave Background anisotropy (CMB) measurements. We investigate the observational constraints from the current CMB anisotropy measurements ... More

Limits on primordial power spectrum resolution: An inflationary flow analysisJun 14 2007Aug 09 2007We investigate the ability of current CMB data to reliably constrain the form of the primordial power spectrum generated during inflation. We attempt to identify more exotic power spectra that yield equally good fits to the data as simple power-law spectra. ... More

Natural Inflation: status after WMAP 3-year dataSep 15 2006Nov 16 2006The model of Natural Inflation is examined in light of recent 3-year data from the Wilkinson Microwave Anisotropy Probe and shown to provide a good fit. The inflaton potential is naturally flat due to shift symmetries, and in the simplest version takes ... More

Planck Limits on Non-canonical Generalizations of Large-field Inflation ModelsSep 28 2016Oct 04 2016In this paper, we consider two case examples of Dirac-Born-Infeld (DBI) generalizations of canonical large-field inflation models, characterized by a reduced sound speed, $c_{S} < 1$. The reduced speed of sound lowers the tensor-scalar ratio, improving ... More

A Comparison of Radio Axis with Host Galaxy Plane Axis in Seyfert GalaxiesNov 20 1996We use the radio axis as an indicator of the orientation of the obscuring torus in Seyfert galaxies, and analyze the difference between the position angles of extended radio structures and host galaxy major axis of Seyfert 1 and Seyfert 2 galaxies. We ... More

The Importance of Shocks in the Ionization of the Narrow Line Region of SeyfertsOct 24 2001We discuss the viability of shocks as the principal source of ionization for the Narrow Line Region of Seyfert galaxies. We present the preliminary results of [OIII]5007A and radio 3.6 cm imaging surveys of Seyferts, discuss the effects of shocks in the ... More

Jet directions in Seyfert galaxies: Radio continuum imaging dataDec 06 2000We present the results of VLA A-array 8.46 GHz continuum imaging of 55 Seyfert galaxies (19 Seyfert 1's and 36 Seyfert 2's). These galaxies are part of a larger sample of 88 Seyfert galaxies, selected from mostly isotropic properties, the flux at 60 mum ... More

The Spectral Energy Distribution of Normal, Starburst and Active GalaxiesMay 15 1997We present the results of an extensive literature search of multiwavelength data for a sample of 59 galaxies, consisting of 26 Starbursts, 15 Seyfert 2's, 5 LINER's, 6 normal spirals and 7 normal elliptical galaxies. The data include soft X-ray fluxes, ... More

A Hubble Space Telescope Survey of Extended [OIII]5007A Emission in a Far-Infrared Selected Sample of Seyfert Galaxies: ObservationsJul 11 2003We present a Hubble Space Telescope (HST) survey of extended [OIII] emission for a sample of 60 Seyfert galaxies (22 Seyfert 1's and 38 Seyfert 2's), selected based on their far infrared properties. The observations for 42 of these galaxies were done ... More

The Orientation of Jets Relative to Dust Disks in Radio GalaxiesApr 15 2002We use HST broad band images, VLA and VLBI continuum data to study the three dimensional orientation of jets relative to nuclear dust disks in 20 radio galaxies. The comparison between the position angles of the jets with those of the dust disks major ... More

SU3 isoscalar factorsSep 28 1995Oct 06 1995A summary of the properties of the Wigner Clebsch-Gordan coefficients and isoscalar factors for the group SU3 in the SU2$\otimes$U1 decomposition is presented. The outer degeneracy problem is discussed in detail with a proof of a conjecture (Braunschweig's) ... More

Symmetry properties of SU3 vector coupling coefficientsSep 22 1993A presentation of the problem of calculating the vector coupling coefficients for $SU3 \supset SU2 \otimes U1$ is made, in the spirit of traditional treatments of SU2 coupling. The coefficients are defined as the overlap matrix element between product ... More

Representations of U(2\infty) and the Value of the Fine Structure ConstantDec 25 2005A relativistic quantum mechanics is formulated in which all of the interactions are in the four-momentum operator and Lorentz transformations are kinematic. Interactions are introduced through vertices, which are bilinear in fermion and antifermion creation ... More

What is the optimum stellar rotation rate for a collapsar?Mar 01 2007We consider low angular momentum, neutrino cooled accretion flows onto newborn black holes in the context of the collapsar model for long Gamma Ray Bursts, and find a considerable energy release for rotation rates lower than those usually considered. ... More

Commutator theory for uniformitiesFeb 26 2002Sep 11 2003We investigate commutator operations on compatible uniformities of an algebra. We present a commutator operation for compatible uniformities of an algebra in a congruence-modular variety which extends the commutator on congruences, and explore its properties. ... More

Newtonian hydrodynamics of the coalescence of black holes with neutron stars IV: Irrotational binaries with a soft equation of stateAug 14 2001We present the results of three-dimensional hydrodynamical simulations of the final stages of inspiral in a black hole-neutron star binary, when the separation is comparable to the stellar radius. We use a Newtonian Smooth Particle Hydrodynamics (SPH) ... More

Advection dominated flows around black holes in two dimensionsNov 07 2000We show the results of two-dimensional, azimuthally symmetric simulations of advection dominated fluid flows around black holes. We use the SPH method, and the alpha-prescription for the viscosity, including all terms in the stress tensor. We have performed ... More

Our climate fix must be big and quickOct 13 2008We need enough new carbon sinks to 1) cancel out any continuing use of fossil fuels, 2) overcome the delayed effect of earlier excesses, and then 3) lower atmospheric CO2 concentrations to the old maximum value of 280 ppm. We need to sink about 25 billion ... More

Starburst Anatomy: Stellar and Nebular Properties of Nearby Giant HII RegionsDec 27 1996Resolution of nearby giant HII regions into their stellar and nebular constituents provides fundamental insights for interpreting more distant and powerful starburst activity. The following summarizes recent advances in our understanding of the stellar ... More

Understanding Data Better with Bayesian and Global Statistical MethodsApr 22 1996To understand their data better, astronomers need to use statistical tools that are more advanced than traditional ``freshman lab'' statistics. As an illustration, the problem of combining apparently incompatible measurements of a quantity is presented ... More

Variations on Gravity - Time scales in compact object mergersDec 14 2009Compact object mergers, or their collisions in dense stellar environments, involve different time scales. Each of these has its own tempo and dictates a characteristic set of consequences which may, or may not, be observable in what we see as a gamma-ray ... More

Newtonian hydrodynamics of the coalescence of black holes with neutron stars III: Irrotational binaries with a stiff equation of stateJul 14 2000We present a hydrodynamical study of the final stages of inspiral in a black hole-neutron star (NS) binary. We use a Newtonian 3D SPH code, and model the NS with a stiff (index G=3 and G=2.5) polytropic equation of state and the black hole as a Newtonian ... More

Modulization and the enveloping ringoidMar 10 2001Let A be an algebra in a variety V. We study the modulization of a pointed A-overalgebra P, show that it is totally in any variety that P is totally in, and apply this theory to the construction of the enveloping ringoid Z[A,V].

Jonssons's theorem in non-modular varietiesMay 07 2000Dec 06 2000A version of Jonsson's theorem, as previously generalized, holds in non-modular varieties.

Regular coverings in filter and ideal latticesMay 13 2000Apr 10 2002The Dedekind-Birkhoff theorem for finite-height modular lattices has previously been generalized to complete modular lattices using the theory of regular coverings. In this paper, we investigate regular coverings in lattices of filters and lattices of ... More

Forced Oscillations in Fluid Tori and Quasi-Periodic OscillationsOct 19 2005The kilo-Hertz Quasi--Periodic Oscillations in X-ray binaries could originate within the accretion flow, and be a signature of non--linear fluid oscillations and mode coupling in strong gravity. The possibility to decipher these systems will impact our ... More

Simulations of black hole-neutron star binary coalescenceJan 09 2001We show the results of dynamical simulations of the coalescence of black hole-neutron star binaries. We use a Newtonian Smooth Particle Hydrodynamics code, and include the effects of gravitational radiation back reaction with the quadrupole approximation ... More

Multi-scale metrics and self-organizing maps: a computational approach to the structure of sensory mapsMay 09 2018This paper introduces the concept of a bi-scale metric for use in the cooperative phase of the self-organizing map (SOM) algorithm. Use of a bi-scale metric allows segmentation of the map into a number of regions, corresponding to anticipated cluster ... More

Uniformities, Superequivalences, and Superuniformities of Algebras in Congruence-Modular VarietiesNov 04 2018We introduce superequivalence and superuniform spaces.

Abelian extensions of algebras in congruence-modular varietiesMay 13 2000We define abelian extensions of algebras in congruence-modular varieties. The theory is sufficiently general that it includes, in a natural way, extensions of R-modules for a ring R. We also define a cohomology theory, which we call clone cohomology, ... More

A cut-and-paste approach to contact topologyOct 07 2002Contact structures on 3-manifolds are analyzed by decomposing the manifold along convex surfaces. Background results of Giroux, Eliashberg, Colin, and Honda are discussed with an emphasis on examples. Convex decompositions are then used to give a new ... More

Direct measurement of the jet geometry in Seyfert galaxiesSep 14 1999We demonstrate that, by combining optical, radio and X-ray observations of a Seyfert, it is possible to provide a direct measurement of the angle $\beta$ between the direction of the radio jet and the normal to the plane of the spiral host galaxy. To ... More

Testing the Unified Model with an Infrared Selected Sample of Seyfert GalaxiesMar 16 2001We present a series of statistical tests done to a sample of 29 Seyfert 1 and 59 Seyfert 2 galaxies selected from mostly isotropic properties, their far infrared fluxes and warm infrared colors. Such selection criteria provide a profound advantage over ... More

Jet directions in Seyfert galaxiesFeb 06 2000We present the study of the relative angle between the accretion disk (or radio jet) and the galaxy disk for a sample of Seyfert galaxies selected from a mostly isotropic property, the 60$\mu$m flux. For each galaxy we have a pair of points ($i$,$\delta$), ... More

The Science Impact of Astronomy PhD Granting Departments in the United StatesNov 03 2008The scientific impact of the research of 36 astronomy PhD granting departments is measured and ranked here. Because of the complex nature of Universities, this study looks at the Universities in two ways; first analyzing the impact of the published work ... More

A Hubble Space Telescope Survey of Extended [OIII]5007A Emission in a Far-Infrared Selected Sample of Seyfert Galaxies: ResultsJul 11 2003We present the results of a Hubble Space Telescope (HST) survey of extended [OIII] emission in a sample of 60 nearby Seyfert galaxies (22 Seyfert 1's and 38 Seyfert 2's), selected by mostly isotropic properties. The comparison between the semi major axis ... More

National Scientific Facilities and Their Science Impact on Non-Biomedical ResearchMay 12 2007H-index, proposed by Hirsch is a good indicator of the impact of a scientist's research. When evaluating departments, institutions or labs, the importance of h-index can be further enhanced when properly calibrated for size. Particularly acute is the ... More

Unification of field theory and maximum entropy methods for learning probability densitiesNov 19 2014Jul 29 2015The need to estimate smooth probability distributions (a.k.a. probability densities) from finite sampled data is ubiquitous in science. Many approaches to this problem have been described, but none is yet regarded as providing a definitive solution. Maximum ... More

WMAPping inflationary physicsMay 12 2003Aug 01 2003We extract parameters relevant for distinguishing among single-field inflation models from the Wilkinson Microwave Anisotropy Probe (WMAP) data set, and from a combination of the WMAP data and seven other Cosmic Microwave Background (CMB) experiments. ... More

Ribbons on the CBR Sky: A Powerful Test of a Baryon Symmetric UniverseApr 09 1997May 02 1997If the Universe consists of domains of matter and antimatter, annihilations at domain interfaces leave a distinctive imprint on the Cosmic Background Radiation (CBR) sky. The signature is anisotropies in the form of long, thin ribbons of width $\theta_W\sim ... More

Horizon-preserving dualities and perturbations in non-canonical scalar field cosmologiesOct 20 2011Nov 08 2011We generalize the cosmological duality between inflation and cyclic contraction under the interchange $a \leftrightarrow H$ to the case of non-canonical scalar field theories with varying speed of sound. The single duality in the canonical case generalizes ... More

Rapid and deterministic estimation of probability densities using scale-free field theoriesDec 23 2013Apr 18 2014The question of how best to estimate a continuous probability density from finite data is an intriguing open problem at the interface of statistics and physics. Previous work has argued that this problem can be addressed in a natural way using methods ... More

Optimal choice of dividing surface for the computation of quantum reaction ratesAug 19 2004Nov 04 2004See http://pubs.acs.org/journals/jpcafh/ for the latest revision