Results for "D. N. Spergel"

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Three Dimensional Structure of the Milky Way DiskJan 16 2001Mar 29 2001We present a three dimensional model for the Milky Way fit to the far-infrared (FIR) and near-infrared (NIR) data from the COBE/DIRBE instrument for Galactic latitudes |b| < 30 degrees and to within 20 degrees of the Galactic center. Because of the low ... More
Primordial Black Holes as Dark Matter: The Power Spectrum and Evaporation of Early StructuresFeb 03 2003We consider the possibility that massive primordial black holes are the dominant form of dark matter. Black hole formation generates entropy fluctuations that adds a Poisson noise to the matter power spectrum. We use Lyman-alpha forest observations to ... More
Using Perturbative Least Action to Run N Body Simulations Back in TimeSep 02 1999In this report, we present a new method for reconstructing N body initial conditions from a proscribed final density field. This method, Perturbative Least Action (PLA) is similar to traditional least action approaches, except that orbits of particles ... More
Using Supernovae to Determine the Equation of State of the Dark Energy: Is Shallow Better than Deep?Apr 04 2002Jun 05 2002Measurements of the flux and redshifts of Type Ia supernovae have provided persuasive evidence that the expansion of the universe is accelerating. If true, then in the context of standard FRW cosmology this suggests that the energy density of hte universe ... More
Terrestrial Planet Finding with a Visible Light CoronagraphMay 28 2003Directly imaging extrasolar planets using a monolithic optical telescope avoids many pitfalls of space interferometry and opens up the prospect of visible light studies of extrasolar planetary systems. Future astronomical missions may require interferometry ... More
Extragalactic Foregrounds of the Cosmic Microwave Background: Prospects for the MAP MissionJun 26 1998Apr 03 2000(Abridged) While the major contribution to the Cosmic Microwave Background (CMB) anisotropies are the sought-after primordial fluctuations produced at the surface of last scattering, other effects produce secondary fluctuations at lower redshifts. Here, ... More
A New Technique for Detecting Supersymmetric Dark MatterSep 09 1994Sep 13 1994We estimate the event rate for excitation of atomic transition by photino-like dark matter. For excitations of several eV, this event rate can exceed naive cross-section by many orders of magnitude. Although the event rate for these atomic excitation ... More
Searching for oscillations in the primordial power spectrumJun 02 2014Aug 21 2014A small deviation from scale invariance in the form of oscillations in the primordial correlation spectra has been predicted by various cosmological models. In this paper we review a recently developed method to search for these features in the data in ... More
Does Chaotic Mixing Facilitate Omega<1 Inflation?Jan 09 1996Jun 03 1996Yes, if the universe has compact topology. Inflation is currently the most elegant explanation of why the universe is old, large, nearly flat, homogeneous on large scales and structured on small scales. One of the weaknesses of the inflationary paradigm ... More
Correlation properties of the kinematic Sunyaev-Zel'dovich effect and implications for Dark EnergyNov 02 2005In the context of a cosmological study of the bulk flows in the Universe, we present a detailed study of the statistical properties of the kinematic Sunyaev-Zel'dovich (kSZ) effect. We first compute analytically the correlation function and the power ... More
Measuring primordial non-Gaussianity in the cosmic microwave backgroundMay 12 2003Aug 11 2005We derive a fast way for measuring primordial non-Gaussianity in a nearly full-sky map of the cosmic microwave background. We find a cubic combination of sky maps combining bispectrum configurations to capture a quadratic term in primordial fluctuations. ... More
The Power Spectrum of the Sunyaev-Zel'dovich EffectDec 09 1999Apr 03 2000(Abridged) The hot gas in the IGM produces anisotropies in the Cosmic Microwave Background (CMB) through the thermal Sunyaev-Zel'dovich (SZ) effect. The SZ effect is a powerful probe of large-scale structure in the universe and must be carefully subtracted ... More
The Formation of Disk GalaxiesNov 27 1996We present a scenario for the formation of disks which explains not only the properties of normal galaxies, but the properties of the population of low surface brightness galaxies (LSBs) as well. We use a gravitationally self-consistent model for disk ... More
The Coalescence Rate of Double Neutron Star SystemsDec 03 2000Mar 21 2001We estimate the coalescence rate of close binaries with two neutron stars (NS) and discuss the prospects for the detection of NS-NS inspiral events by ground-based gravitational-wave observatories, such as LIGO. We derive the Galactic coalescence rate ... More
A WISE measurement of the ISW effectJan 06 2014The Integrated Sachs-Wolfe effect (ISW) measures the decay of the gravitational potential due to cosmic acceleration and is thus a direct probe of Dark Energy. In some of the earlier studies, the amplitude of the ISW effect was found to be in tension ... More
Searching for Oscillations in the Primordial Power Spectrum: Perturbative Approach (Paper I)Aug 16 2013Oct 16 2013In this first of two papers, we present a new method for searching for oscillatory features in the primordial power spectrum. A wide variety of models predict these features in one of two different flavors: logarithmically spaced oscillations and linearly ... More
Searching for Oscillations in the Primordial Power Spectrum: Constraints from Planck (Paper II)Aug 16 2013Aug 21 2014We apply our recently developed code to search for resonance features in the Planck CMB temperature data. We search both for log spaced oscillations or linear spaced oscillations and compare our findings with results of our WMAP9 analysis and the Planck ... More
Circles in the Sky: Finding Topology with the Microwave Background RadiationFeb 20 1996Feb 21 1996If the universe is finite and smaller than the distance to the surface of last scatter, then the signature of the topology of the universe is writ on the microwave background sky. Previous efforts to search for this topology have focused on one particular ... More
THE FORMATION OF LSB GALAXIESMar 26 1995The formation of low surface brightness galaxies is an unavoidable prediction of any hierarchical clustering scenario. In these models, low surface brightness galaxies form at late times from small initial overdensities, and make up most of the faint ... More
Signatures of Bulge Triaxiality from Kinematics in Baade's Window/Sep 12 1994We study a sample of 62 Baade's Window (1,-4) K giants that have published proper motions, radial velocity and metallicity. We construct the velocity ellipsoids for the metal rich stars and metal poor stars. We find a vertex deviation characteristic of ... More
Gravitational Lens Statistics for Generalized NFW Profiles: Parameter Degeneracy and Implications for Self-Interacting Cold Dark MatterJul 24 2000May 27 2001Strong lensing is a powerful probe of the distribution of matter in the cores of clusters of galaxies. Recent studies suggest that the cold dark matter model predicts cores that are denser than those observed in galaxies, groups and clusters. One possible ... More
Measuring the Topology of the UniverseAug 08 1997Observations of microwave background fluctuations can yield information not only about the geometry of the universe, but potentially about the topology of the universe. If the universe is negatively curved, then the characteristic scale for the topology ... More
A Consistent Microlensing Model for the Galactic BarDec 11 1995We compute a microlensing map for the Galactic bar. The predicted event rate and event duration distribution are consistent with the $55$ events recently reported by the MACHO and OGLE collaborations. Most of the events are due to lensing by stars in ... More
Particle Dark MatterMar 06 1996Several lines of evidence suggest that some of the dark matter may be non-baryonic: the non-detection of various plausible baryonic candidates for dark matter inferred, e.g., from galaxy rotation curves and from cluster of galaxy velocity dispersions, ... More
Analytical Galaxy Profiles for Photometric and Lensing AnalysisJul 19 2010This article introduces a family of analytical functions of the form x^{\nu} K_{\nu}(x), where K_{\nu} is the incomplete Bessel function of the third kind. This family of functions can describe the density profile, projected and integrated light profiles ... More
A New Pupil for Detecting Extrasolar PlanetsJan 09 2001The challenge for optical detection of terrestial planet is the 25 magnitude brightness contrast between the planet and its host star. This paper introduces a new pupil design that produces a very dark null along its symmetry axis. By changing the shape ... More
Double Binary Pulsar Test of Dynamical Chern-Simons Modified GravityOct 30 2008Aug 05 2009Chern-Simons modified gravity is a string-theory and loop-quantum-gravity inspired effective theory that modifies General Relativity by adding a parity-violating Pontryagin density to the Einstein-Hilbert action multiplied by a coupling scalar. We strongly ... More
Dark Matter Debris Flows in the Milky WayMay 20 2011Jan 02 2013We show that subhalos falling into the Milky Way create a flow of tidally-stripped debris particles near the galactic center with characteristic velocity behavior. In the Via Lactea-II N-body simulation, this unvirialized component constitutes a few percent ... More
On the Formation of Multiple Stellar Populations in Globular ClustersMay 26 2010Nov 23 2010Nearly all globular clusters (GCs) studied to date show evidence for multiple stellar populations, in stark contrast to the conventional view that GCs are a mono-metallic, coeval population of stars. Building on earlier work, we propose a simple physical ... More
Large-Angle Cosmic Microwave Background Anisotropies in an Open UniverseDec 08 1993If the Universe is open, scales larger than the curvature scale may be probed by large-angle fluctuations in the cosmic microwave background (CMB). We consider primordial adiabatic perturbations and discuss power spectra that are power laws in volume, ... More
Is the Dark Matter a Solid?Dec 01 1998May 16 1999A smooth unclustered dark matter component with negative presure could reconcile a flat universe with the many observations that find a density in ordinary, clustered matter well below the critical density and also explain the recent high redshift supernova ... More
Joint analysis of cluster number counts and weak lensing power spectrum to correct for the super-sample covarianceJul 16 2013Apr 18 2014A coherent over- or under-density contrast across a finite survey volume causes an upward- or downward-fluctuation in the observed number of halos. This fluctuation in halo number adds a significant co-variant scatter in the observed amplitudes of weak ... More
The Number Density of Low Surface Brightness Galaxies with 23<mu_0<25 V-mag/sqr-arcsecondMay 12 1997We present results of a large area CCD survey for low surface brightness galaxies (LSBs) that reaches central surface brightnesses of mu_0=25 mag/sqr-" in V. We have analyzed 17.5 degrees of transit scan data, and identified a statistical subset of 7 ... More
Ultra-Light Dark Matter in Ultra-Faint Dwarf GalaxiesMar 23 2016May 20 2016Cold Dark Matter (CDM) models struggle to match the observations at galactic scales. The tension can be reduced either by dramatic baryonic feedback effects or by modifying the particle physics of CDM. Here, we consider an ultra-light scalar field DM ... More
Wide-Field InfraRed Survey Telescope (WFIRST) Mission and Synergies with LISA and LIGO-VirgoNov 02 2014The Wide-Field InfraRed Survey Telescope (WFIRST) is a NASA space mission in study for launch in 2024. It has a 2.4 m telescope, wide-field IR instrument operating in the 0.7 - 2.0 micron range and an exoplanet imaging coronagraph instrument operating ... More
CMB Lensing and the WMAP Cold SpotSep 26 2008Nov 22 2008Cosmologists have suggested a number of intriguing hypotheses for the origin of the "WMAP cold spot", the coldest extended region seen in the CMB sky, including a very large void and a collapsing texture. Either hypothesis predicts a distinctive CMB lensing ... More
LSST: a Complementary Probe of Dark EnergySep 30 2002The number of mass clusters and their distribution in redshift are very sensitive to the density of matter Omega_m and the equation of state of dark energy w. Using weak lens gravitational tomography one can detect clusters of dark matter, weigh them, ... More
Measuring Distance Ratios with CMB-Galaxy Lensing Cross-correlationsOct 21 2008We propose a method for cosmographic measurements by combining gravitational lensing of the cosmic microwave background (CMB) with cosmic shear surveys. We cross-correlate the galaxy counts in the lens plane with two different source planes: the CMB at ... More
Dark energy and cosmic microwave background bispectrumAug 10 2001Jan 23 2002We compute the cosmic microwave background bispectrum arising from the cross-correlation of primordial, lensing and Rees-Sciama signals. The amplitude of the bispectrum signal is sensitive to the matter density parameter, Omega_0, and the equation of ... More
CMB polarization as a direct test of InflationMay 22 1997Sep 03 1997We study the auto-correlation function of CMB polarization anisotropies and their cross correlation with temperature fluctuations as probe of the causal structure of the universe. Because polarization is generated at the last scattering surface, models ... More
The cosmic microwave background bispectrum as a test of the physics of inflation and probe of the astrophysics of the low-redshift universeDec 09 2000Why is non-Gaussianity interesting? One of generic predictions from inflationary scenarios is that primordial fluctuations are exactly Gaussian in linear order; however, the non-linearity in the inflation will produce weak non-Gaussianity. Thus, measuring ... More
Acoustic Signatures in the Primary Microwave Background BispectrumMay 02 2000Dec 09 2000If the primordial fluctuations are non-Gaussian, then this non-Gaussianity will be apparent in the cosmic microwave background (CMB) sky. With their sensitive all-sky observation, MAP and Planck satellites should be able to detect weak non-Gaussianity ... More
Extending the WMAP Bound on the Size of the UniverseApr 28 2006Clues to the shape of our Universe can be found by searching the CMB for matching circles of temperature patterns. A full sky search of the CMB, mapped extremely accurately by NASA's WMAP satellite, returned no detection of such matching circles and placed ... More
Constraints on the Topology of the Universe: Extension to General GeometriesJun 13 2012We present an update to the search for a non-trivial topology of the universe by searching for matching circle pairs in the cosmic microwave background using the WMAP 7 year data release. We extend the exisiting bounds to encompass a wider range of possible ... More
Measurement of the cosmic microwave background bispectrum on the COBE DMR sky mapsJul 31 2001We measure the angular bispectrum of the cosmic microwave background (CMB) radiation anisotropy from the COBE Differential Microwave Radiometer (DMR) four-year sky maps. The angular bispectrum is the harmonic transform of the three-point correlation function, ... More
Constraining Fundamental Physics with Future CMB ExperimentsMay 20 2010The Planck experiment will soon provide a very accurate measurement of Cosmic Microwave Background anisotropies. This will let cosmologists determine most of the cosmological parameters with unprecedented accuracy. Future experiments will improve and ... More
Probing the Galactic Potential with Next-Generation Observations of Disk StarsMar 24 2009May 20 2009Near-future surveys promise a dramatic improvement in the number and precision of astrometric, photometric and spectroscopic measurements of stars in the Milky Way's disk. We examine the impact of such surveys on our understanding of the Galaxy by "observing" ... More
Halo Properties in Cosmological Simulations of Self-Interacting Cold Dark MatterJun 15 2000We present a comparison of halo properties in cosmological simulations of collisionless cold dark matter (CDM) and self-interacting dark matter (SIDM) for a range of dark matter cross sections. We find, in agreement with various authors, that CDM yields ... More
Constraining the Topology of the UniverseOct 08 2003The first year data from the Wilkinson Microwave Anisotropy Probe are used to place stringent constraints on the topology of the Universe. We search for pairs of circles on the sky with similar temperature patterns along each circle. We restrict the search ... More
Comoving stars in Gaia DR1: An abundance of very wide separation co-moving pairsDec 07 2016Jun 01 2017The primary sample of the {\it Gaia} Data Release 1 is the Tycho-Gaia Astrometric Solution (TGAS): $\approx$ 2 million Tycho-2 sources with improved parallaxes and proper motions relative to the initial catalog. This increased astrometric precision presents ... More
Co-moving stars in Gaia DR1: An abundance of very wide separation co-moving pairsDec 07 2016The primary sample of the Gaia Data Release 1 is the Tycho-Gaia Astrometric Solution (TGAS): $\approx$ 2 million Tycho-2 sources with improved parallaxes and proper motions relative to the initial catalog. This increased astrometric precision presents ... More
Small-Scale Cosmic Microwave Background Anisotropies as a Probe of the Geometry of the UniverseJan 04 1994We perform detailed calculations of cosmic microwave background (CMB) anisotropies in a CDM-dominated open universe with primordial adiabatic density perturbations for a variety of reionization histories. We show that to a great extent, the CMB anisotropies ... More
Separating the Weak Lensing and Kinetic SZ Effects from CMB Temperature MapsSep 29 2006Feb 27 2007A new generation of CMB experiments will soon make sensitive high resolution maps of the microwave sky. At angular scales less than $\sim$10 arcminutes, most CMB anisotropies are generated at z $< 1000$, rather than at the surface of last scattering. ... More
The kinetic Sunyaev-Zel'dovitch effect as a dark energy probeNov 02 2005Upcoming observatories will be able to detect the kinetic Sunyaev-Zel'dovitch (kSZ) effect with unprecendented signal-to-noise, and cross-correlations with foreground signals such as galaxy counts are a promising way to extract additional cosmological ... More
The Microwave Background Bispectrum, Paper I: Basic FormalismNov 16 1998Jan 04 1999In this paper, we discuss the potential importance of measuring the CMB anisotropy bispectrum. We develop a formalism for computing the bispectrum and for measuring it from microwave background maps. As an example, we compute the bispectrum resulting ... More
Photometric Selection of a Luminous Red Galaxy Catalog with $z\geq0.55$Apr 04 2016We present the development of a photometrically selected Luminous Red Galaxy (LRG) catalog at redshift $z\geq 0.55$. LRG candidates are selected using infrared/optical color-color cuts, optimized using ROC curve analysis, with optical data from Sloan ... More
Direct Detection of Dark Matter Debris FlowsJan 31 2012Aug 06 2012Tidal stripping of dark matter from subhalos falling into the Milky Way produces narrow, cold tidal streams as well as more spatially extended "debris flows" in the form of shells, sheets, and plumes. Here we focus on the debris flow in the Via Lactea ... More
SZE Signals in Cluster ModelsJan 06 2006Jul 23 2006The upcoming generation of SZE surveys will shed fresh light onto the study of clusters. What will this new observational window reveal about cluster properties? What can we learn from combining X-ray, SZE, and optical observations? How do variations ... More
Detecting z > 10 objects through carbon, nitrogen and oxygen emission linesMar 20 1998By redshift of 10, star formation in the first objects should have produced considerable amounts of Carbon, Nitrogen and Oxygen. The submillimeter lines of C, N and O redshift into the millimeter and centimeter bands (0.5 mm -- 1.2 cm), where they may ... More
Efficient Power Spectrum Estimation for High Resolution CMB MapsSep 05 2008Estimation of the angular power spectrum of the Cosmic Microwave Background (CMB) on a small patch of sky is usually plagued by serious spectral leakage, specially when the map has a hard edge. Even on a full sky map, point source masks can alias power ... More
A small universe after all?Jun 25 1999Jun 26 1999The cosmic microwave background radiation allows us to measure both the geometry and topology of the universe. It has been argued that the COBE-DMR data already rule out models that are multiply connected on scales smaller than the particle horizon. Here ... More
Lithopanspermia in Star Forming ClustersApr 29 2005This paper considers the lithopanspermia hypothesis in star forming groups and clusters, where the chances of biological material spreading from one solar system to another is greatly enhanced (relative to the field) due to the close proximity of the ... More
On the eigenmodes of compact hyperbolic 3-manifoldsJun 02 1999We present a simple algorithm for finding eigenmodes of the Laplacian for arbitrary compact hyperbolic 3-manifolds. We apply our algorithm to a sample of twelve manifolds and generate a list of the lowest eigenvalues. We also display a selection of eigenmodes ... More
The Gaia inertial reference frame and the tilting of the Milky Way diskJun 01 2014While the precise relationship between the Milky Way disk and the symmetry planes of the dark matter halo remains somewhat uncertain, a time-varying disk orientation with respect to an inertial reference frame seems probable. Hierarchical structure formation ... More
Are Clusters Standard Candles? Galaxy Cluster Scaling Relations With the Sunyaev-Zeldovich EffectJun 19 2001An extensive sample of galaxy clusters will be available in the coming years, detected through their Sunyaev-Zeldovich effect (SZE). We use a semi-analytic model to study the scientific yield of combining SZE data with X-ray and optical follow-up observations. ... More
Using galaxy-galaxy weak lensing measurements to correct the Finger-of-GodJun 08 2011Jan 05 2012For decades, cosmologists have been using galaxies to trace the large-scale distribution of matter. At present, the largest source of systematic uncertainty in this analysis is the challenge of modeling the complex relationship between galaxy redshift ... More
Shear Selected Cluster Cosmology I: Tomography and Optimal FilteringApr 19 2004Jan 31 2005We study the potential of weak lensing surveys to detect clusters of galaxies, using a fast Particle Mesh cosmological N-body simulation algorithm specifically tailored to investigate the statistics of these mass-selected clusters. In particular, we explore ... More
Distinguishing Causal Seeds from InflationMay 30 1996Aug 18 1996Causal seed models, such as cosmological defects, generically predict a distinctly different structure to the CMB power spectrum than inflation, due to the behavior of the perturbations outside the horizon. We provide a general analysis of their causal ... More
Testing Gravity with Gravitational Wave Source CountsFeb 11 2016Jun 23 2016We show that the gravitational wave source counts distribution can test how gravitational radiation propagates on cosmological scales. This test does not require obtaining redshifts for the sources. If the signal-to-noise ratio (SNR, $\rho$) from a gravitational ... More
Joint likelihood function of cluster counts and $n$-point correlation functions: Improving their power through including halo sample varianceJun 12 2014Naive estimates of the statistics of large scale structure and weak lensing power spectrum measurements that include only Gaussian errors exaggerate their scientific impact. Non-linear evolution and finite volume effects are both significant sources of ... More
Threshold Clustering Functions and Thermal Inhomogeneities in the Lyman-Alpha ForestJul 21 2010Oct 01 2011We introduce to astrophysics the threshold probability functions S_2, C_2, and D_2 first derived by \citet{torq+88}, which effectively samples the flux probability distribution (PDF) of the Lya forest at different spatial scales. These statistics are ... More
Topological Defects in an Open UniverseFeb 17 1994(To appear in Nuclear Physics B Supplements Proceedings section) This talk will explore the evolution of topological defects in an open universe. The rapid expansion of the universe in an open model slows defects and suppresses the generation of CBR fluctuations ... More
Observational evidence for self-interacting cold dark matterSep 23 1999Feb 28 2000Cosmological models with cold dark matter composed of weakly interacting particles predict overly dense cores in the centers of galaxies and clusters and an overly large number of halos within the Local Group compared to actual observations. We propose ... More
The bispectrum of polarized galactic foregroundsJan 14 2019Understanding the properties of the galactic emission at millimetre wavelengths is important for studies of the cosmic microwave background (CMB). In this work we explore the bispectrum, the harmonic equivalent of the three point function, from galactic ... More
The Microwave Background Bispectrum, Paper II: A Probe of the Low Redshift UniverseNov 16 1998Jan 04 1999Gravitational fluctuations along the line-of-sight from the surface of last scatter to the observer distort the microwave background in several related ways: The fluctuations deflect the photon path (gravitational lensing), the decay of the gravitational ... More
Photometric Selection of a Massive Galaxy Catalog with $z\geq0.55$Apr 04 2016Dec 08 2016We present the development of a photometrically selected massive galaxy catalog, targeting Luminous Red Galaxies (LRGs) and massive blue galaxies at redshifts $z\geq 0.55$. Massive galaxy candidates are selected using infrared/optical color-color cuts, ... More
The bispectrum of polarized galactic foregroundsJan 14 2019Feb 27 2019Understanding the properties of the galactic emission at millimetre wavelengths is important for studies of the cosmic microwave background (CMB). In this work we explore the bispectrum, the harmonic equivalent of the three point function, from galactic ... More
The Co-Formation of Spheroids and Quasars Traced in their ClusteringNov 26 2006Jun 18 2007We compare observed clustering of quasars and galaxies as a function of redshift, mass, luminosity, & color/morphology, to constrain models of quasar fueling and spheroid-BH co-evolution. High redshift quasars are shown to be drawn from progenitors of ... More
Southern Cosmology Survey III: QSO's from Combined GALEX and Optical PhotometryNov 25 2008We present catalogs of QSO candidates selected using photometry from GALEX combined with SDSS in the Stripe 82 region and Blanco Cosmology Survey (BCS) near declination -55 degrees. The SDSS region contains ~700 objects with magnitude i < 20 and ~3600 ... More
Notch Filter Masks: Practical Image Masks for Planet-Finding CoronagraphsSep 13 2002Apr 22 2003An ideal coronagraph with a band-limited image mask can efficiently image off-axis sources while removing identically all of the light from an on-axis source. However, strict mask construction tolerances limit the utility of this technique for directly ... More
Constraining the LRG Halo Occupation Distribution using Counts-in-CylindersSep 25 2008The low number density of the Sloan Digital Sky Survey (SDSS) Luminous Red Galaxies (LRGs) suggests that LRGs occupying the same dark matter halo can be separated from pairs occupying distinct dark matter halos with high fidelity. We present a new technique, ... More
Signatures of Kinematic Substructure in the Galactic Stellar HaloOct 08 2014Jun 12 2015Tidal debris from infalling satellites can leave observable structure in the phase-space distribution of the Galactic halo. Such substructure can be manifest in the spatial and/or velocity distributions of the stars in the halo. This paper focuses on ... More
How does non-linear dynamics affect the baryon acoustic oscillation?Jun 27 2013Feb 06 2014We study the non-linear behavior of the baryon acoustic oscillation in the power spectrum and the correlation function by decomposing the dark matter perturbations into the short- and long-wavelength modes. The evolution of the dark matter fluctuations ... More
Probing Cosmic Acceleration Beyond the Equation of State: Distinguishing between Dark Energy and Modified Gravity ModelsJul 07 2005Aug 10 2006If general relativity is the correct theory of physics on large scales, then there is a differential equation that relates the Hubble expansion function, inferred from measurements of angular diameter distance and luminosity distance, to the growth rate ... More
Cross-correlating the Sloan Digital Sky Survey with the Microwave SkyJan 22 2000Jul 06 2000While most of the microwave background fluctuations on angular scales greater than a few arcminutes were generated at z > 800, the low redshift universe does distort the microwave background. Since the Sloan Digital Sky Survey (SDSS) traces the structures ... More
Cross-Correlating Cosmic Microwave Background Radiation Fluctuations with Redshift Surveys: Detecting the Signature of Gravitational LensingMay 19 1997Oct 17 1997Density inhomogeneities along the line-of-sight distort fluctuations in the cosmic microwave background. Usually, this effect is thought of as a small second-order effect that mildly alters the statistics of the microwave background fluctuations. We show ... More
Cosmic Microwave Anisotropies from Topological Defects in an Open UniverseAug 31 1994We present a general formalism for computing Cosmic Background Radiation (CBR) and density fluctuations in open models with stiff sources. We find analytic Green's functions for the linearized Einstein equations in the presence of stiff sources and use ... More
Detection of Thermal SZ -- CMB Lensing Cross-Correlation in Planck Nominal Mission DataDec 16 2013Feb 23 2014The nominal mission maps from the Planck satellite contain a wealth of information about secondary anisotropies in the cosmic microwave background (CMB), including those induced by the thermal Sunyaev-Zel'dovich (tSZ) effect and gravitational lensing. ... More
Using Perturbative Least Action to Recover Cosmological Initial ConditionsDec 19 1999Apr 17 2000We introduce a new method for generating initial conditions consistent with highly nonlinear observations of density and velocity fields. Using a variant of the Least Action method, called Perturbative Least Action (PLA), we show that it is possible to ... More
Self-Interacting Dark MatterJun 24 2000Jun 28 2000Spergel and Steinhardt have recently proposed the concept of dark matter with strong self-interactions as a means to address numerous discrepancies between observations of dark matter halos on subgalactic scales and the predictions of the standard collisionless ... More
Microwave Background Constraints on Cosmological ParametersFeb 19 1997Sep 11 1997We use a high-accuracy computational code to investigate the precision with which cosmological parameters could be reconstructed by future cosmic microwave background (CMB) experiments, in particular the two satellite missions MAP and Planck Surveyor ... More
Spiderweb Masks for High-Contrast ImagingMar 03 2003Motivated by the desire to image exosolar planets, recent work by us and others has shown that high-contrast imaging can be achieved using specially shaped pupil masks. To date, the masks we have designed have been symmetric with respect to a cartesian ... More
Is Large Lepton Mixing Excluded?May 03 1993Jun 02 1993The original \bnum -(or $\bar{\nu}_{\tau}$-) energy spectrum from the gravitational collapse of a star has a larger average energy than the spectrum for \bnue since the opacity of \bnue exeeds that of \bnum (or $\nu_{\tau}$). Flavor neutrino conversion, ... More
Rectangular-Mask Coronagraphs for High-Contrast ImagingJan 30 2004We present yet another new family of masks for high-contrast imaging as required for the to-be-built terrestrial planet finder space telescope. The ``best'' design involves a square entrance pupil having a 4-vane spider, a square image-plane mask containing ... More
Circularly Symmetric Apodization via Starshaped MasksMay 03 2003May 15 2003Recently, we introduced a class of shaped pupil masks, called spiderweb masks, that produce point spread functions having annular dark zones. With such masks, a single image can be used to probe a star for extrasolar planets. In this paper, we introduce ... More
Cosmic Microwave Background Observations in the Post-Planck EraJul 20 1999The Microwave Anisotropy Probe and Planck missions will provide low noise maps of the temperature of the cosmic microwave background (CMB). These maps will allow measurement of the power spectrum of the CMB with measurement noise below cosmic variance ... More
Mean-flux Regulated PCA Continuum Fitting of SDSS Lyman-alpha Forest SpectraAug 30 2011Continuum fitting is an important aspect of Lyman-alpha forest science, since errors in the estimated optical depths scale with the fractional continuum error. However, traditional methods of estimating continua in noisy and moderate-resolution spectra ... More
Cross-correlations of the Lyman-alpha forest with weak lensing convergence I: Analytical Estimates of S/N and Implications for Neutrino Mass and Dark EnergyOct 21 2009We expect a detectable correlation between two seemingly unrelated quantities: the four point function of the cosmic microwave background (CMB) and the amplitude of flux decrements in quasar (QSO) spectra. The amplitude of CMB convergence in a given direction ... More
Probing patchy reionization through tau-21cm correlation statisticsMar 15 2013Oct 16 2013We consider the cross-correlation between free electrons and neutral hydrogen during the epoch of reionization. The free electrons are traced by the optical depth to reionization tau, while the neutral hydrogen can be observed through 21 cm photon emission. ... More
Supermassive Black Holes from Ultra-Strongly Self-Interacting Dark MatterDec 30 2014We consider the cosmological consequences if a small fraction ($f\lesssim 0.1$) of the dark matter is ultra-strongly self-interacting, with an elastic self-interaction cross-section per unit mass $\sigma\gg1\ \mathrm{cm^{2}/g}$. This possibility evades ... More