Phase Transition Generated Cosmological Magnetic Field at Large Scales (2009)
Kahniashvili, Tina, Tevzadze, Alexander G., Ratra, Bharat
We constrain a primordial magnetic field (PMF) generated during a phase transitions (PT) using big bang nucleosynthesis (BBN) bounds on the relativistic energy density. The amplitude of the PMF at...
Constraints on dark energy from the lookback time versus redshift test (2009)
Samushia, Lado, Dev, Abha, Jain, Deepak, Ratra, Bharat
We use lookback time versus redshift data from galaxy clusters (Capozziello et al. 2004) and passively evolving galaxies (Simon et al. 2005), in combination with the WMAP determination of the age of...
Constraining dark energy with gamma-ray bursts (2009)
We use the cosmology-independent gamma-ray burst (GRB) distances of Y. Wang (2008) to constrain dark energy cosmological model parameters. Current GRB data alone can not tightly constrain...
Constraints on dark energy models from radial baryon acoustic scale measurements (2008)
We use the radial baryon acoustic oscillation (BAO) measurements of Gaztanaga et al. (2008) to constrain parameters of dark energy models. These constraints are comparable with constraints from other...
Gravitational Radiation from Primordial Helical Inverse Cascade MHD Turbulence (2008)
Kahniashvili, Tina, Campanelli, Leonardo, Gogoberidze, Grigol, Maravin, Yurii, Ratra, Bharat
We consider the generation of gravitational waves by primordial helical inverse cascade magnetohydrodynamic (MHD) turbulence produced by bubble collisions at the electroweak phase transition. We...
Kahniashvili, Tina, Lavrelashvili, George, Ratra, Bharat
We derive the cosmic microwave background temperature anisotropy two-point correlation function (including off-diagonal correlations) from broken spatial isotropy due to an arbitrarily oriented...
Constraints on dark energy from baryon acoustic peak and galaxy cluster gas mass measurements (2008)
We use baryon acoustic peak measurements by \citet{eisensteinetal} and \citet{percivaletal07a} and galaxy cluster gas mass fraction measurements of \citet{allen08} to constrain parameters of three...
Constraints on Dark Energy from Galaxy Cluster Gas Mass Fraction versus Redshift data (2008)
We use the Allen et al. (2008) galaxy cluster gas mass fraction versus redshift data to constrain parameters of three different dark energy models: a cosmological constant dominated one...
Gravitational Radiation from Primordial Helical MHD Turbulence (2008)
Kahniashvili, Tina, Gogoberidze, Grigol, Ratra, Bharat
We consider gravitational waves (GWs) generated by primordial inverse-cascade helical magneto-hydrodynamical (MHD) turbulence produced by bubble collisions at the electroweak phase transitions...
Ken Gangal, Bharat Ratra, Mark A. Lim, Naoshi Sugiyama, Stacy T. Tanaka
We account for experimental and observational uncertainties in likelihood analyses of cosmic microwave background (CMB) anisotropy data from the MAX 4 and MAX 5 experiments. These analyses use CMB...
Large-scale structure in COBE-normalized cold dark matter cosmogonies (2007)
Shaun Cole, David H. Weinberg, Carlos S. Frenk, Bharat Ratra
We study the clustering of the mass distribution in cold dark matter models using large cosmological N-body simulations. We investigate spatially-flat models with a cosmological constant and...
Silviu Podariu, Peter Nugent, Bharat Ratra
We examine the constraints that satellite-acquired Type Ia and IIP supernova apparent magnitude versus redshift data will place on cosmological model parameters in models with and without a constant...
Samushia, Lado, Chen, Gang, Ratra, Bharat
Galaxy cluster gas mass fraction versus redshift data and Hubble parameter versus redshift data are used to jointly constrain dark energy models. These constraints favor the Einstein cosmological...
The Beginning and Evolution of the Universe (2007)
Ratra, Bharat, Vogeley, Michael S.
We review the current standard model for the evolution of the Universe from an early inflationary epoch to the complex hierarchy of structure seen today. We summarize and provide key references for...
CMB anisotropies due to cosmological magnetosonic waves (2006)
Kahniashvili, Tina, Ratra, Bharat
We study scalar mode perturbations (magnetosonic waves) induced by a helical stochastic cosmological magnetic field and derive analytically the corresponding cosmic microwave background (CMB)...
Cosmological Constraints from Hubble Parameter versus Redshift Data (2006)
We use the Simon, Verde, & Jimenez (2005) determination of the redshift dependence of the Hubble parameter to constrain cosmological parameters in three dark energy cosmological models. We consider...
Gamma Ray Burst Constraints on Ultraviolet Lorentz Invariance Violation (2006)
Kahniashvili, Tina, Gogoberidze, Grigol, Ratra, Bharat
We present a unified general formalism for ultraviolet Lorentz invariance violation (LV) testing through electromagnetic wave propagation, based on both dispersion and rotation measure data. This...
Supernova Ia and Galaxy Cluster Gas Mass Fraction Constraints on Dark Energy (2006)
Wilson, Kyle M., Chen, Gang, Ratra, Bharat
We use the Riess et al.(2004) supernova Ia apparent magnitude versus redshift data and the Allen et al.(2004) galaxy cluster gas mass fraction versus redshift data to constrain dark energy models....
Inflation and accelerated expansion TeVeS cosmological solutions (2006)
Diaz-Rivera, Luz Maria, Samushia, Lado, Ratra, Bharat
We find exact exponentially expanding and contracting de Sitter solutions of the spatially homogeneous TeVeS cosmological equations of motion in the vacuum TeVeS model and a power law accelerated...
Polarized Cosmological Gravitational Waves from Primordial Helical Turbulence (2005)
Kahniashvili, Tina, Gogoberidze, Grigol, Ratra, Bharat
We show that helical turbulence produced during a first-order phase transition generates circularly polarized cosmological gravitational waves (GWs). The characteristic frequency of these GWs for an...
Effects of Cosmological Magnetic Helicity on the Cosmic Microwave Background (2005)
Kahniashvili, Tina, Ratra, Bharat
Cosmological magnetic fields induce temperature and polarization fluctuations in the cosmic microwave background (CMB) radiation. A cosmological magnetic field with current amplitude of order...
Neutrino Mass Limit from Galaxy Cluster Number Density Evolution (2005)
Kahniashvili, Tina, Von Toerne, Eckhard, Arhipova, Natalia A., Ratra, Bharat
Measurements of the evolution with redshift of the number density of massive galaxy clusters are used to constrain the energy density of massive neutrinos and so the sum of neutrino masses $\sum...
Kosowsky, Arthur, Kahniashvili, Tina, Lavrelashvili, George, Ratra, Bharat
A primordial cosmological magnetic field induces Faraday rotation of the cosmic microwave background polarization. This rotation produces a curl-type polarization component even when the unrotated...
Using White Dish CMB Anisotropy Data to Probe Open and Flat-A CDM Cosmogonies (2004)
Ratra, Bharat, Ganga, Ken, Sugiyama, Naoshi, Tucker, G. S., Griffin, G. S., Nguyen, H. T., ...
In this paper we present a similar analysis of the Tucker at al. (1993, hereafter T93) White Dish CMB anisotropy data collected at the South Pole. The white dish detector and telescope are described...
MAX 4 and MAX 5 CMB Anisotropy Measurement Constraints on Open and Flat-A CDM Cosmogonies (2004)
Tanaka, Stacy T., Ganga, Ken, Ratra, Bharat
We account for experimental and observational uncertainties in likelihood analyses of cosmic microwave background (CMB) anisotropy data from the MAX 4 and MAX 5 experiments.
Constraints on Scalar-Field Dark Energy from Galaxy Cluster Gas Mass Fraction versus Redshift (2004)
We use the Allen et al. (2004) Chandra measurements of x-ray gas mass fraction of 26 rich clusters to place constraints on the scalar-field dark energy model with inverse power law potential energy...
Looking for Cosmological Alfven Waves in WMAP Data (2004)
Chen, Gang, Mukherjee, Pia, Kahniashvili, Tina, Ratra, Bharat, Wang, Yun
A primordial cosmological magnetic field induces and supports vorticity or Alfven waves, which in turn generate cosmic microwave background (CMB) anisotropies. A homogeneous primordial magnetic field...
Chae, Kyu-Hyun, Chen, Gang, Ratra, Bharat, Lee, Dong-Wook
We use the statistics of strong gravitational lensing based on the Cosmic Lens All-Sky Survey (CLASS) data to constrain cosmological parameters in a spatially-flat, inverse power-law potential energy...
Non-Gaussian Error Distribution of Hubble Constant Measurements (2003)
Chen, Gang, Gott III, J. Richard, Ratra, Bharat
We construct the error distribution of Hubble constant ($H_0$) measurements from Huchra's compilation of 461 measurements of $H_0$ and the WMAP experiment central value $H_0$ = 71 km s$^{-1}$...
COBE-DMR-Normalized Dark Energy Cosmogony (2003)
Mukherjee, Pia, Banday, Anthony J., Riazuelo, Alain, Górski, Krzysztof M., Ratra, Bharat
Likelihood analyses of the COBE-DMR sky maps are used to determine the normalization of the inverse-power-law-potential scalar field dark energy model. Predictions of the DMR-normalized model are...
Median Statistics and the Mass Density of the Universe (2003)
We use weighted mean and median statistics techniques to combine individual estimates of Omega_m0, the present mean mass density in non-relativistic matter, and determine the observed values and...
Galactic Foreground Constraints from the Python V Cosmic Microwave Background Anisotropy Data (2003)
Mukherjee, Pia, Coble, Kim, Dragovan, Mark, Ganga, Ken, Kovac, John, Ratra, Bharat, ...
We constrain Galactic foreground contamination of the Python V cosmic microwave background anisotropy data by cross correlating it with foreground contaminant emission templates. To model foreground...
Mukherjee, Pia, Ganga, Ken, Ratra, Bharat, Rocha, Graca, Souradeep, Tarun, Sugiyama, Naoshi, ...
We use joint likelihood analyses of combinations of fifteen cosmic microwave background (CMB) anisotropy data sets from the DMR, UCSB South Pole 1994, Python I--III, ARGO, MAX 4 and 5, White Dish,...
OVRO CMB Anisotropy Measurement Constraints on Flat-Lambda and Open CDM Cosmogonies (2002)
Mukherjee, Pia, Souradeep, Tarun, Ratra, Bharat, Sugiyama, Naoshi, Górski, Krzysztof M.
We use Owens Valley Radio Observatory (OVRO) cosmic microwave background (CMB) anisotropy data to constrain cosmological parameters. We account for the OVRO beamwidth and calibration uncertainties,...
The Cosmological Constant and Dark Energy (2002)
Peebles, P. J. E., Ratra, Bharat
Physics invites the idea that space contains energy whose gravitational effect approximates that of Einstein's cosmological constant, Lambda; nowadays the concept is termed dark energy or...
Radio Galaxy Redshift-Angular Size Data Constraints on Dark Energy (2002)
Podariu, Silviu, Daly, Ruth A., Mory, Matthew P., Ratra, Bharat
We use FRIIb radio galaxy redshift-angular size data to constrain cosmological parameters in a dark energy scalar field model. The derived constraints are consistent with but weaker than those...
Cosmological Constraints from Compact Radio Source Angular Size versus Redshift Data (2002)
We use the Gurvits, Kellermann, & Frey compact radio source angular size versus redshift data to place constraints on cosmological model parameters in models with and without a constant or...
Mukherjee, Pia, Dennison, Brian, Ratra, Bharat, Simonetti, John H., Ganga, Ken, Hamilton, Jean-Christophe
We study Galactic emission foreground contamination of the OVRO and UCSB South Pole 1994 cosmic microwave background (CMB) anisotropy data by cross-correlating with templates of infrared dust...
Park, Chan-Gyung, Park, Changbom, Ratra, Bharat
We study the effects of diffuse Galactic, far-infrared extragalactic source, and radio point source emission on the cosmic microwave background (CMB) anisotropy data anticipated from the MAP...
Cosmological Parameter Determination from Counts of Galaxies (2001)
Podariu, Silviu, Ratra, Bharat
We study constraints that anticipated DEEP survey galaxy counts versus redshift data will place on cosmological model parameters in models with and without a constant or time-variable cosmological...
Window Function for Non-Circular Beam CMB Anisotropy Experiment (2001)
Souradeep, Tarun, Ratra, Bharat
We develop computationally rapid methods to compute the window function for a cosmic microwave background anisotropy experiment with a non-circular beam which scans over large angles on the sky. To...
Gaussianity of Degree-Scale Cosmic Microwave Background Anisotropy Observations (2001)
Park, Chan-Gyung, Park, Changbom, Ratra, Bharat, Tegmark, Max
We present results from a first test of the Gaussianity of degree-scale cosmic microwave background (CMB) anisotropy. We investigate Gaussianity of the CMB anisotropy by studying the topology of CMB...
Binned Cosmic Microwave Background Anisotropy Power Spectra: Peak Location (2001)
Podariu, Silviu, Souradeep, Tarun, Gott III, J. Richard, Ratra, Bharat, Vogeley, Michael S.
We use weighted mean and median statistics techniques to combine individual cosmic microwave background (CMB) anisotropy detections and determine binned, multipole-space, CMB anisotropy power...
Podariu, Silviu, Nugent, Peter, Ratra, Bharat
We examine the constraints that satellite-acquired Type Ia and IIP supernova apparent magnitude versus redshift data will place on cosmological model parameters in models with and without a constant...
Podariu, Silviu, Nugent, Peter, Ratra, Bharat
We examine the constraints that satellite-acquired Type Ia and IIP supernova apparent magnitude versus redshift data will place on cosmological model parameters in models with and without a constant...
Median Statistics, H_0, and the Accelerating Universe (2000)
Gott III, J. Richard, Vogeley, Michael S., Podariu, Silviu, Ratra, Bharat
(Abridged) We develop median statistics that provide powerful alternatives to chi-squared likelihood methods and require fewer assumptions about the data. Applying median statistics to Huchra's...
Supernovae Ia Constraints on a Time-Variable Cosmological "Constant" (1999)
Podariu, Silviu, Ratra, Bharat
The energy density of a scalar field $\phi$ with potential $V(\phi) \propto \phi^{-\alpha}$, $\alpha > 0$, behaves like a time-variable cosmological constant that could contribute significantly to...
Rocha, Graca, Stompor, Radoslaw, Ganga, Ken, Ratra, Bharat, Platt, Stephen R., Sugiyama, Naoshi, ...
We use Python I, II, and III cosmic microwave background anisotropy data to constrain cosmogonies. We account for the Python beamwidth and calibration uncertainties. We consider open and...
Ratra, Bharat, Stompor, Radoslaw, Ganga, Ken, Rocha, Graca, Sugiyama, Naoshi, Gorski, Krzysztof M.
We use combinations of ten small-scale cosmic microwave background anisotropy data sets from the UCSB South Pole 1994, ARGO, MAX 4 and 5, White Dish and SuZIE experiments to constrain cosmogonies. We...
Graça Rocha, Radoslaw Stompor, Ken Ganga, Bharat Ratra, Stephen R. Platt, Naoshi Sugiyama, ...
We use Python I, II, and III cosmic microwave background anisotropy data to constrain cosmogonies. We account for the Python beamwidth and calibration uncertainties. We consider open and...
ARGO CMB Anisotropy Measurement Constraints on Open and Flat-Lambda CDM Cosmogonies (1998)
Ratra, Bharat, Ganga, Ken, Stompor, Radoslaw, Sugiyama, Naoshi, De Bernardis, Paolo, Gorski, Krzysztof M.
We use data from the ARGO cosmic microwave background (CMB) anisotropy experiment to constrain cosmogonies. We account for the ARGO beamwidth and calibration uncertainties, and marginalize over the...
Ucsb South Pole, Radoslaw Stompor, White Dish, Suzie Data, Ken Ganga, ...
We use combinations of ten small-scale cosmic microwave background anisotropy data sets from the UCSB South Pole 1994, ARGO, MAX 4 and 5, White Dish and SuZIE experiments to constrain cosmogonies. We...
CMB Anisotropy Correlation Function and Topology from Simulated Maps for MAP (1997)
Park, Changbom, Colley, Wesley N., Gott III, J. Richard, Ratra, Bharat, Spergel, David N., Sugiyama, Naoshi
We have simulated cosmic microwave background (CMB) anisotropy maps for several COBE-DMR-normalized cold dark matter (CDM) cosmogonies, to make predictions for the upcoming MAP experiment. We have...
Ganga, Ken, Ratra, Bharat, Lim, Mark A., Sugiyama, Naoshi, Tanaka, Stacy T.
We account for experimental and observational uncertainties in likelihood analyses of cosmic microwave background (CMB) anisotropy data from the MAX 4 and MAX 5 experiments. These analyses use CMB...
Ganga, K., Ratra, Bharat, Church, S. E., Sugiyama, Naoshi, Ade, P. A. R., Holzapfel, W. L., ...
We use arcminute-scale data from the Sunyaev-Zel'dovich Infrared Experiment to set limits on anisotropies in the cosmic microwave background radiation in open and spatially-flat-Lambda cold dark...
Large-scale structure in COBE-normalized cold dark matter cosmogonies (1997)
Cole, Shaun, Weinberg, David H., Frenk, Carlos S., Ratra, Bharat
We study the clustering of the mass distribution in COBE-normalized open and flat CDM models using large N-body simulations. With an age of the universe of 14 Gyr (12 Gyr) for the flat (open) models...
Ganga, Ken, Ratra, Bharat, Gundersen, Josh, Sugiyama, Naoshi
We develop methods to account for experimental and observational uncertainties in likelihood analyses of data from cosmic microwave background (CMB) anisotropy experiments and apply them to an...
Ganga, Ken, Ratra, Bharat, Sugiyama, Naoshi
Goodness-of-fit statistics are used to quantitatively establish the compatibility of CMB anisotropy predictions in a wide range of DMR-normalized, open and spatially-flat $\Lambda$, CDM cosmogonies...
CMB Anisotropy in COBE-DMR-Normalized Flat $\Lambda$ CDM Cosmogony (1995)
Ratra, Bharat, Sugiyama, Naoshi
We compute the cosmic microwave background (CMB) anisotropy in a low-density, flat, cosmological constant, cold dark matter model which is normalized to the two-year COBE DMR sky map. Although...
CMB Anisotropy in COBE-DMR-Normalized Open CDM Cosmogony (1995)
Ratra, Bharat, Banday, Anthony J., Gorski, Krzysztof M., Sugiyama, Naoshi
We compute the CMB anisotropy in an open inflation CDM model which is normalized to the two-year DMR sky map. Presently available CMB data is consistent with $\Omega_0 \sim 0.3 - 0.4$, but does not...
COBE-DMR-normalised Open Inflation, CDM Cosmogony (1995)
Gorski, Krzysztof M., Ratra, Bharat, Sugiyama, Naoshi, Banday, Anthony J.
Fourier analysis on a cut sky of the two-year COBE DMR 53 and 90 GHz sky maps (in galactic coordinates) is used to determine the normalisation of an open inflation model based on the cold dark matter...
CBR Anisotropy in an Open Inflation, CDM Cosmogony (1994)
Kamionkowski, Marc, Ratra, Bharat, Spergel, David N., Sugiyama, Naoshi
We compute the cosmic background radiation anisotropy, produced by energy-density fluctuations generated during an early epoch of inflation, in an open cosmological model based on the cold dark...
CMB Anisotropy Correlation Function and Topology from Simulated Maps for MAP (1469)
Changbom Park, Wesley N. Colley, J. Richard, Gott Iii, Bharat Ratra, David N, ...
We have simulated cosmic microwave background (CMB) anisotropy maps for several COBE-DMR-normalized cold dark matter (CDM) cosmogonies, to make predictions for the MAP experiment, an upcoming...