Phone: (785) 532 6265 (Work) or (785) 532 6786 (Msgs)
Fax: (785) 532 6787 or (785) 532 6806
E-Mail: ratra@phys.ksu.edu
My current research focuses on developing and testing cosmological
models for the large-scale matter
and radiation distributions in the universe.
A primary goal is to test Einstein's general relativity on extremely
large spatial- and temporal-scales,
inaccessible to any other method. More immediate goals include determining
the geometry and contents
of the universe and how large-scale structure in the universe was formed.
The cosmological models
studied include currently popular ones that are spatially open, or
spatially flat and dominated by
quintessence, a time-variable cosmological `constant' (both developed
in collaboration with
Jim
Peebles). Of particular interest are the predictions these models make
for the cosmic microwave
background radiation (CMBR) anisotropy.
The anisotropy in the CMBR, i.e., the variation in the CMBR temperature
from point to point in the
sky, contains information about the geometry and contents of the universe.
Hence the current flood of
CMBR observational data enable inter-comparison of a broad range of
cosmological models, and thus
provides a powerful probe of the large-scale parameters of the universe.
For the past few years we have
been analyzing CMBR anisotropy data sets from the NASA COBE satellite
and other ground-based and
balloon-borne experiments. We should soon be able to significantly
constrain large-scale parameters of
the universe by combining data from a large number of CMBR anisotropy
experiments.
Other interests include inflation,, dark matter, the classical cosmological
tests, cosmological simulations
of low- and intermediate-redshift large-scale structure, and cosmological
magnetic fields.
We collaborate with the Kansas
State University High Energy Physics Group and the
University of Kansas Cosmology
Group and do some of our numerical computations on the HP Convex
Exemplars at the Kansas State University
Center for Scientific Supercomputing.
B. Ratra, "Restoration of Spontaneously Broken Continuous Symmetries
in de Sitter Spacetime",
Phys. Rev. D 31, 1931 (1985). PRD
Online
W. Fischler, B. Ratra, and L. Susskind, "Quantum Mechanics of Inflation",
Nucl. Phys. B 259, 730 (1985). Scanned
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J. Atick, A. Dhar, and B. Ratra, "Superstring Propagation in Curved
Superspace in the Presence of
Background Super Yang-Mills Fields", Phys. Lett. B 169, 54 (1986).
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J. Atick, A. Dhar, and B. Ratra, "Superspace Formulation of Ten Dimensional
N = 1 Supergravity
Coupled to N = 1 Super Yang-Mills Theory", Phys. Rev. D 33, 2824 (1986).
PRD
Online
B. Ratra and L. Yaffe, "Spherically Symmetric Classical Solutions in
SU(2) Gauge Theory with a
Higgs Field", Phys. Lett. B 205, 57 (1988). Scanned
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P.J.E. Peebles and B. Ratra, "Cosmology with a Time-Variable Cosmological
`Constant'",
Astrophys. J. Lett. 325, L17 (1988). ADS
B. Ratra and P.J.E. Peebles, "Cosmological Consequences of a Rolling
Homogeneous Scalar Field",
Phys. Rev. D 37, 3406 (1988). PRD
Online
B. Ratra, "Expressions for Linearized Perturbations in Ideal Fluid Cosmological
Models",
Phys. Rev. D 38, 2399 (1988). PRD
Online
B. Ratra, "Joining Conditions for Cosmological Perturbations at an Equation
of State Transition",
Phys. Rev. D 43, 3802 (1991). PRD
Online
B. Ratra, "Inflation in an Exponential Potential Scalar Field Model",
Phys. Rev. D 45, 1913 (1992).
PRD Online
B. Ratra, "Quantum Mechanics of Exponential Potential Inflation", Phys.
Rev. D 40, 3939 (1989).
PRD Online
B. Ratra, "Some Observational Constraints on Scalar Field Inflation
Models of the Very Early
Universe", Princeton preprint PUPT-1132 (1989). Postscript
B. Ratra, "Inflation in a Quartic Potential Scalar Field Model",
Caltech preprint GRP-217/CALT-68-1594 (1989). Postscript
B. Ratra, "Expressions for Linearized Perturbations in a Massive Scalar
Field Dominated
Cosmological Model", Phys. Rev. D 44, 352 (1991). PRD
Online
B. Ratra, "Inflation and `Reheating' in a Scalar Field Dominated Cosmological
Model",
Caltech preprint GRP-229/CALT-68-1666 (1990). Postscript
B. Ratra, "Effect of `Reheating' on Inflation Epoch Spatial Irregularities",
Caltech preprint GRP-230/CALT-68-1667 (1990). Postscript
B. Ratra, "Dependence of Cosmological Energy Density Irregularities
on the Shape of the Scalar Field
Potential During Inflation and `Reheating'", Phys. Rev. D 44, 365 (1991).
PRD
Online
B. Ratra, "Observationally Constrainable Free Parameters of Scalar Field
Inflation Models",
Phys. Lett. B 260, 21 (1991). Scanned
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B. Ratra, "Is Inflation Observationally `Fine-Tuned'?", in Trends in
Astroparticle Physics, eds. D. Cline
and R. Peccei (World Scientific 1992), p. 143. Postscript
B. Ratra, "Cosmological `Seed' Magnetic Field From Inflation", Astrophys. J. Lett. 391, L1 (1992). ADS
B. Ratra, "Inflation Generated Cosmological Magnetic Field",
Caltech preprint GRP-287/CALT-68-1751 (1991). Postscript
B. Ratra and A. Quillen, "Gravitational Lensing Effects in a Time-Variable
Cosmological `Constant'
Cosmology", Mon. Not. Roy. Astr. Soc. 259, 738 (1992). ADS
B. Ratra, "Comments on `Dependence of Density Perturbations on the Coupling
Constant in a Simple
Model of Inflation'", Princeton preprint PUPT-1345 (1992). Postscript
B. Ratra, "Spontaneously Broken Continuous Symmetries in Hyperbolic
(or Open) de Sitter
Spacetime", Phys. Rev. D 50, 5252 (1994). PRD
Online
B. Ratra and P.J.E. Peebles, "Inflation in an Open Universe", Phys.
Rev. D 52, 1837 (1995).
PRD Online
B. Ratra and P.J.E. Peebles, "Cold Dark Matter Cosmogony in an Open
Universe",
Astrophys. J. Lett. 432, L5 (1994). ADS
M. Kamionkowski, B. Ratra, D.N. Spergel, and N. Sugiyama, "Cosmic Background
Radiation
Anisotropy in an Open Inflation, Cold Dark Matter Cosmogony",
Astrophys. J. Lett. 434, L1 (1994). ADS
B. Ratra, "CDM Cosmogony in an Open Universe", in CMB Anisotropies Two
Years After COBE:
Observations, Theory, and the Future, ed. L.M. Krauss (World Scientific
1994), p. 158. Postscript
K.M. Górski, B. Ratra, N. Sugiyama, and A.J. Banday, "COBE DMR-Normalized
Open
Inflation, Cold Dark Matter Cosmogony", Astrophys. J. Lett. 444, L65
(1995). ADS
B. Ratra, R.M. Kulsrud, and A.C. Quillen, "`Cosmological' Magnetic Braking
and the Formation of
`Primordial' Stars and Black Holes", Princeton preprint PUPT-1535 (1995).
Postscript
B. Ratra, N. Sugiyama, A.J. Banday, and K.M. Górski, "Cosmic
Microwave Background Anisotropy
in COBE-DMR-Normalized Open and Flat- Cold Dark Matter Cosmogonies",
Astrophys. J. 481, 22 (1997). ADS
K. Ganga, B. Ratra, and N. Sugiyama, "Tentative Appraisal of Compatibility
of Small-Scale Cosmic
Microwave Background Anisotropy Detections in the Context of COBE-DMR-Normalized
Open and
Flat-Lambda Cold Dark Matter Cosmogonies", Astrophys. J. Lett. 461,
L61 (1996). ADS
K. Ganga, B. Ratra, J.O. Gundersen, and N. Sugiyama, "UCSB South Pole
1994 Cosmic Microwave
Background Anisotropy Measurement Constraints on Open and Flat-Lambda
Cold Dark Matter
Cosmogonies", Astrophys. J. 484, 7 (1997). ADS
K.M. Górski, B. Ratra, R. Stompor, N. Sugiyama, and A.J. Banday,
"COBE-DMR-Normalized Open
Cold Dark Matter Cosmogonies", Astrophys. J. Supp. 114, 1 (1998). ADS
K. Ganga, B. Ratra, S.E. Church, N. Sugiyama, P.A.R. Ade, W.L. Holzapfel,
P.D. Mauskopf, and
A.E. Lange, "Using Sunyaev-Zel'dovich Infrared Experiment (SuZIE) Arcminute-Scale
Cosmic
Microwave Background Anisotropy Data to Probe Open and Flat-Lambda
Cold Dark Matter
Cosmogonies", Astrophys. J. 484, 517 (1997). ADS
S. Cole, D.H. Weinberg, C.S. Frenk, and B. Ratra, "Large-Scale Structure
in COBE-Normalized Cold
Dark Matter Cosmogonies", Mon. Not. Roy. Astron. Soc. 289, 37 (1997).
ADS
K. Ganga, B. Ratra, M.A. Lim, N. Sugiyama, and S.T. Tanaka, "MAX 4 and
MAX 5 Cosmic
Microwave Background Anisotropy Measurement Constraints on Open and
Flat- Lambda Cold Dark
Matter Cosmogonies", Astrophys. J. Supp. 114, 165 (1998). ADS
B. Ratra, K. Ganga, N. Sugiyama, G.S. Tucker, G.S. Griffin, H.T. Nguyên,
and J.B. Peterson, "Using
White Dish CMB Anisotropy Data to Probe Open and Flat-Lambda CDM Cosmogonies",
Astrophys. J. 505, 8 (1998). ADS
C. Park, W.N. Colley, J.R. Gott III, B. Ratra, D.N. Spergel, and N.
Sugiyama, "Cosmic Microwave
Background Anisotropy Correlation Function and Topology from Simulated
Maps for MAP",
Astrophys. J. 506, 473 (1998). ADS
B. Ratra, K. Ganga, R. Stompor, N. Sugiyama, P. de Bernardis, and K.M.
Górski, "ARGO CMB
Anisotropy Measurement Constraints on Open and Flat-Lambda Cold Dark
Matter Cosmogonies",
Astrophys. J. 510, 11 (1999). ADS
B. Ratra, R. Stompor, K. Ganga, G. Rocha, N. Sugiyama, and K.M. Górski,
"Cosmic Microwave
Background Anisotropy Constraints on Open and Flat-Lambda Cold Dark
Matter Cosmogonies from
UCSB South Pole, ARGO, MAX, White Dish, and SuZIE Data", Astrophys.
J. 517, 549 (1999). ADS
G. Rocha, R. Stompor, K. Ganga, B. Ratra, S.R. Platt, N. Sugiyama, and
K.M. Górski, "Python I, II
and III Cosmic Microwave Background Anisotropy Measurement Constraints
on Open and
Flat-Lambda Cold Dark Matter Cosmogonies", Astrophys. J. 525, 1 (1999).
ADS
S. Podariu and B. Ratra, "Supernova Ia Constraints on a Time-Variable
Cosmological "Constant" ",
Astrophys. J. 532, 109 (2000). ADS
J.R. Gott, M.S. Vogeley, S. Podariu, and B. Ratra, "Median Statistics,
H_0, and the Accelerating
Universe", Astrophys. J., submitted (2000). astro-ph
S. Podariu, P. Nugent, and B. Ratra, "Cosmological-Model-Parameter Determination
from
Satellite-Acquired Type Ia and IIP Supernova Data",
Astrophys. J., submitted (2000). astro-ph
Last updated 28 August 2000.
