Department
of Physics
116 Cardwell Hall
Kansas State University
Manhattan, KS 66506-2601, U.S.A.
Phone: (785) 532 6265 (Work) or (785) 532 6786 (Msgs)
Fax: (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 JPEG pg 1 pg 2 pg 3 pg 4 pg 5 pg 6 pg 7 pg 8
pg 9 pg 10 pg 11 pg 12 pg 13 pg 14 pg 15
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).
Scanned JPEG pg 1
pg 2 pg 3 pg 4 pg 5
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
JPEG pg 1 pg 2 pg
3 pg 4
pg 5
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 JPEG pg 1 pg
2 pg 3
pg 4 pg 5 pg 6
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
Dr.
Pia Mukherjee
Dr Tarun Souradeep
Dr. Graca Rocha, now at University
of Oxford
Last updated 28 August 2000.