8 research outputs found
`Standard' Cosmological model & beyond with CMB
Observational Cosmology has indeed made very rapid progress in the past
decade. The ability to quantify the universe has largely improved due to
observational constraints coming from structure formation Measurements of CMB
anisotropy and, more recently, polarization have played a very important role.
Besides precise determination of various parameters of the `standard'
cosmological model, observations have also established some important basic
tenets that underlie models of cosmology and structure formation in the
universe -- `acausally' correlated initial perturbations in a flat,
statistically isotropic universe, adiabatic nature of primordial density
perturbations. These are consistent with the expectation of the paradigm of
inflation and the generic prediction of the simplest realization of
inflationary scenario in the early universe. Further, gravitational instability
is the established mechanism for structure formation from these initial
perturbations. The signature of primordial perturbations observed as the CMB
anisotropy and polarization is the most compelling evidence for new, possibly
fundamental, physics in the early universe. The community is now looking beyond
the estimation of parameters of a working `standard' model of cosmology for
subtle, characteristic signatures from early universe physics.Comment: 16 pages, 6 figures, Plenary talk, Proc. of GR-19, Mexico City,
Mexico (Jul 5-9, 2010). To appear in a special issue in Class. Q. Gra
Cosmology with CMB anisotropy
Measurements of CMB anisotropy and, more recently, polarization have played a
very important role allowing precise determination of various parameters of the
`standard' cosmological model. The expectation of the paradigm of inflation and
the generic prediction of the simplest realization of inflationary scenario in
the early universe have also been established -- `acausally' correlated initial
perturbations in a flat, statistically isotropic universe, adiabatic nature of
primordial density perturbations. Direct evidence for gravitational instability
mechanism for structure formation from primordial perturbations has been
established. In the next decade, future experiments promise to strengthen these
deductions and uncover the remaining crucial signature of inflation -- the
primordial gravitational wave background.Comment: Plenary talk at the IXth. International Workshop on High Energy
Physics Phenomenology (WHEPP-9), Institute of Physics, Bhubaneshwar, India.
Jan 3-14, 2006; To appear in the Proceedings to be published in Pramana; 12
pages, 2 figure
The current status of observational cosmology
Observational cosmology has indeed made very rapid progress in recent years.
The ability to quantify the universe has largely improved due to observational
constraints coming from structure formation. The transition to precision
cosmology has been spearheaded by measurements of the anisotropy in the cosmic
microwave background (CMB) over the past decade. Observations of the large
scale structure in the distribution of galaxies, high red-shift supernova, have
provided the required complementary information. We review the current status
of cosmological parameter estimates from joint analysis of CMB anisotropy and
large scale structure (LSS) data. We also sound a note of caution on
overstating the successes achieved thus far.Comment: 13 pages, 3 figures, Latex style files included, To appear in the
proceedings of ICGC-04. Minor rewording in the abstract and introductio
Primordial power spectrum from WMAP
The observed angular power spectrum of the cosmic microwave background
temperature anisotropy, , is a convolution of a cosmological radiative
transport kernel with an assumed primordial power spectrum of inhomogeneities.
Exquisite measurements of over a wide range of multipoles from the
Wilkinson Microwave Anisotropy Probe (WMAP) has opened up the possibility to
deconvolve the primordial power spectrum for a given set of cosmological
parameters (base model). We implement an improved (error sensitive)
Richardson-Lucy deconvolution algorithm on the measured angular power spectrum
from WMAP assuming a concordance cosmological model. The most prominent feature
of the recovered is a sharp, infra-red cut off on the horizon scale. The
resultant spectrum using the recovered spectrum has a likelihood far
better than a scale invariant, or, `best fit' scale free spectra
( {\it w.r.t.} Harrison Zeldovich, and, {\it w.r.t.} power law with ). The recovered has a
localized excess just below the cut-off which leads to great improvement of
likelihood over the simple monotonic forms of model infra-red cut-off spectra
considered in the post WMAP literature. The recovered , in particular,
the form of infra-red cut-off is robust to small changes in the cosmological
parameters. We show that remarkably similar form of infra-red cutoff is known
to arise in very reasonable extensions and refinements of the predictions from
simple inflationary scenarios. Our method can be extended to other cosmological
observations such as the measured matter power spectrum and, in particular, the
much awaited polarization spectrum from WMAP.Comment: 20 pages, 12 figures, uses Revtex4, Matches version accepted to Phys.
Rev. D. More extensive discussion of the method in the appendix, references
added and typos correcte
Working group report: Astroparticle and neutrino physics
The working group on astroparticle and neutrino physics at WHEPP-9 covered a wide range of topics. The main topics were neutrino physics at INO, neutrino astronomy and recent constraints on dark energy coming from cosmological observations of large scale structure and CMB anisotropy. © Indian Academy of Sciences