Cosmic Microwave Background Radiation Data Analysis
Principal Investigator
George Smoot,
Lawrence Berkeley National Laboratory
Co-Investigators
Julian Borrill,
Lawrence Berkeley National Laboratory
Andrew Jaffe,
Center for Particle Astrophysics, UC Berkeley
A Map Of The Imprint Of The Universe's Primordial Perturbations In The Cosmic Microwave Background Radiation
Research Objectives
To develop the novel computational techniques necessary to extract fundamental
cosmological parameters from forthcoming CMB datasets.
Computational Approach
Central to our task is being able to locate and describe the maximum of
the likelihood function of the cosmological parameters given the data -
here an N-pixel map generated by any one of the forthcoming CMB observations.
At present N is at most a few thousand, but this will increase to tens
and hundreds of thousands with the MAXIMA and BOOMERANG ballon flights,
and to about a million with the MAP and PLANCK satellite missions. Our
present approach scales as N-squared in size and N-cubed in time so a supercomputer
like the T3E is essential to our work. However, even this will be unable
to handle the largest datasets; we must therefore develop alternative algorithms
either with better scaling properties, or that repeatedly analyse only
a subset of the overall dataset at any time.
Accomplishments
Our project received funding in September 1997. In the two months since
then we have completed the development of two generations of the quadratic
estimator formalism for performing a rapid search of the parameter space
for the maximum of the likelihood function, and have implemented them on
the T3E both in serial and in parallel (using the LAPACK and ScaLAPACK
libraries respectively). We are currently working to demonstrate the ability
of the parallel code to analyse at least the first generation MAXIMA/BOOMERANG
data. To this end we are now developing simulated datasets, comprising
the signal from a known underlying theory and a model of the instrument
noise and sky foregrounds associated with each experiment.
Significance
The Cosmic Microwave Background provides a picture of the universe as it
was a mere 100,000 years after the Big Bang. As the earliest possible photon
image available to us it is our most powerful discriminant between different
cosmological models. The unprecedently detailed CMB datasets obtained in
the next 10 years will allow us to determine the fundamental cosmological
parameters - in many cases currently known to no better than a factor of
2 - to the 1% level.