## Lost in k-space?

**Fig 1***:
Latest constraints on the linear matter power spectrum
*

Here's a combination of all data as of July 2002 taking into account
calibration and beam errors (click on it for ps):

Here are text files with the corresponding
data,
window functions and
correlation matrix.
The window function file above contains 25 columns, giving the
window functions W_l for each of the 25 band power measurements with
the convention
*(dT)^2 = sum W_l (dT_l)^2 = sum l(l+1) W_l C_l/2 pi*.
Note that this differs from the traditional definition by a factor of l
- it's more approptiate to think of the band power as an average
on a linear plot rather than on a log-plot now that we're all plotting
small-scale CMB data with a linear l-axis.
Also, note that some of these window functions go slightly
negative, and that that's OK.
Note that the file gives not the covariance matrix but the dimensionless
correlation matrix *R*, which is related to the covariance matrix
*C* by
*C_ij = R_ij sigma_i sigma_j*.
To test a model against this data, put the first 2000 values
of dT_l^2 = l(l+1) C_l/2 pi into a vector c and compute
*chi2 = (q-Wc)^t C^{-1} (q-Wc)*,
where *q* is our vector of 25 data points and
*W* is our window matrix.
You'll find more data details and links here.
#
Separating the Early Universe from the Late Universe:

cosmological parameter estimation beyond the black box

Please click here to download
our paper.

Click if
you are interested in other research of mine.

###
Authors:

Max Tegmark,
Matias Zaldarriaga
###
Abstract:

We present a method for measuring the cosmic matter budget without assumptions
about speculative Early Universe physics, and for measuring the primordial
power spectrum *P*(k)* non-parametrically, either by combining CMB and LSS
information or by using CMB polarization. Our method complements currently
fashionable ``black box'' cosmological parameter analysis, constraining
cosmological models in a more physically intuitive fashion by mapping
measurements of CMB, weak lensing and cluster abundance into *k*-space, where
they can be directly compared with each other and with galaxy and Lyman alpha
forest clustering. Including the new CBI results, we find that CMB measurements
of *P(k)* overlap with those from 2dF galaxy clustering by over an order of
magnitude in scale, and even overlap with weak lensing measurements. We
describe how our approach can be used to raise the ambition level beyond
cosmological parameter fitting as data improves, testing rather than assuming
the underlying physics.
###
Reference info:

astro-ph/0207047, *Phys. Rev. D*, in press

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This page was last modified October 6, 2002.
max@physics.upenn.edu