Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Nonlinear Effects in the Amplitude of Cosmological Density Fluctuations   The amplitude of cosmological density fluctuations, sigma_8, has been studied
and estimated by analysing many cosmological observations. The values of the
estimates vary considerably between the various probes. However, different
estimators probe the value of sigma_8 in different cosmological scales and do
not take into account the nonlinear evolution of the parameter at late times.
We show that estimates of the amplitude of cosmological density fluctuations
derived from cosmic flows are systematically higher than those inferred at
early epochs from the CMB because of nonlinear evolution at later times. We
discuss the past and future evolution of linear and nonlinear perturbations,
derive corrections to the value of sigma_8 and compare amplitudes after
accounting for these differences.

8
The categories of this paper are: hep-ex
16
The categories of this paper are: stat
11
The categories of this paper are: hep-lat
14
The categories of this paper are: math-ph
24
The categories of this paper are: dg-ga
9
The categories of this paper are: nlin
12
The categories of this paper are: nucl-th
37
The categories of this paper are: supr-con
17
The categories of this paper are: q-fin
30
The categories of this paper are: q-alg
21
The categories of this paper are: adap-org
4
The categories of this paper are: cond-mat
29
The categories of this paper are: funct-an
18
The categories of this paper are: econ
13
The categories of this paper are: quant-ph
28
The categories of this paper are: alg-geom