INVESTIGADORES
GANGUI Alejandro
artículos
Título:
Cosmic Strings and Cosmic Variance
Autor/es:
ALEJANDRO GANGUI; LEANDROS PERIVOLAROPOULOS
Revista:
ASTROPHYSICAL JOURNAL
Editorial:
University of Chicago Press
Referencias:
Año: 1995 vol. 447 p. 1 - 7
ISSN:
0004-637X
Resumen:
By using a simple analytical model based on counting random multiple impulses
inflicted on photons by a network of cosmic strings we show how to construct
the general q-point temperature correlation function of the Cosmic Microwave
Background radiation. Our analysis is sensible specially for large angular
scales where the Kaiser-Stebbins effect is dominant. Then we concentrate our
study on the four-point function and in particular on its zero-lag limit,
namely, the excess kurtosis parameter, for which we obtain a predicted value of
$\sim 10^{-2}$. In addition, we estimate the cosmic variance for the kurtosis
due to a Gaussian fluctuation field, showing its dependence on the primordial
spectral index of density fluctuations $n$ and finding agreement with previous
published results for the particular case of a flat Harrison-Zel'dovich
spectrum. Our value for the kurtosis compares well with previous analyses but
falls below the threshold imposed by the cosmic variance when commonly accepted
parameters from string simulations are considered. In particular the
non-Gaussian signal is found to be inversely proportional to the scaling number
of defects, as could be expected by the central limit theorem.