Nikolaos Tetradis
Nikolaos Tetradis
Nikolaos Tetradis
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Define the spectra, bispectra and trispectra as〈ϕ a (k, η)ϕ b (q, η)〉 ≡δ D (k + q)P ab (k, η)〈ϕ a (k, η)ϕ b (q, η)ϕ c (p, η)〉 ≡δ D (k + q + p)B abc (k, q, p, η)〈ϕ a (k, η)ϕ b (q, η)ϕ c (p, η)ϕ d (r, η)〉 ≡δ D (k + q)δ D (p + r)P ab (k, η)P cd (p, η)+δ D (k + p)δ D (q + r)P ac (k, η)P bd (q, η)+δ D (k + r)δ D (q + p)P ad (k, η)P bc (q, η)+δ D (k + p + q + r)Q abcd (k, p, q, r, η).Essential approximation: Neglect the effect of the trispectrum onthe evolution of the bispectrum.N. <strong>Tetradis</strong> University of AthensThe inhomogeneity of the Universe and the cosmological model