Correlated primordial perturbations in light of CMB and large scale structure data

Abstract

We use cosmic microwave background (CMB) and large scale structure data to constrain cosmological models where the primordial perturbations have both an adiabatic and a cold dark matter (CDM) isocurvature component. We allow for a possible correlation between the adiabatic and isocurvature modes, and for different spectral indices for the power in each mode and for their correlation. We do a likelihood analysis with 11 independent parameters and discuss the effect of choosing the pivot scale for the definition of amplitude parameters. The upper limit to the isocurvature fraction is 18% around a pivot scale k 0:01 Mpc ÿ1 . For smaller pivot wavenumbers the limit stays about the same. For larger pivot wavenumbers, very large values of the isocurvature spectral index are favored, which makes the analysis problematic, but larger isocurvature fractions seem to be allowed. For large isocurvature spectral indices n iso > 2 a positive correlation between the adiabatic and isocurvature mode is favored, and for n iso < 2 a negative correlation is favored. The upper limit to the nonadiabatic contribution to the CMB temperature variance is 7.5%. Of the standard cosmological parameters, determination of the CDM density ! c and the sound horizon angle (or the Hubble constant H 0 ) are affected most by a possible presence of a correlated isocurvature contribution. The baryon density ! b nearly retains its ''adiabatic value''.

Spectator stresses and CMB observables

“…2). Spectator stresses can be treated and discussed in conjunction with a dominant adiabatic mode; absent the adiabatic mode the shapes of the TT correlations have intermediate features between the isocurvature humps of the CDM-radiation mode [9]; the situation is also different from the case of the magnetized CMB observables when the adiabatic mode is absent [5] (see also [13]). There has been recently some confusing statement in the literature.…”

“…If the source of large-scale inhomogeneity resides in a spectator anisotropic stress it will be interesting to compute the dynamical evolution of the relativistic fluctuations of the geometry as well as the temperature and polarization correlations. It will be argued that the "stressed" initial conditions for the CMB anisotropies constitute an intermediate case between the purely adiabatic and the purely non-adiabatic initial conditions (see, e.g., [9]). …”

“…It has been assumed that the power spectrum of σ x is assigned as P σ (k) = B(k/k p ) nx−1 . The amplitude has been left adjustable 9 and, for the purposes of Fig. 2, B = 2.41 × 10 −9 and k p = 0.002 Mpc −1 .…”

“…There are diverse initial conditions which could be imposed to the whole system. They are customarily divided into adiabatic and non-adiabatic [9,10](see also [7,8]). In what follows we shall be interested in enforcing the adiabaticity condition by demanding that, at the onset of the dynamical evolution, the Hamiltonian and the momentum constraints are satisfied.…”

A scale-dependent power asymmetry from isocurvature perturbations

“…The CMB power spectrum may be divided into contributions from adiabatic and isocurvature perturbations [66]:…”