Hemispherical power asymmetry from a space-dependent component of the adiabatic power spectrum

We explore the hemispherical asymmetry predicted in cosmic microwave background polarization when there is an asymmetry in temperature anisotropies due to primordial perturbations. We consider the cases of asymmetries due to adiabatic and isocurvature modes, and tensor perturbations. We show that the asymmetry in the TE, EE and/or BB correlations can be substantially larger than those in the TT power spectrum in certain cases. The relative asymmetry in the different crosscorrelations, as well as the angular scale dependence, can in principle distinguish between different origins for the asymmetry.

“…The upper bound on α, implied from the lack of dipole asymmetry on quasar scales from the findings of [27,28], is α = −0.56. We choose this upper bound for studying this shape.…”

Section: Asymmetry From Adiabatic Perturbationsmentioning

confidence: 94%

Expected dipole asymmetry in CMB polarization

Namjoo

Abolhasani

Assadullahi

et al. 2015

“…[64]) have questioned the significance of the power asymmetry on small scales, it is a persistent anomaly on large scales. There are many suggestions [65][66][67][68][69][70] as to how such an asymmetry might arise, and we study the possibility of the power asymmetry resulting from having more structure in the primordial power spectrum (PPS) in one hemisphere compared to the other.…”

Section: Hemispherical Power Asymmetrymentioning

confidence: 99%

The Knotted Sky I: Planck constraints on the primordial power spectrum

Aslanyan¹,

Price²,

Abazajian³

et al. 2014

Using the temperature data from Planck we search for departures from a powerlaw primordial power spectrum, employing Bayesian model-selection and posterior probabilities. We parametrize the spectrum with n knots located at arbitrary values of log k, with both linear and cubic splines. This formulation recovers both slow modulations and sharp transitions in the primordial spectrum. The power spectrum is well-fit by a featureless, power-law at wavenumbers k > 10 −3 Mpc −1 . A modulated primordial spectrum yields a better fit relative to ΛCDM at large scales, but there is no strong evidence for a departure from a power-law spectrum. Moreover, using simulated maps we show that a local feature at k ∼ 10 −3 Mpc −1 can mimic the suppression of large-scale power. With multi-knot spectra we see only small changes in the posterior distributions for the other free parameters in the standard ΛCDM universe. Lastly, we investigate whether the hemispherical power asymmetry is explained by independent features in the primordial power spectrum in each ecliptic hemisphere, but find no significant differences between them.

“…Instead of the step function forms for A ζ and C ζ that I am adopting, [23,24] takes A ζ ∝ C ζ ∝ k −n . To get sufficient suppression on scales k −1 < x ls /60 one needs n > 0.56, but this also causes strong scale dependence on scales k −1 > x ls /60.…”

mentioning

confidence: 99%

Generatingf_NLat ℓ ≲ 60

Lyth

2015

The CMB anisotropy at 60 seems to have some special features which include (i) a dipole modulation and (ii) a decrease in power. It is known that both of these effects can be generated if a curvaton-type field has a super-horizon perturbation. It is also known that this will generate non-gaussianity f NL in the same range of , whose magnitude has a lower bound coming from the magnitude of the observed CMB quadrupole. I revisit that bound in the present paper, and point out that it may or may not be compatible with current data which should therefore be re-analysed.