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Research output: Contribution to Journal/Magazine › Journal article › peer-review
Research output: Contribution to Journal/Magazine › Journal article › peer-review
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TY - JOUR
T1 - Negative running of the spectral index, hemispherical asymmetry and the consistency of Planck with large r
AU - McDonald, John
PY - 2014/11
Y1 - 2014/11
N2 - Planck favours a negative running of the spectral index, with the likelihood being dominated by low multipoles l less than or similar to 50 and no preference for running at higher /. A negative spectral index is also necessary for the 2-sigma Planck upper bound on the tensor-to-scalar ratio r to be consistent with values significantly larger than 0.1. Planck has also observed a hemispherical asymmetry of the CMB power spectrum, again mostly at low multipoles. Here we consider whether the physics responsible for the hemispherical asymmetry could also account for the negative running of the spectral index and the consistency of Planck with a large value of r. A negative running of the spectral index can be generated if the hemispherical asymmetry is due to a scale- and space-dependent modulation which suppresses the CMB power spectrum at low multipoles. We show that the observed hemispherical asymmetry at low l can be generated while satisfying constraints on the asymmetry at higher l and generating a negative spectral index of the right magnitude to account for the Planck observation and to allow Planck to be consistent with a large value of r.
AB - Planck favours a negative running of the spectral index, with the likelihood being dominated by low multipoles l less than or similar to 50 and no preference for running at higher /. A negative spectral index is also necessary for the 2-sigma Planck upper bound on the tensor-to-scalar ratio r to be consistent with values significantly larger than 0.1. Planck has also observed a hemispherical asymmetry of the CMB power spectrum, again mostly at low multipoles. Here we consider whether the physics responsible for the hemispherical asymmetry could also account for the negative running of the spectral index and the consistency of Planck with a large value of r. A negative running of the spectral index can be generated if the hemispherical asymmetry is due to a scale- and space-dependent modulation which suppresses the CMB power spectrum at low multipoles. We show that the observed hemispherical asymmetry at low l can be generated while satisfying constraints on the asymmetry at higher l and generating a negative spectral index of the right magnitude to account for the Planck observation and to allow Planck to be consistent with a large value of r.
KW - cosmological parameters from CMBR
KW - cosmological perturbation theory
KW - CMBR theory
KW - POWER ASYMMETRY
KW - WMAP DATA
KW - SKY
U2 - 10.1088/1475-7516/2014/11/012
DO - 10.1088/1475-7516/2014/11/012
M3 - Journal article
VL - 2014
JO - Journal of Cosmology and Astroparticle Physics
JF - Journal of Cosmology and Astroparticle Physics
SN - 1475-7516
IS - 11
M1 - 012
ER -