Production of axionlike particles (ALPs) by primordial magnetic fields may have significant impacts on cosmology. We discuss the production of ALPs in the presence of the primordial magnetic fields. We find a region of the ALP mass and photon coupling which realizes the observed properties of the dark matter with appropriate initial conditions for the magnetic fields. This region may be interesting in light of recent indications for the 3.5 keV lines from galaxy clusters. For a small axion mass, a region of previously allowed parameter spaces is excluded by overproduction of ALPs as a hot/warm dark matter component. Since the abundance of ALPs strongly depends on the initial conditions of primordial magnetic fields, our results provide implications for scenarios of magnetogenesis.

We perform the complete stability study of the model of chromo-natural inflation (Adshead and Wyman '12), where, due to its coupling to a SU(2) vector, a pseudo-scalar inflaton χ slowly rolls on a steep potential. As a typical example, one can consider an axion with a sub-Planckian decay constant f . The model was recently studied (Dimastrogiovanni, Fasiello, and Tolley '12) in the mg >> H limit, where mg is the mass of the fluctuations of the vector field, and H the Hubble rate. We show that the inflationary solution is stable for mg > 2H, while it otherwise experiences a strong instability due to scalar perturbations in the sub-horizon regime. The tensor perturbations are instead enhanced at large mg, while the vector ones remain perturbatively small. Depending on the parameters, this model can give a chiral gravity wave signal that can be detected in ongoing or forthcoming CMB experiments. This detection can occur even if, during inflation, the inflaton spans an interval of size ∆χ = O (f ) which is some orders of magnitude below the Planck scale, evading a well known bound that holds for a free inflaton (Lyth '97). The spectral tilt of the scalar perturbations typically decreases with decreasing mg. Therefore the simultaneous requirements of stability, sufficiently small tensor-to-scalar ratio, and sufficiently flat scalar spectrum can pose nontrivial bounds on the parameters of the model.

Abstract.Reheating is a transition era after the end of inflation, during which the inflaton is converted into the particles that populate the Universe at later times. No direct cosmological observables are normally traceable to this period of reheating. Indirect bounds can however be derived. One possibility is to consider cosmological evolution for observable CMB scales from the time of Hubble crossing to the present time. Depending upon the model, the duration and final temperature after reheating, as well as its equation of state, may be directly linked to inflationary observables. For single-field inflationary models, if we approximate reheating by a constant equation of state, one can derive relations between the reheating duration (or final temperature), its equation of state parameter, and the scalar power spectrum amplitude and spectral index. While this is a simple approximation, by restricting the equation of state to lie within a broad physically allowed range, one can in turn bracket an allowed range of n s and r for these models. The added constraints can help break degeneracies between inflation models that otherwise overlap in their predictions for n s and r.

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The kinetic Sunyaev Zel'dovich (kSZ) and polarized Sunyaev Zel'dovich (pSZ) effects are temperature and polarization anisotropies induced by the scattering of CMB photons from structure in the post-reionization Universe. In the case of the kSZ effect, small angular scale anisotropies in the optical depth are modulated by the cosmic microwave background (CMB) dipole field, i.e. the CMB dipole observed at each spacetime point, which is sourced by the primordial dipole and especially the local peculiar velocity. In the case of the pSZ effect, similar small-scale anisotropies are modulated by the CMB quadrupole field, which receives contributions from both scalar and tensor modes. Statistical anisotropies in the cross correlations of CMB temperature and polarization with tracers of the inhomogeneous distribution of electrons provide a means of isolating and reconstructing the dipole and quadrupole fields. In this paper, we present a set of unbiased minimum variance quadratic estimators for the reconstruction of the dipole and quadrupole fields, and forecast the ability of future CMB experiments and large scale structure surveys to perform this reconstruction. Consistent with previous work, we find that a high fidelity reconstruction of the dipole and quadrupole fields over a variety of scales is indeed possible, and demonstrate the sensitivity of the pSZ effect to primordial tensor modes. Using a principle component analysis, we estimate how many independent modes could be accessed in such a reconstruction. We also comment on a few first applications of a detection of the dipole and quadrupole fields, including a reconstruction of the primordial contribution to our locally observed CMB dipole, a test of statistical homogeneity on large scales from the first modes of the quadrupole field, and a reconstruction technique for the primordial potential on the largest scales. * Electronic address: asdeutsch@psu.edu † Electronic address: exd191@case.edu ‡ Electronic address: mjohnson@perimeterinstitute.ca § Electronic address: mmunchmeyer@perimeterinstitute.ca ¶ Electronic address: aterrana@perimeterinstitute.ca arXiv:1707.08129v2 [astro-ph.CO]