Pseudoscalar perturbations and polarization of the cosmic microwave background

Pospelov, Maxim
Ritz, Adam
Skordis, Constantinos
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We show that models of new particle physics containing massless pseudoscalar fields super-weakly coupled to photons can be very efficiently probed with CMB polarization anisotropies. The stochastic pseudoscalar fluctuations generated during inflation provide a mechanism for converting E-mode polarization to B-mode during photon propagation from the surface of last scattering. The efficiency of this conversion process is controlled by the dimensionless ratio H/(2\pi f_a), where H is the Hubble scale during inflation, and f_a^{-1} is the strength of the pseudoscalar coupling to photons. The current observational limits on the B-mode constrain this ratio to be less than 0.07, which in many models of inflation translates to a sensitivity to values of f_a in excess of 10^{14} GeV, surpassing the sensitivity of other tests.
Comment: 4 pages, 1 figure
Astrophysics, High Energy Physics - Phenomenology, High Energy Physics - Theory