Joint constraints on cosmic birefringence and early dark energy from ACT, Planck, DESI, and PantheonPlus

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Abstract
With the increasing number of high-precision astronomical observations, physical quantities that were previously inaccessible to accurate calculations, such as cosmic birefringence, have once again become a focal point of interest. Such phenomena induce a nonvanishing cross-correlation between the E - and B -mode polarizations of the cosmic microwave background (CMB), thereby providing a direct observational signature of parity violation. The Chern-Simons coupling between the scalar field in early dark energy (EDE) models and CMB photons is regarded as a plausible mechanism for generating cosmic birefringence. Recent data from the Atacama Cosmology Telescope (ACT) deliver EB measurements at higher multipole moments than those previously achieved by Planck, while DESI and PantheonPlus datasets provide new and stringent constraints on the late-time expansion history. Using a joint analysis of Planck, DESI DR2, PantheonPlus, and ACT data, we perform a full-parameter constraint on the cosmic birefringence effects induced by the EDE-CMB photon coupling. Our results favor a higher Hubble constant, H 0 = 76.9 +2.9 -2.5 km s -1 Mpc -1 , and a relatively large EDE fraction, f EDE = 0.232 +0.074 -0.047 . By comparing the cosmological evolution of this model across different data combinations, we find that the ACT- EB data combined with Planck + DESI + PantheonPlus provide consistent constraints.

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