We present a search for anisotropic cosmic birefringence in 500 deg2 of southern sky observed at 150 GHz with the SPTpol camera on the South Pole Telescope. We reconstruct a map of cosmic polarization rotation anisotropies using higher-order correlations between the observed cosmic microwave background (CMB) E and B fields. We then measure the angular power spectrum of this map, which is found to be consistent with zero. The nondetection is translated into an upper limit on the amplitude of the scale-invariant cosmic rotation power spectrum, L(L+1)CLαα/2π<0.10×10-4 rad2 (0.033 deg2, 95% C.L.). This upper limit can be used to place constraints on the strength of primordial magnetic fields, B1 Mpc<17 nG (95% C.L.), and on the coupling constant of the Chern-Simons electromagnetic term gaγ<4.0×10-2/HI (95% C.L.), where HI is the inflationary Hubble scale. For the first time, we also cross-correlate the CMB temperature fluctuations with the reconstructed rotation angle map, a signal expected to be nonvanishing in certain theoretical scenarios, and find no detectable signal. We perform a suite of systematics and consistency checks and find no evidence for contamination.
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The authors acknowledge helpful discussions with Dominic Beck, Giulio Fabbian, Toshiya Namikawa, Giuseppe Puglisi, and Caterina Umiltà. S. P. T. is supported by the National Science Foundation through Grants No. PLR-1248097 and No. OPP-1852617. Partial support is also provided by the NSF Physics Frontier Center Grant No. PHY-1125897 to the Kavli Institute of Cosmological Physics at the University of Chicago, the Kavli Foundation, and the Gordon and Betty Moore Foundation Grant No. GBMF 947. This research used resources of the National Energy Research Scientific Computing Center (NERSC), a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. The Melbourne group acknowledges support from the University of Melbourne and an Australian Research Council’s Future Fellowship (FT150100074). B. B. is supported by the Fermi Research Alliance LLC under Contract No. De-AC02-07CH11359 with the U.S. Department of Energy. Work at Argonne National Lab is supported by UChicago Argonne LLC, Operator of Argonne National Laboratory (Argonne). Argonne, a U.S. Department of Energy Office of Science Laboratory, is operated under Contract No. DE-AC02-06CH11357. We also acknowledge support from the Argonne Center for Nanoscale Materials. We acknowledge the use of many python packages: ipython , matplotlib , and scipy .
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