We present measurements of the E-mode (EE) polarization power spectrum and temperature-E-mode (TE) cross-power spectrum of the cosmic microwave background using data collected by SPT-3G, the latest instrument installed on the South Pole Telescope. This analysis uses observations of a 1500 deg 2 region at 95, 150, and 220 GHz taken over a four-month period in 2018. We report binned values of the EE and TE power spectra over the angular multipole range 300 ≤ l < 3000, using the multifrequency data to construct six semi-independent estimates of each power spectrum and their minimum-variance combination. These measurements improve upon the previous results of SPTpol across the multipole ranges 300 ≤ l ≤ 1400 for EE and 300 ≤ l ≤ 1700 for TE, resulting in constraints on cosmological parameters comparable to those from other current leading ground-based experiments. We find that the SPT-3G data set is well fit by a ΛCDM cosmological model with parameter constraints consistent with those from Planck and SPTpol data. From SPT-3G data alone, we find H 0 ¼ 68.8 AE 1.5 km s −1 Mpc −1 and σ 8 ¼ 0.789 AE 0.016, with a gravitational lensing amplitude consistent with the ΛCDM prediction (A L ¼ 0.98 AE 0.12). We combine the SPT-3G and the Planck data sets and obtain joint constraints on the ΛCDM model. The volume of the 68% confidence region in six-dimensional ΛCDM parameter space is reduced by a factor of 1.5 compared to Planck-only constraints, with no significant shifts in central values. We note that the results presented here are obtained from data collected during just half of a typical observing season with only part of the focal plane operable, and that the active detector count has since nearly doubled for observations made with SPT-3G after 2018.

We present a search for anisotropic cosmic birefringence in 500 deg 2 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, LðL þ 1ÞC αα L =2π < 0.10 × 10 −4 rad 2 (0.033 deg 2 , 95% C.L.). This upper limit can be used to place constraints on the strength of primordial magnetic fields, B 1 Mpc < 17 nG (95% C.L.), and on the coupling constant of the Chern-Simons electromagnetic term g aγ < 4.0 × 10 −2 =H I (95% C.L.), where H I 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.

H 0 and the full Planck power spectra, within the EDE model one obtains a non-zero fraction of the total energy density in EDE at the critical redshift, f EDE (z c ) = 0.108 +0.035 −0.028 , with a corresponding Hubble parameter H 0 = 71.5 ± 1.2 km/s/Mpc [30] (adding supernovae (SNe) and baryon acoustic oscillation 'standard ruler' (BAO) data leads to insignificant shifts). Without the SH 0 ES prior, one has instead an upper bound of the form f EDE (z c ) < 0.088 at 95% confidence level (CL) and H 0 = 68.29 +0.75 −1.3 km/s/Mpc [30,31]. 2 Recent analyses of EDE using data from the Atacama Cosmology Telescope's fourth data release (ACT DR4) [34] alone have shown a slight (∼ 2.2σ) preference for the presence of an EDE component with a fraction f EDE (z c ) ∼ 0.15 and H 0 ∼ 74 km/Mpc/s [35,36]. Interestingly, the inclusion of large-scale CMB temperature measurements by the Wilkinson Microwave Anisotropy Probe (WMAP) [37] or the Planck satellite [2] restricted to the WMAP multipole range increases the preference to ∼ 3σ. A similar analysis using the third generation South Pole Telescope 2018 (SPT-3G) data [38] was presented in Ref. [39] (see also Refs. [28,29] for previous studies using SPTpol). There is no evidence for EDE over ΛCDM using SPT-3G alone or when combined with the Planck temperature power spectrum restricted to < 650, giving the marginalized constraint f EDE (z c ) < 0.2 at 95% CL in the latter case. Combining ACT DR4 and/or SPT-3G with the full Planck CMB power spectra returns an upper limit on f EDE (z c ), albeit less restrictive than for Planck alone.In Refs. [35,36] it was argued that the ACT DR4 preference for EDE is mainly driven by a feature in the ACT DR4 EE power spectrum around ∼ 500 when ACT DR4 is considered alone, with an additional broadlydistributed contribution from the TE spectrum when in combination with restricted Planck TT data ( < 650 or < 1060). Ref.[36] also considered the role of Planck polarization data, finding that the evidence for a nonzero f EDE (z c ) and an increased H 0 persists, as long as the Planck TT spectrum is restricted to < 1060.Building on these previous studies, the work presented here explores in more detail how the evidence for EDE using data from ACT DR4, SPT-3G or both data sets is impacted by the inclusion of the more precise intermediatescale (O( ) = 100) polarization measurements by Planck. We test the robustness of the results to changes in the Planck TE polarization efficiency and the dust contamination amplitudes in Planck EE. We also further investigate the role of Planck high-TT data as well as that of several non-CMB probes.This paper is organized as follows. In Section II we briefly summarize the numerical setup and cosmological data sets used in our analysis. In Section III we present

High angular resolution cosmic microwave background experiments provide a unique opportunity to conduct a survey of time-variable sources at millimeter wavelengths, a population that has primarily been understood through follow-up measurements of detections in other bands. Here we report the first results of an astronomical transient survey with the South Pole Telescope (SPT) using the SPT-3G camera to observe 1500 deg 2 of the southern sky. The observations took place from 2020 March to November in three bands centered at 95, 150, and 220 GHz. This survey yielded the detection of 15 transient events from sources not previously detected by the SPT. The majority

SPT-3G is the third survey receiver operating on the South Pole Telescope dedicated to high-resolution observations of the cosmic microwave background (CMB). Sensitive measurements of the temperature and polarization anisotropies of the CMB provide a powerful data set for constraining cosmology. Additionally, CMB surveys with arcminute-scale resolution are capable of detecting galaxy clusters, millimeter-wave bright galaxies, and a variety of transient phenomena. The SPT-3G instrument provides a significant improvement in mapping speed over its predecessors, SPT-SZ and SPTpol. The broadband optics design of the instrument achieves a 430 mm diameter image plane across observing bands of 95, 150, and 220 GHz, with 1.2′ FWHM beam response at 150 GHz. In the receiver, this image plane is populated with 2690 dual-polarization, trichroic pixels (∼16,000 detectors) read out using a 68× digital frequency-domain multiplexing readout system. In 2018, SPT-3G began a multiyear survey of 1500 deg2 of the southern sky. We summarize the unique optical, cryogenic, detector, and readout technologies employed in SPT-3G, and we report on the integrated performance of the instrument.