text: 321,164,1341805376166047749,1117093805499355136,Marilena Loverde,"Do you wonder about CMB+BAO constraints on self-interacting neutrinos if only some of them self-interact? We studied a bunch of examples in this paper led by Thejs Brinckmann. Major congrats to Thejs @ThejsBrinckmann and Jae Hyeok Chang on this nice work! <LINK> Some punchlines: we find no strong evidence for self-interactions or larger/smaller values of Neff. On the other hand, there are some additional modes in parameter space with neutrinos decoupling much later than SM ones should, but they are not preferred. We also weigh in on the H0 tension and find (as others have!), that self-interacting neutrinos are not a solution unless you throw out high-ell CMB polarization data, which we have no reason to do. Interestingly, if you did throw it out we found H0 = 74 km/s/Mpc.",https://arxiv.org/abs/2012.11830,"We perform a comprehensive study of cosmological constraints on non-standard neutrino self-interactions using cosmic microwave background (CMB) and baryon acoustic oscillation data. We consider different scenarios for neutrino self-interactions distinguished by the fraction of neutrino states allowed to participate in self-interactions and how the relativistic energy density, N$_{\textrm{eff}}$, is allowed to vary. Specifically, we study cases in which: all neutrino states self-interact and N$_{\textrm{eff}}$ varies; two species free-stream, which we show alleviates tension with laboratory constraints, while the energy in the additional interacting states varies; and a variable fraction of neutrinos self-interact with either the total N$_{\textrm{eff}}$ fixed to the Standard Model value or allowed to vary. In no case do we find compelling evidence for new neutrino interactions or non-standard values of N$_{\textrm{eff}}$. In several cases we find additional modes with neutrino decoupling occurring at lower redshifts $z_{\textrm{dec}} \sim 10^{3-4}$. We do a careful analysis to examine whether new neutrino self-interactions solve or alleviate the so-called $H_0$ tension and find that, when all Planck 2018 CMB temperature and polarization data is included, none of these examples ease the tension more than allowing a variable N$_{\textrm{eff}}$ comprised of free-streaming particles. Although we focus on neutrino interactions, these constraints are applicable to any light relic particle. ","Self-interacting neutrinos, the Hubble parameter tension, and the Cosmic