https://hal-cea.archives-ouvertes.fr/cea-01223892Huang, ZhiqiZhiqiHuangCIEE - College of Information and Electrical Engineering [Beijing] - CAU - China Agricultural UniversityVernizzi, FilippoFilippoVernizziIPHT - Institut de Physique Théorique - UMR CNRS 3681 - CEA - Commissariat à l'énergie atomique et aux énergies alternatives - Université Paris-Saclay - CNRS - Centre National de la Recherche ScientifiqueFull cosmic microwave background temperature bispectrum from single-field inflationHAL CCSD2014[PHYS.GRQC] Physics [physics]/General Relativity and Quantum Cosmology [gr-qc][PHYS.HPHE] Physics [physics]/High Energy Physics - Phenomenology [hep-ph]De Laborderie, Emmanuelle2015-11-03 16:05:212021-12-13 09:16:042015-11-03 16:05:21enJournal articles10.1103/PhysRevD.89.0213021We compute the full cosmic microwave background temperature bispectrum generated by nonlinearities after single-field inflation. By integrating the photon temperature at second order along a perturbed geodesic in Newtonian gauge, we derive an expression for the observed temperature fluctuations that, for the first time, clarifies the separation of the gravitational lensing and time-delay effects from the purely second-order contributions. We then use the second-order Boltzmann code CosmoLib$2^{\rm nd}$ to calculate these contributions and their bispectrum. Including the perturbations in the photon path, the numerically computed bispectrum exactly matches the expected squeezed limit. Moreover, the analytic squeezed-limit formula reproduces well the signal-to-noise and shape of the full bispectrum, potentially facilitating the subtraction of the bias induced by second-order effects. For a cosmic-variance limited experiment with $l_{\rm max} = 2000$, the bias on a local signal is $f_{\rm NL}^{\rm loc} =0.73$ negligible for equilateral and orthogonal signals. The signal-to-noise ratio is unity at $l_{\rm max} \sim 3000$, suggesting that second-order effects may hopefully be measured in the future.