IR divergence problem in single-field models of inflation

          @misc{ scivideos_PIRSA:10100066,
            doi = {10.48660/10100066},
            url = {https://pirsa.org/10100066},
            author = {Urakawa, Yuko},
            keywords = {Cosmology},
            language = {en},
            title = {IR divergence problem in single-field models of inflation},
            publisher = {Perimeter Institute for Theoretical Physics},
            year = {2010},
            month = {oct},
            note = {PIRSA:10100066 see, \url{https://scivideos.org/index.php/pirsa/10100066}}
          }
          

Abstract

We clarify the origin of IR divergence in single-field models of inflation and provide the correct way to calculate the observable fluctuations. First, we show the presence of gauge degrees of freedom in the frequently used gauges such as the comoving gauge and the flat gauge. These gauge degrees of freedom are responsible for the IR divergences that appear in loop corrections of primordial perturbations. We propose, in this talk, one simple but explicit example of gauge-invariant quantities. Then, we explicitly calculate such a quantity to find that the IR divergence is absent in the slow-roll approximation. In this formalism, we revisit the consistency relation that connects the three-point function in the squeezed limit with the spectral index.