The computation of the false vacuum decay rate in the situation with nearly degenerate vacua can be performed analytically in the well known thin wall approximation. If we depart from the near degeneracy of the vacua, the approximation quickly ceases to work. This statement is known to practitioners of the field, but it has a caveat: it is true only if one works at the leading order of the thin wall approximation. In this talk I will describe how to organize the calculation to systematically include higher order corrections in the thin wall parameter expansion. The first few orders can be computed analytically. It is enough to include them to improve the approximation and get a very accurate estimate of the bounce action also deep into thick wall regimes, where the vacua are far apart. I plan to also briefly discuss how to deal in these cases with the calculation of the functional determinant, also known as the prefactor, in order to have the full proper understanding of the vacuum decay rate. In the whole talk I will only consider flat spacetime, without gravity.
https://indico.ijs.si/event/2133/