Are inflationary predictions sensitive to very high energy physics?

It has been proposed that the successful inflationary description of densityperturbations on cosmological scales is sensitive to the details of physics atextremely high (trans-Planckian) energies. We test this proposal by examininghow inflationary predictions depend on higher-energy scales within a simplemodel where the higher-energy physics is well understood. We find the best ofall possible worlds: inflationary predictions are robust against the vastmajority of high-energy effects, but can be sensitive to some effects incertain circumstances, in a way which does not violate ordinary notions ofdecoupling. This implies both that the comparison of inflationary predictionswith CMB data is meaningful, and that it is also worth searching for smalldeviations from the standard results in the hopes of learning about very highenergies.Comment: 23 pages, 14 figure