Inflation as a probe of short distance physics - art. no. 103502

We show that a string-inspired Planck scale modification of general relativ ity can have observable cosmological effects. Specifically, we present a co mplete analysis of the inflationary perturbation spectrum produced by a phe nomenological Lagrangian that has a standard form on large scales but incor porates a string-inspired short distance cutoff, and find a deviation from the standard result. We use the de Sitter calculation as the basis of a qua litative analysis of other inflationary backgrounds, arguing that in these cases the cutoff could have a more pronounced effect, changing the shape of the spectrum. Moreover, the computational approach developed here can be u sed to provide unambiguous calculations of the perturbation spectrum in oth er heuristic models that modify trans-Planckian physics and thereby determi ne their impact on the inflationary perturbation spectrum. Finally, we argu e that this model may provide an exception to constraints, recently propose d by Tanaka and Starobinsky, on the ability of Planck-scale physics to modi fy the cosmological spectrum.