Monday, July 23, 2012

1207.5038 (Alan Lai et al.)

Spectral action for a one-parameter family of Dirac-type operators on
SU(2) and its inflation model

Alan Lai, Kevin Teh
We analyze the Dirac Laplacian of a one-parameter family of Dirac operators on a compact Lie group, which includes the Levi-Civita, cubic, and trivial Dirac operators. More specifically, we describe the Dirac Laplacian action on any Clifford module in terms of the action of the Lie algebra's Casimir element on finite-dimensional irreducible representations of the Lie group. Using this description of the Dirac Laplacian, we explicitly compute spectrum for the one-parameter family of Dirac Laplacians on SU(2), and then using the Poisson summation formula, the full asymptotic expansion of the spectral action. The technique used to explicitly compute the spectrum applies more generally to any Lie group where one can concretely describe the weights and corresponding irreducible representations, as well as decompose tensor products of an irreducible representation with the Weyl representation into irreducible components. Using the full asymptotic expansion of the spectral action, we generate the inflation potential and slow-roll parameters for the corresponding pure gravity inflationary theory.
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