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## Full-Text Articles in Physics

There Is No Ambiguity In The Radiatively Induced Gravitational Chern-Simons Term, Brett Altschul

#### There Is No Ambiguity In The Radiatively Induced Gravitational Chern-Simons Term, Brett Altschul

*Faculty Publications*

Quantum corrections to Lorentz- and C P T -violating QED in flat spacetime produce unusual radiative corrections, which can be finite but of undetermined magnitude. The corresponding radiative corrections in a gravitational theory are even stranger, since the term in the fermion action involving a preferred axial vector b μ would give rise to a gravitational Chern-Simons term that is proportional b μ , yet which actually does not break Lorentz invariance. Initially, the coefficient of this gravitational Chern-Simons term appears to have the same ambiguity as the coefficient for the analogous term in QED. However, this puzzle is resolved by ...

Bounds On Vacuum-Orthogonal Lorentz And Cpt Violation From Radiative Corrections, Brett Altschul

#### Bounds On Vacuum-Orthogonal Lorentz And Cpt Violation From Radiative Corrections, Brett Altschul

*Faculty Publications*

Certain forms of Lorentz violation in the photon sector are difficult to bound directly, since they are “vacuum orthogonal”—meaning they do not change the solutions of the equations of motion in vacuum. However, these very same terms have a unique tendency to contribute large radiative corrections to effects in other sectors. Making use of this, we set bounds on four previously unconstrained d = 5 photon operators at the 10 − 25 – 10 − 31 GeV − 1 levels.