Basics of generalized unitarity

Generalized unitarity and W+3 jet production at the Tevatron

Light-light amplitude from generalized unitarity in massive QED

We calculate all the four-photon helicity amplitudes at the one-loop level in a massive theory using multiplecut methods. The amplitudes are derived in scalar QED, QED and QED theories. We will see the origin of rational terms. We extend the calculation to the simplest six-photon helicity amplitude where all photons have the same helicity. version June 28, 2009

Unitarity and causality in generalized quantum mechanics for nonchronal spacetimes.

Spacetime must be foliable by spacelike surfaces for the quantum mechanics of matter fields to be formulated in terms of a unitarily evolving state vector defined on spacelike surfaces. When a spacetime cannot be foliated by spacelike surfaces, as in the case of spacetimes with closed timelike curves, a more general formulation of quantum mechanics is required. In such generalizations the trans...

Implications of CKM Unitarity

Three generation CKM Unitarity in the Standard Model predicts |Vud |2 + |Vus| + |Vub| = 1. Nuclear, K`3 and b → u decays currently give |Vud |2 + |Vus| + |Vub| = 0.9991(8). The good agreement between theory and experiment can be used to constrain “new physics” effects at the tree and quantum loop level. Examples considered are: exotic muon decays, heavy quark or lepton mixing, high scale induce...

Light-by-light scattering amplitudes from generalized unitarity in massive QED

We calculate all the four-photon helicity amplitudes at the one-loop level in a massive theory using multiple-cut methods. The amplitudes are derived in scalar QED, QED and QED theories. We will see the origin of rational terms. We extend the calculation to the simplest six-photon helicity amplitude where all photons have the same helicity.