Dressing the Quark with QCD Condensates
A condensate of $\pvec = 0$ partons in the perturbative vacuum gives rise to a term $\propto\delta^4(p)$ in the free PQCD propagators. The leading condensate contribution to the quark propagator can be exactly summed since there is a factor $\delta^4(p)$ associated to each loop. We calculate the dressed quark propagator in the presence of either a gluon or a quark condensate, for a number of colors $N \to \infty$. The dressed quark propagator satisfies a Dyson-Schwinger type equation which can be exactly solved within our framework. In the case of a gluon condensate the dressed quark propagator has no pole, hence quarks cannot appear in asymptotic states, and moreover the DS equation has a solution which spontaneously breaks chiral symmetry. We also calculate the dressed quark-photon vertex and verify that the corresponding Ward-Takahashi identity is satisfied, and that the dressed self-energy correction to the photon propagator does not shift the physical photon pole.
Filling Perturbative Ground States
I discuss a degree of freedom in formulating perturbation theory that is often neglected: the in- and out-states need not be empty. The inclusion of (free) particles in the asymptotic states modifies the on-shell prescription of the free propagator. This affects loop contributions -- but the modified expansion is {\it a priori} as justified as the standard one with Feynman prescription. 
It is possible to dress the quark propagator to all orders with zero-momentum gluons from the perturbative ground state. The dressed quark has no pole and thus cannot appear as an external particle in the S-matrix. Chiral symmetry may be spontaneously broken, but Lorentz and gauge symmetry is exact. Adding loop corrections to this ``dressed tree approximation'' gives a formally exact PQCD expansion.
Legal Process and the Discovery of Better Policies for Fostering Innovation and Growth
Our chapter concerns how legal process can lead to efficient policies for fostering innovation and growth. Future innovation will depend at least as much on how laws are made as on a priori analyses of the optimal content of those laws. Of particular importance is whether U.S. choice of law and choice of forum rules promote an efficient market for law. Our analysis supports three suggestions for improving the law to support growth. First, the rules governing the selection of the jurisdiction whose law governs productive activity can significantly affect growth and innovation. Second, any proposal aimed at increasing growth through a change in law or legal institutions should take account of the existence of multiple jurisdictions and parties’ ability to choose the jurisdiction whose law controls their transactions. Third, we suggest harnessing the power of jurisdictional competition among the states through a federal law enforcing contracting parties’ choice of law except to the extent states legislatively override the choice of law and regulate local transactions. We apply this analysis to several areas of the law that are critical to growth and innovation: non-competition clauses, business associations, the legal profession, internet law, insurance, property law, products liability, and franchise regulation.