Descent and the Koszul duality for locally constant factorization algebras

Generalizing Jacob Lurie's idea on the relation between the Verdier duality and the iterated loop space theory, we study the Koszul duality for locally constant factorization algebras. We formulate an analogue of Lurie's "nonabelian Poincare duality" theorem (which is closely related to earlier results of Graeme Segal, of Dusa McDuff, and of Paolo Salvatore) in a symmetric monoidal stable infinity category carefully, using John Francis' notion of excision. Its proof is done by first studying the Koszul duality for E_n-algebras in detail. As a consequence, we obtain a Verdier type equivalence for factorization algebras by a Koszul duality construction. At a foundational level, we study descent properties of Lurie's topological chiral homology. We prove that this homology theory satisfies descent for a factorizing cover, as defined by Kevin Costello and Owen Gwilliam. We also obtain a generalization of Lurie's approach to this homology theory, which leads to a product formula for the infinity category of factorization algebras, and its twisted generalization.