Christopher A. Sims, 83, Dies; Won Nobel for Modeling Economic Policy

He and Thomas J. Sargent shared the prize in 2011 for devising statistical tools to help guide economic policymakers.

A.I. Writes Buggy Code. A Silicon Valley Start-Up Wants to Fix It.

These start-ups, including Axiom Math and Harmonic, both in Palo Alto, Calif., and Logical Intelligence in San Francisco, hope to create A.I. systems that can automatically verify computer code in ...