Bell Nonlocality

This book discusses the physical and mathematical foundations of modern quantum mechanics and three realistic quantum theories that John Stuart Bell called "theories without observers" because they do not merely speak about measurements but develop an objective picture of the physical world. These are Bohmian mechanics, the GRW collapse theory, and the Many Worlds theory.

This volume provides a broad perspective on the state of the art in the philosophy and conceptual foundations of quantum mechanics. Its essays take their starting point in the work and influence of Itamar Pitowsky, who has greatly influenced our understanding of what is characteristically non-classical about quantum probabilities and quantum logic, and this serves as a vantage point from which they reflect on key ongoing debates in the field.

This collection of essays is above all intended to pay tribute to the fact that while QM today is a refined and incredibly successful instrument, many issues concerning the internal consistency and the interpretation of this theory are still not nearly as well understood as they ought to be.

In this volume, leading experts in experimental as well as theoretical physics (both classical and quantum) and probability theory give their views on many intriguing (and still mysterious) problems regarding the probabilistic foundations of physics.

Bell anchored the logic chain begun by Einstein, Rosen, and Podolsky and tested by Aspect et al., showing that entangled electrons are nonlocal. Feynman showed that free electrons are nonlocal in that they travel between any two points using all possible paths.