CAUSALITY PRINCIPLE AND RETRODICTION IN QUANTUM PHYSICS

The causality principle (CP) states that the cause can only be inside the past light cone of an effect. The principle is used in choosing retarded solutions to field equations and also in the Bogoliubov derivation of dispersion relations. However, using CP leads to the following problem: CP determines a "time arrow" in microphysics and shuts out other ways of explaining time irreversibility in Nature (based on statistical physics, cosmology, etc). It is shown that CP can be replaced by the condition that we consider only prediction problems, sometimes together with the use of a principle which is weaker than CP: the cause cannot be outside an effect's light cones. The retrodiction problem and verification of CP in quantum mechanics are discussed.