Space-time location of causes and effects of events in region 1.
Full specification of what happens in 3 makes events in 2 irrelevant for predictions about 1 in a locally causal theory.
Similar to Fig. 2, except that region 3* (unlike region 3 of Fig. 2) fails to shield off region 1 from the overlapping backward light cones of regions 1 and 2. Thus, following the caption of Fig. 2, even full specification of what happens in 3* does not necessarily make events in 2 irrelevant for predictions about 1 in a locally causal theory.
Space-time diagram illustrating the various beables of relevance for the EPR-Bell setup (see Bell’s diagram in Ref. 7). Separated observers Alice (in region 1) and Bob (in region 2) make spin-component measurements using apparatus settings and , respectively, on a pair of spin- or polarization-entangled particles as indicated by the dashed lines. The measurements have outcomes A and B, respectively. The state of the particle pair in region 3 is denoted by λ. Note that region 3 extends across the past light cones of both regions 1 and 2. It thus not only “completely shields off from 1 the overlap of the backward light cones of 1 and 2”7 but does so also for region 2. Bell’s local causality condition therefore requires both that and B are irrelevant for predictions about the outcome A, and that and A are irrelevant for predictions about the outcome B, once λ is specified.
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