Monroe Are Causality Violations Undesirable ?
نویسنده
چکیده
Causality violations are typically seen as unrealistic and undesirable features of a physical model. The following points out three reasons why causal-ity violations, which Bonnor and Steadman identified even in solutions to the Ein-stein equation referring to ordinary laboratory situations, are not necessarily undesirable. First, a space-time in which every causal curve can be extended into a closed causal curve is singularity free—a necessary property of a globally applicable physical theory. Second, a causality-violating space-time exhibits a nontrivial topology—no closed timelike curve (CTC) can be homotopic among CTCs to a point, or that point would not be causally well behaved—and nontrivial topol-ogy has been explored as a model of particles. Finally, if every causal curve in a given space-time passes through an event horizon, a property which can be called " causal censorship " , then that space-time with event horizons excised would still be causally well behaved.
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