Using a simple nonlinear filter, it is possible to shift arbitrarily complex wave forms produced by systems with a delayed feedback backwards in time. Physically, this corresponds to a seemingly noncausal transmission of signals. Filter chains allow for signals travelling against the coupling direction of the chain. These apparent paradoxes are resolved and possible physical implications are discussed. (C) 2001 Elsevier Science B.V. All rights reserved. [References: 38]
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