Corrections: Is Preacceleration of Particles in Dirac's Electrodynamics a Case of Backward Causation? The Myth of Retrocausation in Classical Electrodynamics

1977 ◽  
Vol 44 (1) ◽  
pp. 177-177
1977 ◽  
Vol 74 (8) ◽  
pp. 475-482 ◽  
Author(s):  
Adolf Grünbaum ◽  
Allen I. Janis ◽  

Author(s):  
Richard R. Freeman ◽  
James A. King ◽  
Gregory P. Lafyatis

Electromagnetic Radiation is a graduate level book on classical electrodynamics with a strong emphasis on radiation. This book is meant to quickly and efficiently introduce students to the electromagnetic radiation science essential to a practicing physicist. While a major focus is on light and its interactions, topics in radio frequency radiation, x-rays, and beyond are also treated. Special emphasis is placed on applications, with many exercises and homework problems. The format of the book is designed to convey the basic concepts of a topic in the main central text in the book in a mathematically rigorous manner, but with detailed derivations routinely relegated to the accompanying side notes or end of chapter “Discussions.” The book is composed of four parts: Part I is a review of basic E&M, and assumes the reader has a had a good upper division undergraduate course, and while it offers a concise review of topics covered in such a course, it does not treat any given topic in detail; specifically electro- and magnetostatics. Part II addresses the origins of radiation in terms of time variations of charge and current densities within the source, and presents Jefimenko’s field equations as derived from retarded potentials. Part III introduces special relativity and its deep connection to Maxwell’s equations, together with an introduction to relativistic field theory, as well as the relativistic treatment of radiation from an arbitrarily accelerating charge. A highlight of this part is a chapter on the still partially unresolved problem of radiation reaction on an accelerating charge. Part IV treats the practical problems of electromagnetic radiation interacting with matter, with chapters on energy transport, scattering, diffraction and finally an illuminating, application-oriented treatment of fields in confined environments.


Author(s):  
Ryan Wasserman

Chapter 5 surveys the various causal paradoxes of time travel. Section 1 introduces the concept of a causal loop and reviews some of the standard arguments against backward causation. Sections 2 focuses on the bootstrapping paradox, and the question of whether or not time travel allows for self-caused events. Section 3 addresses the ex nihilo paradox, and the question of whether or not time travel allows for uncaused events. Section 4 looks at the restoration paradox, and the question of how to understand the life cycle of an object in a causal loop. Section 5 considers D. H. Mellor’s frequency-based argument against causal loops. Section 6 discusses Michael Tooley’s counterfactual-based argument against backward causation.


2008 ◽  
Vol 23 (02) ◽  
pp. 327-351 ◽  
Author(s):  
J. H. FIELD

Standard formulae of classical electromagnetism for the forces between electric charges in motion derived from retarded potentials are compared with those obtained from a recently developed relativistic classical electrodynamic theory with an instantaneous intercharge force. Problems discussed include small angle Rutherford scattering, Jackson's recent "torque paradox" and circular Keplerian orbits. Results consistent with special relativity are obtained only with an instantaneous interaction. The impossibility of stable circular motion with retarded fields in either classical electromagnetism or Newtonian gravitation is demonstrated.


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