I notice this question has been touched in a general physics thread, but the discussions there on relativistic aspects of the question seemed clearly misleading to me. My questions focus specifically on the view from different frames and the application of the principle of equivalence, so this seems the best forum to me. This question was triggered by scanning two papers:(adsbygoogle = window.adsbygoogle || []).push({});

http://arxiv.org/PS_cache/physics/pdf/0506/0506049v5.pdf

http://arxiv.org/PS_cache/arxiv/pdf/1009/1009.3968v1.pdf

These papers come to opposite conclusions about (both argued from special relativity point of view, but the first has, perhaps, more of a GR flavor) what an observer comoving with an accelerating charge would observe (on all other questions, they seem to agree, though using completelhy different techniques; as I understand it, there is one other subtle disagreement: the first paper above suggests that the question of what an accelerating observer would see for an inertial charge is unclear treated using Maxwell/SR, while QFT indicates they would see no radiation; this is at the end of the paper. Meanwhile, the second paper suggests this result can be derived strictly clasically, no quantum theory needed).

One more bit of background before I pose my main question: mine. I studied physics in college as my major for 3 semesters before dropping out and pursuing a career in software. In some ways, I know more than this implies, as tought myself enough tensor calculus and GR in highschool to solve simple problems in GR rigorously. However all of this was 35 years ago. Since, I have avidly followed physics qualitatively but not quantitavely.

My question concerns the following line of reasoning (my own) which leads me to a seemingly impossible conclusion if I accept the first paper's point of view:

The conclusion of the first paper is that a uniformly accelerating charge radiates as observed by an inertial observer, but not as observed by a comoving observer. It must follow that for a charge on the surface of a planet (by equivalence principle), that free falling observer detects radiation but not an observer on the surface. If this were not true (the conclusion from equivalence principle), it would become possible to distinguish acceleration in a rocket from gravity without recourse to tidal effects (put a charge on a table, drop a photon counter; if the result were different in these cases, a closed small lab could distinguish rocket acceleration from gravity non-tidally). Given this conclusion, imagine a charged, nonrotating planet (hey, it's a thought experiment, not plausible reality; non-rotating as otherwise rotating charge effects would swamp other effects). Imagine a network of detectors mounted on pedestals above the surface, and another set of free falling detectors. As they pass each other, the falling set detect outflow of radiation, while the adjacent fixed detectors do not. More generally, distant inertial observers would seem to perceive the planet as radiating (and thus, perforce, losing mass), while the surface observers detect no radiation or mass loss. This seems impossible - one observer sees the planet evaporate, and the other sees no such thing.

The claims of the second paper avoids this contradiction at the expense of saying both obersvers see the planet evaporate (if one uses my equivalence reasoning on the conclusions of the second paper).

-------------------------

Any thoughts on which paper is right or on the merits of my equivalence reasoning would be appreciated, especially from professional physicists. (As a long time physics dabbler who knows real physicists, I perceive a huge gulf between others like me and the professional).

-----------------

From reading the one thread I found vaguely related to this topic on these forums, let me disagree with three opinions expressed there, and make a fourth general observation:

1) Equivalence arguments for uniform acceleration of charges are misleading because of tidal effects. I say nonsense. There is no limit in GR to how closely a planetary field can be free of tidal effects. GR in no way prevents construction of a gravitational field that for a 1 lightyear cube and a year of time differs from uniform acceleration by no more than one part in 10**50 (for example).

2) Principle of equivalence is not really important, e.g. quotes from Synge. Synge is one of the books I read in highschool and loved, but with all due respect, I find his view on this is nonsense. Mathematically, equivalence is precise in the limit, and for any finite region to any chosen experimental sensitivity, in practice (thought not necessarily on earth). Clifford Will has made a career out of precise definitions of flavors of principle of equivalence and which experiments validate which flavor. I think this fully displaces Synge's view.

3) While it is somewhat bizare to imagine a charge on a table radiating, the claim the it can't happen because no work is done is inadequate. To an inertial observer, the work done by atoms of a planet pushing on a 'stationary' charge is just as real as the work done by a rocket pushing on a charge from the point of view an inertial observer in/near the rocket.

4) I am aware that a big issue in all of this is that 'what is radiation' is non-local and non-trivial in Maxwell/SR. Classical fields make the field local, with finite propagation speed, but radiation has no local definition. Instead, you must define some feature propagating in a certain way, or integrate around a region to compute power balance. Meanwhile, in QFT, a field is more complex (virtual particles, one, two, three... loop effects), while radation is local and trivial: did a photon counter detect a photon. I perceive this conundrum is related to why there is disagreement between two papers in the 21st century about something that 'ought' to have been resolved before mid 20th century.

**Physics Forums - The Fusion of Science and Community**

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# 'relativity' of radiation of uniformly accelerating charge

Loading...

Similar Threads - 'relativity' radiation uniformly | Date |
---|---|

I Magnetism and relativity | Mar 16, 2018 |

A The color of deep space | Oct 28, 2016 |

A Capture in a Two-Body System by Gravitational Radiation? | Oct 15, 2016 |

Relativity and Dipole Radiation | Sep 12, 2015 |

Relativity and Energy Transfer via Radiation | Oct 2, 2005 |

**Physics Forums - The Fusion of Science and Community**