CPT transformation analogue of free electron laser?

[jarekduda]

While 2nd law of thermodynamics emphasizes past->future time direction, CPT theorem says that at least microscopic physics has some symmetry between past and future. For example the Feynman-Stueckelberg interpretation suggests to see anti-particles as traveling back in time.
So thermodynamics is one of many examples of symmetry breaking: while the fundamental equations fulfill some symmetry, the solution often breaks it. Even for (time-symmetric) classical mechanics there is Boltzmann H-theorem "proving" that entropy should grow. However, we could reverse time and use the same "proof" to show entropy decrease - getting contradiction. The issue is a subtle hidden assumption of some uniformity ("Stoßzahlansatz") - this problem is very nicely presented in http://www.math.ens.fr/~bodineau/GT_2012/kac-ring.pdf : entropy grows as it should, but then it surprisingly decreases due to symmetry of the model.

Anyway, the CPT symmetry suggests that a CPT analogue of a device should also work (?)
Very interesting would be a CPT analogue of a laser - its stimulated emission should be changed to stimulated absorption (?) - getting lasAr.
Free electron laser (FEL) is conceptually simple - let's think about its CPT analogue:

https://dl.dropboxusercontent.com/u/12405967/freeelectron.jpg

So in FEL we have a high energy electrons, which go through a sequence of opposite magnets, what leads to synchrotron radiation photons.
These photons fly through the optical path and finally hit a deexcited target, exciting it.

CPT analogue of this picture is: excited target emits photons, which fly toward that lasar (stimulated absorption instead of emission), and are absorbed by traveling positron.
What is nontrivial here is that deexication of the target is stimulated by turning the lasar on - earlier by optical path time.

So imagine we take a sodium lamp surrounded by detectors. The lamp is continuously excited, and this energy is seen by detectors.
Now shoot the lasar through a small hole in the detectors (of frequency of sodium lamp) - should turning the laser on change the energy balance of lamp-detectors?

 

[Jeff Rosenbury]

My understanding is that accelerating charges emit photons. This is an effect of special relativity.

What you are describing should work as a receiving antenna, with the incoming photons forcing extra acceleration. But why not just use a regular antenna which seems to be using the principle you are describing?

 

[jarekduda]

This would be a very special receiving antenna, kind of draining antenna - with causation in opposite time direction - turning it on would stimulate (quicken) deexcitation of target:
- standard laser stimulates emission of photons, what causes excitation of target LATER by optical path,
- CPT analogue of laser would stimulate absorption of photons, what causes deexcitation of target EARLIER.

The basic question here is if synchrotron radiation is a CPT symmetric phenomena?
This symmetry suggests that acceleration of electron not only produces (pushes) energy (photons) forward (in space and time), but also kind of pull energy from backward.
The trick is that:
- while laser beam need to hit a deexcited target,
- such anti-beam from CPT analogue of laser needs to hit an excited target (for a given frequency) - like sodium lamp (very narrow spectrum).

If true (?), this effect would be difficult to accidentally observe:
- the target needs to be excited exactly to a given frequency,
- the target needs to be behind the standard free electron laser - toward the electron source.
So the sodium lamp should be continuously excited and surrounded by detectors watching energy balance, disturbed (earlier) when such anti-beam would hit it (through a small hole), speeding-up deexcitation.

To emphasize the meaning of hypothetical being able to send information let say 1 microsecond back in time, it could for example allow to break any cipher within this time.
So imagine we have a ciphered text (or e.g. a NP problem) - we want to find the only crypto key which would transform it into a meaningful sequence (e.g. not noise in Fourier spectrum).
If we could take this key from let say 1 microsecond later in future, we could perform this kind of time-loop computer, enclosing of such loop would make physics solve our problem (e.g. by action optimizing from Lagrangian formalism, or Einstein block universe perspective):
http://dl.dropbox.com/u/12405967/tlc_resize.jpg

This CPT analogue of laser is related to recently popular "anti-laser", also called "time reversed counterpart of a laser", however the causality is only forward in time there
https://en.wikipedia.org/wiki/Coherent_perfect_absorber
http://www.scientificamerican.com/article/antilaser-time-reversed/
http://www.wired.com/2011/02/real-live-antilaser/