Is CPT symmetry still valid for macroscopic physics?

[Duda Jarek]

CPT symmetry (charge, parity, time) is at heart of modern physics:

Quote

The CPT theorem says that CPT symmetry holds for all physical phenomena

However, it seems treated seriously only in scale of Feynman diagrams with a few particles - is it still valid for macroscopic physics? Feynman diagrams of Avogadro's scale numbers of particles?

In other words, if preparing CPT(initial conditions), should they lead to CPT(their evolution) ... including time reversed causality direction?

 

While it seems technically challenging to prepare CPT(initial conditions), in theory general relativity allows to prepare T(initial conditions) - by hypothetical Klein-bottle-like wormholes ( https://en.wikipedia.org/wiki/Non-orientable_wormhole ) e.g. rotating 180 deg. light cones - while standard laser causes excitation of its target, would laser in a rocket traveled through such wormhole cause deexcitation of target?

Edited May 9, 2023 by Duda Jarek

[Markus Hanke]

44 minutes ago, Duda Jarek said:

is it still valid for macroscopic physics?

It is valid in the sense that macroscopic physics (except gravity) are taken to arise from locally interacting quantum fields - which are necessarily subject to CPT invariance. This being said, not all macro-phenomena require this full symmetry set. Consider for example any AC circuit - on a macroscopic (!) level, it makes no difference if the charge carriers within the circuit are negatively or positively charged, you get the same behaviour for whatever elements are in your circuit. So this is macroscopically C-invariant, without needing to be P- or T-invariant. It's only when you look microscopically that you'll realise that positrons in a standard wire won't work out very well, unless you replace the matter the wire is made of by anti-matter.

1 hour ago, Duda Jarek said:

hypothetical Klein-bottle-like wormholes

I'm not aware of any physically reasonable sources and boundary conditions that yield non-orientable solutions to the Einstein equations. Of course you can artificially construct such solutions, but they won't describe physical spacetimes - which is a good thing, since not all physical systems are P-invariant, so you wouldn't want to have such solutions.

[Duda Jarek]

I also think it should remain valid in macroscopis physics - just imagine building larger and larger Feynman diagrams.

However, CPT naively reverses causality direction, like in this hypothetical rocket which traveled through Klein-bottle-like wormhole - what seems highly controversial.

Taking a setting with clear causality direction e.g. this laser causes excitation of its target later, if constructing CPT analogue of this situation, should CPT(laser) cause deexcitation of target earlier?

While building CPT analogue of laser seems technically extremely challenging, at least for free electron laser(FEL) it seems realizable: just replace electrons with positrons traveling in the opposite direction.

To test if it can cause deexcitation of target, we could use e.g. a gas-discharge lamp continuously exciting its atoms as the target - the big question is if such CPT(FEL) could increase deexcitation rate in this direction? (what could be measured monitoring lamp's energy balance)

I don't know and believe only experiment could really answer this question (?) - I would love to conduct (if only getting allowance to place such lamp e.g. in synchrotron?)

[Duda Jarek]

Better diagram for hypothetical https://en.wikipedia.org/wiki/Non-orientable_wormhole - if they are allowed by physics, there should be also allowed T(laser) causing deexictation of target.
If the above test of existence of such effect e.g. in synchrotron will turn out negative (working on it), it could be used e.g. as counterargument against possibility of non-orientable wormholes, or as argument for causality indeed working only in past->future direction (against CPT symmetry).
If the test would turn out positive, already possibility of stimulating deexcitation of target in chosen frequencies should probably quickly find hundreds of applications e.g. in technological processes, chemistry.

Edited May 11, 2023 by Duda Jarek

[Duda Jarek]

I have tried to organize such test of CPT symmetry in synchrotron, but it turns out technically challenging.
However, searching for a different laser having clear time asymmetry, a colleague has suggested that there are ring lasers - using optical isolator as kind of photon diode, enforcing photons traveling in one direction.

Applying CPT symmetry to the below setting, photons would travel in the opposite direction - causing excitation of the target (lamp).
So going back from CPT to to the original setting, shouldn't they cause deexictation of the target?

I am looking for access to ring laser to organize such test of CPT symmetry - please contact me in this case.

[Mordred]

Doubtful that setup would allow detectability of cpt violation. Photons being symmetric bosons seldom self interfere. You would likely have a better chance with including parametric down conversion of monochromatic light with beam splitters. You will want a limited range of frequency modes.

[Duda Jarek]

Applying CPT symmetry to this ring laser setting, would reverse photon directions - CPT(laser) would cause excitation of target ... hence returning from CPT symmetry, it means laser would cause deexcitation of target.

The central question is if after CPT symmetry physics works as ours (assumption used in the above statement) - including macroscopic physics, this experiment is supposed to test.

Maybe it doesn't, what would be also interesting and publishable - as probably first macroscopic CPT test (?), inspiring further experiments.

The problem I see is that, in opposite to free electron laser, such ring laser is not perfect - rather also has some small percentage of photons traveling in the opposite direction, exciting the target - making detection of hypothetical caused deexcitation more difficult.

The frequencies of excited target and laser need to overlap, the more the better, e.g. some gas discharge lamp with narrow spectrum, or maybe another laser.

I don't understand the need for SPDC? For now these are energy balance calorimetric-type measurements requiring high luminosity ... if successful, much better methods will be soon developed.

[swansont]

23 hours ago, Duda Jarek said:

Applying CPT symmetry to this ring laser setting, would reverse photon directions - CPT(laser) would cause excitation of target ... hence returning from CPT symmetry, it means laser would cause deexcitation of target.

Photons cause excitation and de-excitation anyway, without time reversal, so I don’t see why this would be evidence.

[Duda Jarek]

Sure such continously excited lamp would deexcite - normally in isotropic way.

However, applying CPT symmetry to the above setting, CPT of laser would cause excitation of target,  what without CPT translates to additional directional radiation - increase of deexcitation rate in direction toward laser, I would like to test.

Edited June 3, 2023 by Duda Jarek

[Mordred]

1 hour ago, Duda Jarek said:

Sure such continously excited lamp would deexcite - normally in isotropic way.

However, applying CPT symmetry to the above setting, CPT of laser would cause excitation of target,  what without CPT translates to additional directional radiation - increase of deexcitation rate in direction toward laser, I would like to test.

As I mentioned though you would need a better setup. One device used in testing for CPT is the J-PET detector.

https://www.worldscientific.com/doi/abs/10.1142/9789811213984_0005

 Using photons to detect CPT is tricky. As mentioned it would be tricky to separate normal photon interference from CPT effects. 

Edited June 3, 2023 by Mordred

[Duda Jarek]

Thanks, I couldn't access this article ("downloaded 2 times"), but there is accessible another from J-PET team (next building to mine): "The tests of CP and CPT symmetry using the J-PET detector" https://www.epj-conferences.org/articles/epjconf/pdf/2019/04/epjconf_meson2019_05027.pdf

They study decay of positronium - this is microscopic CPT symmetry, while the suggested laser ring experiment is supposed to test macroscopic CPT symmetry ... from microscopic perspective asking if there is CPT analogue of "stimulated emission" as "stimulated absorption"?

Better than ring laser would be free electron laser (FEL), but they are much more difficult to access.

The problem I see is that ring laser, in contrast to FEL, has some percentage of photons traveling in the opposite direction - exciting our target, making its hypothetical stimulate deexcitation more difficult to detect.

What other problems can you point in such ring laser test of CPT symmetry?

Edited June 3, 2023 by Duda Jarek

[swansont]

3 hours ago, Duda Jarek said:

Sure such continously excited lamp would deexcite - normally in isotropic way.

If photons are causing the excitations, they will also cause stimulated emission, which would not be isotropic.

[Duda Jarek]

I imagine there would be both - standard isotropic deexcitation, plus slightly increased probability of deexcitation in the direction of laser.

[swansont]

20 minutes ago, Duda Jarek said:

I imagine there would be both - standard isotropic deexcitation, plus slightly increased probability of deexcitation in the direction of laser.

Why would it be increased? 

[Duda Jarek]

Because in CPT transform of this setting, photon directions would be reversed - laser would excite this target: increase probability of its atoms being excited.
Hence returning from CPT, it translates into increased probability of these atoms being deexcited.

[Mordred]

You might want to take another look at polarity and helicity relations of CPT with regards to that last statement.

[swansont]

2 hours ago, Duda Jarek said:

Because in CPT transform of this setting, photon directions would be reversed - laser would excite this target: increase probability of its atoms being excited.
Hence returning from CPT, it translates into increased probability of these atoms being deexcited.

Photon excitation or de-excitation probability is not dependent on the direction of the photon. 

[MigL]

CPT symmetry is based on Lorentz invariance and the locality of quantum field interactions ( as Markus has mentioned ).
The symmetry is based on the total of the three properties and each individually ( or pairs ) can ( and have been found to ) violate the ruleas long as the emaining property ( or properties ) make up for it, such that total CPT symmetry is conserved.

Since in alarge system ( Avogadro's number of particles ) there are many ways for these individual symmetry violations to occurr, while conserving total CPT symmetry, I don't think there is any way to guarantee that total CPT symmetry of a macro system is conserved.

[Mordred]

I have to agree Migl. The chances of finding a CPT violation is extremely difficult without being a macro system.

To get a rather large summary of the CPT and Lorentz invariant datatables one of my favorite look up references for various relations etc is here

"Data Tables for Lorentz and CPT Violation"

https://arxiv.org/abs/0801.0287

It's a 146 pages of sheer useful datatables lol. It's also been updated this year.

 

Edited June 3, 2023 by Mordred

[Duda Jarek]

Thanks for the list, so I think we agree CPT should be true also in macroscale - but were there experiments really testing macroscopic CPT?

If not, maybe it is worth to design and conduct such tests - like proposed, using time-asymmetric light sources e.g. ring laser or free electron laser.

The only nonstandard in the discussed setting is being "behind" instead of "in front" of the source of coherent light ... but becoming proper "in front" when looking from perspective after applying CPT symmetry. This way we would ask physics if it works the same after applying CPT.

Microscopically, while e.g. laser cooling is CPT analogue of laser heating, we are asking if there exists CPT analogue of stimulated emission - some stimulated absorption.

[Mordred]

33 minutes ago, Duda Jarek said:

Thanks for the list, so I think we agree CPT should be true also in macroscale - but were there experiments really testing macroscopic CPT?

 

 

If you count tests done on atoms as macroscale which it typically is considered then yes.

https://arxiv.org/pdf/hep-ph/0006033.pdf

Penning traps is one of the more common method used

Its also been done with high precision spectrography.

 

[Duda Jarek]

Isn't it lots of microscale tests?

The CPT symmetry seems nonintuitive especially due to time symmetry, e.g. applying it to macroscopic scenario with clear causality, naively it should reverse causality, e.g.:

CPT(laser causes excitation of target) = CPT(laser) causes deexcitation of CPT(target)

microscopically: CPT(stimulated emission) in laser = stimulated absorption

Is it true? If so, it could bring lots of applications, but seems unknown ...

[swansont]

5 hours ago, Duda Jarek said:

Isn't it lots of microscale tests?

The CPT symmetry seems nonintuitive especially due to time symmetry, e.g. applying it to macroscopic scenario with clear causality, naively it should reverse causality, e.g.:

CPT(laser causes excitation of target) = CPT(laser) causes deexcitation of CPT(target)

microscopically: CPT(stimulated emission) in laser = stimulated absorption

Is it true? If so, it could bring lots of applications, but seems unknown ...

How is this a “reversal” of causality? 

[Duda Jarek]

Deexcitation is time/CPT reversal, analogue of excitation - here caused by the action of laser.

[Duda Jarek]

Here is another perspective on the ring laser setting using formulas from https://en.wikipedia.org/wiki/Stimulated_emission

There are two (Einstein's) formulas - for absorption it applies to the central target (pumped crystal), and the standard target on the right.

The symmetric emission formula is considered only for the central target.

However, in perspective after CPT symmetry the targets and equations would switch - hence emission formula should also symmetrically apply to the target on the left - stimulate its deexcitation (if satisfying condition of being excited).

 

 

Some potential applications of such suggested by CPT symmetry stimulated deexcitation, intuitively "pulling of photons":

- low probability nuclear transitions - if they produce some characteristic gammas, then they could be stimulated by such caused deexcitation - these high energy photons are available e.g. in free electron lasers, wigglers/undulators in synchrotron ... also in standard laser setting using above Einstein's equation. Which nuclear transitions would be the most interesting, practical?

- similarly for chemistry - probably useful for many technological processes (which ones?).

- maybe stimulated proton decay - ultimate energy source: complete matter -> energy transition, ~100x energy density than fusion from any matter. Violation of baryon number is required e.g. by baryogenesis, Hawking radiation. They cannot observe it in room temperature water, but maybe it is a matter of proper conditions, like pulling photons of characteristic energies by some powerful free electron laser? Could use normal laser setting.

- ?