Backward Time and Antimatter

[alpha2cen]

Which one is more correct between these two cases?

Does the "backward" mean a back ground time?

[swansont]

Hmm, well I've seen the experiments where spin was discovered or extrapolated, but I still don't see exactly where it comes from. Is there a specific equation than you can use for a 3-D modeling software in either cartesian or polar coordinates where you can actually see some kind of relation between variables that would cause those values?

 

It's angular momentum, so it adds together. Two spin-1/2 particles can combine to form a spin-1 or a spin-0 system, because it's quantized. The more particles you have, the higher the possible potential spin. You don't need 3-D modeling for this. (A table of Clebsch-Gordan coefficients can be helpful, though)

 

A negative energy particle with negative proper time is equivalent to a positive energy particle with positive proper time.

 

AFAIK the salient principle is CPT symmetry. If you reverse time, you reverse CP ( which is where you get the antimatter) and end up with an equivalent system. Under time reversal alone, neither energy nor charge would change — they are "even" variables.

 

http://en.wikipedia.org/wiki/T-symmetry#Effect_of_time_reversal_on_some_variables_of_classical_physics

[Arnaud Antoine ANDRIEU]

 

 

This is really a very good representation.

[elfmotat]

Edit: Nevermind.

Edited January 27, 2013 by elfmotat

[alpha2cen]

This is a more modified figure in the #32.

If the calculated result has a physical meaning, which one is more correct?

 

[elfmotat]

AFAIK the salient principle is CPT symmetry. If you reverse time, you reverse CP ( which is where you get the antimatter) and end up with an equivalent system. Under time reversal alone, neither energy nor charge would change — they are "even" variables.

 

http://en.wikipedia.org/wiki/T-symmetry#Effect_of_time_reversal_on_some_variables_of_classical_physics

 

Yes, you're right. I'm mixing ideas now - I was thinking of the fact that positrons can be considered holes in a negative energy Dirac sea.

[beefpatty]

"Equivalent" is a strong word. An electron-positron system releases energy in the annihilation. If the positron was negative energy, there'd just be the energy from the momentum from the two for the resultant photons.

 

The positron is not negative energy, but rather the electron traveling backward in time has negative energy. You have to take into account the negative proper time.

 

Here is Feynman's original paper on the subject:

http://authors.library.caltech.edu/3520/1/FEYpr49b.pdf

 

The second paragraph in the abstract is where he states:

 

In this solution, the "negative energy states" appear in a form which may be pictured (as by Stückelberg) in space-time as waves traveling away from the external potential backwards in time. Experimentally, such a wave corresponds to a positron approaching the potential and annihilating the electron.

 

and in the final paragraph on the left on page 753:

 

This therefore suggests that negative energy components created by scattering in a potential be considered as waves propagating from the scattering point toward the past, and that such waves represent the propagation of a positron annihilating the electron in the potential.

[Arnaud Antoine ANDRIEU]

AFAIK the salient principle is CPT symmetry. If you reverse time, you reverse CP ( which is where you get the antimatter) and end up with an equivalent system. Under time reversal alone, neither energy nor charge would change — they are "even" variables.

 

 

We can also say : one real time lap (m/s) = 0 to 1 m/s

 

But with the classical clock We can also apply for a "real time lap of 1s" :

 

0 AM --> center-of-the-clock

center of the clock --> 6'30 AM

6'30 AM --> center of the clock

center of the clock --> 1 AM

 

Each segments account for 0.15 seconds : two in the "real time" (the first and fourth) and two in the "paradox time" (the segments of the medium, the second and third). In physic we can only see the first and fourth. Sory my English is bad

 

namely physics (m/s) :

 

0 AM --> center-of-the-clock

center of the clock --> 1 AM

 

This means that the time has its spin and It half too !

[michel123456]

Only one charge's sign is reversed. It's really only an analogy to help demonstrate the idea, so don't take the Coulomb's Law thing too seriously. What's actually going on has to do with the time reversal operator in QFT.

It looks like you repeated something some professor told you without taking the time pondering about it.

It is not an analogy, it is plain wrong.

[ydoaPs]

It would be nice if anti-matter were negative energy matter going back in time since that would solve the "exotic matter" problem for things like Einstein-Rosen bridges and Alcubierre drives, but, as swansont and I said, it's not the case. I'd really like it if we could just step up our containment tech (and put collectors on ships) and be able to travel the stars, but anti-matter has positive energy just like everything else.

[michel123456]

It would be nice if anti-matter were negative energy matter going back in time since that would solve the "exotic matter" problem for things like Einstein-Rosen bridges and Alcubierre drives, but, as swansont and I said, it's not the case. I'd really like it if we could just step up our containment tech (and put collectors on ships) and be able to travel the stars, but anti-matter has positive energy just like everything else.

"antimatter" AFAIK is about the mirroring (the reversal) of EM interaction ONLY.

For antimatter, the 3 other interactions remain unchanged.

 

But is it possible to reverse only one of the 4 interactions leaving the other 3 unchanged?

[beefpatty]

It would be nice if anti-matter were negative energy matter going back in time since that would solve the "exotic matter" problem for things like Einstein-Rosen bridges and Alcubierre drives, but, as swansont and I said, it's not the case. I'd really like it if we could just step up our containment tech (and put collectors on ships) and be able to travel the stars, but anti-matter has positive energy just like everything else.

 

AFAIK, Einstein-Rosen bridges and Alcubierre drives require negative mass propagating forward in time, although I don't know much about them to really say.

 

The two processes are entirely equivalent and give the same answer. Consider the following process in QED.

 

 

At interaction 1 the electron can be scattered back in time by a potential, propagate to interaction 2, and then be scattered forward in time. Equivalently, before the electron reaches point 1 pair production can occur at point 2 due to the potential. This creates both a positron and electron propagating forward in time, and the positron annihilates with the incoming electron at point 1. The two interpretations are equivalent.

[ydoaPs]

"antimatter" AFAIK is about the mirroring (the reversal) of EM interaction ONLY.

For antimatter, the 3 other interactions remain unchanged.

 

But is it possible to reverse only one of the 4 interactions leaving the other 3 unchanged?

IIRC, colour is reversed too where applicable.

[MigL]

The proper analogy is 'Antimatter can be treated mathematically as regular matter travelling backwards in time.'.

A glance at a simple Feynman diagram, which has no foreward or backward direction, will demonstrate this behaviour.

[elfmotat]

It looks like you repeated something some professor told you without taking the time pondering about it.

It is not an analogy, it is plain wrong.

 

It's not really wrong. My point was to demonstrate CPT symmetry, although I agree I didn't really convey it unambiguously. The scenario I was imagining in my head was a charge in a static external electric field. I used Coulomb's Law in my post because I thought it would be easier to imagine like/opposite charges repelling/attracting than it would be to imagine a charge moving in one direction or the other in an electric field, which is slightly more abstract. The unintentional result was that the whole thing became convoluted.

[swansont]

!

Moderator Note

Spin discussion has been moved to http://www.scienceforums.net/topic/72421-question-on-spin-split-from-antimatterbackward-time/

[michel123456]

yes maybe i was too harsh.

 

Now i am thinking:

is it correct to imagine a particle of exotic matter traveling backward in time, alone, surrounded by regular particles of ordinary matter? Like an exotic actor walking backward and speaking "verlan" in a regular movie?

Or is it more correct to imagine a full movie played backward, where all actors undo the same things?

Edited January 28, 2013 by michel123456

[derek w]

In the LHC if particles were going backward in time they would hit the detectors before the collisions took place?

[beefpatty]

In order for their to be a collision they would have to meet at the same location in space and time, regardless of the direction they are traveling in time.

[swansont]

In the LHC if particles were going backward in time they would hit the detectors before the collisions took place?

 

The would be created in the detector by the reverse of the reaction we observed. But once you involve that scope of interaction the model breaks down, because entropy would be decreasing.

[beefpatty]

Ah, I didn't realize that was what you meant with your question. Hmm, that does seem like an interesting idea, but my initial thoughts are that, detecting a negative energy electron going backward in time would be the same as a positron forming out of your detector which, as swansont pointed out, would decrease entropy. So in that sense, for a particle running backward in time entropy should decrease so an increase would violate entropy, while to us running forward in time the opposite is true.

[alpha2cen]

The exotic electrons, which are projected onto the front time as positrons, are really in the other parallel world?

http://phys.org/news/2012-06-neutrons-parallel-world.html

Edited January 29, 2013 by alpha2cen

[beefpatty]

The exotic electrons, which are projected onto the front time as positrons, are really in the other parallel world?

 

They are not exotic since they obey the known laws of physics. That would imply positrons are exotic, which they are not.

[Arnaud Antoine ANDRIEU]

The exotic electrons, which are projected onto the front time as positrons, are really in the other parallel world?

http://phys.org/news/2012-06-neutrons-parallel-world.html

 

Yes. This link is relevant

[alpha2cen]

Without an existance of the background back side something, transforming from energy to particle can happen? At the BigBang point, the high energy seperate away the background back side particles too far. But, current low collision energy does not have a capacity to push away the background back side particles so far. So, antimatters are background back side particles which exist not so far away ?

Edited February 4, 2013 by alpha2cen