Time itself has a biased flow direction.

[RJBeery]

So I don't think you could claim T asymmetry in the electroweak sector of the standard model is wrong without claiming substantial parts of the Standard Model are wrong.

Wait, you're saying T-asymmetry is baked into the Standard Model itself? I thought the apparent T-asymmetry was observed in the labs and the model was "rescued" by expanding the scope to be CPT symmetric. There's a big difference to me between claiming CPT-symmetry (which does not preclude T-symmetry, necessarily) vs claiming T-asymmetry as part of the model.

 

[przyk]

Wait, you're saying T-asymmetry is baked into the Standard Model itself?

Yes. It was built into electroweak theory which is now included as part of the Standard Model.

I thought the apparent T-asymmetry was observed in the labs and the model was "rescued" by expanding the scope to be CPT symmetric.

Something like that, except it was CP violations that were first seen in weak interactions in the 1960s and built into electroweak theory. Since CP violation and CPT symmetry necessarily implies T violation, electroweak theory is also not T symmetric. So we had a theoretical basis for expecting to be able to observe T asymmetry in weak interactions long before we eventually did. In fact, that's what motivated the researchers mentioned in Billy T's OP link to look at data collected on B mesons in the first place: electroweak theory predicted they should be able to see evidence of T asymmetry there.

At least, that's my understanding of the situation. My recollection of some of this stuff is bit hazy.

 

[RealityCheck]

Yes. It was built into electroweak theory which is now included as part of the Standard Model.

Something like that, except it was CP violations that were first seen in weak interactions in the 1960s and built into electroweak theory. Since CP violation and CPT symmetry necessarily implies T violation, electroweak theory is also not T symmetric. So we had a theoretical basis for expecting to be able to observe T asymmetry in weak interactions long before we eventually did. In fact, that's what motivated the researchers mentioned in Billy T's OP link to look at data collected on B mesons in the first place: electroweak theory predicted they should be able to see evidence of T asymmetry there.

At least, that's my understanding of the situation. My recollection of some of this stuff is bit hazy.

Hi guys. Does this have implications for the discussions on whether TIME is a 'proper' dimension (as in proper space dimensions) if time is not symmetric? Are CPT all 'dimensions' as well? How does time compare to the other two as a separate dimension in that case?

Your answers/comments welcomed. Thanks; back tomorrow.

 

[przyk]

Hi guys. Does this have implications for the discussions on whether TIME is a 'proper' dimension (as in proper space dimensions) if time is not symmetric?

No.

Are CPT all 'dimensions' as well?

C, P, and T are transformation operations (charge conjugation, parity transformations, and time inversion, respectively) that may or may not be symmetries of physical systems and laws.

 

[RealityCheck]

Hi przyk.

Thanks for your reply.

To clarify my question regarding time as 'dimension': Since a dimension represents a 'degree of freedom' for some property/value/action etc to vary 'along' that dimensional freedom range, how does the fact that 'time' is claimed to 'break symmetry' then reconciled with the expectation that a valid dimension should have degree of freedom extending symmetrically back/forward, up/down etc etc along whatever dimensional range it is supposed to represent?

Back later or tomorrow to check for your further response. Thanks in advance.

 

[arfa brane]

The problem with the second law of thermodynamics is that it basically asserts that probability theory works one way in time but not the other.

I think what that means is that we believe the probability of a shattered glass reassembling itself is effectively zero, or likewise, the molecules of gas in a container have zero probability of all being on one side of that container.

Penrose points out that we have two rather different quantum 'processes', one is 'smooth', unitary, and time-symmetric, he calls this "U", the other involves distinct 'jumps' to a measured state, or state reduction "R".
Measurement isn't time-symmetric because particles can take more than one path to each other before interacting (in a path-independent way). For instance with a half-silvered mirror, photons which are reflected in the positive time direction travel in the opposite spatial direction than photons reflected in the negative time direction because the mirror has two reflecting sides but only one transmitting interior.

 

[Syne]

Since a dimension represents a 'degree of freedom' for some property/value/action etc to vary 'along' that dimensional freedom range, how does the fact that 'time' is claimed to 'break symmetry' then reconciled with the expectation that a valid dimension should have degree of freedom extending symmetrically back/forward, up/down etc etc along whatever dimensional range it is supposed to represent?

Cite one reference necessitating symmetry in a dimension.

Equations that model reality may be symmetrical, but the model does not define the reality. A degree of freedom can be unidirectional.

 

[RealityCheck]

A degree of freedom can be unidirectional.

Is that a fact? "unidirectional" which way? Can you point to the way that time's 'unidirectional' degree of freedom acts in order to constitute an 'asymmetrical dimension'? Please elaborate.

 

[przyk]

To clarify my question regarding time as 'dimension': Since a dimension represents a 'degree of freedom' for some property/value/action etc to vary 'along' that dimensional freedom range, how does the fact that 'time' is claimed to 'break symmetry' then reconciled with the expectation that a valid dimension should have degree of freedom extending symmetrically back/forward, up/down etc etc along whatever dimensional range it is supposed to represent?

Degrees of freedom aren't required to possess symmetries.

 

[RealityCheck]

Degrees of freedom aren't required to possess symmetries.

What about the obverse of that statement? Are symmetries required to manifest degree of freedom of a 'dimension'?

 

[przyk]

What about the obverse of that statement? Are symmetries required to manifest degree of freedom of a 'dimension'?

If you're asking whether there needs to be a symmetry in order for us to consider something a dimension, then no.

 

[RealityCheck]

If you're asking whether there needs to be a symmetry in order for us to consider something a dimension, then no.

Thanks for your assistance on that. Is there some reference specifically and unambiguously treating/explaining just that point/aspect in the literature? I would be very much obliged if you could point me towards it. Cheers.

 

[przyk]

Thanks for your assistance on that. Is there some reference specifically and unambiguously treating/explaining just that point/aspect in the literature? I would be very much obliged if you could point me towards it. Cheers.

That would be a bit difficult, because you are asking about terminology - specifically the word "dimension" - that is used in multiple different ways in physics. The most relevant definition is probably the dimension of a vector space. The problem here, though, is that that's a mathematical definition and not a physical one, so asking whether something is a "dimension" becomes a question about some particular mathematical expression of physics rather than the point of view of physics as a whole. Very often the same theory can have different mathematical expressions. There are examples in physics where time appears as a dimension (in a vector space) in one way of expressing a theory but not in a different way of mathematically expressing exactly the same theory.

All I can say is that whether time inversion is a symmetry has no relevance to the mathematical vector space definition of dimension and no impact on whether we consider time a dimension either way.

 

[Syne]

Is that a fact? "unidirectional" which way? Can you point to the way that time's 'unidirectional' degree of freedom acts in order to constitute an 'asymmetrical dimension'? Please elaborate.

I am not going to play your usual game here. I have already asked you to cite your reason for assuming "a valid dimension should have degree of freedom extending symmetrically". Now you can go around and around about how you have made no claim, and should not be expected to support any assumption you make, simply because you threw a question mark at the end of a long and convoluted run-on sentence. I will not answer questions from someone who will not reciprocate.

 

[RealityCheck]

I am not going to play your usual game here. I have already asked you to cite your reason for assuming "a valid dimension should have degree of freedom extending symmetrically". Now you can go around and around about how you have made no claim, and should not be expected to support any assumption you make, simply because you threw a question mark at the end of a long and convoluted run-on sentence. I will not answer questions from someone who will not reciprocate.

No games. Why the attitude? I am genuinely interested in all points of view about this aspect which is difficult to ascertain without asking/positing something to get the responses from those interested in the same thing from their own perspective. Thanks for your initial response anyway, it was most helpful to my further explorations on this. Cheers.

 

[RealityCheck]

That would be a bit difficult, because you are asking about terminology - specifically the word "dimension" - that is used in multiple different ways in physics. The most relevant definition is probably the dimension of a vector space. The problem here, though, is that that's a mathematical definition and not a physical one, so asking whether something is a "dimension" becomes a question about some particular mathematical expression of physics rather than the point of view of physics as a whole. Very often the same theory can have different mathematical expressions. There are examples in physics where time appears as a dimension (in a vector space) in one way of expressing a theory but not in a different way of mathematically expressing exactly the same theory.

All I can say is that whether time inversion is a symmetry has no relevance to the mathematical vector space definition of dimension and no impact on whether we consider time a dimension either way.

Understood. Yes, it is hard to pin down exactly what I am looking for in the literature because of what you point out there. Again, thanks, that was very helpful to me to know that I already read the literature right.

In your last sentence you indicate that any symmetry or otherwise in time dimension 'inversion' is mute in context of vector space definition of 'dimension' per se in maths; and that whether we consider time a dimension or not does not depend on any inversion symmetry or not for time degree of freedom? Have I read you right? If so, thanks again. Most helpful. Cheers.

 

[Syne]

No games. Why the attitude? I am genuinely interested in all points of view about this aspect which is difficult to ascertain without asking/positing something to get the responses from those interested in the same thing from their own perspective. Thanks for your initial response anyway, it was most helpful to my further explorations on this. Cheers.

And I asked you why you posited that "a valid dimension should have degree of freedom extending symmetrically". I am more than willing to discuss this with you, if you have the decency to answer questions about what you posit as well. Here it seems you are continuing to dodge any questions of your own assumptions. We have seen this behavior from you before.

 

[RealityCheck]

And I asked you why you posited that "a valid dimension should have degree of freedom extending symmetrically". I am more than willing to discuss this with you, if you have the decency to answer questions about what you posit as well. Here it seems you are continuing to dodge any questions of your own assumptions. We have seen this behavior from you before.

I asked based on 'expectation' of symmetry for a 'dimension'. You answered that symmetry is not necessary for a dimension. Further consideration of the various contextual 'definitions' of dimensions in discussion with przyk regarding what may be specifically treated in the literature regarding time/symmetry etc in the various contexts of 'dimension' definitions. Thank you both for your helpful replies. The 'expectation' was all I based my question on. If you, przyk or anyone have any further helpful info/comments re 'dimensions' and symmetry/asymmetry specific to time as a 'dimension' I welcome them. Thanks again. Cheers.

 

[Gerhard Kemmerer]

You all well know, that the Q of time invites a lot of debate without end, but that does not mean it cannot be figured out.

Part of the solution may be to have a non static/stationary definition of it, and to get away from defining it from the perspective of measuring change in events, and also staying away from 'dimensional talk', because that too is about observation/perseptions of the event.

The 'event' is our experience.

Time should be examined from its cause.

Then we could understand that our experience is subject to unnoticable changes in time/space etc, and that without these fluctuations there would be no matter or movement of it.

One of the best definitions of time I have read on this forum comes from a post in ...

 

[Billy T]

To Gerhard Kemmerer: I think you are speaking of "subjective time" and way off thread subject. Physical time is a coordinate, much like X,Y & Z, the space coordinates are. T and these three tell the location of events.

To give you a hint as to what thread is about imagine the X&Y coordinates are on the surface of a mirror and Z is perpendicular to it with your right hand held in front of it at Z1. At -Z1 you see the image of a hand, but it is a left hand. (A parity change in more technical terms.) Thread is sort about what happens when T is replaced by -T.