What does it mean that physics it time/CPT symmetric?

[Duda Jarek]

Regarding baryon asymmetry, I would say it is statistical symmetry breaking: that symmetric situation is statistically repelling.
Like for e.g. L-amino acids in our life: while there is symmetry, the more one type of them, the easier development of life based on the same (more resources in environment) - making 1/2-1/2 ration statistically repelling, leading to nearly complete domination of one of them - originally chosen e.g. in a random way.

For baryon asymmetry we don't need CPT violation, it is sufficient to have this kind of statistical repelling.
For example that in baryogenesis:
"creation of proton is a bit more likely in presence of electron" plus symmetric
"creation of antiproton is a bit more likely in presence of positron"
such two symmetric rules would make 1/2-1/2 ratio matter-antimatter state statistically repelling, leading to nearly complete domination of one of them, e.g. initially chosen in a random way.

[swansont]

17 minutes ago, Duda Jarek said:

Regarding baryon asymmetry, I would say it is statistical symmetry breaking: that symmetric situation is statistically repelling.
Like for e.g. L-amino acids in our life: while there is symmetry, the more one type of them, the easier development of life based on the same (more resources in environment) - making 1/2-1/2 ration statistically repelling, leading to nearly complete domination of one of them - originally chosen e.g. in a random way.

For baryon asymmetry we don't need CPT violation, it is sufficient to have this kind of statistical repelling.
For example that in baryogenesis:
"creation of proton is a bit more likely in presence of electron" plus symmetric
"creation of antiproton is a bit more likely in presence of positron"
such two symmetric rules would make 1/2-1/2 ratio matter-antimatter state statistically repelling, leading to nearly complete domination of one of them, e.g. initially chosen in a random way.

But you don't create just protons or just antiprotons without violating conservation laws or symmetry. You create both at the same time. That's not the case with an amino acid. You can build just one without such violations.

[Duda Jarek]

Baryogenesis hypothesis requires violation of baryon number conservation - like Hawking radiation or unobserved (at least in room temperature) https://en.wikipedia.org/wiki/Proton_decay : we can search for CPT symmetric rule which makes 1/2-1/2 ratio situation statistically repelling, like 

in presence of some matter (proton, electron) it is a bit more likely to create proton, and symmetrically in presence of antimatter it is a bit more likely to create antiproton.

Otherwise: if baryon number is ultimately conserved, there remains e.g. Cyclic Universe hypothesis: that baryon number was the same in Big Crunch preceding our Big Bang - shifting this problem to minus infinity.

 

Regarding biology,  indeed alternative explanation is that creation of life is so improbable that it just happened only once around here - this way randomly choosing one of chiralities.

Synthetic biology is currently running to synthesize mirror version of a cell, e.g. mirror polymerase was synthesized in 2016, but such mirror life might turn out extremely dangerous as not having natural enemies: https://en.wikipedia.org/wiki/Mirror_life

Edited August 5, 2020 by Duda Jarek

[swansont]

8 hours ago, Duda Jarek said:

Baryogenesis hypothesis requires violation of baryon number conservation - like Hawking radiation or unobserved (at least in room temperature) https://en.wikipedia.org/wiki/Proton_decay : we can search for CPT symmetric rule which makes 1/2-1/2 ratio situation statistically repelling, like 

in presence of some matter (proton, electron) it is a bit more likely to create proton, and symmetrically in presence of antimatter it is a bit more likely to create antiproton.

Simply repeating yourself doesn’t clarify anything 

What, specifically, “is a bit more likely to create a proton”? What’s the reaction?

 And if you start with equal amounts of matter and antimatter, why would this create an asymmetry?

[Duda Jarek]

So assume there is possible proton decay, for simplicity we can write:

proton -> positron + gammas

In hypothetical baryogenesis there would be needed some opposite process, e.g. with leptons from pair creation: gammas -> electron + position.

If possible, it would be still extremely unlikely, its nearly negligible probability (cross section) could be affected by local situation, like "catalyzed by presence of slow positive charge" (e.g. flying nearby, with photon exchange in Feynman diagram) improving a bit this probability - what would be sufficient for statistical symmetry breaking by two CPT symmetric rules:

positron + gammas -> proton (with increased probability in presence of proton)

electron + gammas -> antiproton (with increased probability in presence of antiproton)

This kind of catalyzing property: increased fitness of L-aminoacid based life in presence of L-aminoacid based life, or increased probability of creation of proton in presence of proton, allows for symmetric set of rules leading to statistical symmetry breaking - nearly complete domination of one of them, initially chosen at random.

 

[Duda Jarek]

So you agree or disagree?

Such hypothetical "increased probability in presence" can be alternatively written e.g. as

positron + gammas + proton-> 2 protons

electron + gammas + antiproton -> 2 antiprotons

with some exchange in Feynman diagrams with this additional particle (e.g. electron, proton, neutron).

Our knowledge about violation of baryon number conservation is practically zero - couldn't observe any, which reason might be trying to get proton decay in room temperature, while it is hypothesized for muuuuuch more extreme conditions like baryongenesis or Hawking radiation (so maybe also center of neutron star?)

My point is only that CPT violation is not necessary to explain domination of matter - other ways are e.g.:

- fixed baryon number of the Universe - in Big Crunch preceding our Big Bang,

- statistical symmetry breaking - some positive feedback mechanism like above, making "the more of one type, the easier to get even more" - finally leading to domination of one type, which initially could be chosen at random, analogously to chirality of life.

ps. Regarding claim that proton decay is impossible because we couldn't observe it in room temperature water - we could disprove nuclear fusion in the same way ... some processes just need much more extreme conditions, much more for baryon number violation than for fusion.

Edited August 7, 2020 by Duda Jarek

[drumbo]

It implies that it is possible for there to be a mirror image of our universe that has the same laws as our own.

[Duda Jarek]

Sure, it is also possible that there are teapots flying throughout the Universe ( https://en.wikipedia.org/wiki/Russell's_teapot ).

While we cannot exclude unimaginable amount of stuff, a practical rule to get anywhere is Ockham's razor ( https://en.wikipedia.org/wiki/Occam's_razor ) : "entities should not be multiplied without necessity" - before going to "exciting explanations" (loved by the bibliometric evaluation system), really explore the the nonmagical ones first.

[Phi for All]

8 hours ago, drumbo said:

It implies that it is possible for there to be a mirror image of our universe that has the same laws as our own.

!

Moderator Note

Stay on topic, please.