What parameters of SM can be changed gradually?

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Discussion Overview

The discussion revolves around the parameters of the Standard Model (SM) of particle physics and whether they can be varied gradually. Participants explore the implications of changing parameters such as mass and CKM angles, and the potential effects on phenomena like CP violation and baryogenesis.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants suggest that while the mass spectrum cannot vary due to energy conservation, other parameters like CKM angles might have been different in earlier epochs, potentially affecting CP violation and baryogenesis.
  • Others argue that any variation in the constants of the SM would imply a departure from the SM framework itself, raising questions about the nature of those parameters.
  • It is noted that the SM does not explain why parameters have their observed values, leading to a discussion about the constraints on these parameters.
  • One participant asserts that mass cannot be variable without resulting in fundamentally different physics, while another counters that it is possible to construct a Lagrangian with a dynamical effective mass that conserves energy.
  • Further elaboration includes the idea that in relativistic quantum field theory, mass can become a dynamical quantity due to self-energies, and this concept extends to many-body systems where effective masses can differ from the elementary constituents.

Areas of Agreement / Disagreement

Participants express differing views on whether parameters of the SM can be varied. Some argue for the possibility of variation under certain conditions, while others maintain that such changes would lead to different physics altogether. The discussion remains unresolved with multiple competing perspectives.

Contextual Notes

There are limitations regarding the assumptions made about the nature of parameters in the SM and the implications of changing them. The discussion does not resolve the mathematical or conceptual challenges associated with these ideas.

Dmitry67
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For example, mass spectrum can't vary because energy is conserved (locally).
What's about other parameters? Could CKM angles be different in earlier époque? It could save the Sakharov’s mechanism, if CP violation was more intense during bareogenesis.
 
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The answer depends on what do you mean by "can".
Anything is possible, unless you specify some constraint (which you don't).
In principle, any constant in SM (including the masses) could be a variable, but then it would not be described by SM any more.
 
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SM itself does not explain WHY parameters have the values we observe.
So it does not put any constrains on them.

Mass can't be variable - it would be absolutely different physics, because energy won't be conserved.
 
Dmitry67 said:
SM itself does not explain WHY parameters have the values we observe.
That's true.

Dmitry67 said:
So it does not put any constrains on them.
It puts at least one constraint: They must be - constant!

Dmitry67 said:
Mass can't be variable - it would be absolutely different physics, because energy won't be conserved.
That's not true, it is easy to write a Lagrangian with a dynamical effective mass with a conserved Hamiltonian. In fact, the Lagrangian describing the Higgs mechanism, which is a part of the SM, is one such Lagrangian.
 
Demystifier said:
That's not true, it is easy to write a Lagrangian with a dynamical effective mass with a conserved Hamiltonian. In fact, the Lagrangian describing the Higgs mechanism, which is a part of the SM, is one such Lagrangian.

In fact, in any relativistic QFT "mass" becomes a dynamical quantity through the non-vanishing self-energies of the particles.

In many-body theory this even happens for non-relativistic particles: In the most simple case one can describe the many-body system as a dilute quantum gas of quasi-particles, which may have the same quantum numbers as the elementary constituents (e.g., electrons in a condensed-matter system) but with different effective masses or charges. Other quasi-particle excitations (effective degrees of freedom) may not be medium modifications of elementary constituents but collective modes like phonons (lattice vibrations) in a solid body, plasmons/plasminos (plasma oscillations) in a plasma,...
 
Interesting - I did not think about that.
Thanks
 

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