Is Rest Mass a subjective quantity?

[thephystudent]

The Electron Rest Mass is considered as a fundamental constant of nature.

In relativistic Quantum Field Theory, in contrast, divergences arise. In order to deal with these divergences, one uses renormalization. According to this renormalization, the 'macroscopic' parameters of the lagrangian among which the mass is one, are not the "real" bare quantities. An interacting particle will drag an infinite amount of loop corrections with it in principle, but one has no experimental access to all of these. Instead, all loop corrections above a certain order in perturbation theory cannot be distinguished and are therefore considered as being part of a 'dressed mass'.

But it seems to me the previous implies there is no other fundamental mass constant than the bare mass! The dressed mass depends on the resolution of the measurement, how far you have pushed the renormalization trough. I.e. the dressed mass depends on your knowledge of the system such as for example an entropy does. How can this correspond with the 'electron mass as fundamental constant'?

 

[A. Neumaier]

The dressed mass depends on the resolution of the measurement, how far you have pushed the renormalization through. I.e. the dressed mass depends on your knowledge of the system such as for example an entropy does. How can this correspond with the 'electron mass as fundamental constant'?

No. It only depends on the energy scale. The zero energy limit is what counts as ''the'' rest mass and is fully objective.

 

[thephystudent]

No. It only depends on the energy scale. The zero energy limit is what counts as ''the'' rest mass and is fully objective.

Lol, quick and easy answers are always the best ones.

Small follow-up question: according to my intuition at finite (high) temperatures the observed rest mass of an electron will differ from this universal constant because more loops are added, is this correct?

 

[A. Neumaier]

Lol, quick and easy answers are always the best ones.

Small follow-up question: according to my intuition at finite (high) temperatures the observed rest mass of an electron will differ from this universal constant because more loops are added, is this correct?

No. All loops are already needed to get the zero energy value correct. In terms of the energy scale, high temperature is just high energy, expressed as temperature using the universal gas constant. On the other hand, at high temperature, the electron is a quasiparticle only, which complicates matters.