Is Rest Mass a subjective quantity?

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Discussion Overview

The discussion revolves around the nature of rest mass, particularly the electron rest mass, and whether it is a subjective quantity influenced by measurement resolution and energy scales. Participants explore concepts from relativistic Quantum Field Theory, renormalization, and the implications of temperature on mass measurements.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant asserts that the dressed mass of an electron is influenced by the resolution of measurement and knowledge of the system, questioning the notion of the electron mass as a fundamental constant.
  • Another participant counters that the rest mass is objective and only depends on the energy scale, specifically stating that the zero energy limit is what defines the rest mass.
  • A follow-up question is posed regarding whether the observed rest mass at high temperatures would differ from the universal constant due to additional loop corrections, indicating a potential complexity in the relationship between temperature and mass.
  • A response suggests that all loop corrections are necessary to determine the zero energy value accurately and that high temperature corresponds to high energy, complicating the concept of mass as the electron behaves as a quasiparticle under such conditions.

Areas of Agreement / Disagreement

Participants express differing views on whether rest mass is subjective or objective, with some arguing for its dependence on measurement conditions while others maintain it is a fixed quantity determined by energy scale. The discussion remains unresolved with competing perspectives on the nature of rest mass.

Contextual Notes

Participants reference concepts such as renormalization, dressed mass, and the behavior of particles at different energy scales, indicating a reliance on specific theoretical frameworks that may not be universally accepted or fully resolved.

thephystudent
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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'?
 
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thephystudent said:
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.
 
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A. Neumaier said:
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?
 
thephystudent said:
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.
 
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