Quintessence field equation of state

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Discussion Overview

The discussion revolves around the equation of state parameter w for a quintessence field with a specific potential, m²Phi². Participants explore why this parameter is treated differently from those of usual matter and radiation fields, particularly in the context of whether the scalar field should be considered classical or quantum.

Discussion Character

  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant questions why the equation of state parameter w for a quintessence field is not constrained between 0 and 1/3, suggesting that it may depend on the energy of its particles relative to the mass of the field.
  • Another participant asserts that the scalar field is treated as a classical scalar field rather than a collection of particles.
  • A participant expresses surprise at the understanding of scalar fields in inflation as pure classical fields, noting a belief that modern physics relies on quantum fields.
  • One participant proposes that the treatment of the scalar field as classical might be due to its extremely low mass and large wavelength, drawing a parallel to fuzzy dark matter, but notes a lack of similar arguments for inflation fields.

Areas of Agreement / Disagreement

Participants express differing views on the classification of scalar fields as classical versus quantum, indicating that there is no consensus on the implications of this distinction for the equation of state parameter w.

Contextual Notes

The discussion highlights uncertainties regarding the assumptions made about the nature of scalar fields and their treatment in different contexts, such as inflation and dark matter, without resolving these complexities.

fhenryco
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TL;DR
Quintessence field equation of state
Why the equation of state parameter w for a quintessence field with potential m²Phi² is not in between 0 and 1/3 depending on the energy of its particles relative to the mass of the field instead of the w resulting from formula 9 of https://arxiv.org/pdf/1504.04037.pdf which seems to be assuming that the field is classical ? !

In other words why is the scalar field treated differently than usual matter and radiation field when we want to compute it's w ?
 
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Because it is a classical scalar field, not a collection of particles.
 
It's also what i suspected but i wanted confirmation because i did not realize before that the scalar fields used for instance in inflation are understood as pure classical fields: i believed that in modern physics everything was always quantum and that nobody would accept a field which is not a quantum field !
 
fhenryco said:
It's also what i suspected but i wanted confirmation because i did not realize before that the scalar fields used for instance in inflation are understood as pure classical fields: i believed that in modern physics everything was always quantum and that nobody would accept a field which is not a quantum field !
Another possibility i was thinking about is that they treat it like a classical field because of it's extremely low mass (extremely large wavelength) ... this is what they do for fuzzy dark matter ... but i found nowhere the same argument for inflation fields
 

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