A Quintessence field equation of state

[fhenryco]

TL;DR Summary

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 ?

 

[Orodruin]

Because it is a classical scalar field, not a collection of particles.

 

[fhenryco]

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]

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