Cosmology models and QFT

[KleinMoretti]

TL;DR Summary

Do the various cosmology models modify QFT?

I know that cosmology usually deals with general relativity but what about QFT, is it modified depending on the cosmological model? Or is it not something that change with the model used.

 

[PeterDonis]

QFT is a framework for building models, not a single model. QFT can be done in curved spacetime, so you could do QFT using any cosmological solution (for example the best current $\Lambda C D M$ model) as the background spacetime.

 

[KleinMoretti]

@PeterDonis
yes I understand QFT is a framework and not an individual theory, what i meant is if the basic properties/rules of QFT are modified in models that are different from the $\Lambda C D M$ model

 

[PeterDonis]

what i meant is if the basic properties/rules of QFT are modified in models that are different from the $\Lambda C D M$ model

Why would they be? Since "the basic properties/rules of QFT" are a framework, not a single model, why would you expect them to change from model to model, since the whole point of the framework is to build multiple different models?

 

[KleinMoretti]

Yea I guess that makes sense, either way cosmology is classical right?

 

[PeterDonis]

either way cosmology is classical right?

The $\Lambda C D M$ model is a classical model (using classical GR), yes. However, some of the parameters in the model depend on our knowledge of quantum effects, such as the Standard Model predictions for what ratio of isotopes we should expect from Big Bang nucleosynthesis.

 

[KleinMoretti]

However, some of the parameters in the model depend on our knowledge of quantum effects,

right and this is why I asked if cosmology models modified QFT which you just told me it’s not the case.

 

[PeterDonis]

this is why I asked if cosmology models modified QFT

Having to estimate certain parameters in a classical model using a quantum model is not at all the same as having one's choice of classical model modify QFT. Even choosing which quantum model to use to estimate the classical parameters is not the same as modyfing QFT. The Standard Model is a QFT, but there are other QFTs as well--none of which modify "the basic properties/rules of QFT".

 

[KleinMoretti]

The Standard Model is a QFT, but there are other QFTs as well--none of which modify "the basic properties/rules of QFT".

yes but here you are talking about different QFTs and how they don’t modify the basic properties of QFT but my questions was about cosmology models.

Having to estimate certain parameters in a classical model using a quantum model is not at all the same as having one's choice of classical model modify QFT. Even choosing which quantum model to use to estimate the classical parameters is not the same as modyfing QFT.

by this you do mean cosmology models don’t in fact modify QFT right?

 

[KleinMoretti]

@PeterDonis from what you have said would it be correct to say that the different cosmology models have to take into account predictions made by QFT but they dont modify it

 

[PeterDonis]

here you are talking about different QFTs and how they don’t modify the basic properties of QFT but my questions was about cosmology models.

Which are classical models, so they can't possibly say anything about QFT.

by this you do mean cosmology models don’t in fact modify QFT right?

Yes.

@PeterDonis from what you have said would it be correct to say that the different cosmology models have to take into account predictions made by QFT but they dont modify it

Yes.