The discussion centers on the relationship between a scalar field and the stress-energy tensor, specifically whether coupling to the stress-energy tensor (T=Tμν) implies coupling to the Ricci scalar (R). The participants agree that while contracting Einstein's equations yields R = 8πG T, using the term "couple" in this context may lead to semantic confusion. The conversation emphasizes the importance of precise language in theoretical physics, particularly when discussing interactions in k-space and their implications.
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Hmm, I think this will ultimately just end up being a semantics argument. I see what you are saying, and agree with the statement in that context but it probably is best not to use "couple" in that way.A/4 said:Suppose there is a field that couples to the stress-energy tensor. For simplicity, assume it's a scalar field coupling to [tex]T=T^\mu_\mu[/tex]. Since contracting Einstein's equations with the metric yield the relation [tex]R = 8\pi G T[/tex], is it correct to say that the field also couples to [tex]R[/tex]?