I am trying to reconcile the definition of Inner Product Spaces that I encountered in Mathematics with the one I recently came across in Physics. In particular, if (,) denotes an inner product in the vector space V over F:
(u+v,w)=(u,w)+(v,w) for all u,v,w∈V,
(αv,w)=α(v,w) for all v,w∈V and α∈F,
(v,w)=(w,v)∗ for all v,w∈V, (* denotes complex conjugation)
were some of the properties listed in my mathematics course.
In physics, however, the inner product was said to be linear in the second argument and (v,∑(λiwi))=∑(λi(v,wi)) where v and wi are kets in Hilbert space and λi are complex numbers.
To me, these properties of an Inner Product are not compatible. If the first definition of inner product is correct, then I think (v,∑(λiwi))=∑((λi)∗(v,wi)) where ∗ denotes complex conjugation.
Answer
To formalize the comments as an answer:
The difference between requiring (αu,v)=α(u,v) (mathematician's definition)
The physicist's definition does have the advantage that it extends well to Dirac notation, in the sense that matrix elements such as ⟨ϕ|ˆA|ψ⟩ are linear in ψ, so that the state ˆA|ψ⟩ corresponds to the operator-acting-on-a-vector notation Av. If the bracket were linear in ϕ then we'd have to make operators act to their left. This is again an OK convention but no one uses it.
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