Friday, 2 June 2017

mathematical physics - Are there cases in which we should consider tensors as equivalence classes?



Usually in texts about Physics that uses tensors defines them as multilinear maps. So if V is a vector space over the field F, a tensor is a multilinear mapping:


T:V××V×V××VF.


In texts about multilinear algebra, however, a tensor is defined differently. They consider a collection V1,,Vk of vector spaces over the same field, consider the free vector space M=F(V1××Vk), consider the subspace M0 genereated by vectors of the form


(v1,,vi+vi,,vk)(v1,,vi,,vk)(v1,,vi,,vk)


(v1,,kvi,,vk)k(v1,,vi,,vk)


And then define the tensor product V1Vk=M/M0 and define tensors as elements of such space, which are equivalence classes of functions with finite support in V1××Vk.


Now, is there some cases in Physics where it's better to think as tensors as such equivalence classes rather than multilinear mappings? If so, how then we get some physical intuition behind those objects?




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