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Everything about Component-free Treatment Of Tensors totally explained

In mathematics, the modern component-free approach to the theory of tensors views tensors initially as abstract objects, expressing some definite type of multi-linear concept. Their well-known properties can be derived from their definitions, as linear maps or more generally; and the rules for manipulations of tensors arise as an extension of linear algebra to multilinear algebra. In differential geometry an intrinsic geometric statement may be described by a tensor field on a manifold, and then doesn't need to make references to coordinates at all. The same is true in general relativity, of tensor fields describing a physical property. The component-free approach is also used heavily in abstract algebra and homological algebra, where tensors arise naturally. » Note: This article, which is fairly abstract, requires an understanding of the tensor product of vector spaces without chosen bases. The notion of a tensor product generalizes to vector spaces without chosen bases, and even further, to modules. If you find this article difficult, try reading the main tensor article and the classical or intermediate level treatments first.

Definition: Tensor Product of Vector Spaces

Let V and W be two vector spaces over a common field F. Their tensor product » V otimes_F W

is a vector space over the same field F together with a bilinear map » otimes: V imes W arr V otimes_F W

which is universal in the following sense:
for every vector space X over the field F and every F-bilinear map » Q: V imes W arr X ,

there is a unique F-linear map » Q': V otimes_F W arr X

such that » forall v in V forall w in W Q (v,w) = Q'(votimes w)

It is easy to see that a vector space V otimes_F W is unique up to isomorphism if it exists, and we write "the tensor product" instead of "a tensor product."
   All its properties, except its existence, follow from the abstract definition, although some properties are more easily understood from an explicit model.
   An explicit construction is easy to give using bases _k

In older texts this transformation rule often serves as the definition of a tensor. Formally, this means that tensors were introduced as specific representations of the group of all changes of coordinate systems.
   

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