Examples
In general, the nature of a Lorentz tensor can be identified by its tensor rank, which is the number of indices it has. No indices implies it is a scalar, one that implies it is a vector etc. Furthermore, any number of new scalars, vectors etc. can be made by contracting any kinds of tensors together, but many of these may not have any real physical meaning. Some of those tensors that do have a physical interpretation are listed (by no means exhaustively) below.
Please note, the metric sign convention such that η = diag (1, −1, −1, −1) is used throughout the article.
Read more about this topic: Lorentz Covariance
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