Invariants of tensors

In mathematics, in the fields of multilinear algebra and representation theory, invariants of tensors are coefficients of the characteristic polynomial of the tensor A:

where is the identity tensor and is the polynomial's indeterminate (it is important to bear in mind that a polynomial's indeterminate may also be a non-scalar as long as power, scaling and adding make sense for it, e.g., is legitimate, and in fact, quite useful).