a field theory motivated approach to computer algebra


Turns an object into a generalised Kronecker delta symbol.
Denotes a generalised Kronecker delta symbol. When the symbol carries two indices, it is the usual Kronecker delta. When the number of indices is larger, the meaning is \begin{equation} \delta_{m_1}{}^{n_1}{}_{m_2}{}^{n_2}{}_{... m_k}{}^{n_k} = \delta_{[m 1}{}^{n_1} \delta_{m_2}{}^{n_2} \cdots \delta_{m_k]}{}^{n_k} \,, \end{equation} with unit weight anti-symmetrisation. A symbol which is declared as a Kronecker delta has the property that it can be taken in and out of derivatives. The algorithm eliminate_kronecker eliminates normal Kronecker deltas by appropriately renaming indices (in order to eliminate Kronecker deltas with more than two indices, first use expand_delta).
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