On the symbol-pair distances of repeated-root constacyclic codes of length 2p^s

Let p be an odd prime, and λ be a nonzero element of the finite field 𝔽_p^m. The λ-constacyclic codes of length 2p^s over 𝔽_p^m are classified as the ideals of quotient ring  in terms of their generator polynomials. Based on these generator polynomials, the symbol-pair distances of all such λ-constacyclic codes of length 2p^s are obtained in this paper. As an application, all MDS symbol-pair constacyclic codes of length 2p^s over 𝔽_p^m are established, which produce many new MDS symbol-pair codes with good parameters.