Cohen–Hewitt factorization theorem

In mathematics, the Cohen–Hewitt factorization theorem states that if V is a left module over a Banach algebra B with approximate left unit {u_i}, then an element v in V can be factorized as a product v = bw (for b in B, w in V) whenever lim u_iv = v. The theorem was introduced by Paul Cohen (1959) and Edwin Hewitt (1964).

References

• Cohen, Paul J. (1959), "Factorization in group algebras", Duke Mathematical Journal 26: 199–205, doi:10.1215/s0012-7094-59-02620-1, MR 0104982 
• Hewitt, Edwin (1964), "The ranges of certain convolution operators", Mathematica Scandinavica 15: 147–155, MR 0187016