Peirce projections P-1, P-1/2 and P-0 are one of the fundamental technical tools in the theory of JB*-triples. It is well known that all three of them are contractive. We show that the sum of two Peirce projections need not be contractive. We also give the upper estimate for the norm of such a sum, valid in all JC*-triples, and present a conjecture of the exact value of this norm, based on some numerical experiments.
机构:
Univ Nacl Gral Sarmiento, Inst Ciencias, JM Gutierrez 1150, RA-1613 Los Polvorines, Argentina
Consejo Nacl Invest Cient & Tecn, J M Gutierrez 1150, RA-B1613GSX Los Polvorines, ArgentinaUniv Nacl Gral Sarmiento, Inst Ciencias, JM Gutierrez 1150, RA-1613 Los Polvorines, Argentina