Deformations of chiral two-forms in six dimensions

Motivated by a system consisting of a number of parallel MS-branes, we stud y possible local deformations of chiral two-forms in six dimensions. Workin g to first order in the coupling constant, this reduces to the study of the local BRST cohomological group at ghost number zero; We obtain an exhausti ve list of all possible deformations. None of them allows for a satisfactor y formulation of the MS-branes system leading to the conclusion that no loc al field theory can describe such a system. (C) 1999 Published by Elsevier Science B.V. All rights reserved.