Multisymplectic geometry admits an operation that has no counterpart in
symplectic geometry, namely, taking the product of two multisymplectic
manifolds endowed with the wedge product of the multisymplectic forms. We show
that there is an L-infinity-embedding of the L-infinity-algebra of observables
of the individual factors into the observables of the product, and that
homotopy moment maps for the individual factors induce a homotopy moment map
for the product. As a by-product, we associate to every multisymplectic form a
curved L-infinity-algebra, whose curvature is the multisymplectic form itself.Comment: 27 pages. Version to be published in Journal of Lie Theor