DOI: 10.68381/jca23043 ISSN: 0944-6532

Spaces of d.c. Mappings on Arbitrary Intervals

Libor Veselý, Luděk Zajíček

Let

X X
be a Banach space. Using derivatives in the sense of vector distributions, we show that the space
DC([0,1],X) D C ( [ 0 , 1 ] , X )
of all d.c. mappings from
[0,1] [ 0 , 1 ]
into
X X
, in a natural norm, is isomorphic to the space
M_{bv}([0,1], X) M b v ( [ 0 , 1 ] , X )
of all vector measures with bounded variation. The same is proved for the space
BDC_b((0,\infty), X) B D C b ( ( 0 , ∞ ) , X )
of all bounded d.c. mappings with a bounded control function. The result for the space
DC([0,1], \mathbb{R}) D C ( [ 0 , 1 ] , R )
of all continuous d.c. functions was (essentially) proved by M. Zippin [The space of differences of convex functions on
[0,1] [ 0 , 1 ]
, Serdica Math. J. 26 (2000) 331–352] by a quite different method. The space
BDC_b((0,\infty), \mathbb{R}) B D C b ( ( 0 , ∞ ) , R )
consists of all differences of two bounded convex functions. Internal characterizations of its members were given by O. Böhme [On functions which are the difference of two bounded convex functions on
(0,\infty) ( 0 , ∞ )
, Math. Nachr. 122 (1985) 45–58], but our characterization of its Banach structure is new.