manuscripta math. 112, 313–323 (2003) © Springer-Verlag 2003
Nicola Fusco · Flavia Giannetti · Anna Verde
A remark on the L
1
-lower semicontinuity for integral
functionals in BV
Received: 16 May 2002 / Published online: 15 October 2003
Abstract. We study the L
1
-lower semicontinuity in BV of an integral functional of the
type
f (x, u, ∇u)dx +
-
u
+
(x)
u
-
(x)
f
∞
(x,t,
D
s
u
|D
s
u|
)dtd |D
s
u|. Our assumptions on f
extend previous results recently obtained by Gori, Maggi and Marcellini in the case where
the above functional is restricted to W
1,1
.
1. Introduction
The L
1
-lower semicontinuity of an integral functional G of the type
G(u, ) =
f (x, u, ∇u)dx, (1)
where is an open subset of R
N
and u ∈ W
1,1
(), has been extensively studied
in the past years. The starting point of most of the recent studies on this subject
is a celebrated result by Serrin. In [11] he proved that the functional G is lower
semicontinuous in W
1,1
() with respect to the L
1
-convergence of u under the
assumptions that
f : × R × R
N
→ [0, +∞) is continuous, (2)
f(x,t, ·) is convex in R
N
for every (x,t) ∈ × R, (3)
and that one of the following conditions holds:
(i) f(x,t,ξ) → +∞ as |ξ | → +∞ for every (x,t) ∈ × R;
(ii) f(x,t, ·) is strictly convex for every (x,t) ∈ × R;
(iii) the derivatives f
x
, f
ξ
, f
xξ
exist and are continuous.
After Serrin’s paper, many authors have generalized his result by weakening either
the continuity assumption on f or one of the conditions (i)–(iii) above (see for
instance [5], [6], [1], [3], [7], [8], [9], [10], [4]). In particular, two recent papers,
one by Gori and Marcellini ([9]), the other one by Gori, Maggi and Marcellini
([10]), have shown that condition (iii) can be replaced by a significantly weaker
N. Fusco, F. Giannetti, A. Verde: Dipartimento di Matematica e Applicazioni, Via Cintia,
80126 Napoli, Italy.
e-mail: {n.fusco,giannett,anverde@unina.it}
DOI: 10.1007/s00229-003-0400-6