Abstract.
Motivated by applications to congested optimal transport problems,
we prove higher integrability results for the gradient of solutions to some anisotropic elliptic equations, exhibiting a wide range of degeneracy. The model case we have in mind is the following:
∂
x
(
|
u
x
|
-
δ
1
)
+
q
-
1
u
x
|
u
x
|
+
∂
y
(
|
u
y
|
-
δ
2
)
+
q
-
1
u
y
|
u
y
|
=
f
,
$
\partial _x \biggl [(|u_{x}|-\delta _1)_+^{q-1}\, \frac{u_{x}}{|u_{x}|}\biggr ]+\partial _y \biggl [(|u_{y}|-\delta _2)_+^{q-1}\, \frac{u_{y}}{|u_{y}|}\biggr ]=f,
$
for
2
≤
q
<
∞
${2\le q<\infty }$
and some non-negative parameters
δ
1
,
δ
2
${\delta _1,\delta _2}$
. Here
(
·
)
+
${(\,\cdot \,)_+}$
stands for the positive part. We prove that if
f
∈
L
loc
∞
${f\in L^\infty _{\rm loc}}$
, then
∇
u
∈
L
loc
r
${\nabla u\in L^r_{\rm loc}}$
for every r ≥ 1.