Abstract: - In this paper, we are interested in the singular positive solutions of the inhomogeneous radial equation
|u0|p2u00(r) + N1
r|u0|p2u0(r) + uq(r) + f(r) = 0, r > 0,
where N1,p > 2,q > 1and fis a continuous radial and strictly positive function on (0,+).
More precisely, we study the solutions uthat cannot be extended by continuity at zero, that is, lim
r0u(r) = +.
We give existence and nonexistence results and we describe the behavior of entire solutions near infinity. The
study needs some assumptions on p,q,Nand explicit conditions on the inhomogeneous term f.
Key-Words: - Inhomogeneous elliptic equation; entire solutions; strictly positive solutions; energy function;
asymptotic behavior near infinity.
1 Introduction
The purpose of this paper is to study the following
equation
(|u0|p2u0)0+N1
r|u0|p2u0+uq+f(r) = 0, r > 0,
(1)
where N1,p > 2,q > 1and fis a continuous
radial and strictly positive function on (0,+).
We are interested in the singular positive solutions
of (1) that satisfy lim
r0u(r)=+. The study
is a continuation of the work carried out by [6],
where the authors proved the existence of a maxi-
mal solution udefined on ]0, rmax[such that u
C0(]0, rmax[) C1(]0, rmax[) and |u0|p2u00
C1(]0, rmax[) where 0< rmax +and satisfy-
ing
(P)((|u0|p2u0)0+N1
r|u0|p2u0+uq+f= 0, r > 0,
lim
r0u(r) = +,lim
r0r(N1)/(p1)u0(r) = 0,
where N1,p > 2,q > 1and fis a strictly pos-
itive, continuous radial function on (0,+). They
presented also the behavior of singular solutions near
the origin. In this work, we give the existence of en-
tire solutions of problem (P), present their behavior
near infinity, and prove the nonexistence results.
Equation (1) can be considered as a natural gener-
alization of pure Laplacian case p= 2 studied in the
papers, [2], [3]. It is presented as follows
u00(r)+N1
ru0(r)+uq(r)+f(r) = 0, r > 0,(2)
where p > 1,N3and fis a strictly positive, con-
tinuous radial function on (0,+). Equation (2) ap-
peared in probability theory in the study of stochas-
tic processes. It plays a central role in establish-
ing some limit theorems for super-Brownian motion,
[15]. Therefore, it has been extensively studied in
much literature. [3], studied the existence and nonex-
istence of solutions of equation (2). He proved that
if qN
N2or if q > N
N2and fCr
2q
q1for
some constant C > 0, equation (2) does not have any
solution. But when q > N
N2and fis dominated by
a function of the form C/(1+r)N2
qfor C > 0suffi-
ciently small, equation (2) has a solution. [2], studied
the existence of global positive solutions of equation
(2), and in the paper, [1], presented the asymptotic
behavior near the origin and infinity of positive radial
solutions. We also refer the readers to see, [14], [8],
[17] for more details about the equation (2) and the
references therein.
When f0, equation (2) becomes the classic
Emden-Fowler equation. In [9], [10], [11], Emden-
Fowler gave the existence results and a classification
of global radial solutions on RNand RN\{0}. In the
Behavior of Entire Solutions of a Nonlinear Elliptic Equation with An
Inhomogeneous Singular Term
ARIJ BOUZELMATE, HIKMAT EL BAGHOURI
LaR2A Laboratory, Department of Mathematics,
Faculty of Sciences, Abdelmalek Essaadi University
Tetouan, MOROCCO
Received: July 26, 2022. Revised: February 21, 2023. Accepted: March 17, 2023. Published: April 13, 2023.
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case N > 2, two critical values N
N2and N+ 2
N2
appear. [12], presented local and global results in the
non-radial case when q < N+ 2
N2. [7], have just ex-
tended them to the critical case q=N+ 2
N2.
The motivation to study the equation (1) grew
from earlier work of [16], in case f0and p > 2
for the equation
|u0|p2u00+N1
r|u0|p2u0+uq(r) = 0, r > 0.
(3)
They have shown the existence of two critical val-
ues N(p1)
Npand N(p1) + p
Np. [13], studied
the existence of global solutions and asymptotic be-
havior near the origin of radial solutions when q <
N(p1)
Np. The non-radial case was proved by [5].
In this paper, we shall further extend the analysis
of the equation (3) by adding an inhomogeneous sin-
gular term fwhich has an impact on the existence and
the asymptotic behavior of solutions of equation (1).
We show under some assumptions that if the term f
behaves like rpq/(q+1p)near infinity, then the solu-
tion uof problem (P)behaves like rp/(q+1p)near
infinity. In particular, we have the following results
in the case N > p and q > N(p1)
Np,
(i)If
f(r) = q+ 1 p
p1×
p1
qNpq
q+ 1 p p
q+ 1 pp1!q/(q+1p)
×
rpq/(q+1p),
then problem (P)possesses a positive explicit solu-
tion given by
u(r) = p1
qNpq
q+ 1 p p
q+ 1 pp1!1/(q+1p)
×
rp/(q+1p).(4)
(ii)If f(r)
+lrpq/(q+1p)for some lsuch that
0< l q+ 1 p
p1×
p1
qNpq
q+ 1 p p
q+ 1 pp1!q/(q+1p)
,
then there exists a solution uof problem (P)such that
u(r)
+brp/(q+1p)for some b > 0.
(iii)If f(r)
+lrpq/(q+1p)for some lsuch that
l > q+ 1 p
p1×
p1
qNpq
q+ 1 p p
q+ 1 pp1!q/(q+1p)
,
then problem (P)does not possess any entire solu-
tion.
The rest of the paper is divided in three sections.
In section 2, we give the existence of entire solutions
of problem (P). In section 3, we present the asymp-
totic behavior of solutions near infinity in the cases
q6=N(p1) + p
Npand q=N(p1) + p
Np. The last
section is devoted to the nonexistence results.
2 Existence of Entire Solutions
In this section, we study the existence of entire so-
lutions of problem (P)while recalling that the exis-
tence of maximal solutions of problem (P)defined
on (0, rmax),0< rmax +has been established
if N > p and q > N(p1)
Npin the paper, [6].
Theorem 2.1. Assume that N > p and q >
N(p1)
Np. Then problem (P)possesses an entire so-
lution u.
Proof. Let ube a maximal solution of problem (P)
defined on (0, rmax), where 0< rmax +. We
will proceed in four steps to prove that uis entire.
Step 1.u0<0on the set {r(0, rmax) : u(r)>
0}.
First, we prove that uis strictly decreasing near 0. We
argue by contradiction. Suppose that there exists a
small rsuch that u0(r) = 0, then by equation (1), we
have |u|p2u00(r) = uq(r)f(r)<0(because
f > 0and u > 0near 0). Therefore u06= 0 near
0. Moreover, since lim
r0u(r) = +, then umust be
decreasing near 0. If there exists a first zero r0
(0, rmax)of u0such that u0(r0) = 0 and u(r0)>
0, then |u|p2u00(r0)0, but by equation (1) we
have |u0|p2u00(r0) = uq(r0)f(r0)<0. We
deduce that u0<0on the set {r(0, rmax) : u(r)>
0}.
Step 2.u > 0and u0<0on (0, rmax).
Let r1(0, rmax)the first zero of u. Since u
0on (0, rmax), then necessarily u0(r1) = 0. Using
equation (1), we have
rN1|u0|p2u00(r) = rN1uq(r)rN1f(r).
(5)
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We integrate (5) on (r, r1)for r(0, r1)and since
(uq+f)>0on (0, r1)and u0(r1) = 0, we obtain
u0(r)>0on (0, r1). This contradicts the first step.
Consequently u > 0on (0, rmax)and by the first step
u0<0on (0, rmax).
Step 3.u(r) = Orp
q+1pfor any r(0, rmax).
Since fis positive, then by equation (5), we have for
any r(0, rmax)
rN1|u0|p2u00(r) rN1uq(r).(6)
Integrating this last inequality on r
2, rfor r
(0, rmax)and using the fact that u0(r)<0on
(0, rmax), we obtain for any r(0, rmax)
|u0|p2u0(r)<2N1
N2Nruq(r).
Since u > 0and u0<0on (0, rmax), then for any
r(0, rmax)we have
u0(r)uq/(p1)(r)<2N1
N2N1/(p1)
r1/(p1).
Since q > N(p1)
Np> p 1, then for any r
(0, rmax)we have
u(p1q)/(p1)0(r)>q+ 1 p
p12N1
N2N1/(p1)
×
r1/(p1).
Integrating this last inequality on (0, r)for r
(0, rmax)and using the fact that lim
r0u(r) = +and
q > p 1, we obtain
0< u(r)Mrp/(q+1p)for any r(0, rmax),
(7)
where
M= N2N
2N1p
q+ 1 pp1!1/(q+1p)
.(8)
Step 4.rmax = +.
Suppose by contradiction that rmax <+. Then
lim
rrmax
u(r) = +. But by letting rrmax in (7),
we get a contradiction. Consequently the solution u
is entire.
3 Asymptotic Behavior Near Infinity
In this section, we investigate the asymptotic be-
havior near the infinity of solutions of problem (P).
Under some additional assumptions on f, we prove
that any solution of (P)must behave like rp/(q+1p)
at infinity. The study requires some ideas from [4].
First, let us define for any c6= 0 the following
function
(rcu(r))0=rc1Ec(r),(9)
where
Ec(r) = cu(r) + ru0(r).(10)
By equation (1), for any r > 0such that u0(r)6= 0
we have
(p1) u0
p2(r)E0
c(r) =(p1) cNp
p1×
u0
p2u0(r)ruq(r)
rf(r).(11)
Therefore, if Ec(r0) = 0 for some r0>0, equation
(1) implies that
(p1) rp1
0u0
p2(r0)E0
c(r0) = (p1) cNp
p1×
|c|p2c up1(r0)rp
0uq(r0)
rp
0f(r0)(12)
We start with the following preliminary results.
Proposition 3.1. Let ube a solution of problem (P).
Then
u(r)>0and u0(r)<0,for any r > 0,(13)
Moreover, if q > p 1, then
0< u(r)M rp/(q+1p),(14)
where Mis given by (8).
Proof. We follow the same reasoning of the first three
steps of the proof of Theorem 2.1 by taking rmax =
+.
Proposition 3.2. Assume that N > p. Let ube a
solution of problem (P). Then E(Np)/(p1)(r)>0
for large r.
Proof. Taking c=Np
p1in (11), we see that
E0
(Np)/(p1)(r)<0for any r > 0. Therefore,
E(Np)/(p1)(r)6= 0 for large r. Suppose by contra-
diction that E(Np)/(p1)(r)<0for large r. Then,
lim
r+E(Np)/(p1)(r)[−∞,0[. We distinguish
two cases.
Case 1.lim
r+E(Np)/(p1)(r) = −∞.
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Using Proposition 3.1, we have u(r)>0and u0(r)<
0on (0,+), which implies that lim
r+u(r)exists
and is finite. Now, by relation (10) we have necessar-
ily lim
r+ru0(r) = −∞, which is impossible since u
is positive.
Case 2.−∞ <lim
r+E(Np)/(p1)(r)<0.
Then ru0(r)converges necessarily to 0when r
+. This implies that lim
r+u(r)<0(because
N > p). Which is impossible.
We conclude that E(Np)/(p1)(r)>0for large
r.
Proposition 3.3. Assume that N > p and q > p 1.
Let ube a solution of problem (P). Then the function
rp/(q+1p)+1u0(r)is bounded for large r.
Proof. Using Propositions 3.1 and 3.2, we have uis
strictly decreasing and E(Np)/(p1) >0, for large r.
This implies that
0< r|u0(r)|<Np
p1u(r)for large r. (15)
Recall by Proposition 3.1, that rp/(q+1p)u(r)is
bounded for any r > 0. Therefore, by (15), we easily
get that rp/(q+1p)+1u0(r)is bounded for large r.
Now, to prove the next Theorems, we introduce
the following change of variable which will be very
useful. So let us define the function
υ(t) = rp
q+1pu(r)where t=ln r. (16)
So υsatisfies the following equation
y0(t) + Npq
q+ 1 py(t) + υq(t) + j(t) = 0,
(17)
where
j(t) = epq
q+1ptf(et),(18)
y(t) = |k|p2k(t),(19)
k(t) = υ0(t)p
q+ 1 pυ(t).(20)
It’s easy to see that
k(t) = rp
q+1p+1u0(r).(21)
Proposition 3.4. Assume that N > p and q >
N(p1)
Np. Let ube a solution of problem (P). Sup-
pose that rpq/(q+1p)f(r)and rp/(q+1p)u(r)con-
verge when r+. Then rp/(q+1p)+1u0(r)con-
verges also when r+and
lim
r+rp/(q+1p)+1u0(r) =
p
q+ 1 plim
r+rp/(q+1p)u(r).(22)
Proof. According to Proposition 3.1 and logarithmic
change (16), we have υis bounded for large t, which
gives by Proposition 3.3 that kis bounded for large t.
Therefore by expression (19), we have yis bounded
for large t. We show that yis monotone for large
t. Suppose by contradiction that there exist two se-
quences {γi}and {ρi}going to +as i+such
that {γi}and {ρi}are respectively local minimum
and local maximum of y, satisfying γi< ρi< γi+1
and
<lim inf
t+y(t) = lim
i+y(γi)
<lim sup
t+
y(t) = lim
i+y(ρi)0.(23)
Using equation (17) and the fact that y0(γi) =
y0(ρi) = 0, we obtain
Npq
q+ 1 py(γi) + υq(γi) + j(γi) =
Npq
q+ 1 py(ρi) + υq(ρi) + j(ρi) = 0.
Since υ(t)and j(t)converge when ttends to +and
N > pq
q+ 1 p, then lim
i+y(γi) = lim
i+y(ρi),
which contradicts the estimate (23). Therefore k(t)
converges when t+. So, by (20), υ0(t)
converges necessarily to 0when t+. Con-
sequently, rp/(q+1p)+1u0(r)converges when r
+and (22) is satisfied.
Proposition 3.5. Assume that N > p and q >
N(p1)
Np. Let ube a solution of problem (P). Sup-
pose that lim
r+rpq/(q+1p)f(r) = l > 0.
If lim
r+rp/(q+1p)u(r) = b. Then bis one of the two
roots λ1and λ2of the equation
sqNpq
q+ 1 p p
q+ 1 pp1
sp1+l= 0,
(24)
such that 0< λ1λ2.
In particular, if
l=q+ 1 p
p1×
p1
qNpq
q+ 1 p p
q+ 1 pp1!q/(q+1p)
,
(25)
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then
b=
p1
qNpq
q+ 1 p p
q+ 1 pp1!1/(q+1p)
.
(26)
Proof. Using logarithmic change (16), we have υ(t)
converges to b0when t+. Hence,
combining with Proposition 3.4, k(t)converges also
and lim
t+k(t) = p
q+ 1 pb. Therefore, by
(19), lim
t+y(t) = p
q+ 1 pp1
bp1. Since
lim
t+j(t) = l, then by equation (17), y0(t)converges
necessarily to 0. Therefore, by letting t+in the
same equation, we obtain
bqΛq+1pbp1+l=lψ(b) = 0,(27)
where
Λ = Npq
q+ 1 p p
q+ 1 pp1!1/(q+1p)
.
(28)
and
ψ(s) = Λq+1psp1sq, s 0.(29)
A simple study gives
max
s0ψ(s) = ψ p1
q1/(q+1p)
Λ!=L, (30)
where
L=q+ 1 p
p1p1
qq/(q+1p)
Λq
=q+ 1 p
p1×
p1
qNpq
q+ 1 p p
q+ 1 pp1!q/(q+1p)
.
(31)
Since l > 0, we can easily see that the equation
lψ(s) = 0 has two roots λ1and λ2such that 0<
λ1λ2. Then, by (27), b=λ1>0or b=λ2>0.
Moreover if l=L, this last equation has only one ex-
plicit root, that is, λ1=λ2=p1
q1/(q+1p)
Λ.
Hence by (27) and (30), we have explicitly
b=p1
q1/(q+1p)
Λ
= p1
qNpq
q+ 1 p p
q+ 1 pp1!1/(q+1p)
.
(32)
Proposition 3.6. Assume that N > p and q >
N(p1)
Np. Let ube a solution of problem (P). Sup-
pose that lim
r+rpq/(q+1p)f(r) = l > 0. Then
lim inf
r+rp/(q+1p)u(r)>0(33)
and
lim sup
r+
rp/(q+1p)+1u0(r)<0.(34)
Proof. The proof will be done in two steps.
Step 1.lim inf
r+rp/(q+1p)u(r)>0.
Assume by contradiction that
lim inf
r+rp/(q+1p)u(r) = 0. This means that
lim inf
t+υ(t)=0. Since υ(t)is bounded for large t,
we distinguish two cases.
υ(t)is monotone for large t.
Then lim
t+υ(t) = 0. Since u0(r)<0for any r > 0
and E(Np)/(p1)(r)>0for large r(by Proposition
3.2), then we have for large t,
0<|k(t)|<Np
p1υ(t).(35)
It follows that lim
t+k(t) = 0 and by relation
(19), lim
t+y(t)=0. Therefore, by equation (17),
lim
t+y0(t) = l < 0. But this is a contradiction
with lim
t+y(t) = 0.
υ(t)is oscillating for large t.
Then there exists a sequence {µi}going to +
as i+such that υhas a local minimum
in µi. Therefore using our hypotheses, we have
lim
i+υ(µi) = 0,υ0(µi) = 0 and υ00(µi)0(υ00 ex-
ists because u0<0). Which gives lim
i+k(µi)=0
and k0(µi)0and so lim
i+y(µi) = 0 and
y0(µi)0. Therefore, by equation (17), we have
lim
i+y0(µi) = l < 0. This is a contradiction.
It follows from both cases that
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lim inf
r+rp/(q+1p)u(r)>0.
Step 2.lim sup
r+
rp/(q+1p)+1u0(r)<0.
Since u0<0, we assume by contradiction that
lim sup
r+
rp/(q+1p)+1u0(r)=0. This means that
lim sup
t+
k(t) = 0. In the same way as the first step,
since k(t)is bounded for large t(by Proposition 3.3),
we distinguish two cases.
k(t)is monotone for large t.
Then lim
t+k(t) = 0. That is,
lim
r+rp/(q+1p)+1u0(r) = 0. This yields by
L’Hôpital’s rule that lim
r+rp/(q+1p)u(r) = 0. But
this contradicts the fact that lim inf
r+rp/(q+1p)u(r)>
0by the first step.
k(t)oscillates for large t.
Then there exists a sequence {ρi}going to +as
i+such that khas a local maximum in ρi.
Therefore, lim
i+k(γi)=0and k0(γi)=0and
so lim
i+y(γi)=0and y0(γi)=0. Therefore, by
equation (17), we have lim
i+υq(γi) = l < 0. This
is impossible since υis positive.
We deduce that lim sup
r+
rp/(q+1p)+1u0(r)<0. The
proof is complete.
The following theorem gives a sufficient condition
to obtain explicitly lim inf
r+rp/(q+1p)u(r).
Theorem 3.7. Assume that N > p and q >
N(p1)
Np. Let ube a solution of problem (P). Sup-
pose that
lim
r+rpq/(q+1p)f(r) = q+ 1 p
p1×
p1
qNpq
q+ 1 p p
q+ 1 pp1!q/(q+1p)
.
(36)
Then
lim inf
r+rp/(q+1p)u(r) =
p1
qNpq
q+ 1 p p
q+ 1 pp1!1/(q+1p)
.
Proof. Note that if υconverges, we obtain the result
directly by using Proposition 3.5. Otherwise, since υ
is bounded, it must oscillate. Then there exists a se-
quence {µi}going to +as i+such that υ
has a local minimum in µi. Therefore υ0(µi) = 0 and
υ00(µi)0. Hence, using (20), we have k(µi) =
p
q+ 1 pυ(µi)and k0(µi) = υ00(µi)0. This
yields
y(µi) = p
q+ 1 pp1
υp1(µi)
and
y0(µi) = (p1) |k(µi)|p2k0(µi)0.
Using equation (17) with t=γi, we obtain
0y0(µi) = Λq+1pυp1(µi)υq(µi)j(µi)
=ψ(υ(µi)) j(µi)
Lj(µi),
where ψand Lare respectively given by (29) and
(31). Since lim
t+j(t) = L, then lim
i+ψ(υ(µi)) =
lim
i+j(µi) = L. Hence, according to (30),
lim
i+υ(µi) = lim inf
t+υ(t) = p1
q1/(q+1p)
Λ,
where Λis given by (28). This completes the proof.
Now, we study the convergence of rp/(q+1p)u(r)
at infinity to improve the previous result which gives
only lim inf
r+rp/(q+1p)u(r). For this, we assume that
fis differentiable and satisfies the following condi-
tions:
(K1)Z+
1rpq/(q+1p)f+
rdr < +,
(K2)Z+
1rpq/(q+1p)f
rdr < +.
The study depends on the comparison of qwith
N(p1)
Npand N(p1) + p
Np. We start with the case
N(p1)
Np< q 6=N(p1) + p
Np.
Theorem 3.8. Assume that N > p and q >
N(p1)
Np. Let ube a solution of problem (P). Sup-
pose that lim
r+rpq/(q+1p)f(r) = l > 0and fsat-
isfies
(i) (K1)if q > N(p1) + p
Np,
or
(ii) (K2)if N(p1)
Np< q < N(p1) + p
Np.
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Then
lq+ 1 p
p1×
p1
qNpq
q+ 1 p p
q+ 1 pp1!q/(q+1p)
(37)
and lim
r+rp/(q+1p)u(r) = bwhere bis one of the
two roots λ1or λ2of equation (24) such that 0<
λ1λ2.
To demonstrate Theorem 3.8, we need the classic
result of [12], of which we recall the proof.
Lemma 3.9. Let gbe a positive differentiable func-
tion satisfying
(i)Z+
t0
g(t)dt < +for large t0.
(ii)g0(t)is bounded for large t.
Then lim
t+g(t) = 0.
Proof. We argue by contradiction and we suppose
that lim
t+g(t)6= 0. Then there exist ε > 0and a
sequence {ti}going to +as i+satisfying
g(ti)2ε. Since g0(t)is bounded for large t, then
there exists a constant C > 0such that |g0(t)| Cfor
large t. By the mean value Theorem for g, we have
g(t)εfor |tti|<ε
C.
Choose a subsequence t0
isuch that t0
0> t0and t0
i>
t0
i1+2ε
Ct0
0for i > 1. Therefore
n
X
i=1 Zt0
i
t0
i1
g(t)dt >
n
X
i=1 Zt0
i1+ε/C
t0
i1
g(t)dt
ε2
Cn+as n+.
This implies that
Z+
t0
g(t)dt = +.
This contradiction completes the proof.
Now, we can prove Theorem 3.8.
Proof. Define the following energy function associ-
ated with equation (17),
I(t)= p1
p|k(t)|p+p
q+ 1 py(t)υ(t)
A
pp
q+ 1 pp1
υp(t)
+υq+1(t)
q+ 1 +(t),(38)
where
A=q(Np)(N(p1) + p)
q+ 1 p.(39)
Note that the energy function Iplays a central role
in the study of the convergence of rp/(q+1p)u(r).
First, using Proposition 3.3 we have k(t)is bounded
for large t, which yields that y(t)is bounded for large
t. Hence I(t)is bounded for large t.
The rest of the proof will be done in three steps.
Step 1.The function I(t)converges when t+.
A simple computation gives
I0(t) = AZ(t)(j(t)l)υ0(t),(40)
where
Z(t) =|k(t)|p1p
q+ 1 pp1υp1(t)×
|k(t)| p
q+ 1 pυ(t).(41)
Integrating (40) on (T, t)for large T, we get
I(t) = C(T)AR(t)(j(t)l)υ(t)+Zt
T
j0(s)υ(s)ds,
(42)
where
C(T) = I(T)+(j(T)l)υ(T)(43)
and
R(t) = Zt
T
Z(s)ds. (44)
Since the function ssp1is monotone, then
Z(t)0, which in turn implies that the function
R(t)is positive and increasing. By our hypotheses,
we have A6= 0, then relation (42) can be expressed
as follows:
R(t) = I(t)
A1
A(j(t)l)υ(t) + 1
AZt
T
j0(s)υ(s)ds
+C(T)
A.(45)
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Using the fact that υ(t)and I(t)are bounded for large
t, lim
t+j(t) = l,(j0(s))j0(s)(j0(s))+
and Z+
Tj0(s)+ds < +from (K1)if A > 0
or Z+
Tj0(s)ds < +from (K2)if A < 0,
we obtain R(t)is bounded for large t. Consequently,
R(t)converges when t+, which yields that
Z+
T
Z(s)ds exists. By letting t+in (42), we
deduce that I(t)converges to a real number noted d
when t+.
Step 2.lim
t+υ0(t) = 0.
By expressions (41) and (20) and the fact that k(t)<
0for large t, we have just to prove that lim
t+Z(t) =
0. Since Z+
T
Z(s)ds < +, then by Lemma 3.9,
it suffices to prove that Z0(t)is bounded for large t.
Using expression (41), Z(t)can be written as follows:
Z(t) =|y(t)|p/(p1) +p
q+ 1 pυ(t)y(t)
+p
q+ 1 pp1
υp1(t)υ0(t).(46)
Therefore
Z0(t) = p
p1k(t)y0(t) + p
q+ 1 py(t)υ0(t)
+p
q+ 1 pυ(t)y0(t)+(p1) p
q+ 1 pp1
×
υp2(t)υ02(t) + p
q+ 1 pp1
υp1(t)υ00(t).
(47)
Since υ(t), k(t)and j(t)are bounded for large t,
then combining with (20) and (17), υ0(t)and y0(t)are
bounded also for large t. Hence, it remains to prove
that υ00(t)is bounded for large t. According to (20),
we have
υ00(t) = k0(t) + p
q+ 1 pυ0(t).(48)
Then, it suffices to prove that k0(t)is bounded for
large t.
Since k(t)<0for large t, we have by (19)
k0(t) = 1
p1|k(t)|2py0(t).(49)
According to Proposition 3.6, we have lim sup
t+
k(t)<
0. Therefore, there exists a constant M > 0such that
k(t) Mfor large t. Which implies that, |k(t)|2p
is bounded for large t. Therefore k0(t)is bounded
for large tand by relations (48) and (47), Z0(t)is
bounded for large t. Hence, by Lemma 3.9, we get
lim
t+Z(t) = 0 and therefore lim
t+υ0(t) = 0.
Step 3.υ(t)converges when t+.
Suppose by contradiction that υ(t)is oscillating for
large t. Then there exist two sequences {µi}and {νi}
tend to +when i+such that {µi}and {νi}
are respectively local minimum and local maximum
of υ, satisfying µi< νi< µi+1 and
0<lim inf
t+υ(t) = lim
i+υ(µi) = α
<lim sup
t+
υ(t) = lim
i+υ(νi) = β < +.(50)
Since υ0(µi) = υ0(νi)=0, then by relations (38),
(50), (19) and (20), we obtain
lim
i+I(µi) = ϕ(α)and lim
i+I(νi) = ϕ(β),
(51)
where
ϕ(s) = ls Λq+1p
psp+sq+1
q+ 1 =ls Zs
0
ψ(r)dr,
(52)
for any s0and ψis given by (29). Since
lim
t+I(t) = dby the first step, then
ϕ(α) = ϕ(β) = d. (53)
Then, there exist δ(α, β)and xi(µi, νi)such
that υ(xi) = δ, ϕ0(δ) = 0 and ϕ(δ)6=d. On the other
hand, using step 2, we have lim
i+υ0(xi)=0, so by
(20), we obtain lim
i+k(xi) = p
q+ 1 pδ. There-
fore lim
i+I(xi) = ϕ(δ) = d. Which gives a con-
tradiction. Hence υ(t)converges when t+.
Let lim
t+υ(t) = b. So, by Proposition 3.5, bis one
of the two roots λ1and λ2of equation (24) such that
0< λ1λ2. Finally, by (30), l=ψ(b)Lwhere
Lis given by (31). The proof is complete.
Now we give the following result which deals with
the critical case q=N(p1) + p
Np.
Theorem 3.10. Assume that N > p and q=
N(p1) + p
Np. Let ube a solution of problem (P).
Suppose that lim
r+rpq/(q+1p)f(r) = l > 0and f
satisfies (K1)or (K2). Then usatisfies one of the fol-
lowing cases:
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(i)lim
r+rp/(q+1p)u(r) = λ1or λ2given in The-
orem 3.8.
(ii)rp/(q+1p)u(r)is oscillating and
λ1α=lim inf
r+rp/(q+1p)u(r)< λ2
< β =lim sup
r+
rp/(q+1p)u(r)Γ,(54)
where Γ6=λ1is the root of the equation
lΓ + Γq+1
q+ 1 Λq+1p
pΓp
=p1
pNp
pp
λp
1N(p1) + p
Np λNp/(Np)
1.
(55)
Moreover, αand βsatisfy the following estimates
l=1
pNp
ppβpαp
βα
Np
Np
βNp/(Np)αN p/(Np)
βα(56)
and
pp
N(Np)p1<βpαp
βNp/(Np)αN p/(Np)
1
p1p
NppN(p1) + p
N.(57)
In both cases, we have the estimate (37).
Proof. According to the notations in the proof of The-
orem 3.8, we have A= 0, where Ais given by (39).
Using the fact that υ(t)is bounded, lim
t+j(t) = l,
j0(s)(j0(s))+for (K1)and j0(s) (j0(s))
for (K2), we deduce that the energy function Icon-
verges when t+.
Since υ(t)is bounded, we have two possibilities:
υ(t)converges when t+, then similarly
to Theorem 3.8, lim
t+υ(t) = λ1or λ2, where λ1
and λ2are two roots of the equation (24) such that
0< λ1λ2. Moreover, the estimate (37) is satis-
fied.
υ(t)oscillates, then there exist two sequences {µi}
and {νi}tend to +when i+such that {µi}
and {νi}are respectively local minimum and local
maximum of υ, satisfying µi< νi< µi+1 and re-
lation (50). Therefore k0(µi) = υ00(µi)0and
k0(νi) = υ00(νi)0and so by equation (17), we
have
0y0(µi) = ψ(υ(µi)) j(µi)(58)
and
0y0(νi) = ψ(υ(νi)) j(νi),(59)
where ψis given by (29). On the other hand, accord-
ing to the proof of Theorem 3.8, we have
lim
t+I(t) = ϕ(α) = ϕ(β),
where ϕis given by (52). Since q=N(p1) + p
Np
and α < β, then
l=Λq+1p
p
βpαp
βα1
q+ 1
βq+1 αq+1
βα
=1
pNp
ppβpαp
βα
Np
Np
βNp/(Np)αN p/(Np)
βα.
This proves (56). Now, a simple study of the func-
tion ϕgives ϕ0(λ1) = ϕ0(λ2) = 0,ϕ0(s)>0
for 0< s < λ1,ϕ0(s)<0for λ1< s < λ2,
ϕ0(s)>0for s > λ2and lim
s+ϕ(s) = +. There-
fore, there exists Γ> λ2such that ϕ(Γ) = ϕ(λ1).
Since ψ(λ1) = land q=N(p1) + p
Np, then
ϕ(Γ) = p1
pNp
pp
λp
1N(p1) + p
Np λNp/(Np)
1,
(60)
which gives (55). To prove estimate (54), we let i
+in (58) and (59), we obtain
ψ(β)lψ(α),(61)
that is by (52)
ϕ0(α)0ϕ0(β).(62)
Combining this with the study of ϕand the fact that
ϕ(α) = ϕ(β), we deduce that λ1α < λ2<
β. Moreover, we have βΓ, otherwise ϕ(β)>
ϕ(Γ) = ϕ(λ1)ϕ(α), which contradicts ϕ(α) =
ϕ(β). Consequently, (54) is satisfied. Concerning
(57), we use the fact that l > 0and (56) to obtain
the left inequality. To prove the right inequality of
(57), we have β > α > 0, then by (61), we have
βψ(β)lβ =ϕ(β) + Λq+1p
pβpβq+1
q+ 1
and
αψ(α)lα =ϕ(α) + Λq+1p
pαpαq+1
q+ 1,
which in turn implies that
βψ(β)Λq+1p
pβp+βq+1
q+ 1 ϕ(β) = ϕ(α)
αψ(α)Λq+1p
pαp+αq+1
q+ 1.
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With the expression of ψ, we get
p1
pΛq+1pβpq
q+ 1βq+1
p1
pΛq+1pαpq
q+ 1αq+1.
The right inequality of (57) can be easily obtained
since q=N(p1) + p
Np. The proof is complete.
4 Nonexistence Results
This section concerns the nonexistence theorems of
entire solutions of problem (P). The study depends
on the parameters N, p, q and the comparison of f(r)
with rpq/(q+1p).
Theorem 4.1. Assume that Npor N > p and
p1qN(p1)
Npor N > p and q < p1. Then
problem (P)does not possess any entire solution.
Proof. Let ube a solution of problem (P). We dis-
tinguish five cases.
Case 1. Np.
It’s easy to see by Proposition 3.1 and equation
(5) that the function rrN1|u0|p2u0(r)is de-
creasing and strictly negative on (0,+). Then
lim
r+rN1|u0|p2u0(r)[−∞,0[. Therefore, there
exists a constant M0>0such that
rN1|u0|p2u0(r)<M0,(63)
for large r. So
|u0(r)|> M1/(p1)
0r(1N)/(p1),
for large r. We get a contradiction by integrating
this last inequality for large rand using the fact that
Np.
Case 2. N > p and q=p1.
Recall, by Proposition 3.2, that E(Np)/(p1)(r)>0
for large r. Then estimation (15) is satisfied. Combin-
ing this with equation (1) and the fact that q=p1,
we obtain
|u0|p2u00(r)<up1(r)×
"(N1) Np
p1p1
rp1#,
for large r. In particular, we get |u0|p2u00(r)<0
for large r. Since u0(r)<0, then
lim
r+|u0|p2u0(r)[−∞,0[. Therefore
lim
r+u(r) = −∞, which is impossible.
Case 3. N > p and p1< q < N(p1)
Np.
In this case we have necessarily Np
p1<
p
q+ 1 p, which implies by (14) that
lim
r+rNp
p1u(r)=0. But this contradicts the
fact that rNp
p1u(r)is positive and strictly increasing
by relation (9) and Proposition 3.2.
Case 4. N > p and q=N(p1)
Np.
Using relations (15) and (5), then for large rwe
obtain
rN1|u0|p2u00(r) Np
p1q
rN+q1|u0|q.
(64)
Which can be written as
φ0(r) Np
p1q
r1φq/(p1)(r)for large r,
(65)
where
φ(r) = rN1|u0|p1.(66)
Integrating relation (65) on (R, r)for large Rand us-
ing the fact that q > p 1, we obtain for large r,
φ(p1q)/(p1)(r)φ(p1q)/(p1)(R)
+p1q
p1Np
p1q
ln r
R.
(67)
By letting r+in the last inequality, we get a
contradiction with the fact that φis positive.
Case 5. N > p and q < p 1.
Since fis positive, then by equation (5), we have
rN1|u0|p2u00(r) rN1uq(r)for any r > 0.
(68)
Integrating this last inequality on r
2, rfor r > 0
and using the fact that u0(r)<0on (0,+), we
obtain
|u0|p2u0(r)<2N1
N2Nruq(r)for any r > 0.
Since u > 0and u0<0on (0,+), then for any
r > 0
u0(r)uq/(p1)(r)<2N1
N2N1/(p1)
r1/(p1).
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Integrating this last inequality on (R, r)for large R
and using the fact that q < p 1, we obtain
u(p1q)/(p1)(r)u(p1q)/(p1)(R)
p1q
p2N1
N2N1/(p1)
×
rp/(p1) Rp/(p1).(69)
By letting r+in the last inequality, we get a
contradiction with the fact that uis positive.
we deduce that problem (P)does not possess any en-
tire solution in all cases.
Theorem 4.2. Assume that N > p and q >
N(p1)
Np. Suppose that
lim inf
r+rpq/(q+1p)f(r)>q+ 1 p
p1×
p1
qNpq
q+ 1 p p
q+ 1 pp1!q/(q+1p)
.
Then problem (P)does not possess any entire solu-
tion.
Proof. Let ube a solution of problem (P). First
we show that rp/(q+1p)u(r) is strictly monotone
for large r. This amounts to proving by (9) that
Ep/(q+1p)(r)6= 0 for large r.
Suppose that there exists a large rsuch that
Ep/(q+1p)(r)=0. Taking c=p
q+ 1 pin (12)
and multiplying by rpq/(q+1p)1, we obtain
(p1) rpq/(q+1p)1u0
p2E0
p/(q+1p)(r) =
Λq+1prp(p1)/(q+1p)up1(r)rpq/(q+1p)uq(r)
rpq/(q+1p)f(r),(70)
where Λis given in relation (28).
Using the change of variable (16), we see that the re-
lation (70) is equivalent to
(p1) rpq/(q+1p)1u0
p2(r)E0
p/(q+1p)(r)
=ψ(υ(t)) j(t),(71)
where ψis given respectively by (29). Since
lim inf
r+rpq/(q+1p)f(r)> L, then there exists ε > 0
such that
j(t)L+εfor large t. (72)
Recall, by (30), that max
s0ψ(s) = L, where Lis given
by (31).Then by (71), E0
p/(q+1p)(r)<0and so
Ep/(q+1p)(r)6= 0 for large r.
Now, we have υ(t)is strictly monotone for large t
and bounded by Proposition 3.1, then υ(t)converges
when t+. Let lim
t+υ(t) = b0.
We distinguish two cases according to the monotonic-
ity of υ0(t)for large t.
Case 1. υ0(t)is monotone for large t.
Since k(t)is bounded for large tby Proposition 3.3,
then v0(t)is bounded for large t. Therefore v0(t)con-
verges and necessarily lim
t+υ0(t) = 0 (because υis
bounded). Therefore lim
t+k(t) = p
q+ 1 pband
so lim
t+y(t) = p
q+ 1 pp1
bp1. Accord-
ing to equation (17) and estimate (72), we have
y0(t) Npq
q+ 1 py(t)υq(t)Lε,
for large t. But
lim
t+Npq
q+ 1 py(t)υq(t)Lε
=ψ(b)Lε ε,
Hence there exists a constant M > 0such that y0(t)
Mfor large t. Integrating this last inequality on
(T, t)for large T, we get lim
t+y(t) = −∞. Which
gives a contradiction.
Case 2. υ0(t)is not monotone for large t.
Since υ(t)is strictly monotone for large t, then we
have two possibilities.
υ0(t)>0for large t. Then lim inf
t+υ0(t) = 0.
Otherwise, there exits C > 0such that υ0(t)C
for large t, then integrating this last inequality near
+, we obtain lim
t+υ(t)=+, which is im-
possible. Hence there exists ζitends to +when
i+such that ζiis a local minimum of υ0sat-
isfying lim
i+υ0(ζi)=0. Consequently, we have
lim
i+y(ζi) = p
q+ 1 pp1
bp1.On the other
hand, by deriving relation (20) and taking account
that υ00(ζi)=0, we get lim
i+k0(ζi)=0. There-
fore lim
i+y0(ζi)=0. Taking t=ζiin equation
(17) and tending i+, we obtain lim
i+j(ζi) =
ψ(b)L=max
s0ψ(s). But this contradicts the fact
that lim inf
t+j(t)> L.
υ0(t)<0for large t. In the same way, using the fact
that υis bounded, we deduce that lim
t+sup υ0(t) =
0. Then there exists τitends to +when i
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+such that τiis a local minimum of υ0satisfy-
ing lim
i+υ0(τi) = 0 and υ00(τi) = 0. Therefore
lim
i+y0(τi) = 0 and lim
i+j(τi) = ψ(b)L.
Which is impossible like the previous case.
We conclude that problem (P)does not possess any
entire solution.
5 Conclusion
In this paper, we have studied the existence, the
nonexistence and the asymptotic behavior near
infinity of global singular solutions of problem (P).
The difficulty of this work lies in the influence of
the inhomogeneous term fwhich is positive and is
equivalent to the function rpq/(q+1p)near infinity.
Under some conditions, we prove that the singular
solution of problem (P)is equivalent to the function
rp/(q+1p)near infinity. The cases where fis
not positive or negligible in front to the function
rpq/(q+1p)near infinity are not yet treated and will
be the subject of a future study.
Acknowledgment:
The authors express their gratitude to the editor and
reviewers for their comments and suggestions which
have improved the quality of this paper.
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WSEAS TRANSACTIONS on MATHEMATICS
DOI: 10.37394/23206.2023.22.28
Arij Bouzelmate, Hikmat El Baghouri
E-ISSN: 2224-2880
243
Volume 22, 2023
Arij Bouzelmate and Abdelilah Gmira. It brings
together the techniques of Nonlinear Analysis. All
the demonstrations were carried out by the two
authors Arij Bouzelmate and Hikmat El Baghouri.
Sources of Funding for Research Presented in a
Scientific Article or Scientific Article Itself
No funding was received for conducting this study.
Conflicts of Interest
The authors have no conflicts of interest to declare
that are relevant to the content of this article.
Creative Commons Attribution License 4.0
(Attribution 4.0 International, CC BY 4.0)
This article is published under the terms of the
Creative Commons Attribution License 4.0
https://creativecommons.org/licenses/by/4.0/deed.en
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Contribution of Individual Authors to the
Creation of a Scientific Article (Ghostwriting
Policy)
Arij Bouzelmate proposed the subject of the article
to his Ph.D. student Hikmat El Baghouri. This work
is an extension of a paper published in the Nonlinear
Functional Analysis and Applications journal by
WSEAS TRANSACTIONS on MATHEMATICS
DOI: 10.37394/23206.2023.22.28
Arij Bouzelmate, Hikmat El Baghouri
E-ISSN: 2224-2880
244
Volume 22, 2023