# VALU PROBL FOR NONLI SECOND ORDER

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1 Journal ofapplied Mathematics and Stochastic Analysis 4, Number 1, Spring 1991, NOGATIVE SOLUTIONS OF TO-POT BOUNDARY VALU PROBL FOR NONLI SECOND ORDER INTEGRODIFFEKENTIAL EQUATIONS IN BANACH SPACES 1 DAJUN GUO Department of Mathematics Shandong University, Jinan, PEOPLES REPUBLIC OF CHINA and Department of Mathematics University of Alberta Edmonton, CANADA T6G ABSTILCT In this paper, we combine the fixed point theory, fixed point index theory and cone theory to investigate the nonnegative solutions of two-point BVP for nonlinear second order integrodifferential equations in Banach spaces. As application, we get some results for the third order case. Finally, we give several examples for both infinite and finite systems of ordinary nonlinear integrodifferential equations. Key words: Integrodifferential equation in Banach measure of noncompactness, strict set contraction, fixed point index. space, AMS (MOS) subject classification: 45J, 47G. 1Received" June, Revised: December, Printed in the U.S.A. (C) 1991 The Society of Applied Mathematics, Modeling and Simulation 47

2 48 DAJUN GUO 1. Introduction In [1] (see also [21 Section 5.3), several existence theorems were established for the BVP of nonlinear second order differential equation in Banach space" -x"= f(t,x,x ), 0 < t <_ 1; ax(o) bx (O) = Zo, cx(1)+ dx (1) = x. (1) Now, in this paper, we shall combine the fixed point theory, fixed point index theory and cone theory to extend some results of [1] integrodifferential equation of mixed type in Banach space: to the BVP of nonlinear second order -x" = f(t, x, x, Tx, Sx), ax(o)- bx (O) = xo, 0_<t_<l; cx(1) + dx (1) = x, (2) where T (t) = S (t) = h(t, We get more results about the existence of nontrivial non.negative solutions and multiple nonnegative solutions. As application, we obtain some results for the following BVP of third order integrodifferential equation: -x " = f(t,x, z,x " x(o) = O, ax (O) bx"(o) = xo, 0 <_ t _< 1; cz (1) + dx"(1) = X 1. (4) Finally, we give severn examples for both infinite and finite systems of ordinary nonlinear integrodifferential equations. 2. Several Lemmas Let E be a real Banach space and P be a cone in E which defines a partial ordering in E by z < y iff y-x P. P is said to be normal if there exists a positive constant N such that 0 _< x _< y implies I[=ll Nil,all,

3 Nonnegative Solutions of Two-Point Boundary Value Problems 49 where 19 denotes the zero element of E, and N is called the normal constant of P. P is said to be solid if its interior int(p) is not empty. In this case., we write x << y if y- x int(p). For details on cone theory, see [3]. In the following, I = [0, 1]. LEMMA 1. Let P be a solid cone in E, uo E, 0 <_ to <_ tx <_ 1 and F= {x t C[I, El x(t) >> uo / or t0_<t_<t,}. Then F is e convex open set in C[I, El. PROOF" The convexity of F is obvious, so, we need only to prove that F is open. Choose v e in(p) and let x0 e F. For anyfixed t [t0,t], there exists a sma21 r(t )> 0 such that xo(t ), uo +r(t )v. Since xo(t) is continuous, there is a small interval I(t ) = (t - r,t + r ) such that o(t) > o + (t )v o t e Now, {I(t )" t e [to,t1]} forms an open coveting of [to,tl], so, Heine-Borel theorem implies that a finite set {I(ti)" i = 2,3,...,m} already covers [t0,t]. Hence where r0 = min{r(t2),...,r(tm)} > 0. Since v e int(p), there exists rl > 0 such that v + z 0 fo ny z e E, ilzll x. (6) Let x e C[I, E satisfying i[x x011 < 0. Then, for any t e [to, t], we have by (5) and (6), (t) = o(t)+ (t) o(t) >,o + o[v ((t) o(t))] >_,o,

4 50 DAJUN GUO i.e. z F, and the proof is complete. COROLLARY 1. Le P be a solid cone in E, uo E, 0 < to <_ ti <_ 1 and F= {x C [I,E] x(t) > uo for to <_ t <_ t}. Then F is a convex open se i12 C 1 [I, El. REMARK 1" The norm in space C( )[I,E] will be defined by [[xl[, = max{[ix[[o, I[x l[o,..., ][x(m)llo }, (7) where (n = 0,1,...,m). (8) In particular, when rn = 1 we have Ilxll = mx{llxllo, I! 11o} mx{mxllz(t)ll, maxllz (t)ll}.,e. (9) LEMMA 2. Let H be a bounded set of C[I,E]. Suppose that H = {x " x e H} is equicontinuous. Then a(h) max{sup a(h(t)), sup a(h (t)) } tel tel (10) a(s) = max{a(h(i)), a(h (i)) }, (li) where a denotes the Kuratowski measure of noncompactness, H(t) {x(t) x e H}, H (t)= {x (t) x e H}, H(I)= {x(t) x e S,t e I} and

5 Nonnegative Sohtions of Two.Point Boundary Value Problems 51 r,() = PROOF" (10) is known, see [2] Theorem To prove (11), we first show that For any e>0, H can be expressed as H= USi such that i----1 (12) diam(si) < a(h ) + e, i = 1,2,..., m. (13) Since H is equicontinuous, there exists a partition I such tha {t} (j =0,1,...,n) of Leg Tij = {x (t)" x Si, t I} then H (I)= O U Tij. For any x (t) j=l i=1 V (s) Tij (z,v Si, t,s Ij), we have by (13) and (14), (14) _< s + diam(si) < a(h) + 2e, and therefore diam(tij) _< a(h)+ 2s (i = 1,...,m; j = 1,...,n). a(h (I)) _< a(h)+ 2s, which implies (12) since e is arbitrary. On the other hand, i is known (see [2] Lemma 1.4.4) Hence ((z)) _< (n). (15) Observing (n(t)) _< (n(z)), (n (t)) _< (n (z)), t e z,

6 52 DAJUN GUO (11) follows from (10), (12) and (15). Our 1emma is proved. temark 2" (a) If we only assume that H is a bouaded set in C[I,E], then (see [2] Lemma 1.4.4) > (H (Z)) (6) (b) We will also use the following conclusion (see [2] Remark 1.4.1): Let B be a bounded set of E and S be a bounded set of real numbers. Then, for SB = {tx x B,t S}, we have (7) (c) By the same method, we can prove the following extension of Lemma 2" Let H be a bounded set of c(m)[i,e] (m > 1). Suppose that H (m) = {x(m) x H} is equicontinuous. Then a(h) = max{sup a(s(t)), sup a(h (t)),...,sup a(h(m)(t))} t.i t.i t.i (18) and a(h) max{a (H(I)), a(h (I)),..., a (H(m)(I))}. (19) In order to investigate BVP (2), we first consider the integral operator 1 Am(t) = a(t, s)f (s, x(s), x (s), Tx(s), Sz(s))ds + y(t), (20) where f C[I x P x E x P x P, P], V e C2[I,E], y(t) >_ 8 for ti and a(t,s)= (at+ ( 1- )+d), J-(as + b)(c(1 ]-a b) c( s t)+ d), (.91)

7 Nonnegative Solutions of Two-Point Boundary Value Problems 53 here a_>0, b>0, c>_0, d>0 and J=ac+ad+bc>0. Moreover, T and S are defined by (3), where k e C[D,R+], h e C[Do,R+], D = {(t,s) e R" a,< s _< t_< 1} and Do = {(t,s) R 2 0 <_t, s < 1}. in the following, let BR = { e P" Ilxll < FR = {x e E" Ilxll < R) ( > 0) d k0 = max k(t,s), ho = max h(t,s). (22) (t,s)6d (t,s)6do Furthermore, let cone in C1[I, E]. P(O {x e C[I,E]lx(t) >_ 0 for t e I}. Usually, P(I) is not normal even if P Then, P(I) is a is a normal cone in LEMMA 3. Let f be uniformly continuous on I x BR x FR x BR x BR [or any R > O. Suppose tha here exis constants Li >_ 0 (i = 1, 2, 3, 4) wih L + 2L2 + kola + hol4 < p (23) such that a(f(t,x,y,,z,w)) <_ L,a(X) + La(Y) + La(Z) + L4o( V ) (24) for any bonded X, Z, W C P, Y C E and t 6 I, where p = min{1, q- } (25) ( max{j-l(bc + bd), J-l(ad q= max { ac # 0; ac-- 0o into P(I), A is bounded and continuous and there exists 0 < r < 1 a(a(q)) <_ r(q) for any bounded Q C P(I). such that

8 5,\$ DAJUN GUO PROOF" By direct differentiation of (20), we have for x e P(I), 1 (Ax(t)) = C(t, s)f (s, x(s), x (s), Tx(s), Sx(s))ds -t- (27) where j-1 (--c)(as + b) t < (es) and (Ax(t))" = -f (t,x(t),x (t),tz(t),sx(t)) + y"(t). (29) It is easy to see that the uniform continuity of f on I X B R X FR X B R X B R implies the boundednessof f on IxBRxFRXBRXBR, so, (20) and (27) imply that A is abounded and continuous operator from P(I) into P(.[). Now, let Q C P(I) be bounded. By virtue of(29), {[[(Ax(t))"[] x e Q, t e I} is a bounded set of E, so (A(Q)) is equicontinuous, and hence Lemma 2 implies (see (10)) a(a(q)) = max{sup a(aq(t)), sup a((aq) (t)) }. tei tel (30) On the other hand, it is easy to know from (21), (26) and (28) that O <_G(t,s) <_ S-(as+ b)(c(1-s) + d) <_ q, t, s e I (31) and [Gt(t,s)l_<l, t, s e I, t7 s. (32)

9 Nonnegative Solutions of Two.Point Boundary Value Problems 55 Consequently, for t e I, we have by (20), (17) and (31), ((t)) _< ({fo C(t, s)f(s, =(s), = (s), Tx(s), Sx(s))ds x c= Q}) <_ a(-c6{g(t,s)f(s,z(s),= (s),tz(s),s=(s)) x. = a({g(t,s)f(s,x(s),x (s),tx(s),sx(s)), x.. <_ qcz({f(s,x(s),x (s), Tx(s),Sx(s)). Q, Q, x e Q, s e/}). I}) s c= I}) < qa(f(i, Q(I), Q (I), TQ(I), SQ(I)). (33) Since f is uniformly continuous on IBRFRBRBR for any R>0, we have (see [2], Lemma 1.4.1) a(f(i, Q(I), Q (I), TQ(I), SQ(I))) = sup a(f (t, Q(I), Q (I), TQ(I), SQ(I))). (34) It follows from (33), (34) and (24) that a(aq(t)) <_ q{la(q(i)) + L:a(Q (I)) + Laa(TQ(I)) + L,a(SQ(I))}, t I. (35) By (16) and (17), we have.(q (Z)) < :.(Q)..(Q(Z)) <.(Q) (36) and a(tq(i)) a,({fo = k(t,s)x(s)ds x e Q, t e <_ a( C6{tk(t, s)x(s) x e Q,s e [0, t], t e I}) = a({tk(t,s)x(s)" x Q, s e [O,t], t e <_ o.(q(z)) <_ o.(q). (37)

10 56 DAJUN GUO Similarly, Hence, (35)-(38)imply -(SQ(O) _< (38) a(aq(t)) <_ q(l + 2L: + kola + hol)a(q), t e I. (39) In the same way by using (27) and (32)instead of (20) and (31), we get -- r max{q(l lemma is proved. a((aq) (t)) <_ (L + 2L + kola + hol4)a(q), t e I. (40) It follows from (39), (40), (23) and (30) that a(a(q)) <_ ra(q), where + 2L2 + kola + hol), L1 + 2L2 + kola / hol} < 1, and our 3. Main Theorems Let us list some conditions for convenience (H1) XO O, Xl O; f is uniformly continuous on I x BR x FR x BR X,BR (H:) for any R > 0 and there exist Li >_ 0 (i = 1,2, 3, 4) such that (23) and (24) hold. M(R) lim -R < 2.. where R---,+c m I X BR X FR x BR X BR}, and (26). M(R) = sup{ill(t, x, y, z, w)[[ (t, x, y, z, w) e rn=max{1, k0,h0} and p is defined by(25) (H3) there exist uo > 0 and 0 < to < t < 1 such that f (t, x, y, z, w) >_ rouo for t[t0,t], xku0, ye, zk0, w>_0, where ro = J{(ato + b) (c(l 1 1)-" d)( 1 to)} -1 (41)

11 Nonnegative Solutions of Two-Point Boundary Value Problems 57 cone P is solid and there exist uo >>O and 0 < to < t < 1 such that f(t, x, y, z, w) > ruo for t e [to,t], x > uo, y E, z > 0, w >_ 0, where r > r0 and r0 is defined by (41). there exists Ro > m such that M( 0) p Ro < ), m Ro (42) where fl = J-(a + b + c + d)mx{llxoll, IIxll}. (43) THEOREM 1. Le (Hx) and (H) be satisfied. Then BVP (2) has a leas one nonnegaive solution in Ce[I,E], i.e. solution in C[I,E] P(I). PaOOF" It is well known, the C 2 [I, E] solution of (2) is equivalent to the C 1 [I, E] solution of the following integral equation 1 x(t) = G(t, s)f (, z(s), x (), Tx(s), Sx(s))ds + y(t), (44) where G(t,s) is the Green function given by (21) and y(t) denotes the unique solution of BVP xl (o) b (O) = o, 0 _< t _< 1; CX(1) + dxt(i) = Xl, (45) which is given by v(t) :- {(c(1 t) + d)0 + (t + 6)x }. (46) Evidently, y C2[I,E] f3 P(I). Let operator A be defined by (20). Then condition (H1) and Lemma 3 imply that A is a strict set contraction from

12 58 DAJUN GUO P(I) into P(I). By (H2), there exist r/>0 and Ro >0 such that M(R) R p < for R>_mRo. m+/ (47) Choose R such that m+r + <I R (48) and let U= {x ep(i)" Ilxli <R}. For xeu, we have [Ix [[0 <_ R, ][Tz[10 _< kor, ll&,llo < hor, so, it follows from (20), (27), (31), (32), (47) and (48) that ila:llo < qm(,.) + i111o <,Zp m -!- r m.r + I1ill <- (m+, + )R <, (49) and hence - II(A,) llo < M(mR) + ily llo < m.r m+r + I111 + I111.)R < R, (50) Thus, <- (m+. IIAII < we have shown A(G) C U. (51) Since {z E P(1)" Ilzlll _< R} is a nonempty bounded closed convex set of CI[I,E], Darbo theorem (see [4])implies that A has a fixed point in U, which is a solution of (44), and our theorem is proved. P

13 Nonnegative Solutions of Two-Point Boundary Value Problems 59 TtIEOItEM 2. Le (H), (H) and (H) be satisfied. Then BVP (2) has a leas one nonrivil nonnegaive solution x C2[I, E] which satisfies () > 0, e [0,]. () PItOOF" As in the proof of Theorem 1, we can choose R > [lu011 such that (51) holds. Now, let F = {z e P(I)" IIii n and x(t) >_ uo for t e [t0,tl]}. Obviously, F is bounded closed convex set of C [I, E], and F is nonempty since u F, where u(t) Uo. For xf, we have by (H3)" Consequently, Ax F, and hence implies that A has a fixed point in A(F) C F. Finally, again Darbo theorem F, and the proof is complete. TttEOREM 3. Let cone P and (Hs) are satisfied and be normal and solid. Suppose that (n ), (n), (n, ) lifo I! R0g m (54) where N is the normal constant of P. Then B VP (2) has at least three nonnegative solutions 5i 6 C2[I,E] (i = 1,2,3) such that R0 m fo t e [to,t]. ()

14 60 DAJUN GUO PROOF" By Lemma 3, A is a strict set contraction from isyto om ().d (3) that P(I) into P(I). It (56) Let V = {x P(I)" (42) and (56) imply ]] I]1 < R- 0" }" For x { 1, we have ])x ]I < R_ rn m IlAxl[o <_ qm(no) + IlYllo < q--p (no m) / <_ 1 (Ro m) + R.._o m rn m II(A) ll0 _< M(0) / lly ll0 < p-- (0 m#) / Z < (0 rob) / # -- R 0. m m m Consequently, [[AxII1 < R_ and hence A(U1) C U. (57) As in the proof of Theorem 1, we can choose R > 2[[u0[[ such that (51) holds, where U = {x e P(I)" IIll < }. Let U: = {x e P(I)" Ilx[[1 < R, x(t) > uo for t [t0,tl]}. By Corollary 1, U2 is a bounded open convex set of P(I). U2 is nonempty since v U2, where v(t) = 2u0. Moreover, we have (58) Yl C U U2 C U Vl [* U2 =. In fact, (54) and N k 1 imply R > 11oll >_ 2RoN m >_ 2R0 m so U c U. If x U2, then x(t) >> uo for t [to,t], and therefore Nllxll >_ iluol] >_ Ro vhich implies x-u2. So, U and U2 have no common elements, and (158)is proved. For z U, we have I!11 <- and

15 Nonnegative Solutions of Two-Point Boundary Vahte Problems 61 x(t) >_ uo for t 6 [t0,t]. (51)implies IIAxlI < R, and, simnar to (53), (Ha) implies: t e [to, t] == (/tl r Ax(t) >_ J-(ato + b)(c(1 t) + d)da)ruo = Uo > Uo. Hence Az 6 U2, and so A(V) C U. (59) It follows from (51), (57)-(59) that the fixed point indices of strict set contraction (see [4]) and, (A,U,P(+/-)) = i(a,v,p(z)) = ( =,) i(a, U\( I LI 2), P(/)) -i(a, U,P(I)) -i(a,u,p(i)) -i(a, U2,P(I)) Consequently, A has three fixed points and (55) is obviously satisfied. The proof is complete. temark 3" In case x0 x i = 0, we have fl = 0. So, (H) and (54) are satisfied if li-- M(R)< p (60) R--+0 R m As an application, we consider the following B\, P for third order integrodifferential equation" -x " = f(t,x,x,x",sx), 0 <_ t <_ 1; x(o) = O, ax (O) bx"(o) = Xo, cx (1) + dx"(1) = x. (61)

16 62 DAJUN GUO Let then (t) = (o)+ so, (61) is reduced to the following BVP: -u" = f(t, T u,,, S ), (0)- (0) = 0, cu(1) + du (1) xi, (62) where Tl?2(t) = t%(8)d,, Sl12() h l(t, s)u(s)ds, h (t, s) = h(t, r)dr. Since (62) is a BVP of type (2), we can apply above results to (61). For example, by Theorem 1, we get the following TIIEOREM 4. Let (H1) and (H) be satisfied with the change of ko = 1, f e C[I x P x P x E x P,P] and M(R) -sup{llf(t, x, y, z, w)ll" (,, u, z, w) e I x BR x BR x FR x BR}. Then BVP (61) has at least one nonnegative soiution 4. Examples This section gives several examples for both infinite and finite systems of ordinary nonlinear integrodifferential equations based on the above theorems. EXAMPLE 1" Consider the BVP of infinite system for second order nonlinear integrodifferential equations z.(o)-x. (o) = o, z,,(1) + z,,(1) = 0 (0 < t _< I; n = 1,2,3,...). (63)

17 Nonnegative Solutions of Two.Point Boundary Value Problems 63 CONCLUSION" BVP (63) has at least two nonnegative C solutions (t) = (.il(t),...,.in(t),...) (i = 1, 2) such that 5x,(t) -: 0 (n = 1, 2, 3,... ) (64) and ,(t) > 1 for n 5 <t< (n=l 2,3,...) and e,,(t)0 for e [o, as r --+co PROOF" We need only to prove that BVP (63) has a normegative solution 2(t) which satisfies (65) since (t) = (0,..., 0,... ) is evidently the trivial solution of (63). Let E = co = {x = (zx,...,x,,...)" Xn 0} with norm llzll = up I,1 and P= {Z (Z 1,...,Xn,... ) CO" Z n _> 0, n = 1,2,3,... }. Then, P is a norreal cone of E and (63) can be regarded as a BVP of the form (2), where a=b=c=d= 1, 0 -- Xl : 0, ](:,8) -- 1 q- et--s, h(t,\$) : sin2(t-- 3.), 27 = (Xl,...,Xn,...), Y = (Yl,..., Yn,... ), Z = (Zl,..., Zn,... ), W = (Wl,..., Wn,... ) and f = (f,...,f,...), in which (0 < t < 1; n = 1,2,3,...). (66)

18 64 DAJUN GUO By (66), we have and so (0 _< t _< I; n = 1,2,3,...), (67) I /2 2 Ill(t,,,, z,,)il < 16(11! ) / + (1+11!1)/i1,il e,,(l+llll ), which implies 1 13 R]/2gn (1 + ), M(R) < 16(R 2 + R 2 + 3R2) ]/ + (1 + R) ] R 2 (68) and consequently lira M(R) O. (69) This shows that condition (H2) is satisfied. - f (t, X, Y, Z, W) is relatively compact in P Y C /3 and t E I. In fact, let Z, {w(m)} C W and v, (r) = f,(t,z (,) y(),z (m) W(,)). 16t I,(,,") < (il,(m)ll Obviously, f E C[I x P x E x P x P, P] and f is uniformly continuous on I x B R x FR x B R x B R for any R > 0. We now verify that the set E= co for any bounded X,Z,W C {( )} c x, {(m)} c Y, {z(")} c By (67), we have + I!( ) :(")!1 IIz( )ll)/ + (t + II(m)il)/llw( )il/e,,(1 + lly( )!1) n+l (n, m = 1,2, 3,... ). (7o) () Hence {v } is bounded, so, by the diagonal method, we can select a subsequence

19 {m} of {m} such that Nonnegative Sohttions of Two.Point Boundary Vahte Problems 65 lim v (m) = v, (n = 1, 2, 3,... ). it is easy to see from (70) that v = (v,...,v,,,...) e co and (k --, c). Thus, f(t, X, Y, Z, W) is relatively compact, and therefore (H) L = L = Lz = L4 = 0. is satisfied for Now, let u0 = (1,7,...,,...) and to = g co, u0 > 0. When to _< t _< tl, x _> u0, y co, z >_ 0, w >_ 0 1 -if, zn >_ O, wn >_ 0 for n = 1, 2, 3,...), we have, by virtue of (66), 2 Then (i.e. u0 x, >_ 16t /s f(t,x,y,z,w) > _-;-- x > > qn n 3n 16n (n= 1,2,3,...). This shows that of solution 2(t) 81 (H3) is satisfied since, by (41), ro = 1--g. satisfying (65) follows from Theorem 2. Hence, the existence EXAMPLE 2" Consider the BVP of the finite system for nonlinear integrodifferential equations II = 30t V/ n gn[1 + Xn-1 + f:(e ts + 3t2a3)Xn+l(s)ds] - l-\$in2(xt n tn_ 1 + Xn+l) Jr" (Xtn)2/3(f: COS(t- -.q)xn+l ( s)d\$) 1/3 xn(0) 2x(0) o, 3z.()+.() = o where xo Xm and Xm+l = Xl. (0 _< t _< 1; n = 1, 2,..., m), (71) CONCLUSION" BVP (71) has at least three nonnegative C solutions i(t)

20 66 DAJUN GUO (il(t),...,im(t)) (i =,z, z) such hat ln(t) --: O, n = 1,2,...,m (72) 1 3,,(t)>_l for _< t_< -4 n=l,2,...,m. (73) PROOF" Le /3 = m-dimensional space Em = {z = (ZX,...,Zm)} wih norm Then, P I,! and P = {z = (Xl,...,Zm) x n O, rt 1,2,...,172}. is a normal and solid cone in E and BVP (71) can be regarded as a BVP of the form (2), where a = 1, b = 2, c = 3, d = 1, x0 = xx = O, ]g(t,\$) = Igta +-3t283, h(;,\$) = cos(;--..q), x (al,...,xm), Y = (Yl,.-.,Ym), z = (zl,...,zm), w=(w,...,wm) and f=(fx,...,fm), in which fn(t, x, y, z, w) = 30t x/--nen(1 + x,-a + zn+a) + sin2(yn Yn-I + 1 /3 + g(.)/(w.+) n = 1,2,...,m. (74) Evidently, f C[I x P x E x P x P, P] and (H1) is satisfied since fn are continuous and E is finite dimensional. We have sin(y, y,-a + Z.+l)l _< min{1, lvn Yn--1 "}" Zn+ll} so, (74) implies IIf(t, z, v,, w)ll _< 30t gn(1 + Ilzll + I1=11)+ rain{l, (llvil + Ilzll) = } 1 2/3 1/3 / Ilvll Ilwll V t fi I, z P, V E, z P, w P,

21 Nonnegative Solutions of Two-Point Boundary Vahte Problems 67 and herefore 1 M(R) <_ 30 v/ gn(1 + 2R) + min{1, 9R 2 } + g R. Hence n--.+oo R 6 n--.+0 R 6 (75) On the other hand, it is easy to see that, in this case, 5 q--, p=l, re=e+3. (76) Thus, (75) and (76)imply that (H) and (60) are satisfied. 1 (H4). Let u0 = (1,1,...,1) and t 1. Now, ve check t=i = i" Z Obviously, u0 >> 0 and, for t e [to,t 1], z k u0, y E, z k a, w k 0 (i.e. i<t<_i,z._ > 1, zn > O, Wn > O, n = 1,2,...,m), (74) implies f,(t, x, y, z, w) > 30t n gn(1 + x._) > en 2 (n = 1,2,...,m). (77) On the other hand, we have by (41) r0= 63 < --en2" (78) Hence, (77) and (78)imply that (H4) is satisfied with our conclusion follows from Theorem 3 and Remark 3. r= gn 2. Finally, EXAMPLE 3 Consider the BVP of infinite system for third order nonlinear inte-

22 68 DAJUN GUO grodifferentim equation --ts COS(\$- 8)xn(8)ds] 1/4, (0) = 0, 2 (0) :(0) =,.() + ) = p (0_<t_<l; n=1,2,3,...). (79/ CONCLUSION" BVP (79) has at least one nonnegative C such that X n(t) >_ 0 (n = 1, 2, 3,... ) and n(t) t e [0, 1]. solution (t) = ((t),...,(t), as n + c for any PROOF" Let 1,2,3,... } (61 ), where a=d=2, E = 0 a, nd P = {X (Xl,...,Xn,...) 6. CO Xn O, r\$ = as in Example 1. Then, (79) can be regarded as a BVP of the form b=c= 1 1 1, xo = (1,-,...,-,...) e co, Xl = (1,,...,-,...)6 Co COS(;--8),.T = (Xl,...,Xn,...), y = (Yl,-.-,Yn,.-.), Z (Zl,...,zn,...), W (Wl,... Wn,... ), f = (f,.., f, ), in which A(t,,v,z,) = Now, (80) implies 2 /3 )/3 Xn+l(1 2t y, (+ ) I )3 2;2 1/4 "" (t -[- 1)r [(X2n -[- sin t + n+lwn] (n= 1,2,3,...). (8o) I /3 2/3 2!1/(*, =,u,z,w)ll _< ll=ll (1 + llyll) / [(ll=ll / 1 )3 + Ilzll SO 1 M(R) <_ R/(1 + R) 2/ + [(R + 1) + R3] I/4

23 Nonnegative Solutions of Two-Point Boundary Value Problems 69 and herefore M(R) 1 lim <- (81) R--+oo R 2 This shows that (H) is satisfied since it is easy to calculate that p = m = 1. On the other hand, similar to Example 1, we can check that f(t, X, Y, Z, W) is relatively compact in E = co for any bounded X,Y,W C P, Z C E and t I, so (H) is also satisfied. Finally, our conclusion follows from Theorem 4. PEFERENCES 1. J. Chandra, V. Lakshmikantham and A.R. Mitchell, Exisgence of solugions of boundary value problems for nonlinear second order sysgems in a Banach space, Nonlinear Anal. 2 (1978), V. Lakshmikantham and S. Leela, "Nonlinear Differential Equations in Abstract Spaces," Pergamon Press, Oxford, D. Guo and V. Lakshmikantham, "Nonlinear Problems in Abstract Cones," Academic Press Boston, New York, D. Guo, "Nonlinear Functional Analysis," Shandong Sci. and Tech. Press, Jinan, 1985 (in Chinese).

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