Electronic Journal of Differential Equations, Vol. 2023 (2023), No. 55, pp. 1–15. ISSN: 1072-6691. URL: https://ejde.math.txstate.edu, https://ejde.math.unt.edu DOI: 10.58997/ejde.2023.55 TRAVELING WAVE SOLUTIONS FOR THREE-SPECIES NONLOCAL COMPETITIVE-COOPERATIVE SYSTEMS HONG-JIE WU, BANG-SHENG HAN, SHAO-YUE MI, LIANG-BIN SHEN Abstract. By using a two-point boundary-value problem and a Schauder’s fixed point theorem, we obtain traveling wave solutions connecting (0, 0, 0) to an unknown positive steady state for speed c ≥ c∗ = max{2, 2 √ d2r2, 2 √ d3r3}. Then we present some asymptotic behaviors of traveling wave solutions. In particular we show that the nonlocal effects have a great influence on the final state of traveling wave solutions at −∞. 1. Introduction We consider the three-species nonlocal competitive-cooperative system ut = d1∆u+ r1u[1− a1(φ1 ∗ u)− b1v − c1w], vt = d2∆v + r2v[1− a2(φ2 ∗ v) + b2w − c2u], wt = d3∆w + r3w[1− a3(φ3 ∗ w) + b3v − c3u], (1.1) where (φi ∗ u)(x, t) = ∫ R φi(x− y)u(y, t) dy, x ∈ R, t ∈ R, i = 1, 2, 3. Here the unknown functions u(x, t), v(x, t) and w(x, t) represent the population densities of species at position x and time t, and ai, bi, ci, di, ri (i = 1, 2, 3) are real constants. It is easy to see that the species u competes with the species v and w which cooperate with each other from (1.1). The positive coefficients di, ri (i = 1, 2, 3) indicate the diffusion rate and natural growth rate of u, v, w, respectively. The competition and cooperation coefficients for three species are denoted by the positive parameters ai, bi and ci (i = 1, 2, 3). To simplify the notations, we let t r1 → t, √ d1 r1 x→ x, a1u→ u, a2v → v, a3w → w, b1 a2 → b1, c1 a3 → c1, b2 a3 → b2, c2 a1 → c2, b3 a2 → b3, c3 a1 → c3, d2 d1 → d2, d3 d1 → d3, r2 r1 → r2, r3 r1 → r3, 2020 Mathematics Subject Classification. 35A01, 35C07, 35K55, 35K57. Key words and phrases. Three-species system; competitive-cooperative; nonlocal effect; traveling wave solution; critical speed. ©2023. This work is licensed under a CC BY 4.0 license. Submitted April 6, 2023. Published September 4, 2023. 1 2 H.-J. WU, B.-S. HAN, S.-Y. MI, L.-B. SHEN EJDE-2023/55 then system (1.1) is converted to ut = ∆u+ u[1− (φ1 ∗ u)− b1v − c1w], vt = d2∆v + r2v[1− (φ2 ∗ v) + b2w − c2u], wt = d3∆w + r3w[1− (φ3 ∗ w) + b3v − c3u], (1.2) where the bounded kernel functions φi(x) (i = 1, 2, 3) satisfy the assumptions: (A1) φi(x) ≥ 0 and ∫ R φi(x)dx = 1, i = 1, 2, 3; (A2) ∫ R φi(y)eλy dy <∞ for each λ ∈ (0,max{1, √ r2/d2, √ r3/d3}). In addition, as we shown in the paper, it suffices to assume (A3) 0 < bi, ci < 1 for i = 1, 2, 3. We point out that if w = 0 in (1.2), then the system of equations is reduced to a two-species nonlocal Lotka-Volterra competitive system whose traveling waves have been discussed by Han et al. [6]. When u = 0, (1.2) becomes the two-species nonlocal cooperative system which have been studied by Huang and Zou [10]. In summary, two-species Lotka-Volterra systems have been extensively considered [3, 4, 5, 8, 15, 16, 18, 30]. Of course, there are studies on the traveling waves for three- species competitive systems [17, 28], but little research on cooperative systems due to the technical treatments of cooperative systems are not as convenient as competitive systems. Leung and Hou et al. [13, 14] proved that the two-species Lotka-Volterra cooperative system can be transformed into a competitive system by using variable transformation which cannot be applied to 3-dimension system [1, 2, 22]. To mitigate this technical challenge, Hung [12] proposed the following classical three-species Lotka-Volterra competitive-cooperative system for the first time ut = d1uxx + u(λ1 − c11u− c12v + c13w), x ∈ R, t > 0, vt = d2vxx + v(λ2 − c21u− c22v − c23w), x ∈ R, t > 0, wt = d3wxx + w(λ3 + c31u− c32v − c33w), x ∈ R, t > 0, (1.3) where competition between species u and v (c12, c21 > 0), species v and w (c23, c32 > 0), and cooperation between species u and w (c13, c31 > 0). And by transforming (1.3) into a monotonic system, they proved the existence of the traveling wave solutions for (1.3). After that, Meng and Zhang [20] obtained the asymptotic behavior and uniqueness of the traveling waves for (1.3) by using Ikehare’s theorem. For more results, we can refer to [9, 21, 23, 27]. To make the model more practical in applications, nonlocal effects and time- delays have been considered [3, 6, 7, 10, 23]. Subsequently, the traveling wave solution of this model has been studied and developed, see [11, 18, 19, 25, 29]. But they are mostly concerned with the quasi-monotone case. It is worth noting that, compared with three-species delayed Lotka-Volterra competitive-cooperative systems, there are relatively few studies on nonlocal sys- tems. Recently, Zhang and Bao [26] introduced nonlocal effect to the diffusion term which deduced the system ∂u ∂t = d1(J1 ∗ u− u) + r1u(1− a1u− b1v − c1w), ∂v ∂t = d2(J2 ∗ v − v) + r2v(1− a2v + b2w − c2u), ∂w ∂t = d3(J3 ∗ w − w) + r3w(1− a3w + b3v − c3u), (1.4) EJDE-2023/55 THREE-SPECIES NONLOCAL COMPETITIVE-COOPERATIVE SYSTEMS 3 where Ji ∗ z − z = ∫ R Ji(y)[z(x− y, t)− z(x, t)] dy, i = 1, 2, 3, and gave the existence, uniqueness and asymptotic behavior of the traveling wave solutions of (1.4) by the comparative lemma, the bilateral Laplace transform and the sliding method. We should point out that (1.4) does not destroy the com- parison principle of the classical system which will not hold if nonlocal effects are introduced to the reaction term, and the method based on the comparison principle is not applicable. Therefore, inspired by [6, 24, 26], we try to (partially) solve the existence and asymptotic behavior of the traveling wave solutions of (1.2) by using the Schauder’s fixed point theorem and a two-point boundary value problem. Substituting (u, v, w)(x, t) = (U, V,W )(ξ) into (1.2) and denoting ξ = x − ct where c ≥ {2, 2 √ d2r2, 2 √ d3r3} represents the wave speed, we obtain −U ′′(ξ)− cU ′(ξ) = U(ξ)[1− (φ1 ∗ U)(ξ)− b1V (ξ)− c1W (ξ)], −d2V ′′(ξ)− cV ′(ξ) = r2V (ξ)[1− (φ2 ∗ V )(ξ) + b2W (ξ)− c2U(ξ)], −d3W ′′(ξ)− cW ′(ξ) = r3W (ξ)[1− (φ3 ∗W )(ξ) + b3V (ξ)− c3U(ξ)]. (1.5) Then, we have the following result. Theorem 1.1. Assume that (A1)–(A3) hold. Then, for each c > c∗ = max{2, 2 √ d2r2, 2 √ d3r3}, there exists a traveling wave solution (U, V,W )(ξ) satisfying (1.5) with the boundary conditions lim inf ξ→−∞ (U(ξ) + V (ξ) +W (ξ)) > 0, lim ξ→+∞ U(ξ) = lim ξ→+∞ V (ξ) = lim ξ→+∞ W (ξ) = 0. (1.6) In particular, U , V and W are monotone decreasing on [Z0,+∞) for some Z0 > 0 (which may depend on c). Moreover, such traveling wave solution does not exist for c < c∗. This article is organized as follows. In Section 2, we present the super- and sub-solutions of (1.5). The existence of traveling wave solutions connecting (0, 0) to an unknown positive stea dy state of (1.1) is obtained in Section 3. In Section 4, we show the proof of Theorem 1.1 . 2. Preliminaries In this section, we first use super- and sub-solution to construct the range of traveling waves which will be used for the proof of the existence of the solution in Section 3. In the following, we construct the super- and sub-solutions of (1.5). Supersolution. Let pc(x) = e−λcx, qc(x) = e−ζcx, lc(x) = e−ηcx, for all x ∈ R, where λc > 0, ζc > 0, ηc > 0 are the smaller roots of the equations λ2c − cλc + 1 = 0, d2ζ 2 c − cζc + r2 = 0, d3η 2 c − cηc + r3 = 0, respectively. Then, it holds that − p′′c − cp′c = pc, −d2q′′c − cq′c = r2qc, −d3l ′′ c − cl ′ c = r3lc. (2.1) 4 H.-J. WU, B.-S. HAN, S.-Y. MI, L.-B. SHEN EJDE-2023/55 Subsolution. Let p c (x) = e−λcx −Ae−(λc+ε)x, q c (x) = e−ζcx −Be−(ζc+ε)x, lc(x) = e−ηcx −De−(ηc+ε)x, for all x ∈ R, where small enough ε ∈ (0,min(λc, ζc, ηc)) satisfies κc = −(λc + ε)2 + c(λc + ε)− 1 > 0, ιc = −d2(ζc + ε)2 + c(ζc + ε)− r2 > 0, ϑc = −d3(ηc + ε)2 + c(ηc + ε)− r3 > 0. Moreover, A,B,D > 1 are large enough such that lnA ε > max { 1 λc − ε ln 3Zc1 Aκc , 1 ζc − ε ln 3b1 Aκc , 1 ηc − ε ln 3c1 Aκc } , lnB ε > max { 1 ζc − ε ln 3r2Z c 2 Bιc , 1 ηc ln 3r2b2D Bιc , 1 λc − ε ln 3r2c2 Bιc } , lnD ε > max { 1 ηc − ε ln 3r3Z c 3 Dϑc , 1 ζc ln 3r3b3B Dϑc , 1 λc − ε ln 3r3c3 Dϑc } , where Zc1 = ∫ R φ1(y)eλcydy, Zc2 = ∫ R φ2(y)eζcydy, Zc3 = ∫ R φ3(y)eηcydy. Then, for all x > max { lnA ε , lnBε , lnDε } , it holds that p c > 0, q c > 0, lc > 0. So we have − p′′ c − cp′ c − p c + p c (φ1 ∗ pc) + b1pcqc + c1pclc = (−λ2c + cλc − 1)e−λcx +Ae−(λc+ε)x[(λc + ε)2 − c(λc + ε) + 1] + [e−λcx −Ae−(λc+ε)x](Zc1e −λcx + b1e −ζcx + c1e −ηcx) < −Aκce−(λc+ε)x + e−λcx(Zc1e −λcx + b1e −ζcx + c1e −ηcx) = e−(λc+ε)x[−Aκc + Zc1e −(λc−ε)x + b1e −(ζc−ε)x + c1e −(ηc−ε)x] < 0, − d2q′′c − cq ′ c − r2qc + r2qc(φ2 ∗ qc)− b2r2qclc + c2r2qcpc = (−d2ζ2c + cζc − r2)e−ζcx +Be−(ζc+ε)x[d2(ζc + ε)2 − c(ζc + ε) + r2] + r2[e−ζcx −Be−(ζc+ε)x] ( Zc2e −ζcx − b2e−ηcx + b2De −(ηc+ε)x + c2e −λcx ) < e−(ζc+ε)x[−Bιc + r2Z c 2e −(ζc−ε)x + r2b2De −ηcx + r2c2e −(λc−ε)x] < 0, and − d3l′′c − cl ′ c − r3lc + r3lc(φ3 ∗ lc)− b3r3lcqc + c3r3lcpc = (−d3η2c + cηc − r3)e−ηcx +De−(ηc+ε)x[d3(ηc + ε)2 − c(ηc + ε) + r3] + r3[e−ηcx −De−(ηc+ε)x] ( Zc3e −ηcx − b3e−ζcx + b3Be −(ζc+ε)x + c3e −λcx ) < e−(ηc+ε)x[−Dϑc + r3Z c 3e −(ηc−ε)x + r3b3Be −ζcx + r3c3e −(λc−ε)x] < 0, for all x > max{ lnAε , lnBε , lnCε }. Let p̃c(x) = max{0, p c }, q̃c(x) = max{0, q c }, l̃c(x) = max{0, lc}, x ∈ R, EJDE-2023/55 THREE-SPECIES NONLOCAL COMPETITIVE-COOPERATIVE SYSTEMS 5 then combining this with (2.1), we deduce that −p′′c − cp′c + pc ( φ1 ∗ p̃c + b1q̃c + c1 l̃c ) ≥ pc, −d2q′′c − cq′c + r2 ( φ2 ∗ q̃c + c2p̃c ) qc ≥ r2qc + r2b2lcqc, −d3l ′′ c − cl ′ c + r3 ( φ3 ∗ l̃c + c3p̃c ) lc ≥ r3lc + r3b3qclc, (2.2) where bi, ci (i = 2, 3) satisfy φ2 ∗ q̃c − b2lc + c2p̃c ≥ 0 and φ3 ∗ l̃c − b3qc + c3p̃c ≥ 0. In addition, we can also obtain − p̃′′c − cp̃′c + p̃c(φ1 ∗ pc − b1qc − c1lc) ≤ p̃c, (2.3) for each x 6= ln(A)/x, − d2q̃′′c − cq̃′c + r2(φ2 ∗ qc + c2pc)q̃c ≤ r2q̃c + r2b2q̃c l̃c, (2.4) for each x 6= ln(B)/x, and − d3 l̃′′c − cl̃′c + r3(φ3 ∗ lc + c3pc)l̃c ≤ r3 l̃c + r3b3 l̃cq̃c, (2.5) for each x 6= ln(D)/x. Based on the above setting, we give the existence of the traveling wave solutions of (1.5). 3. Existence of traveling wave solutions of (1.5) The aim of this section is two-fold. Firstly, we provide a specific result assuring the existence of the solutions for the equation (1.5) in a finite interval by applying the super- and sub-solution constructed in Section 2 and a well know argument (Schauder’s fixed point theorem). Secondly, by taking the limit, we derive a exis- tence criterion of solution to (1.5) on the entire interval. A three-point boundary value problem. For c > max { 2, 2 √ d2r2, 2 √ d3r3 } , we study the following system in a finite interval (−a, a): −u′′ − cu′ = u(1− φ1 ∗ u− b1v − c1w), −d2v′′ − cv′ = r2v(1− φ2 ∗ v + b2w − c2u), −d3w′′ − cw′ = r3w(1− φ3 ∗ w + b3v − c3u), u(±a) = p̃c(±a), v(±a) = q̃c(±a), w(±a) = l̃c(±a), (3.1) where a > max{ lnAε , lnBε , lnDε } and u(x) =  u(a), x > a, u(x), x ∈ [−a, a], u(−a), x < −a, v(x) =  v(a), x > a, v(x), x ∈ [−a, a], v(−a), x < −a. w(x) =  w(a), x > a, w(x), x ∈ [−a, a], w(−a), x < −a. Next we first define a convex set Ma = { (u, v, w) ∈ C([−a, a],R2) : p̃c(x) ≤ u(x) ≤ pc, x ∈ (−a, a), 6 H.-J. WU, B.-S. HAN, S.-Y. MI, L.-B. SHEN EJDE-2023/55 q̃c(x) ≤ v(x) ≤ qc, x ∈ (−a, a), l̃c(x) ≤ w(x) ≤ lc, x ∈ (−a, a), u(±a) = p̃c(±a), v(±a) = q̃c(±a), w(±a) = l̃c(±a) } , to study the existence of the solution for (3.1). Then, we construct the three-point boundary value problem −u′′ − cu′ + (φ1 ∗ u0 + b1v0 + c1w0)u = u0, −d2v′′ − cv′ + r2(φ2 ∗ v0 + c2u0)v = r2v0 + r2b2w0v0, −d3w′′ − cw′ + r3(φ3 ∗ w0 + c3u0)w = r3w0 + r3b3v0w0, u(±a) = p̃c(±a), v(±a) = q̃c(±a), w(±a) = l̃c(±a), (3.2) where (u0, v0, w0) ∈Ma and u0(x) =  u0(a), x > a, u0(x), x ∈ [−a, a], u0(−a), x < −a, v0(x) =  v0(a), x > a, v0(x), x ∈ [−a, a], v0(−a), x < −a. w0(x) =  w0(a), x > a, w0(x), x ∈ [−a, a], w0(−a), x < −a. Now, we define a linear operator Ψa which satisfies Ψa(u0, v0, w0) = (u, v, w). It is clear that the fixed point of (3.2) is a solution for (3.1). Obviously, Ψa is compact and continuous. Next, we prove that Ma is an invariant for Ψa. From the definition of Ψa and Ma, we know that Ma ∈ Ψa(Ma). Following, we prove Ψa(Ma) ∈ Ma. Since (u, v, w) = (0, 0, 0) is a sub-solution of (3.2), we know that u(x) > 0, v(x) > 0, w(x) > 0 for each x ∈ (−a, a). Given (u0, v0, w0) ∈ Ma and combining with (2.2), then for x ∈ (−a, a), it holds that − p′′c − cp′c + (φ1 ∗ u0 + b1v0 + c1w0)pc ≥ −p′′c − cp′c = pc ≥ u0 = −u′′ − cu′ + (φ1 ∗ u0 + b1v0 + c1w0)u, − d2q′′c − cq′c + r2(φ2 ∗ v0 + c2u0)qc ≥ −d2q′′c − cq′c + r2(φ2 ∗ q̃c + c2p̃c)qc ≥ r2qc + r2b2lcqc ≥ r2v0 + r2b2w0v0 = −d2v′′ − cv′ + r2(φ2 ∗ v0 + c2u0)v, and − d3l ′′ c − cl ′ c + r3(φ3 ∗ w0 + c3u0)lc ≥ −d3l ′′ c − cl ′ c + r3(φ3 ∗ l̃c + c3p̃c)lc ≥ r3lc + r3b3qclc ≥ r3w0 + r3b3v0w0 EJDE-2023/55 THREE-SPECIES NONLOCAL COMPETITIVE-COOPERATIVE SYSTEMS 7 = −d3w′′ − cw′ + r3(φ3 ∗ w0 + c3u0)w. In addition, we also have u(±a) = p̃c(±a) ≤ pc(±a), v(±a) = q̃c(±a) ≤ qc(±a), w(±a) = l̃c(±a) ≤ lc(±a). Then by using the maximum principle, we obtain u(x) ≤ pc(x), v(x) ≤ qc(x), w(x) ≤ lc(x) for each x ∈ (−a, a). On the other hand, combining with (2.3)-(2.5), it is easy to calculate − p̃′′c − cp̃′c + (φ1 ∗ u0 + b1v0 + c1w0)p̃c ≤ −p̃′′c − cp̃′c + (φ1 ∗ pc + b1qc + c1lc)p̃c ≤ p̃c ≤ u0 = −u′′ − cu′ + (φ1 ∗ u0 + b1v0 + c1w0)u, for each x ∈ (ln(A)/ε, a), − d2q̃′′c − cq̃′c + r2(φ2 ∗ v0 + c2u0)q̃c ≤ −d2q̃′′c − cq̃′c + r2(φ2 ∗ qc + c2pc)q̃c ≤ r2q̃c + r2b2 l̃cq̃c ≤ r2v0 + r2b2w0v0 = −d2v′′ − cv′ + r2(φ2 ∗ v0 + c2u0)v, for each x ∈ (ln(B)/ε, a), and − d3 l̃′′c − cl̃′c + r3(φ3 ∗ w0 + c3u0)l̃c ≤ −d3 l̃′′c − cl̃′c + r3(φ3 ∗ lc + c3pc)l̃c ≤ r3 l̃c + r3b3 l̃cq̃c ≤ r3w0 + r3b3w0v0 = −d3w′′ − cw′ + r3(φ3 ∗ w0 + c3u0)w, for each x ∈ ( lnD ε , a), where u(a) = p̃c(a), u( lnA ε ) > 0 = p̃c( lnA ε ), v(a) = q̃c(a), v( lnB ε ) > 0 = q̃c( lnB ε ) and w(a) = l̃c(a), w( lnD ε ) > 0 = l̃c( lnD ε ). The maximum principle implies u(x) ≥ p̃c for each x ∈ (ln(A)/ε, a), v(x) ≥ q̃c for each x ∈ (ln(B)/ε, a) and w(x) ≥ l̃c for each x ∈ (ln(D)/ε, a). Then we conclude u(x) ≥ p̃c, v(x) ≥ q̃c, w(x) ≥ l̃c for each x ∈ (−a, a), that is (u, v, w) ∈ Ma holds. Thus Ψa(Ma) ⊂Ma. Now, by using the Schauder’s fixed point theorem, we can obtain that Ψa has a fixed point (ua, va, wa) ∈Ma which is the solution of (3.1). Lemma 3.1. There exists a constant M which is independent of the number a and c > c∗ (c∗ = max{2, 2 √ d2r2, 2 √ d3r3}) such that each solution of problem (3.1) satisfies 0 ≤ ua ≤M, 0 ≤ va ≤M, 0 ≤ wa ≤M (3.3) for all a > max { 1 ε ln A(λc+ε) λc , 1ε ln B(ζc+ε) ζc , 1ε ln D(ηc+ε) ηc } and all x ∈ [−a, a]. Proof. Suppose that the maximum points of ua(x), va(x) and wa(x) are xM , xN , xH ∈ [−a, a] respectively, that is Mu = max x∈[−a,a] ua(x) = ua(xM ), Mv = max x∈[−a,a] va(x) = va(xN ), 8 H.-J. WU, B.-S. HAN, S.-Y. MI, L.-B. SHEN EJDE-2023/55 Mw = max x∈[−a,a] wa(x) = wa(xH). Then we have u′a(xM ) = 0, u′′a(xM ) ≤ 0, v′′a(xN ) = 0, v′′a(xN ) ≤ 0, w′a(xH) = 0 and w′′a(xH) ≤ 0. Apart from this, we can also prove xM , xN , xH ∈ [−a, a). Since ua(a) = p̃c(a), va(a) = q̃c(a) and wa(a) = l̃c(a), and p̃c(x), q̃c(x), l̃c(x) are decreasing for x > max { 1 ε ln A(λc+ε) λc , 1ε ln B(ζc+ε) ζc , 1ε ln D(ηc+ε) ηc } , so it holds that xM , xN , xH ∈ [−a, a]. Next we prove the lemma. From the value of −u′′a − cu′a = ua(1− φ1 ∗ ua − b1va − c1wa) at xM , −d2v′′a − cv′a = r2va(1− φ2 ∗ va + b2wa − c2ua) at xN and −d3w′′a − cw′a = r3wa(1− φ3 ∗ wa + b3va − c3ua) at xH , we obtain 1− (φ1 ∗ ua)(xM )− b1va(xM )− c1wa(xM ) ≥ 0, 1− (φ2 ∗ va)(xN ) + b2wa(xN )− c2ua(xN ) ≥ 0, 1− (φ3 ∗ wa)(xH) + b3va(xH)− c3ua(xH) ≥ 0, which implies (φ1 ∗ ua)(xM ) < 1, (φ2 ∗ va)(xN ) < 1 and (φ3 ∗ wa)(xH) < 1, (3.4) and −u′′a − cu′a ≤ ua ≤Mu, −d2v′′a − cv′a ≤ r2va ≤ r2Mv, −d3w′′a − cw′a ≤ r3wa ≤ r3Mw, for small enough b2 and b3. Thus, it holds that (u′ae cx)′ ≥ −Mue cx, ( d2v ′ ae c d2 x )′ ≥ −r2Mve c d2 x, ( d3w ′ ae c d3 x )′ ≥ −r3Mwe c d3 x. Integrating the above inequalities from xM to x > xM , xN to x > xN and xH to x > xH , respectively, we obtain u′a(x) ≥ −Mu c (1− e−c(x−xM )), x ∈ [xM , a), v′a(x) ≥ −r2Mv c (1− e− c d2 (x−xN )), x ∈ [xN , a), w′a(x) ≥ −r3Mw c (1− e− c d3 (x−xH)), x ∈ [xH , a). Integrating the above inequalities in the same interval again, we obtain ua(x) ≥Mu − Mu c (x− xM ) + Mu c ∫ x xm e−c(s−xM )ds = Mu [ 1− x− xM c + 1− e−c(x−xM ) c2 ] = Mu[1− (x− xM )2h(c(x− xM ))] ≥Mu [ 1− 1 2 (x− xM )2 ] , EJDE-2023/55 THREE-SPECIES NONLOCAL COMPETITIVE-COOPERATIVE SYSTEMS 9 va(x) ≥Mv − r2Mv c (x− xN ) + r2Mv c e c d2 xN ∫ x xN e− c d2 sds = Mv [ 1− r2 d2 (x− xN )2 ( 1 c(x−xN ) d2 + e− c d2 (x−xN ) c2(x−xN )2 d22 − 1 c2(x−xN )2 d22 )] = Mv [ 1− r2 d2 (x− xN )2h ( c d2 (x− xN ) )] ≥Mv [ 1− r2 2d2 (x− xN )2 ] , and wa(x) ≥Mw [ 1− r3 2d3 (x− xH)2 ] , where h(y) = e−y+y−1 y2 ≤ 1/2 for y > 0. Since ua(x), va(x), wa(x) ∈Ma, we have ua(a) = p̃c(a) ≤ pc(a) = e−λca ≤ 1, va(a) = q̃c(a) ≤ qc(a) = e−ζca ≤ 1, wa(a) = l̃c(a) ≤ lc(a) = e−ηca ≤ 1, which can further imply Mu[1− 1 2 (a− xM )2] ≤ 1, Mv[1− r2 2d2 (a− xN )2] ≤ 1, Mw[1− r3 2d3 (a− xH)2] ≤ 1. (3.5) Taking x0 = 1/2, if xM ∈ (a− x0, a), it follows from (3.5) that Mu ≤ [ 1− 1 2 (a− xM )2 ]−1 ≤ (1− 1 2 x20 )−1 ≤ 4 3 . If xM ∈ [−a, a− x0), then combining this with (3.4), we have 1 ≥ (φ1 ∗ ua)(xM ) = ∫ R φ1(y)ua(xM − y) dy ≥ ∫ 0 −x0 φ1(y)ua(xM − y) dy ≥Mu ∫ 0 −x0 φ1(y) ( 1− y2 2 ) dy From the definition of x0, we obtain Mu ≤ [ ∫ 0 −x0 φ1(y)(1− y2 2 ) dy ]−1 ≤ 4 3 [ ∫ 0 − √ 1 2 φ1(y) dy ]−1 . From (A1), we know that 4 3 (∫ 0 − √ 1 2 φ1(y) dy )−1 ≥ 4 3 . 10 H.-J. WU, B.-S. HAN, S.-Y. MI, L.-B. SHEN EJDE-2023/55 Thus, for each x ∈ [−a, a), we have Mu ≤ 4 3 (∫ 0 − √ 1 2 φ1(y) dy )−1 . Similarly, take y0 = √ d2/(2r2) and z0 = √ d3/(2r3), then for each x ∈ [−a, a), it holds Mv ≤ 4 3 (∫ 0√ − d2 2r2 φ2(y) dy )−1 and Mw ≤ 4 3 (∫ 0√ − d3 2r3 φ3(y) dy )−1 . Let M = max {4 3 (∫ 0 − √ 1 2 φ1(y) dy )−1 , 4 3 (∫ 0√ − d2 2r2 φ2(y) dy )−1 , 4 3 (∫ 0√ − d3 2r3 φ3(y) dy )−1} , (3.6) then the inequality (3.3) follows. The proof is complete � Limit of (ua, va, wa) as a→ +∞. From Lemma 3.1 and the standard elliptic esti- mates, we know that there existsM0 > 0 such that for each a > max{ lnAε , lnBε , lnDε } and a constant α ∈ (0, 1), it holds that ‖ua‖C2,α(− a2 , a 2 ) ≤M0, ‖va‖C2,α(− a2 , a 2 ) ≤M0, ‖wa‖C2,α(− a2 , a 2 ) ≤M0. Letting a → +∞ (possibly along a subsequence), we have ua → u, va → v and wa → w in C2 loc(R), and (u(x), v(x), w(x)) satisfies −u′′ − cu′ = u(1− φ1 ∗ u− b1v − c1w), x ∈ R, −d2v′′ − cv′ = r2v(1− φ2 ∗ v + b2w − c2u), x ∈ R, −d3w′′ − cw′ = r3w(1− φ3 ∗ w + b3v − c3u), x ∈ R, and p̃c ≤ u(x) ≤ min{M,pc}, q̃c ≤ v(x) ≤ min{M, qc}. l̃c ≤ w(x) ≤ min{M, lc}, which implies lim x→+∞ u(x) = lim x→+∞ v(x) = lim x→+∞ w(x) = 0. (3.7) 4. Proof of Theorem 1.1 To prove Theorem 1.1 we use the following lemmas. Lemma 4.1. There exists a Z0 > 0 such that u(x), v(x) and w(x) are monotoni- cally decreasing for x > Z0. Proof. On the contrary, suppose that u(x) is not always monotonic as x → +∞. From (3.7), then there exists a sequence xn → +∞ (n→ +∞) such that u(xn)→ 0, v(xn) → 0, w(xn) → 0 (n → +∞) and u(x) achieves a local minimum at xn, that is u′(xn) = 0, u′′(xn) ≥ 0. Since −u′′(xn)− cu′(xn) = u(xn)(1− (φ1 ∗ u)(xn)− b1v(xn)− c1w(xn)), for each n ∈ N, it holds that (φ1 ∗ u)(xn) + b1v(xn) + c1w(xn) ≥ 1. (4.1) EJDE-2023/55 THREE-SPECIES NONLOCAL COMPETITIVE-COOPERATIVE SYSTEMS 11 On the other hand, from limx→+∞ u(x) = 0 and the boundedness of u(x) on C2(R), it is easy to find that limn→+∞(φ1 ∗u)(xn) = 0. Then combining this with the fact that limn→+∞ v(xn) = 0, limn→+∞ w(xn) = 0, one can obtain a contradiction of (4.1). Therefore, u(x) is always monotonically decreasing on [Z0,+∞). In the same way, v(x) and w(x) are also monotonically decreasing on [Z0,+∞). This completes the proof. � Lemma 4.2. There exists no traveling wave solutions of (1.5) for speed c < c∗. Proof. Using a contradiction argument, we suppose that there exists a traveling wave solution satisfying (1.5) and (1.6) for c < c∗. Take a sequence {zn} satisfying zn → +∞ as n→ +∞. Denote un(x) = u(x+ zn)/u(zn), vn(x) = v(x+ zn)/u(zn), wn(x) = w(x+ zn)/w(zn), then we have −u′′n(x)− cu′n(x) = un(x)(1− (φ1 ∗ ũn)(x)− b1ṽn(x)− c1w̃n(x)), x ∈ R, −d2v′′n(x)− cv′n(x) = r2vn(x)(1− (φ2 ∗ ṽn)(x) + b2w̃n(x)− c2ũn(x)), x ∈ R, −d3w′′n(x)− cw′n(x) = r3wn(x)(1− (φ3 ∗ w̃n)(x) + b3ṽn(x)− c3ũn(x)), x ∈ R, where ũn(x) = u(x + zn), ṽn(x) = v(x + zn), w̃n(x) = w(x + zn). Notice that un(0) = vn(0) = wn(0) = 1 and un(x), vn(x), wn(x) are monotonic decreasing on [Z0 − zn,+∞) for n ∈ N (where Z0 is defined by Lemma 4.1. Since u(x) → 0, v(x)→ 0 and w(x)→ 0 as x→ +∞, it follows that (ũn, ṽn, w̃n)→ (0, 0, 0) locally uniformly at x as n → +∞. Let (un, vn, wn) → (û(x), v̂(x), ŵ(x)) in C2 loc(R) as n→ +∞, so we have −û′′ − cû′ = û, x ∈ R, −d2v̂′′ − cv̂′ = r2v̂, x ∈ R, −d3ŵ′′ − cŵ′ = r3ŵ, x ∈ R. (4.2) Evidently, v̂, v̂, ŵ are monotonically decreasing and û(0) = v̂(0) = ŵ(0) = 1. In addition, it is easy to get that û, v̂, ŵ are positive. Take û to say, if there exists a point x0 ∈ R such that û(x0) = 0, then from the monotonicity of the nonnegative function û, we know that for each x ≥ x0, û(x0) = 0. By the uniqueness of the solutions of ordinary differential equations (4.2), we can obtain û(x) = 0 in R, which contradicts with the fact û(0) = 1. Therefore, (4.2) admits such a solution (û, v̂, ŵ) if and only if c ≥ max { 2, 2 √ d2r2, 2 √ d3r3 } , that is, there exists no traveling wave solutions for speed c < max { 2, 2 √ d2r2, 2 √ d3r3 } . This completes the proof. � Lemma 4.3. Under assumptions (A1)–(A3), the traveling wave (u(x), v(x), w(x)) of system (1.5) satisfies lim inf x→−∞ (u(x) + v(x) + w(x)) > 0. Proof. Since u(x), v(x), w(x) are non-negative, lim infx→−∞(u(x)+v(x)+w(x)) ≥ 0. Using a contradiction argument, we suppose that lim infx→−∞(u(x) + v(x) + w(x)) = 0 which will lead to a sequence yn satisfying u(yn) → 0, v(yn) → 0, w(yn) → 0 as yn → −∞(n → +∞). Taking ũ(x) = u(−x), ṽ(x) = v(−x), w̃(x) = w(−x) and c̃ = −c, then (ũ(−yn), ṽ(−yn), w̃(−yn)) → (0, 0, 0), and (ũ(x), ṽ(x), w̃(x)) satisfies −ũ′′ − c̃ũ′ = ũ(1− φ1 ⊗ ũ− b1ṽ − c1w̃), −d2ṽ′′ − c̃ṽ′ = r2ṽ(1− φ2 ⊗ ṽ + b2w̃ − c2ũ), 12 H.-J. WU, B.-S. HAN, S.-Y. MI, L.-B. SHEN EJDE-2023/55 −d3w̃′′ − c̃w̃′ = r3w̃(1− φ3 ⊗ w̃ + b3ṽ − c3ũ), where (φi⊗ z)(x) = ∫ R φi(y)z(x+ y) dy (i = 1, 2, 3). As in the proof of Lemma 4.2, we can obtain c̃ ≥ max{2, 2 √ d2r2, 2 √ d3r3}; that is c ≤ min{−2,−2 √ d2r2,−2 √ d3r3} which contradicts Lemma 4.2. The proof is complete. � Lemma 4.4. Assume (A1)–(A3) hold If b1 < 1 2M , ci < 1 2M (i = 1, 2, 3), then the traveling wave (u(x), v(x), w(x)) of the system (1.5) satisfies lim inf x→−∞ u(x) > 0, lim inf x→−∞ v(x) > 0, lim inf x→−∞ w(x) > 0. Proof. Since u(x), v(x), and w(x) are nonnegative functions, we know that lim inf x→−∞ u(x) ≥ 0, lim inf x→−∞ v(x) ≥ 0, lim inf x→−∞ w(x) ≥ 0. We will prove this lemma in two steps. Step 1. We prove that lim infx→−∞ u(x) > 0. By a contradiction argument assume that lim infx→−∞ u(x) = 0. Then there must hold one of the following two cases: u(x)→ 0 in an oscillating or a monotonous manner as x→ −∞. Case 1.1. There exists a sequence xn → −∞ as n→ +∞, such that u(x) attains local minimum at xn and u(xn) → 0 as n → +∞. A well know argument (the Harnack inequality) shows that for each Z > 0 and δ ∈ (0, 1−(b1+c1)M2 ), there exists a constant N > 0 such that u(x) ≤ δ for each n > N and x ∈ (xn − Z, xn + Z) which can conclude that limn→+∞(φ1 ∗ u)(xn) = 0 and −u′′(xn)− cu′(xn) = u(xn)[1− (φ1 ∗ u)(xn)− b1v(xn)− c1w(xn)] ≥ u(xn)[1− (b1 + c1)M − (φ1 ∗ u)(xn)] > 0, for large enough n. On the other hand, it is easy to obtain that −u′′(xn)− cu′(xn) ≤ 0, because u(x) attains local minimum at xn which implies u′(xn) = 0 and u′′(xn) ≥ 0. At this point, we reach a contradiction. Case 1.2. limx→−∞ u(x) = 0 and there exists a large enough constant Z > 0 such that u′(x) ≥ 0 for all x < −Z. From Lemma 4.3, we know that lim inf x→−∞ (v(x) + w(x)) > 0 which can be divided into the following two situations. (a) Without loss of generality, we suppose that lim inf x→−∞ v(x) > 0, lim inf x→−∞ w(x) = 0 which admits a sequence xn → −∞(n→ +∞) such that lim n→+∞ u(xn) = 0, lim n→+∞ v(xn) = lim inf x→−∞ v(x) = A > 0, lim n→+∞ w(xn) = 0, where A is a constant. Let un(x) = u(x+xn)/u(xn), vn(x) = v(x+xn)/v(xn) and wn(x) = w(x+ xn)/w(xn), then we have −u′′n(x)− cu′n(x) = un(x)[1− (φ1 ∗ ûn)(x)− b1v̂n(x)− c1ŵn(x)] for all x ∈ R, where u′n(x), v′n(x) and w′n(x) are defined by Lemma 4.2. Suppose that un(x) → ũ(x), vn(x) → ṽ(x), wn(x) → w̃(x) in C2 loc(R) as n → +∞. Then by the Harnack EJDE-2023/55 THREE-SPECIES NONLOCAL COMPETITIVE-COOPERATIVE SYSTEMS 13 inequality, we can conclude that ûn(x)→ 0, v̂n(x)→ v̂(x), ŵn(x)→ 0 (n→ +∞). Since u′(x) ≥ 0 for x < −Z, it follows that ũ′(x) ≥ 0 for each x ∈ R. Also we that ũ(x) satisfies −ũ′′(x)− cũ′(x) = ũ(x)(1− b1v̂(x)) for all x ∈ R. After integrating from 0 to x > 0, we obtain that −ũ′(x) + ũ′(0)− cũ(x) + cũ(0) = ∫ x 0 ũ(y)(1− b1v̂(y)) dy > (1− b1M)ũ(0)x. (4.3) Since ũ(x) > 0, ũ′(x) ≥ 0, ũ(0) = 1, it follows that (4.3) does hold for large enough x. (b) lim infx→−∞ v(x) > 0, lim infx→−∞ w(x) > 0. Processing w(x) as we did for v(x) in case (a), we obtain −ũ′(x) + ũ′(0)− cũ(x) + cũ(0) > [1− (b1 + c1)M ]ũ(0)x, which also does not hold for large enough x. Hence, lim inf x→−∞ u(x) > 0 for all x ∈ R. Step 2. We prove that lim infx→−∞ v(x) > 0. As in the case above, we assume that lim infx→−∞ v(x) = 0 which implies that there exists a sequence yn → −∞ as n→ +∞ such that u(yn)→ 0(n→ +∞). We also analyze the following two cases. Case 2.1. v(x) attains local minimum at yn. The proof is same as the Case 1.1 in Step 1, except that we take ε ∈ (0, 1−c2M2 ) here such that v(x) < ε for each x ∈ (yn − Z, yn + Z) and n > N . Then we have −d2v′′(yn)− cv′(yn) ≥ r2v(yn)[1− c2M − (φ2 ∗ v)(yn)] > 0, which contradicts −d2v′′(yn)− cv′(yn) ≤ 0, because v(x) attains local minimum at yn. Case 2.2. There exists large enough Z > 0 such that v′(x) ≥ 0 for each x < −Z. As in Case 1.2 in Step 1, one can obtain − d2ṽ′′(x)− cṽ′(x) = r2ṽ(x)(1 + b2ŵ(x)− c2û(x)) for all x ∈ R. (4.4) From Lemma 4.3, we know that lim infx→−∞(u(x) +w(x)) > 0 which implies that lim infx→−∞ u(x) > 0, and either lim infx→−∞ w(x) > 0 or lim infx→−∞ w(x) = 0. Then, after integrating (4.4) from 0 to x > 0, we obtain −d2ṽ′′(x) + d2ṽ ′(0)− cṽ(x) + cṽ(0) = r2 ∫ x 0 ṽ(y)(1 + b2ŵ(y)− c2û(y)) dy ≥ r2 ∫ x 0 ṽ(y)(1− c2û(y)) dy ≥ r2(1− c2M)ṽ(0)x. which does not hold for large enough x because ṽ(x) > 0, ṽ′(x) ≥ 0 and ṽ(0) = 1. Therefore, lim inf x→−∞ v(x) > 0. 14 H.-J. WU, B.-S. HAN, S.-Y. MI, L.-B. SHEN EJDE-2023/55 Note that the proof of lim infx→−∞ v(x) > 0 is similar to the the proof of lim infx→−∞ w(x) > 0; so we omit it. This completes the proof. � Now the proof of Theorem 1.1 follows from Lemmas 4.1, 4.2, 4.2, 4.3, and 4.4. Acknowledgment. We are very grateful to anonymous referees for their careful reading and valuable comments. This work was supported by the Natural Sci- ence Foundation of China (12161052, 11801470, U22A20231), by the Natural Sci- ence Foundation of Sichuan Province(2022NSFSC1819), by the Central Government Funds for Guiding Local Scientific and Technological Development (2021ZYD0010), and by the Fundamental Research Funds for the Central Universities (2682022 ZTPY080). References [1] C.-H. Chang, C.-C. Chen, L.-C. Hung, M. Mimura, T. Ogawa; Existence and stability of non- monotone travelling wave solutions for the diffusive Lotka-Volterra system of three competing species, Nonlinearity 33 (2020), no. 10, 5080–5110. [2] F.-D. Dong, W.-T. Li, J.-B. Wang; Propagation dynamics in a three-species competition model with nonlocal anisotropic dispersal, Nonlinear Anal. Real World Appl. 48 (2019), 232– 266. [3] J. Fang, J.-H. Wu; Monotone traveling waves for delayed Lotka-Volterra competition systems, Discrete Contin. Dyn. Syst. 32 (2012), no. 9, 3043–3058. [4] J.-S. Guo, X. Liang; The minimal speed of traveling fronts for the Lotka-Volterra competition system, J. Dynam. Differential Equations 23 (2011), no. 2, 353–363. [5] J.-S. Guo, C.-H. Wu; Recent developments on wave propagation in 2-species competition systems, Discrete Contin. Dyn. Syst. Ser. B 17 (2012), no. 8, 2713–2724. [6] B.-S. Han, Z.-C. Wang, Z.-J. Du; Traveling Waves for Nonlocal Lotka-Volterra Competition Systems, Discrete Contin. Dyn. Syst. Ser. B 25 (2020), no. 5, 1959–1983. [7] B.-S. Han, Z. Feng, W.-J. Bo; Traveling wave phenomena of a nonlocal reaction-diffusion equation with degenerate nonlinearity. Commun. Nonlinear Sci. Numer. Simul. 103 (2021), Paper No. 105990, 21 pp. [8] B.-S. Han, D.-Y. Kong; Propagation dynamics of a nonlocal reaction-diffusion system, Dis- crete Contin. Dyn. Syst. 43 (2023) 2756–2780. [9] Y.-C. Hao, G.-B. Zhang; Stability of bistable traveling wavefronts for a nonlocal dispersal epidemic system, Electron. J. Differential Equations 2022 (2022), no. 49, 1-21. [10] J.-H. Huang, X.-F. Zou; Traveling wavefronts in diffusive and cooperative Lotka-Volterra system with delays, J. Math. Anal. Appl. 271 (2002), no. 2, 455–466. [11] J.-H. Huang, X.-F. Zou; Existence of traveling wavefronts of delayed reaction diffusion sys- tems without monotonicity, Discrete Contin. Dyn. Syst. 9 (2003), no. 4, 925–936. [12] L.-C. Hung; Traveling wave solutions of competitive-cooperative Lotka-Volterra systems of three species, Nonlinear Anal. Real World Appl. 12 (2011), no. 6, 3691–3700. [13] X.-J. Hou, A. W. Leung; Traveling wave solutions for a competitive reaction-diffusion system and their asymptotics, Nonlinear Anal. Real World Appl. 9 (2008), no. 5, 2196–2213. [14] A. W. Leung, X.-J. Hou, Y. Li; Exclusive traveling waves for competitive reaction-diffusion systems and their stabilities, J. Math. Anal. Appl. 338 (2008), no. 2, 902–924. [15] G.-Y. Lv, M.-X. Wang; Traveling wave front in diffusive and competitive Lotka-Volterra system with delays, Nonlinear Anal. Real World Appl. 11 (2010), no. 3, 1323–1329. [16] K. Li, X. Li; Traveling wave solutions in a delayed diffusive competition system, Nonlinear Anal. 75 (2012), no. 9, 3705–3722. [17] G.-C. Lu, Z.-Y. Lu; Geometric approach for global asymptotic stability for three species competitive Gompertz models, J. Math. Anal. Appl. 445 (2017), no. 1, 13–22. [18] W.-T. Li, G. Lin, S. Ruan; Existence of travelling wave solutions in delayed reaction-diffusion systems with applications to diffusion-competition systems, Nonlinearity. 19 (2006), no. 6, 1253–1273. [19] S.-W. Ma; Traveling wavefronts for delayed reaction-diffusion systems via a fixed point the- orem, J. Differential Equations. 171 (2001), no. 2, 294–314. EJDE-2023/55 THREE-SPECIES NONLOCAL COMPETITIVE-COOPERATIVE SYSTEMS 15 [20] Y.-L. Meng, W.-G. Zhang; Properties of traveling wave fronts for three species Lotka-Volterra system, Qual. Theory Dyn. Syst. 19 (2020), no. 2, Paper No. 67, 28 pp. [21] Z.-H. Ma, X. Wu, R. Yuan; Nonlinear stability of traveling wavefronts for competitive- cooperative Lotka-Volterra systems of three species, Appl. Math. Comput. 315 (2017) 331–346. [22] Q. Liu, S. Liu, K. Y. Lam; Stacked invasion waves in a competition-diffusion model with three species, J. Differential Equations 271 (2021), 665–718. [23] Y.-L. Tian, X.-Q. Zhao; Bistable traveling waves for a competitive-cooperative system with nonlocal delays, J. Differential Equations 264 (2018), no. 8, 5263–5299. [24] C.-Y. Wang, L.-R. Li, Q.-Y. Zhang, R. Li; Dynamical behaviour of a Lotka-Volterra competitive-competitive-cooperative model with feedback controls and time delays, J. Biol. Dyn. 13 (2019), no. 1, 43–68. [25] J.-H. Wu, X.-F. Zou; Traveling wave fronts of reaction-diffusion systems with delay, J. Dy- nam. Differential Equations 13 (2001), no. 3, 651–687. [26] L. Zhang, X.-X. Bao; Propagation dynamics of a three-species nonlocal competitive- cooperative system, Nonlinear Anal. Real World Appl. 58 (2021), 103230, 17 pp. [27] H. Zhao, S.-L. Wu; Regular traveling waves for a reaction-diffusion equation with two nonlocal delays, Electron. J. Differential Equations 2022 (2022), no. 82, 1-16. [28] Y. Zhao, S.-L. Yuan, J.-L. Ma; Survival and stationary distribution analysis of a stochastic competitive model of three species in a polluted environment, Bull. Math. Biol. 77 (2015), no. 7, 1285–1326. [29] X.-F. Zou, J.-H. Wu; Existence of traveling wave fronts in delayed reaction-diffusion systems via the monotone iteration method, Proc. Amer. Math. Soc. 125 (1997), no. 9, 2589–2598. [30] W.-J. Zuo, D.-Q. Jiang, X.-G. Sun, T. Hayat, A. Alsaedi; Long-time behaviors of a stochastic cooperative Lotka-Volterra system with distributed delay, Phys. A 506 (2018), 542–559. Hong-Jie Wu School of Mathematics, Southwest Jiaotong University, Chengdu, Sichuan 611756, China Email address: m17882275716@163.com Bang-Sheng Han (corresponding author) School of Mathematics, Southwest Jiaotong University, Chengdu, Sichuan 611756, China Email address: hanbangsheng@swjtu.edu.cn Shao-Yue Mi School of Mathematics, Southwest Jiaotong University, Chengdu, Sichuan 611756, China Email address: mishaoyue@my.swjtu.edu.cn Liang-Bin Shen School of Mathematics, Southwest Jiaotong University, Chengdu, Sichuan 611756, China Email address: m18871027873@163.com 1. Introduction 2. Preliminaries Supersolution Subsolution 3. Existence of traveling wave solutions of (??) A three-point boundary value problem Limit of (ua,va,wa) as a+ 4. Proof of Theorem ?? Acknowledgment References