In this paper, we study the existence of multiple periodic solutions for coupled asymptotically linear wave equations with variable coefficients under some Sturm-Liouville boundary conditions. Such a mathematical model arises naturally when two seismic waves propagate simultaneously in a nonisotropic medium. By a delicate analysis for the asymptotic character of the spectrum of the variable coefficients wave operator, we construct a suitable functional space and give a non-resonance condition, and then at least three nontrivial periodic solutions are obtained. The main tools are the variational methods and saddle point reduction technique. Finally, our result is applicable to the uncoupled wave equations.
| Citation: |
| [1] |
H. Amann, Saddle points and multiple solutions of differential equations,, Math. Z., 169 (1979), 127-166.
doi: 10.1007/BF01215273.
|
| [2] |
A. Bahri and H. Brézis, Periodic solution of a nonlinear wave equation, Proc. Roy. Soc. Edinburgh Sect. A, 85 (1980), 313-320.
doi: 10.1017/S0308210500011896.
|
| [3] |
V. Barbu and N. H. Pavel, Periodic solutions to nonlinear one dimensional wave equation with $x$-dependent coefficients, Trans. Amer. Math. Soc., 349 (1997), 2035-2048.
doi: 10.1090/S0002-9947-97-01714-5.
|
| [4] |
A. K. Ben-Naoum and J. Mawhin, Periodic solutions of some semilinear wave equation on balls and on spheres, Topol. Methods Nonlinear Anal., 1 (1993), 113-137.
doi: 10.12775/TMNA.1993.010.
|
| [5] |
J. Berkovits and V. Mustonen, On nonresonance for systems of semilinear wave equations, Nonlinear Anal., 29 (1997), 627-638.
doi: 10.1016/S0362-546X(96)00067-3.
|
| [6] |
M. Berti and L. Biasco, Forced vibrations of wave equations with non-monotone nonlinearities, Ann. Inst. H. Poincaré Anal. Non Linéaire, 23 (2006), 439-474.
doi: 10.1016/j.anihpc.2005.05.004.
|
| [7] |
M. Berti and P. Bolle, Sobolev periodic solutions of nonlinear wave equations in higher spatial dimensions, Arch. Ration. Mech. Anal., 195 (2010), 609-642.
doi: 10.1007/s00205-008-0211-8.
|
| [8] |
A. Castro and B. Preskill, Existence of solutions for a semilinear wave equation with non-monotone nonlinearity, Discrete Contin. Dyn. Syst., 28 (2010), 649-658.
doi: 10.3934/dcds.2010.28.649.
|
| [9] |
J. Chen and Z. Zhang, Existence of infinitely many periodic solutions for the radially symmetric wave equation with resonance, J. Differential Equations, 260 (2016), 6017-6037.
doi: 10.1016/j.jde.2015.12.026.
|
| [10] |
J. Chen and Z. Zhang, Existence of multiple periodic solutions to asymptotically linear wave equations in a ball, Calc. Var. Partial Differential Equations, 56 (2017), Paper No. 58, 25 pp.
doi: 10.1007/s00526-017-1154-4.
|
| [11] |
J. Chen, Z. Zhang, G. Chang and J. Zhao, Periodic solutions to Klein-Gordon systems with linear couplings, Adv. Nonlinear Stud., 21 (2021), 633-660.
doi: 10.1515/ans-2021-2138.
|
| [12] |
J. M. Coron, Periodic solutions of a nonlinear wave equation without assumption of monotonicity, Math. Ann., 262 (1983), 273-285.
doi: 10.1007/BF01455317.
|
| [13] |
J. Deng and S. Ji., Multiplicity results of periodic solutions for a coupled system of wave equations, Commun. Pure Appl. Anal., 23 (2024), 195-211.
doi: 10.3934/cpaa.2024006.
|
| [14] |
J. Deng and S. Ji, Periodic solutions for a coupled system of wave equations with $x$-dependent coefficients, Adv. Nonlinear Stud., 24 (2024), 922-940.
doi: 10.1515/ans-2023-0144.
|
| [15] |
M. Feng and N. Deng, Multiple positive doubly periodic solutions to nonlinear telegraph systems, Appl. Math. Lett., 133 (2022), 108233, 6 pp.
doi: 10.1016/j.aml.2022.108233.
|
| [16] |
A. Fonda and A. Sfecci, Periodic solutions of weakly coupled superlinear systems, J. Differential Equations, 260 (2016), 2150-2162.
doi: 10.1016/j.jde.2015.09.056.
|
| [17] |
M. Gao and J. Liu, Quasi-periodic solutions for 1D wave equation with higher order nonlinearity, J. Differential Equations, 252 (2012), 1466-1493.
doi: 10.1016/j.jde.2011.10.006.
|
| [18] |
M. García-Huidobro, R. Manásevich, J. Mawhin and S. Tanaka, Periodic solutions for nonlinear systems of ODE's with generalized variable exponents operators, J. Differential Equations, 388 (2024), 34-58.
doi: 10.1016/j.jde.2023.12.040.
|
| [19] |
X. Han and H. Wei, Multiplicity of the large periodic solutions to a super-linear wave equation with general variable coefficient, Commun. Anal. Mech., 16 (2024), 278-292.
doi: 10.3934/cam.2024013.
|
| [20] |
S. Ji, Time periodic solutions to a nonlinear wave equation with $x$-dependent coefficients, Calc. Var. Partial Differential Equations, 32 (2008), 137-153.
doi: 10.1007/s00526-007-0132-7.
|
| [21] |
S. Ji, Periodic solutions for one dimensional wave equation with bounded nonlineaity, J. Differential Equations, 264 (2018), 5527-5540.
doi: 10.1016/j.jde.2018.02.001.
|
| [22] |
S. Ji and Y. Li, Periodic solutions to one dimensional wave equation with $x$-dependent coeffcients, J. Differential Equations, 229 (2006), 466-493.
doi: 10.1016/j.jde.2006.03.020.
|
| [23] |
S. Ji and Y. Li, Time periodic solutions to one-dimensional wave equation with periodic or anti-periodic boundary conditions, Proc. Roy. Soc. Edinburgh Sect. A, 137 (2007), 349-371.
doi: 10.1017/S0308210505001174.
|
| [24] |
S. Ji and Y. Li, Time periodic solutions to the one-dimensional nonlinear wave equation, Arch. Ration. Mech. Anal., 199 (2011), 435-451.
doi: 10.1007/s00205-010-0328-4.
|
| [25] |
H. Li and Z.-Q. Wang, Multiple nodal solutions having shared componentwise nodal numbers for coupled Schrödinger equations, J. Funct. Anal., 280 (2021), 108872, 44 pp.
doi: 10.1016/j.jfa.2020.108872.
|
| [26] |
W. Li, J. Liu and W. Yan, Global stability dynamics of the quasilinear damped Klein-Gordon equation with variable coefficients, J. Geom. Anal., 33 (2023), 122, 41 pp.
doi: 10.1007/s12220-022-01169-7.
|
| [27] |
P. H. Rabinowtiz, Periodic solutions of nonlinear hyperbolic partial differential equations, Comm. Pure Appl. Math., 20 (1967), 145-205.
doi: 10.1002/cpa.3160200105.
|
| [28] |
P. H. Rabinowitz, Free vibrations for a semilinear wave equation, Comm. Pure Appl. Math., 31 (1978), 31-68.
doi: 10.1002/cpa.3160310103.
|
| [29] |
I. A. Rudakov, Periodic solutions of the quasilinear equation of forced vibrations of an inhomogeneous string, Math. Notes, 101 (2017), 137-148.
doi: 10.1134/S000143461701014X.
|
| [30] |
F. Wang, W. Li and Y. An, Nonnegative doubly periodic solutions for nonlinear telegraph system with twin-parameters, Appl. Math. Comput., 214 (2009), 310-317.
doi: 10.1016/j.amc.2009.03.069.
|
| [31] |
L. Wang, M. Yang and Y. Zheng, Infinitely many segregated solutions for coupled nonlinear Schrödinger systems, Discrete Contin. Dyn. Syst., 39 (2019), 6069-6102.
doi: 10.3934/dcds.2019265.
|
| [32] |
C. E. Wayne, Periodic and quasi-periodic solutions of nonlinear wave equations via KAM theory, Comm. Math. Phys., 127 (1990), 479-528.
doi: 10.1007/BF02104499.
|
| [33] |
H. Wei and S. Ji, Periodic solutions of a semilinear variable coefficient wave equation under asymptotic nonresonance conditions, Sci. China Math., 66 (2023), 79-90.
doi: 10.1007/s11425-020-1900-5.
|
| [34] |
H. Wei and S. Ji, Infinitely many periodic solutions for a semilinear wave equation with $x$-dependent coefficients, ESAIM Control Optim. Calc. Var., 26 (2020), 7, 20 pp.
doi: 10.1051/cocv/2019007.
|
| [35] |
H. Wei and S. Ji, Existence of multiple periodic solutions to a semilinear wave equation with $x$-dependent coefficients, Proc. Roy. Soc. Edinburgh Sect. A, 150 (2020), 2586-2606.
doi: 10.1017/prm.2019.25.
|
| [36] |
H. Wei, M. Ma and S. Ji, Multiple periodic solutions for an asymptotically linear wave equation with $x$-dependent coefficients, J. Math. Phys., 62 (2021), 112703, 20 pp.
doi: 10.1063/5.0048205.
|
| [37] |
L. Yan, S. Ji and L. Sun, Asymptotic bifurcation results for coupled nonlinear wave equations with variable coefffcients, J. Differential Equations, 269 (2020), 7157-7170.
doi: 10.1016/j.jde.2020.05.027.
|
| [38] |
K. Yosida, Functional Analysis, 6th ed, Springer, Berlin, 1985.
|