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Published online by Cambridge University Press: 11 January 2024
We investigate the existence and branching patterns of wave trains in the mass-in-mass (MiM) lattice, which is a variant of the Fermi–Pasta–Ulam (FPU) lattice. In contrast to FPU lattice, we have to solve coupled advance-delay differential equations, which are reduced to a finite-dimensional bifurcation equation with an inherited Hamiltonian structure by applying a Lyapunov–Schmidt reduction and invariant theory. We establish a link between the MiM lattice and the monatomic FPU lattice. That is, the monochromatic and bichromatic wave trains persist near $\mu =0$ in the nonresonance case and in the resonance case $p:q$
where $q$
is not an integer multiple of $p$
. Furthermore, we obtain the multiplicity of bichromatic wave trains in $p:q$
resonance where $q$
is an integer multiple of $p$
, based on the singular theorem.