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Abstract

Homo-energetic solutions to the spatially homogeneous Boltzmann equation have been extensively studied, but their global stability in the inhomogeneous setting remains challenging due to unbounded energy growth under self-similar scaling and the intricate interplay between spatial dependence and nonlinear collision dynamics. In this paper, we introduce an approach for periodic spatial domains to construct global-in-time inhomogeneous solutions in a non-conservative perturbation framework, characterizing the global dynamics of growing energy. The growth of energy is shown to be governed by a long-time limit state that exhibits features not captured in either the homogeneous case or the classical Boltzmann theory. The core of our proof is the derivation of new energy estimates specific to the Maxwell molecule model. These estimates combine three key ingredients: a low-high frequency decomposition, a spectral analysis of the matrix associated with the second-order moment equation, and a crucial cancellation property in the zero-frequency mode of the nonlinear collision term. This last property bears a close analogy to the null condition in nonlinear wave equations.