中科院数学与系统科学研究院

数学研究所

学术报告

调和分析和偏微分方程研讨班

报告人：Dingqun Deng (Tsinghua University)

题  目：Spectrum Analysis of Boltzmann Equation  for Soft Potential

时  间：2022.09.28（星期三）16:00-17:00

地  点：数学院南楼N913

摘  要：It has been unknown in kinetic theory whether the linearized Boltzmann or Landau equation with soft potentials admits a spectral gap in the spatially inhomogeneous setting. Most existing works indicate a negative answer because the spectrum of two linearized self-adjoint collision operators is  accumulated to the origin in case of soft interactions. In this talk, we will prove it in an affirmative way when the space domain is bounded with an inflow boundary condition. The key strategy is to introduce a new Hilbert space with an exponential weight function that involves the inner product of space and velocity variables and also has the strictly positive upper and lower bounds. The action of the transport operator on such space-velocity dependent weight function induces an extra non-degenerate relaxation dissipation in large velocity that can be employed to compensate the degenerate spectral gap and hence give the exponential decay for solutions in contrast with the sub-exponential decay in either the spatially homogeneous case or the case of torus domain. The result reveals a new insight of hypocoercivity for kinetic equations with soft potentials in the specified situation.