Videos

Kinetic Theory: Novel Statistical, Stochastic and Analytical Methods: Convolution estimates for the Boltzmann gain operator with hard spheres

October 23, 2025
Keywords:
  • Kinetic theory and Stochastic particle systems
  • mean field plasma and radiation dynamics
  • Boltzmann and Landau type equations and systems
  • hydrodynamic limits
  • enhanced dissipation
  • quasi-neutral limits
  • swarming and flocking
  • mean-field games
MSC:
  • 35Bxx - Qualitative properties of solutions to partial differential equations
  • 35Lxx - Hyperbolic equations and hyperbolic systems {For global analysis
  • see 58J45}
  • 35Q20 - Boltzmann equations {For fluid mechanics
  • see 76P05
  • for statistical mechanics
  • see 82B40
  • 82C40
  • 82D05}
  • 35Q35 - PDEs in connection with fluid mechanics
  • 35Q40 - PDEs in connection with quantum mechanics
  • 35Q49 - Transport equations {For calculus of variations and optimal control
  • see 49Q22
  • for fluid mechanics
  • see 76F25
  • see 82C70
  • 82D75
  • for operations research
  • see 90B06
  • for mathematical programming
  • see 90C08}
  • 35Q70 - PDEs in connection with mechanics of particles and systems of particles
  • 35Q82 - PDEs in connection with statistical mechanics
  • 35Q83 - Vlasov equations {For statistical mechanics
  • 82D75}
  • 35Q84 - Fokker-Planck equations {For fluid mechanics
  • see 76X05
  • 76W05
  • see 82C31}
  • 35Q89 - PDEs in connection with mean field game theory {For calculus of variations and optimal control
  • see 49N80
  • for game theory
  • see 91A16}
  • 35Q91 - PDEs in connection with game theory
  • economics
  • social and behavioral sciences
  • 35Q92 - PDEs in connection with biology
  • chemistry and other natural sciences
  • 60Gxx - Stochastic processes
  • 60Hxx - Stochastic analysis [See also 58J65]
  • 70Fxx - Dynamics of a system of particles
  • including celestial mechanics
  • 70Lxx - Random and stochastic aspects of the mechanics of particles and systems
  • 82D05 - Statistical mechanics of gases
  • 82D10 - Statistical mechanics of plasmas
Abstract
We will discuss new moment-preserving polynomially weighted convolution estimates for the gain operator of the Boltzmann equation with hard potentials, including the critical case of hard-spheres. Our approach relies crucially on a novel cancellation mechanism dealing with the pathological case of energy-absorbing collisions (that is, collisions that accumulate energy to only one of the outgoing particles). These collisions distinguish hard potentials from Maxwell molecules. Our method quantifies the heuristic that, while energy-absorbing collisions occur with non-trivial probability, they are statistically rare, and therefore do not affect the overall averaging behavior of the gain operator. At the technical level, our proof relies solely on tools from kinetic theory, such as geometric identities and angular averaging.