These notes provide a comprehensive review of the semiclassical approach for calculating multiparticle production rates for initial states with few particles at very high energies. In this work we concentrate on a scalar field theory with a mass gap. Specifically, we look at a weakly-coupled theory in the high-energy limit, where the number of particles in the final state scales with energy, $n\sim E\to \infty$, and the coupling $λ\to 0$ with $n λ$ held fixed. In this regime, the semiclasical approach allows us to calculate multiparticle rates non-perturbatively.

中文翻译：

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高能多粒子产生的半经典形式主义回顾

这些注释提供了对半经典方法的全面回顾，该方法用于计算具有极高能量的少数粒子的初始状态的多粒子生产率。在这项工作中，我们专注于具有质量间隙的标量场理论。具体来说，我们看看高能量极限中的弱耦合理论，其中最终状态的粒子数量随能量成比例，$n\sim E\to \infty$，耦合 $λ\to 0$ $n λ$ 保持固定。在这种情况下，半经典方法允许我们非微扰地计算多粒子率。