Tracer particles coupled to an interacting boson gas

TL;DR

This paper studies the mean-field limit of tracer particles interacting with a boson gas, deriving effective equations and analyzing fluctuations as the number of bosons becomes large.

Contribution

It introduces a rigorous derivation of mean-field equations for tracer particles coupled to an interacting boson field, accounting for particle creation and destruction near the vacuum.

Findings

Effective mean-field equations for tracer particles and boson field.

Estimates for bosonic particle number in fluctuation states.

Handling of boson creation/destruction near vacuum states.

Abstract

In this work, we investigate the mean-field limit of a model consisting in $m \geq 1 $ tracer particles, coupled to an interacting boson field. We assume the mass of the tracer particles and the expected number of bosons to be of the same order of magnitude $N \geq 1 $ and we investigate the $N\rightarrow \infty $ limit. In particular, we show that the limiting system can be effectively described by a pair of variables $( \textbf{X}_t ,\varphi_t ) \in \mathbb{R}^{3m} \times H^1(\mathbb{R}^3)$ that solve a mean-field equation. Our methods are based on proving estimates for the number of bosonic particles in a suitable \textit{fluctuation state} $\Omega_{N,t }$. The main diffculty of the problem comes from the fact that the interaction with the tracer particles can create or destroy bosons for states close to the vacuum.