# Heat radiation and transfer for point particles in arbitrary geometries

## TL;DR

This paper derives exact, general expressions for heat radiation and transfer involving point particles in arbitrary geometries using scattering theory, and demonstrates their application through specific configurations.

## Contribution

It provides a novel, exact formulation for heat transfer and radiation of point particles in complex environments without approximations.

## Key findings

- Heat transfer between two point particles is significantly enhanced by a nearby sphere.
- A point particle's heat emission is affected by the presence of a planar mirror.
- A particle inside a spherical mirror cavity does not radiate energy.

## Abstract

We study heat radiation and heat transfer for pointlike particles in a system of other objects. Starting from exact many-body expressions found from scattering theory and fluctuational electrodynamics, we find that transfer and radiation for point particles are given in terms of the Green's function of the system in the absence of the point particles. These general expressions contain no approximation for the surrounding objects. As an application, we compute the heat transfer between two point particles in the presence of a sphere of arbitrary size and show that the transfer is enhanced by several orders of magnitude through the presence of the sphere, depending on the materials. Furthermore, we compute the heat emission of a point particle in front of a planar mirror. Finally, we show that a particle placed inside a spherical mirror cavity does not radiate energy.