On Feynman's calculation of the Froehlich polaron mass

TL;DR

This paper rederives Feynman's formula for the Froehlich polaron effective mass using projected partition functions, emphasizing the importance of electron-phonon boundary condition correlations in imaginary time.

Contribution

It introduces a new derivation method for the polaron mass based on projected partition functions and clarifies the role of boundary condition correlations.

Findings

Mass is obtained as the inverse diffusion coefficient in imaginary time.

Correlation between electron and phonon boundary conditions is essential for the derivation.

The approach provides a consistent theoretical foundation for Feynman's formula.

Abstract

Feynman's formula for the effective mass of the Froehlich polaron is rederived from the formalism of projected partition functions. The mass is calculated as inverse of the diffusion coefficient of the polaron trajectory in imaginary time. It is shown that correlation between the electron and phonon boundary conditions in imaginary time is necessary for consistent derivation of the Feynman result.