# Discrete eigenvalues of the spin-boson Hamiltonian with two photons: on a problem of Minlos and Spohn

## TL;DR

This paper proves that in a specific quantum model with two photons, there can be at most two bound states when the interaction is strong, under minimal regularity assumptions.

## Contribution

It establishes a bound on the number of bound states in the spin-boson model with two photons, addressing a problem posed by Minlos and Spohn.

## Key findings

- Maximum of two bound states for strong coupling
- Results hold under minimal regularity conditions
- Addresses a longstanding problem in quantum physics

## Abstract

Under minimal regularity conditions on the photon dispersion and the coupling function, we prove that the spin-boson model with two massless photons in $\mathbb{R}^d$ cannot have more than two bound state energies whenever the coupling strength is sufficiently strong.