True Muonium $(\mu^+ \mu^-)$ on the Light Front

Applying Discretized Light Cone Quantization, we perform the first calculation of the spectrum of true muonium, the $\mu^+ \mu^-$ atom, as modified by the inclusion of an $|e\bar e >$ Fock component. The shift in the mass eigenvalue is found to be largest for triplet states. If $m_e$ is taken to be a substantial fraction of $m_\mu$, the integrated probability of the electronic component of the $1 \, {}^3 /! S_1$ state is found to be as large as $O(10^{-2})$. Initial studies of the Lamb shift for the atom are performed. Directions for making the simulations fully realistic are discussed.