# References

[LACN19]

Neill Lambert, Shahnawaz Ahmed, Mauro Cirio, and Franco Nori. Virtual excitations in the ultra-strongly-coupled spin-boson model: physical results from unphysical modes. arXiv preprint arXiv:1903.05892, 2019.

[Tan20]

Yoshitaka Tanimura. Numerically “exact” approach to open quantum dynamics: the hierarchical equations of motion (heom). The Journal of Chemical Physics, 153(2):020901, 2020. URL: https://doi.org/10.1063/5.0011599, doi:10.1063/5.0011599.

[TK89]

Yoshitaka Tanimura and Ryogo Kubo. Time evolution of a quantum system in contact with a nearly gaussian-markoffian noise bath. J. Phys. Soc. Jpn., 58(1):101–114, 1989. doi:10.1143/jpsj.58.101.