Stability of the nonperturbative bosonic string vacuum

Article history: Received 27 March 2017 Received in revised form 8 May 2017 Accepted 8 May 2017 Available online 10 May 2017 Editor: N. Lambert Quantization of the bosonic string around the classical, perturbative vacuum is not consistent for spacetime dimensions 2 < d < 26. Recently we have showed that at large d there is another socalled mean-field vacuum. Here we extend this mean-field calculation to finite d and show that the corresponding mean-field vacuum is stable under quadratic fluctuations for 2 < d < 26. We point out the analogy with the two-dimensional O (N)-symmetric sigma-model, where the 1/N-vacuum is very close to the real vacuum state even for finite N , in contrast to the perturbative vacuum. © 2017 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP3.