= String-frame massless effective action
{title2=$\int\sqrt{-G}e^{-2\Phi}(R+4(\nabla\Phi)^2-H^2/12)$}
The leading massless-sector spacetime action is proportional to $\int\sqrt{-G}e^{-2\Phi}[R+4(\nabla\Phi)^2-H^2/12]$, with $H=dB$. The backgrounds are the <string-frame metric>, <dilaton>, and <Kalb–Ramond field>. Massive string exchange generates higher-derivative corrections ordered by $\alpha'$. This perturbative bosonic massless-sector truncation does not remove the <tachyon> instability.
Back to article page
