@article {Narain2017,
	title = {Real topological string amplitudes},
	journal = {Journal of High Energy Physics},
	volume = {2017},
	number = {3},
	year = {2017},
	month = {Mar},
	pages = {80},
	abstract = {<p>We discuss the physical superstring correlation functions in type I theory (or equivalently type II with orientifold) that compute real topological string amplitudes. We consider the correlator corresponding to holomorphic derivative of the real topological amplitude $\mathcal{G_\chi}$, at fixed worldsheet Euler characteristic $\chi$. This corresponds in the low-energy effective action to $\mathcal{N}=2$ Weyl multiplet, appropriately reduced to the orientifold invariant part, and raised to the power $g{\textquoteright}= -\chi+ 1$. We show that the physical string correlator gives precisely the holomorphic derivative of topological amplitude. Finally, we apply this method to the standard closed oriented case as well, and prove a similar statement for the topological amplitude $\mathcal{F}_g$.</p>},
	issn = {1029-8479},
	doi = {10.1007/JHEP03(2017)080},
	url = {https://doi.org/10.1007/JHEP03(2017)080},
	author = {Narain, K. S. and Nicol{\`o} Piazzalunga and Alessandro Tanzini}
}
