Using the example of Liouville theory, we show how the separation into left- and right-moving degrees of freedom in a nonrational conformal field theory can be made explicit in terms of its integrable structure. The key observation is that there exist separate Baxter Q-operators for left and right-moving degrees of freedom. Combining a study of the analytic properties of the Q-operators with Sklyanin’s Separation of Variables Method leads to a complete characterization of the spectrum. Taking the continuum limit allows us in particular to rederive the Liouville reflection amplitude using only the integrable structure.

We study elliptically fibered $K3$ surfaces, with sections, in toric Fano 3-folds which satisfy certain combinatorial properties relevant to F-theory/heterotic duality. We show that some of these conditions are equivalent to the existence of an appropriate notion of a Weierstrass model adapted to the toric context. Moreover, we show that if in addition other conditions are satisfied, there exists a toric semistable degeneration of the elliptic $K3$ surface which is compatible with the elliptic fibration and F-theory/Heterotic duality.

>We present $NS1+NS5$-brane solutions of heterotic supergravity on curved geometries. They interpolate between a near horizon $\mathrm{AdS}_3 \times X^k \times \mathbb{T}^{7-k}$ region and $\mathbb R^{1,1} \times c(X^k) \times \mathbb{T}^{7-k}$, where $X^k$ (with $k =3,5,6,7$) is a $k$-dimensional geometric Killing spinor manifold, $c(X^k)$, its Ricci-flat cone and $\mathbb{T}^{7-k}$ a $(7-k)$-torus. The solutions require first-order $\alpha'$-corrections to the field equations, and special point-like instantons play an important role, whose singular support is a calibrated submanifold wrapped by the $\mathrm{NS5}$-brane. It is also possible to add a gauge anti-five-brane. We determine the super isometries of the near horizon geometry, which are supposed to appear as symmetries of the holographically dual two-dimensional conformal field theory.

We construct solutions of the vacuum vector constraint equations on manifolds with cylindrical ends.