arXiv subjects

Lorenzo Toni

Publications and source records attributed to Lorenzo Toni.

3 recordsLinked to original sources

arXiv2026

One-loop effect in the charged 2D black hole near extremality

We study the one-loop correction to the near-extremal quantum entropy of the charged two-dimensional black hole introduced in \cite{McGuigan:1992}. In target space this background can be understood as arising from the dimensional reduction of a three-dimensional solution of the low-energy string effective action. On the other hand, its worldsheet description is provided by the dimensionally reduced $\frac{SL(2, \mathbb{R}) \times U(1)}{U(1)}$ WZW model. Using this latter formulation, we compute the torus partition function to extract the temperature dependence of the one-loop stringy correction to the quantum entropy arising from the short-string sector. We show that this result is under control as long as the black hole temperature satisfies the condition $T \gtrsim \frac{1}{4 \pi \sqrt{k}}$, where the saturation of this bound corresponds to the long-string contribution to the free energy becoming divergent. We speculate that this threshold behavior of the partition function can be interpreted as a signature of the black hole/string transition.

hep-th↗

arXiv2025

One-loop determinants in AdS$_3$ supergravity with extended supersymmetry

We re-examine the computation of the one-loop partition function of Type II supergravity theory compactified on $AdS_3 \times \mathbf{S}^3 \times X$, where $X$ can be $K_3$, $T^4$ and $\mathbf{S}^3 \times \mathbf{S}^1$. These backgrounds preserve eight supercharges (four left and four right moving) and are known to be holographically dual to either small or large $N=(4,4)$ superconformal field theories. By extending well-established heat kernel techniques, we evaluate the one-loop determinants associated to these supergravity backgrounds. The resulting expressions are then used to reconstruct the characters of short multiplets of the corresponding dual boundary theories. A distinctive aspect of our analysis is the emergence of contributions from multiple gravitational saddle points in the path integral, reflecting the spectral flow structure present in the boundary theory.

hep-th↗

arXiv2025

Effective dynamics of open 2D CFTs

We analyze the momentum-space representations of causal response functions of scalar primary operators in an arbitrary 2D CFT, which can be exploited to characterize the effective dynamics of open quantum CFTs. We derive our results by analytically continuing Euclidean correlators to Lorentzian signature. While the two- and three-point functions can be continued straightforwardly, the case of the four-point function is more challenging. In principle, the analytic continuation of the four-point function can be performed in full generality using either the Virasoro conformal block expansion or by mapping the conformal blocks to radial coordinates. However, these frameworks are mathematically intractable for explicit momentum-space calculations. We argue that the global block expansion offers a valuable alternative, as it allows us to recover the time-ordered correlators while preserving a relatively simple analytic structure. From these causal configurations, the four-point response function is systematically constructed and its momentum-space representation is evaluated.

hep-th↗