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1. Species scale in diverse dimensions

   https://doi.org/10.1007/JHEP05(2024)112  

   van_de_Heisteeg, Damian; Vafa, Cumrun; Wiesner, Max; Wu, David H (May 2024, Journal of High Energy Physics)

   A<sc>bstract</sc> In a quantum theory of gravity, the species scale Λ_scan be defined as the scale at which corrections to the Einstein action become important or alternatively as codifying the “number of light degrees of freedom”, due to the fact that$$ {\Lambda}_s^{-1} $$ ${\Lambda }_s^{-1}$is the smallest size black hole described by the EFT involving only the Einstein term. In this paper, we check the validity of this picture in diverse dimensions and with different amounts of supersymmetry and verify the expected behavior of the species scale at the boundary of moduli space. This also leads to the evaluation of the species scale in the interior of the moduli space as well as to the computation of the diameter of the moduli space. We also find evidence that the species scale satisfies the bound$$ {\frac{\left|\nabla {\Lambda}_s\right|}{\Lambda_s}}^2\le \frac{1}{d-2} $$ ${\frac{\left(\nabla {\Lambda }_s\right)}{{\Lambda }_s}}^2\le \frac{1}{d-2}$all over moduli space including the interior. 

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2. Two loop mass renormalisation in heterotic string theory: NS states

   https://doi.org/10.1007/JHEP11(2023)052  

   Bhattacharya, Ritabrata (November 2023, Journal of High Energy Physics)

   A<sc>bstract</sc> In this work computation of the renormalised mass at two loop order for the NS sector of heterotic string theory is attempted. We first implement the vertical integration prescription for choosing a section avoiding the spurious poles due to the presence of a required number of picture changing operators. As a result the relevant amplitude on genus 2 Riemann surface can be written as a boundary term. We then identify the 1PI region of the moduli space having chosen a gluing compatible local coordinates around the external punctures. We also identify the relevant integrands and the relevant region of integration for the modular parameters at the boundary. 

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3. Tree-level superstring amplitudes: the Neveu-Schwarz sector

   https://doi.org/10.1007/JHEP09(2024)008  

   Cacciatori, Sergio L; Grushevsky, Samuel; Voronov, Alexander A (September 2024, Journal of High Energy Physics)

   A<sc>bstract</sc> We present a complete computation of superstring scattering amplitudes at tree level, for the case of Neveu-Schwarz insertions. Mathematically, this is to say that we determine explicitly the superstring measure on the moduli space$$ {\mathcal{M}}_{0,n,0} $$ $M_{0,n,0}$of super Riemann surfaces of genus zero withn≥ 3 Neveu-Schwarz punctures. While, of course, an expression for the measure was previously known, we do this from first principles, using the canonically defined super Mumford isomorphism [1]. We thus determine the scattering amplitudes, explicitly in the global coordinates on$$ {\mathcal{M}}_{0,n,0} $$ $M_{0,n,0}$, without the need for picture changing operators or ghosts, and are also able to determine canonically the value of the coupling constant. Our computation should be viewed as a step towards performing similar analysis on$$ {\mathcal{M}}_{0,0,n} $$ $M_{0,0,n}$, to derive explicit tree-level scattering amplitudes with Ramond insertions. 

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4. Stabilizing massless fields with fluxes in Landau-Ginzburg models

   https://doi.org/10.1007/JHEP08(2024)069  

   Becker, Katrin; Rajaguru, Muthusamy; Sengupta, Anindya; Walcher, Johannes; Wrase, Timm (August 2024, Journal of High Energy Physics)

   A<sc>bstract</sc> Recent work on flux compactifications suggests that the tadpole constraint generically allows only a limited number of complex structure moduli to become massive, i.e., be stabilized at quadratic order in the spacetime superpotential. We study the effects of higher-order terms systematically around the Fermat point in the 1⁹Landau-Ginzburg model. This model lives at strong coupling and features no Kähler moduli. We show that indeed massless fields can be stabilized in this fashion. We observe that, depending on the flux, this mechanism is more effective when the number of initially massless fields is large. These findings are compatible with both the tadpole conjecture and the massless Minkowski conjecture. Along the way, we complete the classification of integral flux vectors with small tadpole contribution. Thereby we are closing in on a future complete understanding of all possible flux configurations in the 1⁹Landau-Ginzburg model. 

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5. Computational Mirror Symmetry

   https://doi.org/10.1007/JHEP01(2024)184  

   Demirtas, Mehmet; Kim, Manki; McAllister, Liam; Moritz, Jakob; Rios-Tascon, Andres (January 2024, Journal of High Energy Physics)

   A<sc>bstract</sc> We present an efficient algorithm for computing the prepotential in compactifications of type II string theory on mirror pairs of Calabi-Yau threefolds in toric varieties. Applying this method, we exhibit the first systematic computation of genus-zero Gopakumar-Vafa invariants in compact threefolds with many moduli, including examples with up to 491 vector multiplets. 

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