arXiv subjects

Hector Parra De Freitas

Publications and source records attributed to Hector Parra De Freitas.

3 recordsLinked to original sources

arXiv2026

Dai-Freed anomalies and level matching in heterotic asymmetric orbifolds

We study asymmetric orbifolds of the $E_8\times E_8$ heterotic string from the perspective of worldsheet Dai-Freed anomalies. Focusing on cyclic symmetries $G = \mathbb{Z}_m$ that act chirally on the fermions and symmetrically on the bosons, we compute the corresponding spin-bordism invariants and derive the conditions for the vanishing of global anomalies from this perspective. In the fermionic description, these conditions are exactly the familiar level-matching constraints, together with the additional mod-2 conditions that appear for even $m$. We then discuss the same conditions from the transformation properties of higher-genus fermion partition functions and explain how the anomaly is matched under bosonization for a large class of inner automorphisms of the $E_8\times E_8$ lattice theory. This gives an interpretation of the standard consistency conditions for asymmetric heterotic orbifolds from the Dai-Freed anomaly perspective.

hep-th↗

arXiv2026

A Duality Web for Non-Supersymmetric Strings

Motivated by the recently proposed geometric descriptions of 0A and 0B in M-theory and F-theory, we propose a web of duality among non-supersymmetric strings. In particular we argue that the distinct $\mathbb{Z}_2$ quotients of M-theory on $S^1\vee S^1$ lead to both 0A orientifolds as well as non-supersymmetric 10d heterotic vacua of the E-type, including the tachyon-free $SO(16)\times SO(16)$ strings. Moreover we identify certain $\mathbb{Z}_2$ quotients of F-theory on $(S^1\vee S^1)\times S^1$ with 0B orientifolds (including a tachyon-free model) as well as others with dual to non-supersymmetric heterotic strings of the D-type. Moreover using this picture we resolve some puzzles and provide further evidence for the Bergman-Gaberdiel duality between a particular 0B orientifold in 10 dimensions and the Narain compactification of 26-dimensional bosonic strings on a 16-dimensional torus, as well as the DMS conjecture of a 0A orientifold duality in 10d with a bosonic string orientifold of a Narain compactification to 10d.

hep-th↗

arXiv2024

Non-supersymmetric heterotic strings and chiral CFTs

Non-supersymmetric heterotic strings share various properties with their supersymmetric counterparts. Torus compactifications of the latter live in a component of the moduli space of string vacua with 16 supercharges, and various asymmetric orbifolds thereof realize vacua in other components, exhibiting qualitative differences such as rank reduction. We set out to study the analogous problem for non-supersymmetric heterotic strings, framing it in relation to chiral fermionic CFTs with central charge 24, which were classified recently. We find that for the case analogous to the so-called CHL string, which has gauge group rank reduced by 8, there are in total four non-supersymmetric versions. These include the well known $E_8$ string and three other constructions a la CHL, which can be distinguished qualitatively by how tachyons appear in their classical moduli spaces. We also discuss the classification problem for lower rank theories and the relationship between MSDS models and Scherk-Schwarz reductions.

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