New comments on six-dimensional orientifold vacua with reduced rank and unitarity constraints
Abstract We revisit and extend the construction of six-dimensional orientifolds built upon the T 4/ℤ N orbifolds with a non-vanishing Kalb-Ramond background, both in the presence of N $$ \mathcal{N} $$ = (1, 0) supersymmetry and Brane Supersymmetry Breaking, thus amending some statements present in...
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| Format: | Article |
| Language: | English |
| Published: |
SpringerOpen
2025-06-01
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| Series: | Journal of High Energy Physics |
| Subjects: | |
| Online Access: | https://doi.org/10.1007/JHEP06(2025)062 |
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| Summary: | Abstract We revisit and extend the construction of six-dimensional orientifolds built upon the T 4/ℤ N orbifolds with a non-vanishing Kalb-Ramond background, both in the presence of N $$ \mathcal{N} $$ = (1, 0) supersymmetry and Brane Supersymmetry Breaking, thus amending some statements present in the literature. In the N = 2 case, we show how the gauge groups on unoriented D9 and D5 (anti-)branes do not need to be correlated, but can be independently chosen complex or real. For N > 2 we find that the Diophantine tadpole conditions severely constrain the vacua. Indeed, only the N = 4 orbifold with a rank-two Kalb-Ramond background may admit integer solutions for the Chan-Paton multiplicities, if the ℤ 4 fixed points support O5− planes, both with and without supersymmetry. All other cases would involve a fractional number of branes, which is clearly unacceptable. We check the consistency of the new ℤ 2 and ℤ 4 vacua by verifying the unitarity constraints for string defects coupled to Ramond-Ramond two-forms entering the Green-Schwarz-Sagnotti mechanism. |
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| ISSN: | 1029-8479 |