科研之友
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摘要
We consider D3 branes in presence of an S-fold plane. The latter is a non-perturbative object, arising from the combined projection of an S-duality twist and a discrete orbifold of the R-symmetry group. This construction naively gives rise to 4d N = 3 SCFTs. Nevertheless it has been observed that in some cases supersymmetry is enhanced to N = 4. In this paper we study the explicit counting of degrees of freedom arising from vector multiplets associated to strings suspended between the D3 branes probing the S-fold. We propose that, for trivial discrete torsion, there is no vector multiplet associated to (1; 0) strings stretched between a brane and its image. We then focus on the case of rank 2 N = 3 theory that enhances to SU(3) N = 4 SYM, explicitly spelling out the isomorphism between the BPS-spectrum of the manifestly N = 3 theory and that of three D3 branes in flat spacetime. Subsequently, we consider 3-pronged strings in these setups and show how wall-crossing in the S-fold background implies wall crossing in the flat geometry. This can be considered a consistency check of the conjectured SUSY enhancement. We also find that the above isomorphism implies that a (1; 0) string, suspended between a brane and its image in the S-fold, corresponds to a 3-string junction in the flat geometry. This is in agreement with our claim on the absence of a vector multiplet associated to such (1; 0) strings. This is because the 3-string junction in flat geometry gives rise to a 1/4-th BPS multiplet of the N = 4 algebra. Such multiplets always include particles with spin > 1 as opposed to a vector multiplet which is restricted by the requirement that the spins must be <= 1.
- 出版日期2016-9-6
