TY - JOUR

T1 - Lift of fractional D-brane charge to equivariant Cohomotopy theory

AU - Burton, Simon

AU - Sati, Hisham

AU - Schreiber, Urs

N1 - Publisher Copyright:
© 2020 Elsevier B.V.

PY - 2021/3

Y1 - 2021/3

N2 - The lift of K-theoretic D-brane charge to M-theory was recently hypothesized to land in Cohomotopy cohomology theory. To further check this Hypothesis H, here we explicitly compute the constraints on fractional D-brane charges at ADE-orientifold singularities imposed by the existence of lifts from equivariant K-theory to equivariant Cohomotopy theory, through Boardman's comparison homomorphism. We check the relevant cases and find that this condition singles out precisely those fractional D-brane charges which do not take irrational values, in any twisted sector. Given that the possibility of irrational D-brane charge has been perceived as a paradox in string theory, we conclude that Hypothesis H serves to resolve this paradox. Concretely, we first explain that the Boardman homomorphism, in the present case, is the map from the Burnside ring to the representation ring of the singularity group given by forming virtual permutation representations. Then we describe an explicit algorithm that computes the image of this comparison map for any finite group. We run this algorithm for binary Platonic groups, hence for finite subgroups of SU(2); and we find explicitly that for the three exceptional subgroups and for the first few cyclic and binary dihedral subgroups the comparison morphism surjects precisely onto the sub-lattice of the real representation ring spanned by the non-irrational characters.

AB - The lift of K-theoretic D-brane charge to M-theory was recently hypothesized to land in Cohomotopy cohomology theory. To further check this Hypothesis H, here we explicitly compute the constraints on fractional D-brane charges at ADE-orientifold singularities imposed by the existence of lifts from equivariant K-theory to equivariant Cohomotopy theory, through Boardman's comparison homomorphism. We check the relevant cases and find that this condition singles out precisely those fractional D-brane charges which do not take irrational values, in any twisted sector. Given that the possibility of irrational D-brane charge has been perceived as a paradox in string theory, we conclude that Hypothesis H serves to resolve this paradox. Concretely, we first explain that the Boardman homomorphism, in the present case, is the map from the Burnside ring to the representation ring of the singularity group given by forming virtual permutation representations. Then we describe an explicit algorithm that computes the image of this comparison map for any finite group. We run this algorithm for binary Platonic groups, hence for finite subgroups of SU(2); and we find explicitly that for the three exceptional subgroups and for the first few cyclic and binary dihedral subgroups the comparison morphism surjects precisely onto the sub-lattice of the real representation ring spanned by the non-irrational characters.

KW - Equivariant K-theory

KW - Equivariant cohomology theory

KW - Fractional D-branes

KW - Orbifolds

KW - String theory

UR - http://www.scopus.com/inward/record.url?scp=85097733817&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85097733817&partnerID=8YFLogxK

U2 - 10.1016/j.geomphys.2020.104034

DO - 10.1016/j.geomphys.2020.104034

M3 - Article

AN - SCOPUS:85097733817

SN - 0393-0440

VL - 161

JO - Journal of Geometry and Physics

JF - Journal of Geometry and Physics

M1 - 104034

ER -