Effective actions near singularities

Abstract

We study the heterotic string compactified on K3 × T 2 near the line T = U, where the effective action becomes singular due to an SU(2) gauge symmetry enhancement. By 'integrating in' the light W ± vector multiplets we derive a quantum corrected effective action which is manifestly SU(2) invariant and non-singular. This effective action is found to be consistent with a residual SL(2, Z) quantum symmetry on the line T = U. In an appropriate decompactification limit, we recover the known SU(2) invariant action in five dimensions.

Time-dependent backgrounds from supergravity with gauged non-compact R -symmetry

“…By using a probe analysis for time independent black holes one can show, that even before one reaches the repulson singularity the tension of the probe brane becomes tensionless and at the enhancement point the supergravity solution cannot be trusted anymore and additional massless degrees of freedom have to be taken into account [27]. An analogous mechanism does also apply for (static) domain walls, where the enhancon locus appears before one reaches the space-time singularity [28] and integrating-in the additional modes, the singularity can be avoided (see [29] and references therein).…”

Effective Supergravity Actions for Conifold Transitions

“…In this paper we continue the work of [10]- [14] on such extended LEEA and construct S for conifold transitions in M-theory on CY threefolds. While the vector multiplet sector ofŜ can be found exactly for arbitrary conifold transitions, it is currently out of reach to derive the metric on the hypermultiplet manifold from string or M-theory.…”

“…From the analogous situation in rigid supersymmetric theories one expects that along the Higgs branch the N − r massive vector and hypermultiplets combine into long, non-BPS vector multiplets. 16 The non-BPS na- 14 The extra U(1) is due to the graviphoton, which belongs to the gravity multiplet. 15 From the eleven-dimensional point of view the mass of an M2-brane wrapped on Ci is given by…”

“…In four dimensions, however, second derivatives of the prepotential (gauge couplings) become logarithmically divergent as a function of the modulus controlling the distance to the conifold point [8], while its third derivatives (the 'Yukawa couplings') have a first order pole. However, we expect that it is possible to handle these threshold corrections along the lines of [14], where it was shown that one can 'integrate in' four-dimensional vector multiplets. It would be interesting to extend this work to the case where one also integrates in hypermultiplets.…”

Conifold cosmologies in IIA string theory

“…The search for such LEEA was initiated in [5,6], who considered the case of SU(2)-enhancement in M-Theory compactified on a CY 3 . Subsequent work has covered SU(2)-enhancement in heterotic string compactifications on K3 × T 2 [7], toroidal string compactifications close to the selfdual radius [8], and also flop [9,10] and conifold transitions [11,12,13].…”