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arXiv · 0801.4956

Q-instantons

E. A. Bergshoeff·J. Hartong·A. Ploegh·D. Sorokin
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Abstract

We construct the half-supersymmetric instanton solutions that are electric-magnetically dual to the recently discussed half-supersymmetric Q7-branes. We call these instantons `Q-instantons'. Whereas the D-instanton is most conveniently described using the RR axion χand the dilaton ϕ, the Q-instanton is most conveniently described using a different set of fields χ' and T, where χ' is an axionic scalar. The real part of the Q-instanton on-shell action is a function of T and the imaginary part is linear in χ'. Discrete shifts of the axion χ' correspond to PSL(2,Z) transformations that are of finite order. These are e.g. pure S-duality transformations relating weak and strongly coupled regimes. We argue that near each orbifold point of the quantum axion-dilaton moduli space PSL(2,Z)\PSL(2,R)/SO(2) the higher order R^4 terms in the string effective action contain contributions from an infinite sum of single multiply-charged instantons with the Q-instantons corresponding to the orbifold points τ=i,ρwhere τis the complex axion-dilaton field.

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E. A. Bergshoeff, J. Hartong, A. Ploegh, D. Sorokin. 2008-01-31. Q-instantons. https://doi.org/10.1088/1126-6708%2F2008%2F06%2F028

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