Article

# Supergravity description of spacetime instantons

(Impact Factor: 3.1). 08/2006; 24(3). DOI: 10.1088/0264-9381/24/3/001
Source: arXiv

ABSTRACT We present and discuss BPS instanton solutions that appear in type II string theory compactifications on Calabi-Yau threefolds. From an effective action point of view these arise as finite action solutions of the Euclidean equations of motion in four-dimensional N=2 supergravity coupled to tensor multiplets. As a solution generating technique we make use of the c-map, which produces instanton solutions from either Euclidean black holes or from Taub-NUT like geometries.

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• "It is well known that there is a class of axionic instanton solutions which circumvents this no go theorem, in particular axionic wormhole-type solutions [5] [6] [7] [8], the D-instanton solution of type-IIB supergravity [9] [10] 2 and hypermultiplet and vector multiplet instanton solutions in N = 2 string compactifications [11] [12] [13] [14] [15] [16] [17]. There are three different approaches to such axionic instantons. "
##### Article: Euclidean Actions, Instantons, Solitons and Supersymmetry
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ABSTRACT: Theories with axionic scalars admit three different Euclidean formulations, obtained by Wick rotation, Wick rotation combined with analytic continuation of the axionic scalars, and Wick rotation combined with Hodge dualization. We investigate the relation between these formulations for a class of theories which contains the sigma models of N=2 vector multiplets as a special case. It is shown that semi-classical amplitudes can be expressed equivalently using the two types of axionic actions, while the Hodge dualized version gives a different value for the instanton action unless the integration constants associated with the axion fields are chosen in a particular way. With this choice the instanton action is equal to the mass of the soliton or black hole obtained by dimensional lifting with respect to time. For supersymmetric models we use the Euclidean supersymmetry algebra to derive a Euclidean BPS condition, and we identify a geometrical criterion which distinguishes BPS from non-BPS extremal solutions.
Journal of Physics A Mathematical and Theoretical 11/2010; 44(17). DOI:10.1088/1751-8113/44/17/175403 · 1.69 Impact Factor
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• "The exact fivebrane partition function, which we compute in [1] using S-duality and twistorial techniques, is in general non- Gaussian and non-holomorphic, but it does reduce to this solution in the weak coupling limit. In particular, substituting (18) in (1), we recover the classical fivebrane instanton action expected from the supergravity analysis of [26], "
##### Article: Topology of the hypermultiplet moduli space in type II/CY string vacua
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ABSTRACT: By analyzing qualitative aspects of NS5-brane instanton corrections, we determine the topology of the hypermultiplet moduli space M_H in Calabi-Yau compactifications of type II string theories at fixed value of the dilaton and of the Calabi-Yau metric. Specifically, we show that for fivebrane instanton couplings to be well-defined, translations along the intermediate Jacobian must induce non-trivial shifts of the Neveu-Schwarz axion which had thus far been overlooked. As a result, the Neveu-Schwarz axion parametrizes the fiber of a circle bundle, isomorphic to the one in which the fivebrane partition function is valued. In the companion paper arXiv:1010.5792, we go beyond the present analysis and take steps towards a quantitative description of fivebrane instanton corrections, using a combination of mirror symmetry, S-duality, topological string theory and twistor techniques.
Physical review D: Particles and fields 09/2010; 83(2). DOI:10.1103/PhysRevD.83.026001 · 4.86 Impact Factor
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• "The solutions of the reduced Euclidean theory can be interpreted as instantons and are interesting in their own right. They are of the same type as the D-instanton solution of type-IIB supergravity [41], and the instanton solutions of N = 2 hypermultiplets [42] [43] [44] [45] [46] [25], and they contain the instanton solutions and N = 2 vector multiplets [38] [48] as a subclass. Since the instantons satisfy a Bogomol'nyi bound and lift to extremal black holes, we refer to them as extremal instanton solutions. "
##### Article: LTH 832 Instantons, black holes, and harmonic functions
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ABSTRACT: We find a class of five-dimensional Einstein-Maxwell type Lagrangians which contains the bosonic Lagrangians of vector multiplets as a subclass, and preserves some features of supersymmetry, namely the existence of multi-centered black hole solutions and of attractor equations. Solutions can be expressed in terms of harmonic functions through a set of algebraic equations. The geometry underlying these Lagrangians is characterized by the existence of a Hesse potential and generalizes the very special real geometry of vector multiplets. Our construction proceeds by first obtaining instanton solutions for a class of four-dimensional Euclidean sigma models, which includes those occuring for four-dimensional Euclidean N=2 vector multiplets as a subclass. Comment: 58 pages, minor revision: some references added, discussion of first order flow equations extended, remarks on Hamilton-Jacobi formulation added
Journal of High Energy Physics 06/2009; DOI:10.1088/1126-6708/2009/10/058 · 6.22 Impact Factor