Gibbons-Hawking Ansatz Research Articles

The Gibbons–Hawking Ansatz in Generalized Kähler Geometry

We derive a local ansatz for generalized K\"ahler surfaces with nondegenerate Poisson structure and a biholomorphic $S^1$ action which generalizes the classic Gibbons-Hawking ansatz for invariant hyperK\"ahler manifolds, and allows for the choice of one arbitrary function. By imposing the generalized K\"ahler-Ricci soliton equation, or equivalently the equations of type IIB string theory, the construction becomes rigid, and we classify all complete solutions with the smallest possible symmetry group.

ALF gravitational instantons and collapsing Ricci-flat metrics on the $K3$ surface

We construct large families of new collapsing hyperkahler metrics on the $K3$ surface. The limit space is a flat Riemannian $3$-orbifold $T^3 / \mathbb{Z}_2$. Away from finitely many exceptional points the collapse occurs with bounded curvature. There are at most $24$ exceptional points where the curvature concentrates, which always contains the 8 fixed points of the involution on $T^3$. The geometry around these points is modelled by ALF gravitational instantons: of dihedral type ($D_k$) for the fixed points of the involution on T3 and of cyclic type ($A_k$) otherwise. The collapsing metrics are constructed by deforming approximately hyperkahler metrics obtained by gluing ALF gravitational instantons to a background (incomplete) $S^1$–invariant hyperkahler metric arising from the Gibbons–Hawking ansatz over a punctured $3$-torus. As an immediate application to submanifold geometry, we exhibit hyperkahler metrics on the $K3$ surface that admit a strictly stable minimal sphere which cannot be holomorphic with respect to any complex structure compatible with the metric.

The Kähler Quotient Resolution of $${{\mathbb{C}}^3/ \Gamma}$$ C 3 / Γ Singularities, the McKay Correspondence and $${D = 3\,\,\mathcal{N} = 2}$$ D = 3 N = 2 Chern–Simons Gauge Theories

We advocate that a generalized Kronheimer construction of the K\"ahler quotient crepant resolution $\mathcal{M}_\zeta \longrightarrow \mathbb{C}^3/\Gamma$ of an orbifold singularity where $\Gamma\subset \mathrm{SU(3)}$ is a finite subgroup naturally defines the field content and interaction structure of a superconformal Chern-Simons Gauge Theory. This is supposedly the dual of an M2-brane solution of $D=11$ supergravity with $\mathbb{C}\times\mathcal{M}_\zeta$ as transverse space. We illustrate and discuss many aspects of this of constructions emphasizing that the equation $\pmb{p}\wedge\pmb{p}=0$ which provides the K\"ahler analogue of the holomorphic sector in the hyperK\"ahler moment map equations canonically defines the structure of a universal superpotential in the CS theory. The kernel of the above equation can be described as the orbit with respect to a quiver Lie group $\mathcal{G}_\Gamma$ of a locus $L_\Gamma \subset \mathrm{Hom}_\Gamma(\mathcal{Q}\otimes R,R)$ that has also a universal definition. We discuss the relation between the coset manifold $\mathcal{G}_\Gamma/\mathcal{F}_\Gamma$, the gauge group $\mathcal{F}_\Gamma$ being the maximal compact subgroup of the quiver group, the moment map equations and the first Chern classes of the tautological vector bundles that are in a one-to-one correspondence with the nontrivial irreps of $\Gamma$. These first Chern classes provide a basis for the cohomology group $H^2(\mathcal{M}_\zeta)$. We discuss the relation with conjugacy classes of $\Gamma$ and provide the explicit construction of several examples emphasizing the role of a generalized McKay correspondence. The case of the ALE manifold resolution of $\mathbb{C}^2/\Gamma$ singularities is utilized as a comparison term and new formulae related with the complex presentation of Gibbons-Hawking metrics are exhibited.

On a family of \u03b1\u2032-corrected solutions of the Heterotic Superstring effective action

We compute explicitly the first-order in α′ corrections to a family of solutions of the Heterotic Superstring effective action that describes fundamental strings with momentum along themselves, parallel to solitonic 5-branes with Kaluza-Klein monopoles (Gibbons-Hawking metrics) in their transverse space. These solutions correspond to 4-charge extremal black holes in 4 dimensions upon dimensional reduction on T6. We show that some of the α′ corrections can be cancelled by introducing solitonic SU(2) × SU(2) Yang-Mills fields, and that this family of α′-corrected solutions is invariant under α′-corrected T-duality transformations. We study in detail the mechanism that allows us to compute explicitly these α′ corrections for the ansatz considered here, based on a generalization of the ’t Hooft ansatz to hyperKähler spaces.

The Gibbons–Hawking ansatz over a wedge

We discuss the Ricci-flat `model metrics' on $\mathbb{C}^2$ with cone singularities along the conic $\{zw=1\}$ constructed by Donaldson using the Gibbons-Hawking ansatz over wedges in $\mathbb{R}^3$. In particular we describe their asymptotic behavior at infinity and compute their energies.

Gravitational Instantons of Type D k and a Generalization of the Gibbons–Hawking Ansatz

We describe a quaternionic-based Ansatz generalizing the Gibbons-Hawking Ansatz to a class of hyperk\"ahler metrics with hidden symmetries. We then apply it to obtain explicit expressions for gravitational instanton metrics of type $D_k$.

The field theory of intersecting D3-branes

We examine the defect gauge theory on two perpendicular D3-branes with a 1+1 dimensional intersection, consisting of $U(1)$ fields on the D3-branes and charged hypermultiplets on the intersection. We argue that this gauge theory must have a magnetically charged soliton corresponding to the D-string stretched between the branes. We show that the hypermultiplets do source magnetic as well as electric fields, but the magnetic charges are confined if the hypermultiplet action is canonical. Considerations of periodicity of the hypermultiplet space lead to a nontrivial Gibbons-Hawking metric, and we show that there is then the expected magnetic kink solution. The hypermultiplet metric has a singularity, which we argue must be resolved by embedding in the full string theory. Another interesting feature is that the classical field equations have logarithmic divergences at the intersection, which lead to a classical renormalization group flow in the action.

Doubly-fluctuating BPS solutions in six dimensions

Abstract We analyze the BPS solutions of minimal supergravity coupled to an anti-self-dual tensor multiplet in six dimensions and find solutions that fluctuate non-trivially as a function of two variables. We consider families of solutions coming from KKM monopoles fibered over Gibbons-Hawking metrics or, equivalently, non-trivial T 2 fibrations over an $ {{\mathbb{R}}^3} $ base. We find smooth microstate geometries that depend upon many functions of one variable, but each such function depends upon a different direction inside the T 2 so that the complete solution depends non-trivially upon the whole T 2. We comment on the implications of our results for the construction of a general superstratum.

Notes on emergent gravity

Emergent gravity is aimed at constructing a Riemannian geometry from U(1) gauge fields on a noncommutative spacetime. But this construction can be inverted to find corresponding U(1) gauge fields on a (generalized) Poisson manifold given a Riemannian metric (M, g). We examine this bottom-up approach with the LeBrun metric which is the most general scalar-flat Kahler metric with a U(1) isometry and contains the Gibbons-Hawking metric, the real heaven as well as the multi-blown up Burns metric which is a scalar-flat Kahler metric on C^2 with n points blown up. The bottom-up approach clarifies some important issues in emergent gravity.

A homogeneous Gibbons–Hawking ansatz and Blaschke products

A homogeneous Gibbons–Hawking ansatz is described, leading to 4-dimensional hyperkähler metrics with homotheties. In combination with Blaschke products on the unit disc in the complex plane, this ansatz allows one to construct infinite-dimensional families of such hyperkähler metrics that are, in a suitable sense, complete. Our construction also gives rise to incomplete metrics on 3-dimensional contact manifolds that induce complete Carnot–Carathéodory distances.

Contact Spheres and Hyperkähler Geometry

A taut contact sphere on a 3-manifold is a linear 2-sphere of contact forms, all defining the same volume form. In the present paper we completely determine the moduli of taut contact spheres on compact left-quotients of SU(2) (the only closed manifolds admitting such structures). We also show that the moduli space of taut contact spheres embeds into the moduli space of taut contact circles. This moduli problem leads to a new viewpoint on the Gibbons-Hawking ansatz in hyperkahler geometry. The classification of taut contact spheres on closed 3-manifolds includes the known classification of 3-Sasakian 3-manifolds, but the local Riemannian geometry of contact spheres is much richer. We construct two examples of taut contact spheres on open subsets of 3-space with nontrivial local geometry; one from the Helmholtz equation on the 2-sphere, and one from the Gibbons-Hawking ansatz. We address the Bernstein problem whether such examples can give rise to complete metrics.

Limiting behavior of local Calabi-Yau metrics

We use a generalization of the Gibbons-Hawking ansatz to study the behavior of certain non-compact Calabi-Yau manifolds in the large complex structure limit. This analysis provides an intermediate step toward proving the metric collapse conjecture for toric hypersurfaces and complete intersections.

Harmonic functions, central quadrics and twistor theory

Solutions to the n-dimensional Laplace equation which are constant on a central quadric are found. The associated twistor description of the case n = 3 is used to characterize Gibbons–Hawking metrics with tri-holomorphic SL(2, ℂ) symmetry.

Selfdual Einstein Metrics with Torus Symmetry

It is well-known that any 4-dimensional hyperkähler metric with two commuting Killing fields may be obtained explicitly, via the Gibbons-Hawking Ansatz, from a harmonic function invariant under a Killing field on • 3. In this paper, we find all selfdual Einstein metrics of nonzero scalar curvature with two commuting Killing fields. They are given explicitly in terms of a local eigenfunction of the Laplacian on the hyperbolic plane. We discuss the relation of this construction to a class of selfdual spaces found by Joyce, and some Einstein-Weyl spaces found by Ward, and then show that certain 'multipole' hyperbolic eigenfunctions yield explicit formulae for the quaternion-kähler quotients of • Pm—1 by an (m — 2)-torus studied by Galicki and Lawson. As a consequence we are able to place the well-known cohomogeneity one metrics, the quaternion-kähler quotients of • P2 (and noncompact analogues), and the more recently studied selfdual Einstein Hermitian metrics in a unified framework, and give new complete examples.

Properties of equations of the continuous Toda type

We study a modified version of an equation of the continuous Toda type in 1+1 dimensions. This equation contains a friction-like term which can be switched off by annihilating a free parameter $\ep$. We apply the prolongation method, the symmetry and the approximate symmetry approach. This strategy allows us to get insight into both the equations for $\ep =0$ and $\ep \ne 0$, whose properties arising in the above frameworks are mutually compared. For $\ep =0$, the related prolongation equations are solved by means of certain series expansions which lead to an infinite- dimensional Lie algebra. Furthermore, using a realization of the Lie algebra of the Euclidean group $E_{2}$, a connection is shown between the continuous Toda equation and a linear wave equation which resembles a special case of a three-dimensional wave equation that occurs in a generalized Gibbons-Hawking ansatz \cite{lebrun}. Nontrivial solutions to the wave equation expressed in terms of Bessel functions are determined. For $\ep\,\ne\,0,$ we obtain a finite-dimensional Lie algebra with four elements. A matrix representation of this algebra yields solutions of the modified continuous Toda equation associated with a reduced form of a perturbative Liouville equation. This result coincides with that achieved in the context of the approximate symmetry approach. Example of exact solutions are also provided. In particular, the inverse of the exponential-integral function turns out to be defined by the reduced differential equation coming from a linear combination of the time and space translations. Finally, a Lie algebra characterizing the approximate symmetries is discussed.

The group theoretical analysis of gravitational instanton equations

Group theoretical properties of certain nonlinear partial differential equations playing a distinguished role in the gravitational instanton theory and in complex relativity are studied. It is demonstrated that, in general, the groups of contact transformations admitted by these equations appear to be the first prolongations of appropriate point transformation groups. An exceptional case leading to the Gibbons–Hawking metric is examined in detail.

Complete Ricci-flat K�hler manifolds of infinite topological type

We display an infinite dimensional family of complete Ricci-flat Kahler manifolds of complex dimension 2, for which the second homology is infinitely generated. These are obtained from the Gibbons-Hawking Ansatz [2] by using infinitely many, sparsely distributed centers.