Confinement and D5 branes

In this work we present new solutions of type IIB supergravity based on wrapped D5 branes. We propose that two of these backgrounds are holographically dual to Quantum Field Theories that confine. The high energy regime of the field theories is that of a Little String Theory. We study various observables (Wilson and 't Hooft loops, Entanglement entropy, density of degrees of freedom and the spectrum of spin-two glueballs, among others). We also present two new black membrane backgrounds and analyse some thermodynamic aspects of these solutions.Comment: 32 pages and very detailed appendices. Various figures. v2: Some improvements and references added. v3: Few comments and references added. Version to be published in JHE

Confinement in (1+1)(1+1) dimensions: a holographic perspective from I-branes

In this paper we holographically study the strongly coupled dynamics of the field theory on I-branes (D5 branes intersecting on a line). In this regime, the field theory becomes $(2 + 1)$ dimensional with 16 supercharges. The holographic dual background has an IR singularity. We solve this singularity by compactifiying the theory on a circle, preserving 4 supercharges. We study various aspects of the QFT: confinement, symmetry breaking, Entanglement Entropy, etc. We also discuss a black hole solution and make some comments on the string $\sigma$-model on our backgrounds.Comment: 29 pages plus appendices, 7 figures. Dedicated to the memory of Roman Jacki

Exact oscillations and chaos on a non-Abelian coil

We construct new exact solutions of the Georgi-Glashow model in $3+1$ dimensions. These configurations are periodic in time but lead to a stationary energy density and no energy flux. Nevertheless, they possess a characteristic frequency which manifests itself through non-trivial resonances on test fields. This allows us to interpret them as non-Abelian self sustained coils. We show that for larger energies a transition to chaotic behavior takes place, which we characterize by Poincar\'e sections, Fourier spectra and exponential growth of the geodesic deviation in an effective Jacobi metric, the latter triggered by parametric resonances.Comment: 23 pages, 5 figure

Exact scalar (quasi-)normal modes of black holes and solitons in gauged SUGRA

In this paper we identify a new family of black holes and solitons that lead to the exact integration of scalar probes, even in the presence of a non-minimal coupling with the Ricci scalar which has a non-trivial profile. The backgrounds are planar and spherical black holes as well as solitons of $SU\left( 2\right) \times SU\left( 2\right)$ $\mathcal{N}=4$ gauged supergravity in four dimensions. On these geometries, we compute the spectrum of (quasi-)normal modes for the non-minimally coupled scalar field. We find that the equation for the radial dependence can be integrated in terms of hypergeometric functions leading to an exact expression for the frequencies. The solutions do not asymptote to a constant curvature spacetime, nevertheless the asymptotic region acquires an extra conformal Killing vector. For the black hole, the scalar probe is purely ingoing at the horizon, and requiring that the solutions lead to an extremum of the action principle we impose a Dirichlet boundary condition at infinity. Surprisingly, the quasinormal modes do not depend on the radius of the black hole, therefore this family of geometries can be interpreted as isospectral in what regards to the wave operator non-minimally coupled to the Ricci scalar. We find both purely damped modes, as well as exponentially growing unstable modes depending on the values of the non-minimal coupling parameter. For the solitons we show that the same integrability property is achieved separately in a non-supersymmetric solutions as well as for the supersymmetric one. Imposing regularity at the origin and a well defined extremum for the action principle we obtain the spectra that can also lead to purely oscillatory modes as well as to unstable scalar probes, depending on the values of the non-minimal coupling.Comment: 18 pages, 3 figure

Slowly rotating and the accelerating α′\alpha'-corrected black holes in four and higher dimensions

We consider the low-energy effective action of string theory at order $\alpha '$, including $R^2$-corrections to the Einstein-Hilbert gravitational action and non-trivial dilaton coupling. By means of a convenient field redefinition, we manage to express the theory in a frame that enables us to solve its field equations analytically and perturbatively in $\alpha '$ for a static spherically symmetric ansatz in an arbitrary number of dimensions. The set of solutions we obtain is compatible with asymptotically flat geometries exhibiting a regular event horizon at which the dilaton is well-behaved. For the 4-dimensional case, we also derive the stationary black hole configuration at first order in $\alpha '$ and in the slowly rotating approximation. This yields string theory modifications to the Kerr geometry, including terms of the form $a$, $a^2$, $\alpha '$ and $a\alpha '$. In addition, we obtain the first $\alpha'$ correction to the C-metrics, which accommodates accelerating black holes. We work in the string frame and discuss the connection to the Einstein frame, for which rotating black holes have already been obtained in the literature.Comment: 19 pages, no figures. v2 21 pages, rotating solution added and title modified, one author added. v3 26 pages, accelerating solution added and title accordingly modified. We have also included the explicit mapping to the Einstein frame that allows to relate our solutions with the ones appearing in previous literature. To appear in PR

Mixing "Magnetic'' and "Electric'' Ehlers--Harrison transformations: The Electromagnetic Swirling Spacetime and Novel Type I Backgrounds

In this paper, we obtain a complete list of stationary and axisymmetric spacetimes, generated from a Minkowski spacetime using the Ernst technique. We do so by operating on the associated seed potentials with a composition of Ehlers and Harrison transformations. In particular, assigning an additional ``electric'' or ``magnetic'' tag to the transformations, we investigate the new spacetimes obtained either via a composition of magnetic Ehlers and Harrison transformations (first part) or via a magnetic-electric combination (second part). In the first part, the resulting type D spacetime, dubbed electromagnetic swirling universe, features key properties, separately found in swirling and (Bonnor--)Melvin spacetimes, the latter recovered in appropriate limits. A detailed analysis of the geometry is included, and subtle issues are addressed. A detailed proof that the spacetime belongs to the Kundt family, is included, and a notable relation to the planar-Reissner-Nordstr\"om-NUT black hole is also meticulously worked out. This relation is further exploited to reverse-engineer the form of the solution in the presence of a nontrivial cosmological constant. A Schwarzschild black hole embedded into the new background is also discussed. In the second part, we present four novel stationary and axisymmetric asymptotically nonflat type I spacetimes, which are naively expected to be extensions of the Melvin or swirling solution including a NUT parameter or electromagnetic charges. We actually find that they are, under conditions, free of curvature and topological singularities, with the physical meaning of the electric transformation parameters in these backgrounds requiring further investigation

Confinement in (1 + 1) dimensions: a holographic perspective from I-branes

Abstract In this paper we holographically study the strongly coupled dynamics of the field theory on I-branes (D5 branes intersecting on a line). In this regime, the field theory becomes (2 + 1) dimensional with 16 supercharges. The dual background has an IR singularity. We resolve this singularity by compactifiying the theory on a circle, preserving 4 supercharges. We study various aspects: confinement, symmetry breaking, Entanglement Entropy, etc. We also discuss a black membrane solution and make some comments on the string σ-model on our backgrounds

Gravitational instantons with conformally coupled scalar fields

We present novel regular Euclidean solutions to General Relativity in presence of Maxwell and conformally coupled scalar fields. In particular, we consider metrics of the Eguchi-Hanson and Taub-NUT families to solve the field equations analytically. The solutions have nontrivial topology labeled by the Hirzebruch signature and Euler characteristic that we compute explicitly. We find that, although the solutions are locally inequivalent with the original (anti-)self-dual Eguchi-Hanson metric, their asymptotically locally Euclidean limit leads to the same global properties. We revisit the Taub-NUT solution previously found in the literature, analyze their nuts and bolts structure, and obtain the renormalized Euclidean on-shell action as well as their topological invariants. Additionally, we discuss how the solutions get modified in presence of higher-curvature corrections that respect conformal invariance. In the conformally invariant case, we obtain novel Eguchi-Hanson and Taub-NUT solutions and demonstrate that both Euclidean on-shell action and Noether-Wald charges are finite without any reference to intrinsic boundary counterterms.Comment: v1: Revtex4-1, 29 pages, comments welcome; v2: Dirac index and references added. Accepted for publication in JHEP; v3: typos fixe