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David D. K. Chow

Publications and source records attributed to David D. K. Chow.

At least 19 recordsLinked to original sources
arXiv2022

Schlömilch integrals and probability distributions on the simplex

The Schlömilch integral, a generalization of the Dirichlet integral on the simplex, and related probability distributions are reviewed. A distribution that unifies several generalizations of the Dirichlet distribution is presented, with special cases including the scaled Dirichlet distribution and certain Dirichlet mixture distributions. Moments and log-ratio covariances are found, where tractable. The normalization of the distribution motivates a definition, in terms of a simplex integral representation, of complete homogeneous symmetric polynomials of fractional degree.

math.PR↗
arXiv2022

Properties of the Concrete distribution

We examine properties of the Concrete (or Gumbel-softmax) distribution on the simplex. Using the natural vector space structure of the simplex, the Concrete distribution can be regarded as a transformation of the uniform distribution through a reflection and a location-scale transformation. The Fisher information is computed and the corresponding information metric is hyperbolic space. We explicitly give an explicit transformation of the parameters of the distribution to Poincaré half-space coordinates, which correspond to an orthogonal parameterization, and the Fisher-Rao geodesic distance is computed.

math.PR↗
arXiv2020

Black holes in N=8 supergravity from SO(4,4) hidden symmetries

We detail the construction of the most general asymptotically flat, stationary, rotating, non-extremal, dyonic black hole of the four-dimensional N=2 supergravity coupled to 3 vector multiplets that describes the STU model. It generates through U-dualities the most general asymptotically flat, stationary black hole of N=8 supergravity. We develop the solution generating technique based on SO(4,4)/SL(2,R)^4 coset model symmetries, with an emphasis on the 4-fold permutation symmetry of the gauge fields. We indicate how previously known non-extremal and extremal solutions of the STU model are recovered as limiting cases. Several properties of the general black hole solution are discussed, including its thermodynamics, the quadratic mass formula, the Bogomolny-Prasad-Sommerfield limit, the slow and fast extremal rotating limits, its properties in regards to the Kerr/conformal field theory correspondence, its Killing tensors and the separability of geodesic motion and probe scalars.

hep-th↗
arXiv2019

Rotating Strings in Six-Dimensional Higher-Derivative Supergravity

We construct the first rotating string solution in 6-dimensional Einstein-Gauss-Bonnet supergravity, carrying both electric and magnetic charges. By embedding the known rotating string solution of the 2-derivative theory into 6-dimensional off-shell supergravity, the Killing spinors associated with the underlying supersymmetry can be made off-shell and are universal to all off-shell supergravity models based on the same field content. The near-horizon geometry is S^3 fibred over the extremal BTZ black hole, locally isomorphic to AdS_3*S^3. We compute the higher-derivative corrections to the Brown-Henneaux central charges in a particular R+R^2 model resulting from K3 compactification of type IIA string theory.

hep-th↗
arXiv2018

On Late Time Tails in an Extreme Reissner-Nordström Black Hole: Frequency Domain Analysis

In this brief note, we revisit the study of the leading order late time decay tails of massless scalar perturbations outside an extreme Reissner-Nordström black hole. Previous authors have analysed this problem in the time domain; we analyse the problem in the frequency domain. We first consider initial perturbations with generic regular behaviour across the horizon on characteristic surfaces. For this set-up, we reproduce some of the previous results of Sela [arXiv:1510.06169] using Fourier methods. Next, we consider related initial data on $t=\mbox{const}$ hypersurfaces, and present decay results at timelike infinity, near future null infinity, and near the future horizon. Along the way, using the $r_* \to -r_*$ inversion symmetry of the extreme Reissner-Nordström spacetime, we relate the higher multipole Aretakis and Newman-Penrose constants for a massless scalar in this background.

gr-qc↗
arXiv2016

Higher-dimensional lifts of Killing-Yano forms with torsion

Using a Kaluza-Klein-type lift, it is shown how Killing-Yano forms with torsion can remain symmetries of a higher-dimensional geometry, subject to an algebraic condition between the Kaluza-Klein field strength and the Killing-Yano form. The lift condition's significance is highlighted, and is satisfied by examples of black holes in supergravity.

gr-qc↗
arXiv2016

Hidden symmetries of black holes in five-dimensional supergravity

We consider a general charged, rotating black hole in five-dimensional STU supergravity, and show that its six-dimensional Kaluza-Klein lift admits a Killing-Yano 3-form with torsion. This underlies its known Killing tensors in five dimensions, and is related to the separability of torsion-modified Dirac equations. In the generalization to gauged supergravity, we present a five-dimensional Killing-Yano 3-form with torsion when two of the gauge fields are equal, and a Killing-Stackel tensor in the general 3-charge Wu solution.

hep-th↗
arXiv2014

Dyonic AdS black holes in maximal gauged supergravity

We present two new classes of dyonic anti-de Sitter black hole solutions of 4-dimensional maximal N=8, SO(8) gauged supergravity. They are: (1) static black holes of N=2, U(1)^4 gauged supergravity with 4 electric and 4 magnetic charges, with spherical, planar or hyperbolic horizons; and (2) rotating black holes of N=2, U(1)^2 gauged supergravity with 2 electric and 2 magnetic charges. We study their thermodynamics, and point out that the formulation of a consistent thermodynamics for dyonic anti-de Sitter black holes is dependent on the existence of boundary conditions for the gauge fields. We identify several distinct classes of boundary conditions for gauge fields in U(1)^4 supergravity. We study a general family of metrics containing the rotating solutions, and find Killing-Yano tensors with torsion in two conformal frames, which underlie separability.

hep-th↗
arXiv2013

Seed for general rotating non-extremal black holes of N=8 supergravity

We describe the most general asymptotically flat, stationary, non-extremal, dyonic black hole of the four-dimensional N = 2 supergravity coupled to 3 vector multiplets that describes the low-energy regime of the STU model. Under U-dualities, this can be used as a seed to generate all single-centered stationary black holes of N = 8 supergravity. The independent conserved charges are the mass, angular momentum, four electric charges and four magnetic charges; an independent NUT charge can also be added. Several aspects of the black hole are presented, including thermodynamics, the BPS limit, the near-horizon limit in the extremal fast and slow rotating cases, properties of black hole horizons, the existence of Killing tensors and the separability of probe scalars.

hep-th↗
arXiv2011

Single-rotation two-charge black holes in gauged supergravity

We consider asymptotically AdS, non-extremal, charged and rotating black holes with rotation in a single 2-plane and two independent U(1) charge parameters. Using a common ansatz, solutions are found for 5-dimensional U(1)^3 gauged supergravity, 7-dimensional U(1)^2 gauged supergravity, and 6-dimensional U(1) gauged supergravity coupled to matter. We also find static AdS black holes with two U(1) charges of a certain theory in arbitrary dimensions. Some basic properties of the solutions are studied.

hep-th↗
arXiv2011

Two-charge rotating black holes in four-dimensional gauged supergravity

We obtain an asymptotically AdS, non-extremal, electrically charged and rotating black hole solution of 4-dimensional U(1)^4 gauged supergravity with 2 non-zero and independent U(1) charges. The thermodynamical quantities are computed. We find BPS solutions that are nakedly singular. The solution is generalized to include a NUT parameter and dyonic gauge fields. The string frame metric has a rank-2 Killing-Stackel tensor and has completely integrable geodesic motion, and the massless Klein-Gordon equation separates for the Einstein frame metric.

hep-th↗
arXiv2010

Single-charge rotating black holes in four-dimensional gauged supergravity

We consider four-dimensional U(1)^4 gauged supergravity, and obtain asymptotically AdS_4, non-extremal, charged, rotating black holes with one non-zero U(1) charge. The thermodynamic quantities are computed. We obtain a generalization that includes a NUT parameter. The general solution has a discrete symmetry involving inversion of the rotation parameter, and has a string frame metric that admits a rank-2 Killing-Stackel tensor.

hep-th↗
arXiv2010

Symmetries of supergravity black holes

We investigate Killing tensors for various black hole solutions of supergravity theories. Rotating black holes of an ungauged theory, toroidally compactified heterotic supergravity, with NUT parameters and two U(1) gauge fields are constructed. If both charges are set equal, then the solutions simplify, and then there are concise expressions for rank-2 conformal Killing-Stackel tensors. These are induced by rank-2 Killing-Stackel tensors of a conformally related metric that possesses a separability structure. We directly verify the separation of the Hamilton-Jacobi equation on this conformally related metric, and of the null Hamilton-Jacobi and massless Klein-Gordon equations on the "physical" metric. Similar results are found for more general solutions; we mainly focus on those with certain charge combinations equal in gauged supergravity, but also consider some other solutions.

hep-th↗
arXiv2010

Classification of solutions in topologically massive gravity

We study exact solutions of three-dimensional gravity with a cosmological constant and a gravitational Chern-Simons term: the theory known as topologically massive gravity. After reviewing the algebraic classification, we show that if a solution has curvature of algebraic type D, then it is biaxially squashed AdS_3. Applying the classification, we provide a comprehensive review of the literature, showing that most known solutions are locally equivalent to biaxially squashed AdS_3 or to AdS pp-waves.

hep-th↗
arXiv2010

Kundt spacetimes as solutions of topologically massive gravity

We obtain new solutions of topologically massive gravity. We find the general Kundt solutions, which in three dimensions are spacetimes admitting an expansion-free null geodesic congruence. The solutions are generically of algebraic type II, but special cases are types III, N or D. Those of type D are the known spacelike-squashed AdS_3 solutions, and of type N are the known AdS pp-waves or new solutions. Those of types II and III are the first known solutions of these algebraic types. We present explicitly the Kundt solutions that are CSI spacetimes, for which all scalar polynomial curvature invariants are constant, whereas for the general case we reduce the field equations to a series of ordinary differential equations. The CSI solutions of types II and III are deformations of spacelike-squashed AdS_3 and the round AdS_3, respectively.

hep-th↗