arXiv subjects

C. N. Pope

Publications and source records attributed to C. N. Pope.

At least 19 recordsLinked to original sources

arXiv2025

On The Consistent Supersymmetric Reduction Of Heterotic Supergravity With Geometrically Arising Yang-Mills Symmetries

In the paper arXiv:2501.04771, a novel compactification of heterotic supergravity on a warped product of $\R\times T^{1,1}$ was constructed, where $T^{1,1}$ is a five-dimensional coset space $(SU(2)\times SU(2))/U(1)$. It was shown that this admits a four dimensional Minkowski vacuum solution with ${\cal N}=1$ supersymmetry, and furthermore that in the bosonic sector there exists a remarkable fully consistent truncation in which the gauge bosons of the $SU(2)\times SU(2)$ isometries of the $T^{1,1}$ are retained. In this paper, we examine this reduction further, and show that the consistency can be extended to include the fermionic sector also. Thus the heterotic theory admits a consistent reduction to give an ungauged ${\cal N}=1$ supergravity coupled to $SU(2)\times SU(2)$ Yang-Mills multiplets and a scalar multiplet.

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arXiv2025

$\text{Spin}^h$ Structure, Scalar and Charged Spinor Eigenfunctions on the $SU(3)/SO(3)$ Wu Manifold

Generalised spin structures are necessary for placing fermions on manifolds that do not admit a standard spin structure. This is especially relevant in a dimensional reduction on such a manifold, which can then be compensated by using fermions that are appropriately charged under some Maxwell or Yang-Mills field defined on the internal manifold. A well known example in the physics literature is $\mathbb{CP}^2$, which has four real dimensions and is the coset $SU(3)/U(2)$. In this paper we focus on a five-dimensional coset space, namely the Wu manifold $SU(3)/SO(3)_{\rm max}$, where $SO(3)_{\rm max}$ is maximal in $SU(3)$. Intriguingly, the Wu manifold does not admit a spin structure or spin$^c$ structure, it does admit a spin$^h$ structure. We provide a physical interpretation of the spin$^h$ structure by considering spinors that are coupled to an $SO(3)$ Yang-Mills field defined on the Wu manifold, but which carry half-integer "isospin," thereby canceling the minus sign in the holonomy for uncharged spinors that provides the original obstruction to an ordinary spin structure. We also construct a gauge-covariantly constant spinor in the Wu manifold, and we show how this can be employed in order to construct spin$^h$ spinor harmonics from scalar harmonics. We provide a very explicit construction of all the scalar and spin$^h$ harmonics. In a follow-up paper, we shall employ the results we obtain here in order to discuss dimensional reductions and consistent reductions on the Wu manifold.

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arXiv2025

A Global Isometric Embedding of the Reissner-Nordstr\"om Metric into Pseudo-Euclidean Spacetime

The event horizon of the Schwarzschild black hole has been well studied and the singular behavior of the Schwarzschild metric on horizon is understood as a coordinate singularity rather than an essential singularity. One demonstration of this non-singular behavior on horizon was provided by Fronsdal in 1959, by finding a global isometric embedding of the Schwarzschild metric into a six-dimensional pseudo-Euclidean spacetime. Isometric embeddings for the Reissner-Nordstr\"om metric have also been constructed, but they only embed the region external to the inner horizon or in a single Eddington-Finkelstein patch. This paper presents a global isometric embedding for the maximally extended Reissner-Nordstr\"om spacetime into a nine-dimensional pseudo-Euclidean spacetime. We present the solution in terms of explicit local four-dimensional coordinates, and also as a level-set of functions of the higher-dimensional embedding spacetime. While the Reissner-Nordstr\"om embedding presented has several similarities to the Fronsdal embedding of the Schwarzschild metric, the presence of the second horizon requires additional embedding coordinates and terms not found in the Fronsdal embedding, in order that the embedding is defined and finite on each horizon.

gr-qc↗

arXiv2025

Perturbations of Black Holes in Einstein-Maxwell-Dilaton-Axion (EMDA) Theories

We extend our earlier work on the linearised perturbations of static black holes in Einstein-Maxwell-Dilaton (EMD) theories to the case where the black holes are solutions in an enlarged theory including also an axion. We study the perturbations in a 3-parameter family of such EMDA theories. The systems of equations describing the linearised perturbations can always be separated, but they can only be decoupled when the three parameters are restricted to a 1-parameter family of EMDA theories, characterised by a parameter $b$ that determines the coupling of the axion to the $\epsilon^{\mu\nu\rho\sigma}\, F_{\mu\nu}\, F_{\rho\sigma}$ term. In the specific case when $b=1$, the theory is related to an ${\cal N}=2$ supergravity. In this one case we find that the perturbations in the axial and the polar sectors are related by a remarkable transformation, which generalises one found by Chandrasekhar for the perturbations of Reissner-Nordstr\"om in Einstein-Maxwell theory. This transformation is of a form found in supersymmetric quantum mechanical models. The existence of such mappings between the axial and polar perturbations appears to correlate with those cases where there is an underlying supergravity supporting the solution, even though the black hole backgrounds are non-extremal and therefore not supersymmetric. We prove the mode stability of the static black hole solutions in the supersymmetric EMDA theory. For other values of the parameter $b$ in the EMDA theories that allow decoupling of the modes, we find that one of the radial potentials can be negative outside the horizon if $b$ is sufficiently large, raising the possibility of there being perturbative mode instabilities in such a case.

hep-th↗

arXiv2025

Kaluza-Klein Supergravity 2025

We recall our work in the 1980s taking seriously the maximal eleven dimensions of supergravity, in particular the round, left squashed and right squashed $S^7$ compactifications to $D=4$ yielding $\mathcal N=8$, $\mathcal N=1$ and $\mathcal N=0$, respectively. This involved Kaluza-Kein techniques that have found wider applications such as spontaneous compactification, holonomy and supersymmetry, topology versus geometry, squashing and Higgs, vacuum stability and consistent truncations.

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arXiv2024

On The Perturbations of Gibbons-Maeda Black Holes in Einstein-Maxwell-Dilaton Theories

The study of perturbations around black hole backgrounds in general relativity and Einstein-Maxwell theory has a long history, going back to the work of Regge and Wheeler in the 1950s. As part of a broader investigation of perturbations around black holes in supergravity, we describe here our results for the perturbations around the Gibbons-Maeda static charged black holes in a class of Einstein-Maxwell-Dilaton theories. Our analysis follows the general strategy developed by Chandrasekhar and Xanthopoulos for the perturbations of the Reissner-Nordström black hole. Here, the analysis is considerably more involved, because of the presence of the dilaton field, which couples to the other polar modes. We nonetheless find that the problem is completely solvable, in the sense that one can separate variables and eventually describe all the perturbations in terms of diagonalised second-order radial equations. We are able to prove the mode stability of all the Gibbons-Maeda black hole solutions.

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arXiv2023

Introduction to the special issue dedicated to Michael J. Duff FRS on the occasion of his 70th birthday

This special feature, dedicated to Michael J. Duff FRS on the occasion of his 70th birthday, concerns topics in 'Quantum gravity, branes and M-theory'. These three intertwining subjects have been central to Duff's work; indeed many of his contributions have come to define significant aspects of what we actually mean by these terms. From the discovery of Weyl anomalies to recognising superstrings in 10 dimensions as a special case of membranes in an 11-dimensional M-theory, Duff's insights have shaped major developments across these themes. So it is an apposite setting for such a celebration and we are delighted to be able to include in this collection contributions from many of the pioneers of quantum gravity, branes and M-theory. The breadth of these topics has placed little constraint on the multiplicity of ideas appearing in these pages, from astrophysical black holes to chaotic condensed matter. Again, this is fitting as Duff's scientific remit spans a remarkable diversity of motifs, from the fundamentals of M-theory to entanglement in quantum information.

physics.hist-ph↗

arXiv2023

De-Higgsing In Eleven-Dimensional Supergravity On The Squashed $S^7$

In this paper we construct the subset of modes on $S^7$ that are relevant in the compactification of eleven-dimensional supergravity on a squashed $S^7$ when restricted to the sector that comprises singlets under the $Sp(1)\times Sp(2)$ isometry of the squashed sphere. Some of the properties of these modes, connected to the transition from the round $S^7$ to the squashed $S^7$, are analysed in detail. Special features of the Rarita-Schwinger operator, described in earlier work by Buchdahl, are explained and related to properties of the squashed $S^7$ operator spectrum obtained in previous work by the authors. We then discuss how the singlet modes give rise to supermultiplets in the left-squashed case, the phenomenon of de-Higgsing, and what happens to the AdS$_4$ fields in these supermultiplets under an orientation reversal (``skew-whiffing'') of the squashed $S^7$. Finally, we consider the possible choices of boundary conditions that appear for some of these fields in AdS$_4$ in the case of the right-squashed non-supersymmetric compactification, and how these choices may affect the stability of the gravity theory.

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arXiv2022

BRST Symmetry and the Convolutional Double Copy

Motivated by the results of Anastasiou et al., we consider the convolutional double copy for BRST and anti-BRST covariant formulations of gravitational and gauge theories in more detail. We give a general BRST and anti-BRST invariant formulation of linearised $\mathcal{N}=0$ supergravity using superspace methods and show how this may be obtained from the square of linearised Yang-Mills theories. We demonstrate this relation for the Schwarzschild black hole and the ten-dimensional black string solution as two concrete examples.

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arXiv2022

Mode Stability For Massless Scalars In Five-Dimensional Black Hole Backgrounds

The mode stability of the Kerr black hole in four dimensions was demonstrated by Whiting in 1989, by separating the Teukolsky equation that describes gravitational perturbations and then transforming the radial and angular equations in such a way that the problem can be reformulated as a wave equation in an auxiliary spacetime in which the proof of stability is greatly simplified, owing to the absence of an ergoregion. As a preliminary step towards extending these ideas to higher-dimensional black holes, we study the mode stability of the massless scalar wave equation in the five-dimensional black hole solutions of Einstein gravity and supergravity. We show how the wave equation can again be mapped into one in an auxiliary spacetime in which there is no ergoregion, allowing us to give a proof of the mode stability of the solutions of the scalar wave equation.

gr-qc↗

arXiv2022

Long-Range Forces Between Non-Identical Black Holes With Non-BPS Extremal Limits

Motivated by recent studies of long-range forces beween identical black holes, we extend these considerations by investigating the forces between two non-identical black holes. We focus on classes of theories where charged black holes can have extremal limits that are not BPS. These theories, which live in arbitrary spacetime dimension, comprise gravity coupled to $N$ 2-form field strengths and $(N-1)$ scalar fields. In the solutions we consider, each field strength carries an electric charge. The black hole solutions are governed by the $SL(N+1,R)$ Toda equations. In four dimensions the black-hole solutions in the $SL(3,R)$ example are equivalent to the "Kaluza-Klein dyons." We find that any pair of such extremal black holes that are not identical (up to overall scaling) repel one another. We also show that there can exist pairs of non-extremal, non-identical black holes which obey a zero-force condition. Finally, we find indications of similar results in the higher examples, such as $SL(4,R)$.

hep-th↗

arXiv2021

Asymptotic Weyl Double Copy

A characteristic value formulation of the Weyl double copy leads to an asymptotic formulation. We find that the Weyl double copy holds asymptotically in cases where the full solution is algebraically general, using rotating STU supergravity black holes as an example. The asymptotic formulation provides clues regarding the relation between asymptotic symmetries that follows from the double copy. Using the C-metric as an example, we show that a previous interpretation of this gravity solution as a superrotation has a single copy analogue relating the appropriate Liénard-Wiechert potential to a large gauge transformation.

hep-th↗

arXiv2021

Supergravity Black Holes, Love Numbers and Harmonic Coordinates

To perform realistic tests of theories of gravity, we need to be able to look beyond general relativity and evaluate the consistency of alternative theories with observational data from, especially, gravitational wave detections using, for example, an agnostic Bayesian approach. In this paper we further examine properties of one class of such viable, alternative theories, based on metrics arising from ungauged supergravity. In particular, we examine the massless, neutral, minimally coupled scalar wave equation in a general stationary, axisymmetric background metric such as that of a charged rotating black hole, when the scalar field is either time independent or in the low-frequency, near-zone limit, with a view to calculating the Love numbers of tidal perturbations, and of obtaining harmonic coordinates for the background metric. For a four-parameter family of charged asymptotically flat rotating black hole solutions of ungauged supergravity theory known as STU black holes, which includes Kaluza-Klein black holes and the Kerr-Sen black hole as special cases, we find that all time-independent solutions, and hence the harmonic coordinates of the metrics, are identical to those of the Kerr solution. In the low-frequency limit we find the scalar fields exhibit the same $SL(2,R)$ symmetry as holds in the case of the Kerr solution. We point out extensions of our results to a wider class of metrics, which includes solutions of Einstein-Maxwell-Dilaton theory.

gr-qc↗

arXiv2021

Conformal Symmetries for Extremal Black Holes with General Asymptotic Scalars in STU Supergravity

We present a construction of the most general BPS black holes of STU supergravity (${\cal N}=2$ supersymmetric $D=4$ supergravity coupled to three vector super-multiplets) with arbitrary asymptotic values of the scalar fields. These solutions are obtained by acting with a subset of of the global symmetry generators on STU BPS black holes with zero values of the asymptotic scalars, both in the U-duality and the heterotic frame. The solutions are parameterized by fourteen parameters: four electric and four magnetic charges, and the asymptotic values of the six scalar fields. We also present BPS black hole solutions of a consistently truncated STU supergravity, which are parameterized by two electric and two magnetic charges and two scalar fields. These latter solutions are significantly simplified, and are very suitable for further explicit studies. We also explore a conformal inversion symmetry of the Couch-Torrence type, which maps any member of the fourteen-parameter family of BPS black holes to another member of the family. Furthermore, these solutions are expected to be valuable in the studies of various swampland conjectures in the moduli space of string compactifications.

hep-th↗

arXiv2021

Subleading BMS charges and fake news near null infinity

In this paper we establish a relation between the non-linearly conserved Newman-Penrose charges and certain subleading terms in a large-$r$ expansion of the BMS charges in an asymptotically-flat spacetime. We define the subleading BMS charges by considering a $1/r$-expansion of the Barnich-Brandt prescription for defining asymptotic charges in an asymptotically-flat spacetime. At the leading order, i.e. $1/r^0$, one obtains the standard BMS charges, which would be integrable and conserved in the absence of a flux term at null infinity, corresponding to gravitational radiation, or Bondi news. At subleading orders, analogous terms in general provide obstructions to the integrability of the corresponding charges. Since the subleading terms are defined close to null infinity, but vanish actually at infinity, the analogous obstructions are not associated with genuine Bondi news. One may instead describe them as corresponding to "fake news." At order $r^{-3}$, we find that a set of integrable charges can be defined and that these are related to the ten non-linearly conserved Newman-Penrose charges.

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arXiv2021

Tower of subleading dual BMS charges

We supplement the recently found dual gravitational charges with dual charges for the whole BMS symmetry algebra. Furthermore, we extend the dual charges away from null infinity, defining subleading dual charges. These subleading dual charges complement the subleading BMS charges in the literature and together account for all the Newman-Penrose charges.

hep-th↗

arXiv2021

Dual gravitational charges and soft theorems

We consider the consequences of the dual gravitational charges for the phase space of radiating modes, and find that they imply a new soft NUT theorem. In particular, we argue that the existence of these new charges removes the need for imposing boundary conditions at spacelike infinity that would otherwise preclude the existence of NUT charges.

hep-th↗

arXiv2021

Taub-NUT from the Dirac monopole

Writing the metric of an asymptotically flat spacetime in Bondi coordinates provides an elegant way of formulating the Einstein equation as a characteristic value problem. In this setting, we find that a specific class of asymptotically flat spacetimes, including stationary solutions, contains a Maxwell gauge field as free data. Choosing this gauge field to correspond to the Dirac monopole, we derive the Taub-NUT solution in Bondi coordinates.

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