Involute, minimal, outer and increasingly trapped surfaces (2009)
Eight different refinements of trapped surfaces are proposed, of three basic types, each intended as potential stability conditions. Minimal trapped surfaces are strictly minimal with respect to the...
Invariance of the Tunnelling Method for Dynamical Black Holes (2009)
Di Criscienzo, Roberto, Hayward, Sean A., Nadalini, Mario, Vanzo, Luciano, Zerbini, Sergio
Previous work on dynamical black hole instability is further elucidated within the Hamilton-Jacobi method for horizon tunnelling and the reconstruction of the classical action by means of the...
Involute, minimal, outer and increasingly trapped spheres (2009)
Seven different refinements of trapped surfaces are proposed, each intended as potential stability conditions. This article concerns spherical symmetry, but each condition can be generalized....
Wormhole dynamics in spherical symmetry (2009)
A dynamical theory of traversable wormholes is detailed in spherical symmetry. Generically a wormhole consists of a tunnel of trapped surfaces between two mouths, defined as temporal outer trapping...
Local temperature for dynamical black holes (2008)
Hayward, Sean A., Di Criscienzo, R., Nadalini, M., Vanzo, L., Zerbini, S.
A local Hawking temperature was recently derived for any future outer trapping horizon in spherical symmetry, using a Hamilton-Jacobi tunneling method, and is given by a dynamical surface gravity as...
Dynamics of black holes (2008)
This is a review of current theory of black-hole dynamics, concentrating on the framework in terms of trapping horizons. Summaries are given of the history, the classical theory of black holes, the...
Energy of gravitational radiation in plane-symmetric space-times (2008)
Gravitational radiation in plane-symmetric space-times can be encoded in a complex potential, satisfying a non-linear wave equation. An effective energy tensor for the radiation is given, taking a...
Abstract. Hellaby & Dray have recently claimed that matter conservation fails under a change of signature, compounding earlier claims that the standard junction conditions for signature change...
Comment on "Comparison of approaches to classical signature change" (2007)
Abstract. This is a comment on a reply to a comment on a paper of Hellaby & Dray, repeating the identification of an important mistake which is still being denied by the authors: their proposed...
Angular momentum conservation for uniformly expanding flows (2006)
Angular momentum has recently been defined as a surface integral involving an axial vector and a twist 1-form, which measures the twisting around of space-time due to a rotating mass. The axial...
Angular momentum conservation for dynamical black holes (2006)
Angular momentum can be defined by rearranging the Komar surface integral in terms of a twist form, encoding the twisting around of space-time due to a rotating mass, and an axial vector. If the...
Conservation laws for dynamical black holes (2006)
An essentially complete new paradigm for dynamical black holes in terms of trapping horizons is presented, including dynamical versions of the physical quantities and laws which were considered...
Angular momentum and conservation laws for dynamical black holes (2006)
Black holes can be practically located (e.g. in numerical simulations) by trapping horizons, hypersurfaces foliated by marginal surfaces, and one desires physically sound measures of their mass and...
Formation and evaporation of non-singular black holes (2005)
Regular (non-singular) space-times are given which describe the formation of a (locally defined) black hole from an initial vacuum region, its quiescence as a static region, and its subsequent...
Gravitational radiation from dynamical black holes (2005)
An effective energy tensor for gravitational radiation is identified for uniformly expanding flows of the Hawking mass-energy. It appears in an energy conservation law expressing the change in mass...
The disinformation problem for black holes (pop version) (2005)
The supposed information paradox for black holes is based on the fundamental misunderstanding that black holes are usefully defined by event horizons. Understood in terms of locally defined trapping...
The disinformation problem for black holes (conference version) (2005)
Basic properties of black holes are explained in terms of trapping horizons. It is shown that matter and information will escape from an evaporating black hole. A general scenario is outlined whereby...
Energy and entropy conservation for dynamical black holes (2004)
The Ashtekar-Krishnan energy-balance law for dynamical horizons, expressing the increase in mass-energy of a general black hole in terms of the infalling matter and gravitational radiation, is...
Construction and enlargement of traversable wormholes from Schwarzschild black holes (2004)
Koyama, Hiroko, Hayward, Sean A.
Analytic solutions are presented which describe the construction of a traversable wormhole from a Schwarzschild black hole, and the enlargement of such a wormhole, in Einstein gravity. The matter...
How to make a traversable wormhole from a Schwarzschild black hole (2004)
Hayward, Sean A., Koyama, Hiroko
The theoretical construction of a traversable wormhole from a Schwarzschild black hole is described, using analytic solutions in Einstein gravity. The matter model is pure phantom radiation (pure...
Energy conservation for dynamical black holes (2004)
An energy conservation law is described, expressing the increase in mass-energy of a general black hole in terms of the energy densities of the infalling matter and gravitational radiation. For a...
Kerr black holes in horizon-generating form (2004)
New coordinates are given which describe non-degenerate Kerr black holes in dual-null foliations based on the outer (or inner) horizons, generalizing the Kruskal form for Schwarzschild black holes....
The light cone at infinity (2003)
A recent refinement of Penrose's conformal framework for asymptotically flat space-times is summarized. The key idea concerns advanced and retarded conformal factors, which allow a rigid description...
Spatial and null infinity via advanced and retarded conformal factors (2003)
A new approach to space-time asymptotics is presented, refining Penrose's idea of conformal transformations with infinity represented by the conformal boundary of space-time. Generalizing examples...
Recent progress in wormhole dynamics (2003)
Space-time wormholes were introduced in Wheeler's idea of space-time foam. Traversible wormholes as defined by Morris & Thorne became popular as potential short cuts across the universe and even time...
Construction and enlargement of dilatonic wormholes by impulsive radiation (2002)
Koyama, Hiroko, Hayward, Sean A., Kim, Sung-Won
The dynamical behavior of traversable wormholes and black holes under impulsive radiation is studied in an exactly soluble dilaton gravity model. Simple solutions are presented where a traversable...
Fate of the first traversible wormhole: black-hole collapse or inflationary expansion (2002)
Shinkai, Hisa-aki, Hayward, Sean A.
We study numerically the stability of Morris & Thorne's first traversible wormhole, shown previously by Ellis to be a solution for a massless ghost Klein-Gordon field. Our code uses a dual-null...
Black holes and traversible wormholes: a synthesis (2002)
A unified framework for black holes and traversible wormholes is described, where both are locally defined by outer trapping horizons, two-way traversible for wormholes and one-way traversible for...
Wormholes supported by pure ghost radiation (2002)
Traversible wormhole space-times are found as static, spherically symmetric solutions to the Einstein equations with ingoing and outgoing pure ghost radiation, i.e. pure radiation with negative...
Dilatonic wormholes: construction, operation, maintenance and collapse to black holes (2001)
Hayward, Sean A., Kim, Sung-Won, Lee, Hyunjoo
The CGHS two-dimensional dilaton gravity model is generalized to include a ghost Klein-Gordon field, i.e. with negative gravitational coupling. This exotic radiation supports the existence of static...
Comment on `An extreme critical space-time: echoing and black-hole perturbations' (2001)
Clement, Gerard, Hayward, Sean A.
We show that the black hole perturbations of the Hayward static solution to the massless Einstein-Klein-Gordon equations are actually gauge artifacts resulting from the linearization of a coordinate...
Gravitational-wave dynamics and black-hole dynamics: second quasi-spherical approximation (2001)
Gravitational radiation with roughly spherical wavefronts, produced by roughly spherical black holes or other astrophysical objects, is described by an approximation scheme. The first quasi-spherical...
Gravitational radiation, energy and reaction on quasi-spherical black holes (2000)
Gravitational radiation is locally defined where the wavefronts are roughly spherical. A local energy tensor is defined for the gravitational radiation. Including this energy tensor as a source in...
Quasi-spherical approximation for rotating black holes (2000)
Shinkai, Hisa-aki, Hayward, Sean A.
We numerically implement a quasi-spherical approximation scheme for computing gravitational waveforms for coalescing black holes, testing it against angular momentum by applying it to Kerr black...
Black holes: new horizons (2000)
This is a review of current black-hole theory, concentrating on local, dynamical aspects.
Gravitational energy as Noether charge (2000)
A definition of gravitational energy is proposed for any theory described by a diffeomorphism-invariant Lagrangian. The mathematical structure is a Noether- current construction of Wald involving the...
An extreme critical space-time: echoing and black-hole perturbations (2000)
A homothetic, static, spherically symmetric solution to the massless Einstein- Klein-Gordon equations is described. There is a curvature singularity which is central, null, bifurcate and marginally...
Gravitational waves from quasi-spherical black holes (2000)
A quasi-spherical approximation scheme, intended to apply to coalescing black holes, allows the waveforms of gravitational radiation to be computed by integrating ordinary differential equations.
Gravitational waves, black holes and cosmic strings in cylindrical symmetry (1999)
Gravitational waves in cylindrically symmetric Einstein gravity are described by an effective energy tensor with the same form as that of a massless Klein- Gordon field, in terms of a gravitational...
Quasi-local first law of black-hole dynamics (1999)
Mukohyama, Shinji, Hayward, Sean A.
A property well known as the first law of black hole is a relation among infinitesimal variations of parameters of stationary black holes. We consider a dynamical version of the first law, which may...
How much negative energy does a wormhole need? (1999)
Ida, Daisuke, Hayward, Sean A.
It is known that traversible wormholes require negative energy density. We here argue how much negative energy is needed for wormholes, using a local analysis which does not assume any symmetry. and...
Boundary Terms and Noether Current of Sphereical Black Holes (1998)
Ashworth, Michael C., Hayward, Sean A.
We consider two proposals for defining black hole entropy in spherical symmetry, where the horizon is defined locally as a trapping horizon. The first case, boundary terms in a dual-null form of the...
Dynamic black-hole entropy (1998)
Hayward, Sean A., Mukohyama, Shinji, Ashworth, M. C.
We consider two non-statistical definitions of entropy for dynamic (non-stationary) black holes in spherical symmetry. The first is analogous to the original Clausius definition of thermodynamic...
Inequalities relating area, energy, surface gravity and charge of black holes (1998)
The Penrose-Gibbons inequality for charged black holes is proved in spherical symmetry, assuming that outside the black hole there are no current sources, meaning that the charge e is constant, with...
A new framework is proposed for general dynamic wormholes, unifying them with black holes. Both are generically defined locally by outer trapping horizons, temporal for wormholes and spatial or null...
Relativistic thermodynamics (1998)
A generally relativistic theory of thermodynamics is developed, based on four main physical principles: heat is a local form of energy, therefore described by a thermal energy tensor; conservation of...
Unified first law of black-hole dynamics and relativistic thermodynamics (1997)
A unified first law of black-hole dynamics and relativistic thermodynamics is derived in spherically symmetric general relativity. This equation expresses the gradient of the active gravitational...
Comment on "Comparison of approaches to classical signature change" (1996)
This is a comment on a reply (gr-qc/9601040) to a comment (gr-qc/9606045) on a paper of Hellaby & Dray (gr-qc/9404001), repeating the identification of an important mistake which is still being...
Comment on "Failure of standard conservation laws at a classical change of signature" (1996)
Hellaby & Dray (gr-qc/9404001) have recently claimed that matter conservation fails under a change of signature, compounding earlier claims that the standard junction conditions for signature change...
Complex lapse, complex action and path integrals (1995)
Imaginary time is often used in quantum tunnelling calculations. This article advocates a conceptually sounder alternative: complex lapse. In the ``3+1'' action for the Einstein gravitational field...
Signature Change at Material Layers and Step Potentials (1995)
For a contravariant 4-metric which changes signature from Lorentzian to Riemannian across a spatial hypersurface, the mixed Einstein tensor is manifestly non-singular. In Gaussian normal coordinates,...
COMMENT ON ``BOUNDARY CONDITIONS FOR THE SCALAR FIELD IN THE PRESENCE OF SIGNATURE CHANGE'' (1995)
Fundamental errors exist in the above-mentioned article, which attempts to justify previous erroneous claims concerning signature change. In the simplest example, the authors' proposed ``solutions''...
Gravitational Energy in Spherical Symmetry (1994)
Various properties of the Misner-Sharp spherically symmetric gravitational energy E are established or reviewed. In the Newtonian limit of a perfect fluid, E yields the Newtonian mass to leading...
Spin-Coefficient Form of the New Laws of Black-Hole Dynamics (1994)
General laws of black-hole dynamics, some of which are analogous to the laws of thermodynamics, have recently been found for a general definition of black hole in terms of a future outer trapping...
Quasi-Localisation of Bondi-Sachs Energy Loss (1994)
A formula is given for the variation of the Hawking energy along any one-parameter foliation of compact spatial 2-surfaces. A surface for which one null expansion is positive and the other negative...
Confinement by Black Holes (1994)
The question of whether an observer can escape from a black hole is addressed, using a recent general definition of a black hole in the form of a future outer trapping horizon. An observer on a...
A Cosmological Constant Limits the Size of Black Holes (1993)
Hayward, Sean A., Shiromizu, Tetsuya, Nakao, Ken-ichi
In a space-time with cosmological constant $\Lambda>0$ and matter satisfying the dominant energy condition, the area of a black or white hole cannot exceed $4\pi/\Lambda$. This applies to event...
On the Definition of Averagely Trapped Surfaces (1993)
Previously suggested definitions of averagely trapped surfaces are not well-defined properties of 2-surfaces, and can include surfaces in flat space-time. A natural definition of averagely trapped...
Global Structure of a Black-Hole Cosmos and its Extremes (1993)
Brill, Dieter R., Hayward, Sean A.
We analyze the global structure of a family of Einstein-Maxwell solutions parametrized by mass, charge and cosmological constant. In a qualitative classification there are: (i) generic black-hole...
Junction Conditions for Signature Change (1993)
The change of signature of a metric is explained using simple examples and methods. The Klein-Gordon field on a signature-changing background is discussed, and it is shown how the approach of Dray et...
Quasi-Local Gravitational Energy (1993)
A dynamically preferred quasi-local definition of gravitational energy is given in terms of the Hamiltonian of a `2+2' formulation of general relativity. The energy is well-defined for any compact...
General Laws of Black-Hole Dynamics (1993)
A general definition of a black hole is given, and general `laws of black-hole dynamics' derived. The definition involves something similar to an apparent horizon, a trapping horizon, defined as a...
On Cosmological Isotropy, Quantum Cosmology and the Weyl Curvature Hypothesis (1992)
The increasing entropy, large-scale isotropy and approximate flatness of the universe are considered in the context of signature change, which is a classical model of quantum tunnelling in quantum...
Cosmic Censorship in 2-Dimensional Dilaton Gravity (1992)
The global structure of 2-dimensional dilaton gravity is studied, attending in particular to black holes and singularities. A gravitational energy is defined and shown to be positive at spatial...
The collision of plane waves in general relativity. (1990)
Thesis (Ph. D.)--University of Southampton, 1990.