Dilatonic wormholes: construction, operation, maintenance and collapse to black holes

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 traversible wormhole solutions, analogous to Morris-Thorne wormholes. Since the field equations are explicitly integrable, concrete examples can be given of various dynamic wormhole processes, as follows. (i) Static wormholes are constructed by irradiating an initially static black hole with the ghost field. (ii) The operation of a wormhole to transport matter or radiation between the two universes is described, including the back-reaction on the wormhole, which is found to exhibit a type of neutral stability. (iii) It is shown how to maintain an operating wormhole in a static state, or return it to its original state, by turning up the ghost field. (iv) If the ghost field is turned off, either instantaneously or gradually, the wormhole collapses into a black hole.Comment: 9 pages, 7 figure

Unified first law of black-hole dynamics and relativistic thermodynamics

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 energy E according to the Einstein equation, divided into energy-supply and work terms. Projecting the equation along the flow of thermodynamic matter and along the trapping horizon of a blackhole yield, respectively, first laws of relativistic thermodynamics and black-hole dynamics. In the black-hole case, this first law has the same form as the first law of black-hole statics, with static perturbations replaced by the derivative along the horizon. There is the expected term involving the area and surface gravity, where the dynamic surface gravity is defined as in the static case but using the Kodama vector and trapping horizon. This surface gravity vanishes for degenerate trapping horizons and satisfies certain expected inequalities involving the area and energy. In the thermodynamic case, the quasi-local first law has the same form, apart from a relativistic factor, as the classical first law of thermodynamics, involving heat supply and hydrodynamic work, but with E replacing the internal energy. Expanding E in the Newtonian limit shows that it incorporates the Newtonian mass, kinetic energy, gravitational potential energy and thermal energy. There is also a weak type of unified zeroth law: a Gibbs-like definition of thermal equilibrium requires constancy of an effective temperature, generalising the Tolman condition and the particular case of Hawking radiation, while gravithermal equilibrium further requires constancy of surface gravity. Finally, it is suggested that the energy operator of spherically symmetric quantum gravity is determined by the Kodama vector, which encodes a dynamic time related to E.Comment: 18 pages, TeX, expanded somewhat, to appear in Class. Quantum Gra

Fractional Quantum Hall Physics in Jaynes-Cummings-Hubbard Lattices

Jaynes-Cummings-Hubbard arrays provide unique opportunities for quantum emulation as they exhibit convenient state preparation and measurement, and in-situ tuning of parameters. We show how to realise strongly correlated states of light in Jaynes-Cummings-Hubbard arrays under the introduction of an effective magnetic field. The effective field is realised by dynamic tuning of the cavity resonances. We demonstrate the existence of Fractional Quantum Hall states by com- puting topological invariants, phase transitions between topologically distinct states, and Laughlin wavefunction overlap.Comment: 5 pages, 3 figure

Dynamic wormholes

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 for black and white holes. Thus wormhole horizons are two-way traversible, while black-hole and white-hole horizons are only one-way traversible. It follows from the Einstein equation that the null energy condition is violated everywhere on a generic wormhole horizon. It is suggested that quantum inequalities constraining negative energy break down at such horizons. Wormhole dynamics can be developed as for black-hole dynamics, including a reversed second law and a first law involving a definition of wormhole surface gravity. Since the causal nature of a horizon can change, being spatial under positive energy and temporal under sufficient negative energy, black holes and wormholes are interconvertible. In particular, if a wormhole's negative-energy source fails, it may collapse into a black hole. Conversely, irradiating a black-hole horizon with negative energy could convert it into a wormhole horizon. This also suggests a possible final state of black-hole evaporation: a stationary wormhole. The new framework allows a fully dynamical description of the operation of a wormhole for practical transport, including the back-reaction of the transported matter on the wormhole. As an example of a matter model, a Klein-Gordon field with negative gravitational coupling is a source for a static wormhole of Morris & Thorne.Comment: 5 revtex pages, 4 eps figures. Minor change which did not reach publisher

A complete distribution of redshifts for sub-millimetre galaxies in the SCUBA-2 Cosmology Legacy Survey UDS field

This is a pre-copyedited, author-produced PDF of an article accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review. Available online at https://doi.org/10.1093/mnras/stx1689. © 2017 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.Sub-milllimetre galaxies (SMGs) are some of the most luminous star-forming galaxies in the Universe, however their properties remain hard to determine due to the difficulty of identifying their optical\slash near-infrared counterparts. One of the key steps to determining the nature of SMGs is measuring a redshift distribution representative of the whole population. We do this by applying statistical techniques to a sample of 761 850$\mu$m sources from the SCUBA-2 Cosmology Legacy Survey observations of the UKIDSS Ultra-Deep Survey (UDS) Field. We detect excess galaxies around $> 98.4$ per cent of the 850$\mu$m positions in the deep UDS catalogue, giving us the first 850$\mu$m selected sample to have virtually complete optical\slash near-infrared redshift information. Under the reasonable assumption that the redshifts of the excess galaxies are representative of the SMGs themselves, we derive a median SMG redshift of $z = 2.05 \pm 0.03$, with 68 per cent of SMGs residing between $1.07Peer reviewedFinal Accepted Versio

An extreme critical space-time: echoing and black-hole perturbations

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 trapped. The space-time is therefore extreme in the sense of lying at the threshold between black holes and naked singularities, just avoiding both. A linear perturbation analysis reveals two types of dominant mode. One breaks the continuous self-similarity by periodic terms reminiscent of discrete self-similarity, with echoing period within a few percent of the value observed numerically in near-critical gravitational collapse. The other dominant mode explicitly produces a black hole, white hole, eternally naked singularity or regular dispersal, the latter indicating that the background is critical. The black hole is not static but has constant area, the corresponding mass being linear in the perturbation amplitudes, explicitly determining a unit critical exponent. It is argued that a central null singularity may be a feature of critical gravitational collapse.Comment: 6 revtex pages, 6 eps figure

On the semiclassical treatment of Hawking radiation

In the context of the semiclassical treatment of Hawking radiation we prove the universality of the reduced canonical momentum for the system of a massive shell self gravitating in a spherical gravitational field within the Painlev\'e family of gauges. We show that one can construct modes which are regular on the horizon both by considering as hamiltonian the exterior boundary term and by using as hamiltonian the interior boundary term. The late time expansion is given in both approaches and their time Fourier expansion computed to reproduce the self reaction correction to the Hawking spectrum.Comment: 18 pages, LaTeX, Corrected typo

Talking Appalachian: Voice, Identity, and Community

Tradition, community, and pride are fundamental aspects of the history of Appalachia, and the language of the region is a living testament to its rich heritage. Despite the persistence of unflattering stereotypes and cultural discrimination associated with their style of speech, Appalachians have organized to preserve regional dialects—complex forms of English peppered with words, phrases, and pronunciations unique to the area and its people. Talking Appalachian examines these distinctive speech varieties and emphasizes their role in expressing local history and promoting a shared identity. Beginning with a historical and geographical overview of the region that analyzes the origins of its dialects, this volume features detailed research and local case studies investigating their use. The contributors explore a variety of subjects, including the success of African American Appalachian English and southern Appalachian English speakers in professional and corporate positions. In addition, editors Amy D. Clark and Nancy M. Hayward provide excerpts from essays, poetry, short fiction, and novels to illustrate usage. With contributions from well-known authors such as George Ella Lyon and Silas House, this balanced collection is the most comprehensive, accessible study of Appalachian language available today. Amy D. Clark is professor of English and co-director of the Center for Appalachian Studies at the University of Virginia’s College at Wise. Nancy M. Hayward is professor emeritus of English at the Indiana University of Pennsylvania. This book fills a need in college and secondary classrooms in a unique and exciting way—examining a stigmatized, regional variety that also serves as a strong indicator of in-group membership and identity for many (but not all) of its speakers through the use of both research studies and essays/literary excerpts. This is an ambitious project that will serve students, researchers, and instructors for many years to come. -- Jim Michnowicz, North Carolina State University Clark and Hayward are to be praised for assembling a well-ordered broad spectrum of conversant essays and literary pieces that stand to bring the study, understanding, and appreciation of Appalachian English(es) into a new era of cultivation. -- Chris Green, Director, Loyal Jones Appalachian Center, Berea College Talking Appalachian is a wonderful collection, challenging readers to learn about the many histories that have shaped Appalachian dialectical diversity and to gain tools to counter the linguistic chauvinism that has used Appalachian dialect as a stand-in for other powerful forms of social and economic marginalization, akin to the ways speakers of Gullah and other regional dialects have been marginalized in the U.S.. The excellent use of leading linguistic scholarship, essays, fiction and poetry in this volume makes it a powerful contribution. -- Ann Kingsolver, director of the Appalachian Center at the University of Kentucky This unique book creates an understanding and acceptance of the Appalachian vernacular as an expression of history, identity, and space. Includes bibliographies, index, and short biographies of the contributors. -- Claudene Sproles -- Kentucky Libraries Beginning with a historical and geographical overview of the region that analyzes the origins of its dialects, this volume features detailed research and local case studies investigating their use. . . . With contributions from well-known authors such as George Ella Lyon and Silas House, this balanced collection is the most comprehensive accessible study of Appalachian language available today. -- Paintsville Herald A sense of pride, a strong grip on old traditions, and a unique style of commonality are part of both the marvel and mystery of Appalachia. Talking Appalachia: Voice, Identity, and Community (University Press of Kentucky), edited by Amy D. Clark and Nancy M. Hayward, complies scholarly writing about this area from contributors in a variety of professional disciplines as well as Appalachian writers, including Silas House, Jane Hicks, George Ella Lyon, Ron Rash, and Lee Smith. -- Ina Hughs -- Knoxville News Sentinel An intimate view of regional American language and literature. -- Choice Winner of the Appalachian Writers\u27 Association Book of the Year for Poetry One part qualitative research, another part fiction, Talking Appalachian: Voice, Identity, and Community is an important contribution to ongoing conversations about the Appalachian region. [. . . ] [T]hey add fresh insight to and reiterate or refute some of the old arguments about teaching vernacular-speaking students. -- West Virginia Historyhttps://uknowledge.uky.edu/upk_appalachian_studies/1026/thumbnail.jp