677,187 research outputs found
Proof of a generalized Geroch conjecture for the hyperbolic Ernst equation
We enunciate and prove here a generalization of Geroch's famous conjecture
concerning analytic solutions of the elliptic Ernst equation. Our
generalization is stated for solutions of the hyperbolic Ernst equation that
are not necessarily analytic, although it can be formulated also for solutions
of the elliptic Ernst equation that are nowhere axis-accessible.Comment: 75 pages (plus optional table of contents). Sign errors in elliptic
case equations (1A.13), (1A.15) and (1A.25) are corrected. Not relevant to
proof contained in pape
Extending Sibgatullin's ansatz for the Ernst potential to generate a richer family of axially symmetric solutions of Einstein's equations
The scope of this talk is to present some preliminary results on an effort,
currently in progress, to generate an exact solution of Einstein's equation,
suitable for describing spacetime around a rotating compact object.
Specifically, the form of the Ernst potential on the symmetry axis and its
connection with the multipole moments is discussed thoroughly. The way to
calculate the multipole moments of spacetime directly from the value of the
Ernst potential on the symmetry axis is presented. Finally, a mixed ansatz is
formed for the Ernst potential including parameters additional to the ones
dictated by Sibgatullin. Thus, we believe that this talk can also serve as a
comment on choosing the appropriate ansatz for the Ernst potential.Comment: Talk given in the 11th Conference on Recent Developments in Gravity,
2-5 June 2004, Lesbos, Greec
Matrix Ernst Potentials and Orthogonal Symmetry for Heterotic String in Three Dimensions
A new matrix representation for low-energy limit of heterotic string theory
reduced to three dimensions is considered. The pair of matrix Ernst Potentials
uniquely connected with the coset matrix is derived. The action of the symmetry
group on the Ernst potentials is established.Comment: 10 pages in LaTe
Max Ernst and the Aesthetic of Commercial Tourism: Max Among Some of His Favorite Dolls
abstract: "Max Ernst and the Aesthetic of Commercial Tourism: Max Among His Favorite Dolls" examines Surrealist artist Max Ernst's practice of collecting Hopi and Zuni kachina figurines. Ernst, like some other European Surrealists, was an avid collector of Native Amercian material culture and ceremonial hardware. Surrealists interest in Indigenous material was part of a larger program to destabilize European privileging of the mind and art as rational constructs.
This paper focuses on James Thrall Soby's 1941 photograph of Ernst surrounded by his collection of kachina figurine, which was first published in the April edition of View Magazine. As Soby's portrait of Ernst has been reproduced many times over course of the past six decades, it has become an emblem of the Surrealists general interest in Native Americana.
In contrast to vanguardism with which Ernst and other Surrealist's collecting practices is usually credited, this paper examines Soby portrait of Ernst's within practices of commercial tourism and the souvenir industry in the Southwest. By the mid 1940s, Hopi and Zuni kachina figurine makers had a well-developed commercial kachina figurine industry that targeted the patronage of visitors to the regions. Evidence levied in the development of Ernst's tourist aesthetic includes his mode of collection, display, and stories that surround Max's assemblage of kachina figurines. This paper further differentiates it from the collecting practices of Surrealist counterparts such as André Breton
The Ernst Equation on a Riemann Surface
The Ernst equation is formulated on an arbitrary Riemann surface.
Analytically, the problem reduces to finding solutions of the ordinary Ernst
equation which are periodic along the symmetry axis. The family of (punctured)
Riemann surfaces admitting a non-trivial Ernst field constitutes a ``partially
discretized'' subspace of the usual moduli space. The method allows us to
construct new exact solutions of Einstein's equations in vacuo with non-trivial
topology, such that different ``universes'', each of which may have several
black holes on its symmetry axis, are connected through necks bounded by cosmic
strings. We show how the extra topological degrees of freedom may lead to an
extension of the Geroch group and discuss possible applications to string
theory.Comment: 22 page
The Ernst equation and ergosurfaces
We show that analytic solutions \mcE of the Ernst equation with non-empty
zero-level-set of \Re \mcE lead to smooth ergosurfaces in space-time. In
fact, the space-time metric is smooth near a "Ernst ergosurface" if and
only if \mcE is smooth near and does not have zeros of infinite order
there.Comment: 23 pages, 4 figures; misprints correcte
Photon capture cones and embedding diagrams of the Ernst spacetime
The differences between the character of the Schwarzschild and Ernst
spacetimes are illustrated by comparing the photon capture cones, and the
embedding diagrams of the sections of the equatorial planes
of both the ordinary and optical reference geometry of these spacetimes. The
non-flat asymptotic character of the Ernst spacetime reflects itself in two
manifest facts: the escape photon cones correspond to purely outward radial
direction, and the embedding diagrams of both the ordinary and optical geometry
shrink to zero radius asymptotically. Using the properties of the embedding
diagrams, regions of these spacetimes which could have similar character are
estimated, and it is argued that they can exist for the Ernst spacetimes with a
sufficiently low strength of the magnetic field.Comment: 12 pages, 7 figure
- …