103 research outputs found
Semiclassical and Quantum Field Theoretic Bounds for Traversable Lorentzian Stringy Wormholes
A lower bound on the size of a Lorentzian wormhole can be obtained by
semiclassically introducing the Planck cut-off on the magnitude of tidal forces
(Horowitz-Ross constraint). Also, an upper bound is provided by the quantum
field theoretic constraint in the form of the Ford-Roman Quantum Inequality for
massless minimally coupled scalar fields. To date, however, exact static
solutions belonging to this scalar field theory have not been worked out to
verify these bounds. To fill this gap, we examine the wormhole features of two
examples from the Einstein frame description of the vacuum low energy string
theory in four dimensions which is the same as the minimally coupled scalar
field theory. Analyses in this paper support the conclusion of Ford and Roman
that wormholes in this theory can have sizes that are indeed only a few order
of magnitudes larger than the Planck scale. It is shown that the two types of
bounds are also compatible. In the process, we point out a "wormhole" analog of
naked black holes.Comment: 15 page
On a class of stable, traversable Lorentzian wormholes in classical general relativity
It is known that Lorentzian wormholes must be threaded by matter that
violates the null energy condition. We phenomenologically characterize such
exotic matter by a general class of microscopic scalar field Lagrangians and
formulate the necessary conditions that the existence of Lorentzian wormholes
imposes on them. Under rather general assumptions, these conditions turn out to
be strongly restrictive. The most simple Lagrangian that satisfies all of them
describes a minimally coupled massless scalar field with a reversed sign
kinetic term. Exact, non-singular, spherically symmetric solutions of
Einstein's equations sourced by such a field indeed describe traversable
wormhole geometries. These wormholes are characterized by two parameters: their
mass and charge. Among them, the zero mass ones are particularly simple,
allowing us to analytically prove their stability under arbitrary space-time
dependent perturbations. We extend our arguments to non-zero mass solutions and
conclude that at least a non-zero measure set of these solutions is stable.Comment: 23 pages, 4 figures, uses RevTeX4. v2: Changes to accommodate added
references. Statement about masses of the wormhole correcte
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