1,106 research outputs found
Lightlike Brane as a Gravitational Source of Misner-Wheeler-Type Wormhole
Consistent Lagrangian description of lightlike p-branes (LL-branes) is
presented in two equivalent forms - a Polyakov-type formulation and a dual to
it Nambu-Goto-type formulation. An important characteristic feature of the
LL-branes is that the brane tension appears as a non-trivial additional
dynamical degree of freedom. Next, properties of p=2 LL-brane dynamics (as a
test brane) in D=4 Kerr or Kerr-Newman gravitational backgrounds are discussed
in some detail. It is shown that the LL-brane automatically positions itself on
the horizon and rotates along with the same angular velocity. Finally, a
Misner-Wheeler-type of Reissner-Nordstroem wormhole is constructed in a
self-consistent electrically sourceless Einstein-Maxwell system in the D=4 bulk
interacting with a LL-brane. The pertinent wormhole throat is located precisely
at the LL-brane sitting on the outer Reissner-Nordstroem horizon with the
Reissner-Nordstroem mass and charge being functions of the dynamical LL-brane
tension.Comment: improved derivation in section 4; additional comment in conclusions;
results unchange
Confinement from spontaneous breaking of scale symmetry
We show that one can obtain naturally the confinement of static charges from
the spontaneous symmetry breaking of scale invariance in a gauge theory. At the
classical level a confining force is obtained and at the quantum level, using a
gauge invariant but path-dependent variables formalism, the Cornell confining
potential is explicitly obtained. Our procedure answers completely to the
requirements by 't Hooft for ''perturbative confinement''.Comment: 6 page
Cosmological solutions from models with unified dark energy and dark matter and with inflaton field
Recently, few cosmological models with additional non-Riemannian volume
form(s) have been proposed. In this article we use Supernovae type Ia
experimental data to test one of these models which provides a unified
description of both dark energy via dynamically generated cosmological constant
and dark matter as a "dust" fluid due to a hidden nonlinear Noether symmetry.
It turns out that the model allows various scenarios of the future Universe
evolution and in the same time perfectly fits contemporary observational data.
Further, we investigate the influence of an additional inflaton field with a
step like potential. With its help we can reproduce the Universe inflation
epoch, matter dominated epoch and present accelerating expansion in a seamless
way. Interesting feature is that inflaton undergoes a finite change during its
evolution. It can be speculated that the inflaton asymptotic value is connected
to the vacuum expectation value of the Higgs field.Comment: 10 pages, 4 figures, prepared for the Proceedings of the XII.
International Workshop Lie Theory And Its Applications In Physics (2017
Einstein-Rosen "Bridge" Needs Lightlike Brane Source
The Einstein-Rosen "bridge" wormhole solution proposed in the classic paper
[1] does not satisfy the vacuum Einstein equations at the wormhole throat. We
show that the fully consistent formulation of the original Einstein-Rosen
"bridge" requires solving Einstein equations of bulk D=4 gravity coupled to a
lightlike brane with a well-defined world-volume action. The non-vanishing
contribution of Einstein-Rosen "bridge" solution to the right hand side of
Einstein equations at the throat matches precisely the surface stress-energy
tensor of the lightlike brane which automatically occupies the throat ("horizon
straddling") - a feature triggered by the world-volume lightlike brane
dynamics.Comment: 16 pages, added explicit expressions for pressure and energy density
of the lightlike brane as well as a new paragraph in the conclusions, version
to appear in Physics Letters
Dynamical Couplings, Dynamical Vacuum Energy and Confinement/Deconfinement from R^2-Gravity
We study within Palatini formalism an f(R)-gravity with f(R)= R + \alpha R^2
interacting with a dilaton and a special kind of nonlinear gauge field system
containing a square-root of the standard Maxwell term, which is known to
produce confinement in flat space-time. Reformulating the model in the physical
Einstein frame we find scalar field effective potential with a flat region
where the confinement dynamics disappears, while in other regions it remains
intact. The effective gauge couplings as well as the induced cosmological
constant become dynamical. In particular, a conventional Maxwell kinetic term
for the gauge field is dynamically generated even if absent in the original
theory. We find few interesting classes of explicit solutions: (i)
asymptotically (anti-)de Sitter black holes of non-standard type with
additional confining vacuum electric potential even for the electrically
neutral ones; (ii) non-standard Reissner-Nordstroem black holes with additional
constant vacuum electric field and having non-flat-spacetime "hedgehog"
asymptotics; (iii) generalized Levi-Civitta-Bertotti-Robinson "tube-like"
space-times.Comment: 16 page
Conformally Invariant Braneworld and the Cosmological Constant
A six dimensional braneworld scenario based on a model describing the
interaction of gravity, gauge fields and 3+1 branes in a conformally invariant
way is described. The action of the model is defined using a measure of
integration built of degrees of freedom independent of the metric. There is no
need to fine tune any bulk cosmological constant or the tension of the two (in
the scenario described here) parallel branes to obtain zero cosmological
constant, the only solutions are those with zero 4-D cosmological constant. The
two extra dimensions are compactified in a "football" fashion and the branes
lie on the two opposite poles of the compact "football-shaped" sphere.Comment: 10 pages, latex, no figures, few typos correcte
Emergent Universe from Scale Invariant Two Measures Theory
The dilaton-gravity sector of a linear in the scalar curvature, scale
invariant Two Measures Field Theory (TMT), is explored in detail in the context
of closed FRW cosmology and shown to allow stable emerging universe solutions.
The model possesses scale invariance which is spontaneously broken due to the
intrinsic features of the TMT dynamics. We study the transition from the
emerging phase to inflation, and then to a zero cosmological constant phase. We
also study the spectrum of density perturbations and the constraints that
impose on the parameters of the theory.Comment: 10 pages, 2 figures. Accepted for publication in Phys. Lett.
Conformally Invariant Gauge Theory of 3-Branes in 6D and the Cosmological Constant
It is shown that the gauge theory of relativistic 3-Branes can be formulated
in a conformally invariant way if the embedding space is six-dimensional. The
implementation of conformal invariance requires the use of a modified measure,
independent of the metric in the action. Brane-world scenarios without the need
of a cosmological constant in 6D are constructed. Thus, no ``old'' cosmological
constant problem appears at this level.Comment: 12 pages, Latex, no figures; final version accepted for publication
in Phys.Rev. D; Sect.II expande
Scale Symmetry Breaking from the Dynamics of Maximal Rank Gauge Field Strengths
Scale invariant theories which contain maximal rank gauge field strengths (of
indices in dimensions) are studied. The integration of the equations of
motion of these gauge fields leads to the s.s.b. of scale invariance. The cases
in study are: i) the spontaneous generation of potentials in particle
mechanics in a theory that contains only potentials in the scale
invariant phase, ii) mass generation in scalar field theories iii) generation
of non trivial dilaton potentials in generally covariant theories, iv)
spontaneous generation of confining behavior in gauge theories. The possible
origin of these models is discussed.Comment: 14 pages, latex, no figures, references adde
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