1,162 research outputs found
Stationary perturbations and infinitesimal rotations of static Einstein-Yang-Mills configurations with bosonic matter
Using the Kaluza-Klein structure of stationary spacetimes, a framework for
analyzing stationary perturbations of static Einstein-Yang-Mills configurations
with bosonic matter fields is presented. It is shown that the perturbations
giving rise to non-vanishing ADM angular momentum are governed by a
self-adjoint system of equations for a set of gauge invariant scalar
amplitudes. The method is illustrated for SU(2) gauge fields, coupled to a
Higgs doublet or a Higgs triplet. It is argued that slowly rotating black holes
arise generically in self-gravitating non-Abelian gauge theories with bosonic
matter, whereas, in general, soliton solutions do not have rotating
counterparts.Comment: 8 pages, revtex, no figure
Development of a graphite radiant heater
Design and tests of graphite radiant heater for high heat flux source in spacecraft thermostructural test
Application of genetic markers to the discrimination of European Black Poplar ( Populus nigra ) from American Black Poplar ( P. deltoides ) and Hybrid Poplars ( P. x canadensis ) in Switzerland
European Black Poplar (Populus nigra) is considered a rare and endangered tree species because of severe reduction of its natural riverine habitat and potential hybridisation with the related non-indigenous taxa P. deltoides and P. x canadensis. As it is difficult to distinguish these taxa solely based on their morphology, we applied a PCR-based assay with an easy-to-use and robust molecular marker set (cpDNA trnL-trnF/RsaI RFLP, nDNA win3 and nDNA POPX/MspI RFLP) in order to identify pure P. nigra. Different plant tissues could be used for fast and standardised DNA extraction. The application of the three marker types was tested on a number of different Populus taxa, and they were also used for the verification of pure P. nigra in a sample of 304 putative P. nigra individuals from Switzerland. Cross-checking of the DNA data with those using a traditional allozyme approach resulted in complete agreement. The availability of molecular identification methods is an important prerequisite for the conservation of European Black Poplar, because pure, non-introgressed plant material can then be used in restoration projects of European floodplain
Perturbation theory for self-gravitating gauge fields I: The odd-parity sector
A gauge and coordinate invariant perturbation theory for self-gravitating
non-Abelian gauge fields is developed and used to analyze local uniqueness and
linear stability properties of non-Abelian equilibrium configurations. It is
shown that all admissible stationary odd-parity excitations of the static and
spherically symmetric Einstein-Yang-Mills soliton and black hole solutions have
total angular momentum number , and are characterized by
non-vanishing asymptotic flux integrals. Local uniqueness results with respect
to non-Abelian perturbations are also established for the Schwarzschild and the
Reissner-Nordstr\"om solutions, which, in addition, are shown to be linearly
stable under dynamical Einstein-Yang-Mills perturbations. Finally, unstable
modes with are also excluded for the static and spherically
symmetric non-Abelian solitons and black holes.Comment: 23 pages, revtex, no figure
Controlled lasing from active optomechanical resonators
Planar microcavities with distributed Bragg reflectors (DBRs) host, besides
confined optical modes, also mechanical resonances due to stop bands in the
phonon dispersion relation of the DBRs. These resonances have frequencies in
the sub-terahertz (10E10-10E11 Hz) range with quality factors exceeding 1000.
The interaction of photons and phonons in such optomechanical systems can be
drastically enhanced, opening a new route toward manipulation of light. Here we
implemented active semiconducting layers into the microcavity to obtain a
vertical-cavity surface-emitting laser (VCSEL). Thereby three resonant
excitations -photons, phonons, and electrons- can interact strongly with each
other providing control of the VCSEL laser emission: a picosecond strain pulse
injected into the VCSEL excites long-living mechanical resonances therein. As a
result, modulation of the lasing intensity at frequencies up to 40 GHz is
observed. From these findings prospective applications such as THz laser
control and stimulated phonon emission may emerge
On rotational excitations and axial deformations of BPS monopoles and Julia-Zee dyons
It is shown that Julia-Zee dyons do not admit slowly rotating excitations.
This is achieved by investigating the complete set of stationary excitations
which can give rise to non-vanishing angular momentum. The relevant zero modes
are parametrized in a gauge invariant way and analyzed by means of a harmonic
decomposition. Since general arguments show that the solutions to the
linearized Bogomol'nyi equations cannot contribute to the angular momentum, the
relevant modes are governed by a set of electric and a set of non self-dual
magnetic perturbation equations. The absence of axial dipole deformations is
also established.Comment: 22 pages, Revtex, no figure
Rotating Hairy Black Holes
We construct stationary black holes in SU(2) Einstein-Yang-Mills theory,
which carry angular momentum and electric charge. Possessing non-trivial
non-abelian magnetic fields outside their regular event horizon, they represent
non-perturbative rotating hairy black holes.Comment: 13 pages, including 4 eps figures, LaTex forma
Black hole polarization and new entropy bounds
Zaslavskii has suggested how to tighten Bekenstein's bound on entropy when
the object is electrically charged. Recently Hod has provided a second tighter
version of the bound applicable when the object is rotating. Here we derive
Zaslavskii's optimized bound by considering the accretion of an ordinary
charged object by a black hole. The force originating from the polarization of
the black hole by a nearby charge is central to the derivation of the bound
from the generalized second law. We also conjecture an entropy bound for
charged rotating objects, a synthesis of Zaslavskii's and Hod's. On the basis
of the no hair principle for black holes, we show that this last bound cannot
be tightened further in a generic way by knowledge of ``global'' conserved
charges, e.g., baryon number, which may be borne by the object.Comment: 21 pages, RevTex, Regularization of potential made clearer. Error in
energy of the particle corrected with no consequence for final conclusions.
New references adde
Evidence of re-osseointegration after electrolytic cleaning and regenerative therapy of peri-implantitis in humans: a case report with four implants.
OBJECTIVE
To evaluate re-osseointegration after electrolytic cleaning and regenerative therapy of dental implants with peri-implantitis in humans.
MATERIAL AND METHODS
Four dental implants that developed peri-implantitis underwent electrolytic cleaning followed by regenerative therapy with guided bone regeneration. All four implants developed recurrent peri-implantitis and were therefore explanted 6 to 13Â months later. Radiographic bone level, probing depth, and bleeding on probing were determined at the time of surgery, 6Â months later, and before implant retrieval. The peri-implant tissues were histologically and histomorphometrically analyzed.
RESULTS
All four implants demonstrated radiographic and histological bone gain, reduced probing depth, and bleeding on probing. Radiographic bone gain was 5.8 mm mesially and 4.8 mm distally for implant #1, 3.3 mm and 2.3 mm for implant #2, 3.1 mm and 0.5 mm for implant #3, and 3.5 mm and 2.8 mm for implant #4. The histometric mean and maximum vertical bone gain for implant #1 to #4 was 1.65 mm and 2.54 mm, 3.04 mm and 3.47 mm, 0.43 mm and 1.27 mm, and 4.16 mm and 5.22 mm, respectively. The percentage of re-osseointegration for implant #1 to #4 was 21.0%, 36.9%, 5.7%, and 39.0%, respectively. In one implant, the newly formed bone was deposited directly onto calculus on the implant surface.
CONCLUSIONS
We found that (1) re-osseointegration is possible on a formerly contaminated implant surface and (2) the electrolytic cleaning process seems to be effective enough at sites with calculus residues.
CLINICAL RELEVANCE
Since re-osseointegration can be achieved by electrolytic cleaning, this decontamination technique may be considered as a future treatment concept
Global behavior of solutions to the static spherically symmetric EYM equations
The set of all possible spherically symmetric magnetic static
Einstein-Yang-Mills field equations for an arbitrary compact semi-simple gauge
group was classified in two previous papers. Local analytic solutions near
the center and a black hole horizon as well as those that are analytic and
bounded near infinity were shown to exist. Some globally bounded solutions are
also known to exist because they can be obtained by embedding solutions for the
case which is well understood. Here we derive some asymptotic
properties of an arbitrary global solution, namely one that exists locally near
a radial value , has positive mass at and develops no
horizon for all . The set of asymptotic values of the Yang-Mills
potential (in a suitable well defined gauge) is shown to be finite in the
so-called regular case, but may form a more complicated real variety for models
obtained from irregular rotation group actions.Comment: 43 page
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