8,128 research outputs found
Radiating black hole solutions in Einstein-Gauss-Bonnet gravity
In this paper, we find some new exact solutions to the Einstein-Gauss-Bonnet
equations. First, we prove a theorem which allows us to find a large family of
solutions to the Einstein-Gauss-Bonnet gravity in -dimensions. This family
of solutions represents dynamic black holes and contains, as particular cases,
not only the recently found Vaidya-Einstein-Gauss-Bonnet black hole, but also
other physical solutions that we think are new, such as, the Gauss-Bonnet
versions of the Bonnor-Vaidya(de Sitter/anti-de Sitter) solution, a global
monopole and the Husain black holes. We also present a more general version of
this theorem in which less restrictive conditions on the energy-momentum tensor
are imposed. As an application of this theorem, we present the exact solution
describing a black hole radiating a charged null fluid in a Born-Infeld
nonlinear electrodynamics
Vacuum field correlations and three-body Casimir-Polder potential with one excited atom
The three-body Casimir-Polder potential between one excited and two
ground-state atoms is evaluated. A physical model based on the dressed field
correlations of vacuum fluctuations is used, generalizing a model previously
introduced for three ground-state atoms. Although the three-body potential with
one excited atom is already known in the literature, our model gives new
insights on the nature of non-additive Casimir-Polder forces with one or more
excited atoms.Comment: 9 page
Report on the development of the Manned Orbital Research Laboratory /MORL/ system utilization potential. Task area IV - MORL SYSTEM improvement study, book 4
Communications and telemetry subsystem analyses for Manned Orbital Research Laboratory system improvement stud
Comment on `On the Quantum Theory of Molecules' [J. Chem.Phys. {\bf 137}, 22A544 (2012)]
In our previous paper [J. Chem.Phys. {\bf 137}, 22A544 (2012)] we argued that
the Born-Oppenheimer approximation could not be based on an exact
transformation of the molecular Schr\"{o}dinger equation. In this Comment we
suggest that the fundamental reason for the approximate nature of the
Born-Oppenheimer model is the lack of a complete set of functions for the
electronic space, and the need to describe the continuous spectrum using
spectral projection.Comment: 2 page
Polarization and ellipticity of high-order harmonics from aligned molecules generated by linearly polarized intense laser pulses
We present theoretical calculations for polarization and ellipticity of
high-order harmonics from aligned N, CO, and O molecules generated
by linearly polarized lasers. Within the rescattering model, the two
polarization amplitudes of the harmonics are determined by the
photo-recombination amplitudes for photons emitted parallel and perpendicular
to the direction of the {\em same} returning electron wave packet. Our results
show clear species-dependent polarization states, in excellent agreement with
experiments. We further note that the measured polarization ellipse of the
harmonic furnishes the needed parameters for a "complete" experiment in
molecules.Comment: 4 pages, 4 figure
Born-Infeld electrostatics in the complex plane
The complex method to obtain 2-dimensional Born-Infeld electrostatic
solutions is presented in a renewed form. The solutions are generated by a
holomorphic seed that makes contact with the Coulombian complex potential. The
procedure is exemplified by solving the Born-Infeld multipolar configurations.
Besides, it is shown that the attractive force between two equal but opposite
charges is lower than its Coulombian partner; it decreases up to vanish when
the charges approach each other below a distance ruled by the Born-Infeld
constant.Comment: 15 pages, 4 figure
Ab initio Wannier-function-based many-body approach to Born charge of crystalline insulators
In this paper we present an approach aimed at performing many-body
calculations of Born-effective charges of crystalline insulators, by including
the electron-correlation effects. The scheme is implemented entirely in the
real space, using Wannier-functions as single-particle orbitals. Correlation
effects are computed by including virtual excitations from the Hartree-Fock
mean field, and the excitations are organized as per a Bethe-Goldstone-like
many-body hierarchy. The results of our calculations suggest that the approach
presented here is promising.Comment: 5 pages, to appear in Phys. Rev. B. (Rapid Comm., Dec 15, 2004
Rotating charged Black Holes in Einstein-Born-Infeld theories and their ADM mass
In this work, the solution of the Einstein equations for a slowly rotating
black hole with Born-Infeld charge is obtained. Geometrical properties and
horizons of this solution are analyzed. The conditions when the ADM mass (as in
the nonlinear static cases) and the ADM angular momentum of the system have
been modified by the non linear electromagnetic field of the black hole, are
considered.Comment: Final version and figures in journal. References and comments adde
Capacitive pressure transducer system
Closed loop capacitive pressure transducer with extended frequency response for very low pressure measurement
Effect of computer practice of component gait training facts on choice of ambulation aid and gait pattern by physical therapist assistant students
Health care educational programs are challenged to provide efficient and effective instructional strategies to teach students both the foundation knowledge and problem solving skills that they need to provide quality health care services. In the present study, computer-based text passages and quizzes were used to teach physical therapist assistant (PTA) students the component facts and principles needed for the higher level skill of choosing ambulation aids and gait patterns for patients in described clinical scenarios. The research questions were (a) whether learning component gait training skills would result in better ability to choose ambulation aids and gait patterns for patients in clinical scenarios, and (b) whether practicing the component skills to achieve fluency would lead to greater problem solving performance. Periodic application probes were used to test problem solving skill. Learning component subskills did result in better problem solving ability for 7 out of 8 students, and fluency on 3 critical quizzes was positively correlated with higher application test scores. A final problem solving strategy resulted in further learning gains for 5 out of 6 students, but the strategy did not compensate for faulty factual knowledge. Overall, the findings of the study show that learning component facts and principles can lead to better problem solving skill without specific additional instruction. In fact, mastery of the factual knowledge is essential for mastery of a problem solving task. Because effective health care is dependent upon good problem solving skills, these findings suggests that learning will be more efficient if instructional materials contain contingencies to ensure that students master critical foundation skills
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