26,928 research outputs found
Stability of f(R) black holes
We investigate the stability of (Schwarzschild) black hole obtained
from the gravity. It is difficult to carry out the perturbation analysis
around the black hole because the linearized Einstein equation is fourth order
in gravity. In order to resolve this difficulty, we transform
gravity into the scalar-tensor theory by introducing two auxiliary scalars.
In this case, the linearized curvature scalar becomes a scalaron, showing
that all linearized equations are second order, which are the same equations
for the massive Brans-Dicke theory.
It turns out that the black hole is stable against the external
perturbations if the scalaron does not have a tachyonic mass.Comment: 16 pages, no figures, version to appear in Physical Review
Analog VLSI neural network integrated circuits
Two analog very large scale integration (VLSI) vector matrix multiplier integrated circuit chips were designed, fabricated, and partially tested. They can perform both vector-matrix and matrix-matrix multiplication operations at high speeds. The 32 by 32 vector-matrix multiplier chip and the 128 by 64 vector-matrix multiplier chip were designed to perform 300 million and 3 billion multiplications per second, respectively. An additional circuit that has been developed is a continuous-time adaptive learning circuit. The performance achieved thus far for this circuit is an adaptivity of 28 dB at 300 KHz and 11 dB at 15 MHz. This circuit has demonstrated greater than two orders of magnitude higher frequency of operation than any previous adaptive learning circuit
Quasinormal frequencies and thermodynamic quantities for the Lifshitz black holes
We find the connection between thermodynamic quantities and quasinormal
frequencies in Lifshitz black holes. It is shown that the globally stable
Lifshitz black holes have pure imaginary quasinormal frequencies. We also show
that by employing the Maggiore's method, both the horizon area and the entropy
can be quantized for these black holes.Comment: 21 pages, no figures, version to appear in PR
Epitaxial growth of (111)-oriented LaAlO/LaNiO ultra-thin superlattices
The epitaxial stabilization of a single layer or superlattice structures
composed of complex oxide materials on polar (111) surfaces is severely
burdened by reconstructions at the interface, that commonly arise to neutralize
the polarity. We report on the synthesis of high quality LaNiO/mLaAlO
pseudo cubic (111) superlattices on polar (111)-oriented LaAlO, the
proposed complex oxide candidate for a topological insulating behavior.
Comprehensive X-Ray diffraction measurements, RHEED, and element specific
resonant X-ray absorption spectroscopy affirm their high structural and
chemical quality. The study offers an opportunity to fabricate interesting
interface and topology controlled (111) oriented superlattices based on
ortho-nickelates
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