3,442 research outputs found
The collision of boosted black holes
We study the radiation from a collision of black holes with equal and
opposite linear momenta. Results are presented from a full numerical relativity
treatment and are compared with the results from a ``close-slow''
approximation. The agreement is remarkable, and suggests several insights about
the generation of gravitational radiation in black hole collisions.Comment: 8 pages, RevTeX, 3 figures included with eps
The Droplet State and the Compressibility Anomaly in Dilute 2D Electron Systems
We investigate the space distribution of carrier density and the
compressibility of two-dimensional (2D) electron systems by using the local
density approximation. The strong correlation is simulated by the local
exchange and correlation energies. A slowly varied disorder potential is
applied to simulate the disorder effect. We show that the compressibility
anomaly observed in 2D systems which accompanies the metal-insulator transition
can be attributed to the formation of the droplet state due to disorder effect
at low carrier densities.Comment: 4 pages, 3 figure
Waveform propagation in black hole spacetimes: evaluating the quality of numerical solutions
We compute the propagation and scattering of linear gravitational waves off a
Schwarzschild black hole using a numerical code which solves a generalization
of the Zerilli equation to a three dimensional cartesian coordinate system.
Since the solution to this problem is well understood it represents a very good
testbed for evaluating our ability to perform three dimensional computations of
gravitational waves in spacetimes in which a black hole event horizon is
present.Comment: 13 pages, RevTeX, to appear in Phys. Rev.
Head--on Collision of Two Unequal Mass Black Holes
We present results from the first fully nonlinear numerical calculations of
the head--on collision of two unequal mass black holes. Selected waveforms of
the most dominant l=2, 3 and 4 quasinormal modes are shown, as are the total
radiated energies and recoil velocities for a range of mass ratios and initial
separations. Our results validate the close and distant separation limit
perturbation studies, and suggest that the head--on collision scenario is not
likely to produce an astrophysically significant recoil effect.Comment: 5 pages, 3 figure
Effective Lorentz Force due to Small-angle Impurity Scattering: Magnetotransport in High-Tc Superconductors
We show that a scattering rate which varies with angle around the Fermi
surface has the same effect as a periodic Lorentz force on magnetotransport
coefficients. This effect, together with the marginal Fermi liquid inelastic
scattering rate gives a quantitative explanation of the temperature dependence
and the magnitude of the observed Hall effect and magnetoresistance with just
the measured zero-field resistivity as input.Comment: 4 pages, latex, one epsf figure included in text. Several revisions
and corrections are included. Major conclusions are the sam
The Evolution of Distorted Rotating Black Holes II: Dynamics and Analysis
We have developed a numerical code to study the evolution of distorted,
rotating black holes. This code is used to evolve a new family of black hole
initial data sets corresponding to distorted ``Kerr'' holes with a wide range
of rotation parameters, and distorted Schwarzschild black holes with odd-parity
radiation. Rotating black holes with rotation parameters as high as
are evolved and analyzed in this paper. The evolutions are generally carried
out to about , where is the ADM mass. We have extracted both the
even- and odd-parity gravitational waveforms, and find the quasinormal modes of
the holes to be excited in all cases. We also track the apparent horizons of
the black holes, and find them to be a useful tool for interpreting the
numerical results. We are able to compute the masses of the black holes from
the measurements of their apparent horizons, as well as the total energy
radiated and find their sum to be in excellent agreement with the ADM mass.Comment: 26 pages, LaTeX with RevTeX 3.0 macros. 27 uuencoded gz-compressed
postscript figures. Also available at http://jean-luc.ncsa.uiuc.edu/Papers/
Submitted to Physical Review
Superconducting RF Metamaterials Made with Magnetically Active Planar Spirals
Superconducting metamaterials combine the advantages of low-loss, large
inductance (with the addition of kinetic inductance), and extreme tunability
compared to their normal metal counterparts. Therefore, they allow realization
of compact designs operating at low frequencies. We have recently developed
radio frequency (RF) metamaterials with a high loaded quality factor and an
electrical size as small as 658, ( is the free space
wavelength) by using Nb thin films. The RF metamaterial is composed of truly
planar spirals patterned with lithographic techniques. Linear transmission
characteristics of these metamaterials show robust Lorentzian resonant peaks in
the sub- 100 MHz frequency range below the of Nb. Though Nb is a
non-magnetic material, the circulating currents in the spirals generated by RF
signals produce a strong magnetic response, which can be tuned sensitively
either by temperature or magnetic field thanks to the superconducting nature of
the design. We have also observed strong nonlinearity and meta-stable jumps in
the transmission data with increasing RF input power until the Nb is driven
into the normal state. We discuss the factors modifying the induced magnetic
response from single and 1-D arrays of spirals in the light of numerical
simulations.Comment: 4 pages, 7 figure
Gravitational wave extraction and outer boundary conditions by perturbative matching
We present a method for extracting gravitational radiation from a
three-dimensional numerical relativity simulation and, using the extracted
data, to provide outer boundary conditions. The method treats dynamical
gravitational variables as nonspherical perturbations of Schwarzschild
geometry. We discuss a code which implements this method and present results of
tests which have been performed with a three dimensional numerical relativity
code
Head-on collision of unequal mass black holes: close-limit predictions
The close-limit method has given approximations in excellent agreement with
those of numerical relativity for collisions of equal mass black holes. We
consider here colliding holes with unequal mass, for which numerical relativity
results are not available. We try to ask two questions: (i) Can we get
approximate answers to astrophysical questions (ideal mass ratio for energy
production, maximum recoil velocity, etc.), and (ii) can we better understand
the limitations of approximation methods. There is some success in answering
the first type of question, but more with the second, especially in connection
with the issue of measures of the intrinsic mass of the colliding holes, and of
the range of validity of the method.Comment: 19 pages, RevTeX + 9 postscript figure
Drag resistance of 2D electronic microemulsions
Motivated by recent experiments of Pillarisetty {\it et al}, \prl {\bf 90},
226801 (2003), we present a theory of drag in electronic double layers at low
electron concentration. We show that the drag effect in such systems is
anomolously large, it has unusual temperature and magnetic field dependences
accociated with the Pomeranchuk effect, and does not vanish at zero
temperature
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