10,553 research outputs found
Black Strings and Classical Hair
We examine the geometry near the event horizon of a family of black string
solutions with traveling waves. It has previously been shown that the metric is
continuous there. Contrary to expectations, we find that the geometry is not
smooth, and the horizon becomes singular whenever a wave is present. Both five
dimensional and six dimensional black strings are considered with similar
results.Comment: 14 pages, harvma
Counting States of Black Strings with Traveling Waves
We consider a family of solutions to string theory which depend on arbitrary
functions and contain regular event horizons. They describe six dimensional
extremal black strings with traveling waves and have an inhomogeneous
distribution of momentum along the string. The structure of these solutions
near the horizon is studied and the horizon area computed. We also count the
number of BPS string states at weak coupling whose macroscopic momentum
distribution agrees with that of the black string. It is shown that the number
of such states is given by the Bekenstein-Hawking entropy of the black string
with traveling waves.Comment: 21 pages RevTex. One equation correcte
Analysis of flux-integrated cross sections for quasi-elastic neutrino charged-current scattering off C at MiniBooNE energies
Flux-averaged and flux-integrated cross sections for quasi-elastic neutrino
charged-current scattering on nucleus are analyzed. It is shown that the
flux-integrated differential cross sections are nuclear model-independent. We
calculate these cross sections using the relativistic distorted-wave impulse
approximation and relativistic Fermi gas model with the Booster Neutrino
Beamline flux and compare results with the recent MiniBooNE experiment data.
Within these models an axial mass is extracted from a fit of the measured
cross section. The extracted value of is consistent with
the MiniBooNE result. The measured and calculated double differential cross
sections generally agree within the error of the
experiment. But the Fermi gas model predictions are completely off of the data
in the region of low muon energies and scattering angles.Comment: 23 pages, 8 figure
Where is the Information Stored in Black Holes?
It is shown that many modes of the gravitational field exist only inside the
horizon of an extreme black hole in string theory. At least in certain cases,
the number of such modes is sufficient to account for the Bekenstein-Hawking
entropy. These modes are associated with sources which carry Ramond-Ramond
charge, and so may be viewed as the strong coupling limit of D-branes. Although
these sources naturally live at the singularity, they are well defined and
generate modes which extend out to the horizon. This suggests that the
information in an extreme black hole is not localized near the singularity or
the horizon, but extends between them.Comment: 21 pages, reference corrected and comment adde
Large-Area, Low-Noise, High Speed, Photodiode-Based Fluorescence Detectors with Fast Overdrive Recovery
Two large-area, low noise, high speed fluorescence detectors have been built.
One detector consists of a photodiode with an area of 28 mm x 28 mm and a low
noise transimpedance amplifier. This detector has a input light-equivalent
spectral noise density of less than 3 pW/Hz^1/2, can recover from a large
scattered light pulse within 10 us, and has a bandwidth of at least 900 kHz.
The second detector consists of a 16 mm diameter avalanche photodiode and a
low-noise transimpedance amplifier. This detector has an input light-equivalent
spectral noise density of 0.08 pW/Hz^1/2, also can recover from a large
scattered light pulse within 10 us, and has a bandwidth of 1 MHz.Comment: Submitted to Review of Scientific Instrument
Opportunities for optics in integrated circuits applications
Optics potentially addresses two key problems in electronic chips and systems: interconnects and timing. Short optical pulses (e.g., picoseconds or shorter) offer particularly precise timing. Results are shown for optical and electrical four-phase clocking, with <1 ps rms jitter for the optical case
Correlation of hippocampal theta rhythm with changes in cutaneous temperature
A possible role for the hippocampus in alerting an animal to changes in cutaneous temperature was examined. Following local warming or cooling of the ears of unanesthetized, loosely restrained rabbits, theta waves (4-7 Hz EEG waves) were recorded from electrodes straddling the hippocampus. The onset of the hippocampal theta rhythm was correlated with changes in cutaneous temperature, an observation consistent with studies indicating that the theta rhythm is a nonspecific response evoked by stimulation of several sensory modalities. Additional data from cats and rabbits were correlated with specific neurons within the hippocampus, namely pyramidal cells. Post stimulus time histograms obtained by excitation of the dorsal fornix were interpreted in terms of excitatory and inhibitory inputs to pyramidal cells. Thus, the theta rhythm, which appears to be evoked by changes in cutaneous temperature, can be related to a specific type of hippocampal neuron which is in turn connected with other areas of the brain involved in temperature regulation
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