1,318 research outputs found
Quantum Noise Limits for Nonlinear, Phase-Invariant Amplifiers
Any quantum device that amplifies coherent states of a field while preserving
their phase generates noise. A nonlinear, phase-invariant amplifier may
generate less noise, over a range of input field strengths, than any linear
amplifier with the same amplification. We present explicit examples of such
nonlinear amplifiers, and derive lower bounds on the noise generated by a
nonlinear, phase-invariant quantum amplifier.Comment: RevTeX, 6 pages + 4 figures (included in file; hard copy sent on
request
Possibility to study eta-mesic nuclei and photoproduction of slow eta-mesons at the GRAAL facility
A new experiment is proposed with the aim to study eta-mesic nuclei and
low-energy interactions of eta with nuclei. Two decay modes of eta produced by
a photon beam inside a nucleus will be observed, namely a collisional decay
\eta N \to \pi N inside the nucleus and the radiative decay \eta \to \gamma
\gamma outside. In addition, a collisional decay of stopped S_{11}(1535)
resonance inside the nucleus, S_{11}(1535) N \to N N, will be studied. The
experiment can be performed using the tagged photon beam at ESRF with the
end-point energy 1000 MeV and the GRAAL detector which includes a
high-resolution BGO calorimeter and a large acceptance lead-scintillator
time-of-flight wall. Some results of simulation and estimates of yields are
given.Comment: 20 pages, 19 figure
Report on Chemical Analysis and Further Dating of Dinosaur Bones and Dinosaur Petroglypths
Much of the material in this report was presented at the 1990 ICC poster sessions. Our radiocarbon dates of dinosaur bones and the other information in this report should be alarming to the evolutionary community and should be given serious study considering our preliminary results
On the Velocity Gradient in Stably Stratified Sheared Flows. Part 2: Observations and Models
Peer reviewe
Effect of anisotropy on universal transport in unconventional superconductors
We investigate the universal electronic transport for a mixed
+s-wave superconductor in the presence of an anisotropic
elliptical Fermi surface. Similar to the universal low-temperature transport
predicted in a -wave superconductor with a circular Fermi surface,
anisotropic universal features are found in the low-temperature microwave
conductivity, and thermal conductivity in the anisotropic system. The effects
of anisotropy on the penetration depth, impurity induced suppression, and
the zero-frequency density of states are also considered. While a small amount
of anisotropy can lead to a strong suppression of the effective scattering rate
and hence the density of states at zero frequency, experimental data suggests
that large effects are restored by a negative -component gap admixture.Comment: 8 page
Interlayer pair tunneling and gap anisotropy in YBaCuO
Recent ARPES measurement observed a large -axis gap anisotropy,
, in clean YBaCuO. This
indicates that some sub-dominant component may exist in the -wave
dominant gap. We propose that the interlayer pairing tunneling contribution can
be determined through the investigation of the order parameter anisotropy.
Their potentially observable features in transport and spin dynamics are also
studied.Comment: 4 pages, 3 figure
Asymmetric magnetic interference patterns in 0-pi Josephson junctions
We examine the magnetic interference patterns of Josephson junctions with a
region of 0- and of pi-phase shift. Such junctions have recently been realized
as c-axis YBCO-Pb junctions with a single twin boundary in YBCO. We show that
in general the junction generates self-fields which introduces an asymmetry in
the critical current under reversal of the magnetic field. Numerical
calculations of these asymmetries indicate they account well for the
unexplained features observed in single twin boundary junctions.Comment: 4 pages, 3 figure
Precise Measurement of Sigma Beam Asymmetry for Positive Pion Photoproduction on the Proton from 800 to 1500 Mev
The Sigma beam asymmetry for positive pion photoproduction on the proton has
been measured over an angular range of 40-170 deg at photon energies from 0.8
to 1.5 GeV. The resulting data set includes 237 accurate points, 136 of these
belonging to an almost unexplored domain above 1.05 GeV. Data of such high
precision provide severe constraints for partial wave analyses. The influence
of this experiment on the GW multipole analysis is demonstrated. Significant
changes are found in multipoles connected to the S31(1620) and P13(1720)
resonances. Comparisons using the MAID analysis are also presented.Comment: 11 pages, 4 eps figures. to be published in Physics Letters
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