5,896 research outputs found
User's guide for the Nimbus 7 ERB Solar Analysis Tape (ESAT)
Five years of Nimbus 7 ERB solar data is available in compact form on a single ERB solar analysis tape (ESAT). The period covered is November 16, 1978 through October 31, 1983. The Nimbus 7 satellite performs just under 14 orbits a day and the ERB solar telescope observe the Sun once per orbit as the satellite passes + or - near the south pole. The data were carefully calibrated and screened. Mean orbital and daily values are given for the total solar irradiance plus selected spectral intervals. In addition, selected solar activity indicators are on the tape. The ERB experiment, the solar data calibration and screening procedures, the solar activity indicators, and the tape format are described briefly
Account of the Journey of Hieronimo di Santo Stefano, a Genovese (1495-1496) edited by R. H. Major, re-edited and introduced by Michael W. Charney
This translation of Hieronimo di Santo Stefano’s journey to Pegu in 1495-1496 was originally published in India in the Fifteenth Century Being a Collection of Narratives of Voyages to India, edited by R. H. Major, in 1857. The account was written in the form of a letter to Messer Giovan Jacobo Mainer. Only those portions related to Burma have been included in the version below
Nimbus-7 ERB Solar Analysis Tape (ESAT) user's guide
Seven years and five months of Nimbus-7 Earth Radiation Budget (ERB) solar data are available on a single ERB Solar Analysis Tape (ESAT). The period covered is November 16, 1978 through March 31, 1986. The Nimbus-7 satellite performs approximately 14 orbits per day and the ERB solar telescope observes the sun once per orbit as the satellite crosses the southern terminator. The solar data were carefully calibrated and screened. Orbital and daily mean values are given for the total solar irradiance plus other spectral intervals (10 solar channels in all). In addition, selected solar activity indicators are included on the ESAT. The ESAT User's Guide is an update of the previous ESAT User's Guide (NASA TM 86143) and includes more detailed information on the solar data calibration, screening procedures, updated solar data plots, and applications to solar variability. Details of the tape format, including source code to access ESAT, are included
Towards Loop Quantization of Plane Gravitational Waves
The polarized Gowdy model in terms of Ashtekar-Barbero variables is further
reduced by including the Killing equations for plane-fronted parallel
gravitational waves with parallel rays. The resulting constraint algebra,
including one constraint derived from the Killing equations in addition to the
standard ones of General Relativity, are shown to form a set of first-class
constraints. Using earlier work by Banerjee and Date the constraints are
expressed in terms of classical quantities that have an operator equivalent in
Loop Quantum Gravity, making space-times with pp-waves accessible to loop
quantization techniques.Comment: 14 page
Quantum Dynamics without the Wave Function
When suitably generalized and interpreted, the path-integral offers an
alternative to the more familiar quantal formalism based on state-vectors,
selfadjoint operators, and external observers. Mathematically one generalizes
the path-integral-as-propagator to a {\it quantal measure} on the space
of all ``conceivable worlds'', and this generalized measure expresses
the dynamics or law of motion of the theory, much as Wiener measure expresses
the dynamics of Brownian motion. Within such ``histories-based'' schemes new,
and more ``realistic'' possibilities open up for resolving the philosophical
problems of the state-vector formalism. In particular, one can dispense with
the need for external agents by locating the predictive content of in its
sets of measure zero: such sets are to be ``precluded''. But unrestricted
application of this rule engenders contradictions. One possible response would
remove the contradictions by circumscribing the application of the preclusion
concept. Another response, more in the tradition of ``quantum logic'', would
accommodate the contradictions by dualizing to a space of
``co-events'' and effectively identifying reality with an element of this dual
space.Comment: plainTeX, 24 pages, no figures. To appear in a special volume of {\it
Journal of Physics A: Mathematical and General} entitled ``The Quantum
Universe'' and dedicated to Giancarlo Ghirardi on the occasion of his 70th
birthday. Most current version is available at
http://www.physics.syr.edu/~sorkin/some.papers/ (or wherever my home-page may
be
Quantum-dot saturable absorber and Kerr-lens mode-locked Yb:KGW laser with >450 kW of peak power
The hybrid action of quantum-dot saturable absorber and Kerr-lens mode locking in a diode-pumped Yb:KGW laser was demonstrated. Using a quantum-dot saturable absorber with a 0.7% (0.5%) modulation depth, the mode-locked laser delivered 90 fs (93 fs) pulses with 3.2 W (2.9 W) of average power at the repetition rate of 77 MHz, corresponding to 462 kW (406 kW) of peak power and 41 nJ (38 nJ) of pulse energy. To the best of our knowledge, this represents the highest average and peak powers generated to date from quantum-dot saturable absorber-based mode-locked lasers
About the dynamics and thermodynamics of trapped ions
This tutorial introduces the dynamics of charged particles in a
radiofrequency trap in a very general manner to point out the differences
between the dynamics in a quadrupole and in a multipole trap. When dense
samples are trapped, the dynamics is modified by the Coulomb repulsion between
ions. To take into account this repulsion, we propose to use a method,
originally developed for particles in Penning trap, that model the ion cloud as
a cold fluid. This method can not reproduce the organisation of cold clouds as
crystals but it allows one to scale the size of large samples with the trapping
parameters and the number of ions trapped, for different linear geometries of
trap.Comment: accepted for publication in the "Modern Applications of Trapped Ions"
special issu
Dynamics of axialized laser-cooled ions in a Penning trap
We report the experimental characterization of axialization - a method of
reducing the magnetron motion of a small number of ions stored in a Penning
trap. This is an important step in the investigation of the suitability of
Penning traps for quantum information processing. The magnetron motion was
coupled to the laser-cooled modified cyclotron motion by the application of a
near-resonant oscillating quadrupole potential (the "axialization drive").
Measurement of cooling rates of the radial motions of the ions showed an
order-of-magnitude increase in the damping rate of the magnetron motion with
the axialization drive applied. The experimental results are in good
qualitative agreement with a recent theoretical study. In particular, a
classical avoided crossing was observed in the motional frequencies as the
axialization drive frequency was swept through the optimum value, proving that
axialization is indeed a resonant effect.Comment: 8 pages, 9 figure
Spatial Hypersurfaces in Causal Set Cosmology
Within the causal set approach to quantum gravity, a discrete analog of a
spacelike region is a set of unrelated elements, or an antichain. In the
continuum approximation of the theory, a moment-of-time hypersurface is well
represented by an inextendible antichain. We construct a richer structure
corresponding to a thickening of this antichain containing non-trivial
geometric and topological information. We find that covariant observables can
be associated with such thickened antichains and transitions between them, in
classical stochastic growth models of causal sets. This construction highlights
the difference between the covariant measure on causal set cosmology and the
standard sum-over-histories approach: the measure is assigned to completed
histories rather than to histories on a restricted spacetime region. The
resulting re-phrasing of the sum-over-histories may be fruitful in other
approaches to quantum gravity.Comment: Revtex, 12 pages, 2 figure
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