1,899 research outputs found
Induction flowmeter for dielectric fluids, experimental verification final report
Experimental verification of induction flow meter for use with dielectric fluid
FeH Absorption in the Near-Infrared Spectra of Late M and L Dwarfs
We present medium-resolution z-, J-, and H-band spectra of four late-type
dwarfs with spectral types ranging from M8 to L7.5. In an attempt to determine
the origin of numerous weak absorption features throughout their near-infrared
spectra, and motivated by the recent tentative identification of the E 4\Pi- A
^4\Pi system of FeH near 1.6 microns in umbral and cool star spectra, we have
compared the dwarf spectra to a laboratory FeH emission spectrum. We have
identified nearly 100 FeH absorption features in the z-, J-, and H-band spectra
of the dwarfs. In particular, we have identified 34 features which dominate the
appearance of the H-band spectra of the dwarfs and which appear in the
laboratory FeH spectrum. Finally, all of the features are either weaker or
absent in the spectrum of the L7.5 dwarf which is consistent with the weakening
of the known FeH bandheads in the spectra of the latest L dwarfs.Comment: accepted by Ap
Hypersurface Bohm-Dirac models
We define a class of Lorentz invariant Bohmian quantum models for N entangled
but noninteracting Dirac particles. Lorentz invariance is achieved for these
models through the incorporation of an additional dynamical space-time
structure provided by a foliation of space-time. These models can be regarded
as the extension of Bohm's model for N Dirac particles, corresponding to the
foliation into the equal-time hyperplanes for a distinguished Lorentz frame, to
more general foliations. As with Bohm's model, there exists for these models an
equivariant measure on the leaves of the foliation. This makes possible a
simple statistical analysis of position correlations analogous to the
equilibrium analysis for (the nonrelativistic) Bohmian mechanics.Comment: 17 pages, 3 figures, RevTex. Completely revised versio
Non-Linearity Corrections and Statistical Uncertainties Associated with Near-Infrared Arrays
We derive general equations for non-linearity corrections and statistical
uncertainty (variance) estimates for data acquired with near-infrared detectors
employing correlated double sampling, multiple correlated double sampling
(Fowler sampling) and uniformly-spaced continuous readout techniques. We
compare our equation for the variance on each pixel associated with Fowler
sampling with measurements obtained from data taken with the array installed in
the near-infrared cross-dispersed spectrograph (SpeX) at the NASA Infrared
Telescope Facility and find that it provides an accurate representation of the
empirical results. This comparison also reveals that the read noise associated
with a single readout of the SpeX array increases with the number of
non-destructive reads, n_r, as n_r^0.16. This implies that the {effective} read
noise of a stored image decreases as n_r^-0.34, shallower than the expected
rate of n_r^-0.5. The cause of this read noise behavior is uncertain, but may
be due to heating of the array as a result of the multiple read outs. Such
behavior may be generic to arrays that employ correlated or multiple correlated
double sampling readouts.Comment: 21 pages, accepted by PAS
Near-Infrared Spectroscopy of McNeil's Nebula Object
We present 0.8-5.2 micron spectroscopy of the compact source at the base of a
variable nebula (McNeil's Nebula Object) in the Lynds 1630 dark cloud that went
into outburst in late 2003. The spectrum of this object reveals an extremely
red continuum, CO bands at 2.3-2.5 microns in emission, a deep 3.0 micron ice
absorption feature, and a solid state CO absorption feature at 4.7 microns. In
addition, emission lines of H, Ca II, Mg I, and Na I are present. The Paschen
lines exhibit P Cygni profiles, as do two lines of He I, although the emission
features are very weak in the latter. The Brackett lines, however, are seen to
be purely in emission. The P Cygni profiles clearly indicate that mass outflow
is occurring in a wind with a velocity of ~400 km/s. The H line ratios do not
yield consistent estimates of the reddening, nor do they agree with the
extinction estimated from the ice feature (A_V ~ 11). We propose that these
lines are optically thick and are produced in a dense, ionized wind. The
near-infrared spectrum does not appear similar to any known FUor or EXor
object. However, all evidence suggests that McNeil's Nebula Object is a
heavily-embedded low-mass Class I protostar, surrounded by a disk, whose
brightening is due to a recent accretion event.Comment: 11 pages, 2 ps figures, accepted for publication in ApJ Letter
The density matrix in the de Broglie-Bohm approach
If the density matrix is treated as an objective description of individual
systems, it may become possible to attribute the same objective significance to
statistical mechanical properties, such as entropy or temperature, as to
properties such as mass or energy. It is shown that the de Broglie-Bohm
interpretation of quantum theory can be consistently applied to density
matrices as a description of individual systems. The resultant trajectories are
examined for the case of the delayed choice interferometer, for which Bell
appears to suggest that such an interpretation is not possible. Bell's argument
is shown to be based upon a different understanding of the density matrix to
that proposed here.Comment: 15 pages, 4 figure
Quantum mechanics is about quantum information
I argue that quantum mechanics is fundamentally a theory about the
representation and manipulation of information, not a theory about the
mechanics of nonclassical waves or particles. The notion of quantum information
is to be understood as a new physical primitive -- just as, following
Einstein's special theory of relativity, a field is no longer regarded as the
physical manifestation of vibrations in a mechanical medium, but recognized as
a new physical primitive in its own right.Comment: 17 pages, forthcoming in Foundations of Physics Festschrift issue for
James Cushing. Revised version: some paragraphs have been added to the final
section clarifying the argument, and various minor clarifying remarks have
been added throughout the tex
A Method of Correcting Near-Infrared Spectra for Telluric Absorption
We present a method for correcting near-infrared medium-resolution spectra
for telluric absorption. The method makes use of a spectrum of an A0V star,
observed near in time and close in airmass to the target object, and a
high-resolution model of Vega, to construct a telluric correction spectrum that
is free of stellar absorption features. The technique was designed specifically
to perform telluric corrections on spectra obtained with SpeX, a 0.8-5.5
micron, medium-resolution cross-dispersed spectrograph at the NASA Infrared
Telescope Facility, and uses the fact that for medium resolutions there exist
spectral regions uncontaminated by atmospheric absorption lines. However, it is
also applicable (in a somewhat modified form) to spectra obtained with other
near-infrared spectrographs. An IDL-based code that carries out the procedures
is available for downloading via the World Wide Web from the IRTF website.Comment: 39 pages, 10 figures, To appear in the Feb 2003 issue of PASP; IDL
source code, as well as full resolution versions of the figures, are
available at http://irtfweb.ifa.hawaii.edu/Facility/spex
Solving the measurement problem: de Broglie-Bohm loses out to Everett
The quantum theory of de Broglie and Bohm solves the measurement problem, but
the hypothetical corpuscles play no role in the argument. The solution finds a
more natural home in the Everett interpretation.Comment: 20 pages; submitted to special issue of Foundations of Physics, in
honour of James T. Cushin
- âŠ