23,156 research outputs found
B-R Colors of Globular Clusters in NGC 6166 (A2199)
We have analysed new R-band photometry of globular clusters in NGC 6166, the
cD galaxy in the cooling flow cluster A2199. In combination with the earlier B
photometry of Pritchet \& Harris (1990), we obtain BR colours for 40
globular clusters in NGC 6166. The mean BR is 1.26 0.11, corresponding
to a mean [Fe/H] = 1 0.4. Given that NGC 6166 is one of the most
luminous cD galaxies studied to date, our result implies significant scatter in
the relationship between mean cluster [Fe/H] and parent galaxy luminosity. We
obtain a globular cluster specific frequency of S 9, with a possible
range between 5 and 18. This value is inconsistent with the value of S
4 determined earlier by Pritchet \& Harris (1990) from B-band
photometry, and we discuss possible reasons for the discrepancy. Finally, we
reassess whether or not cooling flows are an important mechanism for forming
globular clusters in gE/cD galaxies.Comment: 8 pages, uuencoded, gzipped tar file with latex file, 6 figures (Fig
1 omitted because of size), and mn.sty file. Figures will be embedded into
the postscript file. Accepted (March 1996) for publication in MNRA
The Microcanonical Functional Integral. I. The Gravitational Field
The gravitational field in a spatially finite region is described as a
microcanonical system. The density of states is expressed formally as a
functional integral over Lorentzian metrics and is a functional of the
geometrical boundary data that are fixed in the corresponding action. These
boundary data are the thermodynamical extensive variables, including the energy
and angular momentum of the system. When the boundary data are chosen such that
the system is described semiclassically by {\it any} real stationary
axisymmetric black hole, then in this same approximation is shown to
equal 1/4 the area of the black hole event horizon. The canonical and grand
canonical partition functions are obtained by integral transforms of that
lead to "imaginary time" functional integrals. A general form of the first law
of thermodynamics for stationary black holes is derived. For the simpler case
of nonrelativistic mechanics, the density of states is expressed as a real-time
functional integral and then used to deduce Feynman's imaginary-time functional
integral for the canonical partition function.Comment: 29 pages, plain Te
Application of remote sensing to state and regional problems
There are no author-identified significant results in this report
Positivity of Spin Foam Amplitudes
The amplitude for a spin foam in the Barrett-Crane model of Riemannian
quantum gravity is given as a product over its vertices, edges and faces, with
one factor of the Riemannian 10j symbols appearing for each vertex, and simpler
factors for the edges and faces. We prove that these amplitudes are always
nonnegative for closed spin foams. As a corollary, all open spin foams going
between a fixed pair of spin networks have real amplitudes of the same sign.
This means one can use the Metropolis algorithm to compute expectation values
of observables in the Riemannian Barrett-Crane model, as in statistical
mechanics, even though this theory is based on a real-time (e^{iS}) rather than
imaginary-time (e^{-S}) path integral. Our proof uses the fact that when the
Riemannian 10j symbols are nonzero, their sign is positive or negative
depending on whether the sum of the ten spins is an integer or half-integer.
For the product of 10j symbols appearing in the amplitude for a closed spin
foam, these signs cancel. We conclude with some numerical evidence suggesting
that the Lorentzian 10j symbols are always nonnegative, which would imply
similar results for the Lorentzian Barrett-Crane model.Comment: 15 pages LaTeX. v3: Final version, with updated conclusions and other
minor changes. To appear in Classical and Quantum Gravity. v4: corrects # of
samples in Lorentzian tabl
Charged particle radiation damage in semiconductors. Part 14 - Study of radiation effects in lithium doped silicon solar cells
Lithium doped silicon solar cells under electron irradiation and determination of semiconductor parameter
Application of remote sensing to state and regional problems
There are no author-identified significant results in this report
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