2,555 research outputs found
The Impact of Contaminated RR Lyrae/Globular Cluster Photometry on the Distance Scale
RR Lyrae variables and the stellar constituents of globular clusters are
employed to establish the cosmic distance scale and age of the universe.
However, photometry for RR Lyrae variables in the globular clusters M3, M15,
M54, M92, NGC2419, and NGC6441 exhibit a dependence on the clustercentric
distance. For example, variables and stars positioned near the crowded
high-surface brightness cores of the clusters may suffer from photometric
contamination, which invariably affects a suite of inferred parameters (e.g.,
distance, color excess, absolute magnitude, etc.). The impetus for this study
is to mitigate the propagation of systematic uncertainties by increasing
awareness of the pernicious impact of contaminated and radial-dependent
photometry.Comment: To appear in ApJ
Causal sites as quantum geometry
We propose a structure called a causal site to use as a setting for quantum
geometry, replacing the underlying point set. The structure has an interesting
categorical form, and a natural "tangent 2-bundle," analogous to the tangent
bundle of a smooth manifold. Examples with reasonable finiteness conditions
have an intrinsic geometry, which can approximate classical solutions to
general relativity. We propose an approach to quantization of causal sites as
well.Comment: 21 pages, 3 eps figures; v2: added references; to appear in JM
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