Random-walk radiocarbon calibration

Geoff Nicholls and J Andres Christen


In this note we check the interesting recent
results of Gomez Portugal Aguilar {it et al} cite{aguilar00}.
These authors fit a simple random walk with Gaussian increments
to the radiocarbon calibration curve. They suggest that the posterior
standard deviation of the calibration curve is smaller between
years where observations were made than it is at those years.
We find that in contrast to their result the posterior standard
deviations of the calibration curve bow out slightly between observation
points in our estimates, for a model of the kind they describe.
In earlier work Christen~cite{christen94} conditions
the random walk to visit the measured calibration values.
Following cite{aguilar00},
we consider the unconditioned posterior distribution for
calibration curves, and thereby improve slightly on
the reconstructions of cite{christen94}.

Radiocarbon calibration, Bayesian inference, Markov chain Monte Carlo, random walk

Math Review Classification
Primary 62M05 ; Secondary 62P99

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6 pages

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