  We present numerical results for the equation of state of an infinite chain
of hydrogen atoms. A variety of modern many-body methods are employed, with
exhaustive cross-checks and validation. Approaches for reaching the continuous
space limit and the thermodynamic limit are investigated, proposed, and tested.
The detailed comparisons provide a benchmark for assessing the current state of
the art in many-body computation, and for the development of new methods. The
ground-state energy per atom in the linear chain is accurately determined
versus bondlength, with a confidence bound given on all uncertainties.
