  We study frictionless and non-adhesive contact between elastic half-spaces
with self-affine surfaces. Using a recently suggested corrective technique, we
ensure an unprecedented accuracy in computation of the true contact area
evolution under increasing pressure. This accuracy enables us to draw
conclusions on the role of the surface's spectrum breadth (Nayak parameter) in
the contact area evolution. We show that for a given normalized pressure, the
contact area decreases logarithmically with the Nayak parameter. By linking the
Nayak parameter with the Hurst exponent (or fractal dimension), we show the
effect of the latter on the true contact area. This effect, undetectable for
surfaces with poor spectral content, is quite strong for surfaces with rich
spectra. Numerical results are compared with analytical models and other
available numerical results. A phenomenological equation for the contact area
growth is suggested with coefficients depending on the Nayak parameter. Using
this equation, the pressure-dependent friction coefficient is deduced based on
the adhesive theory of friction. Some observations on Persson's model of rough
contact, whose prediction does not depend on Nayak parameter, are reported.
Overall, the paper provides a unifying picture of rough elastic contact and
clarifies discrepancies between preceding results.
