Planck's law In 1880, André-Prosper-Paul Crova published a diagram of the three-dimensional appearance of the graph of the strength of thermal radiation as a function of wavelength and temperature. He determined the spectral variable by use of prisms. He analyzed the surface through what he called "isothermal" curves, sections for a single temperature, with a spectral variable on the abscissa and a power variable on the ordinate. He put smooth curves through his experimental data points. They had one peak at a spectral value characteristic for the temperature, and fell either side of it towards the horizontal axis. Such spectral sections are
Shannon capacity of a graph The Lovász number ϑ("G") is a different graph invariant, that can be computed numerically to high accuracy in polynomial time by an algorithm based on the ellipsoid method. The Shannon capacity of a graph "G" is bounded from below by α("G"), and from above by ϑ("G"). In some cases, ϑ("G") and the Shannon capacity coincide; for instance, for the graph of a pentagon, both are equal to . However, there exist other graphs for which the Shannon capacity and the Lovász number differ. Haemers provided another upper bound on the Shannon capacity, which is sometimes better than Lovász bound: where