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
Heawood graph has automorphisms that take any vertex to any other vertex and any edge to any other edge. More strongly, the Heawood graph is 4-arc-transitive. According to the Foster census, the Heawood graph, referenced as F014A, is the only cubic symmetric graph on 14 vertices. It has book thickness 3 and queue number 2. The characteristic polynomial of the Heawood graph is formula_1. It is the only graph with this characteristic polynomial, making it a graph determined by its spectrum. Heawood graph In the mathematical field of graph theory, the Heawood graph is an undirected graph with 14 vertices and 21