No abstract

Periodic minimal nets are defined. It is shown that there is a one-to-one relation between the nets and certain finite graphs. The finite graphs, which completely characterize the nets up to isomorphism, are called the quotient graphs of the nets. For a given ρ the number of pperiodic nets is finite. The 2-and 3-periodic minimal nets are presented together with their quotient graphs. In addition, the quotient graphs of the 4-periodic minimal nets are listed. Nets and quotient graphs are classified according to their eigenvalue spectra.