Variations of the ichthys symbol contains the words "n'Chips", a play on "Fish and Chips". "Sushi" written inside the fish is one more variant. Variations of the ichthys symbol The ichthys symbol, or "Jesus fish", typically used to proclaim an affiliation with or affinity for Christianity, has many variations. Some of these are made by Christians in order to promote a specific doctrine or theological perspective, such as evolutionary creation. Other variations are sometimes intended for the purpose of satire. Both the traditional ichthys fish as well as its variations, are often seen adorning the bumpers or trunks of automobiles, often in the form of
Symbol of a differential operator In the study of hyperbolic and parabolic partial differential equations, zeros of the principal symbol correspond to the characteristics of the partial differential equation. Consequently, the symbol is often fundamental for the solution of such equations, and is one of the main computational devices used to study their singularities. Let "P" be a linear differential operator of order "k" on the Euclidean space R. Then "P" is a polynomial in the derivative "D", which in multi-index notation can be written The total symbol of "P" is the polynomial "p": The leading symbol, also known as the principal symbol, is the