Infinity symbol in bookbinding to indicate that a book is printed on acid-free paper and will therefore be long-lasting. In modern mysticism, the infinity symbol has become identified with a variation of the ouroboros, an ancient image of a snake eating its own tail that has also come to symbolize the infinite, and the ouroboros is sometimes drawn in figure-eight form to reflect this identification, rather than in its more traditional circular form. In the works of Vladimir Nabokov, including "The Gift" and "Pale Fire", the figure-eight shape is used symbolically to refer to the Möbius strip and the infinite, for instance
Hilbert symbol (for "n" prime) used the power residue symbol when "K" has residue characteristic coprime to "n", and was rather complicated when "K" has residue characteristic dividing "n". The Hilbert symbol is (multiplicatively) bilinear: skew symmetric: nondegenerate: It detects norms (hence the name norm residue symbol): It has the "symbol" properties: Hilbert's reciprocity law states that if "a" and "b" are in an algebraic number field containing the "n"th roots of unity then where the product is over the finite and infinite primes "p" of the number field, and where (,) is the Hilbert symbol of the completion at "p". Hilbert's