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A fixed-point theorem is a result saying that at least one fixed point exists, under some general condition. [1] For example, the Banach fixed-point theorem (1922) gives a general criterion guaranteeing that, if it is satisfied, fixed-point iteration will always converge to a fixed point.
A fixed-point representation of a fractional number is essentially an integer that is to be implicitly multiplied by a fixed scaling factor. For example, the value 1.23 can be stored in a variable as the integer value 1230 with implicit scaling factor of 1/1000 (meaning that the last 3 decimal digits are implicitly assumed to be a decimal fraction), and the value 1 230 000 can be represented ...
In mathematics, a variable (from Latin variabilis, "changeable") is a symbol, typically a letter, that refers to an unspecified mathematical object. [1] [2] [3] One says colloquially that the variable represents or denotes the object, and that any valid candidate for the object is the value of the variable. The values a variable can take are ...
For a relational signature X, FO[PFP](X) is the set of formulas formed from X using first-order connectives and predicates, second-order variables as well as a partial fixed point operator used to form formulas of the form [, ], where is a second-order variable, a tuple of first-order variables, a tuple of terms and the lengths of and coincide with the arity of .
The terms "diagonal lemma" or "fixed point" do not appear in Kurt Gödel's 1931 article or in Alfred Tarski's 1936 article. Rudolf Carnap (1934) was the first to prove the general self-referential lemma , [ 6 ] which says that for any formula F in a theory T satisfying certain conditions, there exists a formula ψ such that ψ ↔ F (°#( ψ ...
A topological space has the fixed-point property if and only if its identity map is universal. A product of spaces with the fixed-point property in general fails to have the fixed-point property even if one of the spaces is the closed real interval. The FPP is a topological invariant, i.e. is preserved by any homeomorphism.
In numerical analysis, fixed-point iteration is a method of computing fixed points of a function.. More specifically, given a function defined on the real numbers with real values and given a point in the domain of , the fixed-point iteration is + = (), =,,, … which gives rise to the sequence,,, … of iterated function applications , (), (()), … which is hoped to converge to a point .
A "fixed point" is any predicate for which this is a valid implication. There may be many fixed points, including the always-true predicate; a "least fixed point" is a fixed point that has as few true values as possible. More precisely, its true values should be a subset of the true values of any other fixed point. [22]