Search results
Results From The WOW.Com Content Network
A formal power series can be loosely thought of as an object that is like a polynomial, but with infinitely many terms.Alternatively, for those familiar with power series (or Taylor series), one may think of a formal power series as a power series in which we ignore questions of convergence by not assuming that the variable X denotes any numerical value (not even an unknown value).
Unlike an ordinary series, the formal power series is not required to converge: in fact, the generating function is not actually regarded as a function, and the "variable" remains an indeterminate. One can generalize to formal power series in more than one indeterminate, to encode information about infinite multi-dimensional arrays of numbers.
The partial sums of a power series are polynomials, the partial sums of the Taylor series of an analytic function are a sequence of converging polynomial approximations to the function at the center, and a converging power series can be seen as a kind of generalized polynomial with infinitely many terms. Conversely, every polynomial is a power ...
In mathematics, a formal group law is (roughly speaking) a formal power series behaving as if it were the product of a Lie group. They were introduced by S. Bochner ( 1946 ). The term formal group sometimes means the same as formal group law, and sometimes means one of several generalizations.
In a formal power series, the powers of the variable are used only as position-holders for the coefficients, so that the coefficient of is the fifth term in the sequence. In combinatorics, the method of generating functions uses formal power series to represent numerical sequences and multisets, for instance allowing concise expressions for ...
Formal power series are used in combinatorics to describe and study sequences that are otherwise difficult to handle, for example, using the method of generating functions. The Hilbert–Poincaré series is a formal power series used to study graded algebras.
A formal power series in an indeterminate is an expression of the form + + + …, where no value is assigned to the symbol . [7] This is similar to the definition of a polynomial, except that an infinite number of the coefficients may be nonzero.
Similarly, the formal power series ring R[{[t]}] is the completion of R[t] at (t) (see also Hensel's lemma) A complete ring has much simpler structure than a commutative ring. This owns to the Cohen structure theorem , which says, roughly, that a complete local ring tends to look like a formal power series ring or a quotient of it.