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In a strong formulation, the solution space is constructed such that these equations or conditions are already fulfilled. The Lax–Milgram theorem, named after Peter Lax and Arthur Milgram who proved it in 1954, provides weak formulations for certain systems on Hilbert spaces.
The achievement of Lax and Milgram in their 1954 result was to specify sufficient conditions for this weak formulation to have a unique solution that depends continuously upon the specified datum f ∈ V ∗: it suffices that U = V is a Hilbert space, that B is continuous, and that B is strongly coercive, i.e.
Ritz–Galerkin method (after Walther Ritz) typically assumes symmetric and positive definite bilinear form in the weak formulation, where the differential equation for a physical system can be formulated via minimization of a quadratic function representing the system energy and the approximate solution is a linear combination of the given set ...
It is a generalization of the famous Lax–Milgram theorem, which gives conditions under which a bilinear function can be "inverted" to show the existence and uniqueness of a weak solution to a given boundary value problem. The result is named after the mathematicians Jacques-Louis Lions, Peter Lax and Arthur Milgram.
One may show, via the Lax–Milgram lemma, that whenever (,) is coercive and () is continuous, then there exists a unique solution () to the weak problem (*). If further A ( u , φ ) {\displaystyle A(u,\varphi )} is symmetric (i.e., b = 0 {\displaystyle b=0} ), one can show the same result using the Riesz representation theorem instead.
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In mathematics, a weak solution (also called a generalized solution) to an ordinary or partial differential equation is a function for which the derivatives may not all exist but which is nonetheless deemed to satisfy the equation in some precisely defined sense. There are many different definitions of weak solution, appropriate for different ...
Is Lax–Milgram theorem the same as 'Weak formulation'? Correct in case I'm wrong guys. Thanks! --Luca 15:53, 12 December 2007 (UTC) The Lax-Migram theorem is not the same as 'Weak formulation'. However, this 'Weak formulation' does describe the Lax-Milgram theorem, and the link to Lax–Milgram theorem points back here. Therefore, things are OK.