Part of a series of articles about
Calculus
${\displaystyle \int _{a}^{b}f'(t)\,dt=f(b)-f(a)}$
Fundamental theorem Limits Continuity Rolle's theorem Mean value theorem Inverse function theorem
Differential Definitions Derivative (generalizations) Differential infinitesimal of a function total Concepts Differentiation notation Second derivative Implicit differentiation Logarithmic differentiation Related rates Taylor's theorem Rules and identities Sum Product Chain Power Quotient L'Hôpital's rule Inverse General Leibniz Faà di Bruno's formula Reynolds
Integral Lists of integrals Integral transform Leibniz integral rule Definitions Antiderivative Integral (improper) Riemann integral Lebesgue integration Contour integration Integral of inverse functions Integration by Parts Discs Cylindrical shells Substitution (trigonometric, tangent half-angle, Euler) Euler's formula Partial fractions Changing order Reduction formulae Differentiating under the integral sign Risch algorithm
Series Geometric (arithmetico-geometric) Harmonic Alternating Power Binomial Taylor Convergence tests Summand limit (term test) Ratio Root Integral Direct comparison Limit comparison Alternating series Cauchy condensation Dirichlet Abel
Vector Gradient Divergence Curl Laplacian Directional derivative Identities Theorems Gradient Green's Stokes' Divergence generalized Stokes Helmholtz decomposition
Multivariable Formalisms Matrix Tensor Exterior Geometric Definitions Partial derivative Multiple integral Line integral Surface integral Volume integral Jacobian Hessian
Advanced Calculus on Euclidean space Generalized functions Limit of distributions
Specialized Fractional Malliavin Stochastic Variations
Miscellaneous Precalculus History Glossary List of topics Integration Bee Mathematical analysis Nonstandard analysis
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In science and especially in mathematical studies, a variational principle is one that enables a problem to be solved using calculus of variations, which concerns finding functions that optimize the values of quantities that depend on those functions. For example, the problem of determining the shape of a hanging chain suspended at both ends—a catenary—can be solved using variational calculus, and in this case, the variational principle is the following: The solution is a function that minimizes the gravitational potential energy of the chain.

History

Physics

The history of the variational principle in classical mechanics started with Maupertuis's principle in the 18th century.

Math

Felix Klein's 1872 Erlangen program attempted to identify invariants under a group of transformations.

Examples

In mathematics

• Ekeland's variational principle in mathematical optimization
• The finite element method
• The variation principle relating topological entropy and Kolmogorov-Sinai entropy.

In physics

• The Rayleigh–Ritz method for solving boundary-value problems in elasticity and wave propagation
• Fermat's principle in geometrical optics
• Hamilton's principle in classical mechanics
• Maupertuis' principle in classical mechanics
• The principle of least action in mechanics, electromagnetic theory, and quantum mechanics
• The variational method in quantum mechanics
• Hellmann–Feynman theorem
• Gauss's principle of least constraint and Hertz's principle of least curvature
• Hilbert's action principle in general relativity, leading to the Einstein field equations.
• Palatini variation
• Hartree–Fock method
• Density functional theory
• Gibbons–Hawking–York boundary term
• Variational quantum eigensolver