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Encyclopedia > Least action principle

The principle of least action was first formulated by Pierre-Louis Moreau de Maupertuis, who said that "Nature is thrifty in all its actions". See action (physics). Others who developed the idea included Euler and Leibniz. It should be said that, from the point of view of the calculus of variations, a principle of stationary action is a more accurate formulation. Pierre Louis Maupertuis, here wearing lapmudes or a fur coat from his Lapland expedition. ... In physics, the action principle is an assertion about the nature of motion, from which the trajectory of an object subject to forces can be determined. ... Leonhard Euler aged 49 (oil painting by Emanuel Handmann, 1756) Leonhard Euler (April 15, 1707 - September 18, 1783) (pronounced oiler) was a Swiss mathematician and physicist. ... Gottfried Wilhelm Leibniz (also von Leibni(t)z) (July 1 (June 21 Old Style) 1646, Leipzig – November 14, 1716, Hanover) was a German polymath, deemed a genius in his day and since. ... Calculus of variations is a field of mathematics which deals with functions of functions, as opposed to ordinary calculus which deals with functions of numbers. ... The principle of stationary action for the Action (physics) S (a measure of the energy of the system under study) states that the variation in S is at an extremum, in symbols: where the independent variables are denoted by a set of acting at some time t. ...


Earlier, Pierre de Fermat had introduced the ideas that rays of light, in optical conditions such as refraction and reflection, followed a principle of least time: see Fermat's principle. Pierre de Fermat Pierre de Fermat (August 17, 1601 – January 12, 1665) was a French lawyer at the Parlement of Toulouse, southern France, and a mathematician who is given credit for the development of modern calculus. ... The straw seems to be broken, due to refraction of light as it emerges into the air. ... Spheres reflecting the floor and each other. ... Fermats principle assures that the angles given by Snells law always reflect lights quickest path between P and Q. Fermats principle in optics states: This principle was first stated by Pierre de Fermat. ... Fermats principle assures that the angles given by Snells law always reflect lights quickest path between P and Q. Fermats principle in optics states: This principle was first stated by Pierre de Fermat. ...


The principle of least action led to the development of the Lagrangian and Hamiltonian formulations of classical mechanics. Although they are at first more difficult to grasp, they have the advantage that their world-view is more transferable to the frameworks of relativistic and quantum-mechanical physics than that of Newton's laws. Lagrangian mechanics is a re-formulation of classical mechanics introduced by Joseph Louis Lagrange in 1788. ... Hamiltonian mechanics is a re-formulation of classical mechanics that was invented in 1833 by William Rowan Hamilton. ... Albert Einsteins theory of relativity is a set of two theories in physics: special relativity and general relativity. ... Fig. ... Newtons laws of motion are the three scientific laws which Isaac Newton discovered concerning the behaviour of moving bodies. ...


See also

In physics, the action principle is an assertion about the nature of motion, from which the trajectory of an object subject to forces can be determined. ... A variational principle is a principle in physics which is expressed in terms of the calculus of variations. ... Calculus of variations is a field of mathematics which deals with functions of functions, as opposed to ordinary calculus which deals with functions of numbers. ... In physics, functional integration is integration over certain infinite-dimensional spaces. ... Fermats principle assures that the angles given by Snells law always reflect lights quickest path between P and Q. Fermats principle in optics states: This principle was first stated by Pierre de Fermat. ...

External links


  Results from FactBites:
 
Action (physics) - Wikipedia, the free encyclopedia (1781 words)
In physics, the action is an integral quantity that is used to determine the evolution of a physical system between two defined states using the calculus of variations.
The action is usually an integral over time, but may be integrated over spatial variables as well (for action pertaining to fields); in still other cases, the action is integrated along the path followed by the physical system.
The action corresponding to the various paths is used to calculate the path integral, that gives the probability amplitudes of the various outcomes.
Principle of least action - Wikipedia, the free encyclopedia (1482 words)
In physics, the principle of least action or principle of stationary action is a variational principle by which, when applied to the action of a mechanical system, can be used to obtain the equations of motion for that system.
The principle remains central in modern physics and mathematics, being applied in the theory of relativity, quantum mechanics and quantum field theory, and a focus of modern mathematical investigation in Morse theory.
By contrast, the action principle is not localized to a point; rather, it involves integrals over an interval of time and (for fields) extended region of space.
  More results at FactBites »


 

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