# Recent questions tagged action

The action is the integral of the Lagrangian over time, or the integral of the Lagrangian Density over both time and space. I.e.

$$S=\int L\mbox{ d}t=\iiiint\mathcal L\mbox{ d}x^4$$

This is very useful in the Lagrangian reformulation of Classical Mechanics, where one may apply the least action principle to obtain the equations of motion.

Also useful in Quantum Mechanics, Quantum Field Theory, General Relativity, String Theory, and so on, due to the Path Integral and Variational formulations.

+ 1 like - 0 dislike
1 answer 104 views
+ 5 like - 0 dislike
0 answers 101 views
+ 1 like - 0 dislike
1 answer 240 views
+ 3 like - 0 dislike
2 answers 625 views
+ 7 like - 0 dislike
2 answers 285 views
+ 7 like - 0 dislike
2 answers 77 views
+ 4 like - 0 dislike
0 answers 55 views
+ 3 like - 0 dislike
1 answer 674 views
+ 4 like - 0 dislike
0 answers 324 views
+ 3 like - 0 dislike
2 answers 375 views
+ 2 like - 0 dislike
0 answers 126 views
+ 6 like - 0 dislike
2 answers 98 views
+ 6 like - 0 dislike
5 answers 3170 views
+ 3 like - 0 dislike
1 answer 1213 views
+ 6 like - 0 dislike
2 answers 652 views
+ 8 like - 0 dislike
1 answer 202 views
+ 4 like - 0 dislike
2 answers 109 views
+ 6 like - 0 dislike
1 answer 158 views
To see more, click for the full list of questions or popular tags.