"Lagrangian formulation of electromagetism"의 두 판 사이의 차이

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imported>Pythagoras0
 
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==Lagrangian for a particle==
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* {{수학노트|url=전자기학의_라그랑지안}}
*  Lagrangian for a charged particle in an electromagnetic field <math>L=T-V</math>
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* [[path integral formulation of quantum mechanics]]
:<math>L(q,\dot{q})=m||\dot{q}||-e\phi+eA_{i}\dot{q}^{i}</math>
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* [[Electroweak theory]]
*  action
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[[분류:migrate]]
:<math>S=-\frac{1}{4}\int F^{\alpha\beta}F_{\alpha\beta}\,d^{4}x</math>
 
* Euler-Lagrange equations
 
:<math>p_{i}=\frac{\partial{L}}{\partial{\dot{q}^{i}}}=m\frac{\dot{q}_{i}}{||\dot{q}_{i}||}+eA_{i}=mv_{i}+eA_{i}</math>
 
$$
 
F_{i}=\frac{\partial{L}}{\partial{q^{i}}}=\frac{\partial}{\partial{{q}^{i}}}(eA_{j}\dot{q}^{j})=e\frac{\partial{A_{j}}}{\partial{q}^{i}}\dot{q}^{j}
 
$$
 
*  equation of motion<math>\dot{p}=F</math> Therefore we get
 
:<math>m\frac{dv_{i}}{dt}=eF_{ij}\dot{q}^{j}</math>. This is what we call the Lorentz force law.
 
* force on a particle is same as <math>e\mathbf{E}+e\mathbf{v}\times \mathbf{B}</math>
 
 
 
 
 
==Lagrangian for electromagnetic tensor==
 
* 상호작용이 없는 전자기장의 라그랑지안은 다음과 같다
 
$$\mathcal{L}_{\text{EM}}= - \frac{1}{4}F_{\mu\nu}F^{\mu\nu}=\frac{1}{2}(\mathbf{E}^2-\mathbf{B}^2)$$
 
이 때 <math>F_{\mu\nu} = \partial_\mu A_\nu - \partial_\nu A_\mu \,\!</math>는 전자기텐서, $A=(A_{\mu})$는 전자기 포텐셜
 
* 라그랑지안은 전자기 포텐셜의 다음과 같은 변환에 대하여 불변이다
 
:<math>A_{\mu}(x) \to A_{\mu}(x)-\partial_{\mu}\Lambda(x)</math>
 
여기서 $\Lambda(x)$는 임의의 스칼라장
 
* equation of motion
 
$$
 
0 = \partial_\mu F^{\mu\nu}
 
$$
 
* see http://www.damtp.cam.ac.uk/user/tong/qft/six.pdf
 
 
 
 
 
==memo==
 
* http://dexterstory.tistory.com/888
 
 
 
 
 
 
 
==related items==
 
* [[path integral formulation of quantum mechanics|path integral]]
 
 
 
 
 
 
 
==expositions==
 
* THOMAS YU [http://math.uchicago.edu/~may/REU2012/REUPapers/Yu.pdf LAGRANGIAN FORMULATION OF THE ELECTROMAGNETIC FIELD]
 
* [http://www.physics.sfsu.edu/~lea/courses/grad/fldlagr.PDF The field Lagrangian]
 
* http://www.lecture-notes.co.uk/susskind/classical-mechanics/lecture-8/the-electromagnetic-lagrangian/
 
* http://unapologetic.wordpress.com/2012/07/16/the-higgs-mechanism-part-1-lagrangians/
 
 
 
 
 
==questions==
 
* http://physics.stackexchange.com/questions/3005/derivation-of-maxwells-equations-from-field-tensor-lagrangian?rq=1
 

2020년 11월 13일 (금) 10:43 기준 최신판