All Questions
Tagged with terminology lagrangian-formalism
46
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Is Principle of Least Action a first principle? [closed]
It is on the basis of Principle of Least Action, that Lagrangian mechanics is built upon, and is responsible for light travelling in a straight line.
Is its the classical equivalent of Schrodinger's ...
-2
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2
answers
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On the physical meaning of functionals and the interpretation of their output numbers
I am studying about functionals, and while looking for some examples of functionals in physics, I have run into this handout .
Here are two questions of mine.
1- This handout starts as follows (the ...
user386360
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0
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When does a theory decouple?
The question is very broad, but it seems to me that the term 'to decouple' is also used in various contexts. For example, neutrinos decouple from the photons in the early Universe, when the ...
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On-shell condition in Classical Mechanics [duplicate]
Which is the on-shell condition in classical mechanics? I mean in QFT we use to tell about external particle state as to be in a on-shell condition which means that these particles have to statisfy ...
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1
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When can a "theorem" be raised to a "principle"? [duplicate]
I am taking a 3rd year course in analytical mechanics, taught by a professor of mathematical physics.
One of the important results of analytical mechanics is d'Alembert's principle. According to our ...
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1
answer
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What are Wilson Coefficients?
I have seen this terminology in several papers but I haven't managed to find an explanation of what they actually are. I understand that they are related to effective field theory.
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What is the difference between variational principle, principle of stationary action and Hamilton's principle?
In advanced mechanics, we learn about the variational principle, the principle of stationary action, and the Hamilton's principle. I feel that the difference between them is not very clearly organized ...
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1
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Independent generalized coordinates are dependent
(This is not about independence of $q$,$\dot q$)
A system has some holonomic constraints. Using them we can have a set of coordinates ${q_i}$. Since any values for these coordinates is possible we say ...
- 1,270
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Is the state of a system represented by a point $\textbf{q}=(q_1,q_2,q_3...q_n)^T$ in configuration space?
I was reading the lecture notes titled: 'An introduction to Lagrangian
and Hamiltonian mechanics'.
In these notes, he writes at one place:
We consider mechanical systems that are holonomic and ...
- 1,451
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What are "combinatorial factors" in the Lagragian?
I'm reading "Renormalization" by John C. Collins and in the fifth chapter "Renormalization" under the subchapter 5.6 "Relation to $\mathcal L$", he defines the Lagrangian ...
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How is the kinetic matrix of a Lagrangian defined?
In this question the term kinetic matrix of a Lagrangian is used, but I cannot find a general definition anywhere in wikipedia or elsewhere.
Can anyone tell me the precise definition? What is it used ...
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What is the difference between the applied, external force and the generalized force?
in analytical mechanics, we define the generalized force using the applied force times $dr/dq$. If I want to express the difference between the external and generalized force in words in order to ...
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Precise definition of the vertex factor
Just a short question about the vertex factor in QFT. When I have an interaction Lagrangian
$$\mathcal{L}_{\mathrm{int}}=-\frac{\lambda}{3!}\phi^3$$
with a real scalar field $\phi$, is the vertex ...
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1
answer
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Historical meaning of action
In the Feynman lectures, it is stated
Also, I should say that $S$ is not really called the ‘action’ by the most precise and pedantic people. It is called ‘Hamilton´s first principal function.’ Now ...
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What is meant by homogeneous in $x$ in $n$'th degree?
I'm reading about classical mechanics by Goldstein, and in the section about Hamiltonian mechanics it is stated that in the expression:
$$H(q,p,t)=\dot{q}_ip_i-L(q,\dot{q}, t)$$
the Lagrangian ...
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