15
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Accepted
Relation between energy and time
There are at least three occasions where the notions of Energy and Time show up together in classical and modern physics.
Probably the most elementary situation is related to the fact that the ...
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5
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Relation between energy and time
Why is energy always related to time in physics.
I don't think it is helpful to describe energy as "always related to time" in physics.
That being said, there certainly are a number of ...
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4
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Are there any experiments that examine Hamilton's Principle directly?
Often in theoretical physics, there can be a large gap between the logical starting point of a theory, and the actual experimental tests.
The principle of least action (aka Hamilton's principle) is ...
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3
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Why doesn't Car-Parrinello molecular dynamics require an SCF calculation?
It is not entirely true that Car-Parrinello (CP) Molecular Dynamics (MD) doesn't require a self-consistent field (SCF) calculation at all. The method must start close to the SCF solution (actually a ...
2
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Relation between energy and time
The way I like to look at it (and which may or may not give you the same amount of intuition as it does to me) is as such:
Momentum is what gives rise to changes in position. Clasically, a body ...
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Is First-Class Constraint Generator of matter Gauge Symmetry in EM example?
From @Andrew's comment, I know how to solve it.
In scalar QED, EM field would couple to current $J^{\mu}(x) = \phi^{\star}(x)\partial^{\mu}\phi(x) - \phi(x)\partial^{\mu}\phi^{\star}(x)$, and the ...
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Are there any experiments that examine Hamilton's Principle directly?
About principles in physics:
I want to refer to a discussion by stackexchange contributor Kevin Zhou.
There is a Januari 2020 question titled: 'Why can't the Schrödinger equation be derived?'
In his ...
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Is First-Class Constraint Generator of matter Gauge Symmetry in EM example?
The solution to OP's problem is to include a pertinent matter sector in the E&M Lagrangian (3) (in OP's case: a complex scalar $\phi$). This produces the source term in the first-class secondary ...
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When is the Lagrangian a Lorentz scalar?
An obvious, kind of dumb, answer is that the Lagrangian corresponding to a given Hamiltonian will be a Lorentz scalar if the Hamiltonian has the form,
$$ \mathcal{H} = \pi^a \frac{\partial}{\partial t}...
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When is the Lagrangian a Lorentz scalar?
As far as I know, there are no good ways of stating what conditions on the Hamiltonian will cause the Lagrangian to be a Lorentz scalar other than to just say the Hamiltonian must be derived from a ...
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Does quasi-symmetry preserve the solution of the equation of motion?
Boundary condition is a part of the very definition of your field theory, classical or quantum. When e.g Peskin & Shroeder leaves out the surface term, "all fields and derivatives vanish at ...
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