Lagrangians Definition and 58 Threads

  1. V

    What Are the Correct Equations of Motion for a Magnetic Lagrangian?

    Sorry about the endless stream of questions about Lagrangians. I am actually beginning to detest them a bit;p Anyway, if we have a Lagrangian in three dimensional space: L=\frac{1}{2}m\dot{\vec{x}}^{2}+e\vec{A}.\dot{\vec{x}} where A_{i}=\epsilon_{ijk}B_{j}x_{k} and B is just a constant...
  2. H

    What Are the Steps to Calculate Perturbed Lagrangians in Vector Potential?

    I hope this is the right area to ask this, but does anyone know of a good link which describes perturbation theory? Or even a good book? I have a lagrangian that is a function of the vector potential and I need to figure out the perturbed lagrangian by perturbing the vector potential. That...
  3. C

    Kinetic Energy Calculation for Rigid Body Lagrangians with Two Particles

    Homework Statement two particles, m_{1}, and m_{2} are connected together by a thin masses rod of length d. The system moves under a uniform potential function U(r_{1}^{\rightarrow}, r_{2}^{\rightarrow}). What is the Kinetic energy of the system in cartesian coordinates? Homework Equations...
  4. L

    Lagrangians in Quantum Mechanics

    In classical mechanics the Lagrangian depends only on time, position, and velocity. It is not allowed to depend on any higher order derivatives of position. Does this principle remain true for Lagrangians in non-relativistic quantum mechanics? What about relativistic quantum field theory...
  5. C

    Are lagrangians based on physical observation or mathematics?

    are lagrangians based on physical observation or mathematical reasoning?
  6. M

    Is Angular Momentum Conserved in a Central and Gravitational Force System?

    I have a problem with a particle experiencing a central force towards some origin, as well as a gravitational force downwards. I've calculated the Lagrangian, and the equations of motion. Now I'm being asked to see if the system follows conservation of angular momentum. How do I do this? I...
  7. E

    Quantum mnechanics with lagrangians?

    usually quantum mechanics is made with hamiltonians but..could it be done with lagrangians in the sense that LF=gF where F is the wave function and g plays a role of an eigenvalue what would happen with dq/dtF?..in fact would it be equal to qEnF where En is the energy.. this can be...
  8. E

    Quantization without Lagrangians.

    In fact let us suppose we only have the classical equations of movement x´=f(x1,x2,x3...xn) but we do not have or not know a lagrangian ..how could we quantizy them?..in fact how is a quantization made if we do not have a lagrangian (or hamiltonian)?..
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