Equation of motion from Hamiltonian

In summary, the conversation revolved around the Hamiltonian equation of motion and the dimensions of the partial derivatives involved. The goal was to check if the equations and dimensions were consistent with the definitions provided in the Homework Equations section.
  • #1
LagrangeEuler
717
20

Homework Statement


[tex]H=\sum^N_{i=1}(\frac{p_i^2}{2m}+\frac{1}{2}(x_{i+1}-x_i)^2+(1-\cos(2\pi x_i))[/tex]

Homework Equations


Hamilton equation of motion I suppose
##\dot{q}=\frac{\partial H}{\partial p}##
##\dot{p}=-\frac{\partial H}{\partial q}##[/B]

The Attempt at a Solution


If particles are identical then
##\dot{p}=m \dot{x}##
So if I understand well I will get from here system of equations
##\dot{p_1}=-\frac{\partial H}{\partial x_1}##
If I take for example m=1, then
##\dot{x_1}=-\frac{\partial H}{\partial x_1}##
Is this correct?
 
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  • #2
no. Check the dimensions.
 
  • #3
Ok. Can I get some help?
 
  • #4
Yes: write down the dimensions and check,
 
  • #5
In particular I think BvU is trying to draw your attention to the partial derivatives you wrote in your last statements. Check those dimensions to see if they are consistent with the definitions you wrote in the relevant equations section.
 

Related to Equation of motion from Hamiltonian

1. How is the equation of motion derived from the Hamiltonian?

The equation of motion can be derived from the Hamiltonian using the Hamiltonian equations, which are a set of equations that relate the time derivatives of the position and momentum variables to the Hamiltonian function. These equations are based on the principle of least action and are used to describe the dynamics of a system in classical mechanics.

2. What is the significance of the Hamiltonian in classical mechanics?

The Hamiltonian is a fundamental concept in classical mechanics that represents the total energy of a physical system. It is defined as the sum of the system's kinetic and potential energies and is used to determine the equations of motion for the system.

3. How does the Hamiltonian differ from the Lagrangian in classical mechanics?

The Hamiltonian and Lagrangian are both mathematical expressions that describe the dynamics of a system in classical mechanics. However, the Hamiltonian is a function of position and momentum variables, while the Lagrangian is a function of position and velocity variables. Additionally, the Hamiltonian includes the potential energy of the system, while the Lagrangian does not.

4. Can the equation of motion from Hamiltonian be extended to quantum mechanics?

Yes, the equation of motion from Hamiltonian can be extended to quantum mechanics by using the Schrödinger equation, which is the fundamental equation that describes the evolution of quantum systems. The Hamiltonian is used to define the operator corresponding to the total energy of the system in the Schrödinger equation.

5. Are there any limitations to using the equation of motion from Hamiltonian?

One limitation of using the equation of motion from Hamiltonian is that it is only applicable to systems that can be described by classical mechanics. It cannot be used for systems that exhibit quantum behavior or systems that involve relativistic effects. Additionally, the equation of motion from Hamiltonian assumes that the system is in a state of equilibrium, which may not always be the case in real-world systems.

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