Canonical Transformations, Poisson Brackets

In summary, the conversation discusses a problem from a book involving a system with one degree of freedom described by the Hamiltonian formulation of classical mechanics. A canonical transformation is applied, leading to a transformed Hamiltonian described in terms of transformed coordinates and momenta. It is suggested that the transformed momenta will be canonically conjugate to the transformed coordinates, and that Poisson brackets can be used to check this. The property of the conservation of Poisson brackets in a canonical transformation is also mentioned.
  • #1
UniPhysics90
16
0
This isn't actually a homework problem, but a problem from a book, but as it's quite like a homework problem I thought this forum was probably the best place for it.

Homework Statement



Consider a system with one degree of freedom, described by the Hamiltonian formulation of classical mechanics in terms of the coordinate q, and the canonically conjugate momentum, p. A canonical transformation is applied, such that the transformed Hamiltonian is described in terms of the transformed coordinate Q and the transformed momentum P. Explain whether P will be canonically conjugate to Q, and how Poisson brackets may be used to check this.

Homework Equations





The Attempt at a Solution



P will be canonically conjugate to Q (it says so in a book!) and possibly that Poisson brackets will give a constant value (books seem to suggest either 0 or 1?). If anyone can explain this further I'd really appreciate it!

Thanks
 
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  • #2
As far as I remember, we have for a canonical transformation
[tex]\{q,p\}=\{Q,P\}=0[/tex],
and
[tex]\{q,q\}=\{Q,Q\}=\{p,p\}=\{P,P\}=1[/tex],
i.e. the Poisson brackets are conserved in a canonical transformation.

Even if this property isn't directly mentioned, I found the wiki article on canonical transformations quite good: http://en.wikipedia.org/wiki/Canonical_transformation"

I guess the fact that the Poisson brackets are conserved is a consequence of the fact that the dynamics aren't changed in a canonical transformation.
 
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Related to Canonical Transformations, Poisson Brackets

1. What are canonical transformations?

Canonical transformations are mathematical transformations used in classical mechanics to describe the motion of a system in terms of new variables that are related to the original variables by a set of equations. These transformations preserve the form of Hamilton's equations of motion, which are fundamental equations in classical mechanics.

2. What is the significance of canonical transformations?

Canonical transformations are important because they allow us to simplify the equations of motion for a system. By choosing appropriate new variables, we can often reduce the complexity of the equations and gain insights into the behavior of the system.

3. What are Poisson brackets?

Poisson brackets are mathematical operators that are used to describe the fundamental relationship between variables in a classical mechanical system. They measure the rate of change of one variable with respect to another and are closely related to the Hamiltonian of the system.

4. How are canonical transformations and Poisson brackets related?

Canonical transformations and Poisson brackets are closely related because they both describe the behavior of a system in terms of new variables. In fact, Poisson brackets are used to determine whether a transformation is canonical or not.

5. What are some practical applications of canonical transformations and Poisson brackets?

Canonical transformations and Poisson brackets have many practical applications in physics and engineering. They are used to study the behavior of mechanical systems, such as celestial bodies, and to develop accurate mathematical models for predicting their motion. They are also used in quantum mechanics to describe the behavior of particles on a microscopic scale.

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