Generating function, hamiltonian dynamics

In summary, a canonical transformation from (p,q) to (P,Q) can be made using a generating function F=a*cot(Q), where 'a' is a constant. However, if the generating function does not have a functional dependence on p or q, it may be difficult to find the desired contact transformation. The correct form of the generating function should be F(q,Q) or F(p,Q) to properly connect the transformation.
  • #1
devd
47
1

Homework Statement



A canonical transformation is made from (p,q) to (P,Q) through a generating function F=a*cot(Q), where 'a' is a constant. Express p,q in terms of P,Q.

Homework Equations





The Attempt at a Solution


A generating function is supposed to be a bridge between (p,q) and (P,Q), right? Now, if there is no functional dependence of F on p or q, that is the old variables, how is one supposed to find out the contact transformation asked for?
 
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  • #2
yeah that generating function doesn't make sense. It should be F(q,Q) F(p,Q)

it has to be a function of two variables which connect the transformation Which the given does not
 
  • #3
Thanks a lot! :)
 

1. What is a generating function in Hamiltonian dynamics?

A generating function is a mathematical tool used in Hamiltonian dynamics to transform the coordinates and momenta of a system. It allows for the simplification of the equations of motion and makes it easier to solve for the trajectory of a system.

2. How is a generating function related to the Hamiltonian?

A generating function is closely related to the Hamiltonian, which is the total energy of a system. The partial derivatives of the generating function with respect to the coordinates and momenta are equal to the canonical coordinates and momenta, respectively, and the Hamiltonian can be expressed in terms of the generating function.

3. What is the importance of generating functions in Hamiltonian dynamics?

Generating functions are important in Hamiltonian dynamics because they allow for the simplification of equations of motion and provide a method for finding the canonical coordinates and momenta of a system. They also allow for the identification of constant quantities of motion, known as integrals of motion, which are useful in studying the dynamics of a system.

4. Are there different types of generating functions in Hamiltonian dynamics?

Yes, there are different types of generating functions in Hamiltonian dynamics, including the Lagrange, Jacobi, and Hamilton-Jacobi generating functions. Each type has its own set of properties and is used in different scenarios to simplify the equations of motion.

5. How are generating functions used in practical applications?

Generating functions are used in practical applications to simplify the equations of motion and solve for the trajectory of a system. They are also useful in identifying integrals of motion, which can be used to analyze the behavior of a system. Generating functions are commonly used in fields such as physics, engineering, and mathematics to study the dynamics of various systems.

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