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captain
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what is the difference between these two formalism and when are each used? also is it true the lagrangian formalism is used more in qft, if so i am curious to know why?
genneth said:Well, have you studied them yet? It's good to know at what level the answer is going to be...
melrose said:that is rude. He only asked a question. what is it with this board.?
is this board some kind of pissing contest?
melrose said:that is rude. He only asked a question. what is it with this board.?
is this board some kind of pissing contest?
captain said:lagrangian and hamiltonian formalism
what is the difference between these two formalism and when are each used? also is it true the lagrangian formalism is used more in qft, if so i am curious to know why?
captain said:what is the difference between these two formalism and when are each used? also is it true the lagrangian formalism is used more in qft, if so i am curious to know why?
genneth said:In the Hamiltonian theory (as you would find in textbooks, at least), time tends to play a dominating role, which is in violation of the spirit of special relativity.
http://en.wikipedia.org/wiki/Lagrangian_mechanicscaptain said:what is the difference between these two formalism and when are each used? also is it true the lagrangian formalism is used more in qft, if so i am curious to know why?
Lagrangian and Hamiltonian formalism are two different mathematical approaches used to describe the dynamics of a physical system. In Lagrangian formalism, the system's behavior is described by the Lagrangian function, which is a function of the system's position and velocity. In Hamiltonian formalism, the system is described by the Hamiltonian function, which is a function of the system's position and momentum. The main difference between the two is that Lagrangian formalism is based on the system's kinetic and potential energies, while Hamiltonian formalism is based on the system's total energy.
The principle of least action states that the actual path taken by a system between two points in time is the path that minimizes the action, which is the integral of the Lagrangian function over time. In other words, the system takes the path that requires the least amount of energy to move from its initial state to its final state. This principle is a fundamental concept in Lagrangian formalism and is used to derive the equations of motion for a system.
The Hamiltonian function is related to the Lagrangian function through a mathematical transformation known as the Legendre transformation. The Hamiltonian function is equal to the Lagrangian function minus the product of the system's velocity and its conjugate momentum. This transformation allows us to describe the dynamics of a system in terms of its position and momentum, rather than its position and velocity.
Yes, Lagrangian and Hamiltonian formalism can be used to describe the dynamics of all physical systems. However, the equations of motion derived from these formalisms may be more complex for certain systems, such as systems with non-conservative forces or systems with constraints. In these cases, additional techniques, such as the use of Lagrange multipliers, may be necessary to accurately describe the system's behavior.
One major advantage of using Lagrangian and Hamiltonian formalism is that they provide a more elegant and concise mathematical description of a system's behavior compared to other methods, such as Newton's laws of motion. They also have the ability to handle complex systems with multiple degrees of freedom. Additionally, these formalisms have important applications in fields such as mechanics, electromagnetism, and quantum mechanics.