Help with Poisson Brackets (original paper)

In summary, the conversation discusses the translation of a paper by Poisson about his brackets and the function a=f(q,u,t) not having a second order derivative. It is mentioned that a=f(q,u,t) is a constant of motion and there may be restrictions on second order derivatives for constants of motion. A quotation from the Wolfram website is also mentioned, stating that a first integral associated with the independent variable t will not have any second or higher derivatives of the coordinates. The speaker is confused about why a first integral of the motion cannot have a second order derivative and asks for clarification.
  • #1
gibsonphysics
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0
Here I have a translation from French to English of the original paper by Poisson about his brackets. I cannot understand why the function a=f(q,u,t) doesn't have a second order derivative (in q or u). The problem is on the top of the third page (second .JPG) after he took the time derivative. Can somebody help me?
 

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  • #2
Also, a=f(q,u,t) is a constant of motion. Is there any restriction about second order derivatives for q or u or (p) for a constant of motion?
 
  • #3
Here is a quotation that I found on Wolfram website:

"A first integral associated with the independent variable t exist if f is independent of t and does not contain any second or higher derivatives of the coordinates."

Since we have a=f(q,u,t) as a firt integral, it will not have a second derivative of any canonical variables.

What I can't understand and ;also, I didn't find anywhere is why a first integral of the motion can't have a second order derivative.

Does anybody know?
 

What is the purpose of Poisson brackets in the original paper?

The purpose of Poisson brackets in the original paper is to establish a mathematical framework for studying the dynamics of mechanical systems. It is a way to quantify the relationship between two variables and their rates of change.

How are Poisson brackets calculated?

Poisson brackets are calculated by taking the partial derivative of two variables with respect to their positions and momenta, and then multiplying them together. This results in a single number that represents the strength of the relationship between the two variables.

What is the significance of Poisson brackets in physics?

In physics, Poisson brackets are significant because they provide a way to analyze the behavior and predict the future state of a mechanical system. They allow for the calculation of important quantities such as energy and angular momentum, and are also used in the formulation of Hamilton's equations of motion.

Are there any limitations to using Poisson brackets?

Yes, there are some limitations to using Poisson brackets. They are only applicable to systems that can be described by Hamiltonian mechanics, and they do not take into account effects such as friction or dissipation. Additionally, they may become more complex and difficult to calculate for systems with a large number of variables.

Can Poisson brackets be extended to other fields of science?

Yes, Poisson brackets can be extended to other fields of science such as quantum mechanics and statistical mechanics. They have also been used in economics and finance to study the dynamics of financial systems. However, the specific form and application of Poisson brackets may vary in these different fields.

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