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National Bird Day is celebrated every year on 5 January . This day is observed to spread awareness about birds, their importance in nature, and the need to protect them. Birds are beautiful living beings and play a very important role in keeping our environment healthy. Origin of National Bird Day National Bird Day was first celebrated in the year 2002 . It was started by bird lovers and environmental groups to protect birds from dangers like deforestation, pollution, and illegal hunting. The main aim of this day is to teach people, especially students, why birds are important and how we can help save them. Why Is National Bird Day Celebrated Every Year? National Bird Day is celebrated every year because many bird species are disappearing due to human activities. Cutting trees, using plastic, pollution, and climate change are harming birds and their homes. This day reminds us that: Birds need protection Nature should be respected Everyone has a responsibil...
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Poisson brackets | Identities of Poisson brackets | Classical Mechanics

Poisson brackets and its identities

Poisson brackets

  • A Poisson bracket is a special kind of relation between a pair of dynamical variables of any holonomic system, which is found to remain invariant under any canonical transformation.
  • They are used to construct new integrals of motion from the known integrals.
  • They are classical analogues of commutation relation between operators in quantum mechanics.
  • If u (p, q, t) and v (p, q, t) are two dynamical variables, then the Poisson bracket of these quantities with respect to canonical variables (p, q) is
                

Identities of Poisson brackets

  • [u, v] = – [v, u]


  • Thus the Poisson bracket of any two dynamical variables is anti-commutative.
  • If u = v, then
                
  • [u, u](p, q) = 0
  • [u, u] = [v, v] = 0

  • If c is any constant, then [cu, v] = [u, cv] = c [u, v]

  • Similarly [u, cv] = c [u, v]
  • ∴  [cu, v] = [u, cv] = c [u, v]

  • The Poisson brackets satisfy the distributive property
  • [u + v, w] = [u, w] + [v, w] and [u, v w] = [u, v]w + v[u, w]

  • Similarly [u, v w] = [u, v]w + v[u, w]

  • The partial derivative of Poisson bracket is

  • Jacobi identity of Poisson bracket is [u [v, w]] + [v [w, u]] + [w [u, v]] = 0

  • If F (w1, w2, …, wn) be a differentiable function of w1, w2, …, wn and all w’s be the function of (p, q, t), then

  • Let F (w1, w2) be a differentiable function of w1 and w2

To know about Poisson bracket and its identities please click on the link for English and  click on the link for Hindi
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