Isomorphism between so(3) and su(2)

In summary, the conversation discusses constructing a Lie-algebra isomorphism between su(2) and so(3) using their commutation relations. The important factor is the linear, bijective mapping between the two algebras and checking if it satisfies the commutation relations.
  • #1
MrRobot
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Homework Statement



How do I use the commutation relations of su(2) and so(3) to construct a Lie-algebra isomorphism between these two algebras?

Homework Equations


The commutation relations are [ta, tb] = i epsilonabc tc, the ts being the basis elements of the algebras. They basically have the same commutation relation, only ta are two by two by the su(2) while 3X3 by so(3).

The Attempt at a Solution

 
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  • #2
How they are represented by matrices isn't important. If you have a linear, bijective mapping
$$φ : \mathfrak{su}(2) \longrightarrow \mathfrak{so}(3)$$
e.g. if you map all basis vectors ##t^α \longmapsto {s}^α## then you have to check whether ##φ([t^α,t^β]) = [φ(t^α),φ(t^β)] = [{s}^α,s^β].## If this is the case for all pairs ##(α,β)## then it is a Lie-algebra isomorphism.
 

Related to Isomorphism between so(3) and su(2)

1. What is the isomorphism between so(3) and su(2)?

The isomorphism between so(3) and su(2) is a mathematical relationship that exists between the Lie algebras of these two groups. It states that the Lie algebra of the special orthogonal group in three dimensions (so(3)) is isomorphic to the Lie algebra of the special unitary group in two dimensions (su(2)). This means that these two groups have the same algebraic structure, even though they may represent different physical systems.

2. How is the isomorphism between so(3) and su(2) used in physics?

The isomorphism between so(3) and su(2) is used extensively in physics, particularly in the study of angular momentum and rotation. It allows us to apply the mathematical tools and techniques of one group to problems involving the other group. For example, the quantum mechanics of spin can be described using su(2), while the classical mechanics of rotational motion can be described using so(3).

3. What is the significance of the dimensionality of these groups in the isomorphism?

The dimensionality of a group refers to the number of independent parameters needed to describe its elements. In the case of so(3) and su(2), both groups have three dimensions, which is significant because it allows us to map one group onto the other without losing any information. This makes the isomorphism between these two groups particularly useful in various mathematical and physical applications.

4. How does the Lie bracket operation play a role in the isomorphism between so(3) and su(2)?

The Lie bracket operation is a mathematical operation that takes two elements of a Lie algebra and produces a third element. In the case of so(3) and su(2), the Lie bracket operation is used to define the commutator of two matrices, which is a key component of the isomorphism between these two groups. The commutator of two matrices in so(3) is isomorphic to the commutator of two matrices in su(2), which helps establish the isomorphism between the two groups.

5. Are there any real-world applications of the isomorphism between so(3) and su(2)?

Yes, there are many real-world applications of the isomorphism between so(3) and su(2). Some examples include using the isomorphism to study the behavior of spin in quantum systems, analyzing the rotational dynamics of molecules in chemistry, and understanding the behavior of gyroscopes in physics and engineering. The isomorphism between these two groups has also been used in computer graphics to create realistic 3D rotations and in robotics to model the movements of robotic arms and joints.

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