Rotational Invariance - Application To Quantum Mechanics

Application To Quantum Mechanics

In quantum mechanics, rotational invariance is the property that after a rotation the new system still obeys Schrödinger's equation. That is

= 0 for any rotation R.

Since the rotation does not depend explicitly on time, it commutes with the energy operator. Thus for rotational invariance we must have = 0.

Since = 0, and because for infinitesimal rotations (in the xy-plane for this example; it may be done likewise for any plane) by an angle dθ the rotation operator is

R = 1 + Jz dθ,
= 0;

thus

d/dt(Jz) = 0,

in other words angular momentum is conserved.

Read more about this topic:  Rotational Invariance

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