Why is Orbital Angular Momentum Quantized in Quantum Mechanics?

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Orbital angular momentum in quantum mechanics is quantized, meaning it can only take specific whole-number values, represented as multiples of h(bar). The orbital angular momentum quantum number, which determines these values, is distinct from the actual magnitude of orbital angular momentum, calculated using the formula √[l(l+1)]h(bar). The confusion often arises from the difference between the quantum number and the measured angular momentum itself. Additionally, quantization occurs in relation to the dimensions of space involved. Understanding these concepts clarifies the nature of angular momentum in quantum mechanics.
Amith2006
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When I was trying to learn the reason for the Orbital angular momentum quantum number taking only whole number values, I stumbled across the wiki site on the same, which says that,

Angular momentum in quantum mechanics

In quantum mechanics, angular momentum is quantized – that is, it cannot vary continuously, but only in "quantum leaps" between certain allowed values. The orbital angular momentum of a subatomic particle, that is due to its motion through space, is always a whole-number multiple of h(bar).

If I am not wrong, it is the Orbital angular momentum quantum number which takes whole-number values and not the Orbital angular momentum itself. The magnitude of the Orbital angular momentum is in-fact,
\sqrt{[l(l+1)]}h(bar)
The link to this site is: http://en.wikipedia.org/wiki/Angular_momentum

Oh God! Sometimes even simple things create confusion...
 
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Thats correct, the orbital angular momentum itself is not measured as 0, 1, 2, 3...

The quantum number for angular momentum is the second quantum number that comes about when using 2 dimensions where angular momentum becomes a factor. There is a quantization for every dimension of space(3).
 
Time reversal invariant Hamiltonians must satisfy ##[H,\Theta]=0## where ##\Theta## is time reversal operator. However, in some texts (for example see Many-body Quantum Theory in Condensed Matter Physics an introduction, HENRIK BRUUS and KARSTEN FLENSBERG, Corrected version: 14 January 2016, section 7.1.4) the time reversal invariant condition is introduced as ##H=H^*##. How these two conditions are identical?

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