Note that the case of is allowed, and corresponds to being a permutation.
A, 38, 339 (1972) noticed that the case corresponds to the SAW.
Since the second law of thermodynamics applies to isolated systems, the first case investigated will correspond to this case.
Hence, this case corresponds to a high-pass filter with a very wide stop band.
The eight dimensional case corresponds to the triality property of Spin(8).
The case of two copies corresponds to the famous Klein bottle.
The case (1,1) corresponds to the split-complex numbers.
The zero-field case of the model corresponds physically to the absence of external electric fields.
And indeed this case corresponds to the case when the inner circle is shrunk into a point.
The other extreme case corresponds to the inner circle matching the large circle.