+1 vote
asked by (180 points)

Dear Forum,

Is it safe to declare an IQIndex with 2 quantum number blocks having the same Quantumnumber?

ie:

IQIndex( nameint("M I1 ",imp),
    Index("m ILink ", 5) , QN( 0, 0),
    Index("I3cDc"   , 1) , QN(-2, 0),     //this is the same QN
    Index("I3cDcD"  , 1) , QN( 0,-2),
    Index("I3ccD"   , 1) , QN(-2, 0),    //as this
    Index("I3cc"    , 1) , QN( 0, 2)   );

I know that it works and it gave correct results half a year ago, but I want to make sure this still works and is safe.

best regards,
Florian

1 Answer

+1 vote
answered by (46.3k points)

This should be allowed & I recently constructed an MPO in the newest version of ITensor where some IQIndex blocks had repeated quantum numbers. So far it doesn't seem to cause any problem. I would encourage you to just try it and, as you should always do, do some smaller or lower-accuracy calculations where you know the result ahead of time to test.

commented by (180 points)
Ok, I understand.
Thank you for your answer!
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