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• CommentRowNumber1.
• CommentAuthorUrs
• CommentTimeFeb 13th 2019

added a line on $Pin_\pm(n)$, and added pointer to the example of Pin(2)

• CommentRowNumber2.
• CommentAuthorDmitri Pavlov
• CommentTimeApr 2nd 2019
• (edited Apr 2nd 2019)

The article pin group says

The Pin group Pin(V;q) of a quadratic vector space, def. 2.1, is the subgroup of the group of units in the Clifford algebra Cl(V,q) Pin(V,q)↪GL 1(Cl(V,q)) on those elements which are multiples v_1 \cdots v_{2k} of elements v_i \in V with q(V) = 1.

It appears that this defines the spin group, not the pin group, because 2k is even. For the pin group one needs to allow an arbitrary number of v_i.

The same problem seems to be present in the article spin group.

• CommentRowNumber3.
• CommentAuthorUrs
• CommentTimeApr 2nd 2019

Thanks for catching. Fixed now (both entries). Also fixed the typo right afterwards, (capital $V$ to lower case).

• CommentRowNumber4.
• CommentAuthorDavidRoberts
• CommentTimeMay 16th 2019