Talk:Betti number

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[edit] Relationship with differential forms

I think this subsection should not be here, or should be cut to one sentence. Tosha 03:40, 29 Apr 2004 (UTC)

Certainly the material could be added to the Hodge theory or de Rham cohomology pages instead; and links given instead.

Charles Matthews 06:50, 29 Apr 2004 (UTC)

Could someone at least put back in a link to De Rham cohomology? There are whole swathes of people interested in global analyis or electromagnetics for whom de Rham cohomology is the only algebraic topology they know hence know the Betti numbers as the dimension of these spaces and measuring 'how many closed forms are not exact' is a matter of vector calculus. Billlion 12:20, 20 Sep 2004 (UTC)

OK, fair enough. I've put the bare bones of why that works.

Charles Matthews 13:00, 20 Sep 2004 (UTC)

I think the first betti number of a general Pretzel is the number of the holes but not twice of it.BenlingLi 17:36, 20 October 2006 (UTC)

That's the genus g. B₁ = 2g for orientable surfaces. Charles Matthews 18:50, 20 October 2006 (UTC)