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Article #3978

Re: What's a manifold?

#3978
From: Steven Smith
Date: Thu, 05 Nov 1992 15:15
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pratt@Sunburn.Stanford.EDU (Vaughan R. Pratt) writes:

> What I don't understand here is how "living in R^n" is of itself
> creating complexity and obscurity.  I can see that the
> arbitrariness of f might get in the way.  But where does the
> complexity and obscurity creep in if for example we define a
> manifold to be a smooth retract of an open subset of R^n?

The choice of ambient space is also somewhat arbitrary.  If the
manifold can be imbedded in R^n, then it can also be imbedded in
R^{n+1}, to say nothing of imbeddings in other manifolds.  The point
is that manifolds exists independently of their imbeddings in R^n or
other manifolds.  Any reasonable definition should possess this
invariance.

Steven Smith
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Path: arc1-ca.pugleaf.net!sparky!uunet!ogicse!das-news.harvard.edu!das-news!smith
From: smith@gramian.harvard.edu (Steven Smith)
Newsgroups: sci.physics,sci.math
Subject: Re: What's a manifold?
Message-ID: <SMITH.92Nov5101553@gramian.harvard.edu>
Date: 5 Nov 92 15:15:53 GMT
Article-I.D.: gramian.SMITH.92Nov5101553
References: <1992Nov3.204551.29715@lmpsbbs.comm.mot.com>
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 <1992Nov5.035214.25991@galois.mit.edu>
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In-Reply-To: pratt@Sunburn.Stanford.EDU's message of Thu, 5 Nov 1992 06:04:00 GMT