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View Full Version : [SOLVED] Infinite loop spaces and CP_\infty


Jesse McKeown
May4-04, 10:34 AM
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>So waaaaaaaaaaayy back in\nhttp://www.math.ucr.edu/home/baez/week149.html in the year we locally\ncall 2000, John Baez more or less asked for a nice description of what\nK(Z,3) looks like; and maybe one appears in later weeks, and maybe\nit\'s already been constructed here, but I\'m not quite sure how to go\nlooking for such a thing.\n\nAnd I also don\'t feel the least bit able to construct such a thing\nmyself, but I would like to ask what may be a relevant question, since\nK(Z,2) is identified as being (homotopic to) CP^\\infty, either as a\nforgotten flag of all finite-dimensional CP^n, or as the quotient\nspace of some Hilbert space H by the natural action of C^* on H. So\njust to be absolutely clear, I\'m curious as to which Hilbert space\nthis is; because, as we learned in Analysis last semester, there\'s a\ndistict H_\\kappa with complete ortho-normal system of cardinality\n\\kappa for all cardinals \\kappa, and that for \\kappa &lt; \\lambda, there\nis no continuous surjection from H_\\kappa to H_\\lambda.\n\nI\'m willing to bet that the H in question is H_{\\aleph_0}, because\nCP^{\\aleph_0} is the space one gets with the above definition; and\nthis is maybe interesting because it looks like K(Z,2) is also the set\nof quantum states (\\aleph_0 of them forming a complete ortho-normal\nsystem) of a particle with no structure living in K(Z,1); I can\'t see\nyet why K(Z,1) should be considered the set of quantum states of a\nparticle living in Z = K(Z,0), but perhaps that\'s the wrong thing to\nthink about.\n\nAnyway, that\'s all!\n\n--Jesse\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form">&nbsp;&nbsp;View this Usenet post in original ASCII form </a></div><P></jabberwocky>So waaaaaaaaaaayy back in
http://www.math.ucr.edu/home/baez/week149.html in the year we locally
call 2000, John Baez more or less asked for a nice description of what
K(Z,3) looks like; and maybe one appears in later weeks, and maybe
it's already been constructed here, but I'm not quite sure how to go
looking for such a thing.

And I also don't feel the least bit able to construct such a thing
myself, but I would like to ask what may be a relevant question, since
K(Z,2) is identified as being (homotopic to) CP^\infty, either as a
forgotten flag of all finite-dimensional CP^n, or as the quotient
space of some Hilbert space H by the natural action of C^* on H. So
just to be absolutely clear, I'm curious as to which Hilbert space
this is; because, as we learned in Analysis last semester, there's a
distict H_\kappa with complete ortho-normal system of cardinality
\kappa for all cardinals \kappa, and that for \kappa < \lambda, there
is no continuous surjection from H_\kappa to H_\lambda.

I'm willing to bet that the H in question is H_{\aleph_0}, because
CP^{\aleph_0} is the space one gets with the above definition; and
this is maybe interesting because it looks like K(Z,2) is also the set
of quantum states (\aleph_0 of them forming a complete ortho-normal
system) of a particle with no structure living in K(Z,1); I can't see
yet why K(Z,1) should be considered the set of quantum states of a
particle living in Z = K(Z,0), but perhaps that's the wrong thing to
think about.

Anyway, that's all!

--Jesse

Ilya Zakharevich
May4-04, 02:47 PM
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>[A complimentary Cc of this posting was sent to\nJesse McKeown\n&lt;jesse@math.mcgill.ca&gt;], who wrote in article &lt;c551f644.0405040734.1f506ca@posting.google.com&gt;:\ n&gt; So waaaaaaaaaaayy back in\n&gt; http://www.math.ucr.edu/home/baez/week149.html in the year we locally\n&gt; call 2000, John Baez more or less asked for a nice description of what\n&gt; K(Z,3) looks like;\n\nIs not it the infinite&co-infinite Grassmannian of a Hilbert space?\n\n&gt; and maybe one appears in later weeks, and maybe\n&gt; it\'s already been constructed here, but I\'m not quite sure how to go\n&gt; looking for such a thing.\n\nI think that one does not "look" for meaningful models of K(*,*); it\nis the other way around: sometimes you discover that a particular\nspace has only one homotopy group - and you got a model. E.g., except\nK(Z,3), I do not recollect any "exceptional" model (but I\'m in no way\na specialist).\n\nHope this helps,\nIlya\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form">&nbsp;&nbsp;View this Usenet post in original ASCII form </a></div><P></jabberwocky>[A complimentary Cc of this posting was sent to
Jesse McKeown
<jesse@math.mcgill.ca>], who wrote in article <c551f644.0405040734.1f506ca@posting.google.com>:
> So waaaaaaaaaaayy back in
> http://www.math.ucr.edu/home/baez/week149.html in the year we locally
> call 2000, John Baez more or less asked for a nice description of what
> K(Z,3) looks like;

Is not it the infinite&co-infinite Grassmannian of a Hilbert space?

> and maybe one appears in later weeks, and maybe
> it's already been constructed here, but I'm not quite sure how to go
> looking for such a thing.

I think that one does not "look" for meaningful models of K(*,*); it
is the other way around: sometimes you discover that a particular
space has only one homotopy group - and you got a model. E.g., except
K(Z,3), I do not recollect any "exceptional" model (but I'm in no way
a specialist).

Hope this helps,
Ilya