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Lubos Motl
Jul20-04, 04:25 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>\nHi guys,\nI\'ve read the recent Polish papers\n\nhttp://www.arxiv.org/abs/gr-qc/0407051\nhttp://www.arxiv.org/abs/gr-qc/0407052\n\nthat try to claim that all previous calculations of the black hole entropy\nin loop quantum gravity - despite the claims that they were independent -\nhad the same error in them. They explain that it is not true that the\nentropy is dominated by the punctures of the smallest minimal spin. Their\nresulting entropy therefore does not contain anything such as log(2) or\nlog(3) but rather log of a transcendent number in between.\n\nDo you have some comments about it? I am still not quite decided whether\nthe new papers are correct, at least in some sense.\n\nBest\nLubos\n______________________________________________________________________________\nE-mail: lumo@matfyz.cz fax: +1-617/496-0110 Web: http://lumo.matfyz.cz/\neFax: +1-801/454-1858 work: +1-617/496-8199 home: +1-617/868-4487 (call)\n^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\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>Hi guys,
I've read the recent Polish papers

http://www.arxiv.org/abs/http://www.arxiv.org/abs/gr-qc/0407051
http://www.arxiv.org/abs/http://www.arxiv.org/abs/gr-qc/0407052

that try to claim that all previous calculations of the black hole entropy
in loop quantum gravity - despite the claims that they were independent -
had the same error in them. They explain that it is not true that the
entropy is dominated by the punctures of the smallest minimal spin. Their
resulting entropy therefore does not contain anything such as log(2) or
log(3) but rather log of a transcendent number in between.

Do you have some comments about it? I am still not quite decided whether
the new papers are correct, at least in some sense.

Best
Lubos
__{____________________________________________________________________________}
E-mail: lumo@matfyz.cz fax: +1-617/496-0110 Web: http://lumo.matfyz.cz/
eFax: +1-801/454-1858 work: +1-617/496-8199 home: +1-617/868-4487 (call)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

John Baez
Jul27-04, 01:51 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>\n\nIn article\n&lt;Pine.LNX.4.31.0407200016280.25397-100000@einstein.physics.harvard.edu&gt;,\nLubos Motl &lt;motl@feynman.harvard.edu&gt; wrote:\n\n&gt;Hi guys,\n&gt;I\'ve read the recent Polish papers\n&gt;\n&gt; http://www.arxiv.org/abs/gr-qc/0407051\n&gt; http://www.arxiv.org/abs/gr-qc/0407052\n&gt;\n&gt;that try to claim that all previous calculations of the black hole entropy\n&gt;in loop quantum gravity - despite the claims that they were independent -\n&gt;had the same error in them. They explain that it is not true that the\n&gt;entropy is dominated by the punctures of the smallest minimal spin. Their\n&gt;resulting entropy therefore does not contain anything such as log(2) or\n&gt;log(3) but rather log of a transcendent number in between.\n&gt;\n&gt;Do you have some comments about it? I am still not quite decided whether\n&gt;the new papers are correct, at least in some sense.\n\nI see the error that Lewandowski spotted in the original calculation\nby Ashtekar, Corichi, Krasnov and myself - we had a long discussion with\nhim about this before he came out with his paper. But, I still need to\ncheck the details to make sure Meissner\'s new calculation is correct.\nI have no particular reason to doubt it, so I went ahead and spoke about\nit in Dublin:\n\nhttp://math.ucr.edu/home/baez/lectures#lqg\n\nBut, I\'d like to think about it more; the new papers came out just\nwhile I was busy writing my talk!\n\nBy the way, nobody claimed all the previous loop quantum gravity\ncalculations were completely independent. They all boiled down to\nthe same combinatorics problem in the end: counting lists of spins\nthat satisfy certain conditions. It\'s this combinatorics problem\nthat the new papers are claiming to straighten out.\n\nI\'ll say a bunch more about this in a while. I expect there to be\nstill more interesting twists in this story.\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>In article
<Pine.LNX.4.31.0407200016280.25397-100000@einstein.physics.harvard.edu>,
Lubos Motl <motl@feynman.harvard.edu> wrote:

>Hi guys,
>I've read the recent Polish papers
>
> http://www.arxiv.org/abs/http://www.arxiv.org/abs/gr-qc/0407051
> http://www.arxiv.org/abs/http://www.arxiv.org/abs/gr-qc/0407052
>
>that try to claim that all previous calculations of the black hole entropy
>in loop quantum gravity - despite the claims that they were independent -
>had the same error in them. They explain that it is not true that the
>entropy is dominated by the punctures of the smallest minimal spin. Their
>resulting entropy therefore does not contain anything such as log(2) or
>log(3) but rather log of a transcendent number in between.
>
>Do you have some comments about it? I am still not quite decided whether
>the new papers are correct, at least in some sense.

I see the error that Lewandowski spotted in the original calculation
by Ashtekar, Corichi, Krasnov and myself - we had a long discussion with
him about this before he came out with his paper. But, I still need to
check the details to make sure Meissner's new calculation is correct.
I have no particular reason to doubt it, so I went ahead and spoke about
it in Dublin:

http://math.ucr.edu/home/baez/lectures#lqg

But, I'd like to think about it more; the new papers came out just
while I was busy writing my talk!

By the way, nobody claimed all the previous loop quantum gravity
calculations were completely independent. They all boiled down to
the same combinatorics problem in the end: counting lists of spins
that satisfy certain conditions. It's this combinatorics problem
that the new papers are claiming to straighten out.

I'll say a bunch more about this in a while. I expect there to be
still more interesting twists in this story.

Wolfgang Beirl
Jul31-04, 10:15 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>baez@galaxy.ucr.edu (John Baez) wrote in message news:&lt;ce6317\\$9ts\\$1@glue.ucr.edu&gt;...\n&gt; In article\n&gt; &lt;Pine.LNX.4.31.0407200016280.25397-100000@einstein.physics.harvard.edu&gt;,\n&gt; Lubos Motl &lt;motl@feynman.harvard.edu&gt; wrote:\n&gt;\n&gt; &gt;Hi guys,\n&gt; &gt;I\'ve read the recent Polish papers\n&gt; &gt;\n&gt; &gt; http://www.arxiv.org/abs/gr-qc/0407051\n&gt; &gt; http://www.arxiv.org/abs/gr-qc/0407052\n&gt; &gt;\n&gt; &gt;that try to claim that all previous calculations of the black hole entropy\n&gt; &gt;in loop quantum gravity - despite the claims that they were independent -\n&gt; &gt;had the same error in them. They explain that it is not true that the\n&gt; &gt;entropy is dominated by the punctures of the smallest minimal spin. Their\n&gt; &gt;resulting entropy therefore does not contain anything such as log(2) or\n&gt; &gt;log(3) but rather log of a transcendent number in between.\n&gt; &gt;\n&gt; &gt;Do you have some comments about it? I am still not quite decided whether\n&gt; &gt;the new papers are correct, at least in some sense.\n&gt;\n&gt; I see the error that Lewandowski spotted in the original calculation\n&gt; by Ashtekar, Corichi, Krasnov and myself - we had a long discussion with\n&gt; him about this before he came out with his paper. But, I still need to\n&gt; check the details to make sure Meissner\'s new calculation is correct.\n&gt; I have no particular reason to doubt it, so I went ahead and spoke about\n&gt; it in Dublin:\n&gt;\n&gt; http://math.ucr.edu/home/baez/lectures#lqg\n&gt;\n&gt; But, I\'d like to think about it more; the new papers came out just\n&gt; while I was busy writing my talk!\n&gt;\n&gt; By the way, nobody claimed all the previous loop quantum gravity\n&gt; calculations were completely independent. They all boiled down to\n&gt; the same combinatorics problem in the end: counting lists of spins\n&gt; that satisfy certain conditions. It\'s this combinatorics problem\n&gt; that the new papers are claiming to straighten out.\n&gt;\n&gt; I\'ll say a bunch more about this in a while. I expect there to be\n&gt; still more interesting twists in this story.\n\n\nI would like to ask a (stupid ?) question about area quantization, which\nprevents me from really understanding the calculation of the entropy.\nOn one hand there is the result that areas are quantized as\narea = sqrt( j*(j+1) ),\non the other hand the 4D Barrett-Crane model assigns each area a label\nj = 0, 1/2, 1, 3/2, ...\nHow does this fit together ? I understand that the BC model is defined on\nRiemann geometries, while black holes live in the Lorentz sector. But is\nthis the (mysterious) reason for the different area spectrum ?\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>baez@galaxy.ucr.edu (John Baez) wrote in message news:<ce6317$9ts$1@glue.ucr.edu>...
> In article
> <Pine.LNX.4.31.0407200016280.25397-100000@einstein.physics.harvard.edu>,
> Lubos Motl <motl@feynman.harvard.edu> wrote:
>
> >Hi guys,
> >I've read the recent Polish papers
> >
> > http://www.arxiv.org/abs/http://www.arxiv.org/abs/gr-qc/0407051
> > http://www.arxiv.org/abs/http://www.arxiv.org/abs/gr-qc/0407052
> >
> >that try to claim that all previous calculations of the black hole entropy
> >in loop quantum gravity - despite the claims that they were independent -
> >had the same error in them. They explain that it is not true that the
> >entropy is dominated by the punctures of the smallest minimal spin. Their
> >resulting entropy therefore does not contain anything such as log(2) or
> >log(3) but rather log of a transcendent number in between.
> >
> >Do you have some comments about it? I am still not quite decided whether
> >the new papers are correct, at least in some sense.
>
> I see the error that Lewandowski spotted in the original calculation
> by Ashtekar, Corichi, Krasnov and myself - we had a long discussion with
> him about this before he came out with his paper. But, I still need to
> check the details to make sure Meissner's new calculation is correct.
> I have no particular reason to doubt it, so I went ahead and spoke about
> it in Dublin:
>
> http://math.ucr.edu/home/baez/lectures#lqg
>
> But, I'd like to think about it more; the new papers came out just
> while I was busy writing my talk!
>
> By the way, nobody claimed all the previous loop quantum gravity
> calculations were completely independent. They all boiled down to
> the same combinatorics problem in the end: counting lists of spins
> that satisfy certain conditions. It's this combinatorics problem
> that the new papers are claiming to straighten out.
>
> I'll say a bunch more about this in a while. I expect there to be
> still more interesting twists in this story.


I would like to ask a (stupid ?) question about area quantization, which
prevents me from really understanding the calculation of the entropy.
On one hand there is the result that areas are quantized as
area = \sqrt( j*(j+1) ),
on the other hand the 4D Barrett-Crane model assigns each area a label
j = 0, 1/2, 1, 3/2, ...
How does this fit together ? I understand that the BC model is defined on
Riemann geometries, while black holes live in the Lorentz sector. But is
this the (mysterious) reason for the different area spectrum ?