Arnold Neumaier
Apr14-04, 03:17 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>Phillip Helbig---remove CLOTHES to reply wrote:\n> In article <40745CDC.1060005@univie.ac.at>, Arnold Neumaier\n> <Arnold.Neumaier@univie.ac.at> writes:\n>\n>\n>>>I\'ve often worried that the vaunted accuracy of QED is illusory, that\n>>>is, data are used to "tune" the equipment.\n>>\n>>There is no way to tune the Lamb shift.\n>>\n>>Any equipment has to be calibrated to give maximally consistent\n>>results (i.e., smallest measurement errors), but this is a\n>>completely different matter.\n>\n>\n> When I was studying physics in Hamburg, in the course on electrodynamics\n> (which basically followed Jackson\'s book), the lecturer (Prof. Dr.\n> Heinrich Victor von Geramb) remarked on the good agreement of QED theory\n> and observation, to 13 significant digits or whatever it was at the\n> time. I asked him what happens after the least significant digit: is\n> that as accurate as experiment can get, or are genuine deviations\n> detected. His answer was neither: that\'s as accurate as the theory can\n> get (at present), since the actual numerical calculations are quite\n> involved.\n\nYes. High order radiative corrections require the sum of hundreds\n(if not more) high-dimensional integrals that are hard to compute\nnumerically. Also, the fine structure constant is not known too well.\nFinally, I think, the accuracy is now such that improvements\nrequire corrections from proton form factors, etc., which are not known\nto high precision. Thus it will be difficult to extend the accuracy...\n\n\nArnold Neumaier\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"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>Phillip Helbig---remove CLOTHES to reply wrote:
> In article <40745CDC.1060005@univie.ac.at>, Arnold Neumaier
> <Arnold.Neumaier@univie.ac.at> writes:
>
>
>>>I've often worried that the vaunted accuracy of QED is illusory, that
>>>is, data are used to "tune" the equipment.
>>
>>There is no way to tune the Lamb shift.
>>
>>Any equipment has to be calibrated to give maximally consistent
>>results (i.e., smallest measurement errors), but this is a
>>completely different matter.
>
>
> When I was studying physics in Hamburg, in the course on electrodynamics
> (which basically followed Jackson's book), the lecturer (Prof. Dr.
> Heinrich Victor von Geramb) remarked on the good agreement of QED theory
> and observation, to 13 significant digits or whatever it was at the
> time. I asked him what happens after the least significant digit: is
> that as accurate as experiment can get, or are genuine deviations
> detected. His answer was neither: that's as accurate as the theory can
> get (at present), since the actual numerical calculations are quite
> involved.
Yes. High order radiative corrections require the sum of hundreds
(if not more) high-dimensional integrals that are hard to compute
numerically. Also, the fine structure constant is not known too well.
Finally, I think, the accuracy is now such that improvements
require corrections from proton form factors, etc., which are not known
to high precision. Thus it will be difficult to extend the accuracy...
Arnold Neumaier
> In article <40745CDC.1060005@univie.ac.at>, Arnold Neumaier
> <Arnold.Neumaier@univie.ac.at> writes:
>
>
>>>I've often worried that the vaunted accuracy of QED is illusory, that
>>>is, data are used to "tune" the equipment.
>>
>>There is no way to tune the Lamb shift.
>>
>>Any equipment has to be calibrated to give maximally consistent
>>results (i.e., smallest measurement errors), but this is a
>>completely different matter.
>
>
> When I was studying physics in Hamburg, in the course on electrodynamics
> (which basically followed Jackson's book), the lecturer (Prof. Dr.
> Heinrich Victor von Geramb) remarked on the good agreement of QED theory
> and observation, to 13 significant digits or whatever it was at the
> time. I asked him what happens after the least significant digit: is
> that as accurate as experiment can get, or are genuine deviations
> detected. His answer was neither: that's as accurate as the theory can
> get (at present), since the actual numerical calculations are quite
> involved.
Yes. High order radiative corrections require the sum of hundreds
(if not more) high-dimensional integrals that are hard to compute
numerically. Also, the fine structure constant is not known too well.
Finally, I think, the accuracy is now such that improvements
require corrections from proton form factors, etc., which are not known
to high precision. Thus it will be difficult to extend the accuracy...
Arnold Neumaier