View Full Version : Earlier or later
Jagmeet Singh
Oct3-04, 03:49 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>\n\ngrelbr,what do you mean?According to you,there should be no\ntime order between space-like intervals just because light\ncan\'t get from one point to the other within the time between\nthe two events.On the contrary,because one event can\'t influence\nthe other for space-like separations,the two events should be neatly\nseparated in spacetime.If at all, there could be a problem for time-like\nseparations where there may be blurring of the two events.\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>grelbr,what do you mean?According to you,there should be no
time order between space-like intervals just because light
can't get from one point to the other within the time between
the two events.On the contrary,because one event can't influence
the other for space-like separations,the two events should be neatly
separated in spacetime.If at all, there could be a problem for time-like
separations where there may be blurring of the two events.
<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>John T Lowry Wrote:\n>\n>\n> In non-relativistic (NR) theory of Thomson scattering, only the\n> 1st-order AA "seagull" Feynman graph (simultaneous absorption and\n> emission) is taken into account. In the (more accurate) relativistic\n> theory, on the other hand, that seagull graph is replaced by two\n> graphs,\n> in each of which photons are absorbed and emitted one at a time. One\n> of\n> the graphs has absorption first (in time), the other has emission\n> first.\n>\n> John Lowry\n> Flight Physics\n\nSo what is the conclusion John?If a photon can be emitted even before\nbeing absorbed,does this not mean that the time order is sort of\ngetting blurred here?I\'ve also heard of delayed compton effect---is it\nsimilar in spirit?\n\n------------------------------------------------------------------------\nThis post submitted through the LaTeX-enabled physicsforums.com\nTo view this post with LaTeX images:\nhttp://www.physicsforums.com/showthread.php?t=45267#post328593\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>John T Lowry Wrote:
>
>
> In non-relativistic (NR) theory of Thomson scattering, only the
> 1st-order AA "seagull" Feynman graph (simultaneous absorption and
> emission) is taken into account. In the (more accurate) relativistic
> theory, on the other hand, that seagull graph is replaced by two
> graphs,
> in each of which photons are absorbed and emitted one at a time. One
> of
> the graphs has absorption first (in time), the other has emission
> first.
>
> John Lowry
> Flight Physics
So what is the conclusion John?If a photon can be emitted even before
being absorbed,does this not mean that the time order is sort of
getting blurred here?I've also heard of delayed compton effect---is it
similar in spirit?
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<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>\ngrelbr Wrote:\n>\n> First, orient your x axis so that it runs from one event\'s\n> space location to the other. This reduces the entire thing\n> to one space dimension and one time dimension.\n>\n> The test is quite straightforward. If the distance between\n> the events is smaller than the distance light can travel\n> in the time between the events, the events are called\n> time-like-separated.\n>\n> |x1 - x2| < c |t1 - t2| => time-like\n>\n> If the distance is larger then they are space-like-sep.\n>\n> |x1 - x2| > c |t1 - t2| => space-like\n>\n> If the distance is identical then they are null-separated.\n>\n> |x1 - x2| = c |t1 - t2| => null\n>\n> Space-like means they cannot be uniquely ordered in time.\n> Time-like or null means they can.\n>\n> Another way to think of it: If light can get from one\n> event to the space location of the other event, and do\n> it no later than the other event happens, then this\n> establishes the time ordering. The event light can\n> start at is before, the event light can finish at is after.\n> grelbr\n\nWhat do you mean?According to you,there should be no\ntime order between space-like intervals just because light\ncan\'t get from one point to the other within the time between\nthe two events.On the contrary,because one event can\'t influence\nthe other for space-like separations,the two events should be neatly\nseparated in spacetime.If at all, there could be a problem for\ntime-like\nseparations where there may be blurring of the two events.\n\n------------------------------------------------------------------------\nThis post submitted through the LaTeX-enabled physicsforums.com\nTo view this post with LaTeX images:\nhttp://www.physicsforums.com/showthread.php?t=45267#post329543\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>grelbr Wrote:
>
> First, orient your x axis so that it runs from one event's
> space location to the other. This reduces the entire thing
> to one space dimension and one time dimension.
>
> The test is quite straightforward. If the distance between
> the events is smaller than the distance light can travel
> in the time between the events, the events are called
> time-like-separated.
>
> |x1 - x2| < c |t1 - t2| => time-like
>
> If the distance is larger then they are space-like-sep.
>
> |x1 - x2| > c |t1 - t2| => space-like
>
> If the distance is identical then they are null-separated.
>
> |x1 - x2| = c |t1 - t2| => null
>
> Space-like means they cannot be uniquely ordered in time.
> Time-like or null means they can.
>
> Another way to think of it: If light can get from one
> event to the space location of the other event, and do
> it no later than the other event happens, then this
> establishes the time ordering. The event light can
> start at is before, the event light can finish at is after.
> grelbr
What do you mean?According to you,there should be no
time order between space-like intervals just because light
can't get from one point to the other within the time between
the two events.On the contrary,because one event can't influence
the other for space-like separations,the two events should be neatly
separated in spacetime.If at all, there could be a problem for
time-like
separations where there may be blurring of the two events.
------------------------------------------------------------------------
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John T Lowry
Oct6-04, 08:03 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>"gptejms" <jagmeetus@yahoo.com> wrote in message\nnews:cjs0rn\\$svc\\$1@lfa222122.richmond. edu...\n> John T Lowry Wrote:\n>>\n>>\n>> In non-relativistic (NR) theory of Thomson scattering, only the\n>> 1st-order AA "seagull" Feynman graph (simultaneous absorption and\n>> emission) is taken into account. In the (more accurate) relativistic\n>> theory, on the other hand, that seagull graph is replaced by two\n>> graphs,\n>> in each of which photons are absorbed and emitted one at a time. One\n>> of\n>> the graphs has absorption first (in time), the other has emission\n>> first.\n>>\n>> John Lowry\n>> Flight Physics\n>\n> So what is the conclusion John?If a photon can be emitted even before\n> being absorbed,does this not mean that the time order is sort of\n> getting blurred here?I\'ve also heard of delayed compton effect---is it\n> similar in spirit?\n>\nYes, more or less, although the emitted photon is a different photon\nfrom the absorbed one. First an electron-positron pair is created,\ntogether with the outbound photon, then somewhat "later" the positron is\nannihilated along with the initial electron and the initial photon.\n\nI don\'t know about delayed Compton effect, but check out Sakurai\'s\ndiagrams on pages 215 and 136 of Advanced Quantum Mechanics. So maybe\nyes.\n\nMore and more, it seems, time and space are getting less respect than we\nMacroscopic Earthlings are used to.\n\nJohn Lowry\nFlight Physics\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>"gptejms" <jagmeetus@yahoo.com> wrote in message
news:cjs0rn$svc$1@lfa222122.richmond.edu...
> John T Lowry Wrote:
>>
>>
>> In non-relativistic (NR) theory of Thomson scattering, only the
>> 1st-order AA "seagull" Feynman graph (simultaneous absorption and
>> emission) is taken into account. In the (more accurate) relativistic
>> theory, on the other hand, that seagull graph is replaced by two
>> graphs,
>> in each of which photons are absorbed and emitted one at a time. One
>> of
>> the graphs has absorption first (in time), the other has emission
>> first.
>>
>> John Lowry
>> Flight Physics
>
> So what is the conclusion John?If a photon can be emitted even before
> being absorbed,does this not mean that the time order is sort of
> getting blurred here?I've also heard of delayed compton effect---is it
> similar in spirit?
>
Yes, more or less, although the emitted photon is a different photon
from the absorbed one. First an electron-positron pair is created,
together with the outbound photon, then somewhat "later" the positron is
annihilated along with the initial electron and the initial photon.
I don't know about delayed Compton effect, but check out Sakurai's
diagrams on pages 215 and 136 of Advanced Quantum Mechanics. So maybe
yes.
More and more, it seems, time and space are getting less respect than we
Macroscopic Earthlings are used to.
John Lowry
Flight Physics
Jagmeet Singh
Oct8-04, 06:20 AM
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>\n\nJohn T Lowry <jlowry100@earthlink.net> wrote in message news:<ck0qf6\\$v13\\$1@lfa222122.richmond.edu>...\ n\n> Yes, more or less, although the emitted photon is a different photon\n> from the absorbed one. First an electron-positron pair is created,\n> together with the outbound photon, then somewhat "later" the positron is\n> annihilated along with the initial electron and the initial photon.\n>\n> I don\'t know about delayed Compton effect, but check out Sakurai\'s\n> diagrams on pages 215 and 136 of Advanced Quantum Mechanics. So maybe\n> yes.\n>\n> More and more, it seems, time and space are getting less respect than we\n> Macroscopic Earthlings are used to.\n>\n> John Lowry\n> Flight Physics\n\nI\'ve not been able to find the term delayed Compton effect,but in the\nu-channel of Compton scattering also, the photon is emitted before it\nis absorbed. http://theory.sinp.msu.ru/comphep_html/tutorial/QED/node2.html\nSo it seems,yeah, time at the microscopic level is not quite what we\nare used to.\n\nOne more question follows:-do we need to treat identical particles at\ntwo different closeby spacetime points by a single\nwavefunction(respecting the change in sign on exchange of the two\nparticles for fermoins)?Is this somehow already implicit in\nrelativistic quantum fields?\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>John T Lowry <jlowry100@earthlink.net> wrote in message news:<ck0qf6$v13$1@lfa222122.richmond.edu>...
> Yes, more or less, although the emitted photon is a different photon
> from the absorbed one. First an electron-positron pair is created,
> together with the outbound photon, then somewhat "later" the positron is
> annihilated along with the initial electron and the initial photon.
>
> I don't know about delayed Compton effect, but check out Sakurai's
> diagrams on pages 215 and 136 of Advanced Quantum Mechanics. So maybe
> yes.
>
> More and more, it seems, time and space are getting less respect than we
> Macroscopic Earthlings are used to.
>
> John Lowry
> Flight Physics
I've not been able to find the term delayed Compton effect,but in the
u-channel of Compton scattering also, the photon is emitted before it
is absorbed. http://theory.sinp.msu.ru/comphep_html/tutorial/QED/node2.html
So it seems,yeah, time at the microscopic level is not quite what we
are used to.
One more question follows:-do we need to treat identical particles at
two different closeby spacetime points by a single
wavefunction(respecting the change in sign on exchange of the two
particles for fermoins)?Is this somehow already implicit in
relativistic quantum fields?
John T Lowry
Oct11-04, 03:52 AM
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>\n\n"Jagmeet Singh" <jagmeetus@yahoo.com> wrote in message\nnews:f1cf9788.0410070916.a4601c9@posting. google.com...\n>\n>\n> John T Lowry <jlowry100@earthlink.net> wrote in message\n> news:<ck0qf6\\$v13\\$1@lfa222122.richmond.edu>...\ n>\n>> Yes, more or less, although the emitted photon is a different photon\n>> from the absorbed one. First an electron-positron pair is created,\n>> together with the outbound photon, then somewhat "later" the positron\n>> is\n>> annihilated along with the initial electron and the initial photon.\n>>\n>> I don\'t know about delayed Compton effect, but check out Sakurai\'s\n>> diagrams on pages 215 and 136 of Advanced Quantum Mechanics. So maybe\n>> yes.\n>>\n>> More and more, it seems, time and space are getting less respect than\n>> we\n>> Macroscopic Earthlings are used to.\n>>\n>> John Lowry\n>> Flight Physics\n>\n> I\'ve not been able to find the term delayed Compton effect,but in the\n> u-channel of Compton scattering also, the photon is emitted before it\n> is absorbed.\n> http://theory.sinp.msu.ru/comphep_html/tutorial/QED/node2.html\n> So it seems,yeah, time at the microscopic level is not quite what we\n> are used to.\n>\n> One more question follows:-do we need to treat identical particles at\n> two different closeby spacetime points by a single\n> wavefunction(respecting the change in sign on exchange of the two\n> particles for fermoins)?Is this somehow already implicit in\n> relativistic quantum fields?\n>\nI\'d say that, assuming nothing is either created or destroyed in the\nprocess, keep them as separate field excitations. One can think of two\nphonons being at the same place and time (close 4-region), but then they\nmay "pass through" each other and go on their merry ways.\n\nJohn Lowry\nFlight Physics\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>"Jagmeet Singh" <jagmeetus@yahoo.com> wrote in message
news:f1cf9788.0410070916.a4601c9@posting.google.co m...
>
>
> John T Lowry <jlowry100@earthlink.net> wrote in message
> news:<ck0qf6$v13$1@lfa222122.richmond.edu>...
>
>> Yes, more or less, although the emitted photon is a different photon
>> from the absorbed one. First an electron-positron pair is created,
>> together with the outbound photon, then somewhat "later" the positron
>> is
>> annihilated along with the initial electron and the initial photon.
>>
>> I don't know about delayed Compton effect, but check out Sakurai's
>> diagrams on pages 215 and 136 of Advanced Quantum Mechanics. So maybe
>> yes.
>>
>> More and more, it seems, time and space are getting less respect than
>> we
>> Macroscopic Earthlings are used to.
>>
>> John Lowry
>> Flight Physics
>
> I've not been able to find the term delayed Compton effect,but in the
> u-channel of Compton scattering also, the photon is emitted before it
> is absorbed.
> http://theory.sinp.msu.ru/comphep_html/tutorial/QED/node2.html
> So it seems,yeah, time at the microscopic level is not quite what we
> are used to.
>
> One more question follows:-do we need to treat identical particles at
> two different closeby spacetime points by a single
> wavefunction(respecting the change in sign on exchange of the two
> particles for fermoins)?Is this somehow already implicit in
> relativistic quantum fields?
>
I'd say that, assuming nothing is either created or destroyed in the
process, keep them as separate field excitations. One can think of two
phonons being at the same place and time (close 4-region), but then they
may "pass through" each other and go on their merry ways.
John Lowry
Flight Physics
<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\nJagmeet Singh <jagmeetus@yahoo.com> writes\n>I\'ve not been able to find the term delayed Compton effect,but in the\n>u-channel of Compton scattering also, the photon is emitted before it\n>is absorbed. http://theory.sinp.msu.ru/comphep_html/tutorial/QED/node2.html\n>So it seems,yeah, time at the microscopic level is not quite what we\n>are used to.\n\nI\'m afraid I find this increasingly heartening.\n\nOne is accustomed to a particle being smeared out in space.\nOne is accustomed to a world where space and time must be mixed.\n\nIt would thus be extraordinary, in my view, if a particle were not also\nsmeared out in time.\n\nGenerally the mechanics of a particle are in some sense defined by its\n\'most probable location\', so by implication the \'most probable location\nin time\'. That would mean that there *should* be a chance for a particle\nto be absorbed before it is emitted.\n\nI could (if I knew what I was talking about) suggest that the appearance\nof antiparticles in the terms of any expansion for a particle is its\n\'time smear\' writ large.\n\nHowever the implication of this is that the past is mutable. IMHO the\nimmutable passage of time is a macroscopic effect generated by a highly\nprobable statistical path through time caused by the interaction of a\nmyriad particles. That is we only see the most probable events, and for\nmacroscopic bodies this is probable to the point of certainty.\n\nLess probable events can be seen, particularly in simple systems where\nthe probabilities are less certain and some (probably those involving\nentanglement) are easily generated. This is supported by the fact that\nthese systems need to be isolated from interaction with \'macroscopic\nmatter\' if they are to be observed, which is what we find.\n\nOne then starts to wonder if many quantum mechanical effects are in\nreality just the expression of the local mutability of time.\n\n--\nOz\nThis post is worth absolutely nothing and is probably fallacious.\n\nUse oz@farmeroz.port995.com [ozacoohdb@despammed.com functions].\nBTOPENWORLD address has ceased. DEMON address has ceased.\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>Jagmeet Singh <jagmeetus@yahoo.com> writes
>I've not been able to find the term delayed Compton effect,but in the
>u-channel of Compton scattering also, the photon is emitted before it
>is absorbed. http://theory.sinp.msu.ru/comphep_html/tutorial/QED/node2.html
>So it seems,yeah, time at the microscopic level is not quite what we
>are used to.
I'm afraid I find this increasingly heartening.
One is accustomed to a particle being smeared out in space.
One is accustomed to a world where space and time must be mixed.
It would thus be extraordinary, in my view, if a particle were not also
smeared out in time.
Generally the mechanics of a particle are in some sense defined by its
'most probable location', so by implication the 'most probable location
in time'. That would mean that there *should* be a chance for a particle
to be absorbed before it is emitted.
I could (if I knew what I was talking about) suggest that the appearance
of antiparticles in the terms of any expansion for a particle is its
'time smear' writ large.
However the implication of this is that the past is mutable. IMHO the
immutable passage of time is a macroscopic effect generated by a highly
probable statistical path through time caused by the interaction of a
myriad particles. That is we only see the most probable events, and for
macroscopic bodies this is probable to the point of certainty.
Less probable events can be seen, particularly in simple systems where
the probabilities are less certain and some (probably those involving
entanglement) are easily generated. This is supported by the fact that
these systems need to be isolated from interaction with 'macroscopic
matter' if they are to be observed, which is what we find.
One then starts to wonder if many quantum mechanical effects are in
reality just the expression of the local mutability of time.
--
Oz
This post is worth absolutely nothing and is probably fallacious.
Use oz@farmeroz.port995.com [ozacoohdb@despammed.com functions].
BTOPENWORLD address has ceased. DEMON address has ceased.
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