View Full Version : spin 2 particles
alistair
May31-04, 04:21 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>Is it possible for a spin 2 particle to yield two spin one particles?\nA spin 1 photon gives two spin 1/2 fermions - positron-electron and\nproton-antiproton pairs.I\'m asking because I\'d like to know this: if a\ngraviton\nis emitted by a particle and that graviton had a large enough energy,\ncould it\nyield other force mediating particles like a W or a Z boson?\nGravity could be a particularly weak force because graviton energy is\nbecoming spin 1 bosons.\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>Is it possible for a spin 2 particle to yield two spin one particles?
A spin 1 photon gives two spin 1/2 fermions - positron-electron and
proton-antiproton pairs.I'm asking because I'd like to know this: if a
graviton
is emitted by a particle and that graviton had a large enough energy,
could it
yield other force mediating particles like a W or a Z boson?
Gravity could be a particularly weak force because graviton energy is
becoming spin 1 bosons.
Arnold Neumaier
Jun1-04, 11:43 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\nalistair wrote:\n> Is it possible for a spin 2 particle to yield two spin one particles?\n> A spin 1 photon gives two spin 1/2 fermions - positron-electron and\n> proton-antiproton pairs.\n\n\'Total spin\' is not conserved. A photon may create two spin zero\nHiggs particles of opposite antiness.\n\n\nArnold Neumaier\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>alistair wrote:
> Is it possible for a spin 2 particle to yield two spin one particles?
> A spin 1 photon gives two spin 1/2 fermions - positron-electron and
> proton-antiproton pairs.
'Total spin' is not conserved. A photon may create two spin zero
Higgs particles of opposite antiness.
Arnold Neumaier
Arnold Neumaier
Jun1-04, 02:12 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>Arnold Neumaier wrote:\n> alistair wrote:\n>\n>>Is it possible for a spin 2 particle to yield two spin one particles?\n>>A spin 1 photon gives two spin 1/2 fermions - positron-electron and\n>>proton-antiproton pairs.\n>\n>\n> \'Total spin\' is not conserved. A photon may create two spin zero\n> Higgs particles of opposite antiness.\n\nActually, I was sloppy. One needs two on-shell photons to create\nan on-shell particle-antiparticle pair of any spin and nonzero mass.\nThis is because total 4-momentum is conserved but the sum of two timelike\nmomentum vectors is timelike, hence cannot come from a single photon.\n(The sum of two distinct photon momenta is generally timelike, hence there\nis no such obstacle for two photons.)\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>Arnold Neumaier wrote:
> alistair wrote:
>
>>Is it possible for a spin 2 particle to yield two spin one particles?
>>A spin 1 photon gives two spin 1/2 fermions - positron-electron and
>>proton-antiproton pairs.
>
>
> 'Total spin' is not conserved. A photon may create two spin zero
> Higgs particles of opposite antiness.
Actually, I was sloppy. One needs two on-shell photons to create
an on-shell particle-antiparticle pair of any spin and nonzero mass.
This is because total 4-momentum is conserved but the sum of two timelike
momentum vectors is timelike, hence cannot come from a single photon.
(The sum of two distinct photon momenta is generally timelike, hence there
is no such obstacle for two photons.)
Arnold Neumaier
Franz Heymann
Jun12-04, 07:10 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>"Arnold Neumaier" <Arnold.Neumaier@univie.ac.at> wrote in message\nnews:40BCB57C.1040300@univie.ac.at...\n> Arnold Neumaier wrote:\n> > alistair wrote:\n> >\n> >>Is it possible for a spin 2 particle to yield two spin one particles?\n> >>A spin 1 photon gives two spin 1/2 fermions - positron-electron and\n> >>proton-antiproton pairs.\n> >\n> >\n> > \'Total spin\' is not conserved. A photon may create two spin zero\n> > Higgs particles of opposite antiness.\n>\n> Actually, I was sloppy. One needs two on-shell photons to create\n> an on-shell particle-antiparticle pair of any spin and nonzero mass.\n\nNo. One on-shell and one off-shell photon can do the trick. Think of\npair production by one on-shell photon in the field of a nucleus.\n\n> This is because total 4-momentum is conserved but the sum of two timelike\n> momentum vectors is timelike, hence cannot come from a single photon.\n> (The sum of two distinct photon momenta is generally timelike, hence there\n> is no such obstacle for two photons.)\n\nFranz\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>"Arnold Neumaier" <Arnold.Neumaier@univie.ac.at> wrote in message
news:40BCB57C.1040300@univie.ac.at...
> Arnold Neumaier wrote:
> > alistair wrote:
> >
> >>Is it possible for a spin 2 particle to yield two spin one particles?
> >>A spin 1 photon gives two spin 1/2 fermions - positron-electron and
> >>proton-antiproton pairs.
> >
> >
> > 'Total spin' is not conserved. A photon may create two spin zero
> > Higgs particles of opposite antiness.
>
> Actually, I was sloppy. One needs two on-shell photons to create
> an on-shell particle-antiparticle pair of any spin and nonzero mass.
No. One on-shell and one off-shell photon can do the trick. Think of
pair production by one on-shell photon in the field of a nucleus.
> This is because total 4-momentum is conserved but the sum of two timelike
> momentum vectors is timelike, hence cannot come from a single photon.
> (The sum of two distinct photon momenta is generally timelike, hence there
> is no such obstacle for two photons.)
Franz
Arnold Neumaier
Jun16-04, 03:48 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>Franz Heymann wrote:\n> "Arnold Neumaier" <Arnold.Neumaier@univie.ac.at> wrote in message\n> news:40BCB57C.1040300@univie.ac.at...\n>\n>>Arnold Neumaier wrote:\n>>\n>>>alistair wrote:\n>>>\n>>>\n>>>>Is it possible for a spin 2 particle to yield two spin one particles?\n>>>>A spin 1 photon gives two spin 1/2 fermions - positron-electron and\n>>>>proton-antiproton pairs.\n>>>\n>>>\n>>>\'Total spin\' is not conserved. A photon may create two spin zero\n>>>Higgs particles of opposite antiness.\n>>\n>>Actually, I was sloppy. One needs two on-shell photons to create\n>>an on-shell particle-antiparticle pair of any spin and nonzero mass.\n>\n>\n> No. One on-shell and one off-shell photon can do the trick. Think of\n> pair production by one on-shell photon in the field of a nucleus.\n\nYes, in an external field, 4-momentum is not conserved, and my argument\nbreaks down. In that case, particles may even be created by a sufficiently\nlarge external physical field without involving physical photons.\n(Of course, one could describe the external field in terms of virtual\nphotons, but this is not really helpful.)\n\n\nArnold Neumaier\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"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>Franz Heymann wrote:
> "Arnold Neumaier" <Arnold.Neumaier@univie.ac.at> wrote in message
> news:40BCB57C.1040300@univie.ac.at...
>
>>Arnold Neumaier wrote:
>>
>>>alistair wrote:
>>>
>>>
>>>>Is it possible for a spin 2 particle to yield two spin one particles?
>>>>A spin 1 photon gives two spin 1/2 fermions - positron-electron and
>>>>proton-antiproton pairs.
>>>
>>>
>>>'Total spin' is not conserved. A photon may create two spin zero
>>>Higgs particles of opposite antiness.
>>
>>Actually, I was sloppy. One needs two on-shell photons to create
>>an on-shell particle-antiparticle pair of any spin and nonzero mass.
>
>
> No. One on-shell and one off-shell photon can do the trick. Think of
> pair production by one on-shell photon in the field of a nucleus.
Yes, in an external field, 4-momentum is not conserved, and my argument
breaks down. In that case, particles may even be created by a sufficiently
large external physical field without involving physical photons.
(Of course, one could describe the external field in terms of virtual
photons, but this is not really helpful.)
Arnold Neumaier
alistair
Jun17-04, 06:14 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>Quantum mechanics and General relativity have not yet been combined\ninto a single theory that works over all distance scales.\nThis might mean that quantum mechanics has something wrong with it and\nso the spin of a graviton which is derived from QM might not be equal\nto 2.\nIf the spin of the force mediator for gravity was not 2 , then what\ncould it be? What spins could not be associated with a gravitational\nforce mediator?\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>Quantum mechanics and General relativity have not yet been combined
into a single theory that works over all distance scales.
This might mean that quantum mechanics has something wrong with it and
so the spin of a graviton which is derived from QM might not be equal
to 2.
If the spin of the force mediator for gravity was not 2 , then what
could it be? What spins could not be associated with a gravitational
force mediator?
Doug Sweetser
Jun18-04, 04:40 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>\nHello Alistair:\n\n> Quantum mechanics and General relativity have not yet been combined\n> into a single theory that works over all distance scales.\n> This might mean that quantum mechanics has something wrong with it and\n> so the spin of a graviton which is derived from QM might not be equal\n> to 2.\n\nOr it might mean GR is too complicated to get the job done. We don\'t\nknow, so formally both must be open to question.\n\n> If the spin of the force mediator for gravity was not 2 , then what\n> could it be? What spins could not be associated with a gravitational\n> force mediator?\n\nI didn\'t understand this whole spin issue until I read Brian Hatfield\'s\nintroduction found in "Feynman Lectures on Gravitation." These two\nparagraphs were so clear, I will type them out here:\n\n"In order to produce a _static_ force and not just scattering, the\nemission or absorption of aa single graviton by either particle must\nleave both particles in the same internal state. This rules out the\npossibility that the graviton carries half-integer spin (for example,\nrelated to the fact that it takes a rotation of 720 degrees to return a\nspin-1/2 wavefunction back to itself). Therefore the graviton must\nhave integer spin. Next, to decide which integer spins are possible,\nwe examine th two cases where particles 2 is identical to particle 1\nand where particle 2 is the antiparticle of 1, so that when charged,\nthe two particles will carry the same and opposiet charge,\nrespectively. When the potential is computed in both cases and the\nappropriate limits are taken, we find that when the exchanged particle\ncarries odd integer spin, like charges repel and opposite charges\nattract, just as in the example of electrodynamics. On the other hand,\nwhen the echanged particle carries even integer spin, the potential is\nuniversally atractive (like charges and opposite charges attract).\nHence the spin of the graviton must be 0, 2, 4, ...\n\nTo eliminate the spin 0 possibility we knote that the Eotvos experiment\nand recent refinements empirically indicate that gravity does couple to\nthe energy content of objects, hence things like photons should be\naffected by gravity, e.g., they should "fall" in a gravitational field.\nIf we assume that the exchanged particle is spin 0, then we lose the\ncoupling of the gravity to the spin-1 photon. Since we know that light\nis deflected by massive object, e.,g., the sun, then the graviton\ncannot be spin 0."\n\nThat reasoning sounds solid to me.\n\ndoug\nquaternions.com\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"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>Hello Alistair:
> Quantum mechanics and General relativity have not yet been combined
> into a single theory that works over all distance scales.
> This might mean that quantum mechanics has something wrong with it and
> so the spin of a graviton which is derived from QM might not be equal
> to 2.
Or it might mean GR is too complicated to get the job done. We don't
know, so formally both must be open to question.
> If the spin of the force mediator for gravity was not 2 , then what
> could it be? What spins could not be associated with a gravitational
> force mediator?
I didn't understand this whole spin issue until I read Brian Hatfield's
introduction found in "Feynman Lectures on Gravitation." These two
paragraphs were so clear, I will type them out here:
"In order to produce a _static_ force and not just scattering, the
emission or absorption of aa single graviton by either particle must
leave both particles in the same internal state. This rules out the
possibility that the graviton carries half-integer spin (for example,
related to the fact that it takes a rotation of 720 degrees to return a
spin-1/2 wavefunction back to itself). Therefore the graviton must
have integer spin. Next, to decide which integer spins are possible,
we examine th two cases where particles 2 is identical to particle 1
and where particle 2 is the antiparticle of 1, so that when charged,
the two particles will carry the same and opposiet charge,
respectively. When the potential is computed in both cases and the
appropriate limits are taken, we find that when the exchanged particle
carries odd integer spin, like charges repel and opposite charges
attract, just as in the example of electrodynamics. On the other hand,
when the echanged particle carries even integer spin, the potential is
universally atractive (like charges and opposite charges attract).
Hence the spin of the graviton must be 0, 2, 4, ...
To eliminate the spin possibility we knote that the Eotvos experiment
and recent refinements empirically indicate that gravity does couple to
the energy content of objects, hence things like photons should be
affected by gravity, e.g., they should "fall" in a gravitational field.
If we assume that the exchanged particle is spin 0, then we lose the
coupling of the gravity to the spin-1 photon. Since we know that light
is deflected by massive object, e.,g., the sun, then the graviton
cannot be spin ."
That reasoning sounds solid to me.
doug
quaternions.com
alistair
Jun18-04, 03:23 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>Spin 1/2 particles obey fermi-dirac statistics, spin 1 particles obey\nbose- einstein statistics.What kind of statistics are spin 2 particles\nexpected to obey?\n\n[Moderator\'s note: Particles with integer spin (0,1,2, ...) obey\nBose-Einstein statistics. Particles with integer-plus-1/2 spin (1/2,\n3/2, 5/2, ...) obey Fermi-Dirac statistics. -TB]\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>Spin 1/2 particles obey fermi-dirac statistics, spin 1 particles obey
bose- einstein statistics.What kind of statistics are spin 2 particles
expected to obey?
[Moderator's note: Particles with integer spin (0,1,2, ...) obey
Bose-Einstein statistics. Particles with integer-plus-1/2 spin (1/2,3/2, 5/2, ...) obey Fermi-Dirac statistics. -TB]
I would imagine, deep in the archives of nuclear physics, that a spin two nucleus decays into two spin one particles. or four spin 1/2 particles. That is, such a transition is consistent with conservation of angular momentum. the sticky parts are the restrictions of energy and momentum conservation -- that's why, for example, no one has ever seen proton beta decay -> neutron, positron, and neutrino. RA
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