<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\nSooo ... if I read the evidence right then neutrinos have mass, right?\nThat means that there must be right-handed neutrinos. And *that* means\nthat minimal SU(5) is out of the window as a GUT, whether protons\nactually decay or not. Right? Wrong?\n\nI guess my question is: what would be the "next more complex" symmetry\ngroup that is still allowed by the currently available evidence?\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>Sooo ... if I read the evidence right then neutrinos have mass, right?
That means that there must be right-handed neutrinos. And *that* means
that minimal SU(5) is out of the window as a GUT, whether protons
actually decay or not. Right? Wrong?
I guess my question is: what would be the "next more complex" symmetry
group that is still allowed by the currently available evidence?
Thomas Dent
Jul26-04, 11:32 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\n\nytyourclothes@p.zapto.org (Y. T.) wrote\n\n> Sooo ... if I read the evidence right then neutrinos have mass, right?\n\nYes... they have mass-squared differences, therefore at least 2 of\nthem have mass.\n\n> That means that there must be right-handed neutrinos.\n\nNo, there could be only left-handed neutrinos with Majorana-type\nmasses. This is a bit more difficult to arrange theoretically, but\nright-handed neutrinos are not obligatory by any means.\n\n> And *that* means\n> that minimal SU(5) is out of the window as a GUT, whether protons\n> actually decay or not. Right? Wrong?\n\nWrong, because, first, as I said, you don\'t need right-handed\nneutrinos, and second, even if you do want to have RHNs, you can add\nthem as SU(5) singlets without contradicting any aspect of the SU(5)\nGUT unification. The matter multiplets in SU(5) are already not\nunified, so there is no difficulty to add by hand another field to be\nthe RHN.\n\nOf course, the old-style non-supersymmetric SU(5) GUT is in bad shape\nbecause of imprecise unification and proton decay. The SUSY SU(5) is\ndoubtful because it also has some proton decay problems, although not\nas bad as non-SUSY.\n\n> I guess my question is: what would be the "next more complex" symmetry\n> group that is still allowed by the currently available evidence?\n\nAgain, SUSY SU(5) is not ruled out by neutrino mass data, as one can\nsee in this paper http://arxiv.org/abs/hep-ph/0310292 for example, or\nsee\n\nhttp://www.slac.stanford.edu/spires/find/hep/www?rawcmd=FIND+T+SU5+and+neutrino\nfor a full listing.\n\nHowever, *if you choose* to interpret the data as indicating the\npresence of RHN\'s, and *if you want* to incorporate them into a\nnontrivial representation of a single unified gauge group, the\nsimplest is SO(10). In that group all matter fields fall into a single\n16-dimensional multiplet. See\n\nhttp://www.slac.stanford.edu/spires/find/hep/www?rawcmd=FIND+T+So10+and+neutrino\n\nIn the SO(10) model it is quite difficult to make things work properly\nbecause it is "too unified"... the simplest version gives many\nrelations between the fermion masses which are wrong, so you have to\nadd some extra bells and whistles.\n\nIt depends on how unified you want to be! There is the\npartially-unified "Pati-Salam" model with SU(4)xSU(2)xSU(2) group\nwhere leptons and quarks are in the same multiplets, for example, that\nautomatically gives you RHNs and neutrino masses. In that case you\nmight not need so many bells and whistles, but of course it is not\nquite as predictive as SO(10)...\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>ytyourclothes@p.zapto.org (Y. T.) wrote
> Sooo ... if I read the evidence right then neutrinos have mass, right?
Yes... they have mass-squared differences, therefore at least 2 of
them have mass.
> That means that there must be right-handed neutrinos.
No, there could be only left-handed neutrinos with Majorana-type
masses. This is a bit more difficult to arrange theoretically, but
right-handed neutrinos are not obligatory by any means.
> And *that* means
> that minimal SU(5) is out of the window as a GUT, whether protons
> actually decay or not. Right? Wrong?
Wrong, because, first, as I said, you don't need right-handed
neutrinos, and second, even if you do want to have RHNs, you can add
them as SU(5) singlets without contradicting any aspect of the SU(5)
GUT unification. The matter multiplets in SU(5) are already not
unified, so there is no difficulty to add by hand another field to be
the RHN.
Of course, the old-style non-supersymmetric SU(5) GUT is in bad shape
because of imprecise unification and proton decay. The SUSY SU(5) is
doubtful because it also has some proton decay problems, although not
as bad as non-SUSY.
> I guess my question is: what would be the "next more complex" symmetry
> group that is still allowed by the currently available evidence?
Again, SUSY SU(5) is not ruled out by neutrino mass data, as one can
see in this paper http://arxiv.org/abs/http://www.arxiv.org/abs/hep-ph/0310292 for example, or
see
http://www.slac.stanford.edu/spires/find/hep/www?rawcmd=FIND+T+SU5+and+neutrino
for a full listing.
However, *if you choose* to interpret the data as indicating the
presence of RHN's, and *if you want* to incorporate them into a
nontrivial representation of a single unified gauge group, the
simplest is SO(10). In that group all matter fields fall into a single
16-dimensional multiplet. See
http://www.slac.stanford.edu/spires/find/hep/www?rawcmd=FIND+T+So10+and+neutrino
In the SO(10) model it is quite difficult to make things work properly
because it is "too unified"... the simplest version gives many
relations between the fermion masses which are wrong, so you have to
add some extra bells and whistles.
It depends on how unified you want to be! There is the
partially-unified "Pati-Salam" model with SU(4)xSU(2)xSU(2) group
where leptons and quarks are in the same multiplets, for example, that
automatically gives you RHNs and neutrino masses. In that case you
might not need so many bells and whistles, but of course it is not
quite as predictive as SO(10)...
Franz Heymann
Jul27-04, 01:50 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\n\n"Thomas Dent" <tdent@auth.gr> wrote in message\nnews:cb504c2c.0407260618.11c2897e@posting.google.com...\n>\n>\n>\n>\n> ytyourclothes@p.zapto.org (Y. T.) wrote\n>\n> > Sooo ... if I read the evidence right then neutrinos have mass,\nright?\n>\n> Yes... they have mass-squared differences, therefore at least 2 of\n> them have mass.\n>\n> > That means that there must be right-handed neutrinos.\n>\n> No, there could be only left-handed neutrinos with Majorana-type\n> masses. This is a bit more difficult to arrange theoretically, but\n> right-handed neutrinos are not obligatory by any means.\n\nThe argument is beyond me. Surely if a neutrino has a real mass it\nmoves at speeds less than c. There must therefore exist frames of\nreference which move faster than the neutrino does, relative to me.\nIn such a frame the helicity of the neutrino will be reversed. Where\ndo I go wrong?\n\nIf a Majorana type mass is not a common or garden type mass, then by\nthe definition of a mass, it is not a mass. What is it then?\n\n[snip]\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>"Thomas Dent" <tdent@auth.gr> wrote in message
news:cb504c2c.0407260618.11c2897e@posting.google.com...
>
>
>
>
> ytyourclothes@p.zapto.org (Y. T.) wrote
>
> > Sooo ... if I read the evidence right then neutrinos have mass,
right?
>
> Yes... they have mass-squared differences, therefore at least 2 of
> them have mass.
>
> > That means that there must be right-handed neutrinos.
>
> No, there could be only left-handed neutrinos with Majorana-type
> masses. This is a bit more difficult to arrange theoretically, but
> right-handed neutrinos are not obligatory by any means.
The argument is beyond me. Surely if a neutrino has a real mass it
moves at speeds less than c. There must therefore exist frames of
reference which move faster than the neutrino does, relative to me.
In such a frame the helicity of the neutrino will be reversed. Where
do I go wrong?
If a Majorana type mass is not a common or garden type mass, then by
the definition of a mass, it is not a mass. What is it then?
[snip]
Franz
vBulletin® v3.7.3, Copyright ©2000-2008, Jelsoft Enterprises Ltd.