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CATEGORIES:Quantum Fields and Strings Seminars
SUMMARY:Magnetic scattering: pairwise little group and pai
rwise helicity - Csaba Csaki\, Cornell
DTSTART;TZID=Europe/London:20211028T160000
DTEND;TZID=Europe/London:20211028T170000
UID:TALK163246AThttp://talks.cam.ac.uk
URL:http://talks.cam.ac.uk/talk/index/163246
DESCRIPTION: I discuss how to construct a Lorentz-invariant S-
matrix for the scattering of electrically and magn
etically charged particles. A key ingredient is a
revision of our fundamental understanding of multi
-particle representations of the PoincarĂ© group. S
urprisingly\, the asymptotic states for electric-m
agnetic scattering transform with an additional li
ttle group phase\, associated with pairs of electr
ically and magnetically charged particles. I will
discuss the general construction of such states. T
he resulting "pairwise helicity" is identified wit
h the quantized "cross product" of charges e1 g2-
e2 g1 for every charge-monopole pair\, and repres
ents the extra angular momentum stored in the asym
ptotic electromagnetic field. We define a new kind
of pairwise spinor-helicity variable\, which serv
es as an additional building block for electric-ma
gnetic scattering amplitudes. We then construct th
e most general 3-point S-matrix elements\, as well
as the full partial wave decomposition for the 2
-> 2 fermion-monopole S-matrix. In particular\, we
derive the famous helicity flip in the lowest par
tial wave as a simple consequence of a generalized
spin-helicity selection rule\, as well as the ful
l angular dependence for the higher partial waves.
We will also discuss a possible direction for res
olving Callan's ``semiton" problem: the scattering
amplitude of a positron on a GUT monopole which a
pparently does not have an allowed final state. We
will show that using entagled pairwise helicity s
pinors a simple possible s-wave final state does e
xist.
LOCATION:Online (Zoom)
CONTACT:
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