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SUMMARY:Magnetic scattering: pairwise little group and pairwise helicity [
Special Theoretical Physics Colloquium as part of the DP Roy Memorial Lect
ure]
DTSTART;VALUE=DATE-TIME:20230117T103000Z
DTEND;VALUE=DATE-TIME:20230117T113000Z
DTSTAMP;VALUE=DATE-TIME:20230326T115156Z
UID:indico-event-8757@cern.ch
DESCRIPTION:I discuss how to construct the S-matrix for the scattering of
electrically and magnetically charged particles. A key ingredient is a rev
ision of our fundamental understanding of multi-particle representations o
f the PoincarĂ© group. Surprisingly\, the asymptotic states for electric-m
agnetic scattering transform with an additional little group phase\, assoc
iated with pairs of electrically and magnetically charged particles. I wil
l discuss the general construction of such states. The resulting "pairwise
helicity" is identified with the quantized "cross product" of charges e1
g2- e2 g1 for every charge-monopole pair\, and represents the extra angul
ar momentum stored in the asymptotic electromagnetic field. We define a ne
w kind of pairwise spinor-helicity variable\, which serves as an additiona
l building block for electric-magnetic scattering amplitudes. We then cons
truct the most general 3-point S-matrix elements\, as well as the full par
tial wave decomposition for the 2 -> 2 fermion-monopole S-matrix. In parti
cular\, we derive the famous helicity flip in the lowest partial wave as a
simple consequence of a generalized spin-helicity selection rule\, as wel
l as the full angular dependence for the higher partial waves. We show a
potential resolution of Callan's long-standing semiton problem in our appr
oach. Finally we show how these pairwise states can be understood dynamica
lly as dressed states which incorporate the effects of soft photons\, and
provide a novel fully field theoretic derivation of Dirac quantization in
terms of a geometric Berry phase.\n\nhttps://indico.tifr.res.in/indico/con
ferenceDisplay.py?confId=8757
LOCATION: AG69 and Zoom
URL:https://indico.tifr.res.in/indico/conferenceDisplay.py?confId=8757
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