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SUMMARY:On conformal windows and the phase structure of 2+1d and 3+1d QCD 
 - Ofer Aharony\, Weizmann Institute of Science
DTSTART:20250313T130000Z
DTEND:20250313T140000Z
UID:TALK225289@talks.cam.ac.uk
CONTACT:122734
DESCRIPTION:Many gauge theories\, such as 3+1d and 2+1d SU(N) gauge theori
 es with N_f massless Dirac fermions in the fundamental representation\, ex
 hibit "conformal windows" - a range of values of N_f for which the theory 
 flows to a non-trivial conformal field theory at low energy. It is interes
 ting to ask how these windows end and transition into phases with confinem
 ent and with spontaneous breaking of the flavor symmetry. I will begin by 
 reviewing what is known about 3+1 dimensional QCD\, focusing on the large 
 N and N_f limit and on the conformal window there\, and I will review the 
 standard "merger scenario" for the end of its conformal window. I will the
 n move on to QCD in 2+1 dimensions\, and discuss its phase diagram as a fu
 nction of the mass and of the discrete parameters N\, N_f and the Chern-Si
 mons level k\, focusing again on the limit of large N\, N_f\, k. I will ar
 gue that this theory also has a conformal window (corresponding to a secon
 d order phase transition when changing the mass) but that it does not alwa
 ys end at a merger\, and I will suggest two other possibilities for the en
 d of general conformal windows. The different scenarios can be distinguish
 ed by the behavior of the theory as the boundary of the conformal window i
 s approached from either side. Based on work in progress with Thomas Dumit
 rescu\, Zohar Komargodski and Jiangyuan Qian.
LOCATION:Potter Room (B1.19)
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