TY - JOUR
T1 - Spontaneous breaking of U(1) symmetry in coupled complex SYK models
AU - Klebanov, Igor R.
AU - Milekhin, Alexey
AU - Tarnopolsky, Grigory
AU - Zhao, Wenli
N1 - Publisher Copyright:
© 2020, The Author(s).
PY - 2020/11
Y1 - 2020/11
N2 - As shown in [1], two copies of the large N Majorana SYK model can produce spontaneous breaking of a Z2 symmetry when they are coupled by appropriate quartic terms. In this paper we similarly study two copies of the complex SYK model coupled by a quartic term preserving the U(1) × U(1) symmetry. We also present a tensor counterpart of this coupled model. When the coefficient α of the quartic term lies in a certain range, the coupled large N theory is nearly conformal. We calculate the scaling dimensions of fermion bilinear operators as functions of α. We show that the operator c1i†c2i, which is charged under the axial U(1) symmetry, acquires a complex dimension outside of the line of fixed points. We derive the large N Dyson-Schwinger equations and show that, outside the fixed line, this U(1) symmetry is spontaneously broken at low temperatures because this operator acquires an expectation value. We support these findings by exact diagonalizations extrapolated to large N.
AB - As shown in [1], two copies of the large N Majorana SYK model can produce spontaneous breaking of a Z2 symmetry when they are coupled by appropriate quartic terms. In this paper we similarly study two copies of the complex SYK model coupled by a quartic term preserving the U(1) × U(1) symmetry. We also present a tensor counterpart of this coupled model. When the coefficient α of the quartic term lies in a certain range, the coupled large N theory is nearly conformal. We calculate the scaling dimensions of fermion bilinear operators as functions of α. We show that the operator c1i†c2i, which is charged under the axial U(1) symmetry, acquires a complex dimension outside of the line of fixed points. We derive the large N Dyson-Schwinger equations and show that, outside the fixed line, this U(1) symmetry is spontaneously broken at low temperatures because this operator acquires an expectation value. We support these findings by exact diagonalizations extrapolated to large N.
KW - 1/N Expansion
KW - Holography and condensed matter physics (AdS/CMT)
KW - Spontaneous Symmetry Breaking
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U2 - 10.1007/JHEP11(2020)162
DO - 10.1007/JHEP11(2020)162
M3 - Article
AN - SCOPUS:85097423055
SN - 1126-6708
VL - 2020
JO - Journal of High Energy Physics
JF - Journal of High Energy Physics
IS - 11
M1 - 162
ER -