Holography for Sp(2$N_c$) Gauge Dynamics: from Composite Higgs to Technicolour

We study Sp(2$N_c$) gauge dynamics with two Dirac fermion flavours in the fundamental representation. These strongly coupled systems underlie some composite Higgs models with a global symmetry breaking pattern SU(4)$\rightarrow$Sp(4), leading to a light quartet of pseudo-Goldstone bosons that can play the role of the Higgs. Including four-fermion interactions can rotate the vacuum to a technicolour breaking pattern. Using gauge/gravity duality, we study the underlying gauge dynamics. Our model incorporates the $N_c$-specific running of the fermion anomalous dimension and can thus distinguish between specific gauge groups. We determine the bound-state spectrum of the UV SU(4)$\rightarrow$Sp(4) symmetry breaking model, also including fermion masses and mass splitting, and display the $N_c$ dependence. The inclusion of a four-fermion interaction shows the emergence of three Goldstone bosons on the path to technicolour dynamics.
Comment: 43 pages, 42 figures, 3 tables. v2 added new citations, 44 pages. v3 minor changes. v4 minor changes