MagneticSParameter

Abstract

We propose a direct test of the existence of gauge duals for nonsupersymmetric asymptotically free gauge theories developing an infrared fixed point by computing the S parameter in the electric and dual magnetic description. In particular we show that at the lower bound of the conformal window the magnetic S parameter, i.e., the one determined via the dual magnetic gauge theory, assumes a simple expression in terms of the elementary magnetic degrees of freedom. The results further support our recent conjecture of the existence of a universal lower bound on the S parameter and indicates that it is an ideal operator for counting the active physical degrees of freedom within the conformal window. Our results can be directly used to unveil possible four-dimensional gauge duals and constitute the first explicit computation of a nonperturbative quantity, in the electric variables, via nonsupersymmetric gauge duality.

Massive holographic QCD in the Veneziano limit

“…The mechanism which leads to this discontinuity will be discussed in detail below (from the holographic viewpoint), but it appears rather natural: the S-parameter is O (N f N c ) whenever the geometry has the IR singularity, and vanishes only for zero quark mass in the conformal window where there is an IRFP instead. The result is also consistent with the analysis based on field theory at qualitative level [121][122][123]: the S-parameter is finite except for exactly zero mass in the conformal window.…”

Sparameter at nonzero temperature and chemical potential

“…In particular, the S-parameter is especially relevant for models of electroweak symmetry breaking. Several estimates have appeared in the literature making use of model computations [5][6][7][8][9][10][11][12][13][14][15][16][17] and/or first-principle lattice computations [18,19]. The latter ones are necessarily carried out on finite lattices, i.e.…”

Dual of QCD with one adjoint fermion

“…For example, the magnetic dual allows to predict, in principle, the critical number of flavors below which the electric theory looses large distance conformality. It has also been show in [27] that it is possible to use gauge dualities to compute the S parameter in the nonperturbative regime of the electric theory.…”

“…These are the known extension of technicolor type possessing the smallest intrinsic S parameter [21][22][23][24] while being able to display simultaneously (near) conformal behavior before adding the backreaction due to traditional type extended technicolor interactions (ETC) [25]. For recent analysis of the relevant properties of the S parameter, using also duality arguments we refer to [26][27][28]. As for the issue of the effects of the ETC interactions on the technicolor dynamics and associated conformal window, it has recently been argued in [29] that before adding the ETC interactions the technicolor theory, in isolation, should already be conformal for the combined model to be phenomenologically viable.…”