a way of going up in energy scales does not necessarily lead to a unique gauge theory [@weinberg-largeNc]. Different constructions could give rise to different gauge structures at higher energies. One way that is both simple and phenomenologically appealing is the linear “moose" construction [@georgi-idea]. A version of this class of construction in which an infinite tower of gauge fields are incorporated was proposed as a “dimensionally deconstructed QCD" [@son-stephanov1]. In order to make the construction correctly represent nature up to a given scale, the theory has to be matched to a fundamental theory and “ultraviolet-completed" to go beyond.

As we will elaborate further later, if one wants to study what happens to the vector mesons in medium, this strategy is definitely needed. On a more fundamental level, one can view this as a generic phenomenon of the “emergence" of local gauge degrees of freedom. Examples are numerous, e.g., emergent gravity, emergent space-time, spin-charge separation in high-T superconductivity etc [@horowitz-polchinski].

HLS from string theory
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A novel recent development in both string theory and hadronic physics is that HLS $descends$ naturally via AdS/CFT duality from string theory to holographic QCD. This is a top-down approach to hidden local symmetry theory 