Editing AdS/CFT correspondence (section)

=== Criticism ===
With many physicists turning towards string-based methods to solve problems in nuclear and condensed matter physics, some theorists working in these areas have expressed doubts about whether the AdS/CFT correspondence can provide the tools needed to realistically model real-world systems. In a talk at the [[Quark Matter conference]] in 2006,{{sfn|ps=|McLerran|2007}} an American physicist, [[Larry McLerran]] pointed out that the {{nowrap|1=''N'' = 4}} super Yang–Mills theory that appears in the AdS/CFT correspondence differs significantly from quantum chromodynamics, making it difficult to apply these methods to nuclear physics. According to McLerran,

{{Blockquote|text=''N''&nbsp;=&nbsp;4 supersymmetric Yang–Mills is not QCD&nbsp;... It has no mass scale and is conformally invariant. It has no confinement and no running coupling constant. It is supersymmetric. It has no chiral symmetry breaking or mass generation. It has six scalar and fermions in the adjoint representation&nbsp;... It may be possible to correct some or all of the above problems, or, for various physical problems, some of the objections may not be relevant. As yet there is not consensus nor compelling arguments for the conjectured fixes or phenomena which would insure that the {{nowrap|1=''N'' = 4}} supersymmetric Yang Mills results would reliably reflect QCD.{{sfn|ps=|McLerran|2007}}}}

In a letter to [[Physics Today]], [[Nobel laureate]] [[Philip W. Anderson]] voiced similar concerns about applications of AdS/CFT to condensed matter physics, stating

{{Blockquote|text=As a very general problem with the AdS/CFT approach in condensed-matter theory, we can point to those telltale initials "CFT"—conformal field theory. Condensed-matter problems are, in general, neither relativistic nor conformal. Near a quantum critical point, both time and space may be scaling, but even there we still have a preferred coordinate system and, usually, a lattice. There is some evidence of other linear-T phases to the left of the strange metal about which they are welcome to speculate, but again in this case the condensed-matter problem is overdetermined by experimental facts.{{sfn|ps=|Anderson|2013}}}}