## Chapter 6 

## Improving the IR of Holographic Descriptions of QCD 

As we saw chapter 5, a surprisingly good description of QCD can be obtained from a simple five dimensional gauge theory on a truncated AdS space [2]. However, there are many short-comings of the model: 

• The use of an AdS geometry implicitly means that the background gauge configuration is conformal 

• Hence the UV does not become asymptotically free 

• The existence of a mass gap is imposed by hand by the introduction of an infrared cutoff. It is not the result of a running coupling 

• The fields that holographically describe the quark bilinears are in- cluded phenomenologically 

• The solution for the field holographic to the quark mass and conden- sate is put in by hand - it is not dynamically determined by either the 

