no mechanism to disentangle them from the hadronic modes yet. In order to overcome this problem, it is possible to consider the color brane configuration in non-critical string theory \[41-44\].

The non-critical string is not formulated with the critical dimension, but nonetheless has vanishing Weyl anomaly. A worldsheet theory with the correct central charge can be constructed by introducing a non-trivial target space, commonly by giving an expectation value to the dilaton which varies linearly along some spacetime direction. For this reason non-critical string theory is sometimes called the linear dilaton theory. Since the dilaton is related to the string coupling constant, this theory contains a region where the coupling is weak (and so perturbation theory is valid) and another region where the theory is strongly coupled \[46-47\].

In such backgrounds the string coupling constant is proportional to $\frac{1}{N_c}$, so the large $N_c$ limit corresponds to the small string coupling constant. However, contrary to the critical holographic models, in the large $N_c$ limit, the ’t Hooft coupling is of order one instead of infinity and the scalar curvature of the gravitational background is also of order one. So, it seems the non-critical gauge-gravity correspondence is not very reliable. But studies 