The paper discusses the linear confinement of mesons in QCD, where the masses squared of high-spin or high radial excitation mesons are expected to grow linearly with their spin and excitation number. The authors show that this behavior can be reproduced within a 5-dimensional AdS/QCD model, where the infrared (IR) behavior of the dual theory strongly constrains the spectrum of highly excited mesons. They find that the spectrum of squared masses, \( m_{n,S}^2 \), follows the form \( m_{n,S}^2 \sim (n + S) \). The authors also explore the implications of this result for the axial sector and higher-spin mesons, and discuss the limitations and assumptions of their approach. They suggest that the observed IR behavior could arise from tachyon condensation in string theory, and highlight the need for further investigation into the string theory duals of confining gauge theories.The paper discusses the linear confinement of mesons in QCD, where the masses squared of high-spin or high radial excitation mesons are expected to grow linearly with their spin and excitation number. The authors show that this behavior can be reproduced within a 5-dimensional AdS/QCD model, where the infrared (IR) behavior of the dual theory strongly constrains the spectrum of highly excited mesons. They find that the spectrum of squared masses, \( m_{n,S}^2 \), follows the form \( m_{n,S}^2 \sim (n + S) \). The authors also explore the implications of this result for the axial sector and higher-spin mesons, and discuss the limitations and assumptions of their approach. They suggest that the observed IR behavior could arise from tachyon condensation in string theory, and highlight the need for further investigation into the string theory duals of confining gauge theories.