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different effective charges can differ. Such differences between schemes can naturally explain the smaller IR fixed point values obtained in other computations of the strong coupling, e.g., in Ref. [28] , as qualitatively illustrated on Fig. 3. 

<img src='content_image/361277.jpg'>

Despite the different physics underlying the light-front holographic coupling α AdS s ( Q $^{2}$) and the effective charge α$_{g}$$_{1}$ ( Q $^{2}$) determined empirically from measurements of the Bjorken sum, the shapes of the two running couplings are remarkably close in the infrared regime. The resemblance of α AdS s and α$_{g}$$_{1}$ is understandable if we recall that α AdS s is a natural nonperturbative extension of α$_{V}$ . The scale shift in the CSR between α$_{V}$ and α$_{g}$$_{1}$ is small, making them numerically very close. Furthermore every effective charge satisfies the same pQCD β function to two loops. Thus, the extended α AdS s and α$_{g}$$_{1}$ are also very close at high scales. The AdS and g$_{1}$ couplings share other common features: their β functions have similar structures: zero in the IR, strongly negative in the GeV domain, and zero in the far UV. We can exploit all of these similarities to fix the normalization α AdS s ( Q = 0) = π and 

