We consider the constrained nonlinear Schrödinger problem in $\mathbb{R}^{N}$ ( $N\ge 3$ ) where $2< p,m<2+\tfrac{4}{N}$ , $2^{*}=\tfrac{2N}{N-2}$ , $a,\mu ,\kappa >0$ , and $\gamma >0$ is a parameter.
We prove that there exists an explicit threshold $\gamma _{0}=\gamma _{0}(a,\mu ,\kappa ,N,p,m)>0$ , determined by the variational inequalities and Sobolev embedding constants, such that for every $0<\gamma <\gamma _{0}$ , problem $(P_{a})$ admits a positive normalized ground state $(\lambda ,u)\in \mathbb{R}\times H^{1}(\mathbb{R}^{N})$ with $\lambda <0$ .
The proof is variational and relies on a careful analysis of the energy functional on the $L^{2}$ -sphere, the construction of a Pohozaev manifold as a natural constraint, and concentration–compactness arguments adapted to handle the Sobolev-critical term. The double-subcritical structure ( $|u|^{p-2}u$ and $|u|^{m-2}u$ ) competes with the critical term, and the smallness of γ ensures compactness of minimizing sequences.