Normalized solutions for Schr\"{o}dinger system with subcritical Sobolev exponent and combined nonlinearities

In this paper, we look for solutions to the following coupled Schr\"{o}dinger system \begin{equation*} \begin{cases} -\Delta u+\lambda_{1}u=\alpha_{1}|u|^{p-2}u+\mu_{1}u^{3}+\rho v^{2}u & \text{in} \ \ \mathbb{R}^{N}, -\Delta v+\lambda_{2}v=\alpha_{2}|v|^{p-2}v+\mu_{2}v^{3}+\rho u^{2}v& \text{in} \ \ \mathbb{R}^{N}, \end{cases} \end{equation*} with the additional conditions $\int_{\mathbb{R}^{N}}u^{2}dx=b^{2}_{1}$ and $\int_{\mathbb{R}^{N}}v^{2}dx=b^{2}_{2}.$ Here $b_1, b_2>0$ are prescribed, $N\leq3$, $\mu_{1}, \mu_{2}, \alpha_{1},\alpha_{2},\rho>0$, $p\in (2,4)$ and the frequencies $\lambda_{1},\lambda_{2}$ are unknown and will appear as Lagrange multipliers. In the one dimension case, the energy functional is bounded from below on the product of $L^2$-spheres, normalized ground states exist and are obtained as global minimizers. When $N=2$, the energy functional is not always bounded on the product of $L^2$-spheres, we prove the existence of normalized ground states under suitable conditions on $b_1$ and $b_2$, which are obtained as global minimizers. When $N=3$, we show that under suitable conditions on $b_1$ and $b_2$, at least two normalized solutions exist, one is a ground state and the other is an excited state. We also shows the limit behavior of the normalized solutions as $\alpha_{1},\alpha_{2}\rightarrow 0$. The first solution will disappear and the second solution will converge to the normalized solution of system (1.1) with $\alpha_{1}=\alpha_{2}=0$, which has been studied by T. Bartsch, L. Jeanjean and N. Soave (J. Math. Pures Appl. 2016). Furthermore, by refining the upper bound of the ground state energy, we provide a precise mass collapse behavior of the ground states. The results in this paper complement the main results established by X. Luo, X. Yang and W. Zou (arXiv:2107.08708), where the authors considered the case $N=4$.