Title: On the existence of ground states to Hartree-type equations in $\mathbb{R}^3$ with a delta potential

Abstract: Consider the Hartree-type equation in $\mathbb{R}^3$ with a delta potential formally described by $$ i \partial_t \psi = - \Delta_x \psi + \alpha \delta_0 \psi - (I_\beta \ast |\psi|^p) |\psi|^{p - 2} \psi $$ where $\alpha \in \mathbb{R}$; $0 < \beta < 3$ and we want to solve for $\psi \colon \mathbb{R}^3 \times \mathbb{R} \to \mathbb{C}$. By means of a Poho\v{z}aev identity, we show that if $p = (3 + \beta) / 3$ and $\alpha \geq 0$, then the problem has no ground state at any mass $\mu > 0$. We also prove that if $$ \frac{3 + \beta}{3} < p < \min \left(
\frac{5 + \beta}{3}, \frac{5 + 2 \beta}{4} \right), $$ which includes the physically-relevant case $p = \beta = 2$, then the problem admits a ground state at any mass $\mu > 0$.