An analog to the Goldbach problem and the twin prime problem

Abstract: One of the best approaches to the Goldbach conjectures is the Chen's theorem, showing that every large enough even integer can be represented by a sum of a prime and a $2$-almost prime. In this article, we consider a thinner set than the set of $2$-almost primes, which is $$ \mathbb{P}^{(c)}=(\lfloor p^c \rfloor)_{p\in \mathbb{P}}\quad (c>0,c\notin \mathbb{N}), $$ where $\mathbb{P}$ is the set of prime numbers and $\lfloor \cdot \rfloor$ is the floor function. We prove that for all $c \in (0,\frac{13}{15})$, any large enough integer $N$ can be represented as $$ N=\lfloor p^c\rfloor+q, $$ where $p$ and $q$ are primes. Moreover, for almost all $c \in (0, M)$ and large enough $N$ where $M \ll \log N/ \log\log N$, we also prove that $N \in \mathbb{P}^{(c)} + \mathbb{P}$. It is well known that the twin prime conjecture can be approached by a similar way to the Goldbach conjecture with a different form of the Chen's theorem. We also prove similar results due to the set $\mathbb{P}^{(c)}$ with both an unconditional case and an average case based on the Lebesgue measure, which also improve a theorem by Balog.