Some mean value theorems in the style of Bombieri-Vinogradov’s theorem are discussed. They concern binary and ternary additive problems with primes in arithmetic progressions and short intervals. Nontrivial estimates for some of these mean values are given. As application inter alia, we show that for large odd $n\neg \equiv 1\left(6\right)$, Goldbach’s ternary problem $n=p_1+p_2+p_3$ is solvable with primes $p_1,p_2$ in short intervals $p_i\in [X_i,X_i+Y]$ with $X_i^{{\theta }_i}=Y$, $i=1,2$, and ${\theta }_1,{\theta }_2\ge 0.933$ such that $(p_1+2)(p_2+2)$ has at most $9$ prime factors.

The finite groups having an indecomposable polynomial invariant of degree at least half the order of the group are classified. It turns out that –apart from four sporadic exceptions– these are exactly the groups with a cyclic subgroup of index at most two.