I would like to propose the following conjecture
The PKD Conjecture (PKD)
Let $p,d$ be positive integers with $\gcd(p,d)=1$. There exists a function $$ f:\mathbb{N}\to\mathbb{N}, \quad f(N)<N, $$ such that there always exists an integer $k$ satisfying $$ 0 < k \le f(\max\{p,d\}), \quad q = pk + d \text{ is prime}. $$
Special cases
Case $d<p$: This reduces to the existence of the smallest prime in the residue class $d \pmod p$. This is related to Linnik’s theorem on the least prime in an arithmetic progression.
Case $d>p$: Then the conjecture asserts that a prime appears in the interval $$ (d,\, d+p\cdot f(\max\{p,d\})). $$
Case $p=1$: This is equivalent to Cramér’s prediction, i.e. that there is a prime in the interval $$ (d,\, d+f(d)). $$
Heuristic
A reasonable growth for $f$ is expected to be $$ f(N) \sim 5.7 (\log N)^2, $$ which is consistent with Cramér’s conjecture on prime gaps.
Motivation
This conjecture can be viewed as a “meta-conjecture” that generalizes both:
- the distribution of primes in arithmetic progressions (Linnik-type problems), and
- the distribution of primes in short intervals (Cramér-type problems).
It suggests a unified framework for understanding prime distribution both along progressions and within bounded gaps.
Question
- Has this conjecture (or similar formulations) appeared in the literature?
- Are there known partial results that could support or contradict it?
Any references or insights would be greatly appreciated. link:https://doi.org/10.5281/zenodo.17327717