Koblitz's prime-order conjecture for CM elliptic curves

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Let E/QE/\mathbb{Q} be an elliptic curve with complex multiplication by the ring of integers OK\mathcal{O}_K of an imaginary quadratic field KK. For primes pp that split in KK and do not divide the conductor of EE, define

dE=gcd⁡{∣E(Fp)∣  |  p splits in K, p∤NE}.d_E=\gcd\left\{\lvert E(\mathbb{F}_p)\rvert\;\middle|\;p\text{ splits in }K,\ p\nmid N_E\right\}.

Koblitz's conjecture. There exists a constant C>0C>0 such that

#{p≤x | p splits in K, ∣E(Fp)∣dE is prime}∼Cx(log⁡x)2.\#\left\{p\leq x\,\middle|\,p\text{ splits in }K,\ \frac{\lvert E(\mathbb{F}_p)\rvert}{d_E}\text{ is prime}\right\}\sim C\frac{x}{(\log x)^2}.

This is a CM version of Koblitz's conjecture, with the fixed common divisor dEd_E removed from the elliptic-curve group orders. The source provides no resolution status for this assertion.

References

Primary source

Likun Xie, “Almost Prime Orders of Elliptic Curves Over Prime Power Fields”, arXiv:2504.18732 (2025).

Additional references

4 papers in this index state this conjecture (2007–2025). The statement above is taken from the most recent of them; the others are arXiv:2408.16641, arXiv:1609.01147, arXiv:0711.3484.

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