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Vesselin Dimitrov
  • Member for 12 years, 3 months
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A refinement of Lehmer's conjecture?
Removed a short paragraph from "Added..." to avoid potential confusion as to what my question actually is.
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Are rationally connected varieties uniruled?
... And yes, rationally connected varieties are uniruled. This should be obvious: the standard definition of rational connectivity is that there is a dominant map from $T \times \mathbb{P}^1 \times \mathbb{P^1}$ induced diagonally from a morphism from $T \times \mathbb{P}^1$.
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Are rationally connected varieties uniruled?
PS: I realized I had misread your question. Certainly uniruled varieties need not be rationally connected: e.g., a ruled surface $C \times \mathbb{P}^1$, where $C$ is a curve of positive genus, is not rationally connected as it has non-zero holomorphic $1$-forms (coming from $C$).
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Are rationally connected varieties uniruled?
For surfaces, rational connectivity coincides with rationality. In general, it is even an open problem whether there are any rationality connected varieties which are not unirational. This is called an "embarrassing question" in notes by J. Kock on lectures by Joe Harris: mat.uab.es/~kock/RLN/rcv.pdf . For a recent confirmation that this is still an open problem, see Jason Starr's answer here: mathoverflow.net/questions/131086/… .
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A refinement of Lehmer's conjecture?
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A refinement of Lehmer's conjecture?
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Are there infinitely many integer-valued polynomials dominated by $1.9^n$ on all of $\mathbb{N}$?
Last edit: Gamma(t) had to be changed by n!, as I had neglected that Gamma(n) = (n-1)! rather than n!.
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Are there infinitely many integer-valued polynomials dominated by $1.9^n$ on all of $\mathbb{N}$?
In the follow-up question, "inf" had to be replaced with "sup." My apology for being careless here.
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