Number of solutions mod p and Betti numbersBetti numbers from virtual Betti numbers of a cell decompositionComparison between singular and etale cohomology in Batyrev's paper on Birational Calabi-Yau varietiesHodge numbers of reduction mod $p$Betti numbers of Proper nonprojective varietiesUpper bound on Betti numbers of an intersection of hypersurfaces (or quadrics)Why is there a Parity Problem in Sieve Theory and not a Mod p problem for any other p?Relatively concise English expositions of the proofs of the various Weil conjecturesBounds on Betti numbers of subvarieties?Weight of Weil numbers in the residue field of $overlinemathbbQ_l$Current status of independence of Betti numbers for different Weil cohomology theories

Number of solutions mod p and Betti numbers


Betti numbers from virtual Betti numbers of a cell decompositionComparison between singular and etale cohomology in Batyrev's paper on Birational Calabi-Yau varietiesHodge numbers of reduction mod $p$Betti numbers of Proper nonprojective varietiesUpper bound on Betti numbers of an intersection of hypersurfaces (or quadrics)Why is there a Parity Problem in Sieve Theory and not a Mod p problem for any other p?Relatively concise English expositions of the proofs of the various Weil conjecturesBounds on Betti numbers of subvarieties?Weight of Weil numbers in the residue field of $overlinemathbbQ_l$Current status of independence of Betti numbers for different Weil cohomology theories













6












$begingroup$


Suppose $X$ is proper flat scheme over Sepc$mathbbZ$. If $p$ is a large prime, then by Weil conjectures one can recover the Betti numbers of $X$ from the size of $X(mathbbF_p^n)$ for all $n$. My question is, what if instead of fix a prime and vary $n$, we fix an $n$ and vary $p$?



More precisely, let $N$ be a fixed number, suppose we know the size of $X(mathbbF_p^n)$ for all $n$ between 1 and $N$, and (almost) all prime $p$. Can we recover the Betti numbers of $X$?










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    6












    $begingroup$


    Suppose $X$ is proper flat scheme over Sepc$mathbbZ$. If $p$ is a large prime, then by Weil conjectures one can recover the Betti numbers of $X$ from the size of $X(mathbbF_p^n)$ for all $n$. My question is, what if instead of fix a prime and vary $n$, we fix an $n$ and vary $p$?



    More precisely, let $N$ be a fixed number, suppose we know the size of $X(mathbbF_p^n)$ for all $n$ between 1 and $N$, and (almost) all prime $p$. Can we recover the Betti numbers of $X$?










    share|cite|improve this question







    New contributor



    Heavensfall is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
    Check out our Code of Conduct.






    $endgroup$














      6












      6








      6


      2



      $begingroup$


      Suppose $X$ is proper flat scheme over Sepc$mathbbZ$. If $p$ is a large prime, then by Weil conjectures one can recover the Betti numbers of $X$ from the size of $X(mathbbF_p^n)$ for all $n$. My question is, what if instead of fix a prime and vary $n$, we fix an $n$ and vary $p$?



      More precisely, let $N$ be a fixed number, suppose we know the size of $X(mathbbF_p^n)$ for all $n$ between 1 and $N$, and (almost) all prime $p$. Can we recover the Betti numbers of $X$?










      share|cite|improve this question







      New contributor



      Heavensfall is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.






      $endgroup$




      Suppose $X$ is proper flat scheme over Sepc$mathbbZ$. If $p$ is a large prime, then by Weil conjectures one can recover the Betti numbers of $X$ from the size of $X(mathbbF_p^n)$ for all $n$. My question is, what if instead of fix a prime and vary $n$, we fix an $n$ and vary $p$?



      More precisely, let $N$ be a fixed number, suppose we know the size of $X(mathbbF_p^n)$ for all $n$ between 1 and $N$, and (almost) all prime $p$. Can we recover the Betti numbers of $X$?







      ag.algebraic-geometry nt.number-theory






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      asked 8 hours ago









      HeavensfallHeavensfall

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          $begingroup$

          For the first claim, I think you want to also assume $X$ is smooth (away from some finite set of primes, not including $p$).



          For the second claim, again with the assumption that $X$ is smooth, this would follow from a weak form of the generalized Sato-Tate conjecture. But nothing like this is known currently without very strong additional assumptions on $X$.



          See Nick Katz's article Simple Things We Don't Know which is about almost exactly this question.






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            1 Answer
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            active

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            6












            $begingroup$

            For the first claim, I think you want to also assume $X$ is smooth (away from some finite set of primes, not including $p$).



            For the second claim, again with the assumption that $X$ is smooth, this would follow from a weak form of the generalized Sato-Tate conjecture. But nothing like this is known currently without very strong additional assumptions on $X$.



            See Nick Katz's article Simple Things We Don't Know which is about almost exactly this question.






            share|cite|improve this answer









            $endgroup$

















              6












              $begingroup$

              For the first claim, I think you want to also assume $X$ is smooth (away from some finite set of primes, not including $p$).



              For the second claim, again with the assumption that $X$ is smooth, this would follow from a weak form of the generalized Sato-Tate conjecture. But nothing like this is known currently without very strong additional assumptions on $X$.



              See Nick Katz's article Simple Things We Don't Know which is about almost exactly this question.






              share|cite|improve this answer









              $endgroup$















                6












                6








                6





                $begingroup$

                For the first claim, I think you want to also assume $X$ is smooth (away from some finite set of primes, not including $p$).



                For the second claim, again with the assumption that $X$ is smooth, this would follow from a weak form of the generalized Sato-Tate conjecture. But nothing like this is known currently without very strong additional assumptions on $X$.



                See Nick Katz's article Simple Things We Don't Know which is about almost exactly this question.






                share|cite|improve this answer









                $endgroup$



                For the first claim, I think you want to also assume $X$ is smooth (away from some finite set of primes, not including $p$).



                For the second claim, again with the assumption that $X$ is smooth, this would follow from a weak form of the generalized Sato-Tate conjecture. But nothing like this is known currently without very strong additional assumptions on $X$.



                See Nick Katz's article Simple Things We Don't Know which is about almost exactly this question.







                share|cite|improve this answer












                share|cite|improve this answer



                share|cite|improve this answer










                answered 6 hours ago









                Will SawinWill Sawin

                70.3k7142291




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