Bounds for the distribution of the Frobenius traces associated to a generic abelian variety
Pith reviewed 2026-05-24 12:02 UTC · model grok-4.3
The pith
Under GRH and surjective residual Galois representations, the number of primes p with fixed Frobenius trace t for a dimension-g abelian variety A over Q is at most x to a power strictly less than 1.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
Assuming surjectivity of the residual Galois representations for all sufficiently large ℓ and assuming GRH, one has π_A(x,0) ≪_A x^{1-1/(2g²+g+1)}/(log x)^{1-2/(2g²+g+1)} and π_A(x,t) ≪_A x^{1-1/(2g²+g+2)}/(log x)^{1-2/(2g²+g+2)} for t≠0; consequently the set of primes p with |a_{1,p}(A)| ≤ p^{1/(2g²+g+1)}/(log p)^{2/(2g²+g+1)+ε} has density zero. Under the additional hypotheses of Artin holomorphy and pair correlation the exponents improve to 1-1/(g+1) and 1-1/(g+2) respectively, yielding the stronger lower bound |a_{1,p}(A)| > p^{1/(g+2)-ε} for almost all p.
What carries the argument
The surjectivity assumption on the residual mod-ℓ Galois representations, which permits the application of effective forms of the Chebotarev density theorem inside the division fields of A to control the distribution of Frobenius traces.
If this is right
- For any fixed t the primes with a_{1,p}(A)=t form a zero-density set.
- The typical size of |a_{1,p}(A)| is at least p raised to a positive power that depends only on the dimension g.
- The same counting arguments apply verbatim to the higher traces a_{i,p}(A) once the corresponding Galois representations are known to be surjective.
Where Pith is reading between the lines
- The exponent 1/(2g²+g+1) is an artefact of the current effective Chebotarev error terms; any improvement in those error terms would immediately raise the lower bound on |a_{1,p}(A)|.
- The result supplies a uniform lower bound on the height of the image of the Frobenius conjugacy class inside the adelic Galois representation, which may be useful for studying the distribution of point counts on A mod p.
Load-bearing premise
That the mod-ℓ Galois representation attached to A is surjective for every sufficiently large prime ℓ.
What would settle it
An explicit abelian variety A of dimension g together with a positive-density set of primes p for which |a_{1,p}(A)| stays below p to the power 1/(2g²+g+1) times a slowly growing log factor, contradicting the GRH-derived bound.
read the original abstract
Let $A$ be an abelian variety defined over $\mathbb{Q}$ and of dimension $g$. Assume that, for each sufficiently large prime $\ell$, $A$ has a surjective residual modulo $\ell$ Galois representation. For $t\in \mathbb{Z}$ and $x>0$, denote by $\pi_A(x, t)$ the number of primes $p \leq x$ for which the Frobenius trace $a_{1, p}(A)$ associated to $A \pmod p$ equals $t$. Assuming the Generalized Riemann Hypothesis for Dedekind zeta functions (GRH), we obtain that $\pi_A(x, 0) \ll_A x^{1 - \frac{1}{2g^2+g+1}}/(\log x)^{1 - \frac{2}{2g^2+g+1}}$ and $\pi_A(x, t) \ll_A x^{1 - \frac{1}{2g^2+g+2}}/(\log x)^{1 - \frac{2}{2g^2+g+2}}$ if $t \neq 0$, and deduce that almost all primes $p$ satisfy $|a_{1, p}(A)| > p^{\frac{1}{2 g^2 + g + 1}}/ (\log p)^{\frac{2}{2g^2+g+1}+\varepsilon}$ for any $\varepsilon>0$. Assuming, in addition to GRH, Artin's Holomorphy Conjecture and a Pair Correlation Conjecture for Artin L-functions, we obtain that $\pi_A(x, 0) \ll_A x^{1 - \frac{1}{g+1}}/(\log x)^{1 - \frac{4}{g+1}}$ and $\pi_A(x, t) \ll_A x^{1 - \frac{1}{g+2}}/(\log x)^{1 - \frac{4}{g+2}}$ if $t \neq 0$, and deduce that almost all primes $p$ satisfy $|a_{1, p}(A)|> p^{\frac{1}{g + 2} - \varepsilon }$ for any $\varepsilon>0$.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper assumes surjectivity of the residual Galois representation modulo ℓ for large ℓ for an abelian variety A/Q of dimension g. Under GRH it proves π_A(x,0) ≪_A x^{1-1/(2g²+g+1)}/(log x)^{1-2/(2g²+g+1)} and π_A(x,t) ≪_A x^{1-1/(2g²+g+2)}/(log x)^{1-2/(2g²+g+2)} (t≠0), and deduces that almost all p satisfy |a_{1,p}(A)| > p^{1/(2g²+g+1)}/(log p)^{2/(2g²+g+1)+ε}. Under GRH plus Artin's holomorphy conjecture and a pair-correlation conjecture it obtains the stronger bounds π_A(x,0) ≪_A x^{1-1/(g+1)}/(log x)^{1-4/(g+1)} and π_A(x,t) ≪_A x^{1-1/(g+2)}/(log x)^{1-4/(g+2)}, yielding |a_{1,p}(A)| > p^{1/(g+2)-ε} for almost all p.
Significance. Conditional bounds of this type on the distribution of Frobenius traces a_{1,p}(A) away from small values would refine our understanding of the Lang-Trotter conjecture and the typical size of traces for generic abelian varieties. The derivations rely on standard applications of GRH (and stronger conjectures) to Artin L-functions attached to the Galois representations, which is a natural extension of existing techniques.
major comments (2)
- [Abstract] Abstract (GRH deduction paragraph): the claimed consequence that almost all primes satisfy |a_{1,p}(A)| > p^{1/D}/(log p)^{2/D + ε} with D = 2g² + g + 1 does not follow from the stated bounds. Summing the t ≠ 0 bound over |t| ≤ x^{1/D} produces an upper bound ≫ x^{1 + 1/(D(D+1))} (ignoring logs), which exceeds x and therefore supplies no information on the exceptional set. This is load-bearing for the 'almost all' statement under GRH alone.
- [Abstract] Abstract (Artin+pair-correlation deduction): the manuscript should explicitly confirm that inserting the -ε in the exponent 1/(g+2)-ε makes the corresponding sum over |t| ≤ x^{1/(g+2)-ε} o(x), as the text only notes that the stronger conjectures 'avoid the issue via an explicit -ε'.
minor comments (1)
- The surjectivity assumption on the residual representations is stated only in the first sentence of the abstract; a precise formulation (including the precise meaning of 'sufficiently large') should appear in the introduction or §1.
Simulated Author's Rebuttal
We thank the referee for the careful reading and for identifying these issues in the abstract. We respond to each major comment below.
read point-by-point responses
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Referee: [Abstract] Abstract (GRH deduction paragraph): the claimed consequence that almost all primes satisfy |a_{1,p}(A)| > p^{1/D}/(log p)^{2/D + ε} with D = 2g² + g + 1 does not follow from the stated bounds. Summing the t ≠ 0 bound over |t| ≤ x^{1/D} produces an upper bound ≫ x^{1 + 1/(D(D+1))} (ignoring logs), which exceeds x and therefore supplies no information on the exceptional set. This is load-bearing for the 'almost all' statement under GRH alone.
Authors: We agree with the referee's calculation. Summing the stated bound for π_A(x,t) (t≠0) over O(x^{1/D}) values of t indeed produces a quantity ≫ x^{1 + 1/(D(D+1))}, which is larger than x and therefore does not control the size of the exceptional set. This is an error in the manuscript. We will revise the abstract to remove the 'almost all' claim under GRH alone. revision: yes
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Referee: [Abstract] Abstract (Artin+pair-correlation deduction): the manuscript should explicitly confirm that inserting the -ε in the exponent 1/(g+2)-ε makes the corresponding sum over |t| ≤ x^{1/(g+2)-ε} o(x), as the text only notes that the stronger conjectures 'avoid the issue via an explicit -ε'.
Authors: We agree that an explicit verification is desirable. Let θ = 1/(g+2) − ε. The number of admissible t is O(x^θ). The bound π_A(x,t) ≪_A x^{1−1/(g+2)} (log x)^{−(1−4/(g+2))} then yields a total of O(x^θ ⋅ x^{1−1/(g+2)}) = O(x^{1−ε}), which is o(x). We will insert this short calculation into the revised text. revision: yes
Circularity Check
No significant circularity; bounds derived from external conjectures via standard methods
full rationale
The paper assumes surjectivity of residual Galois representations for large ℓ and derives explicit upper bounds for π_A(x,0) and π_A(x,t) under GRH (and under the additional Artin holomorphy + pair correlation conjectures) by applying standard analytic estimates to the associated Dedekind zeta or Artin L-functions. The exponents 1/(2g²+g+1) etc. arise directly from the zero-free regions or density theorems supplied by those external hypotheses, not from any redefinition or fitting of the target quantities inside the paper. The subsequent claim that almost all primes satisfy a lower bound on |a_{1,p}(A)| is presented as a consequence of summing the π_A bounds; while the skeptic correctly notes that the summation argument as written does not close, this is a potential gap in the deduction step rather than a circular reduction of the claimed result to its own inputs. No self-definitional, fitted-input, or load-bearing self-citation patterns appear in the derivation chain.
Axiom & Free-Parameter Ledger
axioms (3)
- domain assumption Generalized Riemann Hypothesis for Dedekind zeta functions
- domain assumption Surjective residual Galois representation modulo ℓ for all sufficiently large ℓ
- domain assumption Artin's Holomorphy Conjecture and Pair Correlation Conjecture for Artin L-functions
Lean theorems connected to this paper
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IndisputableMonolith/Foundation/AlexanderDuality.leanalexander_duality_circle_linking (D=3 forcing) unclear?
unclearRelation between the paper passage and the cited Recognition theorem.
Theorem 1 … π_A(x,0) ≪_A x^{1−1/(2g²+g+1)}/(log x)^{1−2/(2g²+g+1)} … under GRH for Dedekind zeta functions and surjectivity of residual Galois representations ρ_{A,ℓ} ≃ GSp_{2g}(F_ℓ)
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IndisputableMonolith/Foundation/ArithmeticFromLogic.leanLogicNat ≃ Nat recovery; J-uniqueness via Aczél unclear?
unclearRelation between the paper passage and the cited Recognition theorem.
The proofs … rely on the effective Chebotarev theorems of Lagarias–Odlyzko, Murty–Murty–Saradha, Murty–Murty–Wong applied to the extensions Q(A[ℓ])/Q and their subfields fixed by B_{2g}(F_ℓ), U_{2g}(F_ℓ)
What do these tags mean?
- matches
- The paper's claim is directly supported by a theorem in the formal canon.
- supports
- The theorem supports part of the paper's argument, but the paper may add assumptions or extra steps.
- extends
- The paper goes beyond the formal theorem; the theorem is a base layer rather than the whole result.
- uses
- The paper appears to rely on the theorem as machinery.
- contradicts
- The paper's claim conflicts with a theorem or certificate in the canon.
- unclear
- Pith found a possible connection, but the passage is too broad, indirect, or ambiguous to say the theorem truly supports the claim.
Reference graph
Works this paper leans on
-
[1]
A. Akbari and J. Park, On the Lang-Trotter for two elliptic curves, Ramanujan Journal 49, 2019, pp. 585--623
work page 2019
-
[2]
Aluffi, Algebra: Chapter 0, Graduate Studies in Mathematics Vol
P. Aluffi, Algebra: Chapter 0, Graduate Studies in Mathematics Vol. 104, American Mathematical Society, 2009
work page 2009
-
[3]
Artin, Beweis des allgemeinen Reziprozit\" a tsgesetzes, Hamb
E. Artin, Beweis des allgemeinen Reziprozit\" a tsgesetzes, Hamb. Abh. 5, 1927, pp. 353--363
work page 1927
-
[4]
P. Bayer and J. Gonz\' a lez, On the Hasse-Witt invariants of modular curves, Experimental Mathematics 6, 1997, No. 1, pp. 57--76
work page 1997
-
[5]
Bella\" i che, Th\' e or\` e me de Chebotarev et complexit\' e de Littlewood, Ann
J. Bella\" i che, Th\' e or\` e me de Chebotarev et complexit\' e de Littlewood, Ann. Sci. \' E c. Norm. Sup\' e r. (4) 49, No. 3, 2016, pp. 579--632
work page 2016
- [6]
- [7]
-
[8]
N. Chavdarov, The generic irreducibility of the numerator of the zeta function in a family of curves with large monodromy, Duke Mathematical Journal 87, No. 1, 1997, pp. 151--180
work page 1997
- [9]
-
[10]
A.C. Cojocaru, R. Davis, A. Silverberg, and K.E. Stange, Arithmetic properties of the Frobenius traces defined by a rational abelian variety (with two appendices by J-P. Serre), International Mathematics Research Notices 12, 2017, pp. 3557--3602
work page 2017
-
[11]
A.C. Cojocaru and T. Wang, Bounds for the distribution of the Frobenius traces associated to products of non-CM elliptic curves, Canadian Journal of Mathematics 2022, pp. 1--26, available at http://dx.doi.org/10.4153/S0008414X22000086
-
[12]
G. Cornell and J.H. Silverman (editors), Arithemtic Geometry, Springer-Verlag New York, 1986
work page 1986
-
[13]
Elkies, Distribution of supersingular primes, Ast\' e risque No
N. Elkies, Distribution of supersingular primes, Ast\' e risque No. 198-200, 1991, pp. 127--132
work page 1991
- [14]
- [15]
-
[16]
J. Fulman and R. Guralnick, Bounds on the number and sizes of conjugacy classes in finite Chevalley groups with applications to derangements, Trans. Amer. Math. Soc. 364, No. 6, 2012, pp. 3023--3070
work page 2012
-
[17]
Gallagher, The number of conjugacy classes in a finite group, Math
P.X. Gallagher, The number of conjugacy classes in a finite group, Math. Z. 118, 1970, pp. 175--179
work page 1970
-
[18]
C. Hall, An open image theorem for a general class of abelian varieties, Bulletin of the London Mathematical Society 43, No. 4, 2011, pp. 703--711
work page 2011
-
[19]
K. Hensel, \" U ber die Entwicklung der algebraischen Zahlen in Potenzreihen, Mathematische Annalen 55, 1902, pp. 301--336
work page 1902
-
[20]
T. Honda, Isogeny classes of abelian varieties over finite fields, Journal of the Mathematical Society of Japan 20, 1968, pp. 83--95
work page 1968
-
[21]
J.E. Humphreys, Linear algebraic groups, Graduate Texts in Mathematics 21, Springer-Verlag, New York - Heidelberg, 1975
work page 1975
-
[22]
Katz, Lang-Trotter revisited, Bulletin of the American Mathematical Society 46, No
N.M. Katz, Lang-Trotter revisited, Bulletin of the American Mathematical Society 46, No. 3, 2009, pp. 413--457
work page 2009
-
[23]
N.M. Katz and P. Sarnak, Random matrices, Frobenius eigenvalues, and monodromy, American Mathematical Society Colloquium Publications 45, Providence, RI, 1999
work page 1999
-
[24]
On the Lang--Trotter conjecture for Siegel modular forms
A. Kumar, M. Kumari, and A. Weiss, On the Lang-Trotter conjecture for Siegel modular forms, preprint available at https://arxiv.org/abs/2201.09278
work page internal anchor Pith review Pith/arXiv arXiv
-
[25]
J. Lagarias and A. Odlyzko, Effective versions of the Chebotarev density theorem, in: A. Fr\" o hlich (Ed.), Algebraic Number Fields, Academic Press, New York, 1977, pp. 409--464
work page 1977
-
[26]
Lang, Abelian varieties, Springer - Verlag, New York - Berlin, 1983
S. Lang, Abelian varieties, Springer - Verlag, New York - Berlin, 1983
work page 1983
-
[27]
S. Lang, Algebraic number theory, 2nd edition, Graduate Texts in Mathematics 110, Springer - Verlag, New York - Berlin - Heidelberg, 1994
work page 1994
-
[28]
S. Lang and H. Trotter, Frobenius distributions in _2 -extensions, Lecture Notes in Mathematics 504, Springer Verlag, Berlin - New York, 1976
work page 1976
-
[29]
Milne, Abelian varieties, in Arithmetic geometry, by G
J.S. Milne, Abelian varieties, in Arithmetic geometry, by G. Cornell and J.H. Silverman (editors), Springer-Verlag New York, 1986, pp. 103--150
work page 1986
-
[30]
Mumford, Abelian varieties, Oxford University Press, 1970
D. Mumford, Abelian varieties, Oxford University Press, 1970
work page 1970
-
[31]
V.K. Murty, Explicit formulae for the Lang-Trotter conjecture, Rocky Mountain Journal of Mathematics 15, No. 2, 1985, pp. 535--551
work page 1985
-
[32]
M.R. Murty and V.K. Murty, Prime divisors of Fourier coefficients of modular forms, Duke Mathematical Journal 51, No. 1, 1984, pp. 57--76
work page 1984
-
[33]
M.R. Murty, V.K. Murty, and N. Saradha, Modular forms and the Chebotarev density theorem, Amer. J. Math. 110, No. 2, 1988, pp. 253--281
work page 1988
-
[34]
M.R. Murty, V.K. Murty, and P-J. Wong, The Chebotarev density theorem and the pair correlation conjecture, J. Ramanujan Math. Soc. 33, No. 4, 2018, pp. 399--426
work page 2018
-
[35]
V.K. Murty, Modular forms and the Chebotarev density theorem II, Analytic number theory (Kyoto, 1996), London Math. Soc. Lecture Notes Series 247, Cambridge University Press, 1997, pp. 287--308
work page 1996
-
[36]
V.K. Murty, Frobenius distributions and Galois representations, Automorphic forms, automorphic representations, and arithmetic (Fort Worth, TX, 1996), Proc. Sympos. Pure Math. 66, Part 1, American Mathematical Society, Providence, 1999, pp. 193--211
work page 1996
-
[37]
J. Newton and J. Thorne, Symmetric power functoriality for holomorphic modular forms, II, Publ. Math. Inst. Hautes \' E tudes Sci. 134, 2021, pp. 117--152
work page 2021
-
[38]
O'Meara, Symplectic groups, Mathematical Surveys 16, American Mathematical Society, Providence, 1978
O.T. O'Meara, Symplectic groups, Mathematical Surveys 16, American Mathematical Society, Providence, 1978
work page 1978
-
[39]
Oort, Abelian varieties over finite fields
F. Oort, Abelian varieties over finite fields. Higher-dimensional geometry over finite fields, NATO Sci. Peace Scur. Ser. D Inf. Commun. Secur., 16, IOS, Amsterdam, 2008, pp. 123--188
work page 2008
-
[40]
J. Rouse and J. Thorner, The explicit Sato-Tate conjecture and densities pertaining to Lehmer-type questions, Trans. Amer. Math. Soc. 369, No 5, 2017, pp. 3575--3604
work page 2017
-
[41]
Serre, Abelian -adic representations and elliptic curves, New York - Amsterdam, 1968
J-P. Serre, Abelian -adic representations and elliptic curves, New York - Amsterdam, 1968
work page 1968
-
[42]
J-P. Serre, Propri\' e t\' e s galoisiennes des points d'ordre fini des courbes elliptiques, Inventiones Math. 15, No. 4, 1972, pp. 259--331
work page 1972
-
[43]
Serre, Divisibilit\' e de certaines fonctions arithm\' e tiques, L'Ens
J-P. Serre, Divisibilit\' e de certaines fonctions arithm\' e tiques, L'Ens. Math. 22, 1976, pp. 227--260
work page 1976
-
[44]
Serre, Quelques applications du th\'eor\`eme de densit\'e de Chebotarev, Publ
J-P. Serre, Quelques applications du th\'eor\`eme de densit\'e de Chebotarev, Publ. Math. I. H. E. S., No. 54, 1981, pp. 123--201
work page 1981
-
[45]
Serre, R\' e sum\' e des cours de 1985-1986, in Oeuvres
J-P. Serre, R\' e sum\' e des cours de 1985-1986, in Oeuvres. Collected Papers, Vol. IV, 1985-1998, 2nd edition, Springer Verlag, Heidelberg, 2003, pp. 33--37
work page 1985
-
[46]
Serre, Lettre \` a Marie-France Vign\' e ras du 10/2/1986, in Oeuvres
J-P. Serre, Lettre \` a Marie-France Vign\' e ras du 10/2/1986, in Oeuvres. Collected Papers, Vol. IV, 1985-1998, 2nd edition, Springer Verlag, Heidelberg, 2003, pp. 38--55
work page 1986
-
[47]
J-P. Serre, Propri\' e t\' e s conjecturales des groupes de Galois motiviques et des repr\' e sentations -adiques, in Motives (Seattle, WA, 1991), Proceedings Symposium Pure Mathematics 55, part I, Providence, RI, American Mathematical Society, 1994, pp. 377--400
work page 1991
-
[48]
J-P. Serre and J. Tate, Good reduction of abelian varieties, Annals of Mathematics 88, 1968, pp. 492--517; Oeuvres/Collected Papers OO, Springer Verlag, Berlin, 1985, pp. 472--497
work page 1968
-
[49]
Tate, Endomorphisms of abelian varieties over finite fields, Invent
J. Tate, Endomorphisms of abelian varieties over finite fields, Invent. Math. 2, 1966, pp. 134--144
work page 1966
-
[50]
Wall, On the conjugacy classes in the unitary, symplectic and orthogonal groups, J
G.E. Wall, On the conjugacy classes in the unitary, symplectic and orthogonal groups, J. Austral. Math. Soc. 3, 1963, pp. 1--62
work page 1963
-
[51]
Waterhouse, Abelian varieties over finite fields, Ann
W.C. Waterhouse, Abelian varieties over finite fields, Ann. Sc. Ec. Norm. Sup. 2, 1969, pp. 521--560
work page 1969
-
[52]
Y.G. Zarhin, Hyperelliptic Jacobians without complex multiplication, Mathematical Research Letters 7, No.1, 2000, pp. 123--132
work page 2000
- [53]
-
[54]
D. Zywina, Bounds for the Lang-Trotter Conjectures, in SCHOLAR -- a scientific celebration highlighting open lines of arithmetic research, Contemporary Mathematics 655, American Mathematical Society, Providence, 2015, pp. 235--256
work page 2015
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