53
Introduction Ratios Conjecture Main Results Proofs Conclusions Appendix Refs A Symplectic Test of the L-Functions Ratios Conjecture Steven J Miller Brown University [email protected] [email protected] http://www.math.brown.edu/sjmiller Cornell University, June 5 th , 2008 1

New A Symplectic Test of the L-Functions Ratios Conjecture · 2008. 5. 13. · Introduction Ratios Conjecture Main Results Proofs Conclusions Appendix Refs Identifying the Symmetry

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Page 1: New A Symplectic Test of the L-Functions Ratios Conjecture · 2008. 5. 13. · Introduction Ratios Conjecture Main Results Proofs Conclusions Appendix Refs Identifying the Symmetry

Introduction Ratios Conjecture Main Results Proofs Conclusions Appendix Refs

A Symplectic Test of the L-FunctionsRatios Conjecture

Steven J MillerBrown University

[email protected]@aya.yale.edu

http://www.math.brown.edu/∼sjmiller

Cornell University, June 5th, 2008

1

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Introduction Ratios Conjecture Main Results Proofs Conclusions Appendix Refs

L-functions

Riemann zeta function:

ζ(s) =

∞∑

n=1

1ns =

p

(1 − 1

ps

)−1

.

Dirichlet L-functions:

L(s, χd) =

∞∑

n=1

χd(n)

ns =∏

p

(1 − χd(p)

ps

)−1

.

Elliptic curve L-functions: build up with data related tonumber of solutions modulo p.

2

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Introduction Ratios Conjecture Main Results Proofs Conclusions Appendix Refs

Properties of zeros of L-functions

infinitude of primes, primes in arithmetic progression.

Chebyshev’s bias: π3,4(x) ≥ π1,4(x) ‘most’ of the time.

Birch and Swinnerton-Dyer conjecture.

Goldfeld, Gross-Zagier: bound for h(D) fromL-functions with many central point zeros.

Even better estimates for h(D) if a positivepercentage of zeros of ζ(s) are at most 1/2 − ε of theaverage spacing to the next zero.

3

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Introduction Ratios Conjecture Main Results Proofs Conclusions Appendix Refs

Distribution of zeros

ζ(s) 6= 0 for Re(s) = 1: π(x), πa,q(x).

GRH: error terms.

GSH: Chebyshev’s bias.

Analytic rank, adjacent spacings: h(D).

4

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Introduction Ratios Conjecture Main Results Proofs Conclusions Appendix Refs

Measures of Spacings: n-Level Correlations2 NICHOLAS M. KATZ AND PETER SARNAK

Figure 1. Nearest neighbor spacings among 70 million zeroes be-yond the 1020-th zero of zeta, verses µ1(GUE).

RH (needless to say, in the numerical experiments reported on below all zeroesfound were on the line Re(s) = 1

2 ) and order the ordinates γ:

. . . . . . γ−1 ≤ 0 ≤ γ1 ≤ γ2 . . . .(4)

Then γj = −γ−j, j = 1, 2, . . . , and in fact γ1 is rather large, being equal to14.1347 . . . . It is known (apparently already to Riemann) that

#{j : 0 ≤ γj ≤ T } ∼ T log T

2π, as T → ∞.(5)

In particular, the mean spacing between the γ′js tends to zero as j → ∞. In order

to examine the (statistical) law of the local spacings between these numbers were-normalize (or “unfold” as it is sometimes called) as follows:Set

γj =γj log γj

2πfor j ≥ 1.(6)

The consecutive spacings δj are defined to be

δj = γj+1 − γj , j = 1, 2, . . . .(7)

More generally, the k − th consecutive spacings are

δ(k)j = γj+k − γj , j = 1, 2, . . . .(8)

What laws (i.e. distributions), if any, do these numbers obey?During the years 1980-present, Odlyzko [OD] has made an extensive and pro-

found numerical study of the zeroes and in particular their local spacings. Hefinds that they obey the laws for the (scaled) spacings between the eigenvalues of

n-level correlation: {αj} an increasing sequence ofnumbers, B ⊂ Rn−1 a compact box:

limN→∞

#

{(αj1 − αj2, . . . , αjn−1 − αjn

)∈ B, ji 6= jk ≤ N

}

N

Odlyzko: Normalized spacings of ζ(s) starting at 1020

Montgomery, Hejhal: Pair, triple correlations of ζ(s)Rudnick-Sarnak: n-level correlations for allautomorphic cupsidal L-fnsKatz-Sarnak: n-level correlations for the classicalcompact groupsinsensitive to any finite set of zeros

5

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Introduction Ratios Conjecture Main Results Proofs Conclusions Appendix Refs

Measures of Spacings: n-Level Density and Families

Let gi be even Schwartz functions whose FourierTransform is compactly supported, L(s, f ) an L-functionwith zeros 1

2 + iγf and conductor Qf :

Dn,f (g) =∑

j1,...,jnji 6=±jk

g1

(γf ,j1

log Qf

)· · ·gn

(γf ,jn

log Qf

)

Properties of n-level density:� Individual zeros contribute in limit� Most of contribution is from low zeros� Average over similar L-functions (family)To any geometric family, Katz-Sarnak predict then-level density depends only on a symmetry group (aclassical compact group) attached to the family.

6

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Introduction Ratios Conjecture Main Results Proofs Conclusions Appendix Refs

n-Level Density

n-level density: F = ∪FN a family of L-functions orderedby conductors, gk an even Schwartz function:

Dn,F(g) = limN→∞

1|FN|

f∈FN

j1,...,jnji 6=±jk

g1

(log Qf

2πγj1;f

)· · ·gn

(log Qf

2πγjn;f

)

As N → ∞, 1-level density converges to∫

g(x)W1,G(F)(x)dx =

∫g(u)W1,G(F)(u)du.

Conjecture (Katz-Sarnak)(In the limit) Distribution of zeros near central point agreeswith distribution of eigenvalues near 1 of a classicalcompact group.

7

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Introduction Ratios Conjecture Main Results Proofs Conclusions Appendix Refs

1-Level Densities

Let G be one of the classical compact groups: Unitary,Symplectic, Orthogonal (or SO(even), SO(odd)).If supp(g) ⊂ (−1, 1), 1-level density of G is

g(0) − cGg(0)

2,

where

cG =

0 G is Unitary1 G is Symplectic

−1 G is Orthogonal.

8

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Introduction Ratios Conjecture Main Results Proofs Conclusions Appendix Refs

Some Results

Orthogonal:� Iwaniec-Luo-Sarnak: 1-level density for H±

k (N), Nsquare-free.� Miller, Young: families of elliptic curves.� Güloglu: 1-level for {Symr f : f ∈ Hk(1)}, r odd.Symplectic:� Rubinstein: n-level densities for L(s, χd).� Güloglu: 1-level for {Symr f : f ∈ Hk(1)}, r even.Unitary:� Hughes-Rudnick, Miller: families of primitiveDirichlet characters.

9

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Introduction Ratios Conjecture Main Results Proofs Conclusions Appendix Refs

Identifying the Symmetry Groups

Often an analysis of the monodromy group in thefunction field case suggests the answer.All simple families studied to date are built from GL1or GL2 L-functions.Tools: Explicit Formula, Orthogonality of Characters /Petersson Formula.How to identify symmetry group in general? Onepossibility is by the signs of the functional equation:Folklore Conjecture: If all signs are even and nocorresponding family with odd signs, Symplecticsymmetry; otherwise SO(even). (False!)

10

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Introduction Ratios Conjecture Main Results Proofs Conclusions Appendix Refs

Explicit Formula

π: cuspidal automorphic representation on GLn.Qπ > 0: analytic conductor of L(s, π) =

∑λπ(n)/ns.

By GRH the non-trivial zeros are 12 + iγπ,j.

Satake parameters {απ,i(p)}ni=1;

λπ(pν) =∑n

i=1 απ,i(p)ν.

L(s, π) =∑

nλπ(n)

ns =∏

p

∏ni=1 (1 − απ,i(p)p−s)

−1.

j

g(

γπ,jlog Qπ

)= g(0)−2

p,ν

g(

ν log plog Qπ

)λπ(pν) log ppν/2 log Qπ

11

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Introduction Ratios Conjecture Main Results Proofs Conclusions Appendix Refs

Some Results: Rankin-Selberg Convolution of Families

Symmetry constant: cL = 0 (resp, 1 or -1) if family L hasunitary (resp, symplectic or orthogonal) symmetry.

Rankin-Selberg convolution: Satake parameters forπ1,p × π2,p are

{απ1×π2(k)}nmk=1 = {απ1(i) · απ2(j)} 1≤i≤n

1≤j≤m.

Theorem (Dueñez-Miller)If F and G are nice families of L-functions, thencF×G = cF · cG.

12

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Introduction Ratios Conjecture Main Results Proofs Conclusions Appendix Refs

Ratios Conjecture

13

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Introduction Ratios Conjecture Main Results Proofs Conclusions Appendix Refs

History

Farmer (1993): Considered∫ T

0

ζ(s + α)ζ(1 − s + β)

ζ(s + γ)ζ(1 − s + δ)dt ,

conjectured (for appropriate values)

T(α + δ)(β + γ)

(α + β)(γ + δ)− T 1−α−β (δ − β)(γ − α)

(α + β)(γ + δ).

Conrey-Farmer-Zirnbauer (2007): conjectureformulas for averages of products of L-functions overfamilies:

RF =∑

f∈F

ωfL(

12 + α, f

)

L(1

2 + γ, f) .

14

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Introduction Ratios Conjecture Main Results Proofs Conclusions Appendix Refs

Uses of the Ratios Conjecture

Applications:� n-level correlations and densities;� mollifiers;� moments;� vanishing at the central point;

Advantages:� RMT models often add arithmetic ad hoc;� predicts lower order terms, often to square-rootlevel.

15

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Introduction Ratios Conjecture Main Results Proofs Conclusions Appendix Refs

Inputs for 1-level density

Approximate Functional Equation:

L(s, f ) =∑

m≤x

am

ms + εXL(s)∑

n≤y

an

n1−s ;

� ε sign of the functional equation,� XL(s) ratio of Γ-factors from functional equation.

Explicit Formula: g Schwartz test function,

f∈F

ωf

γ

g(

γlog Nf

)=

12πi

(c)

−∫

(1−c)

R′F(· · · )g (· · · )

� R′F(r) = ∂

∂αRF (α, γ)

∣∣∣α=γ=r

.

16

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Introduction Ratios Conjecture Main Results Proofs Conclusions Appendix Refs

Procedure

Use approximate functional equation to expandnumerator.Expand denominator by generalized Mobius function:cusp form

1L(s, f )

=∑

h

µf (h)

hs ,

where µf (h) is the multiplicative function equaling 1for h = 1, −λf (p) if n = p, χ0(p) if h = p2 and 0otherwise.Execute the sum over F , keeping only main(diagonal) terms.Extend the m and n sums to infinity (complete theproducts).Differentiate with respect to the parameters.

17

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Introduction Ratios Conjecture Main Results Proofs Conclusions Appendix Refs

Main Results

18

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Introduction Ratios Conjecture Main Results Proofs Conclusions Appendix Refs

Symplectic Families

Fundamental discriminants: d square-free and 1modulo 4, or d/4 square-free and 2 or 3 modulo 4.Associated character χd :� χd(−1) = 1 say d even;� χd(−1) = −1 say d odd.� even (resp., odd) if d > 0 (resp., d < 0).

Will study following families:� even fundamental discriminants at most X ;� {8d : 0 < d ≤ X , d an odd, positive square-freefundamental discriminant}.

19

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Introduction Ratios Conjecture Main Results Proofs Conclusions Appendix Refs

Prediction from Ratios Conjecture

1

X∗

d≤X

γd

g(

γdlog X

)=

1

X∗ log X

∫∞

−∞g(τ)

d≤X

[log

d

π+

1

2

Γ′

Γ

(1

iπτ

log X

)]dτ

+2

X∗ log X

d≤X

∫∞

−∞g(τ)

[ζ′

ζ

(1 +

4πiτ

log X

)+ A′

D

(2πiτ

log X;

2πiτ

log X

)

− e−2πiτ log(d/π)/ log XΓ(

14 − πiτ

log X

)

Γ(

14 + πiτ

log X

) ζ

(1 −

4πiτ

log X

)AD

(−

2πiτ

log X;

2πiτ

log X

)]dτ + O(X− 1

2 +ε),

with

AD(−r , r) =∏

p

(1 − 1

(p + 1)p1−2r −1

p + 1

)·(

1 − 1p

)−1

A′D(r ; r) =

p

log p(p + 1)(p1+2r − 1)

.

20

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Introduction Ratios Conjecture Main Results Proofs Conclusions Appendix Refs

Prediction from Ratios Conjecture

Main term is

1X ∗

d≤X

γd

g(

γdlog X

)=

∫ ∞

−∞

g(x)

(1 − sin(2πx)

2πx

)dx

+ O(

1log X

),

which is the 1-level density for the scaling limit ofUSp(2N). If supp(g) ⊂ (−1, 1), then the integral of g(x)against − sin(2πx)/2πx is −g(0)/2.

21

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Introduction Ratios Conjecture Main Results Proofs Conclusions Appendix Refs

Prediction from Ratios Conjecture

Assuming RH for ζ(s), for supp(g) ⊂ (−σ, σ) ⊂ (−1, 1):

−2

X∗ log X

d≤X

∫∞

−∞g(τ) e

−2πiτ log(d/π)log X

Γ(

14 − πiτ

log X

)

Γ(

14 + πiτ

log X

) ζ

(1 −

4πiτ

log X

)AD

(−

2πiτ

log X;

2πiτ

log X

)dτ

= −g(0)

2+ O(X− 3

4 (1−σ)+ε);

the error term may be absorbed into the O(X−1/2+ε) errorif σ < 1/3.

22

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Introduction Ratios Conjecture Main Results Proofs Conclusions Appendix Refs

Main Results

Theorem (M– ’07)

Let supp(g) ⊂ (−σ, σ), assume RH for ζ(s). 1-LevelDensity agrees with prediction from Ratios Conjecture

up to O(X−(1−σ)/2+ε) for the family of quadraticDirichlet characters with even fundamentaldiscriminants at most X;up to O(X−1/2 + X−(1− 3

2 σ)+ε + X− 34 (1−σ)+ε) for our

sub-family. If σ < 1/3 then agrees up to O(X−1/2+ε).

23

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Introduction Ratios Conjecture Main Results Proofs Conclusions Appendix Refs

Numerics (J. Stopple): 1,003,083 negative fundamentaldiscriminants −d ∈ [1012, 1012 + 3.3 · 106]

Histogram of normalized zeros (γ ≤ 1, about 4 million).� Red: main term. � Blue: includes O(1/ log X ) terms.

� Green: all lower order terms.24

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Introduction Ratios Conjecture Main Results Proofs Conclusions Appendix Refs

Sketch of Proofs

25

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Introduction Ratios Conjecture Main Results Proofs Conclusions Appendix Refs

Ratios Calculation

Hardest piece to analyze is

R(g; X ) = − 2X ∗ log X

d≤X

∫ ∞

−∞

g(τ)e−2πiτ log(d/π)log X

Γ(

14 − πiτ

log X

)

Γ(

14 + πiτ

log X

)

· ζ

(1 − 4πiτ

log X

)AD

(− 2πiτ

log X;

2πiτlog X

)dτ,

AD(−r , r) =∏

p

(1 − 1

(p + 1)p1−2r −1

p + 1

)·(

1 − 1p

)−1

.

Proof: shift contours, keep track of poles of ratios of Γ andzeta functions.

26

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Introduction Ratios Conjecture Main Results Proofs Conclusions Appendix Refs

Ratios Calculation: Weaker result for supp(g) ⊂ (−1, 1).

d -sum is X ∗e−2πi(1− log πlog X )τ

(1 − 2πiτ

log X

)−1+ O(X 1/2);

decay of g restricts τ -sum to |τ | ≤ log X , Taylorexpand everything but g: small error term and

|τ |≤log Xg(τ)

N∑

n=−1

an

logn X(2πiτ)ne−2πi(1− log π

log X )τdτ

=N∑

n=−1

an

logn X

|τ |≤log X(2πiτ)ng(τ)e−2πi(1− log π

log X )τdτ ;

from decay of g can extend the τ -integral to R

(essential that N is fixed and finite!), for n ≥ 0 get theFourier transform of g(n) (the nth derivative of g) at1 − π

log X , vanishes if supp(g) ⊂ (−1, 1).27

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Introduction Ratios Conjecture Main Results Proofs Conclusions Appendix Refs

Number Theory Sums

Seven = − 2X ∗

d≤X

∞∑

`=1

p

χd(p)2 log pp` log X

g(

2log p`

log X

)

Sodd = − 2X ∗

d≤X

∞∑

`=0

p

χd(p) log pp(2`+1)/2 log X

g(

log p2`+1

log X

).

28

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Introduction Ratios Conjecture Main Results Proofs Conclusions Appendix Refs

Number Theory Sums

LemmaLet supp(g) ⊂ (−σ, σ) ⊂ (−1, 1). Then

Seven = −g(0)

2+

2log X

∫ ∞

−∞

g(τ)ζ ′

ζ

(1 +

4πiτlog X

)dτ

+2

log X

∫ ∞

−∞

g(τ)A′D

(2πiτlog X

;2πiτlog X

)+ O(X− 1

2+ε)

Sodd = O(X− 1−σ2 log6 X ).

If instead we consider the family of characters χ8d for odd,positive square-free d ∈ (0, X ) (d a fundamentaldiscriminant), then

Sodd = O(X−1/2+ε + X−(1− 32 σ)+ε).

29

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Introduction Ratios Conjecture Main Results Proofs Conclusions Appendix Refs

Analysis of Seven

χd(p)2 = 1 except when p|d . Replace χd(p)2 with 1, andsubtract off the contribution from when p|d :

Seven = −2∞∑

`=1

p

log pp` log X

g(

2log p`

log X

)

+2

X ∗

d≤X

∞∑

`=1

p|d

log pp` log X

g(

2log p`

log X

)

= Seven;1 + Seven;2.

Lemma (Perron’s Formula)

Seven;1 = −g(0)

2+

2log X

∫ ∞

−∞

g(τ)ζ ′

ζ

(1 +

4πiτlog X

)dτ.

30

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Introduction Ratios Conjecture Main Results Proofs Conclusions Appendix Refs

Analysis of Seven: Seven;2

This piece gives us∫

g(τ)A′D(− · · · , · · · ).

Main ideas:� Restrict to p ≤ X 1/2.� For p < X 1/2:

∑d≤X ,p|d 1 = X∗

p+1 + O(X 1/2).� Use Fourier Transform to expand g.

31

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Introduction Ratios Conjecture Main Results Proofs Conclusions Appendix Refs

Analysis of Sodd

Sodd = − 2X ∗

∞∑

`=0

p

log pp(2`+1)/2 log X

g(

log p2`+1

log X

)∑

d≤X

χd(p).

Jutila’s bound

1<n≤Nn non−square

∣∣∣∣∣∣∑

0<d≤Xd fund. disc.

χd(n)

∣∣∣∣∣∣

2

� NX log10 N.

Proof: Cauchy-Schwarz and Jutila: p2`+1 non-square:

∞∑

`=0

p(2`+1)/2≤Xσ

∣∣∣∣∣∑

d≤X

χd(p)

∣∣∣∣∣

2

1/2

� X1+σ

2 log5 X .

32

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Introduction Ratios Conjecture Main Results Proofs Conclusions Appendix Refs

Analysis of Sodd: Extending Support

More technical, replace Jutila’s bound by applyingPoisson Summation to character sums.

LemmaLet supp(g) ⊂ (−σ, σ) ⊂ (−1, 1). For family{8d : 0 < d ≤ X , d an odd, positive square-freefundamental discriminant}, Sodd = O(X− 1

2+ε + X−(1− 32 σ)+ε).

In particular, if σ < 1/3 then Sodd = O(X−1/2+ε).

33

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Introduction Ratios Conjecture Main Results Proofs Conclusions Appendix Refs

Conclusions

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Introduction Ratios Conjecture Main Results Proofs Conclusions Appendix Refs

Conclusions

Ratios Conjecture gives detailed predictions (up toX 1/2+ε).

Number Theory agrees with predictions for suitablyrestricted test functions.

Numerics quite good.

35

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Introduction Ratios Conjecture Main Results Proofs Conclusions Appendix Refs

Appendix

36

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Introduction Ratios Conjecture Main Results Proofs Conclusions Appendix Refs

RH and the Prime Number Theorem

From ζ(s) =∑

n−s =∏

p (1 − p−s)−1, logarithmic derivative is

−ζ ′(s)

ζ(s)=∑ Λ(n)

ns ,

where Λ(n) = log p if n = pk and is 0 otherwise.

Take Mellin transform, integrate and shift contour. Find∑

n≤x

Λ(n) = x −∑

ρ

ρ,

where ρ = 1/2 + iγ runs over non-trivial zeros of ζ(s).

Partial summation gives Prime Number Theorem (to first order, thereare x/ log x primes at most x) if Reρ < 1.

The smaller max Re(ρ) is, the better the error term in the PrimeNumber Theorem. The Riemann Hypothesis (RH) says Re(ρ) = 1/2.

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Primes in Arithmetic Progression

To study number primes p ≡ a mod q, use

L(s, χ) =∑ χ(n)

ns =∏

p

(1 − χ(p)

ps

)−1

.

Key sum: 1φ(q)

∑χ mod q χ(n) is 1 if n ≡ 1 mod q and 0 otherwise.

Similar arguments give

p≡a mod q

log pps = − 1

φ(q)

χ mod q

L′(s, χ)

L(s, χ)χ(a) + Good(s).

Note: To understand {p ≡ a mod q} need to understand all L(s, χ);see benefit of studying a family.

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GSH and Chebyshev’s Bias

π3,4(x) ≥ π1,4(x) and π2,3(x) ≥ π1,3(x) ‘most’ of the time. Useanalytic density:

Denan(S) = lim sup1

log T

S∩[2,T ]

dtt

.

Have π3,4(x) ≥ π1,4(x) with analytic density .9959 (first flip at 26861);π2,3(x) ≥ π1,3(x) with analytic density .9990 (first flip ≈ 6 · 1011).

Non-residues beat residues. Key ingredient Generalized SimplicityHypothesis (GSH): the zeros of L(s, χ) are linearly independent overQ.

Structure of zeros important: GSH used to show a flow on a torus isfull (becomes equidistributed).

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Introduction Ratios Conjecture Main Results Proofs Conclusions Appendix Refs

Class Number

Class number: measures failure of unique factorization (order of idealclass group).

Imaginary quadratic field Q(√

D), fundamental discriminant D < 0, Igroup of non-zero fractional ideals, P subgroup of principal ideals,H = I/P class group, h(D) = #H the class number. Dirichlet proved

L(1, χD) =2πh(D)

wD√

D,

where χD the quadratic character and wD = 2 if D < −4, 4 if D = −4and 6 if D = −3.

Theorem: h(D) = 1 ⇔ −D ∈ {3, 4, 7, 8, 11, 19, 43, 67, 163}.

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Class Number and Distribution of Zeros I

Expect√

|D|

log log |D| � h(D) �√|D| log log |D|. Siegel proved

h(D) > c(ε)|D|1/2−ε (but ineffective).

Goldfeld, Gross-Zagier: f primitive cusp form of weight k , level N,trivial central character, suppose m = ords=1/2L(s, f )L(s, χD) ≥ 3,g = m − 1 or m − 2 so that (−1)g = ω(f )ω(fχD ) (signs of fnal eqs).Then have effective bound

h(D) � (log |D|)g−1∏

p|D

(1 +

1p

)−3(1 +

λ(p)√

pp + 1

)−1

.

Good result from using an elliptic curve that vanishes to order 3 ats = 1/2, application of many zeros at central point.

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Class Number and Distribution of Zeros II

Assume a positive percent of zeros (or cT log T/(log |D|)A) of zeroswith γ ≤ T ) of ζ(s) are at most 1/2 − ε of the average spacing fromthe next zero ζ(s). Then h(D) �

√|D|/(log |D|)B , all constants

computable.

See actual spacings between zeros are tied to number theory (havepositive percent are less than half the average spacing if GUEConjecture holds for adjacent spacings).

Instead of 1/2 − ε, under RH have: .68 (Montgomery), .5179(Montgomery-Odlyzko), .5171 (Conrey-Ghosh-Gonek), .5169(Conrey-Iwaniec) (Montgomery says led to pair correlation conjectureby looking at gaps between zeros of ζ(s) and h(D)).

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