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Complex analysis, holomorphic functions, automorphic group actions and forms, pseudoconvexity, complex geometry, analytic spaces, analytic sheaves.

20 votes

Heuristic argument for the Riemann Hypothesis

The function field model came up in GH from MO's answer, and then also in user54038's. I just want to add some detail to explain how good of an analogy the function field model is. The Riemann zeta …
Will Sawin's user avatar
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17 votes
Accepted

For which rationals is this exponential sum bounded?

As Fedor Petrov expects in the comments, this is true for $x=a/b$ if and only if the order of $2$ modulo $b$ is greater than the order of $2$ modulo the product of prime factors of $b$. To prove this, …
Will Sawin's user avatar
  • 148k
14 votes

Tate's definition of residues

Residues satisfy $$\operatorname{res}_x(fdg) + \operatorname{res}_x(gdf) = \operatorname{res}_x(d (fg)) =0$$ which tells you that they are antisymmetric, and many antisymmetric pairings in math arise …
Will Sawin's user avatar
  • 148k
14 votes
Accepted

Analytic continuation gives a covering space (and not just a local homeomorphism)

Consider the map $f\colon z \mapsto z^3-z$. Then there is a path component $M$ of $\mathcal G$ consisting of germs of the inverse map to $f$. More precisely $M$ is isomorphic to $\mathbb C \setminus \ …
Will Sawin's user avatar
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10 votes
Accepted

Status of Hodge conjecture over subrings of $\mathbb{C}$

The $k$-Hodge conjecture is false for any $k$ containing an irrational real $\alpha$. Indeed we may clearly assume $\alpha$ is negative. Consider the elliptic curve $E = \mathbb C / \langle 1, \sqrt{ …
9 votes
Accepted

Generating series of rational$\times \exp($rational$)$

We have $$ \frac{d}{dx}\left ( f(x) e^{h(x)}\right) = \left( \frac{ f'(x)}{f(x)} + h'(x) \right) \left( f(x) e^{h(x)}\right).$$ Thus $$ \sum_n a_n n x^{n-1} = \left( \frac{ f'(x)}{f(x)} + h'(x) \rig …
Will Sawin's user avatar
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7 votes
Accepted

On some analytic property of the Riemann zeta function

$$\int_x^\infty \{ u\} u^{-s-1} du = \int_x^\infty \left( \{ u\}-\frac{1}{2}\right) u^{-s-1} du + \frac{1}{2} \frac{x^{-s}}{s}$$ and by integration by parts, $$\int_x^\infty \left( \{ u\}-\frac{1}{2} …
Will Sawin's user avatar
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7 votes
Accepted

Dirichlet Series that fail to be L-functions

If $f(z)$ is a holomorphic function in a neighborhood of $z=0$ then $f( p^{-s})$ is a Dirichlet series for any prime (or really any natural number) $p$: we take $a_n=0$ if $n$ is not a power of $p$ an …
Will Sawin's user avatar
  • 148k
7 votes

Size of $\zeta'(s)$ at its zeros

Bounds for the value of zeta take the form $$ |\zeta(\sigma +it) | \ll t^{ f(\sigma)+\epsilon} $$ where $|t|>2$ and $f$ is some function of $\sigma$. We can take $f(1)=0$ and $f(0)=1/2$ and we can al …
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6 votes

Bounding minimal absolute value of a point on a complex algebraic variety

No (for one interpretation of the question). There does not exist a continuous function $b $ from the set of systems of polynomial equations to $\mathbb R^{>0} \cup \{\infty\}$ that takes a finite val …
Will Sawin's user avatar
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6 votes

Automorphic and modular forms for subgroups of modular group and fuchsian groups

If you know them as algebras over $M(SL_2(\mathbb Z))$, almost exactly the procedure you describe works. Since the modular forms with weight a multiple of $12$ are sections of powers of an ample line …
Will Sawin's user avatar
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5 votes

Analytic Chern classes

1 Sort of. It's not totally obvious what "the eigenvalues of the curvature" are because the curvature is not a matrix, but a matrix valued in 2-forms. Also, there's the $1/2\pi i$ thing you mention. O …
Will Sawin's user avatar
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5 votes

Analytic continuation of Euler product $\prod_{p} (1 - e^{-2 \pi i p \alpha}p^{-s})^{-1}$

Suppose $\alpha = a/b$ is rational. All but finitely many primes are relatively prime to $b$. For these primes, we have $$ e^{ 2\pi i ap/b} = \sum_{\chi: (\mathbb Z/b)^\times \to \mathbb C^\times} \c …
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5 votes

Analytic functions & convexity

No. Take a convex set and use an exponential function $e^{2\pi i z/c}$, where $c$ is the difference between two points in the set. The image of the set is no longer simply connected, and thus cannot b …
Will Sawin's user avatar
  • 148k
5 votes
Accepted

How can one test whether a given analytic curve in the plane is algebraic or not?

Let $\Gamma$ be a non-algebraic analytic curve. Let $z_1,\dots, z_n$ be points of $\Gamma$. Let $X_{n,d}$ be the set of algebraic curves of degree $d$ that contain $z_1,\dots, z_n$. Now consider a ran …
Will Sawin's user avatar
  • 148k

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