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

4 votes
Accepted

Bounds of zeta function near $\Re(s)=1$

Heath-Brown (2016) proved that, for any $\varepsilon>0$, $$\zeta(\sigma+it)\ll_\varepsilon t^{\frac{1}{2}(1-\sigma)^{3/2}+\varepsilon},\qquad 0\leq\sigma\leq 1,\qquad t\geq 1.$$ The exponent $1/2$ can …
GH from MO's user avatar
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5 votes
Accepted

Mellin transform at $0$

By definition, $\tilde{f}(0)$ exists if and only if $\int_0^\infty f(x)/x\,dx$ exists. As $f(x)$ is smooth and supported on $[0,2]$, we have that that $$|f(x)|=\left|\int_0^x f'(t)\,dt\right|\leq x\su …
GH from MO's user avatar
  • 105k
14 votes

Integral of $\log|e^{it}-1|$

Well, one definitely needs to work a bit to justify the convergence of the integral at the endpoints. Apart from that, the comment by mathworker21 is on point. Namely, let us consider the holomorphic …
GH from MO's user avatar
  • 105k
3 votes
Accepted

Convergence and meromorphic continuation of a Dirichlet series under RH

Per the OP's request, I prove that if the Dirichlet series of $\zeta(s)F(s)$ converges absolutely in the half-plane $\Re z > c>1/2$, and the Riemann hypothesis is true, then the Dirichlet series of $F …
GH from MO's user avatar
  • 105k
9 votes

Systematic way to compute $\sum_{n=1}^\infty P(n) / Q(n)$ for polynomials $P$ and $Q$

The question is somewhat broad, which makes it hard to answer it. At any rate, the following consequence of the residue theorem is standard and relevant. See also the "Added" section. Theorem. Let $f$ …
GH from MO's user avatar
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3 votes
Accepted

Estimates for the first coefficient of the Taylor expansion of $\zeta$ around a zero

Since $$c_1=\zeta'(s_0)\qquad\text{and}\qquad c_1'=\zeta'(1-\overline{s_0})=\overline{\zeta'(1-s_0)},$$ the question concerns $|\zeta'(s_0)/\zeta'(1-s_0)|$. The functional equation for $\zeta(s)$ can …
GH from MO's user avatar
  • 105k
4 votes
Accepted

On $\Re\frac{\zeta'}{\zeta}(s) \geq -A \log(|t|+4)$ for some $A>0$

If the Riemann Hypothesis fails, then there is no such lower bound. Indeed, if $\zeta(s_0)=0$ and $\Re(s_0)>1/2$, then $$\lim_{\delta\to 0+}\Re\frac{\zeta'(s_0-\delta)}{\zeta(s_0-\delta)}=-\infty.$$ N …
GH from MO's user avatar
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5 votes
Accepted

Sign of $\Re\frac{\xi'(s)}{\xi(s)}$ locally around a zeta zero

If a complex function $f(s)$ has a zero at $s_0$ of order $n\geq 1$, then for suitable $r>0$, $$\frac{f'(s)}{f(s)}=\frac{n}{s-s_0}+O(1),\qquad 0<|s-s_0|<r.$$ Writing $s=s_0+\rho e^{it}$ with $\rho\in( …
GH from MO's user avatar
  • 105k
2 votes
Accepted

Riemann xi function strictly increasing along a half-plane

The result you mention is not due to Matiyasevich-Saidak-Zvengrowsk. Instead, it appeared in Sondow-Dumitrescu: A monotonicity property of Riemann's xi function and a reformulation of the Riemann hypo …
GH from MO's user avatar
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11 votes
Accepted

Bounds for Dirichlet L-functions

As Peter Humphries said in a comment, the best known bound for $\sigma=1/2$ (applying to all $\chi$) is due to Petrow and Young: $$L(1/2 + it,\chi) \ll_{\varepsilon} (q(|t| + 1))^{1/6 + \varepsilon}.$ …
GH from MO's user avatar
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6 votes
Accepted

Is there a scalar product which makes orthonormal the family of complex functions $ (f_n)_{ ...

There is a unique Hilbert function space with that property, and you can read about it here.
GH from MO's user avatar
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6 votes
Accepted

Conditional convergence of Artin $L$-functions

It is known that $L(V,s)$ is analytic and non-vanishing in $\Re(s)\geq 1$. Equivalently, $\log L(V,s)$ is analytic in $\Re(s)\geq 1$. Note that $\log L(V,s)$ is given by an absolutely convergent Diric …
GH from MO's user avatar
  • 105k
4 votes
Accepted

Analyzing a Dirichlet series with log-oscillating terms via Fourier methods

Your series diverges for any $a<1$ and $b\in\mathbb{R}$. This is clear for $b=0$, so we can assume $b>0$ (in case of $b<0$, we replace $b$ by $-b$). We shall show that the series does not satisfy Cauc …
GH from MO's user avatar
  • 105k
5 votes

Bounds for analytic circles

The functions $\xi(s)$ and $$f(s):=\xi\left(\frac{s-i}{2}\right) + \xi\left(\frac{i+s}{2}\right)$$ grow faster than exponentially on the positive axis, hence they do not satisfy the first bound. This …
GH from MO's user avatar
  • 105k
12 votes
Accepted

Lindelöf hypotheses for derivatives of zeta

The Lindelöf hypothesis yields the same bound for each derivative of $\zeta(s)$ via Cauchy's formula. Indeed, let $n\in\mathbb{N}$, $\sigma\in\mathbb{R}$, $T\in(1,\infty)$, $\varepsilon\in(0,1/2)$. Le …
GH from MO's user avatar
  • 105k

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