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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 …
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
$$|f(x)|=\left|\int_0^x f'(t)\,dt\right|\leq x\su …
14
votes
Integral of $\log|e^{it}-1|$
Well, one definitely needs to work a bit to justify the convergence of the integral at the endpoints. Apart from that, the comment by mathworker21 is on point. Namely, let us consider the holomorphic …
3
votes
Accepted
Convergence and meromorphic continuation of a Dirichlet series under RH
Per the OP's request, I prove that if the Dirichlet series of $\zeta(s)F(s)$ converges absolutely in the half-plane $\Re z > c>1/2$, and the Riemann hypothesis is true, then the Dirichlet series of $F …
9
votes
Systematic way to compute $\sum_{n=1}^\infty P(n) / Q(n)$ for polynomials $P$ and $Q$
The question is somewhat broad, which makes it hard to answer it. At any rate, the following consequence of the residue theorem is standard and relevant. See also the "Added" section.
Theorem. Let $f$ …
3
votes
Accepted
Estimates for the first coefficient of the Taylor expansion of $\zeta$ around a zero
Since
$$c_1=\zeta'(s_0)\qquad\text{and}\qquad c_1'=\zeta'(1-\overline{s_0})=\overline{\zeta'(1-s_0)},$$
the question concerns $|\zeta'(s_0)/\zeta'(1-s_0)|$. The functional equation for $\zeta(s)$ can …
4
votes
Accepted
On $\Re\frac{\zeta'}{\zeta}(s) \geq -A \log(|t|+4)$ for some $A>0$
If the Riemann Hypothesis fails, then there is no such lower bound. Indeed, if $\zeta(s_0)=0$ and $\Re(s_0)>1/2$, then
$$\lim_{\delta\to 0+}\Re\frac{\zeta'(s_0-\delta)}{\zeta(s_0-\delta)}=-\infty.$$
N …
5
votes
Accepted
Sign of $\Re\frac{\xi'(s)}{\xi(s)}$ locally around a zeta zero
If a complex function $f(s)$ has a zero at $s_0$ of order $n\geq 1$, then for suitable $r>0$,
$$\frac{f'(s)}{f(s)}=\frac{n}{s-s_0}+O(1),\qquad 0<|s-s_0|<r.$$
Writing $s=s_0+\rho e^{it}$ with $\rho\in( …
2
votes
Accepted
Riemann xi function strictly increasing along a half-plane
The result you mention is not due to Matiyasevich-Saidak-Zvengrowsk. Instead, it appeared in Sondow-Dumitrescu: A monotonicity property of Riemann's xi function and a reformulation of the Riemann hypo …
11
votes
Accepted
Bounds for Dirichlet L-functions
As Peter Humphries said in a comment, the best known bound for $\sigma=1/2$ (applying to all $\chi$) is due to Petrow and Young:
$$L(1/2 + it,\chi) \ll_{\varepsilon} (q(|t| + 1))^{1/6 + \varepsilon}.$ …
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.
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 …
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 …
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 …
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 …