Applications of some exponential sums on prime powers: a survey

A survey paper on some recent results on additive problems with prime powers

Efficient computation of the Euler-Kronecker constants of prime cyclotomic fields

We introduce a new algorithm, which is faster and requires less computing resources than the ones previously known, to compute the Euler-Kronecker constants $\mathfrak{G}_q$ for the prime cyclotomic fields $\mathbb{Q}(\zeta_q)$, where $q$ is an odd prime and $\zeta_q$ is a primitive $q$-root of unity. With such a new algorithm we evaluated $\mathfrak{G}_q$ and $\mathfrak{G}_q^+$, where $\mathfrak{G}_q^+$ is the Euler-Kronecker constant of the maximal real subfield of $\mathbb{Q}(\zeta_q)$, for some very large primes $q$ thus obtaining two new negative values of $\mathfrak{G}_q$: $\mathfrak{G}_{9109334831}= -0.248739\dotsc$ and $\mathfrak{G}_{9854964401}= -0.096465\dotsc$ We also evaluated $\mathfrak{G}_q$ and $\mathfrak{G}^+_q$ for every odd prime $q\le 10^6$, thus enlarging the size of the previously known range for $\mathfrak{G}_q$ and $\mathfrak{G}^+_q$. Our method also reveals that difference $\mathfrak{G}_q - \mathfrak{G}^+_q$ can be computed in a much simpler way than both its summands, see Section 3.4. Moreover, as a by-product, we also computed $M_q=\max_{\chi\ne \chi_0} \vert L^\prime/L(1,\chi) \vert$ for every odd prime $q\le 10^6$, where $L(s,\chi)$ are the Dirichlet $L$-functions, $\chi$ run over the non trivial Dirichlet characters mod $q$ and $\chi_0$ is the trivial Dirichlet character mod $q$. As another by-product of our computations, we will also provide more data on the generalised Euler constants in arithmetic progressions. The programs used to performed the computations here described and the numerical results obtained are available at the following web address: \url{http://www.math.unipd.it/~languasc/EK-comput.html}.Comment: 25 pages, 6 tables, 4 figures. Third known example of negative values for Ek(q) inserted. Complete set of computation of Ek(q) and Ek(q)^+ for every prime up to 10^6; computation of max|L'/L(1,chi)| for the same primes inserted. Two references added, typos correcte

Sums of four prime cubes in short intervals

We prove that a suitable asymptotic formula for the average number of representations of integers $n=p_{1}^{3}+p_{2}^{3}+p_{3}^{3}+p_{4}^{3}$, where $p_1,p_2,p_3,p_4$ are prime numbers, holds in intervals shorter than the the ones previously known.Comment: Unconditional result improved by using a Robert-Sargos estimate (lemmas 6-7); more detailed proof of Lemma 5 inserted. Correction of a typo. 10 page

A Diophantine problem with prime variables

We study the distribution of the values of the form $\lambda_1 p_1 + \lambda_2 p_2 + \lambda_3 p_3^k$, where $\lambda_1$, $\lambda_2$ and $\lambda_3$ are non-zero real number not all of the same sign, with $\lambda_1 / \lambda_2$ irrational, and $p_1$, $p_2$ and $p_3$ are prime numbers. We prove that, when $1 < k < 4 / 3$, these value approximate rather closely any prescribed real number.Comment: submitte

A Ces\`aro Average of Goldbach numbers

Let $\Lambda$ be the von Mangoldt function and $(r_G(n) = \sum_{m_1 + m_2 = n} \Lambda(m_1) \Lambda(m_2))$ be the counting function for the Goldbach numbers. Let $N \geq 2$ be an integer. We prove that $$\begin{align} &\sum_{n \le N} r_G(n) \frac{(1 - n/N)^k}{\Gamma(k + 1)} = \frac{N^2}{\Gamma(k + 3)} - 2 \sum_\rho \frac{\Gamma(\rho)}{\Gamma(\rho + k + 2)} N^{\rho+1}\\ &\qquad+ \sum_{\rho_1} \sum_{\rho_2} \frac{\Gamma(\rho_1) \Gamma(\rho_2)}{\Gamma(\rho_1 + \rho_2 + k + 1)} N^{\rho_1 + \rho_2} + \mathcal{O}_k(N^{1/2}), \end{align}$$ for $k > 1$, where $\rho$, with or without subscripts, runs over the non-trivial zeros of the Riemann zeta-function $\zeta(s)$.Comment: submitte

On the constant in the Mertens product for arithmetic progressions. I. Identities

The aim of the paper is the proof of new identities for the constant in the Mertens product for arithmetic progressions. We deal with the problem of the numerical computation of these constants in another paper.Comment: References added, misprints corrected. 9 page

The number of Goldbach representations of an integer

We prove the following result: Let $N \geq 2$ and assume the Riemann Hypothesis (RH) holds. Then $$\sum_{n=1}^{N} R(n) =\frac{N^{2}}{2} -2 \sum_{\rho} \frac{N^{\rho + 1}}{\rho (\rho + 1)} + O(N \log^{3}N),$$ where $\rho=1/2+i\gamma$ runs over the non-trivial zeros of the Riemann zeta function $\zeta(s)$

A Ces\`aro Average of Hardy-Littlewood numbers

Let $\Lambda$ be the von Mangoldt function and $r_{\textit{HL}}(n) = \sum_{m_1 + m_2^2 = n} \Lambda(m_1),$ be the counting function for the Hardy-Littlewood numbers. Let $N$ be a sufficiently large integer. We prove that $$\begin{align}\sum_{n \le N} r_{\textit{HL}}(n) \frac{(1 - n/N)^k}{\Gamma(k + 1)} &= \frac{\pi^{1 / 2}}2 \frac{N^{3 / 2}}{\Gamma(k + 5 / 2)} - \frac 12 \frac{N}{\Gamma(k + 2)} - \frac{\pi^{1 / 2}}2 \sum_{\rho} \frac{\Gamma(\rho)}{\Gamma(k + 3 / 2 + \rho)} N^{1 / 2 + \rho}\\ &+ 1/2 \sum_{\rho} \frac{\Gamma(\rho)}{\Gamma(k + 1 + \rho)} N^{\rho} + \frac{N^{3 / 4 - k / 2}}{\pi^{k + 1}} \sum_{\ell \ge 1} \frac{J_{k + 3 / 2} (2 \pi \ell N^{1 / 2})}{\ell^{k + 3 / 2}}\\ &- \frac{N^{1 / 4 - k / 2}}{\pi^k} \sum_{\rho} \Gamma(\rho) \frac{N^{\rho / 2}}{\pi^\rho} \sum_{\ell \ge 1} \frac{J_{k + 1 / 2 + \rho} (2 \pi \ell N^{1 / 2})} {\ell^{k + 1 / 2 + \rho}} + \mathcal{O}_k(1).\end{align}$$ for $k > 1$, where $\rho$ runs over the non-trivial zeros of the Riemann zeta-function $\zeta(s)$ and $J_{\nu} (u)$ denotes the Bessel function of complex order $\nu$ and real argument $u$.Comment: submitte

Sum of one prime and two squares of primes in short intervals

Assuming the Riemann Hypothesis we prove that the interval $[N, N + H]$ contains an integer which is a sum of a prime and two squares of primes provided that $H \ge C (\log N)^{4}$, where $C > 0$ is an effective constant.Comment: removed unconditional case; other minor changes inserte