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Search Results: 1 - 10 of 213195 matches for " Jan van de Lune "
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A note on Pólya's observation concerning Liouville's function
Richard P. Brent,Jan van de Lune
Mathematics , 2011,
Abstract: We show that a certain weighted mean of the Liouville function lambda(n) is negative. In this sense, we can say that the Liouville function is negative "on average".
A glimpse inside the mathematical kitchen
Juan Arias-de-Reyna,Jan van de Lune
Mathematics , 2010, DOI: 10.7153/jmi-05-30
Abstract: We prove the inequality sum_{k=1}^infty (-1)^{k+1} r^k cos(k*phi) (k+2)^{-1} < sum_{k=1}^infty(-1)^{k+1} r^k (k+2)^{-1} for 0 < r <= 1 and 0 < phi < pi. For the case r = 1 we give two proofs. The first one is by means of a general numerical technique (maximal slope principle) for proving inequalities between elementary functions. The second proof is fully analytical. Finally we prove a general rearrangement theorem and apply it to the remaining case 0 < r < 1. Some of these inequalities are needed for obtaining general sharp bounds for the errors committed when applying the Riemann-Siegel expansion of Riemann's zeta function.
On the exact location of the non-trivial zeros of Riemann's zeta function
Juan Arias de Reyna,Jan van de Lune
Mathematics , 2013,
Abstract: In this paper we introduce the real valued real analytic function kappa(t) implicitly defined by exp(2 pi i kappa(t)) = -exp(-2 i theta(t)) * (zeta'(1/2-it)/zeta'(1/2+it)) and kappa(0)=-1/2. (where theta(t) is the function appearing in the known formula zeta(1/2+it)= Z(t) * e^{-i theta(t)}). By studying the equation kappa(t) = n (without making any unproved hypotheses), we will show that (and how) this function is closely related to the (exact) position of the zeros of Riemann's zeta(s) and zeta'(s). Assuming the Riemann hypothesis and the simplicity of the zeros of zeta(s), it will follow that the ordinate of the zero 1/2 + i gamma_n of zeta(s) will be the unique solution to the equation kappa(t) = n.
A note on the real part of the Riemann zeta-function
Juan Arias de Reyna,Richard P. Brent,Jan van de Lune
Mathematics , 2011,
Abstract: We consider the real part $\Re(\zeta(s))$ of the Riemann zeta-function $\zeta(s)$ in the half-plane $\Re(s) \ge 1$. We show how to compute accurately the constant $\sigma_0 = 1.19\ldots$ which is defined to be the supremum of $\sigma$ such that $\Re(\zeta(\sigma+it))$ can be negative (or zero) for some real $t$. We also consider intervals where $\Re(\zeta(1+it)) \le 0$ and show that they are rare. The first occurs for $t$ approximately 682112.9, and has length about 0.05. We list the first fifty such intervals.
On the sign of the real part of the Riemann zeta-function
Juan Arias de Reyna,Richard P. Brent,Jan van de Lune
Computer Science , 2012,
Abstract: We consider the distribution of $\arg\zeta(\sigma+it)$ on fixed lines $\sigma > \frac12$, and in particular the density \[d(\sigma) = \lim_{T \rightarrow +\infty} \frac{1}{2T} |\{t \in [-T,+T]: |\arg\zeta(\sigma+it)| > \pi/2\}|\,,\] and the closely related density \[d_{-}(\sigma) = \lim_{T \rightarrow +\infty} \frac{1}{2T} |\{t \in [-T,+T]: \Re\zeta(\sigma+it) < 0\}|\,.\] Using classical results of Bohr and Jessen, we obtain an explicit expression for the characteristic function $\psi_\sigma(x)$ associated with $\arg\zeta(\sigma+it)$. We give explicit expressions for $d(\sigma)$ and $d_{-}(\sigma)$ in terms of $\psi_\sigma(x)$. Finally, we give a practical algorithm for evaluating these expressions to obtain accurate numerical values of $d(\sigma)$ and $d_{-}(\sigma)$.
On some oscillating sums
J. Arias de Reyna,J. van de Lune
Uniform Distribution Theory , 2008,
Abstract: This paper deals with various properties (theoretical as well as computational) of the \sums $S_ \alpha(n) = \sum_{j=1}^n (-1)^{ \lfloor j \alpha \floor}$ where $ \alpha$ is any real number (mostly a positive real quadratic).
Some bounds and limits in the theory of Riemann's zeta function
J. Arias de Reyna,J. van de Lune
Mathematics , 2011, DOI: 10.1016/j.jmaa.2012.06.017
Abstract: For any real a>0 we determine the supremum of the real \sigma\ such that \zeta(\sigma+it) = a for some real t. For 0 < a < 1, a = 1, and a > 1 the results turn out to be quite different.} We also determine the supremum E of the real parts of the `turning points', that is points \sigma+it where a curve Im \zeta(\sigma+it) = 0 has a vertical tangent. This supremum E (also considered by Titchmarsh) coincides with the supremum of the real \sigma\ such that \zeta'(\sigma+it) = 0 for some real t. We find a surprising connection between the three indicated problems: \zeta(s) = 1, \zeta'(s) = 0 and turning points of \zeta(s). The almost extremal values for these three problems appear to be located at approximately the same height.
Algorithms for determining integer complexity
J. Arias de Reyna,J. van de Lune
Mathematics , 2014,
Abstract: We present three algorithms to compute the complexity $\Vert n\Vert$ of all natural numbers $ n\le N$. The first of them is a brute force algorithm, computing all these complexities in time $O(N^2)$ and space $O(N\log^2 N)$. The main problem of this algorithm is the time needed for the computation. In 2008 there appeared three independent solutions to this problem: V. V. Srinivas and B. R. Shankar [11], M. N. Fuller [7], and J. Arias de Reyna and J. van de Lune [3]. All three are very similar. Only [11] gives an estimation of the performance of its algorithm, proving that the algorithm computes the complexities in time $O(N^{1+\beta})$, where $1+\beta =\log3/\log2\approx1.584963$. The other two algorithms, presented in [7] and [3], were very similar but both superior to the one in [11]. In Section 2 we present a version of these algorithms and in Section 4 it is shown that they run in time $O(N^\alpha)$ and space $O(N\log\log N)$. (Here $\alpha = 1.230175$). In Section 2 we present the algorithm of [7] and [3]. The main advantage of this algorithm with respect to that in [11] is the definition of kMax in Section 2.7. This explains the difference in performance from $O(N^{1+\beta})$ to $O(N^\alpha)$. In Section 3 we present a detailed description a space-improved algorithm of Fuller and in Section 5 we prove that it runs in time $O(N^\alpha)$ and space $O(N^{(1+\beta)/2}\log\log N)$, where $\alpha=1.230175$ and $(1+\beta)/2\approx0.792481$.
"How many $1$'s are needed?" revisited
J. Arias de Reyna,J. van de Lune
Mathematics , 2014,
Abstract: We present a rigorous and relatively fast method for the computation of the "complexity" of a natural number (sequence A005245), and answer some "old and new" questions related to the question in the title of this note. We also extend the known terms of the related sequence A005520. We put this paper in the arXiv only for possible reference. This note was written in 2008. It is exactly the copy we have sent to Martin N. Fuller in February 11, 2009 proposing to him to join us as co-author. The ensuing collaboration resulted in a better program and many results about the complexity. We have waited four years in the hope of contacting him again. In the mean time Iraids et al. published arXiv:1203.6462 containing some of our results here. Our program is similar to the one posted in the OEIS by Martin N. Fuller, but its correctness is proved here for the first time.
Labour analgesia effects on foetal heart rate. A mini-review  [PDF]
Nicole Maria Anna Adela Engel, Marc Van de Velde, Jan Gerrit Nijhuis, M. A. E. Marcus
Open Journal of Obstetrics and Gynecology (OJOG) , 2011, DOI: 10.4236/ojog.2011.13020
Abstract: Foetal well-being during labour is of utmost importance. One of the ways to attempt to assess foetal well-being is by recording foetal heart rate (FHR). Loss of variability and deceleration patterns are known to be associated with foetal distress. Decelerations and foetal bradycardia have been described after any type of effective labour analgesia. This review addresses the questions if certain analgesic techniques and/or analgesics lead to clinically relevant FHR changes, what is their aetiology, and how we should manage these FHR changes.
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