2,843 research outputs found

    Unconditional and Conditional Large Gaps between the zeros of the Riemann Zeta-Function

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    In this paper, first by employing inequalities derived from the Opial inequality due to David Boyd with best constant, we will establish new unconditional lower bounds for the gaps between the zeros of the Riemann zeta function. Second, on the hypothesis that the moments of the Hardy Z-function and its derivatives are correctly predicted, we establish some explicit formulae for the lower bounds of the gaps between the zeros and use them to establish some new conditional bounds. In particular it is proved that the consecutive nontrivial zeros often differ by at least 6.1392 (conditionally) times the average spacing. This value improves the value 4.71474396 that has been derived in the literature

    Weak solutions for the dynamic equations xΔ(m)(t)=f(t;x(t))x^{\Delta(m)}(t) = f (t; x(t)) on time scales

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    In this paper we prove the existence of weak solutions of the dynamic Cauchy problem \begin{equation*} \begin{split} x^{(\Delta m)}(t)&=f(t,x(t)),\quad t\in T, \\ x(0)&=0, \\ x^\Delta (0)&=\eta _1 ,\dots,x^{(\Delta (m-1))}(0)=\eta _{m-1},\quad \eta _1 ,\dots,\eta _{m-1} \in E, \end{split} \end{equation*} where x(Δm)x^{(\Delta m)} denotes a weak mm-th order Δ\Delta-derivative, TT denotes an unbounded time scale (nonempty closed subset of R such that there exists a sequence (an)(a_n ) in TT and an)a_n \to \infty ), EE is a Banach space and ff is weakly -- weakly sequentially continuous and satisfies some conditions expressed in terms of measures of weak noncompactness. The Sadovskii fixed point theorem and Ambrosetti's lemma are used to prove the main result. As dynamic equations are a unification of differential and difference equations our result is also valid for differential and difference equations. The results presented in this paper are new not only for Banach valued functions but also for real valued functions

    On the oscillatory behavior for a certain class of third order nonlinear delay difference equations

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    By employing the generalized Riccati transformation technique, we will establish some new oscillation criteria for a certain class of third order nonlinear delay difference equations. Our results extend and improve some previously obtained ones. An example is worked out to demonstrate the validity of the proposed results

    New gaps between zeros of fourth-order differential equations via Opial inequalities

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    In this paper, for a fourth-order differential equation, we will establish some lower bounds for the distance between zeros of a nontrivial solution and also lower bounds for the distance between zeros of a solution and/or its derivatives. We also give some new results related to some boundary value problems in the theory of bending of beams. The main results will be proved by making use of some generalizations of Opial and Wirtinger-type inequalities. Some examples are considered to illustrate the main results

    Conductive-tether design for de-orbiting from given altitude and inclination

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    A bare tether with thin-tape cross section is both i) the most effective electrodinamic tether for given length and mass, and ii) capable of effective design for an arbitrary mission through its three disparate dimensions. It handily beats the fully insulated tether that exchanges current at both ends, a result resting in advantages of 2D current collection as against 3D collection; it has much greater perimeter than the round bare tether and much lower fatal debris-impact rate, leading to greatly faster de-orbiting and greatly higher probability of survival; and it only allows multi-line tethers reaching a few hundred lines to stand competitive. In selecting the disparate values of length L, width w, and thickness h for a de-orbit mission, performance involves three criteria: a) tether-tospacecraft mass ratio must be small; b) probability of survival against the debris environment must be high; and c) de-orbiting must be fast to reduce manoeuvres for avoiding catastrophic collisions with big active/passive satellites around. Beyond determining tether mass through the product Lwh, main dimension parameters affecting performance are L/h2li characterizing ohmic effects, and w determining electron collection. An algorithm for optimal selection of tape dimensions is elaborated
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