J. Nig. Soc. Phys. Sci. 5 (2023) 1017 Journal of the Nigerian Society of Physical Sciences An Accuracy-preserving Block Hybrid Algorithm for the Integration of Second-order Physical Systems with Oscillatory Solutions Joshua Sundaya,∗, Joel N. Ndama, Lydia J. Kwarib aDepartment of Mathematics, University of Jos, Jos 930003, Nigeria bDepartment of Mathematics, Federal College of Education, Pankshin 933105, Nigeria Abstract It is a known fact that in most cases, to integrate an oscillatory problem, higher order A-stable methods are often needed. This is because such problems are characterized by stiffness, chaos and damping, thus making them tedious to solve. However, in this research, an accuracy-preserving relatively lower order Block Hybrid Algorithm (BHA) is proposed for solution of second-order physical systems with oscillatory solutions. The sixth order algorithm was derived using interpolation and collocation of power series within a single step interval [tn, tn+1]. In order to circumvent the Dahlquist-barrier and also obtain an accuracy-preserving algorithm, four off-step points were incorporated within the single step interval. A number of special cases of oscillatory problems were solved using the proposed method and the results obtained clearly showed that it outperformed other existing methods we compared our results with even though the BHA is of lower order relative to such methods. Some of the second-order physical systems considered were the Kepler, Bessel and damped problems. Some important properties of the BHA were also analyzed and the results of the analysis showed that it is consistent, zero-stable and convergent. DOI:10.46481/jnsps.2023.1017 Keywords: Accuracy-preserving, Algorithm, Block hybrid method, Oscillation, Physical systems, Second-order Article History : Received: 28 August 2022 Received in revised form: 05 December 2022 Accepted for publication: 11 December 2022 Published: 14 January 2023 c© 2023 The Author(s). Published by the Nigerian Society of Physical Sciences under the terms of the Creative Commons Attribution 4.0 International license (https://creativecommons.org/licenses/by/4.0). Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Communicated by: T. Latunde 1. Introduction Second-order physical systems with oscillatory solutions find applications in diverse areas of human endeavors like engineer- ing and sciences. Such systems are applied in vibration of mass-spring systems, astrophysics, control theory, mechanics, circuit theory, biology among others [1, 2]. In this research, an accuracy-preserving BHA shall be derived for the direct in- ∗Corresponding author tel. no: +234 7034884482 Email address: sundayjo@unijos.edu.ng (Joshua Sunday) tegration of second order oscillatory physical systems of the form y′′(t) = f ( t, y(t), y′(t) ) (1) subject to the initial conditions y(t0) = y0, y ′(t0) = y ′ 0 (2) on the interval t ∈ [t0, tN ], where f : < × 0. Suppose the function f (t, s0, s1, ..., sn−1) in (3) is non-negative, continuous and non-decreasing in t, and continuous and non- decreasing in sk for each k = 0, 1, ..., n−1 in the region <. If in addition f (t, y0, y1, ..., yn−1) , 0 in < for t > t0, then the initial value problem (3) has at most one solution in <”. The derivation will be carried out via a continuous scheme based on linear multistep method by incorporating four off-step points. The implementation of the algorithm will be effected in a block-by-block mode, thus making it self-starting (i.e. with- out the need for predictors). Equations of the form (1) can be solved by first transform- ing them into their equivalent system of first order differen- tial equations and then employing an appropriate method [4- 6]. However, one of the setbacks of such approach is that some of the vital properties and characteristics of the higher order differential equations are lost in the course of the conversion. Besides, coding such methods are often cumbersome since in most cases subroutines have to be incorporated to provide the starting values. Some methods have also been proposed in literature for the direct solution of special second order differential equations. Such equations are termed ‘special’ because they do not depend on y′, in order words they are of the form y′′ = f (x, y). These methods often require fewer function evaluations and less mem- ory space [7-9]. Over the years, several authors have proposed different meth- ods for the direct solution of oscillatory problems of the form (1). Ref[2] proposed an eleventh order block hybrid method for the direct solution of system of second order differential equations including Hamiltonian systems. The method was derived from continuous scheme via hybrid method approach with several off-step points. The method was implemented in a block manner. Ref[10] formulated a continuous explicit hybrid method for the solution of second order differential equations. The authors interpolated the basis function at both grid and off- grid points while the differential systems were collocated at se- lected points. The authors further derived starting values of the same order with the methods by adopting Taylor series expan- sion to circumvent the inherent disadvantage of starting values of lower order. Ref[11] developed an order eight implicit block method for the solution of second order differential equations. The authors adopted the Hermite polynomial as basis function to construct the method that comprises first and second deriva- tives. The basic properties of the method were analysed and the method was implemented on some linear and nonlinear second order differential equations. Other researchers that also devel- oped direct methods for solving problems of the form (1) are [12-23]. 2. Derivation and Implementation of the BHA 2.1. Derivation of the BHA The accuracy-preserving BHA shall be derived by seeking a continuous approximate solution Y (t) to the second order os- cillatory problems of the form (1) on the interval [tn, tn+1]. This is expressed compactly in a vector form as, Y (t) = [ 1 t t2 ... t7 ]  σ0 σ1 σ2 . . . σ7  (4) where σ0,σ1,σ2, ...,σ7are uniquely determined parameters in