Abstract

The differintegration or fractional derivative of complex order ν, is a generalization of the ordinary concept of derivative of order n, from positive integer ν = n to complex values of ν, including also, for ν = −n a negative integer, the ordinary n‐th primitive. Substituting, in an ordinary differential equation, derivatives of integer order by derivatives of non‐integer order, leads to a fractional differential equation, which is generally a integro‐differential equation. We present simple methods of solution of some classes of fractional differential equations, namely those with constant coefficients (standard I) and those with power type coefficients with exponents equal to the orders of differintegration (standard II). The fractional differential equations of standard I (II), both homogeneous, and inhomogeneous with exponential (power‐type) forcing, can be solved in the Liouville (Riemann) systems of differintegration. The standard I (II) is linear with constant (non‐constant) coefficients, and some results are also given for a class of non‐linear fractional differential equations (standard III).

Highlights

  • The dlfferlntegratlon operator (Ross [I], Oldham and Spanler [2], Lavoie and Tremblay and Osier [3], McBride [4], Nishimoto [5], Campos [6], McBride and Roach [7]may be interpreted as a derivative of complex order +, which reduces to the ordinary n-th derivative for+n (--n) a positive integer

  • May be interpreted as a derivative of complex order +, which reduces to the ordinary n-th derivative for

  • The solution can be conveniently expressed in terms of fractional derivatives of elementary functions, e.g. in the scattering of acoustic waves (Marston [14]) or vibrations of visco-elastic rods (Campos [15])

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Summary

INTRODUCTION

The general homogeneous fractional differential equation (7.1) of Standard II, has particular integrals of the form (9.2a), where a is a root of the dlscrlminant equation r(t + a) m=. If the discriminant equation (9.4) has roots ak with k a,.**,, of multiplicities sk (4.9), the general integral of the homogeneous fractional differential equation of Standard is given by IM z m d. The particular integral (10.2) is replaced by (10.3) The latter (10.3) is deduced by a procedure similar to that used in 5, to derive (5.10) from (5.Sa,b); in the case b is not a root of (9.4), the result (10.3) rlth s 0 coincides tth (10.2). We cannot expect the very simple methods used in the present paper to go very far towards solving a non-llnear F.D.E. such as (11.1); we consider only the question of existence of a power type solution (9.2a), which, when substituted into (II.I) yields:. Less simple properties of differlntegratlons (Campos [36, 37]) may have applications to F.D.E.S

B Sk-1 g
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