## Abstract

The main aim of this paper is to study the Cauchy problem for nonlinear differential equations of fractional order containing the weighted Riemann-Liouville fractional derivative of a function with respect to another function. The equivalence of this problem and a nonlinear Volterra-type integral equation of the second kind have been presented. In addition, the existence and uniqueness of the solution to the considered Cauchy problem are proved using Banach’s fixed point theorem and the method of successive approximations. Finally, we obtain a new estimate of the weighted Riemann-Liouville fractional derivative of a function with respect to functions at their extreme points. With the assistance of the estimate obtained, we develop the comparison theorems of fractional differential inequalities, strict as well as nonstrict, involving weighted Riemann-Liouville differential operators of a function with respect to functions of order δ, 0 < δ < 1.

Original language | English |
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Pages (from-to) | 14106-14129 |

Number of pages | 24 |

Journal | AIMS Mathematics |

Volume | 9 |

Issue number | 6 |

DOIs | |

Publication status | Published - 2024 |

Externally published | Yes |

## Keywords

- Cauchy problem
- comparison theorems
- fixed point theorem
- fractional differential equations
- fractional differential inequalities
- volterra integral equation
- weighted fractional integrals and derivatives