Donal O’Regan

26.3k total citations · 9 hit papers
1.2k papers, 19.8k citations indexed

About

Donal O’Regan is a scholar working on Applied Mathematics, Numerical Analysis and Computational Theory and Mathematics. According to data from OpenAlex, Donal O’Regan has authored 1.2k papers receiving a total of 19.8k indexed citations (citations by other indexed papers that have themselves been cited), including 865 papers in Applied Mathematics, 395 papers in Numerical Analysis and 339 papers in Computational Theory and Mathematics. Recurrent topics in Donal O’Regan's work include Nonlinear Differential Equations Analysis (692 papers), Differential Equations and Numerical Methods (300 papers) and Fractional Differential Equations Solutions (259 papers). Donal O’Regan is often cited by papers focused on Nonlinear Differential Equations Analysis (692 papers), Differential Equations and Numerical Methods (300 papers) and Fractional Differential Equations Solutions (259 papers). Donal O’Regan collaborates with scholars based in Ireland, United States and China. Donal O’Regan's co-authors include Ravi P. Agarwal, Said R. Grace, Eduardo Hernández, Ravi P. Agarwal, Juan J. Nieto, Snezhana Hristova, JinRong Wang, Samir H. Saker, Patricia J. Y. Wong and Maria Meehan and has published in prestigious journals such as SHILAP Revista de lepidopterología, Scientific Reports and Fuzzy Sets and Systems.

In The Last Decade

Donal O’Regan

1.1k papers receiving 18.0k citations

Hit Papers

5 papers align trajectories

What are hit papers?

Hit papers significantly outperform the citation benchmark for their cohort. A paper qualifies if it has ≥500 total citations, achieves ≥1.5× the top-1% citation threshold for papers in the same subfield and year (this is the minimum needed to enter the top 1%, not the average within it), or reaches the top citation threshold in at least one of its specific research topics.

Fixed Point Theory and Applications

2001 603 citations Ravi P. Agarwal, Donal O’Regan et al. profile →
Positive Solutions of Differential, Difference and Integral Equations

1999 549 citations Ravi P. Agarwal, Donal O’Regan et al. profile →
Oscillation Theory for Difference and Functional Differential Equations

2000 428 citations Ravi P. Agarwal, Donal O’Regan et al. profile →
Generalized contractions in partially ordered metric spaces

2008 418 citations Ravi P. Agarwal, Donal O’Regan et al. profile →
On a new class of abstract impulsive differential equations

2012 404 citations Donal O’Regan et al. Proceedings of the American Mathematical Society profile →
Variational approach to impulsive differential equations

2007 346 citations Donal O’Regan et al. profile →
Fixed Point Theory for Lipschitzian-type Mappings with Applications

2009 288 citations D. R. Sahu, Donal O’Regan et al. profile →
Fixed point theorems for generalized contractions in ordered metric spaces

2007 271 citations Donal O’Regan et al. profile →
Dynamic Inequalities On Time Scales

2014 152 citations Ravi P. Agarwal, Donal O’Regan et al. profile →

Peers — A (Enhanced Table)

Peers by citation overlap · career bar shows stage (early→late) cites · hero ref

Name	h						Papers	Cites
Donal O’Regan Ireland	58	14.7k	7.7k	6.4k	4.1k	3.6k	1.2k	19.8k
Ravi P. Agarwal United States	71	20.3k 1.4×	12.7k 1.7×	9.3k 1.5×	4.9k 1.2×	4.0k 1.1×	1.2k	28.0k
V. Lakshmikantham United States	51	11.9k 0.8×	6.1k 0.8×	6.7k 1.0×	3.5k 0.9×	2.4k 0.6×	320	19.2k
Juan J. Nieto Spain	71	12.0k 0.8×	6.2k 0.8×	10.8k 1.7×	3.0k 0.7×	1.6k 0.4×	588	19.7k
Martin Böhner United States	49	11.0k 0.8×	6.1k 0.8×	3.9k 0.6×	1.5k 0.4×	1.5k 0.4×	330	13.9k
Allan Peterson United States	35	9.0k 0.6×	4.8k 0.6×	3.3k 0.5×	1.2k 0.3×	1.1k 0.3×	152	11.0k
Thabet Abdeljawad Saudi Arabia	63	9.6k 0.7×	4.7k 0.6×	13.4k 2.1×	2.3k 0.6×	722 0.2×	827	19.4k
Yong Zhou China	53	10.0k 0.7×	3.8k 0.5×	9.6k 1.5×	876 0.2×	590 0.2×	356	12.1k
Michael G. Crandall United States	47	7.6k 0.5×	2.1k 0.3×	1.8k 0.3×	976 0.2×	6.2k 1.7×	99	14.6k
Mehdi Dehghan Iran	85	4.8k 0.3×	16.1k 2.1×	15.6k 2.4×	476 0.1×	3.5k 1.0×	752	29.7k
Neil S. Trudinger Australia	40	14.4k 1.0×	1.6k 0.2×	818 0.1×	3.4k 0.8×	9.7k 2.7×	125	19.6k

Countries citing papers authored by Donal O’Regan

Since Specialization

Citations

This map shows the geographic impact of Donal O’Regan's research. It shows the number of citations coming from papers published by authors working in each country. You can also color the map by specialization and compare the number of citations received by Donal O’Regan with the expected number of citations based on a country's size and research output (numbers larger than one mean the country cites Donal O’Regan more than expected).

Fields of papers citing papers by Donal O’Regan

Since Specialization

Physical SciencesHealth SciencesLife SciencesSocial Sciences

This network shows the impact of papers produced by Donal O’Regan. Nodes represent research fields, and links connect fields that are likely to share authors. Colored nodes show fields that tend to cite the papers produced by Donal O’Regan. The network helps show where Donal O’Regan may publish in the future.

Co-authorship network of co-authors of Donal O’Regan

This figure shows the co-authorship network connecting the top 25 collaborators of Donal O’Regan. A scholar is included among the top collaborators of Donal O’Regan based on the total number of citations received by their joint publications. Widths of edges represent the number of papers authors have co-authored together. Node borders signify the number of papers an author published with Donal O’Regan. Donal O’Regan is excluded from the visualization to improve readability, since they are connected to all nodes in the network.

All Works

Sort: Min cites: Since: Top N: Style:

20 of 20 papers shown

O’Regan, Donal. (2025). Coincidence theory and KKM type maps. Studia Universitatis Babes-Bolyai Matematica. 70(1). 145–159.

O’Regan, Donal. (2023). A note on noncompact collectively coincidence point theory. Periodica Mathematica Hungarica. 87(2). 293–302.

O’Regan, Donal. (2023). Maximal, equilibrium, and coincidence points for majorized type correspondences. Journal of Mathematics and Computer Science. 32(1). 64–73.

O’Regan, Donal, et al.. (2022). Common fixed point theorems for multivalued mappings via cone-valued measure of noncompactness. Fixed Point Theory. 23(2). 729–740. 1 indexed citations

Tuan, Nguyen Huy, et al.. (2020). Approximation of mild solutions of a semilinear fractional differential equation with random noise. Proceedings of the American Mathematical Society. 148(8). 3339–3357. 6 indexed citations

Yan, Baoqiang, Donal O’Regan, & Ravi P. Agarwal. (2019). Existence of solutions for Kirchhoff-type problems via the method of lower and upper solutions. SHILAP Revista de lepidopterología. 4 indexed citations

Wang, JinRong, et al.. (2019). Nonemptyness and compactness of the solution set for fractional evolution inclusions with non-instantaneous impulses. SHILAP Revista de lepidopterología. 7 indexed citations

O’Regan, Donal & Taher S. Hassan. (2016). Oscillation criteria for solutions to nonlinear dynamic equations of higher order. DergiPark (Istanbul University). 5 indexed citations

O’Regan, Donal, et al.. (2015). Existence of Homoclinic Orbits of Superquadratic Second-Order Hamiltonian Systems. Zeitschrift für Analysis und ihre Anwendungen. 34(1). 27–41. 11 indexed citations

10.

Gasiński, Leszek, Donal O’Regan, & Nikolaos S. Papageorgiou. (2015). Positive Solutions for Nonlinear Nonhomogeneous Robin Problems. Zeitschrift für Analysis und ihre Anwendungen. 34(4). 435–458. 6 indexed citations

11.

Agarwal, Ravi P., Snezhana Hristova, & Donal O’Regan. (2015). Stability with respect to initial time difference for generalized delay differential equations. SHILAP Revista de lepidopterología. 1 indexed citations

12.

Saker, Samir H. & Donal O’Regan. (2015). Extensions of Dynamic Inequalities of Hardy’s Type on Time Scales. Mathematica Slovaca. 65(5). 993–1012. 7 indexed citations

13.

Agarwal, Ravi P., Donal O’Regan, & Svatoslav Staněk. (2011). Positive solutions for mixed problems of singular fractional differential equations. Mathematische Nachrichten. 285(1). 27–41. 81 indexed citations

14.

Ntouyas, Sotiris K. & Donal O’Regan. (2009). Some remarks on controllability of evolution equations in Banach spaces. SHILAP Revista de lepidopterología. 5 indexed citations

15.

Agarwal, Ravi P., Donal O’Regan, & D. R. Sahu. (2007). Fixed point theory for multivalued maps in Fréchet spaces via degree and index theory. 27(2). 399–399. 1 indexed citations

16.

Ntouyas, Sotiris K. & Donal O’Regan. (2007). Existence and controllability results for semilinear neutral functional differential inclusions with nonlocal conditions. 27(2). 213–213. 1 indexed citations

17.

O’Regan, Donal. (2000). A Multiplicity Fixed Point Theorem in Fréchet Spaces. Zeitschrift für Analysis und ihre Anwendungen. 19(3). 853–862. 5 indexed citations

18.

O’Regan, Donal. (1999). A General Coincidence Theory for Set-Valued Maps. Zeitschrift für Analysis und ihre Anwendungen. 18(3). 701–712. 2 indexed citations

19.

Agarwal, Ravi P. & Donal O’Regan. (1999). Coincidence Points for Perturbations of Linear Fredholm Maps of Index Zero. Publications of the Research Institute for Mathematical Sciences. 35(5). 725–736. 3 indexed citations

20.

Frigon, Marlène & Donal O’Regan. (1995). Existence results for some initial and boundary value problems without growth restriction. Proceedings of the American Mathematical Society. 123(1). 207–216. 23 indexed citations

Rankless uses publication and citation data sourced from OpenAlex, an open and comprehensive bibliographic database. While OpenAlex provides broad and valuable coverage of the global research landscape, it—like all bibliographic datasets—has inherent limitations. These include incomplete records, variations in author disambiguation, differences in journal indexing, and delays in data updates. As a result, some metrics and network relationships displayed in Rankless may not fully capture the entirety of a scholar's output or impact.

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