## Research

My research interests are in computational topology and geometry, combinatorial topology, and applied topology (in particular to data analysis and to sensor networks).I recently became the Director of the Applied Algebraic Topology Research Network, which hosts a weekly Online Seminar. Recordings of our seminar are available at our YouTube Channel.

At Colorado State I am a member of the Pattern Analysis Lab, a co-organizer of the Applied Topology Seminar, and an attendee of the Algebraic Combinatorics Seminar.

Here is a 2017 research statement, a 2016 research statement, my PhD thesis, and a related research highlight. See section 4 of this column for some open problems I am interested in.

### Papers on Vietoris-Rips and Čech metric thickenings

Metric thickenings of Euclidean submanifolds.
With Joshua Mirth. Submitted (2018+). [arXiv:1709.02492, Abstract, Joshua's masters thesis, Slides, Poster] |

Metric reconstruction via optimal transport.
With Michał Adamaszek and Florian Frick. Submitted (2018+). [arXiv:1706.04876, Abstract, Poster, Talk Notes, Slides, Video] |

### Papers on Vietoris-Rips and Čech simplicial complexes

Vietoris-Rips complexes of regular polygons.
With Samir Chowdhury, Adam Jaffe, and Bonginkosi Sibanda. In preparation. [Slides, Webpage] |

Vietoris-Rips and Čech complexes of metric gluings.
With Michał Adamaszek, Ellen Gasparovic, Maria Gommel, Emilie Purvine, Radmila Sazdanovic, Bei Wang, Yusu Wang, and Lori Ziegelmeier. To appear in Symposium on Computational Geometry, 2018. [arXiv:1712.06224, Abstract] |

On Vietoris-Rips complexes of ellipses.
With Michał Adamaszek and Samadwara Reddy. Journal of Topology and Analysis (2017), 1-30. [Publisher Link, arXiv:1704.04956, Oberwolfach Preprint, Abstract, Slides] |

The Vietoris-Rips complexes of a circle.
With Michał Adamaszek. Pacific Journal of Mathematics 290 (2017), 1-40. [Publisher Link, arXiv:1503.03669, Abstract, Slides, Poster 1, Poster 2, Talk Video] |

Random cyclic dynamical systems.
With Michał Adamaszek and Francis Motta. Advances in Applied Mathematics 83 (2017), 1-23. [Publisher Link, arXiv:1511.07832, Abstract] |

Nerve complexes of circular arcs.
With Michał Adamaszek, Florian Frick, Chris Peterson, and Corrine Previte-Johnson. Discrete & Computational Geometry 56 (2016), 251-273. [PDF of Paper, Publisher Link, arXiv:1410.4336, Abstract] |

### Papers on sensor networks

Sweeping costs of planar domains.
With Brooks Adams and Colin Roberts. To appear in the AWM-IMA Springer series (2018). [arXiv:1612.03540, Abstract] |

Evasion paths in mobile sensor networks.
With Gunnar Carlsson. International Journal of Robotics Research 34 (2015), 90-104. [Publisher Link, PDF of Paper, Abstract, Slides, Poster, Talk Video, Multimedia] |

### Papers on data analysis

Persistence images: A stable vector representation of persistent homology.
With Sofya Chepushtanova, Tegan Emerson, Eric Hanson, Michael Kirby, Francis Motta, Rachel Neville, Chris Peterson, Patrick Shipman, and Lori Ziegelmeier. Journal of Machine Learning Research 18 (2017), Number 8, 1-35. [PDF of Paper, Publisher Link, arXiv:1507.06217, Abstract, Software] |

Nudged elastic band in topological data analysis.
With Atanas Atanasov and Gunnar Carlsson. Topological Methods in Nonlinear Analysis 45 (2015), 247-272. [Publisher Link, arXiv:1112.1993, Abstract, Slides, Software, Javadoc, Data] |

On the nonlinear statistics of range image patches.
With Gunnar Carlsson. SIAM Journal on Imaging Sciences 2 (2009), 110-117. [Publisher Link, PDF of Paper, Abstract, Data] |

### Conference proceedings on software

Javaplex: A research software package for persistent (co)homology.
With Andrew Tausz and Mikael Vejdemo-Johansson. Proceedings of ICMS 2014, Han Hong and Chee Yap (Eds), LNCS 8592 (2014), 129-136. Software available at http://appliedtopology.github.io/javaplex/. [Publisher Link, Abstract] |

### Software tutorials

- Andrew Tausz and I maintain a PDF tutorial and a wiki tutorial for the Javaplex Software for persistent homology.
- I wrote a Matlab tutorial and a BeanShell tutorial for the JPlex Software for persistent homology.

## What is topology? What are simplicial complexes?

Topology is the study of shapes and surfaces in higher dimensions. One way to build a higher-dimensional space is by gluing simple building blocks together. For example, you can start with a set of vertices (0-dimensional building blocks), glue on a set of edges (1-dimensional building blocks), glue on a set of triangles (2-dimensional building blocks), and then glue on a set of tetrahedra (3-dimensional building blocks). But the fun doesn't stop there - you can continue by gluing on higher-dimensional pieces, to form what's called a*simplicial complex*. I think of this like building a LEGO set. When creating a LEGO set, you follow a list of instructions describing how to attach simple building blocks together. Once done, you can simply look at the LEGO set you built to see and understand its shape. In topology, you are sometimes given a list of instructions for how to glue higher-dimensional building block together. Once done, we can't understand the higher-dimensional shape by simply looking at it, but we can use mathematics to help us visualize the shape we built!