A note on an application of discrete Morse theoretic techniques on the complex of disconnected graphs

Robin Forman’s highly influential 2002 paper A User’s Guide to Discrete Morse Theory presents an overview of the subject in a very readable manner. As a proof of concept, the author determines the topology (homotopy type) of the abstract simplicial complex of disconnected graphs of order n (which wa...

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Main Authors: Anupam Mondal, Pritam Chandra Pramanik
Format: Article
Language:English
Published: Elsevier 2025-06-01
Series:Examples and Counterexamples
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Online Access:http://www.sciencedirect.com/science/article/pii/S2666657X25000011
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author Anupam Mondal
Pritam Chandra Pramanik
author_facet Anupam Mondal
Pritam Chandra Pramanik
author_sort Anupam Mondal
collection DOAJ
description Robin Forman’s highly influential 2002 paper A User’s Guide to Discrete Morse Theory presents an overview of the subject in a very readable manner. As a proof of concept, the author determines the topology (homotopy type) of the abstract simplicial complex of disconnected graphs of order n (which was previously done by Victor Vassiliev using classical topological methods) using discrete Morse theoretic techniques, which are purely combinatorial in nature. The techniques involve the construction (and verification) of a discrete gradient vector field on the complex. However, the verification part relies on a claim that does not seem to hold. In this note, we provide a couple of counterexamples against this specific claim. We also provide an alternative proof of the bigger claim that the constructed discrete vector field is indeed a gradient vector field. Our proof technique relies on a key observation which is not specific to the problem at hand, and thus is applicable while verifying a constructed discrete vector field is a gradient one in general.
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spelling doaj-art-e623f654fb3e41649f8c475f5e59db042025-01-19T06:26:45ZengElsevierExamples and Counterexamples2666-657X2025-06-017100174A note on an application of discrete Morse theoretic techniques on the complex of disconnected graphsAnupam Mondal0Pritam Chandra Pramanik1Institute for Advancing Intelligence (IAI), TCG CREST, Kolkata – 700091, West Bengal, India; Academy of Scientific & Innovative Research (AcSIR), Ghaziabad – 201002, Uttar Pradesh, India; Corresponding author at: Institute for Advancing Intelligence (IAI), TCG CREST, Kolkata – 700091, West Bengal, India.Institute for Advancing Intelligence (IAI), TCG CREST, Kolkata – 700091, West Bengal, India; Department of Mathematics, National Institute of Technology (NIT) Durgapur, Durgapur – 713209, West Bengal, IndiaRobin Forman’s highly influential 2002 paper A User’s Guide to Discrete Morse Theory presents an overview of the subject in a very readable manner. As a proof of concept, the author determines the topology (homotopy type) of the abstract simplicial complex of disconnected graphs of order n (which was previously done by Victor Vassiliev using classical topological methods) using discrete Morse theoretic techniques, which are purely combinatorial in nature. The techniques involve the construction (and verification) of a discrete gradient vector field on the complex. However, the verification part relies on a claim that does not seem to hold. In this note, we provide a couple of counterexamples against this specific claim. We also provide an alternative proof of the bigger claim that the constructed discrete vector field is indeed a gradient vector field. Our proof technique relies on a key observation which is not specific to the problem at hand, and thus is applicable while verifying a constructed discrete vector field is a gradient one in general.http://www.sciencedirect.com/science/article/pii/S2666657X25000011Disconnected graphSimplicial complexDiscrete Morse theoryGradient vector fieldHomotopy
spellingShingle Anupam Mondal
Pritam Chandra Pramanik
A note on an application of discrete Morse theoretic techniques on the complex of disconnected graphs
Examples and Counterexamples
Disconnected graph
Simplicial complex
Discrete Morse theory
Gradient vector field
Homotopy
title A note on an application of discrete Morse theoretic techniques on the complex of disconnected graphs
title_full A note on an application of discrete Morse theoretic techniques on the complex of disconnected graphs
title_fullStr A note on an application of discrete Morse theoretic techniques on the complex of disconnected graphs
title_full_unstemmed A note on an application of discrete Morse theoretic techniques on the complex of disconnected graphs
title_short A note on an application of discrete Morse theoretic techniques on the complex of disconnected graphs
title_sort note on an application of discrete morse theoretic techniques on the complex of disconnected graphs
topic Disconnected graph
Simplicial complex
Discrete Morse theory
Gradient vector field
Homotopy
url http://www.sciencedirect.com/science/article/pii/S2666657X25000011
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