Download this article
 Download this article For screen
For printing
Recent Issues
Volume 18
Volume 16
Volume 15
Volume 14
Volume 13
Volume 12
Volume 11
Volume 10
Volume 9
Volume 8
Volume 6+7
Volume 5
Volume 4
Volume 3
Volume 2
Volume 1
The Journal
About the journal
Ethics and policies
Peer-review process
 
Submission guidelines
Submission form
Editorial board
 
Subscriptions
 
ISSN 2640-7345 (online)
ISSN 2640-7337 (print)
Author Index
To Appear
 
Other MSP Journals
This article is available for purchase or by subscription. See below.
Convex geometry over ordered hyperfields

James Maxwell and Ben Smith

Vol. 22 (2025), No. 1-2, 67–128
Abstract

We initiate the study of convex geometry over ordered hyperfields. We define convex sets and halfspaces over ordered hyperfields, presenting structure theorems over hyperfields arising as quotients of fields. We prove hyperfield analogues of Helly, Radon and Carathéodory theorems. We also show that arbitrary convex sets can be separated via hemispaces. Comparing with classical convexity, we begin classifying hyperfields for which halfspace separation holds. In the process, we demonstrate many properties of ordered hyperfields, including a classification of stringent ordered hyperfields.

PDF Access Denied

We have not been able to recognize your IP address 18.97.14.89 as that of a subscriber to this journal.
Online access to the content of recent issues is by subscription, or purchase of single articles.

Please contact your institution's librarian suggesting a subscription, for example by using our journal-recom­mendation form. Or, visit our subscription page for instructions on purchasing a subscription.

You may also contact us at contact@msp.org
or by using our contact form.

Or, you may purchase this single article for USD 40.00:

Keywords
hyperfield, convexity, halfspace, hemispace, tropical
Mathematical Subject Classification
Primary: 16Y20, 52A30
Secondary: 12J15, 52A35, 52A40
Milestones
Received: 22 March 2024
Revised: 27 March 2025
Accepted: 11 August 2025
Published: 18 September 2025
Authors
James Maxwell
School of Mathematics
University of Bristol
Bristol
United Kingdom
Ben Smith
School of Mathematical Sciences
Lancaster University
Fylde College
Lancaster
United Kingdom