{"abstract":"We investigate 3d de Sitter axion wormholes that contribute to the no-boundary density matrix. We\r\nidentify cosmological necklace solutions: an infinite series of Euclidean saddles corresponding with\r\nrepeated bounces. This results in an unbound gravitational entropy, and a divergent path integral.\r\nTo remedy this, we study the gravitational path integral using a (mostly) Lorentzian lapse contour.\r\nWithin a minisuperspace steepest-descent analysis, we find that a single necklace dominates, leading\r\nto a finite entropy. A crucial element is to take into account an pa \u00d1 \u00b4aq redundancy in the FLRW\r\npath integral, where a is the scale factor. Surprisingly, the dominant solution is not purely Euclidean.\r\nIts entropy turns out to be independent of the axion flux, and equals the empty de Sitter entropy. We\r\nalso study higher-dimensional necklaces, sourced by either an axion flux or by Yang-Mills instantons,\r\nand argue for qualitatively similar results: the single necklace solution dominates along a Lorentzian\r\nlapse contour.","announced":"2026-10-12T00:00:00Z","authors":[{"affiliations":[],"name":"Andreas Blommaert"},{"affiliations":[],"name":"Jonah Kudler-Flam"},{"affiliations":[],"name":"Vladimir Narovlansky"},{"affiliations":[],"name":"Erez Y. Urbach"}],"categories":["hep-th","gr-qc"],"comments":"36 pages","doi":null,"id":"2610.00001","journal_ref":null,"license":"nonexclusive","pdf":"https://1xiv.org/pdf/2610.00001","primary_category":"hep-th","research_program":null,"status":"published","submitted":"2026-10-08T19:56:28Z","title":"The cosmological necklace problem","type":"research","updated":"2026-10-08T19:56:28Z","url":"https://1xiv.org/abs/2610.00001","versions":1}