Entropy became one of the organizing concepts of 21st-century theoretical physics. This page quantifies how much of that is real topical concentration and how much is ordinary publication inflation — and is explicit about which numbers were retrieved and which were reasoned.
Annual output in the entanglement-entropy subfield — the fastest-growing and best-defined strand of the entropy literature. Every value here is an estimate, so the chart shows a per-year range rather than a line pretending to precision it does not have.
The shape matters more than the absolute values. Output rises roughly an order of magnitude between 2006 and 2022, then plateaus — the signature of a subfield that has matured rather than one still compounding.
The plateau is not a decline in interest. It reflects diffusion: entropy work increasingly appears under quant-ph and cond-mat rather than hep-th, so a category-scoped count undercounts the topic's real reach in later years.
These are hard counts from arXiv's own submission statistics. They matter because they establish that the home categories of gravitational entropy work were not themselves growing.
The comparison is the finding. Entanglement-entropy output rose from dozens to several hundred papers a year while hep-th and gr-qc stayed flat. The topic therefore gained share within its own categories — this is concentration, not inflation.
Faster-growing quant-ph and cond-mat absorbed much of the later entropy work, which is why the two literatures below drifted apart.
Running total of the estimated annual figures. The widening band is the honest part: uncertainty compounds along with the count.
Subfield activity and the datable results that moved it. The years are hard; the band widths are qualitative and carry no count.
2006 — Ryu–Takayanagi (hep-th/0603001) tied entanglement entropy in a CFT to the area of a minimal surface in AdS, making entropy a computable bridge between quantum information, field theory, and gravity.
2010 — Verlinde's entropic gravity produced a fast burst of derivative and rebuttal papers, then plateaued as a distinct topic.
2012 — The AMPS firewall reignited the information paradox. 2015 — quantum extremal surfaces supplied the technical bridge. 2019–20 — islands and replica wormholes delivered the steepest citation trajectory of the period.
Annual publication counts lag a result by two to three years. Citation curves respond within months, which makes them the better instrument for locating a surge.
One journal is large enough to distort any keyword search for entropy — and most of its content is not theoretical physics.
Exclude Entropy (MDPI) as a source field before counting, or restrict to its physics sections. Never treat “papers in Entropy” as a proxy for “entropy papers.” Note that the sole prior bibliometric study of this topic was itself published in that journal and identifies it as a major node in its own citation network.
Four mechanisms account for essentially all disagreement between databases:
hep-th + gr-qc + quant-ph is counted up to three times in any category sum.cond-mat and quant-ph statistical-mechanics work; Web of Science and Scopus cover journals but miss arXiv-only preprints.“Theoretical physics” also has no clean database boundary. Entanglement entropy spans hep-th, gr-qc, quant-ph, cond-mat, and math-ph; reasonable analysts will draw the line differently and change the grand total by tens of percent.
title "entanglement entropy", title "black hole entropy", title "island" and title "entropy" — reading the JSON hits.total field and exporting per-year histograms via the earliest_date facet. Highest-value next step by a wide margin.cond-mat/quant-ph strand that INSPIRE under-covers.