JCAP 20th anniversary retrospective: editorial

This year the Journal of Cosmology and Astroparticle Physics (JCAP) celebrates its 20th anniversary. “A journal by scientists for scientists” is the motto that has driven JCAP since its inception, which epitomises its philosophy of being an innovative and community-driven journal. Over the past two decades, JCAP has become one of the premier outlets for high-quality research, now publishing circa 800 papers per year, almost all of which are Open Access (either green or gold route), and with submissions originating from more than 60 countries around the world. JCAP encompasses theoretical, observational, and experimental areas as well as computation and simulation, and this special issue represents a testament to the role of the journal and its impact within the fields of cosmology and astroparticle physics. Over the years, JCAP has published influential papers on topics ranging from the early universe and dark matter to large-scale structure, gravitational waves and high-energy astrophysics, all of which are presented in this celebratory collection of the journal’s 20th year of publication.


Introduction
This year the Journal of Cosmology and Astroparticle Physics (JCAP) celebrates its 20th anniversary. This special issue is a testament to the role of the journal in the fields of cosmology and astroparticle physics and of JCAP's impact in these fields.
After the success of the Journal of High Energy Physics (JHEP) launched by SISSA in 1997, the Journal of Cosmology and Astroparticle Physics was created thanks to a partnership of SISSA and IoPP aimed at covering the new and rapidly expanding research area of cosmology and astroparticle physics: a field situated at the interface between astrophysics and particle physics, but for which there was not a dedicated journal. The founding editorial principle was, and still is, that the real value of scientific journals is the peer-review process.
Hector Rubinstein, JCAP's first scientific director, had several key insights well ahead of the times and timely still today, summarised by the journal's motto "A journal by scientists for scientists" which epitomises the philosophy of being an innovative, communitydriven journal.
The journal's aim and scope were defined only after extensive consultation with the interested community and should not be considered fixed, but evolving over time to adapt to changes in research trends. Full involvement of the scientific community continues: the community remains in charge of all aspects of the peer-review and publication processes. Editors and scientific directors establish the journal's policy and participate in all major decisions of the Journal.

High scientific quality and standards
On the premise that peer review is the most valuable asset of the journal, the JCAP editorial board is composed of world-class, distinguished and active scientists in the field, who are taking responsibility for the peer review process of every submission, thus guaranteeing the high quality of the resulting body of published articles. Today the editorial board is composed of more than 60 editors from about 20 countries and four continents (see the full editorial board, including past editors).

Fast and efficient publication
JCAP started as an online-only journal, which was futuristic then, although today is the norm. The average time from submission to acceptance is around 100 days, and less than a month from acceptance to publication. A peculiar and innovative feature back in 2003, which still characterises JCAP today, is the assignment of preprints to editors based on an algorithm conceived at Sissa, which avoids unnecessary delays in the initial phases of the review process. Moreover, ever since the journal's launch, the rigorous work of in-house professional typesetters, who format articles without affecting their scientific content and follow the process up to their publication, ensures efficient handling of high-quality files and metadata. The long-term preservation and findability of articles greatly rely on them.
Publishing of JCAP is a shared endeavor of SISSA Medialab (editorial and production process) and IoPP (marketing and distribution), with a focus on serving its scientific community.

A journal by scientists for scientists: "A success story"
Over the past two decades, JCAP has become one of the premier outlets for high-quality research in the areas of cosmology and astroparticle physics, now publishing about 800 papers per year (see figure 1), almost all of which available Open Access (either via the green or the gold route) and with submissions originating from more than 60 countries. As the collection of papers presented in this issue attests, JCAP has published influential papers on topics ranging from the early universe and dark matter to large-scale structure, gravitational waves and high-energy astrophysics. As envisioned at its inception, JCAP encompasses theoretical, observational, and experimental areas as well as computation and simulation.Cosmology and astroparticle physics have evolved dramatically since the beginning of 2003. Back then, the standard cosmological model had just been established, the evidence for dark energy was barely 4 years old, the angular power spectrum of the cosmic microwave background temperature anisotropies had just been mapped with enough resolution and sensitivity that -2 -JCAP06(2023)041 only the first peak was detected at high significance and the signature of a couple of other peaks was emerging.
Today the parameters of the standard cosmological model are measured with percent precision, objects at redshift of z = 1 are not any more rare "high redshift objects": the clustering of emission line galaxies and luminous red galaxies is routinely mapped at z ∼ 1 by multi-objects spectrographs. A new window in the cosmos was opened by the detection of gravitational waves signals.
It makes us proud that JCAP and its community have played a constructive role in this progress. For example the algorithm and Boltzmann code that has been used by the Planck collaboration as input to perform cosmological inference (CLASS) was presented in a JCAP publication, along with the advanced numerical approach for neutralino dark matter calculations (DARKSUSY) and the scientific case for major experiments such as Xenon1T dark matter experiment, the Einstein Telescope, the Simons Observatory, and also important observational results such as those of the Atacama cosmology Telescope. These are just few examples, there are many more in this issue.
On this 20th anniversary, we would like to express our gratitude to all our authors, reviewers, editors, and readers: the high scientific quality of the journal is built on your scientific rigour, efforts and your expertise. We know that every submitted article is the result of dedicated continuous effort, and that every referee report and editor report and decision are the result of time, dedication, profound expertise and exercise in scientific integrity.
We would also like to thank the publisher IoPP for two decades of fruitful collaboration and the exceptional editorial team at SISSA Medialab for their dedication and professionalism. The success you help build signifies that JCAP is in an ideal position to continue to disseminate and communicate the future developments of these research areas. We hope you enjoy the selection of articles this issue provides. Here's to the next 20 years of scientific excellence!