How to Write a Journal of Cosmology and Astroparticle Physics Cover Letter

Source: Manusights editorial framework for JCAP covering notes, built on JCAP/SISSA author instructions

The order matters because JCAP editors triage for scope match and routing signal, not literary polish. A note that names the result, places it in a lane, and confirms the arXiv id is faster to route than one that opens with background.

This is the single most JCAP-specific mechanic, and the one researchers from non-physics backgrounds miss. JCAP requires an arXiv article id at submission, and the submitted version must be the same as the arXiv version. You post first, you submit second, and the two must match. If you revise the paper after posting, repost to arXiv and submit that version, not an unposted local edit.

State the arXiv id in any covering note you do write, and treat the preprint as the canonical version: disclose the arXiv link in the note so the editorial office can verify it without a round trip. Authors who want a structured read on this can run the JCAP scope and routing check before posting.

This arXiv-first culture is normal across cosmology and astroparticle physics; it is the opposite of the embargo-conscious, cover-letter-heavy norms at clinical and Cell Press journals, which is why the workflow surprises authors crossing over from those fields.

On revision the cover letter stops being optional. JCAP's instructions require a cover letter that accompanies your reply to the referee report and clearly describes all the changes relative to the previous version, stating whether or not you addressed each editor and referee request. Editors read this before re-reading the manuscript, so it is where a revision is won or lost.

Avoid revision letters that say "we have addressed all comments" and leave the editor to find the changes.
Use revision letters that quote each comment, give a direct response, and point to the exact line, figure, or section that changed.

Keep the reply point-by-point. Number it to match the referee's numbering. When you disagree with a referee, say so plainly and give the physics reason rather than burying the disagreement. A traceable, navigable reply is the strongest signal that the revision is real and not cosmetic.

The opening sentence of any covering note is where scope and routing either land or stall. The one-line rule:

Avoid openers that list the data and pipeline you used.
Use openers that name the cosmology or astroparticle result and the lane it belongs in.

Compare these two full examples.

Weak opener:

"We analyze Planck and BAO data with an MCMC pipeline to constrain cosmological parameters in an extended model."

Why it fails: there is no result, no lane, and no reason a particular editor should read it. It reads like a methods summary, and the keyword routing has nothing to anchor to.

Stronger opener:

"We show that current cosmic microwave background and large-scale structure data already exclude the simplest early dark energy resolution of the Hubble tension at the level our forecast predicted, sharpening which extended models remain viable. The result sits squarely in JCAP's CMBR and large-scale-structure lanes."

Why it works: the cosmology result is a direct claim, it names the subject lanes JCAP routes on, and an editor can see the expertise the paper needs before opening figure one. That is exactly the scope-and-routing match JCAP's keyword software is trying to make.

JCAP assigns an editor from your 2 to 4 keywords, drawn from a fixed list and weighted by relevance. The lanes the journal names publicly are the ones to map your work onto.

Source: JCAP scope and subject areas, IOP and SISSA (accessed June 2026)

JCAP papers do not normally exceed 50 pages, and editors may ask longer theory or simulation papers to shorten. If you are unsure whether your work is JCAP-shaped at all, the honest test is whether removing the cosmology or astroparticle physics framing leaves a paper that belongs in a general physics venue. If it does, the keyword routing will struggle and a closer-fit journal may be the better target.

Three things belong in or alongside a JCAP submission, even when the cover letter itself is light.

The arXiv id and version match. Mandatory at submission; the submitted version must equal the arXiv version. Name the id in your covering note.

Originality and exclusivity. JCAP acceptance criteria are scientific quality, originality, and relevance. State plainly that the manuscript is original, not published previously, and not under consideration elsewhere. JCAP does not ask for suggested referees in its standard submission flow, so do not pad the note with a referee list it has no field for.

Competing interests and authorship. Confirm all authors approved the submission and declare competing interests. When there are none, the standard wording is: "The authors declare no competing interests."

A few mechanics worth knowing while you draft. JCAP is published by IOP Publishing and SISSA, runs its editorial office and submission portal at SISSA (jcap.sissa.it), and is hybrid open access: a subscription route at no author charge, or a gold open-access option under CC BY for an article publication charge. None of that belongs in the cover letter itself, but it shapes the open-access and license language you confirm at submission.

Speaking from the editor's side of the desk: when a JCAP submission lands, the first judgment is not about sophistication, which is assumed in a specialist cosmology and astroparticle physics journal. It is about routing. The keyword-assigned editor is asking, in the abstract and the first figures, one question: is this paper in my lane, and is the cosmology or astroparticle claim real?

If the keywords point one way and the paper reads like general theory with a thin cosmology coating, the routing is already strained and the editor either reassigns or returns it. The submissions that move fastest are the ones where keywords, abstract, and the first figures all agree on what the paper is and which expert should judge it.

If you want a second read on whether your scope and routing signals agree, a JCAP scope and journal fit check scores them before you upload.

In our pre-submission review work with Journal of Cosmology and Astroparticle Physics manuscripts, four scope-and-routing patterns predict friction at the JCAP desk more reliably than anything in the analysis itself. Each is testable against your own submission before you upload.

The paper is general astrophysics with no cosmology or astroparticle angle. This is the single most common JCAP fit failure we see. A galaxy-formation or stellar-population study with a sentence gesturing at cosmology is not a JCAP paper; the keyword routing has nowhere to send it, and the editor reads the abstract and concludes the work belongs in The Astrophysical Journal or Monthly Notices of the Royal Astronomical Society.

The fix is to ask whether the cosmology or astroparticle result is the point of the paper or its decoration, and if it is decoration, to target a broad astronomy journal instead.

A phenomenology paper has no observational or experimental connection. Across JCAP manuscripts coming through pre-submission review, dark-matter and early-universe phenomenology papers stall when the model is never tied to a measurement, a forecast, or a falsifiable prediction. JCAP's relevance criterion expects the cosmology or astroparticle physics to connect to data, even forecast data. We apply a blunt test: cross out every sentence that mentions an observable, a data set, or an experiment.

If the remaining paper is purely formal model-building with no contact to the universe, the relevance screen is at risk and Physical Review D may be the closer home.

Keyword selection and subject lane do not match the manuscript. Many otherwise solid JCAP submissions choose vague or mismatched keywords, so the software assigns an editor whose expertise is one lane away. The abstract says large-scale structure; the keywords lead with a generic theory tag; the assigned editor is a dark-matter specialist. That mismatch slows the first read and weakens the fit case. The strongest submissions weight the keyword that matches the paper's actual lane highest, so routing lands on the closest expert.

The submitted version does not match the arXiv version, or no arXiv id is given. A surprising number of JCAP submissions trip the mandatory arXiv rule: the arXiv id is missing, or the uploaded manuscript differs from the posted preprint after a late local edit. This is a process flag the editorial office catches early, and process gaps invite a closer look at everything else. The fix is mechanical: post the final version to arXiv, then submit that exact version and name the id in your covering note.

These four are all fixable before submission, and they are exactly what a JCAP cover letter and scope check evaluates. The pattern that holds across all four: at JCAP the editor is judging whether the cosmology or astroparticle physics is the discovery and whether your routing signals point to the right expert, not whether your prose is polished.

JCAP sits at the interface of particle physics and cosmology, and choosing it over a neighbor is a scope decision more than a prestige one.

• Physical Review D is the natural home for physics-theoretical cosmology and formal gravitation or particle-cosmology theory, especially when the work is model-building with limited observational contact. If your paper never touches data, PRD is often the closer fit.

• Physical Review Letters wants a single, broad, dramatic result for the whole physics community in a short format.

A focused cosmology claim with wide reach can go to PRL; a full astroparticle analysis belongs in JCAP.

• The Astrophysical Journal and Monthly Notices of the Royal Astronomical Society cover the full breadth of astronomy, including observational cosmology, galaxy surveys, and large-scale structure.

Observational survey results often land there rather than at JCAP, which leans toward the cosmology-and-astroparticle interface.

• Astronomy and Astrophysics similarly carries broad astrophysics and observational cosmology; choose it over JCAP when the work is astronomical first and cosmological second.

• European Physical Journal C overlaps with JCAP on particle-astrophysics and particle-cosmology theory; the choice usually comes down to which community you want as your primary readership.

For target-fit before you write the note, the JCAP submission guide and the JCAP journal fit profile cover scope, keywords, and mechanics; the Physical Review D cover letter guide is the natural cross-check if your work is theory-forward, is Physical Review D a good journal helps weigh the PRD alternative, and the best astrophysics journals overview maps the wider venue landscape.

How this page was created: this guide combines JCAP's published author instructions and scope pages at SISSA, the IOP About-the-journal page, JCAP's referee and revision guidance, and Manusights pre-submission review patterns from cosmology and astroparticle physics manuscripts. We did not access a private SISSA editorial account; the covering-note guidance is built from public JCAP and IOP materials and the editorial routing pattern we see across pre-submission reviews.

The named failure patterns above are drawn from our review data, not from any single submission, and no specific editor or referee is named because rosters change and per-submission attribution is not something this page can verify.