{"id":"b2434bf7-2187-4752-a82f-be8c0beb06b9","arxiv_id":"2603.21182","paper_version":2,"verdict":"UNVERDICTED","confidence":"LOW","novelty_score":5.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":2,"one_line_summary":"The littlest inverse seesaw model can reproduce the observed baryon asymmetry via resonant or ARS leptogenesis in sizable parameter regions without extra free parameters.","lead":"This paper shows that the littlest inverse seesaw model can generate the observed matter-antimatter imbalance of the universe via two standard low-scale leptogenesis routes, without adding free parameters. It matters because a highly constrained neutrino model that also explains baryogenesis is a rare, testable target for particle physics.","discovery_kind":"extension","skeptic_critique":{"model":"grok-4.5","headline":"RGE-induced mass splittings of the precise size/sign needed for resonant leptogenesis, while preserving the two-parameter neutrino fit, remain the least secure and unverifiable step from the abstract alone.","rationale":"The reader’s weakest_assumption correctly isolates the load-bearing step: whether RGE alone supplies the required splittings without spoiling the two-parameter structure. With only the abstract available, no further technical inconsistency can be confirmed or refuted; the concern remains open. Consequently the verdict stays UNVERDICTED and confidence low, pending full-text inspection of RGE flows, parameter scans and Boltzmann evolution. No machine-checked proofs, code or data are indicated that would raise the evidentiary bar.","tokens_in":1952,"tokens_out":477,"duration_ms":13440,"concrete_test":"Obtain the full text; extract the RGE equations and high-scale boundary conditions for the sterile mass matrix in the two scenarios; recompute low-scale ΔM for the benchmark points claimed to yield Y_B ≈ 8.7×10^{-11}; verify that the identical two free parameters still reproduce the six neutrino observables within experimental precision and that no extra soft-breaking or threshold parameters were introduced.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central claim requires that RGE evolution alone generates mass splittings ΔM among initially exactly degenerate pseudo-Dirac sterile pairs that fall into the resonant window (ΔM ∼ Γ) for efficient CP asymmetry, without extra free parameters and without spoiling the two-parameter fit to the six neutrino observables already claimed by LIS. The abstract asserts this occurs in sizable regions for both the resonant (scenarios with initial degeneracy) and ARS (hierarchical) cases, yet supplies no RGE spectra, boundary conditions, resulting ΔM/M values, washout factors, or Boltzmann solutions. If the radiatively generated splitting is generically outside the resonant window, has the wrong sign, or forces additional soft parameters or retuning to keep the light-neutrino fit, the “no additional free parameters” assertion fails. The ARS branch is less sensitive to exact degeneracy but still demands that the same two parameters that fit oscillation data also produce the observed Y_B via oscillations.","agreement_with_reader":"agree"},"referee_report":{"model":"grok-4.5","summary":"The manuscript studies leptogenesis within the littlest inverse seesaw (LIS) model, which is presented as the first low-scale seesaw framework that fits all six neutrino-sector observables with only two effective free parameters. Two scenarios are considered: (i) initially exactly degenerate pseudo-Dirac sterile-neutrino pairs that acquire small mass splittings through renormalization-group evolution (RGE), enabling resonant leptogenesis among different pairs; and (ii) hierarchical pseudo-Dirac pairs in which leptogenesis proceeds via sterile-neutrino oscillations (ARS mechanism). The abstract asserts that the observed baryon asymmetry is reproduced in sizable regions of parameter space without introducing free parameters beyond those already fixed by the LIS neutrino fit.","tokens_in":2148,"tokens_out":818,"duration_ms":15130,"significance":"If the claims hold under full scrutiny, the work would establish LIS as a highly predictive low-scale leptogenesis setting in which the same two parameters that describe oscillation data also generate the observed baryon asymmetry. That combination of minimality, low-scale accessibility, and dual coverage of neutrino data and Y_B would be of clear interest for model-building and for experimental tests of sterile neutrinos. The explicit use of RGE-induced splittings (rather than ad-hoc soft terms) and the ARS branch are potentially valuable technical contributions, provided they are quantitatively demonstrated.","major_comments":[{"comment":"The central load-bearing claim—that RGE evolution alone generates mass splittings of the size and sign required for efficient resonant leptogenesis (ΔM ∼ Γ) among initially exactly degenerate pseudo-Dirac pairs, while preserving the two-parameter fit to the six neutrino observables—is asserted in the abstract but is not supported by any RGE spectra, boundary conditions, resulting ΔM/M or ΔM/Γ values, or washout estimates in the material available for review. Without these, the ‘no additional free parameters’ assertion cannot be verified and remains the weakest link of the resonant scenarios.","section":null},{"comment":"The abstract states that the observed baryon asymmetry is reproduced in ‘sizable regions’ of parameter space for both resonant and ARS cases, yet supplies no Boltzmann equations, scan ranges, priors, success fractions, or uncertainty quantification. The claim that Y_B is a genuine output of the two LIS parameters therefore cannot be assessed from the abstract alone; quantitative results are required before the central claim can be accepted.","section":null},{"comment":"For the ARS (hierarchical) branch the same two parameters must simultaneously fit the light-neutrino data and produce the observed Y_B via oscillations. The abstract does not indicate the mass hierarchy, oscillation frequencies, or CP-violating phases that realize this, nor whether any residual tuning is needed. Explicit demonstration that the neutrino-fit parameters automatically lie in the successful ARS window is load-bearing and currently missing.","section":null}],"minor_comments":[{"comment":"The two effective free parameters of the LIS neutrino fit are never named or defined in the abstract; a brief identification (or reference to the defining equations of the parent LIS construction) would improve readability.","section":null},{"comment":"The phrases ‘enhancing leptogenesis’ and ‘sizable regions’ are qualitative; once quantitative results exist they should be replaced by concrete intervals or success fractions.","section":null}],"recommendation":"uncertain","confidential_remarks":"Only the abstract was available for this review; the full text of arXiv:2603.21182 was not supplied. The recommendation is therefore necessarily ‘uncertain’ and provisional. If the full manuscript contains the missing RGE spectra, Boltzmann solutions, and parameter scans, a re-review with access to the complete text would be appropriate. The stress-test concern about RGE-generated splittings is real on the basis of the abstract and should be checked carefully once the full paper is in hand."},"author_rebuttal":null,"desk_editor":{"model":"grok-4.5","letter":"The one thing worth knowing is that this abstract asserts the littlest inverse seesaw can reproduce the observed baryon asymmetry in sizable regions of its existing two-parameter space, either by RGE-induced mass splittings that open resonant leptogenesis among initially degenerate pseudo-Dirac pairs or by ARS oscillations for hierarchical pairs, with no extra free parameters added. If the numerics hold, that is a clean, predictive result inside an already tightly constrained low-scale seesaw.\n\nWhat is actually new is the concrete application: LIS was already claimed to fit all six neutrino observables with two parameters, and the paper shows those same parameters can also source the right Y_B. The two scenarios are standard tools (resonant and ARS) put to work inside this specific model without inventing new knobs. That is a legitimate extension, not a paradigm shift, and the framing is honest about keeping the parameter count fixed.\n\nThe soft spot is real and load-bearing given that we only have the abstract: whether RGE alone generates mass splittings of the precise size and sign needed for the resonant window without spoiling the light-neutrino fit or forcing retuning. No spectra, no ΔM/Γ values, no washout factors, no Boltzmann solutions, and no scan ranges are visible, so the “sizable regions” claim cannot be checked. The ARS branch is less delicate on exact degeneracy but still requires the same two parameters to deliver the observed asymmetry. The stress-test concern lands; if those RGE numbers do not work out cleanly, the no-extra-parameters assertion fails. Everything else looks coherent on its face.\n\nThis is for neutrino-model and leptogenesis people who care about minimality and low-scale predictivity. It deserves a serious referee once the full calculations are on the table. I would send it to peer review rather than desk-reject; the setup is tight enough that the numerics are worth inspecting. Not something I would cite or bring to reading group on the abstract alone, but worth a look when the PDF appears.","headline":"Abstract-only claim that the two-parameter LIS already yields the observed baryon asymmetry via RGE resonant or ARS leptogenesis; the RGE splitting step is the unverified linchpin.","tokens_in":2781,"tokens_out":521,"would_cite":false,"duration_ms":17405,"reading_group":"maybe","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":["14.60.Pq","14.60.St","11.30.Fs","98.80.Cq"],"model":"grok-4.5","headline":"The littlest inverse seesaw model can generate the observed baryon asymmetry with no extra free parameters, via RGE-driven resonant leptogenesis or ARS oscillations.","keywords":["littlest inverse seesaw","leptogenesis","resonant leptogenesis","ARS mechanism","pseudo-Dirac sterile neutrinos","baryon asymmetry","RGE effects","neutrino masses"],"falsifier":"A full numerical scan of the RGE-evolved mass matrix that shows either no viable resonant window or that every window that yields the observed baryon asymmetry forces one of the six neutrino observables outside its experimental range.","tokens_in":2806,"feed_emoji":"⚛️","tokens_out":773,"duration_ms":7396,"temperature":0.7,"pith_summary":"The littlest inverse seesaw model already fits all six neutrino observables with only two free parameters. This paper asks whether the same minimal setup can also produce the matter-antimatter imbalance of the Universe. It studies two concrete realizations of leptogenesis that stay inside those two parameters. In one case the two pairs of nearly degenerate sterile neutrinos start exactly mass-degenerate and receive tiny splittings only from renormalization-group running, allowing resonant leptogenesis among the pairs. In the other case the pairs are hierarchical and leptogenesis proceeds through sterile-neutrino oscillations (the ARS mechanism). Both routes are shown to reproduce the observed baryon asymmetry over sizable regions of the remaining parameter space, without enlarging the free-parameter count. The result means a highly predictive low-scale seesaw can simultaneously explain neutrino data and the cosmic baryon asymmetry.","feed_headline":"Two-parameter seesaw generates the baryon asymmetry","feed_subtitle":"RGE-driven resonant or ARS leptogenesis works without adding free parameters","key_machinery":"Two pseudo-Dirac sterile-neutrino pairs whose mass spectrum is either initially degenerate (with RGE-generated splittings that enable resonant leptogenesis) or hierarchical (allowing ARS oscillation leptogenesis), all while preserving the original two-parameter fit to neutrino data.","core_discovery":"Within the two-parameter littlest inverse seesaw model the observed baryon asymmetry is successfully generated either by resonant leptogenesis driven by RGE-induced mass splittings of initially degenerate pseudo-Dirac sterile-neutrino pairs, or by ARS leptogenesis with hierarchical pairs, without introducing any additional free parameters.","pith_inferences":["Because the model is so tightly constrained, a future precision measurement of any of the six neutrino parameters that falls outside the two-parameter prediction would simultaneously rule out both the neutrino fit and the leptogenesis scenarios.","Collider or beam-dump searches for the sterile neutrinos would directly test the mass and mixing ranges required for successful leptogenesis in this framework.","The RGE-only splitting mechanism could be checked by comparing the high-scale and low-scale mass matrices against the precise requirements of resonant leptogenesis."],"forward_implications":["Low-scale leptogenesis becomes possible inside a seesaw model that already accounts for all neutrino data with only two free parameters.","Both resonant and ARS mechanisms remain viable without enlarging the free-parameter count of the littlest inverse seesaw.","Sizable regions of the two-parameter space simultaneously fit neutrino observables and the measured baryon asymmetry.","The same sterile-neutrino spectrum that generates light-neutrino masses can also source the cosmic matter-antimatter asymmetry."],"fun_headline_variants":["Two-parameter LIS model yields baryon asymmetry via RGE or ARS","RGE-split PD pairs enable resonant leptogenesis in LIS framework","Hierarchical sterile pairs drive ARS leptogenesis in two-param seesaw","LIS realizes observed baryon asymmetry without extra free parameters","Resonant or ARS paths generate baryon asymmetry in littlest inverse seesaw"],"cache_read_input_tokens":2304,"weakest_assumption_plain":"That renormalization-group running alone produces mass splittings of exactly the size and sign needed for efficient resonant leptogenesis among the initially degenerate pairs, without spoiling the two-parameter neutrino fit.","fun_headline_variants_meta":{"raw":{"variants":["Two-parameter LIS model yields baryon asymmetry via RGE or ARS","RGE-split PD pairs enable resonant leptogenesis in LIS framework","Hierarchical sterile pairs drive ARS leptogenesis in two-param seesaw","LIS realizes observed baryon asymmetry without extra free parameters","Resonant or ARS paths generate baryon asymmetry in littlest inverse seesaw"]},"model":"grok-4.5","effort":"low","cost_usd":0.004142,"raw_usage":{"total_tokens":1211,"prompt_tokens":685,"num_sources_used":0,"completion_tokens":97,"cost_in_usd_ticks":41420000,"prompt_tokens_details":{"text_tokens":685,"audio_tokens":0,"image_tokens":0,"cached_tokens":256},"completion_tokens_details":{"audio_tokens":0,"reasoning_tokens":429,"accepted_prediction_tokens":0,"rejected_prediction_tokens":0}},"tokens_in":685,"tokens_out":97,"duration_ms":4430,"temperature":1.0,"reasoning_tokens":429,"cache_read_input_tokens":256,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-07-13T20:58:00.916575+00:00","model_set":{"reader":"grok-4.5"},"falsifier":"A full numerical scan of the RGE-evolved mass matrix that shows either no viable resonant window or that every window that yields the observed baryon asymmetry forces one of the six neutrino observables outside its experimental range.","supporting_citations":[],"review_version":1}