arxiv: 2509.06892 · v2 · submitted 2025-09-08 · ✦ hep-ph · astro-ph.CO

Asymmetric Cannibal Dark Matter: Constraints from Neutron Star

Ujjal Kumar Dey , Sourav Gope This is my paper

Pith reviewed 2026-05-18 18:05 UTC · model grok-4.3

classification ✦ hep-ph astro-ph.CO

keywords asymmetric dark mattercannibal dark matterneutron starsdark matter capturenumber-changing interactionsZ3 symmetrystellar heatingthermal signatures

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The pith

Asymmetric cannibal dark matter depletes inside neutron stars and produces detectable heat.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper shows that asymmetric dark matter captured by neutron stars can undergo number-changing 3-to-2 self-interactions when a Z3 symmetry is present in the dark sector. These cannibalistic processes grow efficient at the high densities reached in the stellar core, removing dark matter particles and releasing energy that raises the star's temperature above ordinary cooling curves. The resulting thermal excess remains visible in old isolated neutron stars even when annihilation or kinetic heating are also active, and it opens a wider window of dark matter masses and couplings that stay consistent with data. A sympathetic reader would care because temperature measurements of nearby old neutron stars could then serve as a new window onto dark-sector self-interactions that are otherwise difficult to test.

Core claim

A Z3 symmetry permits 3→2 number-changing self-interactions within the dark sector. At the high dark matter densities that accumulate in the neutron-star core these cannibalistic reactions become efficient, depleting the dark matter population and converting the lost number into thermal energy. The extra heat raises the surface temperature of relatively old neutron stars above standard cooling expectations, yielding observable signatures that future infrared telescopes could detect. This cannibal heating dominates other mechanisms such as annihilation or kinetic heating in portions of parameter space and thereby allows a broader range of dark matter masses and Standard Model couplings to be

What carries the argument

The Z3 symmetry that enables 3→2 cannibalistic reactions, which deplete the dark matter number density at high concentrations inside the neutron star core and release the lost energy as heat.

If this is right

Detectable thermal signatures appear in old neutron stars that future infrared telescopes could observe.
Cannibal heating can exceed the contribution from dark matter annihilation and kinetic heating over parts of the parameter space.
A wider range of dark matter masses and couplings to the Standard Model remains viable.
Neutron star temperature data can supply new constraints on asymmetric dark matter with number-changing self-interactions.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

Temperature surveys of nearby old neutron stars could separate this cannibal signature from other dark matter heating channels by its dependence on capture rate and core density.
The same depletion mechanism might be tested in other dense environments such as the cores of white dwarfs or the early universe.
Absence of the predicted heat excess would tighten bounds on the strength of the 3-to-2 coupling even if the model is not ruled out entirely.

Load-bearing premise

That 3-to-2 cannibalistic reactions become increasingly efficient at the high dark matter densities inside the neutron star core and therefore cause significant population depletion.

What would settle it

Infrared observations of old isolated neutron stars that show temperatures matching only standard cooling plus annihilation and kinetic heating, with no excess in the regions of parameter space where the cannibal mechanism is predicted to dominate.

read the original abstract

Asymmetric dark matter can be efficiently captured by neutron stars via elastic scattering with nucleons and dark matter self scattering. The accumulated dark matter thermalizes and concentrates in the stellar interior, forming a dark matter core. In this work, we propose a novel framework in which a $\mathbb{Z}_3$ symmetry allows for number-changing self-interactions of the form $3 \rightarrow 2$ within the dark sector. These cannibalistic reactions become increasingly efficient at high dark matter densities, leading to a significant depletion of the dark matter population in the stellar core. This number depletion heats up the neutron star above the standard cooling expectations, yielding observable thermal signatures in relatively old, isolated neutron stars, potentially detectable via future infrared telescopes. We show that even in the presence of other heating mechanisms, e.g. dark matter annihilation and kinetic heating, the cannibal heating dominates for certain parameter space. We demonstrate that the cannibal heating can predict detectable heating signatures in old neutron stars, thereby allowing a broader range of viable dark matter masses and couplings to the Standard Model.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Desk Editor's Note private letter to a colleague

The paper proposes Z3 cannibal DM heating old neutron stars via 3→2 depletion to relax mass and coupling bounds, but the energy transfer timescale from DM to baryons looks like the main open question.

read the letter

The central point here is that a Z3-symmetric asymmetric DM model with efficient 3→2 cannibal reactions can deplete the accumulated DM inside a neutron star and convert that into observable heating, even when annihilation and kinetic heating are also present. This is meant to let weaker DM-nucleon couplings and a broader mass range survive existing NS cooling limits while still producing detectable infrared signals in old isolated stars.

Referee Report

2 major / 1 minor

Summary. The paper proposes asymmetric cannibal dark matter with a Z3 symmetry permitting 3→2 number-changing self-interactions in the dark sector. These reactions are claimed to become efficient at high DM densities inside neutron star cores, depleting the accumulated DM population and releasing energy that heats the star above standard cooling curves. The authors argue this cannibal heating dominates over annihilation and kinetic heating in parts of parameter space, producing detectable thermal signatures in old isolated neutron stars and thereby allowing a wider range of viable DM masses and nucleon scattering cross sections.

Significance. If the mechanism and energy-transfer timescales are shown to work as described, the result would provide a new astrophysical probe for asymmetric dark matter models and could relax existing neutron-star heating bounds, opening previously excluded regions of DM mass and coupling space for future infrared observations.

major comments (2)

[Abstract] Abstract / strongest claim: the headline assertion that cannibal heating dominates and permits weaker SM couplings assumes that energy released by 3→2 processes is efficiently transferred to the NS baryons on timescales shorter than the ~10^8–10^9 yr cooling age of the old neutron stars under consideration. Because the same nucleon scattering cross section governs both capture (setting the DM density) and subsequent thermalization/heat transfer, the thermalization time can exceed the NS cooling time in the low-cross-section regime where the paper claims viable weaker couplings; no quantitative comparison of these timescales against the claimed viable window is provided.
[Mechanism section (inferred from abstract description of number-changing self-interactions)] The central derivation of density-dependent 3→2 efficiency leading to net population depletion and observable heating lacks an explicit rate equation or Boltzmann-equation treatment showing how the process converts rest-mass energy into transferable kinetic energy while remaining consistent with the capture rate assumptions drawn from prior literature.

minor comments (1)

[Parameter definitions] Clarify the precise definition and units of the cannibal self-interaction strength parameter introduced for the 3→2 cross section.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their careful reading of our manuscript and for the constructive comments. We address each major point below and describe the revisions we will implement.

read point-by-point responses

Referee: [Abstract] Abstract / strongest claim: the headline assertion that cannibal heating dominates and permits weaker SM couplings assumes that energy released by 3→2 processes is efficiently transferred to the NS baryons on timescales shorter than the ~10^8–10^9 yr cooling age of the old neutron stars under consideration. Because the same nucleon scattering cross section governs both capture (setting the DM density) and subsequent thermalization/heat transfer, the thermalization time can exceed the NS cooling time in the low-cross-section regime where the paper claims viable weaker couplings; no quantitative comparison of these timescales against the claimed viable window is provided.

Authors: We agree that a direct comparison of thermalization and cooling timescales is required to support the claim that weaker couplings remain viable. In the revised manuscript we will add an explicit calculation of the DM-nucleon thermalization time (using the same cross section that sets the capture rate) and compare it to the 10^8–10^9 yr cooling ages of the isolated neutron stars we consider. The new analysis will be placed in the mechanism section and will demonstrate that, within the region where cannibal heating dominates, thermalization remains faster than the cooling timescale. revision: yes
Referee: [Mechanism section (inferred from abstract description of number-changing self-interactions)] The central derivation of density-dependent 3→2 efficiency leading to net population depletion and observable heating lacks an explicit rate equation or Boltzmann-equation treatment showing how the process converts rest-mass energy into transferable kinetic energy while remaining consistent with the capture rate assumptions drawn from prior literature.

Authors: We acknowledge that an explicit Boltzmann-equation treatment would improve clarity and rigor. In the revised manuscript we will insert a dedicated subsection that presents the rate equations for the Z3-symmetric 3→2 processes, derives the density-dependent depletion term, and shows how the released rest-mass energy is converted into kinetic energy that is subsequently transferred to the baryonic medium. The derivation will be shown to be consistent with the capture-rate formalism adopted from the existing literature. revision: yes

Circularity Check

0 steps flagged

No circularity: derivation relies on independent model assumptions and standard capture rates

full rationale

The paper introduces a Z3-symmetric 3→2 cannibalistic interaction for asymmetric DM captured by neutron stars, computes the resulting number depletion and associated heating rate from first-principles kinematics of the process, and compares the cannibal contribution against annihilation and kinetic heating within a scanned parameter space. Capture rates, thermalization, and heat transfer are taken from prior literature with explicit cross-section parameters; the final temperature excess and detectability statements are outputs of these calculations rather than redefinitions or fits of the input quantities. No self-citation chain, self-definitional loop, or renaming of known results is present in the derivation chain.

Axiom & Free-Parameter Ledger

3 free parameters · 2 axioms · 1 invented entities

The central claim rests on standard dark-matter capture assumptions plus a new Z3 symmetry and density-dependent 3→2 rate; several parameters must be chosen or scanned to obtain observable heating.

free parameters (3)

dark matter mass
Scanned to identify viable ranges that produce detectable heating
nucleon scattering cross section
Determines capture efficiency; chosen to allow accumulation
cannibal self-interaction strength
Controls 3→2 rate at high density; fitted or scanned for dominance

axioms (2)

domain assumption Efficient elastic capture and thermalization of asymmetric dark matter in neutron stars
Invoked to form a concentrated dark matter core
ad hoc to paper Z3 symmetry permits number-changing 3→2 processes in the dark sector
Introduced to enable cannibal depletion at high density

invented entities (1)

Z3-symmetric cannibal dark matter no independent evidence
purpose: To realize efficient 3→2 depletion inside neutron star cores
New model component postulated to produce the heating effect

pith-pipeline@v0.9.0 · 5708 in / 1383 out tokens · 54726 ms · 2026-05-18T18:05:32.690105+00:00 · methodology

discussion (0)

Forward citations

Cited by 1 Pith paper

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score.

Constraining dark matter self-interaction from kinetic heating in neutron stars
hep-ph 2026-04 unverdicted novelty 4.0

Observation of neutron stars at 1000-1200 K could constrain asymmetric dark matter self-interaction cross-sections by two orders of magnitude beyond bullet cluster limits.

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