A no-go theorem excludes Gamma in [0,d] for typical non-topological non-relativistic spherically symmetric solitons, with the same exclusion for barotropic fluid compact objects, ruling out natural soliton explanations for observed dark matter halo cores with Gamma ~1.7.
Axion dark matter, solitons, and the cusp-core problem
3 Pith papers cite this work. Polarity classification is still indexing.
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abstract
Self-gravitating bosonic fields can support stable and localised field configurations. For real fields, these solutions oscillate in time and are known as oscillatons. The density profile is static, and is soliton. Such solitons should be ubiquitous in models of axion dark matter, with the soliton characteristic mass and size depending on some inverse power of the axion mass. Stable configurations of non-relativistic axions are studied numerically using the Schr\"{o}dinger-Poisson system. This method, and the resulting soliton density profiles, are reviewed. Using a scaling symmetry and the uncertainty principle, the core size of the soliton can be related to the central density and axion mass, $m_a$, in a universal way. Solitons have a constant central density due to pressure-support, unlike the cuspy profile of cold dark matter (CDM). One consequence of this fact is that solitons composed of ultra-light axions (ULAs) may resolve the `cusp-core' problem of CDM. In DM halos, thermodynamics will lead to a CDM-like Navarro-Frenk-White profile at large radii, with a central soliton core at small radii. Using Monte-Carlo techniques to explore the possible density profiles of this form, a fit to stellar-kinematical data of dwarf spheroidal galaxies is performed. In order for ULAs to resolve the cusp-core problem (without recourse to baryon feedback or other astrophysical effects) the axion mass must satisfy $m_a<1.1\times 10^{-22}\text{ eV}$ at 95\% C.L. On the other hand, ULAs with $m_a\lesssim 1\times 10^{-22}\text{ eV}$ are in some tension with cosmological structure formation. An axion solution to the cusp-core problem thus makes novel predictions for future measurements of the epoch of reionisation. On the other hand, this can be seen as evidence that structure formation could soon impose a \emph{Catch 22} on axion/scalar field DM, similar to the case of warm DM.
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UNVERDICTED 3representative citing papers
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A No-Go Theorem for the Mass-Radius Relation of Solitons
A no-go theorem excludes Gamma in [0,d] for typical non-topological non-relativistic spherically symmetric solitons, with the same exclusion for barotropic fluid compact objects, ruling out natural soliton explanations for observed dark matter halo cores with Gamma ~1.7.
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Tunneling and tidal stripping in multifield ultralight dark matter halos
A semiclassical tunneling model shows that two-field ultralight DM halos have stability bounds that can be relaxed for some density-mass ratios but become more stringent across much of the parameter space compared to single-field cases.
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