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The rotation curves of spiral galaxies exhibit a diversity that has been difficult to understand in the cold dark matter (CDM) paradigm. We show that the self-interacting dark matter (SIDM) model provides excellent fits to the rotation curves of a sample of galaxies with asymptotic velocities in the 25-300 km/s range that exemplify the full range of diversity. We assume only the halo concentration-mass relation predicted by the CDM model and a fixed value of the self-interaction cross section. In dark-matter-dominated galaxies, thermalization due to self-interactions creates large cores and reduces dark matter densities. In contrast, thermalization leads to denser and smaller cores in more luminous galaxies and naturally explains the flatness of rotation curves of the highly luminous galaxies at small radii. Our results demonstrate that the impact of the baryons on the SIDM halo profile and the scatter from the assembly history of halos as encoded in the concentration-mass relation can explain the diverse rotation curves of spiral galaxies.

The large-scale distribution of cold dark matter halos is generally assumed to trace the large-scale distribution of matter. In a universe with multiple types of matter fluctuations, as is the case with massive neutrinos, the relation between the halo field and the matter fluctuations may be more complicated. We develop a method for calculating the bias factor relating fluctuations in the halo number density to fluctuations in the mass density in the presence of multiple fluctuating components of the energy density. In the presence of massive neutrinos we find a small but pronounced feature in the halo bias near the neutrino free-streaming scale. The neutrino feature is a small step with amplitude that increases with halo mass and neutrino mass density. The scale-dependent halo bias lessens the suppression of the small-scale halo power spectrum and should therefore weaken constraints on neutrino mass from the galaxy auto-power spectrum and correlation function. On the other hand, the feature in the bias is itself a novel signature of massive neutrinos that can be studied independently., Comment: 14 pages, 8 figures; v2: references added, typos corrected, minor changes to introduction; v3: minor changes to text, references added, matches PRD accepted version

It has been suggested that cold dark matter (CDM) has difficulties in explaining tentative evidence for noncuspy halo profiles in small galaxies, and the low velocity dispersions observed in the largest Milky Way satellites ("too big to fail" problem). Strongly self-interacting dark matter has been noted as a robust solution to these problems. The elastic cross sections required are much larger than predicted by generic CDM models, but could naturally be of the right size if dark matter is composite. We explore in a general way the constraints on models where strongly interacting CDM is in the form of dark "atoms" or "molecules," or bound states of a confining gauge interaction ("hadrons"). These constraints include considerations of relic density, direct detection, big bang nucleosynthesis, the cosmic microwave background, and LHC data., 21 pages, 13 figures; v2: added section on BBN constraints; published version; v3: fixed typos

Dark matter annihilation is proportional to the square of the density and is especially efficient in places of highest concentration of dark matter, such as dark matter spikes. The spikes are formed as a result of contraction of the dark matter density profile caused by adiabatic growth of a supermassive black hole at the center of the dark matter halo or subhalo. We revisit the relation between the properties and mass functions of dark matter halos and spikes, and propose alternative models for the density spikes that can potentially contribute to the isotropic gamma-ray background., Comment: 10 pages, 4 figures; matches published version

N-body simulations of structure formation with scale-invariant primordial perturbations show significantly more virialized objects of dwarf-galaxy mass in a typical galactic halo than are observed around the Milky Way. We show that the dearth of observed dwarf galaxies could be explained by a dramatic downturn in the power spectrum at small distance scales. This suppression of small-scale power might also help mitigate the disagreement between cuspy simulated halos and smooth observed halos, while remaining consistent with Lyman-alpha-forest constraints on small-scale power. Such a spectrum could arise in inflationary models with broken scale invariance., Comment: 5 pages LaTeX, 3 figures

A massive, self-interacting scalar field has been considered as a possible candidate for the dark matter in the universe. We present an observational constraint to the model arising from strong lensing observations in galaxies. The result points to a discrepancy in the properties of scalar field dark matter halos for dwarf and lens galaxies, mainly because halo parameters are directly related to physical quantities in the model. This is an important indication that it becomes necessary to have a better understanding of halo evolution in scalar field dark matter models, where the presence of baryons can play an important role. DOI: 10.1103/PhysRevD.87.021301

We analyze the a set of 17 rotation curves of low surface brightness (LSB) galaxies from The HI Nearby Galaxy Survey (THINGS) with different mass models to study the core structure and to determine a phase transition energy scale (${E}_{c}$) between hot and cold dark matter, due to nonperturbative effects in the bound dark matter (BDM) model. Our results agree with previous ones, implying the cored profiles are preferred over the $N$-body motivated cuspy Navarro-Frenk-White (NFW) profile. We find an average galactic core radius of ${r}_{c}=260\ifmmode\times\else\texttimes\fi{}{10}^{\ifmmode\pm\else\textpm\fi{}1.3}\text{ }\text{ }\mathrm{pc}$ and a phase transition energy ${E}_{c}=0.11\ifmmode\times\else\texttimes\fi{}{10}^{\ifmmode\pm\else\textpm\fi{}0.46}\text{ }\text{ }\mathrm{eV}$, that is of the same order of magnitude as the sum of the neutrino masses.

We develop a theoretical framework for describing the hierarchical structure of the phase space of cold dark matter haloes, due to gravitationally bound substructures. Because it includes the full hierarchy of the cold dark matter initial conditions and is hence complementary to the halo model, the stable clustering hypothesis is applied for the first time here to the small-scale phase space structure. As an application, we show that the particle dark matter annihilation signal could be up to two orders of magnitude larger than that of the smooth halo within the Galactic virial radius. The local boost is inversely proportional to the smooth halo density, and thus is O(1) within the solar radius, which could translate into interesting signatures for dark matter direct detection experiments: The temporal correlation of dark matter detection can change by a factor of 2 in the span of 10 years, while there will be significant correlations in the velocity space of dark matter particles. This can introduce O(1) uncertainty in the direction of local dark matter wind, which was believed to be a benchmark of directional dark matter searches or the annual modulation signal., Comment: 5 pages, 4 figures

It is widely thought that neutralinos, the lightest supersymmetric particles, could comprise most of the dark matter. If so, then dark halos will emit radio and gamma ray signals initiated by neutralino annihilation. A particularly promising place to look for these indicators is at the center of the local group dwarf spheroidal galaxy Draco, and recent measurements of the motion of its stars have revealed it to be an even better target for dark matter detection than previously thought. We compute limits on WIMP properties for various models of Draco's dark matter halo. We find that if the halo is nearly isothermal, as the new measurements indicate, then current gamma ray flux limits prohibit much of the neutralino parameter space. If Draco has a moderate magnetic field, then current radio limits can rule out more of it. These results are appreciably stronger than other current constraints, and so acquiring more detailed data on Draco's density profile becomes one of the most promising avenues for identifying dark matter., Comment: 13 pages, 6 figures

There is mounting evidence that a self-consistent model for particle cold dark matter has to take into consideration spatial inhomogeneities on sub-galactic scales seen, for instance, in high-resolution N-body simulations of structure formation. Also in more idealized, analytic models, there appear density enhancements in certain regions of the halo. We use the results from a recent N-body simulation of the Milky Way halo and investigate the gamma-ray flux which would be produced when a specific dark matter candidate, the neutralino, annihilates in regions of enhanced density. The clumpiness found on all scales in the simulation results in very strong gamma-ray signals which seem to already rule out some regions of the supersymmetric parameter space, and would be further probed by upcoming experiments, such as the GLAST gamma-ray satellite. As an orthogonal model of structure formation, we also consider Sikivie's simple infall model of dark matter which predicts that there should exist continuous regions of enhanced density, caustic rings, in the dark matter halo of the Milky Way. We find, however, that the gamma-ray signal from caustic rings is generally too small to be detectable., 15 pages, 11 figures