TeV-mass dark matter charged under a new GeV-scale gauge force can explain electronic cosmic-ray anomalies. We propose that the CoGeNT and DAMA direct detection experiments are observing scattering of light stable states -- "GeV-Matter" -- that are charged under this force and constitute a small fraction of the dark matter halo. Dark higgsinos in a supersymmetric dark sector are natural candidates for GeV-Matter that scatter off protons with a universal cross-section of 5 x 10^{-38} cm^2 and can naturally be split by 10-30 keV so that their dominant interaction with protons is down-scattering. As an example, down-scattering of an O(5) GeV dark higgsino can simultaneously explain the spectra observed by both CoGeNT and DAMA. The event rates in these experiments correspond to a GeV-Matter abundance of 0.2-1% of the halo mass density. This abundance can arise directly from thermal freeze-out at weak coupling, or from the late decay of an unstable TeV-scale WIMP. Our proposal can be tested by searches for exotics in the BaBar and Belle datasets.
We propose a new thermal freeze-out mechanism for ultra-heavy dark matter. Dark matter coannihilates with a lighter unstable species, leading to an annihilation rate that is exponentially enhanced relative to standard WIMPs. This scenario destabilizes any potential dark matter candidate. In order to remain consistent with astrophysical observations, our proposal necessitates very long-lived states, motivating striking phenomenology associated with the late decays of ultra-heavy dark matter, potentially as massive as the scale of grand unified theories, $M_\text{GUT} \sim 10^{16}$ GeV.
The long standing anomaly in the positron flux as measured by the PAMELA and AMS-02 experiments could potentially be explained by dark matter (DM) annihilations. This scenario typically requires a large "boost factor" to be consistent with a thermal relic dark matter candidate produced via freeze-out. However, such an explanation is disfavored by constraints from CMB observations on energy deposition during the epoch of recombination. We discuss a scenario called late-decaying two-component dark matter (LD2DM), where the entire DM consists of two semi-degenerate species. Within this framework,…
The South Pole Telescope (SPT), Atacama Cosmology Telescope (ACT), and Wilkinson Microwave Anisotropy Probe (WMAP) have each reported measurements of the cosmic microwave background's (CMB) angular power spectrum which favor the existence of roughly one additional neutrino species, in addition to the three contained in the standard model of particle physics. Neutrinos influence the CMB by contributing to the radiation density, which alters the expansion rate of the universe during the epoch leading up to recombination. In this paper, we consider an alternative possibility that the excess kinet…
We present fully nonlinear consistency relations for the squeezed bispectrum of Large Scale Structure. These relations hold when the matter component of the Universe is composed of one or more species, and generalize those obtained in Peloso, Pietroni '13 and Kehagias, Riotto '13 in the single species case. The multi-species relations apply to the standard dark matter + baryons scenario, as well as to the case in which some of the fields are auxiliary quantities describing a particular population, such as dark matter halos or a specific galaxy class. If a large scale velocity bias exists betwe…
Cosmological measurements are affected by the energy density of both active and sterile massive neutrinos. We extend here a recent analysis of current cosmological data to non minimal cosmologies. Several possible scenarios are examined: a constant w \neq -1 dark energy equation of state, a non flat universe, a time varying dark energy component and coupled dark matter dark energy universes or modified gravity scenarios. When considering cosmological data only, (3+2) massive neutrino models with ~0.5 eV sterile species are allowed at 95% CL. This scenario has been shown to reconcile reactor, L…
The constraints on non-minimal dark sectors involving ensembles of unstable dark-matter species are well established and quite stringent in cases in which these species decay to visible-sector particles. However, in cases in which these ensembles decay exclusively to other, lighter dark-sector states, the corresponding constraints are less well established. In this paper, we investigate how information about the expansion rate of the universe at low redshifts gleaned from observations of Type Ia supernovae can be used to constrain ensembles of unstable particles which decay primarily into dark…
It has been thought that only light species could behave as radiation and account for the dark radiation observed recently by Planck, WMAP9, South Pole and ATACAMA telescopes. In this work we will show that GeV scale WIMPs can plausibly account for the dark radiation as well. Heavy WIMPs might mimic the effect of a half neutrino species if some of their fraction were produced non-thermally after the thermal freeze-out. In addition, we will show how BBN, CMB and Structure Formation bounds might be circumvented.
We study non-Gaussian properties of the isocurvature perturbations in the dark radiation, which consists of the active neutrinos and extra light species, if exist. We first derive expressions for the bispectra of primordial perturbations which are mixtures of curvature and dark radiation isocurvature perturbations. We also discuss CMB bispectra produced in our model and forecast CMB constraints on the nonlinearity parameters based on the Fisher matrix analysis. Some concrete particle physics motivated models are presented in which large isocurvature perturbations in extra light species and/or …
Although Planck data supports the standard ΛCDM model, it still allows for the presence of Dark Radiation corresponding up to about half an extra standard neutrino species. We propose a scenario for obtaining a fractional "effective neutrino species" from a thermally produced particle which decays into a much lighter stable relic plus standard fermions. At lifetimes much longer than 1 sec, both the relic particles and the non-thermal neutrino component contribute to Dark Radiation. By increasing the stable-to-unstable particle mass ratio, the relic particle no longer acts as Dark Radiation but…
There is convincing observational evidence for an increasing cosmic-ray positron-to-electron ratio at energies larger than $\sim 10$~GeV, at odds with expectations from secondary positron production. The most recent AMS-02 data exhibit an interesting spectral feature consisting of a bump at an energy around $300$~GeV followed by a drop around $\sim 800$~GeV. A possible explanation to the most recent data is that the excess positron originates from decaying dark matter. Here, we show that models consisting of two dark matter particle species contributing equally to the global cosmological dark …
It is proposed that an ultra-light fermionic species, dubbed cosmic magnino has condensed into a ferromagnetic state in the Universe. The extended structure of domain walls associated with this ferromagnetism accounts for the observed Dark Energy. In modification of the situation with an electron gas, it is proposed that the Stoner criterion is satisfied due to magnetic dipolar repulsion. The cosmological requirements then yeild a lower bound on the magnetic moment of the cosmic magnino. The proposed magnetism is supposed to be associated with a new non-standard electromagnetism. If the magnin…
Dark matter (DM) with sizeable self-interactions mediated by a light species offers a compelling explanation of the observed galactic substructure; furthermore, the direct coupling between DM and a light particle contributes to the DM annihilation in the early universe. If the DM abundance is due to a dark particle-antiparticle asymmetry, the DM annihilation cross-section can be arbitrarily large, and the coupling of DM to the light species can be significant. We consider the case of asymmetric DM interacting via a light (but not necessarily massless) Abelian gauge vector boson, a dark photon.…
The astronomical dark matter could be made of weakly interacting and massive particles. If so, these species would be abundant inside the Milky Way, where they would continuously annihilate and produce cosmic rays. Those annihilation products are potentially detectable at the Earth, and could provide indirect clues for the presence of dark matter species within the Galaxy. We will review here the various cosmic radiations which the dark matter can produce. We will examine how they propagate throughout the Milky Way and compare the dark matter yields with what pure astrophysical processes are e…
Because primordial black holes (PBHs) evaporate into all particle species in nature, PBHs may emit several dark matter (DM) particle species with specific mass spectra. We assume that PBHs are the only source of DMs, and DMs only interact with the standard model particles gravitationally. We show a relation between the number of DM particle species $N_{\rm DM}$ and initial PBH density $β$ and mass $M_{\rm BH}^{\rm in}$. $β$-$M_{\rm BH}^{\rm in}$ curves for different $N_{\rm DM}$ tend to overlap with each other for heavy initial PBHs. We also show that the allowed region of DM masses for multip…
The coherent oscillation of axionic fields naturally drives copious production of dark photon particles in the early universe, due to resonance and tachyonic enhancement. During the process, energy is abruptly transferred from the former to the latter, sourcing gravitational wave generation. The resulting gravitational waves are eventually to be observed as stochastic background today. We report analytical results of this production and connect them to the recent pulsar-timing results by the NANOGrav collaboration. We show an available parameter space, around the mass $m_ϕ\sim 10^{-13} \, {\rm…
We study Dark Matter (DM) phenomenology with multiple DM species consisting of both scalar and vector DM particles. More specifically, we study the Hidden Gauged SU(3) model of Arcadi {\it et al}. Before proceeding to the Hidden Gauged SU(3) model, we study the relic abundances of simplified multi-species DM scenarios to gain some insights when multiple species and interactions are included. In the Hidden Gauged SU(3) model, because of the large parameter space, we restrict ourselves to three representative benchmark points, each with multiple DM species. The relic densities for the benchmark …
Conventional lore from Tremaine and Gunn excludes fermionic dark matter lighter than a few hundred eV, based on the Pauli exclusion principle. We highlight a simple way of evading this bound with a large number of species that leads to numerous non-trivial consequences. In this scenario there are many distinct species of fermions with quasi-degenerate masses and no couplings to the standard model. Nonetheless, gravitational interactions lead to constraints from measurements at the LHC, of cosmic rays, of supernovae, and of black hole spins and lifetimes. We find that the LHC constrains the num…
In most multi-component dark-matter scenarios, two classes of processes generically contribute to event rates at experiments capable of probing the nature of the dark sector. The first class consists of "diagonal" processes involving only a single species of dark-matter particle -- processes analogous to those which arise in single-component dark-matter scenarios. By contrast, the second class consists of "off-diagonal" processes involving dark-matter particles of different species. Such processes include inelastic scattering at direct-detection experiments, asymmetric production at colliders,…
We study the physical conditions for the occurrence of ferromagnetic instability in a neutral plasma of fermions. We consider a system of two species $M$ and $Y$ which are oppositely charged under a local $U(1)_{X}$, with $M$ much lighter than $Y$. The leading correction to free quasiparticle behaviour for the lighter species arises from the exchange interaction, while the heavier species remain spectators. This plasma, which is abelian, asymmetric and idealised, is shown to be naturally susceptible to the formation of a completely spin-imbalanced ferromagnetic state for the lighter species (d…
Scalar field dark matter likely is able to solve all small-scale cosmology problems facing the cold dark matter (CDM), and has become an emerging contender to challenge the CDM. It however requires a particle mass $\sim 1 - 2 \times10^{-22}$eV. We find such an extremely small particle mass can naturally arise from a non-QCD axion mechanism, under fairly general assumptions that a few species of self-interacting light particles of comparable masses and a massless gauge boson decouple from the bright sector since the photon temperature exceeds 200 GeV, and the axion is the dominant dark matter. …
Ultralight scalar dark matter has been proposed to constitute a component of dark matter, though the minimal scenarios have increasingly become constrained. In this work, we analyze scenarios where the dark matter consists of more than one ultralight boson, each with different masses. This potentially leads to formation of gravitationally-bound Bose-Einstein condensates with structures that are very different from condensates composed of a single scalar field. By generalizing from the well-understood single-flavor case, we explore a large range of input parameters, subject to stability criteri…
The increasing observational pressure on the standard cosmological model motivates analyses going beyond the paradigm of the collision-less cold dark matter (DM). Since the only clear evidence for the existence of DM is based on gravitational interactions, it seems particularly fitting to study them in this sector where extensions to the standard model can be naturally introduced. A promising avenue can be obtained using modifications of the space-time metric coupled to DM and induced by the presence of a new ultra-light scalar field $ϕ$. The $ϕ$ field can contribute to the DM density and can …
The early universe may have contained internally thermalized dark sectors that were decoupled from the Standard Model. In such scenarios, the relic dark thermal bath, composed of the lightest particle in the dark sector, can give rise to an epoch of early matter domination prior to Big Bang Nucleosynthesis, which has a potentially observable impact on the smallest dark matter structures. This lightest dark particle can easily and generically have number-changing self-interactions that give rise to "cannibal" behavior. We consider cosmologies where an initially sub-dominant cannibal species com…
In a recent preprint entitled "Searching for dark matter in X-rays: how to check the dark matter origin of a spectral feature" [arXiv:1001.0644v1], the authors have claimed that some archival X-ray data could be used to rule out dark matter in the form of 5-keV sterile neutrinos at the level of 20 sigma. Unfortunately, the limit was derived incorrectly. We point out the shortcomings of this analysis and show that the tentative detection of a spectral feature consistent with a 5-keV sterile neutrino is not in contradiction with existing limits. Future observations of dwarf spheroidal galaxies w…
A fraction of the dark matter may consist of a particle species that interacts much more strongly with the Standard Model than a typical weakly interacting massive particle (WIMP) of similar mass. Such a strongly interacting dark matter component could have avoided detection in searches for WIMP-like dark matter through its interactions with the material in the atmosphere and the Earth that slow it down significantly before reaching detectors underground. These same interactions can also enhance the density of a strongly interacting dark matter species near the Earth's surface to well above th…
Cosmology of Inelastic Self-Interacting Dark Matter: Linear Evolution and Observational Constraints
Key Laboratory of Dark Matter and Space Astronomy, Purple Mountain Observatory, Chinese Academy of Sciences（中国科学院紫金山天文台暗物质与空间天文重点实验室）；School of Astronomy and Space Science, University of Science and Technology of China（中国科学技术大学天文与空间科学学院）；Department of Strategic and Advanced Interdisciplinary Research, Pengcheng Laboratory（鹏城实验室战略与先进交叉研究部）
Recently the problem of singular galactic cores and over-abundant formation of dwarf galaxies, inherent to the standard cold dark matter model, had attracted a great deal of attention. One scenario which may be free of these problems invokes a self-interacting Bose-field. We find the limiting core density in this model due to the self-annihilation of the scalar field into its own relativistic quanta. The limiting density may correspond to the observable one if there is only one dark matter component. Alternatively, there may be more than one dark matter species and the annihilation of one spec…
The acoustic peaks in the angular power spectrum of cosmic microwave background (CMB) temperature and polarization anisotropies play an important role as a probe of the nature of new relativistic particles contributing to the radiation density in the early universe, parametrized by $ΔN_{eff}$. The amplitude and phase of the acoustic oscillations provide information about whether the extra species are free-streaming particles, like neutrinos, or tightly-coupled, like the photons, during eras probed by the CMB. On the other hand, some extensions of the Standard Model produce new relativistic par…
We introduce dark matter (DM) evolution process in the Sun under a two-component DM (2DM) scenario. Both DM species $χ$ and $ξ$ with masses heavier than 1 GeV are considered. In this picture, both species could be captured by the Sun through DM-nucleus scattering and DM self-scatterings, e.g. $χχ$ and $ξξ$ collisions. In addition, the heterogeneous self-scattering due to $χ$ and $ξ$ collision is essentially possible in any 2DM models. This new introduced scattering naturally weaves the evolution processes of the two DM species that was assumed to evolve independently. Moreover, the heterogeneo…
We study systematically which features in the cosmic microwave background (CMB) and large-scale structure (LSS) probe various inhomogeneous properties of the dark sectors (including neutrinos, dark matter, and dark energy). We stress, and quantify by simple formulas, that the primary CMB anisotropies are very susceptible to the gravitational potentials during horizon entry, less at recombination. The CMB thus allows us to scan Φ+Ψand the underlying dark kinetics for all redshifts z~1-10^5. LSS, on the other hand, responds strongest to Φat low redshifts. Dark perturbations are often parameteriz…
We studied Dark Matter (DM) phenomenology with multiple DM species consisting of both scalar and vector DM particles in the Hidden Gauged SU(3) model of Arcadi et al. Because of the large parameter space in the Hidden Gauged SU(3) model we restrict ourselves to three representative benchmark points, each with multiple DM species. The relic densities for the benchmark points were found using a program developed to solve the coupled Boltzmann equations for an arbitrary number of interacting DM species with two particles in the final state. For each case, we varied the mass of the DM particles an…
Multi-Component Dark Matter as a Solution to the Galactic Center GeV Excess
Universidade Federal do Rio Grande do Norte（北里奥格兰德联邦大学）；International Institute of Physics, Universidade Federal do Rio Grande do Norte（北里奥格兰德联邦大学国际物理研究所）；Millennium Institute for Subatomic Physics at the High-Energy Frontier (SAPHIR) of ANID（智利国家研究与发展局高能前沿亚原子物理千年研究所（SAPHIR））；Universidad de La Serena（拉塞雷纳大学）；Observatório Nacional（国家天文台）；Universidad Pedagógica y Tecnológica de Colombia（哥伦比亚教育技术大学）
We consider a modification to the standard cosmological history consisting of introducing a new species $ϕ$ whose energy density red-shifts with the scale factor $a$ like $ρ_ϕ\propto a^{-(4+n)}$. For $n>0$, such a red-shift is faster than radiation, hence the new species dominates the energy budget of the universe at early times while it is completely negligible at late times. If equality with the radiation energy density is achieved at low enough temperatures, dark matter can be produced as a thermal relic during the new cosmological phase. Dark matter freeze-out then occurs at higher tempera…
The amplitude of large-scale matter fluctuations inferred from the observed Sunyaev-Zeldovich (SZ) cluster mass function and from weak gravitational lensing studies, when taken at face value, is in tension with measurements of the cosmic microwave background (CMB) and baryon acoustic oscillation (BAO). In this work, we revisit whether this possible discrepancy can be attributed to new interactions in the dark matter sector. Focusing on a cosmological model where dark matter interacts with a dark radiation species until the epoch of matter-radiation equality, we find that measurements of the Ly…
We consider the minimal model in which dark matter is stabilized by a non-Abelian discrete symmetry. The symmetry group is taken to be D_3, which is the smallest non-Abelian finite group. The minimal model contains (nontrivial) singlet and doublet scalar representations of D_3 which couple to the Standard Model fields via the Higgs portal. This construction predicts two species of dark matter over much of the parameter space. Nontrivial interactions under D_3 lead to a novel thermal history of dark matter, while the multi-component nature of dark matter can be tested by future direct detection…
The excess of high energy neutrinos observed by the IceCube collaboration might originate from baryon number violating decays of heavy shadow baryons from dark mirror sector which produce shadow neutrinos. These sterile neutrino species then oscillate into ordinary neutrinos transferring to them specific features of their spectrum. In particular, this scenario can explain the end of the spectrum above 2 PeV and the presence of the energy gap between 400 TeV and 1 PeV.
We consider a class of models in which thermal dark matter is lighter than an MeV. If dark matter thermalizes with the Standard Model below the temperature of neutrino-photon decoupling, equilibration and freeze-out cools and heats the Standard Model bath comparably, alleviating constraints from measurements of the effective number of neutrino species. We demonstrate this mechanism in a model consisting of fermionic dark matter coupled to a light scalar mediator. Thermal dark matter can be as light as a few keV, while remaining compatible with existing cosmological and astrophysical observatio…
Recent indications from both particle physics and cosmology suggest the existence of more than three neutrino species. In cosmological analyses the effects of neutrino mass and number of species can in principle be disentangled for fixed cosmological parameters. However, since we do not have perfect measurements of the standard Lambda Cold Dark Matter model parameters some correlation remains between the neutrino mass and number of species, and both parameters should be included in the analysis. Combining the newest observations of several cosmological probes (cosmic microwave background, larg…
Production of massive stable relics in $R^2$-modified gravity is considered. It is shown that the cosmological evolution and kinetics of massive species differs significantly from those in the conventional cosmology. The results are applied to the lightest supersymmetric particles and it is argued that they are viable candidates for the constituents of dark matter, if their mass is about 1000 TeV.
The U(1)$_{B-L}$ symmetry could be restored during inflation, since the BICEP2 results suggest a GUT-scale inflation with the Hubble parameter, $H_{\rm inf} \simeq 10^{14}$ GeV, close to the U(1)$_{B-L}$ breaking scale. We consider a scenario in which the ${B-L}$ Higgs field dominates the Universe after inflation, and mainly decays into the U(1)$_{B-L}$ gauge bosons, whose subsequent decays reheat the Universe. Interestingly, if one of the right-handed neutrinos is extremely light and behaves as dark radiation or hot dark matter, its abundance is determined by the $B-L$ charge assignment and t…
The nature of cosmological dark matter finds its explanation in physics beyond the Standard model of elementary particles. The landscape of dark matter candidates contains a wide variety of species, either elusive or hardly detectable in direct experimental searches. Even in case, when such searches are possible the interpretation of their results implies additional sources of information, which provide indirect effects of dark matter. Some nontrivial probes for the nature of the dark matter are presented in the present issue.
We present a simple model of two dark matter species with opposite millicharge that can form electrically neutral bound states via the exchange of a massive dark photon. If bound state formation is suppressed at low temperatures, a sub-dominant fraction of millicharged particles remains at late times, which can give rise to interesting features in the 21 cm absorption profile at cosmic dawn. The dominant neutral component, on the other hand, can have dipole interactions with ordinary matter, leading to non-standard signals in direct detection experiments. We identify the parameter regions pred…
New light states thermally coupled to the Standard Model plasma alter the expansion history of the Universe and impact the synthesis of the primordial light elements. In this work, we carry out an exhaustive and precise analysis of the implications of MeV-scale BSM particles in Big Bang Nucleosynthesis (BBN) and for Cosmic Microwave Background (CMB) observations. We find that, BBN observations set a lower bound on the thermal dark matter mass of $m_χ> 0.4\,\text{MeV}$ at $2σ$. This bound is independent of the spin and number of internal degrees of freedom of the particle, of the annihilation b…
String Axiverse Enhancement of Superradiant Dark Matter Production
University of Groningen（格罗宁根大学）；Faculdade de Ciências e Tecnologia da Universidade de Coimbra（科英布拉大学科学与技术学院）；Centro de Física da Universidade de Coimbra（科英布拉大学物理中心）；Departamento de Física e Astronomia, Faculdade de Ciências, Universidade do Porto（波尔图大学理学院天体物理学系）
We present a unifying treatment of dark energy and modified gravity that allows distinct conformal-disformal couplings of matter species to the gravitational sector. In this very general approach, we derive the conditions to avoid ghost and gradient instabilities. We compute the equations of motion for background quantities and linear perturbations. We illustrate our formalism with two simple scenarios, where either cold dark matter or a relativistic fluid is nonminimally coupled. This extends previous studies of coupled dark energy to a much broader spectrum of gravitational theories.
We study CMB constraints on a model with a cosmological constant and a fraction of dark matter non-minimally coupled to a massless scalar field. In this scenario, there is an extra gravity-like fifth force which can affect the evolution of the Universe enough to have a discernible effect on measurements of cosmological parameters. Using Planck and WMAP polarisation data, we find that up to half of the dark matter can be coupled. The coupling can also be several times larger than in models with a single species of cold dark matter coupled to a quintessence scalar field, as the scalar field does…
Recently, Weinberg proposed a Higgs portal model with a spontaneously broken global $U(1)$ symmetry in which Goldstone bosons may be masquerading as fractional cosmic neutrinos. We extend the model by gauging the $U(1)$ symmetry. This gives rise to the so-called dark photon and dark Higgs. The dark photons can constitute about 0.912 (0.167) to the effective number of light neutrino species if they decouple from the thermal bath before the pions become non-relativistic and after (before) the QCD transition. Restriction on the parameter space of the portal coupling and the dark Higgs mass is obt…
We address the question of whether the upcoming generation of dark matter search experiments and colliders will be able to discover if the dark matter in the Universe has two components of weakly interacting massive particles (WIMPs). We outline a model-independent approach, and we study the specific cases of (1) direct detection with low-background 1 ton noble-gas detectors and (2) a 0.5 TeV center of mass energy electron-positron linear collider. We also analyze the case of indirect detection via two gamma-ray lines, which would provide a verification of such a discovery, although multiple g…
