Mirror matter is a stable self-collisional dark matter candidate. If parity is a conserved unbroken symmetry of nature, there could exist a parallel hidden (mirror) sector of the Universe composed of particles with the same masses and obeying the same physical laws as our (visible) sector, except for the opposite handedness of weak interactions. The two sectors interact predominantly via gravity, therefore mirror matter is naturally "dark". Here I review the cosmological signatures of mirror dark matter, concerning thermodynamics of the early Universe, Big Bang nucleosynthesis, primordial structure formation and evolution, cosmic microwave background and large scale structure power spectra. Besides gravity, the effects on primordial nucleosynthesis of the kinetic mixing between photons and mirror photons are considered. Summarizing the present status of research and comparing theoretical results with observations/experiments, it emerges that mirror matter is not just a viable, but a promising dark matter candidate.
Mirror dark matter interacting with ordinary matter via photon-mirror photon kinetic mixing can explain the DAMA, CoGeNT and CRESSTII direct detection experiments. This explanation requires kinetic mixing of strength $ε\sim 10^{-9}$. Such kinetic mixing will have important implications for early Universe cosmology. We calculate the additional relativistic energy density at recombination, $δN_{eff} [CMB]$. We also calculate the effects for big bang nucleosynthesis, $δN_{eff} [BBN]$. Current hints that both $δN_{eff} [CMB]$ and $δN_{eff} [BBN]$ are non-zero and positive can be accommodated withi…
A simple way to accommodate dark matter is to postulate the existence of a hidden sector. That is, a set of new particles and forces interacting with the known particles predominantly via gravity. In general this leads to a large set of unknown parameters, however if the hidden sector is an exact copy of the standard model sector, then an enhanced symmetry arises. This symmetry, which can be interpreted as space-time parity, connects each ordinary particle ($e, \ ν, \ p, \ n, \ γ, ....)$ with a mirror partner ($e', \ ν', \ p', \ n', \ γ', ...)$. If this symmetry is completely unbroken, then th…
Mirror matter is a stable self-collisional dark matter candidate. If exact mirror parity is a conserved symmetry of nature, there could exist a parallel hidden (mirror) sector of the Universe which has the same kind of particles and the same physical laws of our (visible) sector. The two sectors interact each other predominantly via gravity, therefore mirror matter is naturally "dark". Here I briefly review the cosmological signatures of mirror dark matter, as Big Bang nucleosynthesis, primordial structure formation and evolution, cosmic microwave background and large scale structure power spe…
Mirror dark matter offers a framework to explain the existing dark matter direct detection experiments. Here we confront this theory with the most recent experimental data, paying attention to the various known systematic uncertainties, in quenching factor, detector resolution, galactic rotational velocity and velocity dispersion. We perform a detailed analysis of the DAMA and CoGeNT experiments assuming a negligible channeling fraction and find that the data can be fully explained within the mirror dark matter framework. We also show that the mirror dark matter candidate can explain recent da…
The DAMA/Libra experiment has recently confirmed the annual modulation signal obtained in the earlier DAMA/NaI experiment, providing strong evidence that they have actually detected dark matter. We examine the implications of this experiment for the mirror dark matter candidate. We show that mirror dark matter successfully explains the latest DAMA/Libra data, whilst also being consistent with the null results of other direct detection experiments.
An exact parity replicates the Standard Model giving a Mirror Standard Model, SM $\leftrightarrow$ SM$'$. This "Higgs Parity" and the mirror electroweak symmetry are spontaneously broken by the mirror Higgs, $\left\langle H'\right\rangle = v' \gg \left\langle H\right\rangle$, yielding the Standard Model Higgs as a Pseudo-Nambu-Goldstone Boson of an approximate $SU(4)$ symmetry, with a quartic coupling $λ_{SM}(v') \sim 10^{-3}$. Mirror electromagnetism is unbroken and dark matter is composed of $e'$ and $\bar{e}'$. Direct detection may be possible via the kinetic mixing portal, and in unified t…
We present new fast numerical simulations of cosmic microwave background and large scale structure in the case in which the cosmological dark matter is made entirely or partly of mirror matter. We consider scalar adiabatic primordial perturbations at linear scales in a flat Universe. The speed of the simulations allows us for the first time to use Markov Chain Monte Carlo analyses to constrain the mirror parameters. A Universe with pure mirror matter can fit very well the observations, equivalently to the case of an admixture with cold dark matter. In both cases, the analyses show a clear indi…
Mirror dark matter is a dissipative and self-interacting multiparticle dark matter candidate which can explain the DAMA, CoGeNT and CRESST-II direct detection experiments. This explanation requires photon-mirror photon kinetic mixing of strength $ε\sim 10^{-9}$. Mirror dark matter with such kinetic mixing can potentially leave distinctive signatures on the CMB anisotropy spectrum. We show that the most important effect of kinetic mixing on the CMB anisotropies is the suppression of the height of the third and higher odd peaks. If $ε\stackrel{>}{\sim} 10^{-9}$ then this feature can be observed …
Recently, the CDMS/Si experiment has observed a low energy excess of events in their dark matter search. In light of this new result we update the mirror dark matter explanation of the direction detection experiments. We find that the DAMA, CoGeNT, CRESST-II and CDMS/Si data can be simultaneously explained by halo $\sim Fe'$ interactions provided that $v_{rot} \approx 200$ km/s. Other parameter space is also possible. Forthcoming experiments, including CDMSlite, CDEX, COUPP, LUX, C-4,... should be able to further scrutinize mirror dark matter and closely related hidden sector models in the nea…
We compute the primordial mirror helium He' mass fraction emerging from Big Bang nucleosynthesis in the mirror sector of particles in the presence of kinetic mixing between photons and mirror photons. We explore the kinetic mixing parameter (epsilon) values relevant for cosmology and which are also currently probed by the dark matter direct detection experiments. In particular, we find that for epsilon \sim 10^{-9}, as suggested by the DAMA/Libra and other experiments, a large He' mass fraction (Y_{He'} \approx 90%) is produced. Such a large value of the primordial He' mass fraction will have …
Dark matter might reside in a hidden sector which contains an unbroken $U(1)'$ gauge interaction kinetically mixed with standard $U(1)_Y$. Mirror dark matter provides a well motivated example of such a theory. We show that the DAMA, CoGeNT and CRESST-II experiments can be simultaneously explained within this hidden sector framework. An experiment in the Southern Hemisphere is needed to test this explanation via a diurnal modulation signal.
Mirror dark matter, and other similar dissipative dark matter candidates, need an energy source to stabilize dark matter halos in spiral galaxies. It has been suggested previously that ordinary supernovae can potentially supply the required energy. By matching the energy supplied to the halo from supernovae to that lost due to radiative cooling, we here derive a rough scaling relation, $R_{SN} \propto ρ_0 r_0^2$ ($R_{SN}$ is the supernova rate and $ρ_0, \ r_0$ the dark matter central density and core radius). Such a relation is consistent with dark matter properties inferred from studies of sp…
If mirror matter exists but cannot comprise all of the dark matter (DM) in the universe, we can expect that the additional DM component may only interact with the other sectors gravitationally. One of the natural candidate of a gravitationally interacting component is a primordial black hole (PBH). Therefore, if mirror matter exists but cannot comprise all of the DM in the universe, the existence of PBH may be expected as a candidate of the additional DM component. In this case, the remaining DM components may be PBHs or $SU(3)\times SU(2)\times U(1)$ singlet particles from PBH. We show constr…
We investigate the cosmology of the minimal model of neutral naturalness, the mirror Twin Higgs. The softly-broken mirror symmetry relating the Standard Model to its twin counterpart leads to significant dark radiation in tension with BBN and CMB observations. We quantify this tension and illustrate how it can be mitigated in several simple scenarios that alter the relative energy densities of the two sectors while respecting the softly-broken mirror symmetry. In particular, we consider both the out-of-equilibrium decay of a new scalar as well as reheating in a toy model of twinned inflation, …
Dissipative dark matter, such as mirror dark matter and related hidden sector dark matter candidates, requires an energy source to stabilize dark matter halos in spiral galaxies. It has been proposed previously that supernovae could be the source of this energy. Recently, it has been argued that this mechanism might explain two galactic scaling relations inferred from observations of spiral galaxies. One of which is that $ρ_0 r_0$ is roughly constant, and another relates the galactic luminosity to $r_0$. [$ρ_0$ is the dark matter central density and $r_0$ is the core radius.] Here we derive eq…
An accelerated boundary correspondence (ABC) is solved for the de Sitter moving mirror cosmology. The beta Bogoliubov coefficients reveal the particle spectrum is a Planck distribution with temperature inversely proportional to horizon radius. The quantum stress-tensor indicates a constant emission of energy flux consistent with eternal equilibrium, while the total energy carried by the particles remains finite. The curved spacetime transformation to flat spacetime with an accelerated boundary is illustrated, and also shown for Anti-de Sitter (AdS) spacetime.
These lecture notes aim to provide an introduction to dark matter from the perspective of astrophysics/cosmology. We start with a rapid overview of cosmology, including the evolution of the Universe, its thermal history and structure formation. Then we look at the observational evidence for dark matter, from observations of galaxies, galaxy clusters, the anisotropies in the cosmic microwave background radiation and large scale structure. To detect dark matter we need to know how it's distributed, in particular in the Milky Way, so next we overview relevant results from numerical simulations an…
The CoGeNT collaboration has recently made available new data collected over a period of 15 months. In addition to more accurately measuring the spectrum of nuclear recoil candidate events they have announced evidence for an annual modulation signal. We examine the implications of these new results within the context of mirror/hidden sector dark matter models. We find that the new CoGeNT data can be explained within this framework with parameter space consistent with the DAMA annual modulation signal, and the null results of the other experiments. We also point out that the CoGeNT spectrum at …
We study the parameter space of cold dark matter axions in two cosmological scenarios with non-standard thermal histories before Big Bang nucleosynthesis: the Low Temperature Reheating (LTR) cosmology and the kination cosmology. If the Peccei-Quinn symmetry breaks during inflation, we find more allowed parameter space in the LTR cosmology than in the standard cosmology and less in the kination cosmology. On the contrary, if the Peccei-Quinn symmetry breaks after inflation, the Peccei-Quinn scale is orders of magnitude higher than standard in the LTR cosmology and lower in the kination cosmolog…
Higgs vacuum stability has important consequences for cosmology. In particular, we argue that if the Higgs vacuum is metastable, then the dark matter cannot contain a single black hole of mass less than $10^{15}{\rm g}$ in our entire past light cone. In addition to being the destroyer microscopic black holes, it may be possible that Higgs vacuum decay is a source of primordial black holes during inflation.
Composite dark matter is a natural setting for implementing inelastic dark matter - the O(100 keV) mass splitting arises from spin-spin interactions of constituent fermions. In models where the constituents are charged under an axial U(1) gauge symmetry that also couples to the Standard Model quarks, dark matter scatters inelastically off Standard Model nuclei and can explain the DAMA/LIBRA annual modulation signal. This article describes the early Universe cosmology of a minimal implementation of a composite inelastic dark matter model where the dark matter is a meson composed of a light and …
Up-to-date estimates of the cosmological parameters are presented as a result of numerical simulations of cosmic microwave background and large scale structure, considering a flat Universe in which the dark matter is made entirely or partly of mirror matter, and the primordial perturbations are scalar adiabatic and in linear regime. A statistical analysis using the Markov Chain Monte Carlo method allows to obtain constraints of the cosmological parameters. As a result, we show that a Universe with pure mirror dark matter is statistically equivalent to the case of an admixture with cold dark ma…
Mirror universe is a fundamental way to restore parity symmetry in weak interactions. It naturally provides the lightest mirror nucleon as a unique GeV-scale asymmetric dark matter particle candidate. We conjecture that the mirror parity is respected by the fundamental interaction Lagrangian, and its possible soft breaking arises only from non-interaction terms in the gauge-singlet sector. We realize the spontaneous mirror parity violation by minimizing the vacuum Higgs potential, and derive the corresponding Higgs spectrum. We demonstrate that the common origin of CP violation in the visible …
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.
We obtain the value of the mirror magnetic field during different stages of cosmological evolution. We consider the magnetic field generation in the radiation-dominated era and the post-recombination epoch. We also estimate its galactic low-scale value in the process of dynamo amplification. We discuss a possible effect of the mirror magnetic field on the mirror matter distribution in a galaxy. The model can be generalized by assuming the existence of kinetic mixing between ordinary and mirror particles.
The simplest model of mirror sector dark matter maintains exact mirror symmetry, but has a baryon abundance $Ω_{b'} = βΩ_b$ and a suppressed temperature $T' = x T$ in the mirror sector; hence it depends only on two parameters, $β,x$. For sufficiently small $x$, early cosmological observables may not constrain mirror baryons from constituting all of the dark matter despite their strong self-interactions, depending on the unknown details of structure formation in the hidden sector. Here we close this loophole by simulating mirror structure formation, mapping out the allowed regions of parameter …
Recent observations indicate that about half of the dwarf satellite galaxies around M31 orbit in a thin plane approximately aligned with the Milky Way. It has been argued that this observation along with several other features can be explained if these dwarf satellite galaxies originated as tidal dwarf galaxies formed during an ancient merger event. However if dark matter is collisionless then tidal dwarf galaxies should be free of dark matter - a condition that is difficult to reconcile with observations indicating that dwarf satellite galaxies are dark matter dominated. We argue that dissipa…
We study the mirror world with dark matter arising from the thermal freeze-out of the lightest, stable mirror particle -- the mirror electron. The dark matter abundance is achieved for mirror electrons of mass 225 GeV, fixing the mirror electroweak scale near $10^8$ GeV. This highly predictive scenario is realized by an axion that acts as a portal between the two sectors through its coupling to the QCD and mirror QCD sectors. The axion is more massive than the standard QCD axion due to additional contributions from mirror strong dynamics. Still, the strong CP problem is solved by this "heavy" …
Mirror and more generic hidden sector dark matter models can simultaneously explain the DAMA, CoGeNT and CRESST dark matter signals consistently with the null results of the other experiments. This type of dark matter can be captured by the Earth and shield detectors because it is self-interacting. This effect will lead to a diurnal modulation in dark matter detectors. We estimate the size of this effect for dark matter detectors in various locations. For a detector located in the northern hemisphere, this effect is expected to peak in April and can be detected for optimistic parameter choices…
I review the current status of Big Bang Cosmology, with emphasis on current issues in dark matter, dark energy, and galaxy formation. These topics motivate many of the current goals of experimental cosmology which range from targeting the nature of dark energy and dark matter to probing the epoch of the first stars and galaxies.
Existence of a mirror world in the universe is a fundamental way to restore the observed parity violation in weak interactions and provides the lightest mirror nucleon as a unique GeV-scale dark matter particle candidate. The visible and mirror worlds share the same spacetime of the universe and are connected by a unique space-inversion symmetry -- the mirror parity (P). We conjecture that the mirror parity is respected by the fundamental interaction Lagrangian, and study its spontaneous breaking from minimizing the Higgs vacuum potential. The domain wall problem is resolved by a unique soft b…
The cosmological model of dark energy interacting with cold dark matter without coupling to the baryonic matter, is studied in the background of both classical Einstein and loop quantum cosmology. We consider two types of interacting models. In the former model, the interaction is a linear combination of the densities of two dark sectors, while in the latter model, the interaction with a constant transfer rate depends only on the density of cold dark matter. It is shown that the dynamical results in loop quantum cosmology are different from those in classical Einstein cosmology for both two ki…
B and L violating interactions of ordinary particles with their twin particles from hypothetical mirror world can co-generate baryon asymmetries in both worlds in comparable amounts, $Ω'_B/Ω_B \sim 5$ or so. On the other hand, the same interactions induce the oscillation phenomena between the neutral particles of two sectors which convert e.g. mirror neutrons into our antineutrons. These oscillations are environment dependent and can have fascinating physical consequences.
We discuss astrophysical implications of the modified gravity model in which the two matter components, ordinary and dark, couple to separate gravitational fields that mix to each other through small mass terms. There are two spin-2 eigenstates: the massless graviton that induces universal Newtonian attraction, and the massive one that gives rise to the Yukawa-like potential which is repulsive between the ordinary and dark bodies. As a result the distances much smaller than the Yukawa radius $r_m$ the gravitation strength between the two types of matter becomes vanishing. If $r_m \sim 10$ kpc,…
If dark matter is dissipative then the distribution of dark matter within galactic halos can be governed by dissipation, heating and hydrostatic equilibrium. Previous work has shown that a specific model, in the framework of mirror dark matter, can explain several empirical galactic scaling relations. It is shown here that this dynamical halo model implies a quasi-isothermal dark matter density, $ρ(r) = ρ_0 r_0^2/(r^2 + r_0^2)$, where the core radius, $r_0$, scales with disk scale length, $r_D$, via $r_0/{\rm kpc} = 1.4\left(r_D/{\rm kpc}\right)$. Additionally, the product $ρ_0 r_0$ is roughly…
I consider couplings between the dark energy and dark matter sectors. I describe how the existence of an adiabatic regime, in which the dark energy field instantaneously tracks the minimum of its effective potential, opens the door for a catastrophic instability. This {\it adiabatic instability} tightly constrains a wide class of interacting dark sector models. This talk was presented at, and will appear in the proceedings of the DPF-2009 conference.
We study Einstein's equations with an isotropic but inhomogeneous metric in the cosmic rest frame. The equations are solved perturbatively in the late Universe. The leading plus next-to-leading order results agree with observations without using a cosmological constant or dark matter.
Dark matter has been introduced to explain many independent gravitational effects at different astronomical scales, in galaxies, groups of galaxies, clusters, superclusters and even across the full horizon. This review describes the accumulated astronomical, astrophysical, and cosmological evidence for dark matter. It is written at a non-specialist level and intended for an audience with little or only partial knowledge of astrophysics or cosmology.
We investigate the holographic, new agegraphic and ghost dark energy models in the framework of fractal cosmology. We consider a fractal FRW universe filled with the dark energy and dark matter. We obtain the equation of state parameters of the selected dark energy models in the ultraviolet regime and discuss on their implications.
This paper is a broad-band review of the current status of non-baryonic dark matter research. I start with a historical overview of the evidences of dark matter existence, then I discuss how dark matter is distributed from small scale to large scale, and I then verge the attention to dark matter nature: dark matter candidates and their detection. I finally discuss some of the limits of the $Λ$CDM model, with particular emphasis on the small scale problems of the paradigm.
We investigate the statistical nature of the dark matter particles produced in bouncing cosmology, especially, the evolution of its thermal fluctuations. By explicitly deriving and solving the equation of motion of super-horizon mode, we fully determine the evolution of thermal perturbation of dark matter in a generic bouncing background. And we also show that the evolution of super-horizon modes is stable and will not ruin the background evolution of a generic bouncing universe till the Planck scale. Given no super-horizon thermal perturbation of dark matter appears in standard inflation scen…
We investigate interacting dark energy models in the framework of fractal cosmology. We discuss a fractal FRW universe filled with the dark energy and dark matter which interact with each other. We obtain the equation for the relative density of dark matter and dark energy and the deceleration parameter. This model demonstrates new types of evolution, which are not common to cosmological models with this type of interaction.
The standard model of cosmology is based on the general theory of relativity and demands more than 95\% of the universe to consist of dark matter and dark energy that has no direct observational evidence till date. The foundation of the concept these dark components are based on a fixed relation between the strength of the gravitational field and the matter density. Alternate models are put forward in past to explain the observations without dark components in the universe. Though they have their own merits and draw backs. In this paper we propose a new cosmological model based on Mach's princ…
Understanding the space of possible theoretical explanations for the observed cosmic acceleration is a central challenge of modern cosmology. This brief document sketches selected aspects of approaches to this problem, focusing on the possibility that a modification to General Relativity is responsible for acceleration, as presented as a plenary talk at the ICHEP 2012 conference.
We investigate Holographic Dark Energy Correspondence of Interacting Generalized Chaplygin Gas model in the framework of compact Kaluza-Klein cosmology. The evolution of the modified holographic dark energy and the equation of state parameter is obtained here.Using the present observational value of density parameter a stable configuration is formed which accommodates Dark Energy. we note a connection between Dark Energy and Phantom field and have shown that Dark Energy might have evolved from a Phantom state in the past.
