Terms Of Dark Matter Research Articles

Viscous exotic fluid interacting with dark matter and future infinite singularities

By making use of two viable Lagrangian [Formula: see text] models, we investigate the behavior of the state parameter of the interacting viscous dark energy. We, from constant deceleration parameter, explore the cosmological implications of the viscosity and interaction between the dark energy and dark matter in terms of redshift. We then construct the viscosity and the interaction parameters that are respectively parameterized by [Formula: see text] and [Formula: see text] and obtain interesting results. Later, we investigate the behavior of some bulk viscosity models describing little rip and pseudo rip future singularities within [Formula: see text] modified gravity. We obtain interesting gravitational equations of motion for viscous dark energy coupled with dark matter. The solution of these equations gives us an analytic expression for characteristic properties of these cosmological models.

Anisotropic strong lensing as a probe of dark matter self-interactions

ABSTRACT Galaxy-scale strongly lensed systems have been shown to provide a unique technique for exploring the underlying physics of dark matter at sub-galactic scales. In the past, much attention was given to detecting and studying individual haloes in a strong lens system. In addition to the subhaloes, line-of-sight haloes contribute significantly to the small perturbations in lensed images. In prior work, we demonstrated that these line-of-sight haloes imprint a distinctive anisotropic signature and hence give rise to a detectable non-zero parity-even quadrupole moment in the effective convergence field’s two-point correlation function. In this study, we show that these line-of-sight haloes also produce a non-zero curl component of the effective deflection field with a parity-odd quadrupole moment of the two-point function. These multipole moments have the ability to statistically separate line-of-sight haloes from dark matter substructure. In this paper, we examine how these multipole moments evolve in the presence of warm dark matter and self-interacting dark matter in terms of central density evolution and dark matter halo abundance. Importantly, we show that these different multipole moments display exquisite sensitivity to both the amplitude and the velocity dependence of the dark matter self-interaction cross-section. Our approach opens the door for strong lensing observations to probe dark matter self-interaction over a broad range of relative velocities.

Inflationary entanglement

We investigate the entanglement due to geometric corrections in particle creation during inflation. To do so, we propose a single-field inflationary scenario, nonminimally coupled to the scalar curvature of spacetime. We require particle production to be purely geometric, setting to zero the Bogoliubov coefficients and computing the $S$ matrix associated with spacetime perturbations, which are traced back to inflaton fluctuations. The corresponding particle density leads to a nonzero entanglement entropy whose effects are investigated at primordial time of Universe evolution. The possibility of modeling our particle candidate in terms of dark matter is discussed. The classical backreaction of inhomogeneities on the homogeneous dynamical background degrees of freedom is also studied and quantified in the slow-roll regime.

The non-singular Trautman–Kopczyński big-bang model and a torsional spinor description of dark matter

A view is taken up whereby the non-singular Trautman–Kopczyński big-bang creation of the Universe produced a highly torsional hot state at early stages of the cosmic evolution which particularly brought about the formation of a dark matter cloud. It is thus assumed that the combination of Einstein–Cartan’s theory with the torsionful version of the two-component varepsilon -formalism of Infeld and van der Waerden supplies a natural local description of dark matter in terms of uncharged spin-one massive fields. In the case of either handedness, the pertinent spinor field equation arises directly from a suitable form of the world Bianchi identity. It appears that each such field equation bears a term that is thought of as carrying part of the information on the mass of the fields. The whole information turns out to be extracted by well prescribed derivatives of certain couplings involving the fields and spinor torsion pieces in such a way that the mass of dark matter is really thought of as arising from the interaction between the fields and spinor torsion.

Observational Hubble parameter data constraints on the interactive model of gravity with particle creation

In this study, we consider an open system from the thermodynamic perspective for an adiabatic FRW universe model in which particle creation occurs within the system. In this case, the modified continuity equation is obtained, and then, we make it correspond to the continuity equation of gravity. Therefore, we take gravity with a viscous fluid in the flat-FRW metric, where T is the torsion scalar. We assume the contents of the universe to be dark matter and dark energy and consider an interaction term between them. An interesting point of this study is that we make the modified continuity equation resulting from particle creation equivalent to the matter continuity equation resulting from gravity. The result of this evaluation establishes a relationship between the number of particles and scale factor. In what follows, we write the corresponding cosmological parameters in terms of the number of particles and also reconstruct the number of particles in terms of the redshift parameter. We then parameterize the Hubble parameter derived from power-law cosmology with 51 data points from the Hubble observational parameter data. Next, we plot the corresponding cosmological parameters for dark energy in terms of the redshift to investigate the accelerated expansion of the universe. In addition, by using the sound speed parameter, we discuss the stability and instability analyses of the present model in different eras of the universe. Finally, we plot the density parameter values for dark energy and dark matter in terms of the redshift parameter.

Imprints of decaying dark matter on cosmic voids

The Standard Cosmological Model assumes that more than 85\% of matter is in the form of collisionless and pressureless dark matter. Unstable decaying dark matter has been proposed in the literature as an extension to the standard cold dark matter model. In this paper we investigate a scenario when dark matter decays and the resultant particle moves with respect to the dark matter. A covariant hydrodynamical model is developed in which the decay is modeled by the transfer of energy-momentum between two dark dust fluid components. We parameterise the model in terms of the decay rate $\Gamma$ and injection velocity $v_i$ of the resultant dark matter particles. We apply the framework to study the evolution of cosmic voids which are environments with low content of baryonic matter. Thus, unlike baryon-rich environments, voids provide an opportunity to measure dark matter signals that are less contaminated by complex baryonic processes. We find that the growth of S-type voids is modified by the dark matter decay, leading to imprints at the present day. This paper serves as a proof-of-concept that cosmic voids can be used to study dark mater physics. We argue that future cosmological observations of voids should focus on signs of reported features to either confirm or rule out the decaying dark matter scenario. Lack of presence of reported features could put constraints of the decay of dark matter in terms of $\Gamma > H_0^{-1}$ and $v_i<10$ km/s.

Scalaron\u2013Higgs inflation reloaded: Higgs-dependent scalaron mass and primordial black hole dark matter

We propose an extension of the scalaron-Higgs model by a non-minimal coupling of the Standard Model Higgs boson to the quadratic Ricci scalar resulting in a Higgs-dependent scalaron mass. The model predicts a successful stage of effective single-field Starobinsky inflation. It features a multi-field amplification mechanism leading to a peak in the inflationary power spectrum at small wavelengths which enhances the production of primordial black holes. The extended scalaron-Higgs model unifies inflationary cosmology with elementary particle physics and explains the origin of cold dark matter in terms of primordial black holes without assuming any new particles.

Physics Formalism Helmholtz Iyer Markoulakis Hamiltonian Mechanics Metrics towards Electromagnetic Gravitational Hilbert Coulomb Gauge String metrics

Iyer Markoulakis Helmholtz Hamiltonian metrics have been gauged to Coulombic Hilbert metrics, representing Gilbertian and Amperian natures of electromagnetic fields from mechanics of vortex rotational fields acting with gradient fields, typically in zero-point microblackhole general fields, extending to vacuum gravitational fields gauge. This ansatz general gaging helps to properly isolate field effects with physical analyses – mechanical, electric, magnetic components within the analytical processes. Vacuum gravitational fields and the flavor Higgs-Boson matter inertial gravitational fields have been thus quantified extending to stringmetrics constructs matrix showing charge asymmetry gauge metrics. Physical Analysis with applications to particle physics, Quantum ASTROPHYSICS, as well as grand unification physics have been advanced. Particle physics gauge matrix pointing to Dirac seas of electrons, monopoles with positrons, electron-positron annihilation leading to energy production, and the relativistic energy generating matter provided literature correlations. Quantum astrophysics extending gauge metrix analyzes of superluminal profile of signals velocity generating electron-positron chain like “curdling” action validates formalism with physics literature of electron-photon observed oscillatory fields configurations. Mechanism of creation of neutrino antineutrino pair orthogonal to electron positron “curdling” planes, that may lead to formation of protonic hydrogen of stars or orthogonally muon particles. These proposals will help to explain receding or fast expanding universe with the dark matter in terms of flavor metrics versus gauge associating metrics fields. Vacuum and gravitational monopoles, that are representation of compressed mass out of vortex Helmholtz decomposition fields have been interpolated to energy generation via electron positron monopole particles at cosmos extent of infinity

EDGES signal in the presence of magnetic fields

ABSTRACT We study the 21-cm differential brightness temperature in the presence of primordial helical magnetic fields for redshift z = 10–30. We argue that the α-effect that sets in at earlier time can be helpful in lowering the gas temperature to 3.2 K at z = 17. This effect can arise in the early Universe due to some parity-violating high-energy processes. Using the EDGES (Experiment to Detect the Global Epoch of Reionization Signature) results, we find the upper and lower limits on the primordial magnetic field to be 6 × 10−3 and 5 × 10−4 nG, respectively. We also discuss the effect of Ly α background on the bounds. Our results do not require any new physics in terms of dark matter.

Predictions and Outcomes for the Dynamics of Rotating Galaxies

A review is given of a priori predictions made for the dynamics of rotating galaxies. One theory—MOND—has had many predictions corroborated by subsequent observations. While it is sometimes possible to offer post hoc explanations for these observations in terms of dark matter, it is seldom possible to use dark matter to predict the same phenomena.

Analysis of a possible explanation of the positron anomaly in terms of dark matter

The possibility of explaining the positron anomaly on the basis of models involving the darkmatter annihilation or decay is being widely discussed at the present time. However, such models are severely constrained by data on cosmic gamma radiation. Two different procedures that rely on the χ2 criterion and which permit taking this constraint into account are considered in the present study. In one case, the use of positron data alone in searches for a minimum value of χ2 via varying model parameters is followed by a comparison with gamma-radiation data. In the second case, the χ2 functional is minimized by simultaneously employing positron and gamma-radiation data, whereby a more lenient (more “flexible”) constraint is obtained. Nevertheless, either procedure rules out the possibility of explaining the positron anomaly in terms of unstable dark matter distributed over the whole halo. The assumption that the dark-matter component undergoing annihilation (decay) is concentrated within the galactic disk makes it possible to remove the constraint in either case.

Fermi-LAT kills dark matter interpretations of AMS-02 data. Or not?

A number of papers attempt to explain the positron anomaly in cosmic rays, observed by PAMELA and AMS-02, in terms of dark matter (DM) decays or annihilations. However, the recent progress in cosmic gamma-ray studies challenges these attempts. Indeed, as we show, any rational DM model explaining the positron anomaly abundantly produces final state radiation and Inverse Compton gamma rays, which inevitably leads to a contradiction with Fermi-LAT isotropic diffuse gamma-ray background measurements. Furthermore, the Fermi-LAT observation of Milky Way dwarf satellites, supposed to be rich in DM, revealed no significant signal in gamma rays. We propose a generic approach in which the major contribution to cosmic rays comes from the dark matter disc and prove that the tension between the DM origin of the positron anomaly and the cosmic gamma-ray observations can be relieved. We consider both a simple model, in which DM decay/annihilate into charged leptons, and a model-independent minimal case of particle production, and we estimate the optimal thickness of DM disk. Possible mechanisms of formation and its properties are briefly discussed.

Ultralight repulsive dark matter and BEC

Abstract Ultralight scalar dark matter with mass at or below the eV scale and pressure from repulsive self-interaction could form a Bose–Einstein condensate in the early Universe and maybe in galaxies as well. It has been suggested to be a possible solution to the cusp/core problem or even to explain MOND phenomenology. In this paper, I initiate a study of possible self-interactions of ultralight scalar dark matter from the particle physics point of view. To protect its mass, the scalar dark matter is identified as a pseudo Nambu–Goldstone boson (pNGB). Quite a few pNGB models with different potentials such as the QCD axion and the dilaton lead to attractive self-interactions. Yet if an axion is a remnant of a 5D gauged U ( 1 ) symmetry, its self-interactions could be repulsive provided the masses and charges of the 5D matter contributing to its potential satisfy certain constraints. Collective symmetry breaking could also lead to a repulsive self-interaction yet with too large a strength that is ruled out by Bullet Cluster constraints. I also discuss cosmological and astrophysical constraints on ultralight repulsive dark matter in terms of a parametrization motivated by particle physics considerations.

Linear Newtonian perturbation theory from the Schrödinger-Poisson equations

We obtain solutions to the coupled Schr\odinger-Poisson equations. The solutions describe the evolution of cold dark matter density perturbations in an otherwise homogeneous expanding Friedmann universe. We discuss the relationships between descriptions of cold dark matter in terms of a pressureless fluid, in terms of a wave function, of a classical scalar field, and a quantum scalar field. We identify the regimes where the various descriptions coincide and where they differ.

Octonionic Gravi-Electromagnetism and Dark Matter

An attempt has been made to analyse the the role of octonions in various unified field theories associated with dyons and the dark matter. Starting with the split octonion al- gebra and its properties, we have discussed the octonionic unified gauge formulation for SU(2) ?X U(1) electroweak theory and SU(3) X? SU(2) ?X U(1) grand unified theory. De- scribing the octonion eight dimensional space as the combination of two quaternionic spaces (namely associated with the electromagnetic interaction (EM-space) and linear gravitational interaction (G-space)), we have reexamined the unified picture of EM-G space in terms of oc- tonionic split formulation in consistent manner. Consequently, we have obtained the various field equations for unified gravi-electromagnetic interactions. Furthermore, we have recon- structed the field equations of hot and cold dark matter in terms of split octonions. It is shown that the difference between the octonion cold dark matter (OCDM) and the octonion hot dark matter (OHDM) is significant in the formulating of structure of these two, because the velocities of octonion hot dark matter cause it to wipe out structure on small scales.

The Nature of Dark Matter and of Dark Energy

The aim of the present work is showing that the observed non-Keplerian rotation of the galaxies is predicted by the space dynamic gravitational mechanism without dark matter and that the current explanation of the galactic gravitational dynamics in terms of dark matter is hypothetical. Visibly, the need of dark matter is an emergency created by a mistaken view about the nature of space and gravitation. Furthermore, in the view of the present work, the accelerated expansion of the universe is expansion of the Higgs quantum space itself, driven by minimization of its total energy. Spontaneous breaking of the U(1) gauge symmetry and Bose-Einstein condensation of the Higgs bosons creates a potential energy well in the form of the Mexican sombrero. If the density φφ ∗ of the condensate is larger than the equilibrium density, then the Higgs quantum space can minimize its energy by volumetric expansion. The idea that the accelerated expansion of the universe is driven by a positive potential energy, dubbed dark energy, needs to be unveiled.

Milli-Interacting Dark Matter Interpretation of the Direct-Search Experiments

We reinterpret the results of the direct searches for dark matter in terms of milli-interacting dark particles. The model reproduces the positive results from DAMA/LIBRA and CoGeNT and is consistent with the absence of signal in the XENON100, CDMS-II/Ge, and LUX detectors. Dark atoms, interacting with standard atoms through a kinetic mixing between photons and dark photons and a mass mixing ofσmesons with dark scalars, diffuse elastically in terrestrial matter where they deposit all their energy. Reaching underground detectors through gravity at thermal energies, they form bound states with nuclei of the active medium by radiative capture, which causes the emission of photons that produce the observed signals. The parameter space of the model is explored and regions reproducing the results at the 2σlevel are obtained for each experiment.

Implications of the first AMS-02 measurement for dark matter annihilation and decay

In light of the first measurement ofthe positron fraction by the AMS-02 experiment,we perform a detailed global analysis onthe interpretation of the latest data ofPAMELA, Fermi-LAT, and AMS-02 in terms ofdark matter (DM) annihilation and decayin various propagation models.The allowed regions forthe DM particle mass and annihilation cross section or decay life-timeare obtained for channels with leptonic final states:2e, 2μ, 2τ, 4e, 4μ and 4τ.We show thatfor the conventional astrophysical backgroundthe AMS-02 positron fraction data alone favoura DM particle mass ∼ 500(800) GeVif DM particles annihilate dominantly into 2μ(4μ) final states,which is significantly lower than that favoured bythe Fermi-LAT data of the total flux of electrons and positrons.The allowed regions by the two experiments do not overlapat a high confidence level (99.99999%C.L.).We consider a number of propagation models with differenthalo height Zh, diffusion parameters D0 and δ1/2,and power indices of primary nucleon sources γp1/p2.The normalization and the slope of the electron background arealso allowed to vary.We find that the tension between the two experiments canbe only slightly reduced in the propagation model with large Zh and D0.The consistency of fit is improved forannihilation channels with 2τ and 4τ final stateswhich favour TeV scale DM particle with large cross sections above∼ 10−23 cm3s−1.In all the considered leptonic channels,the current data favour the scenario of DM annihilation over DM decay.In the decay scenario,the charge asymmetric DM decay is slightly favoured.

130 GeV gamma-ray line and generic dark matter model building constraints from continuum gamma rays, radio, and antiproton data

An analysis of the Fermi gamma-ray space telescope data has recently revealed a resolved gamma-ray feature close to the galactic center which is consistent with monochromatic photons at an energy of about 130 GeV. If interpreted in terms of dark matter (DM) annihilating into $\ensuremath{\gamma}\ensuremath{\gamma}$ ($\ensuremath{\gamma}Z$, $\ensuremath{\gamma}h$), this would correspond to a DM particle mass of roughly 130 GeV (145 GeV, 155 GeV). The rate for these loop-suppressed processes, however, is larger than typically expected for thermally produced DM. Correspondingly, one would generically expect even larger tree-level production rates of standard model fermions or gauge bosons. Here, we quantify this expectation in a rather model-independent way by relating the tree level and loop amplitudes with the help of the optical theorem. As an application, we consider bounds from continuum gamma rays, radio, and antiproton data on the tree-level amplitudes and translate them into constraints on the loop amplitudes. We find that, independently of the DM production mechanism, any DM model aiming at explaining the line signal in terms of charged standard model particles running in the loop is in rather strong tension with at least one of these constraints, with the exception of loops dominated by top quarks. We stress that attempts to explain the 130 GeV feature with internal bremsstrahlung do not suffer from such difficulties.

Search for dark matter in the Sun with the ANTARES neutrino telescope in the CMSSM and mUED frameworks

ANTARES is the first neutrino telescope in the sea. It consists of a three-dimensional array of 885 photomultipliers to collect the Cherenkov light induced by relativistic muons produced in CC interactions of high energy neutrinos. One of the main scientific goals of the experiment is the search for dark matter. We present here the analysis of data taken during 2007 and 2008 to look for a WIMP signal in the Sun. WIMPs are one of the most popular scenarios to explain the dark matter content of the Universe. They would accumulate in massive objects like the Sun or the Galactic Center and their self-annihilation would produce (directly or indirectly) high energy neutrinos detectable by neutrino telescopes. Contrary to other indirect searches (like with gamma rays or positrons), the search for neutrinos in the Sun is free from other astrophysical contributions, so the interpretation of a potential signal in terms of dark matter is much more robust.