Matter Clumps Research Articles

Nonrelativistic formation of scalar clumps as a candidate for dark matter

We propose a new mechanism for the formation of dark matter clumps in the radiation era. We assume that a light scalar field is decoupled from matter and oscillates harmonically around its vacuum expectation value. We include self-interactions and consider the nonrelativistic regime. The scalar dynamics are described by a fluid approach where the fluid pressure depends on both quantum and self-interaction effects. When the squared speed of sound of the scalar fluid becomes negative, an instability arises and the fluctuations of the scalar energy-density field start growing. They eventually become nonlinear and clumps form. Subsequently, the clumps aggregate and reach a universal regime. Afterwards, they play the role of cold dark matter. We apply this mechanism first to a model with a negative quartic term stabilised by a positive self-interaction of order six, and then to axion monodromy, where a subdominant cosine potential corrects a mass term. In the first case, the squared speed of sound becomes negative when the quartic term dominates, leading to a tachyonic instability. For axion monodromy, the instability starts very slowly after the squared speed of sound first becomes negative and then oscillates around zero. Initially the density perturbations perform acoustic oscillations due to the quantum pressure. Eventually, they start growing exponentially due to a parametric resonance. In both scenarios, the scalar-field clumps span a wide range of scales and masses, running from the size of atoms to that of galactic molecular clouds, and from $10^{-3} \, {\rm gram}$ to thousands of solar masses. Because of finite-size effects, both from the source and the lens, these dark matter clumps are far beyond the reach of microlensing observations.

Possible formation of ring galaxies by torus-shaped magnetic wormholes

We present the hypothesis that some of ring galaxies were formed by relic magnetic torus-shaped wormholes. In the primordial plasma before the recombination magnetic fields of wormholes trap baryons whose energy is smaller than a threshold energy. They work as the Maxwell’s demons collecting baryons from the nearest (horizon size) region and thus forming clumps of baryonic matter which have the same torus-like shapes as wormhole throats. Such clumps may serve as seeds for the formation of ring galaxies and smaller objects having the ring form. Upon the recombination torus-like clumps may decay and merge. Unlike galaxies, such objects may contain less or even no dark matter in halos. However the most stringent feature of such objects is the presence of a large-scale toroidal magnetic field. We show that there are threshold values of magnetic fields which give the upper and lower boundary values for the baryon clumps in such protogalaxies.

Fundamental physics tests using the propagation of GNSS signals

This paper introduces new tests of fundamental physics by means of the analysis of disturbances on the GNSS signal propagation. We show how the GNSS signals are sensitive to a space variation of the fine structure constant α in a generic framework of effective scalar field theories beyond the Standard Model. This effective variation may originate from the crossing of the RF signals with dark matter clumps and/or solitonic structures. At the macroscopic scale, the subsequent disturbances are equivalent to those which occur during the propagation in an inhomogeneous medium. We thus propose an interpretation of the “measure” of the vacuum permeability as a test of fundamental physics. We show the relevance of our approach by a first quantification of the expected signature in a simple model of a variation of α according to a planar geometry. We use a test-bed model of domain walls for that purpose and focus on the measurable time delay in the GNSS signal carrier.

Resonant instability of axionic dark matter clumps

Axion is a popular candidate for dark matter particles. Axionic dark matter may form Bose-Einstein condensate and may be gravitationally bound to form axion clumps. Under the presence of electromagnetic waves with frequency ω= ma/ 2, where ma is the axion mass, a resonant enhancement may occur, causing an instability of the axion clumps. With analytical and numerical approaches, we study the resonant instability of axionic dark matter clumps with infinite homogeneous mass distribution, as well as distribution with a finite boundary. After taking realistic astrophysical environments into consideration, including gravitational redshift and plasma effects, we obtain an instability region in the axion density—clump size parameter space with given mass and coupling of axions. In particular, we show that, for axion clumps formed by the QCD axions in equilibrium, no resonant instability will occur.

Dark Matter Signatures of Supermassive Black Hole Binaries

Abstract A natural consequence of the galaxy formation paradigm is the existence of supermassive black hole (SMBH) binaries. Gravitational perturbations from a far-away SMBH companion can induce high orbital eccentricities on dark matter (DM) particles orbiting the primary SMBH via the eccentric Kozai–Lidov mechanism. This process yields an influx of DM particles into the primary SMBH ergosphere, where test particles linger for long timescales. This influx results in high self-gravitating densities, forming a DM clump that is extremely close to the SMBH. In such a situation, the gravitational-wave (GW) emission between the dark matter clump and the SMBH is potentially detectable by LISA. If dark matter self-annihilates, the high densities of the clump will result in a unique codetection of GW emission and high-energy electromagnetic signatures.

Connecting direct and indirect detection with a dark spike in the cosmic-ray electron spectrum

Multiple space-borne cosmic ray detectors have detected line-like features in the electron and positron spectra. Most recently, the DAMPE collaboration reported the existence of such a feature at 1.4 TeV, sparking interest in a potential dark matter origin. Such quasi-monochromatic features, virtually free of any astrophysical background, could be explained by the annihilation of dark matter particles in a nearby dark matter clump. Here, we explore the consistency of producing such spectral features with dark matter annihilation from the standpoint of dark matter substructure statistics, constraints from anisotropy, and constraints from gamma-ray emission. We demonstrate that if indeed a high-energy, line-like feature in the electron-positron spectrum originates from dark matter annihilation in a nearby clump, a significant or even dominant fraction of the dark matter in the Solar System likely stems from the clump, with dramatic consequences for direct dark matter searches.

Gravitational collapse of dust fluid and dark energy in the presence of curvature: Black hole formation

Study of gravitational collapse and black hole formation has got much interest in recent years after gravitational waves detection from mergers of black hole binaries. Here, we studied the gravitational collapse of a spherically symmetric clump of matter, constituted of dust fluid, [Formula: see text], in a background of dark energy, [Formula: see text]. We investigate the curvature effect [Formula: see text] on the gravitational collapsing process. Gravitational collapsing process for two different cases is discussed i.e. collapse of dust cloud only and collapse of dark energy. We used equation of state [Formula: see text], [Formula: see text]. For dark energy case, we discuss the collapsing process and curvature effect for different parameter values of equation of state.

Pulsar timing probes of primordial black holes and subhalos

Pulsars act as accurate clocks, sensitive to gravitational redshift and acceleration induced by transiting clumps of matter. We study the sensitivity of pulsar timing arrays (PTAs) to single transiting compact objects, focusing on primordial black holes and compact subhalos in the mass range from ${10}^{\ensuremath{-}12}\text{ }\text{ }{M}_{\ensuremath{\bigodot}}$ to well above $100\text{ }\text{ }{M}_{\ensuremath{\bigodot}}$. We find that the square kilometer array can constrain such objects to be a subdominant component of the dark matter over this entire mass range, with sensitivity to a dark matter subcomponent reaching the subpercent level over significant parts of this range. We also find that PTAs offer an opportunity to probe substantially less dense objects than lensing because of the large effective radius over which such objects can be observed, and we quantify the subhalo concentration parameters which can be constrained.

DESENVOLVIMENTO DA CULTURA E PRESENÇA DE E. COLI NA SALSA IRRIGADA COM ÁGUA RESIDUÁRIA TRATADA POR RADIAÇÃO SOLAR

DESENVOLVIMENTO DA CULTURA E PRESENÇA DE E. COLI NA SALSA IRRIGADA COM ÁGUA RESIDUÁRIA TRATADA POR RADIAÇÃO SOLAR
 
 
 MARIANA ALEXANDRE DE LIMA SALES1 E RODRIGO MÁXIMO SÁNCHEZ ROMÁN2
 
 1 Doutora em Agronomia: Irrigação e Drenagem. Rua Heleni de Souza Costa, 41 – Jardim Ypê, 18.608-710, Botucatu-SP, Brasil. mal_sales@hotmail.com
 2 Departamento de Engenharia Rural, Faculdade de Ciências Agronômicas, Universidade Estadual Paulista (UNESP) Campus de Botucatu. Fazenda Experimental Lageado, Avenida Universitária, nº 3780, Altos do Paraíso, CEP: 18610-034, Botucatu – SP. Brasil. rodrigo.roman@unesp.br
 
 
 1 RESUMO
 
 O objetivo deste trabalho foi avaliar a influência da água residuária doméstica tratada por radiação solar (ARD-TRS) no desenvolvimento da salsa (graúda portuguesa), além de verificar e quantificar a presença de Escherichia coli na cultura. O experimento foi realizado na FCA/UNESP no município de Botucatu - São Paulo, o qual consistiu na aplicação de diferentes porcentagens (0, 25, 50, 75 e 100%) de ARD-TRS na lâmina total de irrigação. Os resultados obtidos foram satisfatórios, visto que no geral houve um aumento nos valores de altura da planta, número de talos, diâmetro do maior talo, diâmetro da touceira e massa da matéria fresca e seca, observando-se diferenças significativas em função da porcentagem de ARD-TRS na lâmina total de irrigação. Assim conclui-se que, a utilização de diferentes porcentagens de ARD-TRS na lâmina total de irrigação influenciou positivamente no desenvolvimento da cultura estudada, apresentando uma população de E. coli na água de irrigação < 100 NMP 100 mL-1 e nas culturas ≤ 1.000 NMP 100 mL-1.
 
 Palavras-chave: reuso da água, SODIS, Petroselinum Crispum, coliformes, produtividade.
 
 SALES, M. A. L.; SÁNCHEZ-ROMÁN, R. M.
 DEVELOPMENT AND PRESENCE OF E. COLI IN PARSLEY IRRIGATED WITH DOMESTIC WASTE WATER TREATED WITH SOLAR RADIATION 
 
 
 2 ABSTRACT
 
 The objective of this study was to evaluate the influence of solar-treated domestic wastewater (ARD-TRS) on the development of parsley (Portuguese coarse), and to verify and quantify the presence of Escherichia coli in the crop. The experiment, carried out at FCA / UNESP, in Botucatu - São Paulo, consisted of the application of different percentages (0, 25, 50, 75 and 100%) of ARD-TRS in the total irrigation depth. The results obtained were satisfactory, since in general there was an increase in values ​​of plant height, number of stalks, diameter of the largest stalk, clump diameter and mass of fresh and dry matter, and significant differences were observed as function of the percent of ARD-TRS in the total irrigation depth. Thus, it was concluded that the use of different percentages of ARD-TRS in the total irrigation depth had a positive influence on the development of the studied culture, presenting a population of E. coli in irrigation water <100 NMP 100 mL-1 and in cultures ≤ 1,000 NMP 100 mL -1.
 
 Keywords: water reuse, SODIS, Petroselinum crispum, coliforms, productivity.

Oscillation modes of ultralight BEC dark matter cores

Structure formation simulations of ultralight bosonic dark matter, ruled by the Gross-Pitaevskii-Poisson (GPP) system of equations, show that dark matter clumps to form structures with density profiles consisting of a core surrounded by a power-law distribution. The core has a density profile similar to that of spherically symmetric equilibrium configurations of the GPP system. These configurations have been shown to be stable under a variety of perturbations and to have attractor properties. It is interesting to know the dominant frequencies of oscillation of these configurations. One reason is that in galaxies the effects of perturbations can trigger observable effects for specific frequency modes. Another reason is that during the process of structure formation, the oscillation modes can help to characterize a core. Based on these motivations, in this manuscript we present a systematic numerical analysis of the reaction of equilibrium configurations to various axi-symmetric perturbations with modes $l=0,1,2,3,4$. We then calculate the first few oscillation frequencies of equilibrium configurations for each mode.

Enhanced n-body annihilation of dark matter and its indirect signatures

We examine the possible indirect signatures of dark matter annihilation processes with a non-standard scaling with the dark matter density, and in particular the case where more than two dark matter particles participate in the annihilation process. We point out that such processes can be strongly enhanced at low velocities without violating unitarity, similar to Sommerfeld enhancement in the standard case of two-body annihilation, potentially leading to visible signals in indirect searches. We study in detail the impact of such multi-body annihilations on the ionization history of the universe and consequently the cosmic microwave background, and find that unlike in the two-body case, the dominant signal can naturally arise from the end of the cosmic dark ages, after the onset of structure formation. We examine the complementary constraints from the Galactic Center, Galactic halo, and galaxy clusters, and outline the circumstances under which each search would give rise to the strongest constraints. We also show that if there is a population of ultra-compact dense dark matter clumps present in the Milky Way with sufficiently steep density profile, then it might be possible to detect point sources illuminated by multi-body annihilation, even if there is no large low-velocity enhancement. Finally, we provide a case study of a model where 3-body annihilation dominates the freezeout process, and in particular the resonant regime where a large low-velocity enhancement is naturally generated.

Through a mini halo, darkly

In this Letter we explore the effects of the scattering of photons incident on a dark matter halo through their interaction with either electrons or photons produced by dark matter annihilation. Particularly, we examine the effects of this scattering upon the observed spectrum of a distant AGN or of the Cosmic Microwave Background. Our results indicate that ultra-compact mini halos and other dense dark matter clumps can induce an observable Comptonisation of AGN spectra as well as a Sunyaev-Zel'dovich effect (SZE) with an optical depth similar to that attained by thermal electrons in the Coma cluster. The rate of encounters between a distant AGN and these dense mini-halos is also estimated using micro-lensing limits existing on the population of dark compact bodies.

Sky rivers.

Streams of stars falling into our galaxy trace its history and mass. They may even record encounters with clumps of dark matter.

Black Hole in a Radiation-Dominated Universe

We study a black hole in an expanding Universe during the radiation-dominated stage. In the case when the black hole radius is much smaller than the cosmological horizon, we present a solution of the Einstein equations for the metric, the matter density and velocity distributions. At distances much smaller than the cosmological horizon the solution features quasi-stationary accretion, while at large distances the solution asymptotes the homogeneous radiation dominated FLRW. We discuss how our solution is related to the McVittie solution. The obtained results can be applied, in particular, for the formation of dark matter density spikes around primordial black holes, and for the evolution of dark matter clumps during the radiation-dominated stage.

Scalar dark matter clumps with angular momentum

The behavior of light scalar dark matter has been a subject of much interest recently as it can lead to interesting small scale behavior. In particular, this can lead to the formation of gravitationally bound clumps for these light scalars, including axions. In ref. [1] we analyzed the behavior of these clumps, assuming spherical symmetry, allowing for both attractive and repulsive self-interactions. There is a maximum allowed mass for the clumps in the case of attractive interactions, and a minimum radius for the clumps in the case of repulsive interactions, which is saturated at large mass. Here we extend this work to include non-spherically symmetric clumps. Since the system tries to re-organize into a BEC ground state, we consider configurations with a conserved non-zero angular momentum, and construct minimum energy configurations at fixed particle number and fixed angular momentum. We find generalizations of the previous spherically symmetric results. In particular, while there is still a maximum mass for the attractive case, its value increases with angular momentum. Also, the minimum radius in the repulsive case is raised to higher radii. We clarify how a recent claim in the literature of an upper bound on angular momentum is due to inaccurate numerics. In a forthcoming paper we shall investigate the possibility of resonance of axion clumps into both visible and hidden sector photons, and analyze how the altered mass and radius from non-zero angular momentum affects the resonance.

Searching for light from a dark matter clump

The DAMPE experiment has recently reported an electron spectrum that can be explained by dark matter annihilation into charged lepton pairs in a nearby dark matter clump. The accompanying bremsstrahlung may yield a gamma-ray excess with a known spectral shape that extends over an angular scale of \U0001d4aa(10̂). We show that such an excess is not present in Fermi-LAT data.

Gravitational collapse of interacting combination of dark matter and dark energy in the context of brane world regime

In the scenario of an optimal consideration that is, homogeneous and flat spacetime, we study the Black Hole (BH) formation from the gravitational collapse of a spherical symmetric clump of matter in the case of the specific Dark Matter (DM) model interacting with Dark Energy (DE) in the context of the brane world regime. This clump of matter constituted of DM, [Formula: see text] and DE, [Formula: see text]. In the present model, we consider anisotropic pressure in the energy–momentum tensor with a polytropic equation of state (EoS), [Formula: see text] and [Formula: see text], [Formula: see text]. Our results show that the gravitational collapse of an interacting combination of DM and DE leads to the formation of BH in the presence of brane tension. Recent work provides the generalization of isotropic pressure to an-isotropic pressure in the energy–momentum tensor for the specific interacting combination model of DM and DE in a brane world regime.

Properties of Merger Shocks in Merging Galaxy Clusters

Abstract X-ray shocks and radio relics detected in the cluster outskirts are commonly interpreted as shocks induced by mergers of subclumps. We study the properties of merger shocks in merging galaxy clusters, using a set of cosmological simulations for the large-scale structure formation of the universe. As a representative case, we focus on the simulated clusters that undergo almost head-on collisions with mass ratio ∼2. Due to the turbulent nature of the intracluster medium, shock surfaces are not smooth, but composed of shocks with different Mach numbers. As the merger shocks expand outward from the core to the outskirts, the average Mach number, , increases in time. We suggest that the shocks propagating along the merger axis could be manifested as X-ray shocks and/or radio relics. The kinetic energy through the shocks, F ϕ , peaks at ∼1 Gyr after their initial launching, or at ∼1–2 Mpc from the core. Because of the Mach number dependent model adopted here for the cosmic-ray (CR) acceleration efficiency, their CR-energy-weighted Mach number is higher with , compared to the kinetic-energy-weighted Mach number, . Most energetic shocks are to be found ahead of the lighter dark matter (DM) clump, while the heavier DM clump is located on the opposite side of clusters. Although our study is limited to the merger case considered, the results such as the means and variations of shock properties and their time evolution could be compared with the observed characteristics of merger shocks, constraining interpretations of relevant observations.

Two chemically similar stellar overdensities on opposite sides of the plane of the Galactic disk.

Our Galaxy is thought to have an active evolutionary history, dominated over the past ten billion years or so by star formation, the accretion of cold gas and, in particular, the merging of clumps of baryonic and dark matter. The stellar halo-the faint, roughly spherical component of the Galaxy-reveals rich 'fossil' evidence of these interactions, in the form of stellar streams, substructures and chemically distinct stellar components. The effects of interactions with dwarf galaxies on the content and morphology of the Galactic disk are still being explored. Recent studies have identified kinematically distinct stellar substructures and moving groups of stars in our Galaxy, which may have extragalactic origins. There is also mounting evidence that stellar overdensities (regions with greater-than-average stellar density) at the interface between the outer disk and the halo could have been caused by the interaction of a dwarf galaxy with the disk. Here we report a spectroscopic analysis of 14 stars from two stellar overdensities, each lying about five kiloparsecs above or below the Galactic plane-locations suggestive of an association with the stellar halo. We find that the chemical compositions of these two groups of stars are almost identical, both within and between these overdensities, and closely match the abundance patterns of stars in the Galactic disk. We conclude that these stars came from the disk, and that the overdensities that they are part of were created by tidal interactions of the disk with passing or merging dwarf galaxies.

Compact clumps of dark matter near the solar surface

The solar surface oscillations observed in the Crimean Astrophysical Observatory (CrAO) at the frequency 104.1890 μHz and in the Solar and Heliospheric Observatory (SoHO) at 220.72 μHz are considered as a result of existence of Compact Clumps of Dark Matter (CCDM) at orbits near the solar surface. These CCDM have to emit Gravitational Waves (GW) which are estimated to be the most intensive ones expected in the vicinity of the Earth and can be easily detected in the near future by means of the Evolved Laser Interferometer Space Antenna (eLISA). In addition to CCDMCrAO and CCDMSoHO some other CCDM may exist in the solar structure. It is shown that GW radiated by most of these CCDM could be detected by eLISA even if the respective solar surface oscillations are too small to be observed.