Matter Model Research Articles

Oscillatons described by self-interacting quartic scalar fields

Abstract In this paper, we will study some properties of oscillatons, spherically symmetric object made of a real time-dependent scalar field, using a self-interaction quartic scalar field potential as a class of what is called Self-Interacting Dark Matter (SIDM) models. Since the oscillatons can be regarded as models for astrophysical objects which play the role of dark matter, therefore investigation of their properties could have an important place in present time of cosmology researches. We investigate the properties of these objects by Numerical Solving the system of differential equations obtained from the Einstein–Klein–Gordon (EKG) equations to show their importance as new candidates for dark matter in the galactic scales.

The dark matter distribution of NGC 5921

We used the neutral atomic hydrogen data of the Very Large Array for the spiral galaxy NGC 5921 with z = 0.0045 at the distance of 22.4 Mpc, to investigate the nature of dark matter. The investigation was based on two theories, namely, dark matter and Modified Newtonian Dynamics (MOND). We presented the kinematic analysis of the rotation curve with two models of dark matter, namely, the Burkert and NFW profiles. The results revealed that the NFW halo model can reproduce the observed rotation curve, with $$\chi ^{2}_{red}\approx 1$$ , while the Burkert model is unable to fit the observation data. Therefore, the dark matter density profile of NGC 5921 can be presented as a cuspy halo. We also tried to investigate the observed rotation curve of NGC 5921 with MOND, along with the possible assumption on baryonic matter and distance. We note that MOND is still incapable of mimicking the rotation curve with the observed data of the galaxy.

Well-tempered n-plet dark matter

We study simple effective models of fermionic WIMP dark matter, where the dark matter candidate is a mixture of a Standard Model singlet and an n-plet of SU2L with n ≥ 3, stabilized by a discrete symmetry. The dark matter mass is assumed to be around the electroweak scale, and the mixing is generated by higher-dimensional operators, with a cutoff scale ≳TeV. For appropriate values of the mass parameters and the mixing we find that the observed dark matter relic density can be generated by coannihilation. Direct detection experiments have already excluded large parts of the parameter space, and the next-generation experiments will further constrain these models.

Reconciling large- and small-scale structure in Twin Higgs models

We study possible extensions of the Twin Higgs model that solve the Hierarchy problem and simultaneously address problems of the large- and small-scale structures of the Universe. Besides naturally providing dark matter (DM) candidates as the lightest charged twin fermions, the twin sector contains a light photon and neutrinos, which can modify structure formation relative to the prediction from the ΛCDM paradigm. We focus on two viable scenarios. First, we study a Fraternal Twin Higgs model in which the spin-3/2 baryon widehat{varOmega}sim left(widehat{b}widehat{b}widehat{b}right) and the lepton twin tau widehat{tau} contribute to the dominant and subcomponent dark matter densities. A non-decoupled scattering between the twin tau and twin neutrino arising from a gauged twin lepton number symmetry provides a drag force that damps the density inhomogeneity of a dark matter subcomponent. Next, we consider the possibility of introducing a twin hydrogen atom Ĥ as the dominant DM component. After recombination, a small fraction of the twin protons and leptons remains ionized during structure formation, and their scattering to twin neutrinos through a gauged U(1)B−L force provides the mechanism that damps the density inhomogeneity. Both scenarios realize the Partially Acoustic dark matter (PAcDM) scenario and explain the σ8 discrepancy between the CMB and weak lensing results. Moreover, the self-scattering neutrino behaves as a dark fluid that enhances the size of the Hubble rate H0 to accommodate the local measurement result while satisfying the CMB constraint. For the small-scale structure, the scattering of widehat{varOmega} ’s and Ĥ’s through the twin photon exchange generates a self-interacting dark matter (SIDM) model that solves the mass deficit problem from dwarf galaxy to galaxy cluster scales. Furthermore, when varying general choices of the twin photon coupling, bounds from the dwarf galaxy and the cluster merger observations can set an upper limit on the twin electric coupling.

Analytic expressions for the dark matter-baryon relations

Recently, some very strong correlations between the distribution of dark matter and baryons (the dark matter-baryon relations) in galaxies with very different morphologies, masses, sizes and gas fractions have been obtained. Some models have been suggested to explain why the dark matter contribution is fully specified by that of the baryons. In this paper, we derive two analytic expressions to explain the observed dark matter-baryon relations based on the cold dark matter (CDM) model. The resultant expressions give excellent agreement with the observational data. The parameters involved in the analytic expressions are closely related to the amount of the baryon content. This model can provide a theoretical understanding of the strong correlations observed. We suggest that the observed relation represents the end product of galaxy formation.

Status of the scalar singlet dark matter model

One of the simplest viable models for dark matter is an additional neutral scalar, stabilised by a mathbb {Z}_2 symmetry. Using the GAMBIT package and combining results from four independent samplers, we present Bayesian and frequentist global fits of this model. We vary the singlet mass and coupling along with 13 nuisance parameters, including nuclear uncertainties relevant for direct detection, the local dark matter density, and selected quark masses and couplings. We include the dark matter relic density measured by Planck, direct searches with LUX, PandaX, SuperCDMS and XENON100, limits on invisible Higgs decays from the Large Hadron Collider, searches for high-energy neutrinos from dark matter annihilation in the Sun with IceCube, and searches for gamma rays from annihilation in dwarf galaxies with the Fermi-LAT. Viable solutions remain at couplings of order unity, for singlet masses between the Higgs mass and about 300 GeV, and at masses above sim 1 TeV. Only in the latter case can the scalar singlet constitute all of dark matter. Frequentist analysis shows that the low-mass resonance region, where the singlet is about half the mass of the Higgs, can also account for all of dark matter, and remains viable. However, Bayesian considerations show this region to be rather fine-tuned.

Mono-X versus direct searches: simplified models for dark matter at the LHC

We consider simplified models for dark matter (DM) at the LHC, focused on mono-Higgs, -Z or -b produced in the final state. Our primary purpose is to study the LHC reach of a relatively complete set of simplified models for these final states, while comparing the reach of the mono-X DM search against direct searches for the mediating particle. We find that direct searches for the mediating particle, whether in di-jets, jets+, multi-b+, or di-boson+, are usually stronger. We draw attention to the cases that the mono-X search is strongest, which include regions of parameter space in inelastic DM, two Higgs doublet, and squark mediated production models with a compressed spectrum.

Simplified models of dark matter with a long-lived co-annihilation partner

We introduce a new set of simplified models to address the effects of 3-point interactions between the dark matter particle, its dark co-annihilation partner, and the Standard Model degree of freedom, which we take to be the tau lepton. The contributions from dark matter co-annihilation channels are highly relevant for a determination of the correct relic abundance. We investigate these effects as well as the discovery potential for dark matter co-annihilation partners at the LHC. A small mass splitting between the dark matter and its partner is preferred by the co-annihilation mechanism and suggests that the co-annihilation partners may be long-lived (stable or meta-stable) at collider scales. It is argued that such long-lived electrically charged particles can be looked for at the LHC in searches of anomalous charged tracks. This approach and the underlying models provide an alternative/complementarity to the mono-jet and multi-jet based dark matter searches widely used in the context of simplified models with s-channel mediators. We consider four types of simplified models with different particle spins and coupling structures. Some of these models are manifestly gauge invariant and renormalizable, others would ultimately require a UV completion. These can be realised in terms of supersymmetric models in the neutralino-stau co-annihilation regime, as well as models with extra dimensions or composite models.

Supersymmetric versus SO(10) models of dark matter

After the results of Run I, can we still “guarantee” the discovery of supersymmetry at the LHC? It is shown that viable dark matter candidates in CMSSM-like models tend to lie in strips (coannihilation, funnel, focus point) in parameter space. The role of grand unification in constructing supersymmetric models is discussed and it is argued that nonsupersymmetric GUTs such as SO(10) may provide alternative solutions to many of the standard problems addressed by supersymmetry.

Reopening the Higgs portal for single scalar dark matter

A real singlet scalar, connected to the Standard Model sector through a portal with the Higgs boson, is one of the simplest and most popular models for dark matter (DM). However, the experimental advances in direct and indirect DM searches, together with the latest results from the LHC, have ruled out vast areas of the parameter space of this scenario; and are expected to probe it completely within the next years, ruling it out if no signal is found. Motivated by the simplicity of this model, in this article we address a minimal, renormalizable extension that could evade detection, consisting of the addition of an extra real singlet scalar field in the dark sector. We analyze the physical constraints on the model and show that the new annihilation and/or coannihilation channels involving the extra singlet allow to reproduce the correct DM relic abundance while avoiding the bounds from direct and indirect searches for any DM mass above 50 GeV. We also show that, in some interesting regions of the parameter space, the extra particle can be integrated-out, leaving a “clever” effective theory (just involving the DM particle and the Higgs), that essentially reproduces the results.

Improved Automatic Segmentation of White Matter Hyperintensities in MRI Based on Multilevel Lesion Features.

Brain white matter hyperintensities (WMHs) are linked to increased risk of cerebrovascular and neurodegenerative diseases among the elderly. Consequently, detection and characterization of WMHs are of significant clinical importance. We propose a novel approach for WMH segmentation from multi-contrast MRI where both voxel-based and lesion-based information are used to improve overall performance in both volume-oriented and object-oriented metrics. Our segmentation method (AMOS-2D) consists of four stages following a "generate-and-test" approach: pre-processing, Gaussian white matter (WM) modelling, hierarchical multi-threshold WMH segmentation and object-based WMH filtering using support vector machines. Data from 28 subjects was used in this study covering a wide range of lesion loads. Volumetric T1-weighted images and 2D fluid attenuated inversion recovery (FLAIR) images were used as basis for the WM model and lesion masks defined manually in each subject by experts were used for training and evaluating the proposed method. The method obtained an average agreement (in terms of the Dice similarity coefficient, DSC) with experts equivalent to inter-expert agreement both in terms of WMH number (DSC=0.637 vs. 0.651) and volume (DSC=0.743 vs. 0.781). It allowed higher accuracy in detecting WMH compared to alternative methods tested and was further found to be insensitive to WMH lesion burden. Good agreement with expert annotations combined with stable performance largely independent of lesion burden suggests that AMOS-2D will be a valuable tool for fully automated WMH segmentation in patients with cerebrovascular and neurodegenerative pathologies.

A model of neutrino mass and dark matter with large neutrinoless double beta decay

We propose a model where neutrino masses are generated at three loop order but neutrinoless double beta decay occurs at one loop. Thus we can have large neutrinoless double beta decay observable in the future experiments even when the neutrino masses are very small. The model receives strong constraints from the neutrino data and lepton flavor violating decays, which substantially reduces the number of free parameters. Our model also opens up the possibility of having several new scalars below the TeV regime, which can be explored at the collider experiments. Additionally, our model also has an unbroken Z2 symmetry which allows us to identify a viable Dark Matter candidate.

Cosmic abundances of SIMP dark matter

Thermal production of light dark matter with sub-GeV scale mass can be attributed to 3 → 2 self-annihilation processes. We consider the thermal average for annihilation cross sections of dark matter at 3 → 2 and general higher-order interactions. A correct thermal average for initial dark matter particles is important, in particular, for annihilation cross sections with overall velocity dependence and/or resonance poles. We apply our general results to benchmark models for SIMP dark matter and discuss the effects of the resonance pole in determining the relic density.

Scalar field dark matter in clusters of galaxies

One alternative to the cold dark matter (CDM) paradigm is the scalar field dark matter (SFDM) model, which assumes dark matter is a spin-0 ultra-light scalar field (SF) with a typical mass $m\sim10^{-22}\mathrm{eV}/c^2$ and positive self-interactions. Due to the ultra-light boson mass, the SFDM could form Bose-Einstein condensates (BEC) in the very early Universe, which are interpreted as the dark matter haloes. Although cosmologically the model behaves as CDM, they differ at small scales: SFDM naturally predicts fewer satellite haloes, cores in dwarf galaxies and the formation of massive galaxies at high redshifts. The ground state (or BEC) solution at zero temperature suffices to describe low-mass galaxies but fails for larger systems. A possible solution is adding finite-temperature corrections to the SF potential which allows combinations of excited states. In this work, we test the finite-temperature multistate SFDM solution at galaxy cluster scales and compare our results with the Navarro-Frenk-White (NFW) and BEC profiles. We achieve this by fitting the mass distribution of 13 \textit{Chandra} X-ray clusters of galaxies, excluding the region of the brightest cluster galaxy. We show that the SFDM model accurately describes the clusters' DM mass distributions offering an equivalent or better agreement than the NFW profile. The complete disagreement of the BEC model with the data is also shown. We conclude that the theoretically motivated multistate SFDM profile is an interesting alternative to empirical profiles and ad hoc fitting-functions that attempt to couple the asymptotic NFW decline with the inner core in SFDM.

Current opinion in Alzheimer's disease therapy by nanotechnology-based approaches.

Nanotechnology typically deals with the measuring and modeling of matter at nanometer scale by incorporating the fields of engineering and technology. The most prominent feature of these engineered materials involves their manipulation/modification for imparting new functional properties. The current review covers the most recent findings of Alzheimer's disease (AD) therapeutics based on nanoscience and technology. Current studies involve the application of nanotechnology in developing novel diagnostic and therapeutic tools for neurological disorders. Nanotechnology-based approaches can be exploited for limiting/reversing these diseases for promoting functional regeneration of damaged neurons. These strategies offer neuroprotection by facilitating the delivery of drugs and small molecules more effectively across the blood-brain barrier. Nanotechnology based approaches show promise in improving AD therapeutics. Further replication work on synthesis and surface modification of nanoparticles, longer-term clinical trials, and attempts to increase their impact in treating AD are required.

Cosmological study in loop quantum cosmology through dark energy model

The interacting generalized ghost version of pilgrim dark energy (GGPDE) is discussed in the framework of loop quantum cosmology (LQC). We analyze the behavior of cosmological parameters (Hubble, equation of state (EoS), deceleration) and cosmological planes ([Formula: see text] and [Formula: see text]-[Formula: see text]) in the present scenario ([Formula: see text] represents the EoS parameter and [Formula: see text] indicates the evolution of the EoS parameter, [Formula: see text],[Formula: see text] are statefinder parameters). It is observed that the deceleration parameter corresponds to the accelerated expansion of the universe. The EoS parameter lies in vacuum and phantom regions for all cases of [Formula: see text] (pilgrim dark energy (PDE) parameter). The [Formula: see text] plane lies in thawing region for all cases of [Formula: see text]. The [Formula: see text] plane corresponds to [Formula: see text] cold dark matter (CDM) and Chaplygin gas model. We have also mentioned the constraints on calculated cosmological parameters and found that all the trajectories of cosmological parameters and planes show the consistence behavior with the observational schemes.

The XENON project for dark matter direct detection at LNGS

The XENON project at INFN Laboratori Nazionali del Gran Sasso, Italy, aims at dark matter direct detection with liquid xenon dual-phase time projection chambers. Latest results of XENON100 detector exclude various models of leptophilic dark matter. A search for low mass weakly interacting massive particles was also performed, lowering the energy threshold for detection to 0.7 keV for nuclear recoils. The multi-ton XENON1T detector is fully installed and operating. It is expected to reach a sensitivity a factor 100 better than XENON100 with a 2 ton·year exposure.

Is the Velocity Interpretation of the Redshift of Spectral Lines in Accordance with Astronomical Data?

Current progress in cosmic microwave background (CMB) anisotropy measurements opens up the possibility of determining Hubble’s constant (H0 = h × 100 km s−1 Mpc−1) from the CMB power spectrum radiation temperature anisotropy. The results show that, besides the Lambda cold dark matter (ΛCDM) model, much simpler Einstein-de Sitter (EdeS) models without the cosmological constant can fit the data as well, or even better, than the ΛCDM model. Calculations with EdeS models yield unexpectedly low values for Hubble’s constant of h = 0.30 and 0.46, respectively. These values are completely inconsistent with the direct determination of h ~ 0.70 from the redshift (RS) of spectral lines. In the present paper I consider whether the gap between h = 0.3 and h = 0.7 could be explained using conventional physics without introducing further hypotheses, or whether the RS of starlight and the RS of the CMB could stem from different physical origins.

Organic matter and heavy metals content modeling in sewage sludge treated with reed bed system

The long process of sludge stabilization (7–15 years) remarkably reduces the organic matter content and causes the process of sludge humifaction. This paper presents the results of using low-cost methods of sludge treatment in the wastewater treatment plant located in Zambrow, Podlaskie Province. The results of studies on the organic matter and heavy metals content in sewage sludge after treatment in a reed bed system are presented. The aim of the research was to evaluate and model organic matter and heavy metals concentrations during sewage stabilization in reed bed lagoons. The lowest concentration, below 1.3 mg/kg DM of the examined seven heavy metals was mercury (Hg). The highest concentration, exceeding 1300 mg/kg DM was zinc (Zn). The obtained results for the heavy metals in sewage sludge from the reed bed lagoons in Zambrow show that the average content of the analyzed heavy metals is approximately 1620 mg/kg DM. The results of the study demonstrate a high efficiency of low-cost methods used in Zambrow WWTP in terms of the quality of the processed sludge. Sewage sludge from the lowest layer of the reed lagoon (12–14 years of dewatering and transformation) is characterized by the lowest organic matter and heavy metals content. The higher a sediment layer lies, i.e. the shorter the time of processing, the higher is the heavy metals content. This indicates a great role of reeds in the accumulation of these compounds.

Bayesian inference of x-ray diffraction spectra from warm dense matter with the one-component-plasma model.

We show that the Bayesian inference of recently measured x-ray diffraction spectra from laser-shocked aluminum [L. B. Fletcher et al., Nat. Photon. 9, 274 (2015)10.1038/nphoton.2015.41] with the one-component-plasma (OCP) model performs remarkably well at estimating the ionic density and temperature. This statistical approach requires many evaluations of the OCP static structure factor, which were done using a recently derived analytic fit. The atomic form factor is approximated by an exponential function in the diffraction window of the first peak. The electronic temperature is then estimated from a comparison of this approximated form factor with the electronic structure of an average atom model. Out-of-equilibrium states, with electrons hotter than ions, are diagnosed for the spectra obtained early after the pump, whereas at a late time delay the plasma is at thermal equilibrium. Apart from the present findings, this OCP-based modeling of warm dense matter has an important role to play in the interpretation of x-ray Thomson scattering measurements currently performed at large laser facilities.