Local probes strongly favor ΛCDM against power-law and R_h=ct universe

We constrain three cosmological models – the concordance cold dark matter plus cosmological constant(ΛCDM) model, the power-law(PL) model, and the Rh =ct model – using the available local probes, which include the JLA compilation of type-Ia supernovae(SNe Ia), the direct measurement of the Hubble constant(H_(z)), and the baryon acoustic oscillations(BAO). For the ΛCDM model, we consider two different cases, i.e. zero and non-zero spatial curvature. We find that by using the JLA alone, the ΛCDM and PL models are indistinguishable, but the Rh =ct model is strongly disfavored. If we combine JLA+H_(z), the ΛCDM model is strongly favored over the other two models. The combination of all three datasets supports ΛCDM as the best model. We also use the low-redshift(z 0.2) data to constrain the deceleration parameter using the cosmography method, and find that only the ΛCDM model is consistent with cosmography. However, there is no strong evidence to distinguish between flat and non-flatΛCDM models by using the local data alone.     

Correlated perturbations from inflation and the cosmic microwave background

We compare the latest cosmic microwave background data with theoretical predictions including correlated adiabatic and cold dark matter (CDM) isocurvature perturbations with a simple power-law dependence. We find that there is a degeneracy between the amplitude of correlated isocurvature perturbations and the spectral tilt. A negative (red) tilt is found to be compatible with a larger isocurvature contribution. Estimates of the baryon and CDM densities are found to be almost independent of the isocurvature amplitude. The main result is that current microwave background data do not exclude a dominant contribution from CDM isocurvature fluctuations on large scales.     

Dark energy versus modified gravity: Impacts on measuring neutrino mass

In this paper,we make a comparison for the impacts of smooth dynamical dark energy,modified gravity,and interacting dark energy on the cosmological constraints on the total mass of active neutrinos.For definiteness,we consider theΛCDM model,the w CDM model,the f(R)model,and two typical interacting vacuum energy models,i.e.,the IΛCDM1 model with Q=βHρc and the IΛCDM2 model with Q=βHρΛ.In the cosmological fits,we use the Planck 2015 temperature and polarization data,in combination with other low-redshift observations including the baryon acoustic oscillations,the type Ia supernovae,the Hubble constant measurement,and the large-scale structure observations,such as the weak lensing as well as the redshift-space distortions.Besides,the Planck lensing measurement is also employed in this work.We find that,the w CDM model favors a higher upper limit on the neutrino mass compared to theΛCDM model,while the upper limit in the f(R)model is similar with that in theΛCDM model.For the interacting vacuum energy models,the IΛCDM1 model favors a higher upper limit on neutrino mass,while the IΛCDM2 model favors an identical neutrino mass with the case ofΛCDM.     

Fine-tuning favors mixed axion/axino cold dark matter over neutralinos in the minimal supergravity model

Over almost all of minimal supergravity (mSUGRA or CMSSM) model parameter space, there is a large overabundance of neutralino cold dark matter (CDM). We find that the allowed regions of mSUGRA parameter space which match the measured abundance of CDM in the universe are highly fine-tuned. If instead we invoke the Peccei–Quinn–Weinberg–Wilczek solution to the strong CP problem, then the SUSY CDM may consist of an axion/axino admixture with an axino mass of order the MeV scale, and where mixed axion/axino or mainly axion CDM seems preferred. In this case, fine-tuning of the relic density is typically much lower, showing that axion/axino CDM ( $a\tilde{a}$ CDM) is to be preferred in the paradigm model for SUSY phenomenology. For mSUGRA with $a\tilde{a}$ CDM, quite different regions of parameter space are now DM-favored as compared to the case of neutralino DM. Thus, rather different SUSY signatures are expected at the LHC in the case of mSUGRA with $a\tilde{a}$ CDM, as compared to mSUGRA with neutralino CDM.     

Study on Z-scan characteristics of multilayer nonlinear media using coordinate transformation method

We present a method that combines coordinate transformation and Crank-Nicholson finite difference scheme to simulate numerically Z-scan measurements of a multilayer nonlinear medium or a complicated multilayer structure. The method would be useful to design and optimize optical limiters and to determine the nonlinearities of cascading medium layers. The method has given a guideline for determining the characteristics of multilayer medium.     

What do gas-rich galaxies actually tell us about modified Newtonian dynamics?

It has recently been claimed that measurements of the baryonic Tully-Fisher relation (BTFR), a power-law relationship between the observed baryonic masses and outer rotation velocities of galaxies, support the predictions of modified Newtonian dynamics for the slope and scatter in the relation, while challenging the cold dark matter (CDM) paradigm. We investigate these claims, and find that (1)?the scatter in the data used to determine the BTFR is in conflict with observational uncertainties on the data, (2)?these data do not make strong distinctions regarding the best-fit BTFR parameters, (3)?the literature contains a wide variety of measurements of the BTFR, many of which are discrepant with the recent results, and (4)?the claimed CDM "prediction" for the BTFR is a gross oversimplification of the complex galaxy-scale physics involved. We conclude that the BTFR is currently untrustworthy as a test of CDM.     

Constraints on neutrino mass in the scenario of vacuum energy interacting with cold dark matter after Planck 2018

In this work, we investigate the constraints on the total neutrino mass in the scenario of vacuum energy interacting with cold dark matter (abbreviated as IΛCDM) by using the latest cosmological observations. We consider four typical interaction forms, i.e. $Q=\beta H{\rho }_{\mathrm{de}}$, $Q=\beta H{\rho }_{{\rm{c}}}$, $Q=\beta {H}_{0}{\rho }_{\mathrm{de}}$, and $Q=\beta {H}_{0}{\rho }_{{\rm{c}}}$, in the IΛCDM scenario. To avoid the large-scale instability problem in interacting dark energy models, we employ the extended parameterized post-Friedmann method for interacting dark energy to calculate the perturbation evolution of dark energy in these models. The observational data used in this work include the cosmic microwave background (CMB) measurements from the Planck 2018 data release, the baryon acoustic oscillation (BAO) data, the type Ia supernovae (SN) observation (Pantheon compilation), and the 2019 local distance ladder measurement of the Hubble constant H₀ from the Hubble Space Telescope. We find that, compared with those in the ΛCDM+$\sum {m}_{\nu }$ model, the constrains on $\sum {m}_{\nu }$ are looser in the four IΛCDM+$\sum {m}_{\nu }$ models. When considering the three mass hierarchies of neutrinos, the constraints on $\sum {m}_{\nu }$ are tightest in the degenerate hierarchy case and loosest in the inverted hierarchy case. In addition, in the four IΛCDM+$\sum {m}_{\nu }$ models, the values of coupling parameter β are larger using the CMB+BAO+SN+H₀ data combination than that using the CMB+BAO+SN data combination, and β>0 is favored at more than 1σ level when using CMB+BAO+SN+H₀ data combination. The issue of the H₀ tension is also discussed in this paper. We find that, compared with the ΛCDM+$\sum {m}_{\nu }$ model, the H₀ tension can be alleviated in the IΛCDM+$\sum {m}_{\nu }$ model to some extent.     

A Comparison of the LVDP and ΛCDM Cosmological Models

We compare the cosmological kinematics obtained via our law of linearly varying deceleration parameter (LVDP) with the kinematics obtained in the ΛCDM model. We show that the LVDP model is almost indistinguishable from the ΛCDM model up to the near future of our universe as far as the current observations are concerned, though their predictions differ tremendously into the far future.     

Growth of linear matter perturbations and current observational constraints

We discuss, using a recently proposed parametrization for the growth index of linear matter perturbations, the observational constraints on the wCDM model and the Dvali—Gabadadze—Porrati (DGP) model with all current growth factor data. We find that the wCDM model is allowed by the observations at the 1$\sigma$ confidence level, while the DGP model is only consistent with observations at 2$\sigma$ confidence level.     

Toward classifying elementary microstructures in thin films by their scattering responses

The coupled dipole method (CDM) and the method of moments (MOM) can both be applied to study the light scattering responses of microstructures commnly found in optical and infrared thin films. A comparative analysis of the MOM and the CDM for these scattering problems is done. Three estimates of the polarizability scalars of subregional volumes are also compared.     

Confronting dark energy models mimicking ΛCDM epoch with observational constraints: Future cosmological perturbations decay or future Rip?

We confront dark energy models which are currently similar to ΛCDM theory with observational data which include the SNe data, matter density perturbations and baryon acoustic oscillations data. DE cosmology under consideration may evolve to Big Rip, type II or type III future singularity, or to Little Rip or Pseudo-Rip universe. It is shown that matter perturbations data define more precisely the possible deviation from ΛCDM model than consideration of SNe data only. The combined data analysis proves that DE models under consideration are as consistent as ΛCDM model. We demonstrate that growth of matter density perturbations may occur at sufficiently small background density but still before the possible disintegration of bound objects (like clusters of galaxies, galaxies, etc.) in Big Rip, type III singularity, Little Rip or Pseudo-Rip universe. This new effect may bring the future universe to chaotic state well before disintegration or Rip.     

Investigations of the electron paramagnetic resonance spectra of VO<Superscript>2+</Superscript> in CaO-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-SiO<Subscript>2</Subscript> system

The EPR spectra for VO²⁺ in CaO-Al₂O₃-SiO₂ system are calculated using complete diagonalization method (CDM) and perturbation theory method (PTM). The calculated results are in good agreement with the observed values. By comparing the calculated results by CDM and PTM in a wide range of crystal field parameters, the validity of the PTM formulas has been studied. It is shown that, the PTM formulas are reasonable and reliable in a wide range of CF parameters.     

Annihilating cold dark matter

Structure formation with cold dark matter (CDM) predicts halos with a central density cusp, which are observationally disfavored. If CDM particles have an annihilation cross section sigmav approximately 10(-29)(m/GeV) cm(2), then annihilations will soften the cusps. We discuss plausible scenarios for avoiding the early Universe annihilation catastrophe that could result from such a large cross section. The predicted scaling of core density with halo mass depends upon the velocity dependence of sigmav, and s-wave annihilation leads to a core density nearly independent of halo mass, which seems consistent with observations.     

Nonthermal production of weakly interacting massive particles and the subgalactic structure of the universe

There is increasing evidence that conventional cold dark matter (CDM) models lead to conflicts between observations and numerical simulations of dark matter halos on subgalactic scales, which rules out the favored candidates for CDM, namely weakly interacting massive particles (WIMPs). We propose a mechanism of nonthermal production of WIMPs and study its implications on the power spectrum. Our results show that, in this context, WIMPs as candidates for dark matter can work well both on large scales and on subgalactic scales.     

Observational Constraints on the Modified Gravity Model (MOG) Proposed by Moffat: Using the Magellanic System

A simple model for the dynamics of the Magellanic Stream (MS), in the framework of modified gravity models is investigated. We assume that the galaxy is made up of baryonic matter out of context of dark matter scenario. The model we used here is named Modified Gravity (MOG) proposed by Moffat (J. Cosmol. Astropart. Phys. 003, 2005). In order to examine the compatibility of the overall properties of the MS under the MOG theory, the observational radial velocity profile of the MS is compared with the numerical results using the χ ² fit method. In order to obtain the best model parameters, a maximum likelihood analysis is performed. We also compare the results of this model with the Cold Dark Matter (CDM) halo model and the other alternative gravity model that proposed by Bekenstein (Phys. Rev. D 70:083509, 2004), so called TeVeS. We show that by selecting the appropriate values for the free parameters, the MOG theory seems to be plausible to explain the dynamics of the MS as well as the CDM and the TeVeS models.     

Quantum gravity and dark matter

We propose a connection between global physics and local galactic dynamics via quantum gravity. The salient features of cold dark matter (CDM) and modified Newtonian dynamics (MOND) are combined into a unified scheme by introducing the concept of MONDian dark matter which behaves like CDM at cluster and cosmological scales but emulates MOND at the galactic scale.     

Leptogenesis and dark matter unified in a non-SUSY model for neutrino masses

We propose a unified explanation for the origin of dark matter and baryon number asymmetry on the basis of a non-supersymmetric model for the neutrino masses. Neutrino masses are generated in two distinct ways, that is, a tree-level seesaw mechanism with a single right-handed neutrino, and one-loop radiative effects by a new additional doublet scalar. A spontaneously broken U(1)^′ brings about a Z₂ symmetry which restricts couplings of this new scalar and controls the neutrino masses. It also guarantees the stability of a CDM candidate. We examine two possible candidates for the CDM. We also show that the decay of a heavy right-handed neutrino related to the seesaw mechanism can generate baryon number asymmetry through leptogenesis.     

非晶态多层膜和单层膜的低角X射线衍射研究

本文对a-Si:H/(a-SiN_x:H)非晶态周期多层膜和单层膜进行了低角X射线衍射研究。在周期数较少的多层膜衍射的布喇格衍射峰的低角侧发现了一系列次级衍射峰;在单层膜样品的低角衍射中也发现了一系列小峰。对此,我们提出了一个用于计算非晶多层膜和单层膜衍射强度的简单公式,使实验结果得到解释,并提出了一种测量膜厚的方法。 关键词：     

An approximate method for calculating scattering and absorption of light by fractal aggregates

A simplified version of the coupled dipole method (CDM) is proposed which allows one to reduce the initial system of 3N×3N equations to a simpler system of N×N equations. The method neglects depolarization effects in the interaction of dipoles but, unlike the mean field approximation, it takes into account local fluctuations of the scalar amplitudes of the excited dipole moments. Simple analytic solutions are obtained for integrated cross sections averaged over aggregate orientations. It is shown by the example of ballistic fractal aggregates that this method provides the accuracy close to that of a standard CDM, being substantially less time-consuming. In the case of biospheres, the approximate method is compared with the exact results of the multipole expansion.     

Analysis of charged device model (CDM) ESD in MEMS

The effect of charge injection due to CDM ESD in capacitive MEMS structures is analyzed. The results show that as feature size is reduced, ESD injected charge produces a change for the stiction effect which is inversely proportional to the square of the plate area and a change in the dielectric layer breakdown which is inversely proportional to the plate area. An electric field model is developed to examine charge and voltage modes in MEMS. A charge injection test method is proposed to determine the susceptibility of MEMS to CDM ESD.