Effect Of Decoupling Research Articles

GeV-scale dark matter with p -wave Breit-Wigner enhanced annihilation

We consider a light scalar dark matter candidate with mass in the GeV range whose p-wave annihilation is enhanced through a Breit-Wigner resonance. The annihilation actually proceeds in the s-channel via a dark photon mediator whose mass is nearly equal to the masses of the incoming particles. We compute the temperature at which kinetic decoupling between dark matter and the primordial plasma occurs and show that including the effect of kinetic decoupling can reduce the dark matter relic density by orders of magnitude. For typical scalar masses ranging from 200 MeV to 5 GeV, we determine the range of values allowed for the dark photon couplings to the scalar and to the standard model particles after requiring the relic density to be in agreement with the value extracted from cosmological observations. We then show that μ and y-distortions of the cosmic microwave background spectrum and x-ray data from XMM-Newton strongly constrain the model and rule out the region where the dark matter annihilation cross section is strongly enhanced at small dispersion velocities. Constraints from direct detection searches and from accelerator searches for dark photons offer complementary probes of the model. Published by the American Physical Society 2024

The Effect of Gravitational Decoupling on Constraining the Mass and Radius for the Secondary Component of GW190814 and Other Self-bound Strange Stars in f(Q) Gravity Theory

Inspired by the conundrum of the gravitational event GW190814, which brings to light the coalescence of a 23 M ⊙ black hole with a yet-to-be-determined secondary component, we look to modeling compact objects within the framework of gravity by employing the method of gravitational decoupling. We impose a quadratic equation of state (EOS) for the interior matter distribution, which in the appropriate limit reduces to the MIT bag model. The governing field equations arising from gravitational decoupling bifurcate into the and sectors, leading to two distinct classes of solutions. Both families of solutions are subjected to rigorous tests, qualifying them to describe a plethora of compact objects, including neutron stars, strange stars, and the possible progenitor of the secondary component of GW190814. Using observational data of mass–radius relations for compact objects LMC X-4, Cen X-3, PSR J1614–2230, and PSR J0740+6620, we show that it is possible to generate stellar masses and radii beyond 2.0 M ⊙ for neutron stars. Our findings reveal that the most suitable and versatile model in this framework is the quadratic EOS, which accounts for a range of low-mass stars and typical stellar candidates describing the secondary component of GW190814.

Reproduction of Natural Resource Capital in the Framework of the Implementation of Vari-ous Priorities of Regional Socio-Economic Development

The use of cognitive modeling tools in the process of studying the influence of the dominants of regional socio-economic development on the parameters of reproduction of the natural resource capital of the territory is considered. Particular attention is paid to the implementation of this process in the agricultural sector, its relationship with the possibility of achieving the effect of resource decoupling.

Magnetization AC losses of MgB2 wires with thin filaments and resistive sheath

Magnetization AC losses of fine-filamentary MgB2 wires with resistive CuNi sheaths were measured. The effects of varying the number of filaments (114–342, corresponding to effective filament diameters of 14–20 μm), twist pitch (10–30 mm) and outer sheath material on the total AC loss were studied. For a better understanding of individual loss contributions, the effects of varying applied temperature, magnetic field, and frequencies were examined. It is found that hysteresis loss per volume decreases with the reduced filament size and that coupling current losses play a dominant role. The effect of decoupling by twisting was clearly observed for the smallest twist pitches. Considering the possible degradation of transport currents by twisting, AC losses were also normalized by the critical currents of the same wires. While twisting to short pitch decreases losses significantly, it apparently does not reduce the transport current. Consequently, the fine-filamentary MgB2 wires with resistive CuNi sheath examined in this paper are excellent candidates for future low loss applications. Unlike ReBCO tapes, round MgB2 wires enable easy single strand twisting, and the braiding or cabling, of wires into a variety of specific shapes and diameters.

Complexity-free Vaidya-Tikekar model describing self-bound compact objects by gravitational decoupling

In this article, using gravitational decoupling under vanishing complexity condition, an anisotropic solution to spherically symmetric compact stars has been investigated. After obtaining the solution, a detailed physical analysis including thermodynamic parameters, mass-radius ratio, and stability analysis of the model corresponding to the secondary component of the GW190814 event has been done. To test the effect of gravitational decoupling on the mass-radius ratio, we fixed the mass of the secondary component of the GW190814 event corresponding to the pure general relativity scenario. Alongside this, we also predicted the radii and mass-radius ratio of 11 different compact stars using observational data of their masses for different values of β. Furthermore, the hydrostatic balance has been analyzed using the modified Tolman-Oppenheimer-Volkoff (TOV) equation. The physical analysis shows that our results are in good agreement as far as observational data is concerned.

A U-shaped and alternately driven ultrasonic motor using three bending coupled modes

Most of ultrasonic motors (USMs) using non-isomorphic hybrid modes have resonance deviation which are easy to produce frequency decoupling, and conventional USMs can only drive rotor once in a working cycle. To overcome these problems, a surface-bonded type of U-shaped USM is proposed in this paper. At the same frequency, three isomorphic fourth-order bending vibration modes can be excited simultaneously and the resonance deviation between modes is eliminated, thus reducing the effect of frequency decoupling. In addition, a fourth-order bending vibration mode on horizontal beam of the U-shaped structure is used to provide pressing force at driving feet, and bending vibration modes on two vertical beams generate driving forces. Under the excitation of orthogonal signals, alternately driven elliptical trajectories are generated at driving feet. Besides, the surface-bonded type USM is more convenient to realize miniaturization and flexible structure. The USM is analyzed by using finite element method. The prototype is fabricated to evaluate performance of the USM. The experimental results show that velocity of the USM is 89.03 mm s−1 when excitation voltage is 180 VP-P and frequency is 86 kHz. The feasibility of working principle is proved by the experimental results.

Understanding Initiation and Evolution of Pitting Corrosion in 7075-T6 Aluminum Alloy by Four-Dimensional X-Ray Microtomography

X-ray microcomputed tomography was conducted on an AA7075-T651 sample immersed in a 3.5 wt% NaCl solution to provide time-resolved measurements of localized corrosion. A nondestructive, volumetric analysis of pitting sites and local microstructural features followed, and quantitative results were combined with 2D and 3D visualizations. During alternating immersion periods, pitting was initiated at cathodic intermetallic inclusions and continued throughout the study. Rates of pit growth varied as a response to the decoupling of inclusions from the matrix, resulting in a start-and-stop trend that was observed in a significant number of examined sites. When a sample with a higher extent of cold rolling was examined with the same procedure, a finer and more homogeneous distribution of inclusions correlated with an increase in the maximum and mean pit depth. This change was attributed to the more frequent exposure of subsurface inclusions by localized corrosion, a phenomenon that mitigated the passivating effect of decoupling. Additionally, the effects of continuous immersion vs. alternate immersion were examined for metallurgically identical samples. Intermittent drying during the alternate immersion period destabilized the passive layer, increasing mean pit depth, while continuous immersion for 20 d produced a uniform and protective layer of corrosion product.

Concealing Dirac neutrinos from cosmic microwave background

The existence of prolonged radiation domination prior to the Big Bang Nucleosynthesis (BBN), starting just after the inflationary epoch, is not yet established unanimously. If instead, the universe undergoes a non-standard cosmological phase, it will alter the Hubble expansion rate significantly and may also generate substantial entropy through non-adiabatic evolution. This leads to a thumping impact on the properties of relic species decoupled from the thermal bath before the revival of the standard radiation domination in the vicinity of the BBN. In this work, considering the Dirac nature of neutrinos, we have studied decoupling of ultra-relativistic right-handed neutrinos (νR s) in presence of two possible non-standard cosmological phases. While in both cases we have modified Hubble parameters causing faster expansions in the early universe, one of the situations predicts a non-adiabatic evolution and thereby a slower redshift of the photon temperature due to the expansion. Considering the most general form of the collision term with Fermi-Dirac distribution and Pauli blocking factors, we have solved the Boltzmann equation numerically to obtain ΔNeff for the three right-handed neutrinos. We have found that for a large portion of parameter space, the combined effect of early decoupling of νR as well as the slower redshift of photon bath can easily hide the signature of right-handed neutrinos, in spite of precise measurement of ΔNeff, at the next generation CMB experiments like CMB-S4, SPT-3G etc. This however will not be applicable for the scenarios with only fast expansion.

Super-planckian thermal radiation in borophene sheets

Recently, borophene, a pioneering two-dimensional metal, has been attracting broad interest due to the in-plane anisotropic polaritons and large electrical tunability. Its attractive electronic and optical properties imply that borophene can find novel applications in electronics, thermionics, and photonics. Here, we study the near-field thermal radiation (NFTR) of monolayer borophene sheets; the results show that the NFTR of monolayer borophene is three-orders of magnitude larger than the black-body limit, even significantly exceeding the NFTR from traditional metals and metallic oxides with metallic behavior. An analysis of the photon tunneling coefficient and plasmon dispersion indicates that the coupling of quasi-elliptic surface plasmon polaritons (SPPs) of the borophene system extends robustly to the near- and mid-infrared frequencies, producing a broadband near-field emission from borophene. We also analyze the possibility of using the electrochemical method (that is, tuning the electron density) to modulate the NFTR between borophene sheets. The results reveal since the suppression on the wave-vector range and the anisotropy of SPPs by electron density, the switching coefficient of such electrochemical method can exceed up to 95%. Finally, the modulate effect of the mechanical decoupling on the NFTR is explored. We clarify the influence of decoupling effect at different frequencies on the mechanical thermal modulation of borophene. All in all, we explore the NFTR of the 2D borophene thoroughly for the first time, opening potential possibility for novel borophene-dependent thermal devices and thermal management.

Super-reaction: The collective enhancement of a reaction rate by molecular polaritons in the presence of energy fluctuations.

Recent experiments have demonstrated that molecular polaritons, hybrid states of light and matter formed by the strong coupling between molecular electronic or vibrational excitations and an optical cavity, can substantially modify the physical and chemical properties of molecular systems. Here, we show that by exploiting the collective character of molecular polaritons in conjunction with the effect of polaron decoupling, i.e., the suppression of environmental influence on the polariton, a super-reaction can be realized, involving a collective enhancement of charge or excitation-energy transfer reaction rate in a system of donors all coupled to a common acceptor. This effect is analogous to the phenomenon of super-radiation. Since the polariton is a superposition state of excitations of all the molecules coupled to the cavity, it is vulnerable to the effect of decoherence caused by energy fluctuations in molecular systems. Consequently, in the absence of a strong light-matter interaction, the reaction rate decreases significantly as the number of molecules increases, even if the system starts from the polariton state. By turning on the light-matter interaction, the dynamic behavior of the system changes dramatically, and the reaction rate increases with the number of molecules, as expected for a super-reaction. The underlying mechanism is shown to be the protection of quantum coherence between different donors as the light-matter interaction becomes stronger.

Friction decoupling and loss of rotational invariance in 2D flooding models

Friction decoupling, i.e. the computation of friction vector components making separate use of the corresponding velocity components, is common in staggered grid models of the SWE simplifications (Zero-Inertia and Local Inertia Approximation), due to the programming simplicity and to the consequent calculations speed-up. In the present paper, the effect of friction decoupling has been studied from the theoretical and numerical point of view. First, it has been found that friction vector decoupling causes the reduction of the computed friction force and the rotation of the friction force vector. Second, it has been demonstrated that decoupled-friction models lack rotational invariance, i.e. model results depend on the alignment of the reference framework. These theoretical results have been confirmed by employing numerical experiments on flat and smoothly variable bed. Since the speed-up obtained with decoupled-friction models is modest, the coupled-friction models, which are more general, should be preferred in every case.

INTELLECTUAL CONTENT OF GREEN GROWTH IN CONDITIONS OF SUSTAINABLE DEVELOPMENT

The article is devoted to the analysis of the essence of the intellectual content of green growth in the framework of the global course of mankind for sustainable development. The gradual transition in scientific works from information economy and knowledge economy to intellectual economy, which is characterized by directing human intellectual activity to environmentally friendly activities aimed at achieving global goals of sustainable development, has been analyzed. It has been noted that the intellectual economy is the foundation of green growth and the importance of knowledge, skills, theoretical and practical competencies, creativity, which act as a driver of development of green sectors of the economy has been highlighted. It has been determined that there are nine types of human capital, of which the intellectual plays a leading role at the present stage of development of socio-economic processes. In the conditions of building a green economy, capital acquires green features, which is manifested through green intellectual capital, the main components of which are green human capital, green organizational capital and green relational capital. The interaction of green human and green organizational capital forms green relational capital, which is expressed in the form of green jobs, inclusiveness and gender equality. It has been noted that in the long run the development of green intellectual capital leads to the effect of decoupling, which is manifested in the gap between indicators of economic prosperity and environmental degradation. That is why strategies for the development of green intellectual capital should be the basis for the development of countries around the world to achieve global goals of sustainable development in terms of green growth.

Sommerfeld enhancements for asymmetric dark matter

We extend the analysis of asymmetric Dark Matter relic density with the Sommerfeld enhancement to the case where the mediator is massive. In asymmetric Dark Matter models, asymmetric Dark Matter is assumed to couple to the light scalar or vector boson. Asymmetric Dark Matter annihilation cross section is enhanced by the Sommerfeld effect which exists due to the distortion of the wavefunction of asymmetric Dark Matter particle and anti–particle by long–range interactions. The impacts of the Sommerfeld enhancement on the relic densities of asymmetric Dark Matter particle and anti–particle are discussed. The effect of kinetic decoupling on the relic density is also probed when the annihilation cross section is boosted by the Sommerfeld enhancement. Finally, the constraints on the parameter space are given using the observational data of the relic density of Dark Matter.

Relic density of asymmetric Dark Matter with Sommerfeld enhancement * *Supported by the National Natural Science Foundation of China (11765021)

We investigate the evolution of abundance of the asymmetric thermal Dark Matter when its annihilation rate at chemical decoupling is boosted by the Sommerfeld enhancement. Next, we discuss the effect of kinetic decoupling on the relic abundance of asymmetric Dark Matter when the interaction rate depends on velocity. Usually, the relic density of asymmetric Dark Matter is analyzed in the frame of chemical decoupling. Indeed, after decoupling from chemical equilibrium, asymmetric Dark Matter particles and anti-particles are still in kinetic equilibrium for a while. This has no effect for the case of s-wave annihilation since there is no temperature dependence in this case. However, kinetic decoupling has impacts for the case of p-wave annihilation and Sommerfeld enhanced s- and p-wave annihilations. We investigate in detail the extent to which kinetic decoupling affects the relic abundance of asymmetric Dark Matter particles and anti-particles. We find the constraints on the cross section and asymmetry factor using observational data of the relic density of Dark Matter.

Effect of the early kinetic decoupling in a fermionic dark matter model

We study the effect of the early kinetic decoupling in a model of fermionic dark matter (DM) that interacts with the standard model particles only by exchanging the Higgs boson. There are two DM-Higgs couplings, namely CP-conserving and CP-violating couplings. If the mass of the DM is slightly below half of the Higgs boson mass, then the couplings are suppressed to obtain the measured value of the DM energy density by the freeze-out mechanism. In addition, the scattering processes of DM off particles in the thermal bath are suppressed by the small momentum transfer if the CP-violating DM-Higgs coupling is larger than the CP-conserving one. Due to the suppression, the temperature of the DM can differ from the temperature of the thermal bath. By solving coupled equations for the number density and temperature of the DM, we calculate the DM-Higgs couplings that reproduce the right amount of the DM relic abundance. We find that the couplings have to be larger than the one obtained without taking into account the difference in the temperatures. A consequence of the enhancement of the DM-Higgs couplings is the enhancement of the Higgs invisible decay branching ratio. The enhancement is testable at current and future collider experiments.

Dependence of grain size and aspect ratio on grain boundary additives in hot-deformed Nd-Fe-B magnets

Commercial Nd13.6Fe73.6Ga0.6Co6.6B5.6 (at.%) powders were mixed with 0–10 wt% Nd80Cu15Al5 alloy powders to prepare hot-deformed Nd-Fe-B magnets. As the increasing Nd80Cu15Al5 content from 0 to 10 wt%, the grain sizes along the c-plane (Dǁ) decreased by more than 35% from 312 to 198 nm while the grain sizes along the ab-plane (D⊥) decreased by less than 7% from 58 to 54 nm, resulting in a decrease of more than 30% in the grain aspect ratio (Dǁ/D⊥) from 5.4 to 3.7. Moreover, the temperature coefficient of coercivity increased significantly from −0.469 to −0.419%/°C by 8 wt% Nd80Cu15Al5 addition. Based on microstructure observations, the improved thermal stability of the magnets without using heavy rare-earth elements is due to combined effect of the exchange decoupling between grains by the nonferromagnetic grain boundary phases, the refinement of grains and the decreased grain aspect ratio.

Do Markets Punish or Reward Corporate Social Responsibility Decoupling?

This article analyzes the relationship between corporate social responsibility (CSR) decoupling and financial market outcomes. CSR decoupling refers to the gap between CSR disclosure and CSR performance. More specifically, we analyze the effect of CSR decoupling on analysts’ forecast errors, cost of capital, and access to finance. We also examine the moderating effect of forecast errors on relationships between CSR decoupling and cost of capital and access to finance. For a sample of U.S. firms consisting of 7,681 firm-year observations for the period 2006–2015, our empirical evidence supports the idea that a wider gap results in higher analysts’ forecast errors, a greater cost of capital, and reduced access to finance. In addition, our results show that forecast errors enhance the effect of the CSR decoupling on cost of capital and access to financial resources. We also note that external monitoring, in the form of greater analysts’ coverage, reduces CSR decoupling.

Numerička analiza armiranobetonskih okvirnih zgrada sa izolovanom zidanom ispunom

Reinforced concrete (RC) buildings with masonry infill walls are widely used in many countries all over the world. Although infills are considered as non-structural elements, they significantly change dynamic characteristics of RC frame structures during earthquake excitation. Recently, significant effort was spent on studying decoupled infills, which are isolated from the surrounding frame usually by adding a gap between frame and infill. In this case, the frame deformation does not activate infill wall, thus infills are not influencing the behaviour of the frame. This paper presents the results of the investigation of the behaviour of RC frame buildings with the INODIS system that decouples masonry infills from the surrounding frame. Effect of masonry infill decoupling was investigated first on the one-bay one-storey frame. This was used as a base for parametric study on the frames with more bays and storeys, as well as on the building level. Change of stiffness and dynamic characteristics was analysed as well as response under earthquake loading. Comparison with the bare frame and traditionally infilled frame was performed. The results show that behaviour of the decoupled infilled frames is similar to the bare frame, whereas behaviour of frames with traditional infills is significantly different and demands complex numerical models. This means that if adequate decoupling is applied, design of infilled frame buildings can be significantly simplified.

Эколого-экономические тенденции в Байкальском регионе и на Дальнем Востоке в условиях институциональных изменений

<span>В статье исследуется динамика эколого-экономического развития субъектов Дальнего Востока и Байкальского региона в условиях формирования новых институтов на Востоке страны. Для каждого региона и РФ были рассчитаны среднедушевые показатели экономического развития и экологической нагрузки за 2009–2012 гг. и 2012–2016 гг. Для выявления рассогласования темпов экономического роста и загрязнения природных сред в анализируемых регионах рассчитывался коэффициент декаплинга. В процессе исследования выявлены диспропорции в эколого-экономическом развитии регионов Востока РФ. Разница по среднедушевому ВРП между территориями с максимальным и минимальным значениями в 2016 г. составила почти пять раз. Заметный разрыв отмечается и по уровню негативного воздействия на окружающую среду. Установлено, что в большей части восточных регионов эффект декаплинга проявляется в отношении сброса загрязненных сточных вод и выбросов загрязняющих атмосферу веществ от стационарных источников. Сделан вывод, что принятые в соответствии с новой моделью развития Дальнего Востока институциональные решения пока не оказали заметного позитивного влияния на эколого-экономические показатели обозначенных территорий.</span>

Dietary Plasticity in a Specialist Predator, the Gyrfalcon (Falco rusticolus): New Insights into Diet During Brood Rearing

Climate and landscape change are expected to affect species' distributions and interactions, with potentially harmful consequences for specialist predators. Availability of optimal prey can affect reproductive success in raptors, especially in the Arctic, where dramatic differences in prey availability occur both within and between years. However, behavioral responses of dietary specialist, resident predators such as Gyrfalcons (Falco rusticolus) to changes in prey availability remain poorly understood. To improve understanding of how climate-driven changes in prey availability may affect diet of avian predators in the Arctic, we characterized Gyrfalcon diet on the Seward Peninsula, Alaska, in 2014 and 2015 from images representing 2008 prey items obtained by motion-activated cameras at 20 nests. We documented two important dietary shifts: the proportion of ptarmigan (Willow Ptarmigan [Lagopus lagopus] and Rock Ptarmigan [L. muta]) in the diet declined throughout the brood-rearing period in both years, and also differed between years. In both cases, ptarmigan were replaced by Arctic ground squirrels (Urocitellus parryii) in the diet. Despite shifts in prey composition, dietary breadth did not change, which revealed a facultative shift in prey use in which Gyrfalcons relied on prey of large size rather than prey of a particular taxon. We describe previously undocumented prey-use patterns during Gyrfalcon breeding, specifically an interchange between two prey species that are keystones in tundra ecology. These results are important for informing predictive models of climate change and adaptive species management plans. Further study of the interchange between prey types described in this study can strengthen insight into key ecosystem processes, and the cause and effect of potential decoupling of predator-prey interactions.