Evolution Of Energy Density Research Articles

Reconciling cosmological tensions with inelastic dark matter and dark radiation in a U(1) D framework

We propose a novel and comprehensive particle physics framework that addresses multiple cosmological tensions observed in recent measurements of the Hubble parameter, S 8, and Lyman-α forest data. Our model, termed `SIDR+z t ' (Self Interacting Dark Radiation with transition redshift), is based on an inelastic dark matter (IDM) scenario coupled with dark radiation, governed by a U(1) D gauge symmetry. This framework naturally incorporates cold dark matter (DM), strongly interacting dark radiation (SIDR), and the interactions between these components. The fluid-like behavior of the dark radiation component which originates from the self-quartic coupling of the U(1) D breaking scalar can suppress the free-streaming effects. Simultaneously, the interacting DM-DR system can attenuate the matter power spectrum at small scales. The inelastic nature of DM provides a distinct temperature dependence for the DM-DR interaction rate determined by the mass-splitting between the inelastic dark fermions which is crucial for resolving the Ly-α discrepancies. We present a cosmologically consistent analysis of the model by solving the relevant Boltzmann equations to obtain the energy density and number density evolution of different species of the model. The DR undergoes two “steps” of increased energy density when the heavier dark species freeze out and become non-relativistic, transferring their entropy to the dark radiation and enhancing ΔN eff. The analysis showcases the model's potential to uphold the Big Bang Nucleosynthesis (BBN) prediction of ΔN eff but dominantly producing additional contributions prior to recombination, while simultaneously achieving correct relic density of DM though an hybrid of freeze-in and non-thermal production.

Inconsistency between the micropolar theory and non-equilibrium thermodynamics in the case of polar fluids

Abstract The balance equation of angular momentum in anisotropic fluids includes a couple stress contribution, also responsible for an antisymmetric contribution to the force stress tensor. We herein derive all balance equations for the simplest anisotropic fluid, i.e., a polar fluid, using the GENERIC formalism of non-equilibrium thermodynamics. In doing so, we find that there is an inconsistency between the internal energy density evolution equation derived using non-equilibrium thermodynamics and the one usually considered in micropolar theory.

Constraints on real scalar inflation from preheating using LATTICEEASY* *Wei Cheng was Supported by the Natural Science Foundation of Chongqing, China (CSTB2022NSCQ-MSX0432), the Science and Technology Research Project of Chongqing Education Commission (KJQN202200621), and the Chongqing Human Resources and Social Security Administration Program (D63012022005). Ruiyu Zhou was Supported by the Chongqing Natural Science Foundation (CSTB2022NSCQ-MSX0534). This work was supported in

In this paper, we undertake a detailed study of real scalar inflation using LATTICEEASY simulations to investigate preheating phenomena. Generally, the scalar inflation potential with non-minimal coupling can be approximated using a quartic potential. We observe that the evolutionary behavior of this potential remains unaffected by the coupling coefficient. Furthermore, the theoretical predictions for the scalar spectral index ( ) and tensor-to-scalar power ratio (r) are independent of this coefficient. Consequently, the coefficients of this model are not constrained by Planck observations. Fortunately, the properties of preheating after inflation provide a viable approach to examining these coefficients. Through LATTICEEASY simulations, we trace the evolution of particle number density, scale factor, and energy density during the preheating process. Subsequently, we derive the parameters, such as the energy ratio (γ) and the e-folding number of preheating ( ), which facilitate further predictions of and r. We successfully validate real scalar inflation model using preheating in LATTICEEASY simulations based on the analytical relationship between preheating and inflation models.

Detection of an intranight optical hard lag with colour variability in blazar PKS 0735+178

ABSTRACT Blazars are a highly variable subclass of active galactic nuclei that have been observed to vary significantly during a single night. This intranight variability remains a debated phenomenon, with various mechanisms proposed to explain the behaviour including jet energy density evolution or system geometric changes. We present the results of an intranight optical monitoring campaign of four blazars: TXS 0506+056, OJ287, PKS 0735+178, and OJ248 using the Carlos Sánchez Telescope. We detect significant but colourless behaviour in OJ287 and both bluer- and redder-when-brighter colour trends in PKS 0735+178. Additionally, the g band shows a lag of $\sim 10\, \mathrm{min}$ with respect to the r, i, zs bands for PKS 0735+178 on 2023 January 17. This unexpected hard lag in PKS 0735+178 is not in accordance with the standard synchrotron shock cooling model (which would predict a soft lag) and instead suggests the variability may be a result of changes in the jet’s electron energy density distribution, with energy injection from Fermi acceleration processes into a post-shocked medium.

Experimental study on the strain energy evolution mechanism of thick and hard sandstone roof in Xinjiang Mining Area

For understanding the mechanical performance and strain energy evolution mechanism of thick hard roof sandstone samples, a sequence of uniaxial compression trials with acoustic emission (AE) monitoring were carried out. The results indicate: (1) The stress-strain curve of the thick hard roof sandstone specimens exhibits distinct stage characteristics. Based on the evolvement of instantaneous axial stiffness, it is separated into Fracture Closure Phase, Elastic Deformation Phase, Steady Fracture Expansion Phase, Unsteady Fracture Expansion Phase, and Post-Peak Phase. (2) The AE energy and cumulative count curves of the thick hard roof sandstone specimens also exhibit significant stage characteristics and can be mutually corroborated with the stage division of the stress-strain curve. (3) Based on the energy conservation principle, the evolution of strain energy density in the thick hard roof sandstone specimens under uniaxial compression loading was analyzed, and plastic strain energy increment was employed to study the stage characteristics of strain energy dissipation. (4) A damage constitutive model for the thick hard roof sandstone specimens was constructed, considering the characteristics of strain energy dissipation. This model effectively describes the stress-strain relationship among the samples, which undergo strain hardening, strain softening, and sudden destruction.

Failure characteristics and energy distributions of surrounding rock in hard rock tunnels subjected to different three-dimensional stress conditions

To study the failure characteristics of surrounding rock near an excavated tunnel under different three-dimensional stress conditions, a TRW3000 rock true triaxial electro-hydraulic servo mutagenesis testing system was used to conduct triaxial loading experiments on granite specimens with a circular hole. A high-definition micro-camera system was used to record the failure process near the circular hole. The results show that spalling failure occurs near the holed specimen under low-stress conditions, and rockburst appears around the holed specimen under high-stress conditions. Increasing the horizontal stress can prevent the occurrence of rockburst. The evolution of strain energy density (SED) in the surrounding rock of the holed specimen under different stress conditions was simulated. The findings show that the distribution of SED around the circular hole decreases with an increase in horizontal stress. The SED distributions around the circular hole are basically consistent with the damage distributions in the experiments, namely, butterfly-shaped, ear-shaped, and ring-shaped.

Multi-scale modelling for optimization of process parameters of laser powder bed fusion processed Inconel 718 surrogate part

This work uses an analytical and multi-scale thermo-mechanical numerical model to optimise the process parameter to prevent porosity while reducing the distortion in the surrogate part. Taguchi’s experimental design technique was used to identify the effect of process parameters on melt pool evolution. A dimensionless relative melt pool depth ratio (d*) ensures the extent of densification in the simulated part for various processing parameters. The Taguchi analysis outcome revealed an increase in d*, solid ratio, residual stress and distortion with increased laser power while a contrary effect with increased hatch spacing and scan speed. A strong interaction is observed for melt pool metrics and residual stress evolution. However, the interactions for residual stress and distortion evolution are more prominent, showing the influence of process parameters on energy density and thermal gradient evolution. The ANOVA analysis also shows a strong influence of process parameters on melt pool development and residual stress evolution. However, for solid ratio development, scan speed shows an insignificant effect. These observations from meso-scale analysis aids in process parameter selection for defect free part fabrication. A reduction in the VED reduced the magnitude of accumulated residual stresses in the surrogate component, thereby reducing the maximum distortion in the part. A decrease of 8.33 % in maximum distortion is observed for a ∼ 20 % reduction in the VED.

Comprehensive analysis of relativistic embedded class-I exponential compact spheres in f(R, ϕ) gravity via Karmarkar condition

In this article, we use the prominent Karmarkar condition to investigate some novel features of astronomical objects in the f(R, ϕ) gravity; R and ϕ represent the Ricci curvature and the scalar field, respectively. It is worth noting that we classify the exclusive set of modified field equations using the exponential type model of the f(R, ϕ) theory of gravity f(R, ϕ) = ϕ(R + α(e β R − 1)). We show the embedded class-I approach via a static, spherically symmetric spacetime with an anisotropic distribution. To accomplish our objective, we use a particular interpretation of metric potential (g rr ) that has already been given in the literature and then presume the Karmarkar condition to derive the second metric potential. We employ distinct compact stars to determine the values of unknown parameters emerging in metric potentials. To ensure the viability and consistency of our exponential model, we execute distinct physical evolutions, i.e. the graphical structure of energy density and pressure evolution, mass function, adiabatic index, stability, equilibrium, and energy conditions. Our investigation reveals that the observed anisotropic findings are physically appropriate and have the highest level of precision.

Quintessence-like features in the late-time cosmological evolution of [formula omitted] symmetric teleparallel gravity

In this study, we investigate the cosmological history within the framework of modified f(Q) gravity, which proposes an alternative theory of gravity where the gravitational force is described by a non-metricity scalar. By employing a parametrization scheme for the Hubble parameter, we obtain the exact solution to the field equations in f(Q) cosmology. To constrain our model, we utilize external datasets, including 57 data points from the Hubble dataset, 1048 data points from the SN dataset, and six data points from the BAO dataset. This enables us to determine the best-fit values for the model parameters involved in the parametrization scheme. We analyze the cosmic evolution of various cosmological parameters, including the deceleration parameter, which exhibits the expected behavior in late-time cosmology and changes its signature with redshift. Further, we present the evolution of energy density, EoS parameter, and other geometrical parameters with respect to redshift. Furthermore, we discuss several cosmological tests and diagnostic analyses. Our findings demonstrate that the late-time cosmic evolution can be adequately described without the need for dark energy by employing a parametrization scheme in modified gravity.

A new [formula omitted] cosmological model with [formula omitted] quadratic expansion

We present a new f(Q) cosmological model capable of reproducing late-time acceleration, i.e. fQ=λ0λ+Qn by supporting certain parametrization of the Hubble parameter. By using observational data from Hubble, Pantheon, and Baryonic Acoustic Oscillations (BAO) dataset, we investigate the constraints on the proposed quadratic Hubble parameter H(z). This proposal caused the Universe to transition from its decelerated phase to its accelerated phase. Further, the current constrained value of the deceleration parameter from the combined Hubble+Pantheon+BAO dataset is q0=−0.285±0.021, which indicates that the Universe is accelerating. We also analyze the evolution of energy density, pressure, and EoS parameters to infer the Universe’s accelerating behavior. Finally, we use a stability analysis with linear perturbations to assure the model’s stability.

Observational constraints on two cosmological models of f(Q) theory

In the past few years, f(Q) theories have drawn a lot of research attention in replacing Einstein’s theory of gravity successfully. The current study examines the novel cosmological possibilities emerging from two specific classes of f(Q) models using the parametrization form of the equation of state (EoS) parameter as omega left( zright) =-frac{1}{1+3beta left( 1+zright) ^{3}}, which displays quintessence behavior with the evolution of the Universe. We do statistical analyses using the Markov chain Monte Carlo (MCMC) method and background datasets like Type Ia Supernovae (SNe Ia) luminosities and direct Hubble datasets (from cosmic clocks), and Baryon Acoustic Oscillations (BAO) datasets. This lets us compare these new ideas about the Universe to the Lambda CDM model in a number of different possible ways. We have come to the conclusion that, at the current level of accuracy, the values of their specific parameters are the best fits for our f(Q) models. To conclude the accelerating behavior of the Universe, we further study the evolution of energy density, pressure, and deceleration parameter for these f(Q) models.

The Failure Characteristics and Energy Evolution Pattern of Compound Coal–Rock under the Action of Cyclic Loading

Based on the entire loading process of compound coal–rock, test pieces with three different coal/rock ratios (1:3, 1:1, and 3:1) have been constructed and the corresponding cyclic loading experiments have been carried out. Through the experiment, the deformation and failure characteristics of the compound coal–rock samples have been explored and the stage evolution characteristics of energy density have been subsequently analyzed. Ultimately, the relation between deformation failure and the energy evolution mechanism has been established, and thus the reasons behind rock bursts in the coal–rock compounds have been discussed. The experimental results indicate that with the increase in cyclic loading, the stress–strain curve of the compound coal–rock demonstrates a positive shift, whereas the change in the hysteretic curve from dense to sparse results in a “hysteresis expansion”. The increase in the coal body height increases the chance of brittleness failure of the compound coal–rock. The coal body, as the main controlling factor of compound coal–rock failure, generates cracks that expand to the rock body along the juncture of the coal and rock, leading to instability. The energy density evolution curve can be described by a quadratic function. The evolution process is initiated from the slow increase in input energy density and elastic energy density. A large amount of energy is stored through the rapid increase in the density mentioned above. At last, the evolution is completed by a surge in dissipated energy. The energy evolution drives the crack expansions in the compound coal–rock under load. The energy accumulation in the compound coal–rock is increased by the exploitation of the clamping effect of the thick and hard top and bottom plate. The risk of rock burst is intensified by the failure of the coal body because of the energy in the coal–rock system. The study results help to comprehend the energy evolution pattern in the surrounding rock of deep mining roadways and expand the prevention methods for impact ground pressure.

Study of compact stars in {mathcal {R}}+ alpha {mathcal {A}} gravity

The main goal of this work is to provide a comprehensive study of relativistic structures in the context of recently proposed {mathcal {R}}+ alpha {mathcal {A}} gravity, where {mathcal {R}} is the Ricci scalar, and {mathcal {A}} is the anti-curvature scalar. For this purpose, we examine a new classification of embedded class-I solutions of compact stars. To accomplish this goal, we consider an anisotropic matter distribution for {mathcal {R}}+ alpha {mathcal {A}} gravity model with static spherically symmetric spacetime distribution. Due to highly non-linear nature of field equations, we use the Karmarkar condition to link the g_{rr} and g_{tt} components of the metric. Further, we compute the values of constant parameters using the observational data of different compact stars. It is worthy to mention here that we choose a set of twelve important compact stars from the recent literature namely 4U~1538{-}52, SAX~J1808.4{-}3658, Her~X{-}1, LMC~X{-}4, SMC~X{-}4, 4U~1820{-}30, Cen~X{-}3, 4U~1608{-}52, PSR~J1903{+}327, PSR~J1614{-}2230, Vela~X{-}1, EXO~1785{-}248. To evaluate the feasibility of {mathcal {R}}+ alpha {mathcal {A}} gravity model, we conduct several physical checks, such as evolution of energy density and pressure components, stability and equilibrium conditions, energy bounds, behavior of mass function and adiabatic index. It is concluded that {mathcal {R}}+ alpha {mathcal {A}} gravity supports the existence of compact objects which follow observable patterns.

Research on mechanical characteristics of bulge formed joint based on plastic strain energy density

Thin-walled structures are widely used in the engineering, and their bearing behavior is important for the structure security. In this paper, the illustration of mechanical characteristics and the evaluation of mechanical state of thin-walled structures in loading process is studied based on the evolution of plastic strain energy density (PSED). The bearing behavior of the thin-walled bulge formed joint under axial load is further analyzed by finite element method (FEM) and stress test. Through comparing the result of FEM with the stress test, it can be verified that PSED can be used to evaluate the mechanical state of the thin-walled bulge formed joint, and illustrate the evolution law of global and local mechanical characteristics in loading process, such as ultimate capacity and stress distribution, which is of great significance in failure analysis, the guidance in design and health monitoring in service of thin-walled structures.

Experimental Study on Mechanical Behavior and Energy Evolution Characteristics of Gas-Filled Deep Coal under Cyclic Loading

To study the mechanical behavior and energy evolution law of gas-filled deep coal, conventional triaxial compression experiments under different confining pressure and gas pressure conditions and cyclic loading and unloading experiments under different gas pressures were carried out. The failure characteristics and mechanical parameters evolution of two loading modes were analyzed. In addition, the energy density and ratio evolution law under cyclic loading was revealed, and based on these findings, an attempt was made to depict the relation of cumulative dissipated energy density and volumetric strain by fitting the experimental data. The results indicated that failure of coal is expressed as a single shear surface under conventional compression, while under cyclic loading mode, coal behaves with multi-fracture crushing failure. Mechanical parameters showed a trend of decay with increasing gas pressure, and that cyclic loading and unloading increases the bearing capacity of coal by 8–38%. The dissipated energy density and ratio grew significantly when coal entered the yield stage. In the compaction stage, the cumulative dissipated energy density rose with volumetric strain in the form of an exponential function, and it increased with relative volumetric strain as a power function.

Phase imaging of irradiated foils at the OMEGA EP facility using phase-stepping X-ray Talbot–Lau deflectometry

Abstract Diagnosing the evolution of laser-generated high energy density (HED) systems is fundamental to develop a correct understanding of the behavior of matter under extreme conditions. Talbot–Lau interferometry constitutes a promising tool, since it permits simultaneous single-shot X-ray radiography and phase-contrast imaging of dense plasmas. We present the results of an experiment at OMEGA EP that aims to probe the ablation front of a laser-irradiated foil using a Talbot–Lau X-ray interferometer. A polystyrene (CH) foil was irradiated by a laser of 133 J, 1 ns and probed with 8 keV laser-produced backlighter radiation from Cu foils driven by a short-pulse laser (153 J, 11 ps). The ablation front interferograms were processed in combination with a set of reference images obtained ex situ using phase-stepping. We managed to obtain attenuation and phase-shift images of a laser-irradiated foil for electron densities above ${10}^{22}\;{\mathrm{cm}}^{-3}$ . These results showcase the capabilities of Talbot–Lau X-ray diagnostic methods to diagnose HED laser-generated plasmas through high-resolution imaging.

Influence of Increasing Mean Stress on Fatigue Properties of Shale during Pulsating Hydraulic Fracturing

During pulsating hydraulic fracturing (PHF), reservoir rock can be subjected to constant amplitude, constant mean stress (CACMS) cyclic loading or constant amplitude, increasing mean stress (CAIMS) cyclic loading. The influence of increasing mean stress on rock fatigue strength, fatigue lifetime, fatigue damage, and energy evolution of shale is rarely investigated, and which type of cyclic loading is more efficient for PHF has not been determined and demonstrated. In this Article, a series of uniaxial compression tests under these two types of cyclic loading are first conducted. A fatigue lifetime model for CAIMS is established. The shale strength and fatigue lifetime for CACMS and CAIMS are then compared. Their differences are explained by their dissipated energy density evolution and damage evolution. Finally, a nonlinear damage accumulation model to predict damage evolution for CAIMS cyclic loading is proposed. It is suggested that CAIMS is a better cyclic loading type when its amplitude is higher than 30% UCS (uniaxial compressive strength) of rock. This provides a meaningful amplitude threshold for CAIMS parameter optimization in the PHF construction. In this case, compared with CACMS cyclic loading, CAIMS cyclic loading significantly decreases the shale strength by up to 20% UCS and the fatigue lifetime from over 500 to 9. Different from an inverted-S-shaped damage evolution for CACMS cyclic loading, damage evolution for CAIMS cyclic loading exhibits a monotonic increasing trend. The damage variable growth rates of CACMS and CAIMS both show a three-stage trend: (1) their growth rates both decrease; (2) the growth rate for CACMS remains stable, while for CAIMS its growth rate slowly increases; and (3) their growth rates both increase sharply. Correspondingly, the dissipated energy density evolutions for CACMS and CAIMS show a similar three-stage trend. It can be concluded that during the second stage, for CAIMS microfractures and plastic deformation inside specimens are developed and accumulated more and faster than those for CACMS cyclic loading. This explains the phenomenon that the fatigue lifetime and strength of CAIMS cyclic loading are less than those of CACMS. The nonlinear damage accumulation model proposed in this Article can well fit experimental results. This model can be used for accurately describing reservoir rock mechanical property degradation during hydraulic fracture simulation induced by PHF.

Thermal and dissipative effects on the heating transition in a driven critical system

We study the dissipative dynamics of a periodically driven inhomogeneous critical lattice model in one dimension. The closed system dynamics starting from pure initial states is well-described by a driven Conformal Field Theory (CFT), which predicts the existence of both heating and non-heating phases in such systems. Heating is inhomogeneous and is manifested via the emergence of black-hole like horizons in the system. The robustness of this CFT phenomenology when considering thermal initial states and open systems remains elusive. First, we present analytical results for the Floquet CFT time evolution for thermal initial states. Moreover, using exact calculations of the time evolution of the lattice density matrix, we demonstrate that for short and intermediate times, the closed system phase diagram comprising heating and non-heating phases, persists for thermal initial states on the lattice. Secondly, in the fully open system with boundary dissipators, we show that the nontrivial spatial structure of the heating phase survives particle-conserving and non-conserving dissipations through clear signatures in mutual information and energy density evolution.

Dynamic Tensile Mechanical Properties of Outburst Coal Considering Bedding Effect and Evolution Characteristics of Strain Energy Density

The evolution of strain energy density of outburst-prone coal is of great significance for analyzing the characteristics of energy accumulation and release in coal and rock masses. The dynamic mechanical properties of coal samples were tested by using the split Hopkinson pressure bar (SHPB) technique. Dynamic tensile mechanical properties, layered effect and density evolution characteristics of strain energy for coal were studied. The dynamic failure and crack propagation process of the specimen were recorded with a high-speed camera. In addition, a digital image correlation (DIC) method was used to analyze the evolution characteristics of the strain field during the deformation process of the specimen. The distribution characteristics of the particle fragments were statistically analyzed. The results show that the bedding orientation of the coal has a significant effect on its deformation and damage features. The presence of weak planes, microcracks and laminae causes its shear damage zone to behave more complex. If the crack plane coincides with the high shear stress plane, the developed shear cracks extend along the weak laminae and the shear damage zones in BD specimens are not symmetrically distributed. When the laminated surface of the coal sample is at a certain angle with the impact loading direction, the damage mode is coupled with tensile and shear damage. The percentage mass distribution of particles and fines increases with increasing bedding orientation. The effect of water on the dynamic damage of coal samples is significant. Based on the principle of pressure expansion of wing-shaped cracks, the formula for calculating the dynamic strength of water-saturated coal samples under dynamic loading was derived.

Coupling of ‘cold’ electron plasma wave via stationary ion inhomogeneity to the plasma bulk

Using high resolution kinetic (VPPM-OMP 1.0) and fluid (BOUT++) solvers, evolution of long-wavelength electron plasma wave (EPW) in the presence of stationary periodic ion background non-uniformity is investigated. Mode coupling dynamics between long-wavelength EPW mode of scale k and ion inhomogeneity of scale k 0 is illustrated. Validity of well known Bessel function J n (x) scaling in the cold plasma approximation (i.e., when phase velocity ω/k ≫ v thermal ) alongwith the effect of ion inhomogeneity amplitude (A) on temporal evolution of energy density in the long-wavelength EPW mode is investigated. Effect of finite system sizes on the Bessel J n (x) scaling is examined and scaling law for τ FM i.e the time required to attain first minimum of energy density of the corresponding perturbed mode (also called phase mixing time for k ⟶ 0 modes) versus ion inhomogeneity amplitude A obtained from both kinetic and fluid solutions for each of the cases studied, alongwith some major differences in τ FM scaling for small system sizes is also reported.