Energy Conditions Research Articles

On effects of the null energy condition on totally umbilic hypersurfaces in a class of static spacetimes

We study the effects of the null energy condition on totally umbilic hypersurfaces in a class of static spacetimes, both in the spacelike and the timelike case, respectively. In the spacelike case, we study totally umbilic warped product graphs and give a full characterization of embedded surfaces with constant spacetime mean curvature using an Alexandrov Theorem by Brendle and Borghini–Fogagnolo–Pinamonti. In the timelike case, we achieve a characterization of photon surfaces with constant umbilicity factor similar to a result by Cederbaum–Galloway.

ANALYSIS OF ENERGY COSUMPTION IN THE NETWORK USING IOT SOLUTIONS

The article explores the importance of implementing IoT systems to analyze energy conditions in current locations. The designed system architecture ensures scalability and flexibility, which allows to effectively collect, save and analyze data. The research results confirm the hypothesis about the value of reduced control and optimization of energy consumption due to automated monitoring and compensation of reactive energy. A practical solution is being developed to automate the monitoring and balance of phase pressures, which promotes energy supply and reduces energy costs.

Developing novel wormhole metrics in finsler-randers geometry using the barthel connection and osculating-riemannian method

In this research, we focus on modelling a wormhole using Finsler-Randers geometry. By applying the Barthel connection from the range of Finslerian connections, we have developed a new wormhole metric, termed the osculating Barthel-Finsler-Randers metric, through the osculating-Riemannian method within the Finsler-Randers framework. The fundamental field equations are formulated in terms of the obtained metric tensor characterised by η(r), which plays a pivotal role in characterizing the anisotropy of the model. To explore the application of Finsler geometry in addressing the existence of a wormhole, we adopt an exponential shape function. Further, in order to streamline the computational aspects of our analysis, and to discuss the effect of anisotropy effect of Finsler Rander geometry, we adopt a specific functional form for the anisotropic parameter η(r)=arn, where α is a constant with implications for the anisotropy, among various possibilities for η(r) a non-zero analytical component of vector field in Randers metric. In addition, we consider three distinct values for the exponent n = −1, 0, and 1 and subsequently, we proceed to develop two distinct models for each of these three values of n with constant and non-constant redshift function. We analyse the physical implications of η(r) on the energy conditions. Our results demonstrate the crucial impact of anisotropy on the stability and structure of wormholes, emphasizing the requirement of exotic matter under specific conditions. This research deepens the understanding of wormhole physics within Finsler geometry, shedding light on the theoretical frameworks essential for the existence and stability of these cosmic structures.

Finch–Skea quintessence models in non-conservative theory of gravity

This study is dedicated to presenting a new solution of the field equations in the Rastall theory with a quintessence field defined by the parameter ωq as −1<ωq<−13 by considering the isotropic matter content inside the sphere. The Finch–Skea ansatz (FS) is used in a static and spherically symmetric geometry to obtain the feasible relativistic solution. The results obtained in the physical evaluation are analyzed analytically and graphically. In the appropriate limit of the Rastall coupling parameter, one can regain the original results in the General Relativity. This complete analysis considers five different compact stars: HerX−1 with mass 0.88M⊙ and radius 7.7 km, VelaX−12 with mass 1.77M⊙ and radius 9.99 km, SAXJ1808−3658(SSI) with mass 1.435M⊙ and radius 7.07 km, 4U1608−52 with mass 1.74M⊙ and radius 9.30 km, 4U1538−52 with mass 0.87M⊙ and radius 7.86 km and PSRJ1416−2230 with mass 1.97M⊙ and radius 10.30 km. The physical validity of the obtained solution is verified by computing the necessary physical parameters like energy density and pressure, quintessence density, energy conditions, sound speed via the Herrera cracking concept, hydrostatic equilibrium of forces, mass function, compactness, Buchdahl limit, and surface redshift and analyze their behavior graphically. To investigate the demeanor of these parameters more closely, we computed the numerical values and manifested them in tabular form. We conclude that our presented mathematical model of compact stars in the Finch–Skea geometry with quintessence field fulfills all the requirements for a physically viable solution.

The effects of acute exercise on food intake and appetite in adolescents with and without obesity: A systematic review and meta-analysis.

This systematic review and meta-analysis synthesized evidence pertaining to consummatory and appetitive responses to acute exercise in children and adolescents with and without obesity (5-18 years). Articles reporting on supervised, controlled trials of any modality, duration, or intensity with laboratory-measured food intake were found using MEDLINE, EMBASE, and Cochrane up to July 2023. Differences between conditions in laboratory energy and macronutrient intake, appetite sensations, and food reward were quantitatively synthesized using random-effects meta-analyses. Thirty-five studies were eligible for the systematic review of energy intake, consisting of 60 distinct intervention arms with lean (n = 374) and overweight/obesity participants (n = 325; k = 51 eligible for meta-analysis). Study quality as indicated by the Effective Public Healthy Practice Project tool was rated as low and moderate risk of bias for 80% and 20% of studies, respectively. Acute exercise had no significant effect on energy intake during an ad libitum test meal (mean difference [MD] = -4.52 [-30.58, 21.54] kcal, p = .729). Whilst absolute carbohydrate intake was lower after exercise (23 arms; MD = -6.08 [-11.26, -0.91] g, p = .023), the proportion of carbohydrate was not (30 arms; MD = -0.62 [-3.36, 2.12] %, p = .647). A small elevation in hunger (27 arms; MD = 4.56 [0.75, 8.37] mm, p = .021) and prospective food consumption (27 arms; PFC; MD = 5.71 [1.62, 9.80] mm, p = .008) was observed post-exercise, but not immediately prior to the test meal (Interval: Mdn = 30 min, Range = 0-180). Conversely, a modest decrease in explicit wanting for high-fat foods was evident after exercise (10 arms; MD = -2.22 [-3.96, -0.47] mm, p = .019). Exercise intensity (p = .033) and duration (p = .013) moderated food intake only in youth with overweight/obesity, indicating lower intake at high intensity and short duration. Overall, acute exercise does not lead to compensation of energy intake or a meaningful elevation of appetite or food reward and might have a modest benefit in youth with overweight/obesity if sufficiently intense. However, conclusions are limited by substantial methodological heterogeneity and the small number of trials employing high-intensity exercise, especially in youth with overweight/obesity.

Initial data sets with dominant energy condition admitting no smooth DEC spacetime extension

Initial data sets with dominant energy condition admitting no smooth DEC spacetime extension

Parity-violating primordial gravitational waves from null energy condition violation

We investigate the parity-violating effects in primordial gravitational waves (GWs) due to null energy condition (NEC) violation in two very early universe scenarios: bounce-inflation and intermediate NEC violation during inflation. In both scenarios, we numerically solve the power spectra of parity-violating primordial GWs generated by coupling the background field and the spectator field with the Nieh-Yan term, respectively. We find that the background field can significantly enhance parity-violating effects at scales corresponding to the maximum of the GW power spectra. In contrast, the parity-violating effects produced by the spectator show significantly weaker observability even if the coupling constant is large. Therefore, in NEC-violating scenarios, the significant observable parity-violating effects in primordial GWs primarily arise from the physics directly related to NEC violation. This result highlights the potential of primordial GWs as crucial tools for exploring NEC-violating and parity-violating physics.

Multiple impact tests on precast reinforced concrete beams with pressed sleeve connections

Buildings may experience impact loads or even multiple impacts during their service life. Precast concrete (PC) structures have been widely used in engineering, with PC beams serving as the primary load-bearing components in these structures. In this study, six PC beams and two cast-in-place reinforced concrete (RC) beams were designed and manufactured, and drop hammer impact tests were conducted. Additionally, static load tests were conducted on two corresponding PC and RC beams. The experimental study provided benchmark data examining the influence of varying drop hammer mass, impact velocity, and level of pre-damage on the dynamic response of the PC beams, including their failure mode, mid-span deflection, impact force, deflection recovery ratio, and deformation energy consumption. The experimental results confirmed the reliability of using pressure sleeve connection as the assembly and connection form of PC beams. Under equivalent energy conditions, an increase in impact mass simultaneously leads to a decrease in peak and residual deflection of PC beams. This reduction is accompanied by an increase in their average impact force. Under the same impact mass and velocity conditions, the peak deflection of beams exhibiting different degrees of damage exceeded that of undamaged beams, although their residual deflection was relatively lower. In addition, the deflection recovery rate of damaged beams is slightly higher than that of undamaged beams.

Charged wormhole solutions in 4D Einstein-Gauss-Bonnet gravity

In the present work, we construct models of static wormholes in 4-dimensional Einstein-Gauss-Bonnet (4D EGB) gravity with an (an)isotropic energy momentum tensor (EMT) and a Maxwell field as supporting matters for the wormhole geometry assuming a constant redshift function. We obtain exact spherically symmetric wormhole solutions in 4D EGB gravity for isotropic and anisotropic matter sources under the effect of electric charge. The solutions are more generalized in the sense of incorporating the charge contributions. Furthermore, we examine the null, weak and strong energy conditions at the wormhole throat of radius r=r0. We demonstrate that at the wormhole throat, the classical energy conditions are violated by arbitrary small amount. Additionally, we analyze the wormhole geometry incorporating semiclassical corrections through embedding diagrams. We discover that the wormhole solutions are in equilibrium as the anisotropic and hydrostatic forces cancel each other.

Chemoexcited Formation and Radiationless Decay Dynamics of Firefly Chromophore.

Multistate nonadiabatic dynamics combined with Mixed-Reference Spin-Flip Time-Dependent Density Functional Theory (MRSF-TDDFT) were performed to investigate the chemoexcitation dynamics of firefly dioxetanone (FDO- in S0) to oxyluciferin (OxyLH- in S1) and its subsequent decay dynamics. The formation of oxyluciferin occurs within approximately 100 fs and is primarily controlled by oscillatory CO2 decarboxylation. Unexpected radiationless decay from oxyluciferin was also observed, facilitated by intramolecular rotation. Simulations under three thermal conditions reveal that higher initial thermal energy not only enhances the formation of oxyluciferin but also increases radiationless decay by surpassing barriers to the ground state. Conversely, lower thermal energy conditions reduce oxyluciferin formation but suppress radiationless decay. These findings suggest that optimal conditions for higher chemiluminescence quantum yield involve initial high thermal energy to accelerate CO2 decarboxylation and gradual thermal dissipation to prevent intramolecular rotation of oxyluciferin. This approach could enhance the chemiluminescence quantum yield beyond the current limit of 40%, offering significant potential for applications in biological imaging and analytical chemistry.

An experimental investigation on surface integrity and wire wear in rough and trim cut modes of WEDM for hybrid composite

PurposeThe purpose of this paper is to investigate the surface integrity features, including surface roughness (SR), recast layer (RL), material migration, topography and wire wear pattern in rough and trim-cut wire electric discharge machine (WEDM) of hybrid composite (Al6061-90%/SiC-2.5%/TiB2-7.5%).Design/methodology/approachEffects of four important factors, namely, rough-cut history (RCH), pulse on time (Ton), peak current (IP) and wire offset (WO) have been assessed on the responses of interest for trim-cut WEDM. Box–Behnken design (RSM) was used to formulate the experimentation plan. Quantitative indices of surface integrity, namely, SR and RL, and selected samples have been investigated for qualitative analysis, namely, surface topography, material migration and wire wear pattern.FindingsTon and IP are found to be most significant, whereas RCH and WO are found insignificant for SR. Ton and WO were found to be the most significant factors affecting RL. After trim cut, an RL of thickness 8.26 µm is observed if the initial rough cut has been accomplished at high discharge energy setting. Whereas the best value of RL thickness, i.e. 5.36 µm, can be realized with low level of RCH. A significant decrease in the presence of foreign materials is recorded, indicating its strong correlation with the discharge energy used during machining.Originality/valueInvestigation on surface integrity features for machining of hybrid composite through rough and trim-cut WEDM has been reported by only a limited number of researchers in the past. This study is attempted at fulfilling few vital gaps by addressing the issues such as evaluation of the efficacy of trim cutting under different discharge energy conditions (using RCH), analysis of wire wear pattern in both rough and trim-cut modes and investigation of the wire breakage phenomenon during machining.

Late time cosmic acceleration through parametrization of Hubble parameter in [formula omitted] gravity

This paper explores the rapid expansion of the Universe during its later stages within the context of f(R,Lm) gravity theory. We present a novel parametrization of the Hubble parameter in a manner independent of any specific model and employ it to analyze the Friedmann equations within the FLRW Universe framework. Using a Markov Chain Monte Carlo (MCMC) approach, we derive the model parameters by analyzing a composite dataset comprising 31 Cosmic Chronometers (CC) data points, 26 independent Baryonic Acoustic Oscillations (BAO) measurements, and 1701 data points from Pantheon+SH0ES dataset. The trajectory of the deceleration parameter highlights the shift from deceleration to acceleration in the evolution of the Universe. Additionally, we delve into the dynamics of fundamental cosmological variables for two nonlinear f(R,Lm) models, including energy density, pressure, equation of state (EoS) parameter, and energy conditions.

Possible wormholes in f(R) gravity sourced by solitonic quantum wave and cold dark matter halos and their repulsive gravity effect

In this paper, we present new generalized wormhole (WH) solutions within the context of f(R) gravity. Specifically, we focus on f(R) gravitational theories formulated in the metric formalism, with our investigation centered on a power-law form represented by f(R)=ϵRχ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$f(R) = \\epsilon R^{\\chi }$$\\end{document}. Here, ϵ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\epsilon $$\\end{document} is an arbitrary constant, and χ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\chi $$\\end{document} is a real number. Notably, this form possesses the advantageous property of reducing to Einstein gravity when ϵ=1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\epsilon =1$$\\end{document} and χ=1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\chi =1$$\\end{document}. To obtain these novel WH solutions, we establish the general field equations for any f(R) theory within the framework of Morris–Thorne spacetime, assuming metric coefficients that are independent of time. By utilizing an anisotropic matter source and a specific type of energy density associated with solitonic quantum wave (SQW) and cold dark matter (CDM) halos, we calculate two distinct WH solutions. We thoroughly investigate the properties of the exotic matter (ExoM) residing within the WH geometry and analyze the matter contents through energy conditions (ECs). Both analytical and graphical methods are employed in this analysis to examine the validity of different regions. Notably, the calculated shape functions for the WH geometry satisfy the necessary conditions in both scenarios, emphasizing their reliability. Our investigations into specific parameter ranges in both scenarios revealed the presence of ExoM. This ExoM is characterized by an energy–momentum tensor that violates the null energy condition (NEC) and, consequently, the weak energy condition as well, in the vicinity of the WH throats. Furthermore, we investigated the repulsive effect of gravity and discovered that its presence results in a negative deflection angle for photons following null geodesics. Importantly, we observed that the deflection angle consistently exhibits negative values across all r0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$r_0$$\\end{document} values in both scenarios, indicating the manifestation of the repulsive gravity effect. Finally, we compare the obtained WH solutions utilizing both distributions, as well as the f(R) power-law-like models, in order to assess the feasibility of energetic configurations for WHs within SQW and CDM systems.

Revisiting Weak Energy Condition and wormholes in Brans-Dicke gravity

It is known that the formation of a wormhole typically involves a violation of the Weak Energy Condition (WEC), but the reverse is not necessarily true. In the context of Brans-Dicke gravity, the generalized Campanelli-Lousto solution, which we shall unveil in this paper, demonstrates a WEC violation that coincides with the appearance of unbounded sheets of spacetime within the region where 0<r<rs. The emergence of a wormhole in the region where r>rs is thus only an indirect consequence of the WEC violation. Whereas the two regions, 0<r<rs and r>rs, in general are disconnected by physical singularities at r=rs, they are both part of the same mathematical solution, and their behavior can provide insights into the WEC, which is a mathematical property of the solution. Furthermore, we utilize the generalized Campanelli-Lousto solution to construct a Kruskal-Szekeres diagram, which exhibits a “gulf” sandwiched between the four quadrants in the diagram, a novel feature in Brans-Dicke gravity. Overall, our findings shed new light onto a complex interplay between the WEC and wormholes in the Brans-Dicke theory.

Cosmic Evolution in a Bianchi type-V Universe with Barrow Holographic Dark Energy with Granda-Oliveros Length Scale as IR Cutoff

In this work, we construct a spatially homogeneous and anisotropic Bianchi type-V cosmological model with a hybrid expansion law by considering the universe to be filled with cold dark matter and non-interacting Barrow holographic dark energy with Granda-Oliveros length scale as IR cutoff. The physical and kinematical characteristics of the resulting model are discussed by studying the evolution of various parameters of cosmological importance such as the Hubble parameter, the deceleration parameter, the anisotropic parameter, the equation of state parameter, jerk parameter etc. We also examine whether the energy conditions are satisfied or violated. Our analysis reveals that the Null,Weak, and Dominant energy conditions are fullfilled, while the Strong Energy Condition is violated, which supports the accelerated expansion of the universe. Statefinder diagnostics have also been performed based on recent cosmological observations in order to compare our model with different dark energy cosmological scenario. Additionally, we establish the correspondence between the quintessence scalar field and the Barrow holographic dark energy model, supporting our description of the universe’s accelerated expansion.

LRS Bianchi Cosmological Model in Saez-Ballester Theory of Gravity with Time Varying Cosmological Constant

The present work deals with the study of a locally rotationally symmetric (LRS) Bianchi type-I cosmological model in the framework of a scalar-tensor theory of gravity formulated by Saez and Ballester with time varying cosmological constant. To obtain the explicit solutions of the Saez-Ballester field equations we assume the average scale factor to obey a power law expansion and the cosmological constant to be proportional to the energy density of the cosmic fluid. The dynamical behaviour of relevant cosmological parameters including the Hubble parameter, the deceleration parameter, the energy density, the pressure, the equation of state parameter, the cosmological constant, the shear scalar, the expansion scalar etc. are investigated graphically by examining their evolution versus the redshift parameter. The validation of the four energy conditions are also checked. We find the outcomes of the constructed model to be in good agreement with the recent observational data.

Pilgrim Dark Energy Bianchi Type-I f(T) Gravity Model

In this work, we have analyzed Bianchi type-I space-time (spatially homogeneous and anisotropic), using an interacting two fluid - dark matter (DM) and Pilgrim dark energy (PDE) in the framework of f(T) gravity by taking into consideration the infrared (IR) cut-off as a candidate of Hubble’s horizon L=1/H. We have also performed the state-finder diagnostics and in addition, energy conditions are discussed to verify accelerating expansion of the universe.

Minimally deformed regular Bardeen black hole solutions in Rastall theory

In this study, we utilize the minimal geometric deformation technique of gravitational decoupling to extend the regular Bardeen black hole, leading to the derivation of new black hole solutions within the framework of Rastall theory. By decoupling the field equations associated with an extended matter source into two subsystems, we address the first subsystem using the metric components of the regular Bardeen black hole. The second subsystem, incorporating the effects of the additional source, is solved through a constraint imposed by a linear equation of state. By linearly combining the solutions of these subsystems, we obtain two extended models. We then explore the distinct physical properties of these models for specific values of the Rastall and decoupling parameters. Our investigations encompass effective thermodynamic variables such as density and anisotropic pressure, asymptotic flatness, energy conditions, and thermodynamic properties including Hawking temperature, entropy, and specific heat. The results reveal that both models violate asymptotic flatness of the resulting spacetimes. The violation of energy conditions indicate the presence of exotic matter, for both models. Nonetheless, the energy density, radial pressure, as well as the Hawking temperature exhibit acceptable behavior, while the specific heat and Hessian matrix suggest thermodynamic stability.

Most general isotropic charged fluid solution for Buchdahl model in ℱ(𝒬) gravity

In this work, we investigated a most general isotropic charged fluid solution for the Buchdahl model via a two-step method in ℱ(𝒬)-gravity framework for the first time. In this context, a linear function of the form ℱ(𝒬) = ζ 1 𝒬 + ζ 2 and a particular transformation is used to solve the Einstein-Maxwell Equations (EMEs) employing the Buchdahl ansatz: e Υ(r) = μ(1+λ r 2)/μ+λ r 2, where ζ 1, ζ 2, λ and μ are constant parameters. The Schwarzschild de Sitter (AdS) exterior solution is joined to the interior solution at the boundary to determine the constant parameters. It should be emphasized that, for a given transformation, the Buchdahl ansatz only offers a mathematically feasible solution in the context of electric charge, where pressure and density are maximum at the center and decrease monotonically towards the boundary when 0 < μ < 1. We taken into account the compact star EX01785-248 with M = (1.3±0.2)M ⊙; Radius = 12.02+0.55 -0.55 km for graphical analysis.The physical acceptability of the model in the context of ℱ(𝒬) gravity has been evaluated by looking at the necessary physical properties, including energy conditions, causality condition, hydrostatic equilibrium, pressure-density ratio, etc. Additionally, we predicted the maximum mass limit of different compact objects for various parameter values along with the mass-radius relation. The maximum masses range (1.927 - 2.321) M ⊙ are obtained for our solution. It can be observed that when the coupling parameter ζ 1 for ℱ(𝒬 gravity is smaller, then our solution yields massive stars. The present investigation provides novel insights and realistic implications regarding the formation of compact astrophysical objects.

Emergence of negative mass in general relativity

We investigate a symmetric traversable wormhole model, integrating Einstein’s gravitational coupling phantom field and a nonlinear electromagnetic field. This work indicates the emergence of negative ADM mass within a specific parameter range, coinciding with distinct alterations in the wormhole’s spacetime properties. Despite violating the Null Energy Condition (NEC) and other energy conditions, the solution exhibits unique characteristics in certain energy-momentum tensor components, potentially accounting for the manifestation of negative mass.