Negative Mass Research Articles

Mediterranean Islands as Refugia for Elasmobranch and Threatened Fishes

ABSTRACTAimThe Mediterranean Sea is one of the most anthropized seas in the world but also a marine biodiversity hotspot with many fish species under threat. The main goal of the study is to test whether on the heavily fished and anthropized Mediterranean coast, the less impacted Corsica and Balearic Islands, can be considered as refugia for threatened and elasmobranch fishes independently of protection by marine reserves.LocationThe French Mediterranean coast and three north‐western Mediterranean islands: Corsica and also Mallorca and Minorca from the Balearic archipelago.MethodsWe performed 187 fish surveys using environmental DNA metabarcoding on three islands and 109 along the continental coast. Of the 78 surveys on islands 22 correspond to no‐take marine reserves and of the 109 continental surveys 26 were carried out within reserves. After eDNA filtration, extraction, amplification, and sequencing we estimated the number of fish species but also the number commercial, threatened and elasmobranch fish species on each sample. We then performed an ANOVA by permutation to test the effect of insularity and protection on these four biodiversity metrics. We also modelled these four biodiversity metrics as a function of protection and human pressure but also environmental, habitat and sampling conditions. We also built species accumulation curves to obtain asymptotes representing the potential regional pools for each species category on both island and continental coasts.ResultsWe obtained a total of 175,982,610 reads over the 187 eDNA samples that were assigned to 153 fish species including 17 elasmobranch species among which 7 were only detected on islands. We observed a higher total fish richness on continental than island surveys regardless of protection but a higher threatened and elasmobranch fish richness on the island than on continental surveys. We obtained a significant, negative and predominant human gravity impact on the diversity of elasmobranch species. The modelled asymptote reached 148 teleostean fish species on islands and 196 on the continental coastline with a very similar rate of diversity increase with sampling effort but the shape of the species accumulation curves differed markedly for elasmobranchs with a stronger increase in diversity with sampling effort on islands.Main ConclusionsOur findings highlight that Mediterranean islands can be refugia for sharks and rays but also threatened fishes in this overexploited region. Our results also suggest that reducing or banning trawling activities may play a key role for conserving vulnerable fishes, beyond the benefits of no‐take marine reserves, which appear limited on these large home‐range species.

Impact of Solar Radiation Management on Andean glacier-wide surface mass balance

Solar Radiation Management (SRM) is a climate intervention strategy aimed at mitigating global warming by reducing incoming solar radiation. We investigate the potential influence of SRM on Andean glacier-wide surface mass balance, as glaciers are crucial for downstream ecological functions along the west coast of South America. We numerically simulate the surface mass balance response of thousands of glaciers to SRM and other climate change scenarios throughout the 21st century. Results indicate Pan-Andean negative mass balance, irrespective of the scenario or glacier-climate regimes. However, SRM tends to modify interannual variability and temperature sensitivity in several regions. Our findings also suggest that if SRM had been implemented in the late 1980’s, it would have been effective in avoiding the negative trajectory seen today. The Andes feature nearly all mountain hydroclimatic regimes, representing a globally relevant example of SRM impacts. These findings emphasize the urgency of drastic emissions reduction.

Research on the Mechanism of Femtosecond Laser Ablation Concave-Convex Microstructure Transformation.

The phenomenon of femtosecond laser ablation of convex structures from the bottom to the top is interesting. In this study, AZ31B magnesium alloy was used as the substrate to analyze the impact of the laser pulse energy and scanning speed on the morphology of concave-convex microstructures. Subsequently, a unified two-dimensional numerical model incorporating solid, liquid, and gas phases was established, and combined with experimental data, the mechanism and formation process of concave-convex transformation in magnesium alloy under laser ablation were revealed. The results indicate that the transition from concave to convex structures is significantly influenced by the laser scanning speed, whereas the laser pulse energy primarily affects the shape and size of the convex structures. During the ablation process, molten material is expelled and gradually accumulates on both sides of the ablation groove under the action of the recoil pressure. During cooling, the molten material at both ends of the groove merges to form protrusions under the combined effects of internal negative pressure, gravity, and Marangoni forces. Moreover, this method of femtosecond laser ablation for generating convex structures deviates from the traditional single-texture approach to concave structures, potentially broadening the application of laser composite processing surfaces.

Spontaneous symmetry breaking, gauge hierarchy, and electroweak vacuum metastability

The so-called metastability bound asserts that an unnaturally small Higgs mass is a necessary condition for electroweak vacuum metastability, offering a new approach toward solving the hierarchy problem. So far, this result relies on the assumption of a negative Higgs mass parameter, or equivalently, on electroweak spontaneous symmetry breaking. We derive a new, corresponding bound for the case of a positive mass parameter. When the new bound is significantly more restrictive than or comparable to its established counterpart, it may offer an explanation for the sign of the Higgs mass parameter, and thus, spontaneous symmetry breaking itself. New physics at scales O(1–10) TeV can lower these bounds as far as the TeV scale. As an illustration, we consider vacuum stability in the presence of additional TeV-scale fermions with Yukawa couplings to the Higgs, as well as a dimension-six term parametrizing new physics in the UV. This scenario requires new physics that couples strongly to the Higgs, and can potentially be probed at future colliders. Finally, to allow for comparison with concrete mechanisms predicting metastability, we provide the mass-dependent lifetime of the electroweak vacuum for this model. Published by the American Physical Society 2024

Decomposition and Growth Pathways for Ammonium Nitrate Clusters and Nanoparticles.

Understanding the formation and decomposition mechanisms of aerosolized ammonium nitrate species will lead to improvements in modeling the thermodynamics and kinetics of aerosol haze formation. Studying the sputtered mass spectra of cation and anion ammonium nitrate clusters can provide insights as to which growth and evaporation pathways are favored in the earliest stages of nucleation and thereby guide the development and use of accurate models for intermolecular forces for these systems. Simulated annealing Monte Carlo optimization followed by density functional theory optimizations can be used reliably to predict minimum-energy structures and interaction energies for the cation and anion clusters observed in mass spectra as well as for neutral nanoparticles. A combination of translational and rotational mag-walking and sawtooth simulated annealing methods was used to find optimum structures of the various heterogeneous clusters identifiable in the mass spectra. Following these optimizations with ωB97X-D3 density functional theory calculations made it possible to rationalize the pattern of peaks in the mass spectra through computation of the binding energies of clusters involved in various growth and dissociation pathways. Testing these calculations against CCSD(T) and MP2 predictions of the structures and binding energies for small clusters demonstrates the accuracy of the chosen model chemistry. For the first time, the peaks corresponding with all detectable species in both the positive and negative ion mass spectra of ammonium nitrate are identified with their corresponding structures. Thermodynamic control of particle growth and decomposition of ions due to loss of ammonia or nitric acid molecules is indicated. Structures and interaction energies for larger (NH4NO3)n nanoparticles are also presented, including the prediction of new particle morphologies with trigonal pyramidal character.

Accelerated glacier mass loss in the mid-latitude Eurasia from 2019 to 2022 revealed by ICESat-2

The dynamics of glaciers serve as one of the most important indicators of climate change. Whilst current research has primarily concentrated on long-term interannual glacier mass balance and its response to climate change, glaciers may respond more rapidly to climate change, highlighting the urgent need for intra-annual mass balance estimations. Investigating seasonal or short-term variations in glacier mass balance not only enhances our understanding of the interactions between glaciers and the climate system but also provides crucial data for water resource management and ecological protection. The ICESat-2 and NASADEM datasets were used to estimate the inter- and intra-annual glacier mass balance changes in the mid-latitude Eurasia from 2019 to 2022. Additionally, the response of glacier mass balance to regional air temperature and precipitation values was analysed using ERA5-Land data and multiple regression analysis, respectively. From 2019 to 2022, glacier mass loss in mid-latitude Eurasia reached −45.02 ± 34.21 Gt per year, contributing to a global sea-level rise of 0.12 ± 0.09 mm per year. The glacier melt rate in the study area from 2019 to 2022 was 2.33 times higher than that from 2000 to 2019. With the exception of the Western Kunlun region, which experienced a weak accumulation rate of 0.04 ± 0.35 m w.e. per year, all other areas experienced ablation states. Seasonal mass balance responds differently to temperature and precipitation variations across seasons: higher temperatures in different seasons lead to more negative mass balances, while increased winter and spring precipitation can slow down glacier melt. Air temperature dominates the glacier mass balance changes in the study area. The intense heat in 2022 raised average glacier temperatures by 1.04 °C compared to 2019–2021, resulting in a more negative mass balance and an increased ice loss of −0.34 ± 1.01 m w.e. per year (−35.07 ± 103.22 Gt per year). This analysis indicates that glacier mass balance is highly sensitive to climate change, even on a seasonal scale. Moreover, the high precision and spatiotemporal resolution ICESat-2 data can facilitate the investigation of large-scale glacier mass balance on short time scales.

Platinum-rhenium-osmium isotope systematics of chromitite and native osmium from the Guli Massif (Maimecha-Kotui Province, Russia)

To gain insight into the source of ore material, this study presents the first Re-Os and Pt-Os isotopic and highly siderophile element (HSE) abundance data for chromitite and osmium minerals from the Guli massif of ultramafic, alkaline rocks and carbonatites located in the Maimecha-Kotui province, Polar Siberia. The study utilized a number of analytical techniques, including electron microprobe analysis, negative thermal ionization mass spectrometry (N-TIMS) and high pressure asher digestion and an isotope dilution-inductively coupled plasma-mass spectrometry. The HSE concentrations in chromitite samples range from 191 to 866 ppb with a predominance of Ir-group platinum-group elements (PGE) (Os, Ir and Ru) over Pt-group PGE (Rh, Pt and Pd) and Re, which is consistent with their platinum-group mineral control (i. e., Os-Ir alloys and laurite, RuS2) within the chromitite. The Re-Os and Pt-Os isotope data indicate that the HSE budget of the chromitite and osmium minerals from the Guli massif was largely controlled by that of the mantle source, which evolved with long-term near-chondritic Re/Os and Pt/Os ratios; this source is within the range of those for the majority of komatiite and abyssal peridotite sources.

The association between mass media news about interethnic contact and relations between ethnic minorities and natives: The perspective of African immigrants in Italy.

The present research investigated the role of a pervasive and often negative form of indirect contact, exposure to mass media news on interethnic contact. Specifically, we examined the associations between mass media exposure and both African immigrants' attitudes toward native Italians and their collective action intentions to achieve higher intergroup equality in the host country. We conducted two survey studies, one cross-sectional (Study 1, N = 285) and the second longitudinal (Study 2, N = 423) with African immigrants living in Italy. Exposure to negative mass media news was linked to less positive attitudes toward native Italians and more collective action of African immigrants. The negative link between negative mass media news exposure and intergroup attitudes was stronger for those African migrants who reported relatively low positive and negative direct intergroup contact. These findings were consistent across both studies. The positive link between negative mass media news exposure and collective action was stronger among African immigrants with relatively low negative direct intergroup contact. The evidence illustrates the independent and combined ways in which the valence of direct and indirect contact can affect immigrants' attitudes toward natives, and their motivation to build a more inclusive and equal society. Overall, results highlighted the greater strength of negative rather than positive indirect contact of immigrants, especially when they reported less positive direct contact experience with native Italians. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Assessing glacier mass balance variations and climate drivers of Shisper and Muchuhar glaciers in the Karakoram region, Pakistan: a remote sensing and GIS approach

ABSTRACT Glaciers in the Karakoram region of Pakistan are crucial water sources for downstream communities, supporting irrigation and power generation. Global warming has led to significant glacier mass loss and size reduction, posing risks to ecology, climate, and water resources. Understanding Glacier Mass Balance (GMB) is essential for climate change insights and predicting future trends, mainly due to limited long-term GMB and Equilibrium Line Altitude (ELA) data from the Karakoram region. We employed hypsometrically controlled methods, Accumulation Area Ratio (AAR) and Accumulation Area Balance Ratio (AABR) to fill this gap. AAR values ranged from 0.4 to 0.8 at 0.5 intervals, and AABR from 0.9 to 2.2 at 0.01 intervals. Findings indicate that Shisper Glacier had a negative mass balance of –1.0 m/y w.e., with the area below ELAs expanding by 1.72 km². Muchuhar Glacier showed a negative mass balance of -0.05 m/y w.e., with the area below ELAs decreasing to 0.96 km². Surface temperature trends indicate 6.44°C in 2023, highlighting a warming trend. Rising average air temperature (Tavg) is the significant factor influencing ELAs (26% and 72%, respectively), followed by average precipitation (Pavg) at 20% and 26%. These findings highlight the critical role of temperature and precipitation in glacier mass balance.

Genetic-algorithm-assisted design of chiral honeycomb membrane acoustic metamaterials for broadband noise suppression

Low-frequency sound wave reduction is hardly feasible for traditional sound absorbers such as porous media. In contrast, locally resonant acoustic metamaterials act as spatial frequency filters, effectively reducing low-frequency noise. However, these materials can have narrow bandgaps, add extra mass to the main system, and function only within a specifically adjusted frequency range. Therefore, this paper proposes a methodology for designing three-dimensional (3D) chiral honeycomb membrane-type acoustic metamaterials (MAM) based on acoustic circular dichroism (ACD), negative effective mass, and local resonance mechanisms (LRM). The paper also uses the genetic algorithm (GA) to maximize sound transmission attenuation and widen bandgaps. The accuracy of the simulations is validated with available experimental data. The key idea of the present study is to automatically design a MAM structure using modern optimization tools. A developed GA aims to maximize the average sound transmission loss (STL) across the desired low-frequency range of 0–850 Hz by optimizing the value of structural parameters associated with the configurations of masses, including rotation and linear offset, as well as their geometrical dimensions, including length and width. COMSOL Livelink with MATLAB is employed as a practical co-simulation tool to find an optimum value for structural parameters. Results indicate a 35% improvement in average STL along with an ultra-wide bandgap with a 507% bandgap coverage factor (BGCF) in the frequency range of interest, verifying the reliability of the developed algorithm. In addition, sound mitigation incidence is justified by exploring the negative effective parameters of the unit cell and displacement vector fields. The proposed designs demonstrate superior performance as both initial and optimized models broke the mass law within the investigated frequency range. Finally, the effect of the selected geometrical parameters on the objective function is observed through sensitivity analysis. This study presents the practical use of optimization algorithms to develop MAMs.

Review Research Paper of Feasibility study on Anti-Gravity Effect for Advance Propulsion system and technologies

The concept of anti-gravity, often portrayed in science fiction as a means to counteract or negate the effects of gravitational force, has intrigued scientists and enthusiasts alike for decades. This paper explores the feasibility of achieving anti-gravity effects through various theoretical and experimental perspectives. Firstly, theoretical frameworks such as general relativity and quantum mechanics are reviewed to understand gravity and its potential manipulation. While these theories provide foundational insights, they also highlight the immense challenges involved in directly counteracting gravitational forces due to their fundamental nature. Next, experimental efforts and hypothetical technologies proposed in scientific literature are examined. Concepts such as negative mass, exotic matter, and gravitational shielding are discussed in terms of their theoretical underpinnings and practical limitations. Experimental evidence, including anomalies in gravitational measurements and speculative engineering proposals, are scrutinized to evaluate their relevance to achieving anti-gravity effects. Furthermore, the paper addresses the technological and ethical implications of developing anti-gravity technology. Considerations such as energy requirements, environmental impact, and societal readiness are explored to provide a holistic perspective on the feasibility and desirability of pursuing anti-gravity research. Ultimately, while the idea of anti-gravity remains a captivating subject of scientific inquiry and fiction, current understanding and technological capabilities suggest significant hurdles that must be overcome before practical anti-gravity effects can be realized. This paper concludes by outlining potential avenues for future research and highlighting the interdisciplinary nature of addressing such a complex phenomenon.

No νs is Good News

The baryon acoustic oscillation (BAO) analysis from the first year of data from the Dark Energy Spectroscopic Instrument (DESI), when combined with data from the cosmic microwave background (CMB), has placed an upper-limit on the sum of neutrino masses, ∑mν< 70 meV (95%). In addition to excluding the minimum sum associated with the inverted hierarchy, the posterior is peaked at ∑mν = 0 and is close to excluding even the minumum sum, 58 meV at 2σ. In this paper, we explore the implications of this data for cosmology and particle physics. The sum of neutrino mass is determined in cosmology from the suppression of clustering in the late universe. Allowing the clustering to be enhanced, we extended the DESI analysis to ∑mν< 0 and find ∑mν =160±90 meV (68%), and that the suppression of power from the minimum sum of neutrino masses is excluded at 99% confidence. We show this preference for negative masses makes it challenging to explain the result by a shift of cosmic parameters, such as the optical depth or matter density. We then show how a result of ∑mν = 0 could arise from new physics in the neutrino sector, including decay, cooling, and/or time-dependent masses. These models are consistent with current observations but imply new physics that is accessible in a wide range of experiments. In addition, we discuss how an apparent signal with ∑mν< 0 can arise from new long range forces in the dark sector or from a primordial trispectrum that resembles the signal of CMB lensing.

Design, fabrication and vibration characteristics of a novel composite auxetic structure embedded with resonators

With the rapid development of shipbuilding and aerospace industries, the mechanical performance requirements for structures are becoming increasingly demanding. Conventional vibration reduction structures cannot meet the requirements for lightweight, high load capacity, low frequency and broadband vibration reduction. Therefore, it is necessary to consider new structural topologies and material systems. Inspired by the lightweight and high strength characteristics of composite materials, the negative Poisson's ratio characteristics and the locally resonating phononic crystal, the carbon fiber composite auxetic structure embedded with resonators is proposed. Embedded resonators within composite auxetic structures can be strategically positioned to introduce gaps, thereby enhancing the vibration damping performance. The basic auxetic structure is prepared by simpler methods including molding and bonding, and the outer shell of resonator is made by 3D printing technology. The method enables the design of appropriate outer shell based on various cavity types within the structure, ensuring a stable connection between resonators and the structure itself. The range of the band gap can be predicted based on the negative effective mass. Vibration behavior and band gap characteristics of the structure are proved through vibration experiments and numerical simulations. It is revealed that the structure can generate local resonant band gaps at lower frequencies. Meanwhile, the coupling relationship between the auxetic structure and the resonator makes an impact to the band gap range. Therefore, the proposed structure can meet the required multi-functional integrated performance requirements. Furthermore, the parametric analysis is carried out, and the relevant conclusions can provide theoretical guidance for designing porous composite structures with effective low-broadband vibration reduction capabilities.

The mechanism of adjusting the low-frequency ultra-wide band gap within lightweight spherical superstructue

Conventional resonant structures can be effective in obtaining broadband, but it is still a challenge to design small-sized and lightweight acoustic metamaterials with a low-frequency ultra-wideband. This paper proposes a new approach of designing a lightweight spherical localized resonance superstructure with adjustable stiffness ratio, and the mechanism of adjusting the low-frequency ultra-wide forbidden band is revealed. Then, the correlation between the zero value of its dynamic equivalent mass and the stiffness ratio of the system is studied. It is found that not only is the upper bound of the negative mass effectively broadened, but also the lower bound is successfully lowered only by adjusting the stiffness ratio of the sphere. Most importantly, based on the regulation mechanism with adjustable stiffness ratio, the lower boundary of the band gap is lowered from 171 Hz to 141 Hz, and the upper boundary is increased from 445 Hz to 710 Hz. Therefore, the low-frequency ultra-wideband of 141–710 Hz is obtained only by adjusting the stiffness ratio of the system and the Finite Element Method, which is highly consistent with theoretical analyses. Obviously, the mechanism of obtaining the low-frequency wideband through adjusting the stiffness ratio not only provides a novel idea for adjusting the low-frequency ultra-wideband, but also provides theoretical guidance for the developing the small-size and lightweight acoustic devices, so it would have potential application in the field of vibration and noise reduction.

Distributed modelling of snow and ice melt in the Naltar Catchment, Upper Indus basin

Energy balance distributed modelling in High Mountain Asia (HMA) is important to examine glaciological and hydrological processes and assess changes in streamflow in the current and future climate. In this study, the Physically based Distributed Snow Land and Ice Model (PDSLIM) using detailed observed meteorological data at hourly scale is employed to simulate the hydrological response of the Naltar catchment, 242.62 km2 in size, (in the Karakoram region in Pakistan to simulate its glaciers’ mass balance as well as daily runoff. The results exhibited overall satisfactory performance in terms of coefficient of determination (R2 = 0.96) and Nash-Sutcliffe Efficiency (NSE=0.95) modelled against satellite-based snow cover areas, for internal model verification, in eight years. The results of runoff simulations compared for external model verification, with observed daily discharge resulted in NSE 0.90 and 0.89 for calibration and validation period respectively. Flow composition analysis revealed that the streamflow regime of Naltar catchment is composed to 40 % by glacier runoff, 42 % by sub-surface runoff and 18 % by surface runoff. The eight year mean value of net mass balance exhibited a slightly negative mass balance (−0.810 ± 0.31 m w.e. a-1) less pronounced than that observed globally in several continental glaciers distinct from the Greenland and Antarctic ice sheets in the current climate. It seems that the ‘Karakoram anomaly’, i.e. the balanced to slightly positive glacier budgets observed in the region in the recent decades, a unique dynamics worldwide, has a moderate impact in the central Karakoram. Overall, the distributed energy-balance model PDSLIM, so far tested in the Alps, results to be a suitable tool to estimate energy and mass balance in the glacierized catchments of Karakoram and Himalaya and to better understand snow and ice melt runoff dynamics and floods in highly complex and glacierized mountain basins in the current and, in our research perspective, in the future climate.

Vector rogue waves in spin-1 Bose–Einstein condensates with spin–orbit coupling

Abstract We analytically and numerically study three-component rogue waves (RWs) in spin-1 Bose–Einstein condensates with Raman-induced spin–orbit coupling (SOC). Using the multiscale perturbative method, we obtain approximate analytical solutions for RWs with positive and negative effective masses, determined by the effective dispersion of the system. The solutions include RWs with smooth and striped shapes, as well as higher-order RWs. The analytical solutions demonstrate that the RWs in the three components of the system exhibit different velocities and their maximum peaks appear at the same spatiotemporal position, which is caused by SOC and interactions. The accuracy of the approximate analytical solutions is corroborated by comparison with direct numerical simulations of the underlying system. Additionally, we systematically explore existence domains for the RWs determined by the baseband modulational instability (BMI). Numerical simulations corroborate that, under the action of BMI, plane waves with random initial perturbations excite RWs, as predicted by the approximate analytical solutions.

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.

Collapsing scenarios of K-essence generalized Vaidya spacetime under [formula omitted] gravity

The paper investigates the collapse of the generalized emergent Vaidya spacetime in the setting of f(R̄,T̄) gravity, specifically in K-essence theory. In this study, the Dirac–Born–Infeld type non-standard Lagrangian is used to calculate the emergent metric Ḡμν, which is not conformally equivalent to the conventional gravitational metric. We use the function f(R̄,T̄) to reflect the additive nature of the emergent Ricci scalar (R̄) and the trace of the emergent energy–momentum tensor (T̄). Our study demonstrates that certain choices of f(R̄,T̄) may result in the existence of a naked singularity caused by gravitational collapse. The alternative f(R̄,T̄) values resulted in an accelerating universe dominated by dark energy. Moreover, the investigation showed the presence of both positive and negative masses, which might suggest the coexistence of dark matter and dark energy. In addition, when a certain amount of kinetic energy is present in the K-essence scalar field, mass is entirely converted into energy, indicating that spacetime is Minkowskian. The K-essence theory may also be employed as a dark energy framework and a basic gravitational theory, making it possible for researchers to investigate a wide ranges of cosmic phenomena.

Enhanced Energy Dissipation of Tuned Negative Stiffness Viscous Mass Damper (TNSVMD) for the Base-Isolated Structure (BIS)

Negative stiffness dampers (NSDs) have garnered significant attention in the research of base-isolated structures (BIS). This study proposes a tuned negative stiffness viscous mass damper (TNSVMD), which includes a tuning spring in series with the NSD and an inerter, to enhance the seismic control effect of the BIS. An analytical model of a BIS with the TNSVMD is initially established, followed by an investigation into frequency response analysis. The analytical expressions for the stochastic responses of the BIS with TNSVMD are derived, and further exploration is conducted on the influences of the negative stiffness ratio, dashpot damping ratio, and inerter mass ratio on the stochastic responses of the BIS. The mechanisms responsible for the damping enhancement and energy dissipation enhancement of the BIS with the TNSVMD are elucidated through the derivation of the analytical solution for the effective damping ratio and dissipated energy of the BIS with the TNSVMD. Two principles are utilized to determine the optimal parameters of the TNSVMD. These principles involve minimizing the earthquake input energy ratio of the BIS and minimizing the stochastic displacement response of the BIS. Finally, the effectiveness of the TNSVMD is validated through a design example using 100 ground motions. The results indicate that the displacement and acceleration responses of the BIS can be simultaneously controlled due to the weakening of stiffness and enhancement of the effective damping ratio, leading to higher energy dissipation efficiency of the TNSVMD. The increase in the inertial mass ratio enhances the seismic mitigation effect and reduces the optimal negative stiffness ratio and optimal dashpot damping ratio. Therefore, it raises the possibility of implementing the TNSVMD. The inherent damping ratio of the BIS has a significant impact on the control efficiency of the TNSVMD. For BIS systems with relatively small inherent damping ratios, the TNSVMD can achieve better control effectiveness.

Is dark energy necessary for the sustainability of traversable wormholes?

Abstract Dark energy is usually the principal ingredient needed for traversability of wormholes by providing the negative gravity effect to keep the throat open. But can the same be achieved without dark energy? It turns out that if we couple the trace of energy-momentum with the standard Einstein-Hilbert Lagrangian and utilise a specific equation of state then dark energy may be obviated. The Casimir stress energy is known to result in the violation of the null energy condition (NEC) on the energy momentum tensor. This phenomenon makes such an equation of state (EoS) an ideal candidate to generate traversable wormhole (WH) geometries. The laboratory proven phenomenon provides a natural mechanism to sustain an open WH throat without having to appeal to dark energy. We generate two classes of WH solutions with this in energy-momentum trace-coupling gravity.&amp;#xD; For the specific choice of the Casimir EoS relating the energy-momentum tensor components [ Kar and Sahdev: Phys. Rev D {\bf 52} 2030 (1995)] and different choices for redshift functions, we determine the WH geometry completely. The obtained WH solutions violate the NECs and all qualitative constraints demanded of physically realisable WHs are satisfied. This is demonstrated via graphical plots for a suitably chosen range of values of the coupling parameter. Furthermore, our study involved an investigation into the repulsive effect of gravity, which revealed that its presence leads to a negative deflection angle for photons traveling along null geodesics. Notably, we observed a consistent pattern of negative values for the deflection angle across all values of $r_0$ in the three scenarios considered, thus indicating the clear manifestation of the repulsive gravity effect. All of this is possible without invoking the existence of dark energy.