Dynamic Spacetime Research Articles

Impact of chaplygin-like equation of state on Joule–Thomson expansion and tidal forces of AdS black holes

This study examines a recently hypothesized black hole. We study the Joule–Thomson coefficient, the inversion temperature and also the isenthalpic curves in the Ti−Pi plane. The Joule–Thomson coefficient, the inversion curves and the isenthalpic curves are discussed in AdS black holes surrounded by Chaplygin dark fluid. In T−P plane, the inversion temperature curves and isenthalpic curves are obtained with different parameters. Next, we explore the radial time-like geodesics that leads us to explore the tidal force effects for a radially in-falling particle in such black hole spacetime. We also numerically solve the geodesic deviation equation for two nearby radial geodesics for a freely falling particle. Our analysis shows that contrary to the Schwarzschild spacetime, the tidal forces do not become zero at spatial infinity due to the lack of asymptotic flatness because of the presence of a non-zero cosmological constant. The geodesic separation profile shows an oscillating trend and depends on the dynamic spacetime parameters q,B and Λ.

Collaborative optimization decision making of cement grinding process operational indicators considering dual dynamic problem

The cement grinding process requires monitoring of unit power consumption and specific surface area indicators to improve production efficiency and product quality. The strong coupling between operational variables necessitates careful adjustment of these variables to prevent production from becoming instability. Furthermore, the continuous and time-dependent nature of the process makes this adjustment particularly challenging. To address this dual dynamic problem, we have developed a multi-objective optimization model, with global optimization as the desired outcome, to optimize unit power consumption and specific surface area. Our optimization algorithm, termed “Optimization Algorithm - Dynamic Search Space and Rolling Time Domain” (OA-DSTR), considers the problem of dynamic production process. First, the algorithm uses a dynamic search space strategy, allowing for changes in the constraint range of the operational variables and introducing a fluctuation coefficient (FC) to measure solution rationality. Second, to deal with the time-dependent problem, we have added a rolling time domain strategy, enabling real-time monitoring of the cement grinding process. The experimental results show that OA-DSTR not only ensures global optimization, but also realizes the tracking of dynamic conditions, improving the stability of the cement grinding process and achieving a lower FC value.

Energy-Space-Time Plateau-Rayleigh Instability, Quantum Phenomenon & the Fundamental Interactions

In general, fluids in motion or at rest tend to minimize their surface area due to their surface tension. It is shown that kinetic energy flow through space-time experience the same Plateau-Rayleigh instability observed in fluid dynamics. Energy, space-time act like fluids, and the space-time reaction to the energy action is the equivalent of an interface tension between energy and space-time. Energy cannot continuously flow through space-time due to an energy-space-time Plateau-Rayleigh instability, space-time compression (contraction) on kinetic energy direction of motion induces an energy wave like motion (a space-time compression wave acting as kinetic energy waveguide), the particle or energy packet must follow when moving through space-time, the reason for the observed wave - particle duality. Quantum phenomenon is simply a consequence of the space-time compression on kinetic energy direction of motion. Kinetic energy and space-time are fluids and energy quanta can reach a critical point when energy quanta can change from linear to circular motion and assume a spherically symmetrical shape (the minimum surface area possible to minimize the tension at the space-time energy interface) and so it condensates as mass energy. It is shown that energy quanta to mass transformation occurs via Plateau–Rayleigh energyspace-time instability and it is governed by an energy-space-time Young-Laplace equation. Electric field lines are described as space contraction energy shock waves induced by a dynamic space-time phase transition at maximum kinetic energy space- time interface tension which is the “charge”. Space-time always reacts to the presence of energy and that reaction is the interface tension at the energy-space-time boundary: gravitational & electric energy fields are consequences of energyspace-time interface tension (at either rest or kinetic energy boundary) also governed by an energy-space-time instability Young-Laplace equation. Gravitational constant G and the fine structure constant ∝ are respectively, the energy interface field’s interaction constants. The Strong force is a consequence of a direct contact between the nucleon's energy-space-time interface tension fields and has no interaction constant. The range and variation in the strength of the Strong force is due to Heisenberg’s uncertainty principle

The flattening of spacetime hierarchy of the N,N-dimethyltryptamine brain state is characterized by harmonic decomposition of spacetime (HADES) framework.

The human brain is a complex system, whose activity exhibits flexible and continuous reorganization across space and time. The decomposition of whole-brain recordings into harmonic modes has revealed a repertoire of gradient-like activity patterns associated with distinct brain functions. However, the way these activity patterns are expressed over time with their changes in various brain states remains unclear. Here, we investigate healthy participants taking the serotonergic psychedelic N,N-dimethyltryptamine (DMT) with the Harmonic Decomposition of Spacetime (HADES) framework that can characterize how different harmonic modes defined in space are expressed over time. HADES demonstrates significant decreases in contributions across most low-frequency harmonic modes in the DMT-induced brain state. When normalizing the contributions by condition (DMT and non-DMT), we detect a decrease specifically in the second functional harmonic, which represents the uni- to transmodal functional hierarchy of the brain, supporting the leading hypothesis that functional hierarchy is changed in psychedelics. Moreover, HADES' dynamic spacetime measures of fractional occupancy, life time and latent space provide a precise description of the significant changes of the spacetime hierarchical organization of brain activity in the psychedelic state.

Elliptical Space with the McVittie Metrics

The main feature of elliptical space—the topological identification of its antipodal points—could be fundamental for understanding the nature of the cosmological redshift. The physical interpretation of the mathematical (topological) structure of elliptical space is made by using physical connections in the form of Einstein-Rosen bridges (also called “wormholes”). The Schwarzschild metric of these structures embedded into a dynamic (expanding) spacetime corresponds to McVittie’s solution of Einstein’s field equations. The cosmological redshift of spectral lines of remote sources in this metric is a combination of gravitational redshift and the time-dependent scale factor of the Friedmann-Lemaitre-Robertson-Walker metric. I compare calculated distance moduli of type-Ia supernovae, which are commonly regarded as “standard candles” in cosmology, with the observational data published in the catalogue “Pantheon+”. The constraint based on these accurate data gives a much smaller expansion rate of the Universe than is currently assumed by modern cosmology, the major part of the cosmological redshift being gravitational by its nature. The estimated age of the Universe within the discussed model is 1.48·1012 yr, which is more than two orders of magnitude larger than the age assumed by using the standard cosmological model parameters.

Dynamic Spacetime: Key to the Mysteries of Dark Matter and Dark Energy

Dynamic Spacetime: Key to the Mysteries of Dark Matter and Dark Energy

Designing an active electronically scanned array as part of onboard equipment of a high-speed radio communication channel

The active electronically scanned array being developed is designed to provide an all-weather high-speed radio communication channel “Spacecraft – Earth”. It is supposed to provide fast, inertia-free observation of space by swinging the antenna beam electrically, and, in fact, is a dynamic space-time filter of the spacecraft. The aim of the work is to identify the basic principles of functioning of the array as part of the spacecraft with inherent limitations in the mass-dimensional and energy characteristics of the onboard equipment and, at the same time, high requirements for the functional characteristics. This paper presents the calculation and the main results of designing an active electronically scanned array complying with the requirements for optimizing the parameters of the antenna system. To assess the effect of scanning on the phase characteristics of the chips, a nonlinear amplifier model was developed. A statistical analysis of the phase characteristics was carried out when the load resistance changed in accordance with the obtained distribution laws. When calculating the resulting directional pattern of the antenna array, destabilizing factors were taken into account in accordance with the results of the study of the prototypes of the antenna array being created. Phase errors were calculated, mainly determined by the errors of the terminal parts of the receiving paths. Measures were implemented to ensure the effect of such phase errors on the directional pattern of the array only on the far side lobes.

Drought cascades across multiple systems in Central Asia identified based on the dynamic space–time motion approach

Abstract. Drought is typically induced by the extreme water deficit stress that cascades through the atmosphere, hydrosphere, and biosphere. Cascading drought events could cause severe damage in multiple systems. However, identifying cascading drought connections considering the dynamic space–time progression remains challenging, which hinders further exploring the emergent patterns of drought cascades. This study proposes a novel framework for tracking drought cascades across multiple systems by utilizing dynamic space–time motion similarities. Our investigation focuses on the four primary drought types in Central Asia from 1980 to 2007, namely precipitation (PCP), evapotranspiration (ET), runoff, and root zone soil moisture (SM), representing the four systems of atmosphere, hydrosphere, biosphere, and soil layer respectively. A total of 503 cascading drought events are identified in this study, including the 261 four-system cascading drought events. Our results show a significant prevalence of the four-system cascading drought pattern in Central Asia with high systematic drought risk, mainly when seasonal PCP droughts with high severity/intensity and sizeable spatial extent are observed. As for the temporal order in the cascading drought events, ET droughts are likely to occur earlier than runoff droughts after PCP droughts, and SM droughts are more likely to occur at last, implying the integrated driven effect of the energy-limited and water-limited phases on the drought progression in Central Asia. Our proposed framework could attain precise internal spatial trajectories within each cascading drought event and enable the capture of space–time cascading connections across diverse drought systems and associated hazards. The identification of cascading drought patterns could provide a systematic understanding of the drought evolution across multiple systems under exacerbated global warming.

Making paths and doing bazaar: Rhythms and techniques of walking‐as‐dwelling

AbstractThis article posits the concept of “walking‐as‐dwelling” as a critical analytical frame to counter the dominant Western conceptualization of walking as an event or novel experience that is set apart from ordinary life. Walking‐as‐dwelling refers to how walking is bound with routines of work, domesticity, and leisure, through which people inhabit and make places. Drawing attention to the situatedness of walking in particular places and subjectivities, the article follows the walking practices of women in the Monday bazaar of Nizamuddin Basti, a low‐income neighborhood in Delhi. It examines how women's walking itineraries, rhythms, and techniques co‐constitute the bazaar as a dynamic spacetime configuration, making and remaking the public and social character of the bazaar. It draws attention to the creative and political potential of ordinary practices of walking through which the Basti's women negotiate constraints of gender and class and, in the process, forge affective ties with the bazaar, perform modes of sociality, and articulate freedom and mobility.

Dynamic adaptive spatio–temporal graph network for COVID‐19 forecasting

AbstractAppropriately characterising the mixed space–time relations of the contagion process caused by hybrid space and time factors remains the primary challenge in COVID‐19 forecasting. However, in previous deep learning models for epidemic forecasting, spatial and temporal variations are captured separately. A unified model is developed to cover all spatio–temporal relations. However, this measure is insufficient for modelling the complex spatio–temporal relations of infectious disease transmission. A dynamic adaptive spatio–temporal graph network (DASTGN) is proposed based on attention mechanisms to improve prediction accuracy. In DASTGN, complex spatio–temporal relations are depicted by adaptively fusing the mixed space–time effects and dynamic space–time dependency structure. This dual‐scale model considers the time‐specific, space‐specific, and direct effects of the propagation process at the fine‐grained level. Furthermore, the model characterises impacts from various space–time neighbour blocks under time‐varying interventions at the coarse‐grained level. The performance comparisons on the three COVID‐19 datasets reveal that DASTGN achieves state‐of‐the‐art results with a maximum improvement of 17.092% in the root mean‐square error and 11.563% in the mean absolute error. Experimental results indicate that the mechanisms of designing DASTGN can effectively detect some spreading characteristics of COVID‐19. The spatio–temporal weight matrices learned in each proposed module reveal diffusion patterns in various scenarios. In conclusion, DASTGN has successfully captured the dynamic spatio–temporal variations of COVID‐19, and considering multiple dynamic space–time relationships is essential in epidemic forecasting.

Dynamic space–time panel data models: An eigendecomposition-based bias-corrected least squares procedure

Jin et al. (2020) proposed an efficient, distribution-free least squares estimation method that utilizes the eigendecomposition of a weight matrix in a dynamic space–time pooled panel data model. Their three-step approach is very powerful compared to the well-known instrumental variable techniques. Unfortunately, for short panels, their method can lead to biased estimates of the autoregressive time dependence parameter and the spatio-temporal diffusion parameter, even when using their bias-corrected estimator. We propose a bias correction method inspired from Bun and Carree (2005, 2006) of the Jin et al. (2020) procedure. We also extend their eigendecomposition-based least squares procedure to the random effects model, the fixed effects model, the Mundlak-type and Chamberlain-type correlated random effects models, the Hausman–Taylor model and the common correlated effects model. Extensive Monte Carlo experiments show the good finite sample properties of the proposed estimators. An application on the link between pollution and economic activities, using a dynamic space–time STIRPAT model with common correlated effects on a panel of 81 countries over 1991–2015, shows the relevance of this approach. It underlines the importance of human activities in the pollution growth while reforestation is one of the most important levers to reduce the CO2 emissions per capita.

Dynamic space-time dark level correction approach for lunar radiometric calibration of the Lunar Observation Imaging Spectrometer.

Lunar radiometric calibration is used to solve the problem of consistent radiometric calibration for multiple satellite platforms and remote sensors. However, the dark level fluctuates when observing the Moon with a short-wave infrared spectrometer, which seriously affects the accuracy of lunar radiation data. In this work, we propose a dynamic space-time dark level correction approach to address the fluctuation of the dark level. This method employs cold space signals in space and time dimensions to estimate the dark level for each frame individually and to reduce errors due to environmental variations. Experiments on lunar observations at multiple phase angles were conducted, and the dark level correction results demonstrate that our proposed method is effective even in the short-wave infrared, and is also superior to currently existing techniques. For a single-band (1700nm) image of the full Moon, the mean background proportion of the proposed method is 1.00%, which is better than that of the static dark correction method (2.25%) and linear dark correction method (5.93%).

Estimation of bit error rate in 2×2 and 4×4 multi-input multi-output-orthogonal frequency division multiplexing systems

<span lang="EN-US">Multiple-input, multiple-output orthogonal frequency-division multiplexing (MIMO-OFDM) systems with multiple input antennas and multiple output antennas in dynamic environments face the challenge of channel estimation. To overcome this challenge and to improve the performance and signal-to-noise ratio, in this paper we used the Kalman filter for the correct estimation of the signal in dynamic environments. To obtain the original signal at the receiver end bit error rate factor plays a major role. If the signal to noise ratio is high and the bit error rate is low then signal strength is high, the signal received at the receiver end is almost similar to the </span><em><span lang="EN-US">i<sup>th</sup></span></em><span lang="EN-US"> transmitted signal. The dynamic tracking characteristic of Kalman filter is used to establish a dynamic space-time codeword and a collection of orthogonal pilot sequences to prevent interference among transmissions in this paper. Using the simulation, the Kalman filter method can be compared to the other channel estimation method presented in this paper that can track time-varying channels rapidly.</span>

Robust dynamic space–time panel data models using $$\varepsilon $$-contamination: an application to crop yields and climate change

Robust dynamic space–time panel data models using $$\varepsilon $$-contamination: an application to crop yields and climate change

Method for reconstruction of axisymmetric capillary wave surface topography using inverse ray-tracing of refracted laser sheet

Capillary waves can be used to measure the fundamental fluid properties such as surface tension as well as, potentially, the viscosity of Newtonian fluids. This requires the measurement of various wave parameters, mainly wavelength, amplitude, and decay coefficient. However, the different scales of magnitudes make it a challenging task. Optical methods are well suited to analyze such problems due to their non-intrusive nature and high dynamic measurement resolution in both space and time. These methods are further categorized as point methods for a single probe measurement and space–time methods for transient measurement of the complete surface. Dynamic space–time methods are preferred despite the associated complex post-processing since they enable reconstruction of the wave surface. Some existing methods are discussed, and an improved method is then proposed to actually solve the associated inverse optics problem. In the method, an axisymmetric wave surface is re-constructed by analyzing the refracted laser sheet. The assumptions, simplifications, and constraints are taken to be compatible with experimental aspects for future validation. It is derived using the fundamental concepts in physics and the only major assumption of the axisymmetric nature of wave surface. The method exploits the underlying symmetry in the topography, making it more versatile, and suited for linear and non-linear capillary waves and waves with planar wavefront. The impact of parameters on the final result is determined through numerical simulations. Very low error (average and maximum) values are observed between reference and reconstructed topography for damped and undamped wave surfaces with a wide range of curvatures. Optimum values of critical parameters and associated reasoning are presented.

A study of McVittie Spacetime in Stationary and Dynamical Regime

AbstractOne of the solutions of the Einstein equations, called McVittie solution, signifying a black hole embedded by the dynamic spacetime is studied. In the stationary spacetime the Mcvittie metric becomes the Schwarzschild‐de Sitter metric (SdS). The geodesic of a freely falling test particle towards the black hole is examined in the SdS spacetime. It is found that unlike the Schwarzschild case the potential of such particle becomes maximum at a point where it eventually stops for a while and then resumes its motion towards the center of the black hole. It is shown that an observer or system of particles is spaghettified near the black hole singularity in the SdS spacetime. The dynamics of the universe in the framework of McVittie metric, being a generalized time dependent SdS solution, is represented in terms of that point, called stationary or turning point. The motion of the stationary point is studied in various regimes of the expanding universe and the possible outcomes are discussed in brief.

The Lagrange’s method in dynamic spacetime

The Lagrange’s method is a kind of commen method in physics on motion particle. Usually, the field is nonconsevative if it had constraint condition vary in time, it lead to the Lagrange’s equaition have inhomogeneous term and many integral. The dynamic spacetime can be constraint the situation of motion of particle, because of this kind of spacetime had the gravitational wave. This paper will be discuess the form of Lagrange’s method in dynamic spacetime.

Tour-Route-Recommendation Algorithm Based on the Improved AGNES Spatial Clustering and Space-Time Deduction Model

This study designed a tour-route-planning and recommendation algorithm that was based on an improved AGNES spatial clustering and space-time deduction model. First, the improved AGNES tourist attraction spatial clustering algorithm was created. Based on the features and spatial attributes, city tourist attraction clusters were formed, in which the tourist attractions with a high degree of correlation among attributes were gathered into the same cluster. It formed the precondition for searching tourist attractions that would match tourist interests. Using tourist attraction clusters, this study also developed a tourist attraction reachability model that was based on tourist-interest data and geospatial relationships to confirm each tourist attraction’s degree of correlation to tourist interests. A dynamic space-time deduction algorithm that was based on travel time and cost allowances was designed in which the transportation mode, time, and costs were set as the key factors. To verify the proposed algorithm, two control algorithms were chosen and tested against the proposed algorithm. Our results showed that the proposed algorithm had better results for tour-route planning under different transportation modes as compared to the controls. The proposed algorithm not only considered time and cost allowances, but it also considered the shortest traveling distance between tourist attractions. Therefore, the tourist attractions and tour routes that were suggested not only met tourist interests, but they also conformed to the constraint conditions and lowered the overall total costs.

Collapsing dust thin shells in Einstein\u2013Gauss\u2013Bonnet gravity

We investigate gravitational collapse of a spherically symmetric thin shell in the Einstein–Gauss–Bonnet (EGB) gravity. Under the recently proposed 4D limit, we find that the collapsing shell will be bounced back at a small radius, without forming a singularity. This bouncing behavior is similar to those of a test particle and a homogeneous spherical dust star, in accordance with the expectation that the Gauss–Bonnet term will modify the small scale behavior of the Einstein gravity. We analyze the causal structure of the dynamic spacetime that represents the bouncing process, finding that the thin shell has an oscillation behavior on the Penrose diagram, which means that the thin shell results in a novel type of black hole with respect to observers outside the event horizon that the collapse forms. We also find that the weak cosmic censorship conjecture holds in this model. Further implications of such a regular gravitational collapse are discussed.

Robust Dynamic Space-Time Panel Data Models Using?-Contamination: an Application to Crop Yields and Climate Change

Robust Dynamic Space-Time Panel Data Models Using?-Contamination: an Application to Crop Yields and Climate Change