Self-gravitating anisotropic star using gravitational decoupling

This paper addresses a new gravitationally decoupled anisotropic solution for the compact star model via the minimal geometric deformation (MGD) approach. We consider a non-singular well-behaved gravitational potential corresponding to the radial component of the seed spacetime and embedding class I condition that determines the temporal metric function to solve the seed system completely. However, two different well-known mimic approaches such as pr = Θ1 1 and ρ = Θ0 0 have been employed to determine the deformation function which gives the solution of the second system corresponding to the extra source. In order to test the physical viability of the solution, we have checked several conditions such as regularity conditions, energy conditions, causality conditions, hydrostatic equilibrium, etc. Moreover, the stability of the solutions has been also discussed by the adiabatic index and its critical value. We find that the solutions set seems viable as far as observational data are concerned.

Feelings of Entrapment during the COVID-19 Pandemic Based on ACE Star Model: A Concept Analysis

This study aimed to analyze the concept of the “feelings of entrapment” during the COVID-19 (coronavirus disease 2019) pandemic using a systematic review. We included literature based on content and outcomes related to feelings of entrapment, such as antecedents, attributes, and consequences. The exclusion criteria were studies that did not have inappropriate subject, content, conceptual definition, and degree thesis was excluded. Walker and Avant’s process of concept analysis was used in this systematic literature review. The attributes of the concept of feelings of entrapment during the COVID-19 pandemic were found to be feelings of: (1) being out of control, (2) no escape, (3) being trapped, (4) being robbed, and (5) hopelessness. The causes for these were identified as (1) the COVID-19 pandemic, (2) lockdown system, (3) restricted situation, (4) uncertain future, (5) economic hardship, and (6) poor coping abilities. Consequences of the concept were: (1) increased suicide, (2) decreased mental health, and (3) decreased well-being. In situations such as COVID-19, it is important need to know what feelings of entrapment’s antecedents and attributes are to prevent suicide and enhance mental health and well-being. Based on the results of this study, counseling services, policies, and systems for relieving feelings of entrapment in the COVID-19 situation are recommended.

Spatio-temporal joint aberrance suppressed correlation filter for visual tracking

The discriminative correlation filter (DCF)-based tracking methods have achieved remarkable performance in visual tracking. However, the existing DCF paradigm still suffers from dilemmas such as boundary effect, filter degradation, and aberrance. To address these problems, we propose a spatio-temporal joint aberrance suppressed regularization (STAR) correlation filter tracker under a unified framework of response map. Specifically, a dynamic spatio-temporal regularizer is introduced into the DCF to alleviate the boundary effect and filter degradation, simultaneously. Meanwhile, an aberrance suppressed regularizer is exploited to reduce the interference of background clutter. The proposed STAR model is effectively optimized using the alternating direction method of multipliers (ADMM). Finally, comprehensive experiments on TC128, OTB2013, OTB2015 and UAV123 benchmarks demonstrate that the STAR tracker achieves compelling performance compared with the state-of-the-art (SOTA) trackers.

Genetic Algorithm Based Improved ESTAR Nonlinear Models for Modelling Sunspot Numbers and Global Temperatures

Smooth Transition Autoregressive (STAR) models are employed to describe cyclical data. As estimation of parameters of STAR using nonlinear methods was time-consuming, Genetic algorithm (GA), a powerful optimization procedure was applied for the same. Further, optimal one step and two step ahead forecasts along with their forecast error variances are derived theoretically for fitted STAR model using conditional expectations. Given the importance of the issue of global warming, the current paper aims to model the sunspot numbers and global mean temperatures. Further, appropriate tests are carried out to see if the model employed is appropriate for the datasets.

Anisotropic Strange Star in 5D Einstein-Gauss-Bonnet Gravity

In this paper, we investigated a new anisotropic solution for the strange star model in the context of 5D Einstein-Gauss-Bonnet (EGB) gravity. For this purpose, we used a linear equation of state (EOS), in particular pr=βρ+γ, (where β and γ are constants) together with a well-behaved ansatz for gravitational potential, corresponding to a radial component of spacetime. In this way, we found the other gravitational potential as well as main thermodynamical variables, such as pressures (both radial and tangential) with energy density. The constant parameters of the anisotropic solution were obtained by matching a well-known Boulware-Deser solution at the boundary. The physical viability of the strange star model was also tested in order to describe the realistic models. Moreover, we studied the hydrostatic equilibrium of the stellar system by using a modified TOV equation and the dynamical stability through the critical value of the radial adiabatic index. The mass-radius relationship was also established for determining the compactness and surface redshift of the model, which increases with the Gauss-Bonnet coupling constant α but does not cross the Buchdahal limit.

Anisotropic stars via embedding approach in Brans–Dicke gravity

In the present article, the solution of the Einstein–Maxwell field equations in the presence of a massive scalar field under the Brans-Dicke (BD) gravity is obtained via embedding approach, which describes a charged anisotropic strange star model. The interior spacetime is described by a spherically symmetric static metric of embedding class I. This reduces the problem to a single-generating function of the metric potential which is chosen by appealing to physics based on regularity at each interior point of the stellar interior. The resulting model is subjected to rigorous physical checks based on stability, causality and regularity for particular object PSR J1903+327. We also show that our solutions describe compact objects such as PSR J1903+327; Cen X-3; EXO 1785-248 and LMC X-4 to an excellent approximation. Novel results of our investigation reveal that the scalar field leads to higher surface charge densities which in turn affects the compactness and upper and lower values imposed by the modified Buchdahl limit for charged stars. Our results also show that the electric field and scalar field which originate from entirely different sources couple to alter physical characteristics such as mass-radius relation and surface redshift of compact objects. This superposition of the electric and scalar fields is enhanced by an increase in the BD coupling constant, $$\omega _{BD}$$ ω BD .

Deconstructing the STAR File Format

The STAR (Self-defining Text Archival and Retrieval) file format for electronic data transfer and archiving was introduced in 1991 [ Hall, 1991 ]. This format was designed to be extensible and flexible to handle all types of data in a machine independent manner. As a file format, STAR encompasses both a model (structure) for the information contained within the file as well as a syntax for defining the layout of the information within the file (serialization). This manuscript reports on an attempt to decompose the model from the layout and in doing so, both highlight differences between variants and versions of STAR as well as propose a simple alternate serialization of the STAR model in XML.