We show that, unlike vacuum general relativity, Einstein-scalar theories allow balanced static, neutral, asymptotically flat, double-black hole solutions, for scalar field models minimally coupled to gravity, with app...
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We show that, unlike vacuum general relativity, Einstein-scalar theories allow balanced static, neutral, asymptotically flat, double-black hole solutions, for scalar field models minimally coupled to gravity, with appropriate self-interactions. These are scalar hairy versions of the double-Schwarzschild (or Bach-Weyl) solution, but regular on and outside the two (topologically spherical) horizons. The balancing repulsive force is provided by the scalar field. An explicit illustration is presented, using a Weyl-type construction adapted to numerical solutions, requiring no partial linearization, or integrability structure, of the Einstein-scalar equations. Fixing the couplings of the model, the balanced configurations form a one-parameter family of solutions, labeled by the proper distance between the black holes.
作者：
Matos, A.Xambre, A.R.Alvelos, H.Department of Economics
Management Industrial Engineering and Tourism University of Aveiro Aveiro3810-193 Portugal Department of Economics
Management Industrial Engineering and Tourism Center for Research and Development in Mathematics and Applications University of Aveiro Aveiro3810-193 Portugal
Purpose - This work discusses a SMED implementation carried out in the assembly department of a sanitary components’ factory, located in Aveiro, Portugal, with the support of quality tools. The case study focused on ...
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For a stationary, axisymmetric, asymptotically flat, ultracompact [i.e., containing light rings (LRs)] object, with a Z2 north-south symmetry fixing an equatorial plane, we establish that the structure of timelike cir...
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For a stationary, axisymmetric, asymptotically flat, ultracompact [i.e., containing light rings (LRs)] object, with a Z2 north-south symmetry fixing an equatorial plane, we establish that the structure of timelike circular orbits (TCOs) in the vicinity of the equatorial LRs, for either rotation direction, depends exclusively on the radial stability of the LRs. Thus, an unstable LR delimits a region of unstable TCOs (no TCOs) radially above (below) it; a stable LR delimits a region of stable TCOs (no TCOs) radially below (above) it. Corollaries are discussed for both horizonless ultracompact objects and black holes. We illustrate these results with a variety of exotic stars examples and non-Kerr black holes, for which we also compute the efficiency associated with converting gravitational energy into radiation by a material particle falling under an adiabatic sequence of TCOs. For most objects studied, it is possible to obtain efficiencies larger than the maximal efficiency of Kerr black holes, i.e., larger than 42%.
Nowadays companies operate in a competitive environment, which means they must focus on continuously improving their processes. Eliminating waste is then crucial to ensure process efficiency, being the main target of ...
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Nowadays companies operate in a competitive environment, which means they must focus on continuously improving their processes. Eliminating waste is then crucial to ensure process efficiency, being the main target of both lean thinking concept and Toyota Production System (TPS). Another important factor to consider is the technological growth, which is beneficial to pursue and combine with continuous improvement and waste elimination. Despite TPS, Lean, and Kaizen traditionally focusing on productive processes and related activities, their fundamental principles are applicable to any part of a company, meaning that processes with the potential for automatization also include back-office processes, which rely heavily on information flows and employee knowledge. This study integrates back-office process improvement with the implementation of technology, through the development of a project based on the Continuous improvement philosophy and A3 Thinking methodology, consisting on automatizing the documentation of standardized work analysis used by an automotive company.
We herein report a new class of impulsive fractional stochastic differential systems driven by mixed fractional Brownian motions with infinite delay and Hurst parameter Ĥ ∈ (1/2, 1). Using fixed point techniques, a q...
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It is shown that the duals of several categories of topological flavour, like the categories of ordered sets, generalised metric spaces, probabilistic metric spaces, topological spaces, approach spaces, are quasivarie...
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Partition problems in graphs are extremely important in applications, as shown in the Data science and Machine learning literature. One approach is spectral partitioning based on a Fiedler vector, i.e., an eigenvector...
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With rapid technological changes and globalized supply chains, intelligent and adaptable logistics systems are crucial, particularly at seaports. Container terminals face increasing volumes and demands, leading to pot...
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With rapid technological changes and globalized supply chains, intelligent and adaptable logistics systems are crucial, particularly at seaports. Container terminals face increasing volumes and demands, leading to potential truck congestion and long queues. Automation offers a solution by optimizing port performance and adapting to dynamic conditions, though port digitalization is complex due to diverse stakeholders and information flows. This work is part of the digital transformation of the Port of Sines - Portugal, specifically in the Smart Gate concept context. For this purpose, the Port of Sines Administration, together with other partners, has established the prerequisite of a pre-gate, which is currently being analysed from the point of view of its processes, the technologies to be included and the information models to be supported. This work aims to dynamically analyse the pre-gate model by testing different scenarios to propose improvements to the inherent processes using simulation. The study culminated in a discrete-event simulation model with Anylogic software to predict pre-gate behaviour and foresee potential issues. By testing various scenarios and evaluating their effects on key performance indicators, this model supports the continuous improvement of pre-gate processes.
In this paper we introduce the concept of matrix-valued q-rational functions. In comparison to the classical case, we give different characterizations with principal emphasis on realizations and discuss algebraic mani...
In this paper we introduce the concept of matrix-valued q-rational functions. In comparison to the classical case, we give different characterizations with principal emphasis on realizations and discuss algebraic manipulations. We also study the concept of Schur multipliers and complete Nevanlinna–Pick kernels in the context of q-deformed reproducing kernel Hilbert spaces and provide first applications in terms of an interpolation problem using Schur multipliers and complete Nevanlinna–Pick kernels.
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