Charging axisymmetric space-times with cosmological constant

Ernst's solution generating technique for adding electromagnetic charge to axisymmetric space-times in general relativity is generalised in presence of the cosmological constant. Ernst equations for complex potentials are found and they are traced back to an affective dual complex dynamical system, whose symmetries are studied. In particular this method is able to generate charged, asymptotically (A)dS black holes from their uncharged version: as an example, it is shown explicitly how to pass from the Kerr-(A)dS to the Kerr-Newman-(A)dS metric. A new solution describing a magnetic universe in presence of the cosmological constant is also generated.Comment: 15 pages, v2: typos correcte

General Gauss-Bonnet brane cosmology

We consider 5-dimensional spacetimes of constant 3-dimensional spatial curvature in the presence of a bulk cosmological constant. We find the general solution of such a configuration in the presence of a Gauss-Bonnet term. Two classes of non-trivial bulk solutions are found. The first class is valid only under a fine tuning relation between the Gauss-Bonnet coupling constant and the cosmological constant of the bulk spacetime. The second class of solutions are static and are the extensions of the AdS-Schwarzchild black holes. Hence in the absence of a cosmological constant or if the fine tuning relation is not true, the generalised Birkhoff's staticity theorem holds even in the presence of Gauss-Bonnet curvature terms. We examine the consequences in brane world cosmology obtaining the generalised Friedmann equations for a perfect fluid 3-brane and discuss how this modifies the usual scenario.Comment: 20 pages, no figures, typos corrected, refs added, section IV changed yielding novel result

ON ACCELERATION OF THERMAL SIMULATION OF URBAN SCENES WITH THE APPLICATION OF AN EVOLUTIONARY ALGORITHM TO TREE PLANTING STRATEGIES

Tree planting is one of the most popular in urban morphology measures for urban heat island reduction since, at a relatively low monetary cost and with a marginal alteration of the scene, trees provide shadows and neutralize harmful gases. Findings for their optimal distribution within the urban scene exist in numerous environmental studies. However, merely the digital twin of the scene possesses the capability to analyze further developments of the scene, such as changes in dominant wind directions. Today’s extensive computational resources allow for thermal simulations of digital twins on multiple (not-yet-existing) urban scene designs, aiming at minimizing the average or peak temperatures. From the point of view of computer graphics, this paper proposes four tools to accelerate an evolutionary algorithm for tree planting strategies. Using GPU arrays for rendering, pre-rendering default scenes, and pre-filtering trees in the early morning and late evening hours helps accelerating the rendering process. Computation of fitness function on different computers allows a further acceleration of the evolutionary algorithm. The total acceleration factor of a scene using computational set-up exceeds 218, thus demonstrating the enormous potential the evolutionary algorithm may bring about in future investigations

Cosmological Constant, Conical Defect and Classical Tests of General Relativity

We investigate the perihelion shift of the planetary motion and the bending of starlight in the Schwarzschild field modified by the presence of a $\Lambda$-term plus a conical defect. This analysis generalizes an earlier result obtained by Islam (Phys. Lett. A 97, 239, 1983) to the case of a pure cosmological constant. By using the experimental data we obtain that the parameter $\epsilon$ characterizing the conical defect is less than $10^{-9}$ and $10^{-7}$, respectively, on the length scales associated with such phenomena. In particular, if the defect is generated by a cosmic string, these values correspond to limits on the linear mass densities of $10^{19}g/cm$ and $10^{21}g/cm$, respectively.Comment: 9 pages, no figures, revte

The family of regular interiors for non-rotating black holes with T00=T11T^0_0 = T^1_1

We find the general solution for the spacetimes describing the interior of static black holes with an equation of state of the type $T^0_0 = T^1_1$ ($T$ being the stress-energy tensor). This form is the one expected from taking into account different quantum effects associated with strong gravitational fields. We recover all the particular examples found in the literature. We remark that all the solutions found follow the natural scheme of an interior core linked smoothly with the exterior solution by a transient region. We also discuss their local energy properties and give the main ideas involved in a possible generalization of the scheme, in order to include other realistic types of sources.Comment: 31 pages, 1 figure, version to appear in Physical Review

PARAMETER OPTIMIZATION FOR A THERMAL SIMULATION OF AN URBAN AREA

Urban heat island (UHI) phenomenon is a significant challenge in urban planning, and accurate temperature predictions are crucial for effective decision-making. The choice of material parameters is crucial to simulate a realistic temperature distribution and identify potential UHIs. This paper introduces a framework for optimizing the material properties based on sensors boxes placed upon surfaces made up by different materials. The methodology covers an optimization approach for the material properties to achieve accurate surface temperature simulation. The results, which involved close-range validation and macro-scale validation, show a significant improvement in the agreement between the simulated and measured temperature time series, especially for tiled roofs and asphalt roads. However, the accuracy for grassland areas decreased, possibly due to differences in soil moisture. Overall, the proposed framework shows promising results for future work in improving the accuracy of thermal simulation of urban areas

The geodesic structure of the Schwarzschild Anti-de Sitter black hole

In the present work we found the geodesic structure of an AdS black hole. By means of a detailed analyze of the corresponding effective potentials for particles and photon, we found all the possible motions which are allowed by the energy levels. Radial and non radial trajectories were exactly evaluated for both geodesics. The founded orbits were plotted in order to have a direct visualization of the allowed motions. We show that the geodesic structure of this black hole presents new type of motions not allowed by the Schwarzschild spacetime.Comment: 17 pages, 11 figure

Counting a black hole in Lorentzian product triangulations

We take a step toward a nonperturbative gravitational path integral for black-hole geometries by deriving an expression for the expansion rate of null geodesic congruences in the approach of causal dynamical triangulations. We propose to use the integrated expansion rate in building a quantum horizon finder in the sum over spacetime geometries. It takes the form of a counting formula for various types of discrete building blocks which differ in how they focus and defocus light rays. In the course of the derivation, we introduce the concept of a Lorentzian dynamical triangulation of product type, whose applicability goes beyond that of describing black-hole configurations.Comment: 42 pages, 11 figure

Presence and levels of galactosyllactoses and other oligosaccharides in human milk and their variation during lactation and according to maternal phenotype

Among the human milk oligosaccharides (HMOS), the galactosyllactoses (GLs) are only limitedly studied. This study aims to describe the presence and relative levels of HMOS, including GLs, in human milk (HM) according to maternal Secretor and Lewis (SeLe) phenotype and lactation stage. Relative levels of 19 HMOS were measured in 715 HM samples collected in the first 4 months postpartum from 371 donors participating in the PreventCD study. From a subset of 24 Dutch women (171 HM samples), samples were collected monthly up to 12 months postpartum and were additionally analyzed for relative and absolute levels of beta 6 '-GL, beta 3 '-GL and alpha 3 '-GL. Maternal SeLe phenotype or HM group was assigned based on the presence of specific fucosylated HMOS. Most HMOS, including beta 6 '- and beta 3 '-GL, were present in the vast majority (>= 75%) of HM samples, whereas others (e.g., LNDFH II, 2 '-F-LNH and alpha 3 '-GL) only occurred in a low number (<25%) of samples. Clear differences were observed between the presence and relative levels of the HMOS according to the maternal phenotype and lactation stage. Absolute concentrations of beta 6 '-GL and beta 3 '-GL were higher in HM group IV samples compared to samples of the other three HM groups. beta 3 '-GL was also higher in HM group II samples compared to HM group I samples. beta 3 '-GL and beta 6 '-GL were stable over lactation stages. In conclusion, presence and levels of HMOS vary according to HM group and lactation stage. Not all HMOS behave similarly: some HMOS depend strongly on maternal phenotype and/or lactation stage, whereas others do not. beta 3 '-GL and beta 6 '-GL were present in low concentrations in over 75% of the analyzed HM samples and showed differences between HM groups, but not between the lactation stages.Transplantation and immunomodulatio