Thermodynamic instability of nonlinearly charged black holes in gravity's rainbow

Motivated by the violation of Lorentz invariancy in quantum gravity, we study black hole solutions in gravity's rainbow in context of Einstein gravity coupled with various models of nonlinear electrodynamics. We regard an energy dependent spacetime and obtain related metric functions and electric fields. We show that there is an essential singularity at the origin which is covered with an event horizon. We also compute the conserved and thermodynamical quantities and examine the validity of the first law of thermodynamics in the presence of rainbow functions. Finally, we investigate thermal stability conditions for these black hole solutions in context of canonical ensemble. We show that thermodynamical structure of the solutions depends on the choices of nonlinearity parameters, charge and energy functions.Comment: 13 pages, 5 figure

Three dimensional nonlinear magnetic AdS solutions through topological defects

Inspired by large applications of topological defects in describing different phenomena in physics, and considering the importance of three dimensional solutions in AdS/CFT correspondence, in this paper we obtain magnetic anti-de Sitter solutions of nonlinear electromagnetic fields. We take into account three classes of nonlinear electrodynamic models; first two classes are the well-known BornInfeld like models including logarithmic and exponential forms and third class is known as the power Maxwell invariant nonlinear electrodynamics. We investigate the effects of these nonlinear sources on three dimensional magnetic solutions. We show that these asymptotical AdS solutions do not have any curvature singularity and horizon. We also generalize the static metric to the case of rotating solutions and find that the value of the electric charge depends on the rotation parameter. Finally, we consider the quadratic Maxwell invariant as a correction of Maxwell theory and in other words, we investigate the effects of nonlinearity as a correction. We study the behavior of the deficit angle in presence of these theories of nonlinearity and compare them with each other. We also show that some cases with negative deficit angle exists which are representing objects with different geometrical structure. We also show that in case of the static only magnetic field exists whereas by boosting the metric to rotating one, electric field appear too.Comment: 22 pages with 24 figures. Accepted for publication in Eur. Phys. J.

The role of thermal history in shaping the microbiome of Red Sea corals

Coral reefs are immensely vulnerable to climate change and particularly the effects of ocean warming; in efforts to understand whether and how reef systems will survive into the future, research is increasingly focusing on present day populations acclimatized to thrive under relatively extreme conditions. Whilst corals thrive along a range of environmental conditions, including relative extremes, within the Red Sea, these coral populations are still considered not well explored of the genetic and physiological signatures throughout this system. Corals microbiota communities (the “microbiome”) are recognized as a major component as to how corals “acclimatize” to different environmental conditions; therefore, this work aimed to investigate the historical thermal variability along the Red Sea and subsequently identify the relative role of coral microbiome associated with differences in coral thermal tolerance. Remotely sensed data (1982-2012) demonstrated migration of Sea Surface Temperature anomalies (i.e. DHW) from the south to the north during this time frame. Analysis of historical bleaching records indicated that coral populations were more tolerant to bleaching in the northern compared to the central/southern Red Sea. Symbiodinium clade type (ITS2) and microbial community (16S rRNA metagenomics) associated with six key coral species persisting across five sites of the northern Red Sea (29°-20°N) were then examined. Symbiodinium clade identity associated with each coral species generally remained highly conserved throughout the sites sampled. In contrast, microbial communities were variable within and between species across the Red Sea sites. Corals from two sites (central-Jeddah and northern-Hurghada) were exposed to a thermal stress experiment which confirmed that corals were more heat resistant at Hurghada (summer SST mean is 3.3 °C less) than Jeddah; however, symbiont ITS2 clade types were the same at both sites. Conversely, microbial community changed in heat stressed samples at Jeddah compared to the control group, while it remained stable at Hurghada. This work provides for the first time genetic analysis on corals’ microbiome inhabiting extreme thermal resistant region (i.e. the northern Red Sea) that contradict the global bleaching pattern. Our findings suggest that plasticity of microbial community may play the key role in acclimation of corals experience thermal anomalies in the Red Sea suggesting presence certain microbial phylotypes fill specific thermal niche. Finally, the higher latitudes of the Red Sea will broadly serve as a potential corals refugia which highlights the importance to conserve and implement a regional management policy to improve corals thermal tolerance of this region to be used as a genetic reservoir

Geometrical thermodynamics and P-V criticality of the black holes with power-law Maxwell field

We study thermodynamical structure of Einstein black holes in the presence of power Maxwell invariant nonlinear electrodynamics for two different cases. The behavior of the temperature and conditions regarding the stability of these black holes are investigated. Since the language of geometry is an effective method in general relativity, we concentrate on the geometrical thermodynamics to build a phase space for studying phase transition. In addition, taking into account the denominator of the heat capacity, we use the proportionality between cosmological constant and thermodynamical pressure to extract the critical values for these black holes. Besides, the effects of the variation of different parameters on thermodynamical structure of these black holes are investigated. In addition, some thermodynamical properties such as volume expansion coefficient, speed of sound and isothermal compressibility coefficient are calculated and some remarks regarding these quantities are given.Comment: 18 pages with 12 captioned figures. Published versio

THE APPROPRIATE BUILDING MATERIALS FOR ENERGY SAVING IN DIFFERENT CLIMATE ZONES IN EGYPT

Nowadays, reducing energy consumption is globally considered a matter of high priority on the different levels of community and economic interest, especially in the developing countries, due to the growing shortage of traditional energy resources with the rapidly increasing energy prices and its impact on the natural environment through the consumption of various energy resources such as fossil fuels. The residential building sector is responsible for consuming a large percentage of energy, especially that used in heating and cooling, which could be reduced through using different passive design strategies, such as designing the building shape, setting the optimum orientation and selecting the most appropriate building materials for the specific climate zones. Therefore, this paper focuses on reducing the energy consumption in the residential building sector in Egypt by evaluating four different non-structural filling wall materials, including red bricks, cement bricks, stone and curtain walls located in different climate zones. Simulation analysis techniques are used to measure the related energy consumption parameters for cooling and/or heating to achieve the thermal comfort zone for building users. These results will aid architects in the pre-design stage to choose the most appropriate material for their designs, depending on the location concerned

CALCULATING VANDALISM RISK ASSESSMENT FOR ARCHAEOLOGICAL FINDINGS WITHIN HERITAGE BUILDINGS: THE CASE OF AL-ATTAR HISTORICAL MOSQUE IN TRIPOLI LEBANON

A heritage building is a genuine witness for the past and it mostly correlates with communities’ collective memory. It involves a considerable economical asset for cultural tourism in addition to other emotional values. However, building archeology is slightly exposed when handling historical buildings; it is subject to reburial to minimize potential risks and to keep it for future generations. The aim of this research is to explore the validity of exposing an archeological feature by establishing an estimation for vandalism risk through an assessment for society’s attitude concerning the new image given to a historic mosque with exposed archeological features. This research handles the ABC calculation method for vandalism risk assessment, and it concludes the risk magnitude by analyzing the social impact for the existence of an archeological feature within Al-Attar historic mosque in Tripoli by performing focus group research targeting persons in direct relation with the subject. The research will open doors for further studies basing on risk magnitude assumption, risk potential sources and different perspectives when handling archeological features; the findings will lead to significant implications for similar cases in Lebanon and in other global similar cases

TREE PROVISION ACHIEVING KID’S THERMAL COMFORT THROUGH FINISHING MATERIAL PERFORMANCE IN SUBTROPICAL OUTDOOR PLAYGROUNDS. COMPARISON BETWEEN KING FAHED AND AL BIAA GARDEN IN TRIPOLI, LEBANON

Outdoor playgrounds are one of the most spaces needed for kids to make different types of activities, and enhancing thermal comfort in such space consist a critical value due to its impact on kids’ health. Unfortunately, the acceleration of urban heat island (UHI) in outdoor spaces, caused by the presence built-up area has affected the temperature of outdoor spaces especially playgrounds. Many researches highlighted the importance of studying outdoor playground materials to achieve kid’s thermal comfort. Nevertheless, analyzing the impact of providing trees on material performance consist a new research perspective. This research highlight on the importance of using trees as natural element to decrease temperature in outdoor playgrounds to achieve kid’s thermal comfort. The aim of this research is to achieve kid’s thermal comfort by enhancing the performance of outdoor playgrounds finishing materials through providing trees. The study will focus on the variation of playground surfaces temperature through simulating different scenario applied in Malek Fahed and Al Biaa garden in Tripoli, Lebanon. The simulation will be applied in subtropical climate using Envi-Met software. The present study provides an overview of outdoor playgrounds finishing materials and its relations with kid’s thermal comfort. Research findings define the performance level of each playground finishing material in chinaberry shading during summer. Results demonstrate that natural surfaces such as sand, grass and stone enhance kids’ thermal comfort more than artificial ones like concrete during summer days

Three-dimensional accelerating AdS black holes in F(R)F(R) gravity

Considering a three-dimensional $C-$metric, we obtain the exact accelerating black holes in the $F(R)$ theory of gravity coupled with and without a matter field. First, we extract uncharged accelerating AdS black hole solutions in $F(R)$ gravity. Then, we study the effects of various parameters on metric function, roots, and the temperature of these black holes. The temperature is always positive for the radii less than $\frac{1}{\alpha }$, and it is negative for the radii more than $\frac{1}{\alpha }$. We extend our study by coupling nonlinear electrodynamics as a matter filed to $F(R)$ gravity to obtain charged black holes in this theory. Next, we evaluate the effects of different parameters such as the electrical charge, accelerating parameter, angular, $F(R)$ gravity, and scalar curvature on the obtained solutions, roots, and temperature of three-dimensional charged accelerating AdS black holes. The results indicate that there is a root in which it depends on various parameters. The temperature of these black holes is positive after this root.Comment: 11 pages, 3 figure