Deflection angle and Shadows by Black Holes in Starobinsky-Bel-Robinson Gravity from M-theory

Motivated by M-theory compactifications, we investigate optical properties of black holes in the Starobinsky-Bel-Robinsion gravity. Precisely, we study the shadows and the deflection angle of light rays by non-rotating and rotating black holes in such a novel gravity. We start by discussing the shadows of the Schwarzschild-type solutions. As expected, we obtain perfect circular shadows where the size decreases with a stringy gravity parameter denoted by $\beta$. We show that this parameter is constrained by the shadow existence. Combining the Newman-Janis algorithm and the Hamilton-Jacobi mechanism, we examine the shadow behaviors of the rotating solutions in terms of one-dimensional real curves. Essentially, we find various sizes and shapes depending on the rotating parameter and the stringy gravity parameter $a$ and $\beta$, respectively. To inspect the shadow geometric deformations, we investigate the astronomical observables and the energy emission rate. As envisaged, we reveal that $a$ and $\beta$ have an impact on such shadow behaviors. For specific values of $a$, we remark that the obtained shadow shapes share certain similarities with the ones of the Kerr black holes in plasma backgrounds. Using the Event Horizon Telescope observational data, we provide predictions for the stringy gravity parameter $\beta$ which could play a relevant role in M-theory compactifications. We finish this work by a discussion on the behaviors of the light rays near to such four dimensional black holes by computing the deflection angle in terms of a required moduli space.Comment: Latex, 27 pages, 10 figures. Authors in alphabetical orde

Light Deflection by Rotating Regular Black Holes with a Cosmological Constant

Using the Gauss-Bonnet theorem, we compute and examine the deflection angle of light rays by rotating regular black holes with a cosmological constant. By the help of optical geometries, we first deal with the Hayward black holes with cosmological contributions. Then, we reconsider the study of the Bardeen solutions. We inspect the cosmological constant effect on the deflection angle of light rays. Concretely, we find extra cosmological correction terms generalizing certain obtained findings. Using graphical analysis, we provide a comparative discussion with respect to the Kerr solutions. The results confirm that the non-linear electrodynamic charges affect the space-time geometry by decreasing the deflection angle of light rays by such cosmological black holes.Comment: latex, 16 pages, 4 figures. Accepted for publication in Chin. J. Phys 202

Light Behaviors around Black Holes in M-theory

We study the deflection angle and the trajectory of the light rays around black holes in M-theory scenarios. Using the Gauss-Bonnet theorem, we first compute and examine the deflection angle of the light rays near four and seven-dimensional AdS black holes obtained from the M-theory compactifications on the real spheres on $S^7$ and $S^4$, respectively. We discuss the effect of the M-theory brane number and the rotating parameter on such an optical quantity. We then investigate the trajectories of the light rays using the equation of motion associated with $M2$ and $M5$ branes.Comment: Latex, 22 pages, 8 figure

TECHNIQUE DE PRELEVEMENT D’UN LAMBEAU LIBRE DU GRAND DORSAL

The free flap of latissimus dorsi muscle has several advantages, the permanence of its vascular pedicle, large size and reliability. Technically, it is easy and reproducible.Usually, it is used to cover large defects secondary to large oncological resections or great disrepair members.Le lambeau libre du muscle grand dorsal a plusieurs avantages dont la constance de son pédicule vasculaire, sa grande taille et sa fiabilité.Sa technique de levée est facilement reproductible permettant la couverture de vastes pertes de substance secondaires aux larges exérèses carcinologiques ou aux grands délabrements des membres

L’HISTOIRE DE LA CHIRURGIE ESTHETIQUE

L'histoire de la chirurgie esthétique est liée à celle du XXe siècle. Les premières interventions autorisées par les progrès de l'anesthésie et de l'asepsie sont la correction des oreilles décollées par Ely [1], puis la rhinoplastie par voie endonasale par Roe [2]. Le premier chirurgien à se spécialiser et à publier des livres sur le sujet est C. C. Miller, qui est considéré par certains comme un précurseur et par d'autres comme un charlatan [3]

Impact du foncier agricole sur une région pastorale

Le nomadisme pastoral a été, pendant des siècles, l’unique forme d’exploitation de la steppe occidentale algérienne. Face à de nombreux échecs dans la modernisation de l’activité pastorale, l’État s’est engagé dans une politique de mise en valeur agricole afin de diversifier ses ressources. Cette réorientation a entraîné une appropriation foncière abusive. Des conflits d’usage entre foncier agricole et activité pastorale sont nés, mettant à mal les collectivités locales en l’absence d’une gouvernance foncière efficiente. Sur les plans spatial et fonctionnel, cette politique s’est soldée par un morcellement de la steppe en une multitude de propriétés privées dans une région où l’usage collectif des parcours est ancestral et qui a, toujours, caractérisé les sociétés pastorales locales.For centuries, pastoral nomadism was the sole type of farming in the western Algerian steppe. Given the numerous stumbling blocks to the modernization of pastoral farming, the State adopted a policy to promote agriculture in order to diversify its resources. This change resulted in excessive land grabbing. Conflicts arose over the use of land for agricultural purposes versus pastoral activities, with local municipalities caught in the middle and confronted with a lack of efficient land governance mechanisms. In spatial and functional terms, this policy resulted in a subdivision of the steppe into a multitude of private properties in a region in which the shared use of land was ancestral and had always characterized local pastoral societies

Homogenization and Trends Analysis of Monthly Precipitation Series in the Fez-Meknes Region, Morocco

High quality and long-term precipitation data are required to study the variability and trends of rainfall and the impact of climate change. In developing countries like Morocco, the quality of climate data collected from various weather stations faces numerous obstacles. This paper presents methods for collecting, correcting, reconstructing, and homogenizing precipitation series of Morocco’s Fez-Meknes region from 1961 to 2019. Data collected from national specialized agencies based on 83 rain gauge stations was processed through an algorithm specially designed for the homogenization of climatic data (Climatol). We applied the Mann-Kendall test and Sen’s slope estimator to raw and homogenized data to calculate rainfall trend magnitudes and significance. The homogenization process allows for the detection of a larger number of stations with statistically significant negative trends with 95% and 90% confidence levels, particularly in the mountain ranges, that threatens the main sources of water in the largest watershed in the country. The regionalization of our rain gauge stations is highlighted and compared to previous studies. The monthly and annual means of raw and homogenized data show minor differences over the three main climate zones of the region