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"Pada tesis ini dipelajari objek kompak anisotropik dengan interior diisi dengan dark energy (energi gelap). Objek yang disebut anisotropik, karena tekanan radial dan tangensial di interior objek tidak sama. Untuk memodelkan keadaan energi gelap, digunakan persamaan keadaan Van der Waals dengan parameter bebas ”γ”, “β̅” dan “φ̅”. Perhitungan dilakukan dengan menyelesaikan persamaan Tolman-Oppenheimer￾Volkof (TOV) dimensonless (tidak berdimensi). Di formalisme ini, radius ” ξ” berharga nol hingga satu. Studi yang dilakukan adalah memeriksa jangkauan dari ”γ”, “β̅” dan “φ̅” agar memenuhi objek yang stabil secara fisis. Kestabilan objek kompak ditinjau dari kuadrat kecepatan suara radial dan tangensial. Hasil diperoleh “γ ∈ [0, 0.38]”, “φ̅ ∈ [-0.05, 0]” dan “β̅ ∈ [-0.58, 0]”, untuk memenuhi objek yang stabil. Melalui jangkauan”γ”, “β̅” dan “φ̅” yang diperoleh, ditinjau profil-profil objek.

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In this thesis, an anisotropic compact object with an interior filled with dark energy is studied. The object is called anisotropic, because the radial and tangential pressures in the interior of the object are not the same. To model the state of dark energy, the Van der Waals equation of state is used with free parameters "γ", "β̅" and "φ̅". The calculation is done by solving the dimensionless Tolman-Oppenheimer-Volkof (TOV) equation. In this formalism, the radius "ξ" has a value of zero to one. The study conducted is to examine the range of "γ", "β̅" and "φ̅" to meet a physically stable object. The stability of the compact object is reviewed from the square of the radial and tangential sound speeds. The results obtained are “γ ∈ [0, 0.38]”, “φ̅ ∈ [-0.05, 0]” and “β̅ ∈ [-0.58, 0]”, to meet the stable object. Through the range of “γ”, “β̅” and “φ̅” obtained, the object profiles are reviewed.."

"This book explores the subject in the context of quantum gravity. A novel approach to uncover the dark faces of the standard model of cosmology. The possibility that dark energy and dark matter are manifestations of the inhomogeneous geometry of our universe. On the history of cosmological model building and the general architecture of cosmological modes. Illustrations on the large scale structure of the universe. A new perspective on the classical static Einstein cosmos. Global properties of world models including their topology. The arrow of time in a universe with a positive cosmological constant. Exploring the consequences of a fundamental cosmological constant for our universe. Exploring why the current observed acceleration of the universe may not be its final destiny. Demonstrating that nature forbids the existence of a pure cosmological constant. Our current understanding of the long term (in time scales that greatly exceed the current age of the universe) future of the universe. And the long term fate and eventual destruction of the astrophysical objects that populate the universe, including clusters, galaxies, stars, planets, and black holes."

"Menguji validitas relativitas umum dapat dilakukan dengan memodifikasinya untuk mencari penyimpangan. Beberapa teori gravitasi termodifikasi menghasilkan potensial gravitasi dengan suku eksponensial yang menyerupai potensial Yukawa untuk aproksimasi medan lemah. Walaupun pengujian eksperimental dari koreksi Yukawa masih terbatas pada skala sistem tata surya, beberapa penelitian terbaru telah menggunakan data dari kurva rotasi galaksi untuk membatasi parameter Yukawa ini secara observasional, namun dengan asumsi bahwa barion terkopel secara lemah dengan gravitasi untuk memenuhi batasan gravitasi lokal. Studi kami mengabaikan asumsi ini dan menganalisis suku koreksi Yukawa baik dalam halo materi gelap maupun komponen bariyonik. Kami menyelidiki empat model: Newton, Almeida, MG, dan MG Duo, berdasarkan keberadaan suku koreksi Yukawa dalam komponennya dan kopling antar jenis partikel. Kami menguji keempat model ini pada tiga set data yang berbeda dari galaksi Bima Sakti, termasuk data Sofue (2015, 2017, dan 2020) dan data kurva rotasi dari Gaia DR3 oleh Wang (2023) dan Zhou (2023). Kami menemukan dukungan statistik yang kuat melalui faktor Bayes untuk model MG Duo yang menunjukkan kopling terpisah antara baryon-baryon dan baryon-DM. Namun, data observasional yang lebih tepat yang mencakup rentang radius galaksi yang lebih luas masih diperlukan untuk meningkatkan pemahaman tentang modifikasi di wilayah dalam galaksi Bima Sakti.

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Testing the validity of general relativity can be done by modifying it to search for potential deviations. Several modified gravity theories introduce a Yukawa-like exponential term in the gravitational potential for weak-field limits. While experimental tests of the Yukawa-correction are limited to Solar system scales, recent studies have used galactic rotation curve data to observationally constrain these Yukawa parameters, although assuming that baryons are weakly coupled to gravity to satisfy local gravity constraints. In our study, we relax this assumption and analyze the Yukawa-correction in both dark matter halo and baryonic components. We investigate four models: Newtonian, Almeida, MG and MG Duo models, based on the presence of the Yukawa-correction term in the components and the coupling between particle species. We tested these models on three Milky Way datasets: Sofue (2015, 2017, 2020) and rotation curves by Wang (2023) and Zhou (2023) derived from Gaia DR3 data. We find strong statistical favor through the Bayes factor for the MG Duo model that presents a separated coupling between baryon-baryon and baryon-DM. However, more precise observational data covering a broader range of galactic radii is still required to enhance our understanding of modifications in the inner regions of the Milky Way."

"A major outstanding problem in physics is understanding the nature of the dark energy that is driving the accelerating expansion of the Universe. This thesis makes a significant contribution by demonstrating, for the first time, using state-of-the-art computer simulations, that the interpretation of future galaxy survey measurements is far more subtle than is widely assumed, and that a major revision to our models of these effects is urgently needed. The work contained in the thesis was used by the WiggleZ dark energy survey to measure the growth rate of cosmic structure in 2011 and had a direct impact on the design of the surveys to be conducted by the European Space Agency's Euclid mission, a 650 million euro project to measure dark energy."

"Telah diketahui dengan baik bahwa simetri azimut hilang untuk lubang hitam yang berotasi, orbit yang terbentuk tidak terbatas hanya pada bidang ekuator. Baru-baru ini ada penelitian tentang orbit sferis non-ekuatorial foton untuk lubang hitam Kerr. Orbit sferis non-ekuatorial merupakan jenis orbit non-ekuatorial yang mungkin dibedakan dengan jari-jari koordinat konstan, seperti yang dibedakan dalam kelas orbit ekuatorial. Orbit ini menandai ambang batas antara orbit non-ekuatorial yang terjun ke bagian dalam lubang hitam dan yang tidak. Ambang orbit memainkan peran penting dalam pemodelan penangkapan foton dan materi, oleh lubang hitam. Dalam tesis ini, kami menyelidiki orbit sferis non-ekuitorial foton di sekitar lubang hitam bermuatan yang berotasi (Kerr-Newman) dan melihat bagaimana distribusi muatan mengubah klasifikasi orbit. Solusi analitik dari persamaan geodesik diturunkan dan beberapa bentuk orbit ditampilkan.

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It is well-known that, since azimuthal symmetry is broken for rotating black hole, the corresponding orbit is not confined to an equatorial plane. Recently there have been studies on the spherical photon orbit for Kerr black hole. Amongst the different types of possible non-equatorial orbits, those with constant coordinate radii are distinguished, just as circular orbits are distinguished in the class of equatorial orbits. Such orbits are known as spherical orbits. This special class of geodesics is obviously simpler to analyse than more general ones. Yet spherical orbits remain astrophysically relevant. For example, they mark the threshold between nonequatorial orbits that plunge into the black hole, and those that do not. Such threshold orbits play an important role in modelling the capture of matter and light by the black hole. In this thesis, we investigate the spherical photon orbits around a rotating charged black hole (Kerr-Newman) and see how the charge alters the classifications of orbits. The analytic solutions of the geodesics equation are derived and several orbital paths are shown."

"The book is organized by ease of observation, lunar phases and the brighter planets come first, while solar eclipses, the aurora, and comets come later. Celestial Delights also includes a hefty dose of sky lore, astronomical history, and clear overviews of current science. It provides a handy reference to upcoming naked-eye events, with information broken out in clear and simple diagrams and tables that are cross-referenced against a detailed almanac for each year covered. Most broad-ranging astronomy field guides focus on stars, constellations, and the deep sky, but tend to ignore planetary events, which are in by far the most widely observable aspects of the changing night sky."

"This title is a comprehensive set of visual descriptions of deep-sky objects visible from the northern hemisphere. It is a record of the most extensive and systematic visual survey of the sky ever done in modern times. 3,000 deep-sky objects are listed with short descriptions of the visual appearance in the author's powerful binocular telescope. Objects in the book are organized by position for easy identification of unknown targets. Full indexes by catalog numbers and names allow searches for specific objects."