Hasil Pencarian  ::  Simpan CSV :: Kembali

"Salah satu konsekuensi fisis dari relativitas umum adalah adanya pembelokan cahaya pada lubang hitam. Pada penelitian ini, kami memberikan solusi numerik dari sudut defleksi kuat dari cahaya. Model lubang hitam yang ditinjau addalah lubang hitam dengan elektrodinamika kruglov. Menggunakan solusi numerik tersebut, kami juga mendapatkan solusi perbesaran gravitasi sebagai konsekuensi dari relativitas umum.

---

One of the physical consequences of general relativity is the bending of light in blackholes. In this research, we provide a numerical solution of the strong deflection angle of light. The black hole model that we use is a black hole with Kruglov electrodynamics. Using these numerical solutions, we also get solutions for the gravitational lensing as a consequence of general relativity."

"This second edition of an extremely well-received book presents more than 250 nonrelativistic quantum mechanics problems of varying difficulty with the aim of providing students didactic material of proven value, allowing them to test their comprehension and mastery of each subject. The coverage is extremely broad, from themes related to the crisis of classical physics through achievements within the framework of modern atomic physics to lively debated, intriguing aspects relating to, for example, the EPR paradox, the Aharonov-Bohm effect, and quantum teleportation. Compared with the first edition, a variety of improvements have been made and additional topics of interest included, especially focusing on elementary potential scattering. The problems themselves range from standard and straightforward ones to those that are complex but can be considered essential because they address questions of outstanding importance or aspects typically overlooked in primers. The book offers students both an excellent tool for independent learning and a ready-reference guide they can return to later in their careers."

"This book gives an introduction to molecular biophysics. It starts from material properties at equilibrium related to polymers, dielectrics and membranes. Electronic spectra are developed for the understanding of elementary dynamic processes in photosynthesis including proton transfer and dynamics of molecular motors. Since the molecular structures of functional groups of bio-systems were resolved, it has become feasible to develop a theory based on the quantum theory and statistical physics with emphasis on the specifics of the high complexity of bio-systems. This introduction to molecular aspects of the field focuses on solvable models. Elementary biological processes provide as special challenge the presence of partial disorder in the structure which does not destroy the basic reproducibility of the processes. Apparently the elementary molecular processes are organized in a way to optimize the efficiency. Learning from nature by means exploring the relation between structure and function may even help to build better artificial solar cells. The reader is exposed to basic concepts in modern biophysics, such as entropic forces, phase separation, potential of mean force, electron and proton transfer, heterogeneous reactions, coherent and incoherent energy transfer as well as molecular motors. Basic knowledge in classical and Quantum mechanics, electrostatics and statistical physics is desirable. Simplified models are presented which can be solved in limited cases analytically from the guiding lines to generate the basis for a fundamental understanding of the more complex biophysical systems. Chapters close with challenging problems whose solutions are provided at the end of the book to complete the pedagogical treatment in the book.To the second edition several new chapters were added. The medium polarization is treated self-consistently using basic elements of polaron theory and more advanced nonlinear Schrödinger equations to describe the dynamics of solvation. Ion transport through a membrane was extended by the discussion of cooperative effects. Intramolecular transitions are now discussed in the new edition in much more detail, including also radiationless transitions. Very recent developments in spectroscopy are included, especially two-dimensional and hole-burning spectroscopy. The discussion of charge transfer processes was extended by including recent results of hole transfer in DNA in connection with the super-exchange mechanism. The chapter on molecular motors was rewritten to include the most recent developments of new models. The book is a useful text for students and researchers wanting to go through the mathematical derivations in the theories presented. This book attracts a group of applied mathematically oriented students and scholars to the exciting field of molecular biophysics. "

"While the first edition of this textbook was based on a one-year course in computational physics with a rather limited scope, its extent has been increased substantially in the third edition, offering the possibility to select from a broader range of computer experiments and to deepen the understanding of the important numerical methods. The computer experiments have always been a central part of my concepts for this book. Since Java applets, which are very convenient otherwise, have become more or less deprecated and their usage in a browser is no longer recommended for security issues, I decided to use standalone Java programs instead and to rewrite all of the old examples. These can also been edited and compiled with the “netbeans” environment and offer the same possibilities to generate a graphical user interface in short time."

"Lubang hitam merupakan objek paling misterius di alam semesta. Ia tercipta dari runtuhnya sebuah bintang yang memiliki gravitasi yang dominan dibanding reaksi termonuklir yang dimiliki. Sampai pada keadaan akhirnya (tersisa gravitasi saja), ”bintang” tersebut hanya memiliki permukaan dan titik singularitas. Pada keadaan ini, massa dari bintang tersebut sangat besar sehingga mempengaruhi kelengkungan ruang dan waktu di dalam dan sekitar objek. Karena sangking masifnya, cahayapun ketika melewati objek tersebut tidak bisa selamat melainkan jatuh ke dalam ”lubang” tersebut yang mengakibatkan tidak adanya pantulan cahaya ke pengamat. Oleh karena itu, bintang yang memiliki fase ini dinamakan lubang hitam.Walaupun lubang hitam dianggap misterius oleh beberapa kalangan, tidak sedikit juga peneliti mempelajari objek tersebut secara teoritis maupun eksperimen. Sampai pada tahun 2019 dunia dihebohkan oleh The Event Horizon Telescope Collaboration dengan ditemukannya citra lubang hitam berotasi. Dari segi teoretis, lubang hitam dipelajari dengan meninjau solusi tensor metriknya. Tidak lama setelah relativitas umum diga- gas, Karl Schwarzschild merupakan orang pertama yang mendapatkan solusi dari per- samaan medan Einstein yang mendeskripsikan massa titik di ruang-waktu statik dan vakum. Karena lubang hitam merupakan konsekuensi dari solusi persamaan medan Ein- stein, solusi ini disebut lubang hitam Schwarzschild. Setengah abad kemudian, Roy Kerr memperoleh lubang hitam berputar. Di lain hal, lubang hitam secara teoretis juga bisa dipelajari dengan meninjau dimensi geometrinya. Salah satunya adalah lubang hitam 3 dimensi (2 dimensi ruang dan 1 dimensi waktu) yang biasa disebut lubang hitam BTZ (Banados, Teitelboim, Zanelli). Di dalam literaturnya, objek ini eksis jika terdapat kon- stanta kosmologi yang negatif (ruang-waktu Anti-de Sitter). Lubang hitam ini yang akan menjadi poin utama dari penelitian penulis. Selain itu, terdapat lubang hitam secara teo- retik yang tidak memiliki singularitas. Objek ini disebut lubang hitam regular, dan sudah banyak literatur yang membahas dalam keadaan statik maupun berrotasi.Di tugas akhir kali ini, penulis mempelajari lubang hitam BTZ (2+1) dan regular di dalam ranah energi rendah teori string heterotik. Konsep ini mengharuskan penulis untuk menyertakan nontrivial dilaton Φ dan medan 3-form Hμνρ. Dengan menggunakan transformasi Hassan-Sen dan lubang hitam BTZ sebagai input, penulis dapatkan solusi tersebut dalam kerangka string. Selain itu, berbagai aspek lubang hitam BTZ dan lubang hitam regular dalam ranah energi rendah teori string heterotik ini penulis pelajari dengan lengkap berupa investigasi terhadap event horizon, ergosphere, perilaku partikel uji di luar dan di dalam limit statik, kecepatan sudut, dan keliling daripada objek tersebut. Dari hasil penulis mengenai lubang hitam BTZ di dalam teori string energi rendah, event horizon nya sekarang diparameterisasi oleh konstanta kosmologi l, massa M, momentum angular J, dan muatan b. Kondisi M > b dan |J| ≠ Ml merupakan syarat untuk lubang hitam agar tetap eksis. Terlebih lagi, partikel yang diam di dalam ergosphere memiliki syarat (ds2 > 0) sehingga harus berputar searah dengan lubang hitam. Hasil kecepatan sudut dan keliling dari lubang hitam tereduksi menjadi kasus vakum ketika muatan dimatikan.Pada kasus lubang hitam regular, penulis dapati solusi pada kerangka string dan Ein- stein. Hasil tersebut tereduksi menjadi referensi penulis ketika muatan dimatikan. Per- samaan untuk mendapatkan horizon dan statik limit sayangnya tidak bisa secara eksak atau analitik. Dengan begitu, penulis mempelajarinya dengan plot grafik dengan variasi parameter bebas k dan muatan. Untuk menguji regularitas, penguji menggunakan dua tipe invarian skalar dan mendapati lubang hitam berrotasi dan bermuatan tersebut tetap mem- pertahankan regularitasnya walaupun terdapat muatan. Penulis menunjukkan pelanggaran minimal untuk kondisi energi rendah.

---

Black holes are the most mysterious objects in the universe. He was created from the col- lapse of a star that has a dominant gravity sector compared to the thermonuclear reaction. Until the final state of a star, they only has a surface and a singularity. In this situation, the mass of the star is huge that it affects the curvature of space and time in and around the object. Because of the magnitude of the interaction of gravity and its curvature, even light cannot escape. Therefore, stars that have this phase are called black holes.

On the other hand, despite of being mysterious, there has been comprehensive study on black hole both on experimentally and theoretically. Until 2019 the world was shocked by The Event Horizon Telescope Collaboration with the discovery of rotating black hole images. From a theoretical point of view, black holes are studied by solving their tensor metric solutions. Shortly after general relativity was conceived, Karl Schwarzschild was the first to obtain a solution from the Einstein field that described the point mass in static and vacuum space-time. Since black holes is the consequences of Einstein field equation, this solution is called the Schwarzschild black hole. Half a century later, Roy Kerr ob- tained a spinning black hole. On the other hand, black holes can also be studied by their geometric dimensions. One of them is a 3-dimensional black hole (2 dimensional space and 1 time dimension) which is commonly called a BTZ black hole (Banados, Teitel- boim, Zanelli). In his literature, this object exist if it has a negative cosmological constant (Anti-de Sitter space-time). This black hole will be the main point of the author’s re- search. Additionally, there are theoretically black holes that have no singularity. This object is called a regular black hole, and there has been a lot of literature discussing both for static and rotating.

In this thesis, the author study the BTZ black holes (2+1 dimensional space-time) in the low energy heterotic string theory (BTZ-Sen BH). This concept requires us to include a non-trivial dilaton Φ and a 3-form Hκμν field. By using the Hassan-Sen transformation and BTZ black hole as a seed solution, we obtain the solution in the string frame. From the result on BTZ black hole in low energy string theory, the event horizons are now parameterized by the cosmological constant l, mass M, angular momentum J, and charge b. Conditions M > b and |J| ≠ Ml are requirement for a black hole to exist. Moreover, the particle resting in the ergosphere have the spacelike condition. So it must rotate in the direction of the black hole. The resulting angular velocity and perimeter of the black hole are reduces to that of BTZ black hole when the charge is turned off.

Another novelty solution is that the regular Kerr-Sen spacetime. This present solution describe a four dimensional rotating regular charged black hole in the low energy string theory. A black hole describe in this section is characterized by its mass, spin or angu- lar momentum, and also electric charged. These well known no hair theorem variable could be obtained by solving the gravitational Hamiltonian in a boundary. We found that the corresponding mass and angular momentum are the same as the Kerr-Sen black hole, and so does electric charge. In order to assure the regularity of a black hole, it seems insufficient to look at the metric tensor itself. Thus, we employ two type of scalar invari- ant; contracted Ricci tensor and Kretschmann scalar (contracted Riemannn tensor). We discover that the inclusion of charge from low energy string theory does not affect the regularity of a rotating black hole. On the other hand, since the vacuum rotating regular black hole appear to be violated the weak energy condition, we hope that our solutions are be able to satisfied the weak energy condition. Unfortunately, it is shown that an existence of our rotating charged regular black holes does not alter the conclusion from the vacuum one; the WEC still violated. But the violation can be very small depends on how we treat the parameter."

"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.

---

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."

"Kami mempelajari solusi orbit terikat cahaya pada lubang hitam bermuatan dalam beberapa ruang waktu reguler dengan dipengaruhi oleh elektrodinamika nonlinier. Ruang waktu yang dipelajari pada penelitian ini adalah ruang-waktu Bardeen dengan sumber Lagrangian dari Ayon-Beato dan Garcia dan juga ruang-waktu Hayward yang dimodifikasi oleh Kruglov dengan menggunakan Lagrangian dari Bronnikov. Solusi orbit pada kedua kasus tersebut dipelajari dalam geometri efektif dari cahaya akibat elektrodinamika nonlinier. Validitas orbit foton dipelajari dengan memeriksa keberadaan singularitas fisis pada geometri efektif dengan menggunakan kelengkungan skalar, selain itu perilaku ruang-waktu di dalam lubang hitam pada kedua model juga dipelajari dengan menggunakan koordinat Eddington-Finkelstein. Berdasarkan perhitungan yang dilakukan, geometri efektif foton dapat memodifikasi bagaimana foton bergerak di sekitar lubang hitam dan memunculkan singularitas fisis yang hanya memengaruhi oleh foton.

---

We study the solutions of photon bound orbits around charged black holes in several regular spacetime models with nonlinear electrodynamics. The space-time models we studied are Bardeen with magnetic monopole source from Ayon-Beato and Garcia and the modified Hayward from Kruglov using the Lagrangian from Bronnikov. The orbital solutions are studied in photon's effective geometry due to nonlinear electrodynamics, the validity of the orbits are examined by checking the existence of singularities within the effective geometry using scalar curvature, we also studied the behavior of space-time inside the black hole using Eddington-Finkelstein coordinate. From what we have studied, the effective geometry of photon could affect how photon moves around the black hole and it will also generate physical singularity that will only affect photon. "