Compact Objects In Modified Gravity

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Compact Objects in Modified Gravity

Author : Adrián Casado Turrión
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (142 download)

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Book Synopsis Compact Objects in Modified Gravity by : Adrián Casado Turrión

Download or read book Compact Objects in Modified Gravity written by Adrián Casado Turrión and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The purpose of this Thesis is to improve our understanding of the strong-field regime of gravitational interactions, where deviations from the theory of General Relativity (GR) are expected to be found on theoretical grounds. In particular, our investigations have been concerned with the formulation and application of junction conditions (which govern stellar collapse, black-hole formation and the dynamics of more exotic compact objects), as well as with other viability criteria necessary for modified gravity theories and their solutions to be physically admissible (such as stability or the avoidance of singularities). We will concentrate on two paradigmatic modifications of GR, namely, f (R) theories (specially on the metric formulation) and the ghost-free sub-class of Poincaré Gauge Gravity...

Gravitational Collapse, Compact Objects and Gravitational Waves in General Relativity and Modified Gravity

Author : Roxana Rosca-Mead
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (119 download)

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Book Synopsis Gravitational Collapse, Compact Objects and Gravitational Waves in General Relativity and Modified Gravity by : Roxana Rosca-Mead

Download or read book Gravitational Collapse, Compact Objects and Gravitational Waves in General Relativity and Modified Gravity written by Roxana Rosca-Mead and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Compact Objects in Exotic Premise and Underlying Gravitational Waves

Author : Surajit Kalita
Publisher : Eliva Press
ISBN 13 : 9789994985135
Total Pages : 0 pages
Book Rating : 4.9/5 (851 download)

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Book Synopsis Compact Objects in Exotic Premise and Underlying Gravitational Waves by : Surajit Kalita

Download or read book Compact Objects in Exotic Premise and Underlying Gravitational Waves written by Surajit Kalita and published by Eliva Press. This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Einstein's theory of general relativity and quantum mechanics were among the most startling discoveries in the 20th century. Based on these theories, the maximum mass of a non-rotating non-magnetized white dwarf was found to be about 1.4 solar mass, known as the Chandrasekhar mass-limit. However, over the past decades, various researchers have indirectly predicted many sub- and super-Chandrasekhar limiting mass white dwarfs (white dwarfs which violate the Chandrasekhar mass-limit) from the luminosity based observations of peculiar type Ia supernovae. Several research groups worldwide, earlier proposed different models, including magnetic fields, rotation, modified gravity, noncommutative geometry, and many more, to explain these peculiar white dwarfs. However, no such white dwarfs have so far been observed directly in any observations and hence to predict the correct theory for white dwarfs is still unclear. In this book, we show that if such white dwarfs rotate in such a way that their magnetic field and rotation axes are not aligned with each other, they can emit continuous gravitational radiation, which in the future, various detectors, such as LISA, TianQin, BBO, DECIGO, Einstein Telescope, etc., can detect with a significant signal-to-noise ratio. Thereby one can predict the structure of the white dwarfs and single out the correct theory of gravity. In the related context of modified gravity, we show that even in vacuum, asymptotically flat solution of the modified Einstein equation is possible. All these results argue that the premise of modified theory of gravity seems to be an excellent platform to explain unsolved astronomical problems.

Compact Objects in the Universe

Author : Eleftherios Papantonopoulos
Publisher : Springer Nature
ISBN 13 : 3031550986
Total Pages : 395 pages
Book Rating : 4.0/5 (315 download)

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Book Synopsis Compact Objects in the Universe by : Eleftherios Papantonopoulos

Download or read book Compact Objects in the Universe written by Eleftherios Papantonopoulos and published by Springer Nature. This book was released on 2024 with total page 395 pages. Available in PDF, EPUB and Kindle. Book excerpt: The main objective of this volume is to discuss the physical properties, observational signals and various probes of compact objects in the Universe. These include black holes, neutron stars, and exotic objects studied in alternative theories of gravity. The text is mainly addressed to postgraduate students and young researchers with the aim of introducing them to these very challenging topics.

Compact Objects in Relativistic Theories of Gravity

Author : Hector Okada da Silva
Publisher :
ISBN 13 :
Total Pages : 366 pages
Book Rating : 4.:/5 (1 download)

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Book Synopsis Compact Objects in Relativistic Theories of Gravity by : Hector Okada da Silva

Download or read book Compact Objects in Relativistic Theories of Gravity written by Hector Okada da Silva and published by . This book was released on 2017 with total page 366 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this dissertation we discuss several aspects of compact objects, i.e. neutron stars and black holes, in relativistic theories of gravity. We start by studying the role of nuclear physics (encoded in the so-called equation of state) in determining the properties of neutron stars in general relativity. We show that low-mass neutron stars are potentially useful astrophysical laboratories that can be used to constrain the properties of the equation of state. More specifically, we show that various bulk properties of these objects, such as their quadrupole moment and tidal deformability, are tightly correlated. Next, we develop a formalism that aims to capture how generic modifications from general relativity affect the structure of neutron stars, as predicted by a broad class of gravity theories, in the spirit of the parametrized post-Newtonian formalism (PPN). Our "post-Tolman-Oppenheimer-Volkoff" formalism provides a toolbox to study both stellar structure and the interior/exterior geometries of static, spherically symmetric relativistic stars. We also apply the formalism to parametrize deviations from general relativity in various astrophysical observables related with neutron stars, including surface redshift, apparent radius, Eddington luminosity. We then turn our attention to what is arguably the most well-motivated and well-investigated generalization of general relativity: scalar-tensor theory. We start by considering theories where gravity is mediated by a single extra scalar degree of freedom (in addition to the metric tensor). An interesting class of scalar-tensor theories passes all experimental tests in the weak-field regime of gravity, yet considerably deviates from general relativity in the strong-field regime in the presence of matter. A common assumption in modeling neutron stars is that the pressure within these object is spatially isotropic. We relax this assumption and examine how pressure anisotropy affects the mass, radius and moment of inertia of slowly rotating neutron stars, both in general relativity and in scalar-tensor gravity. We show that a sufficient amount of pressure anisotropy results in neutron star models whose properties in scalar-tensor theory deviate significantly from their general relativistic counterparts. Moreover, the presence of anisotropy allows these deviations to be considerable even for values of the theory's coupling parameter for which neutron stars in scalar-tensor theory would be otherwise indistinguishable from those in general relativity. Within scalar-tensor theory we also investigate the effects of the scalar field on the crustal torsional oscillations of neutron stars, which have been associated to quasi-periodic oscillations in the X-ray spectra in the aftermath of giant flares. We show that the presence of the scalar field has an influence on the thickness of the stellar crust, and investigate how it affects the oscillation frequencies. Deviations from the predictions of general relativity can be large for certain values of the theory's coupling parameter. However, the influence of the scalar field is degenerate with uncertainties in the equation of state of the star's crust and microphysics effects (electron screening) for values of the coupling allowed by binary pulsar observations. We also derive the stellar structure equations for slowly-rotating neutron stars in a broader class of scalar-tensor theories in which matter and scalar field are coupled through the so-called disformal coupling. We study in great detail how the disformal coupling affects the structure of neutron stars, and we investigate the existence of universal (equation of state-independent) relations connecting the stellar compactness and moment of inertia. In particular, we find that these universal relations can deviate considerably from the predictions of general relativity. (Abstract shortened by ProQuest.)

Compact Objects in the Universe

Author : Eleftherios Papantonopoulos
Publisher : Springer
ISBN 13 : 9783031550973
Total Pages : 0 pages
Book Rating : 4.5/5 (59 download)

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Book Synopsis Compact Objects in the Universe by : Eleftherios Papantonopoulos

Download or read book Compact Objects in the Universe written by Eleftherios Papantonopoulos and published by Springer. This book was released on 2024-08-11 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The main objective of this volume is to discuss the physical properties, observational signals and various probes of compact objects in the Universe. These include black holes, neutron stars, and exotic objects studied in alternative theories of gravity. The text is mainly addressed to postgraduate students and young researchers with the aim of introducing them to these very challenging topics.

General Relativity and its Applications

Author : Valeria Ferrari
Publisher : CRC Press
ISBN 13 : 0429957807
Total Pages : 494 pages
Book Rating : 4.4/5 (299 download)

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Book Synopsis General Relativity and its Applications by : Valeria Ferrari

Download or read book General Relativity and its Applications written by Valeria Ferrari and published by CRC Press. This book was released on 2020-12-21 with total page 494 pages. Available in PDF, EPUB and Kindle. Book excerpt: • Provides a self-contained and consistent treatment of the subject that does not require advanced previous knowledge of the field. • Explores the subject with a new focus on gravitational waves and astrophysical relativity, unlike current introductory textbooks. • Fully up-to-date, containing the latest developments and discoveries in the field.

Modified Gravity: Progresses And Outlook Of Theories, Numerical Techniques And Observational Tests

Author : Baojiu Li
Publisher : World Scientific
ISBN 13 : 9813274018
Total Pages : 324 pages
Book Rating : 4.8/5 (132 download)

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Book Synopsis Modified Gravity: Progresses And Outlook Of Theories, Numerical Techniques And Observational Tests by : Baojiu Li

Download or read book Modified Gravity: Progresses And Outlook Of Theories, Numerical Techniques And Observational Tests written by Baojiu Li and published by World Scientific. This book was released on 2019-10-10 with total page 324 pages. Available in PDF, EPUB and Kindle. Book excerpt: Modified gravity theories have been a main focus of theoretical cosmology research in the past decade or so, and have been quickly developing into a mature research field that attracts attention, interest and effort from both theoretical and observational cosmologists. To be prepared for fully exploiting the future observational data, and to provide a guidance for people who are new to this field, it is useful to have a comprehensive review to summarise the current state of knowledge and to foresee the future developments.This book presents expert reviews on different topics in the field, which are then coordinated and organised in a self-consistent and self-contained manner. It is suitable for graduate students and researchers interested in the frontier research of gravity theories.

Recent Progress on Gravity Tests

Author : Cosimo Bambi
Publisher : Springer Nature
ISBN 13 : 9819728711
Total Pages : 466 pages
Book Rating : 4.8/5 (197 download)

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Book Synopsis Recent Progress on Gravity Tests by : Cosimo Bambi

Download or read book Recent Progress on Gravity Tests written by Cosimo Bambi and published by Springer Nature. This book was released on with total page 466 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Modified and Quantum Gravity

Author : Christian Pfeifer
Publisher : Springer Nature
ISBN 13 : 3031315200
Total Pages : 557 pages
Book Rating : 4.0/5 (313 download)

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Book Synopsis Modified and Quantum Gravity by : Christian Pfeifer

Download or read book Modified and Quantum Gravity written by Christian Pfeifer and published by Springer Nature. This book was released on 2023-11-01 with total page 557 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book discusses theoretical predictions and their comparison with experiments of extended and modified classical and quantum theories of gravity. The goal is to provide a readable access and broad overview over different approaches to the topic to graduate and PhD students as well as to young researchers. The book presents both, theoretical and experimental insights and is structured in three parts. The first addresses the theoretical models beyond special and general relativity such as string theory, Poincare gauge theory and teleparallelism as well as Finsler gravity. In turn, the second part is focused on the observational effects that these models generate, accounting for tests and comparisons which can be made on all possible scales: from the universe as a whole via binary systems, stars, black holes, satellite experiments, down to laboratory experiments at micrometer and smaller scales. The last part of this book is dedicated to quantum systems and gravity, showing tests of classical gravity with quantum systems, and coupling of quantum matter and gravity.

Modified Gravity and Cosmology

Author : Emmanuel N. Saridakis
Publisher : Springer Nature
ISBN 13 : 3030837157
Total Pages : 631 pages
Book Rating : 4.0/5 (38 download)

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Book Synopsis Modified Gravity and Cosmology by : Emmanuel N. Saridakis

Download or read book Modified Gravity and Cosmology written by Emmanuel N. Saridakis and published by Springer Nature. This book was released on 2021-12-10 with total page 631 pages. Available in PDF, EPUB and Kindle. Book excerpt: With a focus on modified gravity this book presents a review of the recent developments in the fields of gravity and cosmology, presenting the state of the art, high-lighting the open problems, and outlining the directions of future research. General Relativity and the ΛCDM framework are currently the standard lore and constitute the concordance paradigm of cosmology. Nevertheless, long-standing open theoretical issues, as well as possible new observational ones arising from the explosive development of cosmology in the last two decades, offer the motivation and lead a large amount of research to be devoted in constructing various extensions and modifications. In this review all extended theories and scenarios are first examined under the light of theoretical consistency, and are then applied in various geometrical backgrounds, such as the cosmological and the spherical symmetric ones. Their predictions at both the background and perturbation levels, and concerning cosmology at early, intermediate and late times, are then confronted with the huge amount of observational data that astrophysics and cosmology has been able to offer in the last two decades. Theories, scenarios and models that successfully and efficiently pass the above steps are classified as viable and are candidates for the description of Nature, allowing readers to get a clear overview of the state of the art and where the field of modified gravity is likely to go. This work was performed in the framework of the COST European Action “Cosmology and Astrophysics Network for Theoretical Advances and Training Actions” - CANTATA.

Centennial Of General Relativity: A Celebration

Author : Cesar Augusto Zen Vasconcellos
Publisher : World Scientific
ISBN 13 : 9814699675
Total Pages : 335 pages
Book Rating : 4.8/5 (146 download)

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Book Synopsis Centennial Of General Relativity: A Celebration by : Cesar Augusto Zen Vasconcellos

Download or read book Centennial Of General Relativity: A Celebration written by Cesar Augusto Zen Vasconcellos and published by World Scientific. This book was released on 2017-02-17 with total page 335 pages. Available in PDF, EPUB and Kindle. Book excerpt: It has been over 100 years since the presentation of the Theory of General Relativity by Albert Einstein, in its final formulation, to the Royal Prussian Academy of Sciences. To celebrate 100 years of general relativity, World Scientific publishes this volume with a dual goal: to assess the current status of the field of general relativity in broad terms, and discuss future directions. The volume thus consists of broad overviews summarizing major developments over the past decades and their perspective contributions.

Gravitational Waves from Compact Objects

Author : Benjamin James Owen
Publisher :
ISBN 13 :
Total Pages : 360 pages
Book Rating : 4.:/5 (437 download)

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Book Synopsis Gravitational Waves from Compact Objects by : Benjamin James Owen

Download or read book Gravitational Waves from Compact Objects written by Benjamin James Owen and published by . This book was released on 1998 with total page 360 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Isolated Objects in Quadratic Gravity

Author : Samuele Silvervalle
Publisher : Springer Nature
ISBN 13 : 3031489942
Total Pages : 197 pages
Book Rating : 4.0/5 (314 download)

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Book Synopsis Isolated Objects in Quadratic Gravity by : Samuele Silvervalle

Download or read book Isolated Objects in Quadratic Gravity written by Samuele Silvervalle and published by Springer Nature. This book was released on 2024-02-11 with total page 197 pages. Available in PDF, EPUB and Kindle. Book excerpt: One of the main unanswered question of modern Physics is "How does gravity behave at small scales?". The aim of this thesis is to illustrate in a comprehensive but accessible way how to look for deviations from Einstein's theory of General Relativity in this regime, looking at the simplest celestial bodies: static and spherically symmetric ones. With a conservative and bottom-up approach, at smaller scales the first corrections to the action of General Relativity are generally considered to be terms quadratic in the curvature tensors; while these modifications do not cure the inconsistency between gravity and quantum mechanics, the solutions of this theory are plausible candidates to be the first-order corrections of the classical ones. Even with such simple modifications, a striking picture emerges from the study of isolated objects: the unique Schwarzschild solution of General Relativity is only a rare bird in the set of solutions, with non-Schwarzschild black holes, wormholes and naked singularities appearing as possible substitutes. Tailored to graduate students and researchers entering this field, this thesis shows how to construct these new solutions from action principles, how to characterize their metric, how to study their physical properties, such as their stability or Thermodynamics, and how to look for phenomenological signatures.

Dynamical Compact Objects in Numerical Relativity

Author : Hyun Lim
Publisher :
ISBN 13 :
Total Pages : 304 pages
Book Rating : 4.:/5 (113 download)

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Book Synopsis Dynamical Compact Objects in Numerical Relativity by : Hyun Lim

Download or read book Dynamical Compact Objects in Numerical Relativity written by Hyun Lim and published by . This book was released on 2019 with total page 304 pages. Available in PDF, EPUB and Kindle. Book excerpt: The work of this dissertation will study various aspects of the dynamics of compact objects using numerical simulations. We consider BH dynamics within two modified or alternative theories of gravity. Within a family of Einstein-Maxwell-Dilaton-Axion theories, we find that the GW waveforms from binary black hole (BBH) mergers differ from the standard GW waveform prediction of GR for especially large axion values. For more astrophysically realistic (i.e. smaller) values, the differences become negligible and undetectable. We establish the existence of a well-posed initial value problem for a second alternative theory fo gravity (quadratic gravity) and demonstrate in spherical symmetry that a linear instability is effectively removed on consideration of the full nonlinear theory. We describe the key components and development of a code for studying BBH mergers for which the mass ratio of the binaries is not close to one. Such intermediate mass ratio inspirals (IMRIs) are much more difficult to simulate and present greater demands on resolution, distributed computing, accuracy and efficiency. To this end, we present a highly-scalable framework that combines a parallel octree-refined adaptive mesh with a wavelet adaptive multiresolution approach. We give results for IMRIs with mass ratios up to 100:1. We study the ejecta from BNS in Newtonian gravity. Using smoothed particle hydrodynamics we develop and present the highly scalable FleCSPH code to simulate such mergers. As part of the ejecta analysis, we consider these mergers and their aftermath as prime candidates for heavy element creation and calculate r-process nucleosynthesis within the post-merger ejecta. Lastly we consider a non-standard, yet increasingly explored, interaction between a BH and a NS that serves as a toy model for primordial black holes (PBH) and their possible role as dark matter candidates. We present results from a study of such systems in which a small BH forms at the center of a NS. Evolving the spherically symmetric system in full GR, we follow the complete dynamics as the small BH consumes the NS from within. Using numerical simulations, we examine the time scale for the NS to collapse into the PBH and show that essentially nothing remains behind. As a result, and in contradiction to other claims in the literature, we conclude that this is an unlikely site for ejecta and nucleosynthesis, at least in spherical symmetry.

Stellar Structure and Evolution

Author : Rudolf Kippenhahn
Publisher : Springer Science & Business Media
ISBN 13 : 3642615236
Total Pages : 480 pages
Book Rating : 4.6/5 (426 download)

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Book Synopsis Stellar Structure and Evolution by : Rudolf Kippenhahn

Download or read book Stellar Structure and Evolution written by Rudolf Kippenhahn and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 480 pages. Available in PDF, EPUB and Kindle. Book excerpt: A complete and comprehensive treatment of the physics of the stellar interior and the underlying fundamental processes and parameters. The text presents an overview of the models developed to explain the stability, dynamics and evolution of the stars, and great care is taken to detail the various stages in a star's life. The authors have succeeded in producing a unique text based on their own pioneering work in stellar modeling. Since its publication, this textbook has come to be considered a classic by both readers and teachers in astrophysics. This study edition is intended for students in astronomy and physics alike.

Effects of Non-locality in Gravity and Quantum Theory

Author : Jens Boos
Publisher : Springer Nature
ISBN 13 : 3030829103
Total Pages : 223 pages
Book Rating : 4.0/5 (38 download)

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Book Synopsis Effects of Non-locality in Gravity and Quantum Theory by : Jens Boos

Download or read book Effects of Non-locality in Gravity and Quantum Theory written by Jens Boos and published by Springer Nature. This book was released on 2021-10-28 with total page 223 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis is devoted to the systematic study of non-local theories that respect Lorentz invariance and are devoid of new, unphysical degrees of freedom. Such theories are attractive for phenomenological applications since they are mostly unconstrained by current experiments. Non-locality has played an increasingly important role in the physics of the last decades, appearing in effective actions in quantum field theory, and arising naturally in string theory and non-commutative geometry. It may even be a necessary ingredient for quantum theories of gravity. It is a feature of quantum entanglement, and may even solve the long-standing black hole information loss problem. “Non-locality” is a broad concept with many promising and fruitful applications in theoretical and mathematical physics. After a historical and pedagogical introduction into the concept of non-locality the author develops the notion of non-local Green functions to study various non-local weak-field problems in quantum mechanics, quantum field theory, gravity, and quantum field theory in curved spacetime. This thesis fills a gap in the literature by providing a self-contained exploration of weak-field effects in non-local theories, thereby establishing a “non-local intuition” which may serve as a stepping stone for studies of the full, non-linear problem of non-locality.