Neutron Stars Within Pseudo-complex General Relativity PDF Download
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Author: Isaac Rodriguez González (Jr.)
Publisher:
ISBN:
Category :
Languages : en
Pages : 122
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Book Description
Author: Isaac Rodriguez González (Jr.)
Publisher:
ISBN:
Category :
Languages : en
Pages : 122
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Book Description
Author: Peter O. Hess
Publisher: Springer
ISBN: 3319250612
Category : Science
Languages : en
Pages : 263
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Book Description
This book explores the role of singularities in general relativity (GR): The theory predicts that when a sufficient large mass collapses, no known force is able to stop it until all mass is concentrated at a point. The question arises, whether an acceptable physical theory should have a singularity, not even a coordinate singularity. The appearance of a singularity shows the limitations of the theory. In GR this limitation is the strong gravitational force acting near and at a super-massive concentration of a central mass. First, a historical overview is given, on former attempts to extend GR (which includes Einstein himself), all with distinct motivations. It will be shown that the only possible algebraic extension is to introduce pseudo-complex (pc) coordinates, otherwise for weak gravitational fields non-physical ghost solutions appear. Thus, the need to use pc-variables. We will see, that the theory contains a minimal length, with important consequences. After that, the pc-GR is formulated and compared to the former attempts. A new variational principle is introduced, which requires in the Einstein equations an additional contribution. Alternatively, the standard variational principle can be applied, but one has to introduce a constraint with the same former results. The additional contribution will be associated to vacuum fluctuation, whose dependence on the radial distance can be approximately obtained, using semi-classical Quantum Mechanics. The main point is that pc-GR predicts that mass not only curves the space but also changes the vacuum structure of the space itself. In the following chapters, the minimal length will be set to zero, due to its smallness. Nevertheless, the pc-GR will keep a remnant of the pc-description, namely that the appearance of a term, which we may call "dark energy", is inevitable. The first application will be discussed in chapter 3, namely solutions of central mass distributions. For a non-rotating massive object it is the pc-Schwarzschild solution, for a rotating massive object the pc-Kerr solution and for a charged massive object it will be the Reissner-Nordström solution. This chapter serves to become familiar on how to resolve problems in pc-GR and on how to interpret the results. One of the main consequences is, that we can eliminate the event horizon and thus there will be no black holes. The huge massive objects in the center of nearly any galaxy and the so-called galactic black holes are within pc-GR still there, but with the absence of an event horizon! Chapter 4 gives another application of the theory, namely the Robertson-Walker solution, which we use to model different outcomes of the evolution of the universe. Finally the capability of this theory to predict new phenomena is illustrated.
Author: Werner Becker
Publisher: Springer Science & Business Media
ISBN: 354076965X
Category : Science
Languages : en
Pages : 702
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Book Description
Neutron stars are the most compact astronomical objects in the universe which are accessible by direct observation. Studying neutron stars means studying physics in regimes unattainable in any terrestrial laboratory. Understanding their observed complex phenomena requires a wide range of scientific disciplines, including the nuclear and condensed matter physics of very dense matter in neutron star interiors, plasma physics and quantum electrodynamics of magnetospheres, and the relativistic magneto-hydrodynamics of electron-positron pulsar winds interacting with some ambient medium. Not to mention the test bed neutron stars provide for general relativity theories, and their importance as potential sources of gravitational waves. It is this variety of disciplines which, among others, makes neutron star research so fascinating, not only for those who have been working in the field for many years but also for students and young scientists. The aim of this book is to serve as a reference work which not only reviews the progress made since the early days of pulsar astronomy, but especially focuses on questions such as: "What have we learned about the subject and how did we learn it?", "What are the most important open questions in this area?" and "What new tools, telescopes, observations, and calculations are needed to answer these questions?". All authors who have contributed to this book have devoted a significant part of their scientific careers to exploring the nature of neutron stars and understanding pulsars. Everyone has paid special attention to writing educational comprehensive review articles with the needs of beginners, students and young scientists as potential readers in mind. This book will be a valuable source of information for these groups.
Author: Swami Vivekanandji Chaurasia
Publisher:
ISBN:
Category :
Languages : de
Pages :
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Book Description
Binary neutron star coalescence lead to extremely violent merger events in the universe. Such events give rise to a variety of observable phenomena in both the gravitational and the electromagnetic channels. In this thesis we study such extreme events in the last milliseconds around the merger. Gravity and its coupling to other physics for such systems is described by Einstein's theory of general relativity. Since these are highly nonlinear coupled set of partial differential equations, no analytical solutions exist for generic and dynamical systems such as binary neutron stars in the strong-field regime. Therefore, the usage of numerical methods is inevitable. In this thesis we consider configurations of binary neutron stars with varying equation of state, spin, eccentricity and spin orientation. In particular we present the first numerical relativity simulations of highly eccentric binary neutron stars in full (3+1)D using consistent initial data, i.e., setups which are in agreement with the Einstein equations and with the equations of general relativistic hydrodynamics in equilibrium. Additionally, we also study precessing binary neutron star systems using full (3+1)D numerical relativity simulations with consistent initial data. Further, we investigate a new numerical approach for solving the equations of general relativistic hydrodynamics using the discontinuous Galerkin method. It combines the key aspects of finite volume and traditional finite element methods, for e.g., element locality and hp-adaptivity besides the benefit of spectral convergence for smooth solutions. Discontinuous Galerkin methods ease the treatment of complex grid geometries and, allow simple and efficient parallelization.
Author: Tomaso M. Belloni
Publisher: Springer Nature
ISBN: 366262110X
Category : Science
Languages : en
Pages : 335
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Book Description
Neutron stars, whether isolated or in a binary system, display a varied and complex phenomenology, often accompanied by extreme variability of many time scales, which takes the form of pulsations due to the object rotation, quasi-periodicities associated to accretion of matter, and explosions due to matter accreted on the surface or to starquakes of highly magnetized objects. This book gives an overview of the current observational and theoretical standpoint in the research on the physics under the extreme conditions that neutron stars naturally provide. The six chapters explore three physical regions of a neutron star: the space around it, where accretion and pulsar companions allow testing of general relativity its surface, where millisecond pulsation and X-ray burts provide clues about general relativistic effects and the equation of state of neutron matter its interior, of course, inaccessible to direct observations, can nevertheless, be probed with all observational parameters related to neutron star variability.
Author: Gregory B. Cook
Publisher:
ISBN:
Category : Neutron stars
Languages : en
Pages : 84
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Book Description
Author: Peter Otto Hess
Publisher: World Scientific
ISBN: 9813234296
Category : Science
Languages : en
Pages : 388
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Book Description
Walter Greiner (1935-2016) was a German physicist of the Goethe University, Frankfurt, well-known for his many contributions in scientific research and developments, in particular the field of nuclear physics. He was a well-respected science leader and a teacher who had supervised batches of young collaborators and students, many of whom are now leaders in both academics and industry worldwide. Greiner had a wide interest of science which covered atomic physics, heavy-ion physics, and nuclear astrophysics. Greiner co-founded GSI, the Helmholtz Centre for Heavy Ion Research, and the multi-disciplinary research center, FIAS (Frankfurt Institute for Advanced Studies). Besides numerous professorship with universities worldwide, including the University of Maryland, Greiner received many prestigious prizes in honor of his outstanding contributions, among others are the Otto Hahn Prize and the Max Born Prize.This memorial volume is a special tribute by Greiner's former colleagues, students, and friends honoring his contributions and passion in science. The volume begins with a writing by Greiner about his early days in science. The subsequent articles, comprising personal and scientific reminiscences of Walter Greiner, serve as timely reviews on various topics of current interest.
Author: Walter Greiner
Publisher: Springer Science & Business Media
ISBN: 3319000470
Category : Science
Languages : en
Pages : 503
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Book Description
Nuclear physics is an exciting, broadly faceted field. It spans a wide range of topics, reaching from nuclear structure physics to high-energy physics, astrophysics and medical physics (heavy ion tumor therapy). New developments are presented in this volume and the status of research is reviewed. A major focus is put on nuclear structure physics, dealing with superheavy elements and with various forms of exotic nuclei: strange nuclei, very neutron rich nuclei, nuclei of antimatter. Also quantum electrodynamics of strong fields is addressed, which is linked to the occurrence of giant nuclear systems in, e.g., U+U collisions. At high energies nuclear physics joins with elementary particle physics. Various chapters address the theory of elementary matter at high densities and temperature, in particular the quark gluon plasma which is predicted by quantum chromodynamics (QCD) to occur in high-energy heavy ion collisions. In the field of nuclear astrophysics, the properties of neutron stars and quark stars are discussed. A topic which transcends nuclear physics is discussed in two chapters: The proposed pseudo-complex extension of Einstein's General Relativity leads to the prediction that there are no black holes and that big bang cosmology has to be revised. Finally, the interdisciplinary nature of this volume is further accentuated by chapters on protein folding and on magnetoreception in birds and many other animals.
Author: Farbod Kamiab
Publisher:
ISBN:
Category : Cosmological constants
Languages : en
Pages : 126
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Book Description
The gravitational aether theory is a modification of General Relativity that decouples vacuum energy from gravity, and thus can potentially address the cosmological constant problem. The classical theory is distinguishable from General Relativity only in the presence of relativistic pressure (or vorticity). Since the interior of neutron stars has high pressure and as their mass and radius can be measured observationally, they are the perfect laboratory for testing the validity of the aether theory. In this thesis, we first solve the hydrostatic equations of stellar structure for the gravitational aether theory and find the predicted mass-radius relation of nonrotating neutron stars using two different realistic proposals for the equation of state of nuclear matter. We find that the maximum neutron-star mass predicted by the aether theory is 12%-16% less than the maximum mass predicted by general relativity assuming these two equations of state. We then study the dynamics of a neutron star in the aether theory and establish that a Cauchy problem can be defined. We derive the dynamical equations, and through analyzing them, we find two modes, one of which is well-posed (expansion of matter in the aether frame) and the other is not well-posed (collapse of matter in the aether frame). Starting from a hydrostatic neutron star configuration that we perturb by adding extrinsic curvature (and radial velocity), we numerically evolve the Einstein field equations for the aether theory in the well-posed mode and find that it evolves towards the not well-posed regime. This feature may pose a serious challenge to our initial value formulation of the aether theory. Whether an alternative formulation can handle the collapsing neutron stars is a question of utmost importance for the viability of the aether theory. It has been clear for some time now that super-critical surface magnetic fields, exceeding 4 x 10^13 G, exist on a subset of neutron stars. These magnetars may harbor interior fields many orders of magnitude larger, potentially reaching equipartition values. However, the impact of these strong fields on stellar structure has been largely ignored, potentially complicating attempts to infer the high density nuclear equation of state. In this thesis, we assess the effect of these strong magnetic fields on the mass-radius relationship of neutron stars. We employ an effective field theory model for the nuclear equation of state that includes the impact of hyperons, anomalous magnetic moments, and the physics of the crust. We consider two magnetic field geometries, bounding the likely magnitude of the impact of magnetic fields: a statistically isotropic, tangled field and a force-free configuration. In both cases even equipartition fields have at most a 30% impact on the maximum mass. However, the direction of the effect of the magnetic field depends on the geometry employed - force-free fields leading to reductions in the maximum neutron star mass and radius while tangled fields increase both - challenging the common intuition in the literature on the impact of magnetic fields.
Author: P. Haensel
Publisher: Springer Science & Business Media
ISBN: 0387473017
Category : Science
Languages : en
Pages : 633
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Book Description
The book gives an extended review of theoretical and observational aspects of neutron star physics. With masses comparable to that of the Sun and radii of about ten kilometres, neutron stars are the densest stars in the Universe. This book describes all layers of neutron stars, from the surface to the core, with the emphasis on their structure and equation of state. Theories of dense matter are reviewed, and used to construct neutron star models. Hypothetical strange quark stars and possible exotic phases in neutron star cores are also discussed. Also covered are the effects of strong magnetic fields in neutron star envelopes.
