Cosmological Consequences of Quantum Gravity Proposals
Author : Marco De Cesare
Publisher :
Page : pages
File Size : 25,37 MB
Release : 2017
Category :
ISBN :
Author : Marco De Cesare
Publisher :
Page : pages
File Size : 25,37 MB
Release : 2017
Category :
ISBN :
Author : Steff Jaywan
Publisher : Dedona Publishing
Page : 47 pages
File Size : 37,45 MB
Release :
Category : Science
ISBN :
Quantum gravity is a field of theoretical physics that aims to describe the gravitational force according to the principles of quantum mechanics. Key Concepts General relativity, developed by Albert Einstein, describes gravity as the curvature of spacetime caused by mass and energy. It works extremely well at large scales, such as in predicting planetary orbits and the behavior of black holes. On the other hand, quantum mechanics deals with the fundamental behavior of particles at the smallest scales, such as atoms and subatomic particles. It incorporates principles like wave-particle duality, quantization, and uncertainty. The Need for Quantum Gravity Despite their success, general relativity and quantum mechanics are fundamentally incompatible. General relativity treats gravity as a smooth, continuous field, while quantum mechanics relies on quantized fields and inherently probabilistic events. When attempting to describe situations where both quantum effects and strong gravitational effects are significant, such as in the vicinity of black holes or during the Big Bang, the theories conflict. Quantum gravity aims to unify these two frameworks. Approaches to Quantum Gravity Several approaches have been proposed to formulate a theory of quantum gravity. String theory proposes that fundamental particles are not point-like but instead one-dimensional "strings" that vibrate at different frequencies. This theory inherently includes gravity and attempts to unify all fundamental forces. Loop quantum gravity (LQG) focuses on quantizing spacetime itself, positing that spacetime has a discrete structure at the smallest scales and attempts to describe the quantum properties of spacetime directly, without relying on a background. Causal dynamical triangulations (CDT) is a method of simulating quantum spacetime by breaking it down into discrete, simplicial building blocks, like triangles or tetrahedra, and studying how these blocks combine to form spacetime. Asymptotic safety aims to define a quantum theory of gravity that remains consistent and finite at all energy scales by identifying a fixed point in the theory's parameter space where the theory remains predictive and well-behaved.
Author : Lawrence B. Crowell
Publisher : World Scientific
Page : 388 pages
File Size : 29,43 MB
Release : 2005
Category : Science
ISBN : 9812565159
Three key aspects of quantum gravity are considered in this book: phenomenology, potential experimental aspects and foundational theory. The phenomenology is the treatment of metric quantum fluctuations as torsional curves that deviate from classical expectations. This leads to possible experimental configurations that may detect such fluctuations. Most of these proposed experiments are quantum optical measurements of subtle quantum gravity effects in the interaction of photons and atoms. The foundational discussions attempt to find an substratum to string theories, which are motivated by the phenomenological treatment. Quantum gravity is not the quantization of general relativity, but is instead the embedding of quantum theory and gravitation into a more fundamental field theoretic framework.
Author : Sydney Coleman
Publisher : World Scientific
Page : 367 pages
File Size : 10,84 MB
Release : 1991-08-12
Category :
ISBN : 9814602590
The subject of Quantum Cosmology is concerned with providing a quantum mechanical description of the universe as a whole and, within that description, to constructing a theory of the universe's initial condition whose predictions can be compared with observation. The recent progress in this area has profound implications for physics at all scales. The lectures at this School describe these theories and their implications. They cover basic quantum mechanics of cosmology, proposals for theories of initial conditions, and their application to the prediction of the large scale features of our universe. A special emphasis of the School is the implication of topological fluctuations of spacetime (wormholes, baby universes) for the observed coupling constants of the low energy interactions of elementary particles and as a potential explanation for the vanishing of the cosmological constant.
Author : Nicolae Sfetcu
Publisher : MultiMedia Publishing
Page : 216 pages
File Size : 27,31 MB
Release :
Category : Science
ISBN : 6060333214
The evolution of gravitational tests from an epistemological perspective framed in the concept of rational reconstruction of Imre Lakatos, based on his methodology of research programmes. Unlike other works on the same subject, the evaluated period is very extensive, starting with Newton's natural philosophy and up to the quantum gravity theories of today. In order to explain in a more rational way the complex evolution of the gravity concept of the last century, I propose a natural extension of the methodology of the research programmes of Lakatos that I then use during the paper. I believe that this approach offers a new perspective on how evolved over time the concept of gravity and the methods of testing each theory of gravity, through observations and experiments. I argue, based on the methodology of the research programmes and the studies of scientists and philosophers, that the current theories of quantum gravity are degenerative, due to the lack of experimental evidence over a long period of time and of self-immunization against the possibility of falsification. Moreover, a methodological current is being developed that assigns a secondary, unimportant role to verification through observations and/or experiments. For this reason, it will not be possible to have a complete theory of quantum gravity in its current form, which to include to the limit the general relativity, since physical theories have always been adjusted, during their evolution, based on observational or experimental tests, and verified by the predictions made. Also, contrary to a widespread opinion and current active programs regarding the unification of all the fundamental forces of physics in a single final theory, based on string theory, I argue that this unification is generally unlikely, and it is not possible anyway for a unification to be developed based on current theories of quantum gravity, including string theory. In addition, I support the views of some scientists and philosophers that currently too much resources are being consumed on the idea of developing quantum gravity theories, and in particular string theory, to include general relativity and to unify gravity with other forces, as long as science does not impose such research programs. CONTENTS: Introduction Gravity Gravitational tests Methodology of Lakatos - Scientific rationality The natural extension of the Lakatos methodology Bifurcated programs Unifying programs 1. Newtonian gravity 1.1 Heuristics of Newtonian gravity 1.2 Proliferation of post-Newtonian theories 1.3 Tests of post-Newtonian theories 1.3.1 Newton's proposed tests 1.3.2 Tests of post-Newtonian theories 1.4 Newtonian gravity anomalies 1.5 Saturation point in Newtonian gravity 2. General relativity 2.1 Heuristics of the general relativity 2.2 Proliferation of post-Einsteinian gravitational theories 2.3 Post-Newtonian parameterized formalism (PPN) 2.4 Tests of general relativity and post-Einsteinian theories 2.4.1 Tests proposed by Einstein 2.4.2 Tests of post-Einsteinian theories 2.4.3 Classic tests 2.4.3.1 Precision of Mercury's perihelion 2.4.3.2 Light deflection 2.4.3.3 Gravitational redshift 2.4.4 Modern tests 2.4.4.1 Shapiro Delay 2.4.4.2 Gravitational dilation of time 2.4.4.3 Frame dragging and geodetic effect 2.4.4.4 Testing of the principle of equivalence 2.4.4.5 Solar system tests 2.4.5 Strong field gravitational tests 2.4.5.1 Gravitational lenses 2.4.5.2 Gravitational waves 2.4.5.3 Synchronization binary pulsars 2.4.5.4 Extreme environments 2.4.6 Cosmological tests 2.4.6.1 The expanding universe 2.4.6.2 Cosmological observations 2.4.6.3 Monitoring of weak gravitational lenses 2.5 Anomalies of general relativity 2.6 The saturation point of general relativity 3. Quantum gravity 3.1 Heuristics of quantum gravity 3.2 The tests of quantum gravity 3.3 Canonical quantum gravity 3.3.1 Tests proposed for the CQG 3.3.2. Loop quantum gravity 3.4 String theory 3.4.1 Heuristics of string theory 3.4.2. Anomalies of string theory 3.5 Other theories of quantum gravity 3.6 Unification (The Final Theory) 4. Cosmology Conclusions Notes Bibliography DOI: 10.13140/RG.2.2.35350.70724
Author : IberĂȘ Kuntz
Publisher : Springer
Page : 88 pages
File Size : 35,84 MB
Release : 2019-05-21
Category : Science
ISBN : 3030211975
Despite the success of general relativity in explaining classical gravitational phenomena, several problems at the interface between gravitation and high energy physics still remain open. The purpose of this thesis is to explore quantum gravity and its phenomenological consequences for dark matter, gravitational waves and inflation. A new formalism to classify gravitational theories based on their degrees of freedom is introduced and, in light of this classification, it is argued that dark matter is no different from modified gravity. Gravitational waves are shown to be damped due to quantum degrees of freedom. The consequences for gravitational wave events are also discussed. The non-minimal coupling of the Higgs boson to gravity is studied in connection with Starobinsky inflation and its implications for the vacuum instability problem is analyzed.
Author : Alessia Benedetta Platania
Publisher :
Page : 142 pages
File Size : 32,15 MB
Release : 2018
Category : Quantum gravity
ISBN : 9783319987958
This book seeks to construct a consistent fundamental quantum theory of gravity, which is often considered one of the most challenging open problems in present-day physics. It approaches this challenge using modern functional renormalization group techniques, and attempts to realize the idea of "Asymptotic Safety" originally proposed by S. Weinberg. Quite remarkably, the book makes significant progress regarding both the fundamental aspects of the program and its phenomenological consequences. The conceptual developments pioneer the construction of a well-behaved functional renormalization group equation adapted to spacetimes with a preferred time-direction. It is demonstrated that the Asymptotic Safety mechanism persists in this setting and extends to many phenomenologically interesting gravity-matter systems. These achievements constitute groundbreaking steps towards bridging the gap between quantum gravity in Euclidean and Lorentzian spacetimes. The phenomenological applications cover core topics in quantum gravity, e.g. constructing a phenomenologically viable cosmological evolution based on quantum gravity effects in the very early universe, and analyzing quantum corrections to black holes forming from a spherical collapse. As a key feature, all developments are presented in a comprehensive and accessible way. This makes the work a timely and valuable guide into the rapidly evolving field of Asymptotic Safety.
Author : Eleftherios Papantonopoulos
Publisher : Springer
Page : 426 pages
File Size : 34,75 MB
Release : 2014-11-08
Category : Science
ISBN : 9783319100715
In the last few years modified gravity theories have been proposed as extensions of Einstein's theory of gravity. Their main motivation is to explain the latest cosmological and astrophysical data on dark energy and dark matter. The study of general relativity at small scales has already produced important results (cf e.g. LNP 863 Quantum Gravity and Quantum Cosmology) while its study at large scales is challenging because recent and upcoming observational results will provide important information on the validity of these modified theories. In this volume, various aspects of modified gravity at large scales will be discussed: high-curvature gravity theories; general scalar-tensor theories; Galileon theories and their cosmological applications; F(R) gravity theories; massive, new massive and topologically massive gravity; Chern-Simons modifications of general relativity (including holographic variants) and higher-spin gravity theories, to name but a few of the most important recent developments. Edited and authored by leading researchers in the field and cast into the form of a multi-author textbook at postgraduate level, this volume will be of benefit to all postgraduate students and newcomers from neighboring disciplines wishing to find a comprehensive guide for their future research.
Author : Thomas Thiemann
Publisher : Cambridge University Press
Page : 739 pages
File Size : 37,7 MB
Release : 2008-11-13
Category : Science
ISBN : 113946759X
This book provides a complete treatise of the canonical quantisation of general relativity and the loop quantum gravity theory. Mathematical concepts are provided, so it can be read by graduate students with a basic knowledge of quantum field theory or general relativity.
Author : Emma Cataneo
Publisher : BoD - Books on Demand
Page : 169 pages
File Size : 37,62 MB
Release : 2023-10-12
Category : Science
ISBN : 2322483729
Discover the universe and consciousness in a revolutionary fusion. A groundbreaking model proposal that unifies quantum physics, cosmology through consciousness. Explore the mysteries of nuclear fusion, black hole singularities, and dark energy. Dive into the interplay of quantum entanglement and the curvature of spacetime. Appreciate the scale of consciousness, where temperature and wave frequency intertwine. Also, discover how expert yogis elevate their level of consciousness, accessing its most subtle dimensions. In short, a captivating and essential book for both the general public and the scientific community, unveiling a new reality where each equation illuminates a hidden truth of the universe while remaining understandable to all.