Homogeneity and Clustering

2020 ◽  
pp. 3-36
Author(s):  
P. J. E. Peebles
Keyword(s):  
General Relativity ◽  
Large Scale ◽  
Albert Einstein ◽  
Large Scale Structure ◽  
Relativity Theory ◽  
Expanding Universe ◽  
History Of ◽  
Edwin Hubble ◽  
The Universe ◽  
Georges Lemaître

This chapter traces the history of the development of ideas on the large-scale structure of the universe. Modern discussions of the nature of the large-scale matter distribution can be traced back to three central ideas. In 1917, Albert Einstein argued that a closed homogeneous world model fits very well into general relativity theory and the requirements of Mach's principle. In 1926, Edwin Hubble showed that the large-scale distribution of galaxies is close to uniform with no indication of an edge or boundary. In 1927, Georges Lemaître showed that the uniform distribution of galaxies fits very well with the pattern of galaxy redshifts. The chapter then assesses several questions. The first is whether the universe really is homogeneous. Could the homogeneity of the universe have been deduced ahead of time from general principles? Or might it be a useful guide to new principles? It also asks how clustering evolves in an expanding universe, what its origin is, and what this reveals about the nature of the universe.

5. Cosmology

2017 ◽  
pp. 58-82
Author(s):  
Timothy Clifton
Keyword(s):  
Dark Matter ◽  
Large Scale ◽  
Gravitational Interaction ◽  
Albert Einstein ◽  
Scientific Discipline ◽  
Normal Matter ◽  
History Of Cosmology ◽  
History Of ◽  
Edwin Hubble ◽  
The Universe

Cosmology began as a scientific discipline at the beginning of the 20th century, with the work of Albert Einstein and Edwin Hubble. Gravitational interaction is fundamental to cosmology, as gravity dominates over all other forces on large-scale distances. ‘Cosmology’ outlines the modern history of cosmology, discussing how studies have provided knowledge on the early Universe and its expansion. The Concordance Model proposes that only c.5 per cent of the energy in the Universe is in the form of normal matter; c.25 per cent is in the form of the gravitationally attractive dark matter; and the remaining c.70 per cent is in the form of the gravitationally repulsive dark energy. But there is still much to learn.

Principles of Physical Cosmology

2020 ◽  
Author(s):  
P. J. E. Peebles
Keyword(s):  
General Relativity ◽  
Large Scale ◽  
Large Scale Structure ◽  
Critical Area ◽  
Nobel Lecture ◽  
Modern Physics ◽  
History Of ◽  
Cosmological Tests ◽  
Physical Cosmology ◽  
The Universe

This book is the essential introduction to this critical area of modern physics, written by a leading pioneer who has shaped the course of the field for decades. The book provides an authoritative overview of the field, showing how observation has combined with theory to establish the science of physical cosmology. The book presents the elements of physical cosmology, including the history of the discovery of the expanding universe; surveys the cosmological tests that measure the geometry of space-time, with a discussion of general relativity as the basis for these tests; and reviews the origin of galaxies and the large-scale structure of the universe. Now featuring the author's 2019 Nobel lecture, the book remains an indispensable reference for students and researchers alike.

scholarly journals The Spectrum of Density Perturbations in an Expanding Universe

1974 ◽  
Vol 63 ◽  
pp. 175-193
Author(s):  
Joseph Silk
Keyword(s):  
Large Scale ◽  
Background Radiation ◽  
Large Scale Structure ◽  
Challenging Problem ◽  
Expanding Universe ◽  
Related Matter ◽  
Widespread Acceptance ◽  
Density Perturbations ◽  
Density Inhomogeneities ◽  
The Universe

Perhaps the most challenging problem confronting a cosmologist is to reconcile the observed large-scale structure of the Universe with the Friedmann-Lemaître cosmological models that have gained such widespread acceptance in recent years (cf. however the alternative viewpoint, as exemplified in this Symposium by Arp and others). In this review, I shall look anew at the spectrum of density inhomogeneities that survive decoupling of matter and radiation at z ~ 1000 and provide the primordial fluctuations that can eventually generate galaxies. A closely related matter, that of the associated fluctuations in the background radiation, is discussed elsewhere in this volume by Doroshkevich, Sunyaev and Zel'dovich.

scholarly journals Modelling the Large Scale Structure of the Universe after COBE

1995 ◽  
Vol 48 (6) ◽  
pp. 1083 ◽  
Author(s):  
PJ Quinn
Keyword(s):  
Dark Matter ◽  
Large Scale ◽  
Cold Dark Matter ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Expanding Universe ◽  
Model Predictions ◽  
Perturbation Spectrum ◽  
The Universe

N-body models running on supercomputers have been widely used to explore the development of structure in the expanding Universe. Recent results from the COBE satellite have provided a global normalisation of these models which now allows detailed comparisons to be drawn between observations and model predictions. Some predictions of the cold dark matter primordial perturbation spectrum are now shown to be consistent with surveys of galaxy redshifts.

scholarly journals Cosmological Tests of Gravity

2019 ◽  
Vol 57 (1) ◽  
pp. 335-374 ◽  
Author(s):  
Pedro G. Ferreira
Keyword(s):  
General Relativity ◽  
Large Scale ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Alternative Theories Of Gravity ◽  
Systematic Uncertainties ◽  
Cosmological Observations ◽  
Theories Of Gravity ◽  
Tests Of Gravity ◽  
The Universe

Cosmological observations are beginning to reach a level of precision that allows us to test some of the most fundamental assumptions in our working model of the Universe. One such assumption is that gravity is governed by the theory of general relativity. In this review, we discuss how one might go about extending general relativity and how such extensions can be described in a unified way on large scales. This allows us to describe the phenomenology of modified gravity in the growth and morphology of the large-scale structure of the Universe. On smaller scales, we explore the physics of gravitational screening and how it might manifest itself in galaxies, clusters, and, more generally, in the cosmic web. We then analyze the current constraints from large-scale structure and conclude by discussing the future prospects of the field in light of the plethora of surveys currently being planned. Key results include the following: ▪ There are a plethora of alternative theories of gravity that are restricted by fundamental physics considerations. ▪ There is now a well-established formalism for describing cosmological perturbations in the linear regime for general theories of gravity. ▪ Gravitational screening can mask modifications to general relativity on small scales but may, itself, lead to distinctive signatures in the large-scale structure of the Universe. ▪ Current constraints on both linear and nonlinear scales may be affected by systematic uncertainties that limit our ability to rule out alternatives to general relativity. ▪ The next generation of cosmological surveys will dramatically improve constraints on general relativity, by up to two orders of magnitude.

Behavior of Irregularities in the Distribution of Matter: Newtonian Approximation

2020 ◽  
pp. 37-137
Author(s):  
P. J. E. Peebles
Keyword(s):  
General Relativity ◽  
Mass Distribution ◽  
Newtonian Mechanics ◽  
Expanding Universe ◽  
Matter Distribution ◽  
Newtonian Approximation ◽  
Limiting Case ◽  
The Universe ◽  
Georges Lemaître

This chapter examines the behavior of a given mass distribution in the Newtonian approximation. Discussion of how irregularities in the matter distribution behave in an expanding universe is greatly simplified by the fact that a limiting approximation of general relativity, Newtonian mechanics, applies in a region small compared to the Hubble length. The rest of the universe can affect the region only through a tidal field. Though the point was clearly made by Georges Lemaître, it has not always been recognized that the Newtonian approximation is not a model but a limiting case valid no matter what is happening in the distant parts of the universe. Because of the importance of this result, the chapter discusses it at some length.

The Large-Scale Structure of the Universe

2020 ◽  
Author(s):  
P. J. E. Peebles
Keyword(s):  
Empirical Evidence ◽  
Large Scale ◽  
Large Scale Structure ◽  
Expanding Universe ◽  
Statistical Measures ◽  
Cosmic Evolution ◽  
Modern Cosmology ◽  
The Subject ◽  
New Generation ◽  
The Universe

An instant landmark on its publication, this book remains the essential introduction to this vital area of research. Written by one of the world's most esteemed theoretical cosmologists, it provides an invaluable historical introduction to the subject, and an enduring overview of key methods, statistical measures, and techniques for dealing with cosmic evolution. With characteristic clarity and insight, the author focuses on the largest known structures — galaxy clusters — weighing the empirical evidence of the nature of clustering and the theories of how it evolves in an expanding universe. A must-have reference for students and researchers alike, this edition introduces a new generation of readers to a classic text in modern cosmology.

scholarly journals A new golden age: testing general relativity with cosmology

2011 ◽  
Vol 369 (1957) ◽  
pp. 4941-4946
Author(s):  
Rachel Bean ◽  
Pedro G. Ferreira ◽  
Andy Taylor
Keyword(s):  
General Relativity ◽  
Large Scale ◽  
Large Scale Structure ◽  
Einstein Gravity ◽  
Field Equations ◽  
The Past ◽  
Cosmological Observations ◽  
Wide Range ◽  
Theories Of Gravity ◽  
The Universe

Gravity drives the evolution of the Universe and is at the heart of its complexity. Einstein's field equations can be used to work out the detailed dynamics of space and time and to calculate the emergence of large-scale structure in the distribution of galaxies and radiation. Over the past few years, it has become clear that cosmological observations can be used not only to constrain different world models within the context of Einstein gravity but also to constrain the theory of gravity itself. In this article, we look at different aspects of this new field in which cosmology is used to test theories of gravity with a wide range of observations.

scholarly journals Using the morphology and magnetic fields of tailed radio galaxies as environmental probes

2014 ◽  
Vol 10 (S313) ◽  
pp. 321-326
Author(s):  
M. Johnston-Hollitt ◽  
S. Dehghan ◽  
L. Pratley
Keyword(s):  
Magnetic Fields ◽  
Large Scale ◽  
Large Population ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Local Conditions ◽  
History Of ◽  
Unique Source ◽  
The Universe ◽  
The Magnetic Field

AbstractBent-tailed (BT) radio sources have long been known to trace over densities in the Universe up to z ~ 1 and there is increasing evidence this association persists out to redshifts of 2. The morphology of the jets in BT galaxies is primarily a function of the environment that they have resided in and so BTs provide invaluable clues as to their local conditions. Thus, not only can samples of BT galaxies be used as signposts of large-scale structure, but are also valuable for obtaining a statistical measurement of properties of the intra-cluster medium including the presence of cluster accretion shocks & winds, and as historical anemometers, preserving the dynamical history of their surroundings in their jets. We discuss the use of BTs to unveil large-scale structure and provide an example in which a BT was used to unlock the dynamical history of its host cluster. In addition to their use as density and dynamical indicators, BTs are useful probes of the magnetic field on their environment on scales which are inaccessible to other methods. Here we discuss a novel way in which a particular sub-class of BTs, the so-called ‘corkscrew’ galaxies might further elucidate the coherence lengths of the magnetic fields in their vicinity. Given that BTs are estimated to make up a large population in next generation surveys we posit that the use of jets in this way could provide a unique source of environmental information for clusters and groups up to z = 2.

scholarly journals Testing general relativity: from local to cosmological scales

2011 ◽  
Vol 369 (1957) ◽  
pp. 5042-5057 ◽  
Author(s):  
Jean-Philippe Uzan
Keyword(s):  
General Relativity ◽  
Large Scale ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Geometric Structures ◽  
Tests Of General Relativity ◽  
The Universe

I summarize various tests of general relativity on astrophysical scales, based on the large-scale structure of the universe but also on other systems, in particular the constants of physics. I emphasize the importance of hypotheses on the geometric structures of our universe while performing such tests and discuss their complementarity as well as their possible extensions.

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