Multiverse in Dynamic Equilibrium
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PRESS RELEASE Solved: the Mystery of the Expansion of the Universe
PRESS RELEASE Geneva | March 10th, 2020 The earth, solar system, entire Milky Way and the few thousand ga- Solved: laxies closest to us move in a vast “bubble” that is 250 million light years in diameter, where the average density of matter is half as large the mystery as for the rest of the universe. This is the hypothesis put forward by a theoretical physicist from the University of Geneva (UNIGE) to solve of the expansion a conundrum that has been splitting the scientific community for a decade: at what speed is the universe expanding? Until now, at least of the universe two independent calculation methods have arrived at two values that are different by about 10% with a deviation that is statistically A UNIGE researcher has irreconcilable. This new approach, which is set out in the journal Phy- solved a scientific sics Letters B, erases this divergence without making use of any “new controversy about the speed physics”. of the expansion The universe has been expanding since the Big Bang occurred 13.8 bil- of the universe by lion years ago – a proposition first made by the Belgian canon and suggesting that it is not physicist Georges Lemaître (1894-1966), and first demonstrated by Edwin Hubble (1889-1953). The American astronomer discovered in totally homogeneous on a 1929 that every galaxy is pulling away from us, and that the most dis- large scale. tant galaxies are moving the most quickly. This suggests that there was a time in the past when all the galaxies were located at the same spot, a time that can only correspond to the Big Bang. -
General Relativity and Cosmology: Unsolved Questions and Future Directions
Article General Relativity and Cosmology: Unsolved Questions and Future Directions Ivan Debono 1,∗,† and George F. Smoot 1,2,3,† 1 Paris Centre for Cosmological Physics, APC, AstroParticule et Cosmologie, Université Paris Diderot, CNRS/IN2P3, CEA/lrfu, Observatoire de Paris, Sorbonne Paris Cité, 10, rue Alice Domon et Léonie Duquet, 75205 Paris CEDEX 13, France; [email protected] 2 Physics Department and Lawrence Berkeley National Laboratory, University of California, Berkeley, 94720 CA, USA 3 Helmut and Anna Pao Sohmen Professor-at-Large, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, 999077 Hong Kong, China * Correspondence: [email protected]; Tel.: +33-1-57276991 † These authors contributed equally to this work. Academic Editors: Lorenzo Iorio and Elias C. Vagenas Received: 21 August 2016; Accepted: 14 September 2016; Published: 28 September 2016 Abstract: For the last 100 years, General Relativity (GR) has taken over the gravitational theory mantle held by Newtonian Gravity for the previous 200 years. This article reviews the status of GR in terms of its self-consistency, completeness, and the evidence provided by observations, which have allowed GR to remain the champion of gravitational theories against several other classes of competing theories. We pay particular attention to the role of GR and gravity in cosmology, one of the areas in which one gravity dominates and new phenomena and effects challenge the orthodoxy. We also review other areas where there are likely conflicts pointing to the need to replace or revise GR to represent correctly observations and consistent theoretical framework. Observations have long been key both to the theoretical liveliness and viability of GR. -
Neutrino Cosmology and Large Scale Structure
Neutrino cosmology and large scale structure Christiane Stefanie Lorenz Pembroke College and Sub-Department of Astrophysics University of Oxford A thesis submitted for the degree of Doctor of Philosophy Trinity 2019 Neutrino cosmology and large scale structure Christiane Stefanie Lorenz Pembroke College and Sub-Department of Astrophysics University of Oxford A thesis submitted for the degree of Doctor of Philosophy Trinity 2019 The topic of this thesis is neutrino cosmology and large scale structure. First, we introduce the concepts needed for the presentation in the following chapters. We describe the role that neutrinos play in particle physics and cosmology, and the current status of the field. We also explain the cosmological observations that are commonly used to measure properties of neutrino particles. Next, we present studies of the model-dependence of cosmological neutrino mass constraints. In particular, we focus on two phenomenological parameterisations of time-varying dark energy (early dark energy and barotropic dark energy) that can exhibit degeneracies with the cosmic neutrino background over extended periods of cosmic time. We show how the combination of multiple probes across cosmic time can help to distinguish between the two components. Moreover, we discuss how neutrino mass constraints can change when neutrino masses are generated late in the Universe, and how current tensions between low- and high-redshift cosmological data might be affected from this. Then we discuss whether lensing magnification and other relativistic effects that affect the galaxy distribution contain additional information about dark energy and neutrino parameters, and how much parameter constraints can be biased when these effects are neglected. -
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Ai miei genitori. ii Indice Introduzione ................................................................................................... 1 1. Cent’anni di Cosmologia ............................................................................ 2 2. Il Modello Cosmologico Standard ΛCDM .................................................. 6 3. Questioni aperte e modelli alternativi (cenni) .......................................... 12 4. Conclusioni .............................................................................................. 14 Bibliografia .................................................................................................. 16 Ringraziamenti ............................................................................................. 18 iii iv “La più sublime, la più nobile tra le Fisiche scienze ella è senza dubbio l’Astronomia. L’uomo s’innalza per mezzo di essa come al di sopra di se medesimo, e giunge a conoscere la causa dei fenomeni più straordinari.” (Giacomo Leopardi 1) Introduzione Il presente lavoro intende offrire un riassunto dello “stato dell’arte” della Cosmologia: dopo averne ripercorso per sommi capi la storia degli ultimi cent’anni (cap.1), verrà illustrato il Modello Cosmologico Standard “ ΛCDM” (cap.2), che è quello generalmente accettato dalla comunità scientifica allo stato attuale delle conoscenze; infine, si farà un breve “excursus” sulle questioni “aperte” e sui modelli cosmologici alternativi (cap.3). La Cosmologia si può definire in maniera sintetica come lo studio dell’Universo -
Rayappa a Kasi Rusch to Riches.Pdf
RUSH TO RICHES The War on Creation Paul Wiegelmann Lectures on Environmental Studies: 2 RUSH TO RICHES The War on Creation Rayappa A. Kasi Dharmaram Publications Bangalore 560 029, India 2011 Rush to Riches: The War on Creation By Rayappa A. Kasi A. Kattupadi Post Vellore 632011, India Website: www.planetschaser.com Email: [email protected]; Phone: 09443537885 Paul Wiegelmann Lectures on Environmental Studies: 2 © Faculty of Philosophy Dharmaram Vidya Kshetram Bangalore 560 029, India Email: [email protected] First Edition, 2011 Published by Dharmaram Publications ISBN: 978-81-89958-45-9 Printed at: National Printing Press, Bangalore Price: INì 395; US$ 40 Dharmaram Publications Dharmaram College, Bangalore 560 029, India Tel. 080/4111 6227; 4111 6137; 4111 6111 E-mail: [email protected] Web: www.dharmarampublications.com In memory of all the species of animals and plants perished in the war on creation Other Publications from the Author 1. Earth: The Lost Paradise of Happiness (2009) 2. Global Warming: Everything You Want to Know! (2009) 3. Biosphere: The Fragility of Our Natural Heritage (2010) 4. Lithosphere: A Destructive Creator (2010) 5. Hydrosphere: The Giver of Life (2010) 6. Atmosphere: A Thin Line between Life and Death (2010) 7. Earth: Designed for Biodiversity (2010) 8. Youth: An Avatar of New Earth (2011) 9. Apes to Angels: Man Reaches his Omega Point (2011) Cover Illustration This picture, the oil-soaked bird from Gulf of Mexico, represents the agony and pain that the Creation is undergoing as a result of human conflict with Nature. It is a loud cry of Creation for help. -
Challenges to Self-Acceleration in Modified Gravity from Gravitational
Physics Letters B 765 (2017) 382–385 Contents lists available at ScienceDirect Physics Letters B www.elsevier.com/locate/physletb Challenges to self-acceleration in modified gravity from gravitational waves and large-scale structure ∗ Lucas Lombriser , Nelson A. Lima Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh, EH9 3HJ, UK a r t i c l e i n f o a b s t r a c t Article history: With the advent of gravitational-wave astronomy marked by the aLIGO GW150914 and GW151226 Received 2 September 2016 observations, a measurement of the cosmological speed of gravity will likely soon be realised. We show Received in revised form 19 December 2016 that a confirmation of equality to the speed of light as indicated by indirect Galactic observations Accepted 19 December 2016 will have important consequences for a very large class of alternative explanations of the late-time Available online 27 December 2016 accelerated expansion of our Universe. It will break the dark degeneracy of self-accelerated Horndeski Editor: M. Trodden scalar–tensor theories in the large-scale structure that currently limits a rigorous discrimination between acceleration from modified gravity and from a cosmological constant or dark energy. Signatures of a self-acceleration must then manifest in the linear, unscreened cosmological structure. We describe the minimal modification required for self-acceleration with standard gravitational-wave speed and show that its maximum likelihood yields a 3σ poorer fit to cosmological observations compared to a cosmological constant. Hence, equality between the speeds challenges the concept of cosmic acceleration from a genuine scalar–tensor modification of gravity. -
Observational Cosmology - 30H Course 218.163.109.230 Et Al
Observational cosmology - 30h course 218.163.109.230 et al. (2004–2014) PDF generated using the open source mwlib toolkit. See http://code.pediapress.com/ for more information. PDF generated at: Thu, 31 Oct 2013 03:42:03 UTC Contents Articles Observational cosmology 1 Observations: expansion, nucleosynthesis, CMB 5 Redshift 5 Hubble's law 19 Metric expansion of space 29 Big Bang nucleosynthesis 41 Cosmic microwave background 47 Hot big bang model 58 Friedmann equations 58 Friedmann–Lemaître–Robertson–Walker metric 62 Distance measures (cosmology) 68 Observations: up to 10 Gpc/h 71 Observable universe 71 Structure formation 82 Galaxy formation and evolution 88 Quasar 93 Active galactic nucleus 99 Galaxy filament 106 Phenomenological model: LambdaCDM + MOND 111 Lambda-CDM model 111 Inflation (cosmology) 116 Modified Newtonian dynamics 129 Towards a physical model 137 Shape of the universe 137 Inhomogeneous cosmology 143 Back-reaction 144 References Article Sources and Contributors 145 Image Sources, Licenses and Contributors 148 Article Licenses License 150 Observational cosmology 1 Observational cosmology Observational cosmology is the study of the structure, the evolution and the origin of the universe through observation, using instruments such as telescopes and cosmic ray detectors. Early observations The science of physical cosmology as it is practiced today had its subject material defined in the years following the Shapley-Curtis debate when it was determined that the universe had a larger scale than the Milky Way galaxy. This was precipitated by observations that established the size and the dynamics of the cosmos that could be explained by Einstein's General Theory of Relativity. -
Introducing Astrogen: the Astronomy Genealogy Project
Journal of Astronomical History and Heritage, 19(3), 298–304 (2016). INTRODUCING ASTROGEN: THE ASTRONOMY GENEALOGY PROJECT Joseph S. Tenn Sonoma State University, Rohnert Park, CA 94928, USA. Email: [email protected] Abstract: The Astronomy Genealogy Project (―AstroGen‖), a project of the Historical Astronomy Division of the American Astronomical Society (AAS), will soon appear on the AAS website. Ultimately, it will list the world‘s astronomers with their highest degrees, theses for those who wrote them, academic advisors (supervisors), universities, and links to the astronomers or their obituaries, their theses when on-line, and more. At present the AstroGen team is working on those who earned doctorates with astronomy-related theses. We show what can be learned already, with just ten countries essentially completed. Keywords: Academic genealogy, astronomers, Ph.D. theses, dissertations 1 INTRODUCTION ries we have studied (listed in Section 3) went to Arthur Williams Wright (Figure 1), who became AstroGen is coming. The Astronomy Genealogy the first person outside Europe to earn a Ph.D. Project will soon appear on the website of the in science and one of the first three Ph.D.s in American Astronomical Society (AstroGen: any subject in the United States. His thesis, https://astrogen.aas.org/). Under construction Having Given the Velocity and Direction of since early 2013, the project will list the world‘s Motion of a Meteor on Entering the Atmosphere doctoral theses (dissertations) on astronomy- of the Earth, to Determine its Orbit about the related topics, along with information about the Sun, Taking into Account the Attraction of Both theses and their authors. -
Letter of Interest Fundamental Physics with Gravitational Wave Detectors
Snowmass2021 - Letter of Interest Fundamental physics with gravitational wave detectors Thematic Areas: (check all that apply /) (CF1) Dark Matter: Particle Like (CF2) Dark Matter: Wavelike (CF3) Dark Matter: Cosmic Probes (CF4) Dark Energy and Cosmic Acceleration: The Modern Universe (CF5) Dark Energy and Cosmic Acceleration: Cosmic Dawn and Before (CF6) Dark Energy and Cosmic Acceleration: Complementarity of Probes and New Facilities (CF7) Cosmic Probes of Fundamental Physics (TF09) Cosmology Theory (TF10) Quantum Information Science Theory Contact Information: Emanuele Berti (Johns Hopkins University) [[email protected]], Vitor Cardoso (Instituto Superior Tecnico,´ Lisbon) [[email protected]], Bangalore Sathyaprakash (Pennsylvania State University & Cardiff University) [[email protected]], Nicolas´ Yunes (University of Illinois at Urbana-Champaign) [[email protected]] Authors: (see long author lists after the text) Abstract: (maximum 200 words) Gravitational wave detectors are formidable tools to explore black holes and neutron stars. These com- pact objects are extraordinarily efficient at producing electromagnetic and gravitational radiation. As such, they are ideal laboratories for fundamental physics and they have an immense discovery potential. The detection of merging black holes by third-generation Earth-based detectors and space-based detectors will provide exquisite tests of general relativity. Loud “golden” events and extreme mass-ratio inspirals can strengthen the observational evidence for horizons by mapping the exterior spacetime geometry, inform us on possible near-horizon modifications, and perhaps reveal a breakdown of Einstein’s gravity. Measure- ments of the black-hole spin distribution and continuous gravitational-wave searches can turn black holes into efficient detectors of ultralight bosons across ten or more orders of magnitude in mass. -
Dark Energy Vs. Modified Gravity Arxiv:1601.06133V4 [Astro-Ph.CO]
Dark Energy vs. Modified Gravity Austin Joyce,1 Lucas Lombriser,2 and Fabian Schmidt3 1Enrico Fermi Institute and Kavli Institute for Cosmological Physics, University of Chicago, Chicago, IL 60637; email: [email protected] 2Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh, EH9 3HJ, U.K.; email: [email protected] 3Max-Planck-Institute for Astrophysics, D-85748 Garching, Germany; email: [email protected] Ann. Rev. Nuc. Part. Sc. 2016. AA:1{29 Keywords Copyright c 2016 by Annual Reviews. All rights reserved cosmology, dark energy, modified gravity, structure formation, large-scale structure Abstract Understanding the reason for the observed accelerated expansion of the Universe represents one of the fundamental open questions in physics. In cosmology, a classification has emerged among physical models for the acceleration, distinguishing between Dark Energy and Modified Gravity. In this review, we give a brief overview of models in both categories as well as their phenomenology and characteristic observable signatures in cosmology. We also introduce a rigorous distinction be- tween Dark Energy and Modified Gravity based on the strong and weak arXiv:1601.06133v4 [astro-ph.CO] 14 Jun 2016 equivalence principles. 1 Contents 1. INTRODUCTION ............................................................................................2 2. OVERVIEW: DARK ENERGY AND MODIFIED GRAVITY ................................................3 2.1. Dark Energy (DE).......................................................................................3 -
Quest to Settle Riddle Over Einstein's Theory May Soon Be Over 10 February 2017
Quest to settle riddle over Einstein's theory may soon be over 10 February 2017 part to play in accounting for dark energy. Without dark energy, the acceleration implies a failure of Einstein's theory of gravity across the largest distances in our Universe. Scientists from the University of Edinburgh have discovered that the puzzle could be resolved by determining the speed of gravity in the cosmos from a study of gravitational waves -space-time ripples propagating through the universe. The researchers' calculations show that if gravitational waves are found to travel at the speed Albert Einstein of light, this would rule out alternative gravity theories, with no dark energy, in support of Einstein's Cosmological Constant. If however, their speed differs from that of light, then Einstein's Astronomy experiments could soon test an idea theory must be revised. developed by Albert Einstein almost exactly a century ago, scientists say. Such an experiment could be carried out by the Laser Interferometer Gravitational-Wave Tests using advanced technology could resolve a Observatory (LIGO) in the US, whose twin longstanding puzzle over what is driving the detectors, 2000 miles apart, directly detected accelerated expansion of the Universe. gravitational waves for the first time in 2015. Researchers have long sought to determine how Experiments at the facilities planned for this year the Universe's accelerated expansion is being could resolve the question in time for the 100th driven. Calculations in a new study could help to anniversary of Einstein's Constant. explain whether dark energy- as required by Einstein's theory of general relativity - or a revised The study, published in Physics Letters B, was theory of gravity are responsible. -
Parametrizations for Tests of Gravity Is Given in Sec
August 22, 2019 0:25 WSPC/INSTRUCTION FILE parametrizations International Journal of Modern Physics D c World Scientific Publishing Company PARAMETRIZATIONS FOR TESTS OF GRAVITY LUCAS LOMBRISER D´epartement de Physique Th´eorique, Universit´ede Gen`eve, 24 quai Ansermet, CH-1211 Gen`eve 4, Switzerland Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh, EH9 3HJ, United Kingdom [email protected] Received Day Month Year Revised Day Month Year With the increasing wealth of high-quality astronomical and cosmological data and the manifold departures from General Relativity in principle conceivable, the development of generalized parameterization frameworks that unify gravitational models and cover a wide range of length scales and a variety of observational probes to enable systematic high-precision tests of gravity has been a stimulus for intensive research. A review is presented here for some of the formalisms devised for this purpose, covering the cos- mological large- and small-scale structure, the astronomical static weak-field regime as well as emission and propagation effects for gravitational waves. This includes linear and nonlinear parametrized post-Friedmannian frameworks, effective field theory approaches, the parametrized post-Newtonian expansion, the parametrized post-Einsteinian formal- ism as well as an inspiral-merger-ringdown waveform model among others. Connections between the different formalisms are highlighted where they have been established and a brief outlook is provided