Dark Energy: Is Itjust'einstein's Cosmological Constant Lambda?
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The State of the Multiverse: the String Landscape, the Cosmological Constant, and the Arrow of Time
The State of the Multiverse: The String Landscape, the Cosmological Constant, and the Arrow of Time Raphael Bousso Center for Theoretical Physics University of California, Berkeley Stephen Hawking: 70th Birthday Conference Cambridge, 6 January 2011 RB & Polchinski, hep-th/0004134; RB, arXiv:1112.3341 The Cosmological Constant Problem The Landscape of String Theory Cosmology: Eternal inflation and the Multiverse The Observed Arrow of Time The Arrow of Time in Monovacuous Theories A Landscape with Two Vacua A Landscape with Four Vacua The String Landscape Magnitude of contributions to the vacuum energy graviton (a) (b) I Vacuum fluctuations: SUSY cutoff: ! 10−64; Planck scale cutoff: ! 1 I Effective potentials for scalars: Electroweak symmetry breaking lowers Λ by approximately (200 GeV)4 ≈ 10−67. The cosmological constant problem −121 I Each known contribution is much larger than 10 (the observational upper bound on jΛj known for decades) I Different contributions can cancel against each other or against ΛEinstein. I But why would they do so to a precision better than 10−121? Why is the vacuum energy so small? 6= 0 Why is the energy of the vacuum so small, and why is it comparable to the matter density in the present era? Recent observations Supernovae/CMB/ Large Scale Structure: Λ ≈ 0:4 × 10−121 Recent observations Supernovae/CMB/ Large Scale Structure: Λ ≈ 0:4 × 10−121 6= 0 Why is the energy of the vacuum so small, and why is it comparable to the matter density in the present era? The Cosmological Constant Problem The Landscape of String Theory Cosmology: Eternal inflation and the Multiverse The Observed Arrow of Time The Arrow of Time in Monovacuous Theories A Landscape with Two Vacua A Landscape with Four Vacua The String Landscape Many ways to make empty space Topology and combinatorics RB & Polchinski (2000) I A six-dimensional manifold contains hundreds of topological cycles. -
The Multiverse: Conjecture, Proof, and Science
The multiverse: conjecture, proof, and science George Ellis Talk at Nicolai Fest Golm 2012 Does the Multiverse Really Exist ? Scientific American: July 2011 1 The idea The idea of a multiverse -- an ensemble of universes or of universe domains – has received increasing attention in cosmology - separate places [Vilenkin, Linde, Guth] - separate times [Smolin, cyclic universes] - the Everett quantum multi-universe: other branches of the wavefunction [Deutsch] - the cosmic landscape of string theory, imbedded in a chaotic cosmology [Susskind] - totally disjoint [Sciama, Tegmark] 2 Our Cosmic Habitat Martin Rees Rees explores the notion that our universe is just a part of a vast ''multiverse,'' or ensemble of universes, in which most of the other universes are lifeless. What we call the laws of nature would then be no more than local bylaws, imposed in the aftermath of our own Big Bang. In this scenario, our cosmic habitat would be a special, possibly unique universe where the prevailing laws of physics allowed life to emerge. 3 Scientific American May 2003 issue COSMOLOGY “Parallel Universes: Not just a staple of science fiction, other universes are a direct implication of cosmological observations” By Max Tegmark 4 Brian Greene: The Hidden Reality Parallel Universes and The Deep Laws of the Cosmos 5 Varieties of Multiverse Brian Greene (The Hidden Reality) advocates nine different types of multiverse: 1. Invisible parts of our universe 2. Chaotic inflation 3. Brane worlds 4. Cyclic universes 5. Landscape of string theory 6. Branches of the Quantum mechanics wave function 7. Holographic projections 8. Computer simulations 9. All that can exist must exist – “grandest of all multiverses” They can’t all be true! – they conflict with each other. -
Modified Standard Einstein's Field Equations and the Cosmological
Issue 1 (January) PROGRESS IN PHYSICS Volume 14 (2018) Modified Standard Einstein’s Field Equations and the Cosmological Constant Faisal A. Y. Abdelmohssin IMAM, University of Gezira, P.O. BOX: 526, Wad-Medani, Gezira State, Sudan Sudan Institute for Natural Sciences, P.O. BOX: 3045, Khartoum, Sudan E-mail: [email protected] The standard Einstein’s field equations have been modified by introducing a general function that depends on Ricci’s scalar without a prior assumption of the mathemat- ical form of the function. By demanding that the covariant derivative of the energy- momentum tensor should vanish and with application of Bianchi’s identity a first order ordinary differential equation in the Ricci scalar has emerged. A constant resulting from integrating the differential equation is interpreted as the cosmological constant introduced by Einstein. The form of the function on Ricci’s scalar and the cosmologi- cal constant corresponds to the form of Einstein-Hilbert’s Lagrangian appearing in the gravitational action. On the other hand, when energy-momentum is not conserved, a new modified field equations emerged, one type of these field equations are Rastall’s gravity equations. 1 Introduction term in his standard field equations to represent a kind of “anti ff In the early development of the general theory of relativity, gravity” to balance the e ect of gravitational attractions of Einstein proposed a tensor equation to mathematically de- matter in it. scribe the mutual interaction between matter-energy and Einstein modified his standard equations by introducing spacetime as [13] a term to his standard field equations including a constant which is called the cosmological constant Λ, [7] to become Rab = κTab (1.1) where κ is the Einstein constant, Tab is the energy-momen- 1 Rab − gabR + gabΛ = κTab (1.6) tum, and Rab is the Ricci curvature tensor which represents 2 geometry of the spacetime in presence of energy-momentum. -
Copyrighted Material
ftoc.qrk 5/24/04 1:46 PM Page iii Contents Timeline v de Sitter,Willem 72 Dukas, Helen 74 Introduction 1 E = mc2 76 Eddington, Sir Arthur 79 Absentmindedness 3 Education 82 Anti-Semitism 4 Ehrenfest, Paul 85 Arms Race 8 Einstein, Elsa Löwenthal 88 Atomic Bomb 9 Einstein, Mileva Maric 93 Awards 16 Einstein Field Equations 100 Beauty and Equations 17 Einstein-Podolsky-Rosen Besso, Michele 18 Argument 101 Black Holes 21 Einstein Ring 106 Bohr, Niels Henrik David 25 Einstein Tower 107 Books about Einstein 30 Einsteinium 108 Born, Max 33 Electrodynamics 108 Bose-Einstein Condensate 34 Ether 110 Brain 36 FBI 113 Brownian Motion 39 Freud, Sigmund 116 Career 41 Friedmann, Alexander 117 Causality 44 Germany 119 Childhood 46 God 124 Children 49 Gravitation 126 Clothes 58 Gravitational Waves 128 CommunismCOPYRIGHTED 59 Grossmann, MATERIAL Marcel 129 Correspondence 62 Hair 131 Cosmological Constant 63 Heisenberg, Werner Karl 132 Cosmology 65 Hidden Variables 137 Curie, Marie 68 Hilbert, David 138 Death 70 Hitler, Adolf 141 iii ftoc.qrk 5/24/04 1:46 PM Page iv iv Contents Inventions 142 Poincaré, Henri 220 Israel 144 Popular Works 222 Japan 146 Positivism 223 Jokes about Einstein 148 Princeton 226 Judaism 149 Quantum Mechanics 230 Kaluza-Klein Theory 151 Reference Frames 237 League of Nations 153 Relativity, General Lemaître, Georges 154 Theory of 239 Lenard, Philipp 156 Relativity, Special Lorentz, Hendrik 158 Theory of 247 Mach, Ernst 161 Religion 255 Mathematics 164 Roosevelt, Franklin D. 258 McCarthyism 166 Russell-Einstein Manifesto 260 Michelson-Morley Experiment 167 Schroedinger, Erwin 261 Millikan, Robert 171 Solvay Conferences 265 Miracle Year 174 Space-Time 267 Monroe, Marilyn 179 Spinoza, Baruch (Benedictus) 268 Mysticism 179 Stark, Johannes 270 Myths and Switzerland 272 Misconceptions 181 Thought Experiments 274 Nazism 184 Time Travel 276 Newton, Isaac 188 Twin Paradox 279 Nobel Prize in Physics 190 Uncertainty Principle 280 Olympia Academy 195 Unified Theory 282 Oppenheimer, J. -
Cosmic Microwave Background
1 29. Cosmic Microwave Background 29. Cosmic Microwave Background Revised August 2019 by D. Scott (U. of British Columbia) and G.F. Smoot (HKUST; Paris U.; UC Berkeley; LBNL). 29.1 Introduction The energy content in electromagnetic radiation from beyond our Galaxy is dominated by the cosmic microwave background (CMB), discovered in 1965 [1]. The spectrum of the CMB is well described by a blackbody function with T = 2.7255 K. This spectral form is a main supporting pillar of the hot Big Bang model for the Universe. The lack of any observed deviations from a 7 blackbody spectrum constrains physical processes over cosmic history at redshifts z ∼< 10 (see earlier versions of this review). Currently the key CMB observable is the angular variation in temperature (or intensity) corre- lations, and to a growing extent polarization [2–4]. Since the first detection of these anisotropies by the Cosmic Background Explorer (COBE) satellite [5], there has been intense activity to map the sky at increasing levels of sensitivity and angular resolution by ground-based and balloon-borne measurements. These were joined in 2003 by the first results from NASA’s Wilkinson Microwave Anisotropy Probe (WMAP)[6], which were improved upon by analyses of data added every 2 years, culminating in the 9-year results [7]. In 2013 we had the first results [8] from the third generation CMB satellite, ESA’s Planck mission [9,10], which were enhanced by results from the 2015 Planck data release [11, 12], and then the final 2018 Planck data release [13, 14]. Additionally, CMB an- isotropies have been extended to smaller angular scales by ground-based experiments, particularly the Atacama Cosmology Telescope (ACT) [15] and the South Pole Telescope (SPT) [16]. -
Annual Review 2011/12
UCL DEPARTMENT OF PHYSICS AND ASTRONOMY PHYSICS AND ASTRONOMY 2011–12 ANNUAL REVIEW PHYSICS AND ASTRONOMY ANNUAL REVIEW 2011–12 Contents Welcome It is an honour to write this WELCOME 1 introduction standing, to misquote Newton, on the shoulders of giants. COMMUNITY FOCUS 3 Jonathan Tennyson finished his Teaching Lowdown 4 tenure as Head of Department in September 2011 and so the majority Student Accolades 4 of the material contained in this Outstanding PhD Theses Published 5 Review records achievements under his leadership. In addition, Tony Career Profiles 6 Harker is currently acting as Head of Science in Action 8 Department in many matters and will continue to do so until October 2012. Alumni Matters 9 This is due to my on-going commitments with the ATLAS experiment on the ACADEMIC SHOWCASE 11 Large Hadron Collider (LHC) at CERN. Staff Accolades 12 I currently spend a large amount of my time in Geneva and I am very grateful Academic Appointments 14 to both Tony and Jonathan, as well as to other members of staff for helping Doctor of Philosophy (PhD) 15 to make this transition a success. In Portrait of Dr Phil Jones 16 particular I would also like to thank Hilary Wigmore as Departmental Manager and Raman Prinja as the new Director of RESEARCH SPOTLIGHT 17 Teaching for their continued support. Atomic, Molecular, Optical and Position Physics (AMOPP) 19 High Energy Physics (HEP) 21 “Success in such long- Condensed Matter and term, high-impact projects Materials Physics (CMMP) 25 requires sustained vision Astrophysics (Astro) 29 and dedicated work by Biological Physics (BioP) 33 excellent scientists over Research Statistics 35 many years.” Staff Snapshot 38 Underpinning this success is the outstanding quality of scientific research and education within the Department. -
The Cosmological Constant Problem Philippe Brax
The Cosmological constant problem Philippe Brax To cite this version: Philippe Brax. The Cosmological constant problem. Contemporary Physics, Taylor & Francis, 2004, 45, pp.227-236. 10.1080/00107510410001662286. hal-00165345 HAL Id: hal-00165345 https://hal.archives-ouvertes.fr/hal-00165345 Submitted on 25 Jul 2007 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. The Cosmological Constant Problem Ph. Brax1a a Service de Physique Th´eorique CEA/DSM/SPhT, Unit´e de recherche associ´ee au CNRS, CEA-Saclay F-91191 Gif/Yvette cedex, France Abstract Observational evidence seems to indicate that the expansion of the universe is currently accelerating. Such an acceleration strongly suggests that the content of the universe is dominated by a non{clustered form of matter, the so{called dark energy. The cosmological constant, introduced by Einstein to reconcile General Relativity with a closed and static Universe, is the most likely candidate for dark energy although other options such as a weakly interacting field, also known as quintessence, have been proposed. The fact that the dark energy density is some one hundred and twenty orders of magnitude lower than the energy scales present in the early universe constitutes the cosmological constant problem. -
The Practical Use of Cosmic Shear As a Probe of Gravity
The Practical use of Cosmic Shear as a Probe of Gravity Donnacha Kirk Thesis submitted for the Degree of Doctor of Philosophy of the University College London Department of Physics & Astronomy UNIVERSITY COLLEGE LONDON April 2011 I, Donnacha Kirk, confirm that the work presented in this thesis is my own. Where information has been derived from other sources, I confirm that this has been indicated in the thesis. Specifically: • The work on luminosity functions and red galaxy fractions in section 2.7 was done by Dr. Michael Schneider (then at Durham) as part of our collaboration on the paper Kirk et al. (2010). • The work in chapters 3 & 4 is my contribution to, and will form the substantial part of, papers in preparation with collaborators Prof. Rachel Bean and Istvan Lazslo at Cornell University. The MG effect on the linear growth function was computed by Istvan Lazslo. • The Great08 section of chapter 6 draws on my contributions to the Great08 Handbook (Bridle et al. 2009), Great08 Results Paper (Bridle et al. 2010a) and Great10 Handbook (Kitching et al. 2010). To Mum and Dad, for everything. Boyle. ... an’ it blowed, an’ blowed – blew is the right word, Joxer, but blowed is what the sailors use... Joxer. Aw, it’s a darlin’ word, a daarlin’ word. Boyle. An’, as it blowed an’ blowed, I often looked up at the sky an’ assed meself the question – what is the stars, what is the stars? Voice of Coal Vendor. Any blocks, coal-blocks; blocks, coal-blocks! Joxer. Ah, that’s the question, that’s the question – what is the stars? Boyle. -
Sum of the Masses of the Milky Way and M31: a Likelihood-Free Inference Approach Pablo Lemos, Niall Jeffrey, Lorne Whiteway, Ofer Lahav, Noam I
Sum of the masses of the Milky Way and M31: A likelihood-free inference approach Pablo Lemos, Niall Jeffrey, Lorne Whiteway, Ofer Lahav, Noam I. Libeskind, Yehuda Hoffman To cite this version: Pablo Lemos, Niall Jeffrey, Lorne Whiteway, Ofer Lahav, Noam I. Libeskind, et al.. Sum ofthe masses of the Milky Way and M31: A likelihood-free inference approach. Phys.Rev.D, 2021, 103 (2), pp.023009. 10.1103/PhysRevD.103.023009. hal-02999468 HAL Id: hal-02999468 https://hal.archives-ouvertes.fr/hal-02999468 Submitted on 26 Apr 2021 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. PHYSICAL REVIEW D 103, 023009 (2021) Sum of the masses of the Milky Way and M31: A likelihood-free inference approach Pablo Lemos ,1,* Niall Jeffrey ,2,1 Lorne Whiteway ,1 Ofer Lahav,1 Noam Libeskind I,3,4 and Yehuda Hoffman5 1Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom 2Laboratoire de Physique de l’Ecole Normale Sup´erieure, ENS, Universit´e PSL, CNRS, Sorbonne Universit´e, Universit´e de Paris, Paris, France 3Leibniz-Institut -
Teleparallel Gravity and Its Modifications
View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by UCL Discovery University College London Department of Mathematics PhD Thesis Teleparallel gravity and its modifications Author: Supervisor: Matthew Aaron Wright Christian G. B¨ohmer Thesis submitted in fulfilment of the requirements for the degree of PhD in Mathematics February 12, 2017 Disclaimer I, Matthew Aaron Wright, confirm that the work presented in this thesis, titled \Teleparallel gravity and its modifications”, is my own. Parts of this thesis are based on published work with co-authors Christian B¨ohmerand Sebastian Bahamonde in the following papers: • \Modified teleparallel theories of gravity", Sebastian Bahamonde, Christian B¨ohmerand Matthew Wright, Phys. Rev. D 92 (2015) 10, 104042, • \Teleparallel quintessence with a nonminimal coupling to a boundary term", Sebastian Bahamonde and Matthew Wright, Phys. Rev. D 92 (2015) 084034, • \Conformal transformations in modified teleparallel theories of gravity revis- ited", Matthew Wright, Phys.Rev. D 93 (2016) 10, 103002. These are cited as [1], [2], [3] respectively in the bibliography, and have been included as appendices. Where information has been derived from other sources, I confirm that this has been indicated in the thesis. Signed: Date: i Abstract The teleparallel equivalent of general relativity is an intriguing alternative formula- tion of general relativity. In this thesis, we examine theories of teleparallel gravity in detail, and explore their relation to a whole spectrum of alternative gravitational models, discussing their position within the hierarchy of Metric Affine Gravity mod- els. Consideration of alternative gravity models is motivated by a discussion of some of the problems of modern day cosmology, with a particular focus on the dark en- ergy problem. -
Curriculum Vitae
CURRICULUM VITAE FULL NAME: George Petros EFSTATHIOU NATIONALITY: British DATE OF BIRTH: 2nd Sept 1955 QUALIFICATIONS Dates Academic Institution Degree 10/73 to 7/76 Keble College, Oxford. B.A. in Physics 10/76 to 9/79 Department of Physics, Ph.D. in Astronomy Durham University EMPLOYMENT Dates Academic Institution Position 10/79 to 9/80 Astronomy Department, Postdoctoral Research Assistant University of California, Berkeley, U.S.A. 10/80 to 9/84 Institute of Astronomy, Postdoctoral Research Assistant Cambridge. 10/84 to 9/87 Institute of Astronomy, Senior Assistant in Research Cambridge. 10/87 to 9/88 Institute of Astronomy, Assistant Director of Research Cambridge. 10/88 to 9/97 Department of Physics, Savilian Professor of Astronomy Oxford. 10/88 to 9/94 Department of Physics, Head of Astrophysics Oxford. 10/97 to present Institute of Astronomy, Professor of Astrophysics (1909) Cambridge. 10/04 to 9/08 Institute of Astronomy, Director Cambridge. 10/08 to present Kavli Institute for Cosmology, Director Cambridge. PROFESSIONAL SOCIETIES Fellow of the Royal Society since 1994 Fellow of the Instite of Physics since 1995 Fellow of the Royal Astronomical Society 1983-2010 Member of the International Astronomical Union since 1986 Associate of the Canadian Institute of Advanced Research since 1986 1 AWARDS/Fellowships/Major Lectures 1973 Exhibition Keble College Oxford. 1975 Johnson Memorial Prize University of Oxford. 1977 McGraw-Hill Research Prize University of Durham. 1980 Junior Research Fellowship King’s College, Cambridge. 1984 Senior Research Fellowship King’s College, Cambridge. 1990 Maxwell Medal & Prize Institute of Physics. 1990 Vainu Bappu Prize Astronomical Society of India. -
Prof. Ofer Lahav: Curriculum Vitae
Prof. Ofer Lahav: Curriculum Vitae Department of Physics and Astronomy Phone: +44 (0) 20 7679 3473 University College London (UCL) Mobile: +44 (0) 7738848597 Gower Street E-mail: [email protected] London WC1E 6BT Web: www.homepages.ucl.ac.uk/~ucapola/ United Kingdom Home address: 3 Monks Close Canterbury CT2 7ET Current position Perren Chair of Astronomy Department of Physics & Astronomy, UCL Other current roles Co-Chair of the Science Committee of the international Dark Energy Survey Vice-Dean for Research, Faculty of Mathematical and Physical Sciences, UCL Holder of a European Research Council Advanced Grant (2012-2017) Date and Place of Birth: 5 April 1959; Tiberias, Israel Citizenship: Israeli and British Education University of Cambridge: Astronomy Ph.D., 1988 (Supervisors: Prof. G. Efstathiou and Prof. D. Lynden-Bell) Ben-Gurion University: Physics M.Sc., 1985 (Supervisor: Prof. J. Bekenstein) Tel-Aviv University: Physics B.Sc., 1980 Positions 2004- Perren Professor of Astronomy, UCL 2011- Vice-Dean for Research, Faculty of Mathematical and Physical Sciences, UCL 2004-2011 Head of Astrophysics, Physics & Astronomy Department, UCL 2000-2003 Reader in Cosmology, Institute of Astronomy, Cambridge University 1998-1999 on leave as Associate Professor, the Hebrew University, Jerusalem 1990-2000 Member of staff, Institute of Astronomy, Cambridge University (Senior Assistant in Research, Assistant Director of Research, Lecturer) 1989 Post-doctoral Fellow, Institute for Advanced Study, Princeton 1988-2003 Research Fellow (1988-91) and then