Phase-Space Analysis of Teleparallel Dark Energy, We Can Now Discuss the Corresponding Cosmological Behavior
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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. -
On Dark Energy Models of Single Scalar Field
Home Search Collections Journals About Contact us My IOPscience On dark energy models of single scalar field This content has been downloaded from IOPscience. Please scroll down to see the full text. JCAP04(2012)003 (http://iopscience.iop.org/1475-7516/2012/04/003) View the table of contents for this issue, or go to the journal homepage for more Download details: IP Address: 140.112.101.4 This content was downloaded on 06/11/2014 at 07:57 Please note that terms and conditions apply. ournal of Cosmology and Astroparticle Physics JAn IOP and SISSA journal On dark energy models of single scalar field JCAP04(2012)003 Mingzhe Li,a,f Taotao Qiu,b,c Yifu Caid and Xinmin Zhange aDepartment of Physics, Nanjing University, Nanjing 210093, P.R. China bDepartment of Physics and Center for Theoretical Sciences, National Taiwan University, Taipei 10617, Taiwan cLeung Center for Cosmology and Particle Astrophysics, National Taiwan University, Taipei 106, Taiwan dDepartment of Physics, Arizona State University, Tempe, AZ 85287, U.S.A. eInstitute of High Energy Physics, Chinese Academy of Sciences, P.O. Box 918-4, Beijing 100049, P.R. China f Joint Center for Particle, Nuclear Physics and Cosmology, Nanjing University — Purple Mountain Observatory, Nanjing 210093, P.R. China E-mail: [email protected], [email protected], [email protected], [email protected] Received January 2, 2012 Accepted March 7, 2012 Published April 2, 2012 Abstract. In this paper we revisit the dynamical dark energy model building based on single scalar field involving higher derivative terms. By imposing a degenerate condition on the higher derivatives in curved spacetime, one can select the models which are free from the ghost mode and the equation of state is able to cross the cosmological constant boundary smoothly, dynamically violate the null energy condition. -
Cosmología De Tiempo Tardío Para Un Campo Escalar Con
Cosmolog´ıa de Tiempo Tard´ıo para un Campo Escalar con Acoplamientos Cinetico´ y de Gauss-Bonnet Edwin Loaiza Acuna˜ Tesis doctoral presentada como requisito parcial para optar al t´ıtulo de Doctor en Ciencias - F´ısica Director: Luis Norberto Granda Velasquez´ Universidad del Valle Facultad de Ciencias Naturales y Exactas Programa Academico´ de postgrado en F´ısica Julio 2016 Abstract In this thesis we study late-time cosmological solutions for a scalar field model with kinetic coupling to curvature and the scalar field coupled to the Gauss-Bonnet inva- riant, in order to explain the late-time accelerated expansion of the universe. Initially, exact cosmological solutions that show the phases of decelerated expansion, accelera- ted expansion and transition to the phantom phase have been found. These phases are necessary for the satisfactory explanation of the early inflation, and the current acce- lerated (super accelerated) expansion of the universe. These solutions have been found by imposing appropriate restrictions on the Gauss-Bonnet and kinetic couplings, ba- sed on the asimptotic limits of the Friedmann equations. Solutions with Big Rip and without Big Rip singularities have been studied. An especific choice of the Gauss- Bonnet coupling, where the squared of the Hubble parameter is proportional to the kinetic term, allows the reconstruction of the model for an appropriate cosmological evolution. The new found solution can describe the three cosmological phases that go from the power-law expansion, that describes a matter dominated universe, to the scalar field dominated phantom phase. For this solution and according to the values of the equation of state parameter during di↵erent epochs, the parameters of the solution can be adjusted in order to obtain di↵erent scenarios with and without Big Rip singularities. -
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]. -
Spinor Quintom Cosmology with Intrinsic Spin
Hindawi Publishing Corporation Advances in High Energy Physics Volume 2016, Article ID 3740957, 10 pages http://dx.doi.org/10.1155/2016/3740957 Research Article Spinor Quintom Cosmology with Intrinsic Spin Emre Dil DepartmentofPhysics,SinopUniversity,Korucuk,57000Sinop,Turkey Correspondence should be addressed to Emre Dil; [email protected] Received 5 October 2016; Revised 5 November 2016; Accepted 7 November 2016 Academic Editor: Dandala R. K. Reddy Copyright © 2016 Emre Dil. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The publication of this article was funded by SCOAP3. We consider a spinor quintom dark energy model with intrinsic spin, in the framework of Einstein-Cartan-Sciama-Kibble theory. After constructing the mathematical formalism of the model, we obtain the spin contributed total energy-momentum tensor giving the energy density and the pressure of the quintom model, and then we find the equation of state parameter, Hubble parameter, deceleration parameter, state finder parameter, and some distance parameter in terms of the spinor potential. Choosing suitable potentials leads to the quintom scenario crossing between quintessence and phantom epochs, or vice versa. Analyzing three quintom scenarios provides stable expansion phases avoiding Big Rip singularities and yielding matter dominated era through the stabilization of the spinor pressure via spin contribution. The stabilization in spinor pressure leads to neglecting it as compared to the increasing energy density and constituting a matter dominated stable expansion epoch. 1. Introduction which is also named as a ghost [17]. -
Dark Energy (De) and Expanding Universe(Eu) an Augmentation -Detrition Model
International Journal of Scientific and Research Publications, Volume 2, Issue 6, June 2012 1 ISSN 2250-3153 DARK ENERGY (DE) AND EXPANDING UNIVERSE(EU) AN AUGMENTATION -DETRITION MODEL 1DR K N PRASANNA KUMAR, 2PROF B S KIRANAGI AND 3 PROF C S BAGEWADI ABSTRACT: A system of dark energy-expanding universe is investigated. It is shown that the time independence of the contributions portrays another system by itself and constitutes the equilibrium solution of the original time independent system. With the methodology reinforced and revitalized with the explanations, we write the governing equations with the nomenclature for the systems in the foregoing. Further papers extensively draw inferences upon such concatenation process, ipso facto,fait accompli desideratum. INDEX TERMS: Dark Energy, Expanding Universe ,Empty Space, Repulsive Force INTRODUCTION: In physical cosmology, astronomy and celestial mechanics, dark energy is a hypothetical form of energy that permeates all of space and tends to accelerate the expansion of the universe. Dark energy is the most accepted hypothesis to explain observations since the 1990s that indicate that the universe is expanding at an accelerating rate. In the standard model of cosmology, dark energy currently accounts for 73% of the total mass-energy of the universe. At the UK-Germany National Astronomy Meeting NAM2012, the Baryon Oscillation Spectroscopic Survey (BOSS) team has just announced the most accurate measurement yet of the distribution of galaxies between five and six billion years ago. This was the key 'pivot' moment at which the expansion of the universe stopped slowing down due to gravity and started to accelerate instead, due to a mysterious force dubbed "dark energy." The nature of this "dark energy" is one of the big mysteries in cosmology today, and scientists need precise measurements of the expansion history of the universe to unravel this mystery -- BOSS provides this kind of data. -
Quintom Potential from Quantum Anisotropic Cosmological Models
Provisional chapter Chapter 9 Quintom Potential from Quantum Anisotropic CosmologicalQuintom Potential Models from Quantum Anisotropic Cosmological Models J. Socorro, Paulo A. Rodríguez , O. Núñez-Soltero, J.Rafael Socorro, Hernández Paulo and A. AbrahamRodríguez, Espinoza-García O. Núñez-Soltero, Rafael Hernández and Abraham Espinoza-García Additional information is available at the end of the chapter Additional information is available at the end of the chapter http://dx.doi.org/10.5772/52054 1. Introduction At the present time, there are some paradigms to explain the observations for the accelerated expansion of the universe. Most of these paradigms are based on the dynamics of a scalar (quintessence) or multiscalar field (quintom) cosmological models of dark energy, (see the ′ review [1–3]). The main discussion yields over the evolution of these models in the ω-ω plane (ω is the equation of state parameter of the dark energy) [4–12, 14–19, 21–25]). In the present study we desire to perform our investigation in the case of quintom cosmology, constructed using both quintessence (σ) and phantom (φ) fields, mantaining a nonspecific potential form V(φ, σ). There are many works in the literature that deals with this type of problems, but in a general way, and not with a particular ansatz, one that considers dynamical systems [12, 13, 20]. One special class of potentials used to study this behaviour corresponds to the case of the exponential potentials [4, 6, 9, 26, 28] for each field, where the corresponding energy density of a scalar field has the range of scaling behaviors [29, 30], i.e, −m it scales exactly as a power of the scale factor like, ρφ ∝ a , when the dominant component has an energy density which scales in a similar way. -
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. -
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.