Modified Newtonian Gravity, Wide Binaries and the Tully-Fisher Relation
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The Philosophy of Physics
The Philosophy of Physics ROBERTO TORRETTI University of Chile PUBLISHED BY THE PRESS SYNDICATE OF THE UNIVERSITY OF CAMBRIDGE The Pitt Building, Trumpington Street, Cambridge, United Kingdom CAMBRIDGE UNIVERSITY PRESS The Edinburgh Building, Cambridge CB2 2RU, UK www.cup.cam.ac.uk 40 West 20th Street, New York, NY 10011-4211, USA www.cup.org 10 Stamford Road, Oakleigh, Melbourne 3166, Australia Ruiz de Alarcón 13, 28014, Madrid, Spain © Roberto Torretti 1999 This book is in copyright. Subject to statutory exception and to the provisions of relevant collective licensing agreements, no reproduction of any part may take place without the written permission of Cambridge University Press. First published 1999 Printed in the United States of America Typeface Sabon 10.25/13 pt. System QuarkXPress [BTS] A catalog record for this book is available from the British Library. Library of Congress Cataloging-in-Publication Data is available. 0 521 56259 7 hardback 0 521 56571 5 paperback Contents Preface xiii 1 The Transformation of Natural Philosophy in the Seventeenth Century 1 1.1 Mathematics and Experiment 2 1.2 Aristotelian Principles 8 1.3 Modern Matter 13 1.4 Galileo on Motion 20 1.5 Modeling and Measuring 30 1.5.1 Huygens and the Laws of Collision 30 1.5.2 Leibniz and the Conservation of “Force” 33 1.5.3 Rømer and the Speed of Light 36 2 Newton 41 2.1 Mass and Force 42 2.2 Space and Time 50 2.3 Universal Gravitation 57 2.4 Rules of Philosophy 69 2.5 Newtonian Science 75 2.5.1 The Cause of Gravity 75 2.5.2 Central Forces 80 2.5.3 Analytical -
Gravitational Anomaly and Hawking Radiation of Apparent Horizon in FRW Universe
Eur. Phys. J. C (2009) 62: 455–458 DOI 10.1140/epjc/s10052-009-1081-4 Letter Gravitational anomaly and Hawking radiation of apparent horizon in FRW universe Ran Lia, Ji-Rong Renb, Shao-Wen Wei Institute of Theoretical Physics, Lanzhou University, Lanzhou 730000, Gansu, China Received: 27 February 2009 / Published online: 26 June 2009 © Springer-Verlag / Società Italiana di Fisica 2009 Abstract Motivated by the successful applications of the have been carried out [8–28]. In fact, the anomaly analy- anomaly cancellation method to derive Hawking radiation sis can be traced back to Christensen and Fulling’s early from various types of black hole spacetimes, we further work [29], in which they suggested that there exists a rela- extend the gravitational anomaly method to investigate the tion between the Hawking radiation and the anomalous trace Hawking radiation from the apparent horizon of a FRW uni- of the field under the condition that the covariant conser- verse by assuming that the gravitational anomaly also exists vation law is valid. Imposing boundary condition near the near the apparent horizon of the FRW universe. The result horizon, Wilczek et al. showed that Hawking radiation is shows that the radiation flux from the apparent horizon of just the cancel term of the gravitational anomaly of the co- the FRW universe measured by a Kodama observer is just variant conservation law and gauge invariance. Their basic the pure thermal flux. The result presented here will further idea is that, near the horizon, a quantum field in a black hole confirm the thermal properties of the apparent horizon in a background can be effectively described by an infinite col- FRW universe. -
Chiral Currents from Anomalies
ω2 α 2 ω1 α1 Michael Stone (ICMT ) Chiral Currents Santa-Fe July 18 2018 1 Chiral currents from Anomalies Michael Stone Institute for Condensed Matter Theory University of Illinois Santa-Fe July 18 2018 Michael Stone (ICMT ) Chiral Currents Santa-Fe July 18 2018 2 Michael Stone (ICMT ) Chiral Currents Santa-Fe July 18 2018 3 Experiment aims to verify: k ρσαβ r T µν = F µνJ − p r [F Rνµ ]; µ µ 384π2 −g µ ρσ αβ k µνρσ k µνρσ r J µ = − p F F − p Rα Rβ ; µ 32π2 −g µν ρσ 768π2 −g βµν αρσ Here k is number of Weyl fermions, or the Berry flux for a single Weyl node. Michael Stone (ICMT ) Chiral Currents Santa-Fe July 18 2018 4 What the experiment measures Contribution to energy current for 3d Weyl fermion with H^ = σ · k µ2 1 J = B + T 2 8π2 24 Simple explanation: The B field makes B=2π one-dimensional chiral fermions per unit area. These have = +k Energy current/density from each one-dimensional chiral fermion: Z 1 d 1 µ2 1 J = − θ(−) = 2π + T 2 β(−µ) 2 −∞ 2π 1 + e 8π 24 Could even have been worked out by Sommerfeld in 1928! Michael Stone (ICMT ) Chiral Currents Santa-Fe July 18 2018 5 Are we really exploring anomaly physics? Michael Stone (ICMT ) Chiral Currents Santa-Fe July 18 2018 6 Yes! Michael Stone (ICMT ) Chiral Currents Santa-Fe July 18 2018 7 Energy-Momentum Anomaly k ρσαβ r T µν = F µνJ − p r [F Rνµ ]; µ µ 384π2 −g µ ρσ αβ Michael Stone (ICMT ) Chiral Currents Santa-Fe July 18 2018 8 Origin of Gravitational Anomaly in 2 dimensions Set z = x + iy and use conformal coordinates ds2 = expfφ(z; z¯)gdz¯ ⊗ dz Example: non-chiral scalar field '^ has central charge c = 1 and energy-momentum operator is T^(z) =:@z'@^ z'^: Actual energy-momentum tensor is c T = T^(z) + @2 φ − 1 (@ φ)2 zz 24π zz 2 z c T = T^(¯z) + @2 φ − 1 (@ φ)2 z¯z¯ 24π z¯z¯ 2 z¯ c T = − @2 φ zz¯ 24π zz¯ z z¯ Now Γzz = @zφ, Γz¯z¯ = @z¯φ, all others zero. -
Dark Energy and Dark Matter As Inertial Effects Introduction
Dark Energy and Dark Matter as Inertial Effects Serkan Zorba Department of Physics and Astronomy, Whittier College 13406 Philadelphia Street, Whittier, CA 90608 [email protected] ABSTRACT A disk-shaped universe (encompassing the observable universe) rotating globally with an angular speed equal to the Hubble constant is postulated. It is shown that dark energy and dark matter are cosmic inertial effects resulting from such a cosmic rotation, corresponding to centrifugal (dark energy), and a combination of centrifugal and the Coriolis forces (dark matter), respectively. The physics and the cosmological and galactic parameters obtained from the model closely match those attributed to dark energy and dark matter in the standard Λ-CDM model. 20 Oct 2012 Oct 20 ph] - PACS: 95.36.+x, 95.35.+d, 98.80.-k, 04.20.Cv [physics.gen Introduction The two most outstanding unsolved problems of modern cosmology today are the problems of dark energy and dark matter. Together these two problems imply that about a whopping 96% of the energy content of the universe is simply unaccounted for within the reigning paradigm of modern cosmology. arXiv:1210.3021 The dark energy problem has been around only for about two decades, while the dark matter problem has gone unsolved for about 90 years. Various ideas have been put forward, including some fantastic ones such as the presence of ghostly fields and particles. Some ideas even suggest the breakdown of the standard Newton-Einstein gravity for the relevant scales. Although some progress has been made, particularly in the area of dark matter with the nonstandard gravity theories, the problems still stand unresolved. -
Wimps and Machos ENCYCLOPEDIA of ASTRONOMY and ASTROPHYSICS
WIMPs and MACHOs ENCYCLOPEDIA OF ASTRONOMY AND ASTROPHYSICS WIMPs and MACHOs objects that could be the dark matter and still escape detection. For example, if the Galactic halo were filled –3 . WIMP is an acronym for weakly interacting massive par- with Jupiter mass objects (10 Mo) they would not have ticle and MACHO is an acronym for massive (astrophys- been detected by emission or absorption of light. Brown . ical) compact halo object. WIMPs and MACHOs are two dwarf stars with masses below 0.08Mo or the black hole of the most popular DARK MATTER candidates. They repre- remnants of an early generation of stars would be simi- sent two very different but reasonable possibilities of larly invisible. Thus these objects are examples of what the dominant component of the universe may be. MACHOs. Other examples of this class of dark matter It is well established that somewhere between 90% candidates include primordial black holes created during and 99% of the material in the universe is in some as yet the big bang, neutron stars, white dwarf stars and vari- undiscovered form. This material is the gravitational ous exotic stable configurations of quantum fields, such glue that holds together galaxies and clusters of galaxies as non-topological solitons. and plays an important role in the history and fate of the An important difference between WIMPs and universe. Yet this material has not been directly detected. MACHOs is that WIMPs are non-baryonic and Since extensive searches have been done, this means that MACHOS are typically (but not always) formed from this mysterious material must not emit or absorb appre- baryonic material. -
Foundations of Newtonian Dynamics: an Axiomatic Approach For
Foundations of Newtonian Dynamics: 1 An Axiomatic Approach for the Thinking Student C. J. Papachristou 2 Department of Physical Sciences, Hellenic Naval Academy, Piraeus 18539, Greece Abstract. Despite its apparent simplicity, Newtonian mechanics contains conceptual subtleties that may cause some confusion to the deep-thinking student. These subtle- ties concern fundamental issues such as, e.g., the number of independent laws needed to formulate the theory, or, the distinction between genuine physical laws and deriva- tive theorems. This article attempts to clarify these issues for the benefit of the stu- dent by revisiting the foundations of Newtonian dynamics and by proposing a rigor- ous axiomatic approach to the subject. This theoretical scheme is built upon two fun- damental postulates, namely, conservation of momentum and superposition property for interactions. Newton’s laws, as well as all familiar theorems of mechanics, are shown to follow from these basic principles. 1. Introduction Teaching introductory mechanics can be a major challenge, especially in a class of students that are not willing to take anything for granted! The problem is that, even some of the most prestigious textbooks on the subject may leave the student with some degree of confusion, which manifests itself in questions like the following: • Is the law of inertia (Newton’s first law) a law of motion (of free bodies) or is it a statement of existence (of inertial reference frames)? • Are the first two of Newton’s laws independent of each other? It appears that -
Scientists Observe Gravitational Anomaly on Earth 21 July 2017
Scientists observe gravitational anomaly on Earth 21 July 2017 strange that they named this phenomenon an "anomaly." For most of their history, these quantum anomalies were confined to the world of elementary particle physics explored in huge accelerator laboratories such as Large Hadron Collider at CERN in Switzerland. Now however, a new type of materials, the so-called Weyl semimetals, similar to 3-D graphene, allow us to put the symmetry destructing quantum anomaly to work in everyday phenomena, such as the creation of electric current. In these exotic materials electrons effectively behave in the very same way as the elementary Prof. Dr. Karl Landsteiner, a string theorist at the particles studied in high energy accelerators. These Instituto de Fisica Teorica UAM/CSIC and co-author of particles have the strange property that they cannot the paper made this graphic to explain the gravitational be at rest—they have to move with a constant speed anomaly. Credit: IBM Research at all times. They also have another property called spin. It is like a tiny magnet attached to the particles and they come in two species. The spin can either point in the direction of motion or in the opposite Modern physics has accustomed us to strange and direction. counterintuitive notions of reality—especially quantum physics which is famous for leaving physical objects in strange states of superposition. For example, Schrödinger's cat, who finds itself unable to decide if it is dead or alive. Sometimes however quantum mechanics is more decisive and even destructive. Symmetries are the holy grail for physicists. -
Dark Matter and the Early Universe: a Review Arxiv:2104.11488V1 [Hep-Ph
Dark matter and the early Universe: a review A. Arbey and F. Mahmoudi Univ Lyon, Univ Claude Bernard Lyon 1, CNRS/IN2P3, Institut de Physique des 2 Infinis de Lyon, UMR 5822, 69622 Villeurbanne, France Theoretical Physics Department, CERN, CH-1211 Geneva 23, Switzerland Institut Universitaire de France, 103 boulevard Saint-Michel, 75005 Paris, France Abstract Dark matter represents currently an outstanding problem in both cosmology and particle physics. In this review we discuss the possible explanations for dark matter and the experimental observables which can eventually lead to the discovery of dark matter and its nature, and demonstrate the close interplay between the cosmological properties of the early Universe and the observables used to constrain dark matter models in the context of new physics beyond the Standard Model. arXiv:2104.11488v1 [hep-ph] 23 Apr 2021 1 Contents 1 Introduction 3 2 Standard Cosmological Model 3 2.1 Friedmann-Lema^ıtre-Robertson-Walker model . 4 2.2 A quick story of the Universe . 5 2.3 Big-Bang nucleosynthesis . 8 3 Dark matter(s) 9 3.1 Observational evidences . 9 3.1.1 Galaxies . 9 3.1.2 Galaxy clusters . 10 3.1.3 Large and cosmological scales . 12 3.2 Generic types of dark matter . 14 4 Beyond the standard cosmological model 16 4.1 Dark energy . 17 4.2 Inflation and reheating . 19 4.3 Other models . 20 4.4 Phase transitions . 21 5 Dark matter in particle physics 21 5.1 Dark matter and new physics . 22 5.1.1 Thermal relics . 22 5.1.2 Non-thermal relics . -
Small Scale Problems of the CDM Model
galaxies Article Small Scale Problems of the LCDM Model: A Short Review Antonino Del Popolo 1,2,3,* and Morgan Le Delliou 4,5,6 1 Dipartimento di Fisica e Astronomia, University of Catania , Viale Andrea Doria 6, 95125 Catania, Italy 2 INFN Sezione di Catania, Via S. Sofia 64, I-95123 Catania, Italy 3 International Institute of Physics, Universidade Federal do Rio Grande do Norte, 59012-970 Natal, Brazil 4 Instituto de Física Teorica, Universidade Estadual de São Paulo (IFT-UNESP), Rua Dr. Bento Teobaldo Ferraz 271, Bloco 2 - Barra Funda, 01140-070 São Paulo, SP Brazil; [email protected] 5 Institute of Theoretical Physics Physics Department, Lanzhou University No. 222, South Tianshui Road, Lanzhou 730000, Gansu, China 6 Instituto de Astrofísica e Ciências do Espaço, Universidade de Lisboa, Faculdade de Ciências, Ed. C8, Campo Grande, 1769-016 Lisboa, Portugal † [email protected] Academic Editors: Jose Gaite and Antonaldo Diaferio Received: 30 May 2016; Accepted: 9 December 2016; Published: 16 February 2017 Abstract: The LCDM model, or concordance cosmology, as it is often called, is a paradigm at its maturity. It is clearly able to describe the universe at large scale, even if some issues remain open, such as the cosmological constant problem, the small-scale problems in galaxy formation, or the unexplained anomalies in the CMB. LCDM clearly shows difficulty at small scales, which could be related to our scant understanding, from the nature of dark matter to that of gravity; or to the role of baryon physics, which is not well understood and implemented in simulation codes or in semi-analytic models. -
A Unifying Theory of Dark Energy and Dark Matter: Negative Masses and Matter Creation Within a Modified ΛCDM Framework J
Astronomy & Astrophysics manuscript no. theory_dark_universe_arxiv c ESO 2018 November 5, 2018 A unifying theory of dark energy and dark matter: Negative masses and matter creation within a modified ΛCDM framework J. S. Farnes1; 2 1 Oxford e-Research Centre (OeRC), Department of Engineering Science, University of Oxford, Oxford, OX1 3QG, UK. e-mail: [email protected]? 2 Department of Astrophysics/IMAPP, Radboud University, PO Box 9010, NL-6500 GL Nijmegen, the Netherlands. Received February 23, 2018 ABSTRACT Dark energy and dark matter constitute 95% of the observable Universe. Yet the physical nature of these two phenomena remains a mystery. Einstein suggested a long-forgotten solution: gravitationally repulsive negative masses, which drive cosmic expansion and cannot coalesce into light-emitting structures. However, contemporary cosmological results are derived upon the reasonable assumption that the Universe only contains positive masses. By reconsidering this assumption, I have constructed a toy model which suggests that both dark phenomena can be unified into a single negative mass fluid. The model is a modified ΛCDM cosmology, and indicates that continuously-created negative masses can resemble the cosmological constant and can flatten the rotation curves of galaxies. The model leads to a cyclic universe with a time-variable Hubble parameter, potentially providing compatibility with the current tension that is emerging in cosmological measurements. In the first three-dimensional N-body simulations of negative mass matter in the scientific literature, this exotic material naturally forms haloes around galaxies that extend to several galactic radii. These haloes are not cuspy. The proposed cosmological model is therefore able to predict the observed distribution of dark matter in galaxies from first principles. -
On the Origin of the Inertia: the Modified Newtonian Dynamics Theory
CORE Metadata, citation and similar papers at core.ac.uk Provided by Repositori Obert UdL ON THE ORIGIN OF THE INERTIA: THE MODIFIED NEWTONIAN DYNAMICS THEORY JAUME GINE¶ Abstract. The sameness between the inertial mass and the grav- itational mass is an assumption and not a consequence of the equiv- alent principle is shown. In the context of the Sciama's inertia theory, the sameness between the inertial mass and the gravita- tional mass is discussed and a certain condition which must be experimentally satis¯ed is given. The inertial force proposed by Sciama, in a simple case, is derived from the Assis' inertia the- ory based in the introduction of a Weber type force. The origin of the inertial force is totally justi¯ed taking into account that the Weber force is, in fact, an approximation of a simple retarded potential, see [18, 19]. The way how the inertial forces are also derived from some solutions of the general relativistic equations is presented. We wonder if the theory of inertia of Assis is included in the framework of the General Relativity. In the context of the inertia developed in the present paper we establish the relation between the constant acceleration a0, that appears in the classical Modi¯ed Newtonian Dynamics (M0ND) theory, with the Hubble constant H0, i.e. a0 ¼ cH0. 1. Inertial mass and gravitational mass The gravitational mass mg is the responsible of the gravitational force. This fact implies that two bodies are mutually attracted and, hence mg appears in the Newton's universal gravitation law m M F = G g g r: r3 According to Newton, inertia is an inherent property of matter which is independent of any other thing in the universe. -
Dark Energy and Dark Matter
Dark Energy and Dark Matter Jeevan Regmi Department of Physics, Prithvi Narayan Campus, Pokhara [email protected] Abstract: The new discoveries and evidences in the field of astrophysics have explored new area of discussion each day. It provides an inspiration for the search of new laws and symmetries in nature. One of the interesting issues of the decade is the accelerating universe. Though much is known about universe, still a lot of mysteries are present about it. The new concepts of dark energy and dark matter are being explained to answer the mysterious facts. However it unfolds the rays of hope for solving the various properties and dimensions of space. Keywords: dark energy, dark matter, accelerating universe, space-time curvature, cosmological constant, gravitational lensing. 1. INTRODUCTION observations. Precision measurements of the cosmic It was Albert Einstein first to realize that empty microwave background (CMB) have shown that the space is not 'nothing'. Space has amazing properties. total energy density of the universe is very near the Many of which are just beginning to be understood. critical density needed to make the universe flat The first property that Einstein discovered is that it is (i.e. the curvature of space-time, defined in General possible for more space to come into existence. And Relativity, goes to zero on large scales). Since energy his cosmological constant makes a prediction that is equivalent to mass (Special Relativity: E = mc2), empty space can possess its own energy. Theorists this is usually expressed in terms of a critical mass still don't have correct explanation for this but they density needed to make the universe flat.