Temporal Naturalism: Time and Laws in Cosmology
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Emergence and Phenomenology in Quantum Gravity
Emergence and Phenomenology in Quantum Gravity by Isabeau Premont-Schwarz´ A thesis presented to the University of Waterloo in fulfillment of the thesis requirement for the degree of Doctor of Philosophy in Physics Waterloo, Ontario, Canada, 2010 © Isabeau Premont-Schwarz´ 2010 AUTHOR’S DECLARATION I hereby declare that I am the sole author of this thesis. This is a true copy of the thesis, including any required final revisions, as accepted by my examiners. I understand that my thesis may be made electronically available to the public. ii AUTHORSHIP STATEMENT This thesis is based on the following five articles: • A. Hamma, F. Markopoulou, I. Pr´emont-Schwarz and S. Severini, “Lieb-Robinson bounds and the speed of light from topological order,” Phys. Rev. Lett. 102 (2009) 017204 [arXiv:0808.2495 [quant-ph]]. • I. Pr´emont-Schwarz ,A. Hamma, I. Klich and F. Markopoulou, “Lieb-Robinson bounds for commutator-bounded operators ,” Phys. Rev. A 81, 040102(R) (2010) .[arXiv:0912.4544 [quant-ph]]. • I. Pr´emont-Schwarz and J. Hnybida, “Lieb-Robinson bounds with dependence on interaction strengths, ” [arXiv:1002.4190 [math-ph]]. • L. Modesto and I. Pr´emont-Schwarz, “Self-dual Black Holes in LQG: Theory and Phenomenology,” Phys. Rev. D 80, 064041 (2009) [arXiv:0905.3170 [hep-th]]. • S. Hossenfelder, L. Modesto and I. Pr´emont-Schwarz, “A model for non-singular black hole collapse and evaporation ,” Phys. Rev. D 81, 044036 (2010) [arXiv:0912.1823 [gr-qc]]. I did the majority of the work in the first article, but the project was initiated by Fotini Markopoulou-Kalamara and Alioscia Hamma and the manuscript was mostly written by Alioscia Hamma. -
What Can We Learn from Shape Dynamics? International Loop Quantum Gravity Seminar
What can we learn from shape dynamics? International Loop Quantum Gravity Seminar Tim A. Koslowski University of New Brunswick, Fredericton, NB, Canada November 12, 2013 Tim A. Koslowski (UNB) What can we learn from shape dynamics? November 12, 2013 1 / 19 Outline 1 Motivation from 2+1 diemsnional qunatum gravity to consider conformal evolution as fundamental 2 Conformal evolution is different from spacetime (i.e. abandon spacetime) 3 Generic dynamical emergence of spacetime in the presence of matter (i.e. regain spacetime) Tim A. Koslowski (UNB) What can we learn from shape dynamics? November 12, 2013 2 / 19 Introduction and Motivation Tim A. Koslowski (UNB) What can we learn from shape dynamics? November 12, 2013 3 / 19 Motivation Canonical metric path integral in 2+1 (only known metric path integral) ab p necessary: 2+1 split and CMC gauge condition gabπ − t g = 0 R 2 ab R ab a pπ c i dtd x(_gabπ −S(N)−H(ξ)) Z = [dgab][dπ ][dN][dξ ]δ[ g − t]δ[F ] det[FP ]e R 2 A R A i dtd x(_τAp −Vo(τ;p;t)) = [dτA][dp ]e [Carlip: CQG 12 (1995) 2201, Seriu PRD 55 (1997) 781] where: τA are Teichm¨ullerparameters, Vo(τ; p; t) denotes on-shell volume, which depends explicitly on time t ) QM on Teichm¨ullerspace, phys. Hamilt. Vo(τ; p; t) [Moncrief: JMP 30 (1989) 2907] Fradkin-Vilkovisky theorem: [cf. Henneaux/Teitelboim: \Quantization of Gauge Systems"] \Partition function depends on gauge fixing cond. only through the gauge equivalence class of gauge fixing conditions." for a discussion and some examples of non-equivalence [see Govaerts, Scholtz: J.Phys. -
The Metaphysical Baggage of Physics Lee Smolin Argues That Life Is More
The Metaphysical Baggage of Physics Lee Smolin argues that life is more fundamental than physical laws. BY MICHAEL SEGAL ILLUSTRATION BY LOUISA BERTMAN JANUARY 30, 2014 An issue on tme would not be complete without a conversaton with Lee Smolin. High school dropout, theoretcal physicist, and founding member of the Perimeter Insttute for Theoretcal Physics in Waterloo, Canada, Smolin’s life and work refect many of the values of this magazine. Constantly probing the edges of physics, he has also pushed beyond them, into economics and the philosophy of science, and into popular writng. Not one to shy away from a confrontaton, his 2008 bookThe Trouble with Physicstook aim at string theory, calling one of the hotest developments in theoretcal physics of the past 50 years a dead end. In his thinking on tme too, he has taken a diferent tack from the mainstream, arguing that the fow of tme is not just real, but more fundamental than physical law. He spoke to me on the phone from his home in Toronto. How long have you been thinking about tme? The whole story starts back in the ’80s when I was puzzling over the failure of string theory to uniquely tell us the principles that determine what the laws of physics are. I challenged myself to invent a way that nature might select what the laws of physics turned out to be. I invented a hypothesis called Cosmological Natural Selecton, which was testable, which made explicit predictons. This wasn’t my main day job; my main day job was working on quantum gravity where it’s assumed that tme is unreal, that tme is an illusion, and I was working, like anybody else, on the assumpton that tme is an illusion for most of my career. -
A Singing, Dancing Universe Jon Butterworth Enjoys a Celebration of Mathematics-Led Theoretical Physics
SPRING BOOKS COMMENT under physicist and Nobel laureate William to the intensely scrutinized narrative on the discovery “may turn out to be the greatest Henry Bragg, studying small mol ecules such double helix itself, he clarifies key issues. He development in the field of molecular genet- as tartaric acid. Moving to the University points out that the infamous conflict between ics in recent years”. And, on occasion, the of Leeds, UK, in 1928, Astbury probed the Wilkins and chemist Rosalind Franklin arose scope is too broad. The tragic figure of Nikolai structure of biological fibres such as hair. His from actions of John Randall, head of the Vavilov, the great Soviet plant geneticist of the colleague Florence Bell took the first X-ray biophysics unit at King’s College London. He early twentieth century who perished in the diffraction photographs of DNA, leading to implied to Franklin that she would take over Gulag, features prominently, but I am not sure the “pile of pennies” model (W. T. Astbury Wilkins’ work on DNA, yet gave Wilkins the how relevant his research is here. Yet pulling and F. O. Bell Nature 141, 747–748; 1938). impression she would be his assistant. Wilkins such figures into the limelight is partly what Her photos, plagued by technical limitations, conceded the DNA work to Franklin, and distinguishes Williams’s book from others. were fuzzy. But in 1951, Astbury’s lab pro- PhD student Raymond Gosling became her What of those others? Franklin Portugal duced a gem, by the rarely mentioned Elwyn assistant. It was Gosling who, under Franklin’s and Jack Cohen covered much the same Beighton. -
Shape Dynamics
Shape Dynamics Tim A. Koslowski Abstract Barbour’s formulation of Mach’s principle requires a theory of gravity to implement local relativity of clocks, local relativity of rods and spatial covariance. It turns out that relativity of clocks and rods are mutually exclusive. General Relativity implements local relativity of clocks and spatial covariance, but not local relativity of rods. It is the purpose of this contribution to show how Shape Dynamics, a theory that is locally equivalent to General Relativity, implements local relativity of rods and spatial covariance and how a BRST formulation, which I call Doubly General Relativity, implements all of Barbour’s principles. 1 Introduction A reflection on Mach’s principle lead Barbour to postulate that rods and spatial frames of reference should be locally determined by a procedure that he calls “best matching,” while clocks should be locally determined by what he calls “objective change.” (For more, see [1].) More concretely, Barbour’s principles postulate lo- cal time reparametrization invariance, local spatial conformal invariance and spatial covariance. The best matching algorithm for spatial covariance and local spatial conformal invariance turns out to be equivalent to the imposition of linear diffeo- morphism and conformal constraints Z Z 3 ab 3 H(x) = d xp (Lx g)ab; C(r) = d xr p; (1) S S Tim A. Koslowski Perimeter Institute for Theoretical Physics, 31 Caroline St. N, Waterloo, Ontario, Canada New address: Department of Mathematics and Statistics, University of New Brunswick Fredericton, New Brunswick E3B 5A3, Canada e-mail: [email protected] 1 2 Tim A. -
Sabine Hossenfelder on “The Case Against Beauty in Physics” Julia
Rationally Speaking #211: Sabine Hossenfelder on “The case against beauty in physics” Julia: Welcome to Rationally Speaking, the podcast where we explore the borderlands between reason and nonsense. I'm your host, Julia Galef, and I'm here with today's guest, Sabine Hossenfelder. Sabine is a theoretical physicist, focusing on quantum gravity. She's a research fellow at the Frankfurt Institute for Advanced Studies, and blogs at Back Reaction. She just published the book, "Lost in Math: How Beauty Leads Physics Astray." "Lost in Math” argues that physicists, in at least certain sub-fields, evaluate theories based heavily on aesthetics, like is this theory beautiful? Instead of simply, what does the evidence suggest is true? The book is full of interviews Sabine did with top physicists, where she tries to ask them: what's the justification for this? Why should we expect beauty to be a good guide to truth? And, spoiler alert, ultimately, she comes away rather unsatisfied with the answers. So, we're going to talk about "Lost in Math" and the case for and against beauty in physics. Sabine, welcome to the show. Sabine: Hello. Julia: So, probably best to start with: what do you mean by beauty, in this context? And is it closer to a kind of “beauty is in the eye of the beholder” thing, like, every physicist has their own sort of aesthetic sense? Or is more like there's a consensus among physicists about what constitutes a beautiful theory? Sabine: Interestingly enough, there's mostly consensus about it. Let me put ahead that I will not try to tell anyone what beauty means, I am just trying to summarize what physicists seem to mean when they speak of beauty, when they say “that theory is beautiful.” There are several ingredients to this sense of beauty. -
On the Axioms of Causal Set Theory
On the Axioms of Causal Set Theory Benjamin F. Dribus Louisiana State University [email protected] November 8, 2013 Abstract Causal set theory is a promising attempt to model fundamental spacetime structure in a discrete order-theoretic context via sets equipped with special binary relations, called causal sets. The el- ements of a causal set are taken to represent spacetime events, while its binary relation is taken to encode causal relations between pairs of events. Causal set theory was introduced in 1987 by Bombelli, Lee, Meyer, and Sorkin, motivated by results of Hawking and Malament relating the causal, conformal, and metric structures of relativistic spacetime, together with earlier work on discrete causal theory by Finkelstein, Myrheim, and 't Hooft. Sorkin has coined the phrase, \order plus number equals geometry," to summarize the causal set viewpoint regarding the roles of causal structure and discreteness in the emergence of spacetime geometry. This phrase represents a specific version of what I refer to as the causal metric hypothesis, which is the idea that the properties of the physical universe, and in particular, the metric properties of classical spacetime, arise from causal structure at the fundamental scale. Causal set theory may be expressed in terms of six axioms: the binary axiom, the measure axiom, countability, transitivity, interval finiteness, and irreflexivity. The first three axioms, which fix the physical interpretation of a causal set, and restrict its \size," appear in the literature either implic- itly, or as part of the preliminary definition of a causal set. The last three axioms, which encode the essential mathematical structure of a causal set, appear in the literature as the irreflexive formula- tion of causal set theory. -
BEYOND SPACE and TIME the Secret Network of the Universe: How Quantum Geometry Might Complete Einstein’S Dream
BEYOND SPACE AND TIME The secret network of the universe: How quantum geometry might complete Einstein’s dream By Rüdiger Vaas With the help of a few innocuous - albeit subtle and potent - equations, Abhay Ashtekar can escape the realm of ordinary space and time. The mathematics developed specifically for this purpose makes it possible to look behind the scenes of the apparent stage of all events - or better yet: to shed light on the very foundation of reality. What sounds like black magic, is actually incredibly hard physics. Were Albert Einstein alive today, it would have given him great pleasure. For the goal is to fulfil the big dream of a unified theory of gravity and the quantum world. With the new branch of science of quantum geometry, also called loop quantum gravity, Ashtekar has come close to fulfilling this dream - and tries thereby, in addition, to answer the ultimate questions of physics: the mysteries of the big bang and black holes. "On the Planck scale there is a precise, rich, and discrete structure,” says Ashtekar, professor of physics and Director of the Center for Gravitational Physics and Geometry at Pennsylvania State University. The Planck scale is the smallest possible length scale with units of the order of 10-33 centimeters. That is 20 orders of magnitude smaller than what the world’s best particle accelerators can detect. At this scale, Einstein’s theory of general relativity fails. Its subject is the connection between space, time, matter and energy. But on the Planck scale it gives unreasonable values - absurd infinities and singularities. -
A Realist Vision of the Quantum World
A realist's vision of the quantum world Kragh, Helge Stjernholm Published in: American Scientist Publication date: 2019 Document version Publisher's PDF, also known as Version of record Document license: Unspecified Citation for published version (APA): Kragh, H. S. (2019). A realist's vision of the quantum world. American Scientist, 107, 374-376. https://www.americanscientist.org/article/a-realist-vision-of-the-quantum-world Download date: 24. sep.. 2021 A reprint from American Scientist the magazine of Sigma Xi, The Scientific Research Honor Society This reprint is provided for personal and noncommercial use. For any other use, please send a request to Permissions, American Scientist, P.O. Box 13975, Research Triangle Park, NC, 27709, U.S.A., or by electronic mail to [email protected]. ©Sigma Xi, The Scientific Research Hornor Society and other rightsholders Scientists’ Nightstand has been the most successful theory of nature, and quantum mechanics The Scientists’ Nightstand, A Realist Vision precludes the sort of realism to which American Scientist’s books of the Quantum Smolin aspires. He describes three dif- section, offers reviews, review ferent kinds of anti-realists: The radical essays, brief excerpts, and more. World anti-realists, such as Niels Bohr, who For additional books coverage, believe that the properties we ascribe please see our Science Culture Helge Kragh to atoms and elementary particles are blog channel, which explores EINSTEIN’S UNFINISHED REVOLUTION: not inherent in them but are created by how science intersects with other The Search for What Lies Beyond the our interactions with them and exist areas of knowledge, entertain- Quantum. -
Annual Report 2013 NARODOWE CENTRUM BADAŃ JĄDROWYCH NATIONAL CENTRE for NUCLEAR RESEARCH
Annual Report 2013 NARODOWE CENTRUM BADAŃ JĄDROWYCH NATIONAL CENTRE FOR NUCLEAR RESEARCH ANNUAL REPORT 2013 PL-05-400 Otwock-Świerk, POLAND tel.: 048 22 718 00 01 fax: 048 22 779 34 81 e-mail: [email protected] http://www.ncbj.gov.pl Editors: N. Keeley K. Kurek Cover design: S. Mirski Secretarial work and layout: G. Swiboda ISSN 2299-2960 Annual Report 2013 3 CONTENTS FOREWORD ............................................................................................................................................................ 5 I. GENERAL INFORMATION ................................................................................................... 7 1. LOCATIONS ...................................................................................................................... 7 2. MANAGEMENT OF THE INSTITUTE ............................................................................ 7 3. SCIENTIFIC COUNCIL ..................................................................................................... 8 4. MAIN RESEARCH ACTIVITIES ................................................................................... 11 5. SCIENTIFIC STAFF OF THE INSTITUTE .................................................................... 13 6. VISITING SCIENTISTS .................................................................................................. 15 7. PARTICIPATION IN NATIONAL CONSORTIA AND SCIENTIFIC NETWORKS .. 23 8. DEGREES ........................................................................................................................ -
A Natural Introduction to Fine-Tuning
A Natural Introduction to Fine-Tuning Julian De Vuyst ∗ Department of Physics & Astronomy, Ghent University, Krijgslaan, S9, 9000 Ghent, Belgium Abstract A well-known topic within the philosophy of physics is the problem of fine-tuning: the fact that the universal constants seem to take non-arbitrary values in order for live to thrive in our Universe. In this paper we will talk about this problem in general, giving some examples from physics. We will review some solutions like the design argument, logical probability, cosmological natural selection, etc. Moreover, we will also discuss why it's dangerous to uphold the Principle of Naturalness as a scientific principle. After going through this paper, the reader should have a general idea what this problem exactly entails whenever it is mentioned in other sources and we recommend the reader to think critically about these concepts. arXiv:2012.05617v1 [physics.hist-ph] 10 Dec 2020 ∗[email protected] 1 Contents 1 Introduction3 2 A Take on Constants3 2.I The Role of Units . .4 2.II Derived vs Fundamental Constants . .5 3 The Concept of Naturalness6 3.I Technical Naturalness . .6 3.I.a A Wilsonian Perspective . .6 3.I.b A Brief History . .8 3.II Numerical/General Naturalness . .9 4 The Fine-Tuning Problem9 5 Some Examples from Physics 10 5.I The Cosmological Constant Problem . 10 5.II The Flatness Problem . 11 5.III The Higgs Mass . 12 5.IV The Strong CP Problem . 13 6 Resolutions to Fine-Tuning 14 6.I We are here, full stop . 14 6.II Designed like Clockwork . -
A Direction of Time in Time-Symmetric Electrodynamics
COLUMBIA UNIVERSITY MASTER’S THESIS A Direction of Time in Time-Symmetric Electrodynamics Author: Supervisor: Kathleen TATEM Dr. Erick WEINBERG A thesis submitted in fulfillment of the requirements for the degree of Master of Arts in the Philosophical Foundations of Physics Graduate School of Arts and Sciences May 17, 2017 ii In grateful memory of my mentor, Dr. John M. J. Madey. iii Columbia University Abstract Departments of Physics and Philosophy Graduate School of Arts and Sciences Master of Arts A Direction of Time in Time-Symmetric Electrodynamics by Kathleen TATEM This thesis introduces a recent analytical verification which is of significance to the philosophical debate on the direction of time in the case of electromagnetic radiation. I give an overview of a the problem of the direction of time in thermodynamics, as well as how it is solved with the Past Hypothesis, a hypothesis that the macrostate of the universe at the moment of the Big Bang was an extremely low-entropy state. I also describe the standard accepted textbook solution to the radiation problem, as well as an alternative time-symmetric theory presented by Feynman and Wheeler that had historically been considered less favorable to physicists. Analytical ver- ification supports that time-symmetric accounts of radiation such as Feynman and Wheeler’s theory are needed for radiation fields to comply with energy conservation and the fundamental equations of electromagnetism. I describe two other philo- sophical accounts of the direction of time in radiation theory, and then argue that proposed experiments based on this recent analytical result can help us rule out some of the alternative philosophical proposals on the origin of the direction of time in radiation theory.