Quantum Physics and Beyond

Transcription

1 Physics 120 John Harris 1

2 Physics 120 Announcements / Issues Quiz next week at beginning of class Covers everything up through last week s class (see next 2 slides), through Reading assignments including that assigned last week for today Homework 1-2, and 3 Lessons 1, 2, 3, 4 40 minutes, 6 8 questions similar to those in homework Questions require short answers (no more than 2-3 sentences unless noted) Example question: Why is the creation of equal amounts of matter and antimatter a problem in our understanding of the Universe? Examples of acceptable answers: Physicists would have expected matter and antimatter to be created in equal amounts because the laws of physics appear to treat particles and antiparticles in the same way (symmetry). or The Universe started out as pure energy before any particles were created and by the (conservation) laws of physics when energy converts into matter (E = mc 2 ) equal amounts of matter and anti-matter must be created from pure energy. Discussion/Study Session Wednesday 3:30 PM John Harris 2

3 Physics 120 Next Week s Quiz Covers 1. Readings & Homework (1-2, 3): John Harris 3

4 Physics 120 Next Week s Quiz Covers 2. Readings & Homework (1-2, 3): Lesson Notes 1 4: John Harris 4

5 Physics 120 Outline of Today s Lesson From Last Week s Reading: Quantum Tunneling and Inflation Review: Critical Energy Density of the Universe Epochs of the Big Bang, Particles and Forces Today s Lesson Alternative View(s) of Inflation Gravitational Waves LIGO LIGO & Virgo Results John Harris 5

6 Quantum Tunneling & Inflation 1/22/2018 John John Harris Harris 6 6

7 Tunneling A Quantum Mechanical Phenomenon Particle in a potential well Seeks lowest energy state could be a vacuum state Classically will be at bottom of well Can be in higher states (excited) Quantum Mechanics Probability to be at different places Probability distribution shown Note can be outside well Origin of Tunneling Has been observed But probability extremely small John Harris 7

8 False Vacuum Real vacuum state in early Universe? Energy minimum False vacuum state? Local minimum Tunneling From false to real vacuum state Quantum probability John Harris 8

9 Symmetry Breaking John Harris 9

10 Inflation A Few Things to Discuss & Know from the Reading Trefil s use of the Higgs Field, it should be read as Inflaton Field Not the Higgs as we now know it today Similar properties creates mass in the Universe (more later when we study the Higgs that has been discovered at CERN!) Energy tied up in the Higgs Field meaning Inflaton Field Inflationary Universe Radius of curvature expands exponentially Inflationary Universe doubles size 70 times in seconds: 2 70 size expansion No inflation doubles size 8 times in seconds: 2 3 size expansion Most of the mass of the Universe is created after tunneling out of the False Vacuum! John Harris 10

11 Inflation John Harris 11

12 Critical Density of the Universe The gravitational effect of matter is to curve space. The fate of the Universe is controlled by the density of the matter within it. A closed Universe has a high density and ultimately re-collapses. Thus, parallel light rays converge at an extremely distant point. This is referred to as a spherical geometry. An open Universe has low density and continues to expand forever, but at a decreasing rate. Here, parallel light rays ultimately diverge. This is referred to as hyperbolic geometry. A flat Universe has exactly the critical density and its expansion is halted only after an infinite time. Light rays remain parallel This is referred to as a flat geometry. Locally parallel lines converge Locally parallel lines diverge Locally parallel lines diverge The critical density (ρ c ) the average density of matter required for the Universe to halt its expansion after an infinite time aka a flat Universe. John Harris 12

13 Critical Density of Universe The critical density (ρ c ) the average density of matter required for the Universe to halt its expansion after an infinite time aka a flat Universe is approximately kg/m 3 (or 10 hydrogen atoms per cubic meter) and given by where H is the Hubble constant and G is Newton s gravitational constant. To calculate use: 3H 2 ρ c = 8πG An accounting approach: estimate mass of objects in a large volume of the Universe. Suffers from lack of knowledge of the amount of dark matter. But, can use the luminous to dark matter ratio to estimate the total mass in the volume. A geometrical approach: use the concept of converging/diverging parallel lines. If the Universe is closed and the parallel lines converge, the observed density of distant galaxies should be less than that expected by extrapolating the local density of galaxies backwards in time. If the Universe is open, the diverging parallel lines would cause the observed density of distant galaxies to be greater than expected. Both approaches give values for the density of the Universe consistent with the critical density ρ c = kg/m 3. So, it seems that we are precisely at ρ c and live in a flat Universe. John Harris 13

14 Time Things to Know About the Big Bang & its Epochs/Eras Temperature s Which Force(s) Freeze? Planck Time GUT Era s Freezes Electroweak Era Which particles? s Freeze Quark Era 10-5 s 3 minutes 380,000 yrs Freeze Particle Era Form Form Yale Physics 120 1/28/2019 John Harris 14

15 An Exercise the Big Bang & its Epochs/Eras Time Temperature s, GeV Fermions (leptons, quarks) Bosons (X-particles, W & Z bosons, gluons, photons) Planck Time GUT Era s, GeV s, 100 GeV Weak & EM Forces Freeze Quark Era Strong, EW Forces Freeze Electroweak Era Fermions, Bosons (W & Z bosons, gluons, photons) 10-5 s, 0.15 GeV 3 minutes 380,000 yrs Quarks freeze into particles Particle Era Nuclei form Atoms form particles Fermions (quarks, leptons), Bosons John Harris 15

16 From Lesson 2 the CMB The Planck Satellite Mission Link: Informational [but boring narration]! Yale Physics 120 1/18/2019 John Harris 16

17 Brief Diversion Things to Know about Fields 1/22/2018 John John Harris Harris 17 17

18 What is a Field? Review Let s take as an example the Electric Field of a point particle! Electric field provides the force F a test particle with charge q will experience in the field divided by the test particle s charge. John Harris 18

19 Field Maps and Force Lines Force field lines of isolated + charge & isolated charge. Place + & charge near each other. John Harris 19

20 Alternative View(s) on Inflation 1/22/2018 John John Harris Harris 20 20

21 Another look at Inflation Pop Goes the Universe, Sci. Am. Feb John Harris 21

22 The String Landscape Energy of each configuration differs Most stable configurations will emerge. Different physical laws in each minimum. John Harris 22

23 Back to Gravity & Gravitation Waves 1/22/2018 John John Harris Harris 23 23

24 Gravity - the Force We Think We Know Gravitational force equation What we can see and feel Everyday life, solar system What we can see but cannot imagine Pulsars etc. What we cannot see Gravity Gravitons (or gravity waves) The Force We Want to Get to Know Better A Problem with Gravity Instantaneous Action of Newtonian Gravity (film clip) What is gravity? Is it a force? If not, what might it be? John Harris 24

25 Black Hole Apocalypse Segments from Black Hole Apocalypse Intro: min LIGO: 4:15 10:30 LIGO observations: 1:34:25 1:49 Black Hole merger 1:49:00 Neutron star merger 1:50:00 1:51 drama John Harris 25

26 Gravitational Waves 1916 Albert Einstein General Theory of Relativity space + time = spacetime large amounts of mass or energy distorts spacetime first confirmation by Arthur Eddington in 1919 massive object shifts apparent position of a star GR predicted gravitational waves John Harris 26

27 What are Gravitational Waves? Details for Reference Ripples in the fabric of space-time Produced by violent events in the Universe e.g. collision of two black holes - or - the cores of supernova explosions. Gravitational waves emitted by accelerating masses analogous to EM waves produced by accelerating charges. These ripples in space-time travel to Earth, bringing information about violent origins, nature of gravity. Have only recently been detected! Influence of gravitational waves (1993 Nobel Prize Physics) Joseph Taylor & Russel Hulse discovered/studied pulsar with radio telescope (timing of pulsars) Neutron binary star system (10 6 miles separation) m1 = 1.4 m m2 = 1.36 m Prediction from General Relativity - orbits spiral inward by 3 mm/orbit - decrease in orbit period flash 17 / s 76 millionths of sec/year orbit 8 hours John Harris 27

28 Some Types of Gravitational Waves Types of Signals Generated Continuous or periodic Inspiral (see Black hole binary merger simulation) Stochastic Burst (could be coincident with EM signals, neutrinos) John Harris 28

29 Some Types of Gravitational Waves Types of Signals Generated Continuous or periodic Single spinning super dense compact objects e.g. rotating neutron star pulsar Inspiral (see Black hole binary merger simulation) Compact binary inspiralling objects e.g. neutron star binary, BH binary, BH-neutron star binary Stochastic Random small waves from various events Could be from Big Bang, relic waves, small background waves Burst (could be coincident with EM signals, neutrinos) Random small waves from various events Supernovae collapses,. John Harris 29

30 Electromagnetic Waves & Polarization (of Light) An oscillating charge produces an EM wave (light) which is a transverse wave Linearly-polarized (or just polarized) light! y E z B What is the orientation of E & B from a light source? A light source emits light from atoms which are randomly oriented. All transverse directions Polaroid lenses (sun glasses)? block horizontally polarized light - mostly reflected z Unpolarized light! y E, B John Harris 30

31 Search for Polarization of Gravitational Waves Early Universe density fluctuations appear only as E-mode polarization. Inflationary gravitational waves would have B-mode polarization. John Harris 31

32 Short Digression Wave Interference Review Interference occurs for all waves e.g. water, sound & light (gravitational waves) Constructive Interference Destructive Interference John Harris 32

33 Laser Interferometer Gravitational-Wave Observatory (LIGO) Hanford Observatory Livingston Observatory John Harris 33

34 Laser Interferometer Gravitational-Wave Observatory (LIGO) LIGO Interferometers vacuum suspended, seismically isolated monitor laser various optics 10 W 6-7 W 200 mw 4 km photodetector Data John Harris 34

35 Discovery of Gravitational Waves Announced! February 11, 2016, New York Times article (and many articles & newscasts around the world): Go to video at: Observation of Gravitational Waves from a Binary Black Hole Merger Physical Review Letter journal article by B. P. Abbott et al.* (LIGO Scientific Collaboration and Virgo Collaboration) published 11 February 2016 John Harris 35

36 Discovery of Gravitational Waves Announced! Observation of Gravitational Waves from a Binary Black Hole Merger Physical Review Letter journal article by B. P. Abbott et al.* (LIGO Scientific Collaboration and Virgo Collaboration), 11 February 2016 John Harris 36

37 Discovery of Gravity Waves Announced! John Harris 37

38 Physics 120 Binary Neutron Star Merger Play Video at: John Harris 38

39 Gravitational Wave Results So Far John Harris 39

40 Binary Neutron Star Merger GW On August 17, 2017, two neutron stars were observed to merge by the LIGO and VIRGO gravitational wave observatories. Short gamma-ray bursts were detected independently by the Fermi and Integral spacecrafts. Follow-up investigations detected this event at x-ray, UV, visible, infrared and radio wavelengths. Future information: deformability, equation of state of dense nuclear matter (states?), other properties (e.g. speed of sound) John Harris 40

41 Gravitational Waves in Space LISA - three spacecrafts, each with a Y-shaped payload, form an equilateral triangle with sides 5 million km in length. John Harris 41

42 Physics 120 Reading Assignment for next week 1) The Moment of Creation, J. Trefil: p (elementary particles and quarks) 2) In Search of Schödinger s Cat by John Gribbin, p Quiz next week John Harris 42