Institute Lecture

Total Page：16

File Type：pdf, Size：1020Kb

Institute Lecture Dark Matter, Dark Energy, Einstein's Cosmological Constant, and the Accelerating Universe Prof. Bharat Ratra, University Distinguished Professor of Physics, Kansas State University 22nd March 2017, Time: 5 PM, Venue: LH-16 Abstract Dark energy is the leading candidate for the mechanism that is responsible for causing the cosmological expansion to accelerate. Prof. Ratra will describe the astronomical data which persuade cosmologists that (as yet undetected) dark energy and dark matter are by far the main components of the energy budget of the universe at the present time. He will review how these observations have led to the development of a quantitative "standard" model of cosmology that describes the evolution of the universe from an early epoch of inflation to the complex hierarchy of structure seen today. He will also discuss the basic physics, and the history of ideas, on which this model is based. About the speaker Prof. Bharat Ratra joined Kansas State University in 1996 as an Assistant Professor of Physics, and is now a University Distinguished Professor of Physics. He was a postdoctoral fellow at Princeton University, the California Institute of Technology and the Massachusetts Institute of Technology. He earned a doctorate in physics from Stanford University and a master's degree from the Indian Institute of Technology, Delhi. He works in the areas of cosmology and astroparticle physics. He researches the structure and evolution of the universe. Two of his current principal interests are developing models for the large-scale matter and radiation distributions in the universe and testing these models by comparing predictions to observational data. In 1988, Prof. Ratra and Jim Peebles proposed the first dynamical dark energy model. Dark energy is the leading candidate for the mechanism that is responsible for causing the cosmological expansion to accelerate. The discovery that the cosmological expansion is accelerating is one of the most significant scientific discoveries of the last quarter of a century. Tea at 4.45 PM All interested are welcome. S. Ganesh Dean of Research and Development, IIT Kanpur .

Copy Link

Recommended publications

IUCAA Bulletin 2016
Editor : Editorial Assistant : Somak Raychaudhury Manjiri Mahabal ([email protected]) ([email protected]) A quarterly bulletin of the Inter-University Centre for Astronomy and Astrophysics ISSN 0972-7647 (An autonomous institution of the University Grants Commission) Available online at http://ojs.iucaa.ernet.in/ 27th IUCAA Foundation Day Lecture Introduction A Natural History of The 27th IUCAA Foundation Day Knowledge Lecture was delivered by the eminent A naturalist lives today in a world of Indian ecologist, Professor Madhav wounds, but for a connoisseur of Gadgil on December 29, 2015. Over a knowledge, ours is a golden age; the career spanning more than four decades, challenge before us is to deploy the strengths Professor Gadgil has championed the of our age to heal the wounds. Life is an effort towards the preservation of information-based, progressive and ecology in India, which includes cooperative enterprise, evolving organisms establishing the Centre for Ecological capable of handling greater and greater Sciences under the aegis of the Indian quantities, of increasingly more complex Institute of Science, Bengaluru in 1983 information, ever more effectively. Social and serving as the Head of the Western animals have taken this to new heights, with be unhappy in this as well as the nether Ghats Ecology Expert Panel of 2010, humans surpassing them, all thanks to the world. The ruling classes have always tried popularly known as the Gadgil language abilities, and the greatly enhanced to keep the populace ignorant as preached Commission. An alumnus of Harvard capacity to learn, teach, and to elaborate by Laozi, a contemporary of Buddha: The University, he is a recipient of the Padma memes, including mythologies and people are hard to rule when they have too Shri and Padma Bhushan from the scientific knowledge.
[Show full text]
Estimating the Vacuum Energy Density E
Estimating the Vacuum Energy Density E. Margan Estimating the Vacuum Energy Density - an Overview of Possible Scenarios Erik Margan Experimental Particle Physics Department, “Jožef Stefan” Institute, Ljubljana, Slovenia 1. Introduction There are several different indications that the vacuum energy density should be non-zero, each indication being based either on laboratory experiments or on astronomical observations. These include the Planck’s radiation law, the spontaneous emission of a photon by a particle in an excited state, the Casimir’s effect, the van der Waals’ bonds, the Lamb’s shift, the Davies–Unruh’s effect, the measurements of the apparent luminosity against the spectral red shift of supernovae type Ia, and more. However, attempts to find the way to measure or to calculate the value of the vacuum energy density have all either failed or produced results incompatible with observations or other confirmed theoretical results. Some of those results are theoretically implausible because of certain unrealistic assumptions on which the calculation model is based. And some theoretical results are in conflict with observations, the conflict itself being caused by certain questionable hypotheses on which the theory is based. And the best experimental evidence (the Casimir’s effect) is based on the measurement of the difference of energy density within and outside of the measuring apparatus, thus preventing in principle any numerical assessment of the actual energy density. This article presents an overview of the most important estimation methods. - 1 - Estimating the Vacuum Energy Density E. Margan - 2 - Estimating the Vacuum Energy Density E. Margan 2. Planck’s Theoretical Vacuum Energy Density The energy density of the quantum vacuum fluctuations has been estimated shortly after Max Planck (1900-1901) [1] published his findings of the spectral distribution of the ideal thermodynamic black body radiation and its dependence on the temperature of the radiating black body.
[Show full text]
Kipac Annual Report 2017
KIPAC ANNUAL REPORT 2017 KAVLI INSTITUTE FOR PARTICLE ASTROPHYSICS AND COSMOLOGY Contents 2 10 LZ Director 11 3 Deputy Maria Elena Directors Monzani 4 12 BICEP Array SuperCDMS 5 13 Zeeshan Noah Ahmed Kurinisky 6 14 COMAP Athena 7 15 Dongwoo Dan Wilkins Chung Adam Mantz 8 16 LSST Camera Young scientists 9 20 Margaux Lopez Solar eclipse Unless otherwise specified, all photographs credit of KIPAC. 22 Research 28 highlights Blinding it for science 22 EM counterparts 29 to gravity waves An X-ray view into black holes 23 30 Hidden knots of Examining where dark matter planets form 24 32 KIPAC together 34 Publications Galaxy dynamics and dark matter 36 KIPAC members 25 37 Awards, fellowships and doctorates H0LiCOW 38 KIPAC visitors and speakers 26 39 KIPAC alumni Simulating jets 40 Research update: DM Radio 27 South Pole 41 On the cover Telescope Pardon our (cosmic) dust We’re in the midst of exciting times here at the Kavli Institute for Particle Astro- physics and Cosmology. We’ve always managed to stay productive, with contri- butions big and small to a plethora of projects like the Fermi Gamma-ray Space Telescope, the Dark Energy Survey, the Nuclear Spectroscopic Telescope Array, the Gemini Planet Imager and many, many more—not to mention theory and data analysis, simulations, and research with publicly available data. We have no shortage of scientific topics to keep us occupied. But we are currently hard at work building a variety of new experimental instru- ments, and preparing to reap the benefits of some very long-range planning that will keep KIPAC scientists busy studying our universe in almost every wavelength and during almost every major epoch of the evolution of the universe, into the late 2020s and beyond.
[Show full text]
Dr. Bharat Ratra
Baylor University and CASPER present: Dr. Bharat Ratra Professor of Cosmology and Astroparticle Physics, Kansas State University Dark Matter, Dark Energy, Einstein's Cosmological Constant, and the Accelerating Universe Abstract: Dark energy is the leading candidate for the mechanism that is responsible for causing the cosmological expansion to accelerate. Dr. Ratra wilI describe the astronomical data which persuaded cosmologists that (as yet undetected) dark energy and dark matter are by far the main components of the energy budget of the universe at the present time. He will review how these observations have led to the development of a quantitative "standard" model of cosmology that describes the evolution of the universe from an early epoch of inflation to the complex hierarchy of structure seen today. He will also discuss the basic physics, and the history of ideas, on which this model is based. Dr. Ratra joined Kansas State University in 1996 as an assistant professor of physics. He was a postdoctoral fellow at Princeton University, the California Institute of Technology and the Massachusetts Institute of Technology. He earned a doctorate in physics from Stanford University and a master's degree from the Indian Institute of Technology in New Delhi. He works in the areas of cosmology and astroparticle physics. He researches the structure and evolution of the universe. Two of his current principal interests are developing models for the large-scale matter and radiation distributions in the universe and testing these models by comparing predictions to observational data. In 1988, Dr. Ratra and Jim Peebles proposed the first dynamical dark energy model.
[Show full text]
ENERGY CONDITIONS and SCALAR FIELD COSMOLOGY by SHAWN WESTMORELAND B.S., University of Texas, Austin, 2001 M.A., University of T
CORE Metadata, citation and similar papers at core.ac.uk Provided by K-State Research Exchange ENERGY CONDITIONS AND SCALAR FIELD COSMOLOGY by SHAWN WESTMORELAND B.S., University of Texas, Austin, 2001 M.A., University of Texas, Austin, 2004 Ph.D., Kansas State University, Manhattan, 2010 A REPORT submitted in partial fulfillment of the requirements for the degree MASTER OF SCIENCE Department of Physics College of Arts and Sciences KANSAS STATE UNIVERSITY Manhattan, Kansas 2013 Approved by: Major Professor Bharat Ratra Copyright Shawn Westmoreland 2013 Abstract In this report, we discuss the four standard energy conditions of General Relativity (null, weak, dominant, and strong) and investigate their cosmological consequences. We note that these energy conditions can be compatible with cosmic acceleration provided that a repulsive cosmological constant exists and the acceleration stays within certain bounds. Scalar fields and dark energy, and their relationships to the energy conditions, are also discussed. Special attention is paid to the 1988 Ratra-Peebles scalar field model, which is notable in that it provides a physical self-consistent framework for the phenomenology of dark energy. Appendix B, which is part of joint-research with Anatoly Pavlov, Khaled Saaidi, and Bharat Ratra, reports on the existence of the Ratra-Peebles scalar field tracker solution in a curvature-dominated universe, and discusses the problem of investigating the evolution of long-wavelength inhomogeneities in this solution while taking into account the gravitational back-reaction (in the linear perturbative approximation). Table of Contents List of Figures vi Acknowledgements vii Dedication viii 1 Energy conditions in classical General Relativity1 1.1 Introduction .
[Show full text]
Supernova Ia Constraints on a Time-Variable Cosmological
THE ASTROPHYSICAL JOURNAL, 532:109È117, 2000 March 20 ( 2000. The American Astronomical Society. All rights reserved. Printed in U.S.A. SUPERNOVA Ia CONSTRAINTS ON A TIME-VARIABLE COSMOLOGICAL ““ CONSTANT ÏÏ SILVIU PODARIU AND BHARAT RATRA Department of Physics, Kansas State University, Manhattan, KS 66506 Received 1999 September 2; accepted 1999 November 3 ABSTRACT The energy density of a scalar Ðeld / with potential V (/) P /~a, a[0, behaves like a time-variable cosmological constant that could contribute signiÐcantly to the present energy density. Predictions of this spatially Ñat model are compared to recent Type Ia supernova apparent magnitude versus redshift data. A large region of model parameter space is consistent with current observations. (These constraints are based on the exact scalar Ðeld model equations of motion, not on the widely used time-independent equation of state Ñuid approximation equations of motion.) We examine the consequences of also incorporating constraints from recent measurements of the Hubble parameter and the age of the uni- verse in the constant and time-variable cosmological constant models. We also study the e†ect of using a noninformative prior for the density parameter. Subject headings: cosmology: observations È large-scale structure of universe È supernovae: general 1. INTRODUCTION 4. The need for mild antibiasing to accommodate the excessive intermediate- and small-scale power predicted in Current observations are more consistent with lower- the COBE DMRÈnormalized Ñat constant-" CDM model density cosmogonies dominated by cold dark matter with a scale-invariant spectrum (see, e.g., Cole et al. 1997). (CDM). For recent discussions see, e.g., Ratra et al.
[Show full text]
2004 Newsletter
2004 Physics Newsletter Editor's Corner Mick O'Shea Greetings from the Physics Department. Our winter started out with a whimper and at the end of January winter arrived in all its glory with lots of snow and university closings occurred for a full day and part of a day. Our campus continues to change slowly. The demolition of Denison Hall will begin this spring semester. The Department of English will be moved from Denison into the old Lafene building early this spring. The name Denison will be retired and held for a possible naming of a new building in the future. A proposal, led by the KSU Foundation, calls for a hotel and parking garage to be built in the current K-State Student Union parking lots. Skyways connecting the garage to the Union. A non-binding contract has been signed with the Shaner Hotel Group to investigate the feasibility of the project. The current occupation of Iraq continues to affect the university community strongly, especially with Fort Riley so close. We all hope that the situation there will be resolved in the near future. Provost James R. Coffman, who has served as the universities chief academic officer for 16 years, will leave this post this summer. He will return to part-time work in the College of Veterinary Medicine after a sabbatical. Our new provost will be M. Duane Nellis who comes to us from West Virginia University, where he has been Dean of the college of Arts and Sciences since 1997. Duane is well known at K-state from his earlier work here as Associate Dean of the college of Arts and Sciences.
[Show full text]
Dr. Bharat Ratra, Distinguished Professor of Physics, Kansas State University Wednesday, 5 February 2020 at 2 Pm, 128 Jabara
Wichita State University Physics Seminar Series A Lecture for the Public The Accelerating Expanding Universe: Dark Matter, Dark Energy, and Einstein’s Cosmological Constant or Why Jim Peebles was Awarded Half of the 2019 Physics Nobel Prize Dr. Bharat Ratra, Distinguished Professor of Physics, Kansas State University Wednesday, 5 February 2020 at 2 pm, 128 Jabara Abstract: Dark energy is the leading candidate for the mechanism that is responsible for causing the cosmological expansion to accelerate. In this non-technical talk, Bharat Ratra will describe the astronomical data which persuade cosmologists that (as yet not directly detected) dark energy and dark matter are by far the main components of the energy budget of the universe at the present time. He will review how these observations have led to the development of a quantitative "standard" model of cosmology that describes the evolution of the universe from an early epoch of inflation to the complex hierarchy of structure seen today. He will also discuss the basic Physics, and the history of ideas (many developed by Jim Peebles), on which this model is based. About the speaker: Dr. Ratra is a distinguished professor of physics at Kansas State University. He works in the areas of cosmology and astroparticle physics, and researches the structure and evolution of the universe. Two of his current principal interests are developing models for the large‐scale matter and radiation distributions in the universe and testing these models by comparing predictions to observational data. In 1988, Dr. Ratra and Jim Peebles proposed the first dynamical dark energy model. Dark energy is the leading candidate for the mechanism that is responsible for causing the cosmological expansion to accelerate.
[Show full text]
"The Cosmological Constant and Dark Energy," PJE Peebles and B. Ratra
Two readings on Theories for Dark Energy 1. "The Cosmological Constant and Dark Energy," P. J. E. Peebles and B. Ratra, Rev. Mod. Phys. 75, 559 (2003). Introduction only. Full text available on course website. 2. "Top 10 Theories About Dark Energy," Paulina Destarac, listverse.com/2017/06/03/top-10-theories-about-dark-energy/ REVIEWS OF MODERN PHYSICS, VOLUME 75, APRIL 2003 The cosmological constant and dark energy P. J. E. Peebles Joseph Henry Laboratories, Princeton University, Princeton, New Jersey 08544 Bharat Ratra Department of Physics, Kansas State University, Manhattan, Kansas 66506 (Published 22 April 2003) Physics welcomes the idea that space contains energy whose gravitational effect approximates that of Einstein’s cosmological constant, ⌳; today the concept is termed dark energy or quintessence. Physics also suggests that dark energy could be dynamical, allowing for the arguably appealing picture of an evolving dark-energy density approaching its natural value, zero, and small now because the expanding universe is old. This would alleviate the classical problem of the curious energy scale of a millielectron volt associated with a constant ⌳. Dark energy may have been detected by recent cosmological tests. These tests make a good scientiﬁc case for the context, in the relativistic Friedmann-Lemaıˆtre model, in which the gravitational inverse-square law is applied to the scales of cosmology. We have well-checked evidence that the mean mass density is not much more than one-quarter of the critical Einstein–de Sitter value. The case for detection of dark energy is not yet as convincing but still serious; we await more data, which may be derived from work in progress.
[Show full text]
Commencement Schedule
Commencement Schedule Friday, December 9, 2016 6 Graduate School Bramlage Coliseum, 1 p.m. 22 Kansas State University Polytechnic Campus Student Life Center, 7 p.m. Saturday, December 10, 2016 26 College of Arts & Sciences Bramlage Coliseum, 8:30 a.m. 31 College of Education Bramlage Coliseum, 10 a.m. 34 College of Business Administration Bramlage Coliseum, 11:30 a.m. 38 College of Agriculture Bramlage Coliseum, 1 p.m. 41 College of Human Ecology Bramlage Coliseum, 2:30 p.m. 45 College of Engineering Bramlage Coliseum, 4 p.m. 1 CelebratingOur Future Dear Graduates, n behalf of the Kansas State University family, we extend our sincerest congratulations and best wishes on Oyour graduation. Your degree represents a great deal of work and commitment on your part and on the part of those who have helped you along your way. Whether it is your family, friends, faculty, staff or fellow students, know that all are proud of your accomplishments. Your commencement marks a milestone in your life and sets you on a journey toward a productive and fulfilling career. We hope you use the knowledge and preparation you received at K-State to move forward and make a difference throughout your life, whether in the career field, in the community or in other worthy pursuits. As you embark and progress in your career and life, know that Kansas State University will always encourage you along the way. You are now part of our network of more than 200,000 proud alumni worldwide. We urge you to remain connected to the university through the K-State Alumni Association, which is providing you and fellow graduates with a year’s free membership.
[Show full text]
Tuesday 19 January 2016 PHYS 692 INTRODUCTION to COSMOLOGY
Tuesday 19 January 2016 PHYS 692 INTRODUCTION TO COSMOLOGY Spring 2016 Tuesdays & Thursdays 9:30{10:45 Cardwell 143 Instructor: Bharat Ratra, Cardwell 32A, 532-6265, [email protected], www.phys.ksu.edu/personal/ratra/ Office Hours: By appointment. Syllabus: Time (and student preparation) permitting, topics to be covered will mostly be selected from: Observational Basics (length scales; isotropy and homogeneity; expansion, redshift, and Hubble's law); Cosmological Models (Newtonian cosmology; non-Euclidean spaces and metrics; Friedmann equation; density parameter, space curvature, and cos- mological constant and dark energy); Constituents of the Universe (luminous matter; dark matter; black body cosmic microwave radiation; dark energy); Early History of the Universe (including synthesis of light elements such as hydrogen and helium); Domain of Validity of the Big Bang Model; Inflation Model of the Very Early Universe; Deviations from Ho- mogeneity and Isotropy in the Large-Scale Matter and Radiation Distributions (including evolution of inhomogeneities, quantum-mechanical zero-point vacuum fluctuations during inflation, measurements of anisotropy in the cosmic microwave radiation, etc). Text: P. J. E. Peebles, Principles of Physical Cosmology (Princeton University Press 1993). This is a standard cosmology book. Not all of it will be covered, and some topics to be covered are not in this book. Other useful books are on reserve in the Math/Physics Library. Grades will be based on: (1) short in-class exams during the usual lecture period | carry a calculator with you when you come to class; (2) homework problem sets; and, possibly (3) a short write up and/or an in-class presentation on an assigned topic.
[Show full text]
692-Syllabus
Tuesday 21 January 2014 PHYS 692 INTRODUCTION TO COSMOLOGY Spring 2014 Tuesdays & Thursdays 1:05{2:20 Cardwell 143 Instructor: Bharat Ratra, Cardwell 32A, 532-6265, [email protected], www.phys.ksu.edu/personal/ratra/ Office Hours: By appointment. Syllabus: Time (and student preparation) permitting, topics to be covered will mostly be selected from: Observational Basics (length scales; isotropy and homogeneity; expansion, redshift, and Hubble's law); Cosmological Models (Newtonian cosmology; non-Euclidean spaces and metrics; Friedmann equation; density parameter, space curvature, and cos- mological constant and dark energy); Constituents of the Universe (luminous matter; dark matter; black body cosmic microwave radiation; dark energy); Early History of the Universe (including synthesis of light elements such as hydrogen and helium); Domain of Validity of the Big Bang Model; Inflation Model of the Very Early Universe; Deviations from Ho- mogeneity and Isotropy in the Large-Scale Matter and Radiation Distributions (including evolution of inhomogeneities, quantum-mechanical zero-point vacuum fluctuations during inflation, measurements of anisotropy in the cosmic microwave radiation, etc). Text: P. J. E. Peebles, Principles of Physical Cosmology (Princeton University Press 1993). This is a standard cosmology book. Not all of it will be covered, and some topics to be covered are not in this book. Other useful books are on reserve in the Math/Physics Library. Grades will be based on: (1) short in-class exams during the usual lecture period | carry a calculator with you when you come to class; (2) homework problem sets; and, possibly (3) a short write up and/or an in-class presentation on an assigned topic.
[Show full text]