What is Quantum cosmology: Definition and 46 Discussions

Quantum cosmology is the attempt in theoretical physics to develop a quantum theory of the Universe. This approach attempts to answer open questions of classical physical cosmology, particularly those related to the first phases of the universe.
Classical cosmology is based on Albert Einstein's general theory of relativity (GTR or simply GR) which describes the evolution of the universe very well, as long as you do not approach the Big Bang. It is the gravitational singularity and the Planck time where relativity theory fails to provide what must be demanded of a final theory of space and time. Therefore, a theory is needed that integrates relativity theory and quantum theory. Such an approach is attempted for instance with loop quantum cosmology, loop quantum gravity, string theory and causal set theory.In quantum cosmology, the universe is treated as a wave function instead of classical spacetime.

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  1. N

    A Friedmann-Lemaitre-Robertson-Walker model

    I am a math student conducting a study on the stability analysis of the FLRW model using the Lyapunov direct function. To do that, I need to find the equilibrium points of FLRW and create a Lyapunov function to carry out the study. Do i find the equilibrium points by setting time derivatives to...
  2. M

    I Is entanglement a consequence of the singularity of the early universe?

    Does it make sense to explain entanglement as a consequence of the ‘singularity' of the early universe? If proto matter/energy was in some mathematically definable ’small’ space, perhaps information was likewise compressed, and entanglement is a consequence of this early cosmological locality...
  3. A

    I What do the authors of the paper mean here exactly by path integral?

    Hi, I am new here so apologies if i am not using the right subforum. I don't have a physics background so i am not very technical but i do have a little bit of understanding. I was reading this paper by hawking/hertog and came across something that ended up confusing me. Here is it: "Pre-big...
  4. S

    B Is There a Cosmological Model That Considers All Possible Laws of Physics?

    Hawking and Hartle proposed a well-known model which postulated a sum over all possible histories considering all compact euclidean metrics to explain the origin of the universe (this is called the No Boundary model). I was wondering whether there is any model or theory (related to cosmology)...
  5. S

    A Hartle-Hawking sum over all possible metrics?

    Physicists Stephen W Hawking and James B Hartle 1 proposed that the universe, in its origins, had no boundary conditions both in space and time. To do that, they proposed a sum over all compact euclidean compact metrics. I have heard that they only considered these metrics in order to simplify...
  6. W

    I Understanding Loop Quantum Cosmology

    As I understand it there have been different attempts to use LQG to make a theory of cosmology. The first one being done by Martin Bojowald and then later one being performed by Ashtekar, Pawloski and Singh. there is a description of what they did that was different but as a non cosmologist I...
  7. W

    I Loop Quantum Cosmology: Explained in Layman's Terms

    I have heard that one of the of the founders of LQC, Martin Bojowald is now rather critical of it. And sample of his criticism can be found here: https://arxiv.org/pdf/1810.00238.pdf I would be really grateful if someone could explain this in more laymen language . Any thoughts on the issues...
  8. S

    I Is the Wheeler-DeWitt equation somehow related to the Multiverse?

    I've seen some articles that relate them (like this one: https://arxiv.org/pdf/1407.3118.pdf) "In this paper we will analyze the third quantization of gravity in path integral formalism. We will use the time-dependent version of WheelerDeWitt equation to analyze the multiverse in this...
  9. G

    B Is quantum physics "retro-deterministic"?

    The question relates to the deterministic views of people like Descartes or Pierre de Laplace, the infamous "an omniscient intelligence who could know precisely the position and momentum of every single particle in the universe would be able to predict the future with total accuracy, past...
  10. K

    I Implications of validating loop quantum cosmology

    suppose, for example, Pre-inflationary universe in loop quantum cosmology Tao Zhu, Anzhong Wang, Gerald Cleaver, Klaus Kirsten, Qin Sheng (Submitted on 22 May 2017 (v1), last revised 4 Jun 2017 (this version, v2)) The evolutions of the flat FLRW universe and its linear perturbations are studied...
  11. durant35

    I Probability of not entering de Sitter

    As far as we know, the universe is undergoing accelerated expansion and heading towards empty de Sitter space. It is assumed that eventually the observable universe will be emptied out of matter and all radiation. Now if we take in account quantum mechanics, there's always non zero probability...
  12. K

    I How do cosmologists view loop quantum cosmology?

    recently this paper Quantum Gravity in the Sky: Interplay between fundamental theory and observations Abhay Ashtekar, Brajesh Gupt (Submitted on 15 Aug 2016 (v1), last revised 12 Nov 2016 (this version, v2)) Observational missions have provided us with a reliable model of the evolution of the...
  13. K

    Loop quantum cosmology vs string cosmology

    which of the two is better supported by observational evidence and is more researched?
  14. A

    Quantum Cosmology and Quantum Computing

    Hello All, I've just recently read David Deutsch and Michael Lockwood article about Time Travel of 1994 in Scientific American.They stated,that although among the physicists Everett's theory remains controversial,it has no alternatives in Quantum Cosmology and Quantum Computing.Is it really...
  15. Garth

    Exact Classical Correspondence in Quantum Cosmology?

    A paper published in 'Gravitation and Cosmology', [21, 208 (2015)] and on today's physics ArXiv claims to have found a solution to the Wheeler-DeWitt equation that exactly corresponds to the classical evolution of a Friedmann model with appropriate matter/energy density: Exact Classical...
  16. V

    Hello, I am Nick, a high school student

    Hello, As per the title - my name is Nick. I am soon to enter my senior year of high school. I come here partly due to recommendation of my teacher. This year, my plan is to participate in my city's annual science and engineering competition, which is connected to the Intel International...
  17. Rajkovic

    General Relativity and Quantum Cosmology

    Space does not exist, so time can http://arxiv.org/abs/0909.1861 Can someone explain to me, what this article means by "space does not exist"?
  18. H

    Required backround for quantum cosmology

    Hello every body. I want to learn about quantum cosmology but I always find lot of difficulties :confused:. I have a very usual background :frown: on Quantum Mechanics and General Relativity. What are the required specific topics of QM or GR that i should learn before I can learn about Quantum...
  19. B

    Thoughts on Quantum Cosmology?

    I just finished reading a book called Three Roads to Quantum Gravity, and in it the author mentioned a few arguments surrounding quantum cosmology. He did not seem too fond of it, but to me (relatively inexperienced) combining the two makes a lot of sense. What are your thoughts on it?
  20. L

    The consistent histories approach to quantum cosmology

    I'm currently reading "Three roads to Quantum Gravity" by Lee Smolin. In the book he describes attending a presentation by Fay Dowker and James Hartle about the consistent histories approach to quantum cosmology. He describes that, "there were worlds that were classical now that were arbitrarily...
  21. wolram

    Loop quantum cosmology status report

    Sorry if this has already been discussed, i couldn't find any thing.arXiv:1108.0893 (cross-list from gr-qc) [pdf, ps, other] Loop Quantum Cosmology: A Status Report Abhay Ashtekar, Parampreet Singh Comments: 136 pages, 15 figures Subjects: General Relativity and Quantum Cosmology...
  22. S

    Intergal result and quantum cosmology

    This article : http://www.sciencedaily.com/releases/2011/06/110630111540.htm claims to rule out "some" string and loop models but doesn't really elaborate, I couldn't find that claim in the original article: http://arxiv.org/abs/1106.1068 anyone care to discuss?
  23. marcus

    Probability of Inflation in Loop Quantum Cosmology (new Ashtekar Sloan paper)

    http://arxiv.org/abs/1103.2475 Probability of Inflation in Loop Quantum Cosmology Abhay Ashtekar, David Sloan 34 pages, 3 figures (Submitted on 12 Mar 2011) "Inflationary models of the early universe provide a natural mechanism for the formation of large scale structure. This success brings...
  24. marcus

    What caused the shift of interest in quantum cosmology?

    This raises an interesting physics question. What physics reason could there be for the shift of researcher interest in quantum cosmology which this Inspire search illustrates? Here is the Inspire top ten quantum cosmo list for 1996-1998...
  25. S

    Exploring Loop Quantum Cosmology with the Planck Satellite

    Will the results from the PLanck satellite shed any light on Loop Quantum Cosmology or any other form of matter bounce?
  26. marcus

    Chalnoth case against Loop Quantum Cosmology

    Loop Quantum Cosmology could be interesting to discuss because 1) it has been radically transformed since 2007 (with what Ashtekar calls "improved dynamics") 2) it has begun a phase of rapid growth (new crop of researchers , publication rate more than doubled since 2006) 3) it now includes...
  27. MathematicalPhysicist

    Quantum Cosmology reading tips

    OK, I have a plan to learn this summer after all of my exams will end, some subjects in physics and maths (GR,QFT, measure theory,DG and some random matrix theory, not sure if this plan is tangible, I'll try), so for GR I think of using Wald's and A First course in GR, maybe I'll also look at...
  28. Physics Monkey

    Loop Quantum Cosmology: Exploring Physics

    Hi everybody, I would like to chat about the physics of loop quantum cosmology. Let me list a few broad topics I'm interested in understanding better: 1. What simplifications/approximations make loop quantum cosmology a solvable simplification of full loop quantum gravity? 2. How is...
  29. E

    What is most influential candidate quantum cosmology today?

    What is the most influential candidate quantum cosmology today? By influential it (a) reproduces known observation, (b) offers speculative ideas in the Planck epoch, (c) professionally researched and published in peer-reviewed journals. I suppose the time line should be 2007-2009 The two I am...
  30. putongren

    Quantum Cosmology - Imaginary Time

    I have trouble understanding the concept of imaginary time. As I understand it (by reading other online sources), imaginary time was developed by Stephen Hawking and Hartle in their theory of quantum cosmology. Quantum cosmology is applying quantum mechanical principles to cosmology as a...
  31. S

    Suggest good articles on Loop Quantum Cosmology

    please suggest good articles on Loop Quantum Cosmology If you have links of good articles and review papers of Loop Quantum Cosmology please post here
  32. marcus

    Video lecture on Loop Quantum Cosmology

    LQC is the dominant approach to quantum cosmology these days, if you gauge by recent peer-review publication and citations in the professional literature. So anybody who wants to know about quantum cosmology could be well advised to get an introduction to LQC. Parampreet Singh is one of the...
  33. E

    Quantum gravity and quantum cosmology books

    At the risk of annoying some people but hopefully also interesting others I would like to mention my new book on the periodic table, which has just been named as one of 7 "outstdanding academic books of the year 2007" in the category for chemistry But the book is as much about physics as it...
  34. marcus

    Bojo in Nature Physics July issue, probing before bigbang with quantum cosmology

    Here is the Penn State press release http://www.eurekalert.org/pub_releases/2007-07/ps-whb062907.php called "What happened before the big bang" the press release evidently covers much of what you need a subscription to read in Nature Physics magazine, or else have to get it at your university...
  35. marcus

    Who the top quantum cosmology researchers are

    By quantum cosmology QC I mean research using a quantized version of the familiar classical Friedman-LeMaitre model used in mainstream cosmology. Quantum cosmology is beginning to have an impact on regular cosmology. It offers answers to certain puzzles and also prospects of testing QC...
  36. marcus

    Hellfire's introduction to quantum cosmology

    If you want an accessible overview of quantum cosmology try this TOC: https://www.physicsforums.com/blogs/hellfire-3727/category/interesting.html Hellfire covers different attempts made since the 1960s, and by comparing them (and showing historical development) makes the whole subject...
  37. jal

    The Quantum Configuration Space of Loop Quantum Cosmology

    Hi marcus! It seems to me that there are many different approaches, from around the world, that are converging at an accelerated pace. Maybe not? … It might just be my desire to understand minimum length. http://arxiv.org/PS_cache/arxiv/pdf/0704/0704.2397v1.pdf The Quantum Configuration...
  38. jal

    Lattice refining loop quantum cosmology, anisotropic models and stability

    CONGRATULATIONS TO Martin Bojowald! http://arxiv.org/PS_cache/arxiv/pdf/0704/0704.1137v1.pdf Lattice refining loop quantum cosmology, anisotropic models and stability Martin Bojowald∗ 09 April 2007 Standard Theory SU(3)xSU(2)xU(1).…. String …. Have not done it. He is the first to...
  39. E

    Cosmologists, astrophysicists, astronomers: loop quantum cosmology or string cosmolog

    There's no debate which post-SM approach the vast majority of HEP/particle physicists prefer: string theory. While I don't know what the vast majority of post-SM, post-GR approach cosmologists, astrophysicists, astronomers prefer, loop quantum cosmology or string cosmology, in solving a...
  40. Y

    Loop Quantum Cosmology dual to Randall-Sundrum Model

    Specifically LGC is dual to RS theory with an extra (large) time-like dimension, as reported by Parampreet Singh today in: http://arxiv.org/PS_cache/gr-qc/pdf/0603/0603043.pdf This is the first connection between loop quantum gravity and string theory that I am aware of. The need for an...
  41. Chronos

    Loop Quantum Cosmology: Martin Bojowald's Awe-Inspiring Work

    Check this out Loop Quantum Cosmology http://www.arxiv.org/abs/gr-qc/0601085 Authors: Martin Bojowald A terrific paper. Frankly, I am awed by this work.
  42. Y

    What resources are available for studying higher dimensional quantum cosmology?

    I going to to study the quantum cosmology. who can give me some advice and supply some papers and books? Thanks.
  43. marcus

    Unruh: Loop Quantum Cosmology paper (new)

    http://arxiv.org/abs/gr-qc/0408074 Bill Unruh has been doing some LQC research Looking at the positive curvature case Bojowald and friends mostly looked at the spatially flat case Unruh found some interesting difficulties with the positive curved universe, especially the kind that...
  44. marcus

    Oscillatory Universes in Loop Quantum Cosmology

    this just out: http://arxiv.org/gr-qc/0406042 Oscillatory Universes in Loop Quantum Cosmology and Initial Conditions for Inflation James E. Lidsey, David J. Mulryne, N. J. Nunes, Reza Tavakol 6 pages, 4 figures LQC continues attracting new researchers: these people are newcomers...
  45. marcus

    Ashtekar quantum cosmology paper new this month

    What I suspect is a major paper by Ashtekar (and others) appeared in arXiv this month----on June 9. Mathematical structure of loop quantum cosmology Ashtekar, Bojowald, Lewandowski arXiv:gr-qc/0304074 http://www.arxiv.org/abs/gr-qc/0304074 Here is the concluding paragraph: "We...
  46. marcus

    A great 16 page paper in quantum cosmology

    http://xxx.lanl.gov/abs/hep-th/9910146 This is only 16 pages and in PDF so easy to print out. It is by Fotini Markopoulou and Lee Smolin and it is called "Holography in a quantum spacetime" I nominate it for the landmark eureka paper of 1999. String theory and branes are on the run...
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