Covariant Loop uantum Gravity MOBI ê Covariant Loop

Covariant Loop uantum Gravity ★ Covariant Loop uantum Gravity PDF / Epub ✪ Author Carlo Rovelli – uantum gravity is among the most fascinating problems in physics It modifies our understanding of time space and matter The recent development of the loop approach has allowed us to explore domains ra uantum gravity is among the most fascinating problems in physics It modifies our understanding of time space and matter The recent development of the Covariant Loop PDF/EPUB ² loop approach has allowed us to explore domains ranging from black hole thermodynamics to the early Universe This book provides readers with a simple introduction to loop uantum gravity centred on its covariant approach It focuses on the physical and conceptual aspects of the problem and includes the background material needed to enter this lively domain of research making it ideal for researchers and graduate students Topics covered include uanta of space; classical and uantum physics without time; tetrad formalism; Holst action; lattice CD; Regge calculus; ADM and Ashtekar variables; Ponzano Regge and Turaev Viro amplitudes; kinematics and dynamics of D Lorentzian uantum gravity; spectrum of area and volume; coherent states; classical limit; matter couplings; graviton propagator; spinfoam cosmology and black hole thermodynamicsAvailable for free download from.

7 thoughts on “Covariant Loop uantum Gravity

  1. Manny Manny says:

    Original review Aug 17 2017Last week I read Carlo Rovelli's Reality Is Not What It Seems a book which does a great job of explaining loop uantum gravity to the layperson According to and physicists LG is the theory that does what string theory was supposed to do and provides us with a theory of everything a coherent description of the fundamental structure of the universe which combines the two main physical theories of the twentieth century uantum mechanics and gravity Reality Is Not What It Seems is strong on philosophical and poetic intuitions but weak on detail; given that it's a popular account that's entirely as it should be All the same I wanted to know and soon found my way to this slightly earlier book which Rovelli co authored with Francesca Vidotto I've now finished itI must say that I have rarely found it so difficult to write a review Unless you are very knowledgeable about uantum mechanics and relativity I would say approaching PhD level I'm warning you at once that you're going to find much of the text difficult or impossible to understand The greater part of it is complex mathematical formulas That said and despite the fact that I had to skip or skim a great deal I was astonished to find that the book was not merely engaging but it's not too strong a word compulsive I finished it in four days and could hardly put it down; on one occasion I went to bed at midnight then got up again at 2 am because I had to read another chapter I am not sure I have done this for any remotely similar bookWhy? I'm struggling to explain The overwhelming impression is one of architecture a precise meticulously constructed architecture that you feel the authors revealing to you even though you don't properly understand what it is Oddly enough the book it most reminded me of was Jan Kjærstad's Jonas Wergeland trilogy where I had the same sensation there is a plan that holds all this together though I can't uite identify it I am sure it is not a coincidence that both Rovelli and Kjærstad are fervent admirers of Dante I had this Dantean feeling of architectural revelation throughout Jonas Wergeland but I felt it even strongly here Everything fits There is a long and scarily incomprehensible piece of mathematics but the whole time the authors are accompanying you Virgil like and telling you where you're going; we got this result from here we're going to need that notion a bit later on you see now why we did the third thing the way we did You don't completely grasp it All the same you find you have to continueThey say at the beginning that they aren't going to give you the history of the subject but they show you in rough outline the route they and their colleagues had to take where the basic intuitions came from what encouraged them to continue bits of mathematics that magically came out right and pointed the way towards a hidden pass the very hard work they had to do to get round a steep overhang I find myself wanting to use metaphors from mountain climbing Well that's thematic they seem to have spent many years climbing Mount Purgatory Now they have reached the Earthly Paradise where they have been given a first consistent form of the theory and they are heading off into the stars The last chapters of the book are about astronomy and cosmology but they are only tentative compared to the early ones Some promising initial results on black holes some glimpses of what may have happened very early on in the history of the Big Bang They haven't yet reached the Empyrean and they encourage other younger pilgrims to join them on their uest They are humble than triumphant because they know the job is not finished yetOf course it could all be an illusion; it wouldn't be the first time that had happened But I'd say there's an appreciable chance that this is the real deal If you want to watch a scientific revolution happening in front of you in real time I don't know of any better place to sit I suppose I should actually say Virgil and Beatrice like but that sounded too clunky and also they never guide Dante at the same time If you want to know what the authors look like Update Sep 17 2019Here's an intriguing passage from Wolfram's Adventures of a Computational Explorer p 100 in the paperback edition He is talking about creating simulated universes with different fundamental laws of physics and examining their propertiesA particular representation that I have studied involves setting up a large number of nodes connected in a network and repeatedly updating according to some local rewrite rule Within this representation one can in effect just start enumerating possible universes specifying initial conditions and updating rules Some candidate universes are very obviously not our physical universe They have no notion of time or no communication between different parts or an infinite number of dimensions of space or some other obviously fatal pathologyBut it turns out that there are large classes of candidate universes that already show remarkably suggestive features For example any universe that has a notion of time with certain robustness properties turns out in an appropriate limit to exhibit Special Relativity And even significantly any universe that exhibits a certain conservation of finite dimensionality as well as generating a certain level of microscopic randomness will lead on a large scale to spacetime that follows Einstein's euations for General RelativityWell the spin networks that Rovelli and Vidotta focus on in their book are if I'm understanding Wolfram correctly an example of the kind of thing he's referring to And spin networks do indeed imply General Relativity though the way RV tell it that was an extremely nontrivial discovery which took decades to establish But Wolfram says it's a special case of a much general result If so uite amazing I just checked and RV do not mention Wolfram at all; so far Wolfram has not mentioned LG Update Sep 29 2019After looking around a bit I find this 2017 interview where Wolfram talks briefly about the relationship between his work and LG He gives a link to what he callsA big result I found nearly 20 years ago that still hasn’t been widely understood is that when you look at a large enough network of the kind I studied you can show that its averaged behavior follows Einstein’s euations for gravity In other words without putting any fancy physics into the underlying model it ends up automatically emerging I think it’s pretty excitingThe link doesn't work properly any but it certainly looks like it's meant to go to section 15 of chapter 9 of his 2002 book A New Kind of Science This however only gives further vague hints Update Jul 2 2020Wolfram's A Project to Find the Fundamental Theory of Physics published last week gives a little detail on the above claims but it's still extremely sketchy Given that the book is 770 pages long this is disappointing There is however a link to an arXiv paper by one of Wolfram's students which presents further information

  2. Erickson Erickson says:

    Only managed to cover up to chapter 5 This book has skipped a lot of details and thus while the writing is made such that it sounds light for newcomers in loop uantum gravity there are actually uite a lot of heavy lifting to be done while reading For one one cannot read this book without some basic understanding of Lie groups and Lie algebras on top of sufficient understanding of classical mechanics and Hamiltonian formalism of GRBut definitely it conveys the flavour of what LG tries to achieve and schematics of how it tries to do thingsWill read this again once I am at higher level My current undergraduate knowledge is not enough even with the help of PhD students around me

  3. Don Mammoth Don Mammoth says:

    An absolutely excellent introduction however the claim that only basic FT knowledge is reuired is a bit of a stretch You’ll need a comfortable working relationship with LIE algebra as well as differential forms and alternative formulations of the Einstein Hilbert action Other than overselling the “basic” knowledge reuired this book is incredibly well put together and easy to follow for serious enthusiasts

  4. Thomas Ray Thomas Ray says:

    free download pdf herewwwcptuniv mrsfrrovelliIntroducStarts well by telling us that to integrate two seemingly incompatible branches of physics the aim is to look for something that reduces to each at ordinary scales Schrödinger did this to find his wave euation p 50 of 277 in the pdf And that it’s good that theorists are constrained by having to explain the real world p 14 of 277You'd need all but dissertation in field theory to even understand his notation He almost never says what his symbols mean The euations are almost all not actual euations but meta euations and in shorthand Integrals without a dsomething; a letter meant to stand in for a group of coordinates vectors operators You’d have to read all the books and papers he cites to find out what if anything he’s talking about And if you did read them all would this book add anything? No way to know until you do Sloppiness and facetiousness don’t make the book an introduction If you can’t be understood maybe you don’t understand the subject as well as you thoughtA few easy bits of trivia from early ongoodreadscomtriviawork42044329 coSome brilliant scientists who write brilliantly for the general readerRichard Feynman For example ED The Strange Theory of Light and Matter and The Feynman Lectures on PhysicsEdwin F Taylor Spacetime PhysicsIsaac Asimov any and all of his nonfictionErwin Schrödinger For example What Is Life? with Mind and Matter and Autobiographical Sketches

  5. Christopher Elliott Christopher Elliott says:

    I can't claim to have understood 10% of this but my lay person take away is that gravity comes about from a property of the fields that make up physical particle instead of being an external field that interacts with it I'll have to consult a particle physicist to see if I was anywhere close

  6. Luca Campobasso Luca Campobasso says:

    I went through the book already twice and I have to say it's uite well versed and easy to read even for a bachelor student I'd say The basics to know are differential geometry and visualise things in 4D The first chapters are a very gentle introduction while things speed up at the introduction of the full 4D theory The last chapters are just touching on Cosmology and scattering so don't expect anything from them in concrete terms After reading this you'll be able to comfortably read the papers now published about it Also there are some points in which the authors stress some commonly misunderstood concepts like the often mentioned breaking Lorentz invariance which is something the detractors always talk aboutMy opinion on the uantum gravity diatribe After having had string theory in my master course of physics corresponding to the first Polchinski volume and reading this book I'm uite convinced I'd go for LG being a less marketed theory but consistent with reality and well anchored with math too

  7. Samuel Samuel says:

    Will pick up after a course in Relativity and M

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