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Topic: Three Roads to Quantum Gravity

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	Guardian Unlimited Books \| By genre \| Review: Three Roads to Quantum Gravity by Lee Smolin
		But as physicist Lee Smolin writes in Three Roads to Quantum Gravity, some of the newest ideas in physics are pointing to a surprising answer: space and time do indeed appear to be made out of such atoms.
		Quantum theory says that something similar should also be true of gravity: just as there is a quantum theory of light, so there should be a quantum theory of gravity.
		Three Roads to Quantum Gravity offers an excellent overview of fascinating ideas that may indeed lead - and quite soon - to such a unified theory.
	books.guardian.co.uk /reviews/scienceandnature/0,6121,438833,00.html (813 words)

	Amazon.ca: Three Roads to Quantum Gravity: Books: Lee Smolin (Site not responding. Last check: 2007-10-31)
		Smolin himself has been driving some of the mathematical heavy equipment needed to construct the second road, which takes general relativity as its starting point and is known as "loop quantum gravity." In this view space is built up of discrete, constantly changing "spin networks" of loops that intersect dynamically.
		The book is described in three parts; the first part is a general introduction, which describes historical development of three theories, the second part introduces LQG and then compares with S.-M and BT theories, and the final part attempts to unify the three approaches into a single theory using Holographic Principle.
		Having worked in both main theories (string theory and loop quantum gravity) and having known many researchers working with other less popular theories he is able to present the pros and cons of each in a way that everyone can understand.
	www.amazon.ca /Three-Roads-Quantum-Gravity-Smolin/dp/0465078354 (2556 words)

	'Three Roads to Quantum Gravity': Space-Time Is of the Essence
		'Three Roads to Quantum Gravity': Space-Time Is of the Essence
		They are trying to formulate a quantum theory that can encompass not just atoms, nuclei, electrons and quarks but the very force of gravity that pulls apples to earth and keeps planets orbiting the sun.
		Quantum mechanics accurately describes realms of the very small, while Einstein's general theory of relativity applies to vast, cosmological distances spanning galaxies or groups of galaxies and to enormously massive objects, such as the billions of stars in them.
	www.lightwatcher.com /old_lightbytes/quantum_gravity.html (1223 words)

	Edge: LOOP QUANTUM GRAVITY
		Quantum gravity is the name we give to the theory that unifies all of physics.
		Loop quantum gravity differs from other approaches to quantum gravity, such as string theory, in that apart from using Ashtekar's formalism we made no modifications to the principles of relativity and quantum theory.
		There are three features of the world that no string theory can so far reproduce: the absence of supersymmetry at low energies, the presence of a cosmological constant with positive sign (more on this later), and the complete absence of a certain kind of field—called a massless scalar field—that string theories predict in abundance.
	www.edge.org /3rd_culture/smolin03/smolin03_print.html (6853 words)

	Amazon.com: Three Roads to Quantum Gravity: Books: Lee Smolin (Site not responding. Last check: 2007-10-31)
		The completion of a quantum theory of gravity (quantum gravity for short) is one of the most challenging problems in science in the twenty-first century.
		The reader who knew nothing about the quantum gravity learns easily the following interesting things: There are three approaches to quantum gravity, i.e., the route from quantum theory (string theory), the road from the theory of general relativity (loop quantum gravity), and the path from fundamental principles.
		The third road, according to Smolin, is a fuzzy collection of speculations invented by the philosophers of various kinds who would like to refuse everything that physicists have learned and to base everything on ill-defined "profound" and "deep" philosophical principles.
	www.amazon.com /Three-Roads-Quantum-Gravity-Smolin/dp/0465078354 (2931 words)

	Quantum Gravity - Table of Contents (Site not responding. Last check: 2007-10-31)
		Understanding the nature of spacetime on the smallest scales is important for understanding environments where quantum and gravitational effects are close to the same magnitudes, such as regions near fl holes and the very early universe.
		The roads are not necessarily theories of quantum gravity but are approaches to understanding the nature of spacetime on the smallest scales.
		All three approaches lead to the conclusion that space and time are comprised of discrete quanta and exhibit quantum behavior.
	mark-a-martin.us /talks/qg (799 words)

	Open Questions: Quantum Gravity
		One key difficulty is that quantum gravity would describe phenomena far outside the range of experimental investigation.
		A quantum theory of gravity has been difficult to develop, in part, because of the tight relationship between gravity and the geometry of spacetime.
		The three roads referred to are string theory, loop quantum gravity, and a small collection of other diverse and very speculative ideas.
	www.openquestions.com /oq-re005.htm (728 words)

	SS > NF reviews > Lee Smolin
		Nevertheless, this beautifully written and fascinating account, by a leading quantum gravity researcher, is of a universe vastly different, and vastly more interesting, than the one we are used to reading about in more "popular" accounts of physics.
		Smolin sets out to explain three different routes to a theory of quantum gravity, and how they might all be leading to the same place, and does so brilliantly.
		Loop quantum gravity is a theory about how space and time are constructed, but the resulting universe doesn't appear to have much else in it.
	www-users.cs.york.ac.uk /~susan/bib/nf/s/smolin.htm (1440 words)

	Edge: LOOP QUANTUM GRAVITY
		The turning point was the invention of not one but two approaches: loop quantum gravity and string theory.
		This is important, because we're in the uncomfortable situation of having two well-developed candidates for the quantum theory of gravity.
		LEE SMOLIN, a theoretical physicist, is concerned with quantum gravity, "the name we give to the theory that unifies all the physics now under construction." More specifically, he is a co-inventor of an approach called loop quantum gravity.
	www.edge.org /3rd_culture/smolin03/smolin03_index.html (628 words)

	Three Roads to Quantum Gravity by Lee Smolin - quantum-world - 03 February 2001 - New Scientist
		Three Roads to Quantum Gravity by Lee Smolin - quantum-world - 03 February 2001 - New Scientist
		Three Roads to Quantum Gravity by Lee Smolin
		And thus as research funding and careers become ever more precarious, the groves of academe now reverberate to the sound of bandwagons carrying hordes of physicists on what they hope will be a voyage of discovery - but which could take them round and round in circles.
	www.newscientist.com /channel/fundamentals/quantum-world/mg16922765.000 (285 words)

	disinformation \| lee smolin: the new einstein? (Site not responding. Last check: 2007-10-31)
		The third approach, which Smolin advocates, is quantum loop gravity: that space-time units have a lattice-like structure and have discrete variations.
		Quantum loop gravity goes beyond John Wheeler's memorable description of the subatomic structure of space-time as messy "space foam" and David Bohm's holographic model of the universe.
		There may only be a minority of scientists who understand the dense mathematics at the heart of quantum gravity research yet Smolin has successfully translated these hermetic mysteries into a secular form for profane readers.
	www.disinfo.com /archive/pages/dossier/id461/pg1 (2661 words)

	Justin Rogers : Pimping another physics book: "Three Roads to Quantum Gravity"
		The use of a Bekenstein bound for discovering the effects of a quantum fl hole are actually really interesting and have direct computer parallels (the Bekenstein bound can be explained in a thought experiment that is equivalent to how we view pixels on a monitor).
		Obviously the creation of a quantum computer would be an amazing thing and everyone would relish the exponential power of such a construct, however, I'm not sure any of us would know how to program the darn thing.
		For a list of 100 elements the average search time for a classical computer would be 50, while the quantum search would take 7.58 (strange that we get a real number result for the number of operations, I'm assuming that the number actually gets clamped to the upper bound of 8 operations).
	weblogs.asp.net /justin_rogers/archive/2004/06/05/149388.aspx (950 words)

	My review of Three roads to Quantum Gravity, Loop Quantum Gravity BBSHTCM
		Reading, Three Roads to Quantum Gravity, by Lee Smolin.
		Smolin is trying to integrate all current theoretical work to find the solution to the problem of quantum gravity.
		Rather than just following his own line of theory, he is looking at all theories (such as string theory) to truly understand gravity.
	www.bobshowto.com /book-review-three-roads-to-quantum-gravity.htm (207 words)

	Three Roads To Quantum Gravity
		To string theorists, "theory of everything" is a propaganda term which means the same thing as "quantum gravity" and refers to the theory that used to be superstrings uniquely.
		One source of information I came across last October may be of interest here, as it was a step forward for Loop Quantum Gravity that showed that it "does not suffer from certain mathematical 'infinities'," and can be read about here http://www.aip.org/enews/physnews/2001/split/562-1.html and the actual paper is available here http://xxx.lanl.gov/abs/gr-qc/0104057.
		The number of people working actively on both loop quantum gravity and string theory could be counted on the fingers of one hand after a serious accident with a cleaver.
	c2.com /cgi/wiki?ThreeRoadsToQuantumGravity (1154 words)

	Brightsurf: Three Roads to Quantum Gravity by Lee Smolin
		Quantum theory says that for every wave there is an associated particle.
		Quantum theory says that, just as there are photons associated with light, there must be gravitons associated with gravitational waves." "As with the photon, the energy of a graviton is proportional to its frequency, so the higher the frequency of a graviton, the more strongly it will interact with another graviton.
		This little book is a great read, and explains clearly and in relatively comprehensible terms what loop quantum gravity is about - or at least leaves this impression to the reader.
	www.brightsurf.com /item.php?ASIN=0465078362 (2954 words)

	Three Roads to Quantum Gravity (Site not responding. Last check: 2007-10-31)
		187 the discovery of a new theory that appears to contain within it both string theory and a form of loop quantum gravity.
		205 The simple fact that we live in an apparently smooth and regular three-dimensional world represents one of the greatest challenges to the developing theory of quantum gravity.
		This is Three Roads to Quantum Gravity page of leefrank.com.
	home.att.net /~leefrank/booknots/book112.html (609 words)

	Lee Smolin’s Background-Independent, Relational Description of Nature—and What it Means for You (Site not responding. Last check: 2007-10-31)
		Three Roads to Quantum Gravity and in his academic papers, and which I find a powerful concept.
		The origin of this physical description is in Smolin’s intensive and voluminous work on the unresolved problem of “quantum gravity”—in a short description, the question of what happens to the tensor geometry of General Relativity at quantum scales (i.e., very very small distance scales) where the precepts of Einstein’s theory basically break down.
		The “background” is constantly fluctuating and foaming (to use the physicist John Wheeler’s “quantum foam” concept).
	people.fas.harvard.edu /~ulm/Vision/smolin_background_independence.htm (1943 words)

	Re: Lee Smolin's Three Roads to Quantum Gravity
		Subject: Re: Lee Smolin's Three Roads to Quantum Gravity
		Re: Lee Smolin's Three Roads to Quantum Gravity
		Prev by thread: Re: Lee Smolin's Three Roads to Quantum Gravity
	www.lns.cornell.edu /spr/2001-12/msg0037962.html (260 words)

	Re: Lee Smolin:Three Roads To Quantum Gravity..?
		All I really got out of the book is that Smolin is hedging his bets about the theoretical future of the subject: some loop gravity, strings and stuff, and topoi, a glorified takeoff on category theory.
		Then it can be claimed that all of mathematics is being brought to bear on the ultimate questions of existence.
		Ask a few of your juiciest questions and maybe some of us will pour through Three Roads and try to figure out what he is saying.
	www.superstringtheory.com /forum/bhboard/messages5/36.html (206 words)

	Jorge Pullin
		There is a small community pursuing this kind of research, which is complementary to the mainstream approach to quantum gravity: string theory.
		Pirenopolis 2000 (Brazil) Canonical quantum gravity 1, 2, 3.
		I am also a member of the editorial boards of the Journals Living Reviews in Relativity, the revolutionary New Journal of Physics, for which I was the Regional Editor for North America until recently, a journal belonging to The Institute of Physics in the United Kingdom.
	www.phys.lsu.edu /faculty/pullin (1411 words)

	Quantum Gravity Resources
		In the popular press there are a handful of articles on quantum gravity and loop quantum gravity (lQG).
		It has been called a quantum gravity observatory (!), the Pierre Auger cosmic ray observatory in the Andes.
		Physically located in Waterloo, Canada, PI focuses on foundational issues in quantum theory, quantum gravity, string theory, and cosmology.
	academics.hamilton.edu /physics/smajor/resources.html (493 words)

	Quantum Gravity (Site not responding. Last check: 2007-10-31)
		Gravity and Strings (Cambridge Monographs on Mathematical Physics)
		Covariant Operator Formalism of Gauge Theories and Quantum Gravity (World Scientific Lecture Notes in Physics)
		Topology, Geometry and Quantum Field Theory: Proceedings of the 2002 Oxford Symposium in Honour of the 60th Birthday of Graeme Segal (London Mathematical Society Lecture Note Series)
	www.spaceguard.ca /index.php?c=95 (100 words)

	0753812614 (Site not responding. Last check: 2007-10-31)
		Prices for Three Roads To Quantum Gravity by Lee Smolin are shown below
		1) Three Roads To Quantum Gravity by Lee Smolin
		The Holy Grail of modern physics is the search for a quantum gravity view of the universe that unites Einstein's general relativity with quantum theory
	www.cheapbob.com /books/0753812614.htm (79 words)

	book? (Site not responding. Last check: 2007-10-31)
		The Fabric of the Cosmos by Brian Greene is pretty good, but it's lengthier than Smolin's Three Roads to Quantum Gravity.
		Fabric of the Cosmos ends up with a rapid survey of what's in Elegant Universe but from a different perspective, and it does the history of twentieth century quantum theory which a lot of other books do too.
		I found that Greene's insight is a reason to read the book, but not a reason sufficient to make me want to buy it.
	www.physicsforums.com /showthread.php?t=54487 (428 words)

	sciforums.com - intro to quantum gravity
		can someone suggest a website or a book gives an introduction to quantum gravity
		For a non technical overview of the subject, see "Three Roads to Quantum Gravity" by Lee Smolin.
		"Three Roads" is the first to pop into my mind, too.
	www.sciforums.com /showthread.php?t=26914 (42 words)

	LRB \| Michael Redhead : Spin Foam (Site not responding. Last check: 2007-10-31)
		Three Roads to Quantum Gravity: A New Understanding of Space, Time and the Universe by Lee Smolin · Phoenix, 231 pp, £6.99
		The old notions of space and time are currently being turned upside down by theoretical physicists in their attempt to reconcile the two great pillars of 20th-century physics: quantum theory and Einstein's general theory of relativity.
		Lee Smolin, a major contributor to the subject, brings us right up to date with it in this book.
	www.lrb.co.uk /v24/n10/print/redh01_.html (299 words)

	Many Observers, not Many Worlds
		quantum theory to the universe as a whole
		is essential for the very structure of quantum mechanics.
		On one occassion this led to loop quantum gravity,
	members.fortunecity.es /lamb1/smolin2.html (1026 words)

	Notes Quantum Gravity (Site not responding. Last check: 2007-10-31)
		Lee Smolin has written an assesment[1] of several of the candidate theories for Quantum Gravity.
		For a very critical assesment of String Theory, and some ruminations on the purpose of a theory and how it should be constructed, see [2].
		[3] Anthony Lasenby, Chris Doran, Stephen Gull, Gravity, Gauge Theories and Geometric Algebra (gauge theory based on Clifford Algebras)
	mcelrath.org /Notes/QuantumGravity (98 words)

	<< Welcome to the UNIVERSITY OF TORONTO Book Store >>
		Renowned theoretical physicist, Lee Smolin, author of The Life of the Cosmos, Three Roads to Quantum Gravity, brings us his latest book Trouble with Physics: Rise of String Theory.
		He is the author of The Life of the Cosmosand Three Roads to Quantum Gravity.
		He has also written three children's books and has written and hosted several radio documentaries, including Cranial Pursuits and The Talk Show.
	www.uoftbookstore.com /online/merchant.ihtml?id=27860&step=2 (547 words)

	Netsurfer Books 05.07 (Site not responding. Last check: 2007-10-31)
		On that date, Orville took the controls and made three successful flights, the first of which covered 120 feet and lasted 12 seconds.
		Such a reminiscence alone would be interesting, but this book succeeds in three additional projects.
		But among the weirder things it has to say about current thinking in quantum physics is that space is granular, that in fact there is a smallest piece of space, beyond which you can no further divide.
	www.netsurf.com /nsb/sub/v05/nsb.05.07.html (6786 words)

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