MetaFilter posts tagged with entropy and physics
http://www.metafilter.com/tags/entropy+physics
Posts tagged with 'entropy' and 'physics' at MetaFilter.Sun, 09 Nov 2014 01:01:15 -0800Sun, 09 Nov 2014 01:01:15 -0800en-ushttp://blogs.law.harvard.edu/tech/rss60The observer at the end of time: Of immortal watchers and imaginary data
http://www.metafilter.com/144331/The%2Dobserver%2Dat%2Dthe%2Dend%2Dof%2Dtime%2DOf%2Dimmortal%2Dwatchers%2Dand%2Dimaginary%2Ddata
<a href="http://www.quantamagazine.org/20141103-in-a-multiverse-what-are-the-odds/">In a Multiverse, What Are the Odds?</a> "Testing the multiverse hypothesis requires measuring whether our universe is statistically typical among the infinite variety of universes. But infinity does a number on statistics." (<a href="http://www.metafilter.com/142211/Multiverse-No-More-a-New-Theory-of-Scale">previously</a>) <blockquote>Bousso and his collaborators' <a href="http://arxiv.org/abs/hep-th/0605263">causal-diamond measure</a> has now racked up a number of successes. It offers a solution to a mystery of cosmology called the "why now?" problem, which asks why we happen to live at a time when the effects of matter and vacuum energy are comparable, so that the expansion of the universe recently switched from slowing down (signifying a matter-dominated epoch) to speeding up (a vacuum energy-dominated epoch). Bousso's theory suggests it is only natural that we find ourselves at this juncture. The most entropy is produced, and therefore the most observers exist, when universes contain equal parts vacuum energy and matter.
In 2010 Harnik and Bousso used their idea to explain the <a href="http://www.metafilter.com/131992/Possibly-the-end-of-The-Big-Bang-Theory-Not-the-TV-show#5192598">flatness of the universe</a> and the amount of infrared radiation emitted by cosmic dust. Last year, Bousso and his Berkeley colleague Lawrence Hall <a href="http://arxiv.org/abs/1304.6407">reported</a> that observers made of protons and neutrons, like us, will live in universes where the amount of ordinary matter and dark matter are comparable, as is the case here.</blockquote>
<a href="http://www.kurzweilai.net/when-parallel-worlds-collide-quantum-mechanics-is-born">When parallel worlds collide, quantum mechanics is born</a> (<a href="http://marginalrevolution.com/marginalrevolution/2014/11/assorted-links-1279.html">via</a>)
<blockquote>First, we postulate a fixed, although truly gigantic, number of worlds. All of these exist continuously through time — there is no "branching."
Second, our worlds are not "fuzzy" — they have precisely defined properties. In our approach, a world is specified by the exact position and velocity of every particle in that world — there is no <a href="https://theconversation.com/explainer-heisenbergs-uncertainty-principle-7512">Heisenberg uncertainty principle</a> that applies to a single world. Indeed, if there were only one world in our theory, it would evolve exactly according to Newtonian mechanics, not quantum mechanics.
Third, our worlds do interact and that interaction is the source of all quantum effects. Specifically, there is a repulsive force of a very particular kind, between worlds with nearly the same configuration (that is, having nearly the same position for every single particle). This "interstitial" force prevents nearby worlds from ever coming to have the same configuration, and tends to make nearby worlds diverge.
Fourth, each one of our worlds is equally real. Probability only enters the theory because an observer, made up of particles in a certain world, does not know for sure which world she is in, out of the set of all worlds. Hence she will assign equal probability to every member of that set which is compatible with her experiences (which are very coarse-grained, because she is a macroscopic collection of particles). After performing an experiment she can learn more about which world she is in, and thereby rule out a whole host of worlds that she previously thought she might be in.
Putting all of the above together gives our theory — the <a href="http://arxiv.org/abs/1402.6144">Many Interacting Worlds</a> approach to quantum mechanics. There is nothing else in the theory. There is no wavefunction, no special role for observation and no fundamental distinction between macroscopic and microscopic.
Nevertheless, we argue, our approach can reproduce all the standard features of quantum mechanics, including twin-slit interference, zero-point energy, barrier tunneling, unpredictability, and the Bell correlations mentioned above.</blockquote>
<a href="http://arstechnica.com/science/2014/11/an-infinite-multiverse-a-bad-idea-or-inescapable/">An infinite multiverse: A bad idea or inescapable?</a> "Two areas of physics say there may be another you in a different universe." (<a href="https://twitter.com/Noahpinion/status/529459910116126720">via</a>)
also btw...
-<a href="http://physics.aps.org/articles/v7/111">Viewpoint: Arrow of Time Emerges in a Gravitational System</a>
-<a href="http://www.perimeterinstitute.ca/news/how-time-flies-tracking-arrow-time">How Time Flies: Tracking the Arrow of Time</a>
-<a href="http://www.perimeterinstitute.ca/news/researchers-tackle-complex-question-times-arrow">Researchers Tackle Complex Question of Time's Arrow</a>
-<a href="http://www.wired.com/2014/11/time-gravity/">How Gravity Explains Why Time Never Runs Backward</a>
-<a href="http://www.wired.com/2014/10/astrophysics-interstellar-black-hole/">How Building a Black Hole for Interstellar Led to an Amazing Scientific Discovery</a>
-<a href="http://www.scientificamerican.com/article/scientists-close-in-on-creating-black-hole-in-lab/">Scientists Close In on Creating Black Hole in Lab</a> tag:metafilter.com,2014:site.144331Sun, 09 Nov 2014 01:01:15 -0800kliulessdirect realism
http://www.metafilter.com/122400/direct%2Drealism
<a href="http://dannyreviews.com/h/Nature_Computation.html">The Nature of Computation</a> - <a href="http://masi.cscs.lsa.umich.edu/~crshalizi/reviews/nature-of-computation.html">Intellects Vast and Warm and Sympathetic</a>: "I hand you a network or graph, and ask whether there is a path through the network that crosses each edge exactly once, returning to its starting point. (That is, I ask whether there is a 'Eulerian' cycle.) Then I hand you another network, and ask whether there is a path which visits each node exactly once. (That is, I ask whether there is a 'Hamiltonian' cycle.) How hard is it to answer me?" (<a href="http://masi.cscs.lsa.umich.edu/~crshalizi/weblog/algae-2011-10.html">via</a>) <blockquote>This is, simply put, the best-written book on the theory of computation I have ever read; one of the best-written mathematical books I have ever read, period... from beginning to end, and all the 900+ pages in between, this was lucid, insightful, just rigorous enough, alive to how technical problems relate to larger issues, and above all, passionate and human.</blockquote>also btw...<ul><li><a href="http://infoproc.blogspot.com/2011/10/on-origin-of-probability-in-quantum.html">On the origin of probability in quantum mechanics</a> - "Because the wave function evolves entirely deterministically in <a href="http://infoproc.blogspot.com/2012/11/schwinger-on-quantum-foundations.html">many worlds</a>, all probabilities are necessarily subjective and the interpretation does not require <a href="http://www.metafilter.com/contribute/search.mefi?q=chaitin&tab=comments&site=mefi&sort=date">true</a> <a href="http://www.metafilter.com/122256/The-Royal-Society-Winton-Prize-2012">randomness</a>, thereby preserving Einstein's requirement that outcomes have causes."
<li><a href="http://johncarlosbaez.wordpress.com/2012/10/08/the-mathematical-origin-of-irreversibility/">The Mathematical Origin of Irreversibility</a> - "The key to this rather profound connection resides in a universal property of Markov processes discovered recently in the context of non-equilibrium statistical mechanics, and known as the '<a href="https://plus.google.com/u/0/117663015413546257905/posts/cLjAKybxWR8">fluctuation theorem</a>'. Typically stated in terms of '<a href="http://masi.cscs.lsa.umich.edu/~crshalizi/notebooks/prigogine.html">dissipated work</a>' or '<a href="http://masi.cscs.lsa.umich.edu/~crshalizi/notebooks/tsallis.html">entropy production</a>', this result can be seen as an extension of the Second Law of Thermodynamics to <i>small</i> systems, where thermal fluctuations cannot be neglected. But <i>it is actually much more than this</i>: it is the mathematical underpinning of irreversibility itself, be it thermodynamical, evolutionary, or else. To make this point clear, let me start by giving a general formulation of the fluctuation theorem that makes no reference to physics concepts such as 'heat' or 'work' "
<li><a href="https://plus.google.com/u/0/117663015413546257905/posts/jYw1fnVTFbY">A nice easy explanation</a> of the <a href="http://www.metafilter.com/119847/Mathematics-world-abuzz-with-a-proof-of-the-ABC-Conjecture">abc</a> <a href="https://plus.google.com/u/0/117663015413546257905/posts/Npu7xDniXMS">conjecture</a> [also btw <a href="http://www.metafilter.com/121668/Grahams-Number">1</a>,<a href="https://plus.google.com/u/0/117663015413546257905/posts/VLkhD7NBAb3">2</a>,<a href="https://plus.google.com/u/0/117663015413546257905/posts/6pbLR5Yyf8h">3</a>,<a href="https://plus.google.com/u/0/117663015413546257905/posts/cqMha2Lz5gr">4</a>,<a href="https://plus.google.com/u/0/117663015413546257905/posts/cLjAKybxWR8">5</a>,<a href="https://plus.google.com/u/0/117663015413546257905/posts/4BZRibN6iKQ">6</a>,<a href="https://plus.google.com/u/0/117663015413546257905/posts/DdA4HkKfMiL">7</a>,<a href="http://www.metafilter.com/107661/Counting">8</a>]
<li><a href="http://en.wikipedia.org/wiki/Hilary_Putnam">An argument for the reality of mathematical entities</a> [<a href="http://en.wikipedia.org/wiki/Max_Tegmark">1</a>,<a href="http://masi.cscs.lsa.umich.edu/~crshalizi/reviews/ballard-natural/">2</a>,<a href="http://andrewsullivan.thedailybeast.com/2012/08/ask-jim-holt-anything-your-favorite-philosopher-and-why.html">3</a>]
<li><a href="http://blogs.discovermagazine.com/cosmicvariance/2012/10/22/from-particles-to-people-the-laws-of-nature-and-the-meaning-of-life/">From Particles to People: The Laws of Nature and the Meaning of Life</a> [<a href="http://blogs.discovermagazine.com/cosmicvariance/2012/04/24/the-particle-at-the-end-of-the-universe/">1</a>,<a href="http://blogs.discovermagazine.com/cosmicvariance/2012/11/13/a-book-full-of-particles/">2</a>,<a href="http://blogs.discovermagazine.com/cosmicvariance/2012/10/11/moving-naturalism-forward/">3</a>,<a href="http://blogs.discovermagazine.com/cosmicvariance/2012/10/18/feynman-on-initial-conditions-evolving-laws-and-what-we-consider-physics/">4</a>,<a href="http://science.slashdot.org/story/12/08/01/2127225/entangled-particles-break-classical-law-of-thermodynamics-say-physicists">5</a>]</li></li></li></li></li></ul><a href="http://www.hpcwire.com/hpcwire/2012-10-10/could_the_universe_reveal_itself_as_a_computer_simulation_.html">Could the Universe Reveal Itself as a Computer Simulation?</a> (<a href="http://www.metafilter.com/119883/WHOA-DUDE-ARE-WE-INSIDE-A-COMPUTER-RIGHT-NOW">previously</a>) tag:metafilter.com,2012:site.122400Sat, 01 Dec 2012 00:12:10 -0800kliulessTEDxCaltech
http://www.metafilter.com/103520/TEDxCaltech
<a href="http://www.ted.com/talks/sean_carroll_distant_time_and_the_hint_of_a_multiverse.html">Sean Carroll: Distant time and the hint of a multiverse</a> also btw <a href="http://www.youtube.com/watch?v=9miKIWIYi4w">Feynman and Computation</a> and <a href="http://www.youtube.com/watch?v=hpjwotips7E">Susskind on Feynman</a>, cf. <a href="http://tedxcaltech.com/">TEDxCaltech</a> (<a href="http://infoproc.blogspot.com/2011/03/tedxcaltech.html">via</a>) tag:metafilter.com,2011:site.103520Sun, 15 May 2011 08:44:38 -0800kliulessspacetime must organise itself in a way that maximises entropy
http://www.metafilter.com/90655/spacetime%2Dmust%2Dorganise%2Ditself%2Din%2Da%2Dway%2Dthat%2Dmaximises%2Dentropy
<a href="http://www.technologyreview.com/blog/arxiv/24975/">Gravity from Quantum Information</a> <br><i>At the heart of their idea is the tricky question of what happens to information when it enters a black hole. Physicists have puzzled over this for decades with little consensus. But one thing they agree on is <a href="http://en.wikipedia.org/wiki/Landauer's_principle">Landauer's principle</a>: that erasing a bit of quantum information always increases the entropy of the Universe by a certain small amount and requires a specific amount of energy.</i> (via <a href="http://www.marginalrevolution.com/marginalrevolution/2010/03/assorted-links-30.html">mr</a>) tag:metafilter.com,2010:site.90655Thu, 01 Apr 2010 20:18:45 -0800kliulessit from bit
http://www.metafilter.com/88471/it%2Dfrom%2Dbit
<a href="http://www.newscientist.com/article/mg20527443.800-the-entropy-force-a-new-direction-for-gravity.html?full=true">Emergent Gravity</a> - <a href="http://en.wikipedia.org/wiki/Erik_Verlinde">Erik Verlinde</a> has <a href="http://en.wikipedia.org/wiki/Gravity_as_an_entropic_force">a theory</a> that "gravitational attraction could be the result of the way information about material objects is organised in space..." Here's <a href="http://badphysics.wordpress.com/2010/01/11/%E2%80%9Con-the-origin-of-gravity-and-the-laws-of-newton%E2%80%9D-by-erik-verlinde/">some</a> <a href="http://motls.blogspot.com/2010/01/erik-verlinde-comments-about-entropic.html">related</a> <a href="http://staff.science.uva.nl/~erikv/page18/page18.html">weblog</a> <a href="http://www.math.columbia.edu/~woit/wordpress/?p=2650">discussions</a> and follow along <a href="http://twitter.com/erikverlinde">on twitter</a>! (via <a href="http://science.slashdot.org/story/10/01/10/1936240/The-End-Of-Gravity-As-a-Fundamental-Force">/.</a> & <a href="http://www.wired.com/beyond_the_beyond/2010/01/gravity-is-an-entropic-form-of-holographic-information/">bruces</a> ;) tag:metafilter.com,2010:site.88471Wed, 20 Jan 2010 14:11:07 -0800kliulessQuantum Mechanics: Myths and Facts
http://www.metafilter.com/69368/Quantum%2DMechanics%2DMyths%2Dand%2DFacts
<a href="http://arxiv.org/PS_cache/quant-ph/pdf/0609/0609163v2.pdf"><em>Quantum Mechanics: Myths and Facts</em></a> <small>(pdf)</small>, a recently-updated paper on the Cornell <a href="http://arxiv.org/">arXiv</a> peer-review site. By Hrvoje Nikolić of the Rudjer Bošković Institute in Croatia. Note: the presence of a paper on arXiv does not necessarily mean it <em>has</em> been reviewed and is not equivalent to having been published in a journal. tag:metafilter.com,2008:site.69368Mon, 25 Feb 2008 13:21:29 -0800XMLiciousDescribing a New Entropy
http://www.metafilter.com/8863/Describing%2Da%2DNew%2DEntropy
<a href="http://www.santafe.edu/sfi/publications/Bulletins/bulletinFall00/features/tsallis.html">Describing a New Entropy </a> A reformulation of Boltzmann-Gibbs entropy by one Constantino Tsallis is causing quite a buzz/stir in the theoretical physics community. It was originally published in 1988, but it sounds like it's only recently hit its stride. There's going to be <a href="http://discuss.santafe.edu/nonextensive2001/">a conference</a> on "Tsallis entropy" in October co-chaired by Murray Gell-Mann! tag:metafilter.com,2001:site.8863Sun, 08 Jul 2001 06:19:39 -0800kliuless