tag:blogger.com,1999:blog-78578519976117828572018-04-25T10:27:52.554-07:00Physics FrontiersJames Rantschlernoreply@blogger.comBlogger29125tag:blogger.com,1999:blog-7857851997611782857.post-40434985459937037712018-04-24T19:58:00.002-07:002018-04-24T19:58:39.684-07:00The Quantum Vacuum and the Casimir Effect<iframe src='https://podomatic.com/embed/html5/episode/8773811?autoplay=false' height='208' width='504'frameborder='0' marginheight='0' marginwidth='0' scrolling='no' allowfullscreen></iframe><br />Recorded: 9/16/2017 Released: 4/24/2018 <br /><br><span style="background-color: white; color: #525252; display: inline; float: none; font-family: "helvetica neue" , "helveticaneue" , "helvetica" , "arial" , sans-serif; font-size: small; font-style: normal; font-weight: 400; letter-spacing: normal; text-align: left; text-indent: 0px; text-transform: none; white-space: pre-line; word-spacing: 0px;">Jim and Randy review two very convincing papers that make the claim that the Casimir effect is due to materials fluctuations and not the zero point energy </span><br /><b></b><i></i><u></u><sub></sub><sup></sup><strike></strike><br />-------------------------------------------<br /><br />Notes:<br /><br />1. The papers we read for this program: <br /><ul><li> Jaffe, R.L. "<a href = https://journals.aps.org/prd/abstract/10.1103/PhysRevD.72.021301>The Casimir Effect and the Quantum Vacuum.</a>" Phys Rev D 72, 021301(R) (2005). [<a href = https://arxiv.org/abs/hep-th/0503158>arXiv</a>]</li><li> Nikolic, N., "<a href = https://www.sciencedirect.com/science/article/pii/S0003491617301410> Is Zero-point Energy Physical? A Toy Model for Casimir-like Effect.</a>" Ann Phys 383, 181 (2017). [<a href = https://arxiv.org/abs/1702.03291>arXiv</a></li></ul><br>2. We discuss an earlier episode on<a href = http://physicsfm-frontiers.blogspot.com/2017/05/vacuum-fluctuations-and-casimir-effect.html> the Casimir Effect and van der Waals forces</a> repeatedly in this episode.<br><br>3. Our <a href="https://www.reddit.com/r/physicsFM/">subreddit</a>. <br><br><div class="blogger-post-footer">(Content provided by Physics Frontiers and PhysicsFM))</div>James Rantschlerhttps://plus.google.com/104496580781469381673noreply@blogger.com0tag:blogger.com,1999:blog-7857851997611782857.post-58322778277241204992018-04-14T17:22:00.000-07:002018-04-23T09:58:01.002-07:00The Gravitational Equivalence Principles<iframe src='https://podomatic.com/embed/html5/episode/8764498?autoplay=false' height='208' width='504'frameborder='0' marginheight='0' marginwidth='0' scrolling='no' allowfullscreen></iframe><br />Recorded: 9/10/2017 Released: 4/14/2018 <br /><br><span style="background-color: white; color: #525252; display: inline; float: none; font-family: "helvetica neue" , "helveticaneue" , "helvetica" , "arial" , sans-serif; font-size: small; font-style: normal; font-weight: 400; letter-spacing: normal; text-align: left; text-indent: 0px; text-transform: none; white-space: pre-line; word-spacing: 0px;">Jim talks to Randy about the different ways in which the equivalence principle of general relativity can be formulated. More than just the equivalence of accelerations, the different possible meanings of the equivalence principle mean different things about how gravity works. From weak to strong, from Einstein's equivalence principle to Schiff's conjecture, the implications of these theories are explored. </span><br /><b></b><i></i><u></u><sub></sub><sup></sup><strike></strike><br />-------------------------------------------<br /><br />Notes:<br /><br />1. The papers we read for this program: <br /><ul><li>Sotiriou, T., Faraoni, V., and Liberati, S, "<a href = https://www.worldscientific.com/doi/abs/10.1142/S0218271808012097>Theory of Gravitation Theories: A No Progress Report.</a>"Intl J Mod Phys D 17, 399 (2008). [<a href = https://arxiv.org/abs/0707.2748>arXiv</a>]</li><li>Di Casola, E. and Liberati, S, "<a href = https://aapt.scitation.org/doi/10.1119/1.4895342>Nonequivalence of Equivalence Principles.</a>" Am J Phys 83, 39 (2015). [<a href = https://arxiv.org/abs/1310.7426>arXiv</a></li></ul><br>2. My review of <a href = http://physicsfm-master.blogspot.com/2017/09/theory-and-experiment-in-gravitational.html>Will's book</a>, which I talk about a little too much in this podcast. <br><br>3. Related Episodes of Physics Frontiers:<br><ul><li>Physics Frontiers 33: The Positive Energy Theorem</li><li>Physics Frontiers 31: The Parameterized Post-Newtonian Formalism</li><li>Physics Frontiers 29: Modified Gravity vs. Dark Energy I</li><li><a href = http://physicsfm-frontiers.blogspot.com/2018/02/dark-energy.html>Physics Frontiers 23: Dark Energy</a></li><li><a href = http://physicsfm-frontiers.blogspot.com/2017/06/requirements-for-gravitational-theories.html>Physics Frontiers 10: Requirements for Gravitational Theories</a></li><li><a href = http://physicsfm-frontiers.blogspot.com/2017/06/fr-theories-of-gravity.html>Physics Frontiers 9: f(R) Theories of Gravity</a></li><li><a href = http://physicsfm-frontiers.blogspot.com/2017/06/fr-theories-of-gravity.html>Physics Frontiers 1: G4V: The Gravitational 4-Vector Formulation of Gravity</a></li></ul><br>4. Our <a href="https://www.reddit.com/r/physicsFM/">subreddit</a>. <br><br>--------------------------------------------<br><br>A review of "<A HREF = https://www.reddit.com/r/arXiv_Plus/comments/8dzkpv/07072748_theory_of_gravitation_theories_a/>Theory of Gravitation Theories</a>" from the <a href = https://www.reddit.com/r/arXiv_Plus/>arXiv_plus</a> subreddit:<br><BR>This delightfully named paper explains the relationship between the equivalence principles – the three equivalence principles listed in Will’s book: weak, Einstein, and strong – and the modified gravities that serve as competitors to general relativity (GR) with a cosmological constant in the quest to explain dark energy. The meat of the text centers around showing that a theory of gravity is a cluster of mathematical representations of that theory that are linked in an analogous way as different gauges in electromagnetism, although no general method of transformation is given, and that in order to satisfy the intermediate level of equivalence only one of these representations must satisfy the metric postulates. This ambiguity in representation is reflected in the way in which the additional fields of modified gravities are represented: whether the field is additional “matter” or a coupling that changes the “geometry” is a matter of the representation, not the theory itself.<br><BR> The metric postulates simply ask a theory to (1) produce a metric g<SUp>mn</SUP> that describes the geometry of space-time and (2) admit only stress-energy tensors whose covariant derivative is zero. This is what you have in GR. It has been shown that the weakest version of the equivalence principle, which in its simplest form means that gravitational provides a preferred set of trajectories for small, uncharged particles to take without reference to their mass, is not, in itself, sufficient to establish these metric postulates. Instead, two other postulates are required, both self-explanatory: Local Lorentz Invariance and Local Position Invariance. These three postulates together form the Einstein equivalence principle and, along with some reasonable limitations on the mathematics, are sufficient to create a general class of metric theories of gravity with an additional scalar field (scalar-tensor theories). Each theory itself will be a cluster of the mathematical representations of the same.<br><BR> One of the take-aways from this paper is that common procedures for determining if a theory satisfies EEP have made an error of checking single mathematical representations in those clusters against the metric postulates or Local Lorentz Invariance and ignoring the equivalent representations. The main example in the text compares the Jordan and Einstein frames in scalar-tensor theories, showing that they are equivalent, but the Einstein representation does not satisfy the metric postulates. However, since the Jordan frame representation of a scalar-tensor theory does satisfy the metric postulates, the theory itself does. This does, however show an issue with the frames that do not satisfy the postulates: changes need to be made in interpreting their metric tensors or geodesic equations, or even the connection in that frame. For example, in moving to the Einstein frame, you add an additional term in the geodesic equations that can be interpreted as:<br><BR> (1) The gradient of the scalar field<br><BR> (2) The variation of the masses of elementary particles in space<br><BR> (3) Changes in the “unit of mass” along the trajectory<br><BR> Although I’m not sure if (2) and (3) are the same or that the relative masses also change, making a coherent standard impossible.<br><BR> Unfortunately, according to the authors, only individual mathematical representations of modified gravities exist in the literature, not more general theories that encompass the all of the representations of those theories, and so miscategorizations are likely. More unfortunately, a way forward towards a more abstract definition of individual theory clusters is not given in the text. <div class="blogger-post-footer">(Content provided by Physics Frontiers and PhysicsFM))</div>James Rantschlerhttps://plus.google.com/104496580781469381673noreply@blogger.com0tag:blogger.com,1999:blog-7857851997611782857.post-33105957834400936862018-03-25T16:58:00.001-07:002018-03-25T19:48:07.810-07:00Antimatter Production at a Potential Boundary<iframe src='https://podomatic.com/embed/html5/podcast/5495687?autoplay=false' height='208' width='504'frameborder='0' marginheight='0' marginwidth='0' scrolling='no' allowfullscreen></iframe><br />Recorded: 6/17/2017 Released: 3/25/2017 <br /><br><span style="background-color: white; color: #525252; display: inline; float: none; font-family: "helvetica neue" , "helveticaneue" , "helvetica" , "arial" , sans-serif; font-size: small; font-style: normal; font-weight: 400; letter-spacing: normal; text-align: left; text-indent: 0px; text-transform: none; white-space: pre-line; word-spacing: 0px;">Randy discusses a proposal for the production of antimatter without using supercolliders with Jim. This proposal would have used Klein's paradox for the production of electron-positron pairs at a very sharp, steep potential boundary produced through the Casimir effect. </span><br /><b></b><i></i><u></u><sub></sub><sup></sup><strike></strike><br />-------------------------------------------<br /><br />Notes:<br /><br />1. The paper we read for this program: <br /><ul><li>Lapointe, M., "<a href = https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20010091016.pdf>Antimatter Production at a Potential Boundary.</a>" NASA/CR 2001-211116 (2001).</li></ul><br><br />2. The <a href = http://www.niac.usra.edu/>NASA Institute for Advanced Concepts</a> no longer exists (apparently it closed down in 2007), but there is now a <a href = https://www.nasa.gov/directorates/spacetech/niac/index.html>NASA Innovative Advanced Concepts</a>, a program with the same acronym that seems to have a similar purpose (if not, tell me the salient difference in the comments). <br><br>3. Our listenership has increased markedly since we recorded this episode last June. We had 1,057 downloads in the first fifteen days of June 2017, and in the first two weeks of March we had 3,117. In both cases there were no podcasts published during the time interval (in the current case because this is my heavy semester at work and it eats into my free time). <br><br>4. Our <a href="https://www.reddit.com/r/physicsFM/">subreddit</a>. <div class="blogger-post-footer">(Content provided by Physics Frontiers and PhysicsFM))</div>James Rantschlerhttps://plus.google.com/104496580781469381673noreply@blogger.com0tag:blogger.com,1999:blog-7857851997611782857.post-55574711756598864062018-03-15T20:12:00.001-07:002018-03-25T19:47:47.167-07:00Gravitational Field Propulsion<iframe src='https://podomatic.com/embed/html5/episode/8736796?autoplay=false' height='208' width='504'frameborder='0' marginheight='0' marginwidth='0' scrolling='no' allowfullscreen></iframe><br /><br /><span style="background-color: white; color: #525252; display: inline; float: none; font-family: "helvetica neue" , "helveticaneue" , "helvetica" , "arial" , sans-serif; font-size: small; font-style: normal; font-weight: 400; letter-spacing: normal; text-align: left; text-indent: 0px; text-transform: none; white-space: pre-line; word-spacing: 0px;">Randy introduces Jim to several ways in which people have theorized that gravity can be used to propel an object through space. In order of likelihood and in inverse order of coolness: <UL><LI>The Slingshot Effect -- Using a gravitational well to increase the energy available to an object. (In use) <LI>The Penrose Process -- Using a rotating black hole to gain energy. (Penrose) <LI>Negative Inertia Mass -- If mass has both a negative charge and inertia, then you can build a device that moves perpetually (RL Forward) <LI>Induced Gravitational Dipoles -- Spinning half of a sphere will (supposedly) propel it in some direction or other. (Jeong) <LI>The Alcubierre Drive -- A process that would sneak around the laws of relativity and allow someone to travel faster than light. (Alcubierre, White) </UL> </span><br /><b></b><i></i><u></u><sub></sub><sup></sup><strike></strike><br />-------------------------------------------<br /><br />Notes:<br /><br />1. The papers we read for this program: <br /><ul><li>Wisdom, J., "<a href = http://science.sciencemag.org/content/299/5614/1865>Swimming in Space-Time: Motion by Cyclic Changes in Body Shape.</a>" Science 299, 1865 (2003).</li><li>Longo, M.J., "<a href = https://aapt.scitation.org/doi/10.1119/1.1773576>Swimming in Newtonian Space-time: Orbital Changes by Cyclic Changes in Body Shape.</a>" American Journal of Physics 72, 1312 (2004).</li><li>Forward, R.L., "<a href = https://arc.aiaa.org/doi/abs/10.2514/3.23219>Negative Matter Propulsion</a>." Journal of Propulsion and Power 6, 28 (1990).</li><li>Forward, R.L., "<a href = https://arc.aiaa.org/doi/abs/10.2514/6.1989-2332>Space Warps: A Review of One Form of Propulsionless Transport.</a>" Proceedings of the 25th Joint Propulsion Conference (1989).</li><li>Jeong, E.J., "Anomalous Center of Mass Shift: Gravitational Dipole Moment." [<a href =https://arxiv.org/abs/gr-qc/9604044>arXiv</a>] </li><li>Alcubierre, M., "<a href = http://iopscience.iop.org/article/10.1088/0264-9381/11/5/001/meta>The Warp Drive: Hyper-Fast Travel Within General Relativity</a>." Classical and Quantum Gravity 11, L73 (1994). [<a href = https://arxiv.org/abs/gr-qc/0009013>arXiv</a>]</li><li>White, H., "<a href = https://ntrs.nasa.gov/search.jsp?R=20110015936>Warp Field Mechanics 101</a>." DARPA/NASA 100 Year Starship Conference (2011).</li> </ul><br><br />2. The slingshot effect is in common use and is a topic viable at the junior mechanics level in such books as <a href = http://amzn.to/2DzJIFY>Taylor's</a> and <a href = http://amzn.to/2pihNWv>Morin's</a>.<br><br>3. There is a problem defining the center of mass in general relativity, and we've recorded at least one podcast related to the topic (although not directly addressing it) between the recording of this last June and its publication in March. But the problem is with defining mass, not the center of mass. And because of the simplicity of the space-time swimmers, I'm still not sure its as much of a problem as some people do.<br><br>4. Popular articles for this program: <br /><ul><li>Gueron, Eduardo, "<a href = https://www.scientificamerican.com/article/surprises-from-general-relativity/>Adventures in Curved Spacetime</a>." Scientific American 301(2), 38 (Aug 2009)</ul><br>5. The video Randy keeps talking about in the podcast he found linking through <a href = http://www.science20.com/hammock_physicist/swimming_through_empty_space>The Hammock Physicist Blog</a> of Johannes Koelman. You can <a href = http://www.iop.org/EJ/mmedia/1367-2630/8/5/068/movie1.avi>download it here</a> from the IOP. I haven't yet found the article IOP attached it to. <br /><br>6. I'll make a video of the non-commutative motion diagrams that I sent Randy and put a link up here.<br><br />7. Our <a href="https://www.reddit.com/r/physicsFM/">subreddit</a>. <div class="blogger-post-footer">(Content provided by Physics Frontiers and PhysicsFM))</div>James Rantschlerhttps://plus.google.com/104496580781469381673noreply@blogger.com0tag:blogger.com,1999:blog-7857851997611782857.post-11393970557647730012018-02-23T20:33:00.001-08:002018-02-23T20:43:51.337-08:00The Island of Stability<iframe src='https://podomatic.com/embed/html5/episode/8716081?autoplay=false' height='208' width='504'frameborder='0' marginheight='0' marginwidth='0' scrolling='no' allowfullscreen></iframe><br /><br /><span style="background-color: white; color: #525252; display: inline; float: none; font-family: "helvetica neue" , "helveticaneue" , "helvetica" , "arial" , sans-serif; font-size: small; font-style: normal; font-weight: 400; letter-spacing: normal; text-align: left; text-indent: 0px; text-transform: none; white-space: pre-line; word-spacing: 0px;">Randy tells Jim about the Island of Stability. This is a theoretically predicted region (or two, in one calculation) where the isotopes of atoms with heavy nuclei are stable. Jim and Randy talk about the islands, how they are attempting to get there, and some of the calculations people use to predict the stability of elements. Along the way, they mispronounce a lot of words. </span><br /><b></b><i></i><u></u><sub></sub><sup></sup><strike></strike><br />-------------------------------------------<br /><br />Notes:<br /><br />1. The papers we read for this program: <br /><ul><li>Karpov, A.V.,Zagrebaev, V.I., Martinez Palenzuela, Y., Felipe Ruiz, L., and Greiner, W., "<a href = http://www.worldscientific.com/doi/abs/10.1142/S0218301312500139?journalCode=ijmpe>Decay Properties and Stability of Heaviest Elements.</a>" International Journal of Modern Physics E 21, 1250013 (2012).</li><li>Oganessian, Y.T., "Synthesis of a New Element with Atomic Number Z = 117." Physical Review Letters 104, 142502 (2010).</li><li>Zagrebaev, V., Karpov, A., and Geiner, W., "<a href = http://iopscience.iop.org/article/10.1088/1742-6596/420/1/012001/meta>Future of Superheavy Element Research: Which Nuclei Could Be Synthesized within the Next Few Years?</a>" Journal of Physics Conference Series 420 012001 (2013) [<a href = https://arxiv.org/abs/1207.5700>arXiv</a>]</ul>2. The book I talked about on fluids that goes into the fluid model of the nucleus is <a href = http://amzn.to/2HGeOyO>Introduction to the Physics of Fluids and Solids</a> by James S. Trefil, which is apparently no longer in print (I have a Dover edition, I love Dover). My favorite Modern Physics text is <a href = http://amzn.to/2FtJR07>Rohlf</a>, mostly because of its focus on scattering, but I taught from <a hreef = http://amzn.to/2GEDFSi>Serway</a>, which is more standard. <br /><br><br />3. Our <a href="https://www.reddit.com/r/physicsFM/">subreddit</a>. <div class="blogger-post-footer">(Content provided by Physics Frontiers and PhysicsFM))</div>James Rantschlerhttps://plus.google.com/104496580781469381673noreply@blogger.com2tag:blogger.com,1999:blog-7857851997611782857.post-53085565073414928492018-02-08T19:38:00.000-08:002018-04-25T10:27:52.504-07:00Dark Energy<iframe src='https://podomatic.com/embed/html5/episode/8701690?autoplay=false' height='208' width='504'frameborder='0' marginheight='0' marginwidth='0' scrolling='no' allowfullscreen></iframe><br /><br /><span style="background-color: white; color: #525252; display: inline; float: none; font-family: "helvetica neue" , "helveticaneue" , "helvetica" , "arial" , sans-serif; font-size: small; font-style: normal; font-weight: 400; letter-spacing: normal; text-align: left; text-indent: 0px; text-transform: none; white-space: pre-line; word-spacing: 0px;">Randy helps Jim get a handle on dark energy. Why do we need it? Why do we want to believe in it now, but didn't earlier? How many different things could it be? What does it have to do with you? How close are we to knowing anything about it? </span><br /><b></b><i></i><u></u><sub></sub><sup></sup><strike></strike><br />-------------------------------------------<br /><br />Notes:<br /><br />1. The papers we read for this program: <br /><ul><li>Carroll, S., "Dark Energy and the Preposterous Universe." [<a href="https://arxiv.org/abs/astro-ph/0107571">arXiv</a>]</li><li>Turner, M., "Dark Energy and the New Cosmology." [<a href="https://arxiv.org/abs/astro-ph/0108103">arXiv</a>]</li><li>Zwicky, F., "On the Masses of Nebulae and Clusters of Nebulae." <i>Astrophys. J.</i> <b>86</b>, 217 (1937) [<a href="https://ned.ipac.caltech.edu/level5/Sept01/Zwicky/Zwicky_contents.html">web</a>]</li><li>Holsclaw, T., Alam, U., Sanso, B, Lee, H., Heitmann, K., Habib, S. and Higdon, D., "New Constraints on the Time-Variation of the Dark Energy Equation of State from Current Supernova Data." [<a href="https://www.soe.ucsc.edu/sites/default/files/technical-reports/UCSC-SOE-10-01.pdf">web</a>]</li></ul>2.I'll review Oyvind Gron's book, <a href = http://amzn.to/2Bj6sfY><I>Lecture Notes on the General Theory of Relativity</I></a> soon. I've been meaning to for a couple of months now.<br /><br>3. Previous Episodes Referenced:<br /><ul><li><a href = http://frontiers.physicsfm.com/7>Virtual Gravitational Dipoles</a></li><li><a href = http://frontiers.physicsfm.com/9>f(R) Theories of Gravity</a></li><li><a href = http://frontiers.physicsfm.com/10>Requirements for Alternative Theories of Gravity</a></li></ul>4. Read <a href = http://physicsfm-master.blogspot.com/2018/04/cosmic-update-by-adams-buchert-and.html>my review</a> of <a href = https://amzn.to/2vGUQlB>Cosmic Update</a>, a book about cosmology in the accelerating universe.<br><br>5.If you or Dragan Hejdukovic wants to supply us with the background energy that would be predicted from virtual gravitational dipoles, please leave us a nice comment with smilies.<br /><br />6. Our <a href="https://www.reddit.com/r/physicsFM/">subreddit</a>. <div class="blogger-post-footer">(Content provided by Physics Frontiers and PhysicsFM))</div>James Rantschlerhttps://plus.google.com/104496580781469381673noreply@blogger.com0tag:blogger.com,1999:blog-7857851997611782857.post-76375100841410968312018-01-21T17:42:00.001-08:002018-01-24T05:51:04.669-08:00Weyl and Quasiparticles<iframe allowfullscreen="" frameborder="0" height="208" marginheight="0" marginwidth="0" scrolling="no" src="https://podomatic.com/embed/html5/episode/8683635?autoplay=false" width="504"></iframe><br /><br /><span style="background-color: white; color: #525252; display: inline; float: none; font-family: "helvetica neue" , "helveticaneue" , "helvetica" , "arial" , sans-serif; font-size: small; font-style: normal; font-weight: 400; letter-spacing: normal; text-align: left; text-indent: 0px; text-transform: none; white-space: pre-line; word-spacing: 0px;">Jim and Randy discuss quasiparticles recently found in condensed matter systems that mirror particles theorized nearly a hundred years ago, but never found in the vacuum. Weyl particles are massless fermions, and once it was hoped that neutrinos would turn out to be this kind of particle, and Majorana fermions have real-valued wave functions and therefore many strange and possibly useful properties. </span><br /><b></b><i></i><u></u><sub></sub><sup></sup><strike></strike><br />-------------------------------------------<br /><br />Notes:<br /><br />1. The papers we read for this program: <br /><ul><li>Pal, P.B., "<a href="http://aapt.scitation.org/doi/full/10.1119/1.3549729">Dirac, Majorana, and Weyl Fermions</a>." <i>Am. J. Phys</i>. <b>79</b>, 485 (2011). [<a href="https://arxiv.org/abs/1006.1718">arXiv</a>]</li><li>Mourik, Zuo, Frolov, Plissard, Bakkers, and Kouwenhoven, "<a href="http://science.sciencemag.org/content/336/6084/1003">Signatures of Majorana Fermions in Hybrid Superconductor-Semiconductor Nanowire Devices</a>." <i>Science</i> <b>336</b>, 1003 (2012). [<a href="https://arxiv.org/abs/1204.2792">arXiv</a>]</li><li>Nadj-Perge, Drozdov, Li, Chen, Jeon, Seo, MacDonald, Bernevig, and Yazsdani, "<a href="http://science.sciencemag.org/content/346/6209/602">Observation of Majorana Fermions in Ferromagnetic Atomic Chains of a Superconductor</a>." <i>Science</i> <b>346</b>, 602 (2014) [<a href="https://arxiv.org/abs/1410.0682">arXiv</a>] </li><li>Xu, et al., "<a href="https://www.nature.com/articles/nphys3437">Discovery of a Weyl Fermion State with Fermi Arcs in Niobium Arsenide</a>." <i>Nat. Phys.</i> <b>11</b>, 748 (2015) [<a href="https://arxiv.org/abs/1504.01350">arXiv</a>]</li><li>Zhang, et al, "<a href="https://www.nature.com/articles/ncomms10735">Signatures of the Adler-Bell-Jackiw Chiral Anomaly in a Weyl Fermion Semimetal</a>." <i>Nat. Comm.</i> 10735 (2016) [<a href="https://www.nature.com/articles/ncomms10735">arXiv</a>]</li></ul>2. Popular papers we may have read:<br /><ul><li>Wilczek, F., "<a href="http://physicstoday.scitation.org/doi/10.1063/1.882086?journalCode=pto">Why are there Analogies between Condensed Matter and Particle Theory?</a>" <i>Physics Today</i> <b>51</b>, 11 (1998).</li><li>Wilczek, F., "<a href="https://www.nature.com/articles/nphys1380">Majorana Returns</a>." <i>Nature Physics</i> <b>5</b>, 614 (2009) </li><li>Balents, Leon, "<a href="https://physics.aps.org/articles/v4/36">Weyl Electrons Kiss</a>." <i>Physics</i> <b>4</b>, 36 (2011).</li><li>"<a href="https://www.nature.com/articles/nphys3481">After a Weyl</a>" Nat. Phys. 11, 697 (2015)</li><li>Bernevig, B.A., "<a href="https://www.nature.com/articles/nphys3454">It's Been a Weyl Coming</a>." Nat. Phys. 11, 699 (2015)</li></ul>3. Original Papers:<br /><ul><li>Weyl, H., "<a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC522457/">Gravitation and the Electron</a>." Proc. Nat. Acad. Sci., 323 (1929). </li><li>Majorana, "<a href="http://www.physics.umanitoba.ca/~tapash/Majorana_1937.pdf">A Symmetric Theory of Electrons and Positrons</a>." Il Nuovo Cimento, 14, 171 (1937).</li></ul>4. I was wrong. "Weyl" rhymes with "pile," not with "pail."<br /><br />5. Our <a href="https://www.reddit.com/r/physicsFM/">subreddit</a>. <div class="blogger-post-footer">(Content provided by Physics Frontiers and PhysicsFM))</div>James Rantschlerhttps://plus.google.com/104496580781469381673noreply@blogger.com0tag:blogger.com,1999:blog-7857851997611782857.post-24223519517586654642018-01-10T19:37:00.001-08:002018-01-10T19:45:18.660-08:00The Origin of Inertia<iframe src='https://podomatic.com/embed/html5/episode/8673771?autoplay=false' height='208' width='504'frameborder='0' marginheight='0' marginwidth='0' scrolling='no' allowfullscreen></iframe><br /><br />Randy tells Jim about a scheme that uses Mach's Principle - the idea that there is a preferred background frame with respect to the fixed stars - to explain the origin of inertia. Why exactly does an object in motion stay in motion? <br /><br />-------------------------------------------<br /><br />Notes:<br /><br />1. The papers we read for this program: <br /><ul><li><a href = https://physics.fullerton.edu/~jimw/general/inertia/index.htm> The Origin of Inertia </a>, James Woodward (blog post, 1998)</li><li><a href = http://adsabs.harvard.edu/full/1953MNRAS.113...34S>On the Origin of Inertia</a>, Sciama, D. W., Monthly Notices of the Royal Astronomical Society 113, 34 (1953)</li><li><a href = https://www.hindawi.com/journals/amp/2013/801574/>Study on Inertia as a Gravity Induced Property of Mass, in an Infinite Hubble Expanding Universe</a>,Jeroen van Engelshoven, Advances in Mathematical Physics 2013, 801574 (2013)</li><li><a href = http://frankwilczek.com/Wilczek_Easy_Pieces/342_Origin_of_Mass.pdf>On the Origin of Mass</a>, Wilczek, F.</li></ul><br>2. In addition, Randy sent me a lot of blog and other forum posts for background:<br><ul><li> https://www.physicsforums.com/threads/the-origin-of-inertia.440707/</li><li> <A href = https://www.physicsforums.com/threads/origin-of-inertia.657760/>https://www.physicsforums.com/threads/origin-of-inertia.657760/</a></li><li> <a href = http://stardrive.org/stardrive/index.php/all-blog-articles/4846-sciamas-1952-paper-on-the-qorigin-of-inertiaq>http://stardrive.org/stardrive/index.php/all-blog-articles/4846-sciamas-1952-paper-on-the-qorigin-of-inertiaq</a></li><li> <a href = http://stardrive.org/stardrive/index.php/all-blog-articles/12297-james-f-woodward-s-book-making-starships-and-stargates-march-10-2014> http://stardrive.org/stardrive/index.php/all-blog-articles/12297-james-f-woodward-s-book-making-starships-and-stargates-march-10-2014</a></li><li> <a href = https://quantumj13.imascientist.org.uk/2013/06/19/is-higgs-field-an-answer-to-the-property-of-inertia-and-whats-the-role-of-higgs-boson-in-it/>https://quantumj13.imascientist.org.uk/2013/06/19/is-higgs-field-an-answer-to-the-property-of-inertia-and-whats-the-role-of-higgs-boson-in-it/</a></li></ul><br /><br />3. Our discussion on <a href = http://physicsfm-frontiers.blogspot.com/2016/12/gravitoelectromagnetism.html>Gravitoelectromagnetism</a>..<br><br>4. Our discussion of Aharonov and Rohrlich's <a href = https://paradoxes-physicsfm.blogspot.com/>Quantum Paradoxes</a>, nine of the ten recorded episodes. I don't think we get into the retrocausal part of it.<br><br>5. Our <a href="https://www.reddit.com/r/physicsFM/">subreddit</a>. <div class="blogger-post-footer">(Content provided by Physics Frontiers and PhysicsFM))</div>James Rantschlerhttps://plus.google.com/104496580781469381673noreply@blogger.com0tag:blogger.com,1999:blog-7857851997611782857.post-42036192176512241552017-12-21T19:44:00.001-08:002017-12-21T19:44:21.817-08:00ExoplanetsEpisode 19 - Exoplanets has been lost. We continue with our original numbering as we attempt to fix it. Go to <a href = http://frontiers.physicsfm.com/20>Episode 20 - Time Crystals</a> for the next episode.<div class="blogger-post-footer">(Content provided by Physics Frontiers and PhysicsFM))</div>James Rantschlerhttps://plus.google.com/104496580781469381673noreply@blogger.com0tag:blogger.com,1999:blog-7857851997611782857.post-72565266897044647872017-12-21T19:29:00.000-08:002018-04-21T16:51:06.069-07:00Time Crystals<iframe allowfullscreen="" frameborder="0" height="208" marginheight="0" marginwidth="0" scrolling="no" src="https://podomatic.com/embed/html5/episode/8657663?autoplay=false" width="504"></iframe> <br /><br />Jim talks to Randy about structures that are periodic in time like crystals are periodic in space. This idea came from Frank Wilczek in 2012, and was realized just recently, providing an extraordinary turn-around time from theory to observation. <br /><br />-------------------------------------------<br /><br />Notes:<br /><br />1. The papers we read for this program: <br /><ul><li><a href="https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.109.16040l">Quantum Time Crystals</a>, Wilczek,, F. <i> Physical Review Letters</i> <b>109</b>, 160401 (2012) [<a href="https://arxiv.org/abs/1202.2539">arXiv</a>] </li><li><a href="https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.118.030401">Discrete Time Crystals: Rigidity, Criticality, and Realizations</a>,Yao, Potter, Potirniche, and Vishwanath. <i> Physical Review Letters</i><b>119</b> 030401 (2017) [<a href="https://arxiv.org/abs/1608.02589">arXiv</a>]</li><li><a href="https://www.nature.com/articles/nature21413">Observation of Discrete Time Crystal</a>, Zhang, Hess, Kyprianidis, Becker, Lee, Smith, Pagano, Potirniche, Potter, Vishwanath, Yao, and Monroe. <i>Nature</i> <b>543</b> 217 (2017) [<a href="https://arxiv.org/abs/1609.08684">arXiv</a>] </li><li><a href="https://www.nature.com/articles/nature21426">Observation of discrete time-crystalline order in a disordered dipolar many-body system</a>, Choi, Choi, Landig, Kucsko, Zhou, Isoya, Jelezko, Onoda, Sumiya, Khemani, von Keyerlingk, Yao, Demler, and Lukin. <i>Nature</i> <b>543</b> 221 (2017) [<a href="https://arxiv.org/abs/1610.08057">arXiv</a>] </li></ul><br />2. Our <a href="https://www.reddit.com/r/physicsFM/">subreddit</a>. <br><br>------------------------------------------------<br><br>The following <a href = "https://www.reddit.com/r/arXiv_Plus/comments/7psi1c/12022539_quantum_time_crystals/">post</a> was made to the <a href = https://www.reddit.com/r/arXiv_Plus/ >arXiv_plus</a> subreddit about these papers:<br><Br>This was an interesting one. Frank Wilczek hypothesized, here, that there would be structures that were periodic in time the way crystals are periodic in space. The wave functions, in time, would be similar to the Bloch functions of condensed matter. The character of the wave functions would be a little like solitons, with an attractive nonlinearity balanced by uncertainty-related dispersion. His original model was to look at coupled superconducting rings. The coupling would repeatedly and periodically reproduce the same state.<br><br> In Discrete time crystals: rigidity, criticality, and realizations, Yao, et al., showed that the ground state wave function cannot have the periodicity required -- but an excited state could. What you would need to do is produce a Hamiltonian that did three things, successively: orient the system, order the system, and finally randomly disorder it.<br><br> Two groups wasted no time at all producing these excited "time crystals," simultaneously publishing in Nature about a year ago. One group looked at what I'd think of as a very artificial system, a few optically-trapped, ultra-cold atoms. In this case each of the effects was programmed by laser interactions. The other group used a real crystal: diamond with nitrogen vacancies at room temperature.<br><br> Both groups successfully reproduced the phenomena of Yao's paper. The nature of the Hamiltonians, if I'm free to interpret them, is a successive Zeeman interaction to align the spins of the atoms, an exchange term like the Heisenberg Hamiltonian, and a diffusion term.<br><br> There is some similarity to spin echos here, but the effects are much more coherent. <div class="blogger-post-footer">(Content provided by Physics Frontiers and PhysicsFM))</div>James Rantschlerhttps://plus.google.com/104496580781469381673noreply@blogger.com0tag:blogger.com,1999:blog-7857851997611782857.post-76642020378262310542017-12-06T09:36:00.000-08:002018-02-09T11:37:12.932-08:00The 2T Physics of Itzhak Bars<iframe allowfullscreen="" frameborder="0" height="208" marginheight="0" marginwidth="0" scrolling="no" src="https://podomatic.com/embed/html5/episode/8632230?autoplay=false" width="504"></iframe> <br /><br />Randy tells Jim about a theory that complements other theories of fundamental physics based upon a phase space symmetry between the 4-position and the 4-momentum of a particle. The upshot of the theory is that there should be a second time dimension and a fourth space dimension, both macroscopic in extent, and the physics we see are 4D projections from the larger 6D space-time. <br /><br />-------------------------------------------<br /><br />Notes:<br /><br />1. The papers we read for this program: <br /><ul><li><a href = https://phys.org/news/2007-05-two-time-universe-physicist-explores-dimension.html>A two Time Universe?</a>, by Tom Siegfried on phys.org. This is a popular article on the theory. <li>The Standard Model as a 2T Physics Theory, Itzhak Bars. AIP Conference Proceedings 903, 550 (2006) [<a href = https://arxiv.org/abs/hep-th/0610187>arXiv</a>]</li><li><a href = https://journals.aps.org/prd/abstract/10.1103/PhysRevD.77.125027>Gravity in 2T Physics</a>, Itzhak Bars, Physical Review D77, 125027 (2008) [<a href = https://arxiv.org/abs/0804.1585>arXiv</a>] </li></ul><br />2. Itzhak Bars lecture on <a href = http://www.perimeterinstitute.ca/videos/2t-physics>2T Physics</a>.<br /><br />3. <a href = http://amzn.to/2C9CgAq><I>Extra Dimensions in Space and Time</I></a>, a book containing a longer, less technical (almost popular) description of 2T physics by Itzhak Bars. That takes up about half the book, the other half is John Terning discussing more traditional extra dimensions in string theory. My review on PhysicsFM is <a href = http://physicsfm-master.blogspot.com/2017/10/extra-dimensions-in-space-and-time-by.html>here</a>.<br /><br />4. Our <a href="https://www.reddit.com/r/physicsFM/">subreddit</a>. <div class="blogger-post-footer">(Content provided by Physics Frontiers and PhysicsFM))</div>James Rantschlerhttps://plus.google.com/104496580781469381673noreply@blogger.com0tag:blogger.com,1999:blog-7857851997611782857.post-14780109205245871972017-11-24T11:12:00.000-08:002017-11-24T15:49:16.702-08:00The Physics of Time Travel<iframe src='https://podomatic.com/embed/html5/episode/8632230?autoplay=false' height='208' width='504'frameborder='0' marginheight='0' marginwidth='0' scrolling='no' allowfullscreen></iframe> <br /><br />Randy and Jim try to get their heads around how time relates to relativity. Of particular interest is Kurt Goedel's 1949 solution to the field equations that shows closed time-like null geodesics (paths followed by massless particles moving at the speed of light). The subject focuses mainly of some implications of general relativity that obey our intuition locally, but not globally. <br /><br />-------------------------------------------<br /><br />Notes:<br /><br />1. The papers we read for this program: <br /><ul><li>An Example of a New Type of Cosmological Solutions of Einstein's Field Equations of Gravitation, Kurt Godel (Rev Mod Phys 21 447 (1949)</li><li>Cauchy Problem in Spacetimes with Closed Timelike Curves, Physical Review D 42, 1915 (1990)</li><li>Closed Timelike Curves, Bryan W. Roberts</li><li>Is Physics Consistent with Closed Timelike Curves? John L. Fiedman, Annals of the New York Academy of Sciences </li><li>Chronology Protection Conjecture, S. W. Hawking, Physical Review D 46, 603 (1992)</li><li>Time Travel and Time Machines, Chris Smeenk and Christian Wuthrich, Oxford Handbook of Time (Oxford)</li></ul><br /><br />2. Kurt Goedel's <a href = https://www.amazon.com/Formally-Undecidable-Propositions-Principia-Mathematica/dp/0486669807/ref=sr_1_fkmr0_3?ie=UTF8&qid=1511550323&sr=8-3-fkmr0&keywords=goedel+impossibility> <I>On Formally Undecidable Propositions of Principa Mathematica and Related Systems</I></a>, which I jabber on a little too much about in the podcast.<br><br>3. <a href =https://www.amazon.com/World-Without-Time-Forgotten-Einstein/dp/0465092942/ref=sr_1_3?s=books&ie=UTF8&qid=1511550446&sr=1-3&keywords=godel+einstein><I> A World Without Time: The Forgotten Legacy of Goedel and Einstein</I></a> by Palle Yourgrau, a popular book on this subject I read a long time ago and I misplaced.<br><br>4. James Gleick's Google talk on <a href = https://www.youtube.com/watch?v=mt023oWeZy8>time travel</a>, and <a href = https://www.amazon.com/Time-Travel-History-James-Gleick/dp/080416892X/ref=sr_1_4?s=books&ie=UTF8&qid=1511550956&sr=1-4&keywords=james+gleick><I>Time Travel: A History</I></a>, the book it's based on.<br><br>5. I dropped about 7 minutes of my recording, which from Randy's comments included a brief discussion of positive probability of backward causation in the Compton effect's path integral formulation. I did include his overview of "Time Travel and Time Machines," after the end of the show which is a philosopher's take on the issue.<br><Br>6. Our <a href="https://www.reddit.com/r/physicsFM/">subreddit</a>. <div class="blogger-post-footer">(Content provided by Physics Frontiers and PhysicsFM))</div>James Rantschlerhttps://plus.google.com/104496580781469381673noreply@blogger.com0tag:blogger.com,1999:blog-7857851997611782857.post-38579640478247806022017-11-06T12:37:00.001-08:002017-11-24T10:45:51.131-08:00Stochastic Resonance Energy Harvesting<iframe allowfullscreen="" frameborder="0" height="208" marginheight="0" marginwidth="0" scrolling="no" src="https://podomatic.com/embed/html5/episode/8615303?autoplay=false" width="504"></iframe><br /><br />Randy tells Jim about ways in which external vibrations can be used to do useful work in large-scale devices. These processes look at have happens when bistable systems (e.g., a bent cantilever) are subjected to random forcing from the environment.<br /><br />-------------------------------------------<br /><br />Notes:<br /><br />1. The papers we read for this program: <br /><ul><li>A Piezomagnetoelastic Structure for Broadband Energy Harvesting (APL2009)</li><li>A Review of the Recent Research on Vibration Energy Harvesting via Bistable Systems (2013)</li><li>An Application of Stochastic Resonance for Energy harvesting (JSV2014)</li><li>An Experimental Study of Stochastic Resonance in a Bistable Mechancial Systems (2012)</li><li>Bistable Vibration Energy Harvesters (2012)</li><li>Feasibility of Energy harvesting Using Stocahstic Resonance (2014)</li><li>Towards Broadband Vibration-Based Energy Harvesting</li></ul><br />2. Past and future shows:<br /><br /><ul><li> Physics Frontiers 4: <a href="http://physicsfm-frontiers.blogspot.com/2017/01/phononics.html">Phononics</a></li><li> Physics Frontiers 12: <a href="http://physicsfm-frontiers.blogspot.com/2017/07/photonic-molecules-and-optical-circuits.html">Photonic Molecules and Optical Circuits</a> [Metamaterials]</li><li> Physics Frontiers 20: <a href="http://physicsfm-master.blogspot.com/2017/09/physics-frontiers-index.html">Time Crystals</a> [Coming Soon]</li></ul><br />3. Bing Crosby, Ac-cent-tchu-ate the Positive:<br /><ul><li><a href="https://www.youtube.com/watch?v=-cgVRwITAfY">Ac-cent-tchu-ate the Positive</a></li></ul><br />4. Our <a href="https://www.reddit.com/r/physicsFM/">subreddit</a>. <div class="blogger-post-footer">(Content provided by Physics Frontiers and PhysicsFM))</div>James Rantschlerhttps://plus.google.com/104496580781469381673noreply@blogger.com0tag:blogger.com,1999:blog-7857851997611782857.post-47017982688583697332017-10-21T19:28:00.002-07:002017-11-06T12:31:38.583-08:00Five Proven Methods of Levitation<iframe allowfullscreen="" frameborder="0" height="208" marginheight="0" marginwidth="0" scrolling="no" src="https://podomatic.com/embed/html5/episode/8599193?autoplay=false" width="504"></iframe><br /><br />Randy shows Jim five different ways in which a body can be levitated: by magnetism, by superconductors, by Lenz' Law, by acoustics, and most recently by thermophoresis.<br /><br />1. The particular magnetic levitation we talk about is diamagnetic. A very, very large magnetic field induces a large magnetic moment in an object as a reaction. If the diamagnetic component of the object's magnetic susceptibility is larger than its paramagnetic component, the resulting magnetic moment will oppose the field.<br />Superconductors also expel magnetic fields from their body by the Meissner effect, which makes a "perfect dielectric." This allows the superconductor to levitate.<br />2. Using Lenz' Law, eddy currents that are induced by time-varying electric fields produce magnetic fields that react with their source, levitating the object.<br />3. Acoustic levitation occurs when standing sound waves are set up in a region, providing areas where particles can levitate.<br />4. Optical traps work in a similar way to acoustic levitation with electromagnetic fields instead of pressure fields.<br />5. Thermophoretic levitation occurs when temperature gradients produce a force that allows small object to float. <br /><br />-------------------------------------------<br /><br />Notes:<br /><br />1. The papers we read for this program: <br /><ul><li>Brandt, E.H., "<a href="http://science.sciencemag.org/content/243/4889/349.long" target="_blank">Levitation in Physics</a>." <i>Science</i> <b>243</b> 349 (1989).</li><li>Zuza, Fuisasola, Michelini, and Sani, "<a href="http://iopscience.iop.org/article/10.1088/0143-0807/33/2/397/meta" target="_blank">Rethinking Faraday's Law for Teaching Motional Electromotive Force</a>." <i> European Journal of Physics</i> <b>33</b> 397 (2012).</li><li>Brandt, E.H., "<a href="https://www.nature.com/nature/journal/v413/n6855/full/413474a0.html" target="_blank">Suspended by Sound</a>." <i>Nature</i> <b>413</b> 474 (2001).</li><li>Ashkin, A., "<a href="http://www.pnas.org/content/94/10/4853.full" target="_blank">Optical Trapping and Manipulation of Neutral Particles Using Lasers</a>." <i>Proceedings of the National Academy of Sciences</i> <b>94</b> 4853 (1997).</li><li>Fung, Usatyuk, DeSalvo, and Chin, "<a href="http://aip.scitation.org/doi/abs/10.1063/1.4974489?journalCode=apl" target="_blank">Stable Thermophoretic Trapping of Generic Particles at Low Pressures</a>." <i>Applied Physics Letters</i> <b>110</b> 034102 (2017). [<a href="https://arxiv.org/abs/1504.01035" target="_blank">arXiv</a>]</li></ul><br />2. Videos of levitating objects:<br /><ul><li><a href="https://www.youtube.com/watch?v=KlJsVqc0ywM">Levitating Frog</a></li><li><a href="https://www.youtube.com/watch?v=Vxror-fnOL4">Superconducting Levitation</a></li><li><a href="https://www.youtube.com/watch?v=KlJsVqc0ywM">Lenz' Law</a></li><li><a href="https://www.youtube.com/watch?v=yd9DgsI95hc">Acoustic Levitation</a></li><li><a href="https://www.youtube.com/watch?v=ju6wENPtXu8">Optical Tweezers</a></li><li><a href="https://www.youtube.com/watch?v=HSDAbjzyAnw">Thermophoretic Leviatation</a> </li></ul><br />3. Our <a href="https://www.reddit.com/r/physicsFM/">subreddit</a>. <div class="blogger-post-footer">(Content provided by Physics Frontiers and PhysicsFM))</div>James Rantschlerhttps://plus.google.com/104496580781469381673noreply@blogger.com0tag:blogger.com,1999:blog-7857851997611782857.post-61427459948299445132017-10-07T10:35:00.000-07:002017-10-07T10:37:58.473-07:00Stochastic Electrodynamics<iframe src='https://podomatic.com/embed/html5/episode/8582858?autoplay=false' height='208' width='504'frameborder='0' marginheight='0' marginwidth='0' scrolling='no' allowfullscreen></iframe><br /><br />Is the entire cosmos awash in a sea of invisible energy? Nikola Tesla thought so. And today a few daring theoretical physicists are pioneering the effort to explain the most exotic characteristics of quantum theory by describing the nature of this universal field of energy and its physical consequences. If they’re right, their theory could revolutionize the energy and transportation sectors around the globe, and perhaps even throw open the door to new forms of spaceflight. On this episode of Physics Frontiers, we’ll investigate the theory of stochastic electrodynamics, one of the most intriguing concepts in modern physics and a rising contender to explain the quantum world. <br /><br />-------------------------------------------<br /><br />Notes:<br /><br />1. The main paper we read for this program: <a href="https://arxiv.org/abs/quant-ph/0501011v2">Contribution from Stochastic Electrodynamics to the Understanding of Quantum Mechanics</a> by de la Peña and Cetto <a href="https://arxiv.org/abs/quant-ph/0501011v2">[arXiv]</a> <br />2. The secondary paper we mentioned in program, predicting spontaneous parametric up-conversion: <a href="https://arxiv.org/abs/quant-ph/0203042v1">Non-Locality: The Party May Be Over</a> by Marshall <a href="https://arxiv.org/abs/quant-ph/0203042v1">[arXiv]</a> <br /><br />3. Our <a href="https://www.reddit.com/r/physicsFM/">subreddit</a>. <div class="blogger-post-footer">(Content provided by Physics Frontiers and PhysicsFM))</div>James Rantschlerhttps://plus.google.com/104496580781469381673noreply@blogger.com0tag:blogger.com,1999:blog-7857851997611782857.post-5219864947418437892017-09-14T11:23:00.001-07:002018-04-21T16:56:05.862-07:00Exotic Photon Trajectories in Quantum Mechanics<iframe src='https://podomatic.com/embed/html5/episode/8563030?autoplay=false' height='208' width='504'frameborder='0' marginheight='0' marginwidth='0' scrolling='no' allowfullscreen></iframe><br /><br />Jim and Randy discuss strange trajectories observed in triple slit experiments with metallic plates. Photons seem to pass through one slit, come back through the middle slit, and out the third due to their interactions with surface plasmons. There are implications in this experiment about the way in which wavefunctions need to be interpreted in non-relativistic quantum mechanics. <br /><br />-------------------------------------------<br /><br />Notes:<br /><br />1. The paper we read for this program: <a href = https://www.nature.com/articles/ncomms13987>Exotic looped trajectories of photons in three-slit interference</a> by Magaña-Loaiza, et al. <a href = https://arxiv.org/abs/1610.08585>[arXiv]</a> <br /><br />2. Our <a href="https://www.reddit.com/r/physicsFM/">subreddit</a>.<br><br>--------------------------------------------<br><br>The following <a href = https://www.reddit.com/r/arXiv_Plus/comments/7311xe/161008585_exotic_looped_trajectories_of_photons/>post</a> was made to the <a href = https://www.reddit.com/r/arXiv_Plus/>arXiv_plue</a> subreddit about this paper:<br><br>This paper discusses deviations from the predictions of the Born rule (the interpretation of the probability of an observation being the norm of the convolution of the wave functions of the initial and final states) that are observed when the interference effects of a triple slit experiment are examined. By using a three slit experiment rather than a two slit experiment, the authors follow the procedure of Sinha, et al., that showed a null result in 2010. This procedure looks at all seven combinations of the three slits (in a random order), subtracting the three slit interference pattern from the interference patterns of the other six combinations. The combination of the six double and single slit interference patterns should exactly match the the triple slit interference pattern if the Born rule held.<br><br> In 2010, they found that the Born rule held, to one part in 100.<br><br> This paper (published in Nature Communications) uses surface plasmons on a gold barrier to "enhance the electromagnetic near-fields" near the slits in a way that increases the likelihood of trajectories that cause violations of the Born rule. These trajectories snake and backtrack through the triple slit apparatus.<br><br> The comparisons between the single, double, and triple slit interference patterns indicate evidence for these snaking trajectories. Whether this really indicates evidence that the Born rule fails, I'm not sure. <div class="blogger-post-footer">(Content provided by Physics Frontiers and PhysicsFM))</div>James Rantschlerhttps://plus.google.com/104496580781469381673noreply@blogger.com0tag:blogger.com,1999:blog-7857851997611782857.post-3919684993732735932017-08-20T14:36:00.000-07:002017-08-21T05:39:45.087-07:00A Gravitational Arrow of Time<iframe src='https://podomatic.com/embed/html5/podcast/5495687?autoplay=false' height='208' width='504'frameborder='0' marginheight='0' marginwidth='0' scrolling='no' allowfullscreen></iframe><br><br>Jim and Randy discuss a cosmological theory that purports to find an explanation for the arrow of time in gravitational theory based on the shape and distribution of matter and how it evolves. <br><br>-------------------------------------------<br><br>Notes:<br><br>1. The paper we read for this program: <a href = https://physics.aps.org/featured-article-pdf/10.1103/PhysRevLett.113.181101>Identification of a Gravitational Arrow of Time</a> by Barbour, Kowslowski, and Mercati.<BR><BR>2. Mentioned in this episode: <a https://www.amazon.com/Physical-Basis-Direction-Frontiers-Collection-ebook/dp/B00DZ112S0/ref=sr_1_1?s=books&ie=UTF8&qid=1503264122&sr=1-1&keywords=physical+basis+for+the+arrow+of+time>The Physical Basis for the Arrow of Time</a> by H. Dieter Zeh.<br><br>3. Mentioned in this episode: <a href = https://www.amazon.com/Gravity-Ground-Up-Introductory-Relativity/dp/0521455065/ref=sr_1_22?s=books&ie=UTF8&qid=1503264276&sr=1-22&keywords=gravity>Gravity From the Ground Up</a>, B. Shutz.<br><br>4. [Update] It came to me in the shower: the word I was looking for is "eschatological."<br><br>5. Our <a href = https://www.reddit.com/r/physicsFM/>subreddit</a>.<div class="blogger-post-footer">(Content provided by Physics Frontiers and PhysicsFM))</div>James Rantschlerhttps://plus.google.com/104496580781469381673noreply@blogger.com0tag:blogger.com,1999:blog-7857851997611782857.post-12369002927257284992017-07-18T11:01:00.001-07:002017-07-18T11:07:48.780-07:00Photonic Molecules and Optical Circuits<iframe src='https://podomatic.com/embed/html5/episode/8505982?autoplay=false' height='208' width='504'frameborder='0' marginheight='0' marginwidth='0' scrolling='no' allowfullscreen></iframe><br><br> Randy tells Jim about photonic molecules, pairs of photons that create bound states like molecules do through a force mediated through an ultracold gas and similar ideas in optical circuits. They also discuss application of the same for quantum computing.<br><br>-------------------------------------------<br><br>Notes:<br><br>1. The papers we read for this program: to be compiled.<BR><BR>2. <a href =http://physicsfm-master.blogspot.com/2017/07/screwing-up-on-quantum-computing.html>My reservations about this episode</a>. Probably just above this one.<br><br>3. Our <a href = https://www.reddit.com/r/physicsFM/>subreddit</a>.<div class="blogger-post-footer">(Content provided by Physics Frontiers and PhysicsFM))</div>James Rantschlerhttps://plus.google.com/104496580781469381673noreply@blogger.com0tag:blogger.com,1999:blog-7857851997611782857.post-67537786437373880302017-06-30T21:14:00.000-07:002017-07-06T19:18:46.405-07:00Requirements for Gravitational Theories<iframe src='https://podomatic.com/embed/html5/episode/8492292?autoplay=false' height='208' width='504'frameborder='0' marginheight='0' marginwidth='0' scrolling='no' allowfullscreen></iframe><br><br>In this episode Jim and Randy talk about how to evaluate alternative gravity theories. What sort of things do we want them to explain, what experiments do they have to predict, and what theoretical requirements do they have to meet. This is in some ways a continuation of Episode 9 - f(R) Theories of Gravity, but the discussion is relevant to all attempts to amend gravitational theory.<br><br>-------------------------------------------<br><br>Notes:<br><br>1. "<a href = https://arxiv.org/abs/0805.1726>f(R) Theories of Gravity, by Thomas Sotiriou and Valerio Faraoni</a>". The basis for this discussion and the last program's, as well.<BR><BR>2. <a href = http://physicsfm-frontiers.blogspot.com/2017/06/list-of-requirements-for-gravitational.html>The list Randy refers to in the episode</a>. Probably just above this one. 3. Our <a href = https://www.reddit.com/r/physicsFM/>subreddit</a>.<div class="blogger-post-footer">(Content provided by Physics Frontiers and PhysicsFM))</div>James Rantschlerhttps://plus.google.com/104496580781469381673noreply@blogger.com0tag:blogger.com,1999:blog-7857851997611782857.post-34223775993221556652017-06-30T21:12:00.002-07:002017-07-06T19:19:02.022-07:00List of Requirements for Gravitational TheoriesHere it is without fanfare. If you have any questions about any part of it, please comment in the comments:<br><br> <br>-------------------------------<br><br>To be theoretically consistent and compatible with experiment, a theory of gravitation must: <br>(1) Predict correct cosmological dynamics <br>a. Big bang nucleosynthesis <br>(2) Produce the correct evolution of cosmological perturbations <br>a. Cosmic microwave background <br>b. Large scale structure <br>(3) Have the correct weak-field limits <br>a. Reproduces Newtonian Mechanics <br>b. Predicts post-Newtonian experiments in weak field <br>c. Produces stable solutions <br>i. Matter-side instabilities (Dolgov-Kawasaki) <br>1. Ground states should be highly symmetric <br>ii. Gravity-side instabilities <br>1. Stable de Sitter solutions <br>iii. Stability of the first loop in quantum gravity <br>iv. Stability in the face of inhomogeneous but isotropic perturbations <br>v. Black hole nucleation <br>(4) Not contain any ghost fields <br>(5) Admit a well-posed Cauchy problem <br>(6) Reasonable theory of gravity waves <br> <div class="blogger-post-footer">(Content provided by Physics Frontiers and PhysicsFM))</div>James Rantschlerhttps://plus.google.com/104496580781469381673noreply@blogger.com0tag:blogger.com,1999:blog-7857851997611782857.post-55500273626684988472017-06-02T16:14:00.001-07:002017-07-06T19:19:16.475-07:00f(R) Theories of Gravity<iframe src='https://podomatic.com/embed/html5/podcast/5495687?autoplay=false' height='208' width='504'frameborder='0' marginheight='0' marginwidth='0' scrolling='no' allowfullscreen></iframe><br><br>Jim and Randy discuss gravitational theories that modify general relativity by changing the action using a polynomial dependence on the Ricci scalar. Although not physically motivated, some of these theories produce effects similar to those of dark matter, dark energy, and cosmological constants.<br><br>-------------------------------------------<br><br>Notes:<br><br>1. "<a href = https://arxiv.org/abs/0805.1726>f(R) Theories of Gravity, by Thomas Sotiriou and Valerio Faraoni</a>". The basis for this discussion and the next program's, as well.<BR><BR>2. Our <a href = https://www.reddit.com/r/physicsFM/>subreddit</a>.<div class="blogger-post-footer">(Content provided by Physics Frontiers and PhysicsFM))</div>James Rantschlerhttps://plus.google.com/104496580781469381673noreply@blogger.com0tag:blogger.com,1999:blog-7857851997611782857.post-30570964908617502412017-05-05T10:38:00.000-07:002017-08-22T20:04:00.711-07:00Vacuum Fluctuations and the Casimir Effect<iframe src='https://podomatic.com/embed/html5/episode/8428676?autoplay=false' height='208' width='504'frameborder='0' marginheight='0' marginwidth='0' scrolling='no' allowfullscreen></iframe> <br><br>What are the latest theoretical and experimental developments with the Casimir effect, and are vacuum fluctuations physical, or simply a convenient model for calculating the effects of quantum noise in the fields of matter? On this episode of Physics Frontiers, we explore some of the surprising discoveries that physicists have made unraveling the strange dynamics of mechanical components so small that they can’t even be seen through an optical microscope. And along the way we consider some of the fundamental mysteries of quantum field theory, as applied physics enters the realm of nanotechnology…and approaches exotic new possibilities like quantum levitation.<br><br>-----------------------------------------------<br><br>Notes:<br><br>(1) <a href = http://www.princeton.edu/~arod/papers/Woods16.pdf>Materials Perspective on Casimir and van der Waals Interactions</a> by Woods, et al., the basis for this discussion.<br><br>(2) <a href = https://www.reddit.com/r/physicsFM/>Our Subreddit</a><div class="blogger-post-footer">(Content provided by Physics Frontiers and PhysicsFM))</div>James Rantschlerhttps://plus.google.com/104496580781469381673noreply@blogger.com0tag:blogger.com,1999:blog-7857851997611782857.post-44646257591301098392017-03-14T16:37:00.001-07:002017-07-06T19:20:23.008-07:00Virtual Graviational Dipoles<iframe src='https://podomatic.com/embed/html5/podcast/5495687?autoplay=false' height='208' width='504'frameborder='0' marginheight='0' marginwidth='0' scrolling='no' allowfullscreen></iframe><br><br><br> Randy discusses what the Cosmological implications of a negative gravitational mass would be with Jim. If there were a negative gravitational mass (as opposed to inertial mass), then every time that an electron-positron pair was created in the vacuum, that would create a gravitational dipole. This in turn would create effects similar to dark matter, dark energy, and a cosmological constant -- and this in turn would have an effect on the origin of the universe.<br><br> Links:<br><br> <a href = https://arxiv.org/ftp/arxiv/papers/1405/1405.5792.pdf>Virtual Gravitational Dipoles: The Key for the Understanding of the Universe?</a> by Dragan Hajducovic. The paper we discuss in the podcast.<br><br><a href = https://www.reddit.com/r/physicsFM/>The reddit.</a><div class="blogger-post-footer">(Content provided by Physics Frontiers and PhysicsFM))</div>James Rantschlerhttps://plus.google.com/104496580781469381673noreply@blogger.com0tag:blogger.com,1999:blog-7857851997611782857.post-2356483026939015532017-02-15T12:00:00.000-08:002017-07-06T19:20:34.032-07:00General Relativity for the Experimentalist<iframe src='https://podomatic.com/embed/html5/episode/8350885?autoplay=false' height='208' width='504'frameborder='0' marginheight='0' marginwidth='0' scrolling='no' allowfullscreen></iframe> Randy shares a couple of his favorite papers with Jim: discussion about general relativity by engineer and science fiction author Robert L. Forward on how general relativity could be used in a terrestrial environment, including proposals for devices and materials.<br><br> Show notes:<br><br><a href = https://en.wikipedia.org/wiki/Robert_L._Forward>Robert L. Forward</a> on Wikipedia.<br><br><a href = http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=4066418>General Relativity for the Experimentalist</a> in the Proceedings of the IRE (on IEEE Xplore).<a href = > </a><br><br><a href = http://aapt.scitation.org/doi/10.1119/1.1969340>Guidelines to Antigravity</a> in the American Journal of Physics (Scitation.org) <a href = http://aapt.scitation.org/doi/10.1119/1.1969340>(alternate)</a>.<br><br>Previous shows mentioned:<br><br><a href = http://physicsfm-frontiers.blogspot.com/2016/10/g4v-gravitational-4-vector-formulation.html>G4V: The Gravitational 4-Vector Formulation of Gravity</a><br><br><a href = http://physicsfm-frontiers.blogspot.com/2016/12/gravitoelectromagnetism.html>Gravitoelectromagnetism</a><br><br> <div class="blogger-post-footer">(Content provided by Physics Frontiers and PhysicsFM))</div>James Rantschlerhttps://plus.google.com/104496580781469381673noreply@blogger.com0tag:blogger.com,1999:blog-7857851997611782857.post-16950488308259409702017-01-26T20:25:00.001-08:002017-07-06T19:20:46.612-07:00Pilot Wave Hydrodynamics<iframe src='https://podomatic.com/embed/html5/episode/8323862?autoplay=false' height='208' width='504'frameborder='0' marginheight='0' marginwidth='0' scrolling='no' allowfullscreen></iframe><br><br> In this episode, Randy and Jim discuss pilot wave hydrodynamics, a physical analogy to quantum mechanics. In it, a small droplet bounces atop a fluid, interacting with its own wave. This allows macroscopic experiments which display many of the properties of quantum mechanics, such as self-interference in a doubles slit experiment. This is equivalent to <a href = http://physicsfm-frontiers.blogspot.com/2016/11/the-de-broglie-bohm-pilot-wave.html>the de Broglie-Bohm interpretation of quantum mechanics</a> that Jim and Randy talked about in the <a href = http://physicsfm-frontiers.blogspot.com/2016/11/the-de-broglie-bohm-pilot-wave.html> second episode </a> and a little in <a href =http://paradoxes-physicsfm.blogspot.com/2015/08/how-can-you-go-from-probabilistic.html>the main podcast</a>, as well as the quantum interpretations special (that currently needs re-editing).<br><br> Show Notes:<br><br> The review paper by <a href = http://www.annualreviews.org/doi/10.1146/annurev-fluid-010814-014506>John W. M. Bush</a> that forms the basis of the discussion.<br><br>The videos by <a href = https://www.youtube.com/watch?v=WIyTZDHuarQ> Veritasium </a> and <a href = https://www.youtube.com/watch?v=KJDEsAy9RyM> Smarter Every Day</a> that we refer to in the podcast that came out while I was editing <a href = http://physicsfm-frontiers.blogspot.com/2016/11/the-de-broglie-bohm-pilot-wave.html> second episode </a> and just before we recorded this.<br><br><div class="blogger-post-footer">(Content provided by Physics Frontiers and PhysicsFM))</div>James Rantschlerhttps://plus.google.com/104496580781469381673noreply@blogger.com0