Recent content by PFfan01

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    I Are All Particle-Rest Inertial Frames the Same?

    Sorry, I did not make it clear. What I mean is: Are all the particle-rest frame the same inertial frame? There are no space rotations (corresponding to space orthogonal transformation) between these particle-rest frames?
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    I Are All Particle-Rest Inertial Frames the Same?

    According to special relativity, all inertial frames of reference are equivalent for descriptions of physical phenomena. Suppose that there is a free particle in free space. Observed in any of the frames, the motion of particle can be described by a velocity, and by Lorentz boost, one can get...
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    Negative Energy Density in EM Waves?

    According to the theory for a plane wave in a moving medium, negative EM energy density can occur when the medium moves opposite to the wave vector at a faster-than-dielectric light speed. See: http://www.nrcresearchpress.com/doi/10.1139/cjp-2015-0167
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    I Is Fermat’s principle appicable to a plane wave?

    What I mean is: For arbitrarily given two terminal points A and B, the real light ray does not necessarily go from A to B in general. In other words, for given two points A and B, generally the path of least time is not a real light ray.
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    I Is Fermat’s principle appicable to a plane wave?

    It seems to me that the book by Born and Wolf (M. Born, E. Wolf, Principles of Optics, Pergamon Press, Oxford, 1986, p. 114) interprets what "path" means for a wave.
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    I Is Fermat’s principle appicable to a plane wave?

    S is not between A and B. The source is at S, and all equiphase surfaces are spherical with the common center S. SA is not parallel to SB or AB.
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    I Is Fermat’s principle appicable to a plane wave?

    I don't think the plane wave example is trivial. A minor fixing can provide a more general challenge as follows. Suppose that there is a point light source at S in free space, with SA not parallel to AB. In such a case, the actual light ray never goes from A to B because the actual light ray...
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    I Is Fermat’s principle appicable to a plane wave?

    The (plane wave) phase function defines equiphase planes of motion (wavefronts), with the wave vector as the normal vector. From one equiphase plane to another equiphase plane, the path parallel to the normal vector is the shortest and has the minimum optical length. According to Fermat’s...
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    I Is Fermat’s principle appicable to a plane wave?

    Fermat’s principle states that light follows the path of least time. In textbooks, a specific formulation of Fermat’s principle is about the optical path between two points, A and B: How can a ray of light, emitted from point A, reach point B? Suppose that there is a plane wave in free space...
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    B Could information travel faster than C

    According to a PRL letter, superluminal communications have been well demonstrated experimentally: “We note that such a superluminal phenomenon ... should consist with the causality and special relativity. Our experiments show that the group velocity of the signal pulse does exceed c ...
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    Why Retraction? New Journal of Physics Investigates

    Seems this is the first time of retraction for New Journal of Physics, and Prof. Ulf Leonhardt once was Associate Editor of this journal.
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    Why Retraction? New Journal of Physics Investigates

    The corresponding author, Prof. Ulf Leonhardt, is known for the optics of invisibility objects: Ulf Leonhardt, Optical Conformal Mapping,Science, Volume 312, Issue 5781, pp. 1777-1780 (2006). Cited by more than 1400 references, http://adsabs.harvard.edu/abs/2006Sci...312.1777L Prof. Ulf...
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    Why Retraction? New Journal of Physics Investigates

    According to New Journal of Physics (http://iopscience.iop.org/1367-2630/page/Forthcoming%20articles) : Retraction: Evidence for subwavelength imaging with positive refraction (2011 <em>New J. Phys</em>. 13 033016) Yun Gui Ma, Sahar Sahebdivan, C K Ong, Tomáˇs Tyc and Ulf Leonhardt Retraction...
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    Does light always travel at light speed?

    D. Giovannini, J. Romero, V. Potoček, G. Ferenczi, F. Speirits, S.M. Barnett, D. Faccio, M.J. Padgett, Spatially structured photons that travel in free space slower than the speed of light, Science 347 (2015) 857-860).
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    No double refraction (birefrigence)?

    Many thanks for your answer to my question. I think I can say: (1) No references have clearly claimed that there is a case of no-double refraction for the Optical Axis neither parallel nor perpendicular to the vacuum-uniaxial crystal interface. (2) No references have presented such...
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