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  1. O

    I Can neutrinos be produced/detected incoherently?

    Yes, but the question was if these weak eigenstates can be produced incoherently, i.e., from e.g. only one mass eigenstate without interference from other mass eigenstates. As Orodruin said in #2, this is certainly possible in theory, but does it have experimental support?
  2. O

    I Can neutrinos be produced/detected incoherently?

    Sure, statistical evidence for incoherent neutrino detection would be fine. Does this exist? But for solar neutrinos, the wave-packet separation is so small that coherence is restored in the detector during the detection process. Thus the detection of solar neutrinos is in itself not evidence...
  3. O

    I Can neutrinos be produced/detected incoherently?

    Produced/detected incoherently: produced/detected as separate mass eigenstates with no interference from different mass eigenstates. (See arXiv:0905.1903) Thank you. Do you have a reference to experiments where neutrinos are produced/detected incoherently?
  4. O

    I Can neutrinos be produced/detected incoherently?

    In the wave-packet approach, different neutrino mass eigenstates have different mass and thus propagate with different speeds. This will eventually lead to wave-packet separation and decoherence. My question is, can neutrinos be produced/detected incoherently? (In other words, can different...
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    What is the current status on MOND

    For spiral galaxies, the observations indicate a very close relationship between the dark halo and the visible matter in the disk; this is called "the disk-halo conspiracy". That is, the dark and the visible matter distributions apparently conspire such that the rotation curve turns out to...
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    How to prove the stretching of space

    This non-relativistic decomposition is arrived at by using a Newtonian approximation to calculate the "gravitational" contribution. But this approach is misguided, and inconsistent with a relativistic approach. The cited statement should not be taken as a criticism of B&H, since the...
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    How to prove the stretching of space

    The problem is B&H's claim that it is "most natural" to interpret the cosmic redshift as a Doppler shift in FLAT space-time for sufficiently small distances. But as I have argued in this thread this claim is false; with a few exceptions said interpretation is in general simply inconsistent with...
  8. O

    How to prove the stretching of space

    A Doppler shift in curved space-time only means that the special-relativistic Doppler formula can be used after the described procedure of parallel-transport. Any further interpretation is not included. In particular, a Doppler shift in curved space-time has nothing to do with any possible...
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    How to prove the stretching of space

    Nothing is arbitrary with the procedure described in #43. That is, the world lines of the FOs and their 4-velocities are not arbitrary and neither are the null curves. (For sufficiently small distances the effects of geodesic deviation can be neglected, so the world lines of the FOs are still...
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    How to prove the stretching of space

    You misunderstand. If the redshift in a general RW-model were purely "kinematic", the procedure described in #43 would yield the same redshift for small enough distances both for the curved space-time geometry and for flat space-time. Since this does not happen in general, the nature of the...
  11. O

    How to prove the stretching of space

    Yes, cosmological redshifts can always be interpreted as Doppler shifts in CURVED space-time. However, they cannot in general be interpreted as Doppler shifts in FLAT space-time, and it is the latter meaning that is usually understood with "kinematic" redshift. There is no obvious intuitive...
  12. O

    How to prove the stretching of space

    Sorry for the late reply (no internet connection for the last week). The redshift depends only on the 4-velocities of the FOs and on the space-time geometry. (This is most easily seen by using said procedure of parallel-transport.) On the other hand, the INTERPRETATION of the redshift depends...
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    How to prove the stretching of space

    It is not a good idea to introduce coordinate-dependent quantities if they are not directly related to coordinate-free objects. That is, the proper objects to consider are the 4-velocities of the FOs and not some independently defined "recession velocities". The question of what speed to use in...
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    How to prove the stretching of space

    The Milne model is equivalent to an empty RW-manifold and is mathematically a subset of Minkowski space-time. The FOs are those observers moving orthogonally to the "preferred" hypersurfaces (with hyperbolic geometry) foliating this RW-manifold. There is no alternative set of observers involved...
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    How to prove the stretching of space

    Coordinates are irrelevant for interpretations of redshifts in the RW-models. What matters is the choice of observers emitting and receiving electromagnetic radiation being redshifted (but these observers are not chosen arbitrary since they are specific observers determined from the symmetry of...
  16. O

    How to prove the stretching of space

    But the fact is that the cosmological redshift in the RW-models is DEFINED in terms of a set of particular observers (the FOs). This means that choosing some other set of observers is simply irrelevant and confuses the issue. That is, in principle the redshifts defined by these alternative...
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    How to prove the stretching of space

    The question of interpretations of the cosmic redshift in Robertson-Walker (RW) models is not a question about a choice of coordinates. The reason for this is simple: in the RW-models there is a set of "preferred" observers (the so-called "fundamental observers" (FOs)) defining the cosmic...
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    Pioneer Anomaly Explained

    No mention was made of the criticism from Anderson & Morris; see J.D. Anderson and J.R. Morris, PRD 85, 0840817 (2012). A & M plotted the alleged "decay" of the anomaly as a function of the radius R from the sun and found that it goes almost exactly as 1/R^2. This behaviour makes it likely...
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    Dark Matter or Modified Gravity ?

    My claim is that the data do not constrain the thermal model sufficiently to reach a conclusion of any reasonable degree of confidence. On the contrary, the fact that the "observed" decay of the anomaly goes as 1/r² indicates that the thermal modelling is fundamentally misguided. For this...
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    Dark Matter or Modified Gravity ?

    The scientific method is about testing theories. Just to come up with a flexible mainstream model where some choice of parameters will fit the data does not automatically shut out other models. Rather, if more models fit the data equally well, the "best" one is the one with the least number...
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    Dark Matter or Modified Gravity ?

    In the sense that 1) The "observed" decay of the anomaly is probably not due to thermal effects but rather to mismodelling of solar pressure force since the decay goes very closely as 1/r² when plotted against the distance from the Sun (see http://arxiv.org/abs/1204.2778). 2) The...
  22. O

    A book about dark matter and energy

    For a book about dark matter (not dark energy), I recommend the book "The Dark Matter Problem: A Historical Perspective" by Robert H. Sanders.
  23. O

    Well-motivated theories with nonzero PPN ζ?

    I don't know any offhand (maybe the Belinfante-Swihart theory (non-viable)), but perhaps you can find something useful on this site http://www.phy.olemiss.edu/~luca/
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    Solving a non-homogeneous ODE with Bessel functions?

    A simple particular solution is easily found by inspection, and it is given by h_p=1/{\lambda}^2.
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    Interpreting the Supernova Data

    But a coasting universe is consistent with observational restrictions on primordial nucleosynthesis - that has been known for some time. See, e.g., astro-ph/9903084, or more recent papers by the same authors.
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    Fine structure constant probably doesn't vary with direction in space!

    But what does the variation of the X-field depend on? Is there a theory of the X-field in flat space-time? It seems that all you have done, is to transfer the problems of varying alpha to the X-field. I am inclined to believe that the universe has some fundamental properties. The reason why...
  27. O

    Fine structure constant probably doesn't vary with direction in space!

    It seems that I did not express myself clearly enough. What I had in mind, was a theory of varying alpha in flat space-time. How do you construct such a theory compatible with SR? Even if you could declare a preferred inertial frame in flat space-time, it would be arbitrary. That is not a...
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    Fine structure constant probably doesn't vary with direction in space!

    I said any given non-gravitational experiment. In your example, two different choices of electric field would give two different experiments.
  29. O

    Fine structure constant probably doesn't vary with direction in space!

    Sure, what I wrote does not make sense, sorry about that. But the crucial question is how to construct a theory of time-varying alpha compatible with SR. See my previous reply to cesiumfrog.
  30. O

    Fine structure constant probably doesn't vary with direction in space!

    (Sorry about the delay in responding to your post.) But that is what local means here - in the tangent space-time where gravitational effects are of higher order in small quantities and can be ignored to arbitrary accuracy by making the volume small enough.. There seems to be a...
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