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I Could "dark matter" be regions where Lambda is lower?

  1. Mar 29, 2016 #1
    We assume that Lambda, the cosmological constant or "dark energy" is constant in all of spacetime (at least all of space). But what if it was not?

    A lower value of Lambda in a certain region of space would mean that space's tendency to expand there is lower, and that might have the appearance of a "boost" of the gravitational attraction of massive particles and bodies in that region of space, perhaps giving the illusion that there is more mass than what we think there is.

    In those regions, gravity would beat space's expansion, unlike the overall situation where expansion beats gravitational attraction and eventual collapse.

    Could it be that the apparent excess of gravitational attraction, which we currently attribute to a mysterious massive matter (dark matter) is actually a lower Lambda value in that region of space, so that the gravitational strength between bodies in that region gets stronger than what we assume it should be?

  2. jcsd
  3. Mar 29, 2016 #2

    Simon Bridge

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    However, the lambda value is supposed to be the energy density of empty space ... space devoid of matter.
    So, by what mechanism would different bits of empty space have a different energy density?

    The part of the energy density that is different in different places is what we call "matter" (and various known fields).

    Note: dark energy and dark matter are technical terms that refer to different things.
  4. Mar 29, 2016 #3


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    That is not the effect that a lower version of lambda would have, and there is no way to tweak the lambda constant in the equations of GR that would lead to the observed effects that are attributed to dark matter.

    Speculation discussions of this sort are not allowed under the Physics Forums rules, so this thread is closed.
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