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Space-Time-Gravity and Magnetism

Posted by Hemos on from the folding-time-and-space dept.

BigDaddyMike wrote to us with a piece from Nature that discusses the latest in gravity and space time magnetism, casting some doubts on the theories of Universe Formation.

2 of 20 comments (clear)

  1. Preprint by JPMH · · Score: 4
    The full paper is available at http://xxx.lanl.gov/abs/astro-ph/0012345

    It's an interesting prospect, if instead of being an effect of the physically rather dubious "dark energy" (vacuum energy density), or the even more dubious "vacuum state tunneling" of inflation, the apparent flatness of space at large scales might be due to plain old magnetic fields.

  2. Not exactly "casting doubts"... by fnordboy · · Score: 4

    Speaking as a physics graduate student whose PhD thesis will be in cosmology, I would consider it a strong overstatement to say that this paper "casts doubts" on our theories of galaxy formation. The paper (available here) describes the possible effects that magnetic fields could have on inflation. Basically, the tension in cosmic magnetic field lines (which act like big rubber bands - the more you stretch the field line, the stronger the tension in it) tends to accelerate spatially closed regions and decelerate open regions. What's important about this is that even weak fields can have a very strong impact in an open universe, suppressing the acceleration phase of inflation. The addition of the magnetic terms to the FRW metric (which describes how the universe curves) causes makes the universe tend towards flatness in an effect which is potentially much stronger than the amount of matter and dark energy in the universe, to a degree.

    However, it would be rather difficult to have a significant net magnetic field in the inflationary era. The universe was basically an incredibly hot, dense soup of plasma at this era and most importantly, is almost totally homogenous and isotropic (ie there are no preferred directions or places in the universe at this time) which would serve to keep magnetic fields somewhat local and randomized. The net result is that there probably weren't large-scale magnetic fields in the early universe.

    All in all, it's a very interesting paper, and makes a very valid point - namely, that magnetic fields have the potential to be very influential in a cosmological model! However, it's important to realize that the author wasn't trying to say that the inflationary theory was wrong, just that in theory things could have turned out much, much differently.