It has been conventional wisdom that the
fundamental laws of physics are not invariant under parity. Now, the
computational complexity of a model that lacks mirror symmetry is
much larger than a similar mirror symmetric
model. It would thus be very strange if Nature is indeed not invariant
under parity.
A small minority of physicists, however, have
taken a different view. They have argued that a so-called mirror world could
exist. Nature would then be symmetric under parity. Their so-called exact parity
model predicts the existence of so-called
''mirror matter''. Each particle is postulated to have a mirror partner with
similar properties (they behave exactly as the mirror image of there
partners, e.g. mirror neutrino's would be right-handed). This is thus similar to
anti-mater, the main difference is that mirror particles and ordinary particles
only have very weak interactions, otherwise they would have been detected
already (mirror neutrino's would thus appear to be sterile right-handed
neutrinos).
Mirror particles could thus act as dark matter. Now, because mirror matter has similar properties as ordinary matter, you could have mirror stars, galaxies, planets etc. Note that mirror stars would be invisible because they would emit mirror photons, which don't interact with ordinary electrons (to be precise there could be a very weak interaction, see below). Besides gravity, there are other ways that mirror matter could interact with ordinary matter. E.g. a term like $ \frac{\epsilon}{2} F_{\mu,\nu} F\prime^{\mu,\nu} $ in the Lagrangian, where $ F\prime $ is the mirror electromagnetic field tensor, gives every charged mirror particle an effective ordinary charge that is epsilon times as small. Epsilon would have to be smaller than about 10^-4 to avoid conflict with experiments performed
to detect millicharged particles.
In the last few years Dr. Foot has proposed
that epsilon could be about
10^{-6} (see [2]). That value would nicely explain
the ortho-positronium lifetime puzzle. Positronium is a bound state consisting
of an electron and a positron. Experiments have yielded conflicting results for
the lifetime of this system. A nonzero value for epsilon would cause the
eigenstates of the Hamiltonian to be linear combinations of positronium and
mirror positronium. So, if you start at t = 0 with positronium, part of it
will have oscillated into mirror positronium. If you measure the rate of decay
of positronium you have to take this into account. Once positronium has
oscillated into mirror positronium it has effectivly disappeared, because it
will subsequently decay into three invisible mirror photons. Now, it makes a difference if the experiment is performed in
vacuum or in some other kind of medium. In a medium containing, say, gas,
the frequent collisions between positronium and the gas molecules will
inhibit the oscillation of positronium into mirror positronium. This effect
is known as the quantum Zeno effect. It was precisely the experiment that
was performed in vacuum that had reported the shortest lifetime for
ortho-positronium.
However, a value as large as 10^-6 for
epsilon would mean that a mirror meteor hitting the earth would dissipate its
energy over a distance of about 10 cm (assuming an impact velocity of about 60
km/s). Large mirror meteors would thus behave in a similar way as ordinary
meteors. Of course, no trace of the meteor would be found, but the crater would
be just as large (see [5]).
Recently a sky
survey detected far fewer potential earth crossing asteroids than had been
expected according to earlier estimates by the late Shoemaker. He arrived
at a much higher estimate by studying the cratering record on the moon.
Maybe there are a lot of invisible mirror meteors
out there!
Saibal
References:
[1] Seven (and a half) reasons to believe in Mirror Matter: From neutrino puzzles to the inferred Dark matter in the Universe R. Foot Acta Phys.Polon. B32 (2001) 2253-2270 ( http://xxx.lanl.gov/abs/astro-ph/0102294 ) [2] Can the mirror world explain the ortho-positronium lifetime puzzle? R. Foot, S. N. Gninenko Phys.Lett. B480 (2000) 171-175 ( http://xxx.lanl.gov/abs/hep-ph/0003278 ) [3] Have mirror planets been observed? R. Foot Phys.Lett. B471 (1999) 191-194 ( http://xxx.lanl.gov/abs/astro-ph/9908276 ) [4] Have mirror stars been observed? R. Foot Phys.Lett. B452 (1999) 83-86 ( http://xxx.lanl.gov/abs/astro-ph/9902065 ) [5] The mirror world interpretation of the 1908 Tunguska event and other more recent events R. Foot Acta Phys.Polon. B32 (2001) 3133 ( http://xxx.lanl.gov/abs/hep-ph/0107132 ) [6] A mirror world explanation for the Pioneer spacecraft anomalies? R. Foot, R. R. Volkas Phys.Lett. B517 (2001) 13-17 ( http://xxx.lanl.gov/abs/hep-ph/0108051 ) [7] Mirror World versus large extra dimensions Z.K. Silagadze Mod.Phys.Lett. A14 (1999) 2321-2328 ( http://xxx.lanl.gov/abs/hep-ph/9908208 ) [8] A quest for weak objects and for invisible stars S.I.Blinnikov http://xxx.lanl.gov/abs/astro-ph/9801015 [9] TeV scale gravity, mirror universe, and ... dinosaurs Z.K. Silagadze Acta Phys.Polon. B32 (2001) 99-128 http://xxx.lanl.gov/abs/hep-ph/0002255 [10] Mirror objects in the solar system? Z.K. Silagadze http://xxx.lanl.gov/abs/astro-ph/0110161 |
- Re: Mirror Symmetry Saibal Mitra
- Re: Mirror Symmetry hpm
- Re: Mirror Symmetry H J Ruhl
- Re: Mirror Symmetry George Levy
- Re: Mirror Symmetry Saibal Mitra