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R. N. Mohapatra
nuclear force, they could be as large as two meters in diameter. Clearly this
would require a new strategy for searching for them [57].
24.3 Is There a Parallel Universe?
The idea that there may be parallel universes as part of our existence has
been considered for decades and centuries in mythological as well as religious
discussions. For example, the concept of heaven, Earth, and hell as three sectors
to human existence has been discussed in many places. But as a scientific
possibility, the idea of parallel universes first appeared in the celebrated parity
violation paper of Lee and Yang, as already stated. They envisioned only two
sectors as a way to maintain parity conservation in the whole universe. In
this subsection, we discuss whether the same parallel (or mirror) sector of the
universe could be the site of dark matter.
A cartoon picture of the mirror model particles is seen in Fig. 24.2. To elaborate, just like in the visible world, we expect the mirror sector quarks to form a
mirror proton, which does not have our electric charge but the corresponding
electric charge from the mirror sector. The mirror sector will also have its
own photon, called the mirror photon [92]. Similarly, corresponding to each
particle of the visible sector, there is a mirror counterpart. The particles of the
mirror sector communicate with our familiar particles (the proton, neutron,
and electron) only via gravitational force. Therefore, it is a very weak force and
Fig. 24.2 The duplicate standard model as the mirror universe. The red particles are
particles that we are familiar with and the blue ones are the mirror particles
R. N. Mohapatra
nuclear force, they could be as large as two meters in diameter. Clearly this
would require a new strategy for searching for them [57].
24.3 Is There a Parallel Universe?
The idea that there may be parallel universes as part of our existence has
been considered for decades and centuries in mythological as well as religious
discussions. For example, the concept of heaven, Earth, and hell as three sectors
to human existence has been discussed in many places. But as a scientific
possibility, the idea of parallel universes first appeared in the celebrated parity
violation paper of Lee and Yang, as already stated. They envisioned only two
sectors as a way to maintain parity conservation in the whole universe. In
this subsection, we discuss whether the same parallel (or mirror) sector of the
universe could be the site of dark matter.
A cartoon picture of the mirror model particles is seen in Fig. 24.2. To elaborate, just like in the visible world, we expect the mirror sector quarks to form a
mirror proton, which does not have our electric charge but the corresponding
electric charge from the mirror sector. The mirror sector will also have its
own photon, called the mirror photon [92]. Similarly, corresponding to each
particle of the visible sector, there is a mirror counterpart. The particles of the
mirror sector communicate with our familiar particles (the proton, neutron,
and electron) only via gravitational force. Therefore, it is a very weak force and
Fig. 24.2 The duplicate standard model as the mirror universe. The red particles are
particles that we are familiar with and the blue ones are the mirror particles