20
Neutrino Mass Hints at Mirror Symmetry in
Nature
The first thing the discovery of neutrino mass says is that the standard model
which is so successful in describing so many phenomena is an incomplete
theory. There must be new physics in order to give the neutrinos a nonzero
mass. What is the nature of this new physics? In previous instances of
understanding new physics, the symmetries have played a role. We saw from
the history of the standard model that the V − A theory suggested a new kind
of local symmetry as early as the 1960s, and eventually that got confirmed,
leading to a new successful theory of the universe. Could there be something
similar happening now? Is the neutrino mass also hinting at a new symmetry
of the universe? If so what is it? Let us explore this possibility. We summarize
the speculations in this chapter.
20.1 Back to Symmetries
For a discussion of symmetries and symmetry breaking, see Sects. 11.3 and 11.4
where some examples of symmetries and their breaking were given. One can
give other examples of symmetric situations: for instance, an empty circle has
a continuous rotation symmetry, which is a larger symmetry than the “empty”
stop sign of Chap. 11, the latter having only an eightfold rotation symmetry. A
spherical soccer ball has a spherical symmetry. The above symmetries, as well
as different ones like them, have played a fundamental role in understanding
the basic laws of nature, as we already saw from the discussion of the standard
model. The reason symmetries are important is that if the basic force laws
© The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer
Nature Switzerland AG 2021
R. N. Mohapatra, The Neutrino Story: One Tiny Particle’s Grand Role in the Cosmos,
https://doi.org/10.1007/978-3-030-51846-2_20
149
Neutrino Mass Hints at Mirror Symmetry in
Nature
The first thing the discovery of neutrino mass says is that the standard model
which is so successful in describing so many phenomena is an incomplete
theory. There must be new physics in order to give the neutrinos a nonzero
mass. What is the nature of this new physics? In previous instances of
understanding new physics, the symmetries have played a role. We saw from
the history of the standard model that the V − A theory suggested a new kind
of local symmetry as early as the 1960s, and eventually that got confirmed,
leading to a new successful theory of the universe. Could there be something
similar happening now? Is the neutrino mass also hinting at a new symmetry
of the universe? If so what is it? Let us explore this possibility. We summarize
the speculations in this chapter.
20.1 Back to Symmetries
For a discussion of symmetries and symmetry breaking, see Sects. 11.3 and 11.4
where some examples of symmetries and their breaking were given. One can
give other examples of symmetric situations: for instance, an empty circle has
a continuous rotation symmetry, which is a larger symmetry than the “empty”
stop sign of Chap. 11, the latter having only an eightfold rotation symmetry. A
spherical soccer ball has a spherical symmetry. The above symmetries, as well
as different ones like them, have played a fundamental role in understanding
the basic laws of nature, as we already saw from the discussion of the standard
model. The reason symmetries are important is that if the basic force laws
© The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer
Nature Switzerland AG 2021
R. N. Mohapatra, The Neutrino Story: One Tiny Particle’s Grand Role in the Cosmos,
https://doi.org/10.1007/978-3-030-51846-2_20
149