There are several proposed types of exotic matter:
Hypothetical particles and states of matter that have not yet been encountered, but whose properties would be within the realm of mainstream physics if found to exist.
Several particles whose existence has been experimentally confirmed that are conjectured to be
exotic hadrons and within the
Standard Model.
Negative mass would possess some strange properties, such as accelerating in the direction opposite of applied
force. Despite being inconsistent with the expected behavior of "normal" matter, negative mass is mathematically consistent and introduces no violation of
conservation of momentum or
energy. It is used in certain speculative theories, such as on the construction of artificial
wormholes and the
Alcubierre drive. The closest known real representative of such exotic matter is the region of pseudo-
negative-pressure density produced by the
Casimir effect.
A hypothetical particle with complex rest mass would always travel faster than the
speed of light. Such particles are called
tachyons. There is no confirmed existence of tachyons.
If the rest mass is complex this implies that the denominator is complex because the total energy is
observable and thus must be
real. Therefore, the quantity under the square root must be negative, which can only happen if
v is greater than
c. As noted by
Gregory Benfordet al.,special relativity implies that tachyons, if they existed, could be used to communicate backwards in time[2] (see
tachyonic antitelephone). Because
time travel is considered to be non-physical, tachyons are believed by physicists either not to exist, or else to be incapable of interacting with normal matter.
At high pressure, materials such as
sodium chloride (NaCl) in the presence of an excess of either chlorine or sodium were transformed into compounds "forbidden" by classical chemistry, such as Na 3Cl and NaCl 3. Quantum mechanical calculations predict the possibility of other compounds, such as NaCl 7, Na 3Cl 2 and Na 2Cl. The materials are thermodynamically stable at high pressures. Such compounds may exist in natural environments that exist at high pressure, such as the deep ocean or inside
planetary cores. The materials have potentially useful properties. For instance, Na 3Cl is a two-dimensional metal, made of layers of pure sodium and salt that can conduct electricity. The salt layers act as insulators while the sodium layers act as conductors.[3][4]
See also
Antimatter – Material composed of antiparticles of the corresponding particles of ordinary matter
Dark energy – Energy driving the accelerated expansion of the universe