In physics, mirror matter, also called shadow matter or Alice matter, is a hypothetical counterpart to regular matter suggested by Tsung Dao Lee and Chen Ning Yang [1] in 1956, when it was discovered that nature violates P-symmetry. A black hole concept drawing by NASA. Physics (from the Greek, φυσικός (physikos), natural, and φύσις (physis), nature) is the science of the natural world dealing with the fundamental constituents of the universe, the forces they exert on one another, and the results produced by these forces. ... U.S. government photo Tsung-Dao Lee (李政道 Pinyin: Lǐ Zhèngdào) (born November 24, 1926) is a Chinese American physicist who did work on high energy particle physics, symmetry principles, and statistical mechanics. ... Dr. Chen Ning Franklin YANG Chen Ning Franklin YANG (楊振寧 pinyin: Yáng Zhènníng) (born September 22, 1922) is a Chinese American physicist, who worked on statistical mechanics and symmetry principles. ... 1956 (MCMLVI) was a leap year starting on Sunday of the Gregorian calendar. ... P-symmetry is simply the spatial symmetry exhibited during a reflection. ...

Modern physics deals with three basic types of spatial symmetry: reflection, rotation and translation. The known elementary particles respect rotation and translation symmetry but do not respect mirror reflection symmetry (also called P-symmetry). Square with symmetry group D4 Symmetry is a characteristic of geometrical shapes, equations, and other objects; we say that such an object is symmetric with respect to a given operation if this operation, when applied to the object, does not appear to change it. ...

It turns out that mirror reflection symmetry can still exist, but only if every particle has a mirror partner [1,2,3]. Mirror particles interact amongst themselves in the same way as ordinary particles, except where ordinary particles have left-handed interactions, mirror particles have right-handed interactions. In this way, it turns out that mirror reflection symmetry can exist as an exact symmetry of nature, provided that mirror matter exists.

Mirror particles have been suggested as candidates for the inferred dark matter in the universe [4,5,6,7,8]. Mirror matter, if it exists, would have to be very weakly interacting with ordinary matter. This is because the forces between mirror particles are mediated by mirror bosons. Mirror particles and ordinary particles can only interact with each other via gravity, via so-called kinetic mixing of mirror bosons with ordinary bosons or via the exchange of as of yet unknown particles. These interactions can only be very weak. This refers to the cosmological use of the term. ... Bosons, named after Satyendra Nath Bose, are particles which form totally-symmetric composite quantum states. ... It has been suggested that gravitation be merged into this article or section. ...

Mirror matter is a far less popular dark matter candidate than WIMPs or Weakly Interacting Massive Particles, which in supersymmetric theories is identified as the neutralino. In English slang, a wimp is a pushover, or a wishy-washy person. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... In particle physics, the neutralino is a hypothetical particle and part of the doubling of the menagerie of particles predicted by supersymmetric theories. ...

Observational effects of mirror matter

If mirror matter is present in the universe with sufficient abundance then its gravitional effects can be detected. Because mirror matter is analogous to ordinary matter, it is then to be expected that a fraction of the mirror matter exists in the form of mirror galaxies, mirror stars, mirror planets etc. These objects can be detected using gravitational lensing. One would also expect that some fraction of stars have mirror objects as their companion. In such cases one should be able to detect periodic Doppler shifts in the spectrum of the star [7]. There are some hints that such effects may already have been observed [9,10]. The Doppler effect is the apparent change in frequency or wavelength of a wave that is perceived by an observer moving relative to the source of the waves. ...

What if mirror matter does exist but has (almost) zero abundance? Like magnetic monopoles, mirror matter could have been diluted to unobservably low densities during the inflation epoch. Sheldon Glashow has shown that if at some high energy scale particles exist which interact strongly with both ordinary and mirror particles, radiative corrections will lead to a mixing between photons and mirror photons [11]. This mixing has the effect of giving mirror electric charges a very weak ordinary electric charge. Another effect of photon-mirror photon mixing is that it induces oscillations between positronium and mirror positronium. Positronium could then turn into mirror positronium and then decay into mirror photons. An experiment to measure this effect is currently being planned [12]. In physics, a magnetic monopole is a hypothetical particle that may be loosely described as a magnet with only one pole (see electromagnetic theory for more on magnetic poles). ... Sheldon Glashow at Harvard University Professor Sheldon Lee Glashow (born December 5, 1932) is an American physicist. ... In physics, an effective field theory is an approximate theory (usually a quantum field theory) that contains the appropriate degrees of freedom to describe physical phenomena occurring at a chosen length scale, but ignores the substructure and the degrees of freedom at shorter distances (or, equivalently, higher energies). ... In physics, the photon (from Greek φως phos, meaning light) is the quantum of the electromagnetic field, for instance light. ...

If mirror matter does exist in large abundances in the universe and if it interacts with ordinary matter via photon-mirror photon mixing, then this could be detected in dark matter direct detection experiments such as DAMA/NaI [13,14]. There would also be consequences for planetary science [15,16]. The DAMA/NaI experiment [1] was designed to detect dark matter using the direct detection technique. ...

It has also been suggested that a mirror particle, when having large amounts of energy applied to it, might enter a state where it would interact with normal matter in highly violent ways, such as passing through the nucleus of an atom, destroying it, and propagating a number of new mirror particles equal to the number of particles in the nucleus in a scale of 1:100,000. It has been stated that in the case of this type of reaction a large scale annihilation would occur which would not stop until the area of the reaction approaches a vacuum.

References

[1] T. D. Lee and C. N. Yang, Question of Parity Conservation in Weak Interactions, Phys. Rev. 104, 254–258 (1956) article.

[2] I. Kobzarev, L. Okun and I. Pomeranchuk, On the possibility of observing mirror particles, Sov. J. Nucl. Phys. 3, 837 (1966).

[3] M. Pavsic, External Inversion, Internal Inversion, and Reflection Invariance, Int. J. Theor. Phys. 9, 229-244 (1974) preprint.

[4] S. I. Blinnikov and M. Yu. Khlopov, On possible effects of 'mirror' particles, Sov. J. Nucl. Phys. 36, 472 (1982).

[5] S. I. Blinnikov and M. Yu. Khlopov, Possible astronomical effects of mirror particles, Sov. Astron. 27, 371-375 (1983).

[6] E. W. Kolb, M. Seckel and M. S. Turner, The shadow world of superstring theories, Nature 314, 415-419 (1985).

[7] M. Yu. Khlopov, G. M. Beskin, N. E. Bochkarev, L. A. Pushtilnik and S. A. Pushtilnik, observational physics of mirror world, Astron. Zh. Akad. Nauk CCCP 68, 42-57 (1991) preprint.

[8] H. M. Hodges, Mirror baryons as the dark matter, Phys. Rev. D 47, 456-459 (1993) article.

[9] R. Foot, Have mirror stars been observed?, Phys. Lett. B 452, 83-86 (1999) preprint.

[10] R. Foot, Have mirror planets been observed?, Phys. Lett. B 471, 191-194 (1999) preprint

[11] S. L. Glashow, Positronium versus the mirror universe, Phys. Lett. B 167, 35-36 (1986) article.

[12] A. Badertscher et al., An apparatus to search for mirror dark matter via the invisible decay of orthopositronium in vacuum, Int. J. Mod. Phys. A 19, 3833-3848 (2004) preprint.

[13] R. Foot, Implications of the DAMA and CRESST experiments for mirror matter-type dark matter, Phys. Rev. D 69, 036001 (2004) preprint.

[14] R. Foot, Reconciling the positive DAMA annual modulation signal with the negative results of the CDMS II experiment, Mod. Phys. Lett. A 19, 1841-1846 (2004) preprint.

[15] R. Foot and S. Mitra, Mirror matter in the solar system: New evidence for mirror matter from Eros, Astropart. Phys. 19, 739-753 (2003) preprint.

[16] R. Foot and Z.K. Silagadze, Do mirror planets exist in our solar system? Acta Phys. Polon. B 32, 2271-2278 (2001) preprint.

External links

• Mirror matter webpage
• A collection of scientific articles on various aspects of mirror matter theory

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