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17 particles that explain the world: The Standard Model of Physics describes the structure of matter and the fundamental forces interacting between matter particles. The forces are mediated by force carriers (gauge bosons): photons transfer the electromagnetic interaction, gluons the strong, and W and Z bosons the weak interaction. No carrier boson has yet been demonstrated for the fourth fundamental interaction, gravitation. Physicists have coined the term "graviton" for this as yet undemonstrated particle.
In his general theory of relativity, Albert Einstein defined gravitation as a geometrical property of spacetime, curved by mass or energy. His theory describes the graviton as a massless, spin-2 particle – in contrast to the already known, spin-1 gauge bosons.
The members of the group "Gravitational theories: Massive spin-2 fields" Group study extended theories of gravity. They focus on spin-2 particles which, in contrast to Einstein's theory, possess mass. A massive spin-2 particle would, in a sense, fill a gap.
This is because the standard model includes both massless and massive, low-spin theories. The particles involved have been demonstrated in experiments. Spin-1 examples include the massless photon or the massive W and Z bosons.
The scientists are working to construct the mathematical foundations for a gravitational theory using massive spin-2 particles. They also investigate how such a particle would influence existing particle physics models and cosmology.
Heavy spin-2 Dark Matter
Eugeny Babichev, Luca Marzola, Martti Raidal, Angnis Schmidt-May, Federico Urban, Hardi Veermäe, Mikael von Strauss
JCAP 1609 (2016) no.09, 016
Recent developments in bimetric theory
Angnis Schmidt-May (Zurich, ETH) , Mikael von Strauss (Paris, Inst. Astrophys.)
J.Phys. A49 (2016) no.18, 183001
Bimetric gravity is cosmologically viable
Yashar Akrami, S.F. Hassan, Frank Könnig, Angnis Schmidt-Ma, Adam R. Solomon