It is proposed to search for observable cosmological signatures of quantum field theoretic effects, which originated during the very early universe. In flat space, the energy-time uncertainty principle allows virtual particles to exist for only very brief periods.
The expansion of space-time relaxes this constraint by diluting the kinetic energy of virtual particles. If such a particle has no mass energy, and if the expansion dilutes its kinetic energy sufficiently rapidly, then the particle can exist forever. Particles, which are mass less and also lack conformal invariance -- such as gravitons and minimally coupled scalars -- are produced copiously during inflation. This process is believed to be responsible for the anisotropies now observed in the cosmic microwave background radiation.
Mass-less particles also mediate long-range interactions and this suggests a wide range of potentially observable effects arising from interactions between the particles produced during inflation. The essential tool in any study of these effects is the Schwinger-Keldysh formalism. The project will also focus on dark matter phenomenology and gravitational lensing, which will be useful in recognizing and quantifying observable signatures. In addition to its immediate and substantial scientific impact, the project can develop into a long-term collaboration in a region of great potential importance to Europe.
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