Speaker
Mr
Wolfram Ratzinger
(Johannes Gutenberg University Mainz)
Description
Conventional approaches to probing axions and axion-like particles (ALPs) typically rely on a coupling to photons. However, if this coupling is extremely weak, ALPs become invisible and are effectively decoupled from the Standard Model. We show that such invisible axions, which are viable candidates for dark matter, can produce a stochastic gravitational wave background in the early universe. This signal is generated in models where the invisible axion couples to a dark gauge boson that experiences a tachyonic instability when the axion begins to oscillate. Quantum fluctuations amplified by the exponentially growing gauge boson modes source chiral gravitational waves. We discuss the parameter space where this signal can possibly be detected by pulsar timing arrays or space/ground-based gravitational wave detectors. Further we present preliminary results how the non-perturbative lattice calculations we are carrying out at the moment might change this picture.
Primary author
Mr
Wolfram Ratzinger
(Johannes Gutenberg University Mainz)
