Axions now and then

This fully funded project is dedicated to axions and axion-like fields and their role in cosmology and astrophysics. Axions are very popular hypothesized pseudo-scalar particles with a number of attractive properties for particle physics, astrophysics and cosmology, for reviews see [1,2,3]. Axions originated from studies of quantum chromodynamics (QCD) to solve the notorious strong CP problem. One of the defining features of axions is that their mass and the low-energy interactions are parametrically suppressed by requirements of classical shift-symmetry. In this project we will investigate axion gravitational couplings, see e.g. [6] and how these couplings influence black holes and other compact objects like in [3,4,5]. Another research direction covers their role in axion inflation and in potential alternatives to inflation. Furthermore, the project involves gravitational waves in the early Universe produced by axion configurations, in particular by domain walls.

This project involves international collaboration with France, Japan, South Korea and the USA.

[1] Axions and the Strong CP Problem; Jihn E. Kim, G. Carosi Rev.Mod.Phys. 82 (2010) 557–602, • e-Print: 0807.3125
[2] Light Pseudoscalars, Particle Physics and Cosmology; Jihn E. Kim Phys.Rept. 150 (1987) 1–177
[3] String Axiverse; A. Arvanitaki, S. Dimopoulos, S. Dubovsky, N. Kaloper, J. March-Russell Phys.Rev.D 81 (2010) 123530 • e-Print: 0905.4720 [hep-th]
[4] Exploring the String Axiverse with Precision Black Hole Physics; A. Arvanitaki, S. Dubovsky Phys.Rev.D 83 (2011) 044026 • e-Print: 1004.3558 [hep-th]
[5] Scalarization; D. Doneva, F. Ramazanoğlu, H.Silva, T. Sotiriou, S. Yazadjiev • e-Print: 2211.01766 [gr-qc]
[6] Gravity and global symmetriesl R. Kallosh, A. Linde, D. Linde, L. Susskind Phys.Rev.D 52 (1995) 912–935 • e-Print: hep-th/9502069 [hep-th]