Gravitational waves from walls bounded by strings in SO(10) model of pseudo-Goldstone dark matter

Abstract

We explore the gravitational wave spectrum generated by string-wall structures in an SO(10) (Spin(10)) based scenario of pseudo-Goldstone boson dark matter (pGDM) particle. This dark matter candidate is a linear combination of the Standard Model (SM) singlets present in the 126 and 16 dimensional Higgs fields. The Higgs 126-plet vacuum expectation value (VEV) 〈126H〉 leaves unbroken the Z2 subgroup of Z4, the center of SO(10). Among other things, this yields topologically stable cosmic strings with a string tension μ∼〈126H〉2. The subsequent (spontaneous) breaking of Z2 at a significantly lower scale by the 16-plet VEV 〈16H〉 leads to the appearance of domain walls bounded by the strings produced earlier. We display the gravitational wave spectrum for Gμ values varying between 10−15 and 10−9 (〈126H〉∼1011 - 1014 GeV), and 〈16H〉∼0.1 - 102 TeV range (G denotes Newton's constant.) These predictions can be tested, as we show, by a variety of (proposed) experiments including LISA, ET, CE and others.