Asymmetric dark matter with a spontaneously broken <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>U</mml:mi><mml:mo stretchy="false">(</mml:mo><mml:mn>1</mml:mn><mml:msup><mml:mrow><mml:mo stretchy="false">)</mml:mo></mml:mrow><mml:mrow><mml:mo>′</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math>: Self-interaction and gravitational waves
Zien Chen, Kairui Ye, Mengchao Zhang
Abstract
Motivated by the collisionless cold dark matter small scale structure problem, we propose an asymmetric dark matter model with the dark sector charged under a dark $U(1{)}^{\ensuremath{'}}$. The mediator between dark matter particles is the dark gauge boson, which obtains its mass through the spontaneous breaking of $U(1{)}^{\ensuremath{'}}$. This model easily avoids the strong limits from cosmic microwave background (CMB) observation, and has a large parameter space to be consistent with small scale structure data. We focus on a special scenario where portals between the dark sector and visible sector are too weak to be detected by traditional methods. We find that this scenario can increase the effective number of neutrinos (${N}_{\mathrm{eff}}$). In addition, the spontaneous $U(1{)}^{\ensuremath{'}}$ symmetry breaking process can generate stochastic gravitational waves with peak frequency around ${10}^{\ensuremath{-}6}--{10}^{\ensuremath{-}7}\text{ }\text{ }\mathrm{Hz}$.