Gauge-independent gravitational waves from cogenesis in a <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mi>B</mml:mi> <mml:mo>−</mml:mo> <mml:mi>L</mml:mi> </mml:math> conserving universe

An analysis of baryogenesis and stochastic gravitational wave production is presented for an extension of the Standard Model where the dark sector consists of dark matter particles charged under a <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mi>U</a:mi> <a:mo stretchy="false">(</a:mo> <a:mn>1</a:mn> <a:msub> <a:mo stretchy="false">)</a:mo> <a:mi>x</a:mi> </a:msub> </a:math> gauge symmetry, while a subset of dark fields also carry lepton number but no <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"> <e:mi>U</e:mi> <e:mo stretchy="false">(</e:mo> <e:mn>1</e:mn> <e:msub> <e:mo stretchy="false">)</e:mo> <e:mi>x</e:mi> </e:msub> </e:math> charge. We demonstrate that, with <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" display="inline"> <i:mi>C</i:mi> <i:mi>P</i:mi> </i:math> violation induced by Yukawa couplings, equal and opposite lepton asymmetries are generated in the visible and hidden sectors. Subsequent evolution preserves the lepton number separately in each sector, and sphaleron interactions partially convert the lepton asymmetry into baryon asymmetry near the temperature of the first-order phase transition. Furthermore, we discuss stochastic gravitational wave background production for the first-order phase transition using a gauge-independent bubble nucleation dynamics which yields spectra also valid in the supercooled low-temperature regime with <k:math xmlns:k="http://www.w3.org/1998/Math/MathML" display="inline"> <k:msub> <k:mi>T</k:mi> <k:mi>p</k:mi> </k:msub> <k:mo>/</k:mo> <k:msub> <k:mi>m</k:mi> <k:msub> <k:mi>A</k:mi> <k:mi>x</k:mi> </k:msub> </k:msub> <k:mo>≪</k:mo> <k:mn>1</k:mn> </k:math> , where <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline"> <m:msub> <m:mi>T</m:mi> <m:mi>p</m:mi> </m:msub> </m:math> is the percolation temperature and <o:math xmlns:o="http://www.w3.org/1998/Math/MathML" display="inline"> <o:msub> <o:mi>m</o:mi> <o:msub> <o:mi>A</o:mi> <o:mi>x</o:mi> </o:msub> </o:msub> </o:math> is the dark photon mass. A parameter-space scan identifies regions that simultaneously account for cogenesis of baryon asymmetry and dark matter and predict stochastic gravitational wave signals within reach of current (NANOGrav, EPTA, and PPTA) and future detectors at higher frequencies, providing a unified framework for cogenesis and associated gravitational wave production.