The Inflaton Portal to a Highly decoupled EeV Dark Matter Particle

We explore the possibility that the dark-matter relic abundance is generated in a context where the inflaton is the only mediator between the visible and the hidden sectors of our universe. Due to the relatively large mass of the inflaton field, such a portal leads to an extremely feeble interaction between the dark and the visible sectors suggesting that the dark sector cannot reach any thermal equilibrium with the visible sector. After the two sectors are populated by the decay of the inflaton, a heavy dark-matter particle thermally decouples within the dark sector. Later, a lighter dark particle, whose decay width is naturally suppressed by the inflaton propagator, decays into the visible sector after it dominates the energy density of universe. This process dilutes the dark-matter relic density by injecting entropy in the visible sector. We show that an inflaton mass of $\mathcal{O}(10^{13})$ GeV together with couplings of order one are fully compatible with a dark-matter relic abundance $\Omega h^2\sim 0.1$. As a general feature of the model, the entropy dilution mechanism is accompanied by a period of early matter domination, which modifies the amount of e-folds of inflation necessary to accommodate Planck data. Moreover, the coupling of the inflaton to the dark and visible sectors brings loop contributions to the inflationary potential which can destabilize the inflation trajectory. Considering all these complementary constraints, we show that, in the context of a plateau-inflation scenario such as the $\alpha$-attractor model, the inflaton can constitute a viable mediator between the visible sector and a $\sim 10$ EeV dark-matter candidate. Furthermore, we show that improved constraints on the tensor-to-scalar ratio and spectral index could potentially rule out dark-matter scenarios of this sort in the future.Comment: 18 pages, 6 figures, new version after publicatio

Stay-at-home Fathers in Contemporary Urban China

This research investigates stay-at-home fathers (SAHFs) as an emerging gendered identity in contemporary urban China. Being a SAHF constitutes an unconventional gender role in China, which has been marginalised by longstanding prejudice against men who are not the main wage-earners in the family unit. My scrutiny of the discourse surrounding this new role contributes to existing literature on the social production of gender difference and hierarchy in urban China. This research is particularly significant now, at a time when gender inequalities in China coexist with an increasingly individualistic culture, and yet these inequalities remain largely unaddressed by government discourse and often reinforced through popular discourse. This research seeks to answer three questions: What motivates men to become SAHFs? How do they perceive, experience, and enact their role as SAHFs? How does the construction of SAHF masculinity intersect with changing representations of urban family life and masculinity in contemporary urban China? To address these three interrelated questions, I examine three sources of data about SAHFs – TV dramas, social media articles, and interviews – focusing on how SAHFs’ perceptions, experiences, and practices are understood both by SAHFs themselves and wider society. Current research on SAHFs has been predominantly focused on the Global North to the extent that this is the first research on SAHFs in mainland China that focuses on how multiple discourses contribute to the construction and reconstruction of familial masculinity and wider family relations. By highlighting the plurality and ongoing reconfiguration of masculinity that has emerged from my three data sources, I show how discourse produced by and about SAHFs not only sustains but also sometimes transforms conventional notions of gender. In doing so, my research adds new perspectives to existing literature on Chinese masculinities and family life, as well as studies of SAHFs and the family in other countries