Freeze-in at stronger coupling

Predictivity of many non-thermal dark matter (DM) models is marred by the gravitational production background. This problem is ameliorated in models with lower reheating temperature $T_R$, which allows for dilution of gravitationally produced relics. We study the freeze-in dark matter production mechanism in the thermal bath with the electroweak scale temperature. The process is Boltzmann-suppressed if the dark matter mass is above $T_R$. In this case, the coupling to the thermal bath has to be significant to account for the observed dark matter relic density. As a result, the direct DM detection experiments already probe such freeze-in models, excluding significant parts of parameter space. The forthcoming experiments will explore this framework further, extending to lower couplings and higher reheating temperatures.Comment: 10 page

Scalar field dark matter and the Higgs field

We discuss the possibility that dark matter corresponds to an oscillating scalar field coupled to the Higgs boson. We argue that the initial field amplitude should generically be of the order of the Hubble parameter during inflation, as a result of its quasi-de Sitter fluctuations. This implies that such a field may account for the present dark matter abundance for masses in the range 10^-6 - 10^-4 eV, if the tensor-to-scalar ratio is within the range of planned CMB experiments. We show that such mass values can naturally be obtained through either Planck-suppressed non-renormalizable interactions with the Higgs boson or, alternatively, through renormalizable interactions within the Randall–Sundrum scenario, where the dark matter scalar resides in the bulk of the warped extra-dimension and the Higgs is confined to the infrared brane

Testing freeze-in with axial and vector Z′ bosons

The freeze-in production of Feebly Interacting Massive Particle (FIMP) dark matter in the early universe is an appealing alternative to the well-known and constrained Weakly Interacting Massive Particle (WIMP) paradigm. Although challenging, the phenomenology of FIMP dark matter has been receiving growing attention and is possible in a few scenarios. In this work, we contribute to this endeavor by considering a Z′ portal to fermionic dark matter, with the Z′ having both vector and axial couplings and a mass ranging from MeV up to PeV. We evaluate the bounds on both freeze-in and freeze-out from direct detection, atomic parity violation, leptonic anomalous magnetic moments, neutrino-electron scattering, collider, and beam dump experiments. We show that FIMPs can already be tested by most of these experiments in a complementary way, whereas WIMPs are especially viable in the Z′ low mass regime, in addition to the Z′ resonance region. We also discuss the role of the axial couplings of Z′ in our results. We therefore hope to motivate specific realizations of this model in the context of FIMPs, as well as searches for these elusive dark matter candidates

Mercados municipais : estruturas decadentes ou polos de animação

Presentes em praticamente todo o território nacional, os Mercados Municipais são geralmente reconhecidos como estruturas tradicionais de comércio retalhista de proximidade, funcionando como posto de abastecimento das populações. Estes espaços apresentaram também ao longo dos tempos uma vertente socioeconómica, cultural e urbana muito forte, revelando-se como uma mais-valia para a evolução e dinamização dos centros dos aglomerados em que se inserem, sejam eles de cariz urbano ou rural. Apesar disso, os Mercados Municipais têm perdido algum destaque como lugar de sucesso, se comparado com o que acontecia noutros tempos. Por esse motivo, defende-se que tais estruturas precisam de ser reinterpretadas, preservadas e animadas, sendo esse o caminho a seguir na ótica da Reabilitação Urbana. Só assim se podem manter como relevantes e, desse modo, projetarem-se para o futuro. A resposta à pergunta base que está na origem deste trabalho (“Mercados Municipais: Estruturas decadentes ou polos de animação?”) começa por uma resenha histórica sobre a origem e evolução do Mercado ao longo dos tempos, debruçando-se depois sobre a caracterização e principais funções de referência dos Mercados Municipais no quotidiano. Uma análise sobre os cenários possíveis de evolução e as hipóteses de desenvolvimento futuro concluem num conjunto de formas possíveis de intervenção de modo a garantir que os Mercados se reinventem e garantam a sua continuidade. E, deste modo, continuarem a ser também polos dinamizadores das comunidades. Para ilustrar a importância deste equipamento coletivo na vida e identidade da comunidade, é desenvolvido um estudo sobre o Mercado de Febres, localizado no centro da vila de Febres, situado no concelho de Cantanhede

Scale-invariant scalar field dark matter through the Higgs portal

We discuss the dynamics and phenomenology of an oscillating scalar field coupled to the Higgs boson that accounts for the dark matter in the Universe. The model assumes an underlying scale invariance such that the scalar field only acquires mass after the electroweak phase transition, behaving as dark radiation before the latter takes place. While for a positive coupling to the Higgs field the dark scalar is stable, for a negative coupling it acquires a vacuum expectation value after the electroweak phase transition and may decay into photon pairs, albeit with a mean lifetime much larger than the age of the Universe. We explore possible astrophysical and laboratory signatures of such a dark matter candidate in both cases, including annihilation and decay into photons, Higgs decay, photon-dark scalar oscillations and induced oscillations of fundamental constants. We find that dark matter within this scenario will be generically difficult to detect in the near future, except for the promising case of a 7 keV dark scalar decaying into photons, which naturally explains the observed galactic and extra-galactic 3.5 keV X-ray line.publishe