1,459 research outputs found
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
Bridging closed and dissipative discrete time crystals in spin systems with infinite-range interactions
We elucidate the role that the dissipation in a bosonic channel plays in the
prevalence and stability of time crystals (TCs) in a periodically driven
spin-boson system described by the Dicke model. Here, the bosons are
represented by photons, and they mediate the infinite-range interactions
between the spin systems. For strong dissipation, we study the dynamics using
an effective atom-only description and the closed Lipkin-Meshkov-Glick model.
By mapping out the phase diagrams for varying dissipation strengths, ranging
from zero to infinitely strong, we demonstrate that the area in the phase
diagram, where a TC exists, grows with the dissipation strength but only up to
an optimal point, beyond which most of the TCs become unstable. We find TCs in
both closed-system and dissipative regimes, but dissipative TCs are shown to be
more robust against random noise in the drive, and are only weakly affected by
the choice of initial state. We present the finite-sized behaviour and the
scaling of the lifetime of the TCs with respect to the number of spins and the
interaction strength within a fully quantum mechanical description.Comment: 16 pages, 14 figure
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