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We propose a new interacting dark sector model, Stepped Partially Acoustic Dark Matter (SPartAcous), that can simultaneously address the two most important tensions in current cosmological data, the H0 and S8 problems. As in the Partially Acoustic Dark Matter (PAcDM) scenario, this model features a subcomponent of dark matter that interacts with dark radiation at high temperatures, suppressing the growth of structure at small scales and thereby addressing the S8 problem. However, in the SPartAcous model, the dark radiation includes a component with a light mass that becomes non-relativistic close to the time of matter-radiation equality. As this light component annihilates away, the remaining dark radiation heats up and its interactions with dark matter decouple. The heating up of the dark sector results in a step-like increase in the relative energy density in dark radiation, significantly reducing the H0 tension, while the decoupling of dark matter and dark radiation ensures that the power spectrum at larger scales is identical to ΛCDM.
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This content will become publicly available on May 4, 2026
Temporal Dark Solitons in an Integrated Optical Parametric Oscillator
We theoretically describe and experimentally demonstrate dark soliton formation in a quadratic nonlinear resonator in lithium niobate nanophotonic. The dark pulses have a temporal duration of 40 fs and form a 120-nm-wide coherent frequency comb.
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- Award ID(s):
- 2408297
- PAR ID:
- 10595488
- Publisher / Repository:
- CLEO 2025
- Date Published:
- Format(s):
- Medium: X
- Location:
- Long Beach, CA
- Sponsoring Org:
- National Science Foundation
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