Cosmology

The 249th AAS meeting convenes the astronomy and astrophysics community in Salt Lake City from 10–14 January 2027, with the Historical Astronomy Division. The programme offers research presentations and community exchange across astronomical subfields. Registration is open through the official meeting site.

Join Eduardo Bañados’s group to investigate early quasars and their environments. The postdoc will analyze JWST PRISM-DAWN integral-field spectroscopy, contribute to Euclid’s quasar programme, and help prepare and reduce Large Binocular Telescope observations. The full-time position lasts three years, with a negotiable start; the first half of 2027 is preferred. This vacancy belongs to the September 2026 Max Planck Postdoc Program call, which accepts applications until 13 October 2026 at 12:00 CEST through the official application platform.

Lyman Page introduces temperature variations and polarization in the cosmic microwave background for researchers outside cosmology, explaining how these measurements underpin the standard cosmological model. He then considers what that model leaves unresolved, especially whether gravitational waves originating in the early Universe are detectable. The talk reviews the Simons Observatory’s experimental search for those primordial signals and its role in addressing this question. Online via Zoom Events in the John Bahcall Colloquium, hosted by the Institute for Underground Science at SURF. The free series welcomes the scientific community across career stages. Wednesday 14 October, 09:00–10:00 MDT (America/Denver), equivalent to 15:00–16:00 UTC. Follow Register on the organizer page, then select this dated session in the Zoom Events registration list.

Uddipan Banik derives a dynamical account of dark-matter halo density profiles using the Boltzmann–Poisson equations for an expanding Universe populated by subhalos of many masses. A self-similar solution links density slope to halo mass growth; including gravitational scattering and subhalo capture gives gamma = 6/(s + 2). Initial collapse with s = 2 produces a prompt cusp of slope 3/2. Hierarchical growth connects the slope to the primordial power spectrum and recovers the Syer–White relation during matter domination. Stable clustering selects an inner Navarro–Frenk–White cusp of slope one, while stalled accretion approaches the outer slope of three. The framework connects these profiles to successive stages of halo assembly.

Fraser Cain and Pamela L. Gay examine possible futures of the universe across vastly different timescales. Topics include the Milky Way and Andromeda, cosmic isolation as expansion continues, the fading microwave background, the end of star formation and the era of stellar remnants. They discuss uncertain processes such as proton decay, black-hole evaporation through Hawking radiation, entropy and heat death, alongside alternative outcomes if dark energy evolves. These are model-dependent projections. Pamela Gay is a senior scientist at the Planetary Science Institute. Published on 21 September 2026, the episode appears in the feed as The Beginning and End of Everything, Part 2. Its original duration is 37 minutes 7 seconds.

Paco Villaescusa examines how simulations and artificial intelligence change the extraction of physical knowledge from precision cosmological surveys. The talk asks how much information lies in large-scale structure beyond power spectra, including nonlinear scales and higher-order statistics, and introduces the Quijote and Backlight simulation programmes. It then addresses the uncertain astrophysical processes that complicate small-scale inference through CAMELS, a framework combining cosmology, galaxy formation and machine learning. DREAMS is presented as a route to predicting dark-matter observables while accounting for baryonic uncertainties. The final part considers coupling simulations with increasingly capable AI: Denario is introduced as an agentic research system that generates hypotheses, designs analyses, writes and executes code, interprets results and refines research directions. The discussion considers what coordinated populations of agents and simulations spanning physical scales could make possible.

Sean Carroll explores explanations for cosmic acceleration beyond a constant vacuum energy. He discusses dynamical dark-energy models, their relationship to particle physics, possible changes to gravity and the observations that could help distinguish competing theories.

Sean Carroll traces the cosmological constant from Einstein's equations to modern evidence for accelerated expansion. He explains why the energy of empty space is difficult to reconcile with particle physics and examines the related puzzles of its observed size and importance in today's universe.

Jim Al-Khalili and Sean Carroll discuss the nature of time, whether it is fundamental or emergent, and how its direction relates to physical laws and human experience. Their conversation connects the arrow of time with unresolved questions in quantum mechanics, biology and cosmology.