Conference

There is no consensus on how baryonic feedback shapes the underlying matter distribution. This uncertainty is a limiting systematic for cosmic shear inference, particularly in the era of LSST, and a fundamental question in the study of galaxy evolution. Modern simulations are tuned to reproduce a variety of galaxy observations, however, previous studies demonstrated that the implied amplitude of baryon feedback is dependent on the chosen observable: e.g., X-ray gas fractions, which are sensitive to material within the virial radius of massive clusters, or kinematic Sunyaev Zeldovich (kSZ) profiles, which extend to a few virial radii [Bigwood+2024, McCarthy+2024]. In this talk, we address the uncertain observational landscape, by adopting a multi-observation view of feedback. We will present measurements for the gas and mass distribution as seen by eROSITA X-rays, DESI+ACT kSZ, and galaxy-galaxy lensing across a wide range of redshifts (0

The impact of feedback from galaxy formation on cosmological probes is typically quantified in terms of the suppression of the matter power spectrum in hydrodynamical compared to gravity-only simulations. In this paper, we instead study how baryonic feedback impacts halo assembly histories and thereby imprints on cosmological observables. We investigate the sensitivity of the thermal Sunyaev-Zel'dovich effect (tSZ) power spectrum, X-ray number counts, weak lensing and kinetic Sunyaev-Zel'dovich (kSZ) stacked profiles to halo populations as a function of mass and redshift. We then study the imprint of different feedback implementations in the FLAMINGO suite of cosmological simulations on the assembly histories of these halo populations, as a function of radial scale. We find that kSZ profiles target lower-mass halos (M200m∼10^13.1M⊙) compared to all other probes considered (M200m∼10^15M⊙). Feedback is inefficient in high-mass clusters with ∼10^15M⊙ at z=0, but was more efficient at earlier times in the same population, with a ∼5-10% effect on mass at 22). These findings are tied together by noting that, regardless of redshift, feedback most efficiently redistributes baryons when halos reach a mass of M200m≃10^12.8M⊙ and ceases to have any significant effect by the time M200m≃10^15M⊙. We put forward strategies for minimizing sensitivity of lensing analyses to baryonic feedback, and for exploring baryonic resolutions to the unexpectedly low tSZ power in cosmic microwave background observations.

Observational surveys of the distribution of matter in the universe are becoming ever more precise and continue to be extended to smaller scales. This necessitates accounting for the fact that baryons do not precisely trace the dark matter. The redistribution of baryons by galactic winds, which is the major bottleneck in our understanding of galaxy evolution, therefore requires a convergence between models of large-scale structure and cosmology. I will discuss some of the insights gained from cosmological, hydrodynamical simulations, and challenges that need to be overcome to make further progress. I will present recent results from the FLAMINGO suite of large-volume cosmological, hydrodynamical simulations, which provide insight into the importance of baryonic effects for cosmology using large-scale structure and galaxy clusters. Finally, I will present the COLIBRE simulations of galaxy formation, a new suite of cosmological hydrodynamical simulations that removes important shortcomings of previous simulations.

Terrestrial ecosystems exhibit ecological stability: If an ecosystem is perturbed, biological feedback drives it back toward an equilibrium state, but an ecosystem does not remain stuck in its equilibrium state because it is continually perturbed. Are galaxies really similar to biological ecosystems in that regard? My talk will consider whether the atmospheres of galaxies have feedback-regulated equilibrium states and what the observational consequences of those states might be. While considering those questions I will lay out a framework for classifying how halo-scale feedback loops operate.

A key question in holography is how to reconstruct bulk operators in the holographic dual. It is especially interesting to reconstruct operators inside the black hole interior, but also especially difficult to do explicitly. Recently, an explicit form for the bulk-to-boundary `holographic’ map was proposed in JT gravity, by Iliesiu, Levine, Lin, Maxfield, and Mezei, who also proposed and studied an explicit `reconstruction’ map on operators. In this talk, I will discuss various pros and cons of their reconstruction map, and propose an alternative map with perhaps nicer properties.

I will use algebras to revisit and generalize the theory of canonical purifications, explain the general concept of "CRT sewing without gravity," and explain how this technology allows the influential-but-complicated "Araki-Yamagami theorem" from the '80s to be proved with 10x less work using a QI-motivated trick. Based on work with Caminiti and Capeccia.

In holography, when two boundary subsystems have large mutual information, they are connected by their entanglement wedge. However, it remains mysterious whether these subsystems are EPR-like entangled. In this talk, I resolve this problem by finding bulk duals of one-shot distillable entanglement. Namely, I show that in one-shot scenarios: i) there is no distillable entanglement only by local operations at leading order in $G_N$, suggesting the absence of bipartite entanglement in a holographic mixed state, and ii) one-way LOCC-distillable entanglement is related to the entanglement wedge cross section, which is further dual to entanglement of formation. By demonstrating an explicit distillation protocol by holographic measurements, I conclude that a connected wedge does not necessarily imply finite distillable entanglement even when one-way LOCC is allowed. This talk is based on arXiv:2411.03426 [hep-th] and 2502.04437 [quant-ph].

The notion of complementarity, first introduced in the context of the information paradox, posits that the experiences of two observers who cannot communicate need not match in quantum gravity. In the context of the previous talk, I will argue that the recent proposals for explicitly taking observers into account provide a way to describe semiclassical closed universes in holography, at the expense of a resort to complementarity. I will then discuss an analogous setup in the case of an evaporating black hole, and propose a set of general principles for black hole complementarity. This talk is based on an ongoing collaboration with Netta Engelhardt and Daniel Harlow.

A number of recent arguments have suggested that baby universes in quantum gravity have a one-dimensional Hilbert space. I will provide a new argument, based on work with E. Gesteau, in favor of this conclusion. The argument makes use of a standard asymptotically AdS spacetime dual to a thermal state below the Hawking-Page transition. In particular, there is a low-energy, low-complexity causal wedge operator whose expectation value in the dual CFT is only consistent with a one-dimensional Hilbert space for baby universes.