Hayley J. Macpherson, Asta Heinesen

Most cosmological data analysis today relies on the Friedmann-Lemaitre-Robertson-Walker (FLRW) metric, providing the basis of the current standard cosmological model. Within this framework, interesting tensions between our increasingly precise data and theoretical predictions are coming to light. It is therefore reasonable to explore the potential for cosmological analysis outside of the exact FLRW cosmological framework. In this work we adopt the general luminosity-distance series expansion in redshift with no assumptions of homogeneity or isotropy. This framework will allow for a full model-independent analysis of near-future low-redshift cosmological surveys. We calculate the effective observational 'Hubble', 'deceleration', 'curvature' and 'jerk' parameters of the luminosity-distance series expansion in numerical relativity simulations of realistic structure formation, for observers located in different environments and with different levels of sky-coverage. With a 'fairly-sampled' sky, we find 2% and 15% cosmic variance in the 'Hubble' and 'deceleration' parameters, respectively, compared to their analogies in the FLRW model. On top of this, we find that typical observers measure maximal sky-variance of 7% and 550% in the same parameters. Our work suggests the inclusion of low-redshift anisotropy in cosmological analysis could be important for drawing correct conclusions about our Universe.

Kamal Hajian, Hikmet Özşahin, Bayram Tekin

The first law of black hole thermodynamics in the presence of a cosmological constant $\Lambda$ can be generalized by introducing a term containing the variation $\delta \Lambda$. Similar to other terms in the first law, which are variations of some conserved charges like mass, entropy, angular momentum, electric charge etc., it has been shown in [1] that the new term has the same structure: $\Lambda$ is a conserved charge associated with a gauge symmetry; and its role in the first law is quite similar to an "electric charge" rather than to the pressure. Besides, its conjugate chemical potential resembles an "electric potential" on the horizon, in contrast with the volume enclosed by horizon. In this work, first we propose and prove the generalized Smarr relation in this new paradigm. Then, we reproduce systematically the "effective volume" of a black hole which has been introduced before in the literature as the conjugate of pressure. Our construction removes the ambiguity in the definition of volume. Finally, we apply and investigate this formulation of "$\Lambda$ as a charge" on a number of solutions to different models of gravity for different spacetime dimensions. Specially, we investigate the applicability and validity of the analysis for black branes, whose enclosed volume is not well-defined in principle.

De-Chang Dai

We use IGETS absolute gravitational acceleration measurement data to study the gravitational acceleration variance. The relative variance of $\delta g /g$ in 22 years is less than $4\times 10^{-8}$. Since $\delta G /G\lessapprox\delta g /g $, this implies the relative variance of Newtonian constant is less than $3\times 10^{-9}$ based on an sine-like oscillation hypothesis. This limit is at least 4 orders of magnitude better than the existing $G$ measurements. The scattered values of reported $G$ measurements coming from different experiments are most probably coming from systematic errors associated with these experiments and not due to intrinsic time variation of $G$. We also find that $\dot{ G} /G<5.61\times 10^{-10} \text{yr}^{-1}$ based on a linear hypothesis. This is the best terrestrial result so far.

Nicolas Chagnet, Shira Chapman, Jan de Boer, Claire Zukowski

We study circuit complexity for conformal field theory states in arbitrary dimensions. Our circuits start from a primary state and move along a unitary representation of the Lorentzian conformal group. We consider different choices of distance functions and explain how they can be understood in terms of the geometry of coadjoint orbits of the conformal group. Our analysis highlights a connection between the coadjoint orbits of the conformal group and timelike geodesics in anti-de Sitter spacetimes. We extend our method to study circuits in other symmetry groups using a group theoretic generalization of the notion of coherent states.