arXiv subjects

Alfred Bovon

Publications and source records attributed to Alfred Bovon.

3 recordsLinked to original sources

arXiv2026

Cosmological Backreaction and the Separate Universe Conjecture: Dynamical volume partitioning of Newtonian cosmologies

We provide a description of general Newtonian cosmologies for collisionless matter in terms of an exact and dynamical volume partitioning of global realizations of Newtonian models. Employing the formalism for the description of cosmological backreaction, an interaction between the inhomogeneities of the formation of structures in the Universe and their average properties can be analyzed. Our results can be regarded as a tool for many potential applications in the context of Newtonian simulations, but they also provide an exact way to assume analytical properties of the universe models on regional scales in conformity with global integral constraints on their average properties. We discuss approaches in relation to `separate Universe conjectures' in the literature and examine their consistency with the exact partitioning framework. In particular, using the Average Expansion Rate Approximation (AvERA) as an example, we show that identifying locally assigned Friedmannian rates with physical regional expansion rates is constrained by the global Newtonian 3-torus condition. Alternatively, when the simulation cells are interpreted as non-material control volumes, Reynolds transport introduces mass flux and flux-backreaction terms, so that their dynamics is not in general that of independent Friedmann domains. We also discuss the corresponding consistency conditions for stable clustering prescriptions.

astro-ph.CO↗

arXiv2025

Holographic deformations of matrix models

We study maximal supergravity in two dimensions, obtained from reduction of IIA supergravity on an $S^8$ sphere. The theory captures the low-lying fluctuations around the non-conformal D0-brane near-horizon geometry, dual to operators in the BFSS matrix model. Upon exciting some of the supergravity scalars, we construct half-supersymmetric domain wall solutions preserving $SO(p)\times SO(9-p)$ subgroups of the original $SO(9)$ symmetry. We determine their uplift to ten dimensions and the corresponding distributions of D0-branes. Finally, we compute the fluctuations around these domain wall backgrounds, corresponding to holographic two-point correlation functions in the Coulomb branch of the matrix model.

hep-th↗

arXiv2020

Optimal mean first-passage time for a Brownian searcher subjected to resetting: experimental and theoretical results

We study experimentally and theoretically the optimal mean time needed by a free diffusing Brownian particle to reach a target at a distance L from an initial position in the presence of resetting. Both the initial position and the resetting position are Gaussian distributed with width $σ$. We derived and tested two resetting protocols, one with a periodic and one with random (Poissonian) resetting times. We computed and measured the full first-passage probability distribution that displays spectacular spikes immediately after each resetting time for close targets. We study the optimal mean first-passage time as a function of the resetting period/rate for different values of the ratio b = L/$σ$ and find an interesting phase transtion at a critical value b = bc. For bc < b < $\infty$, there is a metastable optimum time which disappears for b < bc. The intrinsic diffculties in implementing these protocols in experiments are also discussed.

cond-mat.stat-mech↗