Shaun Hotchkiss's research while affiliated with University of Auckland and other places

... In an attempt to characterise metastability and slow dynamics in glasses, several tools to count and classify the stationary points (local minima, maxima and saddles) of complicated, very non-convex (free)-energy landscapes have been conceived and developed. Given that corrugated landscapes are ubiquitous, these techniques are expected to play a relevant role in other contexts involving rugged landscapes to optimize, being them fitness landscapes in biology [3,4], utility functions in economics [5], cost functions in constraint satisfaction or inference problems [6][7][8], loss landscapes in supervised learning [9], and obviously energy landscapes in condensed and soft matter physics [10], but also string theory and cosmology [11,12]. Most of these settings are naturally high-dimensional: for instance, the space of genotypes over which fitness landscapes are defined is combinatorially large; in the same vein, training huge artificial neural networks like those used in current deep learning applications requires to find good minima of loss landscapes depending on an extremely large number of parameters. ...

... If the inflaton is decoupled from other fields, it fragments through a process of self-resonance for p > 2, which gives rise to a radiation-dominated universe ∼10 e-folds of expansion after the end of inflation [35,36]. If p = 2, the inflaton fragments instead due to gravitational effects at much longer time scales [37]. ...

... The paper is organized in the following manner. In section 2, we review the accretion process of DM spikes around isolated PBHs by closely following the formalism of ref. [46]. In this section, which can be skipped by the expert reader, we describe the density profile of dark matter spikes expected around PBHs. ...

... We run dynamical simulations of FDM using the Python package PyUltraLight [43]. This package solves the Schrödinger-Poisson equation on a grid, where we choose a spatial resolution of 100 pc. ...

... The formation of dark matter halos has been studied through numerical simulations and analytical approaches, specifically targeting those that developed during the matter-dominated era (see, e.g., Gosenca et al. 2017;Delos et al. 2018;White 2022;). On the other hand, halos forming during the radiation-dominated era have the potential to possess significantly higher densities. ...

... Alkhanishvili et al. 2022 ), but using such a model will incur a significantly lower computational cost. One such analytical model that is gaining in popularity when conducting full-shape analyses is the ef fecti ve field theory of large-scale structure (EFTofLSS, Baumann et al. 2012 ;Carrasco, Hertzberg & Senatore 2012 ;Senatore 2015 ;de la Bella et al. 2017 ;Philcox et al. 2020 ;Ivanov 2022 ;Mergulh ˜ ao, Rubira & Voivodic 2023 ;Moretti et al. 2023 ). This perturbation-theory based model maps predictions for the dark matter clustering to that of galaxies via a series of nuisance parameters φ, that are marginalized o v er when putting constraints on the cosmological parameters θ. ...

... Once the stacked image is computed, it is possible to reconstruct the averaged convergence profile of the voids by averaging the pixel value in concentric shells around the image centre. Furthermore, [105] has shown using simulations that these imprints change according to the void population. In fact, the lensing imprint is directly related to the true underlying gravitational potential, and the inner density of cosmic voids -which depends on size and voids definition [90,106] -will impact on the strength of this correlation signal. ...

... These models are studied with matter distributed not only in a single halo cloud but also in various different ways, for example, in onion-like configurations [23,24,25] or in layers of walls [26,27]. Results of these studies can be compared with N-body relativistic simulations in a weak field approximation [22,24,25,28,29]. Furthermore, exact inhomogeneous models are used for building cosmological models in a Swiss cheese arrangement which allows for light propagation studies in more realistic conditions [30,31,32,33]. ...

... Furthermore, galaxies are often used to identify voids observationally, where galaxies of different types populate halos differently. Since halo masses can have a different impact on clustering properties, the resulting void catalogues, which depend on the minimum halo mass cut, can have different abundances and void profiles [95,338]. As a complementary approach, peaks of the void lensing map can also be used to identify voids, also resulting in a higher signal-to-noise ratio relative to galaxy-identified voids [335,339]. ...

... Thus, it is not unnatural to find some discrepancy between voids in data and the spherical void model. For example, the shell-crossing density threshold derived from the statistics of voids in data is inconsistent with the prediction based on the spherical void approximation (Chan et al. 2014;Achitouv et al. 2015;Nadathur & Hotchkiss 2015). This motivates a search for a new definition and identification method for voids that mitigate the inconsistency between voids in theory and data. ...