218 citations · 807 across the 31 of their papers we have counts for
33 papers
Which Saddles Contribute? The South-East Rule for Multidimensional Integrals
Inês Aniceto, Job Feldbrugge, Christopher J. Howls
In this paper, we introduce and demonstrate a simple geometric algorithm to determine which critical points, both complex as well as real, contribute to the asymptotic evaluation o…
Caustic Skeleton and the Local Cosmic Web: the Coma Cluster node and the Pisces-Perseus ridge
Amelie Read, Job Feldbrugge, Celine Boehm +2
We apply caustic skeleton theory to the Manticore-Local simulations, which are Bayesian constrained reconstructions of the Local Universe from the 2M++ galaxy catalogue, and extrac…
Galaxy Populations in the IllustrisTNG Caustic Skeleton
Benjamin Hertzsch, Job Feldbrugge, Rien van de Weygaert
The caustic skeleton is a parameter-free and mathematically rigorous formalism for tracing the hierarchical formation history of the multiscale cosmic web from the singularities in…
Resurgence and Hyperasymptotics in Wave Optics Astronomy
Job Feldbrugge, Samuel Crew, Ue-Li Pen
With the discovery of gravitational waves and fast radio bursts, wave optics has become increasingly relevant in astrophysics. This paper studies the behaviour of random gravitatio…
A universal approach to saddle-point methods in attosecond science
Anne Weber, Job Feldbrugge, Emilio Pisanty
Light-matter interactions within the strong-field regime, where intense laser fields can ionise a target via tunnelling, give rise to fascinating phenomena such as the generation o…
A New Recipe for Caustic Pancakes: On the Reality of Walls in the Cosmic Web
Benjamin Hertzsch, Job Feldbrugge, Maé Rodriguez +1
The caustic skeleton model is a mathematically rigorous framework for studying the formation history of the emerging cosmic web from the caustics in the underlying dark matter flow…
The real-time Feynman path integral for step potentials
Job Feldbrugge, Ue-Li Pen
Complex (semi-)classical paths, or instantons, form an integral part of our understanding of quantum physics. Whereas real classical paths describe classically allowed transitions…
Efficient evaluation of real-time path integrals
Job Feldbrugge, Joshua Y. L. Jones
The Feynman path integral has revolutionized modern approaches to quantum physics. Although the path integral formalism has proven very successful and spawned several approximation…
Wave optics for rotating stars
Béatrice Bonga, Job Feldbrugge, Ariadna Ribes Metidieri
Gravitational lensing in wave optics is a rich field combining caustic singularities, general relativity and interference phenomena. We present a detailed evaluation of wave optics…
What makes a cosmic filament? The dynamical origin and identity of filaments I. fundamentals in 2D
Job Feldbrugge, Rien van de Weygaert
Cosmic filaments are the main transport channels of matter in the Megaparsec universe, and represent the most prominent structural feature in the matter and galaxy distribution. He…
Phase-Space Delaunay Tessellation Field Estimator
Job Feldbrugge
The reconstruction of density and velocity fields is of central importance to the interpretation of -body simulations. We propose a phase-space extension of the Delaunay tessell…
Crossing singularities in the saddle point approximation
Job Feldbrugge, Dylan L. Jow, Ue-Li Pen
We describe a new phenomenon in the study of the real-time path integral, where complex classical paths hit singularities of the potential and need to be analytically continued bey…
Complex classical paths in quantum reflections and tunneling
Job Feldbrugge, Dylan L. Jow, Ue-Li Pen
The real-time propagator of the symmetric Rosen-Morse, also known as the symmetric modified Pöschl-Teller, barrier is expressed in the Picard-Lefschetz path integral formalism usin…
Orthogonality relations for conical functions of imaginary order
Job Feldbrugge, Nynke M. D. Niezink
Orthogonality relations for conical or Mehler functions of imaginary order are derived and expressed in terms of the Dirac delta function. This work extends recently derived orthog…
Complex evaluation of angular power spectra: Going beyond the Limber approximation
Job Feldbrugge
Angular power spectra are central to the study of our Universe. In this paper, I develop a new method for the numeric evaluation and analytic estimation of the angular cross-power…
Statistics of tidal and deformation eigenvalue fields in the primordial Gaussian matter distribution: the two-dimensional case
Job Feldbrugge, Yihan Yan, Rien van de Weygaert
We study the statistical properties of the eigenvalues of the primordial tidal and deformation tensor for random Gaussian cosmic density fields. With the tidal and deformation tens…
Cosmic Web & Caustic Skeleton: non-linear Constrained Realizations -- 2D case studies
Job Feldbrugge, Rien van de Weygaert
The cosmic web consists of a complex configuration of voids, walls, filaments, and clusters, which formed under the gravitational collapse of Gaussian fluctuations. Understanding u…
Existence of real time quantum path integrals
Job Feldbrugge, Neil Turok
Many interesting physical theories have analytic classical actions. We show how Feynman's path integral may be defined non-perturbatively, for such theories, without a Wick rotatio…
Regimes in astrophysical lensing: refractive optics, diffractive optics, and the Fresnel scale
Dylan L. Jow, Ue-Li Pen, Job Feldbrugge
Astrophysical lensing has typically been studied in two regimes: diffractive optics and refractive optics. Diffractive optics is characterized by a perturbative expansion of the Ki…
Persistent homology of the cosmic web. I: Hierarchical topology in CDM cosmologies
Georg Wilding, Keimpe Nevenzeel, Rien van de Weygaert +5
Using a set of CDM simulations of cosmic structure formation, we study the evolving connectivity and changing topological structure of the cosmic web using state-of-the-art tool…
Multi-plane lensing in wave optics
Job Feldbrugge
Wave effects in lensing form a rich phenomenon at the intersection of classical caustic singularities and quantum interference, yet are notoriously difficult to model. A large numb…
Gravitational lensing of binary systems in wave optics
Job Feldbrugge, Neil Turok
We present the first detailed computations of wave optics effects in the gravitational lensing of binary systems. The field is conceptually rich, combining the caustic singularitie…
Oscillatory path integrals for radio astronomy
Job Feldbrugge, Ue-Li Pen, Neil Turok
We introduce a new method for evaluating the oscillatory integrals which describe natural interference patterns. As an illustrative example of contemporary interest, we consider as…
Stochastic Homology of Gaussian vs. non-Gaussian Random Fields: Graphs towards Betti Numbers and Persistence Diagrams
Job Feldbrugge, Matti van Engelen, Rien van de Weygaert +2
The topology and geometry of random fields - in terms of the Euler characteristic and the Minkowski functionals - has received a lot of attention in the context of the Cosmic Micro…