About

I am Niko Sarcevic, a cosmologist working on weak lensing cosmology, astrophysical systematics, and statistical inference. I am currently a Postdoctoral Associate at Duke University, where I work on connecting observations, galaxy astrophysics, and cosmological inference.

My research is motivated by the challenge of making precision cosmology robust: understanding how astrophysical and observational effects enter our measurements, modeling their impact, and developing methods to mitigate them. I am also interested in open scientific software, reproducible analysis workflows, and making scientific tools more accessible.

I am an active member of the LSST Dark Energy Science Collaboration (DESC) and the NASA Roman Space Telescope HLIS Cosmology PIT. I also contribute to the Dark Energy Survey (DES), and I collaborate with the Subaru Hyper Suprime-Cam (HSC) and 4MOST teams.

Before joining Duke, I completed my PhD at Newcastle University, where my thesis focused on modeling and mitigating systematics in weak lensing measurements. Earlier, I studied in the AstroMundus Master program and completed my undergraduate degree in Astronomy and Astrophysics at the University of Novi Sad.

All images were taken by my late brother. I include them here to honor his memory.

Research

My research focuses on weak lensing cosmology, astrophysical systematics, and statistical inference for precision cosmology. I am interested in how galaxy formation, intrinsic alignments, baryonic effects, selection effects, and observational systematics impact cosmological measurements.

A central theme of my work is building models, tools, and analysis pipelines that make these effects easier to quantify, mitigate, and propagate into cosmological inference. I work across theory, simulations, forecasting, and data analysis, with an emphasis on reproducibility and open scientific software.

Research Themes

  • Weak lensing systematics
    I study astrophysical and observational effects that can bias weak lensing measurements and cosmological constraints, with a focus on modeling, mitigation, and robust inference.
  • Intrinsic alignments
    I work on understanding correlations between galaxy shapes and the large scale structure, including their connection to galaxy astrophysics and their impact on weak lensing analyses.
  • Galaxy samples and selection effects
    I am interested in how galaxy populations, luminosity functions, color fractions, tomographic binning, and sample definitions affect cosmological measurements.
  • Forecasting and inference
    I develop tools for Fisher forecasting, likelihood approximations, derivative based inference, combined probe analyses, and uncertainty propagation.
  • Scientific software
    I build open source tools for cosmology workflows, with an emphasis on clear interfaces, reusable components, testing, documentation, and reproducibility.

Collaborations

My research is connected to several large survey collaborations and analysis efforts, including the LSST Dark Energy Science Collaboration (DESC), the NASA Roman Space Telescope HLIS Cosmology PIT, the Dark Energy Survey (DES), the Subaru Hyper Suprime-Cam (HSC), and 4MOST.

Doctoral Research

My doctoral work at Newcastle University focused on modeling and mitigating systematic effects in weak lensing measurements. My thesis, " Modelling and Mitigating the Systematics in Weak Lensing Measurements", explored how astrophysical and observational systematics affect cosmological inference and how they can be incorporated into analysis frameworks.

Earlier Research

Before moving into weak lensing cosmology, I worked on electric field simulations and detector design in the XENON collaboration, including work on the electric field cage of the XENONnT detector. My earlier academic work also included gamma ray source populations and nuclear physics applications.

Publications

Find my publications and related works on the following platforms:

Professional Service

I serve as a peer reviewer for the following journals:

Books

I enjoy writing and have worked on two books in nuclear physics during my undergraduate studies in Serbian.

  • Osnove Nuklearne Fizike (Basics of Nuclear Physics)
    This is the second edition of a book originally authored by L. Marinkov. In 2010, I collaborated with two colleagues to prepare and update the material for this edition. The book was published by the University of Novi Sad.
    Download
  • Uvod u Nuklearnu Fiziku (Introduction to Nuclear Physics)
    In 2013, I worked with Prof. M. Krmar to turn his lecture notes into a book. I performed a full physics review, language editing, prepress, and other tasks. The book was published by the University of Novi Sad.
    Download

Projects

Discover my peer-reviewed articles, conference papers, and other scholarly works that contribute to the field of astrophysics and cosmology.

Projects

In addition to my research, I have contributed to several projects that aim to build scientific communities, promote science communication, and advance data visualization practices. Below are some highlights.

Coding Projects

My coding projects are open source and freely available. Below are some highlights of my work.

  • DerivKit
    DerivKit is a model agnostic Python package for numerical derivatives, Fisher forecasts, higher order derivative likelihood approximations, and inference workflows. It is designed to make derivative based forecasting more robust, reusable, and easier to integrate into any pipeline, regardless of the underlying model or scientific application.
    GitHub repository
  • Binny
    Binny is a Python toolkit for tomographic binning, redshift distributions, and survey sample utilities. It supports flexible bin construction for cosmological analyses and forecasting pipelines.
    GitHub repository
  • LFKit
    LFKit is a Python toolkit for luminosity functions, conditinoal luminosity functions, photometric corrections, and galaxy sample modeling. It connects luminosity functions to number densities, sample selections, and survey forecasts.
    GitHub repository
  • DSF
    DSF is a Python package for general Delta Sigma modeling and forecasting. I contribute to its development within LSST DESC, where it supports LSST Delta Sigma forecast analyses while remaining useful for Delta Sigma modeling beyond a single survey or application.
    GitHub repository
  • CosmΩracle
    CosmΩracle (GitHub repository) is a web app developed in collaboration with Matthijs van der Wild and Marco Bonici. It serves as a computing aid for cosmological distance measures, providing results for parameters like comoving distance, luminosity distance, angular diameter distance, lookback time, and more at any given redshift. The app is fully responsive and works seamlessly on desktop, tablet, and mobile devices.
  • Standard Model of Particle Physics with Bokeh
    An interactive visualization of the Standard Model using Bokeh. The project includes particle symbols and data, presented with hover functionality. Initially conceptualized by me and co-developed with Matthijs, this visualization showcases particle properties interactively.
    GitHub repository
  • Map of Europe with GeoPandas and Bokeh
    An interactive map representing EuCAPT member institutions and general data visualization use cases. Developed for EuCAPT, this project simplifies mapping for various datasets without relying on Google APIs. The interactive map leverages GeoPandas and Bokeh for customizability and user-friendly visualization.
    GitHub repository

Community Efforts

  • Cosmology from Home
    Cosmology from Home is an innovative online cosmology conference designed to foster dynamic and collaborative interactions in the virtual domain. The conference format combines pre-recorded talks, asynchronous discussions, and scheduled live sessions, along with a freely navigable discussion space that encourages organic, ongoing conversations.
    The conference has been a resounding success, bringing together cosmologists worldwide to discuss the interface of theory and observations. To date, over 500 talks are publicly available on our YouTube channel, serving as a valuable resource for the community. We take pride in the conference's impact and its role in promoting global collaboration in cosmology.
  • European Consortium for Astroparticle Theory (EuCAPT)
    EuCAPT brings together theoretical astrophysicists and cosmologists across Europe to address some of the most profound challenges in the field, such as the nature of dark matter and dark energy, the origin of cosmic rays, and the matter-antimatter asymmetry.
    From 2020 to 2025, I have been a junior contributor to the consortium, supporting its mission by managing the website and social media communications. EuCAPT's focus on fostering collaboration, coordinating scientific activities, and providing a fair and open environment for young scientists has made it an invaluable platform for advancing the field.
  • UK Cosmology
    UK Cosmology is an organization of cosmology researchers at universities across the UK. The aim of the organization is to connect researchers at all academic stages and organize events such as workshops, conferences, and seminars where the latest advancements in cosmology are shared.
    As part of the organizing team, I worked alongside David Seery (Sussex) and S. Sevillano (Durham) to modernize and update the organization's content and resources. I also managed the community's social media presence via the official Twitter account and contributed to maintaining and enhancing the website.
  • HEP-ASTRO-COSMO
    HEP-ASTRO-COSMO is a community-driven effort to collect all open-source packages, libraries, and tools related to high-energy physics, astrophysics, and cosmology in one centralized place.
    This project invites contributions from everyone in the community, with package descriptions sourced directly from their respective pages. It serves as a collaborative resource hub for researchers and developers alike.

Teaching

Below are the courses I have taught at Newcastle University, UK, and the University of Freiburg, Germany, along with my roles and responsibilities.

Newcastle University, UK

  • Introductory Cosmology
    Teaching Assistant, SS 2022
    Undergraduate course on cosmology.
  • Advanced Quantum & Atoms, Molecules, Nuclei & Particles (PHY3044)
    Lecturer, SS 2022
    Undergraduate course on advanced quantum, atomic, nuclear, and particle physics.
  • Stellar Structure and Evolution (PHY3040)
    Teaching Assistant, WS 2021/2022
    Undergraduate course on stellar physics (physics students).
  • Introductory Astrophysics (PHY1021)
    Teaching Assistant, WS 2021/2022
    Undergraduate course on astrophysics (physics students).
  • MSP Skills & Employability (LaTeX Skills)
    Teaching Assistant, WS 2021/2022
    Assisted in the LaTeX Skills workshop for students of all stages.
  • Geophysical & Astrophysical Fluids (MAS8810-PHY8049)
    Teaching Assistant, SS 2021
    Graduate course on geophysical and astrophysical fluids.
  • Fluid Dynamics (MAS2803-MAS2805-PHY2033)
    Teaching Assistant, SS 2021
    Undergraduate course on fluid dynamics.
  • Algebra, Multivariable Calculus & Differential Equations (PHY1035-MAS1609)
    Teaching Assistant, SS 2021
    Undergraduate course on algebra, multivariate calculus, and differential equations.
  • Advanced Quantum & Atoms, Molecules, Nuclei & Particles (PHY3044)
    Teaching Assistant, SS 2021
    Undergraduate course on advanced quantum and atomic physics.
  • Methods for Differential Equations & Partial Differential Equations & Non-Linear Waves (MAS3810)
    Teaching Assistant, WS 2020/2021
    Undergraduate course on differential equations and non-linear waves. Tutoring included marking and assessment.
  • Linear Analysis & Topology (MAS3711-MAS8711)
    Teaching Assistant, WS 2020/2021
    Undergraduate course on linear analysis and topology. Tutoring included marking and assessment.
  • Laboratory Physics 1 (PHY1030)
    Laboratory Assistant, 2020-2024
    Undergraduate experimental course. Supervised the Photoelectric Effect and Radioactivity experiments.

University of Freiburg, Germany

  • Physiklabor für Fortgeschrittene II
    Laboratory Assistant, SS 2020
    Graduate experimental course. Supervised the Raman Spectroscopy experiment.
  • Physiklabor für Fortgeschrittene I
    Laboratory Assistant, WS 2019/2020
    Undergraduate experimental course. Supervised the I2 Spectroscopy experiment.
  • Experimental Physik II
    Teaching Assistant, SS 2019
    Undergraduate course on electromagnetism and optics. Conducted in-class tutorials.
  • Physiklabor für Fortgeschrittene I
    Laboratory Assistant, WS 2018/2019
    Undergraduate experimental course. Supervised the Hanle Effect experiment.
  • Astroparticle Physics
    Teaching Assistant, SS 2018
    Graduate course on astroparticle physics. Conducted in-class tutorials.