Astrophysics PhD - Gravitation Expert

Obsidian; Greater London; Remote; GBP 83,000 - 114,000; Full time

Benefits offered by this job

Remote work

Flexible schedule

Asynchronous collaboration

Job summary

Obsidian is seeking collaborators for research-grade physics problems in gravitation, cosmology or astroparticle physics. You will tackle frontiers in torsionful gravity, Nieh-Yan and Chern-Simons terms, with assignments matched to your publications and subfield.

This role is remote, 10 hours per week over 8–10 weeks, with compensation of $80 to $110 per hour, reflecting depth of subdomain match. You will produce rigorous written reasoning and share verifiable evidence from your arXiv/DOI papers.

Qualifications

• PhD in gravitation or cosmology required.
• Publications on the specified phenomena with arXiv IDs or DOIs preferred.
• English at B2 or higher, with clear written reasoning.
• Experience with numerical methods and cosmological field equations.
• Ability to work remotely on a flexible, task-based schedule.

Skills

Einstein-Cartan-Palatini

Tetrad spin-connection

Nieh-Yan invariant

Chern-Simons gravity

Cosmological perturbation theory

Numerical cosmology

Astroparticle modelling

Education

PhD in gravitation/cosmology/astroparticle physics

Tools

LaTeX

Python

SymPy

Jupyter

Job description

About the work

CritPt is a public benchmark of research-level physics challenges, built to test whether frontier AI models can carry out genuine physics research reasoning rather than textbook problem solving. The benchmark paper is arXiv:2509.26574 and we recommend reading it before applying. It will tell you quickly whether this work interests you.

We are engaging physicists to work on research-level physics problems in their own subfield. Depending on where your publication record fits, that can mean creating problems, solving them, reviewing completed work, or auditing it. We agree the specific assignment with you once you are matched to an area.

This is research-grade work rather than volume work. Whatever you produce has to be complete enough for another specialist in your subfield to follow and verify independently, so written reasoning is part of every assignment.

Research areas in this panel

Four areas, three in torsionful gravity and axion inflation and one in high-energy astrophysics. We match narrowly: you need to have published on one of these specific phenomena, not in gravitation broadly. Each area lists the methods it requires.

1. Einstein-Cartan and Nieh-Yan axion inflation: perturbations and power spectrum: Einstein-Cartan-Palatini first-order gravity, Nieh-Yan topological invariant, spacetime torsion in the tetrad formalism, pseudoscalar axion inflation, natural inflation potentials, cosmological perturbation theory, Mukhanov-Sasaki mode equation, primordial curvature power spectrum, slow-roll approximation.

2. Einstein-Cartan and Nieh-Yan axion inflation: FRW background dynamics: First-order Palatini formulation of gravity, tetrad and spin-connection variables, Einstein-Cartan gravity with torsion, Nieh-Yan topological term, axionic natural inflation potential, FRW background cosmological dynamics, numerical integration of background field equations.

3. Dynamical Chern-Simons gravity in Palatini formalism, parity-violating inflation: First-order Palatini and Einstein-Cartan formulations of gravity, tetrad and spin-connection variables, spacetime torsion and contorsion decomposition, gravitational Chern-Simons coupling of a pseudoscalar to the Pontryagin density, parity violation in the gravitational sector, FRW background cosmology and slow-roll inflation, numerical integration of coupled cosmological field equations.

4. High-energy astrophysics: blazar jets, photohadronic emission, multimessenger constraints: Relativistic jet beaming and Doppler boosting, photopion production at the Delta resonance, photohadronic interaction optical depth, electromagnetic cascade emission, synchrotron target photon fields, one-zone blazar emission modeling, variability-based causality constraints, multimessenger X-ray constraints.

Methods we expect to find in your own publications

You should be able to point to your own papers demonstrating at least one of the following families:

• First-order gravity: Einstein-Cartan-Palatini formalism, tetrad and spin-connection variables, spacetime torsion and contorsion decomposition
• Topological terms in gravity: Nieh-Yan topological invariant, gravitational Chern-Simons coupling to the Pontryagin density
• Cosmological perturbation theory: Mukhanov-Sasaki mode equation, primordial curvature power spectrum, slow-roll approximation
• Numerical cosmology: integration of coupled background field equations in modified gravity
• Astroparticle modelling: relativistic beaming and Doppler boosting, photohadronic processes, electromagnetic cascades, one-zone emission models

Who we are looking for

A PhD in gravitation, cosmology, astroparticle physics or a closely related field. This is a hard requirement. Postdoctoral researchers, research scientists and junior faculty are the strongest fit. Senior PhD students with a strong first-author record are welcome to apply.

Published work on the specific phenomenon above, not the adjacent one. This is the single most common reason we decline otherwise excellent physicists. Working in modified gravity is not enough if your papers are not on torsion, Nieh-Yan or Chern-Simons terms. Command of the numerical methods is not enough if you have not published on the phenomenon itself.

A verifiable publication record. Three to five representative papers with arXiv IDs or DOIs, ideally from the last five years. First author strongly preferred. Every paper you list will be checked against the public record.

Sign-convention discipline. Work in this area turns on tetrad and spin-connection conventions, and we are looking for people who are precise about them.

Working proficiency with LaTeX, Python, SymPy and Jupyter. Some familiarity with an agentic coding extension in VS Code is useful. Gaps here are acceptable if you declare them honestly.

English at B2 or above, including written reasoning. A large part of the value you add is how clearly you set out your argument.

Commitment and rate

10 hours per week, sustained across an 8 to 10 week window, starting immediately. Remote and asynchronous with no fixed hours.

$80 to $110 per hour, set by depth of subdomain match.