Extreme astrophysical environments provide rare opportunities to test the fundamental laws of nature under conditions that go beyond the limitations of terrestrial laboratories. In my research, I develop the theory and phenomenology of well-motivated microphysical models. I then use these to identify and, when relevant, search for observational signals from new fundamental physics that may be imprinted on astronomical or cosmological observables.

Astronomical axion searches

The axion is a hypothetical particle that first appeared as a solution to a puzzling problem in particle physics. Axions and the related "axion-like particles" (ALPs) appear frequently in extensions of the Standard Model of particle physics, including compactifications of string theory. Unfortunately, they are notoriously hard to detect.

Astronomical observations provide exciting opportunities to search for axions and ALPs. I have previously demonstrated that X-ray observations of galaxy clusters have an unmatched sensitivity to light ALPs, and can be used to derive some of the strongest limits on their couplings. Upcoming X-ray satellite missions may shed light on the nature and couplings of dark matter, and the fundamental particle content of the universe.

Early universe cosmology

The enormous energy density of the early, Big Bang universe provides a unique window to physics at scales not readily accessible through terrestrial experiments. I have previously invented theoretical techniques for studying new particles present in the early universe (in particular, during and after inflation), and for determining the imprints these may have left on cosmological observables such as the cosmic microwave background and the large-scale distribution of galaxies in the universe.

Upcoming observations will study these observables with an unprecedented precision. My research aims to cease the opportunities these present to search for new fundamental physics from the early universe.

String compactifications and cosmology

String theory is the leading candidate theory for ‘completing’ particle physics at very high energies, and is hypothetically connected to our four-dimensional spacetime by a compactification of additional spatial dimensions. The geometry of the tiny compactification manifold determines many of the properties of the theory at low energies, and can give rise to novel observational signals.

I have previously investigated a number of aspects of string compactifications, including how these may explain the present accelerated expansion of the universe, and how novel mathematical techniques from random matrix theory can be used to confront the theoretical complexity of these theories.



Stockholms universitet, Fysikum
106 91 Stockholm

Citizenship: Swedish
Hometown: Frösön: "Storsjöns pärla, Jämtlands Jamaica".

david.marsh(add at
+46(0)8 553 785 97

Positions Held

(2019-present) Assistant Professor
The Oskar Klein Centre for Cosmoparticle Physics,
Department of Physics, Stockholm University.
(2015-2019) Stephen Hawking Advanced Fellow
Centre for Theoretical Cosmology,
Department of Applied Mathematics and Theoretical Physics, University of Cambridge.
(2012-2015) Postdoctoral Research Associate
Rudolph Peierls Centre for Theoretical Physics,
University of Oxford.


(2012) Ph.D. in Physics, Cornell University.
Adviser: Liam McAllister.
(2007) M.Sc. in Physics, Uppsala University.
Thesis adviser: Antti Niemi.


(2019-2022) VR Starter Grant.
(2012) Olle Engqvist fellowship.
(2012) Fellow of the Carl-Erik Levin Foundation.
(2011) Fellow of the Gålö Foundation.
(2008) Graduate fellowship from the Swedish-American Society.
(2007) Graduate fellowship from the Thanks to Scandinavia Foundation.
(2005-2007) Thun's fellowship (fourfold recipient).


I have given a large number of invited research seminars and conference plenary talks over the past few years. Here are the slides from a few of them (warning: large files).

(2017) Institut Astrophysique de Paris,
"Manyfield inflation" (pdf).
(2017) University of Bologna,
"A new class of de Sitter vacua in type IIB compactifications" (pdf).
(2015) The International Centre for Theoretical Physics, Trieste,
"ALPs and galaxy cluster X-rays as a window to the dark sector" (pdf).

Teaching Experience

(2016 -...) PhD advisor of Theodor Björkmo, DAMTP, University of Cambridge.
(2016) Lecturer, Part II Principles of Quantum Mechanics, DAMTP, University of Cambridge.
(2015, 2016) Lecturer, Part III Cosmology, DAMTP, University of Cambridge.
Fourth year thesis adviser for Callum Brodie, University of Oxford.
Developed into publication in JHEP (2016).
(2014) Visiting Lecturer, M.Sc. Particle Physics, Birzeit University, Palestine (2 months).
Lectures, tutorials, examinations. Course organised by the ICTP.
(2013-2014) Stipendiary Lecturer, St John's College, Oxford.
Tutorials with first and second year students, internal examinations, college admissions.
(2010) Co-lecturer in Statistical Physics, Cornell University.
(2009-2012) Teaching Assistant, Cornell University.
Electromagnetism and Waves, Statistical Physics, and General Relativity (4 terms).


Referee: JCAP, JHEP, EPJ-C, ICP.
(2017-2018) "The DAMTP HEP/GR colloquium", University of Cambridge.
(2016, 2017) "The Palestinian Advanced Physics School".
(2015-2017)"The Cambridge Cosmology Journal Club", University of Cambridge.
(2012-2013)"The Particles and Fields Seminar", University of Oxford.
(2009-2011) Student string theory journal club, Cornell University.

Publication list