Amin Abouibrahim
My research covers areas of theoretical high energy physics (phenomenology and model building) and particle cosmology. I'm interested in studying the nature of the dark sector comprised of dark matter and dark energy and possibly other particles that can have direct or indirect interactions with our visible sector. I'm currently focused on understanding the origins of the recent cosmological tensions between late-time and early-time measurements of some observables. My work addresses these issues by implementing field-theoretic alternatives to the concordance \( \Lambda\)CDM model. Parameter inference is done through the use of publicly available codes such as MontePython and Cobaya and interfaced with the Boltzmann solver CLASS. Here you’ll find a short overview, links to papers, and teaching resources.
In a recent work, we studied an interacting dark matter-dark energy model and examined the constraints on the dark energy equation of state from a field-theoretic model. The analysis combines DESI DR2 + CMB + SNe data to extract the 68% and 95% CL regions in the \(w_0\)–\(w_a\) plane.
We examine a field-theoretic model where dark matter and dark energy are spin-zero fields and interact via a term \((\lambda/2)\chi^2\phi^2\). A sizable interaction can lead to dark energy transmutation from scaling freezing to thawing. We impose constraints on the interaction term as well as other model parameters using the recent cosmological data including DESI DR2.
arXiv:2411.11177 [astro-ph.CO]
We study the effect of spin-zero dark matter and dark energy fields and their interaction (including DM self-interaction) on current cosmological tensions. This field-theoretic model can resolve the \(S_8\) tension while only mildly alleviating the Hubble tension for particular data sets. Constraints on model parameters are placed.
JCAP 09, 076 (2024).
We include in dark matter calculations the full elastic collision term in the full momentum-dependent Boltzmann equation as well as in a set of fluid equations that couple the evolution of the number density and dark matter temperature for a simplified model featuring forbidden dark matter annihilations into muon or tau leptons through a scalar mediator. The updated relic density calculation results in a significant reduction of the experimentally allowed parameter space compared to the traditional approach.
JCAP 08, 075 (2023).
In this series of work, we consider a dark sector of our universe where dark matter (and possibly other particles) resides. This sector has feeble interactions with our visible sector and potentially at a different temperature. We look for experimental signatures and effects that such a sector has on the DM relic density, the extra relativistic degrees of freedom, to name a few. These hidden sectors can lead to tiny changes to \(\Delta N_{\rm eff}\) which can be probed at CMB-S4.
E. Di Valentino et al. [CosmoVerse Network]
Phys. Dark Univ. 49, 101965 (2025) doi:10.1016/j.dark.2025.101965
A. Aboubrahim and P. Nath
arXiv:2411.11177 [astro-ph.CO]
A. Aboubrahim and P. Nath
JCAP 09, 076 (2024) doi:10.1088/1475-7516/2024/09/076
A. Aboubrahim, M. Klasen and L. P. Wiggering
JCAP 08, 075 (2023) doi:10.1088/1475-7516/2023/08/075
A. Aboubrahim, M. M. Altakach, M. Klasen, P. Nath and Z. Y. Wang
JHEP 03, 182 (2023) doi:10.1007/JHEP03(2023)182
A. Aboubrahim, M. Klasen and P. Nath
JCAP 04, no.04, 042 (2022) doi:10.1088/1475-7516/2022/04/042
Modern Physics (University of Hartford)