Professor
Research Interests:
I am interested in understanding the fundamental laws of physics. Particle physics and Cosmology have recently celebrated the experimental confirmation of their respective “standard models”. However, in both areas there are also intriguing discrepancies between predictions of the model and experimental observations. These suggest that there could be physics beyond the Standard Models already contributing to current data, waiting for us to discover, understand better and confirm. My work involves constructing new models which could explain these discrepant observations, studying the viability of such alternate scenarios, and making suggestions for new experiments which could help confirm or refute them.
In the area of Cosmology, I am interested in physics of “dark sectors”. Dark sectors describe particles which are not directly observable in laboratory experiments but which interact gravitationally and impact our universe on large scales. They also contribute to the energy budget of the universe and therefore affect its expansion history. We already know that the dark sector of our Universe contains cold dark matter and dark energy, but it could also contain additional relativistic and non-relativistic particles with interactions. Recently, my research group has shown that the “Hubble tension” could be pointing towards dark sectors with “stepped radiation”, and we also showed that “stepped radiation” could be responsible for the lower than expected clustering of galaxies observed at scales of ~1-10 Mpc.
In the area of particle phenomenology, I recently published several works on the theory and phenomenology of Leptoquarks. These are hypothetical new particles with couplings to quarks and leptons simultaneously, hence the name. My collaborator Hiller and I were first to point out that Leptoquarks might be behind observed violations of lepton flavor universality in experiments at LHCb and Belle. They could be discovered either directly or indirectly through their signatures at the LHC or future colliders.
Currently, my group members include postdoc Nick DePorzio and graduate student Eashwar Sivarajan. My CV.
Please visit the BU cosmology group website for more information.
Honors/Awards:
- Fellow of the American Physical Society
- Humboldt Research Award
- Board Member of the Aspen Center for Physics
- Gambrinus Fellow :)
- Alfred P. Sloan Foundation Research Fellow
- DOE Outstanding Junior Investigator Award
Selected Recent Publications:
“Confronting interacting radiation models for the Hubble tension with Lyman-α data”, Hengameh Bagherian, Melissa Joseph, Martin Schmaltz, Eashwar N. Sivarajan, Phys.Rev.D 111 (2025) 4, 043513.
“Dark Radiation from Neutrino Mixing after Big Bang Nucleosynthesis”, Daniel Aloni, Melissa Joseph, Martin Schmaltz, Neal Weiner, Phys.Rev.Lett. 131 (2023) 22, 221001.
“A Step in Understanding the Hubble Tension”, Daniel Aloni, Asher Berlin, Melissa Joseph, Martin Schmaltz, Neal Weiner, Phys.Rev.D 105 (2022) 12, 123516.
“The Leptoquark Hunter’s Guide”, Bastian Diaz, Martin Schmaltz, Yi-Ming Zhong, JHEP 10 (2017) 097.
“Evidence for dark matter interactions in cosmological precision data?” Julien Lesgourgues, Gustavo Marques-Tavares, Martin Schmaltz, JCAP 1602 (2016) no.02, 097.
“Non-Abelian dark matter and dark radiation”, Manuel A. Buen-Abad, Gustavo Marques-Tavares, Martin Schmaltz, Phys.Rev.D 92 (2015) 2, 023531.
“RK and future b→sℓℓ physics beyond the standard model opportunities”, Gudrun Hiller, Martin Schmaltz, Phys.Rev.D 90 (2014) 054014.
For a full list of publications, please see Google Scholar or INSPIRE .