Advanced Science News interviewed me about our paper (published in Scientific Reports) showing that EHT observations rule out mimetic gravity. You can find their nice piece below:
www.advancedsciencenews.com/black-hole-images-deliver-a-deathblow-to-alternative-theory-of-gravity/
Enjoy the read!
EHT and mimetic gravity paper published in Scientific Reports!
My paper with Mohsen Khodadi and Javad Firouzjaee, where we show that the EHT observations of M87* and Sgr A* rule out the baseline version of mimetic gravity (see this earlier news item), has now officially been published in Scientific Reports (making this my second proper Nature publication)! The full bibliographic coordinates for the paper are Sci. Rep. 14 (2024) 26932. Here is the link to the paper (which is published Open Access).
EHT and mimetic gravity paper accepted in Scientific Reports!
My paper with Mohsen Khodadi and Javad Firouzjaee, where we show that the EHT observations of M87* and Sgr A* rule out the baseline version of mimetic gravity (see this earlier news item), has been accepted for publication in Scientific Reports, part of the Nature Portfolio collection of journals (therefore making this my second proper Nature publication)! The most significant addition compared to the earlier version is a new figure with examples of null geodesics in the space-times we studied, which shows in a very clear way why their shadow properties are pathological. You can read the preprint version of the paper on arXiv: 2408.03241.
EHT and mimetic gravity
Another exciting paper out today! With Mohsen Khodadi and Javad Firouzjaee, we show that the Event Horizon Telescope (EHT) observations basically rule out compact objects in mimetic gravity, a framework of modified gravity which has received a lot of interest as a candidate for explaining both dark matter and dark energy, and first proposed (explicitly) by Mukhanov and Chamseddine in 2013. Mohsen and collaborators studied compact objects in mimetic gravity in 2020, finding them to be highly non-trivial: in practice, the theory supports only a naked singularity, and a black hole obtained through a particular gluing procedure. What we showed in today’s paper is that the shadow properties of both these space-times are pathological, since the naked singularity does not cast a shadow, whereas the black hole casts a shadow which is way too small: for these reasons, both compact objects (and by extension mimetic gravity or, more precisely, the baseline version proposed in 2013) appear to be excluded by the EHT images of M87* and Sgr A*. You can read our results in the preprint we just posted on arXiv: 2408.03241.
Sgr A* horizon-scale tests paper published in CQG!
My paper with Rittick Roy, Yu-Dai Tsai, Luca Visinelli, Misba Afrin, Alireza Allahyari, Parth Bambhaniya, Dipanjan Dey, Sushant Ghosh, Pankaj Joshi, Kimet Jusufi, Mohsen Khodadi, Rahul Kumar Walia, Ali Övgün, and Cosimo Bambi on horizon-scale tests of gravity theories and fundamental physics from the EHT image of Sgr A*, which I previously reported on in an earlier news item, has now officially been published in CQG! The full bibliographic coordinates for the paper are Class. Quant. Grav. 40 (2023) 165007. Here is the link to the paper (which is published Open Access).
Sgr A* horizon-scale tests paper accepted in CQG!
I’m really excited that my paper on horizon-scale tests of gravity theories and fundamental physics from the Event Horizon Telescope (EHT) image of Sagittarius A* (Sgr A*) has been accepted for publication in CQG! This is a huge paper I led with 14 other authors spread throughout the world (our countries of affiliation include Italy, UK, China, USA, India, Iran, Canada, South Africa, North Macedonia, and Turkey): Rittick Roy, Yu-Dai Tsai, Luca Visinelli, Misba Afrin, Alireza Allahyari, Parth Bambhaniya, Dipanjan Dey, Sushant Ghosh, Pankaj Joshi, Kimet Jusufi, Mohsen Khodadi, Rahul Kumar Walia, Ali Övgün, and Cosimo Bambi. We used the EHT image of Sgr A* to test over 50 well-motivated theoretical scenarios, ranging from theories of gravity, novel fundamental physics frameworks, and black hole mimickers such as naked singularities and wormholes. This paper was initially (see v1) written only with Rittick, Yu-Dai, and Luca, tirelessly and also shamelessly ambulance-chased over a weekend following the exciting EHT announcement on May 12, 2022, but was then substantially polished and extended throughout summer 2022 with the addition of all the new authors - it is easily one of the most impactful papers I’ve ever written and at the same time likely the paper that drained the most energy out of me, and I’m really relieved to finally see it accepted for publication, after a very long refereeing process (one of the referee reports was a 4-page long pdf in 10pt font!). You can find the preprint version of the paper on arXiv: 2205.07787.
