My paper with with Luis Escamilla, William Giarè, Eleonora Di Valentino, and Rafael Nunes, where we present state-of-the-art constraints on the dark energy equation of state from a number of cosmological probes (see this earlier news item), has been accepted in JCAP! There were a few changes, mostly making a few parts of the discussion clearer, but the results are otherwise completely unchanged compared to the previous version we posted this summer. You can read the preprint version of the paper on arXiv: 2307.14802.
Laniakea paper accepted in JCAP!
My paper with Leo Giani, Cullan Howlett, Khaled Said, and Tam Davis, where we show how the Hubble tension is worsened when properly accounting for local effects of Laniakea (see this earlier news item), has been accepted in JCAP - excellent Christmas present! There were a few minor changes compared to the previous version, and I especially want to highlight the first sentence from the referee report, which in my opinion really sums up the impact of the paper and of Leo’s exceptional work: “I found this paper to be a significant contribution to the characterization of our local spacetime“ (thank you so much referee, whoever you are!). You can read the preprint version of the paper on arXiv: 2311.00215.
Negative cosmological constant and JWST paper accepted in JCAP!
My paper with Shahnawaz Adil, Upala Mukhopadhyay, and Anjan Sen, where we show how a dark energy model featuring a negative cosmological constant with an evolving component on top can potentially explain the puzzling JWST observations (see this earlier news item), has been accepted for publication in JCAP! The revision requested was pretty minor, but a notable (and in my opinion rather important) addition is the new Fig. 1 I produced, where we show the effective equation of state of this dark energy model. In some cases it goes through a singularity, which indicates the point where the total energy density of the dark energy switches sign. The singularity is nothing to worry about, as we argued. You can read the preprint version of the paper on arXiv: 2307.12763.
Inflationary gravitational waves and PTA paper accepted in JHEAp!
My single-author paper where I examine an inflationary interpretation of the signal observed by PTA experiments (see this earlier news item) has been accepted for publication in JHEAp! For once, after papers which went through extremely long journeys, this was a very quick turnaround, as the referee report clearly highlighted the timeliness and importance of the results. You can read the preprint version of the paper on arXiv: 2306.16912.
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.
Asteroid precession and fifth forces paper accepted in JCAP!
My paper with Yu-Dai Tsai, Youjia Wu, and Luca Visinelli, where we use asteroids as a probe of fifth forces, including those mediated by new ultralight particles which could be the dark matter, has been accepted for publication in JCAP! We find that we can potentially set some of the leading fifth force constraints in a certain range of mediator mass. This is another paper which has gone through a really long journey, as it was conceived during a brainstorm Zoom call in October 2020. We are now developing a number of follow-up ideas with asteroid experts, so stay tuned for more! You can find the preprint version of the paper on arXiv: 2107.04038.
Early dark energy and massive neutrinos paper accepted in MNRAS!
My paper with Alex Reeves, Laura Herold, Blake Sherwin, and Elisa Ferreira (a very international collaboration, spanning 6 different countries - Switzerland, Germany, Italy, UK, Japan, and Brazil!), where we study whether a cosmological model featuring early dark energy (EDE) and massive neutrinos can alleviate cosmological tensions in a way which bypasses the potential problems EDE faces with galaxy clustering data, has been accepted for publication in MNRAS! We show that the answer is…“yes and no”, in the sense that our paper really reinforces the idea that prior volume effects are very important for EDE, to the extent that some of those which were previously described as problems, just maybe aren’t really problems in the first place. Kudos to Alex and Laura, two outstanding PhD students (though Laura is off to her first postdoc as a Miller fellow at JHU), who did all the heavy-lifting on this paper! It has been quite a journey, considering this paper was born out of Alex’s MSc thesis (Alex did his Part III in Cambridge with me, Blake, and George Efstathiou), whose project was conceived on a stuffy afternoon of July 2020, deep in lockdown period, while the first referee report was humongous to say the least, but really helped improve the paper! You can find the preprint version of the paper on arXiv: 2207.01501.
LQG and Sgr A* paper accepted in ApJ!
The year is off to a truly great start research-wise: my paper with Misba Afrin and Sushant Ghosh, where we test two Loop Quantum Gravity (LQG, which is an interesting candidate framework for quantum gravity)-inspired rotating black hole space-times against the Event Horizon Telescope image of Sgr A*, the black hole at the center of our galaxy, has just been accepted for publication in ApJ! We use the size and shape of the shadow to place limits on a parameter which basically quantifies the strength of LQG effects. Our bounds are of course comparatively weak, but at the same time are interesting as a proof of principle given that there are very few ways (if any at all!) to test LQG from the observational point of view. And kudos to Misba, an outstanding PhD student at Jamia Millia Islamia, who did basically all the heavy-lifting on this paper! You can find the preprint version of the paper on arXiv: 2209.12584.
Primordial graviton background paper accepted in ApJ Letters!
My latest paper with Avi Loeb has just been accepted for publication in ApJ Letters! I can confidently say that is at the same time one of the simplest yet most exciting papers I have ever written (Avi is really good at coming up with simple yet profound ideas, and I won’t lie, the idea behind this paper is entirely his). The short idea is that one can (with some caveats) rule out the whole inflationary paradigm, without reference to any specific model, by finding a background of relic gravitons with certain specific properties, the reason being that inflation should have washed it out: we show that this will be extremely challenging, but not impossible (I will likely have retired by the time it will even be possible). You can find the preprint version of the paper, which is also the first one I have written with my new Trento affiliation, on arXiv: 2208.14088.
