IIT Bombay wins 77th Gravity Research prize

Indian Institute of Technology Bombay researchers won first prize in the Gravity Research Foundation’s 2026 essay competition, according to the foundation’s awards page published this month. The winning entry was titled “The Gravitational Spectral Radio Forest: A Signature of Primordial Black Holes,” and the foundation listed a $4,000 first prize for the paper. IIT Bombay highlighted the result in a May 22 post on X, calling it a first-place finish in the 77th competition. The authors are P. George Christopher, K. Hari and S. Shankaranarayanan of IIT Bombay’s Department of Physics. ### Who won, and what exactly did they submit? The Gravity Research Foundation’s 2026 awards page lists the IIT Bombay essay as the first-place winner among that year’s awards for essays on gravitation. The foundation identified the paper by full title and named all three IIT Bombay authors with institutional email addresses and the Mumbai department affiliation. The foundation’s competition page says the annual contest offers five awards for short essays on gravitation, its theory, applications or effects. (gravityresearchfoundation.org) The same site describes 2027 as its seventy-eighth competition, which places the 2026 awards in the seventy-seventh year referenced by IIT Bombay. ### What is the paper trying to detect? The arXiv preprint says the paper proposes a way to look for primordial black holes using a radio signature in hydrogen gas. (gravityresearchfoundation.org) Primordial black holes are hypothetical black holes formed in the early universe and are often studied as a possible component of dark matter, according to IIT Bombay’s physics department research pages describing related work in cosmology, dark matter and black holes. (gravityresearchfoundation.org) The preprint’s abstract says the authors focus on a 9.9 GHz hydrogen absorption line and argue that gravity near a primordial black hole would redistribute that signal into what they call a “gravitational spectral radio forest.” They write that the effect would spread across a bandwidth of about 2 GHz and could provide a “concrete, high-contrast target” for future radio surveys aimed at constraining primordial black hole populations. (arxiv.org) ### Why does the paper use the phrase “radio forest”? The phrase comes from the paper’s central claim that one line in hydrogen would not remain a single narrow feature near a primordial black hole. The authors say relativistic effects would break that feature into a wider set of absorption signatures, producing the “forest” described in the title and abstract. The Gravity Research Foundation awards page mirrors that title exactly, which indicates the foundation judged the essay under the same framing later posted by IIT Bombay. (arxiv.org) IIT Bombay’s social-media post used a shorter description, referring to a “Gravitational Spectral Forest” signature in hydrogen gas. That appears to be a shortened reference to the full essay title rather than a different paper, based on the matching authors and subject. ### Who are the researchers behind it? S. Shankaranarayanan is listed by IIT Bombay as a physics faculty member working in gravitational physics, quantum field theory, early-universe cosmology and black holes. IIT Bombay’s department page also lists dark matter, cosmology and particle astrophysics among the astronomy, cosmology and gravity research themes tied to the group. The Gravity Research Foundation page identifies the co-authors as P. (gravityresearchfoundation.org) George Christopher and K. Hari, both using IIT Bombay addresses. IIT Bombay’s physics webpages place the work within a department research cluster focused on astronomy, cosmology and gravity. ### Where can readers find the work next? The Gravity Research Foundation has posted the winning essay on its 2026 awards page and in its year-by-year archive of award essays. (homepages.iitb.ac.in) The authors have also posted a preprint on arXiv, where the paper appears under identifier 2605.13042. The foundation’s next milestone is its 2027 competition, which its rules page says will announce awards on May 15, 2027. (gravityresearchfoundation.org) For this year’s result, the named participants remain P. George Christopher, K. Hari and S. Shankaranarayanan, with the essay available through the foundation archive and arXiv posting. (gravityresearchfoundation.org)