2025: A Year Wrapped In Physics

2025 began with administrative work, not physics.

At the end of 2024 I made a costly mistake: I forgot to renew my residence permit on time, and I had to return to Bangladesh for four months. This was extremely depressing at first as my work-rate decreases exponentially in Bangladesh and on top of that I was finishing up a project with my supervisor and a collaborator at my institute. However, things took an interesting turn soon. Together with Mahbub Majumdar—my undergraduate mentor and close friend—and an incredible team of friends and volunteers (Jim, Tasnuva, Walid, Tahmid, Arko, Fahim to name a few) from BRAC University, we organized the Jamal Nazrul Islam Winter School in late January 2025. We raised nearly €20,000 in corporate funding and hosted Bangladesh’s first residential winter school in theoretical physics. It was a hard-earned victory: December and January disappeared into the organisation of the school. In parallel, I was assembling visa documents—another small mountain of un-physicsed life.

But the school itself felt like a gift. I spent those days in long conversations with Ashoke Sen, Michele Cicoli, and Suvrat Raju. Michele had been my master’s supervisor, and I’d worked with him before; seeing him in Bangladesh—watching him meet our people and culture—felt quietly unreal. He remains one of my favorite minds, and one of my favorite humans, in academia. And in a time when Bangladesh–India relations were tense, it meant a lot that Suvrat and Ashoke still came. Ashoke has been an idol of mine for as long as I can remember. Having him in Bangladesh, and talking with him throughout his stay, was one of those moments the younger version of me would not have believed. Among other small topics, I was mostly conversing with him on two broad topics. First discussion focused on my paper with my supervisor Linus Wulff and very good friend Steven Hsia. It was about an obstruction we found at order $\alpha'^3$ for manifestly T-duality invariant approaches like generalised geometry and double-field theory. We did a very interesting proof based on Ashoke's paper from the 90's based on the symmetry O(d,d) being present at all orders in \alpha'. I consider it to be one of my favourite works and to get input and his thoughts about it from Ashoke was quite nice. Another direction we talked about is the construction of time-dependent backgrounds which resulted in a paper at the end of 2025-we come back to this later again.

In March, I left Bangladesh with a lot of nice memories - starting with two groups of my thesis students (Dipro, Saif and Sitima) defending their undergraduate thesis. Dipro worked on the information paradox and Saif and Sitima worked on Axion Monodromy Inflation and KKLT - both of which were quite non-trivial topics for undergraduate students. It gave me a bit of confidence that I am not a bad supervisor to undergraduates. My friends, students and juniors at Brac University gave me a very nice birthday surprise on the 31st of January at the residential campus which will always be memorable to me. I also met one of my closest friends-Rafsanjany Jim for the last time for a while as he has now gone for PhD in mathematics in the US.

From March, after I returned to Czechia, I was back to working full-time—often across three projects at once. Two papers came out in June. The first was with my Bangladeshi collaborators—Mishaal Hai, Noshin Shamma, and Shaikot Jahan—on inflation with Kähler moduli. The second, with Linus Wulff, Steven Hsia, Aviral Aggarwal, and Subhroneel Chakrabarty, studied the reduction of a one-loop term in 11-dimensional supergravity and its matching with type IIA supergravity. The two projects were very different, and that was the best part: I had to learn new tools and ways of thinking for each. The inflation work felt like a personal milestone. I was able to propose an idea of my own and build a model that fits current data. The one-loop project was exciting too—I finally got to work hands-on with 11D supergravity, a topic I’d been wanting to understand properly for a long time. On a different note, I should mention that my respect and admiration towards my PhD advisor Linus increased many folds as he supported me relentlessly throughout my "deportation to Bangladesh" period. He has been super -supportive since day 1 and also his physics approach is something that I really admire and want to replicate more often in my life. Outside physics, things were good as well. My friend Ratul Mahanta visited Brno from Winnipeg, and we had a great time together. Soon after, prominent Bangladeshi mathematician Syed Hasibul Hassan Chowdhury visited Prague, and I got to spend time with him and his family—we all had a wonderful time. I also went to Pesaro in Italy with my friends Mishaal, Shamma, Chiara and Giusseppe and enjoyed the lovely summer in Italy. Hanging out with them is always wonderful!

August and September was quite hectic as I was working full time on the project on time-dependent background with Ratul Mahanta. Things started to take shape for us as we finally were able to get hold of the dangerously non-linear system of PDEs. I also visited two schools and conferences. Among them, the highlight was the conference on integrability and dualities at NORDITA, Stockholm. I and my friend Steven presented our work with Linus Wulff on the obstruction of manifestly T-duality invariant approaches. We had a nice discussion with Falk Hassler and his PhD students from Wroclaw who was quite interested to understand the obstruction and devise a way to get around it. I also got to finally meet my friend Onirban bhai in September in a school. He is a very hardcore mathematical physicist who has a very intuitive take on physics. September came to an end with me packing my bag again to visit a place that I always wanted to: CERN!

As a child, CERN seemed like a magical place mostly due to the experiments conducted at CERN. While much of my work lives with the possibility of never showing up in nature, CERN is where we test what the universe is made of and learn about the fundamental building blocks of nature. I was visiting the theory group-specifically the group of Irene Valenzuela at CERN. I had a wonderful time at CERN and their theory group is quite active. Irene and her group studying the swampland program tries to go for crepé once a week or so and discuss some papers on the swampland program. It was quite nice as they were patiently explaining me every little thing. I got quite interested in non-supersymmetric string theory due to those meetings. I plan to look into those sometime soon. Meetings with Irene was also quite fruitful as I explained to her my the-then ongoing work on time dependent backgrounds and she made very interesting remarks. My first month at CERN was focused on the work on time dependent background with Ratul bhaiya and also finishing up a paper with Dibya Chakrabarty, Mishaal Hai, Sayeda Jahan and Shaikot Jahan Shuvo. It was quite nice as we constructed a model (in our usual perturbative moduli stabilisation scenario) which connects both early and late time accelerated expansion of the universe in a coherent fashion. It also matches experimental data quite nicely and it came out on arxiv in the later half of November. At the end of the first month, I started talking to Markus Dierigl on a project on string universality in 8 spacetime dimensions. The idea of string universality is quite nice as it asks a fairly important question- Does every consistent quantum gravity in every dimension are the ones we get from string theory? It’s certainly true in 10 dimensions with N=1 one and N=2 SUSY and proving this was not quite trivial. Markus and collaborators made some very interesting progress in understanding the idea in 8 dimensions whose details I won’t bother the reader (if any) with. On a positive note, I got to learn about F-theory, elliptic curves and how beautifully F-theory compactification connects with type IIB. The two month stay at CERN ended with me returning to Brno for two weeks before coming back again to Bangladesh.

December was also interesting on a professional level as I just worked to finish the paper with Ratul on time-dependent backgrounds which was quite fascinating. We looked at constructing explicit time-dependent backgrounds with all the type IIB fluxes being time-dependent. The discussion was followed by a generalisation of the well-known Maldacena-Nunez no-go theorem for constructions with 4D Ricci scalar greater than zero. We considered a time-dependent factor in front of the 6D compact which apparently could lead to scale seperation as pointed out by Andriot, Cribiori and Van Riet. Collaborating with Ratul bhaiya was quite fun as he always teaches me a lot of things and his mathematical maturity is quite inspirational. My student Yeshan Juberi also defended his undergraduate thesis on higher form symmetries and axion physics- a project he is continuing with me and another student from the University of Dhaka.

Lastly, I poured a huge amount of time and energy this year into building ICTP PWF Bangladesh together with Nabil Iqbal, Mishaal Hai, and Sayeda Jahan—and it has been one of the most rewarding parts of my year.We ran schools on General Relativity and Quantum Field Theory, and I’m deeply grateful to the lecturers—Nafiz Ishtiaque, Arpit Das, Hassaan Saleem and Luca Brunelli—and to our seminar speakers—Cliff Burgess, Francisco Pedro, and Edward Witten—for taking the time to teach and engage with our students. Alongside the schools, we also launched a mentorship program: around 45 students from across Bangladesh were selected and introduced to current research directions in physics and mathematics. Seeing students tackle genuinely challenging material—and watching some of them continue their projects beyond the program—felt like a real milestone. It’s honestly exciting to see the idea Nabil and I started with—helping strengthen the research culture in Bangladesh—turn into something concrete. We’re thrilled, and even more motivated for what comes next.

On a less physics side—and a much more emotional one—I finally got to meet my school friend and brother, Shemonto Das, after a long time. He lives in Canada now, so seeing him again felt genuinely special. Shemonto, Aparup, and I went to Cox’s Bazar and made the kind of memories best left undocumented—let’s just say those three days were a blur, and I don’t think I was sober for even a second. I also visited Chittagong, the city I grew up in. That place always hits me differently. It’s full of old memories—some sweet and mostly heavy—walking through the streets again felt like seeing a past version of myself. I went back to the neighborhoods I knew, stood quietly in front of familiar roads and buildings, and remembered a happier, livelier boy who once lived there. Sometimes I’m still tempted to drop everything and settle in the hills of my beautiful Chittagong.

Coming back to the one part of my life I have somewhat figured out: physics. Overall, 2025 was productive. I managed to meet roughly 60–70% of the goals I set at the start of the year, and I’m genuinely happy with the progress. If I have one complaint, it’s this: most of my attention stayed on gravity and cosmology. Those are the questions I naturally drifted towards in the previous years—but particle physics is a direction I want to commit to more seriously in the coming years. Lately I’ve been circling two problems in particular: the Strong CP problem and the problem of neutrino masses. I would like to spend more time with these kinds of deep puzzles that shaped the Standard Model—questions my standard model heroes worked on for decades, and where I still have a lot to learn.