Today and tomorrow I am visiting the beautiful city of Zurich. I was invited by Jaiyul Yoo to give a seminar (“Seven hints that early-time new physics alone is not sufficient to solve the Hubble tension”, slides here) at the Department of Astrophysics of the University of Zurich, and I will also be paying a quick visit to ETH, mostly to catch up with my former student Alex Reeves. It has been a very interesting and productive visit so far, and I learned a lot about what one could call using the umbrella term of “relativistic effects” in galaxy surveys, the study of which is something where Jaiyul’s group is probably one of the leading groups in the world. Non-scientific highlights included a fantastic Spanish dinner, and a very enjoyable drive through the Alps!
Media INAF coverage for Laniakea paper
Media INAF, the official news bulletin of INAF, the Italian National Institute for Astrophysics, posted a very nice interview to Leo Giani discussing the results of our Laniakea paper recently published in JCAP. The interview is in Italian, but Google translate does a good job, and you can read it here:
www.media.inaf.it/2024/02/12/laniakea-tensione-hubble/
Enjoy the read, and once more excellent job on this paper Leo!
Laniakea paper published in JCAP!
My paper on Laniakea with Leo Giani, Cullan Howlett, Khaled Said, and Tam Davis, which I previously reported on in an earlier news item, has now officially been published in JCAP! The full bibliographic coordinates for the paper are JCAP 2401 (2024) 071. Here is a link to the paper (which is published Open Access).
CosmoVerse seminar
Today I delivered a CosmoVerse seminar by the title of Seven hints that early-time new physics alone is not sufficient to solve the Hubble tension, no surprise focused on my seven hints paper (slides here). The seminar was recorded and posted on YouTube, here is the link. A long and stimulating discussion followed, with several very interesting questions and comments from experts in the field, including Adam Riess, Vivian Poulin, and Leandros Perivolaropoulos. For other videos in this seminar series, check out the CosmoVerse YouTube channel. The next seminar from Stefano Anselmi is one which promises to be very interesting!
YouTube videos on our Laniakea paper
A number of well-known YouTubers have provided in-depth coverage of our Laniakea paper over the past two months, with their videos tallying up over a million views! Three stand our particularly:
Anton Petrov - link
Dr. Becky (Rebecca - Becky - Smethurst) - link
PBS Space Time (Matt O’Dowd) - link
I found all three to be excellently presented, and rather accurate scientifically. Funnily enough, I didn’t come across them myself, but they were pointed out to me by three different students (“Prof., your work is on YouTube” 😅). I really enjoyed watching these videos, and I hope you do too!
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.
Universe Today interview
A few weeks ago I had the pleasure to be interviewed by Fraser Cain, publisher of Universe Today, for his well-known Universe Today Podcast YouTube channel. We mostly talked about my seven hints paper (at a level I would say accessible to those within the general public who are interested in cosmology and keep up at a popular science level with what is going on in the field), as well as a few other things including my current research obsessions (spoiler: it has to do with dark energy). The video interview is now available on YouTube, and you can find it here, or if you prefer you can listen to it on Spotify. In the frame below, I was clearly very amused by something Fraser had just said, whereas he was equally surprised by what I had just said 😄 It was really great fun chatting with Fraser, and I hope you enjoy the interview!
Media coverage for Laniakea paper
Our Laniakea paper has been picked up by Universe Today, who write a nice piece which you can find here:
www.universetoday.com/164198/if-you-account-for-the-laniakea-supercluster-the-hubble-tension-might-be-even-larger/
The same piece was later picked up by Phys.org, and our results were mentioned in passing in the Spanish newspaper El Confidencial (as well as a number of other news outlets). Enjoy the read!
Laniakea and the Hubble tension
Extremely excited about my latest work with Leo Giani, Cullan Howlett, Khaled Said, and Tam Davis (all four from the University of Queensland), where we study the impact of Laniakea, the supercluster hosting the Milky Way (also known as our home in the Cosmos) on local cosmological measurements and in particular measurements of the Hubble constant. Our initial hope was that taking into account the local inhomogeneities and anisotropies induced by Laniakea could help alleviate the Hubble tension - surprisingly, we found the opposite! The reason in short is that Laniakea is on average overdense compared to the cosmological background in which it resides, so its effect is the opposite of the prototype one would need to alleviate the Hubble tension locally (e.g. a void) - in other words, if one accounts for Laniakea’s impact on distances when inferring the Hubble constant locally, one should find an even higher Hubble constant, by an amount which we quantify exactly. Congratulations to Leo, who did basically all the heavy-lifting on this paper (incidentally this is what we were working on when he visited), which I expect can become a very important one! You can read our results in the preprint we just posted on arXiv: 2311.00215.
Science Magazine interview
I was recently interviewed by Adrian Cho for Science Magazine on the current status of the Hubble tension and what could solve it, with part of the discussion motivated by my seven hints paper. Adrian’s extremely nice piece appeared today and, besides from myself, contains quotes from a number of well-known scientists, including Adam Riess, Tanvi Karwal, Johannes Eskilt, Ryan Keeley, Marc Kamionkowski, and Samuel Goldstein. You can read the full article here:
www.science.org/content/article/universes-puzzlingly-fast-expansion-may-defy-explanation-cosmologists-fret
I had great fun talking to Adrian, and I hope you enjoy the interview!
Seven hints paper makes cover page of September issue!
My seven hints paper - Universe 9 (2023) 393 - has been selected as cover story for the September 2023 issue (Volume 9, Issue 9) of Universe! The production team did a very nice job in designing the cover story image, which you can find here. My paper was also selected as a Feature Paper and an Editor’s Choice. I also recommend to take a look at the Special Issue where my paper was published, which features a bunch of other really interesting papers!
Corfu2023 Workshop on Tensions in Cosmology
Straight after the XXV SIGRAV conference, I am travelling to Corfu, Greece, to attend the Corfu2023 Workshop on Tensions in Cosmology. The workshop, as the name suggests, is focused on cosmological tensions, with special attention to the Hubble tension. I have been particularly looking forward to this workshop, firstly because it will be an occasion to catch up with some friends colleagues I haven’t seen in a long time (e.g. Vivian Poulin), and finally meet several people I’ve written many papers with (e.g. Eleonora Di Valentino) or frequently interacted with online (Leandros Perivolaropoulos, Jackson Levi Said, and Özgür Akarsu, to name but a few), but never actually met in person, but also because I’ve never been to Greece before. I will also be delivering a plenary talk on “Seven hints that early-time new physics alone is not sufficient to solve the Hubble tension” (whose slides you can find here), obviously focused on my “seven hints” paper. I look forward to lots of fruitful discussions, and interesting workshop, and a series of exciting social events (including a boat trip and a traditional Greek dinner)!
Media coverage for seven hints paper
My seven hints paper has been picked up by Universe Today, who write a nice piece which you can find here:
www.universetoday.com/163026/its-going-to-take-more-than-early-dark-energy-to-resolve-the-hubble-tension/
The same piece was later picked up by Phys.org. Enjoy the read! 😃
Three recent talks
In the past three days I delivered three (online) seminars, all by the title of Seven hints that early-time new physics alone is not sufficient to solve the Hubble tension. I gave the talks “at” IPM, Tehran (Iran); the Institute of Advanced Studies in Science and Technology of Babes-Bolyai University (Romania), within Tiberiu Harko’s highly recommended seminar series in Gravitation, Cosmology, and Astrophysics; and at the conference Recent Advances in Mathematical Sciences and Interdisciplinary Areas 2023 at GLA University (India). I basically reported about a work in progress which I expect will be out in the next three months (so stay tuned!), and all the slides are available on my talks page. A pictorial summary of the work, made by my wife, is shown below.
