iiinova — where your digital self keeps evolving

Ben Safdi @bensafdi.bsky.social · 20/04/2026

Very thrilled to have received a New Horizons in Physics Prize: breakthroughprize.org/Laureates/1/.... I hope this helps, in whatever small way it can, bring a spotlight on to the search for dark matter and more broadly the need for experiments and the funding to innovate, build, and operate them.

breakthroughprize.org

Breakthrough Prize – Fundamental Physics Breakthrough Prize Laureates – Benjamin R. Safdi

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Ben Safdi @bensafdi.bsky.social · 23/01/2026

lol, I don't know how I feel that your subconscious thinks of me as an internet troll!

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Ben Safdi @bensafdi.bsky.social · 23/07/2025

Excited to put out arxiv.org/abs/2507.15934 with Linda Xu (SLAC) where we use Fermi data to conclusively rule out the thermal wino as DM, in addition to the quintuplet and 7-plet. The doublet (higgsino) is the remaining, untested minimal DM model and a strong motivation for future searches.

arxiv.org

Wino and Real Minimal Dark Matter Excluded by Fermi Gamma-Ray Observations

We show that minimal, fermionic dark matter (DM) models in the $n$-dimensional representation of the weak force with zero hypercharge that make up 100% of the DM under the standard cosmological histor...

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Ben Safdi @bensafdi.bsky.social · 11/06/2025

Higgsinos are one of the best-motivated WIMP dark matter candidates, but mostly invisible to direct detection. We showed today arxiv.org/abs/2506.08084 that the soon-to-be operational CTAO-North detectors in the Canary Islands might be able to detect higgsino annihilation in gamma-rays before 2030!

arxiv.org

Discovering the Higgsino at CTAO-North within the Decade

We demonstrate that higgsino dark matter (DM) could be discovered within the next few years using the Cherenkov Telescope Array Observatory's soon-to-be-operational northern site (CTAO-North). A 1.1 T...

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Ben Safdi @bensafdi.bsky.social · 29/05/2025

Fun times at PLANCK 2025 in Padua

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Ben Safdi @bensafdi.bsky.social · 23/05/2025

New paper youtu.be/nuWv7HtBsTA arxiv.org/abs/2505.15884 out today showing that axions from string theory need to have sub-microelectronvolt masses to be consistent with grand unification. This provides additional motivation to think about experiments such as ABRACADABRA/DMRadio and CASPEr.

youtu.be

String Theory and Grand Unification Suggest a Sub-Microelectronvolt QCD Axion

Ben Safdi @bensafdi.bsky.social · 18/04/2025

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Fun paper youtu.be/Ma0Pc0M6v8k arxiv.org/abs/2504.12377 led by my grad student Josh Benabou along with Chris Dessert and Alex Filippenko's group in Berkeley astronomy. We used Keck and Lick to look for axion-induced polarization from white dwarfs. No luck this time -- but we set strong limits!

youtu.be

Search for Axions in Magnetic White Dwarf Polarization at Lick and Keck Observatories

Ben Safdi @bensafdi.bsky.social · 14/03/2025

New paper - youtu.be/ZyNDm764obQ arxiv.org/abs/2503.09682 - searching for axions produced through the axion-electron coupling in stars converting to X-rays in galactic B-fields. We looked with NuSTAR data towards M82/M87/M31 and didn't see a signal, setting upper limits. The search continues!

youtu.be

Probing the Axion-Electron Coupling with NuSTAR Observations of Galaxies

Benjamin Fry @bluejekyll.bsky.social · 03/03/2025

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Reposted by Ben Safdi

Hey, Berkeley, it turns out a huge majority of us want more bike infrastructure. Don’t listen to all the haters, all the anti-safety Save Hopkins people, they represent less than 20% of folks. www.berkeleyscanner.com/2025/03/03/t...

berkeleyscanner.com

New survey supports a strong Berkeley Bike Plan: Op-ed

The authors commissioned a professional poll from a nonpartisan research agency to learn more about what Berkeley wants in its bike infrastructure.

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Ben Safdi @bensafdi.bsky.social · 25/02/2025

We are hosting a workshop on axion physics at UC Berkeley and LBNL from May 7 - 9, 2025: indico.physics.lbl.gov/event/3134/. Talks will range from experiments to string theory. Abstract submission closes March 14 -- junior researchers are especially encouraged. Spread the word!

indico.physics.lbl.gov

Berkeley Axion Workshop 2025

Axion dark matter has deep motivations from string theory to the strong CP problem. However, only recently has it been understood how to build instruments that can probe much of the most well motivate...

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Liza Lutzker @lizalutzker.bsky.social · 16/02/2025

Hey Berkeleyans! Does your kid bike to school? Do you wish they could but don't feel it's safe enough? There’s a BUSD-specific listening session on the Bike Plan update: Tue 2/25, 6:30-8:30pm at King! Would be great to get input from families on how Berkeley can make it safer to bike to school.

berkeleybikeplan.org

Berkeley Bike Plan Focused Update - Public Input Map & Survey

The City of Berkeley is updating its Bicycle Plan for everyone who wants to bike or roll in Berkeley – including skateboarding, scooting, or other personal wheeled mobility devices.

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Laura Baudis @lbaudis.bsky.social · 14/02/2025

The COSINE-100 experiment in South Korea achieved an improved energy threshold of 0.7 keV in their NaI(Tl) crystals and now fully excludes the DAMA/LIBRA signal as originating from dark matter interactions: arxiv.org/abs/2501.13665

WIMP-nucleon, spin-independent cross section as a function of the WIMP mass. The new COSINE-100 exclusion limit is shown as a black curve, together with the green and yellow 1- and 2-sigma band, respectively.

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Telegraph For People @telegraphforpeople.bsky.social · 09/02/2025

Let’s make Telegraph car-free! Join TFP on Monday at 7pm to make the next big step towards pedestrianizing the 2nd busiest pedestrian street in the East Bay.

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David Ho @davidho.bsky.social · 05/02/2025

I don't know how else to put this: This is fucking insane. NSF, a $10 billion grantmaking agency, is planning to lay off between a quarter and a half of its staff in the next two months.

politico.com

Science funding agency threatened with mass layoffs

National Science Foundation staff heard the plans at a meeting Tuesday.

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Ben Safdi @bensafdi.bsky.social · 29/01/2025

My thoughts today, precisely.

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Sean Carroll @seanmcarroll.bsky.social · 23/01/2025

Diversity, equity, and inclusion are all good things. They don’t happen automatically, we have to actively work to bring them about. Shout it from the rooftops.

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Ben Safdi @bensafdi.bsky.social · 19/01/2025

Such a pleasure to have lunch with Georg Raffelt today in Berkeley after the “Baha Balantekin and George Fuller Fest.” He is an inspiration and has been doing axion physics since well before it was cool 😎. Also very neat to hear stories about his time in Berkeley in the 80’s.

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Ben Safdi @bensafdi.bsky.social · 15/01/2025

I had lots of fun today giving a blackboard talk at #kitp on “What is axion theory?” Any talk followed by surfing in the sunshine is a success 🏄‍♂️

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Emily Hunt @emily.space · 12/01/2025

The @esa.int Gaia satellite will take its final scientific measurements on Wednesday. 🔭 This will conclude a 12 year series of continuous observations. Larger Gaia data releases are still in progress, but Gaia has already had a HUGE impact on our understanding of the #milkyway. (Image: ESA)

An artist's impression of the Gaia spacecraft.

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Ben Safdi @bensafdi.bsky.social · 12/01/2025

He was asked to give an intro set of lectures on dark matter to postdocs and faculty in adjacent fields. I believe he agreed so long as he “didn’t have to do rotation curves” 😆. It was actually super informative. He described effectively every known DM production mechanism.

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Ben Safdi @bensafdi.bsky.social · 10/01/2025

Josh Ruderman doing a heroic job on the “Joy of Dark Matter” at KITP

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Ben Safdi @bensafdi.bsky.social · 10/01/2025

Less than 2 weeks ago we were hiking in Malibu and playing on the beach in Pacific Palisades and Santa Monica. Absolutely tragic to see what is happening down there and especially surreal being in Santa Barbara, which is so close but also feeling — for now — very normal.

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Ben Safdi @bensafdi.bsky.social · 06/01/2025

California has its problems but is a pretty amazing place. Spent the past two weeks on a family road trip from skiing in Tahoe to surfing the coast to rock climbing in Joshua Tree. Upcoming: #KITP at #UCSB to discuss "What is Particle Theory?"

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Ben Safdi @bensafdi.bsky.social · 05/01/2025

So cool! I hope this will come to SF next to help support public transit and safer streets for bikers and pedestrians.

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We searched with Fermi data towards 4 "recent" SN, from the 1600's to a SN from this year. No evidence for axions :-( -- 2 sigma from SN1987A, but it is busy in the LMC. Still, we ruled out a lot of parameter space and maybe this method leads to a future discovery. It is motivated parameter space!

We consider ~MeV - GeV axions that couple to QCD and QED, as expected if there are e.g. GUTs. They don't solve strong CP but also could exist with a lighter QCD axion that does, as in axiverse constructions. They are produced in supernovae and decay to gamma rays with significant time delays.

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Time-delayed gamma-ray signatures of heavy axions from core-collapse supernovae

Excited to get out my last paper of the year today "Time-delayed gamma-ray signatures of heavy axions from core-collapse supernovae" with a great group of Berkeley students + postdocs. Check out the video abstract by my student Yujin Park youtu.be/sv0qHuz-2Y4 and the paper arxiv.org/abs/2412.13247

youtube.com

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Great question! Someone asked this during the talk and the answer Matt gave was that this would apply to scalars in higher-dim reps the same as it does for fermions since the arguments are essentially just group theoretic.

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Ben Safdi @bensafdi.bsky.social · 18/12/2024

We hosted Matt Baumgart today for our last seminar of the semester on his paper from yesterday, 2412.13192, on how to falsify string theory by finding higher-dimensional electroweak representations. It's reassuring to know the 9-plet is likely in the swampland :-)

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This seems like a cool result about the uniqueness of string theory

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Ciaran O'Hare @cajohare.bsky.social · 13/12/2024

I feel like I need to break the ice here somehow... I suppose I will just announce that I will be posting my annual AxionLimits yearly round-up on this account soon, so stay tuned i guess

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It would also be nice if there was a common platform here. It is annoying having to deal with multiple different sites & slight question variations (1%, 10%, top 1% in 5 year!?) as a reference writer. Probably even more so as an applicant.

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We now understand better how strings contribute to the dark matter, but we also find that domain walls could be even more important from preliminary simulations. I guess the story is not over! At the moment, somewhere between 40 and 300 micro-eV is our best guess for the axion mass. To be continued.

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We performed large-scale numerical simulations -- using the Perlmutter supercomputer at @nersc.bsky.social -- of axion string cosmology to predict the mass of the axion in this scenario. It is cliché, but in many ways this work brought up more questions than it answered.

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Enabling Axion String Simulations with Adaptive Mesh Refinement

New paper today on "Axion mass prediction from adaptive mesh refinement cosmological lattice simulations" with some very nice animations tinyurl.com/AxionStrings... thanks to my awesome collaborators. Check out our video abstract tinyurl.com/rxfnbt9c and the paper arxiv.org/abs/2412.08699 for more

tinyurl.com

Enjoy the videos and music you love, upload original content, and share it all with friends, family, and the world on YouTube.

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Ben Safdi @bensafdi.bsky.social · 10/12/2024

One of the best parts of my day: mornings working outside on my office balcony. This is unique but very cool aspect of our BCTP office space.

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Bike East Bay @bikeeastbay.bsky.social · 07/12/2024

Thanks to everyone who biked in the Emeryville car-free holiday parade tonight, our free bike valet was busy! See you Saturday at Berkeley’s Youth Featival at Aquatic Park too?

photo looking down from above at a large number of bicycles parked on valet racks set up on a barricaded street at Bay Street Mall in Emeryville

photo of staff and volunteers smiling and posing at the Bike East Bay table and tent

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Ben Safdi @bensafdi.bsky.social · 05/12/2024

Fun having Peter Graham visiting from Stanford today to tell us about constraining the DM power spectrum through the dynamical heating of stars in dwarf galaxies by sub halos. Also he brought out our biggest BCTP speaker dinner of the semester with around 14 people!

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Ben Safdi @bensafdi.bsky.social · 04/12/2024

Also first ever single-day work trip involving air travel. It is exhausting! 😩