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.

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!

Fun times at PLANCK 2025 in Padua

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.

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!

😔

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!

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...

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!

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.

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

I’m down for that.

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.

Can we have no nice things anymore? www.sfchronicle.com/california/a...

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.

My thoughts today, precisely.

Berkeley’s updating its bike plan! Learn more and weigh in at upcoming events. www.berkeleyside.org/2025/01/21/b...

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.

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.

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 🏄‍♂️

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)

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

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.

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?"

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

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

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 :-)

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

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

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

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.

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?

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!

Had a nice visit to UW today for a particle theory seminar on astrophysical signatures of axions and axion cosmology sims. It’s a beautiful place with a great group!

Chris Dessert @nyuphysics.bsky.social bringing us the thermal axion background in the axiverse

“We don't right now have any information about who put them up. We do know that they're very professionally designed signs. They're very large. They're very well done. So someone went to a lot of trouble to put these large signs up.”

Proud of this paper out in PRL yesterday journals.aps.org/prl/abstract...! QCD axions produced in supernova convert to gamma-rays in the stellar fields. We need full-sky gamma-ray instrumentation to be ready for next time. Also thanks Berkeley News for the coverage: news.berkeley.edu/2024/11/21/a...

By the time I felt ready to joint twitter it wasn't cool anymore! Maybe this will be different. Excuse my clumsiness as I discover how social media works :-)