Jiachen Bai
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astrobai.bsky.social
Jiachen Bai
@astrobai.bsky.social
250 followers 1.3K following 17 posts
PhD student at the Institute for Astronomy, University of Edinburgh, interested in cosmology.
astrobai.github.io
Posts Replies Media Videos
Reposted by Jiachen Bai
aas.org
The American Astronomical Society is gravely concerned by the deep cuts to NASA science funding reported to be in the draft President’s Budget Request for Fiscal Year 2026. Read more here: aas.org/press/aas-st... and take action now: aas.org/urge-nasa-su...
April 11, 2025 at 8:04 PM
Reposted by Jiachen Bai
natastron.nature.com
Shan, Hu et al. suggest that gravitational waves trigger wave-optics effects in microlensing, revealing host galaxies and opening a new window to the discovery of compact objects. https://bit.ly/3Y6V8gf #AstroSci
An interference-based method for the detection of strongly lensed gravitational waves - Nature Astronomy
The microlensing of strongly lensed gravitational waves by compact objects leads to interference patterns in the waveform, the detection of which facilitates the identification and localization of the gravitational wave source.
bit.ly
April 1, 2025 at 2:01 PM
astrobai.bsky.social
If you are looking for tools to analyse MCMC chains generated by Cobaya in VSCode, you can try this extension: VSDist.
I develop the extension for quick preview of chain files on servers because I'm bothered with downloading them or writing scripts to visualise them. #cosmology
VSDist - Visual Studio Marketplace
Extension for Visual Studio Code - GetDist Tool for Visual Studio Code
marketplace.visualstudio.com
April 1, 2025 at 2:31 PM
Reposted by Jiachen Bai
aas.org
🆕 Suwei Wang and Lile Wang (Peking Univ) chat about new software instruments in the latest video from the AAS Journal Author Series: youtu.be/N-hvYXf6v-k

The AAS Journal Author Series connects authors with their article, their human story & the larger #astronomy community. 🔭
AAS Journal Author Series: Suwei Wang and Lile Wang on 2025ApJS..276...40W
YouTube video by AAS
youtu.be
March 28, 2025 at 2:17 PM
Reposted by Jiachen Bai
justshaun.bsky.social
What if I told you there is no S8 tension?

youtu.be/PIQKe-tW1xQ
KiDS­ Legacy - The Final Cosmology Results
YouTube video by Cosmology Talks
youtu.be
March 26, 2025 at 11:30 AM
Reposted by Jiachen Bai
astroroyalscot.bsky.social
🥳 It's paper day for the completed #ESO Kilo-Degree Survey. We end our journey with a consistent picture of #cosmology 😲
I've been co-leading KiDS for 12yrs & I'm so proud of what the team's achieved. If you're at the #Euclid meet, go to Angus Wright's talk @10am today!🔭

ℹ️: arxiv.org/pdf/2503.19441
A two panel figure. The x-axis is omega_m, the fraction of matter in the Universe. The y-axis is S8 on the left and sigma_8 on the right. Both are measures of the 'clumpiness' of dark matter. The contours show that the KiDS data (two measurements using slightly different statistics, COSEBIs and Bandpowers) agree with the data from the Planck CMB survey.
March 26, 2025 at 8:01 AM
Reposted by Jiachen Bai
cosmonautico.bsky.social
☄️Today at the @icc-ub.bsky.social at Uni Barcelona we had one of the first presentations of the @desisurvey.bsky.social BAO DR2 results!🔭🧪
You can check it out on Youtube!
youtu.be/tuDzhR1SVDg?...
Presentation of the DESI DR2 BAO Results at ICCUB - Héctor Gil Marín
YouTube video by Cosmology at home
youtu.be
March 20, 2025 at 1:47 PM
Reposted by Jiachen Bai
cosmonautico.bsky.social
🔊 New BAO analysis from the 3-year observations (DR2). Long story short, as follows.
1. DESI alone is consistent with LCDM. 👉 Boring
2. DESI and Planck have a 2.3 discrepancy in Ωm-H0rd plane. 👉Interesting.
March 20, 2025 at 1:12 AM
Reposted by Jiachen Bai
astroroyalscot.bsky.social
Congrats to @desisurvey.bsky.social - it's looking more & more like dark energy isn't Einstein's cosmological constant! If you've woken up to the news & are searching for the publications, they don't appear to be on arxiv 🤷‍♀️ but they are online. 🔭 #cosmology 🧪
ℹ️: data.desi.lbl.gov/public/paper...
A graph of the evolution of the dark energy (vertical axis) as a function of time (redshift on the horizontal axis) - showing an offset from the cosmological constant (a flat horizontal line). Here is the figure caption from the paper: FIG. 12. Comparison of the constraints on the equation of state of dark energy using the CPL parametrization and a bin- ning reconstruction approach, using DESI+CMB+DESY5. The solid green line shows the best-fit w(z) based on w0 and wa inference and the green contours around it represent the 68% and 95% confidence intervals. We also show in blue the constraints from the binning approach [47], with the hori- zontal bars indicating the bin width (which is fixed) and the vertical bars representing the 1σ error. Additionally, we in- clude in gray the 1D posterior for each binning parameter. The ΛCDM limit corresponds to the horizontal gray dashed line.
March 20, 2025 at 7:27 AM
Reposted by Jiachen Bai
fabianschussler.bsky.social
“The Science of the Einstein Telescope”: An overview of what the next-generation gravitational wave observatory will enable. The sheer volume speaks for itself—550 pages full of science! 🔭🧪⚛️☄️
Freely accessible on arxiv.org/abs/2503.12263
March 18, 2025 at 8:34 PM
Reposted by Jiachen Bai
desisurvey.bsky.social
🚨 BIG NEWS ALERT! 🚨
We’re just 24 HOURS AWAY from a MAJOR DESI release! 🌉🔭

Tomorrow at 3 PM PT, DESI is unveiling DR1, our first official Data Release—the largest dataset of its kind, packed with information on 18.7 million galaxies, quasars, and stars! But that’s not all…
March 18, 2025 at 10:11 PM
Reposted by Jiachen Bai
eucliduk.bsky.social
Are you ready for it…?

Make room in your calendar for 19th March at 11:00, when stunning results with contributions from UK scientists will be revealed. 🚨 🗓️

#Euclid #Q1Release #Astronomy #Cosmology
The left of a mosaic of photographs from Euclid’s Early Release Observations in the background, containing stars, galaxies and glowing dust. “ONE WEEK UNTIL…” is written in large font in the foreground. The right of a mosaic of photographs from Euclid’s Early Release Observations in the background, containing stars, galaxies and glowing dust. “Q1 DATA RELEASE” is written in large font in the foreground. Also shown is the Euclid Consortium logo and “#EUCLIDUK”.
March 12, 2025 at 3:51 PM
Reposted by Jiachen Bai
beebrookshire.bsky.social
🥹
A person holding a sign which says “I am here so my little sister can dream of becoming a scientist.”
March 7, 2025 at 7:01 PM
Reposted by Jiachen Bai
ajsteinmetz.com
Very cool. Here's the paper: dx.doi.org/10.1038/s415...

arXiv: dx.doi.org/10.48550/arx...

#Science #Astronomy #Physics #Cosmology 🧪🔭⚛️
February 8, 2025 at 4:35 PM
Reposted by Jiachen Bai
science.esa.int
This is the first time that the ring of light surrounding the centre of NGC 6505 is detected, thanks to Euclid’s high-resolution instruments.

🔭🧪
#cosmology
A thin ring of a perfect circular shape and a piercingly bright white disc in its middle are the protagonists of this image. They stand out against a uniformly coloured background of a hazy dark grey. The ring appears as if it was a faint brush stroke, where at four evenly spaced spots more pressure was applied on the brush. These stand out in the ring as four brighter and thicker spots. The white disc within the ring gives the impression of a gaping hole in the image, through its stark contrast to the dark background.
February 10, 2025 at 8:31 AM
astrobai.bsky.social
Happy Chinese New Year！🎉🎉🎉
January 28, 2025 at 1:19 PM
Reposted by Jiachen Bai
kittehkat8.bsky.social
Wishing everyone a Happy Chinese New Year!!!

#katdraws
A snake lady in a Chinese dress, celebrating her year (2025)
January 28, 2025 at 12:20 AM
Reposted by Jiachen Bai
jrdmb.bsky.social
Cosmology Researcher Talks database 2024 stats:

1132 talks by 899 speakers re 1180 arXiv papers

Top 10 sources:
94 Cosmology fr Home
93 Perimeter Inst
92 Kyoto U, YITP
80 CosmoVerse
76 Misc
57 KITP
52 ICTP-SAIFR
42 CERN
31 Neutrinos fr Home
30 Parity Violation fr Home

jrdmb.netlify.app/crt.html
Search Talks
jrdmb.netlify.app
January 8, 2025 at 7:01 PM
Reposted by Jiachen Bai
reasonsbot.bsky.social
more books to read
December 14, 2024 at 4:10 AM
astrobai.bsky.social
Paper day! 🎉
My second work is now available on arXiv!
In this work, we test f(R) gravity with the state-of-the-art measurements of cosmic shear combined with CMB and BAO data.
We find an upper limit on the f(R) parameter, with log(fR0) constrained to be less than -4.79 (95% C.L.).
🧪🔭⚛️ #cosmology
Testing $f(R)$ Gravity from Cosmic Shear Measurements
In this work, we perform a detailed analysis to constrain the Hu-Sawicki $f(R)$ gravity model, using cosmic shear data from three prominent Stage-III weak lensing surveys: DES-Y3, KiDS-1000, and HSC-Y...
arxiv.org
December 9, 2024 at 4:27 AM
Reposted by Jiachen Bai
physgal.bsky.social
Hi I am Physgal and I will be adding physicists to the Science feed. Please respond below with evidence that you are a physicist to be added to the feed.

teammates: @physgal.bsky.social / @quarkcharme.bsky.social
January 11, 2024 at 8:36 PM
Reposted by Jiachen Bai
asclnet.bsky.social
Today's random code is fkpt: Compute LCDM and modified gravity perturbation theory using fk-kernels
ascl.net/2403.006
fkpt computes the 1-loop redshift space power spectrum for tracers in LCDM and Modified Gravity models using perturbation theory.#astronomy
December 6, 2024 at 1:00 PM
astrobai.bsky.social
I just submitted my second paper.
Cheers!
December 6, 2024 at 6:43 AM
astrobai.bsky.social
Amazing work!
The Multimodal Universe: Enabling Large-Scale Machine Learning with 100TB of Astronomical Scientific Data
We present the MULTIMODAL UNIVERSE, a large-scale multimodal dataset of scientific astronomical data, compiled specifically to facilitate machine learning research. Overall, the MULTIMODAL UNIVERSE co...
arxiv.org
December 4, 2024 at 5:14 PM
Reposted by Jiachen Bai
pomarede.bsky.social
Science Magazine astronomy covers

The Cosmic Web

This special issue published in 2008 featured some of the latest research on the filamentary structure of dark and visible matter that fills the Universe. #cosmology 🧪

www.science.org/toc/science/...
A cover of Science Magazine, published 4 January 2008, featuring an artits's view of the cosmic web, a structure of filaments and knots separating voids. The structure is rendered using a color palette that ranges from black for underdense, evolves to blueish for intermediate levels of density, and reaches white for the highest densities. Image: Shigemi Numazawa/Atlas Photo Bank/Photo Researchers Inc.
December 2, 2024 at 2:28 PM