Background on "FLRW cosmology":
en.wikipedia.org/wiki/Friedma...
en.wikipedia.org/wiki/Friedma...
Friedmann–Lemaître–Robertson–Walker metric - Wikipedia
en.wikipedia.org
August 12, 2025 at 1:35 PM
Background on "FLRW cosmology":
en.wikipedia.org/wiki/Friedma...
en.wikipedia.org/wiki/Friedma...
Several thousand people gathered in Bosnia and Herzegovina on Wednesday to take part in a peace march in memory of the victims of the genocide and the survivors who fled the town of Srebrenica in July 1995. #EuropeNews
➡️ https://l.euronews.com/fLRw
➡️ https://l.euronews.com/fLRw
July 9, 2026 at 3:36 AM
Several thousand people gathered in Bosnia and Herzegovina on Wednesday to take part in a peace march in memory of the victims of the genocide and the survivors who fled the town of Srebrenica in July 1995. #EuropeNews
➡️ https://l.euronews.com/fLRw
➡️ https://l.euronews.com/fLRw
Thermodynamics of arbitrary spherical surfaces in FLRW spacetimes
https://arxiv.org/pdf/2609.25763
Xun Gong, Jun Wang, Chen-Yang Zhang.
https://arxiv.org/pdf/2609.25763
Xun Gong, Jun Wang, Chen-Yang Zhang.
https://arxiv.org/abs/2609.25763
arXiv abstract link
arxiv.org
September 27, 2026 at 10:51 AM
Thermodynamics of arbitrary spherical surfaces in FLRW spacetimes
https://arxiv.org/pdf/2609.25763
Xun Gong, Jun Wang, Chen-Yang Zhang.
https://arxiv.org/pdf/2609.25763
Xun Gong, Jun Wang, Chen-Yang Zhang.
I’d think the mimicking-something-smooth would have very similar answers as “why can we model a universe that is inhomogeneous on small scales as perfectly homogeneous FLRW”. Not a big leap from one to the other. Accepting FLRW means expecting deviations from FLRW to be, if anything, small, no?
December 27, 2024 at 3:00 PM
I’d think the mimicking-something-smooth would have very similar answers as “why can we model a universe that is inhomogeneous on small scales as perfectly homogeneous FLRW”. Not a big leap from one to the other. Accepting FLRW means expecting deviations from FLRW to be, if anything, small, no?
🧵 (1/3) Do our late-time distance data actually pass the FLRW consistency check?
New preprint led by Cléa Millard (graduate student in our group):
arxiv.org/abs/2601.20293
#cosmology #astrophysics
New preprint led by Cléa Millard (graduate student in our group):
arxiv.org/abs/2601.20293
#cosmology #astrophysics
Model independent test of the FLRW metric and the curvature in light of DESI DR2
We perform a data-driven test of the FLRW metric and the flatness of the Universe, independently of any Dark Energy model, and in light of the latest DESI DR2 results. We use Pantheon+ and DESY5 SNIa ...
arxiv.org
January 29, 2026 at 7:22 AM
🧵 (1/3) Do our late-time distance data actually pass the FLRW consistency check?
New preprint led by Cléa Millard (graduate student in our group):
arxiv.org/abs/2601.20293
#cosmology #astrophysics
New preprint led by Cléa Millard (graduate student in our group):
arxiv.org/abs/2601.20293
#cosmology #astrophysics
Non, le billet le plus long, c'est sur la cosmologie: www.madore.org/~david/weblo...
L'Univers et la cosmologie de FLRW
www.madore.org
September 16, 2026 at 8:55 PM
Non, le billet le plus long, c'est sur la cosmologie: www.madore.org/~david/weblo...
Xun Gong, Jun Wang, Chen-Yang Zhang
Thermodynamics of arbitrary spherical surfaces in FLRW spacetimes
https://arxiv.org/abs/2609.25763
Thermodynamics of arbitrary spherical surfaces in FLRW spacetimes
https://arxiv.org/abs/2609.25763
September 23, 2026 at 12:49 PM
Xun Gong, Jun Wang, Chen-Yang Zhang
Thermodynamics of arbitrary spherical surfaces in FLRW spacetimes
https://arxiv.org/abs/2609.25763
Thermodynamics of arbitrary spherical surfaces in FLRW spacetimes
https://arxiv.org/abs/2609.25763
This paper explores an alternative cosmological model-- a conformal transformation of the standard FLRW metric. This way, we find that what we call the Conformal Scaling Function (the exponential that multiplies the FLRW metric) gives different constraints depending on whether we consider a LCDM+
September 21, 2025 at 6:52 PM
This paper explores an alternative cosmological model-- a conformal transformation of the standard FLRW metric. This way, we find that what we call the Conformal Scaling Function (the exponential that multiplies the FLRW metric) gives different constraints depending on whether we consider a LCDM+
Thermodynamics of arbitrary spherical surfaces in FLRW spacetimes
https://arxiv.org/pdf/2609.25763
Xun Gong, Jun Wang, Chen-Yang Zhang.
https://arxiv.org/pdf/2609.25763
Xun Gong, Jun Wang, Chen-Yang Zhang.
https://arxiv.org/abs/2609.25763
arXiv abstract link
arxiv.org
September 23, 2026 at 9:33 AM
Thermodynamics of arbitrary spherical surfaces in FLRW spacetimes
https://arxiv.org/pdf/2609.25763
Xun Gong, Jun Wang, Chen-Yang Zhang.
https://arxiv.org/pdf/2609.25763
Xun Gong, Jun Wang, Chen-Yang Zhang.
Xun Gong, Jun Wang, Chen-Yang Zhang: Thermodynamics of arbitrary spherical surfaces in FLRW spacetimes https://arxiv.org/abs/2609.25763 https://arxiv.org/pdf/2609.25763 https://arxiv.org/html/2609.25763
September 23, 2026 at 6:54 AM
Xun Gong, Jun Wang, Chen-Yang Zhang: Thermodynamics of arbitrary spherical surfaces in FLRW spacetimes https://arxiv.org/abs/2609.25763 https://arxiv.org/pdf/2609.25763 https://arxiv.org/html/2609.25763
Instead, the current best fit to what we see is a FLRW model where only about 27% of what’s out there gravitating qualifies as matter. About 4/5 of that is “dark matter." There's a negligible (from a gravitational standpoint) amount of radiation. The rest is probably* a cosmological constant. (23/n)
May 6, 2025 at 3:03 PM
Instead, the current best fit to what we see is a FLRW model where only about 27% of what’s out there gravitating qualifies as matter. About 4/5 of that is “dark matter." There's a negligible (from a gravitational standpoint) amount of radiation. The rest is probably* a cosmological constant. (23/n)
Couple days ago I tried to start thinking of LLMs in terms of astronomy.
Now I'm thinking of it in terms of cosmology.
If you plot the average activation norms through all the transformer layers, they sure do look like they scale just like exp(L). Just like the scale term in the FLRW metric…
Now I'm thinking of it in terms of cosmology.
If you plot the average activation norms through all the transformer layers, they sure do look like they scale just like exp(L). Just like the scale term in the FLRW metric…
I've gone through linear algebra to bathymetry to differential geometry and none of those has worked for me as a mental framework. I think I'm going to try astronomy.
Tokens are the stars in our universe. There are exactly 151,936 of them. They are scattered through space all around us.
Tokens are the stars in our universe. There are exactly 151,936 of them. They are scattered through space all around us.
October 30, 2025 at 12:26 AM
Couple days ago I tried to start thinking of LLMs in terms of astronomy.
Now I'm thinking of it in terms of cosmology.
If you plot the average activation norms through all the transformer layers, they sure do look like they scale just like exp(L). Just like the scale term in the FLRW metric…
Now I'm thinking of it in terms of cosmology.
If you plot the average activation norms through all the transformer layers, they sure do look like they scale just like exp(L). Just like the scale term in the FLRW metric…
The rate at which the log of the scale factor changes is called the "Hubble parameter." In an exponentially expanding or contracting universe, the Hubble parameter is constant. For the models explored by the folks mentioned earlier – collectively referred to as "FLRW" – it changes over time. (18/n)
May 6, 2025 at 2:55 PM
The rate at which the log of the scale factor changes is called the "Hubble parameter." In an exponentially expanding or contracting universe, the Hubble parameter is constant. For the models explored by the folks mentioned earlier – collectively referred to as "FLRW" – it changes over time. (18/n)
Published in #MNRAS: "Cold collapse and bounce of an FLRW cloud", Pradhan et al. Below is the abstract. To read the paper please visit academic.oup.com/mnras/articl...
@rasjournals.bsky.social @royalastrosoc.bsky.social
#cosmology #universe
#BlackHoles #icgportsmouth #iiserkolkata
@rasjournals.bsky.social @royalastrosoc.bsky.social
#cosmology #universe
#BlackHoles #icgportsmouth #iiserkolkata
February 14, 2025 at 1:57 PM
Published in #MNRAS: "Cold collapse and bounce of an FLRW cloud", Pradhan et al. Below is the abstract. To read the paper please visit academic.oup.com/mnras/articl...
@rasjournals.bsky.social @royalastrosoc.bsky.social
#cosmology #universe
#BlackHoles #icgportsmouth #iiserkolkata
@rasjournals.bsky.social @royalastrosoc.bsky.social
#cosmology #universe
#BlackHoles #icgportsmouth #iiserkolkata
But a zero-density FLRW will expand still at whatever initial rate it possessed!
It _CAN_ be Minkowski, but this isn't a necessity.
It _CAN_ be Minkowski, but this isn't a necessity.
June 26, 2025 at 9:25 PM
But a zero-density FLRW will expand still at whatever initial rate it possessed!
It _CAN_ be Minkowski, but this isn't a necessity.
It _CAN_ be Minkowski, but this isn't a necessity.
In cosmology, the typical working assumption is that the solution is close (in a certain sense) to a metric which is FLRW. FLRW has a preferred frame. We can use any coordinate system we want, so the local structure group is GL(3,1), but that is not the isometry group of the metric.
April 28, 2025 at 8:01 PM
In cosmology, the typical working assumption is that the solution is close (in a certain sense) to a metric which is FLRW. FLRW has a preferred frame. We can use any coordinate system we want, so the local structure group is GL(3,1), but that is not the isometry group of the metric.
Friedmann-Lemaître-Robertson-Walker (FLRW)-Metrik
July 16, 2025 at 12:21 PM
Friedmann-Lemaître-Robertson-Walker (FLRW)-Metrik
I mean - that obviously what Alan talked about when he introduced the term, but it is not something that can happen in a simple FLRW model.
September 14, 2025 at 9:24 PM
I mean - that obviously what Alan talked about when he introduced the term, but it is not something that can happen in a simple FLRW model.
New short math note: full scalar–tensor derivation behind the TCC–EFT (metric variation + FLRW reduction). No physics, just the formal steps.
doi.org/10.5281/zeno...
#physics
#theoreticalphysics
#cosmology
#scalartensor
#gravity
#eft
#flrw
#gr
#mathphys
#research
doi.org/10.5281/zeno...
#physics
#theoreticalphysics
#cosmology
#scalartensor
#gravity
#eft
#flrw
#gr
#mathphys
#research
TCC–EFT Mathematical Note (2025): Scalar–Tensor Background Derivation
This technical note provides the full mathematical derivation of the scalar–tensor background used in the TCC–EFT Overview (v1.2).The document includes the metric variation, scalar-field variation, ho...
doi.org
November 17, 2025 at 2:42 PM
New short math note: full scalar–tensor derivation behind the TCC–EFT (metric variation + FLRW reduction). No physics, just the formal steps.
doi.org/10.5281/zeno...
#physics
#theoreticalphysics
#cosmology
#scalartensor
#gravity
#eft
#flrw
#gr
#mathphys
#research
doi.org/10.5281/zeno...
#physics
#theoreticalphysics
#cosmology
#scalartensor
#gravity
#eft
#flrw
#gr
#mathphys
#research
Basic message: distant WISE sources show a velocity dipole like that in the CMB. Same direction but larger amplitude; inconsistent with FLRW at over 4 sigma.
Just to *not* complain, currently I’m listening to a really interesting talk by Roya Mohayaee about testing the cosmological principle.
May 30, 2025 at 2:57 PM
Basic message: distant WISE sources show a velocity dipole like that in the CMB. Same direction but larger amplitude; inconsistent with FLRW at over 4 sigma.
The frame in which the universe is (well approximated at large scales as) homogeneous and isotropic. This is the frame singled out in a FLRW cosmology:
en.wikipedia.org/wiki/Friedma...
en.wikipedia.org/wiki/Friedma...
https://en.wikipedia.org/wiki/Friedmann–Lemaître–Robertson–Walker_metric
June 19, 2025 at 10:10 PM
The frame in which the universe is (well approximated at large scales as) homogeneous and isotropic. This is the frame singled out in a FLRW cosmology:
en.wikipedia.org/wiki/Friedma...
en.wikipedia.org/wiki/Friedma...
Maybe we're thinking about this differently?
To me, Milne is just FLRW with density set to zero and a curvature term as the only non-zero term on the RHS.
Which is identical to placing 100% of your energy density as cosmic strings (density ~ 1/a^2).
But I solve for a and t; what do you solve for?
To me, Milne is just FLRW with density set to zero and a curvature term as the only non-zero term on the RHS.
Which is identical to placing 100% of your energy density as cosmic strings (density ~ 1/a^2).
But I solve for a and t; what do you solve for?
June 26, 2025 at 9:08 PM
Maybe we're thinking about this differently?
To me, Milne is just FLRW with density set to zero and a curvature term as the only non-zero term on the RHS.
Which is identical to placing 100% of your energy density as cosmic strings (density ~ 1/a^2).
But I solve for a and t; what do you solve for?
To me, Milne is just FLRW with density set to zero and a curvature term as the only non-zero term on the RHS.
Which is identical to placing 100% of your energy density as cosmic strings (density ~ 1/a^2).
But I solve for a and t; what do you solve for?
New #Science paper day! 🎉⚛️🧪 We employ the #Physics Standard Model + FLRW #Cosmology to describe the Universe's compositional evolution from #QGP to electron-positron plasma.
Rafelski, J., Birrell, J., Grayson, C. et al. Quarks to Cosmos. Eur. Phys. J. Spec. Top. (2025). doi.org/10.1140/epjs...
Rafelski, J., Birrell, J., Grayson, C. et al. Quarks to Cosmos. Eur. Phys. J. Spec. Top. (2025). doi.org/10.1140/epjs...
Quarks to Cosmos: - The European Physical Journal Special Topics
We describe in the context of the particle physics (PP) standard model (SM) ‘PP-SM’ the understanding of the primordial properties and composition of the Universe in the temperature range $$130\,\text...
doi.org
June 24, 2025 at 6:29 PM
New #Science paper day! 🎉⚛️🧪 We employ the #Physics Standard Model + FLRW #Cosmology to describe the Universe's compositional evolution from #QGP to electron-positron plasma.
Rafelski, J., Birrell, J., Grayson, C. et al. Quarks to Cosmos. Eur. Phys. J. Spec. Top. (2025). doi.org/10.1140/epjs...
Rafelski, J., Birrell, J., Grayson, C. et al. Quarks to Cosmos. Eur. Phys. J. Spec. Top. (2025). doi.org/10.1140/epjs...
Updated overview of the Cosmic Tension–Compression EFT (TCC–EFT).
A concise IR scalar–tensor cosmological EFT restricted to FLRW dynamics
DOI → doi.org/10.5281/zeno...
#cosmology #darkenergy #EFT #scalartensor #physics #astro
A concise IR scalar–tensor cosmological EFT restricted to FLRW dynamics
DOI → doi.org/10.5281/zeno...
#cosmology #darkenergy #EFT #scalartensor #physics #astro
TCC–EFT Overview (V1.2): Cosmic Tension–Compression Effective Field Theory
AbstractThis updated Overview (v1.2) presents a concise and fully revised description of the Cosmic Tension–Compression Effective Field Theory (TCC–EFT), an infrared scalar–tensor framework designed t...
doi.org
November 14, 2025 at 1:20 PM
Updated overview of the Cosmic Tension–Compression EFT (TCC–EFT).
A concise IR scalar–tensor cosmological EFT restricted to FLRW dynamics
DOI → doi.org/10.5281/zeno...
#cosmology #darkenergy #EFT #scalartensor #physics #astro
A concise IR scalar–tensor cosmological EFT restricted to FLRW dynamics
DOI → doi.org/10.5281/zeno...
#cosmology #darkenergy #EFT #scalartensor #physics #astro