Video

17:28 The presented results assume homogeneity and isotropy, so if one gets rid of homogeneity and isotropy (as is hinted at by recent dipole surveys) then it is still possible to modify something between the BAO scales and the supernovae/redshift z=0 to resolve the Hubble tension.

Thank you for your work. Time dilation in gravtaional waves are an interesting research field, if it´s measurable.

Very intriguing. I also wonder if the use of photometric information of the foreground galaxies will impact the results in this study. The fun part is, my comment also goes down in the history of this talk. :)

There is no such thing as “time dilatation” 😅 This is the speed of the light (electromagnetic wave) that vary depending on the “emitter environment” speed 😉

I like your quesitons and your explanations.

This tension reaches 4.5sigma today, as indendently reported by a different team in arXiv:2406.13388, led by Shi-Fan Chen.

That was a great discussion. If the choices are between tired light and expansion, looks like you gotta go with expansion. There is another option though, called the Time Dilated Past hypothesis. This exchanges a dynamic space for a dynamic time, one that speeds up. This is basically saying cosmic time dilation is real, but without an expanding universe.

*Index to Key Parts of the Talk* [00:00] Shaun's intro [02:46] Overview of this work by Ryan and Tamara [06:08] Supernova light curves in different bands across redshifts [10:55] Picking similar light curves out of different bands [11:23] Stacked light curves [13:55] Scale light curves in time by function of source z [18:02] The 'width' of each individual light curve [18:43] Quantifying time dilation [21:44] Why do we expect time dilation? [27:58] Scatter in widths from noise & intrinsic SN light curve variation [38:00] Where to next? [40:56] What current cosmology work is interesting but underappreciated?

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*Index to Key Parts of the Talk* [00:00] Shaun's intro [01:20] Searching for gravitational lensing of SNe [04:24] Two takeaways to remember [05:43] Motivation for this work and why it could be done now [10:22] The Hubble diagram of SN Ia [11:16] What does a clumpy universe do to SN Ia? [13:37] But can we detect it? [14:46] Our data [16:37] Our lensing estimator [20:52] Correlate lensing estimate with Hubble diagram residuals [27:01] The shape of dark matter haloes [27:43] 'Adaptive optics' for dark matter [30:49] What's next? [34:23] Key results from DES-SN5YR weak lensing [45:05] Further work anticipated?

Now after a second watch of this work, this particular CT needs to be more widely seen because it represents the reason DES and/or DESI projects are done: we want to know what is really there vs. what is modeled. Beginning @6:15 we are offered what these DES data can do to guide selection of models that represent the expansion of the Universe. This is fundamental! Based a previous comment by Shaun after the original CT by these two presenters, Ryan (he's young) will likely witness the unveiling of how the Universe expanded which awaits future data presented by Vera Rubin Observatory and the space-based observatories.

*Index to Key Parts of the Talk* [00:00] Shaun's intro [01:41] Opening comments by Ryan [02:20] Two takeaways to remember [03:06] Motivation for this work, starting with ΛCDM overview [05:01] So why go beyond ΛCDM? [06:13] What is beyond ΛCDM? Testing different models [07:18] Parametric forms of Λ [09:28] Dvali-Gabadadze-Porrati (DBP) models [10:04] Chaplygin Gas models [11:13] Timescape cosmology [14:12] Why these models were tested vs other options [15:31] Observations -> Hubble Diagram [16:08] DES-SN5YR Pipeline [23:10] The Omega_m - w degeneracy; intro of Q_H parameter [25:21] Model constraints [29:43] Model comparisons [35:37] What's next?

*Index to Key Parts of the Talk* [00:00] Shaun's intro [01:32] Opening comments by Ryan [01:51] Two takeaways to remember [03:31] Distance ladder and why supernovae calibration is needed [06:00] Inverse distance ladder [07:09] Cosmography [07:48] DES-SN + DESI-BAO [08:18] Results [15:46] Sean's comment on what SN add to the inverse distance ladder [18:12] Where to next? [20:56] What current cosmology work is interesting but underappreciated?

A quick other note, as Tamara mentioned, it would be great to have a log plot on the x-axis to really show the constraints at the lowest redshift.

Excellent talk, and thanks for taking our place and asking the great questions.

This presentation is exemplary in that it thoroughly discusses and displays what was done to produce the information presented. I particularly consider the "pencil beam" graphic @16:35 as a representation of the outstanding work presented in this talk; it is so clear just what DES actually did to get its data. I didn't realize that red shift data were collected on a different instrument and that red shift comes from the host galaxy not the SN itself. I, too, (your question @ 17:35) wondered about how do you confirm that the SN photometric data DO come from the galaxy from which spectroscopic data emerge . I note that DES includes DESI data; I recall in the DESI talk, presented on this "CT" channel, NO DES data were presented ( I need to check that point). However, I do sense that the DES and DESI presenters of these CT talks are very cautious about any claims that the EOS w parameter is NOT -1 which the Lambda CDM model requires.

*Index to Key Parts of the Talk* [0:00:00] Shaun's intro [0:01:11] Intro by the 3 speakers to this work [0:02:43] Two takeaways to remember [0:05:54] Supernova cosmology basics [0:29:47] DES Analysis Details [0:48:10] DES SN Cosmology Results [1:00:09] Is dark energy a cosmological constant? [1:01:22] A few months later...DESI supports DES, finding similar result for w_a [1:02:39] Big Questions: Is the expansion of the Universe accelerating? Yes! [1:03:35] Big Questions: Is dark energy a cosmological constant? Maybe? Union 3 also prefer w > -1 [1:10:23] Big Questions: How old is the Universe? Slightly younger than we thought? [1:11:12] Big Questions: Does DES best fit resolve the Hubble tension? No, DES doesn't constrain H_0 [1:12:04] Bonus Science!!! [1:16:08] What current cosmology work is interesting but underappreciated?

Thanks for organising recent works in the field.

Super nice!

*Index to Key Parts of the Talk* [0:00:00] Shaun's intro [0:02:05] Opening comments by Elisabeth Krause [0:03:13] Two things to remember about this talk [0:04:56] The history of this idea [0:06:19] Why the team used this approach [0:08:43] Getting into the details [0:13:31] Redshift-space results in σ8 and Ωm (Figs. 21, 1 in paper) [0:18:10] Light-cone and Real-space Results (Figs 3, 4) [0:19:28] Takeaways [0:22:53] The Methods and How They Work: Participating Analyses (Table 1) [0:24:14] Importance of k_max [0:27:18] Overview of EFT Methods [0:35:47] Overview of HOD Methods [0:41:43] 2-min overviews of each specific method [0:55:50] Post unmasking insights and updated results [1:04:49] Lessons learned and future reflections

Excellent everyone, there are confirmation biases everywhere. A great approach.

I wrote a PhD on the theoretical physics of ultracold atoms. It seemed to me that this topic was very far from cosmology and I switched to particle physics.

*Index to Key Parts of the Talk* [00:00] Shaun's intro [01:04] Opening remarks by Lucia and Mark [04:47] Timing & enabling investments in Quantum 2.0 technologies [09:18] How are atoms cooled to <1 millionth degree above absolute zero? [15:50] Ultracold atoms, setup in the lab, laser system [20:12] Movie - Lithium MOT [21:05] Evaporative cooling - Lithium [26:02] Li_2 Bose-Einstein Condensate [27:47] Quantum 2.0 sensors [32:15] 3D printed chambers [34:23] Printed surfaces [35:17] Parts for Quantum 2.0 technologies; New manufacturing techniques [37:53] New hybrid shielding/magnetic bias product [39:34] Printed vapour cells [41:34] Spectroscopy and magnetic sensors [42:36] Compact, printed Laser system [44:22] A printed gravimeter for space [46:16] Printed cold atom system [49:35] Where to next? [53:42] Other ideas on the horizon? [58:02] What current work in cold atoms is interesting but underappreciated?

22:49

*Index to Key Parts of the Talk* [00:00] Shaun's intro [01:20] Opening remarks by Minh and Beatriz [02:39] Takeaways to remember about this talk [05:48] Motivation for this work [08:45] Getting into the details: Amplitude of Structure Growth [09:52] Galaxy clustering can distinguish scenarios of new physics [10:49] Galaxy bias - response of galaxy formation to fluctuations [11:47] Galaxy bias spoils constraint from galaxy clustering [12:30] Effective Field Theory of galaxy bias [15:45] FBI (field-level Bayesian inference) and SBI (simulation-based inference) posteriors [18:46] Extended discussion at the Field-Level Inference slide [29:17] Apple-to-apple comparison of FBI and SBI P+B [31:12] Simulation-based inference [33:06] Neural Posterior Estimation (NPE) [34:35] Normalizing flows [35:37] SBI wrap-up putting it all together [40:37] Improvement increases with scale cuts [43:02] Robust improvement across samples [44:50] Where to next? [49:30] What current work in cosmology is interesting but underappreciated by the community? [50:24] Beyond 2-point mock data challenge

Fantastic talk, thank you for it I really enjoyed it, very well presented. The DESI result is very interesting. Particularly the final par. Our observations are also that the different SN datasets prefer different cosmology which is very intriguing by itself. Congratulations to the DESI team.

1:15:03

czcams.com/video/9DsMphPfrjI/video.html So, your results for the "equantion of state of vacuum" parameter value was found to be less than -1 in the ΛCDM model thus for exmaple -0.8 or -0.6 which actually favors the Quintessence model over ΛCDM with a maximum conficdnce in the results you report of 3.9σ. Thus, the universe will end up in a Big crunch.

So does this infer that dark energy may be getting weaker as a function of time, weaker at lower redshifts? Or weaker at higher redshifts?

*Index to Key Parts of the Talk* [00:00] Shaun's intro [01:14] Opening remarks by Russell [02:02] Two things to remember about this talk [04:08] Motivation for this work (The Final Parsec Problem) [06:49] Ultralight Dark Matter [09:07] Objective [12:10] Explaining use of the Schrodinger-Poisson equations [13:44] Getting into the details - Setup [17:14] Dynamical Friction Theory [22:24] Semi-Analytic Model [25:28] Simulation Behavior [30:01] Numerical Dependencies [33:19] Black Hole Mass Dependence [34:46] ULDM Mass Dependence [36:38] Soliton Mass Dependence [38:22] Semi Analytic Model Comparison [40:51] Overdensities [43:12] Force Comparison [45:40] Conclusion [51:48] What next? [56:34] What current work in cosmology is interesting but underappreciated by the community?

Hi, could I download this talk and upload to another platform called "bilibili"? My BSc Thesis's topic is related to BAO, I would like to share it to more people. I will cite the source. Thank you!

I have watch the complete talk. At the end with the impact of the data "hinting" a time varying equation of state, I sense Shawn's concern/questioning about the Wa and W0 "hints"; however, the presenters were consistently stating that these are the data even though the time varying model is just a "toy". As I understand Einstein's GR, Lambda can't change; it must be constant to satisfy the Bianchi Identities. Now these are quite impactful "hints". So, I naively ask, are these data "hinting" about the currently accepted acceleration of the Universe?

Great presentation and intriguing results! I have two questions: 1) The impact of an incorrect fiducial cosmology for converting redshifts to distances has been verified to be minimal. However, what is the impact of an incorrect fiducial cosmology during the reconstruction process? 2) For the next data release, will you consider utilizing mocks based on a non-LCDM fiducial cosmology?

*Index to Key Parts of the Talk* [0:00:00] Shaun's intro [0:00:36] Opening overview and quick peak of results by Andreu and Sesh [0:01:37] BAO results from DESI DR1 [0:02:14] DESI BAO and Dark Energy [0:04:54] DESI BAO and neutrino masses [0:05:18] DESI BAO and the Hubble Tension [0:06:31] Main talk: background, details, results (starting with BAO) [0:09:43] DESI: the instrument [0:11:05] DESI: the survey [0:12:04] DESI Data Release 1 (DR1) [0:18:11] BAO measurements with galaxies & quasars at z<2 [0:21:32] Non-linear evolution and Density field reconstruction [0:23:41] How is the DESI BAO analysis different? [0:30:08] Tests of systematic errors [0:34:02] Unblinded data results! [0:39:16] BAO measurements from the Lyman-α forest at z>2 [0:45:16] Lyα BAO: Analysis Validation [0:48:41] Lyα BAO: Unblinding! [0:51:10] DESI DR1 Lyα BAO: Publications [0:53:42] Cosmological Constraints: Flat ΛCDM from DESI BAO [0:58:02] Breaking the H_0-r_d degeneracy [1:01:35] DESI BAO and the Hubble Tension [1:03:54] DESI BAO and neutrino masses [1:10:52] DESI BAO and Dark Energy [1:23:06] Summary [1:24:00] What's next?

WOW, how exciting. I hear it in your expression, too. Along with data from DES, the hints of tension with Lambda CDM are really emerging yet still need more work/time. I have long believed that BAO will provide a cosmological time base vs. redshift; a real temporal profile of the expansion of the universe meaning scale factor vs. red shift. I am just 6 min. into the talk so more comments are likely. Also, I live just 100km east of DESI in Tucson - I can see the KECK building.

Thanks for putting this up. I had seen the materials released by Berkeley, but that w_a/w_0 graph is what I had read was the most significant (excuse the pun).

*Index to Key Parts of the Talk* [0:00:00] Shaun's intro [0:02:17] Sylvia's overview [0:03:49] Two takeaways from this talk [0:06:36] The motivation and reason for timing of this work [0:09:54] Two probabilistic questions [0:10:22] 1. Probability of inflation [0:11:03] 2. Predictability problem [0:14:27] Infinite phase space [0:16:01] Probability formalisms [0:19:20] Paradox: fair infinite lottery [0:20:56] Standard probability theory [0:23:07] Paradox: fair lottery on N [0:26:40] Finitely additive probability [0:33:00] Non-Archimedean probability [0:41:10] Non-normal quasi-probability [0:45:27] Infinite lottery logic (ILL) [0:47:53] Implications for inflation theory? [1:02:05] Where to next? [1:08:27] What current work in cosmology is particularly underappreciated by the community?

Difficult topic but great explanation !!

*Index to Key Parts of the Talk* [00:00] Shaun's intro [01:26] Overview by Pritha and Chris and 2 takeaways from the talk [02:34] What is the motivation for this work? [05:03] Why the 4-pt correlation function is needed [05:58] Recent work by others [09:37] Large Scale Surveys [11:35] Real Space to Redshift Space - Power Spectrum [15:36] Real Space to Redshift Space - Bipectrum [19:38] Tree Level Trispectrum [20:59] Trispectrum Geometry [21:43] Third order number counts [26:30] Trispectrum [26:55] Calculating the Trispectrum [30:50] 15-min Q & A segment [46:10] What current work in cosmology is particularly underappreciated by the community?

Nice talk. I'd hoped to hear something more about constraints. Eg, we heard that there might be dark universe constraints in the very early universe that would be detectable from the density or temperature, but it wasn't clear what those constraints might be. Eg percentage measured DM in the early universe. I also wondered if WIMPs might be in thermal equilibrium with the rest of the universe before the weak force was frozen out, and that might give you a limit on WIMP mass. I also was surprised how much our knowledge has grown in the last few years. Nice point about Cosmic Neutrino Background. Thanks.

Shaun, I struggled with this presentation which I understand is just a definition and calculation guide, a cheat sheet not the resultant paper. I seem to sense your struggle but perhaps on a more lofty level. As a physicist, I always struggle with gravational lensing computations not the existence of Einstein's rings features imaged by Hubble or JWST. What bothers me is the actual DM distribution that is seemingly missing yet when modeling the background - imaged - galaxy, some assumptions MUST be make regarding that DM distribution. Is this not a classical inversion problem not unlike "what object cast this shadow? NOW, I learn that another feature/finding, Intrinsic Alignment can be present both in the lensing and the imaged galaxies and thus another set of assumptions about IAs must be prepared Of course, when simulating, one gets to unravel both of these issues but sadly, not in the real world. OK, a cheat sheet but can this be the basis of anything substantial? My complaints don't even begin to add my apprehension about DM, itself.

*Index to Key Parts of the Talk* [0:00:00] Shaun's intro [0:01:13] What are intrinsic alignments? plus IA cheat sheet [0:02:54] Two things to remember from this talk [0:03:17] Getting into the background and details [0:10:04] Ellipticity (section 2 of paper*) [0:12:38] Galaxy types and shapes [0:16:31] IA Correlation Function Notation (section 4*) [0:19:02] IA Correlation Functions (section 5*) [0:23:01] Correlations [0:23:34] Shear (section 3*) [0:30:54] 3D IA Power Spectrum (section 6*) [0:38:33] 2D IA Power Spectrum (section 7*) [0:46:01] Modeling (section 8*) [1:00:41] Where to next? [1:06:44] What current work in cosmology is particularly underappreciated by the community?

18:16 DESI says Dark Energy starts/turnes on at about z=1, does this conflict with the latest eRosita where they claim 'all time and space'. (A laypersons question), thank you).

*Index to Key Parts of the Talk* [00:00] Shaun's intro [01:04] Overview comments by Keir and Viv [03:25] Two things to remember from this talk [06:45] Motivations for this work [11:35] Getting into the Details [15:57] All the cosmological info in the eBOSS Lyα forest compressed to two parameters [17:20] This compression is valid for all the models we consider (Fig. 4 from paper) [18:26] 4.9σ tension between eBOSS Ly-αf & Planck CMB (Fig. 1) [20:11] Clarifying comments by Shaun (editing insert) [23:27] CMB+BAO+SNe vs Lyα; power spectrum running, ULA, WDM (Fig. 2 top) [34:40] Tension missed when looking at omega_8, n_s (Fig. 2 bottom [36:35] Planck CMB+BAO+SNe+eBOSS Ly-αf constraints on primordial power spectrum (Fig. 3) [37:39] Planck CMB+BAO+SNe+eBOSS Ly-αf constraints on nature of dark matter (Fig. 3) [39:25] What else may be causing this discrepancy? [41:35] Where to next? [51:29] Vivian's supplemental comment on neutrino mass contraints [52:38] Keir - follow-up coming from DESI [52:59] What current work in cosmology is particularly underappreciated by the community? [55:23] Final question to Keir about how these findings relate to work discussed in an earlier Cosmology Talk

Just 5%? Doesn´t sound like an ultimate solution. Thank you anyway for this interesting talk and your work.

Hmm, *warm* dark matter - sounds promising!

Very awesome video - thanks for this everyone, it was super interesting!

*Index to Key Parts of the Talk* [00:00] Shaun's intro [00:39] Overview comments by Kate [01:21] Two things to remember from this talk [02:07] Motivations for this work (Fig. 1 from the paper) [04:42] Detecting Dark Domain Walls [05:57] What is a Domain Wall? [08:45] Infinite Domain Walls [09:37] Vacuum Chamber Experiment [12:49] Thin Domain Walls (Fig. 2) [14:41] Thick Domain Walls (Fig. 3) [16:00] What Next? [24:48] What current work in cosmology is particularly underappreciated by the community?

Hi Shaun, with regard to modeling mass from milli-charged dark quanta, if we model that milli-charge as weak hypercharge (rather than electric charge), could we interact such dark quanta with a Higgs type field rather than with electric fields? Since a Higgs type field can be modeled as a condensate of weak hypercharge, might milli-charging (one type of) quanta of dark mass with weak hypercharge make for an easier fit with standard theory? PS: Thanks for making this excellent series of cosmology talks! Nigel

Seems that quasars have been an early warning of the problems that JWST is uncovering.