CosmoPhys

cosmology

New Location – This blog is no longer maintained here.

The cosmology researcher talks database app is a continuing work-in-progress on a collection that currently lists thousands of online talks by cosmology researchers intended for an audience of other researchers working in the field. The data is gathered from diverse sources (called 'series') that host talks from conferences, seminars, workshops, course lectures, summer schools, colloquia, etc.

This collection was started out of personal interest as a service to the cosmology community because no one site was found that comprehensively compiles such data from a wide range of sources. There are many sources available so this represents only a fraction of the total that's out there; still, it's a starter attempt to extend beyond what's otherwise available in one place.

Read more...

New Location – This post is no longer maintained here and has been expanded and moved to this new location.

This is a simple list referencing examples of the work that I find interesting by some current early career physicists (primarily in cosmology and astroparticle physics). I may expand it later with more comments, but here it is for now:

Cosmologist Sunny Vagnozzi reviews 3 papers per week on cosmology and astroparticle physics on his blog. His PhD thesis, Cosmological searches for the neutrino mass scale and mass ordering, was selected for a Springer Thesis Award as one of the best PhD theses of 2019 and will be re-published as a book in the Springer Theses collection. He is active on twitter. Here is a list of video links to talks he presented at various conferences, seminars, etc. A talks page on his website includes talk slides in addition to video links. A one-page listing of all the papers he's reviewed on his blog is here along with topic tags links.

Marius Millea, @cosmic_mar on twitter, is currently a BCCP Fellow at Berkeley Center for Cosmological Physics. He is a member of the Planck and South Pole Telescope collaborations and an advocate for the Julia programming language (e.g., see CMSLensing.jl along with his other Julia github repositories). In 2019, he teamed up with his former thesis advisor Lloyd Knox to write the widely known paper in the field, The Hubble Hunter's Guide. Another impactful paper relating to the Hubble tension problem that he was an author on is Sounds Discordant: Classical Distance Ladder & ΛCDM-based Determinations of the Cosmological Sound Horizon. A more recent paper is about his work in developing a new CMB lensing analysis tool, Optimal CMB Lensing Reconstruction and Parameter Estimation with SPTpol Data. The video of a talk he presented at the Perimeter Institute about it is here. His full publication list is here and this is a list of video links to other talks he has given.

Deanna C. Hooper is currently a postdoc researcher at the University of Helsinki. One of her recent papers is [1910.04619] The synergy between CMB spectral distortions and anisotropies, which she summarized in a 20-tweet thread. More info and a link to her other papers here. She also has recorded a series of general talks about the universe on happs.tv and earlier on pscp.tv. In April 2020, she gave an interview presentation in the Cosmology Talk series on the topic: CMB spectral distortions are a prime untapped resource, based on the 1910.04619 paper.

Read more...

Two sets of White Paper submissions, Science and APC1, are available in response to the Astro2020 Decadal Survey. CSV files of info on them are available at that site. I took those source files and created searchable HTML pages with links to the PDF files for each paper. What's searchable is the paper title, the principal author and their institution, a short description of the paper, and (for the Science White Papers) the NASA ADS Bibcode record. The ADS data was extracted from an AAS Bulletin.

Each of the two searchable webpages has a link to the other, as well as to the source data. The webpages are self-contained with all the data included in the html file, which contains the javascript code for the searches and the CSS for styling.

The original purpose in doing this was because many of the submissions were not on the arXiv, and I wanted to see what else was available and also so the PDF file link were all on one page. In addition, though, the search feature has been very useful.

Read more...

This online-only conference featured 5 days of talks by cosmologists from 22-Jun-2020 to 26-Jun-2020. For anyone interested in the H0 tension problem, this is an excellent and highly recommended resource. Here are links to key resource information covering the conference.

Read more...

A KITP-UCSB program running from Jan 6 to Mar 13, 2020 is an excellent resource for topics related to primordial universe cosmology (e.g., inflation, reheating (aka the Hot Big Bang), baryogenesis, non-gaussianity, dark sectors, cosmological sources of gravitational waves, Hubble tension, etc). The program agenda with links to videos and slides is here.

I'd like to point out an excellent overview talk from this program by Raphael Flauger on Feb. 28 that reviews Hubble measurement physics and results from each of the major determination methods and discusses current status on Hubble tension. The video for Flauger's talk is here. That page does not have the talk slides (at least not yet anyway) but the slides are available in PDF format here. Update: the slides are also now available on the KITP video page. Here is a PDF of the slides.

Read more...

Link to paper: [2003.07355] Early Dark Energy Does Not Restore Cosmological Concordance, by J. Colin Hill, Evan McDonough, Michael W. Toomey, Stephon Alexander

Updates since this was originally posted:

Background

Going back at least several years [1], but increasingly since late-2018 [2-7], there has been growing theoretical interest for the Hubble tension issue that suggests new physics models may be needed for the early universe prior to recombination that do not cause changes to late time cosmology, since that is tightly-constrained [4, 8].

For example, papers [2, 5] propose models for a new form of early dark energy (EDE) present at z ≳ 3000 that then dilutes away, resulting in a reduced sound horizon at decoupling. This results in a larger inferred $H_0$ value from CMB data versus Planck results, thus reducing the disparity between early and late time $H_0$ results.

These EDE proposals for resolving $H_0$ tension were characterized as being somewhere on the spectrum between “most plausible” [3] to “least unlikely” [4].

Read more...

New developments since this post was originally created:

January 2020: In new paper arXiv: 2001.09213, the MCP reports an updated $H_0$ value of 73.9 ± 3.0 based on improved distance measurements for 4 of the 6 systems they previously reported on. MCP researchers Braatz, Pesce, Condon, Reid, et al teamed up with SH0ES team members Scolnic and Riess for this paper. Here is a clip of Figure 1 from the paper. Additional details in this reddit thread.

July 2019: video and slides of a presentation by Mark Reid at the KITP-UCSB conference Tensions between the Early and the Late Universe on July 16, 2019: H0: NGC 4258 and the Megamaser Cosmology Project -—

This post is about the paper Science with the ngVLA: H2O Megamaser Cosmology, which was posted on the arXiv preprint server in Oct. 2018.

What's This About? A recent comment by one of the people I regularly follow (who writes excellent posts on astronomy/cosmology topics) mentioned this NRAO key project as providing direct geometric measurements of the Hubble Constant (H_0) independent of the Cosmic Microwave Background (CMB) and standard candle methods. The megamaser method gives angular diameter distances to water megamasers1 in the nuclear regions of host active galaxies within ~0.1 pc of the SMBH. The galaxies are typically well into the Hubble flow at between 50 – 200 Mpc distance. This slide compares the distances to various studied megamasers to those for Cepheids. As indicated in the slide, these megamaser distances can be used to calibrate other distance methods.

Read more...

Colossus1 is a recently available open-source, pure-python (nothing to compile) calculations toolkit developed by computational astrophysicist Benedikt Diemer during his PhD thesis work at University of Chicago.2

There are 3 separate python modules for cosmology, LSS, and DM Halos. You can choose to work with any of 20 built-in cosmology models based on results from Planck18 (with or w/o BAO), Planck15, Planck13, WMAP, etc. You can also create your own cosmology model by specifying values for a minimum of 6 parameters.

A paper on it is available at https://arxiv.org/abs/1712.04512. The code is available at this BitBucket repository. You can clone the repo, or download a zip file, or you can install it using pip. Documentation with many examples in html format is available here and the docs on the 3 modules are also available as interactive, live-code Jupyter notebooks here. The html tutorials doc files are just exports from the Jupyter notebooks.

Read more...

I had in mind to create a list of recent papers I found of interest that also had an author's talk available and in some cases a review. But after starting this post, I realized it's really so much better to have this data input into the recently initiated and excellent ResearchSeminars.org site, which has great listing and filtering capabilities and is becoming widely used. So I volunteered to the organizers of two cosmology talk series to input their data: Cosmology Talks on youtube hosted by Shaun Hotchkiss and CosmoConβ on youtube, aka Cosmology from Home. The target audience for these are researchers in the field. Now at the Research Seminars site, both Cosmology Talks and CosmoConβ are listed with all their current talks. Also, the Cosmology Talks series includes indexed links to the times of major sections of each talk as a convenience and helpful reference feature.

Read more...