{"id":27,"date":"2026-08-10T15:14:57","date_gmt":"2026-08-10T19:14:57","guid":{"rendered":"https:\/\/sites.bu.edu\/desi\/?page_id=27"},"modified":"2026-08-11T08:17:26","modified_gmt":"2026-08-11T12:17:26","slug":"cosmology","status":"publish","type":"page","link":"https:\/\/sites.bu.edu\/desi\/cosmology\/","title":{"rendered":"Cosmology &#8211; James (Jim) Rohlf"},"content":{"rendered":"<p>Cosmology pages and tools from Jim Rohlf, Professor of Physics at Boston University and a member of the DESI collaboration \u2014 the model, what DESI measures, and where the model is under strain.<\/p>\n<h2>Start here<\/h2>\n<ul>\n<li><a href=\"https:\/\/jamesrohlf.github.io\/outreach\/calculator.html\">Cosmology calculator<\/a> \u2014 distances, ages and the BAO scale at any redshift, with a cosmic timeline you can jump through<\/li>\n<li><a href=\"https:\/\/jamesrohlf.github.io\/outreach\/w0wa.html\">Evolving dark energy calculator<\/a> \u2014 set w<sub>0<\/sub> and w<sub>a<\/sub> and see what the DESI BAO distances allow<\/li>\n<li><a href=\"https:\/\/jamesrohlf.github.io\/outreach\/how-desi-works.html\">How DESI works<\/a> \u2014 the light path from galaxy to CCD, and the focal plane built at BU<\/li>\n<\/ul>\n<h2>The standard model of cosmology<\/h2>\n<ul>\n<li><a href=\"https:\/\/jamesrohlf.github.io\/outreach\/lcdm.html\">\u039bCDM<\/a> \u2014 dark energy and cold dark matter in six parameters, and the cosmic timeline from the Planck era to today<\/li>\n<li><a href=\"https:\/\/jamesrohlf.github.io\/outreach\/cpe.html\">Cosmological parameter estimation<\/a> \u2014 how the six numbers are actually fitted<\/li>\n<li><a href=\"https:\/\/jamesrohlf.github.io\/outreach\/full-shape.html\">Full shape<\/a> \u2014 what the whole galaxy power spectrum adds beyond the BAO peak<\/li>\n<\/ul>\n<h2>What DESI measures<\/h2>\n<ul>\n<li><a href=\"https:\/\/jamesrohlf.github.io\/outreach\/bao.html\">Baryon acoustic oscillations<\/a> \u2014 where the 147 Mpc standard ruler comes from<\/li>\n<li><a href=\"https:\/\/jamesrohlf.github.io\/outreach\/tracers.html\">Tracers<\/a> \u2014 the galaxies, quasars and Lyman-\u03b1 forest that map the volume<\/li>\n<li><a href=\"https:\/\/jamesrohlf.github.io\/outreach\/lyman-alpha.html\">Lyman-\u03b1<\/a> \u2014 using absorption in quasar spectra to reach the highest redshifts<\/li>\n<li><a href=\"https:\/\/jamesrohlf.github.io\/outreach\/results.html\">Results<\/a> \u2014 what DESI adds to the expansion history<\/li>\n<li><a href=\"https:\/\/jamesrohlf.github.io\/outreach\/dr1.html\">Data Release 1<\/a> \u2014 the first thirteen months of observations<\/li>\n<\/ul>\n<h2>Open questions<\/h2>\n<ul>\n<li><a href=\"https:\/\/jamesrohlf.github.io\/outreach\/hubble-tension.html\">The Hubble tension<\/a> \u2014 why the early- and late-time measurements of H\u2080 disagree by about five standard deviations<\/li>\n<li><a href=\"https:\/\/jamesrohlf.github.io\/outreach\/lcdm.html#evolving-dark-energy\">Evolving dark energy<\/a> \u2014 DESI&#8217;s BAO, with the CMB and supernovae, prefers a dark energy density that changes with time<\/li>\n<\/ul>\n<h2>Groups and collaborations<\/h2>\n<ul>\n<li><a href=\"https:\/\/physics.bu.edu\/desi\/\">Boston University DESI group<\/a> \u2014 the group, its people and its publications<\/li>\n<li><a href=\"https:\/\/www.desi.lbl.gov\/\">DESI collaboration<\/a> \u2014 the survey and its data releases<\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"<p>Cosmology pages and tools from Jim Rohlf, Professor of Physics at Boston University and a member of the DESI collaboration \u2014 the model, what DESI measures, and where the model is under strain. Start here Cosmology calculator \u2014 distances, ages and the BAO scale at any redshift, with a cosmic timeline you can jump through [&hellip;]<\/p>\n","protected":false},"author":19334,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":[],"_links":{"self":[{"href":"https:\/\/sites.bu.edu\/desi\/wp-json\/wp\/v2\/pages\/27"}],"collection":[{"href":"https:\/\/sites.bu.edu\/desi\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/sites.bu.edu\/desi\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/sites.bu.edu\/desi\/wp-json\/wp\/v2\/users\/19334"}],"replies":[{"embeddable":true,"href":"https:\/\/sites.bu.edu\/desi\/wp-json\/wp\/v2\/comments?post=27"}],"version-history":[{"count":10,"href":"https:\/\/sites.bu.edu\/desi\/wp-json\/wp\/v2\/pages\/27\/revisions"}],"predecessor-version":[{"id":39,"href":"https:\/\/sites.bu.edu\/desi\/wp-json\/wp\/v2\/pages\/27\/revisions\/39"}],"wp:attachment":[{"href":"https:\/\/sites.bu.edu\/desi\/wp-json\/wp\/v2\/media?parent=27"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}