## January 12, 2021

### This Week’s Finds (1–50)

#### Posted by John Baez

Take a copy of this!

This Week’s Finds in Mathematical Physics (1-50), 242 pages.

These are the first 50 issues of This Week’s Finds of Mathematical Physics. This series has sometimes been called the world’s first blog, though it was originally posted on a “usenet newsgroup” called sci.physics.research — a form of communication that predated the world-wide web. I began writing this series as a way to talk about papers I was reading and writing, and in the first 50 issues I stuck closely to this format. These issues focus rather tightly on quantum gravity, topological quantum field theory, knot theory, and applications of n-categories to these subjects. There are, however, digressions into elliptic curves, Lie algebras, linear logic and various other topics.

Tim Hosgood kindly typeset all 300 issues of This Week’s Finds in 2020. They will be released in six installments of 50 issues each, for a total of about 2610 pages. I have edited the issues here to make the style a bit more uniform and also to change some references to preprints, technical reports, etc. into more useful arXiv links. This accounts for some anachronisms where I discuss a paper that only appeared on the arXiv later.

The process of editing could have gone on much longer; there are undoubtedly many mistakes remaining. If you find some, please contact me and I will try to fix them.

By the way, sci.physics.research is still alive and well, and you can use it on Google. But I can’t find the first issue of This Week’s Finds there — if you can find it, I’ll be grateful. I can only get back to the sixth issue. Take a look if you’re curious about usenet newsgroups! They were low-tech compared to what we have now, but they felt futuristic at the time, and we had some good conversations.

Posted at January 12, 2021 5:13 PM UTC

TrackBack URL for this Entry:   https://golem.ph.utexas.edu/cgi-bin/MT-3.0/dxy-tb.fcgi/3286

### Re: This Week’s Finds (1–50)

Your energy is as amazing as your talent as an expositor. Thank you for all you have written over so many years.

Posted by: Dan F. on January 12, 2021 8:30 PM | Permalink | Reply to this

### Re: This Week’s Finds (1–50)

Thanks very much! I hope my energy continues to be amazing, since I still have 2400 pages of This Week’s Finds to edit. Why did I write so much?

Posted by: John Baez on January 12, 2021 8:35 PM | Permalink | Reply to this

### Re: This Week’s Finds (1–50)

The earliest mention of ‘baez’ in 1993 that I could find is this “informational” posting from the 19th Feb.

This search returns everything before and up to TWF#6, and there doesn’t seem to be any posts at all kept from before the 18th February 1993. It’s possible it got lost!

Posted by: David Roberts on January 13, 2021 10:58 AM | Permalink | Reply to this

### Re: This Week’s Finds (1–50)

Thanks for checking! Maybe I started posting them on sci.physics before sci.physics.research was created.

Posted by: John Baez on January 13, 2021 6:57 PM | Permalink | Reply to this

### Re: This Week’s Finds (1–50)

If you did, they are not listed here (that’s apparently everything you posted in January 1993 to sci.physics.research).

Aha, here’s Week 3, in sci.math

Posted by: David Roberts on January 14, 2021 2:01 AM | Permalink | Reply to this

### Re: This Week’s Finds (1–50)

Additional searching on sci.math and globally turned up nothing older than Week 3. The number of search results changes when simple parameters like the sorting of search results (relevance vs date), so it seems the searching algorithm is really badly behaved. And only certain search parameters even find Week 3, when it looks like all of the ones I tried should find it.

Here is Week 3 in sci.physics, though, for what it’s worth.

Posted by: David Roberts on January 14, 2021 2:32 AM | Permalink | Reply to this

### Re: This Week’s Finds (1–50)

Back in the 1990s, I thought it was a good idea to print out lots of issues of TWF. I have a ring-binder full of them.

(Click for hi-res.) I certainly wasn’t reading in 1993, though.

Posted by: Tom Leinster on January 13, 2021 4:34 PM | Permalink | Reply to this

### Re: This Week’s Finds (1–50)

That’s great, Tom!

Scott and others will be glad to know that in editing the LaTeX version of This Week’s Finds I removed all the email addresses I saw. 1993 was a different age. There was no arXiv except for physics. At the time, it seemed perfectly reasonable to publish a mathematician’s email address so people could contact them for electronic preprints. I apologize for all the spam Scott has received in subsequent years.

In “week46”, written in December 1994, I chart the rise of the arXiv up to that point:

• High Energy Physics — Theory (hep-th), started 8/91

• High Energy Physics — Lattice (hep-lat), started 2/92

• High Energy Physics — Phenomenology (hep-ph), started 3/92

• Astrophysics (astro-ph), started 4/92

• Condensed Matter Theory (cond-mat), started 4/92

• General Relativity & Quantum Cosmology (gr-qc), started 7/92

• Nuclear Theory (nucl-th), started 10/92

• Chemical Physics (chem-ph), started 3/94

• High Energy Physics — Experiment (hep-ex), started 4/94

• Accelerator Physics (acc-phys), started 11/94

• Nuclear Experiment (nucl-ex), started 11/94

• Materials Theory (mtrl-th), started 11/94

• Superconductivity (supr-con), started 11/94

I also describe the brand new American Mathematical Society preprint server, which never caught on.

Later I announced the mathematics arXiv.

Posted by: John Baez on January 13, 2021 6:54 PM | Permalink | Reply to this

### Re: This Week’s Finds (1–50)

Very minor item: In week 6 (p. 29), the paragraph beginning “Quantizing gravity is mighty hard” has some inline math that isn’t in math mode ($\exp(-i H t)$, $t$, $H$).

Posted by: Blake Stacey on January 14, 2021 4:48 AM | Permalink | Reply to this

### Re: This Week’s Finds (1–50)

Thanks! I fixed it in my own files. Every so often I’ll release an improved version. But not very often. First I want to edit the remaining issues and put them on the arXiv.

It would be great if someone good at computers could automatically create a version with an index, or at least some sort of index of papers discussed. But I don’t have the energy to do that myself, at least not now. Besides TWFs, I want to write some books based on courses I’ve taught, starting with one on Lagrangian mechanics and one on category theory.

Posted by: John Baez on January 15, 2021 8:47 PM | Permalink | Reply to this

### Re: This Week’s Finds (1–50)

stupid question: re Lagrangian mechanics, what’s wrong with Goldstein and Marion?

Posted by: Keith Harbaugh on January 27, 2021 12:15 AM | Permalink | Reply to this

### Re: This Week’s Finds (1–50)

Nothing’s exactly “wrong” with Goldstein and Marion, but there’s a lot they don’t do. For example, they don’t describe Lagrangian mechanics using modern differential geometry, so they’re not in a good position to explain applications to particles moving on general curved spacetimes and other examples that are best formulated in this language. They don’t explain the history of the principle of least action, or its connection to other minimum principles. Also, they talk about a lot of other things! So there’s room, I think, for a book on Lagrangian mechanics that focuses on this subject and digs deeper into some aspects using more math.

Posted by: John Baez on January 27, 2021 6:50 AM | Permalink | Reply to this

### Re: This Week’s Finds (1–50)

Thanks for the information!

Posted by: Keith Harbaugh on January 27, 2021 8:38 AM | Permalink | Reply to this

### Re: This Week’s Finds (1–50)

On page 6 of the classical mechanics notes:

it wants to spend a lot much time near the top of its trajectory

Posted by: Blake Stacey on January 29, 2021 2:45 PM | Permalink | Reply to this

### Re: This Week’s Finds (1–50)

Thanks! I’m going to be teaching a course based on that book starting in April, and I want to use that to keep working on that book. Unfortunately my TeX installation doesn’t succeed in processing some of the figures in the book so my last pile of changes are not visible in the version that also has all the pictures, and I don’t even remember which version I decided to make available to the world at that link.

Posted by: John Baez on January 29, 2021 3:48 PM | Permalink | Reply to this

### Re: This Week’s Finds (1–50)

On the course notes page, that was the newer version (fewer typos but worse pictures).

Posted by: Blake Stacey on January 29, 2021 6:34 PM | Permalink | Reply to this

### Re: This Week’s Finds (1–50)

More minor glitches in week 40:

• quotation marks around “computer science”
• Journal of Philosophical Logic should be italicized
• use it up should be italicized instead of asterisked
• spacing and quotation marks around “at once”
• “by available at” in reference 2
• URL in reference 3 runs off the page
Posted by: Blake Stacey on January 16, 2021 5:52 PM | Permalink | Reply to this

### Re: This Week’s Finds (1–50)

Fixed, thanks! I’ll update the copy on my website more often than the arXiv version, and your changes so far are there.

In “week40” I also changed “premiss” to “premise”, since I’m not really trying to pretend to be British.

Posted by: John Baez on January 16, 2021 6:21 PM | Permalink | Reply to this

### Re: This Week’s Finds (1–50)

One more! In week 35 (p. 176), there’s a parenthetical

(See “tangles”.)

that looks like it should point somewhere but doesn’t. It’s also a nonlink in the website version of TWF35. Looking back at the Usenet version, maybe the target was intended to be an older version of this page?

Posted by: Blake Stacey on January 18, 2021 12:31 AM | Permalink | Reply to this

### Re: This Week’s Finds (1–50)

Yes, I must have been linking to that page. But I think I’ll just get rid of the link (except on my website, where I’ll fix it).

In the process I caught some more mistakes. There’s an endless number!

Posted by: John Baez on January 18, 2021 2:00 AM | Permalink | Reply to this

### Re: This Week’s Finds (1–50)

In week 37, top of page 186:

in the Bargmann [representation] multiplication

Punctuation of jointly-authored things is inconsistent in Week 38. It has “Ponzano-Regge” (hyphen) as well as “Turaev–Viro” (en dash) and “Turaev/Viro”.

In week 39 (p. 193), I think “DeRham cohomology” should be “de Rham cohomology”.

On p. 194, a preprint by Lisa C. Jeffrey is listed as “available from Princeton U. Mathematics Department”; it has coordinates arXiv:alg-geom/9404012.

In week 40, page 195, there’s an unbalanced quotation:

“computer science’

Week 43, page 213: “Bohm-Aharonov” should be “Bohm–Aharonov” to match convention (and the use earlier in the paragraph). Likewise, in week 44 (page 216), “Stiefel-Whitney” should be “Stiefel–Whitney”.

Week 48, page 233: For consistency with the paper title, the “$r$” in “$r$-matrices” should be in math mode.

Week 50, page 239: “Journal of Mathematical Physics” should be italicized. Page 240: “rotational symmetry [and] hence angular momentum”; the following sentence obeys conservation of apostrophes but needs a little rearrangement.

Posted by: Blake Stacey on January 24, 2021 6:49 PM | Permalink | Reply to this

### Re: This Week’s Finds (1–50)

Thanks, Blake — that’s a nice lot of corrections.

I’ve been trying to change hyphens to en dashes in joint-authored concepts but I hadn’t caught all of them: now Ponzano–Regge, Bohm–Aharonov and Stiefel–Whitney are correct. The first appearance of the barbaric “Turaev/Viro” was in the abstract of someone else’s paper, but I’ve decided to use my authorial power and change even that one to “Turaev–Viro”.

I’ve always been a bit fuzzy about the correct spelling of “de Rham”, but you’re right. While I was at it, I also changed “Cech” to “Čech” and “Kaehler” to “Kähler”. I’d earlier fixed “Schrödinger” and “Gödel”.

It’s fun to reread these articles and see how much of the math I remember. The newly fixed version is here:

Posted by: John Baez on January 24, 2021 8:13 PM | Permalink | Reply to this

### Re: This Week’s Finds (1–50)

Here’s what I’ve got for the first 100 pages.

Week 1, page 4: two instances where a period and parenthesis should be exchanged since the parenthetical is part of the sentence, “time.)” and “UCR.)” Also, “Proc. Symp. in Pure Math.” should be italicized.

Week 4, pages 20–21:

(For a brief intro to functors and natural transformations, try the file “categories” in the collection of my expository papers — see the end of this post.)

Since the part at the end of the post has been deleted, perhaps this parenthetical should be too.

Week 5, page 24:

A whole book on 22 matrices??

Page 25: extra space in “finite- dimensional”.

Week 7, page 37: “r direction” should be “$r$ direction”.

Week 8, page 41: “Temperley Lieb” should be “Temperley–Lieb” (it’s in a quoted talk title, but now we’ve precedent for changing quotes). Space missing before publisher name in reference 2. “Journal of knot theory and its ramifications” should be italicized instead of quoted. Article titles should be quoted in reference 3.

Page 42: “require the consideration” should be “requiring the consideration”.

Page 43: “which can be obtained in a manner described at the end of this post” is obsolete.

Page 44: citation to Temperley and Lieb is formatted differently from the standard.

Week 9, page 45: “Mobius” should have an umlaut.

Week 10, page 51: “Discover” should be italicized, and the two book titles should be italicized instead of quoted.

Week 11, page 56: “Arnowitt-Deser-Misner” should be “Arnowitt–Deser–Misner”.

Week 12, page 59: “cf” should have a period.

Page 60: “Capovilla-Dell-Jacobson” should be “Capovilla–Dell–Jacobson”.

Week 14, page 68: “Wheeler-DeWitt” should be “Wheeler–DeWitt” (twice).

Week 15, page 74: “a vector field A” should be “a vector field $A$”.

Week 16, page 80: “dissasemble” should be “disassemble”.

Page 84: “Arnowitt-Deser-Misner” should be “Arnowitt–Deser–Misner”.

Page 86: “Capovilla-Dell-Jacobson” should be “Capovilla–Dell–Jacobson”.

Week 18, page 91: extra space after “Smolin”.

Week 19, page 96: “Week 5” is not hyperlinked.

Week 20, page 99: “ones lawn” should be “one’s lawn”.

Posted by: Blake Stacey on January 24, 2021 10:01 PM | Permalink | Reply to this

### Re: This Week’s Finds (1–50)

Wow — thanks, Blake! I’ll make these changes later, but you will then be thanked in the preface!

Posted by: John Baez on January 24, 2021 10:16 PM | Permalink | Reply to this

### Re: This Week’s Finds (1–50)

One more batch! Now I can say that I have indeed gone through the entire document for typographical glitches at least. I’m very glad to help make the experience of reading TWF a little smoother.

Week 21, page 108: The book title “Knots and Physics” should be italicized instead of quoted. “Moebius” should get the umlaut treatment.

Page 111: space needed after “Mathematicians use the term”, and the quotation mark should be reversed. “Moebius” again.

Week 22, page 112: “Proceedings of the London Mathematical Society” should be italicized. Reference 3 is in an atypical format.

Week 24, page 124: space missing after “Thompson,”

Page 125: quotation mark before “what came before the big bang” has incorrect orientation and is unclosed.

Week 25, page 126: extraneous character in “Birkhauser” (maybe a corrupted a-with-umlaut?).

Pages 128 and 129: “Kac-Moody” should be “Kac–Moody”

Week 27, page 137: extraneous character in “Birkhauser” again.

Page 139: “Einstein-Podolsky-Rosen” should be “Einstein–Podolsky–Rosen”.

Week 28, page 148: missing quotation mark after “Kähler metric”; missing space and quotation mark in wrong orientation before “geodesic length functions”.

Week 29, page 150: extra comma in second item of reference list 1. Missing period after “eds” in third item. Extraneous space in “higher- dimensional”.

Week 30, page 153: “Wheeler-DeWitt” should be “Wheeler–DeWitt” (this is another that probably merits a global search for any instances that I’ve missed).

Week 34, page 172: “Ashtekar-Sen” should be “Ashtekar–Sen”.

Posted by: Blake Stacey on January 25, 2021 1:37 AM | Permalink | Reply to this

### Re: This Week’s Finds (1–50)

Thanks yet again! The new version is on my website!

An annoying feature of LaTeX installations with “smart quotes” is that when you type Birkh"auser, it converts the double quote into two separate single quotes, which creates an error.

Posted by: John Baez on January 25, 2021 5:56 AM | Permalink | Reply to this

### Re: This Weeks Finds (150)

Great to see these again. I can’t remember when I first tuned in.

I didn’t even have my own email address until around 1996, having used a colleague’s when necessary.

Posted by: David Corfield on January 15, 2021 10:49 AM | Permalink | Reply to this

### Re: This Weeks Finds (150)

It’s amazing how much communication methods have changed during the last 30 years or so. The future of communications seemed so rosy back then, before we thought hard about spam, cyber-warfare, propaganda, and the echo chamber effect.

Posted by: John Baez on January 15, 2021 8:49 PM | Permalink | Reply to this

### Re: This Week’s Finds (1–50)

thanks a lot for making the Finds available - they bring back nice memories of spr and Usenet in general (and the regret that this great medium didn’t really survive - even though IMHO nothing better came after). I glad to take this opportunity to say thanks for your time and effort to spread knowledge - I enjoyed following TWFs (and other threads - photons, schmotons come to mind) back then as a physics student (though most were over my head). I was then (and remain) impressed by your erudite, eloquent and extensive explanations - and seeing TWFs in toto reinforces that.

I noticed a few minor typos (in quotes, but I don’t suppose they’re there on purpose):

Week 27, p141: “even if the sates is” and “the vluae of a field”.

p143: “therefor”; “much to complicated”; “which sit eh one exploited”

Posted by: Geza on January 19, 2021 9:50 AM | Permalink | Reply to this

### Re: This Week’s Finds (1–50)

Thanks! Yes, reading This Week’s Finds reminds me, too, of a happy bygone age. By the way, Michael Weiss, who coauthored the Photons, Schmotons thread, has recently been explaining nonstandard models of arithmetic to me in a similar long series of dialogues! So not everything from that bygone age is gone.

Thanks for the corrections. I have trouble believing I wrote “vluae” for “value”, but there it is. Now it’s fixed, I hope.

Posted by: John Baez on January 19, 2021 8:26 PM | Permalink | Reply to this

Post a New Comment