Peter LeFanu Lumsdaine

Stockholm, Sweden

http://peterlefanulumsdaine.com

Mathematician, math.LO/math.CT, currently postdoc at Stockholm University. Mainly working in categorical logic, especially homotopy type theory and higher categories.

Previously worked at Institute for Advanced Study, Princeton; Dalhousie University, Halifax, Nova Scotia; and Carnegie Mellon University, Pittsburgh.

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Pedagogy: How to cure students of the "law of universal linearity"?

algebra-precalculus education teaching asked Jan 7, 2014 at 16:10

math.stackexchange.com

68 votes

When Frodo offers her the ring, is Galadriel really tempted, or just making a point?

lord-of-the-rings tolkien-legendarium the-one-ring asked Apr 20, 2015 at 10:56

scifi.stackexchange.com

46 votes

Non-examples of model structures, that fail for subtle/surprising reasons?

ct.category-theory at.algebraic-topology model-categories homotopy-theory higher-category-theory asked May 2, 2010 at 18:07

mathoverflow.net

45 votes

Applications of Zorn’s lemma that aren’t chain-complete/directed-complete?

lo.logic axiom-of-choice posets asked Apr 18, 2021 at 14:48

mathoverflow.net

41 votes

Haskell how to hide (exclude) a function from module without explicitly listing all the non hidden functions?

haskell module asked Jun 21, 2013 at 17:55

stackoverflow.com

38 votes

Redundancy in bib file: conditionally suppress url if same as doi?

bibliographies bibtex conditionals urls doi asked Nov 19, 2010 at 23:09

tex.stackexchange.com

29 votes

Abbreviation “n.d.” in citation?

abbreviations citation asked Mar 24, 2011 at 19:51

english.stackexchange.com

27 votes

Align large vertical delimiters (brackets) to rows of a table?

tables brackets delimiters asked Apr 8, 2011 at 1:33

tex.stackexchange.com

24 votes

Suffixes for verbification: -ify, -icise, -ificate

verbs connotation suffixes morphological-domains asked May 24, 2011 at 10:03

english.stackexchange.com

24 votes

Is Lemma D4.5.3 in the Elephant correct? (“In a topos, weakly projective implies internally projective.”)

ct.category-theory topos-theory internalization asked Mar 4, 2016 at 16:02

mathoverflow.net

Top Answers

289

How do you explain to a 5th grader why division by zero is meaningless?

math.stackexchange.com

200

How do I ask for an espresso if there's a good chance they don't know how to make it?

interpersonal.stackexchange.com

124

Is it unethical to take a photograph of my question sheets from a sit-down exam I've just finished if I am not allowed to take them home?

academia.stackexchange.com

111

How to deal with a professor who grades assignments and exams incorrectly

academia.stackexchange.com

My name was omitted from a paper I (mostly) authored - what should I do?

academia.stackexchange.com

What does "Et In Arcadia, Ego" refer to?

scifi.stackexchange.com

Writing a recommendation letter for a student I reported for academic dishonesty

academia.stackexchange.com

Why should we believe in the axiom of regularity?

mathoverflow.net

Has politics always been so polarized?

politics.stackexchange.com

Is it correct to say Person A is the "spitting image" or the "splitting image" of Person B?

english.stackexchange.com

"Paid" vs "payed"

english.stackexchange.com

Are dagger categories truly evil?

mathoverflow.net

Parents attending thesis defense?

academia.stackexchange.com

How to differentiate "imposter syndrome" from actual lack of suitability for grad. school/academia?

academia.stackexchange.com

Why do people say Gödel's sentence is true when it is true in some models but false in others?

mathoverflow.net

Which is correct, "neither is" or "neither are"?

english.stackexchange.com

Interesting examples of vacuous / void entities

mathoverflow.net

Why are matrices ubiquitous but hypermatrices rare?

mathoverflow.net

When your 10-year old boy says “It’s meta,” what does it mean? In what situation and of what sort of object they use this phrase?

english.stackexchange.com

Proofs where higher dimension or cardinality actually enabled much simpler proof?

mathoverflow.net

Should I tell my supervisor that I added his/her name as a reference for my next academic position?

academia.stackexchange.com

Can 'revert' be used as a synonym of 'reply'?

english.stackexchange.com

An interesting problem with "decomposing" natural numbers.

math.stackexchange.com

Is it a good practice to refer to countries, ships etc using the feminine form?

english.stackexchange.com

Is this a junk preamble?

tex.stackexchange.com

Is a vector space naturally isomorphic to its dual?

mathoverflow.net

Differentiate between the numbers from 1 to 5 with one single yes/no question

puzzling.stackexchange.com

Should I give full credit for a correct answer different from the expected one to an exam question?

academia.stackexchange.com

When your main character is a misogynist or a racist, how do you tell your readers that you don't subscribe to his racist views by merely showing?

writing.stackexchange.com

What could Trump hope to gain from a *second* Georgia "recount"?

politics.stackexchange.com