Talk:Farkas' lemma

spelling question
In English, words ending in S do not take 'S as a suffix, but just '. Shouldn't this therefore be Farkas' lemma? Encyclops 03:28, 16 January 2006 (UTC)


 * According to Apostrophe (mark), English is not that simple. -- Jitse Niesen (talk) 08:32, 16 January 2006 (UTC)


 * Words that should have an apostrophe with no s are plural, eg the cat's feet. Plenty of words end in an s and still have 's when posessing something, eg the double bass's strings. This definitely should be Farkas's lemma, but I'm not going to change it because it'll just be reverted. Loads of papers use the (wrong) Farkas' lemma, so what's the point in fighting it. --RatnimSnave (talk) 11:35, 2 February 2012 (UTC)


 * A comment to "Loads of papers use the (wrong) Farkas' lemma": In German, "Farkas' Lemma" is correct.  Lots of authors are native German speakers: they just carry their notation from German to English without being aware of the fact that English rules for apostrophes might be different.
 * Actually in German there is no apostrophe to indicate the possessive (genitive case). So it would be "Farkas Lemma" or Farkassche Lemma". Both sound awkward in modern German, so the German article is at "Lemma von Farkas" for a reason. Lots of German native speakers do use incorrect (English) apostrophes in German though...86.183.163.41 (talk) 11:55, 13 May 2021 (UTC)

From Strunk and White's _Elements of Style_, a broadly accepted reference: "Rule #1: Form the possessive singular of nouns by adding 's. Follow this rule whatever the final consonant." One of the examples they give, "Burns's poems", is especially apropos here. Strunk and White give as exceptions biblical characters, similar to the ones described as exceptions in the above-linked wikipage on the Apostrophe. That page provides several sources on grammar (and even a Supreme Court majority!) that advise the use of 's in all cases, and only offer out-of-date sources or authors who just don't like it as support for the omission of the 's. Farkas was not a character in the Bible, so it seems there's just no support for "Farkas' lemma" (Or Bayes' theorem, btw). B k (talk) 04:12, 31 December 2016 (UTC)

To comment more, the s in the Hungarian name Farkas is pronounced as sh (like shell in English, and not like snake). Not writing it as Farkas's is just plain weird to a native Hungarian speaker, as it does not correspond to the three-syllable pronunciation "far-kash-is" BarroColorado (talk) 20:24, 22 March 2018 (UTC)

Currently the page is inconsistent on the spelling. In 13 places (including the title) it is "Farkas' lemma" --incorrect English. In one place it is "the Farkas' lemma" --incorrect English. In another place it is "Farkas's lemma" --correct English. Also correct would be "the Farkas lemma". I'd suggest someone rename the page to either "The Farkas lemma" or "Farkas's lemma" and make all uses agree. Theodore.norvell (talk) 14:29, 16 April 2018 (UTC)

It is Farkas's just like in Bridget Jones's Diary. However, Fowler noted that certain names, e.g. that of Jezus, traditionally take the apostrophe only. Nobody says: In Jezus's name. Thus, if custom and convention deems that Farkas is in this special category, then apparently this is a thing that can be condoned in English. Fowler gave a few non-Biblical examples as well, but I cannot remember them. In any event, the argument that Farkas is not in de Bible and thus is denied special treatment is untenable. Just think of the Mormon perspective on this, as they have one whole extra testament.2A01:CB0C:CD:D800:75C2:298D:BE50:ABCA (talk) 14:38, 28 February 2020 (UTC)

Hahn-Banach theorem
Somebody in the know should check whether this quotation from the book "Polytopes, Rings, and K-Theory" by Winfried Bruns and Joseph Gubeladze (Springer, isbn 978-0-387-76355-2) is applicable for the Farkas' Lemma this article discusses:

"Separation theorems like 1.32 often appear as Farkas' lemma (see Ziegler). A far reaching generalization is the Hahn-Banach separation theorem."

The quote appears on page 21 of Bruns-Gubeladze, and i think that would be very reasonable to mention the relationship between Farkas and Hahn-Banach, as Hahn-Banach is a very important theorem in real analysis (and virtually everybody getting an advanced degree in mathematics has to make peace with it at some point or other).

Son of eugene (talk) 03:40, 17 February 2012 (UTC)

Denote the convex cone ...
Denote the convex cone generated by the columns of A \mathbf {A} by C ( A ) = { A x ∣ x ≥ 0 } {\displaystyle C(\mathbf {A} )=\{\mathbf {A} \mathbf {x} \mid \mathbf {x} \geq 0\}}. Then C ( A ) {\displaystyle C(\mathbf {A} )} is a closed convex cone. The vector x \mathbf {x} proves that b \mathbf {b} lies in C ( A ) {\displaystyle C(\mathbf {A} )}, while the vector y \mathbf {y} gives a linear functional that separates b \mathbf {b} from C ( A ) {\displaystyle C(\mathbf {A} )}.

"The vector proves that" is gibberish. Did someone forget to write "the existence of" ? In any event, this paragraph needs to be edited for sense. 2A01:CB0C:CD:D800:7CED:723B:4A24:EF24 (talk) 16:44, 5 June 2020 (UTC)

Gordan's theorem
Last paragraph discusses Gordan's theorem, but the link leads to Gordan's lemma. As far as I understand, this is a mistake? Those are two different statements (though belonging to the same topic more or less). Nikita Medved (talk) 15:18, 10 September 2021 (UTC)