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Posts by Jan-Magnus Økland

4 months ago 0 0 0 0
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Unknotting number is not additive under connected sum We give the first examples of a pair of knots $K_1$,$K_2$ in the 3-sphere for which their unknotting numbers satisfy $u(K_1\#K_2)<u(K_1)+u(K_2)$ . This answers question 1.69(B) from Kirby's problem li...
7 months ago 1 0 0 0

Master’s in Bergen and outside algebraic geometry, there’s also a Vienna lineage (Friehsach, Mühlwenzel, Petzval…Hurewicz…)-Per Hag. Kari Hag has a new progenitor as well (Pollard)

7 months ago 0 0 0 0

Mathematicians outside algebraic geometry, but still tied to Bergen’s pure mathematics, lead to lineages (Ørsted-…Lie…Thue)-Skolem/Ljunggren-Selmer. Tverberg(-Holmsen), (Fok…)-Markina, (Leibniz…Chebyshev…)-Vasiljev, (Leibniz-…Jacobi…)-Munthe-Kaas, Dundas, Brun, Schlichtkrull

7 months ago 0 0 1 0

Dan Laksov’s getting a master’s in Bergen and becoming a professor elsewhere doesn’t add a progenitor. Ranestad may have moved to Oslo before the master’s. Holme’s offspring Ådlandsvik/Dale have citations but didn’t carry on with algebraic geometry that I know

7 months ago 0 0 1 0

Lineages with a (maybe associate) professor in Bergen at some time, having published in algebraic geometry: (Paoli-…Castelnuovo…-Hironaka)-Holme-Vatne, (60s Paris-Laudal)-Strømme-Fløystad, (Euler/Leibniz-…Chasles…-Peskine)-Johnsen-Knutsen (Euler/Leibniz-…Gauss…-Pareschi)-Tirabassi.

7 months ago 0 0 1 0

Dan Laksov came back to Bergen from time to time, while his mother lived and when he got his honorary doctorate. He would say stuff like how he admired the not much older Helge Tverberg while doing his master’s there. The thesis was called «Lineær rekursjon», so maybe Dan also had Selmer as advisor?

7 months ago 1 0 0 0

«but more importantly because we shall give a more up-to-date version below. From the following presentation of quadrics on the one hand and the correlations and collineations on the other, it will become apparent that the two theories are completely analogous.»

7 months ago 1 0 0 0

«41. D. Laksov, Notes on the evolution of complete correlations, Enumerative and Classical Algebraic Geometry (Proc., Nice, 1981), Progress in Math., vol. 24, Birkhäuser, 1982,
pp. 107-132.»

7 months ago 0 0 1 0
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«We shall not at this point enter into the definitions and properties of correlative figures, partly because we have given elsewhere [41] a geometric description of correlations and collineations similar to that given for conics above,»

7 months ago 0 0 1 0

Apropos of

7 months ago 0 0 1 0

«The theory was extended to dimension three and partly four by Hirst (32, 36], and by Visalli (63, 65). Again, mainly through works of Schubert (49, 51], G. de Prete (20], and G. Z. Giambelli [27), the theory was extended to higher dimensions.»

7 months ago 0 0 1 0

From Laksov87: «About ten years after Chasles introduced the two characteristic numbers for systems of conics and gave the formulas (1) for the degenerate conics, T. A. Hirst (31, 33-35] observed that a similar theory could be built up around correlative plane figures.»

7 months ago 0 0 1 0

Intrigued by «the variety of completed quadrics, which plays for the Iarrobino scheme a role similar to that played by the Grassmannian for the Quot scheme» Particularly like the citing of Dan Laksov; Completed quadrics and linear maps. Interesting times, learned about Tevelev degrees just last week

7 months ago 1 0 1 0

Anything to the news coming out of Japan of artificial blood in trial?

10 months ago 0 0 0 0
The long view
The long view YouTube video by Logic, Philosophy and Gödel

Colin McLarty on the long view youtu.be/nNtCv25kQIU

10 months ago 0 0 0 0
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The tangent cone method: y-x^2=0 around (x,y)=(t,t^2) is (expand y+t^2-(x+t)^2): (y-t^2)-(x-t)^2-2t(x-t)=0 and take linear terms in x,y: (y-t^2)-2t(x-t)=0, so the slope is 2t at x=t. Works when we can parametrize an algebraic curve.

11 months ago 1 0 0 0
Video

Holy moly this is fun: gofigure.impara.ai #MathSky

1 year ago 20 5 3 0

«But I have a way to go. People excite me, they turn me on. A new person can trigger things in you that you didn't even know you had. If it's musical that's even better. The unknown turns me on.»

1 year ago 0 0 0 0

More Björk: «I want to work on my character. I think it's in there, a good person. I don't believe in just doing good things, I want to feed my demon as well. One should learn to live both the demon and the angel, you know?»

1 year ago 0 0 1 0
Bjork TV
Bjork TV YouTube video by G4jima
1 year ago 0 0 0 0
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Torricelli’s trumpet is not counterintuitive There is nothing counterintuitive about an infinite shape with finite volume, contrary to the common propaganda version of the calculus trope known as Torricelli’s trumpet. Nor was this result seen as...

ICYMI there's a new episode of @viktorblasjo.bsky.social's podcast out this week, first new episode in over a year. A fun listen as always

1 year ago 8 3 0 0

Takk for det gamle! (Thank you for the year that was, and remember 2025=(20+25)^2=(0+1+2+3+4+5+6+7+8+9)^2=0^3+1^3+2^3+3^3+4^3+5^3+6^3+7^3+8^3+9^3)

1 year ago 0 0 0 0
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The observations en.wikipedia.org/wiki/Giusepp... and the observations used www.actuaries.digital/wp-content/u...

1 year ago 2 0 0 0

#Introduction. I'm a programmer at BCEPS (Bergen Center for Ethics and Priority Setting in health), where we develop FairChoices; a decision support tool for national priority setting processes. Math interests: projective duality, rational curves (think conics) and enumerative geometry.

1 year ago 1 0 0 0