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Vaidotas Zemlys

Attended Vilnius University

Lived in villeneuve d'ascq

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### Vaidotas Zemlys

Shared publicly -**Do hybrid open-access journals double dip?**

That is, do they arrange to be paid twice for the same OA articles, once by reader-side subscriptions and then again by author-side article processing charges? Yes.

From +Bernhard Mittermaier:"The pros and cons of hybrid open access are heavily disputed. A main point of discussion is whether ‘double dipping’ takes place, i.e. paying twice to publish and read the same article. To prove publishers’ assertions that they do not double dip, a survey was conducted of 24 publishers with detailed questions about their pricing policy using concrete examples. The outcome is quite sobering: the results range from partial double dipping to full double dipping, and in no instance did a ‘no double-dipping’ policy mean that no double dipping takes place."

https://juser.fz-juelich.de/record/190180/files/Double%20Dipping.pdf

#oa #openaccess #hybridoa

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### Vaidotas Zemlys

Shared publicly -Piechart at its worst. The blue is for people who died, the yellow is for funerals with priest present.

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### Vaidotas Zemlys

Shared publicly -**An impossible dream**

Kepler, the guy who discovered that planets go in ellipses around the Sun, was in love with geometry. Among other things, he tried to figure out how to tile the plane with regular pentagons (dark blue) and decagons (blue-gray). They fit nicely at a corner... but he couldn't get it to work.

Then he discovered he could do better if he also used 5-pointed stars!

Can you tile the whole plane with these three shapes?

*No!*The picture here is very tempting... but if you continue you quickly run into trouble. It's an impossible dream.

However, Kepler figured out that he could go on forever if he also used

*overlapping*decagons, which he called 'monsters'. Look at this picture he drew:

https://plus.maths.org/issue45/features/kaplan/kepler.gif

If he had worked even harder, he might have found the Penrose tilings, or similar things discovered by Islamic tiling artists. Read the whole story here:

• Craig Kaplan, The trouble with five, https://plus.maths.org/content/trouble-five

How did Kepler fall in love with geometry? He actually started as a theologian. Let me quote the story as told in the wonderful blog

*The Renaissance Mathematicus*:

**Kepler was born into a family that had known better times, his mother was an innkeeper and his father was a mercenary. Under normal circumstances he probably would not have expected to receive much in the way of education but the local feudal ruler was quite advanced in his way and believed in providing financial support for deserving scholars. Kepler whose intelligence was obvious from an early age won scholarships to school and to the University of Tübingen where he had the luck to study under Michael Mästlin one of the very few convinced Copernican in the later part of the 16th century. Having completed his BA Kepler went on to do a master degree in theology as he was a very devote believer and wished to become a theologian. Recognising his mathematical talents and realising that his religious views were dangerously heterodox, they would cause him much trouble later in life, his teacher, Mästlin, decided it would be wiser to send him off to work as a school maths teacher in the Austrian province.**

**Although obeying his superiors and heading off to Graz to teach Protestant school boys the joys of Euclid, Kepler was far from happy as he saw his purpose in life in serving his God and not Urania (the Greek muse of astronomy). After having made the discovery that I will shortly describe Kepler found a compromise between his desire to serve God and his activities in astronomy. In a letter to Mästlin in 1595 he wrote:**

*I am in a hurry to publish, dearest teacher, but not for my benefit… I am devoting my effort so that these things can be published as quickly as possible for the glory of God, who wants to be recognised from the Book of Nature… Just as I pledged myself to God, so my intention remains. I wanted to be a theologian, and for a while I was anguished. But, now see how God is also glorified in astronomy, through my efforts.***So what was the process of thought that led to this conversion from a God glorifying theologian to a God glorifying astronomer and what was the discovery that he was so eager to publish? Kepler’s God was a geometer who had created a rational, mathematical universe who wanted his believers to discover the geometrical rules of construction of that universe and reveal them to his glory. Nothing is the universe was pure chance or without meaning everything that God had created had a purpose and a reason and the function of the scientist was to uncover those reasons. In another letter to Mästlin Kepler asked whether:**

*you have ever heard or read there to be anything, which devised an explanation for the arrangement of the planets? The Creator undertook nothing without reason. Therefore, there will be reason why Saturn should be nearly twice as high as Jupiter, Mars a little more than the Earth, [the Earth a little more] than Venus and Jupiter, moreover, more than three times as high as Mars.***The discovery that Kepler made and which started him on his road to the complete reform of astronomy was the answer to both the question as to the distance between the planets and also why there were exactly six of them: as stated above, everything created by God was done for a purpose.**

**On the 19th July 1595 Kepler was explaining to his students the regular cycle of the conjunctions of Saturn and Jupiter, planetary conjunctions played a central role in astrology. These conjunctions rotating around the ecliptic, the apparent path of the sun around the Earth, created a series of rotating equilateral triangles. Suddenly Kepler realised that the inscribed and circumscribed circles generated by his triangles were in approximately the same ratio as Saturn’s orbit to Jupiter’s. Thinking that he had found a solution to the problem of the distances between the planets he tried out various two-dimensional models without success. On the next day a flash of intuition provided him with the required three-dimensional solution, as he wrote to Mästlin:**

*I give you the proposition in words just as it came to me and at that very moment: “The Earth is the circle which is the measure of all. Construct a dodecahedron round it. The circle surrounding that will be Mars. Round Mars construct a tetrahedron. The circle surrounding that will be Jupiter. Round Jupiter construct a cube. The circle surrounding it will be Saturn. Now construct an icosahedron inside the Earth. The circle inscribed within that will be Venus. Inside Venus inscribe an octahedron. The circle inscribed inside that will be Mercury.”*This model, while approximately true, is now considered completely silly! We no longer think there should be a simple geometrical explanation of why planets in our Solar System have the orbits they do.

So: a genius can have a beautiful idea in a flash of inspiration and it can still be

*wrong*.

But Kepler didn't stop there! He kept working on planetary orbits until he noticed that Mars didn't move in a circle around the Sun. He noticed that it moved in an ellipse! Starting there, he found the correct laws governing planetary motion... which later helped Newton invent classical mechanics.

So it pays to be persistent - but also not get stuck believing your first good idea.

Read

*The Renaissance Mathematicus*here:

https://thonyc.wordpress.com/2010/11/15/kepler%E2%80%99s-divine-geometry/

**Puzzle:**can you tile the plane with shapes, each of which has at least the symmetry group of a regular pentagon?

So, regular pentagons and decagons are allowed, and so are regular 5-pointed stars, and many other things... but not Kepler's monsters. The tiling itself does not need to repeat in a periodic way.

#geometry #astronomy

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galima pažiūrėti ką pats autorius mano https://www.youtube.com/watch?v=th3YMEamzmw

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### Vaidotas Zemlys

Shared publicly -15 years between submission and publication. Surely this is some record.

I'm on the editorial board of Combinatorica. Whether I should be is another matter, since it is a journal owned by Springer, one of the big commercial publishers. But I am, and as a result I have a free subscription to the journal. Today I found the latest issue in my pigeonhole, and the last paper in the issue was a paper by Csaba Tóth, entitled, "The Szemerédi-Trotter theorem in the complex plane."

This paper is remarkable for two reasons. One, which provokes this post, is that at the beginning of the paper it says, "Received December 1999, Revised May 16 2014." So the paper is coming out over 15 years after it was submitted. Doubtless this isn't a record, but it's still a pretty big gap. I noticed it because my first reaction on seeing the title was, "But I thought this had been done a long time ago."

The other reason is the result itself. The Szemerédi-Trotter theorem states that if you have n points and m lines in the plane, then the number of incidences (that is, pairs (P,L) where P is a point in your collection, L is a line in your collection, and P is a point in L) is at most C(n + m + n^{2/3}m^{2/3}). This slightly curious looking bound is best possible up to the constant C and is more natural than it looks.

The known proofs of the theorem relied heavily on the topological properties of the plane, which meant that it was far from straightforward to generalize the result to lines and points in the complex plane (by which I mean C^2 and not C). Indeed, it was an open problem to do so, and that was what Tóth solved.

If you're feeling ambitious, there is also a lovely conjecture in the paper. Define a d-flat in R^{2d} to be an affine subspace of dimension d. Suppose now that you have n points and m d-flats with the property that no two of the d-flats intersect in more than a point. Is it the case that the number of incidences is at most C(n + m + n^{2/3}m^{2/3})? The constant C is allowed to depend on the dimension d but not on anything else. Note that even for d=2 this would be a new result, since Tóth's theorem is the special case where the d-flats are complex lines.

I should say that I haven't checked whether there has been any progress on this conjecture, so I don't guarantee that it is open. If anyone knows about its status, it would be great if you could comment below.

#spnetwork DOI: 10.1007/s00493-014-2686-2

This paper is remarkable for two reasons. One, which provokes this post, is that at the beginning of the paper it says, "Received December 1999, Revised May 16 2014." So the paper is coming out over 15 years after it was submitted. Doubtless this isn't a record, but it's still a pretty big gap. I noticed it because my first reaction on seeing the title was, "But I thought this had been done a long time ago."

The other reason is the result itself. The Szemerédi-Trotter theorem states that if you have n points and m lines in the plane, then the number of incidences (that is, pairs (P,L) where P is a point in your collection, L is a line in your collection, and P is a point in L) is at most C(n + m + n^{2/3}m^{2/3}). This slightly curious looking bound is best possible up to the constant C and is more natural than it looks.

The known proofs of the theorem relied heavily on the topological properties of the plane, which meant that it was far from straightforward to generalize the result to lines and points in the complex plane (by which I mean C^2 and not C). Indeed, it was an open problem to do so, and that was what Tóth solved.

If you're feeling ambitious, there is also a lovely conjecture in the paper. Define a d-flat in R^{2d} to be an affine subspace of dimension d. Suppose now that you have n points and m d-flats with the property that no two of the d-flats intersect in more than a point. Is it the case that the number of incidences is at most C(n + m + n^{2/3}m^{2/3})? The constant C is allowed to depend on the dimension d but not on anything else. Note that even for d=2 this would be a new result, since Tóth's theorem is the special case where the d-flats are complex lines.

I should say that I haven't checked whether there has been any progress on this conjecture, so I don't guarantee that it is open. If anyone knows about its status, it would be great if you could comment below.

#spnetwork DOI: 10.1007/s00493-014-2686-2

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### Vaidotas Zemlys

Shared publicly -Help Timothy Gowers with this important query :)

If you Google Pietro Boselli you find him described as the hottest mathematician in the world, a title he qualifies for by being a fashion model and a lecturer at UCL at the same time. However, it turns out that he is not quite a mathematician in the sense I would understand it: his PhD is in engineering and his maths lectures are not, I think, to mathematics students. So has anyone ever been both a fashion model (I would allow former fashion model here) and the author of a paper published in a reputable mathematical journal? I couldn't find anything by Boselli on arXiv.

Twenty-six-year-old maths lecturer and PhD student Pietro Boselli describes himself as 'nerdy', but the internet would beg to differ.

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1,960 people

### Vaidotas Zemlys

Shared publicly -Nice!

#sausagebot1

Taip jau kartais nutinka, kad darbe savaitėlę hackinam ką norim. Šiemet polėkis nunešė padaryt, ką nors labiau pačiupinėjamo, nei programinis kodas.

Problema šį kartą pati pasitaikė po ranka: kartais Apple įrenginiai "išprotėja" ir nebepasitiki kompiuteriu prie kurio pajungti. Maždaug taip: https://support.apple.com/library/content/dam/edam/applecare/images/en_US/iphone/iphone5s/trust_this_computer.png. Jei taip nutinka automatinio testavimo fermoje, reikia siųsti žmogų į misiją, užgesintį šią lentelę. Nepatogu...

Sprendimas 1: imti Arduino, prijungti žingsninį variklį, prie jo primontuoti tapšnokliams skirtą lazdelę (stilių). Deja, paaiškėjo, kad tos lazdelės veikia tik laikomos rankoje (kurią išnaudoją kaip elektrinę talpą).

Sprendimas 2: padėti monetą ant iPad'o ekrano ir per kondensatorių įžeminti į korpusą, sprendimas dalinai veikė, bet neturėjom priemonių jį automatizuoti (nutraukti bei vėl sujungti grandinę per Arduino)

Tada teko improvizuoti ir taip atsirado sprendimas 3: kaip liečiamąjį elementą panaudoti dešrelę, tik ją dar papildomai teko įžeminti per korpusą ir visą tai primontuoti prie mechanizmo aptarto sprendime 1.

Prikabinu vaizdo įrodymus, kad botas veikia :)

Taip jau kartais nutinka, kad darbe savaitėlę hackinam ką norim. Šiemet polėkis nunešė padaryt, ką nors labiau pačiupinėjamo, nei programinis kodas.

Problema šį kartą pati pasitaikė po ranka: kartais Apple įrenginiai "išprotėja" ir nebepasitiki kompiuteriu prie kurio pajungti. Maždaug taip: https://support.apple.com/library/content/dam/edam/applecare/images/en_US/iphone/iphone5s/trust_this_computer.png. Jei taip nutinka automatinio testavimo fermoje, reikia siųsti žmogų į misiją, užgesintį šią lentelę. Nepatogu...

Sprendimas 1: imti Arduino, prijungti žingsninį variklį, prie jo primontuoti tapšnokliams skirtą lazdelę (stilių). Deja, paaiškėjo, kad tos lazdelės veikia tik laikomos rankoje (kurią išnaudoją kaip elektrinę talpą).

Sprendimas 2: padėti monetą ant iPad'o ekrano ir per kondensatorių įžeminti į korpusą, sprendimas dalinai veikė, bet neturėjom priemonių jį automatizuoti (nutraukti bei vėl sujungti grandinę per Arduino)

Tada teko improvizuoti ir taip atsirado sprendimas 3: kaip liečiamąjį elementą panaudoti dešrelę, tik ją dar papildomai teko įžeminti per korpusą ir visą tai primontuoti prie mechanizmo aptarto sprendime 1.

Prikabinu vaizdo įrodymus, kad botas veikia :)

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Mantas Puida

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Nereiktų per daug rimtai vertinti :) Tiesiog įžeminta lazdelė neveikė, per kondensatorių irgi ne, bet greičiausiai neteisinga talpa buvo, viskas iš to, kad buvo nedidelis komponentų pasirinkimas po ranka.

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### Vaidotas Zemlys

Shared publicly -After one successful round, the game was disabled :)

The best game on the iPhone ;)

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### Vaidotas Zemlys

Shared publicly -Įdomu Lietuvoje kokių nors sąsajų su geologija būtų ar ne? Spėju labiau su vežimu į Sibirą, bet čia wild guess.

How geology affects politics. I've also seen a similar map of the American South with polling stations giving majorities for Obama reflecting the areas that had higher concentrations of plantations in the past--basically due to soil type distrubution.

#ge2015

#ge2015

@VaughanRoderick Yn bendant. A dylai'r wobr bod These Poor Hands, gan B.L. Coombes. Pristine first edition wrth gwrs. Bruce Roberts. 14h14 hours ago. Bruce Roberts @WxmBruce. @VaughanRoderick We need to start looking for coal in London. Branwen Llewellyn ...

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Londone kasyklų nebuvo. Bet yra metro :)

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### Vaidotas Zemlys

Shared publicly -Morphisms in action :)

New project with +Keenan Crane: A topologist can't tell the difference between a coffee mug and a doughnut/donut.

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### Vaidotas Zemlys

Shared publicly -Ką čia bepridursi. Jėga.

Atviro Vilniaus prisistatymas, pietų pertraukai :)

Vilniaus miesto mero patarėjas IT ir atvirų duomenų klausimais: Nieko nėra blogiau už sugaištą valandą susitikimui, kuris turėjo būti el. laiškas.

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In his circles

1,960 people

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Econometrician

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Previously

villeneuve d'ascq - vilnius - klaipėda - girionys

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10k reputation in http://stats.stackexchange.com. Not much to brag about :)

Education

- Vilnius UniversityB. Sc in applied mathematics, 1998 - 2002
- Vilnius UniversityM. Sc in mathematics, 2002 - 2004
- Université des Sciences et Technologies de LillePh. D in applied mathematics, 2005 - 2008

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