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Who Is Alexander Grothendieck? (2008) [pdf]

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Re: Who Is Alexander Grothendieck? (2008) [pdf]

#11
Grothendieck's work is, for me, a rather perfect example of what's happened in the 20th century to mathematics, where the boundaries of knowledge have been pushed so hard and so far that there is almost no hope for anyone to even begin to understand the substance of the work outside a very tiny circle of people who pretty much dedicated life to that arcane corner of the field.

I really wish vulgarization was an actual scientific disciple rather than being done in an ad-hoc fashion by people who happen to be good at it.

I also really wish I could read a vulgarized summary of Grothendieck's body of work, and specifically:

    . why everyone is so excited about the work
    . what potential practical application do (or will) exist.

Re: Who Is Alexander Grothendieck? (2008) [pdf]

#12

Grothendieck's work is, for me, a rather perfect example of what's happened in the 20th century to mathematics, where the boundaries of knowledge have been pushed so hard and so far that there is almost no hope for anyone to even begin to understand the substance of the work outside a very tiny circle of people who pretty much dedicated life to that arcane corner of the field. I really wish vulgarization was an actua…

As another commenter mentioned, currently Ravi Vakil is teaching a course in modern algbraic geometry.

The course is largely based on Vakil's book in progress, which he titled The Rising Sea, after a quote from Grothendieck:

> I can illustrate the ... approach with the ... image of a nut to be opened. The first analogy that came to my mind is of immersing the nut in some softening liquid, and why not simply water? From time to time you rub so the liquid penetrates better, and otherwise you let time pass. The shell becomes more flexible through weeks and months — when the time is ripe, hand pressure is enough, the shell opens like a perfectly ripened avocado! . . .

> A different image came to me a few weeks ago. The unknown thing to be known appeared to me as some stretch of earth or hard marl, resisting penetration ... the sea advances insensibly in silence, nothing seems to happen, nothing moves, the water is so far off you hardly hear it ... yet finally it surrounds the resistant substance.

Here is, roughly speaking, a theorem that illustrates what modern algebraic geometry is good for.

Theorem. If you have two conic sections in the plane, which don't share a common component, then they intersect in exactly four points.

Here a "conic section" is just any quadratic equation in two variables, e.g. x^2 + y^2 + 3xy + 4x = 1. "Common component" means that the conic sections are identical or overlap in an entire line.

Now, here are some "examples".

Concentric circles, e.g. x^2 + y^2 = 1 and x^2 + y^2 = 4. They don't intersect at all, right? Ah, except you forgot to count points over the complex numbers, where they do.

Tangency, e.g. y = x^2 and x^2 + (y - 1)^2 = 1. These curves are tangent at (0, 0), so you have to count this point with multiplicity.

One major goal of modern algebraic geometry is to wrap these sorts of considerations into the foundations. So you have to work a lot harder to even say what a conic section is, or what it means for two of them to intersect. But, once you've laid the foundations in this manner, there are no special cases.

Re: Who Is Alexander Grothendieck? (2008) [pdf]

#13
Stories like these suggest to me that genius level creativity equals intrinsic motivation plus time.

They also demonstrate that such motivation cannot be adjusted at will. It amounts to one's deepest understanding of where personal progress or best direction lies. Thus when Grothendieck or Swedenborg had religious experiences later in life their technical output ceased because their motivations had changed irrevocably.

Re: Who Is Alexander Grothendieck? (2008) [pdf]

#14
post #10

I am currently learning modern algebraic geometry (scheme theory) from Ravi Vakil's algebraic geometry in the time of COVID: https://math216.wordpress.com/agittoc-2020/ . It's a great ongoing course that offers amazing intuition into scheme theory. We're divided into "working group(oid)s" where we discuss the mathematics and solve the weekly homework assigned by Ravi. Best of all, anyone [all over the world] can join…

I'm also learning some algebraic geometry at the moment:

Some resources I have used are:

* video lectures by Richard Borcherds

* Lecture notes by Andreas Gathmann (https://www.mathematik.uni-kl.de/~gathmann/class/alggeom-200...)

* This blog: https://rigtriv.wordpress.com/ag-from-the-beginning/

* An infinite large napkin, by Evan Chen (https://venhance.github.io/napkin/Napkin.pdf)

It also found it helpful to learn some (algebraic) number theory, to get a sense of where some of the motivation comes from (e.g. elliptic curves, modular forms). Grothendieck's work is abstract, but he was always motivated by concrete problems (e.g. Weil conjectures).

Re: Who Is Alexander Grothendieck? (2008) [pdf]

#15

Stories like these suggest to me that genius level creativity equals intrinsic motivation plus time. They also demonstrate that such motivation cannot be adjusted at will. It amounts to one's deepest understanding of where personal progress or best direction lies. Thus when Grothendieck or Swedenborg had religious experiences later in life their technical output ceased because their motivations had changed irrevocabl…

> their technical output ceased

I think Grothendieck was still writing multi-1000-page mathematical manuscripts up until he died.

I know there are such unpublished manuscripts floating around the mathematical community.

As Wikipedia states " he lived secluded, still working tirelessly on mathematics until his death in 2014".

https://en.wikipedia.org/wiki/Alexander_Grothendieck

Re: Who Is Alexander Grothendieck? (2008) [pdf]

#16

Stories like these suggest to me that genius level creativity equals intrinsic motivation plus time. They also demonstrate that such motivation cannot be adjusted at will. It amounts to one's deepest understanding of where personal progress or best direction lies. Thus when Grothendieck or Swedenborg had religious experiences later in life their technical output ceased because their motivations had changed irrevocabl…

> their technical output ceased I think Grothendieck was still writing multi-1000-page mathematical manuscripts up until he died. I know there are such unpublished manuscripts floating around the mathematical community. As Wikipedia states " he lived secluded, still working tirelessly on mathematics until his death in 2014". https://en.wikipedia.org/wiki/Alexander_Grothendieck

Some of his manuscripts can be downloaded here https://grothendieck.umontpellier.fr/archives-grothendieck/# but according to this (reliable) radio program [1] he was fascinated by the devil and only wrote about this at the end of his life

[1] https://www.franceculture.fr/emissions/la-conversation-scien...

Re: Who Is Alexander Grothendieck? (2008) [pdf]

#17

Grothendieck's work is, for me, a rather perfect example of what's happened in the 20th century to mathematics, where the boundaries of knowledge have been pushed so hard and so far that there is almost no hope for anyone to even begin to understand the substance of the work outside a very tiny circle of people who pretty much dedicated life to that arcane corner of the field. I really wish vulgarization was an actua…

You aren't wrong. Until extremely recently, algebraic geometry was a field by and for the purest of the pure mathematicians. These days algebraic geometry has made its way into string theory.

https://en.wikipedia.org/wiki/Gromov%E2%80%93Witten_invarian...

A couple of his contributions:

1. A far reaching generalization of the Riemann-Roch theorem, which is now called the Grothendieck-Riemann-Roch theorem. As with a great deal of his work, it's about drawing conclusions about global structure from local data:

https://en.wikipedia.org/wiki/Riemann%E2%80%93Roch_theorem

2. Creating the machinery used to solve the Riemann hypothesis for finite number fields.

https://en.wikipedia.org/wiki/Weil_conjectures

His work wasn't focused on solving particular problems so much as it was on finding the right language with which to describe problems. The philosophy is that, with the right language, your proofs should become obvious. This is somewhat in the same spirit as Leibniz's quest for the 'Universal Characteristic'.

https://en.wikipedia.org/wiki/Characteristica_universalis

Re: Who Is Alexander Grothendieck? (2008) [pdf]

#18

Stories like these suggest to me that genius level creativity equals intrinsic motivation plus time. They also demonstrate that such motivation cannot be adjusted at will. It amounts to one's deepest understanding of where personal progress or best direction lies. Thus when Grothendieck or Swedenborg had religious experiences later in life their technical output ceased because their motivations had changed irrevocabl…

> their technical output ceased I think Grothendieck was still writing multi-1000-page mathematical manuscripts up until he died. I know there are such unpublished manuscripts floating around the mathematical community. As Wikipedia states " he lived secluded, still working tirelessly on mathematics until his death in 2014". https://en.wikipedia.org/wiki/Alexander_Grothendieck

Good point and it's not cut and dried but the character of his output had changed to the extent that it was not published in technical journals as it had been:

>Relatively little of his work after 1960 was published by the conventional route of the learned journal, circulating initially in duplicated volumes of seminar notes; his influence was to a considerable extent personal. His influence spilled over into many other branches of mathematics, for example the contemporary theory of D-modules. (It also provoked adverse reactions, with many mathematicians seeking out more concrete areas and problems.)

My guess would be that he was working on himself rather than on the mathematics. Mathematics was merely the means and the medium. But I haven't read the material...!

Re: Who Is Alexander Grothendieck? (2008) [pdf]

#19

>> Alexander Grothendieck was a mathematician who became the leading figure in the creation of modern algebraic geometry. His research extended the scope of the field and added elements of commutative algebra, homological algebra, sheaf theory and category theory to its foundations, while his so-called "relative" perspective led to revolutionary advances in many areas of pure mathematics. He is considered by many to…

what is the point of this? usually this type of comment is when there's something inscrutable in the title of a post but the title of this post is literally "Who Is Alexander Grothendieck?"; if you didn't know who he was before clicking you certainly know afterwards.

Re: Who Is Alexander Grothendieck? (2008) [pdf]

#20

Grothendieck's work is, for me, a rather perfect example of what's happened in the 20th century to mathematics, where the boundaries of knowledge have been pushed so hard and so far that there is almost no hope for anyone to even begin to understand the substance of the work outside a very tiny circle of people who pretty much dedicated life to that arcane corner of the field. I really wish vulgarization was an actua…

As another commenter mentioned, currently Ravi Vakil is teaching a course in modern algbraic geometry. The course is largely based on Vakil's book in progress, which he titled The Rising Sea , after a quote from Grothendieck: > I can illustrate the ... approach with the ... image of a nut to be opened. The first analogy that came to my mind is of immersing the nut in some softening liquid, and why not simply water? F…

> Concentric circles, e.g. x^2 + y^2 = 1 and x^2 + y^2 = 4. They don't intersect at all, right? Ah, except you forgot to count points over the complex numbers, where they do.

How is this possible? Are you saying that there are pairs of complex numbers (x,y) such that x^2 + y^2 = 1 = 4?

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