First of all, really, I'm very deeply touched.

And by my deepest thanks to Karl Heinz, Professor Hoffmann and Günther, Professor Leugering

for these words.

And I think the best thing I could do now is to say, okay, we go out and have a glass

of champagne because everything that I can do can make it only worse.

And now I could answer for hours and comment for hours what has been said, but then I really

get into trouble with my talk.

I will only give you, I will make only maybe two comments.

The one is, if we now look back on these problems, then it's correct to say, oh gosh, what kind

of simple problems these people did in those days.

But one also has to remember what kind of a time this was and that shows also the enormous

pioneering work which Karl Heinz Hoffmann did.

I don't know how it developed.

We sort of found these free boundary problems.

Actually nobody looked at, or the people who looked at were isolated and distributed in

the world.

There were a few in Italy.

There was one in China who was in prison for quite a while during the Cultural Revolution.

And Professor Hoffmann, he just said, okay, we bring everybody together.

We asked these Chinese people when nobody knew whether they still live or to come to

Oberwolfach.

So he really initiated new interactions which were, of course, it was not the time of the

internet already.

So this led to a flourishing subject of, for example, free boundary problems.

There also then a series of conferences emerged where he also was responsible.

So one sees this enormous pioneering work he did which was then also reflected in his

work as a science manager.

I don't want to say too much about that just for the sake of time, but only one thing from

the papers he wrote at that time, of course, I learned how to prepare my negotiations here

in Erlangen.

So I basically copied everything from his papers.

And for the astonishment of everybody, I also got everything I asked for.

So maybe as a comment to Günther's remark that these chairs were quite well equipped,

but they also had, of course, quite some duties.

Now, oh, I don't have a picture.

No, I don't have a picture.

Okay, so let me start with my talk because it's much, much too long.

So what I would like to, and I do not want to spoil the coffee break totally, only a

little bit.

So you see the title, I would like to speak about the mathematics of porous media.

Okay, maybe I...

Hopefully nobody's on the transparency, so I start.

Yeah, the first question is, is there something like a mathematics of porous media?

I would say yes, and I would like to convince you.

And as usual, also in philosophy, there is one, but it's not unique.

There are possibly several mathematics of porous media.

And you can see this, that at least the notion of the porous medium equation has made its

way also to pure mathematics.

This notion will show up.

It will not be as prominent as one might expect, but it plays a role, certainly.