### Welcome to our community

#### Janssens

##### Well-known member
Hello all,

Approximately a week ago I discovered this forum. This happened when I found a post about your PotW on Physics Forums (PF), where some of the MHB members recently became active.

My forum name (here and on PF) is a reference to A.N. Krylov, a Russian mathematician and engineer from the second half of the 19th, first half of the 20th century. It reflects my interests in Russian mathematics, but unlike your intimidating looking Администратор, I do not know the language, unfortunately.

More precisely, I am interested in the analysis of ordinary differential equations and delay equations, functional analytic methods and related applications.

So, thank you very much for your nice PotWs so far, and perhaps see you around somewhere on MHB!

Best regards,

Sebastiaan Janssens.

#### Klaas van Aarsen

##### MHB Seeker
Staff member
Hi Sebastiaan, welcome to MHB,

Nice to see a fellow countryman!

#### MarkFL

Staff member
Hello, and welcome to MHB, Sebastiaan!

#### Euge

##### MHB Global Moderator
Staff member
Welcome, Sebastiaan!

I'm glad you joined. I saw your solution to the intermediate PotW on PF, very well written. As director of the grad POTW, I hope you'll enjoy some of my problems as well.

#### Jameson

Staff member
Welcome Sebastian! I'm very glad you found us and hope to see you around.

Staff member
Welcome!

#### Ackbach

##### Indicium Physicus
Staff member
Welcome! And thanks for keeping me honest on the Intermediate PotW!

#### Janssens

##### Well-known member
Firstly, thank you all very much for your very friendly welcome!

Welcome, Sebastiaan!

I'm glad you joined. I saw your solution to the intermediate PotW on PF, very well written. As director of the grad POTW, I hope you'll enjoy some of my problems as well.
Thank you for your positive comment. Regarding the advanced POTW, it made me realize that I am (even) less advanced than I thought: I didn't think I know enough to be able to give an answer. Fortunately some others were better prepared.

Surely, when you post future problems here or on PF, I will have a look and, when time and background knowledge permit, I will give it a go!

Welcome! And thanks for keeping me honest on the Intermediate PotW!
It was instructive to me, too. Actually, when I first saw the problem statement, I myself had to get used to the idea of $B$ being negative. I suppose this is because Gronwall is so often used in norm-estimates where the various constants are naturally $\ge 0$. The condition of non-negativity is then understandably forgotten.