Episode 11: From playing the organ to geometric group theory with Benjamin Brück

00:00:03: From Mathematics Münster, this is On A Tangent.

00:00:13: The podcast where we tell the stories behind mathematics and explore a fascinating path that lead early career researchers to Münster.

00:00:20: My name is Carlo Kauld.

00:00:21: I'm PhD student in Arithmetic Geometry And have the privilege of bringing new stories for you In the month to come.

00:00:28: For the fourth episode Of This Season.

00:00:29: i am joined by Benjamin Brück.

00:00:32: Benjamin pursued with mathematical training at Germany At the University of Münster & Bielefeld University Where he completed his undergraduate master's degree Following his PhD in twenty-twenty, he worked as a postdoctoral researcher at the University of Copenhagen and as a Heilmannweil Instructor at Etihad Zürich.

00:00:51: Subsequently returned to the university of Münster completing his habilitation in twenty twenty five.

00:00:57: Since twenty twenty four He has also served an investigator In young research group joined with Romans Roker Focusing on high dimensional comology Of arithmetic groups.

00:01:07: So it's great.

00:01:08: have you been here me?

00:01:09: The podcast typically starts with the question of what is your first mathematical memory in you life?

00:01:15: First mathematical memory.

00:01:17: I think, that has something to do with math.

00:01:20: was an elementary school when we did a game called Eckenrechen or some thing We need...the teacher gave us some kind of calculations.

00:01:28: he needed doing it ahead and then.. ..the point would be somewhat quicker than the others And i remember That I wasn't good but not best in our class.

00:01:37: Something else still remembered And yeah, I don't know actually until today somehow doing calculations quickly in my head is not really My top strength.

00:01:45: That would say now try to push that through the computer when possible nowadays

00:01:49: right?

00:01:50: and The first maybe more Actually more mathematical thing that I remember as when I was Maybe in year five or six in school so eleven twelve years old and there were some kind of math.

00:02:07: I know what there's some kind of extra classes, but they weren't offered at our school.

00:02:12: But in a town nearby and my math teacher... So i liked the mathematics in school there And at some point My math teachers suggested that if like this maybe it could also go to these.

00:02:26: Yeah They were quite extra classes but somehow meeting Maybe once per week or every other week unknown afternoon?

00:02:33: Then There was I don't know nice exercise.

00:02:37: Nice topics presented that you didn't need in school, but there was somehow Interesting exercises to solve something.

00:02:42: this is something i really enjoyed.

00:02:44: so You were eleven or twelve said that early on they had some offer something like This

00:02:50: yeah?

00:02:50: I mean it's

00:02:50: very nice.

00:02:51: actually i'm Actually not sure who organized this notice?

00:02:53: just no the town where It wasn't and this Is Where The Teacher Lived.

00:02:56: I think this is why even the classes probably Some Probably there were teachers actually from the school, but they weren't only people in one school.

00:03:06: And that was somehow very enjoyable.

00:03:08: of course you didn't need to do any exams or something... I remember for example we did something about exponential growth as it is remembered and found cool at this point because it seemed so intuitive with what.

00:03:21: I think it's rare that these types of things are offered at the early stage.

00:03:25: Usually, only later you have advanced classes but someone took initiative... Where was this?

00:03:33: So i grew up near Frankfurt on the countryside there.

00:03:36: The classes were in Gaenhausen and maybe fifteen or twenty minutes away from where I lived.

00:03:45: But it was already clear during the beginning of your high school that you really liked math and were good at math, so I started early on.

00:03:54: Yeah somehow...I think i basically always enjoyed mouth classes.

00:04:00: And how was a typical day in High School?

00:04:04: So did you privately think about Math or How does this look

00:04:09: like?

00:04:10: Okay..so I mentioned these extra class but apart from them I think i did a lot of mathematical things besides school at that time.

00:04:20: Okay, maybe actually... At age eleven or twelve?

00:04:22: I don't remember how exactly my days

00:04:24: were

00:04:25: but later on towards the end in general I did more music at that times.

00:04:30: Ah

00:04:31: yeah!

00:04:33: Also afterwards continued into different choirs and had some singing classes and played organ And then at this point Okay, also play video games and kind of things but Say from the more.

00:04:46: so other things that as did besides school were more into music especially in The last yes.

00:04:51: Maybe I know ages fifteen till seventeen.

00:04:53: more video games And then what's the end-of-school?

00:04:57: more music.

00:04:57: So was it like a church choir?

00:05:00: Because you also said, You play the organ and can only do that in the Church right?

00:05:03: Yeah!

00:05:03: That's true.

00:05:04: so actually my... I started with piano.

00:05:07: well okay at very beginning i start with recorder class but already teacher there who played the organ In our town.

00:05:18: And then when I learned the Piano With Her At some point don't know how I first got interested into the organ but definitely my teacher also played organs and she Also showed it to me at some point.

00:05:30: And this is how i got into there, so The First choir that I sang in was also She did yeah.

00:05:37: She Was the conductor then.

00:05:40: So Yeah That was treasury late damage.

00:05:42: he was employed At the town To play the organ.

00:05:48: Was it also a possibility in your head that you might want to pursue music further, or was there more hobby for you always?

00:05:56: No.

00:05:56: It was more of a hobby actually – I enjoyed it and especially towards the end of school I invested time on it but...I don't know…it's nothing seriously thought about doing as a job at some point later.

00:06:12: Okay, did you always want to pursue mathematics further or when did you realize that this might be something you wanted to study?

00:06:20: I think it was pretty clear for me that i would have wanted to do something science-like.

00:06:26: I wasn't super fixed your math until the end of school but also chemistry and physics for example biology a bit less in school And then towards the end, I think in the last years of school it was clear that i wanted to study something and do either math or

00:06:44: physics.

00:06:47: Then there were two things which influenced me both away from physics and toward math.

00:06:53: So first thing is a physics.

00:06:56: This again was our physics teacher who suggested one day event where you could go to Darmstadt.

00:07:04: so this wasn't far away And it was some basic introduction about something to the experiments performed at CERN this time.

00:07:20: So, there were explanations in the morning on how... I mean a very short introduction for people who are eighteen years old and what kind of collider experiment is conducted here?

00:07:35: And that was something I really enjoyed, but then the afternoon we were...I think they thought it was a cool part where you could analyse actual data coming from

00:07:43: this experience.

00:07:43: Yeah

00:07:44: and also thought for some reason there's super cool of all But i don't know what we did in our afternoons to look at some kind of tables and statistics which wasn't so exciting to me.

00:07:55: So probably..at least this part of the experimental part isn't much more interesting.

00:08:04: So, this is something that maybe shifted me a bit away from physics.

00:08:10: And then actually another thing... Actually at one of these fruit-playing organ I got to know one person who studied so she was PhD student at the time or maybe Master... No!

00:08:22: I think PhD student.

00:08:23: and she recommended some extra activity which was by the University of Stuttgart.

00:08:29: it's called Cohespondenz Zirkel I would say now in retrospect basically they send you every week like or Every month an exercise sheet a bit as it is.

00:08:39: Now, uh As you have it and regular math lectures on the first semester.

00:08:42: so yeah

00:08:43: There was a few pages text about For example complex numbers are.

00:08:47: remember wasn't introduction?

00:08:48: what complex numbers?

00:08:48: And then there were maybe I don't know ten pages of something like this with an Introduction What what it's about Some examples and then you could.

00:08:58: they also had an exercise sheet And you could solve the exercise and send them.

00:09:01: to send the exercise to them.

00:09:03: You got them back.

00:09:05: That was very nice because there again somehow They just picked of course a nice topics that were

00:09:11: yeah, I've got

00:09:12: it Could be presented well?

00:09:13: This is something i really enjoyed.

00:09:15: It was challenging and interesting.

00:09:17: But you never had any classes, it's all like... You have to teach everything yourself?

00:09:22: And do only these exercises or...?

00:09:24: So in this course... Yeah I think i've never met someone in person!

00:09:31: The great exercise.

00:09:32: she's back with some comments on the site, but that is all.

00:09:34: Otherwise you just got some text once per month and then...

00:09:37: You didn't share this with anybody?

00:09:38: You really did it your own way?

00:09:40: Yeah I

00:09:40: had to do so my own

00:09:41: way!

00:09:42: Did not have a group or something which...

00:09:43: No..I don´t remember.

00:09:45: maybe It wasn´t secret thing That we talked about someone But it was also for me motivation because i told the student That I was a student at that point, and maybe doing math but wasn't quite sure what one actually did.

00:10:05: And

00:10:07: in school it's very hard to get an idea of what one does after school.

00:10:12: Then she said ah, there is something similar for her here.

00:10:18: Yeah, I can really relate to both of you actually.

00:10:20: It's a bit funny because i also had this certain thing.

00:10:23: for me it was even worse because online during corona time.

00:10:29: So I really thought before this, oh wow that's so exciting.

00:10:32: We're going to talk about it.

00:10:33: and then what we actually did was really unexciting for me.

00:10:38: And there also a program at my hometown university but It wasn't easy because they offered in person.

00:10:43: That is why i asked them What would have probably been hard for you go to Darmstadt Because its not so near right?

00:10:50: Right!

00:10:52: So later on when I started, they realized that there were a few people who also went to university classes during school.

00:10:57: But for me it was never so much as an option because i wasn't too close with any University.

00:11:01: I mean okay, Frankfurt would probably have been the closest but still not doable...

00:11:08: Did you meet this Mathematics PhD student at your organ playing?

00:11:15: So did math and music have a connection for you at that time?

00:11:19: Or was it just both passions of yours, which didn't connect them in any way.

00:11:24: because people are always saying math is like the typical thing.

00:11:26: And I think actually we really see that among PhD students... For example also in Münster many people very musically talented.

00:11:33: Yeah yeah that's true.

00:11:35: um i mean i'm not sure how much.

00:11:38: so okay for me personally there wasn't so much of a connection.

00:11:42: might be that it attracts similar people.

00:11:44: Yeah, I think that's true.

00:11:46: yeah...

00:11:46: Might also be that people from a similar background are into get music castes and do mouths later on.

00:11:52: so not too sure but definitely for me It was..I don't know i never thought through the connection with them.

00:11:58: there were just two different things that I liked and they're rangeable.

00:12:03: And after you graduated from school did you start studying immediately?

00:12:07: or how does this go?

00:12:09: Yes Yes, I start immediately.

00:12:12: So actually the months in between are used to finish some organ classes that you can do some kind of basically exam in an organ at a certain level and this is something i did right after school.

00:12:22: but there was just for another these few month's in-between where.

00:12:26: so it had lot music during summer I don't know, October.

00:12:32: I started studying math right away.

00:12:33: and where did you study?

00:12:35: Actually here in Münster.

00:12:37: How

00:12:37: does this happen?

00:12:38: because it's not so near from Frankfurt.

00:12:39: Yeah that is true.

00:12:43: So after school i wanted to move away And thought maybe...I was looking for something at a distance That still doable For weekend home but I don't know, so a lot of my friends went to Darmstadt and thought that was for me too close.

00:13:00: I wanted to see something else And then i also wanted go some kind of student town.

00:13:10: Then at this point i looked from the site.

00:13:14: there were students who recommended it because they had no idea where mathematics departments were big or something.

00:13:22: Bonn-Münster and a few other places were on top of the list.

00:13:24: And Münster, I thought this sounds like a student town and roughly the distance that i was looking for... Yeah?

00:13:31: ...I think it's only in Münster.

00:13:32: maybe once before I actually moved here but something new and A lot students sounded good everyone saying yeah!

00:13:41: This is nice town and everyone said oh yeah!

00:13:44: I know from Tartos

00:13:47: Did you meet your expectations

00:13:49: at this point?

00:13:50: Yes A lot of other towns would have as well with a nice atmosphere.

00:13:55: Especially the first years when I started to study were very, very nice having all these people that are also interested in this same thing and this mathematics class was something i enjoyed alot.

00:14:06: And yeah Münster was great but I think in retrospect it would've been much better than many cities

00:14:11: Of course!

00:14:12: Did you ever mine?

00:14:14: Physics.

00:14:15: Ah, okay.

00:14:15: so you came back to physics and... Yeah

00:14:17: I mean right the theoretical part is still like that

00:14:22: And it's i think if you do a minor of physics with math then to do mostly theoretical physics, right?

00:14:27: Yes exactly.

00:14:29: Well okay you need also experimental physics classes.

00:14:32: so some experiments are conducted for you.

00:14:37: I mean i would have been fine with doing some experiments but we didn't really needed any.

00:14:41: no never did anything.

00:14:44: and the theory part is still interesting.

00:14:46: yeah i think i like theoretical physics.

00:14:49: it even helps sometimes in your math can also be beneficial sometimes.

00:14:57: Yeah, you get some kind of intuition... Also the physics classes in the math part were always a few semesters ahead from what we learned in mathematics like solving partial differential equations already in the first semester

00:15:09: or slightly different way right?

00:15:11: In a different way!

00:15:12: You need to skip many steps on how to do this but still Right, it was still nice to have this perspective for why you would maybe be interested in the math questions.

00:15:23: And did you also do your master's in Minster then?

00:15:26: Yes most of it.

00:15:26: so that last semester I was in Lyon writing a Master thesis.

00:15:30: How does this possibility appear for use or is there some connection with a minster professor?

00:15:37: yes So at that point i asked Katrin Tent about... Sorry!

00:15:43: I knew that wanted go another place and I think i realized it towards the beginning of my masters, but that was already comparably late because you need to play to plan at once and so on.

00:15:55: And then um...I wrote my I mean my bachelor thesis.

00:15:59: I had written with her and then asked her at that point That I wanted to go somewhere else?

00:16:04: And I thought probably for the master thesis would be the right time Because otherwise there wasn't much more time left.

00:16:08: Yeah yeah

00:16:09: of course

00:16:10: Asked whether she had recommendations of places.

00:16:12: This is how I got to...I think she also recommended some other places, but Lyon sounded nice and I learned French in school.

00:16:21: That's very helpful!

00:16:23: So this would be a nice occasion too.

00:16:27: Was it in Lyon that you got into your current research topic?

00:16:29: Or was already before or later?

00:16:32: No actually changed a bit.

00:16:34: so what i did in Lyons was combination of automorphisms.

00:16:38: Nowadays im doing geometric group theory more with topological direction And I was going to a geometric group theory class in Münster, actually.

00:16:48: I mean by Katrin Tendt and the master thesis was somehow combining geometric group-theory with model-theorie... ...and it is something that i enjoyed.

00:17:02: but i realized that i enjoyed the geometric-group theory part of it more Yeah!

00:17:07: Then afterwards It was clear to me That I wanted do something in geometric groups theories.

00:17:11: So In this sense it's helpful.

00:17:14: The model theory part wasn't bad, but it was clear for me that the geometric group theory... ...was one I wanted

00:17:20: to pursue.

00:17:22: Did you realise immediately or was it clear maybe that you want to pursue a PhD after your Masters?

00:17:29: At this point not when i started to study But towards last year's I had an impression especially during my Master thesis.

00:17:38: Well, basically the first time that I could actually read research articles still took a lot of time at point and so on.

00:17:45: And thought it would be somehow shame to stop now where one arrived... At the beginning what was current research?

00:17:54: but then i definitely want do a PhD also something on my own.

00:17:59: The mass of these were bit independent.

00:18:04: Yeah, I really relate to that.

00:18:06: If you have studied so much and finally come up with the point of being able read some new research then it's just... You have to continue because you've put in all your work And also it gets nicer and nicer right?

00:18:20: Because you understand more about theory and connections.

00:18:25: So this was at least for me.

00:18:28: I also didn't know whether i wanted to go on the beginning of my bachelor's or even at the end.

00:18:35: But once, when they learned more and more algebraic geometry... ...and then had such a knowledge gap in my head that now need really do something with it so.. So I relate this motivation as well!

00:18:48: How did your PhD applications?

00:18:51: Or decisions where you went?

00:18:53: how was his process for you ?

00:18:57: And there I asked for... How did that actually go?

00:19:06: So, I remember asking my advisors.

00:19:09: Okay, Katrin Tendt was the advisor but she was an official one in Münster and wasn't really... I mean it wasn't in Münstern.

00:19:15: Yeah right!

00:19:15: Makes sense.

00:19:17: For me also a option to stay at Münste at this point.

00:19:23: But I think Katrin was about or maybe it wasn't clear whether she would stay in Münster, I think at that point somehow.

00:19:32: And then asked also my advisors in Lyon if they had recommendations for people with geometric group theory and not so... My girlfriend was studying Wuppertal So i thought somewhere roughly in the area to be possible

00:19:53: see

00:19:55: each other at least on the weekends and so then they gave me a list of names, I had to look what these people did with their webpages.

00:20:05: So this was in Bielefeld right?

00:20:08: And how does life between Münster & Bielefelt compare for you?

00:20:14: The largest difference definitely is that I still get wrong today.

00:20:18: In Münster you need to put in the Mensa, The Cutlery or on the plates right?

00:20:22: Yeah.

00:20:22: And then Bielefeld You always need to Put it next.

00:20:24: Oh

00:20:24: okay and

00:20:25: in both places Working there will complain if we do it incorrectly.

00:20:28: Ah yeah of course!

00:20:29: So that was a big culture shock

00:20:31: for me.

00:20:31: I learned this

00:20:32: for five years Was taught the hard way To Always put the cutlery On the Plates.

00:20:38: Apart from That Yeah i mean bielefeld is much less off A tourist town.

00:20:44: certainly I don't know.

00:20:48: I like Bielefeld, but it's less of the tourist town that you would know from a Tartot or other people say... I mean, in Münster often they're like, ah!

00:20:55: You saw this in the Tarton?

00:20:56: It seems to be nice place.

00:20:57: and at Bielefeld there are lots of people who don't relate much with the city.

00:21:00: But living here was fine.

00:21:01: The department actually ...I think i'm also lucky to go to the department back then where the group was very active.

00:21:09: What also what I liked and was there weren't so many PhD students in the group.

00:21:16: So, I think we had probably even more postdocs than PhD students Yeah.

00:21:19: So it didn't a still have enough had enough PhD students In the same group to talk to say about the Topics typical for PhD student.

00:21:27: that will still already clear That we were integrated in this same lunch group For example, so one already I don't know Was they're at The conversations about publishing and journals yeah kind of things which i found interesting And couldn't.

00:21:39: So for me that was a, yeah and also the people in the group were very inviting.

00:21:44: And I remember on the first week maybe second week so there wasn't archive seminar where you needed to present... So every weeks someone presented an article which had come into the archive from the week before.

00:21:55: And now i remember when they went there for their first time then one of the post-docs immediately told them why don't we do it next week?

00:22:03: Maybe I knew that the archive existed, but i certainly hadn't gone to it and looked for articles.

00:22:07: So stuff in my master thesis was all published things... ...and then I looked at how to sign them.

00:22:11: so first need an introduction on how the archive

00:22:14: works....

00:22:15: ...then look into articles of the archive to find something interesting.

00:22:19: In this sense is nice to integrate quickly with other ones as well.

00:22:26: I just learned a few weeks ago that you can subscribe to the archive and last night, as subscribed to relevant topics from me.

00:22:32: So now i'm also an archive expert!

00:22:35: And

00:22:37: after Bielefeld where did you go then?

00:22:42: My first postdoc was in Copenhagen but there it right at the beginning of Covid times It was always supposed to be just half a year.

00:22:50: So I already knew when I applied for postdocs, so basically got two positions one in Zurich and that Was the one that then followed afterwards but would only start in October.

00:22:59: And then Copenhagen were supposed to pee the half-year before Before going to Surigen after end of the PhD.

00:23:05: yeah, and In The End i wasn't A lot in Copenhagen person because One Couldn't cross the borders at That Point

00:23:13: And that's a shame, right?

00:23:14: Because Copenhagen is really beautiful.

00:23:16: Yeah it is!

00:23:17: I mean in the end there was this first summer where everything opened suddenly and... That was very nice then but i think for maybe five or six weeks only in Copenhagen in person.

00:23:28: But actually this was still a very influential time because most of my projects worked on them.

00:23:33: The following years really got me online with people especially at least to me.

00:23:39: Yeah, and Copenhagen?

00:23:42: the people weren't so mentioned necessarily in Copenhagen But everyone was open to do some kind of social activity.

00:23:46: And there I don't know after they over at a seminar that wasn't Dinner on zoom and these kinds of things.

00:23:53: So I got to know people actually Reasonably well i would say it also.

00:23:57: then when I went to Copenhagen I started if you project had really influenced The work in the years afterwards.

00:24:03: Mm-hmm lot yeah.

00:24:05: Then I moved to Zurich in October.

00:24:07: how long did he stay in Zurich?

00:24:08: for three yes?

00:24:09: Okay And so this was probably then the time where you developed all these ideas.

00:24:15: You've gotten in Copenhagen or how would describe your time at Zurich?

00:24:19: Yeah, I also did some other things but a lot of times working on projects from Copenhagen for a lot together with Robin who is here as well.

00:24:29: Do

00:24:29: you met him in Zurich ?

00:24:31: In Copenhagen?

00:24:33: Actually had been to Copenhagen year before.

00:24:36: So i knew Robin form summer school because He said he wasn't Copenhagen and I was about to give a seminar talk in Copenhagen.

00:24:43: then asked him About the group in Copenhague, and this is how we got to talk over.

00:24:47: This summer school boys in Paris not

00:24:49: okay But by

00:24:50: chance Robin was there and said ah i am In Copenhagen And I knew I was able To give it this talk they're but didn't know much about the department.

00:24:56: yeah

00:24:57: um so We already knew each other and at The Summer School had talked about different topics.

00:25:02: Mm-hmm

00:25:02: when I came to Copenhagen you also want or when?

00:25:04: I don't know, start with the position which was still in Germany but online.

00:25:09: We were looking for topics to work on together right and then the Zurich time.

00:25:14: a lot of us... So initially there's just one project.

00:25:19: it became clear that in order solve this many steps need to be done and these came as side projects or maybe not even side-projects.

00:25:29: they needed first and other collaborators joined who weren't in Copenhagen in person but came from this Copenhagen connection thing.

00:25:38: I mean, also started some collaborations with people in Zurich.

00:25:41: But i would say the main research direction was still with this Copenhagian group and people then From the US Who were related to Robin And Peter Pazto was at that point Also in Copenhague.

00:25:54: And after Zurich you realized You wanted To go back to Miss?

00:25:59: My wife Still stayed...I Mean she worked In Bielefeld At That Point.

00:26:07: At first she wanted to move to Switzerland, but then in Covid times there weren't a lot of jobs advertised and at some point it became clear that maybe not worth anymore for applying anything because my position would end only year-and-a-half later.

00:26:22: So I want her back more on something that is okay from Bielefeld's day.

00:26:28: or was Priority to search something there and this is at that point I contacted a cartoon again was asking about whether what kind of possibilities There could be in Munster for positions.

00:26:37: Yeah, because topic wise it's somehow fit here in Münster also very well with me.

00:26:42: yeah

00:26:42: Of course i mean

00:26:43: okay in principle.

00:26:44: also Bielefeld could have been option but at that Pointi went more Mathematically say the in Copenhagen.

00:26:50: That Was More.

00:26:51: I was more In The topology Group And They Are Close Connections To Several People Here and It Was Clear That Somehow That Could Be A Good I mean, topic-wise a good connection.

00:27:00: And then right this is how our first contacted cartoon asked about options and in the end...

00:27:06: Cool!

00:27:07: Do you now live in Münster or...?

00:27:10: No i mainly live in Bielefeld.

00:27:12: there also have room in Scherzflat hier in Münstern but say that main focus is on Bielefield.

00:27:18: So when are you in Münste?

00:27:19: what do like to most if your time for outside university?

00:27:25: In Münster.

00:27:28: So okay, now I have to say.

00:27:29: Now the days where i'm in Münster are mostly really quite work-filled

00:27:33: Makes sense because

00:27:34: I try to package the work and these days on other days.

00:27:38: Yeah you had to have it more right too.

00:27:40: focus here in Münstern bit more of a work part.

00:27:43: But I so here for example go running as still meet some friends from From when I studied.

00:27:49: if you were still hear this was actually also nice.

00:27:52: yeah start from scratch again.

00:27:56: So where do you go running?

00:27:57: I also go running, that's why I'm asking.

00:27:59: Yeah here in Münster and mostly around the Azi.

00:28:02: This is not far from my place this year... In Bielefeld there are more areas around it.

00:28:12: I like the city in Münster, but see... The countryside around it is maybe a bit flat.

00:28:18: Yeah right!

00:28:19: Which

00:28:19: is okay for running But i prefer more hilly areas.

00:28:23: It's better than Bielefeld Right?

00:28:24: If one likes to run in a little bit more hillier area then that would be easier to go into the Teutobock Forest

00:28:32: Cool.

00:28:32: So probably you don't have much time besides mathematics and your family, but do you pursue any other hobbies or anything else that you would do to relax after hard days of doing research?

00:28:44: As I said it has changed a lot now.

00:28:46: My son is two years old.

00:28:48: since then as well before i still did more music I don't know, often the days are.

00:28:59: So usually after work i pick up my son from daycare when im in Bielefeldt and then we spend the afternoon with him...I actually also go running for a jogging stroller.

00:29:09: so this

00:29:10: is something nice but basically until he's in bed it's very much

00:29:16: focused around kids.

00:29:18: You still try to pursue music?

00:29:21: A bit, but not a lot.

00:29:23: I didn't start a choir at the moment and still have an electronic piano at home... I played a bit organ again in the end of last year But somehow Not that much anymore.

00:29:34: Also now i feel like The running part may be more because it's more stupid.

00:29:43: At some point In school was looking for a challenge And then the organ also.

00:29:48: you need to think It's comparatively technical.

00:29:53: Singing is much more natural or closer to the body say, but now I also prefer them all.

00:30:00: so i started running only actually during covid times and thought it was a nice... ...I like its stupidity in some sense after day of work.

00:30:07: So

00:30:08: yeah

00:30:09: cool Yeah do you just usual stuff?

00:30:11: Like meeting friends on playing board games?

00:30:13: with nothing

00:30:13: Of course!

00:30:15: Now that we've gotten to know Benjamin We will come to this second part of his podcast The so called A or B game.

00:30:21: For this game, which will consist of roughly thirty A or B questions I would ask Benjamin to answer as quickly as possible in order to get an idea about his intuitive thoughts.

00:30:30: Zero or one?

00:30:32: Zero

00:30:33: Analysis or algebra.

00:30:34: Algebra

00:30:35: Coffee or tea

00:30:37: In the morning tea and later on coffee.

00:30:40: Okay that's fair.

00:30:41: The beach are the mountains.

00:30:42: The

00:30:42: mountains

00:30:43: Snooze are waking up.

00:30:45: Waking Up.

00:30:46: Order or chaos?

00:30:47: Order.

00:30:48: Autumn Or spring

00:30:50: Spring.

00:30:52: Python or Julia?

00:30:53: Julia.

00:30:54: Homotopy or homology?

00:30:57: Homotopy.

00:30:59: Top dimension, or co-dimension.

00:31:01: two?

00:31:03: Top dimension!

00:31:04: Model theory or astrophysics?

00:31:07: Oh that's a tough one.

00:31:12: That is very hard to decide... No this one I need to skip.

00:31:17: The T's building of three factor complexes?

00:31:21: Prefactor complexes

00:31:23: Lyon or Oxford?

00:31:25: Lyon.

00:31:26: Copenhagen or Zurich?

00:31:29: Oh, that's a very tough one!

00:31:31: Copenhagen.

00:31:33: Geometry or combinatorics?

00:31:36: Geometry.

00:31:37: Ancye or amboise?

00:31:40: Oh... Amboise.

00:31:42: Conceptual proofs are technical proofs.

00:31:47: Unfortunately I end up more with the technical proof.

00:31:49: usually

00:31:49: Work at home or work in the office?

00:31:54: Yeah share between two.

00:31:56: maybe work at home

00:31:58: Playing the organ or singing?

00:32:01: Singing.

00:32:02: Invented, or discovered?

00:32:06: Invent it!

00:32:07: Mensa-or cook at home?

00:32:11: Mensa

00:32:12: Clapping on knocking?

00:32:15: Knocking

00:32:16: To be or not to be?

00:32:19: To Be

00:32:20: Great.

00:32:20: so you've already done that.

00:32:22: This was my I don't know... twenty five AOB questions And for the final part of the podcast i always ask some Five questions, five very general questions.

00:32:35: Very open question where I will ask you to answer like in one or two sentences as briefly it's possible but yeah.

00:32:45: so the first question is what are your favorite mathematical theorem?

00:32:50: It was quite a tough one!

00:32:51: Yeah that's

00:32:52: a tough on favourite theorem...

00:32:55: I got this question because when i helped with orientation period of new students Like the first week they come to university and I think that's a kind of... They don't know many theorems, but it is good icebreaker.

00:33:10: Yeah maybe I like Kantos theorem saying there are basically arbitrarily big cardinals

00:33:18: so that

00:33:19: there can be infinities of different sizes something very fascinating.

00:33:23: yeah It's also good for science communication.

00:33:28: There is always a nice header, so there are different infinities... Yeah and it's really

00:33:34: not what you would

00:33:34: think from the beginning!

00:33:37: I learned this before going to university when i was very excited about that.

00:33:42: Which of your results or achievements are most proud?

00:33:46: So it doesn't have to be math but can be math.

00:33:50: In Math i'd say i like paper about symplectic groups with Robin where we showed something about high-degree homology of symplectic groups.

00:34:00: It was a long project, with lots of things going on and took place in many places.

00:34:06: Which mathematical field might you have chosen if not your current one?

00:34:12: Actually I feel like i'm between fields.

00:34:14: somehow this is really something that I enjoy.

00:34:16: so as I said do it geometric group theory but somewhere between topology group theory sometimes geometry combinatorics.

00:34:26: So I think with any of these, that could have

00:34:28: become happy.

00:34:28: Okay Is there something in your professional life you might have done differently from the viewpoint today?

00:34:37: No i don't think There's something very specific...I mean Of course You would never know if he had decided differently but not like a great creative certain decision.

00:34:43: no

00:34:45: Great.

00:34:46: and what advice Would you give to student considering mathematics research Today?

00:34:50: so this may be the toughest one for them at

00:34:52: The end?

00:34:54: PhD students?

00:34:56: No, no like a bachelor student.

00:34:59: I think it's good to look into different topics and choose one that actually likes because It takes some time to develop some mathematical.

00:35:08: how do you say taste?

00:35:09: i would say so for me...i tried different mathematical directions And uh..I mean before was always super hard to judge whether i'd like this direction or not.

00:35:20: yeah only after doing for some time I realized that some topics are just like more and some kind of techniques.

00:35:27: So, I would suggest to try it also be fine with changing something else.

00:35:33: if one realizes this is not the type...

00:35:34: Yeah!

00:35:35: This can really hard but yeah i think its great advice.

00:35:37: so thank you very much.

00:35:39: It was a great getting to know you And now we will go into second part where we get to know something about your research as well.

00:35:48: Ok, thanks.

00:35:50: If you enjoyed the conversation with Benjamin as much I did, please consider sharing this episode with a friend or colleague.

00:35:56: In show notes you can also find link to video part of my conversation with Benyamin where he demonstrates how geometry of modular spaces of grass governs the co-homology of outer automorphism groups!