# The Spectre of Math

## March 29, 2013

### Math is a series of trivial observations

Filed under: Mathematics,Personal — jlebl @ 4:38 pm

Mathematical proof is essentially a series of completely trivial observations wrapped in complicated-sounding notation (not complicated on purpose hopefully). The trick is not to understand the proof once it is written, but to notice those trivial observations to write a proof in the first place. I think this is what’s sometimes discouraging people from research mathematics. You work for two weeks on something that feels like a very hard problem, and then the solution seems trivial once found. In my case there are two operations and a limit involved. And the things you are trying to bound are not continuous with respect to that limit, so you flail around trying to do all sorts of complicated schemes. Then last night I think … hey why not do these two operations in reverse. I get rid of the limit and the problem becomes almost trivial after a bit of linear algebra. It feels good. But on the other hand it feels like: Why didn’t I think of this two weeks ago.

## March 11, 2013

### Moving to Oklahoma

Filed under: Personal — jlebl @ 8:06 pm

So, moving to OSU in Stillwater in the fall. This entails for the first time in my life quitting a job before it sort of naturally ends. The consulting gigs don’t really count I don’t think, and Eazel laid me off in the process of going under, so that counts as natural end of a job. At Red Hat it was just a summer gig, so there was no expectation of staying longer. Then at SDSU and UCSD I was a grad student, so any employment also ended when I graduated. In Urbana, they did make me send a “resignation letter”, but my appointment ended anyway as I stayed the whole 3 years I was hired for. At UCSD then I was hired for 1 year and stayed for one year. So now … I was hired for 3 and I am leaving after 2. Six years of postdoc in 3 different places are enough I think. One can always keep changing jobs every few years, but it’s nice to know I don’t have to now, I just can if I want to.

## November 3, 2012

### Linus has way too much time on his hands

Filed under: Linux,Personal,Technology — jlebl @ 8:44 pm

So latest news comes that Linus has switched to KDE. This apparently after first switching to XFCE, then I guess back to GNOME. Hmmm.

I’m still on XFCE. Can’t be bothered to try anything else. Yes XFCE is somewhat sucky, but once you fix its stupidities (such as the filemanager taking a minute to start up due to some vfs snafu that’s been apparently around forever), it’s there. I’ve entertained the thought of trying something else, but it’s not an exciting enough proposition.

Now I am wondering what to do once Fedora 16 stops being supported. Should I spend the afternoon upgrading to 18? The issue is that I can’t do the normal upgrade thing since that would boot into it’s own environment and would not load a necessary module that I do on startup that turns off the bad nvidia card with a screwed up heatsink. It’s impossible to do this in BIOS (stupid stupid Lenovo, never buying another Lenovo again). Anyway, that means having to do it right after boot, but before the GUI comes up since that would (even if using the intel card) turn the laptop into a portable oven, and it will just turn off and die nowdays. I am thinking that maybe if the upgrade happens during the wintertime, I could just stick the laptop on snow (and wait till it’s at least 20 below freezing) and then it could stay sane for the duration of the upgrade perhaps. I will probably try to do the upgrade by yum only, but that seems like it could be bug prone and would require some manual tinkering, and I just don’t care enough to do that.

Next time picking a distro I’m going with something LTS I think. And … Get off my lawn!!!

## January 20, 2012

### Biking

Filed under: Personal — jlebl @ 10:02 pm

So, it was -15 celsius (barely positive farenheit) and snowing this morning, actually it’s still -15 and still snowing. Surely only a complete moron would bike to work today. Actually the ride was pretty good. Yesterday it was -18 and I think I can tell the difference (though it was not snowing). The downside of biking in this weather is that the gears are refusing to shift. The levers just sort of stick and nothing happens. Fortunately, I’m in a reasonable gear right now.

Another downside is that I have these cool hybrid tires on the mountain bike. Sort of like road tires with spikes only on the sides, which is reasonable in terrain and much smoother than regular mountain bike tire on the road. They were really good at the UCSD campus (San Diego) where I’d go off road often and it never snowed. Because they kind of suck on snow.

## August 27, 2011

### Wisconsin

Filed under: Personal — jlebl @ 2:29 am

On the way to Madison we were trying to see what the Wisconsin ski resorts look like. Seems like the toughest runs are rated double-black-bunny.

## June 27, 2011

### Army of math

Filed under: Mathematics,Personal — jlebl @ 5:45 pm

Doing math is like being in the military it seems, at least if you want to be in the academia. You don’t really get much of a choice where you go work, you sort of get an assignment. Especially in this job market. The idea is the following: you send about 100 applications (if looking for research jobs), then about 50 of those you won’t consider anyway, though you don’t know that when applying. Then out of the next 50 you might get some interviews, and some of those you decide you don’t want to go to. Then you get an offer from a place you didn’t interview at, for a postdoc, for which you didn’t really apply (actually I got two such offers this year). The whole process takes about half a year, though then you get 2 weeks to decide once you get an offer.

My first job application 4 years ago when I went to Illinois was a bit simpler. I applied to 100 places. 50 of those were tenure-track positions where I had no chance straight out of the PhD. The 50 were postdocs, out of which probably 5 I was a reasonable candidate for since no place will hire a postdoc unless they have a group in your area. Out of that I got two offers around the same time, and one sort of informal offer. Then you pick, and go live in the midwest for 3 years.

So we spent 3 years in Illinois, 1 year in San Diego, next up to 3 years in Wisconsin, then …? Wisconsin will be the 3rd state that Maia will be living in and she’s only going to be 5. So when someone asks her “Where’d you grow up?” Then instead of saying: “We moved around, my dad was in the military” she’ll sat “We moved around, my dad was a mathematician.”

Well at least it will make for a more interesting story. I wish the job market gets better so that I can find a permanent job I like. I know it sounds like whining, since I have a guaranteed job for next 3 years (though it’s also guaranteed I will not have that job in 3 years time).

Academia is one of those careers where you’re well in your thirties before you really can possibly settle down. And before your salary starts reflecting the level of eduction you got. Professors at top schools do get paid well, but it takes a long time. As a programmer, I could be making the amount of money I hope to be making 10 years from now as a mathematician, 10 years ago.

Then you hear someone say “Oh this or that person couldn’t get a job in the industry so he went to academia” … yeah right … that’s the easy way out.

## November 11, 2010

### New chapter for the Diffy Qs book

Filed under: Mathematics,Personal,Teaching — jlebl @ 7:14 pm

I’ve written up a new short (14 pages) chapter for the Differential Equations textbook. I’ve put a draft on the web for my students as I’ll start covering it tomorrow (it’s only going to be 2 lectures, though the chapter should be usable for up to 3 lectures).

I suppose after Monday (after I finish lecturing on it), I’ll feel good enough about it to post a new version of the whole book with the chapter 7 in there.

I’ve caught quite a few typos and errors in the book this quarter, though I would say not any more than one can find in any first edition textbook. It seems that commercial publishers are very good at catching English grammar errors, but are terrible at catching mathematical mistakes. My book has probably more bad English than your average textbook. But I’m now feeling pretty good now about the mathematical content being correct.

A funky news is that apparently someone at Dartmouth College is planning to use the book for a course in their Winter term. I only heard from the bookstore that they asked if they can make copies of the book for the students, not actually from the instructor. I wonder how many courses have already used the book. I only know of a few …

## May 27, 2010

### Never use Chase bank!

Filed under: Personal — jlebl @ 9:49 pm

So I just found out that Chase has just subtracted another monthly payment from my checking account for a car loan that was paid off two months ago. Apparently, once you set up automatic payments, they are impossible to cancel. Also now the account is dead so I cannot access it and they said they can’t cancel payments either. I didn’t quite understand when they will give us back our money. I went to my bank and they said it’s not possible to block future payments to chase without a stop payment fee.

I did cancel the automatic payments (I don’t understand why you need to do that since the account is paid off) when the account was paid off. But that only canceled the April payment and not the May payment, and apparently now they will keep taking our money.

So the lesson is: never, ever, use chase as your bank, including for a loan. In case it is chase that does your auto (or some other) loan, make sure to never give them your account information to set up automatic payment. Perhaps it’s easier to just not get a loan with chase.

This follows their earlier nonsense of taking out more than the payoff amount on the last payment and then having to give us back a check for the difference.

## May 24, 2010

### Hockey world championship final game not interesting here

Filed under: Personal — jlebl @ 1:50 pm

So yesterday it was the final game in the hockey world championship, and it was not on TV here. All I can say is WTF? I don’t normally watch hockey (or any sport), but a finals game I wanted to (especially since czech was playing … and won). It seems that everyone is pretending the championship doesn’t exist simply because US didn’t get far enough.

I had to watch the thing in really bad quality on the internet in danish.

An interesting statistic is that in the past 20 years (ever since Czech republic existed that is), Czech won the most times (6), Canada 5 times, Russia 3 times. So hardly the underdogs nowadays, even if Russia is rated better.

## May 11, 2010

### Yay! End of semester!

Filed under: Mathematics,Personal,Teaching — jlebl @ 9:01 pm

It is finally end of semester. Still have to grade some finals, but other than that, I’m done. It’s also the end of my time at UIUC, next year I’m off to UCSD for a year.

I finished off, at least in a rough draft sort of way, my notes on Hermitian forms and CR geometry, a half semester minicourse I gave at UIUC. Perhaps those will be useful to others. I can’t really say that they will be “bug free,” I am sure there are many typos. There are even some previously unpublished results (though probably previously known). For example, suppose that you have a real analytic function $r(z,\bar{z})$ such that the series (in multiindex notation)

$\sum_{\alpha,\beta} c_{\alpha \beta} z^\alpha \bar{z}^\beta$

converges in the neighbourhood of the unit polydisc (converges absolutely at the point $z = (1,1,1,\ldots,1)$). Then the Hermitian matrix $C = [ c_{\alpha\beta} ]_{\alpha\beta}$ defines a bounded operator on $\ell^2$ (actually it defines a compact operator). For a long time I was always doing all these matrix operations with the coefficient matrices formally. And then you have to be very careful. Once you rescale so that the coefficient matrix is a compact operator, then it’s just like doing linear algebra, and all the subtleties go away.

I also kept updating the differential equations notes like crazy this semester. The students could have gotten up to 3% extra credit for finding errors, but only a handful did. Majority of typos I found myself. The good news is that the notes, especially chapters 0,1,2, and 4 are reasonably bug free. Chapters 3,5,6 also got some bug-spray treatment, but not as much. I still have a bunch of minor grammatical errors pending and I’ll wait for a week maybe before putting out another version just in case somebody still finds some more.

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