Jack M

I can see that the focal version is higher priority than the jammy ones for python3.10

is there a way to "remove" entries from apt-cache policy?

I will keep documenting the problem here

okay, thanks

then I get

sudo apt install --dry-run libpython3.10-minimal=3.10.12-1~22.04.3

If I try

I get a slightly different error - libpython3.10-stdlib : Depends: libpython3.10-minimal (= 3.10.12-1~22.04.3) but 3.10.14-1+focal1 is to be installed

@ArchismanPanigrahi Did you mean apt-cache policy? I updated the post. I've been running apt update at various times all day in between attempts, so yeah

@ArchismanPanigrahi When I run software-properties-gtk, every single source in the "Other software" tab is unchecked. I'm not sure if I can trust this front-end, though. Is there a config file I can check to be sure?

@ArchismanPanigrahi Sure

that's probably a better way than what I'd been trying so far

yeah

so there are some relationships between the coefficients

and the $\beta$-s are all positive

given $\sum \lambda_i \beta_i$, and $\sum \beta_i$

the problem is to maximize/minimize $\sum_i \lambda_i^{-1}\beta_i$

should I expect that to be annoying to do in closed form?

in n (unknown) dimensions

so if I have say, two linear equality constraints and one inequality constraint, and want to maximize a linear function subject to that

we never did them at school, and whenever I get into a situation where I need to maximize a linear form subject to linear constraints, I feel like it should be the easiest thing ever, but I end up filling a page and getting nowhere

Am I just stupid, or are linear programming problems as hard as they seem to me?

it's been years since I looked at it but it's just incredibly dense, with absolutely no time devoted to actually explaining any of the concepts in it

it's designed for a mathematician specialized in abstract algebra to pull off the shelf when they need a reference for something

If you can get a copy of Lang for free then give it a shot, but it's just not designed for self-teaching

Definitely linear algebra first (I like Jim Hefferson's book, personally)

Great to see you turned up in the chat by the way, your question was not a bad one but just wasn't suitable for the rigid question/answer format of the main site

@MarkosAndres Lang is a terrible book to learn from, it's more like a reference, sort of like a dictionary. I liked "A Book Of Abstract Algebra" by Pinter, I think it would be appropriate for someone in your situation

Does anyone have any thoughts on this question? I asked it several days ago and have been continually coming back and thinking about it, but I still don't have a good answer. math.stackexchange.com/questions/3842835/…

but that's clearly wrong

My understanding was that what that formula meant is that if the "vector representation of the circular motion of A around B" (I'm going to avoid any attempts at technical terminology because I'm clearly utterly confused about it) is added to the vector representation of the motion of B around C, you get the vector representation of the motion of A around C

So I was trying to understand where it comes from, and that addition formula on Wikipedia seemed like a good motivation

That convention always struck me as arbitrary (sure, it takes three free parameters to describe uniform circular motion in space, so you can pack them into a vector if you want, but why do that?)

Ultimately what I'm trying to do is understand is this convention of representing uniform circular motion by a vector (direction gives the axis, magnitude gives the angular speed).

Hi there, thanks for your time

@ja72 I always thought angular velocity was just a useful convention for representing a uniform circular motion. You take a vector parallel to the axis of rotation, and set its magnitude equal to the radians per second of the rotation. That's always how I understood it at school. Does that concept not exist at all?

@ja72 I'm reading Physics For Mathematicians by Spivak in which he defines "the angular velocity of a particle" to be the cross-product $c\times v$ where $c$ is the position of the particle and $v$ its velocity. Is this concept usually known by a different name?

@ja72 The angular velocity of a point $A$ relative to a point $B$ is determined by the axis of rotation and the radians per second, right? In this case everything is happening in a plane, so we only have to worry about radians per second.

@ja72 My understanding of that Wikipedia article is that if we know the angular velocity of $A$ about $B$ and of $B$ about $C$, then we can determine the angular velocity of $A$ about $C$. In figures 1 and 2, the angular velocity of $B$ about $A$ and of $C$ about $B$ are both the same (in each case they are rotating clockwise with some given speed), and yet sure the angular velocity of $C$ about $A$ is different in each figure.

@ja72 Everything is happening in a flat plane. $C$ is rotating around $B$, $B$ is rotating around $A$. The arrows attached to $B$ and $C$ represent their velocity vectors and are $u$ and $v$ respectively.

and right now the not-waking-from-sleep seems to have gone away mysteriously, so we'll see how that develops

the shell freezing turned out to be my fault, caused seemingly by my turning off of Secure Boot in UEFI (which someone somewhere recommended for the audio issue)

I fixed that with the grub config patch that's been recommended here

@dessert Well a bunch of people on this site have made threads about audio not working in the past two days

and I can see a whole bunch of threads in the past two days about the audio issue

waking from suspend broken, audio broken until I patched the grub config, and the shell keeps totally freezing every few minutes

I'm suddenly experiencing a whole bunch of problems on my laptop with Ubuntu 19.10, was there a kernel update recently or something?

without knowing about control theory or what specifically you're trying to do, I can't really advise you on what direction to go in

presumably ODEs are used there which is why you're trying to fit one to this problem