u/Gargantuar314

I'm relatively new to representation theory and want to read up on the very basics. Most introductory representation theory books actually cover the theory of algebras over a field, but I'd like to read more general results from non-commutative algebra, i.e. over non-commutative rings and associative algebras.

During my online search, it seems that Lam's First Course is the canonical recommendation, but I find it incredibly hard to read (up to sec. 3).

• Some more elementary facts are just assumed (homomorphisms of finite direct products can be written as matrices, although Lam blackboxes this to linear algebra over division rings??),
• some I think important parts are not covered (general isotypic decompositions are only a small exercise, and a quick search almost never mentions them),
• they always go on a complete side tangent at the end of sections (e.g. a lot of theory on 2×2-matrices in sec. 1, twisted and differential polynomial rings in sec. 3).

But I must say the exercises are quite good.

Is there another well-written, well-motivated yet comprehensive book on that matter? I'm thinking of books similar to Atiyah-MacDonald or even Matsumura's Commutative Ring Theory. Or even Stein-Shakarchi's Complex Analysis.

I loved my Sony WH-H900N for the past 10 years, and I'm looking for something similar. IMO, they had a relatively even sound profile across bass, mid and treble, and they can be used wired passively without the need for Digital Sound Processing (DSP). Also, there were always replacement cushions after all those years (not necessarily from Sony).

• I'm searching for over-ear headphones for daily use (commute, cooking, music, movies, podcasts, etc.) with relatively even sound profile.
• I want to use them almost always wired passively (i.e. with cable without turning the headphones on). Bluetooth is a nice to have, but not necessary.
• I realized that I don't care about noise cancelling at all.
• Would be nice if I could use them for a long time (replacement cushions are a must).
• My budget is around 200€ in Germany.

I'm learning "Passeio No Rio" by Luiz Bonfa, arranged by Carlos Barbosa-Lima. The piece is alright, but I find the continuous staccato in the base extremely difficult.

Do you have any tips for that? How long should the staccato be? (I aim for a 16th, making it easier if the melody is also just a 16th, so I stop the base while playing the second 16th.) How to make the staccato consistent? How to play the staccato if there is a triad on top (might be also staccato)? (For example in Roland Dyens's arrangement of "A Felicidade", staccato is almost always played by lifting the left fretting hand.)

Thx for your input.

This is a minor annoyance. I use greetd with gtkgreet as my login manager. The problem is that if my laptop boots up, I can't enter my username right away but need to move the mouse a little (anywhere) in order for the username field to be selected.

How can I fix this so that the field is selected and ready for keyboard input right away? It's maybe a general GTK problem, but I don't know.

I'm having difficulty customizing the gtkgreet greeter from greetd with CSS (I use sway, so I don't have a GTK theme). This might not be a greetd issue but my missing knowledge about GTK/CSS.

The gtkgreet man pages are very minimal (e.g. compared to wofi), and the source code seems to set names input-field, command-selector, window, clock and body. Also, I find the CSS overview of GTK3 very confusing.

Do you know any GTK/CSS tutorial on customising GTK elements (in particular which are available/their hierarchy) for beginners like me? Or are there examples of gtkgreet CSS-style files? How do I test my theming without restarting my laptop?