Ciro Santilli @cirosantilli 37

For every continuous symmetry in the system (Lie group), there is a corresponding conservation law.

Furthermore, given the symmetry, we can calculate the derived conservation law, and vice versa.

As mentioned at buzzard.ups.edu/courses/2017spring/projects/schumann-lie-group-ups-434-2017.pdf, what the symmetry (Lie group) acts on (obviously?!) are the Lagrangian generalized coordinates. And from that, we immediately guess that manifolds are going to be important, because the generalized variables of the Lagrangian can trivially be Non-Euclidean geometry, e.g. the pendulum lives on an infinite cylinder.

64 bits is still too much address for current RAM sizes, so most architectures will use less bits.

x86_64 uses 48 bits (256 TiB), and legacy mode's PAE already allows 52-bit addresses (4 PiB). 56-bits is a likely future candidate.

12 of those 48 bits are already reserved for the offset, which leaves 36 bits.

If a 2 level approach is taken, the best split would be two 18 bit levels.

But that would mean that the page directory would have 2^18 = 256K entries, which would take too much RAM: close to a single-level paging for 32 bit architectures!

Therefore, 64 bit architectures create even further page levels, commonly 3 or 4.

x86_64 uses 4 levels in a 9 | 9 | 9 | 9 scheme, so that the upper level only takes up only 2^9 higher level entries.

The 48 bits are split equally into two disjoint parts:

A 5-level scheme is emerging in 2016: software.intel.com/sites/default/files/managed/2b/80/5-level_paging_white_paper.pdf which allows 52-bit addresses with 4k pagetables.

Ross Ulbricht told her about Silk Road, but then later said he had sold the website to someone else, without really doing that.

As of 2023, she's apparently a photographer with a porny focus (boudoir photography).

Some sources:

Matches the quantum superposition probability proportional to the square law. Poor Étienne-Louis Malus, who died so much before this was found.

At least they have a fucking clear course schedule unlike the undergrad.

Hello world: stackoverflow.com/questions/16829351/is-there-a-hello-world-example-for-sparql-with-rdflib

Have a look at some interesting examples under nodejs/sequelize/raw/many_to_many.js.

Kudos for being a not-for-profit. Also, anyone can create content: e-learning websites must allow students to create learning content. Oh, but TODO is possible for anyone to make content publicly visible? Course join links lik: www.khanacademy.org/join/MJZ6NSV7 require login. webapps.stackexchange.com/questions/165132/how-to-create-a-course-that-is-publicly-visible-without-the-need-to-login-on-kha If that's the case, it is a fatal flaw not shared by OurBigBook.com.

Another cool aspect is that they have the "physical world teacher pull student accounts in" approach built-in quite well at course creation. This is a very good feature.

As of 2021 they were a bit struggling for money it seems: www.youtube.com/watch?v=I8XdUy-wyyM?

Unit of mass.

Defined in the 2019 redefinition of the SI base units via the Planck constant. This was possible due to the development of the Kibble balance.

Described for example in lecture 1.

Each transaction isolation level specifies what can or cannot happen when two queries are being run in parallel, i.e.: the memory semantics of the system.

Remember that queries can affects thousands of rows, and database systems like PostgreSQL can run multiple such queries at the same time.

Good summary on the PostgreSQL page: www.postgresql.org/docs/14/transaction-iso.html

Implementation specifics:

Can produce two entangled particles.

Paging makes it easier to compile and run two programs or threads at the same time on a single computer.

For example, when you compile two programs, the compiler does not know if they are going to be running at the same time or not.

So nothing prevents it from using the same RAM address, say, 0x1234, to store a global variable.

And thread stacks, that must be contiguous and keep growing down until they overwrite each other, are an even bigger issue!

But if two programs use the same address and run at the same time, this is obviously going to break them!

Paging solves this problem beautifully by adding one degree of indirection:

(logical) ------------> (physical)
             paging

Where:

Compilers don't need to worry about other programs: they just use simple logical addresses.

As far as programs are concerned, they think they can use any address between 0 and 4 GiB (2^32, FFFFFFFF) on 32-bit systems.

The OS then sets up paging so that identical logical addresses will go into different physical addresses and not overwrite each other.

This makes it much simpler to compile programs and run them at the same time.

Paging achieves that goal, and in addition:

Or if you like non-funny jokes:

Information about ARM paging can be found at: cirosantilli.com/linux-kernel-module-cheat#arm-paging