Ciro Santilli @cirosantilli 35

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Spacetime interval  Updated 2024-12-23  +Created 1970-01-01

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In the Galilean transformation, there are two separate invariants that two inertial frame of reference always agree on between two separate events:

time
length, given by the Pythagorean theorem

However, in special relativity, neither of those are invariant separately, since space and time are mixed up together.

Instead, there is a new unified invariant: the spacetime-interval, given by:

c Δ t^{2} - (Δ x^{2} + Δ y^{2} + Δ z^{2})

(1)

Note that this distance can be zero for two events separated.

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Spacelike-separated event  Updated 2024-12-23  +Created 1970-01-01

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Mathematically, we can decide if two events are timelike-separated or spacelike-separated by just looking at the sign of the spacetime interval between them.

On the light cone, these are events on the left/right part of the cone.

Different observers might not agree on the order of two spacelike-separated events.

Further discussion at Section "Light cone".

The opposite of those events are timelike-separated events.

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Special unitary of degree 2  Updated 2024-12-23  +Created 1970-01-01

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en.wikipedia.org/wiki/Representation_theory_of_SU(2)

Double cover of

S O (3)

Isomorphic to the quaternions.

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Automated theorem proving by halting problem reduction  Updated 2024-12-23  +Created 1970-01-01

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If you can reduce a mathematical problem to the Halting problem of a specific turing machine, as in the case of a few machines of the Busy beaver scale, then using Turing machine deciders could serve as a method of automated theorem proving.

That feels like it could be an elegant proof method, as you reduce your problem to one of the most well studied representations that exists: a Turing machine.

However it also appears that certain problems cannot be reduced to a halting problem... OMG life sucks (or is awesome?): Section "Turing machine that halts if and only if Collatz conjecture is false".

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The perfect privacy messaging software features  Updated 2024-12-23  +Created 1970-01-01

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Haven't found the one yet:

open source software, doh
end-to-end encryption...
has browser frontend and Android app
public URL without sharing your mobile phone: messaging software that force you to have a mobile phone
self-destroying messages (turned on by default please)
user base large enough to give some confidence that it was reviewed for security issues
easy/built-in setup over Tor

Optional but really ideal:

can delete messages from the device of the person you sent it to, no matter how old
decentralized, your username is a public key

The state of messaging is ridiculous as of 2020.

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Spin experiments  Updated 2024-12-23  +Created 1970-01-01

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Stern-Gerlach experiment
fine structure split in energy levels
anomalous Zeeman effect
of a more statistical nature, but therefore also macroscopic and more dramatically observable:
- ferromagnetism
- Bose-Einstein statistics vs Fermi-Dirac statistics. A notable example is the difference in superfluid transition temperature between superfluid helium-3 and superfluid helium-4.

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Connected components of the orthogonal group  Updated 2024-12-23  +Created 1970-01-01

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The orthogonal group has 2 connected components:

one with determinant +1, which is itself a subgroup known as the special orthogonal group. These are pure rotations without a reflection.
the other with determinant -1. This is not a subgroup as it does not contain the origin. It represents rotations with a reflection.

It is instructive to visualize how the

\pm 1

looks like in

S O (3)

you take the first basis vector and move it to any other. You have therefore two angular parameters.
you take the second one, and move it to be orthogonal to the first new vector. (you can choose a circle around the first new vector, and so you have another angular parameter.
at last, for the last one, there are only two choices that are orthogonal to both previous ones, one in each direction. It is this directio, relative to the others, that determines the "has a reflection or not" thing

As a result it is isomorphic to the direct product of the special orthogonal group by the cyclic group of order 2:

O (n) ≅ S O (n) \times C_{2}

(1)

A low dimensional example:

O (1) ≅ S O (2) \times C_{2}

(2)

because you can only do two things: to flip or not to flip the line around zero.

Note that having the determinant plus or minus 1 is not a definition: there are non-orthogonal groups with determinant plus or minus 1. This is just a property. E.g.:

M = [2132]

(3)

has determinant 1, but:

M^{T} M = [58811]

(4)

M

is not orthogonal.

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AGI research entity  Updated 2024-12-23  +Created 1970-01-01

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www.quora.com/What-are-some-good-research-schools-PhD-for-Artificial-General-Intelligence-not-Machine-Learning/answer/Ciro-Santilli What are some good research schools (PhD) for Artificial General Intelligence (not Machine Learning)?
2020 towardsdatascience.com/four-ai-companies-on-the-bleeding-edge-of-artificial-general-intelligence-b17227a0b64a Top 4 AI companies leading in the race towards Artificial General Intelligence
Douglas Hofstadter according to www.theatlantic.com/magazine/archive/2013/11/the-man-who-would-teach-machines-to-think/309529/ The Man Who Would Teach Machines to Think (2013) by James Somers
Pei Wang from Temple University: cis.temple.edu/~wangp/

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Chinese semiconductor industry  Updated 2024-12-23  +Created 1970-01-01

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Video 1.

China's Making x86 Processors by Asianometry (2021)

Source.

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Executable hd  Updated 2024-12-23  +Created 1970-01-01

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Running:

hd hello_world.out

gives:

00000000  7f 45 4c 46 02 01 01 00  00 00 00 00 00 00 00 00  |.ELF............|
00000010  02 00 3e 00 01 00 00 00  b0 00 40 00 00 00 00 00  |..>.......@.....|
00000020  40 00 00 00 00 00 00 00  10 01 00 00 00 00 00 00  |@...............|
00000030  00 00 00 00 40 00 38 00  02 00 40 00 06 00 03 00  |....@.8...@.....|
00000040  01 00 00 00 05 00 00 00  00 00 00 00 00 00 00 00  |................|
00000050  00 00 40 00 00 00 00 00  00 00 40 00 00 00 00 00  |..@.......@.....|
00000060  d7 00 00 00 00 00 00 00  d7 00 00 00 00 00 00 00  |................|
00000070  00 00 20 00 00 00 00 00  01 00 00 00 06 00 00 00  |.. .............|
00000080  d8 00 00 00 00 00 00 00  d8 00 60 00 00 00 00 00  |..........`.....|
00000090  d8 00 60 00 00 00 00 00  0d 00 00 00 00 00 00 00  |..`.............|
000000a0  0d 00 00 00 00 00 00 00  00 00 20 00 00 00 00 00  |.......... .....|
000000b0  b8 01 00 00 00 bf 01 00  00 00 48 be d8 00 60 00  |..........H...`.|
000000c0  00 00 00 00 ba 0d 00 00  00 0f 05 b8 3c 00 00 00  |............<...|
000000d0  bf 00 00 00 00 0f 05 00  48 65 6c 6c 6f 20 77 6f  |........Hello wo|
000000e0  72 6c 64 21 0a 00 2e 73  79 6d 74 61 62 00 2e 73  |rld!...symtab..s|
000000f0  74 72 74 61 62 00 2e 73  68 73 74 72 74 61 62 00  |trtab..shstrtab.|
00000100  2e 74 65 78 74 00 2e 64  61 74 61 00 00 00 00 00  |.text..data.....|
00000110  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00000150  1b 00 00 00 01 00 00 00  06 00 00 00 00 00 00 00  |................|
00000160  b0 00 40 00 00 00 00 00  b0 00 00 00 00 00 00 00  |..@.............|
00000170  27 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |'...............|
00000180  10 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000190  21 00 00 00 01 00 00 00  03 00 00 00 00 00 00 00  |!...............|
000001a0  d8 00 60 00 00 00 00 00  d8 00 00 00 00 00 00 00  |..`.............|
000001b0  0d 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000001c0  04 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000001d0  11 00 00 00 03 00 00 00  00 00 00 00 00 00 00 00  |................|
000001e0  00 00 00 00 00 00 00 00  e5 00 00 00 00 00 00 00  |................|
000001f0  27 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |'...............|
00000200  01 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000210  01 00 00 00 02 00 00 00  00 00 00 00 00 00 00 00  |................|
00000220  00 00 00 00 00 00 00 00  90 02 00 00 00 00 00 00  |................|
00000230  08 01 00 00 00 00 00 00  05 00 00 00 07 00 00 00  |................|
00000240  08 00 00 00 00 00 00 00  18 00 00 00 00 00 00 00  |................|
00000250  09 00 00 00 03 00 00 00  00 00 00 00 00 00 00 00  |................|
00000260  00 00 00 00 00 00 00 00  98 03 00 00 00 00 00 00  |................|
00000270  4c 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |L...............|
00000280  01 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000290  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000002a0  00 00 00 00 00 00 00 00  00 00 00 00 03 00 01 00  |................|
000002b0  b0 00 40 00 00 00 00 00  00 00 00 00 00 00 00 00  |..@.............|
000002c0  00 00 00 00 03 00 02 00  d8 00 60 00 00 00 00 00  |..........`.....|
000002d0  00 00 00 00 00 00 00 00  01 00 00 00 04 00 f1 ff  |................|
000002e0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000002f0  11 00 00 00 00 00 02 00  d8 00 60 00 00 00 00 00  |..........`.....|
00000300  00 00 00 00 00 00 00 00  1d 00 00 00 00 00 f1 ff  |................|
00000310  0d 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000320  00 00 00 00 04 00 f1 ff  00 00 00 00 00 00 00 00  |................|
00000330  00 00 00 00 00 00 00 00  2d 00 00 00 10 00 01 00  |........-.......|
00000340  b0 00 40 00 00 00 00 00  00 00 00 00 00 00 00 00  |..@.............|
00000350  34 00 00 00 10 00 02 00  e5 00 60 00 00 00 00 00  |4.........`.....|
00000360  00 00 00 00 00 00 00 00  40 00 00 00 10 00 02 00  |........@.......|
00000370  e5 00 60 00 00 00 00 00  00 00 00 00 00 00 00 00  |..`.............|
00000380  47 00 00 00 10 00 02 00  e8 00 60 00 00 00 00 00  |G.........`.....|
00000390  00 00 00 00 00 00 00 00  00 68 65 6c 6c 6f 5f 77  |.........hello_w|
000003a0  6f 72 6c 64 2e 61 73 6d  00 68 65 6c 6c 6f 5f 77  |orld.asm.hello_w|
000003b0  6f 72 6c 64 00 68 65 6c  6c 6f 5f 77 6f 72 6c 64  |orld.hello_world|
000003c0  5f 6c 65 6e 00 5f 73 74  61 72 74 00 5f 5f 62 73  |_len._start.__bs|
000003d0  73 5f 73 74 61 72 74 00  5f 65 64 61 74 61 00 5f  |s_start._edata._|
000003e0  65 6e 64 00                                       |end.|
000003e4

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Artificial general intelligence  Updated 2024-12-23  +Created 1970-01-01

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Given enough computational power per dollar, AGI is inevitable, but it is not sure certain ever happen given the end of end of Moore's Law.

Alternatively, it could also be achieved genetically modified biological brains + brain in a vat.

Imagine a brain the size of a building, perfectly engineered to solve certain engineering problems, and giving hints to human operators + taking feedback from cameras and audio attached to the operators.

This likely implies transhumanism, and mind uploading.

Ciro Santilli joined the silicon industry at one point to help increase our computational capacity and reach AGI.

Ciro believes that the easiest route to full AI, if any, could involve Ciro's 2D reinforcement learning games.

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Link to an image or video in another file that has an \x on title from another file  Updated 2024-12-23  +Created 1970-01-01

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= Programming language

\Image[https://raw.githubusercontent.com/cirosantilli/media/master/python-logo.jpg]
{title=The \x[python-programming-language] logo}

== Python
{c}
{disambiguate=programming-language}

Now, when rendering \x[image-the-python-logo], we would need to fetch two IDs:

But after group all SQL queries together was done, there was no way to know that rendering image-the-python-logo would imply also fetching python-programming-language.

This was solved by adding a new database entry type, REFS_TABLE_X_TITLE_TITLE to the existing References table, which tracks dependencies between IDs.

After this was setup, we can now know that image-the-python-logo depends on image-the-python-logo, and then fetch both of them together in a single JOIN.

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Chinese regional cuisine  Updated 2024-12-23  +Created 1970-01-01

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Chinese book  Updated 2024-12-23  +Created 1970-01-01

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Chinese poetry anthology  Updated 2024-12-23  +Created 1970-01-01

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Length contraction  Updated 2024-12-23  +Created 1970-01-01

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Suppose that a rod has is length

L

measured on a rest frame

S

(or maybe even better: two identical rulers were manufactured, and one is taken on a spaceship, a bit like the twin paradox).

Question: what is the length

L^{'}

than an observer in frame

S^{'}

moving relative to

S

as speed

v

observe the rod to be?

The key idea is that there are two events to consider in each frame, which we call 1 and 2:

the left end of the rod is an observation event at a given position at a given time: $x_{1}$ and $t_{1}$ for $S$ or $x_{1}^{'}$ and $t_{1}^{'}$ for $S^{'}$
the right end of the rod is an observation event at a given position at a given time : $x_{2}$ and $t_{2}$ for $S$ or $x_{2}^{'}$ and $t_{2}^{'}$ for $S^{'}$

Note that what you visually observe on a photograph is a different measurement to the more precise/easy to calculate two event measurement. On a photograph, it seems you might not even see the contraction in some cases as mentioned at en.wikipedia.org/wiki/Terrell_rotation

Measuring a length means to measure the

x_{2} - x_{1}

difference for a single point in time in your frame (

t 2 = t 1

So what we want to obtain is

x_{2}^{'} - x_{1}^{'}

for any given time

t^{'} 2 = t^{'} 1

In summary, we have:

L L^{'} = x_{2} = x_{2}^{'} - x_{1} - x_{1}^{'} t_{2}^{'} = t_{1}^{'}

(1)

By plugging those values into the Lorentz transformation, we can eliminate

t_{2} a n d t_{1}

, and conclude that for any

t_{2}^{'} = t_{1}^{'}

, the length contraction relation holds:

L^{'} = \frac{L}{γ}

(2)

The key question that needs intuitive clarification then is: but how can this be symmetric? How can both observers see each other's rulers shrink?

And the key answer is: because to the second observer, the measurements made by the first observer are not simultaneous. Notably, the two measurement events are obviously spacelike-separated events by looking at the light cone, and therefore can be measured even in different orders by different observers.

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Plane wave function  Updated 2024-12-23  +Created 1970-01-01

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In this solution of the Schrödinger equation, by the uncertainty principle, position is completely unknown (the particle could be anywhere in space), and momentum (and therefore, energy) is perfectly known.

The plane wave function appears for example in the solution of the Schrödinger equation for a free one dimensional particle. This makes sense, because when solving with the time-independent Schrödinger equation, we do separation of variable on fixed energy levels explicitly, and the plane wave solutions are exactly fixed energy level ones.

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Breakthroughs  Updated 2024-12-23  +Created 1970-01-01

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Some less-trivial breakthroughs:

finding 2013 DNS Census
CGI comms characterization
secure subdomain search on 2013 DNS Census let to a few hits
2013 DNS Census virtual host cleanup heuristic keyword searches was massive and led to many new ranges

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Are there .org hits?  Updated 2024-12-23  +Created 1970-01-01

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Previously it was unclear if there were any .org hits, until we found the first one with clear comms: web.archive.org/web/20110624203548/http://awfaoi.org/hand.jar

Later on, two more clear ones were found with expired domain trackers:

azerinews.org
autism-news.org

further settling their existence. Later on newimages.org also came to light.

Others that had been previously found in IP ranges but without clear comms:

65.61.127.177: material-science.org
212.4.17.61: tech-stop.org

Others in IP ranges by unarchived:

74.116.72.244 arborstribune.org

.org is very rare, and has been excluded from some of our search heuristics. That was a shame, but likely not much was missed.

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Atomic, Molecular and Optical Physics  Updated 2024-12-23  +Created 1970-01-01

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AMO is a slightly more general area than condensed matter physics, including related phenomena with smaller numbers atoms and optics. The two terms are however sometimes used as synonyms. The term AMO has gained wide usage and acceptability, see e.g.:

www.sussex.ac.uk/amo/ at University of Sussex

If Ciro had had greater foresight, this might have been what he studied at university!

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