Dima Pasechnik 🇺🇦 🇳🇱

https://mathoverflow.net/users/11100/dima-pasechnik

USSR->Australia (Perth)->Netherlands->Germany->Netherlands->Singapore->Oxford (UK)->Evanston, Illinois (USA)

Lecturer at CS Department, mathematician interested in "computer algebra".

My Erdős number is 2 in two different ways, via Lex Schrijver, and via Michel Deza.

Homepage: https://pasechnik.info/dima
Keyoxide: https://keyoxide.org/2557439DF23BADA01AE11271A24B0B1E37C90531

Public Key

npub1pkcue49c92gjkl6g5klsfsxzcejjlm7ck0f6fyk2us6svmythhwqhzqy0t

NIP-05 Address

[email protected]

Profile Code

nprofile1qqsqmvwv6juz4yft0ay2t0cycrpvvef0alvt85ayjt9wgdgxdj9mmhqpz3mhxue69uhhyetvv9ujuerpd46hxtnfduqs6amnwvaz7tmwdaejumr0dstptpmc

Publishing to

relay.damus.io

nos.lol

Author Public Key

npub1pkcue49c92gjkl6g5klsfsxzcejjlm7ck0f6fyk2us6svmythhwqhzqy0t

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Last Notes

2026-06-14 21:53:18 UTC

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1-sided is fine, just not put over 30-40 pounds there, then it might start to affect steering...

2026-06-14 21:51:24 UTC

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why is it mounted so insanely high? Move it down as low as the wheel allows.
Trust me on this, I am a naturalized Dutch (and have cycling mileage in the range of 100000 miles - that's what not driving does to you...)

2026-06-14 18:28:56 UTC

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you'd have tried germs our kid brings from school. Makes me want to isolate at home... Maybe it's the way nature tells me that getting kids after turning 45 is not a good idea 😞

2026-05-29 18:34:02 UTC

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it's just about the ways the steam is made (nuclear power stations heat water to create steam to rotate turbines, IIRC)

2026-03-17 01:18:52 UTC

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John - nLabs is written all over you already 🙂
I'd buy one - assuming it's not boring

2026-02-21 22:57:36 UTC

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John, Issac Goldbring wrote extensively on this range of topics lately. I don't know whether quantum logic(s) appear in his work.

2026-02-21 17:47:10 UTC

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with continuous logic being a considerable part of that very tricky quantum physics, demystifying quantum computing this way would be great.
https://ncatlab.org/nlab/show/continuous+logic
@npub1nf4…nqe4

2026-02-21 04:43:43 UTC

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It's actually funny how the progress has been made; it started indeed with quantum complexity theorists, and then the author of the notes I cited removed all quantum stuff from the picture, realising that's it's actually something called continuous logic.

2026-02-21 02:52:07 UTC

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quantum complexity theory is alive, well, and produced few years ago a very deep result in pure maths. Here is a survey with a bit of explaining
https://www.math.uci.edu/~isaac/godel100.pdf

2026-01-28 02:19:48 UTC

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Expect a defamation lawsuit demanding a gazillion billion $$$ from every Brit who didn't buy a ticket ..

2025-10-25 16:05:37 UTC

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one can skip k, as b^k is interger for integer b and k 🙂

2025-10-25 16:02:45 UTC

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if you give a talk in English to a primary English speaking audience, shouldn't you make an effort to use right language idioms? Otherwise your point might be lost. Indeed, "sounds like Chinese to me" means "sounds like Greek to me" in a number of European languages - although not in (American) English.

2025-10-25 15:47:38 UTC

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This physics work is from 2017 or so? I am aware of maths work done back in 2020/21, namely
https://arxiv.org/abs/2108.11747
and found the motivation behind the effort a bit lacking.
I just saw maths work
https://arxiv.org/abs/2502.12815
and as maths it looks interesting etc, but is it relevant to physics? I have no idea.

2025-10-23 21:06:16 UTC

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an interesting take on Fibonacci numbers... For a change, Mathematica appears to be correct 🙂
sage: k=12; (1/int((k-1)*"9"+"8"+k*"9")).n(4000)
1.00000000000100000000000200000000000300000000000500000000000800000000001300000000002100000000003400000000005500000000008900000000014400000000023300000000037700000000061000000000098700000000159700000000258400000000418100000000676500000001094600000001771100000002865700000004636800000007502500000012139300000019641800000031781100000051422900000083204000000134626900000217830900000352457800000570288700000922746500001493035200002415781700003908816900006324598600010233415500016558014100026791429600043349443700070140873300113490317000183631190300297121507300480752697600777874204901258626902502036501107403295128009905331629117308626757127213958386244522585143371736543529616259128672987995672202604254800875592250473078196505273953788755747031985261020985774016768017759277789003533294557021292572346024825866903046118439249070944306152117062745401188007051553305069796954493076848507798146645462291223493970089370139432380593633402469963772834850557406237320521179072171078585309491599764381662678349691154278114072816956463763971234577836788191041600759425619437547616661038307042280475854658941514161701221990016360163504178061385494194421548998372482934492566904483490939387417983506291901474445679319e-24

2025-09-17 23:19:23 UTC

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yeah, they are pure evil indeed.

2025-08-26 21:25:14 UTC

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the money which go to commercial publishers of maths/CS journal from universities around the world would more than suffice to have a a dedicated non-profit to maintain and develop TeX etc 🙂
The commercial publishers milk open-source software landscape without giving anything in return. Same to a large extent applies to big tech - at best they fund bare minimum and make sure what they need gets in - think of Linux development, or llvm/clang development.
Some commercial publishers, e.g. de Gruyter, prefer to take your TeX files and ship them to a low-cost country to get them converted into Word so that they can take advantage of a smooth, although sub-optimal, modern way to publish as cheaply as possible. Your formulae get screwed and typos get introduced, but the shareholders are happy.

2025-08-17 16:53:55 UTC

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not sure if #FreeBSD or #OpenBSD folks agree - they don't have much GNU stuff is their base installs 🙂

2025-08-11 02:27:27 UTC

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on our Mastodon instance we have a much larger number of characters limit, 1728. Lobby your instance admins to get more than 500, which is kind of tight....

2025-07-17 15:26:22 UTC

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the only people who really can't fly in US without a Real ID are these who cannot get a (biometric?) passport. While it's a bit more convenient to carry a card instead of a passport, the other benefits seem to be absent. (Needless to say, such people exist, and I suppose US has millions of them, but, still, what is the point?)

2025-07-07 22:52:24 UTC

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I guess "State" would be a better translation than "National"

2025-04-13 21:27:28 UTC

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hmm, there are algebraic integers with norm as close to 1 as you wish, e.g. a positive real root of $x^n-2=0$ goes to 1 as $n\to\infty$ right? Lehmer number has minimal norm in a much subtler settings,

2025-03-31 20:18:40 UTC

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EU/EEA, and beyond (e.g. Ukraine, Israel,...), 87 countries in total, have International Bank Account Numbers (IBAN).
If your bank supports transfers to IBAN, and I gather all the banks which allow incoming IBAN also allow outgoing ones, you can send money to an IBAN account from your (internet, or not) banking system. In many countries only transactions using IBAN are supported.
here is a reasonably up to date list of IBAN countries:
https://www.natwest.com/support-centre/banking-from-home/make-payments/do-you-have-a-list-of-iban-compliant-countries.html

2025-03-19 18:16:57 UTC

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the committee included two, not one, higher ups in the Russian security services. This alone is a huge red flag, a throwback to the USSR times.
I should also correct myself - two of the three Fields medalists did respond, see more details here:
https://www.math.columbia.edu/~woit/wordpress/?p=12717

2025-03-19 17:07:52 UTC

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that info isn't really helpful. It's more interesting how the things were in Jan 2022:
https://web.archive.org/web/20220128222229/https://icm2022.org/organization
I don't think the 2 Fields medalists on the committee ever said a word in public on the whole hoopla...

2025-03-19 16:13:56 UTC

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the only advantage of looking back into history here is that it's harder to learn about the current examples: Russia, China, Turkey, etc. due to a lot of self-censoring bias.
Everyone still hopefully remembers the last ICM, the composition of its original organisation committee in St Petersburg, how the distinguished mathematicians there were silent, etc.

2025-03-19 00:59:12 UTC

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let me quote from the preface by the translator:
"Mathematics is like vodka. Drink, and you may forget the oppressive world around you...."
https://media.mathstodon.xyz/media_attachments/files/114/186/383/903/998/934/original/e666345d77769641.png

2025-03-19 00:47:32 UTC

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you can certainly find texts on how it was to do science in USSR.
Your monographs or PhD theses were to cite classics of Marxism-Leninism, and if you were a "suspicious" ethnic minority, you'd have a lot of extra trouble (starting from being unable to enter the best undergrad programs - however USA isn't a stanger to this sort of discrimination: it discriminated Afro-Americans, Jews, Asians, although it often wasn't a centrally administered discrimination). Etc etc etc, I can write a lot more - on censorship, on The Party role, etc. Here is a text to give you some ideas.
See e.g. https://archive.org/details/itseemsiamjewsam0000frei

2025-03-17 01:59:40 UTC

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it's a "combinatorial embedding", i.e. collection of distinguished cycles in the graph, so that every edge appears in exactly two of these cycles.
I am not sure how to pick up a basis for the homology group of the 2-holed donut (the join of 2 tori), which is isomorphic to $\mathbb{Z}^4$. It seems there is still something to specify - these is a number of topologically inequivalent ways each cycle can be embedded. The distinguished cycles are embedded in the contractible way, but you can't freely move them around the surface, as there are the remaining simple cycles.

2025-03-16 20:47:06 UTC

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there should be an embedding of this graph into a genus 2 surface - can you see it? (I am told the genus of it by SageMath).

2025-03-16 17:57:37 UTC

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there was an outcry when these rules were changed, but it was only a part of the scandal. There was also a mass (tens of thousands) cancellation of student visas for these who were deemed to cheat on their visa-related English tests - something that didn't contribute to the perception of UK as a good destination for students.
I bet that US anno 2025 is much less attractive to students than in the Biden's years, but it might be a bit of a tough going for UK right now.

2025-03-14 04:28:48 UTC

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100 Gb a month? This probably counts generated data, no? I cannot imagine they get 100 Gb of TeX files a month. One medium length paper is about 50 Kb, rougly.

2025-03-08 01:27:36 UTC

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we'll be riding a night train to Memphis during the spring break - one of not too many such options from Chicago...

2025-03-05 18:49:43 UTC

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not sure about "typical", but there certainly are much less toxic sciences journalists than her. These who don't chase clicks and ad revenue

2025-03-02 20:22:17 UTC

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they are competing for clicks/views on a monetised platform.
This is an adtech-driven bullshit factory, not a social media. It's an antisocial media - the more outrageous the content, the trolling, the more attractive and profitable it gets, doesn't matter whether it has any truth in it.

2025-03-01 01:54:42 UTC

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the world 'leader" can't recall this event, as he admitted on the camera to journos just recently.
He's certainly a dangerous bug, but the bug's memory management is buggy too...

2025-02-15 19:16:58 UTC

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corporations too?
Can one delay/refuse paying federal taxes?
And how is it enforced? Can one ask the employer to not deduct taxes automatically?
I don't see how a party which refuses to obey courts' orders enforce much without direct violence.

2025-02-15 19:11:50 UTC

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are US foundations subject to federal regulations? Then the central government can start selectively revoking their tax privileges/charity status.

2025-02-15 19:06:44 UTC

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I lived through one coup playing out on the streets near my apartment block in Moscow, and I am worried about inability to enforce injunctions against DOGE which are already in place. Will states start to refuse paying federal taxes? This seems to be the most serious means they have, short of sending National Guard to DC...

2025-02-15 18:28:33 UTC

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the recent appearance of Apple Intelligence and Microsoft Copilot - they can be used as keyloggers/data stealers etc, rises a suspicion that it's how they are getting prepared for eventual US govt orders...

2025-02-15 18:18:34 UTC

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you might gonna regret going full-Apple, too

2025-02-15 18:00:18 UTC

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While I don't think privately owned companies fall directly under DOGE/Musk, you never know.
Please make sure to have good copies of what you have on GitHub, preferably on a EU resource, such as https://sr.ht/ or

2025-02-12 05:05:01 UTC

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Denmark already has a petition going to buy California, by the way...

2025-02-07 07:39:08 UTC

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I dealt with VFS last year, while trying to get new passports for my son and myself. Cause the Dutch govt in its infinite wisdom all but outsourced provision of passports to the residing abroad citizens to it. VFS is a true clusterfuck. We ended up getting our passports in the Netherlands instead.

2025-02-06 15:31:45 UTC

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something implemented in a language with the only implementation controlled by Google is less secure than GnuPG. Sorry.

2025-02-06 15:24:13 UTC

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I frankly don't care if someone hacks into my Linux laptop to find out that I have a github account from the pass' data. Because in this case I surely would have much worse problems to solve.
At least with pass I can leave my smartphone at home, this is much more important to me.
And you probably don't know an asymmetric open source alternative to PGP/GPG either, so this is also out of place.

2025-02-05 23:11:09 UTC

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I know just one password manager which also doubles up as 2FA code generator. It's called pass, and it's a CLI application. It encrypts the data using GPG, and distributes/backs up data using git.
Just added a new key? Well, do "pass git push" to send it over, encrypted, to your git server. Yes, you'll need to do "pass git pull" on the other installs.
I can only complain that adding 2FA keys is somewhat painful.

2025-02-02 01:47:11 UTC

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I prefer to call them Vandals. Move fast, break things, nothing new/creative

2025-01-21 16:10:08 UTC

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you can see the denial explained here:
https://sagemath.blogspot.com/2015/09/the-simons-foundation-and-open-source.html
They just won't be bothered to deal with a proposal, should it ever come, so it wasn't written.

2025-01-21 14:51:08 UTC

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NSA is the biggest user of Magma, and the biggest employer of mathematicians in USA. Magma has the best availabile tools, in number theory and in group theory, for the kind of cryptography-related maths they need.
William Stein failed to get any grant money for SageMath from Simons, despite - or I suppose because of - being in position to develop open-source alternatives to Magma.
https://wstein.org/grants/
In an article I can't find any more he records his interactions with Simons Foundation. It's an interesting read.
EDIT: @npub1zr5…7n3t kindly pointed at the link I wasn't finding:
https://sagemath.blogspot.com/2015/09/the-simons-foundation-and-open-source.html

2025-01-21 14:46:10 UTC

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Well, they had a choice - either go all in for Democrats, spending large, very large sums of money, 100s of millions, speaking forcefully against Trump, conducting targeted social media campaigns (if FB chose to influence the outcome of elections, they have tools, as we learened, tools used by rightwing politicians) with a chance that Trump still wins and damages their businesses by withholding contracts, unleashing regulators on them, etc. But they haven't done so. They prefer money to democracy. See e.g.
https://www.cnn.com/2024/10/25/media/washington-post-wont-endorse-presidential-candidate/index.html

2025-01-21 06:18:28 UTC

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I don't read it as "they give in". I read it as they are seeing new business opportunities.

2025-01-21 05:35:26 UTC

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OTOH, at one point Simons has pleased (indirectly, but still) NSA, the biggest user of the computer algebra system Magma, by funding Magma licenses on the US campuses. Ruined careers of some people we know along the way.

2025-01-21 05:30:48 UTC

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the system where the corporations can play such an outsize role in politics has been set up in the US long ago (started back in Reigan times, no?). Them seizing power was a question of time, there isn't that much new now.

2025-01-11 01:40:04 UTC

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I am with whoever (von Neumann ?) said that we never understand a maths concept, we just get used to it.

2024-12-28 18:03:59 UTC

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I'm also not joining any corp-run things any more. Sooner or later bsky will either follow the twitter way, or google+ way...
I also find it alarming that mathoverflow is seemingly losing popularity, and is plagued by glory-seeking trolls who copy-paste various LLM-generated stuff there.

2024-12-28 17:02:38 UTC

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you actually don't have to "go" to bsky to let people there follow you and converse with you. All you need to do is to follow [@bsky.brid.gy](https://bsky.brid.gy/ ) - this automatically sets up an account they can follow/converse with (I am trying this, although I'm too busy doing a stuff called vacation now)

2024-12-19 02:16:35 UTC

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by the way, we have a Math. Ann. geometric group theory paper from late 1970s translated from German to English, and plan to translate a few more.
What's a procedure to make it officially public? Do we have to ask the authors for a permission? The publisher?

2024-12-09 04:16:44 UTC

status update: apologies for neglecting this space since late Oct. The excuse: we have moved across the pond (I misspelled it "pont", which (pontus, to be precise) is a Greek word for sea coast)) to the shore of Lake Michigan, to work at Northwestern University, in Greater Chicago.
Main reasons:
* NHS won't treat well most acute health problems of our son
* the state of education for kids like him in UK is really of collapse
* I won't need to claim my somewhat shaky rights for making my job open-ended, with possible fun things such as Employment Tribunal etc
Needless to say, of the 1st 5 weeks, most of the time went into dealing with various bureaucracy (formsss!!! and yes, Social Security Numbers office misspelt my name on the card, and the university tax office put down our citizenships as UK (wrong), etc etc) and, hmm, hardware issues: while most of our possessions are making it over on a ship, I spent time getting and assembling the minimal furniture (yes, we actually bought a house, as rental options are somewhat miserable here), fixing heating (the company who did it needed 10 days, including 5 preliminary visits and aborted attempts).
And new school and doctors for the kid, health insurance, bicycle tire punctures, the bank which is obsessed with security and blocks my card now and then, etc etc.

2024-10-20 21:50:37 UTC

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an hour of sunny weather for the day, the rest washed away by rain and high wind

2024-10-20 20:52:20 UTC

Greetings from Edinburgh. I'll spend a week at ICMS working with two colleagues from France/Canada.
https://media.mathstodon.xyz/media_attachments/files/113/341/721/735/660/809/original/23873883389846f6.jpg

2024-09-29 21:30:28 UTC

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Thanks John, I appreciate your comment a lot. Making jokes on the net is hard work.
By the way, we're about to move to the US, to Northwestern University. I hope I'll survive my totally unintended insults of the locals over there. 🙂

2024-09-29 20:44:18 UTC

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I certainly haven't meant anything like this. I meant to suggest, jokingly, that you don't enjoy hearing "steenkolen Engels" - i.e. the way Dutch butcher English language.
You know, everybody there speaks quite some English, but often has no idea about the proper idioms, e.g. tourists coming from NL over here say that they "live" here rather than "stay", etc.

2024-09-29 19:58:14 UTC

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oops, probably "to have a beef" is very rude English expression, sorry, I have no idea...
I "learnt" the language at school from Morning Star, the only freely available English language source from abroad (and yes, compulsory reading - the schoolkids from USSR thus subsidised UK Commies). 😞
Anyhow, I don't care about Formula 1, and I don't drive. And I wish this country pays more attention to needs of the pedestrians, and less to cars.
Just yesterday we had to cross A40 at Forest Hill turn, that's about halfway between Oxford and Wheatley, a 6-lane semi-motorway, to get to a bus stop to Oxford. No signs, no zebra crossing, nothing. Only a narrow path on the middle separation of the traffic. The 1st bus didn't stop (whooshing past at about 80km/h). The driver of the 2nd bus, which I had to hail stepping onto the road and frantically waving my mobile phone with the torch on, said that they are not used to getting any passengers there.
How such a road layout is even legal? Forest Hill is a sizeable village 500m from A40, without any weekend bus services (and very poor ones on the weekdays).
And you wonder why there are so many traffic jams...

2024-09-29 19:15:29 UTC

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it seems you have a beef with the Dutch 🙂
Mind you, what's acceptable in Dutch newspapers and in the parliament (basically various f*k and relatives, to quite some extent) might come is extremely rude in English. To me the English "silly", or even "stupid", it not swearing, and I really don't get what the fuss is all about.
E.g. the following heading is roughly (it's a bit stronger word there - there is no double meaning, etc) translated as "old dicks at a danse lesson"
https://www.noordhollandsdagblad.nl/regio/west-friesland/ouwe-lullen-op-dansles/20756165.html
And, pardon me, I'm having huge difficulty attempting to convey in English that sometimes is silly without saying "silly" or "stupid" - and I gather that Verstappen has this even more (after all my exposure to Dutch was shorter than his :-))

2024-09-13 19:35:12 UTC

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you might need an OS which is open-source, to start with 🙂

2024-09-08 19:49:21 UTC

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"pull the string to reboot"