OVH is forcing me to pay $2k upfront for a server I don't plan on using.

I seriously can’t believe what I’m going through.
Back in 2019, I decided to purchase a RISE-3 Server for 1 year, paid approximately 1.6k … | Read the rest of

dnd 5e – Should forcing open doors be Strength or Strength (Athletics)

RAW Forcing open a door is a Strength Check

Comparing Strength with Strength (Athletics) as described in the PHB, we can conclude that forcing open a door should be a Strength check.

Let’s start with Strength checks. The PHB says (175/176 – emphasis mine) says

A Strength check can model any attempt to lift, push, pull, or break something, to force your body through a space, or to otherwise apply brute force to a situation…
The DM might also call for a Strength check when you try to accomplish tasks like
the following:
Force open a stuck, locked, or barred door
• Break free of bonds
• Push through a tunnel that is too small
• Hang on to a wagon while being dragged behind it
• Tip over a statue
• Keep a boulder from rolling

We note first that Strength checks are explicitly called out as being used for forcing doors open, as well as breaking things in general. On a more subtle note, we can see that they reflect short bursts of ‘brute force’, single events that either succeed or fail immediately.

On Strength (Athletics) checks, however, the PHB (175 – emphasis mine) says:

The Athletics skill reflects aptitude in certain kinds of Strength checks…Your Strength (Athletics) check covers difficult situations you encounter while climbing, jumping, or swimming. Examples include the following activities:
• You attempt to climb a sheer or slippery cliff, avoid hazards while scaling a wall, or cling to a surface while something is trying to knock you off.
• You try to jump an unusually long distance or pull off a stunt midjump.
• You struggle to swim or stay afloat in treacherous currents, storm-tossed waves, or areas of thick seaweed. Or another creature tries to push or pull you underwater
or otherwise interfere with your swimming.

By their nature, Athletics checks are not used for events, but rather for situations. There is some complex process that you are attempting over a period of time, and the DM calls for a check to see if you can pass the most difficult or dangerous part of the process. (Grammarians should note the shift from the simple tense descriptions of Strength checks to the progressive tenses of the Strength (Athletics) checks.)

Two people with equal Strengths might be equally good at the “burst strength” required to tip over a statue. But, by virtue of their Athletic training, a person with the Athletics skill would have the stamina, focus, balance, and determination needed for a long climb up a sheer cliff that someone with untrained raw strength would lack.

Applying this background understanding to the specific question of opening doors, we can assume that most doors would be subject to a single instance of burst strength, a single event of applying enough force to break through their structural integrity (lock, latch, bar, hinges, or what have you). A portcullis has a certain weight – if the character can lift the weight in a single burst (Strength), the portcullis can be lifted.

But there are situations in which Athletics could rightly be considered

A Strength (Athletics) check might be properly called for when opening the door or lifting the portcullis is no longer an event but has become a prolonged and difficult situation. For example – the gate of the palisade is thick and barred from the other side, and no simple burst of strength will sunder it. You can eventually chop through it with your axe, but can you do that before the orcs arrive?

You can lift the portcullis; you are strong enough for that, but can you hold it open for several rounds while the rest of the party makes it under and you are being subjected to missile and spell fire?

axiom of choice – Does ZF + BPI alone prove the equivalence between “Baire theorem for compact Hausdorff spaces” and “Rasiowa-Sikorski Lemma for Forcing Posets”?

Rasiowa-Sikorski Lemma (for forcing posets)is the statement: For any p.o. $mathbb{P}$ (i.e. $mathbb{P}$ is a reflexive transitive relation) and for any countable family of dense subsets of $mathbb{P}$ there is a generic filter which intersects all dense subsets of the countable family. It is well-known that this statement is equivalent to the Baire Category Theorem for Complete Metric Spaces – and thus it is also equivalent to the Principle of Dependent Choices.

A masters student of mine has found in the literature the following statement: “Rasiowa-Sikorski Lemma is equivalent to the Baire Category Theorem for Compact Hausdorff Spaces, modulo the Boolean Prime Ideal Theorem”. We understood this as the assertion that the theory ZF + BPI alone is able to prove the equivalence between the Baire Category Theorem for Compact Hausdorff Spaces and the Rasiowa-Sikorski Lemma.

Well, I asked my student to verify such claim, and at first glance I suggested him to follow the results 3.1 to 3.4 of Chapter II of Kunen’s book, where there are proofs for some equivalences of Martin’s Axiom at $kappa$, MA($kappa$): the idea was to discard the hypothesis “c.c.c.” and adapt the reasoning, arguing for $kappa = omega$. It turns out that it was not a good suggestion, because in 3.1 a kind of Downward-Lowenheim-Skolem argument is done, to show that it is equivalent to work with a restricted form of the forcing axiom, considering only partial orders of bounded cardinality. However, such argument seems to require the Axiom of Choice, or some part of it other than BPI.

Does any of you know if it is indeed possible to prove the equivalence between “Baire Category Theorem for Compact Hausdorff Spaces” and “Rasiowa-Sikorski Lemma for forcing posets” from ZF + BPI alone ? Any suggestions or references would be appreciated.

Forcing a webpage to completely reload content (Not CTRL-F5)

I’m developing a page analyzer – the site is VERY anti-scraping and appears to not show the newest data immediately when you load a page.

If you refresh the page, it doesn’t always update. It seems like it will only let you see the newest data every 10-20 minutes. Even a CTRL-F5 refresh doesn’t update it.

Opening a new incognito browser seems to get the newest data. But then you need to close the browser and re-open to get it again.

Using a VPN does not appear to affect it, so it’s not IP based. Logging in/out doesn’t change it so not account based – it must be cookie/cache based?

Any suggestions on ways to allow the page to continue to auto-refresh, without closing/reopening an incognito browser?

postgresql – Forcing a fresh start with Postgres after updating major version

On my Manjaro machine, I updated packages, and Postgres got updated to version 13.2-1.

Before the update, I had some databases on the previous version. Now Postgres won’t start because it recognises that the existing databases are from the old version. When I attempt to start Postgres, I get:

~|⇒ sudo systemctl status postgresql
● postgresql.service - PostgreSQL database server
     Loaded: loaded (/usr/lib/systemd/system/postgresql.service; disabled; vendor preset: disabled)
     Active: failed (Result: exit-code) since Fri 2021-03-12 21:30:02 GMT; 2min 53s ago
    Process: 3173 ExecStartPre=/usr/bin/postgresql-check-db-dir ${PGROOT}/data (code=exited, status=1/FAILURE)

Mar 12 21:30:01 xps systemd(1): Starting PostgreSQL database server...
Mar 12 21:30:02 xps postgres(3173): An old version of the database format was found.
Mar 12 21:30:02 xps postgres(3173): See
Mar 12 21:30:02 xps systemd(1): postgresql.service: Control process exited, code=exited, status=1/FAILURE
Mar 12 21:30:02 xps systemd(1): postgresql.service: Failed with result 'exit-code'.
Mar 12 21:30:02 xps systemd(1): Failed to start PostgreSQL database server.

Those databases weren’t important. They were for my personal pet projects and I’m happy to delete them.

How do I do that? Postgres won’t start, so I can’t delete them through psql. How can I force the latest version to start afresh? Ignore or delete the existing databases.

set theory – Reference request: forcing diamond at every stationary subset of every regular cardinal

I’m in search of a published proof that there is a (class) iteration that forces $Diamond_kappa(S)$ to hold for all regular uncountable $kappa$ and all stationary $S subseteq kappa$.

It’s OK if the citation assumes GCH. Surprisingly, I’ve been unable to find such a thing. Any suggestions?

Easton support iteration of adding Cohen sets at uncountable regular cardinals works, and the proof is routine to a set theorist. But the intended audience of the paper I’m writing may not know iterated forcing, and I’d prefer to just give a citation.

ct.category theory – sheaf-theoretic approach to forcing

Inspired by the question here, I have been trying to understand the sheaf-theoretic approach to forcing, as in MacLane–Moerdijk’s book “Sheaves in geometry and logic”, Chapter VI.

A general comment is that sheaf-theoretic methods do not a priori produce “material set theories”. Here “material set theory” refers to set theory axiomatized on the element-of relation $in$, as usually done, in ZFC. Rather, they produce “structural set theories”, where “structural set theory” refers to set theory axiomatized on sets and morphisms between them, as in the elementary theory of the category of sets ETCS. I will always add a collection (equivalently, replacement) axiom to ETCS; let’s denote it ETCSR for brevity. Then Shulman in Comparing material and structural set theories shows that the theories ZFC and ETCSR are “equivalent” (see Corollary 9.5) in the sense that one can go back and forth between models of these theories. From ZFC to ETCSR, one simply takes the category of sets; in the converse direction, one builds the sets of ZFC in terms of well-founded extensional trees (modeling the “element-of” relation) labeled by (structural) sets.

So for this question, I will work in the setting of structural set theory throughout.

There are different ways to formulate the data required to build a forcing extension. One economic way is to start with an extremally disconnected profinite set $S$, and a point $sin S$. (The partially ordered set is then given by the open and closed subsets of $S$, ordered by inclusion.) One can endow the category of open and closed subsets $Usubset S$ with the “double-negation topology”, where a cover is given by a family ${U_isubset U}_i$ such that $bigcup_i U_isubset U$ is dense. Let $mathrm{Sh}(S)$ denote the category of sheaves on $S$ with respect to this topology.

Then $mathrm{Sh}(S)$ is a boolean (Grothendieck) topos satisfying the axiom of choice, but it is not yet a model of ETCSR. But with our choice of $sin S$, we can form the ($2$-categorical) colimit
$$varinjlim_{Uni s} mathrm{Sh}(U)$$
called the filter-quotient construction by MacLane–Moerdijk. I’m highly tempted to believe that this is a model of ETCSR — something like this seems to be suggested by the discussions of forcing in terms of sheaf theory — but have not checked it. (See my answer here for a sketch that it is well-pointed. Edit: I see that well-pointedness is also Exercise 7 of Chapter VI in MacLane–Moerdijk.)


  1. Is it true that $varinjlim_{Uni S} mathrm{Sh}(U)$ is a model of ETCSR?
  2. If the answer to 1) is Yes, how does this relate to forcing?

Note that in usual presentations of forcing, if one wants to actually build a new model of ZFC, one has to first choose a countable base model $M$. This does not seem to be necessary here, but maybe this is just a sign that all of this does not really work this way.

Here is another confusion, again on the premise that the answer to 1) is Yes (so probably premature). An example of an extremally disconnected profinite set $S$ is the Stone-Cech compactification of a discrete set $S_0$. In that case, forcing is not supposed to produce new models. On the other hand, $mathrm{Sh}(S)=mathrm{Sh}(S_0)=prod_{S_0} mathrm{Set}$, and if $s$ is a non-principal ultrafilter on $S_0$, then $varinjlim_{Uni s} mathrm{Sh}(U)$ is exactly an ultraproduct of $mathrm{Set}$ — which may have very similar properties to $mathrm{Set}$, but is not $mathrm{Set}$ itself. What is going on?

How to enable USB Tethering without forcing me to use mobile data plan?

I wanted to tether my phone’s connection to my pc via this old phone that i found, there’s a setting for USB tethering but when i turn it on it says to turn on the mobile data?? I went to the help thingy in the settings for the USB tethering and this showed, is there no way to stop forcing me to turn on my data just to share my connection to my pc?enter image description here

set theory – Are generic filters that produce the same forcing extension related by a ground-model automorphism?

Suppose $M$ is a countable transitive model of some fragment of $mathbf{ZFC}$, $mathbb{P}in M$ is a forcing notion and $G, H$ are $mathbb{P}$-generic such that $M(G)=M(H)$. Does it then follow that there is some automorphism $pi:mathbb{P}longrightarrowmathbb{P}$ such that $piin M$ and $pi(G)=H$?

If the answer is no, are there natural restrictions one could impose on $mathbb{P}$ (maybe apart from $mathbb{P}$ being finite) such that the above sentence holds?

Brute Forcing DVWA with Hydra

I am attempting to brute-force ‘DVWA/vulnerabilities/brute/’ with Hydra, rockyou.txt password list.
I tried using this command:

hydra -V -l admin -P rockyou.txt http-get-form "/DVWA/vulnerabilities/brute/:username=^USER^&password=^PASS^&Login=Login:F=Username and/or password incorrect.:H=Cookie: security=low; PHPSESSID=0tp8jmqci1c8qblpgocgkuck0p"

And the output of this is:

[80][http-get-form] host: localhost   login: admin   password: iloveyou
[80][http-get-form] host: localhost   login: admin   password: princess
[80][http-get-form] host: localhost   login: admin   password: 1234567
[80][http-get-form] host: localhost   login: admin   password: 123456
[80][http-get-form] host: localhost   login: admin   password: 12345
[80][http-get-form] host: localhost   login: admin   password: 123456789
[80][http-get-form] host: localhost   login: admin   password: password
[80][http-get-form] host: localhost   login: admin   password: 12345678
[80][http-get-form] host: localhost   login: admin   password: nicole
[80][http-get-form] host: localhost   login: admin   password: rockyou
[80][http-get-form] host: localhost   login: admin   password: abc123
[80][http-get-form] host: localhost   login: admin   password: daniel
[80][http-get-form] host: localhost   login: admin   password: babygirl
[80][http-get-form] host: localhost   login: admin   password: monkey
[80][http-get-form] host: localhost   login: admin   password: lovely
[80][http-get-form] host: localhost   login: admin   password: jessica
1 of 1 target successfully completed, 16 valid passwords found

16 passwords that doesn’t even work…
I tried changing ‘’ with ‘localhost’, changing Cookie…

What am I doing wrong ?