Tag links in network search page go to stackexchange.com rather than the searched-for site I recently discovered that the top bar on  searches the entire network. For instance, if you , you can find all the questions on the network about shoes:    But if you click on one of the tags, you'll be sent to a non-existent page: . I would have expected to land a the site's tag page instead:.  For what it's worth, this is a very minor bug and unlikely to bother too many people as I do not believe the network search is widely known. (But it's really handy and more people should know about it!)
Clicking on tags in global search results is broken If you search for something on "all sites" (using the searchbox at the top of , you'll reach the search results, e.g.  .  If you click directly on a tag on that page, e.g.        You get 404 Page Not Found error, e.g.     Steps to reproduce   Go to  and enter e.g. "keyforge" into the "Search all sites" field. Arrive at  Click on the "keyforge" tag below a search entry. Reach  (404 page not found)   Expected behaviour  Reach   System Info  Happens in both Firefox and Vivaldi browsers on Windows 10.
Flag indicator present on Meta, but no flags visible Why does second pre-image resistance imply pre-image resistance I am studying hash functions. I can understand why collision resistance implies second preimage resistance, but I don't get why second preimage resistance should imply first preimage resistance. Could anybody be help me with this argument from Introduction to Modern Cryptography by Katz &amp; Lindell, please?   Collision resistance: This is the strongest notion and the one we have considered so far.  Second pre-image resistance: Informally speaking, a hash function is second pre-image resistant if given $s$ and $x$ it is infeasible for a probabilistic polynomial-time adversary to find $x' \ne x$ such that $H^s(x') = H^s(s)$.  Pre-image resistance: Informally, a hash function is pre-image resistant if given $s$ and $y = H^s(x)$ (but not $x$ itself) for a randomly chosen $x$, it is infeasible for a probabilistic polynomial-time adversary to find a value $x'$ such that $H^s(x') = y$. (Looking ahead to later chapters in the book, this essentially means that $H^s$ is one-way.)   [...] Likewise, any hash function that is second pre-image resistant is also pre-image resistant. This is due to the fact that if it is possible to invert $y$ and find an $x^\prime$ such that $H^s (x^\prime ) = y$ then it is possible to take $x$, compute $y = H^s (x)$ and invert it again obtaining $x^\prime$. Since the domain of $H$ is infinite, it follows that with good probability $x \neq x^\prime$. We conclude that the above three security requirements form a hierarchy with each definition implying the one below it. New Chain causing skipping on cassette - will this work itself out or is it unsafe? I just installed a new chain on my 2002 Trek 2200 Road Bike.  The old chain was a Shimano 9 speed that I installed 18 months and about 5000 miles ago.  It had stretched modestly and was full of winter cruft/grime.  The new chain is a SRAM 9 speed, my first time using the gold snap ring system.  I followed instructions and made sure I have the same link count as the chain that came off the bike.  The cassette was new with the old chain, so it has about 5000 miles on it and doesn't appear to have significant wear.  After installation and a clean/wipe/lube/wipe, I took it for a 15 mile easy ride at about 15-16 mph.  It shifts perfectly and I didn't have to make any adjustments to either derailleur.  Three times, however, when putting it under stain (once on a modest hill climb, once starting from a stop sign in a fairly big gear, and once on an acceleration coming out of a sharp turn) it skipped several teeth and caused my foot to slam down hard.  On the hill, it actually hurt as I had my weight off the saddle (not really standing) and I came down hard on the inside of my thigh.  I think all three were on the right side (power train side) pedal stroke, and I don't think they were all in the same gear.  I'm pretty sure it was the rear cassette that skipped, not the front chainring, but it did happen really fast each time.  I will also say that it's not like these were the only three times I put substantial pressure on the pedals in the ride - I wasn't going hard, but I wasn't being tentative or anything.  Also, in case it's relevant, it was cold, about 40 degrees F or about 4 degrees Centigrade.    My question:  Is this going to get me hurt, or will the new chain 'settle in' over a few rides?  I searched here and pretty much got confirmation of what I had previously thought, that you always get a new chain when you get a new cassette, but you should be able to get a few chains out of each cassette.  Thanks! $x^p-c$ has no root in a field $F$ if and only if $x^p-c$ is irreducible? Find the population size that maximizes the probability that two random samples of size $20$ will have exactly $2$ members in common Ten fish are caught in a lake, marked, and then returned to the lake. Two days later 20 fish are again caught, 2 of which have been marked.  (a) Find the probability of 2 of the 20 fish being marked if the lake has $k$ fish (assuming the fish are caught at random). (b) What value of k maximizes the probability?    Progress:     I got the (a), $$\binom{10}{2}\binom{k-10}{18}\bigg/ \binom{k}{20}$$ But how do I get part (b) where $k$ is to maximize the probability? Change elements on different positions within a list Solving ODE with negative expansion power series I am solving a series of ODE, such that each DE is equal to some degree of term that I'm expanding to. For instance, one DE is this:  $\xi^r\partial_r g_{rr}+2g_{tt}\partial_t\xi^t=\mathcal{O}(r)$  $g_{ii}$ are given, from metric, but that's not important. I need to assume that the solution (since I'm looking for components of $\xi^\mu$, which is a vector with components $\xi^t,\xi^r,\xi^\phi$) is given with power series of the form:  $\xi^\mu=\sum\limits_{n}\xi^\mu_n(t,\phi)r^n$, and this is to be seen as expansion around $1/r$ (expansion around $r=\infty$).  Now when I plug this in the ODE I get this  $\frac{2}{l^2}\sum_n\xi^r_nr^{n+1}+2\sum_n\xi^t_{n,t} r^n+\frac{2}{l^2}\sum_n\xi^t_{n,t}r^{n+2}=\mathcal{O}(r)$, where   $\xi^\mu_{n,i}$   is the derivative with the respect to i-th component.   What troubles me is, how to expand this? Do I set n=0,-1,-2,... until my $\mathcal{O}(r)$ terms cancel each other out? Or?  I'm kinda stuck :\ How to rotate the curve but not the axes? How many connected components does $\mathrm{GL}_n(\mathbb R)$ have? gedit: search and replace with regular expressions I want to replace this with gedit:   1299465 |  2003415 | 2015-09-06 05:35:34.59662+02  1299449 |  2009400 | 2015-09-06 05:35:32.301683+02  1299450 |  2008465 | 2015-09-06 05:35:32.451393+02  1299457 |  2015211 | 2015-09-06 05:35:33.451049+02   to that:  2003415 2009400 2008465 2015211   How can I do this with gedit?  Background: I want to do it with gedit and not sed/python/.... since the replace needs to be done interactive. On found exact duplicates, should these be voted to close directly against a preferred, or ultimate, canonical question?   Or is a chain of possible duplicates (where one question is closed as duplicate of another, which itself is a duplicate of another, and so on and so on) allowable or OK?  One example of this situation can be found . Recently, I was in a car and noticed a plane in the sky. What was interesting was that the plane seemed to go slower than my car because I passed the plane. Is there a physics reason to this? I got a stomach flu or I got the stomach flu or I got stomach flu? pdf of a quotient of uniform random variables Suppose $x_1, x_2$ are IDD random variables uniformly distributed on the interval $(0,1)$.  What is the pdf of the quotient $x_2 / x_1$? Can you 'exit' a loop in PHP? How to align prices in columns when both 2 digit and 4 digit variations of a price exist? What is a mixin, and why are they useful? Why do a lot of questions from around 2008 seem to have really high upvotes? I have seen this a lot but i ran into this question today:    And the answer (while good) has 83 upvotes which seemed a little over the top.  I see dozens of answers of this caliber every week that only seem to get a few upvotes.    Was there some sort of SO policy that encouraged people to upvote more during this period?  Am I just imagining that answers from this period received more votes than comparable ones now? Prove that if $d \mid n \in \mathbb{N}$, then $\varphi(d) \mid \varphi(n)$. I want to prove that if $d \mid n \in \mathbb{N}$, then $\varphi(d) \mid \varphi(n)$.  It's given that $d \mid n$, so we know that $n = dm$, for some $m \in \mathbb{Z}$. Now, I want to show that $\varphi(d) \mid \varphi(n)$, i.e. that $\varphi(n) = k\varphi(d)$, for some $k \in \mathbb{Z}$. Drawing a blank of where to go from here. Is it really possible to break the speed of light by flicking your wrist with a laser pointer?