- Is it true that varnish doesn’t work with HTTPS?
- Is there an alternative that works well with magento 2? For two reasons, one I don’t think it works with HTTPS, and two it’s causing me too much trouble and breaking my site.

# Tag: about

## essay about united nations

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essay about united nations

## How do Course Aggregating sites like ClassCentral & CourseRoot gather data about courses? [on hold]

I am trying to understand How these course aggregator sites gather data about courses. Do they use API to get access to data or use web crawlers.

## I have a question about domain transfer

Hi,

this may seem a newbie question but this is confusing for me.

If anyone can explain this, I would be greatful.

I have this website (domain+hosting) with a company. registered on Sep 18, 2018 for one year.

The hosting package + domain is going to expire on Sep 17, 2019.

I want to keep this domain but not with this company.

So do I have to transfer this domain or renew with another company?

And when?

If I transfer this domain to new company, today on June 23, 2019.

Will it be…

I have a question about domain transfer

## About an argument in the paper “Commutators on $\ell_\infty$” by Dosev and Johnson

In the paper “Commutators on $ \ell_\infty$ ” by Dosev and Johnson, in Lemma 4.2 Cas II, the authors have said that “There exists a normalized bock basis $ \{u_i\}$ of $ \{x_i\}$ and a normalized block basis $ \{v_i\}$ of $ \{y_i\}$ such that $ \|u_i-v_i\|<\frac{1}{i}.$ Does anyone have any idea to prove this?

More elaborately, we have two subspaces $ X$ and $ Y$ of $ \ell_\infty$ both isomorphic to $ c_0.$ $ \{x_i\}$ and $ \{y_i\}$ are bases of $ X$ and $ Y$ respectively which are equivalent to standard base of $ c_0$ . We have also $ X\cap Y=\{0\}$ and $ d(X,Y):=\inf\{\|x-y\|:x\in X,y\in Y, \|x\|=1\}=0.$ Now how to show “There exists a normalized bock basis $ \{u_i\}$ of $ \{x_i\}$ and a normalized block basis $ \{v_i\}$ of $ \{y_i\}$ such that $ \|u_i-v_i\|<\frac{1}{i}.$ ” ?

## Would this pure class theory about ordinals and their relations raise concerns about its arithmetic soundness?

The following theory is a class theory, where all classes are either classes of ordinals, or relations between classes of ordinals, i.e. classes of Kuratowski ordered pairs of ordinals, or otherwise classes of unordered pairs of ordinals. However, the size of its universe is weakly inaccessible. Ordinals are defined as von Neumann ordinals. The theory is formalized in first order logic with equality and membership.

**Extensionality:** $ \forall z (z \in x \leftrightarrow z \in y) \to x=y$

**Comprehension:** if $ \phi$ is a formula in which the symbol $ “x”$ is not free, then all closures of: $ $ \exists x \forall y (y \in x \leftrightarrow \exists z(y \in z) \land \phi)$ $ ; are axioms.

**Ordinal pairing:** $ \forall \text{ ordinals } \alpha \beta \ \exists x (\{\alpha,\beta\} \in x) $

*Define:* $ \langle \alpha \beta \rangle = \{\{\alpha\},\{\alpha,\beta\}\}$

**Ordinal adjunction:**: $ \forall \text { ordinal } \alpha \ \exists x (\alpha \cup \{\alpha\} \in x)$

**Relations:** $ \forall \text{ ordinals } \alpha \beta \ \exists x (\langle \alpha, \beta \rangle \in x)$

**Elements:** $ \exists y (x \in y) \to ordinal(x) \lor \exists \text{ ordinals } \alpha \beta \ (x=\langle \alpha,\beta \rangle \lor x=\{\alpha,\beta\})$

**Size:** $ ORD \text { is weakly inaccessible}$

Where $ ORD$ is the class of all element ordinals.

/Theory definition finished.

Now this theory clearly can define various extended arithmetical operations on element ordinals. Also it proves transfinite induction over element ordinals. In some sense it can be regarded as stretching arithmetic to the infinite world. Of course $ PA$ is interpretable in the finite segment of this theory.

In this posting Nik Weaver in his answer raised the concern of ZFC being arithmetically unsound.

My question: assuming this theory to be consistent, is the concern of it being arithmetically unsound is the same as that with ZFC?

The motive for this question is that it appears to me that the above theory is just a naive extension of numbers to the infinite world, it has no power set axiom nor the alike. One can say that this theory is in some sense purely mathematical in the sense that it’s only about numbers and their relations. Would this raise the same kind of suspicion about arithmetic unsoundness that is raised with ZFC.

My reasoning about that is that generally speaking when one raises the concern of arithmetic unsoundness of some theory, especially if that theory is well received by mathematicians working in set theory and foundations, then there must be some technical or intuitive argument behind that suspicion, otherwise that suspicion would be unfounded. The suspicion must not depend merely on the strength of the theory in question. Otherwise we’d not define any theory stronger than $ PA$ based on such concerns.

From Nik Weaver’s answer it appears to me that his concern is based on ZFC not capturing a clear concept intuitively speaking. Now this theory is based on an intuitive concept that is generally similar to the one behind defining arithmetic for finite sets. It extends it in a very clear intuitive manner, higher ordinals are *defined* from prior ones in successive manner, and it doesn’t generally feel to be so different from the intuitive underpinnings of arithmetic in the finite world. So the question here is about if this theory still fall a prey to the arguments upon which the concerns about arithmetic unsoundness of ZFC are based.

## What’s the point of DHS warning passengers about Manila airport?

I’ve seen the following warning printed next to all TSA checkpoints in a US airport:

The Department of Homeland Security (DHS) today announced the determination that aviation security at Ninoy Aquino International Airport (MNL), which serves as a last-point-of-departure airport for flights to the United States, does not maintain and carry out effective security consistent with the security standards established by the International Civil Aviation Organization (ICAO).

What is the point of this warning? Are they warning passengers that direct flights to Manila will be cancelled soon? Or is it just a generic warning designed to force Manila airport to improve their security?

## Proof of lemma from Hong’s article about multi-threaded max flow algorithm

I’m struggling to prove Lemma 3 and Lemma 4 from an article about parallel version of push-relabel algorithm: A lock-free multi-threaded algorithm for the maximum flow problem.

Lemma 3.Any trace of two push and/or lift operations is equivalent to either a stage-clean trace or a stage-stepping trace.

And

Lemma 4.For any trace of three or more push and/or lift operations, there exists an equivalent trace consisting of a sequence of non-overlapping traces, each of which is either stage-clean or stage-stepping.

Pdf version of the article can be found here

## I’m travelling from Canada with a criminal record. Which countries are sticky about criminal records?

I’m wondering which countries may not let me in with a criminal record.

I’m planning on doing a bunch of travelling in the next few years and I wanna know which countries might give me a hard time getting in and which ones won’t. and which charges these countries care about.

Thanks!

## European airport policy about certain chemical substances [on hold]

As title tells, i want to know if airports are restricted on some chemical reagents, including: iodine, potassium nitrate, sulfur, silver, copper hydroxide, copper metal, carbon electrodes, potassium bisulfite and simillar things. I want to mention that listed stuff is all solid stuff that is allowed to non licensed trade like on eBay and so on, only some of them are on watchlist due to drug and explosives manufacture, like iodine, potassium nitrate and sulfur. I know that they got tendency to freak out with liquids and anything that even looks little bit suspicious, im gonna proper pack & label everything and if additional questions are needed, im able to answear them all. Is it possible?

For example, if i want to travel from EU to UK by aircraft, and i have my goods in small quantities in original packing that are all inside my backpack in a box. None of them are illegal, some are watched, none of them are liquids, none of them are really hazardous, poisonous or corrosive. For example they scan my luggage and decide to ask me some questions, i got nothing to hide so ill answer them all. My three additional questions are, -Can they still turn me back and not let me in, even if my ticket is already booked? -If yes, is there any way to avoid it by early declaration about my “special” possibly hazardous stuff? -If yes, would it cost much more? (i imagine yes)