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PhysicsOverflow at the 5th Offtopicarium

Since Wednesday lat evening, I am back happy and still a bit tired from the 5th Offtopicarium in Wegierska Gorka, Poland.  As the Offtopicarium is organized by science nerds for nerds ;-), it was a lot of fun to be together with the very nice small (about 30 people) group of young people. The program was rather interdisciplinary, ranging from biology, history, constructed languages, space projects of students, science communication and education, and many more things. I hope all talks will be accessible soon from the official homepage. In particular the talk about Opening Science  could be worthwhile to consider in some detail, as there is some overlap to what we want to achieve by the Reviews section. Getting to Wegierska Gorka from Bad Doberan (Germany) was a bit cumbersome and time-consuming.  From Katowice I still had to take another train for 2 hours. Considering different means of public transportation, proper time of the trip can not be reduced to less than 14h+  which is therefore the global minimum. route Therefore I was not able to arrive before Saturday afternoon. The meeting had begun on Thursday already and missed therefore about the first half of the talks. All talks have been very good and impressive generally, here you can see  for example Piotr Migdal giving a talk about how often the best and most innovative things are done by people with greatest passion and motivation in their free time, even though (or because) they do not get paid for it. As PhysicsOverflow for example …  😉 IMAG0284 My talk about PhysicsOverflow Happily, my talk about PhysicsOverflow was soon enough ready as you can see below. And surprisingly I realised that I did not even have to take notes about what I’m going to say (as for other talks related to my work) but I could just go on blathering  without effort … ! When bragging about PhysicsOverflow, I am obviously unstoppable 😛 Unfortunately, my laptop refused to connect to the WLAN in the meeting room, so I could not show a live demonstration :-/. You can find the slides of my talk here (the quality was better in PPT than it now is in PDF)  🙂 IMAG0290 In the introduction, I first explained why a new higher-level physics site was urgently needed, how PhysicsOverflow is organised in different parts such as Reviews, Q&A, Meta, etc as well as our most important principles and characteristics. On the next slides, I introduced the Q&A part as a physics analog of MathOverflow and explained the most basic things about how it works, scope, etc … To introduce the Reviews section I ranted a bit about how present journal peer-reviewing sucks ;-), then explained how paper reviewing is done on PhysicsOverflow, and showed two examples of a negatively and a positively reviewed paper. I also got a very good discussion to my talk (nicely supported by Piotr Migdal) , the following issues have been discussed (not in exactly the order listed here):

  • Why did we have to creat something new instead of using something that already exists, such as for example the SE platform?

To answer this, I had prepared in advance a slide (22) that summarises a bit why the goals of the SE company IMO clash with the intentions of a high-level academic community. Somebody mentioned that there are academic sites in the network too which is true but works only  for exceptional cases (I only know MO and CST) … Piotr helped by explaining that very high-level questions are not really high-lighted on SE for example. Also, conversely to the time when MathOverflow was created almost exactly 5 years ago (congratulations!) , SE does no longer give away its software today. There have also been

  • Some discussion about partitioning the site instead of supporting other communities in starting their own site (for example PhysicsUnderflow) to build an Overflow network

This is in principle doable as we have categories in addition to tags,  as for example explained on slide 20  about the differences between the PO and SE software.

  • Of course, I also called for a second developer

which resulted in the suggestion to upload the code on Github for other people to help us with the development and debugging, but as Polarkernel said we are not yet ready to do this … There have also been some

  • Questions about how many people we have, how many papers are submitted, etc :

About 250 newly registered, not all are active at the same time of course … The Reviews section (Reviews I) went online later than the Q&A section, so it is natural for it to have less content  (48 papers at present) than the Q&A section. Another questions was about

  • What could endanger the success of the site?

Here I said that at  the beginning, I and probably others were too enthusiastic about the Reviews section finally getting started, so we were too permissive about accepting submissions. But this is fixed now by our “reject to review policy”. There was also

  • Some discussions about the formula to calculate the final score of submissions:

Strong nonlinearity, the effect of additional points for one unit  accuracy and originality depends in  not plain obvious way on the votes the paper already has… As the accuracy determines the sign of the final score, crackpots who make unfounded “revolutionary” claims are punished which is a good feature. Does this formula really what we want to achieve in all cases? Final remarks The meeting was really fun, and there have been many cool nice people  :-). I am very happy about the positive response I got to my introduction of PhysicsOverflow and will also reconsider some of the other great talks I have seen. And I really liked it to meet Piotr Migdal in person 🙂 BTW he has now submitted his PhD thesis, congratulations ! Only the mud (literally!) sucked on our trip to the mountains because it was rainy the days before …  😀 P1110416 Joking … The trip was fun too 🙂

A long step towards the adult PhysicsOverflow

Today, the new category system, which allows an unrestricted number of category-levels, has been installed on PhysicsOverflow. This system was required to enable the categorization of submissions beyond the four levels provided by the actual Question2Answer (Q2A) framework. This new system is almost invisible for the user, but has the important function to make a (future) large number of submissions searchable by the user. About two and a half months have been required to develop this system, you had to wait for a long time. Therefore I like to give you some insights.

The original category system of the Q2A framework is a hierarchical database model. Every node (a category) is linked to its parent by the ID of the parent node. Such a model enables a fast writing of new nodes (you just create the node and link it to its parent), while queries through the tree are usually slow. Q2A solved this issue by a fixed number of 4 category levels. To be able to find parents in a short time, the path to the parent is hard-coded in every post. This means that every post contains four indices storing the way back through the tree. This is a clever and fast solution. However, it can not be extended to an unrestricted number of categories, it even gets slow if extended to 8 levels for instance. The category system is written in the core code of Q2A and spread over a large part of the system.

Another issue arising when we increase the number of category levels is the user interface. Actually, when the user asks a question, he has to select the category for this post. The user interface uses select tags like:


It is clear that for instance for eight categories, the place on the page is too small to display all these tags side by side. Therefore also the user interface had to be changed. The new user interface take much less room and looks like this:


For the new category system, I have implemented another database model, called nested set model. It allows for an unrestricted number of category levels. While queries through the categories become very fast, the insertion of nodes is slow, because all indices of the whole tree have to be changed. However, changes on the categories will be used much less frequent than for instance to display the tree. Like this, it is well adapted to our needs.

As already mentioned, the original category system is placed in the core code of Q2A and is active in almost all pages provided by the framework (even in pages I never expected this). I had to replace 9 files completely, all select specifications for database accesses to the category system had to be renewed and, naturally, the code for the nested set model had to be written. To give you an impression on the size of the task, here some numbers: The original Question2Answer framework consists of about 36’000 lines of code. Until today, I have written 18’100 new lines of code for PhysicsOverflow in form of plugins, layers, overrides and changes in the core code, about half of the size of the system. The new system required 5’800 additional lines of code, which explains, why it took that long to realize it. I hope now that I was able to test all use-cases so that there remain eventually only minor bugs.

The next development step will be a surprise, stay tuned!


PhysicsOverflow is Living and Animated

Wondering what happened on PhysicsOverflow while I have developed the preliminary phase of PhysicsOverflows reviews section, Reviews I, I have looked on the host providers statistic and have done some queries in the event log of our database. Here are some numbers illustrating the pleasant activity on our site:

Number of visits in May 2014 (provider’s statistic):


As you can see, the number is slightly growing. The number of visits has been above 300 all the time approaching now 400 by end of the month. Maybe somebody has an explanation for the peak after the second weekend?

In the event log table of the database, 14’482 events have been logged in May 2014. Some interesting numbers are

  • 4126 times, a user has logged in.
  • 200 questions have been written.
  • 353 answers have been posted.
  • 1002 comments have been added.
  • 4995 upvotes have been given.
  • 86 new users have registered on the site.

I think this is really not bad for the second month after publishing the site. Maybe we will already have quite a number of submissions in the reviews section by end of next month? Interested? Submit a paper to PhysicsOverflow!

Reviews I: complete

We have decided to launch the reviews section earlier, an its preliminary phase, Reviews I.

We don’t yet have all the fancy features that will come in Reviews II, such as the automatic paper imports, the fancy paper sorting system, and so on and so forth, but the preliminary version is here! So, how does Reviews I work?

Basically, since the plugins for mass-importing, daily importing, and importing by users aren’t ready yet, only administrators can currently create submissions. Users may request the submission of any paper for review, and claim authorship to a paper in the following threads respectively:

Submission Creation Requests

Claims of Paper Authorship

If an administrator can create a submission, why didn’t you just open this feature up to everyone?

Because the plugin isn’t perfect yet.

The main issue I see so far is that the plugin allows you to submit as submission to any section, including Q&A, Reviews, Meta, and even the section Closed Questions.

In the final version of the plugin that will eventually be available to all users, the plugin will only ask for the ArXiV paper ID, e.g. “1403.1254”, and other things like Paper title, Date of submission, paper URL, etc., will be automatically found by the plugin itself. This also prevents users from misusing the plugin to fake the date at which the paper was submitted, and so on. The plugin should also verify that a paper with the submitted paper ID exists. And even if people don’t misuse it, we should be able to advertise the reviews section as “Just enter the ArXiV ID to submit your paper.” : )

What next?

  • Mass-import all physics papers from the ArXiV.
  • Make a bot which imports all new physics papers on the ArXiV daily.
  • Simplify and secure the plugin as mentioned above.
  • Increase the maximum category depth to allow for a hierarchial tag system.
  • Start mass-retagging all the papers. I’d stick to “mass-retag all new papers, and twice the number of old papers as new papers everyday”. Sorry Ron, but I don’t think it’s practical to rush through the entire ArXiV and put it in an elaborate tag system in a few hours. The community needs to be told “Retag every paper you see that you can.”.

And then there are plans for continuous development, including locally hosting contributions, locally editing contributions with a full-fledged TeX editor like, academic advertising of papers to pay for hosting, and so on.

So what are you waiting for? Submit a paper to PhysicsOverflow!


A “beginners” complementation to PhysicsOverflow?

PhysicsOverflow has always been, and will always be a site for physics and has always maintained, and will continue to forever maintain a minimum level or standard for questions. Specifically, every question posted on PhysicsOverflow must be at least at a graduate level. For example, in terms of theoretical physics, quantum field theory and advanced general relativity mark the bottom level for questions.

However, we have recently had private discussions with a user who has preferred to remain anonymous, about setting up a lower-level completion to PhysicsOverflow. I personally consider this to be an absolutely brilliant idea. When we first talked about starting a new physics forum or Question & Answer site, we immediately wanted to have a site at a higher level because we felt that a free, frank, and non-censorious environment was most needed for a site at a higher level as opposed to a site for basic physics. When we conducted our poll for the level of our site nearly last year, “graduate level” won the poll. However, now that PhysicsOverflow is up and running, we realise that every community that discusses a scientific discipline needs a free, frank, and non-censorious environment to develop.

First of all, let me note that we are NOT planning to allow lower-level physics on PhysicsOverflow. PhysicsOverflow shall maintain its level forever. Our plan is to set up an additional site at a lower level than PhysicsOverflow at a domain like They will get to use our software (since our software contains many additional plugins made by polarkernel to the freely available, open-source Question2Answer software). This was not the first time we have seen the lack of a free, frank, and non-censorious site for lower-level physics. Another user, whose preference for anonymity is unknown, has also previously expressed that there is no undergraduate-level counterpart for PhysicsOverflow. The plan is therefore to set up an additional site (PhysicsUnderflow?) at a subdomain of PhysicsOverflow, like or

Will this positively affect PhysicsOverflow?

Yes, of course!

  • Post migration – This is the main positive impact of a “PhysicsUnderflow” on PhysicsOverflow. If a question is too basic for PhysicsOverflow or too advanced for “PhysicsUnderflow”, the question can be migrated between the sites. There is a Question2Answer plugin for this.
  • More contributors – I mean positive contributors. If someone enjoys participating on “PhysicsUnderflow”, they have a greater likelihood of participating on PhysicsOverflow, when they’re ready to participate on PhysicsOverflow.
  • Post diversion – Currently, we tell new users in their confirmation emails that PhysicsOverflow is a site for physics at a graduate-level and above; basic questions go here: If we have a brother site, “PhysicsUnderflow”, we can tell users to participate on PhysicsUnderflow for lower-level physics.

How can I help?

The PhysicsOverflow team is unfortunately uncapable of providing our full attention to “PhysicsUnderflow”, since we all have long to-do lists for PhysicsOverflow itself. The “PhysicsUnderflow” project requires:

  • At least one Super-administrator. This is essential. A super-administrator’s tasks include: executing the will of the community and managing the site in general, importing of posts from StackExchange, if the PhysicsUnderflow deems this necessary.
  • It would be nice to have a Developer to assist polarkernel at least in the beginning for setting up this site. This developer would have to voluntarily support the development of a “PhysicsUnderflow”, i.e. to put it straightforwardly, we, as a very small team, are currently incapable of paying an additional developer for the development of a “PhysicsUnderflow”.
  • Most importantly, the site needs to have a Community. There are no minimum criteria for activity (unlike in some dystopic settings across the internet), but people who are interested in a “PhysicsUnderflow”.

If you want to make the idea of a “PhysicsUnderflow” a reality, then please try to help out.

I am willing to be a super-administrator on “PhysicsUnderflow”! What next?

The first step in setting up a “PhysicsUnderflow”, in my opinion, is to set up a public blog for organised disucssion on this matter, like how PhysicsOverflow set up this very blog as per John McVirgo’s suggestion. You are encouraged to use as structure similar to that of this blog when writing posts for comment discussion on this blog of a “PhysicsUnderflow”. So please tell us if you are willing (and have the time, capacity, and inclination) to be a super-administrator, and tell us the URL of the blog that you have set up so we can link to it from the top of this post.

How will PhysicsOverflow support PhysicsUnderflow?

  • Helping you install all the PhysicsOverflow software (including the Question2Answer core, all our plugins, our theme, admin panel code, and everything) on it.
  • Providing you with a list of our custom pages.
  • Telling you how we deal with community moderation, provide a list of our community moderation posts.
  • Advising you on managing a “PhysicsUnderflow”, etc., ; for example, do you think it that this beginners site would also need to import posts from SE? In that case, it would be a pretty huge burden on you, since there are a lot of basic questions on SE. Maybe you should just import questions with at least 10 votes and not graduate-level+.
  • Promote the beginners site on the tpproposal blog and on the meta of PhysicsOverflow (done)

Eventually, I hope to see more and more “*erflow” (where “*” could be “und” or “ov”) sites form, and eventually form some sort of a large “Erflow” network with each scientific discipline having two sites, one overflow, and one underflow. Like a, etc. Anyway, that will probably take years : )

Physics Overflow is going to go public!

Finally, a long-awaited announcement. Physics Overflow’s private beta will end next week at midnight on Thursday, i.e. at 0000 hours, 4 April 2014!

This means that the public beta, which is the fifth phase in the history of Physics Overflow is going to begin. The phases so far are:

  • The TRF thread
  • The blog
  • The offline site [Foetushood]
  • The private beta [Infanthood]
  • The public beta (will begin next week) [Childhood]
  • Site Graduation… (in late August or beyond) [Adulthood]

So Physics Overflow will reach it’s childhood at the age of one and a half months next week! Sorry, couldn’t resist from giving stupid analogies.

Seriously, these things remain to be done, with the deadline (I copy an answer of mine from Physics Overflow):


I think that the TP.SE question Public beta: Attracting users? is also relevant to us.

In my opinion, there are some plug-ins (a job for polarkernel) remaining to be installed as soon as possible, such as

These plug-ins are good to have, and the first one is almost a necessity. I wonder why Q2A does not incorporate it in it’s core.

The second one gives admins some great tools to see how well the site is faring at a glance. It could even be made public I hope.

Additionally, we also may want to decide on solutions for having a chat room. That somehow reminds me; we may also consider retaining the tpproposal blog as a (hopefully $\infty$) life-long blog for Physics Overflow. The chat room; I’m not sure if we should wait for the public beta to start or not, but I just thought of reminding everyone about it.

From the things you have listed the following need to be done by 0000 hours, [CEST]

  • Sunday:
  • Tuesday:
    • We should invite everyone listed in the blog post.
    • We should announce on the TRF thread and invite Lubos too. Dilaton will write a guest post on TRF.
    • We should obviously announce on the blog.
    • On the blog, user10001 (dushya) had the idea of promoting the site to various physicists in the world.
  • Wednesday: 
    • I (and anyone else who is interested) need to finish 14 and 15 of the FAQ.
    • The long users need to be corrected (I will do this).
    • The main page needs to be set to Q&A.
  • Thursday:  
    • Change permissions
    • Edit robots.txt (a job for polarkernel)
    • Changing all admin-added links (in the sidebar, navbar, etc.)

What to expect and do when Physics Overflow goes online for it’s public beta?

What to Expect?

When I posted my last post, we were under the impression that when going online, we will bring both the Q&A category and the Reviews (paper refereeing) category online together. However, we later realised that this is not possible, as bringing Q&A online will be (relatively) less work than bringing Reviews online. For bringing the reviews section online, we need to have a plugin for a new species of questions with 2 voting criteria. Then the ArXiV papers need to be imported by a bot (which means basically every ArXiV paper has a question with a link to the paper). Polarkernel’s first estimate for all this is about 3 months.

After this, we need to sort all these imported ArXiV papers into a hierarchical categorial system. If about 3 or 4 people help out in this during their weekends, giving it 6 hours a day, this will take around 2 months. Of course, I hope that more people than 3 or 4 could volunteer. Anyway, the development of the plugin and the recategorisation will together take about 5 months, so we expect the reviews section to go online around mid- or late- August.

But Q&A is going to go online sooner than that. We have to do the following things before we can bring Q&A online:

  • Elect our first moderators. (we just need Ron to agree to become a moderator)
  • Exclude the reviews section from the percentage of answered questions etc. (even though reviews is not going online so soon)
  • Expand the FAQ a bit, and mark the parts that can be expanded later. (simple)
  • Fix a bug with our notification box.
  • Have a plugin for community wiki posts. (may not be so essential)
  • Hide post revisions from search engines and other bots (simple)
  • Install a plugin that increases SEO.  (simple

Import of SE questions will go on for a while in the background.

So when we go online for our public, expect to see the Q&A and meta categories ready!

What to do?

If you participated on the Theoretical Physics Stack Exchange, or the Physics Stack Exchange, then your posts may already have been imported, so you may already have an account on Physics Overflow.  Please search for your account to check if this is the case.

Search to see if your account already exists

Enter your username, and press “Search”.

Enter your username

If you are lead to your profile, your account exists. Then you can regain access to your imported account. To do so, click on “Regain SE account” in the sidebar sidebox. Enter the email, username, and password that you used on TheoreticalPhysics.SE or Physics.SE.

Regain Stack Exchange account

Then press “Register”. You will then be logged in to your account, where you are recommended to change your password.

If your SE account is deleted, you can register as a new user and ask for your imported posts to be assigned to your account as described in the sidebar sidebox.

If you accidentally register as a new user, even though you have posts which were imported, you can ask for your accounts to be merged as described in the sidebar sidebox.

If you don’t remember your account particulars, you can ask an administrator to send them to you as described in the regain account page.

If you never had an SE account, or never had graduate-level posts on SE, just register as a new user.