There are various ways doing backup. In this post, I will briefly walk through the options available.

1. Old School

The most easiest way to back up files is to use a USB flash memory stick or an external hard drive. Just connect it to your computer and copy the files over. The downside of this approach is that it is easy to forget to backup in the first place, and sometimes it is annoying.

2. Tivoli Storage Manager

The University provides a backup program and storage for graduate students and faculty members. The program they use is IBM Tivoli Storage Manager (TSM). In contrast of the first old school approach, this is a massive professional solution to get backup done. It transfers the data on your computer to three different backup servers installed somewhere in the corners of the University network.

To use TSM, the computer should be connected to the University network directly, because of bandwidth issues. For instructions on how to setup a TSM backup for your computer, visit the HFS webpage of the OUCS.

3. Time Machine (for Mac)

Mac OS X 10.5, also called as Leopard, has a built-in automatic backup solution called the Time Machine. It supports over the network backup and external hard drives. (Unfortunately not USB sticks.) Also, it is easy to setup just flick a switch on the Time Machine panel.

For details visit, Time Machine features page, and this Time Machine How-To tutorial.

4. Distributed Revision Control (for Unix, Linux and Macs)

Personally I use this solution, because it is free and I can track changes of my files. It is recommended to people who mostly use text files, like TeX files or source files etc. I have written a post on how to make this work.

Git as a Backup Solution

Oriel College has one squash court in JMH. To use the squash court, you should book the court online.

1. Where is it?

The squash is in David Paterson House in James Mellon Hall of Oriel College annex.

Oriel squash court on Google Maps.

2. How do I book it?

The squash court booking system is on the Oriel JCR website. You will need a JCR website ID and password. The account information is not the same as the Oxford University single sign-on system. To get an account contact the JCR computing officer:

Oliver Constance, oliver.constance@oriel.ox.ac.uk

3. The squash ladder

We have a fully automated online Oriel squash ladder. This also has a separate login ID. You will need to sign up freshly for the ladder. You can only challenge up to 3 position above you.

4. I want to take it more serious!

Also you can join the Oriel Squash team. Currently the captain is,

Seb Byas, seb.byas@oriel.ox.ac.uk

It’s not new at all. Starting mid time last year, there were indicators that the economy will go through a down turn. This didn’t really affect me until I was laid off by my college as a web-sub editor. The bright side: I have more free time, and hopefully have some more time to blog.

I am planning to write mostly about computers. This is because I am the Oriel MCR computing officer, and I would like to write some posts that will help the MCR members. The first post I am planning to write about is about “backup”.

My friend pointed out that the Clay Mathematics Institute has released books in PDF format, and are available on the CMI Lecture Notes and Articles page.

There are some interesting books, such as

• Ricci Flow and the Poincaré Conjecture
  John Morgan and Gang Tian
• Mirror Symmetry
  Cumrun Vafa and Eric Zaslow
• Strings and Geometry
  Michael Douglas, Jerome Gauntlett, Mark Gross

They are all wonderful books. The Mirror Symmetry book, which I often use as a reference, is the most complete literature survey I have found on the subject; it is nearly a 1000 pages! Thanks to the PDF version, now I can just grab my laptop and move around the world with all the heavy books right next to me!

I have decided to relaunch my blog, and cover things that are not related to work, but closely related to my hobbies. Work related stuff will be posted on my institute homepage, and hopefully on the arXiv. Meanwhile, I am going to write mostly about:

• Reviews of books
• Squash
• Technology

I know it is a random mixture of things, and I do not intend to aim at a specific audience. In the end, blogging is for fun.

I also changed my blog’s name; it used to be The Art of Equations, I intended to be a pun of The Art of Computer Programming, but it didn’t work out as I hoped it to. I changed my blog’s name to “.square”. Why? I have something in mind, but maybe only the French will get it.

I have been busy lately, working on my mini-project writing a review article on D-branes, homological algebra, and category theory. I have posted the review on my homepage, but if you want to learn it seriously I recommend reading Aspinwall, D-Branes on Calabi-Yau Manifolds. I had to compress the 132-page-long lecture notes and also Witten’s Mirror Manifolds and Topological Field Theory in just 15 pages for my essay, so I couldn’t build up homological mirror symmetry from scratch.

I also gave a talk on this subject for the Part III return conference in Cambridge, which was held for theoretical physicists that did Part III last year. It was nice to see all my friends again. Here is a cute teaser by Flip for the fifth Part III return conference. I was initially planning to blog about the conference, but I decided against it. Mostly because I didn’t understand most of the talks, except for Cyril’s talk on spin geometry.

Since all of the dust has settled down, I will (attempt to) start blogging regularly. I can’t promise anything now, but I am hoping to write about generalized complex geometry. There is one problem, though, I have to learn it beforehand! So patience and silence might be needed.

T. D. Lee and C. N. Yang received a Nobel Prize in Physics for their theory in weak force interactions between elementary particles. They predicted that weak interaction between elementary particles do not have parity symmetry (P). This was confirmed in a famous experiment by Chien-Shiung Wu. There is an interesting episode on this experiment.

Pauli and Schwinger had formulated CPT theorem before people learned that in weak interactions, actually P is not conserved. (Even though P is not conserved in weak interaction, CPT theorem is not violated in the end. – I don’t know how to show this, but I know it is well-known (to others).) Before Pauli knew the results of the experiment of Wu, he wrote to Weisskopf in a letter dated January 17, 1957[1]:

[...] I do not believe the Lord is a left-hander, and I am ready to bet a very high sum that the experiment will give symmetric angular distribution of the electrons. [...]

Georges M. Temmer was on a laboratory tour in western Europe at that time, and Pauli asked him what was the latest news from the States. Temmer said that parity is no longer assumed to be “conserved”. Pauli replied with great surprise “that’s total nonsense”. Temmer said “I assure you that the experiment says not”. Pauli curtly, “then it must be repeated!”. [2]

After knowing the results of the experiment, Pauli wrote to Weisskopf in January 27, 1957.

[...] Now the first shock is over and I began to pull myself together. [...] It is good that I did not make a bet. I can afford making a fool out of myself, but cannot afford loosing money. [1, and re-translated by my friend]

But stories around weak interaction does not end on Pauli. T. D. Lee and C. N. Yang are also well known to have been in bad relationship for a long time.

It was when C. N. Yang was in Princeton. T. D. Lee came from Chicago and visited him and had a private conversation in his office. After a few minutes, people in the hallway could hear both of them shouting at each other, and T. D. Lee burst out of Yang’s office and slammed the door behind. Unfortunately, nobody around could understand Chinese, and the reason of quarrel has been a mystery since. People guess it was about who, among them, first proposed the idea of parity non-conservation for weak interaction.

There is another episode. It happened when Yang was visiting Malaysia for a conference. The Malaysian press were interested at the Nobel Laureate, and asked “what do you regret most in your life?”. Yang said, “the fact that I selected T. D. Lee”. [3]

Sources
[1] Tung-Mow Yan, Professor C. N. Yang’s Impact on Physics
[2] David R Lide, A Century of Excellence in Measurements, Standards, and Technology
[3] ExtraD, C. N. Yang and T. D. Lee (Korean)

Prof. Dominic Joyce is a good lecturer. In his lectures he concentrates on delivering the ideas rather than all the messy details with humor. His style is reflected in his lecture notes and his website. (His page about his book `Compact manifolds with special holonomy‘ is hilarious.)

His lecture notes `Riemannian holonmy groups and calibrated geometry‘ is a summary of his books, but it is more geared toward SYZ conjecture. It is similar to the first section of `Calabi-Yau manifolds and Related Symmetry‘ (Springer), but has less material, thus making it ideal for people who do not want to learn all the details in the area.

The lecture notes take the differential geometer’s point of view. Rather than working with indecies intensively, mostly it uses index free notation. It starts from the very basics to establish notation, it defines tensors and forms, connections, holonomy groups, and Berger’s classification of holonomy groups. I really liked this way of approaching manifolds. I must say even though this lecture notes did not have direct impact on my research, when I was reading it, it was one of the happy moments that I couldn’t wait to go back to my office and read more about it.

The lecture notes quickly move onto Kahler manifolds and Calabi-Yau manifolds. Most of the materials are stated without great details, because Dominic wants to move on into calibrated geometry. I guess if you are not familiar with complex manifolds, the lecture notes might feel challenging by this point. For introductory notes on complex manifolds, there are Candelas, Bouchard, Nakahara. For people who are more mathematically minded there is also Huybrechts, but don’t get fooled by its title that claims it is an introduction, it is quite advanced.

After discussing all the preliminary material, Dominic moves on to calibrated geometry. But why calibrated geometry? It is because he wants to discuss about the SYZ conjecture. Calibrated geometry turns out to be the most natural framework to work in. This is how the idea goes roughly: if we define what a calibration is carefully, we can show that a calibrated submanifold is a volume-minimizing manifold in its homology class. This corresponds to BPS states and D-branes in the SYZ conjecture. (To be honest, I do not know how to derive that BPS states and D-branes are calibrated submanifolds. This is originally dicussed in Becker, Becker, Strominger 1995. Later it was noticed that this is equivalent to calibrated geometry, which Harvey and Lawson had already formulated in 1982.)

The lecture notes devote three sections on calibrated geometry. Priori reading these lecture notes, I had no background knowledge in calibrated geometry, but had no problem in following the lecture notes. It gives a very friendly introduction to calibrated geometry and moves on and discuss the deformation of special Lagrangian submanifolds.

Finally, the lecture notes land on the SYZ conjecture, which is one of Dominic’s primary field of research. There is not that much known about the SYZ conjecture, and the SYZ conjecture is a area with high research activity. In the last section Dominic gives an excellent overview of what are the open problems and what has been happening recently.

Riemannian holonomy groups and calibrated geometry lecture notes is a perfect place to learn about calibrated geometry and SYZ conjecture without getting lost in the details. You can see through Dominic’s eyes where mathematical gears fit together and how the engine runs. I highly recommend reading it.

Further readings

1. Gross, Huybrechts, Joyce, Calabi-Yau Manifolds and Related Geometry.
2. Joyce, Riemannian Holonomy Groups and Calibrated Geometry.
3. Joyce, Compact Manifolds with Special Holonomy.
4. Salamon, Riemannian geometry and holonmy groups.
5. Harvey and Lawson, Calibrated geometrie, Acta Mathematica 148 (1982), 47-157.
6. McLean, Deformations of calibrated submanifolds, Comm. in Analysis and Geometry 6 (1998) 705-747.
7. Strominger, Yau, and Zaslow, Mirror Symmetry is T-duality, hep-th/9606040