Likely values of the Higgs vev

Andi Ross, Koushik Dutta, Max Tegmark and I recently put our paper on the likely values of the Higs vev on the web – here is a link. This touches on the issue that maybe the constraints on the existence of atoms may be related to the unnaturally small value of the Higgs vacuum expectation value (vev). This idea was first suggested in my paper with Steve Barr, Dave Seckel and V Agrawal. We had been inspired by Weinberg’s anthropic discussion of the cosmological constant and realized that the constraint that atoms exist could explain the key puzzle – called the fine tuning problem – of why the Higgs mass scale was so low. In this work we considered the variation of the vev with all other parameters of the Standard Model held fixed.
In the present work with Andi, Koushik and Max we address what would happen if the other parameters of the Standard Model were also variable. We argue that the most relevant ones are the Yukawa couplings that are related to quark and lepton masses. For these, we use the experimentally observed mass distribution, found in previous work..
Since the Yukawa couplings vary, there is not just an allowed window for the vev, but rather a liklihood distribution. It is this that we describe in the paper. The result works in the sense that there is a modest spread about the most likely value, and the observed value is pretty typical of the allowed values. While this observation certainly does not show that the atomic constraints are responsible for the low value of the vev, nevertheless the results support the possibility that atomic constraints are at play in this hep puzzle.

Thursday class cancelled due to UMass delay

It is unfortunate that UMass is closed until 11:00 today (Jan 29), especially when coupled with my being away next week. I had been counting on finishing the basic construction of a field today. I will adjust the plans for the classes and update you later today. I will put together an email list for everyone who signed up on Tuesday and will send around information that way. I will also post all info here. Enjoy the morning off, but check back later for more info.

First day of QFT

Here is theĀ  syllabus for the QFT course. I have also produced the video of the first class. Folks who are registered in the course can find both the notes from the class and the video on SPARK – log in here . While in general I will only post on SPARK, save for rare exceptions, I will also make the first few classes available on Screencast so that anyone can see them – for example if someone joins the class late. The Screencast version is posted here.

Finally, if you are interested in stopping by my office to chat (which I strongly encourage), you can see some of my official conflicts by consulting my Google calendar .

Videos of lectures

I am experimenting with making videos of some lectures, and will be doing this with my field theory course in Spring 2009. The idea is to archive these for future students to use at a time when the field theory course is not being offered. I have been planning on using SPARK, which will be password protected. But I am also experimenting with Screencast. Here is a sample, from my test run in my E&M class. It is from the unit on the Foundations of E&M, in particular on the action principle for fields. (Note added 1/27/09: I have removed the link to Screencast because this is now out of date. You will be able to access the Screencast version of the first few QFT classes in subsequent posts.)

Academic Genealogy

Barry Holstein and I once wasted some time figuring out our academic genealogy – i.e. tracing back the PhD advisors of our PhD advisors. Interestingly it goes back through some pretty big names, all the way to Bernoulli, who was self-taught. Here is the link to the genealogy tree. Of course this sets us up for the appropriate joke about how the standards have deteriorated in modern times. But nevertheless, this is an interesting – at least to us.

P.S. Continuing this family tree in the other direction, you can find a link to a listing of my PHD students here.

Books for QFT

In Spring 2009, I will be teaching Quantum Field Theory I. The second semester course will be offered in Fall 2009. The Spring course will be designed for students of all areas, and will match on to our core graduate curriculum. The second semester will cover topics which, while still useful for all, are of particular interest for particle/nuclear/gravitational types.

I am going to ask that you choose your own book. I will not follow any one book in detail and there are many good books available. I have prepared a summary of many of the standard choices – you can find the summary here. If you want to chat about the options, feel free to stop by my office.

Research and teaching pages for John Donoghue