## Polchinski, Smolin, Polchinski, …

Posted in Book Reviews, Quantum Gravity on May 21, 2007 by Christine

Now the machine seems to be running. A scientific public debate is going on over the blogosphere between Smolin, author of The Trouble with Physics, and Polchinski, a string theorist who reviewed his book recently.

## Ernst Mach, a pan-mathematician?

Posted in Book Reviews, Philosophy, Physics on May 5, 2007 by Christine

I will take forever to go through the 600+ pages of “A History of Mechanics”, by Rene Dugas. My hunsband gave me a copy as a gift last year and from a quick browsing it was evident that the book provided a scholarly, chronological overview of mechanics that I have never found elsewhere. With so many books to read, I wonder when will be my time to go through this monumental work.

Anyone interested in foundational issues of physics should go some day in his/her life through the history of this giant pillar — mechanics. There are several surprising facts along this fascinating endeavor. The notion of inertia pervades the history of mechanics and is very intriguing by itself.

Ernst Mach is well known for having influenced Einstein in the development of his general relativity theory, which includes, among others, his ideas on the origin of inertia. This is something I will write about some time in the future. However, in a recent browising of Dugas’ book, have found the very curious passage (page 444, my boldface):

In the terminology of modern philosophy, Mach, reducing science to a well-formed language, would be called a pan-mathematician.

This was the very first time I ever met such a reference to Mach! Unfortunately, Dugas closes the section about Mach in his book exactly at this point with apparently no further explanations about what he means by Mach as a pan-mathematician. I googled around and found nothing. Well, the form “pan” evidently refers to an all-inclusive form, that is, Mach would be seen today as someone who embraces the whole of mathematics. What does this mean?

Dugas refers to Mach’s philosophy of expelling “all mysticism” from science by the use of an “economic” principle. So perhaps Dougas is raising an issue here concerning mathematics as a means of the necessary “economic language” that Mach advocates.

In his book (page 444), Dougas quotes the following passage from Mach (I suppose, from his Science of Mechanics):

According to us all science has the mission of replacing experiment. Consequently it must remain partly in the domain of experiment and must partly go beyond this, always awaiting corroboration or denial from the latter. Where it is impossible to corroborate or deny, science has nothing to do. It always moves in the domain of incomplete experiment… The agreement between theory and experiment can always be improved by the perfection of observational techniques.

It is interesting that Mach does not mention in particular the role of mathematics in the context raised by Dougas (as far as I see). But if we “must partly go beyond this” (ie, the domain of experiment, as Mach states) there is no way to do it without mathematics.

The whole problem then resides in the notion of “partly”.

And today this is certainly the fundamental issue of… er.. pan-quantum gravity.

## Smolin’s Response to Review by Joe Polchinski

Posted in Book Reviews, Quantum Gravity on April 29, 2007 by Christine

Lee Smolin, author of the book “The Trouble with Physics”, replies to a review by string theorist Joe Polchinski posted over at Cosmic Variance last December.

Sabine over at Backreaction has a nice list of past reviews, apart from her own. My review can be found over at my old blog, Background Independence. Recently, Lieven le Bruyn posted about group think over at his blog NeverEndingBooks.

## QFT review

Posted in Book Reviews, Physics, Quantum Field Theory on January 12, 2007 by Christine

An American Physics Student in England has written a nice review of books and lecture notes on Quantum Field Theory for beginners.

I’ve been patiently(*) studying Zee’s book for some time now (it’s been a while since I last opened a page of it, though). Sigh. It seems I am an eternal beginner… But that is all right: the important thing is keep moving (forward). I have so many interests that distract me. But I hope this year I can find more discipline in me — and hence, more time for so many interesting books out there.

(*) That means: making all exercises and thinking about them… Yet, I don’t believe I’ll get Peskin and Schroeder this year yet, although I’d like to.

Ref.: [Zee]

Edited: BTW, it seems I cannot get some factors of $2\pi$right. For instance, I get it in the denominator instead of the nominator in the derivations of page 11; I get a $(2\pi)^n$in equation (20) on page 15, and etc etc. Not important, but I get annoyed not to know where my mistakes are…