New blog

Announcing my new (tentative) blog, Toy Universes.

Blog is shutdown.

All contents will be available as far as there is a host out there in the internet “cloud” making it accessible. I will not delete this blog, so you may be able to access the archives for some time, I guess.

Comments will be shutdown, however.

Thanks and good-bye!

News on Gravity Probe B – Nov. 2009

Read mission status below:

Closing in on Einstein: Frame-Dragging Clearly Visible

News on Garrett Lisi’s E8 theory

Lisi posted this yesterday over at Physics Forums; I reproduce here:

Hello PF folk.

If you believe the Dirac equation in curved spacetime, and you believe Spin(10) grand unification, then a Spin(3,11) GraviGUT, acting on one generation of fermions as a 64 spinor, seems… inevitable.

Also, it’s pretty.

And it’s up to you whether or not to take seriously or not the observation that this whole structure fits in E8. Personally, I take it seriously. Slides are up for a talk I gave at Yale:

http://www.liegroups.org/zuckerman/slides.html

Best,
Garrett

I am not certain whether it addresses Distler’s previous objections (as I am not certain whether the issue was even settled at that time– see here and here, which goes as far as I could follow. More (older) personal opinions can be found here, here and here in reverse chronological order).

Edit: I forgot to add. I do find the theory beautiful and interesting. I hope it can be properly tested.

Edit: Here are further links that are relevant to this post.

There is no “Theory of Everything” inside E8 by Jacques Distler and Skip Garibaldi.

Here is Distler’s blog entry on his paper.

There was a discussion of Distler and Garibaldi’s paper at Physics Forums some time ago.

There was also a discussion at n-Category Café some time ago.

Quantum Gravity quote

A pessimist might say that combining string theory and loop quantum gravity is like combining epicycles and aether.

(John Baez, TWF281)

Connexions

Just learned about this:

Connexions is:

a place to view and share educational material made of small knowledge chunks called modules that can be organized as courses, books, reports, etc. Anyone may view or contribute:

authors create and collaborate
instructors rapidly build and share custom collections
learners find and explore content

This sounds a formidable initiative.

Scientific Philosophy

From the PhilPhys – Philosophy of Physics Mail Group, I received this (and I share the same thoughts on its rationale — “philosophical theses and arguments should be just as clear and precise as scientific ones”):

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Workshop on

Scientific Philosophy: Past and Future

Tuesday 13 April 2010

Tilburg University, The Netherlands

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Various philosophers of the past – and many philosophers of today – believe that there can be real progress in philosophy and that such progress is facilitated crucially by a close interaction between philosophy and the sciences. “Scientific Philosophy” maintains that philosophical theses and arguments should be just as clear and precise as scientific ones; philosophers ought to build theories and models much as scientists do; and the application of mathematical methods as well as input from empirical studies are often necessary in order to gain new insights into old philosophical questions and to progress to new and deeper ones. This workshop will address what Scientific Philosophy is all about, what it has in common with science and where it might diverge from it, what we can learn from its historical successes and failures, and, most importantly, how we should assess its future prospects.

The invited speakers include:

Michael Friedman, Stanford

Christopher Hitchcock, Caltech

Volker Peckhaus, Paderborn

Organizers:

Stephan Hartmann, Tilburg

Hannes Leitgeb, Bristol

Jan Sprenger, Tilburg

There’ll be three to four slots for contributed papers. If you are interested in presenting something, please send an extended abstract of up to 1500 words to TiLPS@uvt.nl by 15 January 2010. Decisions will be made by 1 February 2010.

There is no registration fee. However, participants have to register by sending an email to TiLPS@uvt.nl by 15 March 2010.

The workshop takes place on the day before the conference “The Future of Philosophy of Science”. Check.