Reservior of old news from previous SRGR camps
Summer Institute 2005
July 7, 2005
Hey, it was great meeting all of you and I hope you have
a safe journey home. Try to give your brain a break but just
remember that relativity is nothing but geometry.
Gary's rant available from arxiv preprint server.
and here is the
bibliography of books reviewed.
News Singapore 2004
December 10, 2004
Congrats to all of you and it was a pleasure having you in the course.
Thanks for listening to me ramble on about physics.
If I manage to navigate Orchard Road and get a smart card reader,
I'll post the pics we took this afternoon.
And again, feel free to email me about any questions or comments you may have.
July 27: If you want to keep up with the progress of Gravity Probe B
go to this site.
Note the control room pictures, the building is about 3 or 4 bldgs away
from our classroom. (About 400 yards, I pass it everyday).
July 21: Today Stephen Hawking announced he has solved the
Black Hole information paradox. Says he will present his findings
at a conference in Ireland next week. Remind me next week to check up
on this and maybe we can discuss it in the 3rd week.
He gives his talk on Wednesday. Here's the description (enjoy!):
Stephen Hawking (Cambridge)
- The information paradox for black holes
The Euclidean path integral over all topologically trivial metrics can be done by time slicing and so is unitary when analytically continued to the Lorentzian. On the other hand, the path integral over all topologically non-trivial metrics is asymptotically independent of the initial state. Thus the total path integral is unitary and information is not lost in the formation and evaporation of black holes. The way the information gets out seems to be that a true event horizon never forms, just an apparent horizon.
From his website
At the GR17 conference in Dublin, Professor Hawking gave a controversial lecture on his new calculations regarding Black Hole Information Loss.
One of the most intriguing problems in theoretical physics has been solved by Professor Stephen Hawking of the University of Cambridge. He presented his findings at GR17, an International Conference in Dublin, on Wednesday 21 July.
Black holes are often thought of as being regions of space into which matter and energy can fall, and disappear forever. In 1974, Stephen Hawking discovered that when one fused the ideas of quantum mechanics with those of general relativity, it was no longer true that black holes were completely black. They emitted radiation, now known as Hawking radiation. This radiation carried energy away from the black hole which meant that the black hole would gradually shrink and then disappear in a final explosive outburst.
These ideas led to a fundamental difficulty, the information paradox, the resolution of which is to be revealed in Dublin. The basic problem is that black holes, as well as eating matter, also appear to eat quantum mechanical information. Yet the most fundamental laws of physics demand that this information be preserved as the universe evolves. The information paradox was explored and formalised by Hawking in 1975. Since then, many have tried to find a solution.
Whilst most physicists think that there must be a resolution of the paradox, nobody has really produced a believable explanation. In fact, seven years ago the issue prompted Hawking, together with Kip Thorne of Caltech, to make a wager against John Preskill also of Caltech, that the information swallowed by black holes could never be recovered.
On Wednesday, Hawking conceded that he has lost the bet.
The way his new calculations work is to show that the event horizon, which is the surface of the black hole, has quantum fluctuations in it. These are the same uncertainties in position that were made famouA complete description of this work will be published in professional journals and on the web in due course.s by Heisenberg
If you want to read up on the background of the information paradox,
see the links below under Black Hole Thermodynamics. Especially the first.