Hannover Diary

I did! I managed 6 hours sleep midway both legs, so that helped a great deal with the lag. Hannover itself was a hoot, and I also took the fast train each way between Frankfurt and Hannover. They have deer in the countryside like we have kangaroos .... :-)

Sure thing.

There were six lectures really, five on the day of the event and on Monday I got to sit in upon Ben Knispel's doctoral thesis presentation/defense ( which was a longer version of his Saturday presentation ).

Bruce kicked off Saturday with an overview of E@H in the last six years and the announcement of the new Fermi LAT work for E@H. How exciting! The satellite used to be called GLAST ( Gamma ray Large Area Space Telescope ) but was renamed in honor of Enrico Fermi. I've been reading up on the specs for this gadget which are quite impressive. You can't focus gamma's per se, so when one passes thru the detector - nearby a heavy metal nucleus - then it may convert to an electron/positron pair. It is this pair that is detected by a layered grid arrangement of plates backed by a calorimeter crystal. This way you get an energy and a direction to the sky source for each gamma photon. The surrounds of the detector have a trigger for cosmic rays ( gammas won't fire that up ) so serves to reject - 'anti-coincidence' - those sources, plus onboard electronics do some other sorting of candidates with the best being punted along the downlink. So that gives the data stream for our analysis. What are gamma ray pulsars? Well they are periodic in the way that the radio ones are, by definition, but one might assume the electrons that get ripped off the neutron star crust and follow the magnetic fields lines will be of higher energy and/or accelerated more to yield the synchrotron radiation that we see beaming toward us. I guess that suggests a more compact object?

Then there was Bikeman giving a great explanation of why it is that one can't just throw anything at a fast video card and expect a good result ie. can one massively parallelise? Maybe you'd like to come in on this thread HB ?

Michael Kramer came to talk to us about the exciting new prospects for the Square Kilometer Array - I cross my fingers for an Aussie siting of this - a ground based radio telescope array. The centre is a square kilometer but it also has 'arms' that sweep away from that for ? ~ 1000 km ? It is a coherent array meaning that we get phase information from each component ( ten meter dish ) so can effectively 'steer' the beam. Not to forget that many targets can be observed simultaneously by sub-arrays ! I will surely read up more on this, and I suspect there could well be a place for E@H in this scheme one day. :-)

Jonathan Leong talked of the design aspects of GW IFO's. He amusingly demonstrated how a high frequency oscillation will be barely absorbed by a lower fundamental frequency pendulum, and the active damping of a laser beam using feedback control to keep pointing steady. Recall that for the ET that will be a mirror 10km away! I think I understand 'light squeezing' now : one can arrange matters to 'park' the laser noise in one 'quadrature'. One way to represent Fourier series is with sines and cosines. Essentially one can go 'below' the uncertainty principle limit for noise in the sine component at the expense of blowing it out in the cosine part. Or put another way, on the Argand plane using a complex representation, one can think of noise compression along say the x-axis dimension going under Heisenberg but in compensation increasing in the perpendicular y-axis direction. In any case one just works with the less noisier part of the cycle for IFO purposes, pretending that you don't look at the noisy bit. I think .... :-) :-)

Now Ben Knispel's PhD presentation was a real treat, a convenient coincidence as regards timing the event. His research using E@H led to those two radio pulsar detections last year ( I was pleased to meet the Colvin's ) and naturally E@H enabled his data processing. I reckon this is a solid example of credible science done with the assistance of volunteer computing ie. the two-way street that 'citizen science' represents. He gave an overview of radio pulsars and how they come to be in terms of stellar evolution, the fraction that have the right geometry for us to perceive, and how to scan the sky for candidate objects. One key point is the Dispersion Modulus which is code/proxy for the length of the column of space between us and the source - containing free electrons that alter the pulse with the effect of higher frequencies arriving before lower ones. So one has to take guesses at the DM - our work units have that as a search parameter - in the hope that by correcting for that ( de-dispersing ) one can obtain a 'purer note' that can be identified as a pulsar waveform. There is a lot of 'hack work' in this type of research, checks and checks and checks. He made a good fist of the presentation, passed for sure, and had this great decorated 'mortar board' hat for us to inspect at the post-defense booze-up. :-0

Cheers, Mike.