NPA Seminar: Mike Lisa, Ohio State University

 

The talk will begin with a brief review of the technique and history of stellar intensity interferometry (SII) and its evolution into a tool for studying the space-time structure of the quark-gluon plasma. We will discuss the very recent explosive renaissance of SII, with a focus on pioneering work at the VERITAS observatory, including the first measurement at visual wavelengths of the anisotropic shape of an extreme rapid rotator. We shall conclude with an outlook for this newly emerging field, including prospects at the Cherenkov Telescope Array.

 

Abstract: 

Seventy years ago, two radio engineers emerged from the frenzy of World War II and entered the new field of radio astronomy. Robert Hanbury Brown and Richard Twiss developed an entirely new instrument and technique, based on “correlated noise,” to measure the angular radius of previously unresolvable stars. Initially greeted with skepticism, their work led directly to the birth of quantum optics.  At nearly the same time, Goldhaber et al discovered a tiny unexpected correlation in the first true particle physics experiments. At first, this "GGLP effect” played a minor role in particle physics.  It would take another 15 years until the connection between these apparently disparate phenomena was realized by Shuryak and others around 1976, just as the new field of heavy ion physics was emerging.  Thus did Hanbury Brown's discovery give birth to femtoscopy, the most direct method to probe space and time at the scales of 1e-15 meter and 1e-22 second.  Femtoscopic measurements continue to be invaluable in extracting the space-time structure of the quark gluon plasma in experiments like STAR at RHIC. Meanwhile, technical limitations led to the abandonment of stellar intensity interferometry (SII) in the early 1970s.
   
After this somewhat historical introduction, I will spend most of my time on the very recent renaissance of SII, made possible due to the availability of very large Cherenkov telescope arrays and high-speed electronics and storage. I’ll focus on recent pioneering measurements by the VERITAS collaboration that include not only the first modern visual measurements of photosphere sizes, but very recently the first measurement of the anisotropic shape of the extreme rapid rotator gamma Cassiopeia. I’ll conclude on impact and outlook for this rapidly-growing field.

Host: John Harris