Abstract for Seminar by Craig Roberts

Craig Roberts
Argonne National Labs
USA
Tuesday, February 18, 3.30pm
4th Floor, CSSM



Quantum effects with an X-ray free electron laser



Abstract:

It is a longstanding prediction that the QED vacuum, the "empty space" ground state of electromagnetically interacting matter, is unstable in the presence of a strong, constant electric field. It must decay via the production of pairs of electrons and positrons. However, the enormous electric field required to realize this has hitherto been impossible to create on earth. That may soon change. It is possible that the new x-ray free-electron lasers being developed at Deutsches Elektronen Synchrotron in Germany, and at Stanford Linear Accelerator Center in California, with their unique ability to provide high-power tightly-focused laser x-ray pulses, will enable the experimental verification of this fundamentally nonperturbative effect in quantum field theory. The next generation of facility may expose an additional, remarkable effect. In quantum field theory the production of pairs of electrons and positrons is non-Markovian; i.e., non-local in time, so that temporally separted production events are not independent and the time evolution of the system is irreversible. Increasing the laser power by just one additional order of magnitude will generate a plasma, directly from the QED vacuum, a plasma whose evolution and behaviour can expose the essentially non-Markovian nature of the particle production mechanism. The implications are far reaching because this particle production phenomenon is important wherever intense electric fields can appear, such as in cosmology and astrophysics.


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