Research areas
Quantum vacuum
Dispersive medium
Quantum fluctuations
Virtual particles
We know that the vacuum plays a key role in our physical theories, nevertheless our understanding of the physical vacuum is still relatively limited. In classical physics, the vacuum is merely the unchanging background in which physical phenomena occur. However the quantum vacuum is understood to consist of virtual particles, many of which are charged. An external electromagnetic field can couple to these virtual charges, which in turn affects the behaviour of real particle processes.
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When a strong electromagnetic field is present, the virtual charges, which form virtual dipoles, start to separate under the influence of the field \cite{GreRei02}. In the Schwinger limit, where an electric field ($1.3 \times 10^{18}$ V/m) does the work equivalent to separating two rest masses over a Compton wavelength, the vacuum state becomes unstable and the field is predicted to induce vacuum pair production
Resonant transitions in laser-electron interactions
Quasi-energy levels
Probe photons
Strong laser, a0=1
Strong field physics theory predicts observable, novel resonant phenomena at field strengths well below the Schwinger limit (an electric field of 10^18 V/m). When the strong field is provided by a laser field, the key parameter is a ratio $a_0\approx 1$ of the energy provided by the strong field to the relativistic mass of the electron (at an intensity of I~ 10^{19} Wcm^{-2} for a 1 $\mu$m wavelength laser). These intensities can already be produced in the laboratory with today's technology. Required, is an interaction involving strong laser, relativistic electrons and probe photons.
Strong field effects in collider charge bunch collisions
Squeezed e+e-charge bunches
Strong, constant crossed, background fields
Exact solutions of Dirac equation
Physics experiments in particle colliders involve the overlap of dense bunches of charged particles which interact to produce final states of interest. The treatment of the individual interactions which produce new particles is of course well known and thoroughly carried out in physics analysis. By comparison, the treatment of collective effects from the strong electromagnetic fields has been limited to beamstrahlung and background pair production processes only. Nevertheless, the overwhelming bulk of physics processes take place in strong overlapping charge bunch fields.
