Exotic Physics and Theory

Exotic Physics and Theory

Ultra-high fields of high-power, short-pulse lasers pose very important possibilities for fundamental physics. The main goal of this Research Activity is to explore both theoretically and experimentally the ultra-relativistic (above 10²³ W/cm²) regime of laser-matter interaction, called Exotic physics.

Research Activity Description

This largely untouched intensity territory will provide access to fundamental physical effects with much higher characteristic energies and will regroup many subfields of contemporary physics (atomic physics, plasma physics, particle physics, nuclear physics, gravitational physics, nonlinear field theory, ultrahigh-pressure physics, astrophysics and cosmology). In a longer-term perspective, relativistic compression offers the potential of intensities exceeding 10²⁵ W/cm², which will challenge the vacuum critical field as well as provide a new avenue to ultrafast attosecond (10^-18 s) and even zeptosecond (10^-21 s) studies of laser-matter interaction.
The technological breakthrough of laser chirped-pulse amplification has led to unprecedented laser powers and intensities, the current experimental record being about PW and 10²² W/cm², respectively. Up to 3 orders of magnitude may be achieved at the planned ELI facility. For laser intensity of 10²⁶ W/cm², an electron will undergo an acceleration of 10²⁷ g, comparable to the gravitational acceleration at the event horizon of a black hole. This high acceleration can be used to study Unruh radiation generation. At sufficiently high intensities, even vacuum can be broken down. The field necessary to achieve pair creation (“boil the vacuum”) is the so-called Schwinger field limit.
ELI will offer much higher intensity levels either directly with the laser or by relativistic compression. The optical field could then reach the critical field value. In this limit the laser pulse-plasma interaction demonstrates effects of the radiation friction force and quantum electrodynamics effects of nonlinear vacuum polarization and electron-positron pair creation. In this limit, novel mechanisms of ion acceleration occur. Since the energy of the resulting ion bunch can be over 100 GeV per nucleon, this ion acceleration regime would be suitable for quark-gluon plasma studies and could be used in the investigation of neutrino oscillations. In essence, ultra-relativistic intensities could unify nuclear physics, high-energy physics, astrophysics and cosmology.
Apart from these truly exotic research fields, other nonlinear quantum electrodynamics effects could be accessed at slightly modest fields. The ELI community is eager to study such phenomena which consist in converting photon energy directly into creation of electrons and positrons. There are plenty of strong-field QED processes, which may be roughly categorized into two classes: “loop” (strong-field vacuum polarization, spontaneous pair production) and “tree-level” (perturbative pair production, pair annihilation, Compton scattering) processes. For petawatt-class lasers, a nontrivial electron-positron pair can be created. Nowadays positron emission from direct interaction of petawatt laser pulses with solid targets has the main disadvantage of no operation at high repetition rate, thus limiting the yield of positron emission. However this limit will be easily overcome at the future ELI facility. From this point of view, ELI will explore new regimes and try to map out the basic phenomena concerning the QED theory. Distorting the vacuum with lasers has been suggested long time ago but never achieved experimentally due to the lack of sufficient laser power. ELI laser intensity regime will open up the way towards novel experimental capabilities.

Some of the particular QED phenomena that will be studied at ELI are:

1. Electron-positron plasmas
2. Vacuum four-wave mixing
3. Vacuum polarisation
4. Vacuum birefringence
5. Unruh radiation
6. QED cascades: Inverse Compton Scattering
7. Quark-gluon plasmas

Main outcomes of the Research Activity

The unprecedented laser intensities available at ELI will allow to test the fundamental predictions of Quantum Electrodynamics (QED) in external strong laser fields. Within this Research Activity, we will theoretically investigate purely quantum electrodynamical (classically forbidden) processes that occur in the presence of extremely intense laser field and which can be observed experimentally at ELI. In particular, we will consider absorptive vacuum polarization effects and dispersive vacuum polarization effects. The main outputs will be advanced theories describing QED processes relevant to exotic physics, numerical modelling, and preparation of proof-of-principle experiments. A versatile target area with multiple high intensity beams will be designed. Some of these experiments will be based on a configuration of two counter propagating fundamental beams focussed to the highest possible intensity. Specialized workshops/brainstorming to discuss these ultimate scientific challenges of ELI will be regularly organized.

credit : http://www.eli-beams.eu/science/exotic-physics-and-theory/