A tutorial focussing on the theory of strong field QED - more details to follow.
Numerical simulations are an essential tool in plasma physics: they help us understand the dynamics of complex systems, interpret experimental results, and design novel radiation and particle sources. This is especially true in the high-intensity regime, where strong-field QED interactions affect, and are affected by, classical, collective plasma processes. In this talk I will give a tutorial...
Strong-field quantum electrodynamics is the epitome of what happens when a quantum many-body system is pushed to the extreme. It tests our understanding of non-equilibrium physics, fundamental particle physics and everything we think we know about emergent phenomena and collective dynamics [1]. In particular, identifying the formation time of an electron-positron pair within a background field...
Production of electron-positron pairs by a high-energy γ photon and a bichromatic laser wave is considered where the latter is composed of a strong low-frequency and a weak high-frequency component, both with circular polarization. An expression for the production rate is derived that accounts for the strong laser mode to all orders and for the weak laser mode to first order. The structure of...
Quantum electrodynamics (QED) cascades describe the exponential growth of an electron-positron-photon plasma in an intense electromagnetic (EM) field. Exponential growth is only possible if both electric and magnetic fields are present. In a nutshell, the electric field allows for every new generation of leptons to be re-accelerated after their creation. In contrast, the magnetic field plays a...
Plasmas immersed in ultra-intense electromagnetic fields radiate through QED channels high-energy photons which can decay into pairs. These pairs, if created in sufficient amounts, can significantly impact the background field. This is especially true in the context of QED avalanches created by intense lasers, where the exponentially growing density will eventually reach a critical value...
The quantum electrodynamic (QED) theory predicts the photon emission and pair creation in QED cascades mainly occur in a forward cone with finite angular spread $\Delta\theta \sim 1/\gamma_{i}$ along the momenta of incoming particles. This finite beaming effect has been assumed to be negligible because of the particles' ultra-relativistic Lorentz factor $\gamma_{i}\gg1$ in laser-driven QED...
Since the initial prediction of the onset of selfsustained QED cascades upon injection of particles in certain electromagnetic field configurations [1], the pivotal theory questions remain the same: (i) What are the general conditions required to trigger such cascades? (ii) How many electron-positron pairs can be produced? (iii) What is the threshold of the phenomenon, particularly in the...
I discuss high-harmonic generation from the vacuum in strong-field QED. Using the semi-classical approximation, I explicitly calculate the number of photons and the resulting harmonic spectrum in the presence of a spatially uniform linearly-polarized AC electric field, at the leading order in the fine-structure constant $\alpha$. I briefly compare the obtained results with the previous ones,...
Coherency can crucially modify the properties of radiation emitted by many particles compared to a single particle. We study the conditions for coherent radiation of an electron bunch driven by a counterpropagating strong pulsed electromagnetic plane wave [1,2]. We derive the spectrum of the coherent radiation and show that it is emitted backwards with respect to the laser propagation...
Quantum field theory in the presence of strong background fields contains interesting problems where quantum computers may someday provide a valuable computational resource. In the noisy intermediate-scale quantum (NISQ) era it is useful to consider simpler benchmark problems in order to develop feasible approaches, identify critical limitations of current hardware, and build new simulation...
The SLAC experiment 320 (E-320) collaboration is probing Strong-Field QED (SFQED), by colliding a $\sim 10\, \textrm{GeV}$ electron beam, generated by the FACET-II linear accelerator, with $\sim 10\, \textrm{TW}$ NIR laser pulses [1,2]. The main objectives of E-320 are: a) the investigation of the transition from the multiphoton to the strong background-field regime, where the laser can no...
The progressive development of high-power lasers over the last few decades has made it possible to study the generation of gamma radiation by laser-matter interactions. In the limit of ultra-high fields, this process occurs via nonlinear Compton scattering. Gamma-ray bursts are a phenomenon of wide interest, attracting the attention of researchers working in fields ranging from astrophysics to...
At the frontier of ultra-high electromagnetic intensities, it is now possible to access peak laser intensities of up to ∼ $10^{23}$ W/cm$^2$ [1], with even higher intensities envisaged at upcoming multi-petawatt class facilities [2]. The interaction of an ultra-relativistic electron beam with electromagnetic fields of this magnitude represents an ideal experimental configuration to access...
We consider birefringent (i.e., polarization changing) scattering of x-ray photons at the superposition of two optical laser beams of ultrahigh intensity and study the resonant contributions of axions or axionlike particles, which could also be short-lived. Applying the specifications of the Helmholtz International Beamline for Extreme Fields (HIBEF), we find that this setup can be more...
Direct measurement of the elastic scattering of real photons on an electromagnetic field would allow the fundamental low-energy constants of quantum electrodynamics (QED) to be experimentally determined. We show that scenarios involving the collision of three laser beams have several advantages over conventional two-beam scenarios. The kinematics of a three-beam collision allows for a higher...
I summarize recent progress in the application of the worldline formalism to the calculation of one-loop photon amplitudes in strong-field QED with a non-perturbative treatment of the background field. The examples include constant, plane-wave, Redmond, Coulomb and Sauter fields.
Strong electromagnetic fields perturb the quantum fluctuations, thereby modifying the properties of the vacuum. This effect is called vacuum polarization. In QED, the thus emergent interaction is described by the second and the omitted higher-order terms in the Heisenberg-Euler action
$\qquad \qquad \qquad S = ! \int d^4x \left(
\frac{\mathfrak{F}}{4\pi} + \frac{\alpha}{360 \pi^2 E_c^2}...
The trajectories of relativistic particles in an intense electromagnetic field can be described by the Landau-Lifshitz equation, where the effect of radiation emission is accounted for via a self-force, and interparticle fields are often neglected as an approximation. Yet, the inclusion of interparticle fields is necessary to ensure energy-momentum conservation, particularly during coherent...
Highly magnetized neutron stars have quantum refraction effects on pulsar emission due to the non-
linearity of the quantum electrodynamics (QED) action. In this context, we investigate the strong-field
QED effects on the following properties in pulsar emission: (i) the propagation and polarization
vectors, (ii) the polarization states. With regard to (i), we determine the leading-order...
Despite some methodological limitations, particle-in-cell simulations can be used to analyze laser-driven QED cascades and dynamics of the emergent QED plasmas. These processes, however, can quickly run into extreme regimes in terms of number of particles and their density causing extraordinary computational demands. We discuss possibilities to overcome some key limitations of the PIC method...
Lasers at moderate intensities propagating through a plasma waveguide have demonstrated the potential for generating high-frequency radiation [1] as well as high-charge (>100 nC) electron beams [2] via direct laser acceleration (DLA). Such electron beams in a strong field background can emit multi-MeV photons, which have many potential applications in laboratory astrophysics, photonuclear...
In extreme astrophysical environments such as neutron stars, pulsars and magnetars, magnetic fields can reach strengths as high as 1015 Gauss. Due to the fast rotation of the star, a very large electric field is associated with these strong magnetic fields which accelerates charged particles to energies from GeV to TeV and provides an excellent environment for so-called QED shower [1-2]....
Objects such as pulsars, magnetars and black holes all have sufficiently strong magnetic fields to reach the Schwinger limit in which strong field quantum electrodynamics (SF-QED) effects become important. Understanding the effects
of SF-QED on radiation and radiation reaction, the recoil force experienced by a particle as it radiates remains an important investigation in the field of high...
