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We present an extensive experimental study of the distributions of the real and imaginary parts of the off-diagonal elements of the scattering matrix $\hat S$ and the Wigner's reaction $\hat K$-matrix for open microwave networks with broken time ($T$) reversal invariance. Microwave Faraday circulators were applied in order to break $T$-invariance. The experimental distributions of the real and imaginary parts of the off-diagonal entries of the scattering matrix $\hat S$ are compared with the theoretical predictions from the supersymmetry random matrix theory [A. Nock, S. Kumar, H.-J. Sommers, and T. Guhr, Annals of Physics {\bf 342}, 103-132 (2014)]. Furthermore, we show that the experimental results are in very good agreement with the recent predictions for the distributions of the real and imaginary parts of the off-diagonal elements of the Wigner's reaction $\hat K$-matrix obtained within the framework of the Gaussian unitary ensemble of random matrix theory (RMT) [S. B. Fedeli and Y. V. Fyodorov, J. Phys. A: Math. Theor. {\bf 53}, 165701 (2020)]. Both theories include losses as tunable parameters and are therefore well adapted to the experimental verification.

We consider an optically thick spherical agglomerate of magneto-optical scatterers with a central isotropic, unpolarized light source, placed in a homogeneous magnetic field. The Photon Hall Effect induces a rotating Poynting vector, both inside and outside the medium. We show that electromagnetic (orbital) angular momentum leaks out and induces a torque proportional to the injection power of the source and the photon Hall angle. This effect represents a novel class of optical phenomena, generating angular momentum from diffusive magneto-transport., Comment: 3 figures, submitted to Physical Review

We consider the angular momentum of a charge q rotating in a homogeneous magnetic field and study the role of the electromagnetic quantum vacuum. Its orbital angular momentum is caused by the recoil of energetic vacuum photons that grows as n^2, i.e. faster than the kinetic angular momentum -2n\hbar of a Landau level.

This work investigates the theory behind a thought experiment that intends to measure momentum and angular momentum of matter exposed to `isotropic radiative noise'. Radiative momentum has been a controversial subject for decades. The momentum of isotropic noise is intuitively expected to be zero. We formulate the general features of the isotropic noise such as equipartition of energy and the vanishing of integrated Poynting vector. We demonstrate that in bi-anisotropic materials, a finite radiative momentum persists that performs work on the matter when its parameters change slowly. We find that Faraday rotation in the scattering of the radiative noise induces an angular momentum along the applied external magnetic field. Also, a Poynting vector starts circulating around the matter, raising the question whether it really describes the energy flow. These effects are small and hard to measure in any real experiment. Yet, they are surprising predictions of the classical, macroscopic Maxwell equations, and make contact with the outcome of recent QED calculations done for the quantum vacuum.

We develop a perturbative treatment of induced dipole-dipole interactions in the diffusive transport of electromagnetic waves through disordered atomic clouds. The approach is exact at order two in the atomic density and accounts for the vector character of light. It is applied to the calculation of the electromagnetic energy stored in the atomic cloud - which modifies the energy transport velocity - and of the light scattering and transport mean free paths. Results are compared to those obtained from a purely scalar model for light., Comment: revised version

Using a cutoff-free formulation of the coherent transport theory, we show that the interference terms at the origin of localization strongly affect the transport anisotropy. In contrast to the common hypothesis, we then find that the anisotropies of incoherent and coherent diffusion are significantly different, in particular at criticality. There, we show that the coherent transport anisotropy is mainly determined by the properties of the disorder-averaged effective scattering medium while the incoherent transport contributions become irrelevant.

In a recent publication [Phys. Rev. Lett. 111, 143602] we have shown using a QED approach that, in the presence of a magnetic field, the quantum vacuum coupled to a chiral molecule provides a kinetic momentum directed along the magnetic field. Here we explain the physical mechanisms which operate in the transfer of momentum from the vacuum to the molecule. We show that the variation of the molecular kinetic energy originates from the magnetic energy associated with the vacuum correction to the magnetization of the molecule. We carry out a semiclassical calculation of the vacuum momentum and compare the result with the QED calculation., Comment: minor corrections made to agree with the published version

We report on ultrasonic measurements of the propagation operator in a strongly scattering mesoglass. The backscattered field is shown to display a deterministic spatial coherence due to a remarkably large memory effect induced by long recurrent trajectories. Investigation of the recurrent scattering contribution directly yields the probability for a wave to come back close to its starting spot. The decay of this quantity with time is shown to change dramatically near the Anderson localization transition. The singular value decomposition of the propagation operator reveals the dominance of very intense recurrent scattering paths near the mobility edge., Comment: 5 pages, 4 figures

In a classical description, a neutral, polarizable object acquires a kinetic momentum when exposed to crossed electric and magnetic fields. In the presence of only a magnetic field no such momentum exists classically, although it is symmetry-allowed for an object lacking mirror symmetry. We perform a full QED calculation to show that the quantum vacuum coupled to a chiral molecule provides a kinetic "Casimir" momentum directed along the magnetic field, proportional to its rotatory power and the fine structure constant., Comment: 5 pages + Supplemental material

The Abraham force exerted by a time-dependent electromagnetic field on neutral, polarizable matter has two contributions. The one induced by a time-varying magnetic field and a static electric field is reported here for the first time. We discuss our results in the context of the radiative momentum in matter. Our observations are consistent with Abraham's and Nelson's versions for radiative momentum., Comment: 5 pages, to appear in Phys. Rev. Lett

We develop a QED approach to find the contribution of the quantum vacuum to the electromagnetic Abraham force. Semi-classical theories predict diverging contributions from the quantum vacuum. We show that the divergencies disappear by Kramers-Bethe mass-renormalization. The finite remainder is compared to the relativistic corrections to the Abraham force. This work generalizes an earlier paper [1], dedicated to the harmonic oscillator, to the hydrogen atom and corrects two subtle errors.

We predict a photon Hall effect in the optical cross-section of atomic hydrogen, which is caused by the interference between an electric quadrupole transition and an electric dipole transition from the ground state to $3D_{3/2}$ and $3P_{3/2}$. This induces a magneto-transverse acceleration comparable to a fraction of $g$. In atoms with a two level electric dipole transition, a much smaller transverse force is generated only when the atom is moving.

We report the first observation of mechanical momentum transferred to atoms and molecules upon application of crossed electric and magnetic fields. We identify this momentum as the microscopic analogue of the classical Abraham force. Several predictions of additional magneto-electrically induced mechanical momentum are addressed. One of them, proposed to result from the interaction with the quantum vacuum, is experimentally refuted, others are found to be currently below experimental detection., Comment: 4 pages, 3 figures, one table

We consider a simple atomic two-body bound state system that is overall charge neutral and placed in a static electric and magnetic field, and calculate the magneto-electric response function as a function of frequency. This is done from first principles using a two-particle Hamiltonian for both an harmonic oscillator and Coulomb binding potential. In the high frequency limit, the response function falls off as 1/\omega^2 whilst at low frequencies it tends to a constant value., Comment: 6 pages, 4 figures

We consider a scattering formulation of radiative momentum transfer to a Magneto-Chiral system that is subjected to a constant background magnetic field. The system takes the form of a collection magnetic dipoles that exhibit the Faraday effect. It is shown that the first non-trivial contribution of the momentum transfer to the object from the radiation field occurs at fourth order in the Born series., Comment: 4 pages, 3 figures

In this work we re-formulate and solve the self-consistent theory for localization to a Bose-Einstein condensate expanding in a 3D optical speckle. The long-range nature of the fluctuations in the potential energy, treated in the self-consistent Born approximation, make the scattering strongly velocity dependent, and its consequences for mobility edge and fraction of localized atoms have been investigated numerically., Comment: 8 pages, 11 figures

The electromagnetic vacuum is known to have energy. It has been recently argued that the quantum vacuum can possess momentum, that adds up to the momentum of matter. This ``Casimir momentum'' is closely related to the Casimir effect, in which case energy is exchanged. In previous theory it was treated semi-classically. We present a non-relativistic quantum theory for the linear momentum of electromagnetic zero-point fluctuations, considering an harmonic oscillator subject to crossed, quasi-static magnetic and electric and coupled to the quantum vacuum. We derive a contribution of the quantum vacuum to the linear pseudo-momentum and give a new estimate for the achievable speed. Our analysis show that the effect exists and that it is finite., Comment: 4,4 pages

We report the first experimental observation of strong multifractality in wave functions at the Anderson localization transition in open three-dimensional elastic networks. Our results confirm the recently predicted symmetry of the multifractal exponents. We have discovered that the result of multifractal analysis of the real data depends on the excitation scheme used in the experiment., Comment: 4 pages, 3 figures

We have studied the partition of shear, compressional and kinetic energies in the coda of ten earthquakes recorded on a dense array, located at Pinyon Flats Observatory (PFO), California. We observe a clear stabilization of the shear to compressional ($W^s/W^p$) energy ratio in the coda, with an average value of about 2.8. The ratio between the vertical and horizontal kinetic energies ($V^2/H^2$) can be measured from 5 to 25Hz and shows an abrupt transitionfrom 0.1 in the 5-10Hz band, to about 0.8 in the 15-25Hz band. These measured values are in sharp contrast with the theoretical prediction for equipartitioned elastic waves in a homogeneous half-space. To explain these observations, we have developed a theory of equipartition in a layered elastic half-space. Using a rigorous spectral decomposition of the elastic wave equation, we define equipartition as a white noise distributed over the complete set of eigenfunctions. The theory predicts that close to the resonance frequency of a low-velocity layer, the ratio between shear and compressional energies strongly decreases. Using a detailed model of the subsurface at PFO, this conterintuitive result is found to be in good qualitative and quantitative agreement with the observations.

In this paper, we revisit one-channel time reversal (TR) experiments through multiple scattering media in the framework of the self-consistent multiple scattering theory. The hyper resolution and the self-averaging property are retrieved. The developed formalism leads to a deeper understanding of the role of the ladder and most-crossed diagrams in a TR experiment, and also establishes the link between TR and Coherent Backscattering (CBS). Especially, we show that when the initial source and the time reversal point are at the same location, the time-reversed amplitude is twice higher. Surprisingly, this enhancement is due to the ladder diagrams and not to the most-crossed ones, contrary to CBS. These theoretical predictions are confirmed by experimental results. The experiments are performed with ultrasonic waves propagating through a random collection of parallel steel rods.

A theory for multiple scattering of elastic waves is presented in a random medium bounded by two ideal free surfaces, whose horizontal size is infinite and whose transverse size is smaller than the mean free path of the waves. This geometry is relevant for seismic wave propagation in the Earth crust. We derive a time-dependent, quasi-2D radiative transfer equation, that describes the coupling of the eigenmodes of the layer (surface Rayleigh waves, SH waves, and Lamb waves). Expressions are found that relate the small-scale fluctuations to the life time of the modes and to their coupling rates. We discuss a diffusion approximation that simplifies the mathematics of this model significantly, and which should apply at large lapse times. Finally, coherent backscattering is studied within the quasi-2D radiative transfer equation for different source and detection configurations., Comment: REVTeX, 36 pages with 10 figures. Submitted to Phys. Rev. E

We present a microscopic theory for multiple light scattering occurring in inhomogeneous 3D media subject to an external magnetic field. Magneto-optical effects (the Faraday effect and the Cotton-Mouton effect) occur inside the small inhomogeneities. We thereby take into account the spatial anisotropy, time-reversal-symmetry breaking and birefringence caused by the magnetic field, and discuss the consequences for the diffusion tensor and the polarization characteristics of the diffuse light. We will frequently compare our findings to a similar phenomenon in dilute polyatomic gases: the Beenakker-Senftleben effect. Coherent Backscattering and the field-field correlator $\left< E_i({\bf B}) \bar{E}_j({\bf 0}) \right>$ are addressed, which have both been obtained experimentally by the group of Maret {\em etal.}. All modifications in transport theory due to the magnetic field exhibit a rather sensitive dependence on the scattering phase shift of the individual scatterers., Comment: 44 pages PostScript, 9 figures