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Register a new userPropagation of Light in Cantor Media
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We numerically find that transmission coefficients have a rich structure as a function of wavelength in Cantor media. Complete transmission and complete reflection are observed. We also find that light propagation has scalings with respect to number of layers.
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We numerically study energy spectra and localization properties of the double exchange model at irrational filling factor. To obtain variational ground state, we use a mumerical technique in momentum space by ``embedded boundary condition which has no finite size effect a priori. Although the Hamiltonian has translation invariance, the ground state spontaneously exhibits a self-similarity. Scaling and multi-fractal analysis for the wave functions are performed and the scaling indices $alpha$s are obtained. The energy spectrum is found to be a singular continuous, so-called the Cantor set with zero Lebesque measure.
Solving the challenging problem of the amplification and generation of an electromagnetic field in nanostructures enables to implement many properties of the electromagnetic field at the nanoscale in novel practical applications. A first-principles quantum mechanical consideration of such a problem is sufficiently restricted by the exponentially large number of degrees of freedom, and does not allow the electromagnetic field dynamics to be described if it involves a high number of interacting atoms and modes of the electromagnetic field. Conversely, the classical description of electromagnetic fields is incorrect at the nanoscale due to the high level of quantum fluctuations connected to high dissipation and noise levels. In this paper, we develop the framework with a significantly reduced number of degrees of freedom, which describes the quantum spatial dynamics of electromagnetic fields interacting with atoms. As an example, we consider the interaction between atoms placed in a metallic subwavelength groove, and demonstrate that a spontaneously excited electromagnetic pulse propagates with the group velocity. The developed approach may be exploited to describe non-uniform amplification and propagation of electromagnetic fields in arbitrary dispersive dissipative systems.
We present a comprehensive analytic model of a relativistic jet propagation in expanding media. This model is the first to cover the entire jet evolution from early to late times, as well as a range of configurations that are relevant to binary neutron star mergers. These include low and high luminosity jets, unmagnetized and mildly magnetized jets, time-dependent luminosity jets, and Newtonian and relativistic head velocities. We also extend the existing solution of jets in a static medium to power-law density media with index $alpha<5$. Our model, which is tested and calibrated by a suite of 3D RMHD simulations, provides simple analytic formulae for the jet head propagation and breakout times, as well as a simple breakout criterion which depends only on the jet to ejecta energy ratio and jet opening angle. Assuming a delay time $ t_d $ between the onset of a homologous ejecta expansion and jet launching, the system evolution has two main regimes: strong and weak jets. The regime depends on the ratio between the jet head velocity in the ejecta frame and the local ejecta velocity, denoted as $ eta $. Strong jets start their propagation in the ejecta on a timescale shorter than $t_d$ with $eta gg 1$, and within several ejecta dynamical times $eta$ drops below unity. Weak jets are unable to penetrate the ejecta at first (start with $eta ll 1$), and breach the ejecta only after the ejecta expands over a timescale longer than $ t_d $, thus their evolution is independent of $ t_d $. After enough time, both strong and weak jets approach an asymptotic phase where $eta$ is constant. Applying our model to short GRBs, we find that there is most likely a large diversity of ejecta mass, where mass $ lesssim 10^{-3}~{rm M}_{odot} $ (at least along the poles) is common.
Manipulation of the magnetization by external energies other than magnetic field, such as spin-polarized current1-4, electric voltage5,6 and circularly polarized light7-11 gives a paradigm shift in magnetic nanodevices. Magnetization control of ferromagnetic materials only by circularly polarized light has received increasing attention both as a fundamental probe of the interactions of light and magnetism but also for future high-density magnetic recording technologies. Here we show that for granular FePt films, designed for ultrahigh-density recording, the optical magnetic switching by circularly polarized light is an accumulative effect from multiple optical pulses. We further show that deterministic switching of high anisotropy materials by the combination of circularly polarized light and modest external magnetic fields, thus revealing a pathway towards technological implementation.
Surveys on wave propagation in dispersive media have been limited since the pioneering work of Sommerfeld [Ann. Phys. 349, 177 (1914)] by the presence of branches in the integral expression of the wave function. In this article, a method is proposed to eliminate these critical branches and hence to establish a modal expansion of the time-dependent wave function. The different components of the transient waves are physically interpreted as the contributions of distinct sets of modes and characterized accordingly. Then, the modal expansion is used to derive a modified analytical expression of the Sommerfeld precursor improving significantly the description of the amplitude and the oscillating period up to the arrival of the Brillouin precursor. The proposed method and results apply to all waves governed by the Helmholtz equations.
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