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The concept of a point dipole is potentially ambiguous due to inherent singularity of electro-magnetic fields at its location. We discuss this concept from several points of view. First, we consider a point dipole as a singular point in space whose sole ability is to be polarized due to the external electric field. We introduce the source Green's dyadic that provides a unified albeit empiric description of the contribution of the dipole to the electromagnetic properties of the whole space. We argue that this is the most complete, concise, and unambiguous definition of a point dipole and its polarizability. Next, we revisit classic expressions for absorption and emission power by integration of Poynting vector over a surface enclosing the point dipole, thereby avoiding the singularity. We also consider the energy balance between the fluctuating dipole moment and the medium (thermal bath) to derive the fluctuation-dissipation theorem in terms of fluctuating dipole moment. This solves the long-standing controversy in the literature. Second, the same results can be obtained for a very small homogeneous sphere, in which the internal field is known to be constant. This leads to unambiguous microscopic definition of the particle dipole moment and polarizability in terms of its size and refractive index. Third, and most interestingly, we generalize this microscopic description to small particles of arbitrary shape. Both bare (electrostatic) and dressed (corrected) polarizabilities are defined as double integrals of the corresponding dyadic transition operator over the particle's volume. [ABSTRACT FROM AUTHOR]

Forms of technologies like interferometer and electromagnetic detectors are in existence for detection of Gravitational waves. In this paper a method is put forward where metric perturbation attests the existences of the linearized gravitational waves and an system with the aid of greens function helps for the detection of linearized gravitational waves. Dipole arrangement characteristic of its high frequency electromagnetic waves and dipole moment forms the basic arrangement. System is built which tunes in accordance with that of linearized gravitational waves. Dipole radiation characteristic of accelerating of radiating charge makes up for the rest of the system. Poynting vector treatment on the domain scale and power calculations makes up for the penultimate arrangement. Greens function idiosyncratic of point charges helps finally for the detection the linearized gravitational waves. [ABSTRACT FROM AUTHOR]

In this article the time-moments of the Poynting vector associated with an electromagnetic pulse are used to characterize the traversal time and the pulse width as the pulse propagates through highly dispersive media. The behaviour of these quantities with propagation distance is analyzed in two physical cases: Lorentz absorptive medium, and Raman gain doublet amplifying medium. It is found that the superluminal pulse propagation in these two cases with anomalous dispersion is always accompanied by pulse compression and eventually the pulse becomes subluminal with increasing distance of propagation. [ABSTRACT FROM AUTHOR]

One of the key open question for gamma-ray bursts (GRBs) jets, is the magnetization of the outflow. Here we consider the photospheric emission of Poynting flux dominated outflows, when the dynamics is mediated by magnetic reconnection. We show that thermal three-particle processes, responsible for the thermalization of the plasma, become inefficient far below the photosphere. Conservation of the total photon number above this radius, combined with Compton scattering below the photosphere enforces kinetic equilibrium between electrons and photons. This, in turn, leads to an increase in the observed photon temperature, which reaches ≳ 8 MeV (observed energy) when decoupling the plasma at the photosphere. This result is weakly dependent on the free model parameters. The predicted peak energy is more than an order of magnitude higher than the observed peak energy of most GRBs, which puts strong constraints on the magnetization of these outflows. [ABSTRACT FROM AUTHOR]

The paper considers regular trends of propagation of plane optic and acoustic waves in crystals, periodical structures and metamaterials. It is stated that mutually opposite directions of wave vectors and Poynting vectors are typical of plane waves in «metamaterials» and «negative media». It is also demonstrated that in crystals with a strong anisotropy of optic and elastic properties, a wave vector and a Poynting vector may be directed with respect to each other at angles as wide as ψ = 740. It is proved that the anisotropy of materials may result in unusual propagation and reflection of plane waves in these media. A few examples of peculiar wave behavior in the crystalline materials are described in the presentation. A diagram is proposed showing possible orientations of group velocity vector relatively to the phase velocity vector of waves in the anisotropic media. [ABSTRACT FROM AUTHOR]

Observations of GRB 100724B with the Fermi Gamma-Ray Burst Monitor (GBM) find that the spectrum is dominated by the typical Band functional form, which is usually taken to represent a non-thermal emission component, but also includes a statistically highly significant thermal spectral contribution [14]. The simultaneous observation of the thermal and non-thermal components allows us to confidently identify the two emission components. The fact that these seem to vary independently favors the idea that the thermal component is of photospheric origin while the dominant non-thermal emission occurs at larger radii. Our results imply either a very high efficiency for the non-thermal process, or a very small size of the region at the base of the flow, both quite challenging for the standard fireball model. These problems are resolved if the jet is initially highly magnetized and has a substantial Poynting flux. [ABSTRACT FROM AUTHOR]

Using the scattering matrix approach and Poynting's theorem in the form of an energy balance equation we determine the total power that is dissipated by a thin metal film. We are able to demonstrate the existence of two absorbing modes that are correlated as well as non equivalent, contrary to what happens in more complex systems. Also, we show the dependence of the total absorption on the width of the film, as well as a function of the frequency. [ABSTRACT FROM AUTHOR]

We apply Poynting's theorem to the dielectric-conductor interface to determine the intensity of the absorbing mode (parasitic channel), when plane waves incide with an angle of incidence. By applying boundary conditions we are able to describes the scattering at the interface by means of a subunitary scattering matrix. The energy balance equation allows to determine the lack of unitarity (absorbance) as a function of the frequency and the angle of incidence. Also, it allows to write a unitary scattering matrix which contains the subunitary one and a single parasitic channel with transmission intensity given by the absorbance. [ABSTRACT FROM AUTHOR]

The dispersion relation determining guided TE and TM modes are found for the slab hyperbolic waveguide. The waveguide is consisting of an isotropic dielectric slab bounded by hyperbolic media. Some differences between the features of the waveguide under consideration and conventional ones are obtained. In particular, in the case of hyperbolic waveguide TM modes have two cutoff frequencies. As a result the number of modes is limited. Both TE and TM modes have nonzero cutoff frequencies, even though waveguide is symmetric one. For the TE and TM modes the Poynting vector component along the wave's propagation axis could be equal to zero. [ABSTRACT FROM AUTHOR]

The article presents the research on sub-terahertz (THz) technology for dynamic nuclear polarization in nuclear magnetic resonance (DNP NMR). It states that the mechanism that allows DNP to improve nuclear spin polarization signals is based on coherent spin polarization transfer. It mentions that the simulated complex spatial distribution of amplitudes and angular dependence of poynting and electric field vectors is the result of transverse confinement.