Which part of the Brillouin zone contributes most to the high-harmonic radiation?

Utilizing realistic simulations of high-harmonic generation (HHG) in several materials, we study how different regions of the Brillouin zone contribute to the nonlinear response. It is often assumed that only the vicinity of the Gamma point is predominantly responsible for the HHG spectrum, but it is shown here that such an approximation is inaccurate in general. While examples can be identified where merely 0.4% of the Brillouin zone produces semi-quantitatively accurate HHG-spectra, in most situations one must include at least thirty to fifty percent of the Brillouin-zone volume to obtain accurate above-the-gap harmonics. For the harmonic peaks below the bandgap energy, the current-density responses from the entire Brillouin zone must always be integrated. We also identify the minimal set of electronic bands necessary for the construction of reduced but still realistic HHG-models. The results should be useful for a number of HHG applications, including all-optical reconstructions of the band-structure and light-matter couplings, or considerations involving semi-classical approaches to solid-state high-harmonic radiation

CRITICAL EXPONENTS OF THE 3D ANTIFERROMAGNETIC THREE-STATE POTTS MODEL USING THE COHERENT-ANOMALY METHOD

The antiferromagnetic three-state Potts model on the simple-cubic lattice is studied using the coherent-anomaly method (CAM). The CAM analysis provides the estimates for the critical exponents which indicate the XY universality class, namely $\alpha=-0.011$, $\beta= 0.351$, $\gamma= 1.309$ and $\delta= 4.73$. This observation corroborates the results of the recent Monte Carlo simulations, and disagrees with the proposal of a new universality class.Comment: 11 pages, latex, 1 postscript figure, changes: an incorrect reference omitte

Carrier field shock formation of long wavelength femtosecond pulses in dispersive media

We numerically demonstrate the formation of carrier field shocks in various dispersive media for a wide variety of input conditions using two different electric field propagation models. In addition, an investigation of the impact of numerous physical effects on carrier wave shock is performed. It is shown that in many cases a field shock is essentially unavoidable and therefore extremely important in the propagation of intense long wavelength pulses in weakly dispersive nonlinear media such as noble gases, air, and single-crystal diamond. The results presented here are expected to have a significant impact in the field of ultrashort nonlinear optics, attosecond pulse generation, and wavepacket synthesis where the use of mid-IR wavelengths is becoming increasingly more important.Comment: 14 pages, 17 figure

Experimental Tests of the New Paradigm for Laser Filamentation in Gases

Since their discovery in the mid-1990s, ultrafast laser filaments in gases have been described as products of a dynamic balance between Kerr self-focusing and defocusing by free electric charges that are generated via multi-photon ionization on the beam axis. This established paradigm has been recently challenged by a suggestion that the Kerr effect saturates and even changes sign at high intensity of light, and that this sign reversal, not free-charge defocusing, is the dominant mechanism responsible for the extended propagation of laser filaments. We report qualitative tests of the new theory based on electrical and optical measurements of plasma density in femtosecond laser filaments in air and argon. Our results consistently support the established paradigm.Comment: 4 pages, 4 figure

Accurate Estimates of 3D Ising Critical Exponents Using the Coherent-Anomaly Method

An analysis of the critical behavior of the three-dimensional Ising model using the coherent-anomaly method (CAM) is presented. Various sources of errors in CAM estimates of critical exponents are discussed, and an improved scheme for the CAM data analysis is tested. Using a set of mean-field type approximations based on the variational series expansion approach, accuracy comparable to the most precise conventional methods has been achieved. Our results for the critical exponents are given by \alpha=\afin, \beta=\bfin, \gamma=\gfin and \delta=\dfin.Comment: 16 pages, latex, 1 postscript figur

Leaky Modes of Solid Dielectric Spheres

In the absence of external excitation, light trapped within a dielectric medium generally decays by leaking out, and also by getting absorbed within the medium. We analyze the leaky modes of solid dielectric spheres by examining solutions of Maxwell's equations for simple homogeneous, isotropic, linearly dispersive media that admit complex-valued oscillation frequencies. We show that, under appropriate circumstances, these leaky modes constitute a complete set into which an initial electromagnetic field distribution inside a dielectric sphere can be expanded. We provide the outline of a completeness proof, and also present results of numerical calculations that illustrate the close relationship between the leaky modes and the resonances of solid dielectric spherical cavities.Comment: 19 pages, 9 figures, 24 equations, 28 references, one Appendix. (There exists some overlap with the corresponding conference paper, "Leaky Modes of Dielectric Cavities," by M. Mansuripur, M. Kolesik, and P. Jakobsen, Proceedings of SPIE 9931, 99310B~1:20 (2016); also available at arXiv:1610.00045.

Extreme Long-time Dynamic Monte Carlo Simulations

We study the extreme long-time behavior of the metastable phase of the three-dimensional Ising model with Glauber dynamics in an applied magnetic field and at a temperature below the critical temperature. For these simulations we use the advanced simulation method of projective dynamics. The algorithm is described in detail, together with its application to the escape from the metastable state. Our results for the field dependence of the metastable lifetime are in good agreement with theoretical expectations and span more than fifty decades in time.Comment: 13 pages with embedded eps figures. Int. J. Mod. Phys. C, in pres

CEReS Newsletter No.42, May 2009

[掲載記事] 「CEReSの衛星・環境データアーカイブの現状（その２）」ほ