On exponential cosmological type solutions in the model with Gauss-Bonnet term and variation of gravitational constant

A D-dimensional gravitational model with Gauss-Bonnet term is considered. When ansatz with diagonal cosmological type metrics is adopted, we find solutions with exponential dependence of scale factors (with respect to "synchronous-like" variable) which describe an exponential expansion of "our" 3-dimensional factor-space and obey the observational constraints on the temporal variation of effective gravitational constant G. Among them there are two exact solutions in dimensions D = 22, 28 with constant G and also an infinite series of solutions in dimensions D \ge 2690 with the variation of G obeying the observational data.Comment: 21 pages, 12 figures, LaTex; eq. (2.1) is modified, several sentences are added, a typo in eq. (3.13) is eliminate

Calibrating an interferometric laser frequency stabilization to MHz precision

We report on a calibration procedure that enhances the precision of an interferometer based frequency stabilization by several orders of magnitude. For this purpose the frequency deviations of the stabilization are measured precisely by means of a frequency comb. This allows to implement several calibration steps that compensate different systematic errors. The resulting frequency deviation is shown to be less than $5.7$MHz (rms $1.6$MHz) in the whole wavelength interval $750 - 795$nm. Wide tuning of a stabilized laser at this exceptional precision is demonstrated.Comment: http://dx.doi.org/10.1364/AO.51.00551

Double-scale Pulses Generated by Mode-locked Fibre Lasers and Their Applications

This chapter presents a detailed analysis of properties of double-scale pulses (also called noise-like pulses and femtosecond clusters) generated in fibre lasers and gives an in-depth discussion of promising applications of such pulses

Mode-locked fiber lasers with significant variability of generation regimes

We demonstrate a great variability of single-pulse (with only one pulse/wave-packet traveling along the cavity) generation regimes in fiber lasers passively mode-locked by non-linear polarization evolution (NPE) effect. Combining extensive numerical modeling and experimental studies, we identify multiple very distinct lasing regimes with a rich variety of dynamic behavior and a remarkably broad spread of key parameters (by an order of magnitude and more) of the generated pulses. Such a broad range of variability of possible lasing regimes necessitates developing techniques for control/adjustment of such key pulse parameters as duration, radiation spectrum, and the shape of the auto-correlation function. From a practical view point, availability of pulses/wave-packets with such different characteristics from the same laser makes it imperative to develop variability-aware designs with control techniques and methods to select appropriate application-oriented regimes

Exact (1+3+6)(1 + 3 + 6)-dimensional cosmological-type solutions in gravitational model with Yang-Mills field, Gauss-Bonnet term and Λ\Lambda-term

We consider $10$-dimensional gravitational model with $SO(6)$ Yang-Mills field, Gauss-Bonnet term and $\Lambda$-term. We study so-called cosmological type solutions defined on product manifold $M = R \times R^3 \times K$, where $K$ is $6d$ Calabi-Yau manifold. By putting the gauge field 1-form to be coinciding with 1-form spin connection on $K$, we obtain exact cosmological solutions with exponential dependence of scale factors (upon $t$-variable), governed by two non-coinciding Hubble-like parameters: $H >0$, $h$, obeying $H + 2 h \neq 0$. We also present static analogs of these cosmological solutions (for $H \neq 0$, $h \neq H$ and $H + 2 h \neq 0$). The islands of stability for both classes of solutions are outlined.Comment: 17 pages, 3 figures, LaTex, Revised version: 3 paragraphs are added into Introduction, new references are included and few references (self-citations) are omitte