Homology of spaces of non-resultant polynomial systems in R^2 and C^2

The resultant veriety in the space of systems of homogeneous polynomials of given degrees consists of such systems having non-trivial solutions. We calculate the integer cohomology groups of all spaces of non-resultant systems of polynomials $R^2 \to R$, and also the rational cohomology groups of similar systems in $C^2$

Cohomology of spaces of complex knots

We develop a technique for calculating the cohomology groups of spaces of complex parametric knots in ${\mathbb C}^k$, $k \geq 3$, and carry out these calculations to obtain these groups of low dimensions

Cohomology of spaces of Hopf equivariant maps of spheres

For any natural $k \leq n$, the rational cohomology ring of the space of continuous maps $S^{2k-1} \to S^{2n-1}$ (respectively, $S^{4k-1} \to S^{4n-1}$) equivariant under the Hopf action of the circle (respectively, of the group $S^3$ of unit quaternions) is naturally isomorphic to that of the Stiefel manifold $V_k({\mathbb C}^n)$ (respectively, $V_k({\mathbb H}^n)$)

Complements of caustics of simple real function singularities

All local connected components of complements of caustics of simple function singularities are listed, and generators of their homology groups are realized

Simplified numerical form of universal finite type invariant of Gauss words

In the present paper, we study the finite type invariants of Gauss words. In the Polyak algebra techniques, we reduce the determination of the group structure to transformation of a matrix into its Smith normal form and we give the simplified form of a universal finite type invariant by means of the isomorphism of this transformation. The advantage of this process is that we can implement it as a computer program. We obtain the universal finite type invariant of degree 4, 5, and 6 explicitly. Moreover, as an application, we give the complete classification of Gauss words of rank 4 and the partial classification of Gauss words of rank 5 where the distinction of only one pair remains.Comment: 12 pages, 3 table

Whispering gallery mode resonator based ultra-narrow linewidth external cavity semiconductor laser

We demonstrate a miniature self-injection locked DFB laser using resonant optical feedback from a high-Q crystalline whispering gallery mode resonator. The linewidth reduction factor is greater than 10,000, with resultant instantaneous linewidth less than 200 Hz. The minimal value of the Allan deviation for the laser frequency stability is 3x10^(-12) at the integration time of 20 us. The laser possesses excellent spectral purity and good long term stability.Comment: To be published in Optics Letter