In this paper we are concerned with labelled apparent contours, namely with apparent contours of generic orthogonal projections of embedded surfaces in R, endowed with a suitable depth information. We show that there exists a finite set of elementary moves (i.e. local topological changes) on labelled apparent contours such that the following theorem holds: two generic embeddings of a closed sur...

We study the L2 → L∞ norms of spectral projections and spectral multipliers of left-invariant elliptic and subelliptic second-order differential operators on homogeneous Lie groups. We obtain a precise description of the L2 → L∞ norms of spectral multipliers for some class of operators which we call quasi-homogeneous. As an application we prove a stronger version of Alexopoulos’ spectral multip...

We consider a 2 d.o.f. Hamiltonian system with one degree of freedom corresponding to fast motion and the other corresponding to slow motion. The ratio of the time derivatives of slow and fast variables is of order 0 < ε ≪ 1. At frozen values of the slow variables there is a separatrix on the phase plane of the fast variables and there is a region in the phase space (the domain of separatrix cr...

We propose to realize Weyl semimetals in a cubic optical lattice. We find that there exist three distinct Weyl semimetal phases in the cubic optical lattice for different parameter ranges. One of them has two pairs of Weyl points and the other two have one pair of Weyl points in the Brillouin zone. For a slab geometry with (010) surfaces, the Fermi arcs connecting the projections of Weyl points...

Our survey of private manufacturing firms finds the size of hidden ‘unofficial’ activity to be much larger in Russia and Ukraine than in Poland, Slovakia and Romania. A comparison of cross-country averages shows that managers in Russia and Ukraine face higher effective tax rates, worse bureaucratic corruption, greater incidence of mafia protection, and have less faith in the court system. Our f...

Sequential Pattern Mining is a widely addressed problem in data mining, with applications such as analyzing Web usage, examining purchase behavior, and text mining, among others. Nevertheless, with the dramatic increase in data volume, the current approaches prove inefficient when dealing with large input datasets, a large number of different symbols and low minimum supports. In this paper, we ...

To Ed EEros, on the occasion of his 60th birthday. We prove a local nite dimensional approximation result for unital C*-algebras that are simple, have a trace, contain suuciently many projections and are quasidiagonal.

In this study, we analyzed whether parents' receipt of welfare affects children's educational attainment in early adulthood, independent of its effect through changing family income. We used data from the Panel Study of Income Dynamics with information on parents' welfare receipt over the first 15 years of childhood. Cross-sectional results show that greater exposure to welfare is significantly...

Viewing vector/matrix multiplications as " projections onto linear subspaces " is one of the most useful ways to think about these operations. In this note, I'll put together necessary pieces to achieve this understanding.

We examine the relation between firms’ financial structures and their risky investment strategies in Taiwan’s banking industry. Regressions cover two subperiods: before the first financial reform (1996– 2000) and after the first financial reform (2001–2006), to address the impacts of the first financial reform on banking firms’ financial structures. Our first result demonstrates that the restri...