Subset models for justification logic

We introduce a new semantics for justification logic based on subset relations. Instead of using the established and more symbolic interpretation of justifications, we model justifications as sets of possible worlds. We introduce a new justification logic that is sound and complete with respect to our semantics. Moreover, we present another variant of our semantics that corresponds to traditional justification logic. These types of models offer us a versatile tool to work with justifications, e.g.~by extending them with a probability measure to capture uncertain justifications. Following this strategy we will show that they subsume Artemov's approach to aggregating probabilistic evidence

Orthogonal Graph Drawing with Inflexible Edges

We consider the problem of creating plane orthogonal drawings of 4-planar graphs (planar graphs with maximum degree 4) with constraints on the number of bends per edge. More precisely, we have a flexibility function assigning to each edge $e$ a natural number $\mathrm{flex}(e)$, its flexibility. The problem FlexDraw asks whether there exists an orthogonal drawing such that each edge $e$ has at most $\mathrm{flex}(e)$ bends. It is known that FlexDraw is NP-hard if $\mathrm{flex}(e) = 0$ for every edge $e$. On the other hand, FlexDraw can be solved efficiently if $\mathrm{flex}(e) \ge 1$ and is trivial if $\mathrm{flex}(e) \ge 2$ for every edge $e$. To close the gap between the NP-hardness for $\mathrm{flex}(e) = 0$ and the efficient algorithm for $\mathrm{flex}(e) \ge 1$, we investigate the computational complexity of FlexDraw in case only few edges are inflexible (i.e., have flexibility~$0$). We show that for any $\varepsilon > 0$ FlexDraw is NP-complete for instances with $O(n^\varepsilon)$ inflexible edges with pairwise distance $\Omega(n^{1-\varepsilon})$ (including the case where they induce a matching). On the other hand, we give an FPT-algorithm with running time $O(2^k\cdot n \cdot T_{\mathrm{flow}}(n))$, where $T_{\mathrm{flow}}(n)$ is the time necessary to compute a maximum flow in a planar flow network with multiple sources and sinks, and $k$ is the number of inflexible edges having at least one endpoint of degree 4.Comment: 23 pages, 5 figure

The Gender Earnings Gap inside a Russian Firm: First Evidence from Personnel Data – 1997 to 2002

Using unique personnel data from one Russian firm for the years 1997 to 2002 we study the size, development and determinants of the gender earnings gap in an internal labor market during late transition. The gap is sizable but declines strongly over the entire period. Gender earnings differentials are largest for production workers who constitute the largest employee group in the firm. Various decompositions show that these differentials and their dynamics remain largely unexplained by observable characteristics at the mean and across the wage distribution. Our analysis also reveals that the earnings differentials for production workers largely stem from job assignment, as women are predominately assigned to lower paid jobs. Earnings gaps within job levels are small and almost fully explained by observed characteristics.internal labor market, personnel data, gender earnings gap, Russia

Wage Policies of a Russian Firm and the Financial Crisis of 1998: Evidence from Personnel Data – 1997 to 2002

We use a rich personnel data set from a Russian firm for the years 1997 to 2002 to analyze how the financial crisis in 1998 and the resulting change in external labor market conditions affect the wages and the welfare of workers inside a firm. We provide evidence that large shocks to external conditions affect the firm’s personnel policies, and show that the burden of the shock is not evenly spread across the workforce. The firm takes advantage of a high-inflationary environment and of a fall in workers’ outside options after the financial crisis and cuts real wages. Earnings are curbed most for those who earned the highest rents, resulting in a strong compression of real wages. The fact that real wages and real compensation levels never recovered to pre-crisis levels even though the firm’s financial situation was better in 2002 than before the crisis and the differential treatment of employee groups within the firm can be taken as evidence that market forces strongly influence the wage policies of our firm.internal labor markets, wage policies of a firm, personnel data, Russia