Self-healing systems and virtual structures

Modern networks are large, highly complex and dynamic. Add to that the mobility of the agents comprising many of these networks. It is difficult or even impossible for such systems to be managed centrally in an efficient manner. It is imperative for such systems to attain a degree of self-management. Self-healing i.e. the capability of a system in a good state to recover to another good state in face of an attack, is desirable for such systems. In this paper, we discuss the self-healing model for dynamic reconfigurable systems. In this model, an omniscient adversary inserts or deletes nodes from a network and the algorithm responds by adding a limited number of edges in order to maintain invariants of the network. We look at some of the results in this model and argue for their applicability and further extensions of the results and the model. We also look at some of the techniques we have used in our earlier work, in particular, we look at the idea of maintaining virtual graphs mapped over the existing network and assert that this may be a useful technique to use in many problem domains

Is the Convergence of the Racial Wage Gap Illusory?

I demonstrate that the literature on the racial wage gap has systematically overstated the gains made by African American men by ignoring their withdrawal from the labor force. Three sources of selection-bias are identified: imposing sample selection criteria based on labor supply, trimming wages on the basis of real-dollar cutoffs, and making inferences based on Current Population Survey (CPS) data whose truncated sampling design excludes the growing incarcerated population. To recover the counterfactual distribution of skill-prices for non-workers, I implement a quasi-bounds estimator that does not require the use of arbitrary exclusion restrictions for identification and find that: (1) Corrected estimates of the racial wage gap indicate a substantial role for the efficacy of the Civil Rights Act and related initiatives in affecting convergence in segregated states; ignoring selection causes estimates of convergence in the South as well as the within-cohort component of this change to be understated. (2) In contrast to the sharp convergence observed in standard wage series from 1970-90, selectivity corrected estimates indicate complete stagnation over this period with a divergence of 3.5 to 6 percentage points between 1980 and 1990. Almost half of this divergence is missed through the exclusion of the incarcerated population. The selective withdrawal hypothesis can explain 85 percent of the observed convergence between 1970 and 1990 and 40 percent of the 1960-90 convergence. (3) The disproportionate presence of highly skilled blacks in the armed forces (who are also excluded from CPS analysis) causes estimates of the racial gap to be overstated by 1 to 2 percentage points. (4) The relative increase in non-participation is a supply-side effect driven more by a massive increase in reservation wages for blacks at the bottom of the skill distribution, than by falling offer wages. (5) The significant gains made by black men during the 1960s and 1970s occured almost exclusively in the bottom offer wage decile, where significant numbers of black men were pushed out of the lowest white wage decile into higher quintiles. These gains constitute the primary location of black economic progress in the latter half of the 20th century.

A black hole instability in five dimensions?

We study the moduli-space scattering of a two-charge supertube in the background of a rotating BPS D1-D5-P black hole in 4+1 dimensions, extending the static analysis of Bena and Kraus (hep-th/0402144). While the magnetic forces associated with this motion change the details considerably, the final conclusion is similar to that of the static analysis: we find that one can bring the supertube to the horizon, so that the BMPV black hole and the supertube merge. However, our analysis shows that this can occur even at significantly larger values of the angular momentum than was indicated by the static analysis. For a range of parameters, conservation laws and the area theorem forbid the result of the merger from being any single known object: neither near-extremal black holes nor non-supersymmetric black rings are allowed. Such results suggest that the merger triggers an instability of the rotating D1-D5-P black hole, perhaps leading to bifurcation into a pair of black objects.Comment: 25 pages, 4 figures; v2: references adde

Urbanisation and Migration: An Analysis of Trends, Patterns and Policies in Asia

The present paper overviews urbanisation and migration process in Asian countries at macro level since 1950s, including the projections made till 2030. It questions the thesis of southward movement of urbanisation and that of urban explosion in Asia. Increased unaffordability of urban space and basic amenities, negative policy perspective towards migration and various rural development pogrammes designed to discourage migration are responsible for this exclusionary urban growth and a distinct decline in urban rural growth differential, with the major exception of China. The changing structure of urban population across different size categories reveals a shift of growth dynamics from large to second order cities and stagnation of small towns. The pace of urbanization has been modest to high in select countries in Asia, not because of their level of economic growth but its composition and labour intensity of rapidly growing informal sectors. Several countries have launched programmes for improving governance and infrastructural facilities in a few large cities, attracting private investors from within as well as outside the country. These have pushed out squatter settlements, informal sector businesses along with a large number of pollutant industries to a few pockets and peripheries of the cities. The income level and quality of basic amenities in these cities, as a result, have gone up but that has been associated with increased intra-city disparity and creation of degenerated periphery. Nonetheless, there is no strong evidence that urbanization is associated with destabilization of agrarian economy, poverty and immiserisation, despite the measures of globalization resulting in regional imbalances. The overview of the trend and pattern suggests that the pace of urbanization would be reasonably high but much below the level projected by UNPD in the coming decades.urbanisation, migration, exclusion, periphery, informalisation, small towns, economic concentration, urban rural growth differential, Asia, China and India

A New Cryptosystem Based On Hidden Order Groups

Let $G_1$ be a cyclic multiplicative group of order $n$. It is known that the Diffie-Hellman problem is random self-reducible in $G_1$ with respect to a fixed generator $g$ if $\phi(n)$ is known. That is, given $g, g^x\in G_1$ and having oracle access to a `Diffie-Hellman Problem' solver with fixed generator $g$, it is possible to compute $g^{1/x} \in G_1$ in polynomial time (see theorem 3.2). On the other hand, it is not known if such a reduction exists when $\phi(n)$ is unknown (see conjuncture 3.1). We exploit this ``gap'' to construct a cryptosystem based on hidden order groups and present a practical implementation of a novel cryptographic primitive called an \emph{Oracle Strong Associative One-Way Function} (O-SAOWF). O-SAOWFs have applications in multiparty protocols. We demonstrate this by presenting a key agreement protocol for dynamic ad-hoc groups.Comment: removed examples for multiparty key agreement and join protocols, since they are redundan