Spacetime Dependent Lagrangians and Weak-Strong Duality : Sine Gordon and Massive Thirring Models

The formalism of spacetime dependent lagrangians developed in Ref.1 is applied to the Sine Gordon and massive Thirring models.It is shown that the well-known equivalence of these models (in the context of weak-strong duality) can be understood in this approach from the same considerations as described in [1] for electromagnetic duality. A further new result is that all these can be naturally linked to the fact that the holographic principle has analogues at length scales much larger than quantum gravity. There is also the possibility of {\it noncommuting coodinates} residing on the boundaries. PACS: 11.15.-q: 11.10/EfComment: Latex, 16 pages, article shortened, references added, minor typos correcte

Fluctuating Fuzzy Funnels

It is well known that a D-string ending on a D3, D5 or D7 brane is described in terms of a non-commutative fuzzy funnel geometry. In this article, we give a numerical study of the fluctuations about this leading geometry. This allows us to investigate issues related to the stability and moduli space of these solutions. We comment on the comparison to the linearized fluctuations in supergravity.Comment: 24 pages, 3 figures; v2 references added and correcte

Free volume theory explains the unusual behavior of viscosity in a non-confluent tissue during morphogenesis

A recent experiment on zebrafish blastoderm morphogenesis showed that the viscosity ({\eta}) of a non-confluent embryonic tissue grows sharply until a critical cell packing fraction ({\phi}S). The increase in {\eta} up to {\phi}S is similar to the behavior observed in several glass-forming materials, which suggests that the cell dynamics is sluggish or glass-like. Surprisingly, {\eta} is a constant above {\phi}S. To determine the mechanism of this unusual dependence of {\eta} on {\phi}, we performed extensive simulations using an agent-based model of a dense non-confluent two-dimensional tissue. We show that polydispersity in the cell size, and the propensity of the cells to deform, results in the saturation of the available free area per cell beyond a critical packing fraction. Saturation in the free space not only explains the viscosity plateau above {\phi}S but also provides a relationship between equilibrium geometrical packing to the dramatic increase in the relaxation dynamics.Comment: 19 pages, 5 figures, accepted for publication in eLif

National Rural Employment Guarantee as Social Protection

This article is an attempt to highlight issues around the implementation of NREGA with a focus on its institutions, governance and innovations. The main proposition considered is that institutions and governance play an important role in determining the functioning of NREGA, and the trajectory of its success. The attempt is to identify the conditions for success (or failure) in the process, to draw lessons for mid?course corrections to the programme. This includes examining political, administrative and bureaucratic dynamics that may ensure better realisation of the ‘right to work’. Based on a field study in three Indian states, it was found that differential impacts and achievements of the NREGA are related to variations in the commitment of local leadership, levels of institutional preparedness and governance capacities. The experience of these states offers certain insights which may help improve implementation policy of the NREGA

Mechanical feedback controls the emergence of dynamical memory in growing tissue monolayers

The growth of a tissue, which depends on cell-cell interactions and biologically relevant process such as cell division and apoptosis, is regulated by a mechanical feedback mechanism. We account for these effects in a minimal two-dimensional model in order to investigate the consequences of mechanical feedback, which is controlled by a critical pressure, pc. A cell can only grow and divide if the pressure it experiences, due to interaction with its neighbors, is less than pc. Because temperature is an irrelevant variable in the model, the cell dynamics is driven by self-generated active forces (SGAFs) that are created by cell division. It is shown that even in the absence of intercellular interactions, cells undergo diffusive behavior. The SGAF-driven diffusion is indistinguishable from the well-known dynamics of a free Brownian particle at a fixed finite temperature. When intercellular interactions are taken into account, we find persistent temporal correlations in the force-force autocorrelation function (FAF) that extends over timescale of several cell division times. The time-dependence of the FAF reveals memory effects, which increases as pc increases. The observed non-Markovian effects emerge due to the interplay of cell division and mechanical feedback, and is inherently a non-equilibrium phenomenon.</jats:p