Aharonov-Bohm Effect at liquid-nitrogen temperature: Frohlich superconducting quantum device

The Aharonov-Bohm (AB) effect has been accepted and has promoted interdisciplinary scientific activities in modern physics. To observe the AB effect in condensed matter physics, the whole system needs to maintain phase coherence, in a tiny ring of the diameter 1 micrometer and at low temperatures below 1 K. We report that AB oscillations have been measured at high temperature 79 K by use of charge-density wave (CDW) loops in TaS3 ring crystals. CDW condensate maintained macroscopic quantum coherence, which extended over the ring circumference 85 micrometer. The periodicity of the oscillations is h/2e in accuracy within a 10 percent range. The observation of the CDW AB effect implies Frohlich superconductivity in terms of macroscopic coherence and will provide a novel quantum interference device running at room temperature.Comment: 11 pages, 4 figure

Internal Josephson Effects in Spinor Dipolar Bose--Einstein Condensates

We theoretically study the internal Josephson effect, which is driven by spin exchange interactions and magnetic dipole-dipole interactions, in a three-level system for spin-1 Bose--Einstein condensates, obtaining novel spin dynamics. We introduce single spatial mode approximations into the Gross--Pitaevskii equations and derive the Josephson type equations, which are analogous to tunneling currents through three junctions between three superconductors. From an analogy with two interacting nonrigid pendulums, we identify unique varied oscillational modes, called the 0--$\pi$, 0--$running$, $running$--$running$, 2n\pi & running--$2\pi$, $single nonrigid pendulum$, and $two rigid pendulums$ phase modes. These Josephson modes in the three states are expected to be found in real atomic Bose gas systems.Comment: 9 pages, 13 figure

Dynamics of fine particles due to quantized vortices on the surface of superfluid 4^4He

Peculiar dynamics of a free surface of the superfluid 4He has been observed experimentally with a newly established technique utilizing a number of electrically charged fine metal particles trapped electrically at the surface by Moroshkin et al. They have reported that some portion of the particles exhibit some irregular motions and suggested the existence of quantized vortices interacting with the metal particles. We have conducted calculations with the vortex filament model, which turns out to support the idea of the vortex-particle interactions. The observed anomalous metal particle motions are roughly categorized into two types; (1) circular motions with specific frequencies, and (2) quasi-linear oscillations. The former ones seem to be explained once we consider a vertical vortex filament whose edges are terminated at the bottom and at a particle trapped at the surface. Although it is not yet clear whether all the anomalous motions are due to the quantum vortices, the vortices seem to play important roles for the motions.Comment: 7 pages, 10 figure

Dynamics of the vortex-particle complexes bound to the free surface of superfluid helium

We present an experimental and theoretical study of the 2D dynamics of electrically charged nanoparticles trapped under a free surface of superfluid helium in a static vertical electric field. We focus on the dynamics of particles driven by the interaction with quantized vortices terminating at the free surface. We identify two types of particle trajectories and the associated vortex structures: vertical linear vortices pinned at the bottom of the container and half-ring vortices travelling along the free surface of the liquid

Economic impact of political protests (strikes) on manufacturing firms : evidence from Bangladesh

Political protests in the form of strikes, locally known as hartal, remain quite common in the Indian subcontinent countries. Such a form of protests is associated with mass movement, intended to cause a total shutdown of economic activities and often results in coercion, violence, and damage to both public and private properties. Utilizing the World Bank Enterprise survey data of 2007 and 2013 of Bangladesh, this study examines the impacts of hartals on manufacturing firms. We find that political protests significantly increase costs for firms. Using flexible cost function based on factor analysis we see that the factor-neutral effect of strikes is positive and statistically significant, showing evidence of a reduction in firm productivity due to hartals. However, we did not find any evidence for systematic factor re-optimization by firms – in response to political strikes – suggesting that firms do not reallocate factor shares to tackle uncertain and irregular shocks like hartals

Partition, independence, and population geography in Bengal

This study quantitatively explores the changing population geography in Bengal, with a particular focus on Partition in India in 1947 and Independence of Bangladesh in 1971. Based on decadal census data from 1901 to 2001 at the district level, this paper explores how trends in regional population growth evolved with such historical events. Following Redding and Sturm (2008), Differences-in-Differences estimation is also employed. Estimation results show that there were different shocks on both sides and from both events. In West Bengal, the change in the regional population trends occurred in 1947 and remained similar thereafter. On the other hand, in East Bengal, the population growth became statistically significant after 1971. Further robustness checks show that the impacts were not uniform with respect to the distance from the border. Overall analyses show that the emergence of the international border in Bengal had asymmetric impacts on both sides

Displacement in Bengal, revisited

Bengal was divided twice in the 20th century. At the first occasion, both sides were still within British India. Then, on the second occasion, Bengal split the two into different countries, India and Pakistan. We examine the displacements in Bengal after the partition in 1947 with the finest geographical level at thana. The results show that there were significantly negative impacts on population growth on the region which changed their side from East in 1905 to West in 1947. They also experienced an increase in the share of literate population, suggesting the impact of population exchange in different levels of literacy