Can Skill Biased Technological Progress Have a Role in the Decline of the Savings Rate?

This paper explores the consequences of skill biased technological progress on the savings rates. The literature, both theoretical and empirical, on the causes and consequences of skill biased technological progress in the past few years has burgeoned considerably. So has the literature on declining household savings, motivated by the American experience over the past couple of decades. I present a general equilibrium model where declining savings rates emerges as an outcome of exogenously driven skill biased technological progress. The link between the two is attributed to optimizing behavior of altruistic households. In an overlapping generations model, parents are assumed to derive utility from both spending on their children's education and making monetary transfers (or bequests). I show that increases in the growth rate of skill biased technological change causes a shift in allocations away from bequests in favor of education- leading to a decline in domestic capital accumulation. The analysis is extended to incorporate life cycle savings both under certainty and uncertainty regarding the timing of death.Technological Change, Savings, overlapping Generations,Human Capital, Growth

Q criterion for disc stability modified by external tidal field

The standard Q criterion (with Q > 1) describes the local stability of a disc supported by rotation and random motion. Most astrophysical discs, however, are under the influence of an external gravitational field which can affect their stability. A typical example is a galactic disc embedded in a dark matter halo. Here we do a linear perturbation analysis for a disc in an external field, and obtain a generalized dispersion relation and a modified stability criterion. An external field has two effects on the disc dynamics: first, it contributes to the unperturbed rotational field, and second, it adds a tidal field term in the stability parameter. A typical disruptive tidal field results in a higher modified Q value and hence leads to a more stable disc. We apply these results to the Milky Way, and to a low surface brightness galaxy UGC 7321. We find that in each case the stellar disc by itself is barely stable and it is the dark matter halo that stabilizes the disc against local, axisymmetric gravitational instabilities. This result has been largely missed so far because in practice the value for Q for a galactic disc is obtained in a hybrid fashion using the observed rotational field that is set by both the disc and the halo, and hence is higher than for a pure disc.Comment: 7 pages, 3 figures, submitted to MNRA

Large-Scale Asymmetry of Rotation Curves in Lopsided Spiral Galaxies

Many spiral galaxies show a large-scale asymmetry with a cos\phi dependence in their rotation curves as well as in their morphology, such as M101 and NGC 628. We show that both these features can be explained by the response of a galactic disk to an imposed lopsided halo potential. A perturbation potential of 5 % is deduced for the morphologically lopsided galaxies in the Rix & Zaritsky (1995) sample. This is shown to result in a difference of 10 % or about 20-30 kms^{-1} in the rotation velocity on the two sides of the major axis. Interestingly, the observed isophotal asymmetry in a typical spiral galaxy is not much smaller and it results in a velocity asymmetry of 7 % or about 14-21 kms^{-1} . Hence, we predict that most galaxies show a fairly significant rotational asymmetry. The rotation velocity is shown to be maximum along the elongated isophote - in agreement with the observations along the SW in M101, while it is minimum along the opposite direction. This result leads to the distinctive asymmetric shape of the rotation curve which rises more steeply in one half of the galaxy than the other, as observed by Swaters et al. (1999). This shape is shown to be a robust feature and would result for any centrally concentrated disk. The net disk lopsidedness and hence the asymmetry in the rotation curve is predicted to increase with radius and hence can be best studied using HI gas as the tracer.Comment: 30 pages, accepted for publication in A &

Effects of external magnetic field and hydrostatic pressure on magnetic and structural phase transitions in Pr0.6Sr0.4MnO3

We investigate the effect of hydrostatic pressure on temperature dependence of magnetization and also the influence of magnetic field on linear thermal expansion in polycrystalline Pr0.6Sr0.4MnO3, which is ferromagnetic at room temperature (TC = 305 K) but its magnetization undergoes an abrupt decrease at TS = 89 K within the ferromagnetic state. Normal and inverse magnetocaloric effects around TC and TS, respectively, were reported earlier in this single phase compound [D. V. M. Repaka et al., J. Appl. Phys. 112, 123915 (2012)]. The thermal expansion shows an abrupt decrease at TS in zero magnetic field but it transforms into an abrupt increase at the same temperature under 7 T, which we interpret as the consequence of magnetic field-induced structural transition from a low-volume monoclinic (I2/a symmetry) to a high volume orthorhombic (Pnma symmetry) phase in corroboration with a published neutron diffraction study in zero magnetic field. While the external magnetic field does not change TS, application of a hydrostatic pressure of P = 1.16 GPa shifts the magnetic anomaly at TS towards high temperature. The pressure induced shift of the low-temperature anomaly (deltaTS = 27 K) is nine-times more than that of the ferromagnetic Curie temperature (deltaTC = 3K). Our results suggest that while hydrostatic pressure stabilizes the low temperature monoclinic phase at the expense of orthorhombic phase, magnetic field has an opposite effect.Comment: 16 pages, 5 figure

The Influence of Capital Controls on Long Run Growth: Where and How Much?

The recent financial crisis in East Asia generated a revival of interest in the merits of financial openness. The ensuing debate on the benefits of openness has focused more on short and medium run issues than on the long run effects. Within the empirical literature on economic growth, little or no attention has been paid to the effects of financial openness. Contrary to the orthodox position, the few results that exist suggest that capital controls have no effect on economic growth. This paper argues that this conclusion emerges from a failure to account for underlying differences across countries with similar degrees of capital controls. I show that the degree of ethnic and linguistic heterogeneity in a country plays a significant role in explaining the effects of controls on economic growth. For countries with relatively higher degrees of ethnic heterogeneity, the effects are particularly adverse whereas for countries with high degrees of homogeneity, capital controls actually have a net positive effect on economic growth. On balance, more developing countries suffered due to controls than not. Within the sample of 57 non OECD countries that did implement controls for the period 1975-95, as many as 39 saw a reduction in their growth rates. This result is robust to a number of variables commonly used in the economic growth regressions.Economic Growth, Capital Controls, Ethno-Linguistic Fractionalization

Off-centred dark matter halo leading to strong central disc lopsidedness

There is increasing evidence now from simulations and observations that the centre of dark matter halo in a Milky Way type galaxy could be off-centred by a few 100 pc w.r.t. the galactic disc. We study the effect of such an offset halo on the orbits and kinematics in the central few kpc of the disc. The equations of motion in the disc plane can be written in terms of the disc and halo potentials when these two are concentric and a perturbation term due to the offset halo. This perturbation potential shows an m=1 azimuthal variation, or is lopsided, and its magnitude increases at small radii. On solving these equations, we find that the perturbed orbit shows a large deviation of ~ 40 % in radius at R = 1.5 kpc, and also strong kinematical lopsidedness. Thus even a small halo offset of 350 pc can induce surprisingly strong spatial and kinematical lopsidedness in the central region within ~ 3 kpc radius. Further, the disc would remain lopsided for several Gyr, as long as the halo offset lasts. This would have important implications for the dynamical evolution of this region.Comment: 6 pages, 6 figures, Submitted to MNRA

Measurement of non-axisymmetry in centres of advanced mergers of galaxies

We measure the non-axisymmetry in the luminosity distribution in the inner few kpc of the remnants of advanced mergers of galaxies with a view to understand the relaxation in the central regions. For this, we analyze the images from the 2MASS archival data for a selected sample of 12 merging galaxies, which show signs of interaction but have a single nucleus. The central regions are fitted by elliptical isophotes whose centres are allowed to vary to get the best fit. The centres of isophotes show a striking sloshing pattern with a spatial variation of up to 20-30 % within the central 1 kpc. This indicates mass asymmetry and a dynamically unrelaxed behaviour. Next, we Fourier-analyze the galaxy images while keeping the centre constant and measure the deviation from axisymmetry in terms of the fractional Fourier amplitudes (A_1, A_2 etc) as a function of radius. All mergers show a high value of lopsidedness (upto A_1 ~ 0.2) in the central 5 kpc. The m=2 asymmetry is even stronger, with values of A_2 upto ~ 0.3, and in three cases these are shown to represent bars. The corresponding values denoting non-axisymmetry in inner regions of a control sample of eight non-merger galaxies are found to be several times smaller. Surprisingly, this central asymmetry is seen even in mergers where the outer regions have relaxed into a smooth elliptical-like r^{1/4} profile or a spiral-like exponential profile. Thus the central asymmetry is long-lived, estimated to be ~ 1 Gyr, and hence lasts for over 100 local dynamical timescales. These central asymmetries are expected to play a key role in the future dynamical evolution of the central region of a merger, and can help in feeding a central AGN.Comment: 14 pages, 3 figures, accepted for publication in MNRA