Passive Curvaton

We propose a class of curvaton models which we call passive curvaton. In this paper, two kinds of passive curvaton is considered. The first one is a pseudoscalar curvaton couples to a gauge field. Different from the inflaton case, the constraint from formation of primordial black holes (PBHs) is much weaker and large non-gaussianity (of the equiliteral type) can be produced. The second model is a dilaton-like scalar curvaton couples to a gauge field. We investigate the scale dependence of non-gaussianity in this model. In both models, the spectrum and non-Gaussianity are enhanced by the slow-roll parameter of the curvaton field. Other possible passive curvaton models are also mentioned.Comment: 9 pages, 2 figures, to appear in PL

A statistical study of the subsurface structure and eruptivity of solar active regions

A statistical study of 77 solar active regions (ARs) is conducted to investigate the existence of identifiable correlations between the subsurface structural disturbances and the activity level of the active regions. The disturbances examined in this study are $$,$$, and . where $\Gamma_1$ and $c$ are the thermodynamic properties of first adiabatic index and sound speed modified by magnetic field, respectively. The averages are over three depth layers: $0.975-0.98 R_\odot$, $0.98-0.99 R_\odot$ and $0.99-0.995 R_\odot$ to represent the structural disturbances in that layer. The level of the surface magnetic activity is measured by the Magnetic Activity Index (MAI) of active region and the relative and absolute MAI differences (rdMAI and dMAI) between the active and quiet regions. The eruptivity of each active region is quantified by its Flare Index, total number of coronal mass ejections (CMEs), and total kinetic energy of the CMEs. The existence and level of the correlations are evaluated by scatter plots and correlation coefficients. No definitive correlation can be claimed from the results. While a weak positive trend is visible between dMAI and and $<|\delta c^2/c^2|>$ in the layer $0.975-0.98 R_\odot$, their correlation levels, being approximately 0.6, are not sufficiently high to justify the correlation. Some subsurface disturbances are seen to increase with eruptivity indices among ARs with high eruptivity. The statistical significance of such trend, however, cannot be ascertained due to the small number of very eruptive ARs in our sample.Comment: 11 pages, 8 figure

An Estimation of Elasticities of Consumption Demand and Investment Demand for Owner-Occupied Housing in Taiwan : A Two-Period Model

Buying a house usually satisfies housing consumption demand and housing investment demand, simultaneously. In order to disentangle the above two types of demand, households, in this study, are separated into three subtenure groups i.e. renters, owners owning one house, and owners buying a second or more houses. Presumably, renting a house is for consumption only, while buying a second house is usually for investment purposes. Applying a two-period model and two data sets from DGBAS and from Land Bank of Taiwan, the estimated results are as follows: Firstly, the income elasticity of pure consumption demand for housing is very close to unity (1.0413). Secondly, the income elasticity for a pure investment demand is greater than one (1.2643). Finally, for a household owning only one house, the shares for consumption motive and for investment motive are 26% and 74%, respectively.Consumption demand, investment demand, elasticity and housing, Taiwan