Analysis of Political Party Twitter Accounts' Retweeters During Japan's 2017 Election

In modern election campaigns, political parties utilize social media to advertise their policies and candidates and to communicate to the electorate. In Japan's latest general election in 2017, the 48th general election for the Lower House, social media, especially Twitter, was actively used. In this paper, we analyze the users who retweeted tweets of political parties on Twitter during the election. Our aim is to clarify what kinds of users are diffusing (retweeting) tweets of political parties. The results indicate that the characteristics of retweeters of the largest ruling party (Liberal Democratic Party of Japan) and the largest opposition party (The Constitutional Democratic Party of Japan) were similar, even though the retweeters did not overlap each other. We also found that a particular opposition party (Japanese Communist Party) had quite different characteristics from other political parties.Comment: WI 2018 Workshop : The International Workshop on Web Personalization, Recommender Systems, and Social Media (WPRSM2018

Numerical Simulations of Flare-productive Active Regions: delta-sunspots, Sheared Polarity Inversion Lines, Energy Storage, and Predictions

Solar active regions (ARs) that produce strong flares and coronal mass ejections (CMEs) are known to have a relatively high non-potentiality and are characterized by delta-sunspots and sheared magnetic structures. In this study, we conduct a series of flux emergence simulations from the convection zone to the corona and model four types of active regions that have been observationally suggested to cause strong flares, namely the Spot-Spot, Spot-Satellite, Quadrupole, and Inter-AR cases. As a result, we confirm that delta-spot formation is due to the complex geometry and interaction of emerging magnetic fields, with finding that the strong-field, high-gradient, highly-sheared polarity inversion line (PIL) is created by the combined effect of the advection, stretching, and compression of magnetic fields. We show that free magnetic energy builds up in the form of a current sheet above the PIL. It is also revealed that photospheric magnetic parameters that predict flare eruptions reflect the stored free energy with high accuracy, while CME-predicting parameters indicate the magnetic relationship between flaring zones and entire ARs.Comment: Accepted for publication in ApJ. Movies for Figures 3, 4, 5, 6, and 7 will be available in the published versio

Detection of the Horizontal Divergent Flow prior to the Solar Flux Emergence

It is widely accepted that solar active regions including sunspots are formed by the emerging magnetic flux from the deep convection zone. In previous numerical simulations, we found that the horizontal divergent flow (HDF) occurs before the flux emergence at the photospheric height. This Paper reports the HDF detection prior to the flux emergence of NOAA AR 11081, which is located away from the disk center. We use SDO/HMI data to study the temporal changes of the Doppler and magnetic patterns from those of the reference quiet Sun. As a result, the HDF appearance is found to come before the flux emergence by about 100 minutes. Also, the horizontal speed of the HDF during this time gap is estimated to be 0.6 to 1.5 km s^-1, up to 2.3 km s^-1. The HDF is caused by the plasma escaping horizontally from the rising magnetic flux. And the interval between the HDF and the flux emergence may reflect the latency during which the magnetic flux beneath the solar surface is waiting for the instability onset to the further emergence. Moreover, SMART Halpha images show that the chromospheric plages appear about 14 min later, located co-spatial with the photospheric pores. This indicates that the plages are caused by plasma flowing down along the magnetic fields that connect the pores at their footpoints. One importance of observing the HDF may be the possibility to predict the sunspot appearances that occur in several hours.Comment: 32 pages, 8 figures, 3 tables, accepted for publication in Ap

Numerical Experiments on the Two-step Emergence of Twisted Magnetic Flux Tubes in the Sun

We present the new results of the two-dimensional numerical experiments on the cross-sectional evolution of a twisted magnetic flux tube rising from the deeper solar convection zone (-20,000 km) to the corona through the surface. The initial depth is ten times deeper than most of previous calculations focusing on the flux emergence from the uppermost convection zone. We find that the evolution is illustrated by the two-step process described below: the initial tube rises due to its buoyancy, subject to aerodynamic drag due to the external flow. Because of the azimuthal component of the magnetic field, the tube maintains its coherency and does not deform to become a vortex roll pair. When the flux tube approaches the photosphere and expands sufficiently, the plasma on the rising tube accumulates to suppress the tube's emergence. Therefore, the flux decelerates and extends horizontally beneath the surface. This new finding owes to our large scale simulation calculating simultaneously the dynamics within the interior as well as above the surface. As the magnetic pressure gradient increases around the surface, magnetic buoyancy instability is triggered locally and, as a result, the flux rises further into the solar corona. We also find that the deceleration occurs at a higher altitude than in our previous experiment using magnetic flux sheets (Toriumi and Yokoyama). By conducting parametric studies, we investigate the conditions for the two-step emergence of the rising flux tube: field strength > 1.5x10^4 G and the twist > 5.0x10^-4 km^-1 at -20,000 km depth.Comment: 42 pages, 13 figures, 2 tables, accepted for publication in ApJ. High-resolution figures will appear in the published versio

Scale-Dependent Newton's Constant G in the Conformal Newtonian Gauge

In classical gravity deviations from the predictions of the Einstein theory are often discussed within the framework of the conformal Newtonian gauge, where scalar perturbations are described by two potentials $\phi$ and $\psi$. In this paper we use the above gauge to explore possible cosmological consequences of a running Newton's constant $G (\Box)$, as suggested by the nontrivial ultraviolet fixed point scenario arising from the quantum field-theoretic treatment of Einstein gravity with a cosmological constant term. Here we focus on the effects of a scale-dependent coupling on the so-called gravitational slip functions $\eta = \psi / \phi -1$, whose classical general relativity value is zero. Starting from a set of manifestly covariant but non-local effective field equations derived earlier, we compute the leading corrections in the potentials $\phi$ and $\psi$ for a nonrelativistic, pressureless fluid. After providing an estimate for the quantity $\eta$, we then focus on a comparison with results obtained in a previous paper on matter density perturbations in the synchronous gauge, which gave an estimate for the growth index parameter $\gamma$, also in the presence of a running $G$. Our results indicate that, in the present framework and for a given $G (\Box)$, the corrections tend to be significantly larger in magnitude for the perturbation growth exponents than for the conformal Newtonian gauge slip function.Comment: 37 page

Polchinski's exact renormalisation group for tensorial theories: Gaussian universality and power counting

In this paper, we use the exact renormalisation in the context of tensor models and tensorial group field theories. As a byproduct, we rederive Gaussian universality for random tensors and provide a general power counting for Abelian tensorial field theories with a closure constraint, leading us to a only five renormalizable theories.Comment: 22 pages, 4 figure

Three-dimensional magnetohydrodynamic simulation of the solar magnetic flux emergence: Parametric study on the horizontal divergent flow

Solar active regions are formed through the emergence of magnetic flux from the deeper convection zone. Recent satellite observations have shown that a horizontal divergent flow (HDF) stretches out over the solar surface just before the magnetic flux appearance. The aims of this study are to investigate the driver of the HDF and to see the dependency of the HDF on the parameters of the magnetic flux in the convection zone. We conduct three-dimensional magnetohydrodynamic (3D MHD) numerical simulations of the magnetic flux emergence and vary the parameters in the initial conditions. An analytical approach is also taken to explain the dependency. The horizontal gas pressure gradient is found to be the main driver of the HDF. The maximum HDF speed shows positive correlations with the field strength and twist intensity. The HDF duration has a weak relation with the twist, while it shows negative dependency on the field strength only in the case of the stronger field regime. Parametric dependencies analyzed in this study may allow us to probe the structure of the subsurface magnetic flux by observing properties of the HDF.Comment: 7 pages, 5 figures, 1 table, accepted for publication in Astronomy & Astrophysic