Toho University
Prospect theory is widely viewed as the best available descriptive model of how people evaluate risk in experimental settings. According to prospect theory, people are risk-averse with respect to gains and risk-seeking with respect to losses, a phenomenon called "loss aversion". Despite of the fact that prospect theory has been well developed in behavioral economics at the theoretical level, there exist very few large-scale empirical studies and most of them have been undertaken with micro-panel data. Here we analyze over 28.5 million trades made by 81.3 thousand traders of an online financial trading community over 28 months, aiming to explore the large-scale empirical aspect of prospect theory. By analyzing and comparing the behavior of winning and losing trades and traders, we find clear evidence of the loss aversion phenomenon, an essence in prospect theory. This work hence demonstrates an unprecedented large-scale empirical evidence of prospect theory, which has immediate implication in financial trading, e.g., developing new trading strategies by minimizing the effect of loss aversion. Moreover, we introduce three risk-adjusted metrics inspired by prospect theory to differentiate winning and losing traders based on their historical trading behavior. This offers us potential opportunities to augment online social trading, where traders are allowed to watch and follow the trading activities of others, by predicting potential winners statistically based on their historical trading behavior rather than their trading performance at any given point in time.
We investigated the interlayer magnetoresistance in an organic massless Dirac electron system α\alpha-(BEDT-TTF)2_2I3_3 under pressure. We experimentally demonstrate that the width of the zero mode owing to carrier scattering is much narrower than that of the other Landau levels.
Helimagnets, characterized by a helical arrangement of magnetic moments, possess unique internal degrees of freedom, including the spin phase, defined by the phase of the helical magnetic structure. Electrical detection of the spin phase is essential for both practical applications and fundamental research in helimagnets. Here, we demonstrate the electrical detection of the spin phase in a van der Waals nanoscale chiral helimagnet CrNb3_3S6_6 using nonlocal spin valve measurements. Due to the short spin diffusion length in CrNb3_3S6_6 (5\sim5~nm), the surface magnetic moment direction, which corresponds to the spin phase, can be detected via spin currents. The experimentally observed magnetic field dependence of the nonlocal spin valve signal is consistent with that of the surface magnetic moment in the helical magnetic structure, as supported by micromagnetic simulations. Our results establish spin currents as a powerful tool for detecting the spin phase in helimagnets, opening avenues for utilizing the spin phase as a novel internal degree of freedom in nanoscale spintronic devices.
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Charged lepton flavor violation is forbidden in the Standard Model but possible in several new physics scenarios. In many of these models, the radiative decays τ±±γ\tau^{\pm}\rightarrow\ell^{\pm}\gamma (=e,μ\ell=e,\mu) are predicted to have a sizeable probability, making them particularly interesting channels to search at various experiments. An updated search via τ±±γ\tau^{\pm}\rightarrow\ell^{\pm}\gamma using full data of the Belle experiment, corresponding to an integrated luminosity of 988 fb1^{-1}, is reported for charged lepton flavor violation. No significant excess over background predictions from the Standard Model is observed, and the upper limits on the branching fractions, B(τ±μ±γ)\mathcal{B}(\tau^{\pm}\rightarrow \mu^{\pm}\gamma) \leq 4.2×1084.2\times10^{-8} and B(τ±e±γ)\mathcal{B}(\tau^{\pm}\rightarrow e^{\pm}\gamma) \leq 5.6×1085.6\times10^{-8}, are set at 90\% confidence level.
We study bond percolation on a one-parameter family of hierarchical small-world network, and find a meta-transition between the inverted BKT transition and the abrupt transition driven by changing the network topology. It is found that the order parameter is continuous and fractal exponent is discontinuous in the inverted BKT transition, and oppositely, the former is discontinuous and the latter is continuous in the abrupt transition. The gaps of the order parameter and fractal exponent in each transition go to vanish as approaching the meta-transition point. This point corresponds to a marginal power-law transition. In the renormalization group formalism, this meta-transition corresponds to the transition between transcritical and saddle-node bifurcations of the fixed point via a pitchfork bifurcation.
We report the synthesis of single crystals of Ce2_2SnS5_5 through a two-stage chemical vapor transport method. The Ce2_2SnS5_5 system is a member of the orthorhombic PbamPbam (No. 55) space group and realizes a distorted trigonal tricapped prism (TTP) crystal field around each cerium site. We characterized the sample through orientation-dependent magnetization and heat capacity measurements to probe the magnetic anisotropy in the system characteristic of XY-like anisotropic Heisenberg model behavior. Ce2_2SnS5_5 furthermore enters a zero-field ordered phase under TN=T_N = 2.4 K; powder neutron diffraction measurements reveal incommensurate magnetic order near TNT_N. The system locks into a commensurate structure with a $(q_x, q_y, q_z) = (1/3,0,0)$ propagation vector below approximately 1.2 K.
We report the synthesis of single crystals of Gd2_2B5_5 through a ruthenium-gadolinium flux method. The Gd2_2B5_5 system is a member of the monoclinic P21/cP21/c (No. 14) space group and realizes lattices of gadolinium atoms in the (100)(1\,0\,0) plane. We characterized the sample through orientation-dependent electrical transport, magnetization, magnetic torque, and heat capacity measurements to probe the magnetic anisotropy of the system and map out its phase diagram. Gd2_2B5_5 realizes two zero-field ordered phases M1_1 and M2_2, as well as a third field-induced ordered phase M_\perp arising when the magnetic field is applied in the (100)(1\,0\,0) plane.
We present measurements of B+ -> Dbar*0 tau+ nu_tau and B+ -> Dbar^0 tau+ nu_tau decays in a data sample of 657 x 10^6 BBbar pairs collected with the Belle detector at the KEKB asymmetric-energy e+e- collider. We find 446^{+58}_{-56} events of the decay B+ -> Dbar*0 tau+ nu_tau with a significance of 8.1 standard deviations, and 146^{+42}_{-41} events of the decay B+ -> Dbar0 tau+ nu_tau with a significance of 3.5 standard deviations. The latter signal provides the first evidence for this decay mode. The measured branching fractions are B(B+ -> Dbar*0 tau+ nu_tau)=(2.12^{+0.28}_{-0.27} (stat) +- 0.29 (syst)) % and B(B+ -> Dbar0 tau+ nu_tau)=(0.77 +- 0.22 (stat) +- 0.12 (syst)) %.
We report measurements of the branching fractions for B0π+πB^0\to\pi^+\pi^-, K+πK^+\pi^-, K+KK^+K^- and K0π0K^0\pi^0, and B+π+π0B^+\to\pi^+\pi^0, K+π0K^+\pi^0, K0π+K^0\pi^+ and K+Kˉ0K^+\bar{K}{}^0. The results are based on 10.4 fb1^{-1} of data collected on the Υ\Upsilon(4S) resonance at the KEKB e+ee^+e^- storage ring with the Belle detector, equipped with a high momentum particle identification system for clear separation of charged π\pi and KK mesons. We find ${\cal B}(B^0\to\pi^+\pi^-) =(0.56^{+0.23}_{-0.20}\pm 0.04)\times 10^{-5},, {\cal B}(B^0\to K^+\pi^-) =(1.93^{+0.34 +0.15}_{-0.32 -0.06})\times 10^{-5},, {\cal B}(B^+\to K^+\pi^0) =(1.63^{+0.35 +0.16}_{-0.33 -0.18})\times 10^{-5},, {\cal B}(B^+\to K^0\pi^+) =(1.37^{+0.57 +0.19}_{-0.48 -0.18})\times 10^{-5},and, and {\cal B}(B^0\to K^0\pi^0) =(1.60^{+0.72 +0.25}_{-0.59 -0.27})\times 10^{-5}$, where the first and second errors are statistical and systematic. We also set upper limits of ${\cal B}(B^+\to\pi^+\pi^0)<1.34\times 10^{-5},, {\cal B}(B^0\to K^+K^-)<0.27\times 10^{-5},and, and {\cal B}(B^+\to K^+\bar{K}{}^0)<0.50\times 10^{-5}$ at the 90% confidence level.
CIZA J1358.9-4750 is a nearby galaxy cluster in the early phase of a major merger. The two-dimensional temperature map using XMM-Newton EPIC-PN observation confirms the existence of a high temperature region, which we call the "hot region", in the "bridge region" connecting the two clusters. The ~ 500 kpc wide region between the southeast and northwest boundaries also has higher pseudo pressure compared to the unshocked regions, suggesting the existence of two shocks. The southern shock front is clearly visible in the X-ray surface brightness image and has already been reported by Kato et al. (2015). The northern one, on the other hand, is newly discovered. To evaluate their Mach number, we constructed a three-dimensional toy merger model with overlapping shocked and unshocked components in line of sight. The unshocked and preshock ICM conditions are estimated based on those outside the interacting bridge region assuming point symmetry. The hot region spectra are modeled with two-temperature thermal components, assuming that the shocked condition follows the Rankin-Hugoniot relation with the preshock condition. As a result, the shocked region is estimated to have a line-of-sight depth of ~ 1 Mpc with a Mach number of ~ 1.3 in the southeast shock and ~ 1.7 in the northwest shock. The age of the shock waves is estimated to be ~ 260 Myr. This three dimensional merger model is consistent with the Sunyaev-Zeldovich signal obtained using the Planck observation within the CMB fluctuations. The total flow of the kinetic energy of the ICM through the southeast shock was estimated to be ~ 2.2 x 104210^{42} erg/s. Assuming that 10 % of this energy is converted into ICM turbulence, the line-of-sight velocity dispersion is calculated to be ~ 200 km/s, which is basically resolvable via coming high spectral resolution observations.
The broad energy range spanned by ASTRO-H instruments, from ~0.3 to 600 keV, with its high spectral resolution calorimeter and sensitive hard X-ray imaging, offers unique opportunities to study black holes and their environments. The ability to measure polarization is particularly novel, with potential sources including blazars, Galactic pulsars and X-ray binaries. In this White Paper, we present an overview of the synergistic instrumental capabilities and the improvements over prior missions. We also show how ASTRO-H fits into the multi-wavelength landscape. We present in more detail examples and simulations of key science ASTRO-H can achieve in a typical 100 ksec observation when data from all four instruments are combined. Specifically, we consider observations of black-hole source (Cyg X-1 and GRS 1915+105), blazars (Mrk 421 and Mrk 501), a quasar (3C 273), radio galaxies (Centaurus A and 3C 120), and active galaxies with a strong starburst (Circinus and NGC 4945). We will also address possible new discoveries expected from ASTRO-H.
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We report new measurements of the total cross sections for e+eΥ(nS)π+πe^+e^-\to \Upsilon(n{\rm S})\pi^+\pi^- (nn = 1, 2, 3) and e+ebbˉe^+e^-\to b\bar b from a high-luminosity fine scan of the region s=10.63\sqrt{s} = 10.63-11.0511.05 GeV with the Belle detector. We observe that the Υ(nS)π+π\Upsilon(n{\rm S})\pi^+\pi^- spectra have little or no non-resonant component and extract from them the masses and widths of Υ(10860)\Upsilon(10860) and Υ(11020)\Upsilon(11020) and their relative phase. We find M10860=(10891.1±3.21.7+0.6)M_{10860}=(10891.1\pm3.2^{+0.6}_{-1.7}) MeV/c2c^2 and Γ10860=(53.75.6+7.15.4+1.3)\Gamma_{10860}=(53.7^{+7.1}_{-5.6}\,^{+1.3}_{-5.4}) MeV and report first measurements M11020=(10987.52.5+6.42.1+9.0)M_{11020}=(10987.5^{+6.4}_{-2.5}\,^{+9.0}_{-2.1}) MeV/c2c^2, Γ11020=(6119+920+2)\Gamma_{11020}=(61^{+9}_{-19}\,^{+2}_{-20}) MeV, and ϕ11020ϕ10860=(1.0±0.40.1+1.4)\phi_{\rm 11020}-\phi_{\rm 10860} = (-1.0\pm0.4\,^{+1.4}_{-0.1}) rad.
Subtleties arising in the non-relativistic limit of relativistic branes are resolved, and a reparametrization-invariant and kappa-symmetric non-relativistic super p-brane action is obtained as a limit of the action for a relativistic super p-brane in a Minkowski vacuum. We give explicit results for the D0-brane, which provides a realization of the super-Bargmann algebra, the IIA superstring and the 11-dimensional supermembrane.
Gravitational-wave observation together with a large number of electromagnetic observations shows that the source of the latest gravitational-wave event, GW170817, detected primarily by advanced LIGO, is the merger of a binary neutron star. We attempt to interpret this observational event based on our results of numerical-relativity simulations performed so far paying particular attention to the optical and infra-red observations. We finally reach a conclusion that this event is described consistently by the presence of a long-lived hypermassive or supramassive neutron star as the merger remnant, because (i) significant contamination by lanthanide elements along our line of sight to this source can be avoided by the strong neutrino irradiation from it and (ii) it could play a crucial role to produce an ejecta component of appreciable mass with fast motion in the post-merger phase. We also point out that (I) the neutron-star equation of state has to be sufficiently stiff (i.e., the maximum mass of cold spherical neutron stars, M_max, has to be appreciably higher than 2M_sun in order that a long-lived massive neutron star can be formed as the merger remnant for the binary systems of GW170817, for which the initial total mass is >~ 2.73M_sun and (II) no detection of relativistic optical counterpart suggests a not-extremely high value of M_max approximately as 2.15-2.25M_sun.
The two-dimensional S=1/2S=1/2 XY model is investigated with an extensive quantum Monte Carlo simulation. The helicity modulus is precisely estimated through a continuous-time loop algorithm for systems up to 128×128128 \times 128 near and below the critical temperature. The critical temperature is estimated as TKT=0.3427(2)JT_{\rm KT} = 0.3427(2)J. The obtained estimates for the helicity modulus are well fitted by a scaling form derived from the Kosterlitz renormalization group equation. The validity of the Kosterlitz-Thouless theory for this model is confirmed.
We report results of numerical relativity simulations for {\it new} 26 non-spinning binary neutron star systems with 6 grid resolutions using an adaptive mesh refinement numerical re\ lativity code {\tt SACRA-MPI}. The finest grid spacing is 64\approx 64--8585 m, depending on the systems. First, we derive long-term high-precision inspiral gravitational waveforms and show that the accumulated gravitational-wave phase error due to the finite grid resolution is less than 0.50.5 rad during more than 200200 rad phase evolution irrespective of the systems. We also find that the gravitational-wave phase error for a binary system with a tabulated equation of state (EOS) is comparable to that for a piecewise polytropic EOS. Then we validate the SACRA inspiral gravitational waveform template, which will be used to extract tidal deformability from gravitational wave observation, and find that accuracy of \ our waveform modeling is 0.1\lesssim 0.1 rad in the gravitational-wave phase and 20%\lesssim 20 \% in the gravitational-wave amplitude up to the gravitational-wave frequency 10001000 Hz.\ Finally, we calibrate the proposed universal relations between a post-merger gravitational wave signal and tidal deformability/neutron star radius in the literature and show that th\ ey suffer from systematics and many relations proposed as universal are not very universal. Improved fitting formulae are also proposed.
Electronic properties of crystals can be manipulated using spatially periodic modulations. Long-wavelength, incommensurate modulations are of particular interest, exemplified recently by moiré patterned van der Waals (vdW) heterostructures. Bulk vdW superlattices hosting interfaces between clean 2D layers represent scalable bulk analogs of vdW heterostructures and present a complementary venue to explore incommensurately modulated 2D states. Here we report the bulk vdW superlattice SrTa2_2S5_5 realizing an incommensurate 1D modulation of 2D transition metal dichalcogenide (TMD) HH-TaS2_2 layers. High-quality electronic transport in the HH-TaS2_2 layers, evidenced by quantum oscillations, is made anisotropic by the modulation and shows commensurability oscillations akin to lithographically modulated 2D systems. We also find unconventional, clean-limit superconductivity (SC) in SrTa2_2S5_5 with a pronounced suppression of interlayer coherence relative to intralayer coherence. Such a hierarchy can arise from pair-density wave (PDW) SC with mismatched spatial arrangement in adjacent superconducting layers. Examining the in-plane magnetic field HabH_{ab} dependence of interlayer critical current density JcJ_c, we find anisotropy with respect to HabH_{ab} orientation: JcJ_c is maximized (minimized) when HabH_{ab} is perpendicular (parallel) to the stripes, consistent with 1D PDW SC. From diffraction we find the structural modulation is shifted between adjacent HH-TaS2_2 layers, suggesting mismatched 1D PDW is seeded by the striped structure. With a high-mobility Fermi liquid in a coherently modulated structure, SrTa2_2S5_5 is a promising host for novel phenomena anticipated in clean, striped metals and superconductors. More broadly, SrTa2_2S5_5 establishes bulk vdW superlattices as macroscopic platforms to address long-standing predictions for modulated electronic phases.
The differential cross sections for the process $\gamma \gamma \to \pi^0 \pi^0havebeenmeasuredinthekinematicrange0.6GeV have been measured in the kinematic range 0.6 GeV < W < 4.1$ GeV, |\cos \theta^*|&lt;0.8 in energy and pion scattering angle, respectively, in the γγ\gamma\gamma center-of-mass system. The results are based on a 223 fb1^{-1} data sample collected with the Belle detector at the KEKB e+ee^+ e^- collider. The differential cross sections are fitted in the energy region 1.7 GeV &lt; W &lt; 2.5 GeV to confirm the two-photon production of two pions in the G wave. In the higher energy region, we observe production of the χc0\chi_{c0} charmonium state and obtain the product of its two-photon decay width and branching fraction to π0π0\pi^0\pi^0. We also compare the observed angular dependence and ratios of cross sections for neutral-pion and charged-pion pair production to QCD models. The energy and angular dependence above 3.1 GeV are compatible with those measured in the π+π\pi^+\pi^- channel, and in addition we find that the cross section ratio, σ(π0π0)/σ(π+π)\sigma(\pi^0\pi^0)/\sigma(\pi^+\pi^-), is $0.32 \pm 0.03 \pm 0.05$ on average in the 3.1-4.1 GeV region.
We report the first observation of the charmless vector-vector decay process B+ ->rho+ rho0. The measurement uses a 78 fb^{-1} data sample collected with the Belle detector at the KEKB asymmetric e+e- collider operating at the Upsilon(4S) resonance. We obtain a branching fraction of Br(B+ ->rho+ rho0)=(31.7+-7.1(stat.)+3.8-6.7(sys.))*10^{-6}. An analysis of the rho helicity-angle distributions gives a longitudinal polarization of Gamma_{L}/Gamma=(94.8+-10.6(stat.)+-2.1(sys.))%.
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The first detected gravitational wave from a neutron star merger was GW170817. In this study, we present J-GEM follow-up observations of SSS17a, an electromagnetic counterpart of GW170817. SSS17a shows a 2.5-mag decline in the zz-band from 1.7 days to 7.7 days after the merger. Such a rapid decline is not comparable with supernovae light curves at any epoch. The color of SSS17a also evolves rapidly and becomes redder for later epochs; the zHz-H color changed by approximately 2.5 mag in the period of 0.7 days to 7.7 days. The rapid evolution of both the optical brightness and the color are consistent with the expected properties of a kilonova that is powered by the radioactive decay of newly synthesized rr-process nuclei. Kilonova models with Lanthanide elements can reproduce the aforementioned observed properties well, which suggests that rr-process nucleosynthesis beyond the second peak takes place in SSS17a. However, the absolute magnitude of SSS17a is brighter than the expected brightness of the kilonova models with the ejecta mass of 0.01 \Msun\Msun, which suggests a more intense mass ejection (0.03\Msun\sim 0.03 \Msun) or possibly an additional energy source.
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