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Search Results: 1 - 10 of 1974 matches for " Sotaro Sasaki "
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Perturbation Analysis of Superconductivity in the Trellis-Lattice Hubbard Model
Sotaro Sasaki,Hiroaki Ikeda,Kosaku Yamada
Physics , 2004, DOI: 10.1143/JPSJ.73.2822
Abstract: We investigate pairing symmetry and transition temperature in the trellis-lattice Hubbard model. We solve the \'Eliashberg equation using the third-order perturbation theory with respect to the on-site repulsion $U$. We find that a spin-singlet state is very stable in a wide range of parameters. On the other hand, when the electron number density is shifted from the half-filled state and the band gap between two bands is small, a spin-triplet superconductivity is expected. Finally, we discuss a possibility of unconventional superconductivity and pairing symmetry in Sr$_{14-x}$Ca$_x$Cu$_{24}$O$_{41}$.
Perturbation Theory for a Repulsive Hubbard Model in Quasi-One-Dimensional Superconductors
Sotaro Sasaki,Hiroaki Ikeda,Kosaku Yamada
Physics , 2003, DOI: 10.1143/JPSJ.73.815
Abstract: We investigate pairing symmetry and a transition temperature in a quasi-one-dimensional repulsive Hubbard model. We solve the Eliashberg equation using the third-order perturbation expansion with respect to the on-site repulsion $U$. We find that when the electron number density is shifted from the half-filled, a transition into unconventional superconductivity is expected. When one dimensionality is weak, a spin-singlet state is favorable. By contrast, when one dimensionality is strong and electron number density is far from the half-filled, a spin-triplet state is stabilized. Finally, we discuss the possibility of unconventional superconductivity caused by the on-site Coulomb repulsion in $\beta$-Na$_{0.33}$V$_2$O$_5$.
Analysis of Superconductivity in d-p Model on Basis of Perturbation Theory
Sotaro Sasaki,Hiroaki Ikeda,Kosaku Yamada
Physics , 2005, DOI: 10.1143/JPSJ.74.1397
Abstract: We investigate the mass enhancement factor and the superconducting transition temperature in the d-p model for the high-$\Tc$ cuprates. We solve the \'Eliashberg equation using the third-order perturbation theory with respect to the on-site Coulomb repulsion $U$. We find that when the energy difference between d-level and p-level is large, the mass enhancement factor becomes large and $\Tc$ tends to be suppressed owing to the difference of the density of state for d-electron at the Fermi level. From another view point, when the energy difference is large, the d-hole number approaches to unity and the electron correlation becomes strong and enhances the effective mass. This behavior for the electron number is the same as that of the f-electron number in the heavy fermion systems. The mass enhancement factor plays an essential role in understanding the difference of $\Tc$ between the LSCO and YBCO systems.
Socially Anxious Tendencies Affect Autonomic Responses during Eye Gaze Perception  [PDF]
Yuki Tsuji, Sotaro Shimada
Psychology (PSYCH) , 2015, DOI: 10.4236/psych.2015.613160
Abstract: Social anxiety disorder is a common psychiatric disorder. The gaze of others is known to frequently induce social anxiety. We conducted a gaze detection experiment to examine the effects of social anxiety on autonomic response, namely heart rate (HR) response. We used the maximum HR deceleration between 0 s and 3 s after stimulus onset as an indicator of emotional stress. Participants were assigned to a high social anxiety (HSA) or low social anxiety (LSA) group on the basis of cut-off scores indicative of clinical levels of stress as per the Japanese version of the Liebowitz Social Anxiety Scale (LSAS-J). Our results showed that HR deceleration was greater for the HSA compared with the LSA group. Moreover, the higher the LSAS-J score was, the greater the increase was in HR deceleration (correlation coefficient rs = 0.52, p < 0.01). Our results suggest that the eye gaze of others can be processed as a threat in individuals with a high tendency towards social anxiety.
Modulation of Motor Area Activity by the Outcome for a Player during Observation of a Baseball Game
Sotaro Shimada
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0008034
Abstract: Observing competitive games such as sports is a pervasive entertainment among humans. The inclination to watch others play may be based on our social-cognitive ability to understand the internal states of others. The mirror neuron system, which is activated when a subject observes the actions of others, as well as when they perform the same action themselves, seems to play a crucial role in this process. Our previous study showed that activity of the mirror neuron system was modulated by the outcome of the subject's favored player during observation of a simple competitive game (rock-paper-scissors). However, whether the mirror neuron system responds similarly in a more complex and naturalistic sports game has not yet been fully investigated.
The Effects of Trajectory and Endpoint Errors in a Reaching Movement on the Sense of Agency  [PDF]
Takuro Zama, Yoshiyuki Takahashi, Sotaro Shimada
Psychology (PSYCH) , 2017, DOI: 10.4236/psych.2017.814146
Abstract: The sense of agency (SoA) refers to the subjective feeling that an individual can control their own action with their own will. However, it is still unclear which aspects of the motor control process precisely affect the sense of agency. In this study, we investigated how the SoA is modulated by the online motor performance (trajectory error) and the outcome of the reaching movement (endpoint error). The results showed that the invalid priming and the visual feedback delay significantly increased both the trajectory and endpoint errors and that these errors significantly attenuated the SoA. The further correlation analyses showed that the decrease in SoA was significantly correlated with the trajectory error, but not with the endpoint error, when the error was explicitly noticed. We suggest that the deterioration in online motor performance, at least in a reaching movement, is the main cause of the attenuation in the SoA.
Inferior Parietal Lobe Activity in Visuo-Motor Integration during the Robot Hand Illusion  [PDF]
Mohamad Arif Fahmi Bin Ismail, Sotaro Shimada
Psychology (PSYCH) , 2018, DOI: 10.4236/psych.2018.915174
Abstract: The robot hand illusion (RoHI) is the participant’s illusion of the self-ownership and the self-agency of a robot hand that appears to be moving consistently with their own hand, and feel as if the robot hand belongs to them. Mismatching between motor and visual information disrupt the effect of RoHI respect to the robot hand. In our previous study, we found that participants felt that the virtual hand was their own when the visual feedback was delayed by less than 200 ms. Moreover, although they did not feel that the virtual hand was their own, the participants felt that they could control the virtual hand even with a visual delay of 300 - 500 ms. Here, we used near-infrared spectroscopy (NIRS) to investigate brain activity associated with the RoHI under different delayed visual feedback conditions (100 ms, 400 ms, and 700 ms). We found significant activation in the supramarginal gyrus and superior temporal gyrus in the 100 ms feedback delay condition. An ANOVA indicated that this activation was significantly different from that in other conditions (p < 0.01). These results demonstrate that activity in the inferior parietal cortex was modulated by the delay between the motor command and the visual feedback regarding the movement of the robot hand. We propose that the inferior parietal lobe is essential for integrating motor and visual information that enables one to distinguish their own body from those of others.
Proposal on Tunneling Effect between Quantum Hall States  [PDF]
Shosuke Sasaki
Journal of Modern Physics (JMP) , 2013, DOI: 10.4236/jmp.2013.49A001

In the integer and fractional quantum Hall effects, the electric current flows through a thin layer under the strong magnetic field. The diagonal resistance becomes very small at integer and specific fractional filling factors where the electron scatterings are very few. Accordingly the coherent length is large and therefore a tunneling effect of electrons may be observed. We consider a new type of a quantum Hall device which has a narrow potential barrier in the thin layer. Then the electrons flow with tunneling effect through the potential barrier. When the oscillating magnetic field is applied in addition to the constant field, the voltage steps may appear in the curve of voltage V versus electric current I. If the voltage steps are found in the experiment, it is confirmed that the 2D electron system yields the same phenomenon as that of the ac-Josephson effect in a superconducting system. Furthermore the step V is related to the transfer charge Q as V = (hf)/Q where f is the frequency of the oscillating field and h is the Planck constant. Then the detection of the step V determines the transfer charge Q. The ratio Q/e (e is the elementary charge) clarifies the

Weierstrass’ Elliptic Function Solution to the Autonomous Limit of the String Equation of Type (2,5)*  [PDF]
Yoshikatsu Sasaki
Advances in Pure Mathematics (APM) , 2014, DOI: 10.4236/apm.2014.48055

In this article, we study the string equation of type (2,5), which is derived from 2D gravity theory or the string theory. We consider the equation as a 4th order analogue of the first Painlevé equation, take the autonomous limit, and solve it concretely by use of the Weierstrass’ elliptic function.

Erratum to “Weierstrass’ Elliptic Function Solution to the Autonomous Limit of the String Equation of Type (2,5)” [Advances in Pure Mathematics 4 (2014), 494-497]  [PDF]
Yoshikatsu Sasaki
Advances in Pure Mathematics (APM) , 2014, DOI: 10.4236/apm.2014.412077
Abstract: In this note, we analyze a few major claims about . As a consequence, we rewrite a major theorem, nullify its proof and one remark of importance, and offer a valid proof for it. The most important gift of this paper is probably the reasoning involved in all: We observe that a constant, namely t, has been changed into a variable, and we then tell why such a move could not have been made, we observe the discrepancy between the claimed domain and the actual domain of a supposed function that is created and we then explain why such a function could not, or should not, have been created, along with others.
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