Entity

Time filter

Source Type


Maedan S.,Tokyo National College of Technology
Progress of Theoretical Physics | Year: 2010

It is known that, in the chiral limit, spatially inhomogeneous chiral condensate occurs in the Nambu-Jona-Lasinio (NJL) model at finite density within a mean-field approximation. We study here how the introduction of current quark mass affects the ground state with the spatially inhomogeneous chiral condensate. Numerical calculations show that, even if the current quark mass is introduced, the spatially inhomogeneous chiral condensate can take place. To obtain the ground state, the thermodynamic potential is calculated with a mean-field approximation. The influence of finite current mass on the thermodynamic potential consists of the following two parts. One is a part coming from the field energy of the condensate, which favors the inhomogeneous chiral condensate. The other is a part coming from the Dirac sea and Fermi sea, which favors the homogeneous chiral condensate. We also find that when the spatially inhomogeneous chiral condensate occurs, the baryon number density becomes spatially inhomogeneous. Source


Matsumoto R.,Tokyo Polytechnic University | Nakajima M.,Tokyo Polytechnic University | Akuzawa N.,Tokyo National College of Technology
Solid State Communications | Year: 2010

Calcium graphite intercalation compounds (Ca-GICs; the composition is CaC6) and GICs containing CaC6 are synthesized from Grafoil and PGS graphite sheets, and the Seebeck coefficients are measured. The absolute values of the Seebeck coefficient of these GICs are very small; in some cases, the values are positive. This phenomenon observed in the Seebeck coefficient of GICs containing CaC6 is very different from that of general GICs such as alkali-metal GICs. The temperature dependence of the Seebeck coefficient of these GICs is to that of general GICs; that is, the absolute values of the Seebeck coefficient decrease with a decrease in the temperature. © 2010 Elsevier B.V. All rights reserved. Source


Saito S.,Tokyo National College of Technology
Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B | Year: 2010

This study focuses on water hammer pumps that can effectively use the water hammer phenomenon and allow fluid transients without drive sources, such as electric motors. An understanding of water hammer pumps' operating conditions and an evaluation of their basic hydrodynamic characteristics are significant for determining whether they can be widely used as an energy-saving device in the future. However, these conventional studies have not described the pump performance in terms of pump head and flow rate, common measures indicating the performance of pumps, and are not useful in fully evaluating the pump characteristics. As a first stage for the understanding of water hammer pump performance in comparison to the characteristics of typical turbo pumps, this study focuses on understanding the basic hydrodynamic characteristics of water hammer pumps and experimentally examines how the hydrodynamic characteristics are affected by the inner diameter of the drive and lifting pipes, the form and capacity of the air chamber, and the angle of the drive pipe, which are believed to be representative geometric form factors. Source


Kamimura H.,Tokyo University of Science | Ushio H.,Tokyo National College of Technology
Journal of Superconductivity and Novel Magnetism | Year: 2012

In this Festschrift paper celebrating Prof. Jacques Friedel 90 years' birthday, we review the latest developments of the model proposed by Kamimura and Suwa, which bears important characteristics born from the interplay of Jahn-Teller physics and Mott physics. First it is shown that the feature of Fermi surfaces is the Fermi pockets constructed by doped holes under the coexistence of a metallic state and of local antiferromagnetic order. Then the phonon-involved mechanism based on the Kamimura- Suwa model is discussed; it leads to d-wave superconductivity. Further it is shown that T c is higher in the cuprates with CuO 5 pyramid than those with CuO 6 octahedron. Finally a recent theoretical result on the energy distribution curves (EDCs) of angle-resolved photoemission spectroscopy (ARPES) below T c is presented, and a remark is made on the phase diagram for underdoped cuprates. © Springer Science+Business Media, LLC 2012. Source


Kamimura H.,Tokyo University of Science | Sasaoka K.,University of Tokyo | Ushio H.,Tokyo National College of Technology
Journal of the Physical Society of Japan | Year: 2011

Central issues in the electronic structure of underdoped cuprate superconductors are to clarify the shape of the Fermi surfaces and the origin of the pseudogap. On the basis of the model proposed by Kamimura and Suwa, which bears important features originating from the interplay of Jahn-Teller physics and Mott physics, the feature of Fermi surfaces in underdoped cuprates is the presence of Fermi pockets constructed from doped holes under the coexistence of a metallic state and a local antiferromagnetic order. Below Tc, the holes on Fermi pockets form Cooper pairs with d-wave symmetry in the nodal region. In the antinodal region, there are no Fermi surfaces. In this study we calculate the energy distribution curves (EDCs) of angle-resolved photoemission spectroscopy (ARPES) below Tc. It is shown that the feature of ARPES profiles of underdoped cuprates consists of a coherent peak in the nodal region and real transitions of photoexcited electrons from occupied states below the Fermi level to a free-electron state above the vacuum level in the antinodal region, where the latter transitions form a broad hump. From this feature, the origin of the two distinct gaps observed by ARPES is elucidated without introducing the concept of the pseudogap. Finally, a remark is made on the phase diagram of underdoped cuprates. © 2011 The Physical Society of Japan. Source

Discover hidden collaborations