[en] Using the recently proposed holon-pair boson theory of the t-J Hamiltonian [Phys. Rev. B 64 (2001) 052501] that we developed recently, we report the temperature dependence of the superfluid weight. It is shown that at low hole doping concentration x and at low temperatures T there exists a propensity of a linear decrease of the superfluid weight n_s/m^* with temperature, and a tendency of doping independence in the slope of ((n_s)/(m^*))(x,T) vs. T in accordance of the relation ((n_s)/(m^*))(x,T)=((n_s)/(m^*))(x,0)-αT with α, a constant

[en] Emphasis on the analysis of the t-J Hamiltonian is made by showing coupling between the charge and the spin degrees of freedom. Based on an improved SU(2) slave-boson approach which shows the coupling, we derive a satisfactory phase diagram of high T_c cuprates which displays both the superconducting and the pseudogap phases in the plane of temperature vs. hole doping rate

[en] An equation considering the influence of scattered radiation in radiography is suggested. In experiment with Ir-192 to a carbon steel step wedge, the trend of estimated build-up factors shows increasing with thickness and changes to decreasing for larger thicknesses. Comparing the measured contrast to the calculated one which is obtained without considering the effect of scattered radiations, it is shown that the measured contrast is lower than the calculated one. On the other hand, in the experiment with poly-energetic X-ray, the trend of estimated build-up factors shows decreasing with thickness and then changes to increasing for larger thickness. The measured contrast is also higher than the calculated one for smaller thickness and then changes to lower compared to the calculated with increment of thickness. It is found that the peculiar behaviors of build-up factors and contrast with X-ray has been caused by considering the linear absorption coefficient as a constant.

[en] Using the anti-de Sitter/conformal field theory correspondence, we calculate a fermionic spectral function in a 2+1 dimensional nonrelativistic quantum field theory which is dual to a gravitational theory in the AdS₄ background with a charged black hole. The spectral function shows no quasiparticle peak but the Fermi surface is still well-defined. Interestingly, all momentum points inside the Fermi surface are critical and the gapless modes are defined in a critical Fermi ball in the momentum space.

[en] Relatively local Hamiltonians are a class of background independent non-local Hamiltonians from which local theories emerge within a set of short-range entangled states. The dimension, topology and geometry of the emergent local theory is determined by the initial state to which the Hamiltonian is applied. In this paper, we study dynamical properties of a simple relatively local Hamiltonian for N scalar fields in the large N limit. It is shown that the coordinate speeds at which entanglement spreads and local disturbance propagates in space strongly depend on state in the relatively local Hamiltonian.

[en] We study the low-energy effective theory for a non-Fermi-liquid state in 2+1 dimensions, where a transverse U(1) gauge field is coupled with a patch of Fermi surface with N flavors of fermion in the large N limit. In the low-energy limit, quantum corrections are classified according to the genus of the two-dimensional surface on which Feynman diagrams can be drawn without a crossing in a double line representation and all planar diagrams are important in the leading order. The emerging theory has the similar structure to the four-dimensional SU(N) gauge theory in the large N limit. Because of strong quantum fluctuations caused by the abundant low-energy excitations near the Fermi surface, low-energy fermions remain strongly coupled even in the large N limit. As a result, there are infinitely many quantum corrections that contribute to the leading frequency dependence of the Green's function of fermion on the Fermi surface. On the contrary, the boson self-energy is not modified beyond the one-loop level and the theory is stable in the large N limit. The nonperturbative nature of the theory also shows up in correlation functions of gauge-invariant operators.

[en] Supersymmetry is a symmetry between a boson and a fermion. Although there is no apparent supersymmetry in nature, its mathematical consistency and appealing properties have led many people to believe that supersymmetry may exist in nature in the form of a spontaneously broken symmetry. In this paper, we explore an alternative possibility by which supersymmetry is realized in nature, that is, supersymmetry dynamically emerges in the low-energy limit of a nonsupersymmetric condensed matter system. We propose a (2+1)-dimensional lattice model which exhibits an emergent space-time supersymmetry at a quantum critical point. It is shown that there is only one relevant perturbation at the supersymmetric critical point in the ε expansion and the critical theory is the two copies of the Wess-Zumino theory with four supercharges. Exact critical exponents are predicted

[en] Based on the local U(1) gauge slave-boson approach to the t-J Hamiltonian, we examine a possibility of hole pairing at finite temperature and hole doping rate. It is found that as a result of symmetry breaking d-wave holon pairing with finite gap can occur. In addition a holon-spinon supersymmetry condition at T = 0K is obtained based on spinon and holon excitations at a critical doping region between antiferromagnetic and superconducting phases

[en] Based on the assumption that film density increases exponentially with exposure in the industrial radiographic film. An equation representing the characteristic curves of industrial radiographic films and a new density-thickness relation are suggested. The accuracy and reliability of the suggested relation has been tested using radiographs of a carbon steel step wedge with known thickness variation by polychromatic X-ray and γ-ray (Ir¹⁹²). The experimental results were well agreed to the proposed relation in the range of film densities from 1.0 to 3.5 and it was more accurate than the conventional relation. It is also found that γ-ray is more effective in this purpose than polychromatic X-ray, which results in variation of effective linear absorption coefficient due to beam hardening effect as thickness increases. Therefore using the equation and experimentally determined parameters the quantitative evaluation of thickness variation is possible and it can be used to evaluate the depth of local corrosion of pressure vessels in plants

[en] We propose that general D-dimensional quantum field theories are dual to (D+1)-dimensional local quantum theories which in general include objects with spin two or higher. Using a general prescription, we construct a (D+1)-dimensional theory which is holographically dual to the D-dimensional O(N) vector model. From the holographic theory, the phase transition and critical properties of the model in dimensions D>2 are described.