Lattice study on a tetra-quark state TbbT_{bb} in the HAL QCD method

We study a doubly-bottomed tetra-quark state $(bb\bar{u}\bar{d})$ with quantum number $I(J^P)=0(1^+)$, denoted by $T_{bb}$, in lattice QCD with the Non-Relativistic QCD (NRQCD) quark action for $b$ quarks. Employing $(2+1)$-flavor gauge configurations at $a \approx 0.09$ {fm} on $32^3\times 64$ lattices, we have extracted the coupled channel potential between $\bar{B}\bar{B}^*$ and $\bar{B}^* \bar{B}^*$ in the HAL QCD method, which predicts an existence of a bound $T_{bb}$ below the $\bar{B}\bar{B}^*$ threshold. By extrapolating results at $m_\pi\approx 410,\, 570,\, 700$ {MeV} to the physical pion mass $m_\pi\approx140$ {MeV}, we obtain a biding energy with its statistical error as $E_{\rm binding}^{\rm (single)} = 155(17)$ MeV and $E_{\rm binding}^{\rm (coupled)} = 83(10)$ MeV, where ``coupled" means that effects due to virtual $\bar{B}^* \bar{B}^*$ states are included through the coupled channel potential, while only a potential for a single $\bar{B}\bar{B}^*$ channel is used in the analysis for ``single". A comparison shows that the effect from virtual $\bar{B}^* \bar{B}^*$ states is quite sizable to the binding energy of $T_{bb}$. We estimate systematic errors to be $\pm 20$ MeV at most, which are mainly caused by the NRQCD approximation for $b$ quarks.Comment: 27 pages, 8 figure

Computing longest common square subsequences

A square is a non-empty string of form YY. The longest common square subsequence (LCSqS) problem is to compute a longest square occurring as a subsequence in two given strings A and B. We show that the problem can easily be solved in O(n^6) time or O(|M|n^4) time with O(n^4) space, where n is the length of the strings and M is the set of matching points between A and B. Then, we show that the problem can also be solved in O(sigma |M|^3 + n) time and O(|M|^2 + n) space, or in O(|M|^3 log^2 n log log n + n) time with O(|M|^3 + n) space, where sigma is the number of distinct characters occurring in A and B. We also study lower bounds for the LCSqS problem for two or more strings

RESEARCH ON ROBUSTNESS OF BRIDGE SYSTEMS USING SEISMIC ISOLATION BEARINGS AND SEISMIC DAMPERS

不確定性が高い地震外力に対してロバスト性の高い構造システムの重要性が示されており，そのような構造システムが求められている．免震構造と制震構造を組み合わせることにより，ロバスト性の高い橋梁構造を実現するための取り組みがなされている．本研究では，免震支承と制震ダンパーを併用した橋梁システムを対象とし，そのロバスト性に及ぼす免震・制震デバイスの特性の影響について検討を行った．地震応答特性の変動が小さいことをロバスト性が優れていることであると考え，免震支承と制震ダンパーを併用した橋梁システムを2質点2自由度系にモデル化し，地震応答解析結果に基づき橋脚の最大応答変位の変動係数等を評価した．検討の結果，免震支承と制震ダンパーの特性は，橋脚の最大応答変位の変動係数等に顕著な影響を与えることがわかった．The importance of a structural system with high robustness against seismic forces with high uncertainty has been shown, and such a structural system is required. Efforts are being made to realize a highly robust bridge structure by combining seismic isolation bearings and seismic dampers. In this study, we investigated the influence of characteristics of seismic isolation bearings and seismic dampers on the robustness of bridge systems using seismic isolation bearings and seismic dampers. It was found that characteristics of seismic isolation bearings and seismic dampers have a great influence on the coefficient of variation of the maximum response displacement of a pier and maximum plasticity rate

On-line Identification of Electro-Conductivity in Electrolytic Solutions

An on-line method is proposed to identify electro-conductivity in electrolytic solutions. The method uses a model of a cell of electrolytic solutions in a micro reactor modeled by an electronic circuit. The circuit consists of a cell part with a resister and a capacitor connected in series and a measurement part having a resister. Then the resistance and the capacitance of the cell part are identified to calculate the electro-conductivity. The identification scheme is the least-square method with a forgetting factor calculated on-line. To avoid the effect of differentiation of measured signals, a filter is added to the identification method. The effectiveness of the proposed control scheme is shown by numerical simulation.</p