A universal nonlinear relation among boundary states in closed string field theory

We show that the boundary states satisfy a nonlinear relation (the idempotency equation) with respect to the star product of closed string field theory. This relation is universal in the sense that various D-branes, including the infinitesimally deformed ones, satisfy the same equation, including the coefficient. This paper generalizes our analysis (hep-th/0306189) in the following senses. (1) We present a background-independent formulation based on conformal field theory. It illuminates the geometric nature of the relation and allows us to more systematically analyze the variations around the D-brane background. (2) We show that the Witten-type star product satisfies a similar relation but with a more divergent coefficient. (3) We determine the coefficient of the relation analytically. The result shows that the alpha parameter can be formally factored out, and the relation becomes universal. We present a conjecture on vacuum theory based on this computation.Comment: 35 pages, 7 figures, references added, v3:PTPTeX, typos correcte

Cardy states as idempotents of fusion ring in string field theory

With some assumptions, the algebra between Ishibashi states in string field theory can be reduced to a commutative ring. From this viewpoint, Cardy states can be identified with its idempotents. The algebra can be identified with a fusion ring for the rational conformal field theory and a group ring for the orbifold. This observation supports our previous observation that boundary states satisfy a universal idempotency relation under closed string star product.Comment: 8 page

Magnetic structure and spin dynamics of quasi-one-dimensional spin-chain antiferromagnet BaCo2V2O8

We report a neutron diffraction and muon spin relaxation muSR study of static and dynamical magnetic properties of BaCo2V2O8, a quasi-one-dimensional spin-chain system. A proposed model for the antiferromagnetic structure includes: a propagation vector k_AF = (0, 0, 1), independent of external magnetic fields for fields below a critical value H_c(T). The ordered moments, of 2.18 \mu_B per Co ion, are aligned along the crystallographic c-axis. Within the screw chains, along the c axis, the moments are arranged antiferromagnetically. In the basal planes the spins are arranged ferromagnetically (forming zig-zags paths) along one of the axis and antiferromagnetically along the other. The temperature dependence of the sub-lattice magnetization is consistent with the expectations of the 3D Ising model. A similar behavior is observed for the internal static fields at different muon stopping sites. Muon time spectra measured at weak longitudinal fields and temperatures much higher than T_N can be well described using a single muon site with an exponential muon spin relaxation that gradually changes into an stretched exponential on approaching T_N. The temperature-induced changes of the relaxation suggest that the Co fluctuations dramatically slow down and the system becomes less homogeneous as it approaches the antiferromagnetic state.Comment: 7 pages, 9 figure

キソク コウシ マンガン サンカブツ ノ ソウブンリ オヨビ スピン デンカ キドウ セイレツ ノ カクジキ キョウメイ オヨビ μSR ニヨル ケンキュウ

Nuclear magnetic resonance and μSR measurements have been made to study the phase separation, spin, charge and orbital ordering in A-site ordered manganese oxides. In the antiferromagnetic YBaMn2O6, the magnetic moments of Mn4+ and Mn3+ ions are estimated to be 3.0 μB and 3.6 μB from the observed NMR spectra at 295 MHz and 320 MHz, respectively, which agree with the expected spins S=3/2 and S=2 of Mn4+ and Mn3+ ions, respectively. In the μSR experimental results in YBaMn2O6, the intensity of positrons shows the typical time decay of a single exponential function in the paramagnetic phase and the oscillation in the antiferromagnetic phase, which indicates that the antiferromagnetic phase in YBaMn2O6 is similar to the ordinary antiferromagnetic phase. 55Mn NMR spectra in LaBaMn2O6 at low temperature consists of the signals from both ferromagnetic and antiferromagnetic phases, which gives the evidence for the coexistence of the ferromagnetic and antiferromagnetic phases in the ground state in LaBaMn2O6 from the microscopic point of view. In the μSR experimental results in LaBaMn2O6, the intensity of positrons shows the typical time decay of a single exponential function in the paramagnetic phase but still shows no oscillation in the ferromagnetic phase, which indicates that the ferromagnetic phase in LaBaMn2O6 is very different from the ordinary ferromagnetic phase. On the contrary, in the coexisting antiferromagnetic phase in the ground state the intensity of positrons shows the typical time decay of oscillation due to the internal field, which indicates that the coexisting antiferromagnetic phase in LaBaMn2O6 is similar to the ordinary antiferromagnetic phase. These results may be concerned with the fact that the antiferromagnetic phase is created in the ferromagnetic phase

Cardy states, factorization and idempotency in closed string field theory

We show that boundary states in the generic on-shell background satisfy a universal nonlinear equation of closed string field theory. It generalizes our previous claim for the flat background. The origin of the equation is factorization relation of boundary conformal field theory which is always true as an axiom. The equation necessarily incorporates the information of open string sector through a regularization, which implies the equivalence with Cardy condition. We also give a more direct proof by oscillator representations for some nontrivial backgrounds (torus and orbifolds). Finally we discuss some properties of the closed string star product for non-vanishing $B$ field and find that a commutative and non-associative product (Strachan product) appears naturally in Seiberg-Witten limit.Comment: 44 pages, 6 figures, references added, typos correcte

Impairment of cerebellar long‑term depression and GABAergic transmission in prion protein deficient mice ectopically expressing PrPLP/Dpl

Prion protein (PrPC) knockout mice, named as the “Ngsk” strain (Ngsk Prnp0/0 mice), show late-onset cerebellar Purkinje cell (PC) degeneration because of ectopic overexpression of PrPC-like protein (PrPLP/Dpl). Our previous study indicated that the mutant mice also exhibited alterations in cerebellum-dependent delay eyeblink conditioning, even at a young age (16 weeks of age) when neurological changes had not occurred. Thus, this electrophysiological study was designed to examine the synaptic function of the cerebellar cortex in juvenile Ngsk Prnp0/0 mice. We showed that Ngsk Prnp0/0 mice exhibited normal paired-pulse facilitation but impaired long-term depression of excitatory synaptic transmission at synapses between parallel fibres and PCs. GABAA-mediated inhibitory postsynaptic currents recorded from PCs were also weakened in Ngsk Prnp0/0 mice. Furthermore, we confirmed that Ngsk Prnp0/0 mice (7–8-week-old) exhibited abnormalities in delay eyeblink conditioning. Our findings suggest that these alterations in both excitatory and inhibitory synaptic transmission to PCs caused deficits in delay eyeblink conditioning of Ngsk Prnp0/0 mice. Therefore, the Ngsk Prnp0/0 mouse model can contribute to study underlying mechanisms for impairments of synaptic transmission and neural plasticity, and cognitive deficits in the central nervous system