Unambiguous probe of parity-mixing of Cooper pairs in noncentrosymmetric superconductors

We propose an experimental scheme to detect unambiguously parity-mxing of Cooper pairs in noncentrosymmetric superconductors, which utilizes crossed Andreev reflection processes between two oppositely spin-polarized normal metal leads and a noncentrosymmetric superconductor. It is demonstrated that a non-local conductance exhibits a clear signature of parity breaking of Cooper pairs, and thus, can be a direct probe for the parity-mixing.Comment: 4 pages, 2figure

Topological Hall Effect in Inhomogeneous Superconductors

We propose a possible mechanism of topological Hall effect in inhomogeneous superconducting states. In our scenario, the Berry phase effect associated with spatially modulated superconducting order parameter gives rise to a fictitious Lorentz force acting on quasiparticles. In the case of the Fulde-Ferrell-Larkin-Ovchinnikov state, the topological Hall effect is detected by applying an electromagnetic wave with a tuned wave number on a surface of the system.Comment: 4 page

Chain breaks and the susceptibility of Sr_2Cu_{1-x}Pd_xO_{3+\delta} and other doped quasi one-dimensional antiferromagnets

We study the magnetic susceptibility of one-dimensional S=1/2 antiferromagnets containing non-magnetic impurities which cut the chain into finite segments. For the susceptibility of long anisotropic Heisenberg chain-segments with open boundaries we derive a parameter-free result at low temperatures using field theory methods and the Bethe Ansatz. The analytical result is verified by comparing with Quantum-Monte-Carlo calculations. We then show that the partitioning of the chain into finite segments can explain the Curie-like contribution observed in recent experiments on Sr_2Cu_{1-x}Pd_xO_{3+\delta}. Possible additional paramagnetic impurities seem to play only a minor role.Comment: 4 pages, 3 figures, final versio

Quantum Disordered Ground States in Frustrated Antiferromagnets with Multiple Ring Exchange Interactions

We present a certain class of two-dimensional frustrated quantum Heisenberg spin systems with multiple ring exchange interactions which are rigorously demonstrated to have quantum disordered ground states without magnetic long-range order. The systems considered in this paper are s=1/2 antiferromagnets on a honeycomb and square lattices, and an s=1 antiferromagnet on a triangular lattice. We find that for a particular set of parameter values, the ground state is a short-range resonating valence bond state or a valence bond crystal state. It is shown that these systems are closely related to the quantum dimer model introduced by Rokhsar and Kivelson as an effective low-energy theory for valence bond states.Comment: 6 pages, 4 figure

Magnetohydrodynamic Simulations of A Rotating Massive Star Collapsing to A Black Hole

We perform two-dimensional, axisymmetric, magnetohydrodynamic simulations of the collapse of a rotating star of 40 Msun and in the light of the collapsar model of gamma-ray burst. Considering two distributions of angular momentum, up to \sim 10^{17} cm^2/s, and the uniform vertical magnetic field, we investigate the formation of an accretion disk around a black hole and the jet production near the hole. After material reaches to the black hole with the high angular momentum, the disk is formed inside a surface of weak shock. The disk becomes in a quasi-steady state for stars whose magnetic field is less than 10^{10} G before the collapse. We find that the jet can be driven by the magnetic fields even if the central core does not rotate as rapidly as previously assumed and outer layers of the star has sufficiently high angular momentum. The magnetic fields are chiefly amplified inside the disk due to the compression and the wrapping of the field. The fields inside the disk propagate to the polar region along the inner boundary near the black hole through the Alfv{\'e}n wave, and eventually drive the jet. The quasi-steady disk is not an advection-dominated disk but a neutrino cooling-dominated one. Mass accretion rates in the disks are greater than 0.01 Msun/sec with large fluctuations. The disk is transparent for neutrinos. The dense part of the disk, which locates near the hole, emits neutrino efficiently at a constant rate of < 8 \times 10^{51} erg/s. The neutrino luminosity is much smaller than those from supernovae after the neutrino burst.Comment: 42 pages, accepted for publication in the Astrophysical Journal. A paper with higher-resolution figures available at http://www.ec.knct.ac.jp/~fujimoto/collapsar/mhd-color.pd

The origin of HE0107-5240 and the production of O and Na in extremely metal-poor stars

We elaborate the binary scenario for the origin of HE0107-5240, the most metal-poor star yet observed ([Fe/H] = -5.3), using current knowledge of the evolution of extremely metal-poor stars. From the observed C/N value, we estimate the binary separation and period. Nucleosynthesis in a helium convective zone into which hydrogen has been injected allows us to discuss the origin of surface O and Na as well as the abundance distribution of s-process elements. We can explain the observed abundances of 12C, 13C, N, O, and Na and predict future observations to validate the Pop III nature of HE0107-5240.Comment: 4 pages, 3 figures, proceedings of the conference, "Nuclei in the Cosmos VIII", Nuclear Physics A in pres

All-order evaluation of weak measurements: --- The cases of an operator A{\bf A} which satisfies the property A2=1{\bf A}^{2}=1 ---

Some exact formulae of the expectation values and probability densities in a weak measurement for an operator ${\bf A}$ which satisfies the property ${\bf A}^{2}=1$ are derived. These formulae include all-order effects of the unitary evolution due to the von-Neumann interaction. These are valid not only in the weak measurement regime but also in the strong measurement regime and tell us the connection between these two regime. Using these formulae, arguments of the optimization of the signal amplification and the signal to noise ratio are developed in two typical experimental setups.Comment: 17 pages, 10 figures (v1); Fig.3 and some typos are corrected (v2); Comments and references are added and some typos are corrected (v3

Classical and nonclassical randomness in quantum measurements

The space of positive operator-valued measures on the Borel sets of a compact (or even locally compact) Hausdorff space with values in the algebra of linear operators acting on a d-dimensional Hilbert space is studied from the perspectives of classical and non-classical convexity through a transform $\Gamma$ that associates any positive operator-valued measure with a certain completely positive linear map of the homogeneous C*-algebra $C(X)\otimes B(H)$ into $B(H)$. This association is achieved by using an operator-valued integral in which non-classical random variables (that is, operator-valued functions) are integrated with respect to positive operator-valued measures and which has the feature that the integral of a random quantum effect is itself a quantum effect. A left inverse $\Omega$ for $\Gamma$ yields an integral representation, along the lines of the classical Riesz Representation Theorem for certain linear functionals on $C(X)$, of certain (but not all) unital completely positive linear maps $\phi:C(X)\otimes B(H) \rightarrow B(H)$. The extremal and C*-extremal points of the space of POVMS are determined.Comment: to appear in Journal of Mathematical Physic

XMM-Newton observation of the ULIRG NGC 6240: The physical nature of the complex Fe K line emission

We report on an XMM-Newton observation of the ultraluminous infrared galaxy NGC 6240. The 0.3-10 keV spectrum can be successfully modelled with: (i) three collisionally ionized plasma components with temperatures of about 0.7, 1.4, and 5.5 keV; (ii) a highly absorbed direct power-law component; and (iii) a neutral Fe K_alpha and K_beta line. We detect a significant neutral column density gradient which is correlated with the temperature of the three plasma components. Combining the XMM-Newton spectral model with the high spatial resolution Chandra image we find that the temperatures and the column densities increase towards the center. With high significance, the Fe K line complex is resolved into three distinct narrow lines: (i) the neutral Fe K_alpha line at 6.4 keV; (ii) an ionized line at about 6.7 keV; and (iii) a higher ionized line at 7.0 keV (a blend of the Fe XXVI and the Fe K_beta line). While the neutral Fe K line is most probably due to reflection from optically thick material, the Fe XXV and Fe XXVI emission arises from the highest temperature ionized plasma component. We have compared the plasma parameters of the ultraluminous infrared galaxy NGC 6240 with those found in the local starburst galaxy NGC 253. We find a striking similarity in the plasma temperatures and column density gradients, suggesting a similar underlying physical process at work in both galaxies.Comment: 8 pages including 9 figures. Accepted for publication in A&