Orbital symmetry of a triplet pairing in a heavy Fermion superconductor UPt_3

The orbital symmetry of the superconducting order parameter in UPt_3 is identified by evaluating the directionally dependent thermalconductivity and ultrasound attenuation in the clean limit and compared with the existing data for both basal plane and the c-axis of a hexagonal crystal. The resulting two component orbital part expressed by (\lambda_x(k), \lambda_y(k)) is combined with the previously determined triplet spin part, leading to clean limit and compared with the existing data for both basal plane and the c-axis of a hexagonal crystal. The resulting two component orbital part expressed by (\lambda_x(k), \lambda_y(k)) is combined with the previously determined triplet spin part, leading to the order parameter of either the non-unitary bipolar state of the form: d(k) = b \lambda_x(k) + i j \lambda_y(k) or the unitary planar state of the form: d(k) = b \lambda_x(k) + j \lambda_y(k) where b \perp j = c, or a with the hexagonal unit vectors a, b and c. The d vector is rotatable in the plane spanned by a and c perpendicular to b under weak applied c-axis field because of the weak spin orbit coupling. Experiments are proposed to distinguish between the equally possible these states.Comment: 8 pages, 8 eps figure

Protostellar Jet and Outflow in the Collapsing Cloud Core

We investigate the driving mechanism of outflows and jets in star formation process using resistive MHD nested grid simulations. We found two distinct flows in the collapsing cloud core: Low-velocity outflows (sim 5 km/s) with a wide opening angle, driven from the first adiabatic core, and high-velocity jets (sim 50 km/s) with good collimation, driven from the protostar. High-velocity jets are enclosed by low-velocity outflow. The difference in the degree of collimation between the two flows is caused by the strength of the magnetic field and configuration of the magnetic field lines. The magnetic field around an adiabatic core is strong and has an hourglass configuration. Therefore, the low-velocity outflow from the adiabatic core are driven mainly by the magnetocentrifugal mechanism and guided by the hourglass-like field lines. In contrast, the magnetic field around the protostar is weak and has a straight configuration owing to Ohmic dissipation in the high-density gas region. Therefore, high-velocity jet from the protostar are driven mainly by the magnetic pressure gradient force and guided by straight field lines. Differing depth of the gravitational potential between the adiabatic core and the protostar cause the difference of the flow speed. Low-velocity outflows correspond to the observed molecular outflows, while high-velocity jets correspond to the observed optical jets. We suggest that the protostellar outflow and the jet are driven by different cores (the first adiabatic core and protostar), rather than that the outflow being entrained by the jet.Comment: To appear in the proceedings of the "Protostellar Jets in Context" conference held on the island of Rhodes, Greece (7-12 July 2008

Impact of Protostellar Outflow on Star Formation: Effects of Initial Cloud Mass

Star formation efficiency controlled by the protostellar outflow in a single cloud core is investigated by three-dimensional resistive MHD simulations. Starting from the prestellar cloud core, the star formation process is calculated until the end of the main accretion phase. In the calculations, the mass of the prestellar cloud is parameterized. During the star formation, the protostellar outflow is driven by the circumstellar disk. The outflow extends also in the transverse direction until its width becomes comparable to the initial cloud scale, and thus, the outflow has a wide opening angle of >40 degrees. As a result, the protostellar outflow sweeps up a large fraction of the infalling material and ejects it into the interstellar space. The outflow can eject at most over half of the host cloud mass, significantly decreasing star formation efficiency. The outflow power is stronger in clouds with a greater initial mass. Thus, the protostellar outflow effectively suppresses star formation efficiency in a massive cloud. The outflow weakens significantly and disappears in several free-fall timescales of the initial cloud after the cloud begins to collapse. The natal prestellar core influences the lifetime and size of the outflow. At the end of the main accretion phase, a massive circumstellar disk comparable in mass to the protostar remains. Calculations show that typically, ~30% of the initial cloud mass is converted into the protostar and ~20% remains in the circumstellar disk, while ~40% is ejected into the interstellar space by the protostellar outflow. Therefore, a single cloud core typically has a star formation efficiency of 30-50%.Comment: 43 pages, 14 figures, Submitted to MNRAS. For high resolution figures see http://jupiter.geo.kyushu-u.ac.jp/machida/arxiv/sfe.pd

Recurrent Planet Formation and Intermittent Protostellar Outflows Induced by Episodic Mass Accretion

The formation and evolution of a circumstellar disk in magnetized cloud cores is investigated from prestellar core stage until sim 10^4 yr after protostar formation. In the circumstellar disk, fragmentation first occurs due to gravitational instability in a magnetically inactive region, and substellar-mass objects appear. The substellar-mass objects lose their orbital angular momenta by gravitational interaction with the massive circumstellar disk and finally fall onto the protostar. After this fall, the circumstellar disk increases its mass by mass accretion and again induces fragmentation. The formation and falling of substellar-mass objects are repeated in the circumstellar disk until the end of the main accretion phase. In this process, the mass of fragments remain small, because the circumstellar disk loses its mass by fragmentation and subsequent falling of fragments before it becomes very massive. In addition, when fragments orbit near the protostar, they disturb the inner disk region and promote mass accretion onto the protostar. The orbital motion of substellar-mass objects clearly synchronizes with the time variation of the accretion luminosity of the protostar. Moreover, as the objects fall, the protostar shows a strong brightening for a short duration. The intermittent protostellar outflows are also driven by the circumstellar disk whose magnetic field lines are highly tangled owing to the orbital motion of fragments. The time-variable protostellar luminosity and intermittent outflows may be a clue for detecting planetary-mass objects in the circumstellar disk.Comment: 48 pages, 16 figures, accepted for publication in Ap

Fixed field alternating gradient

The concept of a fixed field alternating gradient (FFAG) accelerator was invented in the 1950s. Although many studies were carried out up to the late 1960s, there has been relatively little progress until recently, when it received widespread attention as a type of accelerator suitable for very fast acceleration and for generating high-power beams. In this paper, we describe the principles and design procedure of a FFAG accelerator.Comment: presented at the CERN Accelerator School CAS 2011: High Power Hadron Machines, Bilbao, 24 May - 2 June 201