981 research outputs found
Lattice study on two-color QCD with six flavors of dynamical quarks
We study the dynamics of SU(2) gauge theory with NF=6 Dirac fermions by means
of lattice simulation to investigate if they are appropriate to realization of
electroweak symmetry breaking. The discrete analogue of beta function for the
running coupling constant defined under the Schroedinger functional boundary
condition are computed on the lattices up to linear size of L/a=24 and preclude
the existence of infrared fixed point below 7.6. Gluonic observables such as
heavy quark potential, string tension, Polyakov loop suggest that the target
system is in the confining phase even in the massless quark limit.Comment: 7 pages, 9 figures, Proceedings of The 30th International Symposium
on Lattice Field Theory, June 24-29, 2012, Cairns, Australi
Evolution of Giant Planets in Eccentric Disks
We investigate the interaction between a giant planet and a viscous
circumstellar disk by means of high-resolution, two-dimensional hydrodynamical
simulations. We consider planet masses that range from 1 to 3 Jupiter masses
(Mjup) and initial orbital eccentricities that range from 0 to 0.4. We find
that a planet can cause eccentricity growth in a disk region adjacent to the
planet's orbit, even if the planet's orbit is circular. Disk-planet
interactions lead to growth in a planet's orbital eccentricity. The orbital
eccentricities of a 2 Mjup and a 3 Mjup planet increase from 0 to 0.11 within
about 3000 orbits. Over a similar time period, the orbital eccentricity of a 1
Mjup planet grows from 0 to 0.02. For a case of a 1 Mjup planet with an initial
eccentricity of 0.01, the orbital eccentricity grows to 0.09 over 4000 orbits.
Radial migration is directed inwards, but slows considerably as a planet's
orbit becomes eccentric. If a planet's orbital eccentricity becomes
sufficiently large, e > ~0.2, migration can reverse and so be directed
outwards. The accretion rate towards a planet depends on both the disk and the
planet orbital eccentricity and is pulsed over the orbital period. Planet mass
growth rates increase with planet orbital eccentricity. For e~0.2 the mass
growth rate of a planet increases by approximately 30% above the value for e=0.
For e > ~0.1, most of the accretion within the planet's Roche lobe occurs when
the planet is near the apocenter. Similar accretion modulation occurs for flow
at the inner disk boundary which represents accretion toward the star.Comment: 20 pages 16 figures, 3 tables. To appear in The Astrophysical Journal
vol.652 (December 1, 2006 issue
Anisotropic magnetic fluctuations in the ferromagnetic superconductor UCoGe studied by angle-resolved ^{59}Co NMR
We have carried out direction-dependent ^{59}Co NMR experiments on a single
crystal sample of the ferromagnetic superconductor UCoGe in order to study the
magnetic properties in the normal state. The Knight shift and nuclear
spin-lattice relaxation rate measurements provide microscopic evidence that
both static and dynamic susceptibilities are ferromagnetic with strong Ising
anisotropy. We discuss that superconductivity induced by these magnetic
fluctuations prefers spin-triplet pairing state.Comment: 4 pages, 4 figure
Superconductivity induced by longitudinal ferromagnetic fluctuations in UCoGe
From detailed angle-resolved NMR and Meissner measurements on a ferromagnetic
(FM) superconductor UCoGe (T_Curie ~ 2.5 K and T_SC ~ 0.6 K), we show that
superconductivity in UCoGe is tightly coupled with longitudinal FM spin
fluctuations along the c axis. We found that magnetic fields along the c axis
(H || c) strongly suppress the FM fluctuations and that the superconductivity
is observed in the limited magnetic field region where the longitudinal FM spin
fluctuations are active. These results combined with model calculations
strongly suggest that the longitudinal FM spin fluctuations tuned by H || c
induce the unique spin-triplet superconductivity in UCoGe. This is the first
clear example that FM fluctuations are intimately related with
superconductivity.Comment: 4 pages, 5 figures, to appear in PR
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