6,356 research outputs found
Axial symmetry at high temperature in 2-flavor lattice QCD
We investigate the axial symmetry breaking above the critical
temperature in two-flavor lattice QCD. The ensembles are generated with
dynamical M\"obius domain-wall or reweighted overlap fermions. The
susceptibility is extracted from the low-modes spectrum of the overlap Dirac
eigenvalues. We show the quark mass and temperature dependences of
susceptibility. Our results at imply that the
symmetry is restored in the chiral limit. Its coincidence with vanishing
topological susceptibility is observed.Comment: 8 pages, 4 figures, Proceedings of the 35th International Symposium
on Lattice Field Theory, June 18-24, 2017, Granada, Spai
Axial U(1) symmetry and Dirac spectra in high-temperature phase of lattice QCD
The axial symmetry in the high-temperature phase is investigated with
lattice QCD simulations. The gauge ensembles are generated with
M\"obius domain-wall fermions, and the overlap/domain-wall reweighting is
applied. We find that the susceptibility evaluated from the spectrum
of overlap-Dirac eigenvalues is strongly suppressed in the chiral limit. We
also study its volume dependence.Comment: 7 pages, 2 figures, talk presented at the 36th International
Symposium on Lattice Field Theory (Lattice 2018), 22-28 July, 2018, Michigan,
US
Spin Fluid Dynamics Observed by Magnetic Fountain Effect and Mechano-Spin Effect in the Ferromagnetic Superfluid He A Phase
Systematic observations of the magnetically generated fountain pressure in
the superfluid He A have been carried out in a newly built apparatus
designed to reduce the effect of thermal gradients. In the same apparatus,
mechanical pumping and filtering of polarized nuclear spins were realized by
the pneumatic pumping action of an electrostatically actuated membrane. In both
experiments, the measured induced pressure was observed to decay at all
temperatures where the A phase appeared in magnetic fields up to 13 T and
liquid pressures between 1 and 29 bar. The inferred spin relaxation rate tended
to increase as the low temperature phase boundary with the A phase
(T) was approached. The increase in spin relaxation rate near T
can be explained by the presence of a minority spin condensate in the A
phase as predicted by Monien and Tewordt and by the application of the
Leggett-Takagi theory of spin relaxation in superfluid He.Comment: 12 pages, 15 figures, to appear in Physical Review
Partition functions of Supersymmetric Gauge Theories in Noncommutative R^{2D} and their Unified Perspective
We investigate cohomological gauge theories in noncommutative R^{2D}. We show
that vacuum expectation values of the theories do not depend on noncommutative
parameters, and the large noncommutative parameter limit is equivalent to the
dimensional reduction. As a result of these facts, we show that a partition
function of a cohomological theory defined in noncommutative R^{2D} and a
partition function of a cohomological field theory in R^{2D+2} are equivalent
if they are connected through dimensional reduction. Therefore, we find several
partition functions of supersymmetric gauge theories in various dimensions are
equivalent. Using this technique, we determine the partition function of the
N=4 U(1) gauge theory in noncommutative R^4, where its action does not include
a topological term. The result is common among (8-dim, N=2), (6-dim, N=2),
(2-dim, N=8) and the IKKT matrix model given by their dimensional reduction to
0-dim.Comment: 45 pages, no figures, Appendices B and C are added, changes in the
text, references are adde
Superfluidity of liquid 4He confined to one-dimensional straight nanochannel structures
Superfluidity of liquid 4He confined in one-dimensional (1D) nanometer-size channels has been studied by means of a torsional oscillator. When the channel is larger than 2.8 nm in diameter, liquid 4He becomes superfluid at low temperatures and a dissipation due to quantized vortex is observed. The superfluid onset temperature is 1.8 K at 0.14 MPa for the 4.7 nm channel and 0.89 K at 0.01 MPa for the 2.8 nm channel. For the latter, it is suppressed strongly under the application of pressure, and continuously approaches zero at around 2.1 MPa at absolute zero, which suggests a quantum phase transition between the superfluid and nonsuperfluid states in the 1D channel
Effect of wing mass in free flight of a two-dimensional symmetric flapping wing-body model
The effect of wing mass in the free flight of a flapping wing is investigated by numerical simulations based on an immersed boundary-lattice Boltzmann method. We consider a model consisting of two-dimensional symmetric flapping wings with uniform mass density connected by a body represented as a point mass. We simulate free flights of the two-dimensional symmetric flapping wing with various mass ratios of the wings to the body. In free flights without gravity, it is found that the time-averaged lift force becomes smaller as the mass ratio increases, since with a large mass ratio the body experiences a large vertical oscillation in one period and consequently the wing-tip speed relatively decreases. We define the effective Reynolds number Reeff taking the body motion into consideration and investigate the critical value of Reeff over which the symmetry breaking of flows occurs. As a result, it is found that the critical value is Re-eff similar or equal to 70 independently of the mass ratio. In free flights with gravity, the time-averaged lift force becomes smaller as the mass ratio increases in the same way as free flights without gravity. In addition, the unstable rotational motion around the body is suppressed as the mass ratio increases, since with a large mass ratio the vortices shedding from the wing tip are small and easily decay.ArticleFLUID DYNAMICS RESEARCH.49(5):055504(2017)journal articl
Higher Order Hybrid Monte Carlo at Finite Temperature
The standard hybrid Monte Carlo algorithm uses the second order integrator at
the molecular dynamics step. This choice of the integrator is not always the
best. Using the Wilson fermion action, we study the performance of the hybrid
Monte Carlo algorithm for lattice QCD with higher order integrators in both
zero and finite temperature phases and find that in the finite temperature
phase the performance of the algorithm can be raised by use of the 4th order
integrator.Comment: 13 pages, 6 figure
Three-orbital study on the orbital distillation effect in the high Tc cuprates
Our recent study has revealed that the mixture of the dz2 orbital component
into the Fermi surface suppresses Tc in the cuprates such as La2CuO4. We have
also shown that applying hydrostatic pressure enhances Tc due to smaller mixing
of the Cu4s component. We call these the "orbital distillation" effect. In our
previous study, the 4s orbital was taken into account through the hoppings in
the dx2-y2 sector, but here we consider a model in which of the dx2-y2, dz2 and
4s orbitals are all considered explicitly. The present study reinforces our
conclusion that smaller 4s hybridization further enhances Tc.Comment: 4 pages, 2 figures, submitted as a proceeding of ISS2012(Tokyo
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