2,697 research outputs found
Signatures of pairing mechanisms and order parameters in ferromagnetic superconductors
Two predictions are made for properties of the ferromagnetic superconductors
discovered recently. The first one is that spin-triplet, p-wave pairing in such
materials will give the magnons a mass inversely proportional to the square of
the magnetization. The second one is based on a specific mechanism for p-wave
pairing, and predicts that the observed broad anomaly in the specific heat of
URhGe will be resolved into a split transition with increasing sample quality.
These predictions will help discriminate between different possible mechanisms
for ferromagnetic superconductivity.Comment: 4 pp., 1 ps fi
Theory of helimagnons in itinerant quantum systems
The nature and effects of the Goldstone mode in the ordered phase of helical
or chiral itinerant magnets such as MnSi are investigated theoretically. It is
shown that the Goldstone mode, or helimagnon, is a propagating mode with a
highly anisotropic dispersion relation, in analogy to the Goldstone mode in
chiral liquid crystals. Starting from a microscopic theory, a comprehensive
effective theory is developed that allows for an explicit description of the
helically ordered phase, including the helimagnons, for both classical and
quantum helimagnets. The directly observable dynamical spin susceptibility,
which reflects the properties of the helimagnon, is calculated.Comment: 20 pp., 1 eps fig; corrects various typos and incorrect prefactors in
Phys Rev B versio
The Supercooling of a Nematic Liquid Crystal
We investigate the supercooling of a nematic liquid crystal using fluctuating
non-linear hydrodynamic equations. The Martin-Siggia-Rose formalism is used to
calculate renormalized transport coefficients to one-loop order. Similar
theories for isotropic liquids have shown substantial increases of the
viscosities as the liquid is supercooled or compressed due to feedback from the
density fluctuations which are freezing. We find similar results here for the
longitudinal and various shear viscosities of the nematic. However, the two
viscosities associated with the nematic director motion do not grow in any
dramatic way; i.e.\ there is no apparent freezing of the director modes within
this hydrodynamic formalism. Instead a glassy state of the nematic may arise
from a ``random anisotropy" coupling of the director to the frozen density.Comment: Late
Trigonometric Parallaxes of Massive Star Forming Regions: IV. G35.20-0.74 and G35.20-1.74
We report trigonometric parallaxes for the high-mass star forming regions
G35.20-0.74 and G35.20-1.74, corresponding to distances of 2.19 (+0.24 -0.20)
kpc and 3.27 (+0.56 -0.42) kpc, respectively. The distances to both sources are
close to their near kinematic distances and place them in the
Carina-Sagittarius spiral arm. Combining the distances and proper motions with
observed radial velocities gives the locations and full space motions of the
star forming regions. Assuming a standard model of the Galaxy, G35.20-0.74 and
G35.20-1.74 have peculiar motions of ~13 km/s and ~16 km/s counter to Galactic
rotation and ~9 km/s toward the North Galactic Pole.Comment: 16 pages, 8 figure
Real Space Renormalization Group for Langevin Dynamics in Absence of Translational Invariance
A novel exact dynamical real space renormalization group for a Langevin
equation derivable from a Euclidean Gaussian action is presented. It is
demonstrated rigorously that an algebraic temporal law holds for the Green
function on arbitrary structures of infinite extent. In the case of fractals it
is shown on specific examples that two different fixed points are found at
variance with periodic structures. Connection with growth dynamics of
interfaces is also discussed.Comment: 22 pages, RevTex 3.0, 5 figures available upon request from
[email protected], to be published in J.Stat.Phy
Humin Formation on SBA-15-pr-SO3H Catalysts during the Alcoholysis of Furfuryl Alcohol to Ethyl Levulinate: Effect of Pore Size on Catalyst Stability, Transport, and Adsorption
Herein, the alcoholysis of furfuryl alcohol in a series of SBA-15-pr-SO3H catalysts with different pore sizes is reported. Elemental analysis and NMR relaxation/diffusion methods show that changes in pore size have a significant effect on catalyst activity and durability. In particular, the decrease in catalyst activity after catalyst reuse is mainly due to carbonaceous deposition, whereas leaching of sulfonic acid groups is not significant. This effect is more pronounced in the largest-pore-size catalyst C3, which rapidly deactivates after one reaction cycle, whereas catalysts with a relatively medium and small average pore size (named, respectively, C2 and C1) deactivate after two reaction cycles and to a lesser extent. CHNS elemental analysis showed that C1 and C3 experience a similar amount of carbonaceous deposition, suggesting that the increased reusability of the small-pore-size catalyst can be attributed to the presence of SO3H groups mostly present on the external surface, as corroborated by results on pore clogging obtained by NMR relaxation measurements. The increased reusability of the C2 catalyst is attributed to a lower amount of humin being formed and, at the same time, reduced pore clogging, which helps to maintain accessible the internal pore space
Inspiratory muscle training reduces blood lactate concentration during volitional hyperpnoea
Although reduced blood lactate concentrations ([lac−]B) have been observed during whole-body exercise following inspiratory muscle training (IMT), it remains unknown whether the inspiratory muscles are the source of at least part of this reduction. To investigate this, we tested the hypothesis that IMT would attenuate the increase in [lac−]B caused by mimicking, at rest, the breathing pattern observed during high-intensity exercise. Twenty-two physically active males were matched for 85% maximal exercise minute ventilation (V˙Emax) and divided equally into an IMT or a control group. Prior to and following a 6 week intervention, participants performed 10 min of volitional hyperpnoea at the breathing pattern commensurate with 85% V˙Emax
Conductivity and quasinormal modes in holographic theories
We show that in field theories with a holographic dual the retarded Green's
function of a conserved current can be represented as a convergent sum over the
quasinormal modes. We find that the zero-frequency conductivity is related to
the sum over quasinormal modes and their high-frequency asymptotics via a sum
rule. We derive the asymptotics of the quasinormal mode frequencies and their
residues using the phase-integral (WKB) approach and provide analytic insight
into the existing numerical observations concerning the asymptotic behavior of
the spectral densities.Comment: 24 pages, 3 figure
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