1,123 research outputs found
Criticality of the universality via global solutions to nonperturbative fixed-point equations
Fixed-point equations in the functional renormalization group approach are
integrated from large to vanishing field, where an asymptotic potential in the
limit of large field is implemented as initial conditions. This approach allows
us to obtain a global fixed-point potential with high numerical accuracy, that
incorporates the correct asymptotic behavior in the limit of large field. Our
calculated global potential is in good agreement with the Taylor expansion in
the region of small field, and it also coincides with the Laurent expansion in
the regime of large field. Laurent expansion of the potential in the limit of
large field for general case, that the spatial dimension is a continuous
variable in the range , is obtained. Eigenfunctions and
eigenvalues of perturbations near the Wilson-Fisher fixed point are computed
with the method of eigenperturbations. Critical exponents for different values
of and of the universality class are calculated.Comment: 10 pages, 4 figures, 1 table; v2: minor changes, discussions and
references adde
Universality of pseudo-Goldstone damping near critical points
Recently, in studies of holographic models and hydrodynamics with spontaneous
breaking of approximate symmetries, it has been proposed that the damping of
pseudo-Goldstone modes at finite temperatures is universally constrained in the
way that in the broken
phase, where and are the relaxation rate at
zero wavenumber and the mass of pseudo-Goldstones, is the
Goldstone diffusivity in the limit of purely spontaneous breaking. In this
paper, we investigate the pseudo-Goldstone damping in a purely relaxational
O() model by performing the functional renormalization group calculations at
the full quantum and stochastic level within the Schwinger-Keldysh formalism.
We find that, away from the critical temperature, the proposed relation is
always valid. When the temperature is very close to the critical value such
that the mass of the Higgs mode is comparable to the mass of the
pseudo-Goldstone modes, the pseudo-Goldstone damping displays a novel scaling
behavior that follows with a correction controlled by the
critical universalities. Moreover, we study how the correction depends on the
value of and show that when fluctuations are
infinitely suppressed in the large limit. In this case, the proposed
relation works even in the critical region. Finally, we match our results to
the dissipative sector of the pion dynamics near the chiral phase transition.Comment: V2:minor revision, references added, discussion on the pure SSB case
has been moved to the supplemen
New Cobalt-Mediated Radical Polymerization (CMRP) of Methyl Methacrylate Initiated by Two Single-Component Dinuclear β-Diketone Cobalt (II) Catalysts
Two dinuclear cobalt complexes based on bis-diketonate ligands (ligand 1: 3,3′-(1,3-phenylene)bis(1-phenylpropane-1,3-dione); ligand 2: 3,3′-(1,4-phenylene)bis(1-phenylpropane-1,3-dione)) were successfully synthesized. The two neutral catalysts all showed satisfactory activities in the cobalt-mediated radical polymerization (CMRP) of methyl methacrylate (MMA) with the common initiator of azodiisobutyronitrile (AIBN). The resulting polymerizations have all of the characteristics of a living polymerization and displayed linear semilogarithmic kinetic plots, a linear correlation between the number-average molecular weight and the monomer conversion, and low polydispersities. Mono- or dicomponent low polydispersity polymers could be obtained by using the two dinuclear catalysts under proper reaction conditions. All these improvements facilitate the implementation of the acrylate CMRP and open the door to the scale-up of the syntheses and applications of the multicomponent low polydispersity polymers
Soft modes in hot QCD matter
The chiral crossover of QCD at finite temperature and vanishing baryon
density turns into a second order phase transition if lighter than physical
quark masses are considered. If this transition occurs sufficiently close to
the physical point, its universal critical behaviour would largely control the
physics of the QCD phase transition. We quantify the size of this region in QCD
using functional approaches, both Dyson-Schwinger equations and the functional
renormalisation group. The latter allows us to study both critical and
non-critical effects on an equal footing, facilitating a precise determination
of the scaling regime. We find that the physical point is far away from the
critical region. Importantly, we show that the physics of the chiral crossover
is dominated by soft modes even far beyond the critical region. While scaling
functions determine all thermodynamic properties of the system in the critical
region, the order parameter potential is the relevant quantity away from it. We
compute this potential in QCD using the functional renormalisation group and
Dyson-Schwinger equations and provide a simple parametrisation for
phenomenological applications.Comment: 7+8 pages, 5+4 figure
Measurement of Stimulated Raman Side-Scattering Predominance and Energetic Importance in the Compression Stage of the Double-Cone Ignition Approach to Inertial Confinement Fusion
Due to its particular geometry, stimulated Raman side-scattering (SRSS)
drives scattered light emission at non-conventional directions, leading to
scarce and complex experimental observations. Experimental campaigns at the
SG-II UP facility have measured the scattered light driven by SRSS over a wide
range of angles, showing an emission at large polar angles, sensitive to the
plasma profile and laser polarization. Furthermore, direct comparison with
back-scattering measurement has evidenced SRSS as the dominant Raman scattering
process in the compression stage, leading to the scattering loss of about 5\%
of the total laser energy. The predominance of SRSS was confirmed by 2D
particle-in-cell simulations, and its angular spread has been corroborated by
ray-tracing simulations. The main implication is that a complete
characterization of the SRS instability and an accurate measurement of the
energy losses require the collection of the scattered light in a broad range of
directions. Otherwise, spatially limited measurement could lead to an
underestimation of the energetic importance of stimulated Raman scattering
Phase transitions associated with magnetic-field induced topological orbital momenta in a non-collinear antiferromagnet
Resistivity measurements are widely exploited to uncover electronic
excitations and phase transitions in metallic solids. While single crystals are
preferably studied to explore crystalline anisotropies, these usually cancel
out in polycrystalline materials. Here we show that in polycrystalline
Mn3Zn0.5Ge0.5N with non-collinear antiferromagnetic order, changes in the
diagonal and, rather unexpected, off-diagonal components of the resistivity
tensor occur at low temperatures indicating subtle transitions between magnetic
phases of different symmetry. This is supported by neutron scattering and
explained within a phenomenological model which suggests that the phase
transitions in magnetic field are associated with field induced topological
orbital momenta. The fact that we observe transitions between spin phases in a
polycrystal, where effects of crystalline anisotropy are cancelled suggests
that they are only controlled by exchange interactions. The observation of an
off-diagonal resistivity extends the possibilities for realising
antiferromagnetic spintronics with polycrystalline materials.Comment: 4 figures, 1 tabl
Shear Tensile And Flexural Performance Of Sandwich Composite With Hexagonal Cell Wood Core Variation
Current industry demands product with better sustainability and efficiency in terms of weight. This particular demand can be met with introduction of lightweight materials with renewable sources. This article presents a study of sandwich composite with different honeycomb wood core variants and
suggests a direction for future development. Six types of sandwich composites, made with rubber wood (RW), pine wood (PW), balsa wood (BW), honeycomb rubber wood (HRW), honeycomb pine wood (HPW), and honeycomb balsa wood (HBW) implemented with hexagonal cells together with glass fibre reinforced polymer skins are studied. Shear
tensile and flexural performance of sandwich composites are tested according to ASTM standards. The results reveal that HRW core sandwich composite exhibits good flexural strength amongst the sandwich composite tested while having a proper weight reduction of about 513.92 kg/m3 compared to solid wood cores. It was also found that, the implementation of hexagonal cells in the wood cores increases the shear
tensile performance of the sandwich composites. The results provided may facilitate future applications improvement as well as sustainability developmen
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