57 research outputs found
Critical thermodynamics of three-dimensional MN-component field model with cubic anisotropy from higher-loop \epsilon expansion
The critical thermodynamics of an -component field model with cubic
anisotropy relevant to the phase transitions in certain crystals with
complicated ordering is studied within the four-loop \ve expansion using the
minimal subtraction scheme. Investigation of the global structure of RG flows
for the physically significant cases M=2, N=2 and M=2, N=3 shows that the model
has an anisotropic stable fixed point with new critical exponents. The critical
dimensionality of the order parameter is proved to be equal to
, that is exactly half its counterpart in the real hypercubic
model.Comment: 9 pages, LaTeX, no figures. Published versio
Critical behavior of certain antiferromagnets with complicated ordering: Four-loop \ve-expansion analysis
The critical behavior of a complex N-component order parameter
Ginzburg-Landau model with isotropic and cubic interactions describing
antiferromagnetic and structural phase transitions in certain crystals with
complicated ordering is studied in the framework of the four-loop
renormalization group (RG) approach in (4-\ve) dimensions. By using
dimensional regularization and the minimal subtraction scheme, the perturbative
expansions for RG functions are deduced and resummed by the Borel-Leroy
transformation combined with a conformal mapping. Investigation of the global
structure of RG flows for the physically significant cases N=2 and N=3 shows
that the model has an anisotropic stable fixed point governing the continuous
phase transitions with new critical exponents. This is supported by the
estimate of the critical dimensionality obtained from six loops
via the exact relation established for the complex and real
hypercubic models.Comment: LaTeX, 16 pages, no figures. Expands on cond-mat/0109338 and includes
detailed formula
Stable spinning optical solitons in three dimensions
We introduce spatiotemporal spinning solitons (vortex tori) of the
three-dimensional nonlinear Schrodinger equation with focusing cubic and
defocusing quintic nonlinearities. The first ever found completely stable
spatiotemporal vortex solitons are demonstrated. A general conclusion is that
stable spinning solitons are possible as a result of competition between
focusing and defocusing nonlinearities.Comment: 4 pages, 6 figures, accepted to Phys. Rev. Let
An overview of using small punch testing for mechanical characterization of MCrAlY bond coats
Considerable work has been carried out on overlay bond coats in the past several decades because of its excellent oxidation resistance and good adhesion between the top coat and superalloy substrate in the thermal barrier coating systems. Previous studies mainly focus on oxidation and diffusion behavior of these coatings. However, the mechanical behavior and the dominant fracture and deformation mechanisms of the overlay bond coats at different temperatures are still under investigation. Direct comparison between individual studies has not yet been achieved due to the fragmentary data on deposition processes, microstructure and, more apparently, the difficulty in accurately measuring the mechanical properties of thin coatings. One of the miniaturized specimen testing methods, small punch testing, appears to have the potential to provide such mechanical property measurements for thin coatings. The purpose of this paper is to give an overview of using small punch testing to evaluate material properties and to summarize the available mechanical properties that include the ductile-to-brittle transition and creep of MCrAlY bond coat alloys, in an attempt to understand the mechanical behavior of MCrAlY coatings over a broad temperature range
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