7,878 research outputs found
Massive field contributions to the QCD vacuum tunneling amplitude
For the one-loop contribution to the QCD vacuum tunneling amplitude by quarks
of generic mass value, we make use of a calculational scheme exploiting a large
mass expansion together with a small mass expansion. The large mass expansion
for the effective action is given by a series involving higher-order
Seeley-DeWitt coefficients, and we carry this expansion up to order
, where denotes mass of the quark and the instanton
size parameter. For the small mass expansion, we use the known exact expression
for the particle propagation functions in an instanton background and evaluate
explicitly the effective action to order . A smooth interpolation of
the results from both expansions suggests that the quark contribution to the
instanton tunneling amplitude have a relatively simple -dependent
behavior.Comment: revtex, 4figures, 33page
Solutions of Schr\"odinger equations\\ with symmetry in orientation preserving tetrahedral group
We consider the nonlinear Schr\"odinger equation \begin{equation*} \Delta u =
\big( 1 +\ve V_1(|y|)\big)u - |u|^{p-1}u
\quad \text{in} \quad \mathbb{R}^N, \quad N\ge 3, \quad p \in \left(1,
\frac{N+2}{N-2}\right).\end{equation*} The phenomenon of pattern formation has
been a central theme in the study of nonlinear Schr\"odinger equations.
However, the following nonexistence of symmetry breaking solution is
well-known: if the potential function is radial and radially nondecreasing, any
positive solution must be radial. Therefore, solutions of interesting patterns,
such as those with symmetry in a discrete subgroup of , can only exist
after violating the assumptions. For a potential function that is radial but
asymptotically decreasing, a solution with symmetry merely in a discrete
subgroup of has been presented. These observations pose the question of
whether patterns of higher dimensions can appear. In this study, the existence
of nonradial solutions whose symmetry group is a discrete subgroup of ,
more precisely, the orientation-preserving regular tetrahedral group is shown
Rarity and shifts in occurrence of endangered butterflies in South Korea
Endangered species are often the focus of public attention, partly because of their vulnerability to environmental changes, such as climate and land use change, and subsequently being at high risk of extinctions. Hence, red lists of endangered species play anessential in nature conservation. Although several endangered butterfly species have been previously listed as endangered species by government and/or individuals in South Korea, these red listsrarely include reliable quantitative population data. This has led to endless and unproductive debates on the selection of endangered species. Following Korean butterfly atlases, we assessed the population status of Korean endangered butterfly species whose distributions have been previously published. We hypothesized that these endangered species are rare and are decreasing in occurrence. We found that the decrease in occurrence is more important in determining endanger status than rarity. Using values of rarity and shifts in species occurrence, we selected endangered species from the previously published endangered species. Only eight species of 20 previous endangered species were defined as endangered by this semi-quantitative classification. This finding suggests that the subjective determination based on expert's perception would define more species as endangered compared to the quantitative determination based on population data.Article信州大学農学部紀要 50(1-2): 37-42(2014)departmental bulletin pape
Evaluation of tensile properties using instrumented indentation technique for small scale testing
The Instrumented indentation technique (IIT) is a useful tool for estimating various mechanical properties such as tensile properties, fracture toughness, and residual stress by analyzing the load and depth curve. Unlike conventional test such as tensile test, CTOD, since IIT makes an indent with rigid indenter and measures load and depth continuously, it requires only a localized area and small area on the target material. IIT also has merits of simple specimen preparation and experimental procedure in terms of time and cost. Also, it can be applied to in-field structures nondestructively. In this study, we introduce a method for evaluating tensile properties, primary yield strength and tensile strength using representative stress-strain beneath the rigid spherical indenter through numerous investigations of instrumented indentation curves. Analytic models and procedures for estimating the mechanical characterization of materials using IIT are proposed. The representative stress-strain method directly correlates indentation stress and strain beneath indenter to true stress and strain of the tensile test by taking into account the plastic constraint effect. The experimental results from IIT were verified by comparing results from the uniaxial tensile test. In particular, the applications of IIT in small scale and localized area of materials are presented.
Reference
1) D. Tabor: Hardness of metal, (first ed. Clarendon Press, New York, 1951)
2) W.C. Oliver and G.M. Pharr, J. Mater, Res, Vol. 7, (1992), p. 1564
3) S.-K. Kang, Y.-C. Kim, K.-H. Kim, J.-Y. Kim and D. Kwon, Int. J. Plast. 49, 1 (2013
Relative entropy technique in terms of position and momentum and its application to Euler-Poisson system
This paper presents a systematic study of the relative entropy technique for
compressible motions of continuum bodies described as Hamiltonian flows. While
the description for the classical mechanics of particles involves a
Hamiltonian in terms of position and momentum vectors, that for the continuum
fluid involves a Hamiltonian in terms of density and momentum. For space
dimension , the Hamiltonian functional has a non-convex dependency on
the deformation gradient or placement map due to material frame indifference.
Because of this, the applicability of the relative entropy technique with
respect to the deformation gradient or the placement map is inherently limited.
Despite these limitations, we delineate the feasible applications and
limitations of the technique by pushing it to its available extent.
Specifically, we derive the relative Hamiltonian identity, where the
Hamiltonian takes the position and momentum field as its primary and conjugate
state variables, all within the context of the referential coordinate system
that describes the motion.
This approach, when applicable, turns out to yield rather strong stability
statements. As instances, we consider Euler-Poisson systems in one space
dimension. For a specific pressureless model, we verify non-increasing
state differences before the formation of -shock. In addition,
weak-strong uniqueness, stability of rarefaction waves, and convergence to the
gradient flow in the singular limit of large friction are shown. Depending on
the presence or absence of pressure, assumptions are made to suitably
accommodate phenomena such as -shocks, vacuums, and shock
discontinuities in the weak solutions.Comment: 35 page
Density functional calculations of the electronic structure and magnetic properties of the hydrocarbon K3picene superconductor near the metal-insulator transition
We have investigated the electronic structures and magnetic properties of of
K3picene, which is a first hydrocarbon superconductor with high transition
temperature T_c=18K. We have shown that the metal-insulator transition (MIT) is
driven in K3picene by 5% volume enhancement with a formation of local magnetic
moment. Active bands for superconductivity near the Fermi level E_F are found
to have hybridized character of LUMO and LUMO+1 picene molecular orbitals.
Fermi surfaces of K3picene manifest neither prominent nesting feature nor
marked two-dimensional behavior. By estimating the ratio of the Coulomb
interaction U and the band width W of the active bands near E_F, U/W, we have
demonstrated that K3picene is located in the vicinity of the Mott transition.Comment: 5 pages, 5 figure
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