3,273 research outputs found
Properties of nanostructured diamond-silicon carbide composites sintered by high pressure infiltration technique
A high-pressure silicon infiltration technique was applied to sinter diamond–SiC composites with different diamond crystal sizes. Composite samples were sintered at pressure 8 GPa and temperature 2170 K. The structure of composites was studied by evaluating x-ray diffraction peak profiles using Fourier coefficients of ab initio theoretical size and strain profiles. The composite samples have pronounced nanocrystalline structure: the volume-weighted mean crystallite size is 41–106 nm for the diamond phase and 17–37 nm for the SiC phase. The decrease of diamond crystal size leads to increased dislocation density in the diamond phase, lowers average crystallite sizes in both phases, decreases composite hardness, and improves fracture toughness
Pion transition form factor in the Domain model of QCD vacuum
Domain model of QCD allows for description of wide range of meson
observables, dynamical chiral symmetry breaking, and resolution of and
strong problems. The purpose of the present study is transition
form-factor of neutral pseudoscalar mesons, and how they are influenced by the
typical vacuum configurations of the model -- almost everywhere homogeneous
Abelian (anti-)self-dual fields. Asymptotic behavior of the calculated pion
form-factor supports Belle trend, but the asymptotic value of
differs from the prediction of factorization
theorems.Comment: Talk given at The XXIII International Baldin Seminar on High Energy
Physics Problems "Relativistic Nuclear Physics and Quantum Chromodynamics",
September 19 to 24, 2016, Dubna (Russia); 4 pages, 3 figure
Efficient Algorithms for CUR and Interpolative Matrix Decompositions
The manuscript describes efficient algorithms for the computation of the CUR
and ID decompositions. The methods used are based on simple modifications to
the classical truncated pivoted QR decomposition, which means that highly
optimized library codes can be utilized for implementation. For certain
applications, further acceleration can be attained by incorporating techniques
based on randomized projections. Numerical experiments demonstrate advantageous
performance compared to existing techniques for computing CUR factorizations
Neutrino propagation in media and axis of complete polarization
We construct a spectral representation of neutrino propagator in moving
matter or in external magnetic field. In both cases there exists fixed
four-dimensional axis of polarization, such that the corresponding spin
projectors commute with propagator. As a result, all eigenvalues of propagator
and, consequently, dispersion laws for neutrino in media are classified
according to spin projection onto this axis. Use of the found spin projectors
simplifies essentially the eigenvalue problem and allows to build spectral
representation of propagator in moving matter or external magnetic field in
analogy with the vacuum propagator.Comment: 16 pages, journal versio
- …