1,338 research outputs found
Nuclear pasta structures and the charge screening effect
Non uniform structures of the nucleon matter at subnuclear densities are
numerically studied by means of the density functional theory with relativistic
mean-fields coupled with the electric field. A particular role of the charge
screening effects is demonstrated.Comment: 11 pages, 9 figures, submitted to PR
A structural characterization for certifying robinsonian matrices
A symmetric matrix is Robinsonian if its rows and columns can be
simultaneously reordered in such a way that entries are monotone nondecreasing
in rows and columns when moving toward the diagonal. The adjacency matrix of a
graph is Robinsonian precisely when the graph is a unit interval graph, so that
Robinsonian matrices form a matrix analogue of the class of unit interval
graphs. Here we provide a structural characterization for Robinsonian matrices
in terms of forbidden substructures, extending the notion of asteroidal triples
to weighted graphs. This implies the known characterization of unit interval
graphs and leads to an efficient algorithm for certifying that a matrix is not
Robinsonian.Comment: 21 pages, 1 figur
A structural characterization for certifying Robinsonian matrices
A symmetric matrix is Robinsonian if its rows and columns can be simultaneously reordered in such a way that entries are monotone nondecreasing in rows and columns when moving toward the diagonal. The adjacency matrix of a graph is Robinsonian precisely when the graph is a unit interval graph, so that Robinsonian matrices form a matrix analogue of the class of unit interval graphs. Here we provide a structural characterization for Robinsonian matrices in terms of forbidden substructures, extending the notion of asteroidal triples to weighted graphs. This implies the known characterization of unit interval graphs and leads to an efficient algorithm for certifying that a matrix is not Robinsonian
Brillouin laser-driven terahertz oscillator up to 3 THz with femtosecond-level timing jitter
The terahertz (THz) frequency range, spanning 0.1 to 10 THz, is a field ripe
for innovation with vast, developing potential in areas like wireless
communication and molecular spectroscopy. Our work introduces a dual-wavelength
laser design that utilizes stimulated Brillouin scattering in an optical fiber
cavity to effectively generate two highly coherent optical Stokes waves with
differential phase noise inherently mitigated. To guarantee robust operation,
the Stokes waves are optically injected into their respective pump lasers,
which also serves to greatly improve the resulting coherence. The frequency
difference between the two wavelengths is converted into THz waves through a
uni-traveling-carrier photodiode. This innovative design facilitates the
generation of THz waves with phase noise levels of less than -100 dBc/Hz,
translating to timing noise below 10~ at 10
kHz Fourier frequency, over a carrier frequency range from 300 GHz to 3 THz.
This development in phase noise reduction establishes a new benchmark in the
spectral purity of tunable THz sources. Such advances are pivotal for
applications to move beyond oscillator constraints
Possibility of \Lambda\Lambda pairing and its dependence on background density in relativistic Hartree-Bogoliubov model
We calculate a \Lambda\Lambda pairing gap in binary mixed matter of nucleons
and \Lambda hyperons within the relativistic Hartree-Bogoliubov model. Lambda
hyperons to be paired up are immersed in background nucleons in a normal state.
The gap is calculated with a one-boson-exchange interaction obtained from a
relativistic Lagrangian. It is found that at background density
\rho_{N}=2.5\rho_{0} the \Lambda\Lambda pairing gap is very small, and that
denser background makes it rapidly suppressed. This result suggests a
mechanism, specific to mixed matter dealt with relativistic models, of its
dependence on the nucleon density. An effect of weaker \Lambda\Lambda
attraction on the gap is also examined in connection with revised information
of the \Lambda\Lambda interaction.Comment: 8 pages, 6 figures, REVTeX 4; substantially rewritten, emphasis is
put on the LL pairing in pure neutron matte
Effect of self-ion irradiation on hardening and microstructure of tungsten
AbstractThe irradiation hardening and microstructures of pure W and W–3%Re for up to 5.0 dpa by self-ion irradiation were investigated in this work. The ion irradiation was conducted using 18 MeV W6+ at 500 and 800°C. A focused ion beam followed by electro-polishing was used to make thin foil specimens for transmission electron microscope observations. Dislocation loops were observed in all the irradiated samples. Voids were observed in all of the specimens except the W–3%Re irradiated to 0.2 dpa. The hardness was measured by using nanoindentation. The irradiation hardening was saturated at 1.0 dpa for pure W. In the case of W–3%Re, the irradiation hardening showed a peak at 1.0 dpa. The correlation between the microstructure and hardening was investigated
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