16,091 research outputs found
The Largest Laplacian and Signless Laplacian H-Eigenvalues of a Uniform Hypergraph
In this paper, we show that the largest Laplacian H-eigenvalue of a
-uniform nontrivial hypergraph is strictly larger than the maximum degree
when is even. A tight lower bound for this eigenvalue is given. For a
connected even-uniform hypergraph, this lower bound is achieved if and only if
it is a hyperstar. However, when is odd, it happens that the largest
Laplacian H-eigenvalue is equal to the maximum degree, which is a tight lower
bound. On the other hand, tight upper and lower bounds for the largest signless
Laplacian H-eigenvalue of a -uniform connected hypergraph are given. For a
connected -uniform hypergraph, the upper (respectively lower) bound of the
largest signless Laplacian H-eigenvalue is achieved if and only if it is a
complete hypergraph (respectively a hyperstar). The largest Laplacian
H-eigenvalue is always less than or equal to the largest signless Laplacian
H-eigenvalue. When the hypergraph is connected, the equality holds here if and
only if is even and the hypergraph is odd-bipartite.Comment: 26 pages, 3 figure
Surjective endomorphisms of projective surfaces -- the existence of infinitely many dense orbits
Let be a surjective endomorphism of a normal projective
surface. When , applying an (iteration of)
-equivariant minimal model program (EMMP), we determine the geometric
structure of . Using this, we extend the second author's result to singular
surfaces to the extent that either has an -invariant non-constant
rational function, or has infinitely many Zariski-dense forward orbits;
this result is also extended to Adelic topology (which is finer than Zariski
topology)
Surface plasmon polaritons in topological insulator
We study surface plasmon polaritons on topological insulator-vacuum
interface. When the time-reversal symmetry is broken due to ferromagnetic
coupling, the surface states exhibit magneto-optical Kerr effect. This effect
gives rise to a novel transverse type surface plasmon polariton, besides the
longitudinal type. In specific, these two types contain three different
channels, corresponding to the pole of determinant of Fresnel reflection
matrix. All three channels of surface plasmon polaritons display tight
confinement, long lifetime and show strong light-matter coupling with a dipole
emitter.Comment: 6 pages, 4 figure
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