13,931,593 research outputs found
Observation of the Radiative Decay D^(*+) → D^+y
We have observed a signal for the decay D^(*+)→D^+γ at a significance of 4 standard deviations. From the measured branching ratio B(D^(*+)→D^+γ)/B(D^(*+)→D^+π^0) = 0.055±0.014±0.010 we find B(D^(*+)→D^+γ) = 0.017±0.004±0.003, where the first uncertainty is statistical and the second is systematic. We also report the highest precision determination of the remaining D^(*+) branching fractions
The line shape of the radiative open-charm decay of Y(4140) and Y(3930)
In this work, we study the radiative open-charm decays and under the
assignments of and as molecular states for
Y(4140) and Y(3930) respectively. Based on our numerical result, we propose the
experimental measurement of the photon spectrum of and can further test the
molecular assignment for Y(4140) and Y(3930).Comment: 4 pages, 4 figures. More references and discussions added, typos
corrected. Accepted by Phys. Rev.
Commutator inequalities via Schur products
For a self-adjoint unbounded operator D on a Hilbert space H, a bounded
operator y on H and some complex Borel functions g(t) we establish inequalities
of the type
||[g(D),y]|| \leq A|||y|| + B||[D,y]|| + ...+ X|[D, [D,...[D, y]...]]||.
The proofs take place in a space of infinite matrices with operator entries,
and in this setting it is possible to approximate the matrix associated to
[g(D), y] by the Schur product of a matrix approximating [D,y] and a scalar
matrix. A classical inequality of Bennett on the norm of Schur products may
then be applied to obtain the results.Comment: 16 page
A Note on Long non-Hamiltonian Cycles in One Class of Digraphs
Let be a strong digraph on vertices. In [3, Discrete Applied
Math., 95 (1999) 77-87)], J. Bang-Jensen, Y. Guo and A. Yeo proved the
following theorem: if (*) and for every pair of non-adjacent vertices
with a common in-neighbour or a common out-neighbour, then is hamiltonian.
In this note we show that: if is not directed cycle and satisfies the
condition (*), then contains a cycle of length or .Comment: 7 pages. arXiv admin note: substantial text overlap with
arXiv:1207.564
A sufficient condition for a balanced bipartite digraph to be hamiltonian
We describe a new type of sufficient condition for a balanced bipartite
digraph to be hamiltonian. Let be a balanced bipartite digraph and be
distinct vertices in . dominates a vertex if
and ; in this case, we call the pair dominating. In
this paper, we prove that a strong balanced bipartite digraph on
vertices contains a hamiltonian cycle if, for every dominating pair of vertices
, either and or and
. The lower bound in the result is sharp.Comment: 12 pages, 3 figure
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