3,356 research outputs found
Affine semigroups having a unique Betti element
We characterize affine semigroups having one Betti element and we compute
some relevant non-unique factorization invariants for these semigroups. As an
example, we particularize our description to numerical semigroups.Comment: 8 pages, 1 figure. To appear in Journal of Algebra and its
Application
Helico-conical optical beams self-heal
An optical beam is said to be self-healing when, distorted by an obstacle,
the beam corrects itself upon propagation. In this letter, we show through
experiments supported by numerical simulations, that Helico-conical optical
beams (HCOBs) self-heal. We observe the strong resilience of these beams with
different types of obstructions, and relate this to the characteristics of
their transverse energy flow.Comment: 4 pages, 5 figure
Supergroup BF action for supergravity
General relativity can be formulated as a SU(2) BF-theory with constraints,
as has been shown, by Pleba\'nski. The cosmological constant term can be
obtained from the constraint term, following from the consistency of the
equations of motion, as recently shown by Krasnov. We consider an
invariant, supergravity extension of this theory, for which the consistency of
the equations of motion and the constraints contribute as well to the
cosmological constant terms of Townsend's supergravity. The Kalb-Ramond
invariance is shortly discussed.Comment: 14 page
Anharmonic effects in magnetoelastic chains
We describe a new mechanism leading to the formation of rational
magnetization plateau phases, which is mainly due to the anharmonic spin-phonon
coupling. This anharmonicity produces plateaux in the magnetization curve at
unexpected values of the magnetization without explicit magnetic frustration in
the Hamiltonian and without an explicit breaking of the translational symmetry.
These plateau phases are accompanied by magneto-elastic deformations which are
not present in the harmonic case.Comment: 5 pages, 3 figure
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