61,790 research outputs found
Electronic oscillations in paired polyacetylene chains
An interacting pair of polyacetylene chains are initially modeled as a couple
of undimerized polymers described by a Hamiltonian based on the tight-binding
model representing the electronic behavior along the linear chain, plus a
Dirac's potential double well representing the interaction between the chains.
A theoretical field formalism is employed, and we find that the system exhibits
a gap in its energy band due to the presence of a mass-matrix term in the
Dirac's Lagrangian that describes the system. The Peierls instability is
introduced in the chains by coupling a scalar field to the fermions of the
theory via spontaneous symmetry breaking, to obtain a kink-like soliton, which
separates two vacuum regions, i.e., two spacial configurations (enantiomers) of
the each molecule. Since that mass-matrix and the pseudo-spin operator do not
commute in the same quantum representation, we demonstrate that there is a
particle oscillation phenomenon with a periodicity equivalent to the Bloch
oscillations.Comment: 4 pages, 1 figure.to appear in Solid State Communication
Photon mass as a probe to extra dimensions
In this manuscript we show that the geometrical localization mechanism
implies a four dimensional mass for the photon. The consistence of the model
provides a mass given exactly by where is the Ricci
scalar. As a consequence, the cosmological photon has a mass related to the
vacuum solution of the Einstein equation. At the present age of the universe we
have a dS vacuum with , where Lambda is a positive cosmological
constant. With this we find that kg, which
is below the present experimental upper bounds, and such correction may be
observed in the next years with more precise measurements. By considering the
value of inside some astrophysical sources and environments we find that
the bound is also satisfied. The experimental verification of this mass, beyond
pointing to the existence of extra dimensions, would imply in a fundamental
change in cosmology, astrophysics and in particle physics since the same
mechanism is valid for non-abelian gauge fields.Comment: 4 page
Texture Zeros and Weak Basis Transformations
We investigate the physical meaning of some of the "texture zeros" which
appear in most of the Ansatze on quark masses and mixings. It is shown that
starting from arbitrary quark mass matrices and making a suitable weak basis
transformation one can obtain some of these sets of zeros which therefore have
no physical content. We then analyse the physical implications of a
four-texture zero Ansatz which is in agreement with all present experimental
data.Comment: 11 pages, typeset using revte
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