6,073 research outputs found
El mercado de producción independiente en España ante la aparición de Cuatro y laSexta
La aparición en el mercado televisivo analógico de las nuevas ofertas de Cuatro y laSexta no sólo ha modificado el equilibrio entre cadenas sino que también se ha hecho notar en el ámbito de la producción independiente. El presente artÃculo cuantifica este impacto comparando la última temporada sin su presencia y la de su debut, trazando los patrones de aprovisionamiento de producción independiente detectados en el mercado español. El texto concluye que la aparición de estos dos canales influyó en el incremento del volumen de producción independiente pero no alteró de forma significativa las cuotas de mercado de las diferentes productora
Gapless Hamiltonians for the toric code using the PEPS formalism
We study Hamiltonians which have Kitaev's toric code as a ground state, and
show how to construct a Hamiltonian which shares the ground space of the toric
code, but which has gapless excitations with a continuous spectrum in the
thermodynamic limit. Our construction is based on the framework of Projected
Entangled Pair States (PEPS), and can be applied to a large class of
two-dimensional systems to obtain gapless "uncle Hamiltonians".Comment: 8 pages, 2 figure
Quantum mechanical spectral engineering by scaling intertwining
Using the concept of spectral engineering we explore the possibilities of
building potentials with prescribed spectra offered by a modified intertwining
technique involving operators which are the product of a standard first-order
intertwiner and a unitary scaling. In the same context we study the iterations
of such transformations finding that the scaling intertwining provides a
different and richer mechanism in designing quantum spectra with respect to
that given by the standard intertwiningComment: 8 twocolumn pages, 5 figure
Bubble collapse near porous plates
A gas or vapour bubble near a solid boundary collapses towards the boundary
due to the asymmetry induced by the nearby boundary. High surface pressure and
shear stress from this collapse can damage, or clean, the surface. A porous
boundary, such as a filter, would act similarly to a solid boundary but with
reduced asymmetry and thus reduced effect. Prior research has measured the
cleaning effect of bubbles on filters using ultrasonic cleaning, but it is not
known how the bubble dynamics are fundamentally affected by the porosity of the
surface. We address this question experimentally by investigating how the
standoff distance, porosity, pore size, and pore shape affect two collapse
properties: bubble displacement and bubble rebound size. We show that these
properties depend primarily on the standoff distance and porosity of the
boundary and extend a previously developed numerical model that approximates
this behaviour. Using the numerical model in combination with experimental
data, we show that bubble displacement and bubble rebound size each collapse
onto respective single curves
Geometric Phases and Mielnik's Evolution Loops
The cyclic evolutions and associated geometric phases induced by
time-independent Hamiltonians are studied for the case when the evolution
operator becomes the identity (those processes are called {\it evolution
loops}). We make a detailed treatment of systems having equally-spaced energy
levels. Special emphasis is made on the potentials which have the same spectrum
as the harmonic oscillator potential (the generalized oscillator potentials)
and on their recently found coherent states.Comment: 11 pages, harvmac, 2 figures available upon request; CINVESTAV-FIS
GFMR 11/9
Coherent states for Hamiltonians generated by supersymmetry
Coherent states are derived for one-dimensional systems generated by
supersymmetry from an initial Hamiltonian with a purely discrete spectrum for
which the levels depend analytically on their subindex. It is shown that the
algebra of the initial system is inherited by its SUSY partners in the subspace
associated to the isospectral part or the spectrum. The technique is applied to
the harmonic oscillator, infinite well and trigonometric Poeschl-Teller
potentials.Comment: LaTeX file, 26 pages, 3 eps figure
Extension of Tensor-Product Generalized and Dense-Norm Summation-by-Parts Operators to Curvilinear Coordinates
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