From conformal to volume-law for the entanglement entropy in exponentially deformed critical spin 1/2 chains

An exponential deformation of 1D critical Hamiltonians gives rise to ground states whose entanglement entropy satisfies a volume-law. This effect is exemplified in the XX and Heisenberg models. In the XX case we characterize the crossover between the critical and the maximally entangled ground state in terms of the entanglement entropy and the entanglement spectrum.Comment: Accepted for the Special Issue: Quantum Entanglement in Condensed Matter Physics. 11 pages, 9 figures (with enhanced size to focus on the details) and new reference

Entanglement in low-energy states of the random-hopping model

We study the low-energy states of the 1D random-hopping model in the strong disordered regime. The entanglement structure is shown to depend solely on the probability distribution for the length of the effective bonds $P(l_b)$, whose scaling and finite-size behavior are established using renormalization-group arguments and a simple model based on random permutations. Parity oscillations are absent in the von Neumann entropy with periodic boundary conditions, but appear in the higher moments of the distribution, such as the variance. The particle-hole excited states leave the bond-structure and the entanglement untouched. Nonetheless, particle addition or removal deletes bonds and leads to an effective saturation of entanglement at an effective block size given by the expected value for the longest bond

Many-body Lattice Wavefunctions From Conformal Blocks

We introduce a general framework to construct many-body lattice wavefunctions starting from the conformal blocks (CBs) of rational conformal field theories (RCFTs). We discuss the different ways of encoding the physical degrees of freedom of the lattice system using both the internal symmetries of the theory and the fusion channels of the CBs. We illustrate this construction both by revisiting the known Haldane-Shastry model and by providing a novel implementation for the Ising RCFT. In the latter case, we find a connection to the Ising transverse field (ITF) spin chain via the Kramers-Wannier duality and the Temperley-Lieb-Jones algebra. We also find evidence that the ground state of the finite-size critical ITF Hamiltonian corresponds exactly to the wavefunction obtained from CBs of spin fields

“REFLEXIONES EN TORNO A LA NUEVA LEY 13/2003, DE 23 DE MAYO,REGULADORA DEL CONTRATO DE CONCESIÓN DE OBRAS PÚBLICAS”

La Ley 13/2003, de 23 de mayo, reguladora del contrato de concesión de obras públicas en vigor desde el 24 de Agosto de 2003, ha supuesto la puesta al día de esta institución concesional que cuenta con una larga tradición en España, modificando el Real Decreto Legislativo 2/2000, de 16 de junio, por el que se aprueba el texto refundido de la Ley de Contratos de las Administraciones Públicas, texto en el que se incorpora por recomendación del Consejo de Estado. (...

Regulación electoral de los sondeos a pie de urna en España : asignaturas pendientes y obsolescencia ante las nuevas formas de comunicación = Electoral regulation of exit polls in Spain : unfinished topics and obsolescence in the face of new forms of communication

En los países europeos hemos asistido en las últimas citas electorales a la filtración de datos parciales de estimaciones durante la jornada electoral a través de redes sociales. Por otra parte, la incorporación de nuevas tecnologías en los procesos de recuento y la eventual introducción del voto electrónico ocasionan dudas sobre la continuidad de las encuestas a pie de urna por la reducción del lapso temporal entre la publicación de los pronósticos electorales y los primeros datos de voto escrutado. Estos nuevos retos y viejas cuestiones pendientes sobre las encuestas electorales se analizan desde la óptica del caso español.In European countries we have witnessed leakage of partial data in the latest elections during Election Day through social networks. The incorporation of new technologies in the counting process and the introduction of electronic voting cast doubts about the continuation of the exit polls due to the reduced time lag between the publication of electoral forecasts and the first data of votes counted. These new challenges and old outstanding issues on election polls are analyzed from the Spanish viewpoint