Evidences of evanescent Bloch waves in Phononic Crystals

We show both experimentally and theoretically the evanescent behaviour of modes in the Band Gap (BG) of finite Phononic Crystal (PC). Based on experimental and numerical data we obtain the imaginary part of the wave vector in good agreement with the complex band structures obtained by the Extended Plane Wave Expansion (EPWE). The calculated and measured acoustic field of a localized mode out of the point defect inside the PC presents also evanescent behaviour. The correct understanding of evanescent modes is fundamental for designing narrow filters and wave guides based on Phononic Crystals with defects.Comment: 8 pages, 3 figure

Gravitational lensing by spherically symmetric lenses with angular momentum

Following Sereno (2002a), we discuss the bending of light rays by spherically symmetric lenses with angular momentum. For several astrophysical systems, such as white dwarfs and galaxies, gravitomagnetism induces a correction on the deflection angle as large as 0.1%.Comment: 6 pages, To appear in A&

A new scenario for string unification

We present a new scenario for gauge coupling unification in flipped SU(5) string models, which identifies the $M_{32}$ scale of SU(3) and SU(2) unification with the empirical $M_{\rm LEP}\sim10^{15-16}$~GeV scale, and the $M_{51}$ scale of SU(5) and U(1) unification with the theoretical $M_{\rm string}\sim5\times10^{17}$~GeV string unification scale. The vacuum shift necessary for the cancellation of the anomalous $\rm U_A(1)$ and an SU(4) hidden sector with fractionally-charged particles, play a crucial role in the dynamical determination of all intermediate mass scales in this scenario.Comment: 8 pages, LaTeX, 2 figures (uuencoded

Transitionless quantum drivings for the harmonic oscillator

Two methods to change a quantum harmonic oscillator frequency without transitions in a finite time are described and compared. The first method, a transitionless-tracking algorithm, makes use of a generalized harmonic oscillator and a non-local potential. The second method, based on engineering an invariant of motion, only modifies the harmonic frequency in time, keeping the potential local at all times.Comment: 11 pages, 1 figure. Submitted for publicatio

Estudio comparativo de las epidermis foliares de las licopodiaceas ibericas I. Estomas

Se realiza un estudio comparativo de los estomas, tanto de los esporofilos como de los trofofilos, de Huperzia selago (L.) Bernh ex Schrank & Mart., Lycopodium annotinum L.,Lycopodium clavatum L., Diphasiastrum alpinum (L.) Holub y Lycopodiella inundata (L.) Holub aportando datos sobre la localización de los estomas en la lámina foliar, su distribución y número.A comparative study of stomates was made, both in sporophylles and trophophylles of Huperzia selago (L.) Bernh ex Schrank & Mart.,Lycopodium annotinum L. ,Lycopodium clavatum L.,Diphasiastrum alpinum (L.) Holub and Lycopodiella inundata (L.) Holub, giving new data about the localization of stomates on the foliar lamina, their distribution and number

S,O-Ligand Promoted meta-C−H Arylation of Anisole Derivatives via Palladium/Norbornene Catalysis

Reversing the conventional site-selectivity of C−H activation processes provides new retrosynthetic disconnections to otherwise unreactive bonds. Here, we report a new catalytic system based on palladium/norbornene and an S,O-ligand for the meta-C−H arylation of aryl ethers that significantly outperforms previously reported systems. We demonstrate the unique ability of this system to employ alkoxyarene substrates bearing electron donating and withdrawing substituents. Additionally, ortho-substituted aryl ethers are well tolerated, overcoming the “ortho constraint”, which is the necessity to have a meta-substituent on the alkoxyarene to achieve high reaction efficiency, by enlisting novel norbornene mediators. Remarkably, for the first time the monoarylation of alkoxyarenes is achieved efficiently enabling the subsequent introduction of a second, different aryl coupling partner to rapidly furnish unsymmetrical terphenyls. Further insight into the reaction mechanism was achieved by isolation and characterization of some Pd-complexes—before and after meta C−H activation—prior to evaluation of their respective catalytic activities

Entanglement of excited states in critical spin chians

Renyi and von Neumann entropies quantifying the amount of entanglement in ground states of critical spin chains are known to satisfy a universal law which is given by the Conformal Field Theory (CFT) describing their scaling regime. This law can be generalized to excitations described by primary fields in CFT, as was done in reference (Alcaraz et. al., Phys. Rev. Lett. 106, 201601 (2011)), of which this work is a completion. An alternative derivation is presented, together with numerical verifications of our results in different models belonging to the c=1,1/2 universality classes. Oscillations of the Renyi entropy in excited states and descendant fields are also discussed.Comment: 23 pages, 13 figure

Flavor changing neutral current constraints on standard-like orbifold models

We examine for standard-like orbifold compactification models the constraints due to quarks and leptons generation non-universality of soft supersymmetry breaking interactions. We follow the approach initiated by Ibanez and Lust and developed by Brignole, Ibanez and Munoz. The breaking of supersymmetry is represented in terms of dilaton and moduli auxiliary field components and, consistently with a vanishing cosmological constant, is parametrized in terms of the dilaton-moduli mixing angle $\theta$ and the gravitino mass scale $m_g$. The soft breaking interactions (gaugino masses, squarks and sleptons mass matrices, scalars interactions A and B coupling constants) are calculable as a function of these parameters and of the discrete set of modular weight parameters specifying the modular transformation properties of the low-energy fields. We solve the renormalization group one-loop equations for the full set of gauge, Yukawa and supersymmetry breaking coupling constants.Comment: 32 page

Non anomalous U(1)_H gauge model of flavor

A non anomalous horizontal $U(1)_H$ gauge symmetry can be responsible for the fermion mass hierarchies of the minimal supersymmetric standard model. Imposing the consistency conditions for the absence of gauge anomalies yields the following results: i) unification of leptons and down-type quarks Yukawa couplings is allowed at most for two generations. ii) The $\mu$ term is necessarily somewhat below the supersymmetry breaking scale. iii) The determinant of the quark mass matrix vanishes, and there is no strong $CP$ problem. iv) The superpotential has accidental $B$ and $L$ symmetries. The prediction $m_{\rm up}=0$ allows for an unambiguous test of the model at low energy.Comment: 5 pages, RevTex. Title changed, minor modifications. Final version to appear in Phys. Rev.