Ward Identities and chiral anomalies for coupled fermionic chains

Coupled fermionic chains are usually described by an effective model written in terms of bonding and anti-bonding spinless fields with linear dispersion in the vicinities of the respective Fermi points. We derive for the first time exact Ward Identities (WI) for this model, proving the existence of chiral anomalies which verify the Adler-Bardeen non-renormalization property. Such WI are expected to play a crucial role in the understanding of the thermodynamic properties of the system. Our results are non-perturbative and are obtained analyzing Grassmann functional integrals by means of Constructive Quantum Field Theory methods.Comment: TeX file, 26 pages, 7 figures. Published version, new section added to answer referee remarks and derive the Ward Identites, no modifications in the main resul

Larval condition and growth of Sardinella brasiliensis (Steindachner, 1879): preliminary results from laboratory studies

Brazilian sardine, the most important resource along the southeastern Brazilian coast, presented great variations and declines in its stocks. The main factors contributing to this are: oceanographic structure changes; recruitment failures; excessive catches of juveniles and increase in fishery effort. In spite of this, no alterations in the density-dependent parameters were detected. Consequently, methods analysing the condition of the larvae coupled with methods determining growth using sagittae otolith increment width were applied to evaluate growth under experimental conditions. The results of the readings on the sagittae were compared with the age of the laboratory-reared sardine larvae and confirmed that increments are formed on a daily basis. Under poor feeding conditions, sardine larvae showed a low growth expressed by dry weight, RNA/DNA ratio and tryptic enzyme activity and by the narrow and low contrast increments in the otoliths. The results of the biochemical indices showed an unexpected decline in the feeding group coupled with a decrease in width of increment numbers 8 and 10. Other factors than food availability were affecting the condition of the larvae and might be indicative of physiological processes and ontogenetic changes occurring in sardine larvae

Initial pseudo-steady state & asymptotic KPZ universality in semiconductor on polymer deposition

The Kardar-Parisi-Zhang (KPZ) class is a paradigmatic example of universality in nonequilibrium phenomena, but clear experimental evidences of asymptotic 2D-KPZ statistics are still very rare, and far less understanding stems from its short-time behavior. We tackle such issues by analyzing surface fluctuations of CdTe films deposited on polymeric substrates, based on a huge spatio-temporal surface sampling acquired through atomic force microscopy. A \textit{pseudo}-steady state (where average surface roughness and spatial correlations stay constant in time) is observed at initial times, persisting up to deposition of $\sim 10^{4}$ monolayers. This state results from a fine balance between roughening and smoothening, as supported by a phenomenological growth model. KPZ statistics arises at long times, thoroughly verified by universal exponents, spatial covariance and several distributions. Recent theoretical generalizations of the Family-Vicsek scaling and the emergence of log-normal distributions during interface growth are experimentally confirmed. These results confirm that high vacuum vapor deposition of CdTe constitutes a genuine 2D-KPZ system, and expand our knowledge about possible substrate-induced short-time behaviors.Comment: 13 pages, 8 figures, 2 table

Dos torres de Oíza : Notas sobre crítica y arquitectura a partir de una lectura de Ezra Pound

Ezra Pound makes a critical classification of literature recognizing the significance of different kinds of authors. Sáenz de Oiza says we only have to apply this to architecture and the concept remains valid. This makes us reflect on the importance of carrying out a critical selection of all the antecedents that influence architectural design. Moreover, it leads us to consider the architectural work itself as a critical action. Torres Blancas and Banco de Bilbao, the two major works of Oíza in Madrid, are used to illustrate the reflection on these topics.Ezra Pound hace una clasificación crítica de la literatura, reconociendo la significación de diferentes tipos de autores. Sáenz de Oíza dice que solo tenemos que transponerla a la arquitectura y sigue siendo válida. Ello nos hace reflexionar sobre la importancia de realizar una selección crítica de todos los antecedentes que influyen en el proyecto arquitectónico. Por otra parte, nos lleva a considerar la obra arquitectónica en sí como una acción crítica. Torres Blancas y Banco de Bilbao, las dos principales obras de Oíza en Madrid, se utilizan para ilustrar la reflexión sobre estos temas

Ising t-J model close to half filling: A Monte Carlo study

Within the recently proposed doped-carrier representation of the projected lattice electron operators we derive a full Ising version of the t-J model. This model possesses the global discrete Z_2 symmetry as a maximal spin symmetry of the Hamiltonian at any values of the coupling constants, t and J. In contrast, in the spin anisotropic limit of the t-J model, usually referred to as the t-J_z model, the global SU(2) invariance is fully restored at J_z=0, so that only the spin-spin interaction has in that model the true Ising form. We discuss a relationship between those two models and the standard isotropic t-J model. We show that the low-energy quasiparticles in all three models share the qualitatively similar properties at low doping and small values of J/t. The main advantage of the proposed Ising t-J model over the t-J_z one is that the former allows for the unbiased Monte Carlo calculations on large clusters of up to 10^3 sites. Within this model we discuss in detail the destruction of the antiferromagnetic order by doping as well as the interplay between the AF order and hole mobility. We also discuss the effect of the exchange interaction and that of the next nearest neighbour hoppings on the destruction of the AF order at finite doping. We show that the short-range AF order is observed in a wide range of temperatures and dopings, much beyond the boundaries of the AF phase. We explicitly demonstrate that the local no double occupancy constraint plays the dominant role in destroying the magnetic order at finite doping. Finally, a role of inhomogeneities is discussed.Comment: 24 pages, 10 figure

Relación angular radiológica de las superficies articulares de la tibia en sujetos asintomáticos

Se efectuó un estudio radiológico para determinar la relación angular existente entre las superficies articulares proximal y distal de 108 tibias correspondientes a 54 pacientes asintomáticos, de edades entre 14 y 72 años (media: 29,8). La medición se llevó a cabo con un «cobbometro» de Oxford en proyección anteroposterior y lateral. El ángulo medio entre ambas superficies fue de 3,3 ± 2,6° (intervalo de confianza al 95%: 2,8-3,8°) en proyección anteroposterior y de 5,5 ± 3,9° (intervalo de confianza: 4,7-6,3°) en proyección lateral. Cuando se consideró para cada paciente, la diferencia media de esta relación angular entre las tibias derechas e izquierdas fue inferior a 0,5° en ambas proyecciones.The angular relationship between proximal and distal articular surfaces was determined, through an Oxford Cobbometer, in 108 tibiae of 54 asymptomalic patients aging 14 to 72 years (mean: 30). Mean angle between both surfaces was 3.3 ± 2.6° (95% confidence interval: 2.8-3.8°) for the anteroposterior view and 5.5 ± 3.9° (95% confidence interval: 4.7-6.3°) for the lateral view. When considered individually for each patient, mean difference of this angular relationship among right and left tibiae was lesser than 0.5° for both projections

Cuidados na manutenção em estufas.

bitstream/CNPDIA/10219/1/RT11_98.pd

Ward identities for the Anderson impurity model: derivation via functional methods and the exact renormalization group

Using functional methods and the exact renormalization group we derive Ward identities for the Anderson impurity model. In particular, we present a non-perturbative proof of the Yamada-Yosida identities relating certain coefficients in the low-energy expansion of the self-energy to thermodynamic particle number and spin susceptibilities of the impurity. Our proof underlines the relation of the Yamada-Yosida identities to the U(1) x U(1) symmetry associated with particle number and spin conservation in a magnetic field.Comment: 8 pages, corrected statements about infintite flatband limi