6,227 research outputs found
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 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
Measurements relationship among compost bedded pack barn farms in six European countries during the winter and spring season
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
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
- …