18,221 research outputs found
Comments on Anomaly Cancellations by Pole Subtractions and Ghost Instabilities with Gravity
We investigate some aspects of anomaly cancellation realized by the
subtraction of an anomaly pole, stressing on some of its properties in
superspace. In a local formulation these subtractions can be described in terms
of a physical scalar, an axion and related ghosts. They appear to be necessary
for the unitarization of the theory in the ultraviolet, but they may generate
an infrared instability of the corresponding effective action, signalled by
ghost condensation. In particular the subtraction of the superanomaly multiplet
by a pole in superspace is of dubious significance, due to the different nature
of the chiral and conformal anomalies. In turn, this may set more stringent
constraints on the coupling of supersymmetric theories to gravity.Comment: 18 pages. Revised version. To appear in "Classical and Quantum
Gravity
A Bit-String Model for Biological Aging
We present a simple model for biological aging. We studied it through
computer simulations and we have found this model to reflect some features of
real populations.Comment: LaTeX file, 4 PS figures include
Ecosystem respiration: Drivers of daily variability and background respiration in lakes around the globe
We assembled data from a global network of automated lake observatories to test hypotheses regarding the drivers of ecosystem metabolism. We estimated daily rates of respiration and gross primary production (GPP) for up to a full year in each lake, via maximum likelihood fits of a free‐water metabolism model to continuous high‐frequency measurements of dissolved oxygen concentrations. Uncertainties were determined by a bootstrap analysis, allowing lake‐days with poorly constrained rate estimates to be down‐weighted in subsequent analyses. GPP and respiration varied considerably among lakes and at seasonal and daily timescales. Mean annual GPP and respiration ranged from 0.1 to 5.0 mg O2 L−1 d−1 and were positively related to total phosphorus but not dissolved organic carbon concentration. Within lakes, significant day‐to‐day differences in respiration were common despite large uncertainties in estimated rates on some lake‐days. Daily variation in GPP explained 5% to 85% of the daily variation in respiration after temperature correction. Respiration was tightly coupled to GPP at a daily scale in oligotrophic and dystrophic lakes, and more weakly coupled in mesotrophic and eutrophic lakes. Background respiration ranged from 0.017 to 2.1 mg O2 L−1 d−1 and was positively related to indicators of recalcitrant allochthonous and autochthonous organic matter loads, but was not clearly related to an indicator of the quality of allochthonous organic matter inputs
A Comparison of Exclusion and Trial-and-Error Procedures: Primary and Secondary Effects
Results of a study that compared exclusion and trial-and-error procedures in children with intellectual disabilities
Entanglement and localization in long-range quadratic Lindbladians
Existence of Anderson localization is considered a manifestation of coherence
of classical and quantum waves in disordered systems. Signatures of
localization have been observed in condensed matter and cold atomic systems
where the coupling to the environment can be significantly suppressed but not
eliminated. In this work we explore the phenomena of localization in random
Lindbladian dynamics describing open quantum systems. We propose a model of
one-dimensional chain of non-interacting, spinless fermions coupled to a local
ensemble of baths. The jump operator mediating the interaction with the bath
linked to each site has a power-law tail with an exponent . We show that the
steady state of the system undergoes a localization entanglement phase
transition by tuning which remains stable in the presence of coherent
hopping. Unlike the entanglement transition in the quantum trajectories of open
systems, this transition is exhibited by the averaged steady state density
matrix of the Lindbladian. The steady state in the localized phase is
characterised by a heterogeneity in local population imbalance, while the jump
operators exhibit a constant participation ratio of the sites they affect. Our
work provides a novel realisation of localization physics in open quantum
systems.Comment: 12 pages and 13 figure
Editorial: Congenital and perinatal infections: How to prevent sequelaes in neonates and children
The current severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) pandemic has overwhelmingly absorbed attention and health resources for 2 years, allowing us to reflect that infections are a permanent health and social problem, causing morbidity and mortality. They require organization, important prevention measures, and containment. This is particularly true in the neonatal age, where infections remain a complex problem with serious consequences
Observation and theoretical description of the pure Fano-effect in the valence-band photo-emission of ferromagnets
The pure Fano-effect in angle-integrated valence-band photo-emission of
ferromagnets has been observed for the first time. A contribution of the
intrinsic spin polarization to the spin polarization of the photo-electrons has
been avoided by an appropriate choice of the experimental parameters. The
theoretical description of the resulting spectra reveals a complete analogy to
the Fano-effect observed before for paramagnetic transition metals. While the
theoretical photo-current and spin difference spectra are found in good
quantitative agreement with experiment in the case of Fe and Co only a
qualitative agreement could be achieved in the case of Ni by calculations on
the basis of plain local spin density approximation (LSDA). Agreement with
experimental data could be improved in this case in a very substantial way by a
treatment of correlation effects on the basis of dynamical mean field theory
(DMFT).Comment: 11 pages, 3 figures accepted by PR
ANÁLISE COMPORTAMENTAL DA APRENDIZAGEM DE LEITURA E ESCRITA
This article presents the conceptual approach of behavior analysis applied to reading and spelling. It covers the heorethical view of reading and spelling in terms of stimulus control over verbal behavior and equivalence relations. he work also makes a review (not intending to be exhaustive) of research on reading and spelling based on this approach.Key-words: behavioral analysis, verbal behavior, reading, spellingEste artigo apresenta uma revisão da aprendizagem de leitura e escrita de acordo com a abordagem da Análise o Comportamento. O artigo trata da análise conceitual da leitura e escrita em termos de controle de estímulos sobre comportamento verbal e de redes de relações de equivalência. O trabalho faz também uma revisão, sem pretender xaurir o assunto, de pesquisas sobre leitura e escrita com base nesta abordagem.Palavras-chave: análise do comportamento, comportamento verbal, leitura, escrit
- …