11,928 research outputs found
Geometric classical and total correlations via trace distance
We introduce the concepts of geometric classical and total correlations
through Schatten 1-norm (trace norm), which is the only Schatten p-norm able to
ensure a well-defined geometric measure of correlations. In particular, we
derive the analytical expressions for the case of two-qubit Bell-diagonal
states, discussing the superadditivity of geometric correlations. As an
illustration, we compare our results with the entropic correlations, discussing
both their hierarchy and monotonicity properties. Moreover, we apply the
geometric correlations to investigate the ground state of spin chains in the
thermodynamic limit. In contrast to the entropic quantifiers, we show that the
classical correlation is the only source of 1-norm geometric correlation that
is able to signaling an infinite-order quantum phase transition.Comment: v2: published versio
Hadrons in AdS/QCD models
We discuss applications of gauge/gravity duality to describe the spectrum of
light hadrons. We compare two particular 5-dimensional approaches: a model with
an infrared deformed Anti-de Sitter metric and another one based on a dynamical
AdS/QCD framework with back-reacted geometry in a dilaton/gravity background.
The models break softly the scale invariance in the infrared region and allow
mass gap for the field excitations in the gravity description, while keeping
the conformal property of the metric close to the four-dimensional boundary.
The models provide linear Regge trajectories for light mesons, associated with
specially designed infrared gravity properties. We also review the results for
the decay widths of the f0's into two pions, as overlap integrals between
mesonic string amplitudes, which are in qualitative agreement with data
Dark/Visible Parallel Universes and Big Bang Nucleosynthesis
We develop a model for visible matter-dark matter interaction based on the
exchange of a massive gray boson called herein the Mulato. Our model hinges on
the assumption that all known particles in the visible matter have their
counterparts in the dark matter. We postulate six families of particles five of
which are dark. This leads to the unavoidable postulation of six parallel
worlds, the visible one and five invisible worlds. A close study of big bang
nucleosynthesis (BBN), baryon asymmetries, cosmic microwave background (CMB)
bounds, galaxy dynamics, together with the Standard Model assumptions, help us
to set a limit on the mass and width of the new gauge boson. Modification of
the statistics underlying the kinetic energy distribution of particles during
the BBN is also discussed. The changes in reaction rates during the BBN due to
a departure from the Debye-Hueckel electron screening model is also
investigated.Comment: Invited talk at the Workshops "CompStar: the physics and astrophysics
of compact stars", Tahiti, June 4-8, 2012, "New Directions in Nuclear
Astrophysics", Castiglion Fiorentino, Italy, June 18-22, 2012, and
"Carpathian Summer School of Physics", Sinaia, Romania, June 24 - July 7,
2012. To be published in AIP Proceeding
Irrigation cutoff on 'BRS Clara' seedless grapevines during berry ripening stage.
The seedless table grape cultivar 'BRS Clara' (Vitis vinifera L.) presents yellowish-green berries and was developed for growing in tropical regions. In Brazilian tropical areas irrigation is usually an essential tool. Irrigation cutoff during berry ripening stage is sometimes adopted by grape growers to reduce water application and to increase water use efficiency. This study aimed to evaluate the response of 'BRS Clara' grapevines to irrigation cutoff during ripening stage. The experiment was carried out in Jales, SP, Brazil (20º16'S, 50º33'W, 483m), from June to October 2010, using ?BRS Clara? plants grafted on ?IAC-572? and conducted in a overhead trellis system. The vineyard was irrigated by microsprinklers and covered with polyethylene screen, that is a common practice in the region to protect the grapes against bat and bird attacks. The soil moisture conditions were monitored employing tensiometers installed at 15 cm and 45 cm deep. The experimental design was completely randomized with two treatments, with irrigation (CI) and without irrigation (SI) during fruit ripening. Production and fruit quality variables were evaluated including berry and bunch mass, yield per plant, diameter and length of berries, soluble solids and titratable acidity. There was no difference between treatments for all parameters evaluated. In irrigation treatment (CI) it was applied 41.9 mm during the ripening period, representing 16.1% of total irrigation. The soil water potential in the CI treatment stayed near field capacity, whereas the treatment without irrigation (SI) showed a decrease trend during part of the period, reaching values closed to 70kPa. This reduction did not affect subsequent culture performance. It must be considered, however, that rainfall occurrence was registered since the last week of September and during October, rewetting the soil and approaching the soil water potential values in both treatments.Resumo expandido apresentado no 18º Simpósio Internacional GiESCO, 7 a 11 de julho de 2013, Porto
Non-Markovianity through entropy-based quantum thermodynamics
We introduce a generalized approach to characterize the non-Markovianity of
quantum dynamical maps via breakdown of monotonicity of thermodynamic
functions. By adopting an entropy-based formulation of quantum thermodynamics,
we use the relationship between heat and entropy to propose a measure of
non-Markovianity based on the heat flow for single-qubit quantum evolutions.
This measure can be applied for unital dynamical maps that do not invert the
sign of the internal energy. Under certain conditions, it can also be extended
for other thermodynamic functions, such as internal energy and work flows. In
this context, a natural connection between heat and quantum coherence can be
identified for dynamical maps that are both unital and incoherent. As
applications, we explore dissipative and non-dissipative quantum dynamical
processes, illustrating the compatibility between our thermodynamic quantifiers
and the well-establish measure defined via quantum coherence.Comment: 7 pages, 3 figure
Vortex and gap generation in gauge models of graphene
Effective quantum field theoretical continuum models for graphene are
investigated. The models include a complex scalar field and a vector gauge
field. Different gauge theories are considered and their gap patterns for the
scalar, vector, and fermion excitations are investigated. Different gauge
groups lead to different relations between the gaps, which can be used to
experimentally distinguish the gauge theories. In this class of models the
fermionic gap is a dynamic quantity. The finite-energy vortex solutions of the
gauge models have the flux of the "magnetic field" quantized, making the
Bohm-Aharonov effect active even when external electromagnetic fields are
absent. The flux comes proportional to the scalar field angular momentum
quantum number. The zero modes of the Dirac equation show that the gauge models
considered here are compatible with fractionalization
Does human milk composition predict later risk of obesity? A systematic review
BACKGROUND: Possible mechanisms behind the association of breastfeeding with a lower risk of later obesity are unknown but one possibility is the unique composition of human milk. Here, we systematically reviewed the evidence linking breast-milk macronutrient and hormonal composition with later obesity. METHODS: We searched 7 databases for studies that included infants predominantly breast-fed for the first 3 months and which analysed associations between a measure of breast-milk composition and later (> 6 months) measures of obesity or body composition. RESULTS: 47 publications were identified for full-text screening, of which 10 were eligible and only 3 found significant associations. Higher leptin concentration in breast milk at age 1 month was associated with lower infant BMI at 12, 18 and 24 months of age (1 study). Higher breast-milk adiponectin concentration at 6 weeks and 4 months were associated with adiposity at age 12 and 24 months (1 study). In 1 study, breast-milk carbohydrate content was positively associated, and fat content negatively associated, with adiposity at age 12 months. No significant associations were found between other hormones or macronutrients in human milk and later risk of obesity or body composition. CONCLUSIONS: The evidence linking breast-milk composition with later obesity was inconsistent and confined to single, individual studies. Our review highlights the methodological limitations of previous studies and the need for further research in this area
A consistent scalar-tensor cosmology for inflation, dark energy and the Hubble parameter
The authors are grateful for financial support to the Cruickshank Trust (CW), EPSRC/GG-Top (CW, JR), Omani Government (MA), Science Without Borders programme, CNPq, Brazil (DR), and STFC/CfFP (CW, AM, RB, JM). CW and AM acknowledge the hospitality of CERN, where this work was started. The University of Aberdeen and University of Edinburgh are charitable bodies registered in Scotland, with respective registration numbers SC013683 and SC005336.Peer reviewedPostprin
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