19,331 research outputs found
Interplay between chiral and axial symmetries in a SU(2) Nambu--Jona-Lasinio Model with the Polyakov loop
We consider a two flavor Polyakov--Nambu--Jona-Lasinio (PNJL) model where the
Lagrangian includes an interaction term that explicitly breaks the U
anomaly. At finite temperature, the restoration of chiral and axial symmetries,
signaled by the behavior of several observables, is investigated. We compare
the effects of two regularizations at finite temperature, one of them, that
allows high momentum quarks states, leading to the full recovery of chiral
symmetry. From the analysis of the behavior of the topological susceptibility
and of the mesonic masses of the axial partners, it is found in the SU(2) model
that, unlike the SU(3) results, the recovery of the axial symmetry is not a
consequence of the full recovery of the chiral symmetry. Thus, one needs to use
an additional idea, by means of a temperature dependence of the anomaly
coefficient, that simulates instanton suppression effects.Comment: 21 pages, 5 figures; PRD versio
Influence of the external pressure on the quantum correlations of molecular magnets
The study of quantum correlations in solid state systems is a large avenue
for research and their detection and manipulation are an actual challenge to
overcome. In this context, we show by using first-principles calculations on
the prototype material KNaCuSiO that the degree of quantum
correlations in this spin cluster system can be managed by external hydrostatic
pressure. Our results open the doors for research in detection and manipulation
of quantum correlations in magnetic systems with promising applications in
quantum information science
Adubação de pastagens
Análise de solo; Recomendação de correção do solo e adubação; Sistemas de produção e estratégicas de adubação
Observational Constraints on Visser's Cosmological Model
Theories of gravity for which gravitons can be treated as massive particles
have presently been studied as realistic modifications of General Relativity,
and can be tested with cosmological observations. In this work, we study the
ability of a recently proposed theory with massive gravitons, the so-called
Visser theory, to explain the measurements of luminosity distance from the
Union2 compilation, the most recent Type-Ia Supernovae (SNe Ia) dataset,
adopting the current ratio of the total density of non-relativistic matter to
the critical density () as a free parameter. We also combine the SNe
Ia data with constraints from Baryon Acoustic Oscillations (BAO) and CMB
measurements. We find that, for the allowed interval of values for ,
a model based on Visser's theory can produce an accelerated expansion period
without any dark energy component, but the combined analysis (SNe Ia + BAO +
CMB) shows that the model is disfavored when compared with CDM model.Comment: 6 pages, 4 figure
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