21,527 research outputs found
Gluon and Ghost Dynamics from Lattice QCD
The two point gluon and ghost correlation functions and the three gluon
vertex are investigated, in the Landau gauge, using lattice simulations. For
the two point functions, we discuss the approach to the continuum limit looking
at the dependence on the lattice spacing and volume. The analytical structure
of the propagators is also investigated by computing the corresponding spectral
functions using an implementation of the Tikhonov regularisation to solve the
integral equation. For the three point function we report results when the
momentum of one of the gluon lines is set to zero and discuss its implications.Comment: Proceedings of Light Cone 2016, held in Lisbon, September 2016. Minor
changes in text. To appear in Few B Sy
The gluon propagator from large asymmetric lattices
The Landau-gauge gluon propagator is computed for the SU(3) gauge theory on
lattices up to a size of . We use the standard Wilson action
at and compare our results with previous computations using large
asymmetric and symmetric lattices. In particular, we focus on the impact of the
lattice geometry and momentum cuts to achieve compatibility between data from
symmetric and asymmetric lattices for a large range of momenta.Comment: Poster presented at Lattice2007, Regensburg, July 30 - August 4, 200
Some properties of two Nambu--Jona-Lasinio -type models with inputs from lattice QCD
We investigate the phase diagram of the so-called
Polyakov--Nambu--Jona-Lasinio (PNJL) model at finite temperature and nonzero
chemical potential. The calculations are performed in the light and strange
quark sectors (, , ), which includes the 't Hooft instanton induced
interaction term that breaks the axial symmetry, and the quarks are coupled to
the (spatially constant) temporal background gauge field. On one hand, a
special attention is payed to the critical end point (CEP). The strength of the
flavor-mixing interaction alters the CEP location, since when it becomes weaker
the CEP moves to low temperatures and can even disappear. On the other hand, we
also explore the connection between QCD, a nonlocal Nambu--Jona-Lasinio type
model and the Landau gauge gluon propagator. Possible links between the
quenched gluon propagator and low energy hadronic phenomenology are
investigated.Comment: Contribution to the International Meeting "Excited QCD", Peniche,
Portugal, 06 - 12 May 201
Does The Lattice Zero Momentum Gluon Propagator for Pure Gauge SU(3) Yang-Mills Theory Vanish in the Infinite Volume Limit?
The Cucchieri-Mendes bounds for the gluon propagator are discussed for the
four dimensional pure gauge SU(3) theory. Assuming a pure power law dependence
on the inverse of the lattice volume, the lattice data gives a vanishing zero
momentum gluon propagator in the infinite volume limit. Our investigation shows
that this result is robust against variations of the lattice volumes and
corrections to the power law. Moreover, it is consistent with the
Gribov-Zwanziger horizon condition and contradicts the SU(2) analysis, which
assumed the same type of dependence on the inverse of the volume. Our analysis
considers also more general ansatze that, although not conclusive, open the
possibility of having in the infinite volume limit. A solution to
this puzzle requires further investigations.Comment: Minor changes. Figures redone using a different axis variabl
Constraints on the IR behavior of the gluon propagator in Yang-Mills theories
We present rigorous upper and lower bounds for the zero-momentum gluon
propagator D(0) of Yang-Mills theories in terms of the average value of the
gluon field. This allows us to perform a controlled extrapolation of lattice
data to infinite volume, showing that the infrared limit of the Landau-gauge
gluon propagator in SU(2) gauge theory is finite and nonzero in three and in
four space-time dimensions. In the two-dimensional case we find D(0) = 0, in
agreement with Ref. [1]. We suggest an explanation for these results. We note
that our discussion is general, although we only apply our analysis to pure
gauge theory in Landau gauge. Simulations have been performed on the IBM
supercomputer at the University of Sao Paulo.Comment: 4 pages, 3 figures, 1 tabl
Quantum simulation of the Anderson Hamiltonian with an array of coupled nanoresonators: delocalization and thermalization effects
The possibility of using nanoelectromechanical systems as a simulation tool
for quantum many-body effects is explored. It is demonstrated that an array of
electrostatically coupled nanoresonators can effectively simulate the
Bose-Hubbard model without interactions, corresponding in the single-phonon
regime to the Anderson tight-binding model. Employing a density matrix
formalism for the system coupled to a bosonic thermal bath, we study the
interplay between disorder and thermalization, focusing on the delocalization
process. It is found that the phonon population remains localized for a long
time at low enough temperatures; with increasing temperatures the localization
is rapidly lost due to thermal pumping of excitations into the array, producing
in the equilibrium a fully thermalized system. Finally, we consider a possible
experimental design to measure the phonon population in the array by means of a
superconducting transmon qubit coupled to individual nanoresonators. We also
consider the possibility of using the proposed quantum simulator for realizing
continuous-time quantum walks.Comment: Replaced with new improved version. To appear in EPJ Q
Nitrogen compounds prevent H9c2 myoblast oxidative stress-induced mitochondrial dysfunction and cell death
Oxidative stress has been connected to various
forms of cardiovascular diseases. Previously, we have been
investigating the potential of new nitrogen-containing
synthetic compounds using a neuronal cell model and
different oxidative stress conditions in order to elucidate
their potential to ameliorate neurodegenerative diseases.
Here, we intended to extend these initial studies and
investigate the protective role of four of those new synthetic
compounds (FMA4, FMA7, FMA762 and FMA796)
against oxidative damage induced to H9c2 cardiomyoblasts
by tert-butylhydroperoxide (t-BHP). The data indicates that
FMA762 and FMA796 decrease t-BHP-induced cell death,
as measured by both sulforhodamine B assay and nuclear
chromatin condensation evaluation, at non-toxic concentrations.
In addition, the two mentioned compounds inhibit
intracellular signalling mechanisms leading to apoptotic
cell death, namely those mediated by mitochondria, which
was confirmed by their ability to overcome t-BHP-induced
morphological changes in the mitochondrial network, loss
of mitochondrial membrane potential, increased expression
of the pro-apoptotic proteins p53, Bax and AIF and activation
of caspases-3 and -9. Importantly, our results indicate
that the compounds’ ROS scavenging ability plays
a crucial role in the protection profile, as a significant
decrease in t-BHP-induced oxidative stress occurred in
their presence. Data obtained indicates that some of the test
compounds may clearly prove valuable in a clinical context
by diminishing cardiac injury associated to oxidative stress
without any toxicity.Fundação para a Ciência e a Tecnologia (FCT) - Bolsa SFRH/BD/17174/2004, PTDC/QUI/
64358/200
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