1,846 research outputs found
On the phase structure and thermodynamics of QCD
We discuss the phase structure and thermodynamics of QCD by means of
dynamical chiral effective models. Quark and meson fluctuations are included
via the functional renormalization group. We study the influence of confinement
in addition to the impact of fluctuations by comparing the results of the
chiral models to their Polyakov-loop extended versions. Furthermore, we discuss
the mass sensitivity of the phase structure and thermodynamics and find
interesting modifications close to the chiral limit.Comment: 13 pages, 11 figures; Appendix added; published versio
Role-similarity based functional prediction in networked systems: Application to the yeast proteome
We propose a general method to predict functions of vertices where: 1. The
wiring of the network is somehow related to the vertex functionality. 2. A
fraction of the vertices are functionally classified. The method is influenced
by role-similarity measures of social network analysis. The two versions of our
prediction scheme is tested on model networks were the functions of the
vertices are designed to match their network surroundings. We also apply these
methods to the proteome of the yeast Saccharomyces cerevisiae and find the
results compatible with more specialized methods
Landau gauge Yang-Mills correlation functions
We investigate Landau gauge Yang-Mills theory in a systematic vertex
expansion scheme for the effective action with the functional renormalisation
group. Particular focus is put on the dynamical creation of the gluon mass gap
at non-perturbative momenta and the consistent treatment of quadratic
divergences. The non-perturbative ghost and transverse gluon propagators as
well as the momentum-dependent ghost-gluon, three-gluon and four-gluon vertices
are calculated self-consistently with the classical action as only input. The
apparent convergence of the expansion scheme is discussed and within the
errors, our numerical results are in quantitative agreement with available
lattice results.Comment: 20 pages, 13 figure
Exploring the Phase Structure and Thermodynamics of QCD
We put forward a Polyakov-loop extended quark meson model, where matter as
well as glue fluctuations are taken into account, cf. [1]. The latter are
included via a Polyakov-loop potential. Usually such a glue potential is based
on Yang-Mills lattice data only. We show that a parametrisation of unquenching
effects as proposed in [2], together with the inclusion of fluctuations via the
functional renormalisation group [3,4], accounts for the relevant dynamics.
This is demonstrated by a comparison of order parameters and thermodynamic
observables to recent lattice results at vanishing chemical potential, where we
find very good agreement.Comment: 11 pages, 2 figures, contribution to "QCD-TNT-III: From quarks and
gluons to hadronic matter: A bridge too far?", ECT*, Trento (Italy),
September 2-6, 201
Sarma phase in relativistic and non-relativistic systems
We investigate the stability of the Sarma phase in two-component fermion
systems in three spatial dimensions. For this purpose we compare
strongly-correlated systems with either relativistic or non-relativistic
dispersion relation: relativistic quarks and mesons at finite isospin density
and spin-imbalanced ultracold Fermi gases. Using a Functional Renormalization
Group approach, we resolve fluctuation effects onto the corresponding phase
diagrams beyond the mean-field approximation. We find that fluctuations induce
a second order phase transition at zero temperature, and thus a Sarma phase, in
the relativistic setup for large isospin chemical potential. This motivates the
investigation of the cold atoms setup with comparable mean-field phase
structure, where the Sarma phase could then be realized in experiment. However,
for the non-relativistic system we find the stability region of the Sarma phase
to be smaller than the one predicted from mean-field theory. It is limited to
the BEC side of the phase diagram, and the unitary Fermi gas does not support a
Sarma phase at zero temperature. Finally, we propose an ultracold quantum gas
with four fermion species that has a good chance to realize a zero-temperature
Sarma phase.Comment: version published in Phys.Lett.B; 10 pages, 5 figure
Developing a Yeast Model of Amyotrophic Lateral Sclerosis Involving the SOD1 Gene
Amyotrophic lateral sclerosis (ALS), one of the most common neuromuscular diseases in the world, is an unremittingly progressive disease that degenerates motor neurons in the brain and spinal cord. Roughly 10% of ALS cases are considered familial and can result from mutations in more than dozen different genes. The most common mutations in familial ALS occur in the SOD1 gene. SOD1 encodes a copper-zinc superoxide dismutase that detoxifies oxygen free radicals. To date, approximately 140 mutations in SOD1 (many of which are missense) have been linked to familial ALS. Evidence suggests that these mutations induce SOD1 protein misfolding and aggregation into cytotoxic structures. We are developing a yeast model of ALS based on the expression of mutant human SOD1 proteins. Such a yeast system will permit high throughput genetic screens to identify genes that enhance or suppress the toxic phenotypes associated with mutant SOD1 expression (thereby identifying critical supporting or suppressing pathways), as well as chemical screens to identify compounds that inhibit mutant SOD1 toxicit
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