50 research outputs found
Pion and kaon condensation in a 3-flavor NJL model
We analyze the phase diagram of a three-flavor Nambu-Jona-Lasinio model at
finite temperature and chemical potentials . We study
the competition of pion and kaon condensation and we propose a physical
situation in which kaon condensation could be led only by light quark finite
densities.Comment: 21 pages, 8 figures include
Quark coalescence based on a transport equation
We employ the Boltzmann equation for describing hadron production from a
quark-gluon plasma (QGP) in ultrarelativistic heavy-ion collisions. We propose
resonance formation in quark-antiquark scattering as the dominant
meson-production channel, which, in particular, ensures that energy is
conserved in the recombination process. This, in turn, facilitates a more
controlled extension of hadronization to low transverse momenta (), and to
address the experimentally observed transition from a hydrodynamic regime to
constituent quark-number scaling (CQNS). Based on input distributions for
strange and charm quarks with azimuthal asymmetries, , characteristic
for RHIC energies, we recover CQNS at sufficiently high , while at low
a scaling with transverse kinetic energy is found, reminiscent to
experiment. The dependence of the transition regime on microscopic QGP
properties, i.e. resonance widths and -values in the
process, is elucidated.Comment: 7 pages, 6 figure
A NJL-based study of the QCD critical line
We employ a 3 flavor NJL model to stress some general remarks about the QCD
critical line. The dependence of the critical curve on
and is discussed. The quark masses are varied to
confirm that, in agreement with universality arguments, the order of transition
depends on the number of active flavors . The slope of the critical curve
vs. chemical potential is studied as a function of . We compare our
results with those recently obtained in lattice simulations to establish a
comparison among different models.Comment: 17 pages, 5 figure
QCD in One Dimension at Nonzero Chemical Potential
Using an integration formula recently derived by Conrey, Farmer and
Zirnbauer, we calculate the expectation value of the phase factor of the
fermion determinant for the staggered lattice QCD action in one dimension. We
show that the chemical potential can be absorbed into the quark masses; the
theory is in the same chiral symmetry class as QCD in three dimensions at zero
chemical potential. In the limit of a large number of colors and fixed number
of lattice points, chiral symmetry is broken spontaneously, and our results are
in agreement with expressions based on a chiral Lagrangian. In this limit, the
eigenvalues of the Dirac operator are correlated according to random matrix
theory for QCD in three dimensions. The discontinuity of the chiral condensate
is due to an alternative to the Banks-Casher formula recently discovered for
QCD in four dimensions at nonzero chemical potential. The effect of temperature
on the average phase factor is discussed in a schematic random matrix model.Comment: Latex, 23 pages and 5 figures; Added two references and corrected
several typo
Resonance Recombination Model and Quark Distribution Functions in the Quark-Gluon Plasma
We investigate the consequences of space-momentum correlations in quark
phase-space distributions for coalescence processes at the hadronization
transition. Thus far it has been proved difficult to reconcile such
correlations with the empirically observed constituent quark number scaling
(CQNS) at the Relativistic Heavy-Ion Collider (RHIC). To address this problem
we combine our earlier developed quark recombination model with quark
phase-space distributions computed from relativistic Langevin simulations in an
expanding Quark-Gluon Plasma (QGP). Hadronization is based on resonance
formation within a Boltzmann equation which recovers thermal equilibrium and
obeys energy conservation in the quark-coalescence process, while the fireball
background is adjusted to hydrodynamic simulations of semi-central Au-Au
collisions at RHIC. To facilitate the applicability of the Langevin process, we
focus on strange and charm quarks. Their interactions in the QGP are modeled
using leading-order perturbative QCD augmented by effective Lagrangians with
resonances which smoothly merge into hadronic states formed at T_c. The
interaction strength is adjusted to reproduce the empirical saturation value
for the quark-elliptic flow, v_{2,q}^{sat}~7-8%. The resulting phi and J/\psi
elliptic flow recover CQNS over a large range in transverse momentum (p_T)
within a few percent. As a function of transverse kinetic energy, both the
quark spectra from the Langevin simulations and the meson spectra generated via
resonance recombination recover CQNS from zero to at least 3 GeV.Comment: 10 pages, 6 figures; v2: modified title, light-quark results taken
out, version accepted for publication in PR
Ladder-QCD at finite isospin chemical potential
We use an effective QCD model (ladder-QCD) to explore the phase diagram for
chiral symmetry breaking and restoration at finite temperature with different
quark chemical potentials. In agreement with a recent investigation based
on the Nambu-Jona-Lasinio model, we find that a finite pion condensate shows up
for high enough isospin chemical potential . For
small the phase diagram in the plane shows two first
order transition lines and two critical ending points.Comment: Typed in RevTex4, pages 12, figures 2. Two references adde
Native Study of the Behaviour of Magnetite Nanoparticles for Hyperthermia Treatment during the Initial Moments of Intravenous Administration
Magnetic nanoparticles (MNPs) present outstanding properties making them suitable
as therapeutic agents for hyperthermia treatments. Since the main safety concerns of MNPs are
represented by their inherent instability in a biological medium, strategies to both achieve longterm stability and monitor hazardous MNP degradation are needed. We combined a dynamic
approach relying on flow field flow fractionation (FFF)-multidetection with conventional techniques
to explore frame-by-frame changes of MNPs injected in simulated biological medium, hypothesize
the interaction mechanism they are subject to when surrounded by a saline, protein-rich environment,
and understand their behaviour at the most critical point of intravenous administration. In the first
moments of MNPs administration in the patient, MNPs change their surrounding from a favorable
to an unfavorable medium, i.e., a complex biological fluid such as blood; the particles evolve
from a synthetic identity to a biological identity, a transition that needs to be carefully monitored.
The dynamic approach presented herein represents an optimal alternative to conventional batch
techniques that can monitor only size, shape, surface charge, and aggregation phenomena as an
averaged information, given that they cannot resolve different populations present in the sample
and cannot give accurate information about the evolution or temporary instability of MNPs. The
designed FFF method equipped with a multidetection system enabled the separation of the particle
populations providing selective information on their morphological evolution and on nanoparticle–
proteins interaction in the very first steps of infusion. Results showed that in a dynamic biological
setting and following interaction with serum albumin, PP-MNPs retain their colloidal properties,
supporting their safety profile for intravenous administration
Occupational risk of nano-biomaterials: Assessment of nano-enabled magnetite contrast agent using the BIORIMA Decision Support System
The assessment of the safety of nano-biomedical products for patients is an essential prerequisite for their market authorization. However, it is also required to ensure the safety of the workers who may be unintentionally exposed to the nano-biomaterials (NBMs) in these medical applications during their synthesis, formulation into products and end-of-life processing and also of the medical professionals (e.g., nurses, doctors, dentists) using the products for treating patients. There is only a handful of workplace risk assessments focussing on NBMs used in medical applications. Our goal is to contribute to increasing the knowledge in this area by assessing the occupational risks of magnetite (Fe3O4) nanoparticles coated with PLGA-b-PEG-COOH used as contrast agent in magnetic resonance imaging (MRI) by applying the software-based Decision Support System (DSS) which was developed in the EU H2020 project BIORIMA. The occupational risk assessment was performed according to regulatory requirements and using state-of-the-art models for hazard and exposure assessment, which are part of the DSS. Exposure scenarios for each life cycle stage were developed using data from literature, inputs from partnering industries and results of a questionnaire distributed to healthcare professionals, i.e., physicians, nurses, technicians working with contrast agents for MRI. Exposure concentrations were obtained either from predictive exposure models or monitoring campaigns designed specifically for this study. Derived No-Effect Levels (DNELs) were calculated by means of the APROBA tool starting from in vivo hazard data from literature. The exposure estimates/measurements and the DNELs were used to perform probabilistic risk characterisation for the formulated exposure scenarios, including uncertainty analysis. The obtained results revealed negligible risks for workers along the life cycle of magnetite NBMs used as contrast agent for the diagnosis of tumour cells in all exposure scenarios except in one when risk is considered acceptable after the adoption of specific risk management measures. The study also demonstrated the added value of using the BIORIMA DSS for quantification and communication of occupational risks of nano-biomedical applications and the associated uncertainties
A calculation of the QCD phase diagram at finite temperature, and baryon and isospin chemical potentials
We study the phases of a two-flavor Nambu-Jona-Lasinio model at finite
temperature , baryon and isospin chemical potentials:
, . This study
completes a previous analysis where only small isospin chemical potentials
were consideredComment: 21 pages, 13 figures included, two more refernces adde
Degenerate distributions in complex Langevin dynamics: one-dimensional QCD at finite chemical potential
We demonstrate analytically that complex Langevin dynamics can solve the sign
problem in one-dimensional QCD in the thermodynamic limit. In particular, it is
shown that the contributions from the complex and highly oscillating spectral
density of the Dirac operator to the chiral condensate are taken into account
correctly. We find an infinite number of classical fixed points of the Langevin
flow in the thermodynamic limit. The correct solution originates from a
continuum of degenerate distributions in the complexified space.Comment: 20 pages, several eps figures, minor comments added, to appear in
JHE