In this work we show how by using a Padé type analytical continuation scheme, based on the Schlessinger point method, it is possible to find higher production thresholds in hadron physical problems. ...Recently, an extension of this numerical approach to the complex energy plane enabled the calculations of auto-ionization decay resonance poles in atomic and molecular systems. Here we use this so-called Resonances via Padé (RVP) method, to show its convergence beyond the singular point in hadron physical problems. In order to demonstrate the capabilities of the RVP method, two illustrations for the ability to identify singularities and branch points are given. In addition, two applications for hadron physical problems are given. In the first one, we identify the decay thresholds from a numerically calculated spectral function. In the second one, we use experimental data. First, we calculate the resonance pole of the f0(500) or σ meson using the S0 partial wave amplitude for ππ scattering in very good agreement with the literature. Second, we use data on the cross section ratio R(s) for e+e− collisions and discuss the prediction of decay thresholds which proves to be difficult if the data is noisy.
Within the proper-time renormalization group approach, the chiral phase diagram of a two-flavor quark–meson model is studied. In the chiral limit, the location of the tricritical point which is ...linked to a Gaussian fixed point, is determined. For quark chemical potentials smaller than the tricritical one the second-order phase transition belongs to the
O
(
4
)
universality class. For temperatures below the tricritical one we find initially a weak first-order phase transition which is commonly seen in model studies and also in recent lattice simulations. In addition, below temperatures of
T
≲
17
MeV
we find two phase transitions. The chiral restoration transition is initially also of first-order but turns into a second-order transition again. This leads to the possibility that there may be a “second tricritical” point in the QCD phase diagram in the chiral limit.
Phase structure of the Polyakov-quark-meson model Schaefer, B.-J.; Pawlowski, J. M.; Wambach, J.
Physical review. D, Particles, fields, gravitation, and cosmology,
10/2007, Letnik:
76, Številka:
7
Journal Article
The formation of inhomogeneous chiral condensates in QCD matter at nonzero density and temperature is investigated for the first time with Dyson–Schwinger equations. We consider two massless quark ...flavors in a so-called chiral density wave, where scalar and pseudoscalar quark condensates vary sinusoidally along one spatial dimension. We find that the inhomogeneous region covers the major part of the spinodal region of the first-order phase transition which is present when the analysis is restricted to homogeneous phases. The triple point where the inhomogeneous phase meets the homogeneous phases with broken and restored chiral symmetry, respectively, coincides, within numerical accuracy, with the critical point of the homogeneous calculation. At zero temperature, the inhomogeneous phase seems to extend to arbitrarily high chemical potentials, as long as pairing effects are not taken into account.
The knowledge and skills expected for board certification in Neonatal-Perinatal Medicine (NPM) should reflect the clinical practice of neonatology. First, a 14-member panel of practicing ...neonatologists, convened by the American Board of Pediatrics (ABP), drafted a practice analysis document which identified the practice domains, tasks, knowledge, and skills deemed essential for clinical practice. NPM fellowship program directors provided feedback via online survey resulting in revisions to the document. During the second phase of the project, the panel organized testable knowledge areas into content domains and subdomains to update the existing ABP NPM content outline. All ABP board-certified neonatologists were asked to review via online survey, and results were used to guide final revisions to the content outline. The NPM practice analysis document and the updated NPM content outline should serve as helpful resources for educators, trainees, and practicing neonatologists.
Convergence properties of Taylor expansions of observables, which are also used in lattice QCD calculations at non-zero chemical potential, are analyzed in an effective Nf=2+1 flavor Polyakov ...quark–meson model. A recently developed algorithmic technique allows the calculation of higher-order Taylor expansion coefficients in functional approaches. This novel technique is for the first time applied to an effective Nf=2+1 flavor Polyakov quark–meson model and the findings are compared with the full model solution at finite densities. The results are used to discuss prospects for locating the QCD phase boundary and a possible critical endpoint in the phase diagram.
We present experimental results for the density of states (DOS) of a superconducting microwave Dirac billiard which serves as an idealized model for the electronic properties of graphene. The DOS ...exhibits two sharp peaks which evolve into van Hove singularities with increasing system size. They divide the band structure into regions governed by the relativistic Dirac equation and by the nonrelativistic Schrodinger equation, respectively. We demonstrate that in the thermodynamic limit, a topological transition appears as a neck-disrupting Lifshitz transition in the number susceptibility and as an excited-state transition in the electronic excitations. Furthermore, we recover the finite-size scaling typical for excited-state quantum phase transitions involving logarithmic divergences and identify a quasiorder parameter.
.
To complete earlier studies of the properties of the electric pygmy dipole resonance (PDR) obtained in various nuclear reactions, the excitation of the 1
-
states in
140
Ce by
(
e
,
e
)
scattering ...for momentum transfers
q
=
0
.
1
--
1
.
2
fm
-1
is calculated within the plane-wave and distorted-wave Born approximations. The excited states of the nucleus are described within the Quasiparticle Random Phase Approximation (QRPA), but also within the Quasiparticle-Phonon Model (QPM) by accounting for the coupling to complex configurations. It is demonstrated that the excitation mechanism of the PDR states in
(
e
,
e
)
reactions is predominantly of transversal nature for scattering angles
θ
e
≈
90
∘
--
180
∘
. Being thus mediated by the convection and spin nuclear currents, the
(
e
,
e
)
like the
(
γ
,
γ
)
reaction, may provide additional information to the one obtained from Coulomb and hadronic excitations of the PDR in
(
p
,
p
)
,
(
α
,
α
)
, and heavy-ion scattering reactions. The calculations predict that the
(
e
,
e
)
cross sections for the strongest individual PDR states are in general about three orders of magnitude smaller as compared to the one of the lowest 2
+
1
state for the studied kinematics, but that they may become dominant at extreme backward angles.
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