Speaker. Péter Pósfay Authors: P. Pósfay, G.G. Barnaföldi, A. Jakovác Abstract: Various studies shows the relelvance of bosonic quantum fluctuations at zero temperature and high chemical potential in the behaviour of nuclear matter [1]. We proposed a novel, more efficient technique to calculate the effect of bosonic quantum fluctuations using the Functional Renormalization Group (FRG) method . Within this framework we studied the effect of the running self interaction coupling in a simple effective model of nuclear matter and shown that how these changes manifest in the mass and radius of the resulting neutron stars [3]. The difference in results corresponding to different levels of approximation in the calculation of the bosonic fluctuations is also studied, and it is shown that different levels of approximation translates into 2-3% difference in neutron star observeables. These
 

In the talk I review the problem of quantum measurement theory from the point of view of quantum mechanics, quantum field theory and functional renormalization group. Using the quartic scalar model spontaneous symmetry breaking as a prototype of a measurement, I suggest an interpretation of the quantum measurement based on renormalization group perspective. I will also discuss some famous quantum measurements and paradoxes.
 

The excitation spectra of a Yukawa-theory with U_A(1)xU_V(1) symmetry is investigated with help of a Renormalisation Group analysis of its effective action in the first two approximations of the gradient expansion. The spectrum is computed in the phase of the spontanously broken U_A(1) symmetry. A focusing effect is discovered in the renormalisation flow, which leads to a unique prediction for the mass ratio in the boson sector. It is shown that this effect is due to the existence of a fixed point in the Local Potential Approximation, which is the first approximation in the gradient expansion of the effective action.
 

TBA
 

 

To study out-of-equilibrium effects on the evolution of heavy stars, we propose the following scenario: In the small volume somewhere within the low metallicity star we assume the species P, D, He_4 and photons to be in a local equilibrium characterized by the (high) temperature T and chemical potentials mu_P, mu_D, and mu_He4. The nuclear fusion reactions release hard (~5MeV) photons: P+D --> He_3+gamma. Photons are produced with reaction rate R_gamma and destroyed by pair production damping rate (using one photon from heat bath)R_D. The "balance" is reached at density of hard photons R_gamma/R_D. The hard photons significantly enhance the pressure above the equilibrium values. We try to answer the question: At which temperatures and particle densities does the above pressure enhancement produce observable effects? Could it influence the evolution and destiny of stars?
 

Properties of bound states obtained from the Dyson-Schwinger and Bethe-Salpeter equations can be reproduced within the Functional Renormalization Group via dynamical hadronization using sophisticated truncations. Preliminary results obtained in a low-energy QCD model, the Quark-Meson model, will be shown.
 

The Chiral Magnetic Effect (CME) and the related anomalous current is investigated using the real time Dirac-Heisenberg-Wigner formalism. This method is widely used for describing strong field physics and QED vacuum tunneling phenomena as well as pair production in heavy-ion collisions. We extend earlier investigations of the CME in constant flux tube configuration by considering time dependent fields. In this model we can follow the formation of axial charge separation, formation of axial current and then the emergence of the anomalous electric current. Qualitative results are shown for special field configurations that help to interpret the predictions of CME related effects in heavy-ion collisions at the RHIC Beam Energy Scan program.
 

In binary neutron star mergers the dynamical backcoupling of the electroweak interaction to the neutron matter is relevant. To desribe this, a coupled non-perturbative treatment of both sectors is necessary. Functional methods, like Bethe-Salpeter-Equations and the Functional-Renormalization-Group can be used for this purpose. Since the dominant process is beta-decay, a first necessary step is to describe the weak pion decay with these methods. We present how to implement this process in these functional methods, and provide first results of this description.
 

Our main goal is to give a comprehensive and detailed Monte Carlo study of the linear sigma model. Concerned topics are e.g. the order of the phase transition, the Linde-Weinberg bound, comparison to 2PI results for thermodynamic quantities and the question of triviality. We lay out the main pitfalls of solving the lattice model and discuss preliminary results.
 

 

Using multipoint Padé approximants, we investigate whether low energy effective model results could help in the process of analytic continuation from imaginary to real chemical potential of QCD lattice results for Tc.
 

 

Quantum theories are usually considered with a local potential. We can make them less local by taking into account the higher order terms in the gradient expansion, and with its technique we could consider a infinitesimally small environment of the space points. The bilocal potential considers two points in the space, which can be well separated, therefore it provides us a more general treatment in this respect than the gradient expansion. The inclusion of a nonlocal potential is unavoidable when we use the closed time path formalism, which seems to provide a better framework of the description of several physical processes. We also note that the bilocal potential is an obvious generalization of the traditional treatments with local potentials.We investigate a one-component scalar field theory including a bilocal potential in the action.
 

In the recent decade, various novel real-space renormalization group methods have been developed for treating different quantum spin models. The success and failure of these methods turned out to be intimately connected to the entanglement structure of the eigenstates of these models. In this talk we give an overview of this field and discuss its relevance for quantum field theories in the continuum.
 

The one component scalar field theory is considered including a bilocal potential in the action. Its phase phase is mapped out in the framework of the functional renormalization group method. The vacuum structure is determined by minimizing the action of the bilocal model. It is found that the vacuum can be trivial, or it can be a homogeneous one, similar to the ferromagnetic ground states. The vacuum of the bilocal model can also have an inhomogeneous structure, analogously to the antiferromagnetic ground states.
 

QCD-like theories provide testing grounds for truncations of functional equations at non-zero density, since comparisons with lattice results are possible due to the absence of the sign problem. As a first step towards such a comparison, we determine for various theories the chiral and confinement/deconfinement transitions from the quark propagator Dyson-Schwinger equation by calculating the chiral and dual chiral condensates, respectively.
 

We solve the Dyson-Schwinger equation for the quark propagator and the Bethe-Salpter equation for the pion including contributions from pion cloud. In addition we parametrize the quark propagator using a complex conjugate pole model to solve the pion Bethe-Salpeter equation.
 

The description of the exclusive hard processes with mesons within the perturbative QCD framework will be renewed. The application of such approach will be demonstrated on both pseudoscalar and scalar meson transition form factors, as well as, on deeply virtual production of mesons. The relevant recent Belle experimental results will be commented.