International Journal of Modern Physics: Conference Series

The mechanism of colour confinement by dual superconductivity of the $QCD$ vacuum is discussed. Its gauge invariant formulation and the recent improvements in its lattice verification are reported.

The Hadronic Paschen-Back effect (HPBE) is a new phenomenon induced by the interplay between finite orbital angular momenta of hadrons and external strong magnetic fields. We review the HPBE in P-wave charmonia and show its mass spectra, deformed wave functions, and mixing ratios, which are evaluated by the constituent quark models in a magnetic field and the cylindrical Gaussian expansion method.

Within the framework of the instanton Liquid Model (ILM) we evaluate the heavy quark $Q\bar{Q}$ potential at finite temperature. The potential in the ILM has two components: direct instantons contribution and the ILM modified one-gluon exchange contribution. The dynamical ”electric” mass $M_{el}(q,T)$, which was generated by rescattering of the gluons from the ILM instantons, was taken into account.

Charmed dibaryon states with the spin-parity $J^{\pi }=0^{+},1^{+}$, and $2^{+}$ are predicted for the two-body $Y_{c}N$ ($={\mathrm{\Lambda }}_c$, ${\mathrm{\Sigma }}_c$, or ${\mathrm{\Sigma }}_c^{\ast }$) systems. We employ the complex scaling method for the coupled channel Hamiltonian with the $Y_{c}N$-CTNN potentials, which were proposed in our previous study. We find four sharp resonance states near the ${\mathrm{\Sigma }}_{c}N$ and ${\mathrm{\Sigma }}_c^{\ast }N$ thresholds. From the analysis of the binding energies of partial channel systems, we conclude that these resonance states are Feshbach resonances. We compare the results with the $Y_{c}N$ resonance states in the heavy quark limit, where the ${\mathrm{\Sigma }}_{c}N$ and ${\mathrm{\Sigma }}_c^{\ast }N$ thresholds are degenerate, and find that they form two pairs of the heavy-quark doublets in agreement with the heavy quark spin symmetry.

Exotic hadrons reported in the heavy flavor sector have attracted much interest in hadron and nuclear physics. Especially near the thresholds, the hadron-hadron interaction is important to understand these exotic structures. In this talk, the short range $\pi J/\psi -D{\bar{D}}^{\ast }$ potential whose importance is indicated by the Lattice QCD is studied by the $D^{(\ast )}$ meson exchange model, and the Born-order quark exchange model. We find the large difference between the results of the $D^{(\ast )}$ meson exchange and the quark exchange calculations.

The equations for the QED effective action derived in Ref. 3 are considered using singular perturbation theory. The effective action is divided into regular and singular (in coupling constant) parts. It is shown that expression for the regular part coincides with usual Feynman perturbation series over coupling constant, while the remainder has essential singularity at the vanishing coupling constant: $e\to 0$. This means that in the frame of quantum field theory it is impossible “to switch off” electromagnetic interaction in general and pass on to “free electron”.

We discuss the properties of nucleons in nuclear matter and the properties of nucleonic systems in the framework of an in-medium modified Skyrme Lagrangian. The modification is achieved by introducing the medium functionals into the original Skyrme Model Lagrangian in free space${}^{1,2}$. The parameters of the medium functionals are related to the low density phenomenology (i.e. to the pionic atoms³) from the one side and to the properties of nuclear matter at the saturation density ${\rho }_0=0.16{\mathrm{\text{fm}}}^{-3}$ from the other side. After fitting the parameters of the model, the extrapolations into the low density and high density regions showed that the model can successfully describe the Equations of State (EoS) of nuclear matter in the wide range of densities including the high critical densities existing in the interiors of neutron stars.

Projectile-nucleus capture by a target nucleus at bombarding energies in the vicinity of the Coulomb barrier is treated with the reduced-density-matrix formalism. The effects of dissipation and fluctuations on the capture process are taken self-consistently into account within the quantum model suggested. The excitation functions for the capture in the reactions ${}^{16}$O, ${}^{19}$F, ${}^{26}$Mg, ${}^{28}$Si, ${}^{32,34,36,38}$S, ${}^{40,48}$Ca, ${}^{50}$Ti, ${}^{52}$Cr $+$ ${}^{208}$Pb are calculated and compared with the experimental data.

The allowed Gamow-Teller (GT) strength distributions and associated weak interaction rates on fp-shell nuclei play crucial role in several astrophysical processes, particularly in nucleosynthesis, stellar evolution and supernova explosions. Results from simulation show that the electron capture (EC) rates on medium-heavy nuclei have a significant impact on decreasing the electron-to-baryon ratio of the stellar matter during the late stages of star formation. In this work we present the computation of allowed charge-changing transitions for odd-A fp-shell nuclei by using the deformed pn-QRPA model. The calculated GT strength distributions are compared with previous calculations (including shell and other QRPA models) and measured charge-changing reaction results. The associated EC rates are computed in stellar environment and are compared with previous theoretical results. It is concluded that our results are in good accordance with measured data. For ${}^{45}$Sc, ${}^{51}$V and ${}^{59}$Co, at high stellar temperatures, our calculated EC rates are bigger than the independent-particle and shell model rates. For ${}^{55}$Mn we generally calculate smaller EC rates than previous calculations. The differences with previous calculations may have consequences for supernovae simulators.

Resonant reactions play an important role in astrophysics as they might significantly enhance the cross section with respect to the direct reaction contribution and alter the nucleosynthetic flow. Moreover, resonances bear information about states in the intermediate compound nucleus formed in the reaction. However, nuclear reactions in stars take place at energies well below $\sim 1$ MeV and the Coulomb barrier, exponentially suppressing the cross section, and the electron screening effect, due to the shielding of nuclear charges by atomic electrons, make it very difficult to provide accurate input data for astrophysics. Therefore, indirect methods have been introduced; in particular, we will focus on the Trojan Horse Method. We will briefly discuss the theory behind the method, to make clear its domain of applicability, the advantages and the drawbacks, and two recent cases will be shortly reviewed: the ${}^{19}\mathrm{\text{F}}{(p,\alpha )}^{16}\mathrm{\text{O}}$ reaction, which is an important fluorine destruction channel in the proton-rich outer layers of asymptotic giant branch (AGB) stars, and the ${}^{12}\mathrm{\text{C}}+{}^{12}\mathrm{\text{C}}$ reactions, which play a critical role in astrophysics to understand stellar burning scenarios in carbon-rich environments.

In the last years the ${}^{19}\mathrm{\text{F}}{(\mathrm{\text{p}},\alpha )}^{16}$O and the ${}^{19}$F($\alpha$,p)${}^{22}$Ne reactions have been studied via the Trojan Horse Method in the energy range of interest for astrophysics. These are the first experimental data available for the main channels of ${}^{19}$F destruction that entirely cover the energy regions typical of the stellar H- and He- burning. In both cases the reaction rates are significantly larger than the previous estimations available in the literature. We present here a re-analysis of the fluorine nucleosynthesis in Asymptotic Giant Branch stars by employing in state-of-the-art models of stellar nucleosynthesis the THM reaction rates for ${}^{19}$F destruction.

Big Bang Nucleosynthesis (BBN) requires several nuclear physics inputs and nuclear reaction rates. An up-to-date compilation of direct cross sections of $\mathrm{\text{d(d, p)t}}$, ${\mathrm{\text{d(d, n)}}}^3$He and ${}^3\mathrm{\text{He}}{(\mathrm{\text{d, p}})}^4$He reactions is given, being these ones among the most uncertain bare-nucleus cross sections. An intense experimental effort has been carried on in the last decade to apply the Trojan Horse Method (THM) to study reactions of relevance for the BBN and measure their astrophysical S(E)-factor. The reaction rates and the relative error for the four reactions of interest are then numerically calculated in the temperature ranges of relevance for BBN $(0.01<{\mathrm{\text{T}}}_9<10)$. These value were then used as input physics for primordial nucleosynthesis calculations in order to evaluate their impact on the calculated primordial abundances and isotopical composition for H, He and Li. New results on the ${}^7\mathrm{\text{Be}}{(\mathrm{\text{n}},\alpha )}^4$He reaction rate were also taken into account.These were compared with the observational primordial abundance estimates in different astrophysical sites. Reactions to be studied in perspective will also be discussed.

The original version of the activation method is presented and yield of the astrophysical relevant reaction ${}^{12}C{(p,\gamma )}^{13}N$ has been measured at the energy region 190–650keV using this method. The rate of this reaction was calculated within the temperature region $0.01\le T_9\le 1.0$ through the yield values. The possibility of improving the method for measuring very small yields or cross sections was demonstrated.

The reaction rates of the direct astrophysical capture processes ${}^3\mathrm{\text{He}}{(\alpha ,\gamma )}^7\mathrm{\text{Be}}$ and ${}^3\mathrm{\text{H}}{(\alpha ,\gamma )}^7\mathrm{\text{Li}}$, as well as the abundance of the ${}^7\mathrm{\text{Li}}$ element are estimated in the framework of a two-body potential model. The estimated ${}^7\mathrm{\text{Li/H}}$ abundance ratio of ${}^7\mathrm{\text{Li/H}}=(5.07\pm 0.14)\times 10^{-10}$ is in a very good agreement with the recent measurement ${}^7\mathrm{\text{Li/H}}=(5.0\pm 0.3)\times 10^{-10}$ of the LUNA collaboration.

The astrophysical S-factor for the direct $\alpha {(d,\gamma )}^6\mathrm{\text{Li}}$ capture reaction is calculated in a three-body model based on the hyperspherical Lagrange-mesh method. A sensitivity of the E1 and E2 astrophysical S-factors to the orthogonalization method of Pauli forbidden states in the three-body system is studied. It is found that the method of orthogonalising pseudopotentials (OPP) yields larger isotriplet ($T=1$) components than the supersymmetric transformation (SUSY) procedure. The E1 astrophysical S-factor shows the same energy dependence in both cases, but strongly different absolute values. At the same time, the E2 S-factor does not depend on the orthogonalization procedure. As a result, the OPP method yields a very good description of the direct data of the LUNA collaboration at low energies, while the SUSY transformation strongly underestimates the LUNA data.

An asymptotic theory is proposed for the peripheral transfer $A(x,y)B$ reaction at low energies within the three-body ($A$, $a$ and $y$) model by combining the dispersion theory and DWBA, where $x=y+a$, $B=A+a$ and $a$ is a transferred particle. The contribution of the three-body ($A$, $a$ and $y$) Coulomb dynamics of the transfer mechanism both to the peripheral partial amplitudes for the partial wave $l_i\gg 1$ and to the DWBA amplitude is investigated. The results of the analysis of the differential cross sections of the specific proton transfer reactions at above-barrier energies are presented. New estimates and their uncertainties are obtained for values of the asymptotic normalization coefficients for ${}^9\mathrm{\text{Be}}+p\to {}^{10}\mathrm{\text{B}}$ and ${}^{11}\mathrm{\text{B}}+p\to {}^{12}\mathrm{\text{C}}$ as well as for the direct astrophysical $S$ factors at stellar energy of the radiative capture ${}^9\mathrm{\text{Be}}{(\mathrm{\text{p}},\gamma )}^{10}\mathrm{\text{B}}$ and ${}^{11}\mathrm{\text{B}}{(\mathrm{\text{p}},\gamma )}^{12}\mathrm{\text{C}}$ reactions.

The results of the analysis of the new experimental astrophysical S factors $S_{24}^{\mathrm{\text{exp}}}(E)$ [D. Trezzi et al., Astropart. Phys. 89, 57 (2017)] and those measured earlier [R. G. Robertson et al., Phys. Rev. Lett. 47, 1867 (1981)] for the nuclear-astrophysical $d{(\alpha ,\gamma )}^6\mathrm{\text{Li}}$ reaction directly measured at extremely low energies $E$, which is derived within the modified two-body potential method, are presented. New estimates and their uncertainties have been obtained for values of the asymptotic normalization coefficient for $\alpha +d\to {}^6\mathrm{\text{Li}}$ and for the direct astrophysical $S$ factors at Big Bang energies.

We study in the weak field limit the gravitational lensing by spherically symmetric compact object immersed in an asymptotically uniform magnetic field in the presence of plasma and our approach is based on the medium modified Hamiltonian one. We show that the magnetized plasma in the environment of compact object may lead to split of the Einstein cross, creating additional lensed components. Finally we calculate magnification and time delay related to the individual images.

The analytical expression for Goldreich-Julian (GJ) charge density at the polar cap of magnetized neutron star has been obtained in braneworlds for inclined neutron star through solving Maxwell equations and shown that the value of GJ charge density decreases with increasing the value of the brane charge. The analytical expressions for scalar potential and parallel electric field on the region greater than the polar cap region of the neutron star have also been obtained by solving Poisson equation in braneworlds.

We investigate the effect of magnetic field on the process of overcharging magnetized Reissner–Nordström black hole. It is well known that a four dimensional charged black hole could be overcharged. Contrary to this, we show that a magnetized charged black hole could not be overcharged beyond threshold value of the magnetic field. This occurs because the magnetic field does not allow for particle to reach black hole horizon. Thus magnetic field beyond its threshold value could restore the cosmic censorship conjecture.