International Journal of Modern Physics A

Chen Ning Yang returned to Tsinghua University as a full professor in 2003. Regarding the fact that very few people know what Professor Yang has contributed to science and to China after his return, in this article new contributions of Chen Ning Yang are introduced as far as the author knows, including his leading role in China’s sciences, the research in statistical physics, the role in cultivating gifted students, his research in history of science, and all other aspects relating to China’s developments.

We discuss semiclassical Nariai black holes in the framework of f(T)-gravity. For a diagonal choice of tetrads, stable Nariai metrics can be found, emitting Bekenstein–Hawking radiation in semiclassical limit. However, for a nondiagonal choice of tetrads, evaporation and anti-evaporation instabilities are turned on. In turn, this causes a backreaction effect suppressing the Bekenstein–Hawking radiation. In particular, evaporation instabilities produce a new radiation — different by Bekenstein–Hawking emission — nonviolating unitarity in particle physics sector.

We study $SU(2)\times U(1)$ gauge theory with Chern–Simons term, coupled to scalar field in adjoint, in Einstein–Gauss–Bonnet gravity. We explore phases of holographic superconductor in terms of the condensates and free energies in the background of AdS black hole and AdS soliton. In the case of black hole, we find with increasing strength of higher curvature terms, transition temperature decreases. For AdS soliton, the critical value of chemical potential increases as the higher curvature terms dominate.

A new version of the $k_T$ factorization approach is formulated for the high energy heavy quark production. The results are in reasonable agreement with the experimental data at LHC energies.

Based on the original combination of analytical methods, computer algebra tools and numerical calculations, proposed recently in Refs. 1–3, the nonperturbative vacuum polarization effects in the 2+1D supercritical Dirac–Coulomb system with $Z>Z_{\mathrm{\text{cr}},1}$ are explored. Both the vacuum charge density ${\rho }_{\mathrm{\text{V P}}}(\overrightarrow{r})$ and vacuum energy ${{ℰ}}_{\mathrm{\text{V P}}}$ are considered. The main result of the work is that in the overcritical region ${{ℰ}}_{\mathrm{\text{V P}}}$ turns out to be a rapidly decreasing function $\sim -{\eta }_{\mathrm{\text{eff}}}{Z}^3/R$ with ${\eta }_{\mathrm{\text{eff}}}>0$ and $R$ being the size of the external Coulomb source. Due to a lot of details of calculation the whole work is divided into two parts I and II. In the present part I, we consider the evaluation and behavior of the vacuum density ${\rho }_{\mathrm{\text{V P}}}$, which further is used in part II for evaluation of the vacuum energy, with emphasis on the renormalization, convergence of the partial expansion for ${\rho }_{\mathrm{\text{V P}}}$ and behavior of the integral induced charge $Q_{\mathrm{\text{V P}}}$ in the overcritical region.

Nonperturbative vacuum polarization effects are explored for a supercritical Dirac–Coulomb system with $Z>Z_{\mathrm{\text{cr}},1}$ in 2+1D, based on the original combination of analytical methods, computer algebra and numerical calculations, proposed recently in Refs. 1–3. Both the vacuum charge density ${\rho }_{\mathrm{\text{V P}}}(\overrightarrow{r})$ and vacuum energy ${{ℰ}}_{\mathrm{\text{V P}}}$ are considered. Due to a lot of details of calculation the whole work is divided into two parts I and II. Taking account of results, obtained in the part I⁴ for ${\rho }_{\mathrm{\text{V P}}}$, in the present part II, the evaluation of the vacuum energy ${{ℰ}}_{\mathrm{\text{V P}}}$ is investigated with emphasis on the renormalization and convergence of the partial expansion for ${{ℰ}}_{\mathrm{\text{V P}}}$. It is shown that the renormalization via fermionic loop turns out to be the universal tool, which removes the divergence of the theory both in the purely perturbative and essentially nonperturbative regimes of the vacuum polarization. The main result of calculation is that for a wide range of the system parameters in the overcritical region ${{ℰ}}_{\mathrm{\text{V P}}}$ turns out to be a rapidly decreasing function $\sim -{\eta }_{\mathrm{\text{eff}}}{Z}^3/R$ with ${\eta }_{\mathrm{\text{eff}}}>0$ and $R$ being the size of the external Coulomb source. To the end the similarity in calculations of ${{ℰ}}_{\mathrm{\text{V P}}}$ in 2+1 and 3+1D is discussed, and qualitative arguments are presented in favor of the possibility for complete screening of the classical electrostatic energy of the Coulomb source by the vacuum polarization effects for $Z\gg Z_{\mathrm{\text{cr}},1}$ in 3+1D.

We study the cosmological evolution of some nonlocal gravity models, when the initial conditions are set during a phase of primordial inflation. We examine in particular three models, the so-called RT, RR and ${\mathrm{\Delta }}_4$ models, previously introduced by our group. We find that, during inflation, the RT model has a viable background evolution, but at the level of cosmological perturbations develops instabilities that make it nonviable. In contrast, the RR and ${\mathrm{\Delta }}_4$ models have a viable evolution even when their initial conditions are set during a phase of primordial inflation.

Boundary condition effects are explored for size-dependent models in thermal equilibrium. Scalar and fermionic models are used for $D=1+3$ (films), $D=1+2$ (hollow cylinder) and $D=1+1$ (ring). For all models, a minimal length is found, below which no thermally-induced phase transition occurs. Using quasiperiodic boundary condition controlled by a contour parameter $𝜃$ ($𝜃=0$ is a periodic boundary condition and $𝜃=1$ is an antiperiodic condition), it results that the minimal length depends directly on the value of $𝜃$. It is also argued that this parameter can be associated to an Aharonov–Bohm phase.

We consider the nonlinear realisation of the semi-direct product of $E_{11}$ and its vector representation which leads to a space-time with tangent group that is the Cartan involution invariant subalgebra of $E_{11}$. We give an alternative derivation of the invariant tangent space metric that this space–time possesses and compute this metric at low levels in eleven, five and four dimensions. We show that one can gauge fix the nonlinear realisation in an $E_{11}$ invariant manner.

In this paper, we explore the perspectives for canonical simulations in the worldline formulation of a lattice field theory. Using the charged ${\varphi }^4$ field in two dimensions as an example, we present the details of the canonical formulation based on worldlines and outline the algorithmic strategies for canonical worldline simulations. We discuss the steps for converting the data from the canonical approach to the grand canonical picture which we use for cross-checking our results. The canonical approach presented here can easily be generalized to other lattice field theories with a worldline representation.

In this paper, we construct the Möbius domain wall fermions (MDWFs) in the Schrödinger functional (SF) scheme for the SU(3) gauge theory by adding a boundary operator at the temporal boundary of the SF scheme setup. Using perturbation theory, we investigate the properties of several constructed MDWFs, including the optimal type domain wall, overlap, truncated domain wall, and truncated overlap fermions. We observe the universality of the spectrum of the effective four-dimensional operator at the tree-level, and fermionic contribution to the universal one-loop beta function is reproduced for MDWFs with a sufficiently large fifth-dimensional extent.