Modern Physics Letters A

In this review, we analyze some of the most important theoretical attempts to challenge the invariance of the light speed postulated by the Special Theory of Relativity (STR). Most of those studies, however, show that STR has great stability with respect to various kinds of modifications in its axioms. This stability probably is due to the fact that in these modifications there is no so much a violation of the physical postulate of the invariance of the speed of light, as its mathematical expansion in the form of making resort to a more general affine space. In these modifications, we refer to more general transformation groups, including scale transformation of the speed of light and time $c^{\prime }=\gamma c$, $t^{\prime }={\gamma }^{-1}t$.

We consider the general ${𝒩}=1$ supersymmetric gauge theory with matter, regularized by higher covariant derivatives without breaking the BRST invariance, in the massless limit. In the $\xi$-gauge we obtain the (unrenormalized) expression for the two-point Green function of the quantum gauge superfield in the one-loop approximation as a sum of integrals over the loop momentum. The result is presented as a sum of three parts: the first one corresponds to the pure supersymmetric Yang–Mills theory in the Feynman gauge, the second one contains all gauge-dependent terms, and the third one is the contribution of diagrams with a matter loop. For the Feynman gauge and a special choice of the higher derivative regulator in the gauge fixing term, we analytically calculate these integrals in the limit $k\to 0$. In particular, in addition to the leading logarithmically divergent terms, which are determined by integrals of double total derivatives, we also find the finite constants.

The moments $〈r^m〉$ of the spherical three-parameter Fermi distribution (3pF) are presented for $m=1$ to 8 as a function of the parameter $w$, the half-density radius $c$ and the diffuseness parameter $a$ through the introduced parameter $\beta =\pi a/c$, which can be applied to study the neutron skin in neutron rich nuclei. The general expression of the moment can be written as the combination of integrals $I_n(k,w)$ with $k=c/a$. The errors of the analytic moments $〈r^m〉$ are estimated with the typical values of the parameters in 3pF compared with the numerical results.

We study matrix Darboux transformation (MDT) for the generalized N-wave interactions (local/nonlocal) and express multi-soliton solutions in terms of ratios of determinants. In order to explain our construction, we obtain explicit expressions of single and double soliton solutions for local/nonlocal 3-wave and 4-wave interactions.

Mapping of fundamental branes to their worldsheet (ws) multiplets originating from spontaneous breaking of the Poincaré symmetry is studied. The interaction Lagrangian for fields of the Nambu–Goldstone multiplet is shown to encode $R^2$ gravity on the ws. The power law $k_p\sim T_p^{\frac{3-p}{2(p+1)}}$ for the $\mathrm{\text{SO}}(D-p-1)$ gauge coupling $k_p$ as the function of the $p$-brane tension $T_p$ is assumed. It points to the presence of asymptotic freedom and confinement phases in brane matter. Their connection with collapse and inflation of the branes is discussed.

We propose a new model of nonlinear electrodynamics (NLED) with three parameters. Born–Infeld (BI) electrodynamics and exponential electrodynamics are particular cases of this model. The phenomenon of vacuum birefringence in the external magnetic field is studied. We show that there is no singularity of the electric field at the origin of point-like charged particles. The corrections to Coulomb’s law at $r\to \infty$ are obtained. We calculate the total electrostatic energy of charges, for different parameters of the model, which is finite.

The post-accelerator of isotope separation on-line (ISOL) system for rare isotope science project (RISP) is a superconducting linear accelerator (SC-linac) with a DC equivalent voltage of around 160 MV. An isotope beam extracted from the ISOL is in a charge state of $1+$ and its charge state is increased to $n+$ by charge breeding with an electron beam ion source (EBIS). The charge breeding takes tens of ms and the pulse width of extracted beam from the EBIS is tens of $\mu$s, which operates at up to 30 Hz. Consequently a large portion of radio frequency (rf) time of the post SC-linac is unused. The post-linac is equipped also with an electron cyclotron resonance (ECR) ion source for stable ion acceleration. Thanks to the large phase acceptance of SC-linac, it is possible to accelerate simultaneously both stable and radioisotope ions with a similar charge to mass ratio by sharing rf time. This operation scheme is implemented for RISP with the addition of an electric chopper and magnetic kickers. The facility will be capable of providing the users of the ISOL and in-flight fragmentation (IF) systems with different beams simultaneously, which would help nuclear science users in obtaining a beam time as high-precision measurements often need long hours.