Hollow nuclear matter

It is generally considered that an atomic nucleus is always compact. Based on the isospin-dependent Boltzmann nuclear transport model, here I show that large block nuclear matter or excited nuclear matter may both be hollow. The size of the inner bubble in these matter is affected by the charge number of nuclear matter. The existence of hollow nuclear matter may have many implications in nuclear or atomic physics or astrophysics as well as some practical applications.

Figure 1

Time evolution of the contour density distribution of the hypothetical superheavy atomic nucleus ${}_{100}^{900}\mathrm{X}$ in the $X\text{−}Y$ plane with the Boltzmann nuclear transport model. Density becomes larger as color changes from light to dark. The bubble configuration appears after 50 fm/$c$ in the compact nucleus ${}_{100}{}^{900}\mathrm{X}$.

Figure 2

Time evolution of the contour density distribution of the hypothetical superheavy atomic nucleus ${}_{400}{}^{900}\mathrm{X}$ in the $X\text{−}Y$ plane with the Boltzmann nuclear transport model. Density becomes larger as color changes from light to dark. The bubble configuration appears after 40 fm/$c$ in the compact nucleus ${}_{100}{}^{900}\mathrm{X}$.

Figure 3

Time evolution of the contour density distribution of the relatively light atomic nucleus ${}_{79}^{197}\mathrm{Au}$ in the $X\text{−}Y$ plane with the Boltzmann nuclear transport model. Density becomes larger as color changes from light to dark. The bubble configuration does not appear in the compact nucleus ${}_{79}^{197}\mathrm{Au}$.

Figure 4

Time evolution of the contour density distribution of the relatively light atomic nucleus ${}_{79}^{197}\mathrm{Au}$ in the $X\text{−}Y$ plane with the Boltzmann nuclear transport model. The giving excitation energy is an average of 5 MeV per nucleon. Density becomes larger as color changes from light to dark. The bubble configuration appears after 30 fm/$c$ in the compact nucleus ${}_{79}^{197}\mathrm{Au}$.

Figure 5

Time evolution of the contour density distribution in the $X\text{−}Y$ plane in the head-on ${}_{79}^{197}\mathrm{Au}$ + ${}_{79}^{197}\mathrm{Au}$ collision with the same Boltzmann nuclear transport model. The incident beam energy (in $Z$ direction) is 35 MeV per nucleon. Density becomes larger as color changes from light to dark. The bubble configuration of the compressed nuclear matter appears after 90 fm/$c$.

Figure 6

Time evolution of the radial velocity ${\beta }_r$ $\left(=v_r/c\right)$ of emitting nucleons in the head-on ${}_{79}^{197}\mathrm{Au}$ + ${}_{79}^{197}\mathrm{Au}$ collision with the same Boltzmann nuclear transport model. The incident beam energy (in $Z$ direction) is 35 MeV per nucleon. The red solid squares denote radial velocity of all emitting nucleons while the blue hollow squares denote radial velocity of inner nucleons with spherical radius $r=2$ fm and $\mid Z\mid \le 1$ fm in center of mass frame.