The masses of pure gauge glueballs are calculated with the use of relativistic string Hamiltonian without fitting parameters. The string tension $\sigma_f=0.184$~GeV$^2$ in fundamental representation is fixed, using the Necco-Sommer lattice data, and to calculate the vector coupling $\alpha_{\rm V}(r)$ the value of $\Lambda_{\overline{MS}}^0=238$~MeV ($N_f=0$) is taken. The spin-spin potential, defined via the vacuum correlation function, is shown to produce a screening effect and decrease a hyperfine splittings between tensor and scalar glueballs. The masses of first and second $0^{++}$, $2^{++}$ excitations are predicted. For the ground states the masses $M(0^{++})=1508$~MeV, $M(2^{++})=2292$~MeV (in case A), in agreement with those of $f_0(1500),~f_2(2300)$ are obtained, and the first excitation mass $M(0^{++})=2613$~MeV is predicted. In case B $M(0^{++})=1.669$~MeV, $M(2^{++})=2212$~MeV are obtained.

We introduce a dilated coordinate method to address computational challenges in nuclear lattice effective field theory (NLEFT) for weakly-bound few-body systems. The approach employs adaptive mesh refinement via analytic coordinate transformations, dynamically adjusting spatial resolution to resolve short-range nuclear interactions with fine grids while efficiently capturing long-range wave function tails with coarse grids. Numerical demonstrations for two- and three-body systems confirm accelerated convergence towards infinite-volume limit compared to uniform lattices, particularly beneficial for accessing highly excited states and shallow bound states near the continuum threshold. This method establishes a foundation for \textit{ab initio} studies of exotic nuclear systems near the dripline and light hypernuclei, with direct extensions to scattering and reaction processes.

Quantum simulation offers a powerful approach to studying quantum field theories, particularly (2+1)D quantum electrodynamics (QED$_3$), which hosts a rich landscape of physical phenomena. A key challenge in lattice formulations is the proper realization of topological phases and the Chern-Simons terms, where fermion discretization plays a crucial role. In this work, we analyze staggered and Wilson fermions coupled to $\text{U}(1)$ background gauge fields in the Hamiltonian formulation and demonstrate that staggered fermions fail to induce (2+1)D topological phases, while Wilson fermions admit a variety of topological phases including Chern insulator and quantum spin Hall phases. We additionally uncover a rich phase diagram for the two-flavor Wilson fermion model in the presence of a chemical potential. Our findings resolve existing ambiguities in Hamiltonian formulations and provide a theoretical foundation for future quantum simulations of gauge theories with topological phases. We further outline connections to experimental platforms, offering guidance for implementations on near-term quantum computing architectures.