Numerical Study of the Simplest String Bit Model

String bit models provide a possible method to formulate a string as a discrete chain of pointlike string bits. When the bit number $M$ is large, a chain behaves as a continuous string. We study the simplest case that has only one bosonic bit and one fermionic bit. The creation and annihilation operators are adjoint representations of the $Uleft(Nright)$ color group. We show that the supersymmetry reduces the parameter number of a Hamiltonian from 7 to 3 and, at $N=infty$, ensures a continuous energy spectrum, which implies the emergence of one spatial dimension. The Hamiltonian $H_{0}$ is constructed so that in the large $N$ limit it produces a world sheet spectrum with one Grassmann world sheet field. We concentrate on numerical study of the model in finite $N$. For the Hamiltonian $H_{0}$, we find that the would-be ground energy states disappear at $N=left(M-1right)/2$ for odd $Mleq11$. Such a simple pattern is spoiled if $H$ has an additional term $xiDelta H$ which does not affect the result of $N=infty$. The disappearance point moves to higher (lower) $N$ when $xi$ increases (decreases). Particularly, the $pmleft(H_{0}-Delta Hright)$ cases suggest a possibility that the ground state could survive at large $M$ and $Mgg N$. Our study reveals that the model has stringy behavior: when $N$ is fixed and large enough, the ground energy decreases linearly with respect to $M$, and the excitation energy is roughly of order $M^{-1}$. We also verify that a stable system of Hamiltonian $pm H_{0}+xiDelta H$ requires $xigeqmp1$.