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We use a transfer-matrix method to study the localization properties of vibrations in a `mass and spring model with simple cubic lattice structure. Disorder is applied as a box-distribution to the force-constants $k$ of the springs. We obtain the reduced localization lengths $Lambda_M$ from calculated Lyapunov exponents for different system widths to roughly locate the squared critical transition frequency $omega_{text{c}}^2$. The data is finite-size scaled to acquire the squared critical transition frequency of $omega_{text{c}}^2 = 12.54 pm 0.03$ and a critical exponent of $ u = 1.55 pm 0.002$.
Numerical studies of amorphous silicon in harmonic approximation show that the highest 3.5% of vibrational normal modes are localized. As vibrational frequency increases through the boundary separating localized from delocalized modes, near omega_c=7
We propose a new approach to probing ergodicity and its breakdown in quantum many-body systems based on their response to a local perturbation. We study the distribution of matrix elements of a local operator between the systems eigenstates, finding
We analyze many-body localization (MBL) to delocalization transition in Sherrington-Kirkpatrick (SK) model of Ising spin glass (SG) in the presence of a transverse field $Gamma$. Based on energy resolved analysis, which is of relevance for a closed q
We focus on the many-body eigenstates across a localization-delocalization phase transition. To characterize the robustness of the eigenstates, we introduce the eigenstate overlaps $mathcal{O}$ with respect to the different boundary conditions. In th
Many-body localization (MBL) provides a mechanism to avoid thermalization in many-body quantum systems. Here, we show that an {it emergent} symmetry can protect a state from MBL. Specifically, we propose a $Z_2$ symmetric model with nonlocal interact