Scalar Clouds and Quasinormal Modes

In this thesis, Maggiore’s method (MM), which evaluates the transition frequency that appears in the adiabatic invariant from the highly damped quasinormal mode frequencies (QNMFs), is used to investigate the entropy and area spectra of the Garfinkle-Horowitz-Strominger black hole (GHSBH), the four-dimensional Lifshitz black hole with zero dynamical exponent (ZZLBH), and the rotating linear dilaton black hole (RLDBH), respectively. For studying the GHSBH's quantization, instead of ordinary quasinormal modes (QNMs), the boxed QNMs (BQNMs) that are the characteristic resonance spectra of the confined scalar fields in the GHSBH geometry are computed. To this end, it is assumed that the GHSBH has a confining mirror placed in the vicinity of its event horizon. It is then shown how the complex resonance frequencies of this caged black hole (BH) are computed considering the scalar perturbations around the event horizon. Additionally, the resonance modes (RMs) and the RM frequencies (RMFs) of the GHSBH are computed by using the confined scalar waves with high azimuthal quantum number. The entropy and area quantizations are shown to be independent of the GHSBH's parameters, however, both spectra are equally spaced. The spectroscopy of ZZLBH is studied by solving the Klein-Gordon equation (KGE). Based on the exact solution to the near-horizon (NH) Schrödinger-like equation (SLE) of the massive scalar waves, the QNMs of the ZZLBH are computed by employing the adiabatic invariant quantity. The Dirac equations for the fermionic perturbations of this spacetime are solved in the framework of Newman-Penrose (NP) formalism. In particular, the effective potential for the Zerilli equation (ZE) is analyzed and the existence of the Dirac BQNMs is proved. The entropy and area spectra of the ZZLBH are shown to be evenly spaced. The characteristic resonance spectra of the confined scalar fields in the RLDBH geometry are studied analytically. The KGE is solved and the boxed QNMFs (BQNMFs) of the caged RLDBH are obtained. Employing MM, the entropy and area spectra of the RLDBH are investigated, as well as the wave dynamics of a charged massive scalar field propagating in a maximally RLDBH (MRLDBH) geometry by solving the Klein-Gordon-Fock equation (KGFE). The existence of a discrete and infinite family of resonances describing non-decaying scalar configurations enclosing the MRLDBHs, which can indicate the possible existence of dark matter distributions around them is proved. Particularly, the effective heights of those clouds above the center of the MRLDBH are analytically computed. Keywords: Garfinkle-Horowitz-Strominger black hole, Lifshitz black hole, rotating linear dilaton black hole, dark matter, confining cage, scalar and fermionic field perturbations, Klein-Gordon equation, Klein-Gordon-Fock equation, Dirac equation, Newman-Penrose formalism, scalar cloud, quasinormal mode, boxed quasinormal mode, resonance mode, black hole spectroscopy, entropy and area quantization.