An asymmetric thick domain wall solution with de Sitter (dS) expansion in five dimensions can be constructed from a symmetric one by using a same scalar (kink) with different potentials. In this paper, by presenting the mass-independent potentials of Kaluza–Klein (KK) modes in the corresponding Schröodinger equations, we investigate the localization and mass spectra of various bulk matter fields on the symmetric and asymmetric dS thick branes. For spin 0 scalars and spin 1 vectors, the potentials of KK modes in the corresponding Schrodinger equations are the modified P¨oschl-Teller potentials, and there exist a mass gap and a series of continuous spectrum. It is shown that the spectrum of scalar KK modes on the symmetric dS brane contains only one bound mode (the massless mode). However, for the asymmetric dS brane with a large asymmetric factor, there are two bound scalar KK modes: a zero mode and a massive mode. For spin 1 vectors, the spectra of KK modes on both dS branes consist of a bound massless mode and a set of continuous ones, i.e., the asymmetric factor does not change the number of the bound vector KK modes. For spin 1/2 fermions, two types of kink-fermion couplings are investigated in detail. For the usual Yukawa coupling, there exists no mass gap but a continuous gapless spectrum of KK states. For the scalar-fermion couplingsin(0) cos−(0) with a positive coupling constant, there exist some discrete bound KK modes and a series of continuous ones. The total number of bound states increases with the coupling constant. For the case of the symmetric dS brane and positive, there are NL(NL1) left chiral fermion bound states (including zero mode and massive KK modes) and NL −1 right chiral fermion bound states (including only massive KK modes).For the asymmetric dS brane scenario, the asymmetric factor a reduces the number of the bound fermion KK modes. For large enough a, there would not be any right chiral fermion bound mode, but at least one left chiral fermion zero mode.

In this paper, we mainly investigate the WM2,s WL2,s system, in which the matter and the Liouville subsystems generate WM2,s and WL2,s algebras respectively. We first give a brief discussion of the physical states for corresponding W stings. The lower states are given by freezing the spin-2 and spin-s currents.Then, introducing two pairs of ghost-like fields, we give the realizations of W1,2,s algebras. Based on these linear realizations, BRST operators for W2,s algebras are obtained. Finally, we construct new BRST charges of Liouville system for WL2,s strings at the specific values of central charges c: c = −225/5 for WL2,3 algebra,c = −24 for WL2,4 algebra and c = −2,−286 /3 for WL2,6 algebra, at which the corresponding WL 2,s algebras are singular.

In Phys. Rev. D 78 (2008) 104018 [arXiv:0807.1481], the conclusion that“entropy eigenvalues of GB black hole are discrete and equally spaced, but the area spacing is not equidistant” was firstly presented by Kothawala, Padmanabhan and Sarkar. In this paper, using the new physical interpretation of quasinormal modes proposed by Maggiore,we calculate the quantum spectra of entropy for various types of non-rotating black holes with no charge. The spectrum is obtained by imposing Bohr-Sommerfeld quantization condition to the adiabatic invariant quantity. We conjecture that the spacing of entropy spectrum is equidistant and is independent of the dimension of spacetime. However, the spacing of area spectrum depends on gravity theory. In Einstein’s gravity, it is equally spaced, otherwise it is non-equidistant. This conjecture agrees with the result of Kothawala,Padmanabhan and Sarkar.

The fact that certain non-linear W2,s algebras can be linearized by the inclusion of a spin-1 current can provide a simple way to realize W2,s algebras from linear W1,2,s algebras. In this paper, we first construct the explicit field realizations of linear W1,2,s algebras with double-scalar and doublespinor,respectively. Then, after a change of basis, the realizations of W2,s algebras are presented.The results show that all these realizations are Romans-type realizations.

In arXiv:0901.3543, the simplest Yukawa coupling was considered for a two-scalargenerated Bloch brane model. Fermionic resonances for both chiralities were obtained, and their appearance is related to branes with internal structure. Inspired on this result, we investigate the localization and resonance spectrum of fermions on a one-scalar-generated dS thick brane with a class of scalar-fermion couplings-k with positive odd integer k. A set of massive fermionic resonances for both chiralities are obtained when provided large couple constant. We find that the masses and life-times of left and right chiral resonances are almost the same, which demonstrates that it is possible to compose massive Dirac fermions from the left and right chiral resonances.The resonance with lower mass has longer life-time. For a same set of parameters, the number of resonances increases with k and the life-time of the lower level resonance for larger k is much longer than the one for smaller k.