We extensively study the exact solutions of the massless Dirac equation in 3D de Sitter spacetime that we published recently. Using the Newman-Penrose formalism, we find exact solutions of the equations of motion for the massless classical fields of spin s = 12 , 1, 2 and to the massive Dirac equation in 4D de Sitter metric. Employing these solutions, we analyze the absorption by the cosmologic...

String theory is a promising candidate for a fundamental quantum theory of all interactions including Einstein gravity. Some solutions in string theory can be interpreted as black holes. Using the semi-analytic method and WKB method,the quasinormal modes(QNMs)of 1+1 dimensional black hole in string theory are studied.The QNMs of 1+3 dimensional black hole in string theory are also calculated th...

let $h$, $l$ and $x$ be subgroups of a finite group$g$. then $h$ is said to be $x$-permutable with $l$ if for some$xin x$ we have $al^{x}=l^{x}a$. we say that $h$ is emph{$x$-quasipermutable } (emph{$x_{s}$-quasipermutable}, respectively) in $g$ provided $g$ has a subgroup$b$ such that $g=n_{g}(h)b$ and $h$ $x$-permutes with $b$ and with all subgroups (with all sylowsubgroups, respectively) $v$...

We study the scattering of gravitational waves by a Schwarzschild black hole and its perturbed siblings to investigate influences proposed spectral instability quasinormal modes on ringdown signal. Our results indicate that information dominant signals, which are ascribed fundamental (i.e., least damping) mode unperturbed holes, is imprinted in phase shift defined from transmission amplitude ($...

Introduction. It has been shown in a previous paper [3]1 that every algebra A with radical R, such that A/R is separable, is a homomorphic image of a certain maximal algebra which is determined to within an isomorphism by A/R, the A/R-modu\e (two-sided) R/R1, and the index of nilpotency of R. Furthermore, some indication was given of how the structure of maximal algebras can be determined in si...

in this paper we classify fuzzy subgroups of the dihedral group $d_{pqrs}$  for distinct primes  $p$, $q$, $r$ and $s$. this follows similar work we have done on distinct fuzzy subgroups of some dihedral groups.we present formulae for the number of (i) distinct maximal chains of subgroups, (ii) distinct fuzzy subgroups and (iii) non-isomorphic classes of fuzzy subgroups under our chosen equival...