arXiv subjects
Publications and source records attributed to M. O. Taha.
It is shown how the relation $ds=cdτ$ between the proper distance $s$ and the proper time $τ$ is obtained in general relativity. A general relation in curved spacetime between $dτ$ and $dt$ is given. This relation reduces to the special relativistic one for flat spacetime.
We consider the low-energy effective string action in four dimensions including the leading order-$α'$ terms. An exact homogeneous solution is obtained. It represents a non-singular expanding cosmological model in which the tensor fields tend to vanish as $t\to \infty$. The scale factor $a(t)$ of the very early universe in this model has the time dependence $a(t)^2=a_0^2+t^2$. The violation of the strong energy condition of classical General Relativity to avoid the initial singularity requires that the central charge deficit of the theory be larger than a certain value. The significance of this solution is discussed.
We discuss the notion that quantum fields may induce an effective time-dependent cosmological constant which decays from a large initial value. It is shown that such cosmological models are viable in a non-de Sitter spacetime.
We impose the condition that the eigenvalues of the mass matrix in the shifted Lagrangian density be positive at ϕ=ϕ_{0}, the vacuum expectation value of the scalar field. Using the one-loop effective potential of the standard model, this condition leads to an upper bound on the Higgs boson mass m_{H}: m_{H}<230GeV, for a top quark mass of 175GeV.