The Standard Model of particle physics and General Relativity are very successful in describing present experimental results. Both of them, however, are assumed to be low-energy approximations of a more complete theory. There are several candidate theories that are proposed to be part of a new conceptual structure beyond the Standard Model. To solve the Hierarchy problem, the energy threshold of the new theories is expected to be the TeV scale. One paradigm, low energy quantum gravity, combines the Standard Model with General Relativity and assumes the existence of extra dimensions. This paradigm predicts that TeV black holes can be produced in the Large Hadron Collider (LHC). In this dissertation we describe a black-hole simulator, BlackMax, for coming accelerators. The generator is based on the Monte Carlo technique and predicts the signatures of black-hole production at the LHC.
The remainder of the dissertation is an example of the violation of Birkhoff's law. Birkhoff's law is analogous to a famous result of Newtonian theory, that the gravitational acceleration due to a spherical shell vanishes inside the shell. Since the universe is homogeneous and isotropic on large scales, local gravitational phenomena can be treated as local events only; and one can always ignore the influence from the distant mass distribution. This law is violated in modified gravity theories. It is shown that a spherical shell can affect the geometry in the extra dimensions. The change of geometry in the extra dimensions also changes the geometry inside the shell. The gravitational acceleration inside a spherical shell does not vanish.