I show that quantum corrections due to a massive particle generates non-local term in the gravitational effective action which is of zeroth order derivative expansion, much like cosmological constant. It carries fixed coefficient very larger than constant, and cannot be fine-tuned. The interaction active at scales above particle's mass. This form $m^4 (\frac1{\Box}R)_x "...

An one-parameter regularization freedom of the Hamiltonian constraint for loop quantum gravity is analyzed. The corresponding spatially flat, homogenous and isotropic model includes two well-known models cosmology as special cases. bounce nature tenable in generalized For positive value parameter, effective leads to an asymptotic de-Sitter branch Universe connecting standard Friedmann by bounce...

We study a mechanism, inspired from the mechanism for generating the gauge hierarchy in RandallSundrum model, to investigate the cosmological constant problem. First we analyze the bulk cosmological constant and brane vacuum energies in RS model. We show that the five-dimensional bulk cosmological constant and the vacuum energies of the two branes all obtain their natural values. Finally we arg...