1993 (IPP)

Permanent URI for this collectionhttp://localhost:4000/handle/11007/2786

Browse

Filters

20155

Settings

Subject: search.filters.subject.Cosmology

Search Results

Now showing 1 - 5 of 5
  • No Thumbnail Available
    Item
  • No Thumbnail Available
    Item
    On the smallness of the cosmological constant
    (2015-01-17) Masafumi, Seriu,
    We investigate the possible values of the cosmological constant allowed by quantum cosmology. If we formulate quantum cosmology respecting the causal nature of fundamental equations in the semiclassical regime of the universe, then any classical universe should have at least one symmetric surface on which every component of the extrinsic curvature vanishes. Combined with the Hamiltonian constrain, this implies that the allowed values of the cosmological constant are bounded from above. Applying this argument to the Robertson- Walker Universe, we obtain the theoretical upperbound for the cosmological constant, being of order (H0 / c)2 . This upperbound can also be interpreted as being determined by the adiabatic Schwarzshild radius of the whole universe. In this way, the question as to why the cosmological constant is so small is reduced to the question, why there is so much matter in our universe.
  • No Thumbnail Available
    Item
    Cosmology today-models and constraints
    (2015-01-17) Padmanabhan, T.
  • No Thumbnail Available
    Item
    On singularity free cosmological model
    (2015-01-13) Dadhich, Naresh; Tikekar, R.; Patel, L.K.
  • No Thumbnail Available
    Item
    Topology selection through quantum cosmology
    (2015-01-13) Seriu, Masafumi
    We argue that in order to obtain causal semiclassical Einstein equation at the stage much later than the planck time, we have to regard the in-in pathintegral formalism as fundamental in quantum cosmology. We then deduce that any classical universe should allow at least one maximal surface. If the natural energy condition holds, this mean that (1) the classical universe should be a wheeler universe, i.e. it start from and end in a singularity, and (2) the possible topologies of classical universe are strongly restricted. The implication of the recent observation of the cosmic microwave background radiation is also discussed.