9 research outputs found
Deflation at Turnaround for Oscillatory Cosmology
It is suggested that dark energy in a brane world can help reconcile an
infinitely cyclic cosmology with the second law of thermodynamics. A cyclic
cosmology is described, in which dark energy with constant equation of state
leads to a turnaround at finite future time, when entropy is decreased by a
huge factor equal to the inverse of its enhancement during the initial
inflation. Thermodynamic consistency of cyclicity requires the arrow of time to
reverse during contraction. Entropy reduction in the contracting phase is
infinitesimally smaller than entropy increase during expansion.Comment: 11 pages late
Entropy of Contracting Universe in Cyclic Cosmology
Following up a recent proposal \cite{BF} for a cyclic model based on phantom
dark energy, we examine the content of the contracting universe (cu) and its
entropy . We find that beyond dark energy the universe contains on
average zero or at most a single photon which if present immediately after
turnaround has infinitesimally energy which subsequently blue shifts to produce
pairs. These statements are independent of the equation of state
of dark energy provided . Thus and
if observations confirm the entropy problem is solved. We discuss
the absence of a theoretical lower bound on , then
describe an anthropic fine tuning argument that renders unlikely extremely
small . The present bound already implies a time
until turnaround of Gy.Comment: 5 pages late
A Cyclic Cosmology
It is speculated how dark energy in a braneworld can help reconcile an infinitely cyclic cosmology with the second law of thermodynamics. A cyclic model featuring dark energy with a phantom (w 100 Gy. The requirement that our universe satisfy a CBE-condition (Comes Back Empty) imposes a lower bound on the number Ncp of causal patches which separate at turnaround. This bound depends on the dark energy equation of state w = p \\ rho = -1 - phi with phi > 0. More accurate measurement of phi will constrain Ncp. The critical density rhoc in the model has a lower bound rhoc is greater than or equal to ge (109 GeV)4 or rhoc is greater than or equal to ge (1018 GeV)4 when the smallest bound state has size 10-15m, or 10-35m, respectively
Constraints on Deflation from the Equation of State of Dark Energy
In cyclic cosmology based on phantom dark energy the requirement that our
universe satisfy a CBE-condition ({\it Comes Back Empty}) imposes a lower bound
on the number of causal patches which separate just prior to
turnaround. This bound depends on the dark energy equation of state with . More accurate measurement of will
constrain . The critical density in the model has a lower
bound or
when the smallest bound state has size m, or m,
respectively.Comment: 23 pages, 3 figures, typos fixe