Everpresent Lambda

@inproceedings{Ahmed2002EverpresentL,
  title={Everpresent Lambda},
  author={Maqbool Ahmed and Scott Dodelson and Patrick B. Greene and Rafael Sorkin},
  year={2002}
}
A variety of observations indicate that the universe is dominated by dark energy with negative pressure, one possibility for which is a cosmological constant. If the dark energy is a cosmological constant, a fundamental question is: Why has it become relevant at so late an epoch, making today the only time in the history of the universe at which the cosmological constant is of order the ambient density. We explore an answer to this question drawing on ideas from unimodular gravity, which… 

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References

SHOWING 1-10 OF 22 REFERENCES

A SMALL BUT NONZERO COSMOLOGICAL CONSTANT

Recent astrophysical observations seem to indicate that the cosmological constant is small but nonzero and positive. The old cosmological constant problem asks why it is so small; we must now ask, in

Implications of a cosmological constant varying as R-2.

  • ChenWu
  • Physics
    Physical review. D, Particles and fields
  • 1990
TLDR
It is shown that such a time-varying {Lambda} leads to creation of matter with a rate at present which is comparable to that in the steady-state cosmology, and alleviates some problems in reconciling observations with the inflationary scenario.

Turning the cosmological constant into black holes

It is known that there is a quantum mechanical tunneling process which, through nucleation of a membrane, induces a transition between two de Sitter spaces, lowering the cosmological constant. It is

A mechanism for reducing the value of the cosmological constant

New globular cluster age estimates and constraints on the cosmic equation of state and the matter density of the universe

New estimates of globular cluster distances, combined with revised ranges for input parameters in stellar evolution codes and recent estimates of the earliest redshift of cluster formation allow us

Instantons and unitarity in quantum cosmology with fixed four-volume

We find a number of complex solutions of the source-free Einstein equations in the so-called unimodular version of general relativity, and we interpret them as saddle points yielding estimates of a

“Renormalization” transformations induced by cycles of expansion and contraction in causal set cosmology

We study the ``renormalization group action'' induced by cycles of cosmic expansion and contraction, within the context of a family of stochastic dynamical laws for causal sets derived earlier. We

Forks in the road, on the way to quantum gravity

In seeking to arrive at a theory of “quantum gravity,” one faces several choices among alternative approaches. I list some of these “forks in the road” and offer reasons for taking one alternative

The origin of Lorentzian geometry