We present some solutions showing evolution from early inflation to late time acceleration in FLRW space time with Gauss-Bonnet term and ideal fluid. In the late time era, we have either quintessence, or phantom or de-Sitter era of expansion depending on the parameters. The Chameleon mechanism shows that the correction to the Newton's law could be small.

No abstract

A few Euclidean wormhole configurations are presented using both the analytic and numerical solutions of the field equations in four-dimensional Robertson–Walker Euclidean background with Einstein–Gauss–Bonnet dilaton interaction. In one analytic solution we present transition from a wormhole to an exponential expansion with Lorentzian time [Formula: see text] using [Formula: see text] after passing through an era of oscillating Euclidean wormhole. The numerical solutions of the scale factor [Formula: see text] show multiple local maxima and minima about a global minimum for inverse power law potentials, while for exponential potential the wormholes have a single minimum. An inflationary cosmic scenario away from the throat of the wormhole can be obtained from the Hubble parameter and deceleration parameter obtained by curve fit of [Formula: see text] of the numerical solution invoking analytic continuation by [Formula: see text]. The potential is also observed to decay sharply.

We present some solutions in a modified theory of gravity with R 2 and 1 R terms in the Einstein-Hilbert action with an ideal fluid in FLRW spacetime. Graceful exit from early inflation to radiation dominated era is obtained in the strong curvature regime preceding a fluctuation of effective equation of state parameter at the end of inflation. In the weak curvature regime the universe evolves through a radiation era that subsequently turns to a matter era and finally transits to late time accelerating era.

We present some solutions in Friedmann–Lemaître–Robertson–Walker (FLRW) spacetime in the modified theory of gravity with a general Gauss–Bonnet (GB) term f(G) and R2 including an ideal fluid. We present evolution of the universe introducing an ansatz without a prior choice of f(G) in one approach, while in other class of model, the solutions are obtained assuming few simple forms of f(G). Some of the solutions show early inflationary expansion, further in one solution the fluctuation of the deceleration parameter q is evident at the end of inflation. In all cases, late-time transition to accelerating universe at redshift z [Formula: see text] 0.7 is realizable.