420 likes | 511 Views
How to Build an Alternative to Inflation. 朴 云 松 中国科学院研究生院. The idea behind inflation should be more interesting than inflation self, which may bring us more thoughts are there alternatives to inflation ?. Problems of Big Bang cosmology Why inflation is successful ?
E N D
How to Build an Alternative to Inflation 朴 云 松 中国科学院研究生院
The idea behind inflation should be more interesting than inflation self, which may bring us more thoughts are there alternatives to inflation ?
Problems of Big Bang cosmology • Why inflation is successful ? • How to build an alternative • Summary
inflation a period of accelerated expansion of early universe
if it is actually inflation, the amusements left are play models and fit observations
the game is actually ... however, it may be not inflation ?
There can be a scenario ? it can solve same problems (or some of problems) with those solved by inflation generate scale invariant primordial perturbation
Thus if there can be a solution to the problem of standard cosmology
contraction expansion
what is the efolding number ? for perturbation, not for scale factor
inflation inflation slow expansion slow contraction
slow contraction slow expansion
contraction expansion what can lead the scale invariant scalar spectrum ?
and are same only in
The reason is is the increasing mode when
constant mode increasing mode cyclic universe Piao (03) island universe (05,07)
island universe
The cyclic and island a is nearly unchanged. H is rapidly increased. The inflation a is rapidly increased. H is nearly unchanged. This duality is a natural result of duality between their background evolutions.
how to distinguish inflation ( ) and scenarios with i.non-Gaussianity In general, non-Gaussianity for inflation, it is small, however, it can be large by other methods. for , it is natural large for example, if ,
cyclic universe (Steinhardt et.al.) island universe
ii. Tensor spectrum Steinhardt et.al.
For there are lots of studies. However, the problems It is not an attractor solution. It leads to
Thus contraction expansion ? There are only a little points responsible for scale invariance. However, the perturbation is induced by background field. This is natural.
some “unnatural” mechanisms i. non background field recall “curvaton” in inflation game Thus the perturbation can be induced by also light field. it initially is used in PBB picture. contraction expansion PBB
In principle, the scale invariance can be obtained for any . however, it requires a special behavior of field. In general, a. non minimal coupled kinetic term b. change of mass with time
contraction expansion ? background field non background field
some “unnatural” mechanisms ii. change speed of sound it might be scale Invariant for any and any evolutions however, some problems of standard cosmology will remain. expansion contraction ?
Summary the idea behind inflation is more interesting than inflation self. inflation is consistent, however, there are alternatives. may be tested by coming observations.
Have all possibilities been explored ? …… Thank You