樸云松科學(xué)院研究生院

1、樸 云 松 中國科學(xué)院研究生院,How to Build an Alternative to Inflation,,The idea behind inflation should be more interesting than inflation self, which may bring us more thoughtsare there alternatives to inflat

2、ion ?,Problems of Big Bang cosmologyWhy inflation is successful ?How to build an alternative Summary,i.,ii.,iii.,a period of accelerated expansion of early universe,inflation,if it is actually inflation, the amu

3、sements left are,play models andfit 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 infla

4、tion generate scale invariant primordial perturbation,it requires a|H| increases with time,Thus if,,,,,there can be a solution to the problem of standard cosmology,expansion,contraction,what is the efolding numb

5、er ? for perturbation, not for scale factor,inflation,,,slow contraction,,slow expansion,,,,inflation,slow contraction,slow expansion,expansion,contraction,what can lead

6、 the scale invariant scalar spectrum ?,and are same only in,is the increasing modewhen,The reason is,,,,,for,Piao (03)island universe (05,07),cyclic universe,constant mode,increasing mode,,,island universe,The cyclic

7、 and islanda is nearly unchanged. H is rapidly increased.The inflationa is rapidly increased.H is nearly unchanged.,This duality is a natural result of duality between their background evolutions.,how to distin

8、guish inflation ( ) and scenarios with,i.non-GaussianityIn general, non-Gaussianity for inflation, it is small, however, it can be large by other methods.for , it is natural largefor

9、 example, if ,,island universe,cyclic universe,(Steinhardt et.al.),ii. Tensor spectrum,Steinhardt et.al.,,For there are lots of studies.However, the problemsIt is not an attractor solution. It leads to,Thu

10、s,,,,？,expansion,contraction,,There are only a little points responsible for scale invariance.However, the perturbation is induced by background field. This is natural.,i. non background f

11、ield recall “curvaton” in inflation game Thus the perturbation can be induced by also light field.it initially is used in PBB picture.,,PBB,expansion,contraction,some “unnatural” mechanisms,In princi

12、ple, 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,,expansion,

13、contraction,,,,,？,background field,non background field,,,ii. change speed of sound it might be scaleInvariant for any and any evolutions,,expansion contraction ?,however, some problems of standard cosm

14、ology will remain.,some “unnatural” mechanisms,Summarythe idea behind inflation is more interesting than inflation self. inflation is consistent, however, there are alternatives. may be tested by