The Games for Universe
Yun-Song Piao
Interdisciplinary Center of Theoretical Studies
Chinese Academy of Sciences
Some of Rceent Works
Piao, hep-th/0407258,
Can Universe Experience Many Cycles with
Different Vacua ?
accepted in Phys.Rev.D (Rapid Communication)
Piao, Feng, Zhang, hep-th/0310206,
Suppressing CMB Quadrupole with a Bounce from
Contracting Phase to Inflation
Phys.Rev.D69 103520(2004)
Piao, gr-qc/0410206
Preheating and Dark Sector of Universe
The notion that the number of vacua is astronomical
has received much attentions, recently
1) String Theory
2) Explaining Observation
The dynamical mechanism
(might select some in which we live)
1) Eternal Inflation
various regions (bubbles) with different vacua
2) Other ?
for example, various periods (cycles) with
different vacua
It is wellknown that
1) For an expanding universe with dS minimum, it will arrive at a dS
regime symptotically.
2)
The universe with AdS minimum can not approach an AdS
regime, and instead it will stop expanding and enter into a
collapsing phase. During the collapsing process, its energy goes up
rapidly. The singularity will become inevitable unless there is a
mechanism responsible for the bounce.
3) When the universe is in the contracting phase, the field can be
driven and roll up along its potential, and arrive at a large enough
value for asuccessful inflation to occur in expanding phase for a
feasible bounce.
The potential for our purpose
When the field rolls down to the minima of its
potential, the universe will collapse eventually. In
the minima of potential
The anti-frictional term can be neglected.
The motion of equation becomes
whose solution is
When the anti-frictional term can be not neglected any
more, the oscillations of field ends. The universe enters
into the regime dominated by kinetic energy.
In high energy regime, we take for the bounce
During a cycle, the change of field value is approximately
Some Comments
1) The efficience of cycle
2) If cycle is efficient, when the number of cycles is
large or approaches infinity, whichever minima is
initially in, it can run over almost all minima of
potential.
3) If there is a final theory where some vacua suitable
us exist, there are certainly some cycles in which we
can live.
4) In this sense, the universe with a early successful
inflation and a late time small cosmological constant
may be anthropic one of many cycles.
Matching CMB Observation
The connection between different vacua provides a
suppression of scalar perturbation spectrum on large scale
For kinetic dominated and potential dominated phase
after matching background
The equation of scalar perturbation
For kinetic dominated phase
For inflation phase
Piao, Tsujikawa, Zhang, hep-th/0312139
Matching Dark Sector Observations
Taking the potential as
Considering a coupe to a massive field
When phi field crosses the oringin, the occupation number
of chi particles suddenly acquire the value
The number density of chi particles is approximately
The density of dark energy is about the same as dark energy’s
at present requires
Making phi stay in a false vacumm up to today requires
The comoving free streaming scale for nonthermal
produced particles is
which requiresi
Summary
1) The universe can experience many cycles with different
vacua, under certain conditions.
2) The connection between two different vacua may give a
possible explanation to the suppression of power spectrum
on large scale,
3) The production of light particles may make the universe
stay in some state with very long time.
Further, there might few vacua satisfying such conditions,
in which dark matter produced during preheating can trap us
in a cycle dominated by dark energy at late time.