- #1
saleh
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HI,...
This is my first post here on this forum ...
I wonder if anyone here can help me to clarify some concepts to me in the paper of alan guth 2007 named "Eternal inflation and its implications"
and this is my question here ...
he says in the abstract the following :"Although inflation is generically eternal into the future,
it is not eternal into the past: it can be proven under reasonable assumptions that the
inflating region must be incomplete in past directions, so some physics other than
inflation is needed to describe the past boundary of the inflating region."
and in p.14 :"If the universe can be eternal into the future, is it possible that it is also eternal into
the past? Here I will describe a recent theorem [43] which shows, under plausible
assumptions, that the answer to this question is no"
that seems to me -if I understand correctly-that he suggests a past incompleteness which is synonimous to "beginning" ,But then he says
"There is of course no conclusion that an eternally inflating model must have a
[unique beginning], and no conclusion that there is an upper bound on the length of
all backwards-going geodesics from a given point. There may be models with regions
of contraction embedded within the expanding region that[ could evade our theorem]."
so any thoughts on the subjects ?!, It could really be helpful
Thanks
This is my first post here on this forum ...
I wonder if anyone here can help me to clarify some concepts to me in the paper of alan guth 2007 named "Eternal inflation and its implications"
and this is my question here ...
he says in the abstract the following :"Although inflation is generically eternal into the future,
it is not eternal into the past: it can be proven under reasonable assumptions that the
inflating region must be incomplete in past directions, so some physics other than
inflation is needed to describe the past boundary of the inflating region."
and in p.14 :"If the universe can be eternal into the future, is it possible that it is also eternal into
the past? Here I will describe a recent theorem [43] which shows, under plausible
assumptions, that the answer to this question is no"
that seems to me -if I understand correctly-that he suggests a past incompleteness which is synonimous to "beginning" ,But then he says
"There is of course no conclusion that an eternally inflating model must have a
[unique beginning], and no conclusion that there is an upper bound on the length of
all backwards-going geodesics from a given point. There may be models with regions
of contraction embedded within the expanding region that[ could evade our theorem]."
so any thoughts on the subjects ?!, It could really be helpful
Thanks