text
stringlengths
0
44.4k
FIG. 4. Cascade creation of bubble universes. In this figure,
we assume trajectory Ais the eternal inflation trajectory, and
trajectory Bis the non-eternal inflation trajectory.
of the spatial volume remain in the old bubble universe
at the instant of tunneling.
If bifurcations of multi-stream inflation happen dur-
ing eternal inflation, two kinds of new bubble universes
can be created with similar probabilities. In this case,
at the instant of bifurcation, both kinds of bubble uni-
verseshavenearlyequalspatialvolume. Withachangeof
probabilities, the measures for eternal inflation should be
reconsideredformulti-streamtype bubble creationmech-
anism.
If the inflation trajectories recombine after a period of
inflation, the different bubble universes will eventually
have the same physical laws and constants of nature. On
the other hand, if the different inflation trajectories do
not recombine, then the different bubble universes cre-
ated by the bifurcation will have different vacuum ex-
pectation values of the scalar fields, resulting to different
physical laws or constants of nature. It is interesting
to investigate whether the bifurcation effect is more ef-
fective than the tunneling effect to populate the string
theory landscape.
Note that in multi-stream inflation, it is still possi-
ble that different trajectorieshaveexponentiallydifferent
probabilities, as discussed in the previous section. In this
case, multi-stream inflation behaves similar to Hawking
Moss instantons during eternal inflation.
Local terminations for eternal inflation . It is possible
that during multi-stream inflation, a inflation trajectory
bifurcates in to one eternal inflation trajectory and one
non-eternal inflation trajectory with similar probability.
Inthiscase,theinflatonintheeternalinflationtrajectory
frequently jumps back to the bifurcation point, resulting
in a cascade creation of bubble universes, as illustrated
in Fig. 4. This cascade creation of bubble universes, if4
realized, is more efficient in producing reheating bubbles
than tunneling effects. Thus it reduces the measure for
eternal inflation.
There are some other interesting issues for bifurcation
in the multiverse. For example, the bubble walls may
be observable in the present observable universe, and the
bifurcations can lead to multiverse without eternal infla-
tion. These possibilities are discussed in [5].
IV. CONCLUSION AND DISCUSSION
To conclude, webriefly reviewedmulti-stream inflation
during observable inflation. Some new issues such as do-main fences and connection with quasi-single field infla-
tion are discussed. We also discussed multi-stream infla-
tion in the context of eternal inflation. The bifurcation
effect in multi-stream inflation provides an alternative
mechanism for creating bubble universes and populating
the string theory landscape. The bifurcation effect also
provides a very efficient mechanism to locally terminate
eternal inflation.
ACKNOWLEDGMENT
We thank Yifu Cai for discussion. This work was sup-
ported by NSERC and an IPP postdoctoral fellowship.
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arXiv:1001.0009v1 [q-bio.BM] 30 Dec 2009Jamming proteins with slipknots and their free energy lands cape
Joanna I. Su/suppress lkowska1, Piotr Su/suppress lkowski2,3,4and Jos´ e N. Onuchic1
1Center for Theoretical Biological Physics,
University of California San Diego,
Gilman Drive 9500, La Jolla 92037,